Co-reporter:Zongpeng Li;Hongtao Guan;Ning Yu;Ichiro Imae;Junyu Wei
The Journal of Physical Chemistry C June 10, 2010 Volume 114(Issue 22) pp:10119-10125
Publication Date(Web):Publication Date (Web): May 18, 2010
DOI:10.1021/jp101342h
In this study, we report a facile and efficient method using supercritical (SC) CO2 to help a p-type conducting polymer, conjugated polymer MDMO-PPV wrapping on carbon nanotubes (CNTs). One-dimensional CNTs were periodically decorated with the congeries of MDMO-PPV molecular chains forming functional nanohybrid structures. The solubility and light emission of the hybrid MDMO-PPV/CNTs can be controlled by varying SC CO2 pressure. Using FT-IR, we can observe there exists chemical interaction between MDMO-PPV and CNTs, and the interaction not only bestowed CNTs desired solubility but also added functionality of light emission to CNTs. The fluorescence spectroscopy of the MDMO-PPV/CNTs shows their light emission is strongly depend on solvent. For DMSO as the solvent, the higher SC CO2 pressure ensures the excellent dispersion and solubility of MDMO-PPV/CNTs, and accordingly causes the light quenching of the hybrid. For DMAc as the solvent, the enhanced emission light can be observed from the MDMO-PPV/CNTs, especially at higher SC CO2 pressure. We anticipate this work opens a gateway for making use of SC CO2 to help functionalize CNTs with conjugated polymer for use in polymer solar cells, light-emitting diodes, and others.
Co-reporter:Shiyu Guo;Pengfei Yuan;Jianan Zhang;Pengbo Jin;Hongming Sun;Kaixiang Lei;Xinchang Pang;Fangyi Cheng
Chemical Communications 2017 vol. 53(Issue 71) pp:9862-9865
Publication Date(Web):2017/08/31
DOI:10.1039/C7CC05476A
A one-step in situ nanoconfined pyrolysis strategy was developed to anchor highly active single Co atoms on the P,N-doped porous carbon@carbon nanotube coaxial nanocables (Co-P,N-CNT), which exhibit remarkable enhanced ORR electrocatalytic activity in both acidic and alkaline media.
Co-reporter:Xuzhe Wang, Weili Cui, Meng Chen, Qun Xu
Materials Letters 2017 Volume 201(Volume 201) pp:
Publication Date(Web):15 August 2017
DOI:10.1016/j.matlet.2017.04.110
•The MoO3 nanosheets are exfoliated with the assistance of supercritical CO2.•A topotactic phase transformation was achieved through the exfoliation process.•A possible mechanism has been proposed to explain the phase transformation.The metastable hexagonal phase of molybdenum oxide (h-MoO3) have drawn much attention due to the novel one-dimensional tunnel structure and enhanced properties in physical, optical, chemical and electronic fields. Most of the researchers focused on the hydrothermal reaction to obtain h-MoO3 using NH4+, Na+ or K+ ion as the structure-directing agents and stabilizer of the h-MoO3, which will definitely hinder the further application of h-MoO3. In this work, for the first time, we demonstrate a novel top-down method to obtain metastable h-MoO3 via a topotactic phase transformation with the assistance of supercritical carbon dioxide (SC CO2). Our study indicates that this successful phase transformation is due to distortion of MoO6 octahedra units that might be induced by the surface tension change.Download high-res image (220KB)Download full-size image
Co-reporter:Weili Cui;Shanshan Xu;Bo Yan;Zhihua Guo;Bobby G. Sumpter;Jingsong Huang;Shiwei Yin;Huijun Zhao;Yun Wang
Advanced Electronic Materials 2017 Volume 3(Issue 7) pp:
Publication Date(Web):2017/07/01
DOI:10.1002/aelm.201700024
Recently the applications of 2D materials have been broadened by engineering their mechanical, electronic, and optical properties through either lateral or vertical hybridization. Here, the successful design and fabrication of a novel triphasic 2D material by vertically stacking lateral 2H-/1T′-molybdenum disulfide (MoS2) heterostructures on graphene with the assistance of supercritical carbon dioxide is reported. This triphasic structure is experimentally shown to significantly enhance the photocurrent densities for hydrogen evolution reactions. First-principles theoretical analyses reveal that the improved photoresponse should be ascribed to the beneficial band alignments of the triphasic heterostructure. More specifically, electrons can efficiently hop to the 1T′-MoS2 phase via the highly conductive graphene layer as a result of their strong vertical interfacial electronic coupling. Subsequently, the electrons acquired on the 1T′-MoS2 phase are exploited to fill the photoholes on the photoexcited 2H-MoS2 phase through the lateral heterojunction structure, thereby suppressing the recombination process of the photoinduced charge carriers on the 2H-MoS2 phase. This novel triphasic concept promises to open a new avenue to widen the molecular design of 2D hybrid materials for photonics-based energy conversion applications.
Co-reporter:Zhimin Chen;Jingjing Cao;MingMing Fang;Qiuge Tian
Colloid and Polymer Science 2017 Volume 295( Issue 11) pp:2151-2161
Publication Date(Web):06 September 2017
DOI:10.1007/s00396-017-4187-5
In this paper, using the soft-core/hard-shell polystyrene–divinylbenzene microspheres prepared by soap-free emulsion polymerization as building blocks, hexagon bowl-like polymer microspheres (BLPM) with ordered array and same orientation were successfully prepared through direct pyrolysis. The rim thickness and the morphology of the BLPM could be adjusted through changing the content of a cross-linking agent or the calcination conditions such as temperature, time, and heating rate. Besides, extrusion between microspheres also plays an important role on the cavity size and the hexagonal structure. The morphology of BLPM was characterized by SEM and TEM. FT-IR, EDS, and differential scanning calorimetry–thermogravimetric were also used to analyze the mechanism. Due to these, cross-linked BLPM have some special properties such as high thermal stability, solvent resistance, narrow size distribution, and ordered array, which will broaden their applications in many areas.
Co-reporter:Xiaofang Zhou, Xiaoli Zheng, Bo Yan, Tao Xu, Qun Xu
Applied Surface Science 2017 Volume 400(Volume 400) pp:
Publication Date(Web):1 April 2017
DOI:10.1016/j.apsusc.2016.12.072
•We establish a facile strategy by solvothermal reaction and hydrogenation to synthesize 2D WO3 ultrathin nanosheets with abundant oxygen vacancies.•We find that the hydrogenated WO3 ultrathin nanosheets exhibit outstanding electrochromism properties.•Moreover, the hydrogenated WO3 nanosheets also exhibit remarkable photocatalytic performance.•The outstanding electrochromism and photoelectrochemical performances are mainly due to increased oxygen vacancies and narrowed band gap.The capability of introduction of oxygen vacancies in a controlled way has emerged as the heart of modern transition metal oxide semiconductor chemistry. As chemical defects, the oxygen vacancies have been proposed as electron donors, which are prone to increase carrier density and promote charge carrier separation. Herein, we have successfully prepared 2D WO3 ultrathin nanosheets with abundant surface oxygen vacancies by a combination of facile solvothermal reaction and hydrogenation method. The resultant hydrogenated WO3 ultrathin nanosheets exhibit remarkable electrochromism and photocatalytic performances compared with the non-hydrogenated samples, mainly due to their increased oxygen vacancies, narrowed band gap coupled with fast charge transfer and enhanced adsorption of visible light.Download high-res image (161KB)Download full-size image
Co-reporter:Jing-Hui Zhang, Tai Sun, Aping Niu, Yu-Mei Tang, Shun Deng, Wei Luo, Qun Xu, Dapeng Wei, De-Sheng Pei
Biomaterials 2017 Volume 133(Volume 133) pp:
Publication Date(Web):1 July 2017
DOI:10.1016/j.biomaterials.2017.04.026
Graphene quantum dots (GQDs) has been widely used in enormous fields, however, the inherent molecular mechanism of GQDs for potential risks in biological system is still elusive to date. In this study, the outstanding reduced graphene quantum dots (rGOQDs) with the QY as high as 24.62% were successfully synthesized by the improved Hummers method and DMF hydrothermal treatment approach. The rGOQDs were N-doped photoluminescent nanomaterials with functional groups on the surface. The fluorescent bio-imaging was performed by exposing zebrafish in different concentrations of the as-prepared rGOQDs, and the distribution of rGOQDs was successfully observed. Moreover, the developmental toxicity and genotoxicity were evaluated to further investigate the potential hazard of rGOQDs. The result indicated that rGOQDs were responsible for the dose-dependent abnormalities on the development of zebrafish. Since the real-time polymerase chain reaction (RT-PCR) results showed that the expression of cyp1a was the highest expression in the selected genes and significantly up-regulated 8.49 fold in zebrafish, the perturbation of rGOQDs on aryl hydrocarbon receptor (AhR) pathway was investigated by using the Tg(cyp1a:gfp) zebrafish for the first time. The results demonstrated that rGOQDs significantly increased the green fluorescent protein (GFP) expression promoted by cyp1a in a dose-dependent manner, which was also further confirmed by the western blotting. This study offered an opportunity to reveal the potential hazards of in vivo bio-probes, which provided a valuable reference for investigating the graphene-based materials on the disturbance of AhR pathway in biological organisms.
Co-reporter:Chuanhui Zhu, Qun Xu, Wei Liu, Yumei Ren
Applied Surface Science 2017 Volume 425(Volume 425) pp:
Publication Date(Web):15 December 2017
DOI:10.1016/j.apsusc.2017.06.248
•In this study the h-MoO3/1T-MoS2 heterostructures were successfully fabricated.•The h-MoO3/1T-MoS2 heterostructures display strong optical absorption at NIR region.•The peculiar heterostructures have an increased photoelectrocatalytic performance.Combining the peculiar properties of different ingredients in one ultimate material is an efficient route to achieve the desired functional materials. Compared to 2H-MoS2, 1T-MoS2 nanosheets display the perfect performance of hydrogen evolution reaction (HER) because of the excellent electronic conductivity. However, how to further realize HER in the visual and near-infrared (NIR) region is a great challenge. Herein, we develop an efficient method to locally pattern h-MoO3 on the ultrathin metallic 1T-MoS2 nanosheets and obtain the novel heterostructures of h-MoO3/1T-MoS2. The enhanced photoelectrochemical performance of the as-prepared heterostructures has been demonstrated. Our study indicates it is originated from the synergistic effect between h-MoO3 and 1T-MoS2, i.e., the strong optical absorption of h-MoO3 in the visible and NIR region, the excellent electronic conductivity of 1T-MoS2 and as well as the efficient separation of the photo-induced carriers from the heterostructures.An efficient strategy has been developed to locally pattern h-MoO3 on the ultrathin metallic 1T-MoS2 nanosheets, and obtained a heterostructures of h-MoO3/1T-MoS2. The as-prepared heterostructures displays an enhanced photoelectrocatalytic preformance, which is originated from the synergistic effect between plasmonic h-MoO3 and 1T-MoS2.Download high-res image (153KB)Download full-size image
Co-reporter:Mingming Fang, Zhimin Chen, Qiuge Tian, Yanxia Cao, Chong Wang, Yuan Liu, Jianwei Fu, Jianan Zhang, Lichen Zhu, Chong Yang, Jiafu Chen, Qun Xu
Applied Surface Science 2017 Volume 425(Volume 425) pp:
Publication Date(Web):15 December 2017
DOI:10.1016/j.apsusc.2017.06.279
•Uniform discrete cage-like nitrogen-doped hollow carbon spheres were synthesized.•The microspheres have tunable direct large mesoporous (18–30 nm) on the shells.•The large mesoporous can effectively reduce the mass-transfer resistance.•The microspheres exhibit an ultrahigh supercapacitive performance.Uniform discrete cage-like nitrogen-doped hollow porous carbon spheres (CN-HPCS) with tunable direct large mesoporous (18–30 nm) have been successfully synthesized for the first time by using the carboxylated polystyrene spheres and silica particles as a dual-template and dopamine as the carbon and nitrogen sources. When they are used as the electrode for supercapacitors, these CN-HPCS exhibit a high specific capacitance of 257 F g−1 at 1 A g−1 and 194 F g−1 at 10 A g−1 with excellent rate capability and cycling stability.Uniform discrete cage-like nitrogen-doped hollow porous carbon spheres with tunable direct large mesoporous were firstly synthesized for ultrahigh supercapacitive performance.Download high-res image (174KB)Download full-size image
Co-reporter:Xiaodan Xu;Lu Cai;Xiaoli Zheng
Physical Chemistry Chemical Physics 2017 vol. 19(Issue 24) pp:16062-16070
Publication Date(Web):2017/06/21
DOI:10.1039/C7CP01277B
In this work we carried out molecular dynamics (MD) simulations to explore the mechanism of solvent-exfoliation and stabilization of graphene in the presence of (compressed) carbon dioxide (cpCO2), p-xylene and pyrene–polyethylene glycol (Py–PEG) polymers. We studied the role of each component in graphene exfoliation and stabilization by setting different experimental variables. The simulation results show that the cpCO2 molecules played a “wedge” role in the exfoliation process, firstly wedging into the interlayer, and then helping solvent molecules to insert into the interlayer. The solvent molecules between the graphene sheets are the main reasons that graphene exfoliation is achieved. And the Py–PEG polymer chains mainly act as stabilizers to prevent the exfoliated graphene sheets from restacking. This work provides detailed theoretical clues to better understand the mechanism of exfoliation and stabilization of graphene.
Co-reporter:Huicong Xia;Jianan Zhang;Zhao Yang;Shiyu Guo;Shihui Guo
Nano-Micro Letters 2017 Volume 9( Issue 4) pp:
Publication Date(Web):2017 October
DOI:10.1007/s40820-017-0144-6
Metal–organic frameworks (MOFs) are of great interest as potential electrochemically active materials. However, few studies have been conducted into understanding whether control of the shape and components of MOFs can optimize their electrochemical performances due to the rational realization of their shapes. Component control of MOFs remains a significant challenge. Herein, we demonstrate a solvothermal method to realize nanostructure engineering of 2D nanoflake MOFs. The hollow structures with Ni/Co- and Ni-MOF (denoted as Ni/Co-MOF nanoflakes and Ni-MOF nanoflakes) were assembled for their electrochemical performance optimizations in supercapacitors and in the oxygen reduction reaction (ORR). As a result, the Ni/Co-MOF nanoflakes exhibited remarkably enhanced performance with a specific capacitance of 530.4 F g−1 at 0.5 A g−1 in 1 M LiOH aqueous solution, much higher than that of Ni-MOF (306.8 F g−1) and ZIF-67 (168.3 F g−1), a good rate capability, and a robust cycling performance with no capacity fading after 2000 cycles. Ni/Co-MOF nanoflakes also showed improved electrocatalytic performance for the ORR compared to Ni-MOF and ZIF-67. The present work highlights the significant role of tuning 2D nanoflake ensembles of Ni/Co-MOF in accelerating electron and charge transportation for optimizing energy storage and conversion devices.
Co-reporter:Jianwei Fu, Qianqian Xin, Xuechen Wu, Zhonghui Chen, Ya Yan, Shujun Liu, Minghuan Wang, Qun Xu
Journal of Colloid and Interface Science 2016 Volume 461() pp:292-304
Publication Date(Web):1 January 2016
DOI:10.1016/j.jcis.2015.09.017
Polydopamine (PDA) microspheres, synthesized by a facile oxidation polymerization route, were evaluated as a potential adsorbent for selective adsorption and separation of organic dyes. The adsorption processes towards nine water-soluble dyes (anionic dyes: methyl orange (MO), eosin-Y (EY), eosin-B (EB), acid chrome blue K (ACBK), neutral dye: neutral red (NR), and cationic dyes: rhodamine B (RhB), malachite green (MG), methylene blue (MB), safranine T (ST)) were thoroughly investigated. The adsorption selectivity of organic dyes onto PDA microspheres was successfully applied for the separation of dyes mixtures. Various influential factors such as solution pH, temperature, and contact time were employed to ascertain the optimal condition for adsorption of representative organic dyes including MB, MG and NR. The pseudo-first-order and pseudo-second-order kinetics models were used to fit the adsorption kinetics process. Five isothermal adsorption models (Langmuir, Dubnin–Radushkevich, Temkin, Freundlich and Harkins–Jura) were used to investigate the adsorption thermodynamics properties. The results showed that the PDA microspheres owned good selective adsorption ability towards cationic dyes. The adsorption kinetics process conformed to the pseudo-second-order kinetics model and the Langmuir isotherm model was more appropriate for tracing the adsorption behavior than other isotherm models. Thus, we can conclude PDA microspheres may be a high-efficiency selective adsorbent towards some cationic dyes.PDA microspheres were demonstrated to be a high-efficiency selective adsorbent towards cationic dyes, and the selective behavior was related to electrostatic interaction and π–π stacking between adsorbent and dye molecules.
Co-reporter:Shujun Liu, Jianwei Fu, Minghuan Wang, Ya Yan, Qianqian Xin, Lu Cai, Qun Xu
Journal of Colloid and Interface Science 2016 Volume 469() pp:69-77
Publication Date(Web):1 May 2016
DOI:10.1016/j.jcis.2016.02.011
Magnetic Fe3O4–polydopamine (PDA) hybrid hollow microspheres, in which Fe3O4 nanoparticles were firmly incorporated in the cross-linked PDA shell, have been prepared through the formation of core/shell PS/Fe3O4–PDA composites based on template-induced covalent assembly method, followed by core removal in a tetrahydrofuran solution. The morphology, composition, thermal property and magnetic property of the magnetic hybrid hollow microspheres were characterized by SEM, TEM, FT-IR, XRD, TGA, and vibrating sample magnetometer, respectively. Results revealed that the magnetic hybrid hollow microspheres had about 380 nm of inner diameter and about 30 nm of shell thickness, and 13.6 emu g−1 of magnetization saturation. More importantly, the Fe3O4–PDA hybrid hollow microspheres exhibited intrinsic peroxidase-like activity, as they could quickly catalyze the oxidation of typical substrates 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide. Compared with PDA/Fe3O4 composites where Fe3O4 nanoparticles were loaded on the surface of PDA microspheres, the stability of Fe3O4–PDA hybrid hollow microspheres was greatly improved. As-prepared magnetic hollow microspheres might open up a new application field in biodetection, biocatalysis, and environmental monitoring.Magnetically separable and reusable Fe3O4–polydopamine hybrid hollow microspheres based on template-induced covalent assembly method exhibit highly efficient peroxidase mimetic catalytic activity and stability.
Co-reporter:Yumei Ren, Tianjiao Wang, Zhimin Chen, Jing Li, Qiuge Tian, Hongxia Yang, Qun Xu
Applied Surface Science 2016 Volume 385() pp:521-528
Publication Date(Web):1 November 2016
DOI:10.1016/j.apsusc.2016.05.146
Highlights
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In this study conductive chiral MWCNTs@NCC nanopapers were prepared.
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The introduction of the MWCNTs has a pronounced effect on the chiral structure of the as-prepared nanopaper.
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The multiple weak molecular interactions existing between MWCNTs and NCC are responsible for the effective dispersion and stabilization of MWCNTs.
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The resulting nanopaper has an increased conductivity.
Co-reporter:Ya Yan, Jianwei Fu, Minghuan Wang, Shujun Liu, Qianqian Xin, Zhimin Chen and Qun Xu
RSC Advances 2016 vol. 6(Issue 30) pp:24921-24928
Publication Date(Web):01 Mar 2016
DOI:10.1039/C6RA02158A
Ag–Au bimetallic nanoparticles (NPs) are deposited on poly(cyclotriphosphazene-co-4,4′-sulfonyldiphenol) (PZS) nanotubes by a facile and effective co-reduction method, wherein the PZS nanotubes with abundant hydroxyl groups have been prepared via an in situ template approach. Upon varying the feeding amounts of the Ag and Au precursors, the bimetallic compositions of the PZS nanotubes can be readily tuned resulting in a series of bimetallic catalysts with different Ag to Au molar ratios, thus leading to the tunable catalytic properties. Characterization results show that the Ag–Au bimetallic nanoparticles with smaller size and good dispersibility are well anchored onto the surface of the PZS nanotubes. Furthermore, the reduction of 4-nitrophenol (4-NP) into 4-aminophenol (4-AP) by NaBH4 is applied as a model reaction to study the effect of different Ag-to-Au molar ratios on the catalytic capabilities of the resulting composites. It is found that the catalytic capability is remarkably enhanced when the Au content is increased. The maximum activity parameter value reaches 92.2 s−1 g−1, which is far higher than that of PZS nanotubes decorated with either Ag or Au nanoparticles alone.
Co-reporter:Min Hong, Jiafu Chen, Minxin Zhang, Xin Huang and Qun Xu
RSC Advances 2016 vol. 6(Issue 20) pp:16141-16149
Publication Date(Web):01 Feb 2016
DOI:10.1039/C5RA25932K
A novel and facile template-free method referred to as “secondary-crosslinking pyrolysis” to fabricate discrete and dispersible hollow carbon spheres (HCSs) with hierarchical porous shells and tailorable shell thicknesses has been successfully developed by using the deformed poly(styrene-co-divinylbenzene) (P(St-co-DVB)) capsules as precursors. The samples are characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, Raman spectroscopy and N2 adsorption/desorption. Our experimental results indicate that the carbon particles obtained via the designed “secondary-crosslinking pyrolysis” method present a perfect spherical shape and hollow structure, which is dependent on an interesting phenomenon where the deformed P(St-co-DVB) capsules can recover to hollow spheres through the hypercrosslinking reaction. Moreover the obtained HCSs are uniform, discrete and highly dispersible, and more importantly, they have the hierarchical pore structures that can be used as electrode materials for supercapacitors. And the test results indicate that they exhibit a high specific capacitance up to 192 F g−1 at 5 mV s−1, and the formation mechanism behind these phenomena is discussed.
Co-reporter:Bo Yan, Pengshang Zhou, Qun Xu, Xiaofang Zhou, Dongdong Xu and Jianhua Zhu
RSC Advances 2016 vol. 6(Issue 8) pp:6133-6137
Publication Date(Web):05 Jan 2016
DOI:10.1039/C5RA24126J
We successfully prepared exotic electronic 2D TiO2 nanosheets and then engineered disorder into them to obtain black TiO2 nanosheets. The structural changes induced by this engineering were carefully investigated. The salient properties of the black TiO2 nanosheets were made evident by their enhanced photocurrent and H2 evolution properties.
Co-reporter:Yuanyuan Li, Zhimin Chen, Jianan Zhang and Qun Xu
RSC Advances 2016 vol. 6(Issue 11) pp:9180-9185
Publication Date(Web):15 Jan 2016
DOI:10.1039/C5RA27230K
Heteroatoms dual-doped carbon with three dimensional interconnected architecture is a promising candidate as electrode for high performance energy storage, but the rational design and cost-effective preparation of such materials is still a challenge. Herein, intriguing P and N co-doped porous CNT@carbon core@shell nano-networks (PN-CNTs) have been facilely achieved by a one-step carbonization process of N containing CNT@polymer with triphenylphosphine (TPP). Significantly, such interesting structure provides the synergistic effects of the 3D interconnected networks consisting of 1D core–shell structure (offering continuous pathway for electron transport), hierarchical porous texture (acting as ion-buffering reservoirs) and P and N dual-doped (optimizing the electron donor/acceptor characteristics of carbon). With the advantages of heteroatoms dual-doping effect and rational interconnected porous structure, the PN-CNTs exhibit an ultra-high specific capacitance of 332.56 F g−1, much higher than N-doped carbon@carbon nanotubes (284 F g−1) and CNTs (32 F g−1), good rate capability and a robust cycling performance (almost no capacity fading even after 8000 cycles). The present work provides a novel passway to engineering multi-heteroatoms doped carbon with hierarchical nanoarchitectures through a facile and general route for high-performance renewable energy storage.
Co-reporter:Lu Cai, Wenzhen Lv, Hong Zhu, Qun Xu
Physica E: Low-dimensional Systems and Nanostructures 2016 Volume 81() pp:226-234
Publication Date(Web):July 2016
DOI:10.1016/j.physe.2016.03.021
Highlights•Conformational Entropy, besides binding energy of SWNT-polymer adsorption processes are calculated and the results give quantitatively insight on the effect of solvent polarity.•We focus on the ultrathin SWNT with diameter less than 1nm, which has more highlight performance than normal SWNT.•The roles of aromatic tail of polymer in different solvents are different, not only for the adsorption dynamics process, but also for the final adsorption conformation.The mechanism of the adsorption of pyrene-polyethylene (Py-PE) onto ultrathin single-walled carbon nanotube (SWNT) was studied by using all-atom molecular dynamics (MD) simulations. We found that solvent polarity and pyrene group are two critical factors in the Py-PE decoration on ultrathin SWNT. Combined MD simulations with free energy calculations, our results indicate that larger solvent polarity can decrease the contribution of conformation entropy, but contributes little to the interaction energy, moreover, larger SWNT diameter can decrease the contribution of conformation entropy but lead to the increasing of the interaction energy. In polar organic solvent (N, N-Dimethylacetamide), the pyrene group plays a key role in the adsorption of Py-PE onto ultrathin SWNT, not only facilitates the spontaneous adsorption of Py-PE onto ultrathin SWNT, but also helps to form compact structure between themselves in the final adsorption states. While in aqueous solution, pyrene group no longer works as an anchor, but still affects a lot to the final adsorption conformation. Our present work provides detailed theoretical clue to understand the noncovalent interaction between aromatic segment appended polymer and ultrathin SWNT, and helps to explore the potential application of ultrathin SWNT in the fields of hybrid material, biomedical and electronic materials.
Co-reporter:Yuhang Qi, Qun Xu, Yun Wang, Bo Yan, Yumei Ren, and Zhimin Chen
ACS Nano 2016 Volume 10(Issue 2) pp:2903
Publication Date(Web):February 3, 2016
DOI:10.1021/acsnano.6b00001
Molybdenum disulfide (MoS2) is a promising non-precious-metal catalyst, but its performance is limited by the density of active sites and poor electrical transport. Its metallic 1T phase possesses higher photoelectrocatalytic activity. Thus, how to efficiently increase the concentration of the 1T phase in the exfoliated two-dimensiaonal (2D) MoS2 nanosheets is an important premise. In this work, we propose a strategy to prepare a 2D heterostructure of MoS2 nanosheets using supercritical CO2-induced phase engineering to form metallic 1T-MoS2. Theoretical calculations and experimental results demonstrate that the introduced CO2 in the 2H-MoS2 host can prompt the transformation of partial 2H-MoS2 lattices into 1T-MoS2. Moreover, the electrical coupling and synergistic effect between 2H and 1T phases can greatly facilitate the efficient electron transfer from the active sites of MoS2, which significantly improves the photocatalytic performance.Keywords: heterostructure; molybdenum disulfide; phase engineering; photoelectrocatalysis; supercritical CO2;
Co-reporter:Shanshan Xu, Qun Xu, Nan Wang, Zhimin Chen, Qiuge Tian, Hongxia Yang, and Kaixi Wang
Chemistry of Materials 2015 Volume 27(Issue 9) pp:3262
Publication Date(Web):April 13, 2015
DOI:10.1021/acs.chemmater.5b00092
Mass production of graphene with low cost and excellent properties is essential for its practical applications in energy, composites, biotechnology, and electronics. Here for the first time we demonstrate that graphite powder can be efficiently exfoliated into monolayered and few-layered nanosheets based on the driving forces originating from the phase inversion, i.e., from micelles to reverse micelles in the emulsion microenvironment built by supercritical carbon dioxide (SC CO2). A series of surfactants have been studied, and the experimental results indicate that efficient exfoliation of graphene depends on the suitable surfactant chosen in the SC CO2 solution system. In this work, polyvinylpyrrolidone (PVP) is confirmed to be an excellent surfactant to play the critical role on exfoliation of graphite, which leads to a high-yield graphene nanosheets (87.7%, ≤3 layers) with concentration of 1.93 mg/mL, large lateral size (up to 5 μm) and low oxidation degree (a C/O ratio of 20.28). And the dispersible graphene can be ink-brushed on A4-size paper to form highly conductive films (2.41 Ω s q–1), which confirms that our exfoliation method remains the integrity of the perfect structure in graphene to the largest extent. Further, the exfoliated graphene was used to prepare electrospun graphene-beaded carbon fibers for supercapacitors. The obtained materials deliver a high specific capacitance of 371.25 F/g, which is 71.6% higher than that of the pristine carbon fibers, and exhibit an excellent rate performance. Thus, this strategy utilizing reverse-micelle-induced method for exfoliation of graphite to graphene can pave a way for the green solution-processable production of more two-dimensional (2D) nanosheets, which will have great application potential on electronic, biotechnology, energy, and information storage, etc.
Co-reporter:Dongdong Xu, Huanan Yu, Qun Xu, Guiheng Xu, and Kaixi Wang
ACS Applied Materials & Interfaces 2015 Volume 7(Issue 16) pp:8750
Publication Date(Web):April 10, 2015
DOI:10.1021/acsami.5b01156
In this work, we report a simple method to fabricate smart polymers engineered with hierarchical photonic structures of Morpho butterfly wing to present high performance that are capable of color tunability over temperature. The materials were assembled by combining functional temperature responsivity of poly(N-isopropylacrylamide)-co-acrylic acid (PNIPAm-co-AAc) with the biological photonic crystal (PC) structure of Morpho butterfly wing, and then the synergistic effect between the functional polymer and the natural PC structure was created. Their cooperativity is instantiated in the phase transition of PNIPAm-co-AAc (varying with the change of temperature) that can alter the nanostructure of PCs, which further leads to the reversible spectrum response property of the modified hierarchical photonic structures. The cost-effective biomimetic technique presented here highlights the bright prospect of fabrication of more stimuli-responsive functional materials via coassembling smart polymers and biohierarchical structures, and it will be an important platform for the development of nanosmart biomaterials.Keywords: biomaterials; functional polymers; photonic crystals; polymerization; temperature-responsive;
Co-reporter:Huanan Yu, Dongdong Xu and Qun Xu
Chemical Communications 2015 vol. 51(Issue 67) pp:13197-13200
Publication Date(Web):10 Jul 2015
DOI:10.1039/C5CC04009D
A hierarchical meso- and microporous metal–organic framework (MOF) was facilely fabricated in an ionic liquid (IL)/supercritical CO2 (SC CO2)/surfactant emulsion system. Notably, CO2 exerts a dual effect during the synthesis; that is, CO2 droplets act as a template for the cores of nanospheres while CO2-swollen micelles induce mesopores on nanospheres.
Co-reporter:Yuhang Qi, Nan Wang, Qun Xu, Hongxiang Li, Pengshang Zhou, Xin Lu and Guoqiang Zhao
Chemical Communications 2015 vol. 51(Issue 31) pp:6726-6729
Publication Date(Web):09 Feb 2015
DOI:10.1039/C5CC00106D
We show that bulk MoS2 can be efficiently exfoliated into ultrathin nanosheets in supercritical CO2 with ethanol as cosolvent. Moreover, such tailored MoS2 nanostructures, when they are directly used as labels for bioimaging, show excellent imaging effects with strong fluorescence and nontoxicity.
Co-reporter:Jianmin Zhang, Yumei Ren, Tao Xu, Hongxia Yang and Qun Xu
RSC Advances 2015 vol. 5(Issue 115) pp:94809-94813
Publication Date(Web):23 Oct 2015
DOI:10.1039/C5RA16539C
A series of graphene oxide (GO) nanosheets with monolayer, bilayer and multilayer structures were prepared merely via a simple centrifugation method. It is noticeable that the as-prepared bilayer and multilayer GO nanosheet aqueous dispersions exhibit liquid crystal (LC) behavior. Not only the liquid- but also the solid-state of the obtained GO presented prominent functional LC behavior. Then, GO films were fabricated via simple drop-casting of concentrated GO (cGO) aqueous dispersions that retain the radial schlieren texture and show excellent electrical conductivities of 12 S cm−1 after chemical reduction. Thus it can be expected that utilizing the coating property of GO aqueous dispersions as well as the prominent birefringent linear features of the cGO films will have great potential for preparation of functional anti-counterfeiting components and energy materials.
Co-reporter:Yuanyuan Li, Wei Xia, Ruqiang Zou, Jianan Zhang, Zhimin Chen and Qun Xu
RSC Advances 2015 vol. 5(Issue 117) pp:96580-96586
Publication Date(Web):28 Oct 2015
DOI:10.1039/C5RA18624B
Developing a facile and cost-effective design and fabrication method to realize an optimal carbon nanoarchitecture containing hierarchical pores, appropriate N doping and high conductivity for high-performance in energy storage and conversion is still a challenge. Herein, we have facilely achieved an intriguing heterostructure of N-doped hierarchical porous carbon@CNT coaxial nanocables (HPNCNTs) via a one-step carbonization of resorcinol–melamine–formaldehyde resin (RMF)@CNT shell@core nanostructures. Significantly, we have demonstrated that the RMF@CNT shell@core nanostructures, with their inherent microporous structure and proper N-containing functionalities, represent the ideal precursor for realizing carbon heterostructures for electrochemical performance optimization for supercapacitors and in the oxygen reduction reaction (ORR). The results show that the HPNCNTs exhibit a specific capacitance of 284 F g−1, much higher than that of CNTs and most of the reported N-doped carbons, a good rate capability and a robust cycling performance with no capacity fading even after 6000 cycles. Furthermore, HPNCNTs show high electrocatalytic activity for the ORR with an onset potential of −0.04 V (vs. Ag/AgCl), a dominant four-electron pathway (n = 3.84), long-term stability, and excellent resistance to crossover effects superior to that of the commercial Pt/C. The present investigation opens the avenue for creating carbon heterostructures with a desirable porous tissue and morphology through a facile and general route for future high-performance renewable energy storage and conversion devices.
Co-reporter:Xianglan Zhang, Wenfu Yan, Jianan Zhang, Yuanyuan Li, Wanyu Tang and Qun Xu
RSC Advances 2015 vol. 5(Issue 80) pp:65532-65539
Publication Date(Web):09 Jul 2015
DOI:10.1039/C5RA10937J
The development of a highly stable and efficient catalyst for sluggish electrooxidation in the electro-determination for ascorbic acid (AA), dopamine (DA) and uric acid (UA) is extremely important for the long-term operation and commercialization of a biosensor device, but it remains a challenge. Herein, we demonstrated an interesting structure of NiCo alloy nanocrystals embedded in hierarchically structured N-doped carbon nanoplates (NiCo-NPs-in-N/C), which is facilely synthesized via a one-step in situ reduction pyrolysis strategy. The two-dimensional N-doped porous carbon shells not only offered the effective confinement effect of NiCo nanocrystals avoiding detachment, dissolution, migration, and aggregation during catalysis process, but also allowed a fast transport pathway for the access of electrolyte to the NiCo surface. As a result, such an intriguing structure shows superior catalytic activity towards the electrooxidation of AA, DA, and UA. The well-separated voltammetric peaks between AA–DA, DA–UA, and AA–UA at the NiCo-NPs-in-N/C are up to 178, 122, and 300 mV, respectively, which is much better than graphene@N-doped carbon core@shell nanoplate (graphene@N/C) and NiCo alloy. Furthermore, the NiCo-NPs-in-N/C also exhibits good reproducibility and stability. The attractive features of NiCo-NPs-in-N/C make it a promising electrocatalyst for the simultaneous determination of AA, DA, and UA.
Co-reporter:Xuzhe Wang, Jianwei Fu, Zhonghui Chen, Qiong Li, Xuebing Wu and Qun Xu
RSC Advances 2015 vol. 5(Issue 43) pp:33720-33728
Publication Date(Web):07 Apr 2015
DOI:10.1039/C5RA00560D
Hollow poly(cyclotriphosphazene-co-4,4′-sulfonyldiphenol) (PZS) microspheres with cross-linked chemical structure have been prepared under mild conditions by using polystyrene (PS) microspheres as sacrificial templates, hexachlorocyclotriphosphazene (HCCP) and 4,4′-sulfonyldiphenol (BPS) as comonomers, and triethylamine (TEA) as acid-acceptor. A template-induced assembly mechanism has been proposed to explain the formation of the hollow PZS microspheres. The as-prepared PS@PZS composites and hollow PZS microspheres were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectrometry, thermogravimetric analysis (TGA), and elemental analysis. The shell thickness of the hollow PZS microspheres can be controlled by adjusting the feed ratio of sacrificial templates to comonomers. An application study for the hollow PZS microspheres as a support of Au nanoparticles was carried out. The results show that Au nanoparticles with a size of about 5–8 nm were uniformly attached to the surface of the hollow PZS microspheres and the hollow PZS/Au hybrids displayed good catalytic properties with the reduction of 4-nitrophenol to 4-aminophenol as the model catalysis reaction.
Co-reporter:Minghuan Wang, Jianwei Fu, Jianhua Zhu, Ya Yan and Qun Xu
RSC Advances 2015 vol. 5(Issue 36) pp:28080-28084
Publication Date(Web):16 Mar 2015
DOI:10.1039/C5RA02823J
Novel N-doped porous carbon microspheres were synthesized facilely from polyphosphazene. These carbons exhibit a considerable performance for CO2 capture with high uptake, excellent selectivity, and good recyclability, and also show good electrocatalytic activity for oxygen reduction reaction.
Co-reporter:Bo Yan, Zhonghui Chen, Lu Cai, Zhimin Chen, Jianwei Fu, Qun Xu
Applied Surface Science 2015 Volume 356() pp:39-47
Publication Date(Web):30 November 2015
DOI:10.1016/j.apsusc.2015.08.024
Highlights
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The PAni hydrogel was synthesized using phytic acid as a dopant and cross-linking agent.
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The synthesized PAni hydrogel has a big adsorption capacity for MB.
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The pseudo-second-order model is available to describe the adsorption of MB.
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The Langmuir model is adaptive for the adsorption of MB.
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The adsorbent was a specific adsorbent for the removal of MB.
Co-reporter:Jing Li, Shijun Zheng, Xiaobo Wang, Hongxia Yang, Katja Loos, Qun Xu
Materials Letters 2015 Volume 158() pp:147-150
Publication Date(Web):1 November 2015
DOI:10.1016/j.matlet.2015.05.043
•The PFFB/GO nanohybrids were obtained with the assistance of SC CO2.•SC CO2 played a key role in enhancing the PL intensity of the nanohybrids.•SC CO2 can help PFFB transfer from one morphology to another.Fluorinated polyylidenefluorenes derivative, poly [(9-ylidene-{2-tetradecyloxy-5-tetrafluorophthalimide-phenyl}fluorenyl-2,7-diyl)-alt-(1,4-phenyl)] (PFFB)/graphene oxide (GO) nanohybrids (SC-PFFB/GO) were successfully fabricated via a facile method with the assistance of supercritical CO2 (SC CO2). It was fascinating to observe that the photoluminescence (PL) intensity at 410 nm of SC-PFFB/GO was 6 times that of PFFB/GO. The experimental results of TEM characterization indicated that PFFB preferred to crystallize rather than form amorphous aggregates on GO nanosheets with the assistance of SC CO2. So our experimental results are a proof of concept that SC CO2 is an efficient method to help PFFB transfer from one morphology to another and the fluorescent behavior of the obtained nanohybrids can be improved greatly due to the effect of SC CO2.
Co-reporter:Minghuan Wang, Jianwei Fu, Zhonghui Chen, Xuzhe Wang, Qun Xu
Materials Letters 2015 Volume 143() pp:201-204
Publication Date(Web):15 March 2015
DOI:10.1016/j.matlet.2014.12.114
•Amino-terminated polyphosphazene microspheres were easily fabricated.•The PZS-NH2 microspheres act as both reductant and stabilizer.•The Au nanoparticles possess uniform size and good dispersibility.•The Au/PZS-NH2 composites show high catalytic activity and good recyclability.Cross-linked polyphosphazene microspheres with amino-groups have been successfully prepared by precipitation polymerization of hexachlorocylotriphosphazene and 4,4′-diaminodiphenyl ether. Then Au nanoparticles (Au NPs) were synthesized by in situ growth on the surface of amino-terminated polyphosphazene (PZS-NH2) microspheres, which serve as a reducer and a stabilizer. The PZS-NH2 microspheres and the Au/PZS-NH2 composites were characterized by scanning electron microscopy, FT-IR spectrum, transmission electron microscopy equipped with energy-dispersive X-ray spectroscopy, and X-ray diffraction techniques. The results showed that Au NPs with good dispersibility and uniform size were well located on the surfaces of the PZS-NH2 microspheres. The catalytic performance of the Au/PZS-NH2 composites was studied in the oxidation of alcohols to the corresponding carboxylic acids with air as the oxidant in aqueous solutions. More than 94% conversion of alcohol was obtained at the reaction temperature of 50 °C for 24 h. The Au/PZS-NH2 catalyst was recycled six times without loss of catalytic activity.
Co-reporter:Pengshang Zhou; Qun Xu;Hongxiang Li;Dr. Yun Wang;Bo Yan;Dr. Yunchun Zhou;Dr. Jiafu Chen;Dr. Jianan Zhang;Kaixi Wang
Angewandte Chemie 2015 Volume 127( Issue 50) pp:15441-15445
Publication Date(Web):
DOI:10.1002/ange.201508216
Abstract
Two-dimensional (2D) lateral heterostructures have emerged as a hot topic in the fast evolving field of advanced functional materials , but their fabrication is challenging. The layer-structured WS2 was theoretically demonstrated to be inert to oxidation except for the monolayer, which can be selectively oxidized owing to the simultaneous interaction of oxygen with both sides. Combined with the theoretical calculations, a new method was developed for the successful construction of 2D lateral heterostructures of WS2/WO3⋅H2O in an ambient environment, based on a simple liquid-phase solution exfoliation. These lateral heterostructures of WS2/WO3⋅H2O have interesting properties, as indicated by enhanced photocatalytic activity toward the degradation of methyl orange (MO).
Co-reporter:Pengshang Zhou; Qun Xu;Hongxiang Li;Dr. Yun Wang;Bo Yan;Dr. Yunchun Zhou;Dr. Jiafu Chen;Dr. Jianan Zhang;Kaixi Wang
Angewandte Chemie International Edition 2015 Volume 54( Issue 50) pp:15226-15230
Publication Date(Web):
DOI:10.1002/anie.201508216
Abstract
Two-dimensional (2D) lateral heterostructures have emerged as a hot topic in the fast evolving field of advanced functional materials , but their fabrication is challenging. The layer-structured WS2 was theoretically demonstrated to be inert to oxidation except for the monolayer, which can be selectively oxidized owing to the simultaneous interaction of oxygen with both sides. Combined with the theoretical calculations, a new method was developed for the successful construction of 2D lateral heterostructures of WS2/WO3⋅H2O in an ambient environment, based on a simple liquid-phase solution exfoliation. These lateral heterostructures of WS2/WO3⋅H2O have interesting properties, as indicated by enhanced photocatalytic activity toward the degradation of methyl orange (MO).
Co-reporter:Jianan Zhang, Kaixi Wang, Qun Xu, Yunchun Zhou, Fangyi Cheng, and Shaojun Guo
ACS Nano 2015 Volume 9(Issue 3) pp:3369
Publication Date(Web):February 25, 2015
DOI:10.1021/acsnano.5b00760
To well address the problems of large volume change and dissolution of Fe3O4 nanomaterials during Li+ intercalation/extraction, herein we demonstrate a one-step in situ nanospace-confined pyrolysis strategy for robust yolk–shell nanospindles with very sufficient internal void space (VSIVS) for high-rate and long-term lithium ion batteries (LIBs), in which an Fe3O4@Fe3C core@shell nanoparticle is well confined in the compartment of a hollow carbon nanospindle. This particular structure can not only introduce VSIVS to accommodate volume change of Fe3O4 but also afford a dual shell of Fe3C and carbon to restrict Fe3O4 dissolution, thus providing dual roles for greatly improving the capacity retention. As a consequence, Fe3O4@Fe3C–C yolk–shell nanospindles deliver a high reversible capacity of 1128.3 mAh g–1 at even 500 mA g–1, excellent high rate capacity (604.8 mAh g–1 at 2000 mA g–1), and prolonged cycling life (maintaining 1120.2 mAh g–1 at 500 mA g–1 for 100 cycles) for LIBs, which are much better than those of Fe3O4@C core@shell nanospindles and Fe3O4 nanoparticles. The present Fe3O4@Fe3C–C yolk–shell nanospindles are the most efficient Fe3O4-based anode materials ever reported for LIBs.Keywords: core−shell structure; iron carbonide; iron oxide; lithium ion battery; yolk−shell structure;
Co-reporter:Lianren Hu, Yumei Ren, Hongxia Yang, and Qun Xu
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 16) pp:14644
Publication Date(Web):August 6, 2014
DOI:10.1021/am503995s
In this work, three-dimensional (3D) hierarchical MoS2/polyaniline (PANI) nanoflowers were successfully fabricated via a simple hydrothermal method. The crystal structure and morphology of the MoS2/PANI nanoflowers were characterized by SEM, TEM, XRD, XPS, and FT-IR spectra, revealing that the nanoflowers were composed of ultrathin nanoplates which consisted of few-layered MoS2 nanosheets with enlarged interlayer distance of the (002) plane and PANI. The excellent electrochemical performance of the 3D hierarchical MoS2/PANI nanoflowers was demonstrated. Further 3D hierarchical MoS2/C nanoflowers can be prepared conveniently by annealing the MoS2/PANI sample in a N2 atmosphere at 500 °C for 4 h. The obtained MoS2/C sample exhibited more excellent electrochemical performance due to its excellent electronic conductivity resulting from the close integration of MoS2 nanosheets with carbon matrix. High reversible capacity of 888.1 mAh g–1 with the Coulombic efficiency maintained at above 90% from the first cycle were achieved at a current density of 100 mA g–1. Even at a current density of 1000 mA g–1, the reversible capacity of the MoS2/C sample could be retained at 511 mAh g–1. The excellent electrochemical performance of these two samples could be attributed to the combined action of enlarged interlayer distance of the ultrathin MoS2 nanosheets, 3D architectures, hierarchical structures, and conductive material. Thus, these 3D hierarchical nanoflowers are competent as promising anode materials for high-performance lithium-ion batteries.Keywords: conductive material; hierarchical structures; lithium-ion batteries; MoS2; nanoflowers
Co-reporter:Nan Wang, Fang Wei, Yuhang Qi, Hongxiang Li, Xin Lu, Guoqiang Zhao, and Qun Xu
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 22) pp:19888
Publication Date(Web):November 7, 2014
DOI:10.1021/am505305g
MoS2 nanosheets with polydispersity of the lateral dimensions from natural mineral molybdenite have been prepared in the emulsions microenvironment built by the water/surfactant/CO2 system. The size, thickness, and atomic structure are characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM), and laser-scattering particle size analysis. Meanwhile, by the analysis of photoluminescence spectroscopy and microscope, the MoS2 nanosheets with smaller lateral dimensions exhibit extraordinary photoluminescence properties different from those with relatively larger lateral dimensions. The discovery of the excitation dependent photoluminescence for MoS2 nanosheets makes them potentially of interests for the applications in optoelectronics and biology. Moreover, we demonstrate that the fabricated MoS2 nanosheets can be a nontoxic fluorescent label for cell-targeted labeling application.Keywords: cell labeling; lateral dimensions control; molybdenum disulfide; nanosheets; photoluminescence
Co-reporter:Dongdong Xu, Qun Xu, Kaixi Wang, Jun Chen, and Zhimin Chen
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 1) pp:200
Publication Date(Web):December 10, 2013
DOI:10.1021/am404799a
A hierarchical high-performance electrode with nanoacanthine-style polyaniline (PANI) deposited onto a carbon nanofiber/graphene oxide (CNF/GO) template was successfully prepared via an in situ polymerization process. The morphology analysis shows that introducing one-dimensional (1D) CNF could significantly decrease/inhibit the staking of laminated GO to form an open-porous CNF/GO architecture. Followed with in situ facial deposition of PANI, the as-synthesized PANI modified CNF/GO exhibits three-dimensional (3D) hierarchical layered nanoarchitecture, which favors the diffusion of the electrolyte ions into the inner region of active materials. The hierarchical free-standing electrodes were directly fabricated into sandwich structured supercapacitors using 1 M H2SO4 as the electrolyte showing a significant specific capacitance of 450.2 F/g at the voltage scan rate of 10 mV/s. The electrochemical properties of the hierarchical structure can be further improved by a reduction procedure of GO before the deposition of PANI.Keywords: carbon nanofiber; free-standing film; graphene oxide; hybrid structure; supercapacitors; three-dimensional;
Co-reporter:Shoupei Wang, Jianan Zhang, Pei Shang, Yuanyuan Li, Zhimin Chen and Qun Xu
Chemical Communications 2014 vol. 50(Issue 81) pp:12091-12094
Publication Date(Web):14 Aug 2014
DOI:10.1039/C4CC04832F
N-doped carbon spheres with hierarchical micropore-nanosheet networks (HPSCSs) were facilely fabricated by a one-step carbonization and activation process of N containing polymer spheres by KOH. With the synergy effect of the multiple structures, HPSCSs exhibit a very high specific capacitance of 407.9 F g−1 at 1 mV s−1 (1.2 times higher than that of porous carbon spheres) and a robust cycling stability for supercapacitors.
Co-reporter:Yumei Ren, Qun Xu, Jianmin Zhang, Hongxia Yang, Bo Wang, Daoyuan Yang, Junhua Hu, and Zhimin Liu
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 12) pp:9689
Publication Date(Web):June 2, 2014
DOI:10.1021/am502035g
Functionalized porous carbon materials with hierarchical structure and developed porosity coming from natural and renewable biomass have been attracting tremendous attention recently. In this work, we present a facile and scalable method to synthesize MnO2 loaded carbonaceous aerogel (MnO2@CA) composites via the hydrothermal carbonaceous (HTC) process. We employ two reaction systems of the mixed metal ion precursors to study the optimal selective adsorption and further reaction of MnO2 precursor on CA. Our experimental results show that the system containing KMnO4 and Na2S2O3·5H2O exhibits better electrochemical properties compared with the reaction system of MnSO4·H2O and (NH4)2S2O8. For the former, the obtained MnO2@CA displays the specific capacitance of 123.5 F·g–1. The enhanced supercapacitance of MnO2@CA nanocomposites could be ascribed to both electrochemical contributions of the loaded MnO2 nanoparticles and the porous structure of three-dimensional carbonaceous aerogels. This study not only indicates that it is vital for the reaction systems to match with porous carbonaceous materials, but also offers a new fabrication strategy to prepare lightweight and high-performance materials that can be used in energy storage devices.Keywords: aerogel; carbonaceous materials; MnO2; supercapacitors;
Co-reporter:Jianan Zhang, Kaixi Wang, Shaojun Guo, Shoupei Wang, Zhiqiang Liang, Zhimin Chen, Jianwei Fu, and Qun Xu
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 3) pp:2192
Publication Date(Web):January 16, 2014
DOI:10.1021/am405375s
Hollow carbon capsules with multimodal pores are highly promising for developing novel electrode materials for high-performance electrochemical devices due to their more active sites for ion and electron transfer. However, at present, most of the previous efforts are focused on the multistep process for the synthesis of hollow carbon nanostructures with individual pores. Herein, hollow carbon nanococoons (HCNCs) with non-spherical cavity and multimodal hierarchical pores have been facilely synthesized via a one-step carbonization of a Fe2O3/carbon precursor core/shell nanospindle at 850 °C. We interestingly found that during the carbonization, Fe2O3 was automatically “escaped” from the inside nanospindle, leading to the formation of new HCNCs. Most importantly, the spindle-shaped cavity of the obtained HCNCs with high conductivity can offer a multimodal ion diffusion pathway, which can facilitate the reaction kinetics in a supercapacitor. As a result, the HCNCs-based supacapacitor exhibits the capacitance of 220.0 F g–1 at a given scan rate of 5 mV s–1, 3.5 times higher than that of hollow carbon spheres, high stability with 98% of the initial capacity maintained even after 1000 cycles, and high rate capability. This work provides a new and facile avenue for enhancing performance of a HCNCs-based supercapacitor by using the non-spherical hollow structures with multimodal pores.Keywords: hollow carbon capsules; hollow carbon nanococoon; microporous materials; one-step carbonization; supercapacitor;
Co-reporter:Jianan Zhang, Xianglan Zhang, Yunchun Zhou, Shaojun Guo, Kaixi Wang, Zhiqiang Liang, and Qun Xu
ACS Sustainable Chemistry & Engineering 2014 Volume 2(Issue 6) pp:1525
Publication Date(Web):May 12, 2014
DOI:10.1021/sc500221s
Controlled synthesis of carbon nanomaterials with particular shape, composition, architecture, and doping is very important, yet still a great challenge, for enhancing supercapacitor performance with high energy and power densities and long lifetime. Herein, we demonstrate an interesting process combining surfactantless and templateless wet chemical and post-high-temperature carbonization strategies for obtaining a new class of nitrogen-doped hierarchical porous carbon nanowhisker ensembles supported on carbon nanofibers (NHCNs) with tunable micropores and a nitrogen-doping level for high-performance supercapacitors. Under the optimal pore size and nitrogen doping controlled by carbonization at different temperatures, the NHCNs (NHCNs-750) carbonized at 750 °C shows an optimal specific capacitance of 210.1 F g–1 at 5 mV s–1, which is much higher than other one-dimensional carbon nanostructures (e.g., pure carbon nanofibers (2.6 F g–1) and carbon nanotubes (10.6 F g–1) at 5 mVs–1). NHCNs-750 also showed good rate capability of 78.5% and 75.2% capacitance retention at 100 mV s–1 and 200 mV s–1, respectively, and excellent cycling stability of 96.2% capacitance retention after 3000 cycles. Furthermore, we found that the specific capacitance of NHCNs can be further increased to 254.3 F g–1 by a KOH-assisted high-temperature process. The present work opens a new route to design advanced 1D hierarchical carbon nanomaterials with tunable pores and nitrogen doping for enhancing energy storage and conversion applications.Keywords: Carbon nanofiber; Hierarchical structure; Nanowhisker; Porous structure; Supercapacitors
Co-reporter:Shanshan Xu, Hongxia Yang, Kaixi Wang, Bo Wang and Qun Xu
Physical Chemistry Chemical Physics 2014 vol. 16(Issue 16) pp:7350-7357
Publication Date(Web):04 Feb 2014
DOI:10.1039/C3CP54957G
In this paper, supercritical carbon dioxide (SC CO2) was first reported to help prepare unique flexible free-standing graphene oxide/nanofiber (GC) films. A novel hierarchical superior electrode material with polypyrrole (PPy) deposited on GO/CNF-SC (GC-SC) films was prepared via an in situ polymerization process. Our experimental results indicate that SC CO2 can not only enlarge the space between GO sheets but also improve the conductivity of the films. The electrochemical measurements show that the as-obtained PPy-coated GC-SC products display remarkably higher capacitive properties than pristine GC/PPy products as electrode materials. Excellent rate performance and stable capacitance retention (89% after 5000 cycles) were observed during the continuous charge–discharge cycles, which verify that SC CO2 provides a convenient route to the scalable production of hierarchical GO/CNF/PPy films for potential application in supercapacitors.
Co-reporter:Yang Liu, Jianan Zhang, Shoupei Wang, Kaixi Wang, Zhimin Chen and Qun Xu
New Journal of Chemistry 2014 vol. 38(Issue 9) pp:4045-4048
Publication Date(Web):01 Aug 2014
DOI:10.1039/C4NJ00816B
Three-dimensional (3D) porous NiCo2S4 nanonetworks were fabricated on nickel foam (NF) through an anion exchange reaction between NiCo2O4 nanosheets (hydrothermally grown on NF) and Na2S, and showed a very high specific capacitance of 1501.2 F g−1 at 1 A g−1 (even 2.5 times higher than that of NiCo2O4 nanosheets) and robust cycling stability for supercapacitors.
Co-reporter:Yumei Ren, Jianmin Zhang, Qun Xu, Zhimin Chen, Daoyuan Yang, Bo Wang and Zheng Jiang
RSC Advances 2014 vol. 4(Issue 45) pp:23412-23419
Publication Date(Web):05 May 2014
DOI:10.1039/C4RA02109F
Functionalized carbonaceous materials with a hierarchical structure and developed porosity are highly desired in energy storage and conversion fields. In this work, a facile and scalable hydrothermal methodology was established to synthesise three-dimensional (3D) N-doped carbonaceous aerogels using biomass-based starting materials and polypyrrole as the N-source. The effect of different calcination temperatures on the structural properties, type and content of N-species and electrochemical performance of the 3D N-doped carbonaceous aerogels was revealed. Because of the combinatorial effect of the appropriate N content and porous structure, the obtained samples exhibited excellent electrochemical performance, in particular, an outstanding specific capacitance of 281.0 F g−1 achieved for the sample calcined at 600 °C. This methodology offers a new fabrication strategy to prepare nanoscale carbonaceous materials with desirable morphology and a hierarchical architecture with great potential for applications in energy fields.
Co-reporter:Bo Wang, Zhimin Chen, Jianan Zhang, Jingjing Cao, Shuxia Wang, Qiuge Tian, Ming Gao, Qun Xu
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2014 Volume 457() pp:318-325
Publication Date(Web):5 September 2014
DOI:10.1016/j.colsurfa.2014.06.006
•PVA/GO/TiO2 composite nanofibers were fabricated for the first time.•GO-doping greatly increased the mechanical properties of the nanofibers.•GO-doping is a key point for fabricating fibers with core–shell structure.Electrospun TiO2 nanofibers with desired structures and high specific surface area are expected to be used in various applications such as dye-sensitized solar cell, environmental purification, hydrogen production and photocatalytic filter. In this work, polyvinyl alcohol (PVA) nanofibers doped with different amount of graphene oxide (GO) were fabricated by electrospinning method. Followed with interface sol–gel reaction, the PVA/GO/TiO2 core–shell fibers were obtained. The experimental results indicate that GO-doping decreased the decomposition temperature and elongation at break of PVA nanofibers, at the same time, increased the degree of crystallinity and tensile strength. The GO-doped PVA nanofibers could be used as hard template to assist the growth of TiO2. In the experiment, the incorporation of GO can help to control the growth of TiO2 on PVA fibers, which is a key point for preparing GO doped PVA/TiO2 core–shell fibers. The ideal micromorphology and structure of TiO2 will benefit its applications in various fields.
Co-reporter:Minghuan Wang, Jianwei Fu, Dandan Huang, Chao Zhang and Qun Xu
Nanoscale 2013 vol. 5(Issue 17) pp:7913-7919
Publication Date(Web):07 May 2013
DOI:10.1039/C3NR00010A
Herein, we report the preparation of poly (cyclotriphosphazene-co-4,4′-sulfonyldiphenol) (PZS) nanotubes decorated with Ag nanoparticles (NPs). The PZS nanotubes have been synthesized firstly via an in situ template approach, and then Ag nanoparticles were prepared via in situ reduction of AgNO3 with NaBH4 as the reductant, supported on the surface of the PZS nanotubes. The as-obtained PZS nanotubes and PZS@Ag NPs composites were characterized by means of Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) equipped with energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), atomic absorption spectroscopy (AAS), thermogravimetric analysis (TGA), and UV-vis spectroscopy. Characterization results showed that Ag NPs with good dispersibility were well anchored onto the surface of the PZS nanotubes with superior thermal stability. In addition, the catalytic activities and reusability of these composites were investigated by employing the reduction of 4-nitrophenol (4-NP) into 4-aminophenol (4-AP) by NaBH4 as a model reaction.
Co-reporter:Guiheng Xu, Qun Xu, Anjun Qin, Jingtao Cheng, Nan Wang, Junyi Wei, Chengliang Zhang, Zhenzhong Yang and Ben Zhong Tang
Journal of Materials Chemistry A 2013 vol. 1(Issue 9) pp:1717-1721
Publication Date(Web):23 Jan 2013
DOI:10.1039/C3TC00827D
We report a facile method for the fabrication of a nanocomposite that consists of AIE-active poly(aroxycarbonyltriazole) PACT polymer uniformly decorated on polydivinylbenzene (PDVB) nanotubes in the form of nanoparticles via the supercritical carbon dioxide (SC CO2)-assisted method. The on/off fluorescence switching for organic vapor and solvent was demonstrated with PACT/PDVB nanocomposite films.
Co-reporter:Lihua Li, Xiaoli Zheng, Jianjun Wang, Qiang Sun, and Qun Xu
ACS Sustainable Chemistry & Engineering 2013 Volume 1(Issue 1) pp:144
Publication Date(Web):October 9, 2012
DOI:10.1021/sc3000724
Graphite was successfully exfoliated into graphene by pyrene and another three derivatives (1-pyrenecarboxylic acid (PCA), 1-pyrenebutyric acid (PBA), and 1-pyrenamine (PA)) with the assistance of supercritical carbon dioxide (SC CO2) in this work. The resulting graphene was characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), Raman spectra, and fluorescence spectra. High-quality and noncovalent functionalized single or few layer graphene were obtained. van der Waals corrected first-principles approach within density functional theory (vdW-DFT2) was used to investigate the interaction energy of different pyrene-derivatives on graphene and inside the two graphene. The results showed that pyrene and pyrene-derivatives can act as a “molecular wedge” to exfoliate graphene from graphite well. A further graphene/gold nanoparticle composite was also successfully obtained, which indicates that pyrene-derivatives firmly adsorbed on the surface of graphene can act as the interlinkers between graphene and Au NPs or other rare metal nanoparticles. Therefore, the functionalized graphene with different pyrene-derivatives will have potential applications in nanofunctional materials, nanoreactor devices, and catalysis fields.Keywords: Density Functional Theory; Graphene; Pyrene Derivatives; Supercritical CO2
Co-reporter:Lihua Li, Jianan Zhang, Yuqing Liu, Weimin Zhang, Hongxia Yang, Jun Chen, and Qun Xu
ACS Sustainable Chemistry & Engineering 2013 Volume 1(Issue 5) pp:527
Publication Date(Web):March 4, 2013
DOI:10.1021/sc4000016
In this paper, noncovalent functionalized graphene nanosheets are prepared through solvent-exfoliation expanded graphite with the aid of supercritical (SC) CO2 and 1-pyrenamine (PA). Then, it is used as supporting materials for platinum to investigate the potential application of the obtained nanocomposite in direct methanol fuel cells (DMFCs). Transmission electron microscope (TEM) images reveal that Pt nanoparticles are evenly dispersed on the PA-modified graphite nanosheets (PA-GNS) with an average size of 3.0 nm. The high quality of PA-GNS is also confirmed through Raman spectra analysis. PA-GNS/Pt nanocomposites exhibit better electrocatalytic activity (1.4 times) and stability (3.5 times) toward methanol oxidation than commercial catalyst JM-C/Pt. The results suggest that noncovalent functionalization of GNS by PA can be a method used to create highly efficient and stable catalyst supports for methanol electrooxidation in DMFCs.Keywords: Graphene nanosheets; Methanol electrooxidation; Noncovalent functionalization; Pt nanoparticles
Co-reporter:Jiafu Chen, Zhanlin Lang, Qun Xu, Bo Hu, Jianwei Fu, Zhimin Chen, and Jianan Zhang
ACS Sustainable Chemistry & Engineering 2013 Volume 1(Issue 8) pp:1063
Publication Date(Web):May 24, 2013
DOI:10.1021/sc400124b
A simple and effective template-free method to prepare monodisperse carbon spheres has been successfully developed using solid poly(styrene-co-divinylbenzene) (P(St-co-DVB)) nanospheres as the raw material, anhydrous aluminum chloride as the Friedel–Crafts catalyst, and carbon tetrachloride as a cross-linker and solvent. The pore structure in the spheres can be tailored by substituting hollow P(St-co-DVB) capsules (HPCs) for solid P(St-co-DVB) spheres (SPSs). Experimental results show that the micropore size of the spheres obtained from HPCs increases compared to that of the spheres obtained from SPSs, and the pore volume and the specific surface area also have changed. The mechanism behind these phenomena and the hydrogen storage properties of the obtained carbon spheres at 77 K and 1 atm are further studied in this work.Keywords: Hydrogen storage; Monodisperse carbon spheres; Pore structure; Template-free construction
Co-reporter:Jiafu Chen, Zhanlin Lang, Qun Xu, Jianan Zhang, Jianwei Fu and Zhimin Chen
Physical Chemistry Chemical Physics 2013 vol. 15(Issue 41) pp:17786-17792
Publication Date(Web):02 Sep 2013
DOI:10.1039/C3CP52736K
A simple and efficient method to produce discrete, hierarchical porous carbon hemispheres (CHs) with high uniformity has been successfully developed by constructing nanoreactors and using low crosslinked poly(styrene-co-divinylbenzene) (P(St-co-DVB)) capsules as precursors. The samples are characterized by scanning and transmission electron microscopy, Fourier transform infrared and Raman spectroscopy, X-ray diffraction, and N2 adsorption and desorption. Considering their application, the cyclic voltammetry and electrochemical impedance spectroscopy characterization are tested. The experimental results show that the achievement of discrete and perfect carbon hemispheres is dependent on the proper amount of DVB in the P(St-co-DVB) capsules, which can contribute to the ideal thickness or mechanical strength of the shells. When the amount of DVB is 35 wt% in the precursors, a high Brunauer–Emmett–Teller surface area of 676 m2 g−1 can be obtained for the carbon hemispheres, and the extremely large pore volume of 2.63 cm3 g−1 can also be achieved at the same time. The electrochemical test shows the carbon hemispheres have a higher specific capacitance of ca. 83 F g−1 at 10 mV s−1, compared to other carbon materials. So this method supplies a platform to extend the fabrication field of carbon materials and supplies more chances for the application of carbon materials including carbon hemispheres that are important components and substrates for supercapacitors.
Co-reporter:Zhimin Chen, Jianwei Fu, Qun Xu, Yuanlong Guo, Hailian Zhang, Jiafu Chen, Jianan Zhang, Guo Tian, Bai Yang
Journal of Colloid and Interface Science 2013 Volume 391() pp:54-59
Publication Date(Web):1 February 2013
DOI:10.1016/j.jcis.2012.09.071
A steric hindrance colloidal microspheres approach (SHCMA) has been developed for the fabrication of ordered Pt or Pt/Ag nanoparticles composite interconnected hollow hemispheres via colloidal lithography and physical vapor deposition. Monolayer ordered silica or silica/Ag nanoparticles composite microspheres partly embedded into the polydimethylsiloxane (PDMS) were used as template, and Pt was sputtered on it. Due to the PDMS stamp functionalized as a steric hindrance substrate, which guaranteed that the ordered silica or silica/Ag nanoparticles composite microspheres were only coated with Pt film on the sides that exposed in air. After removing the template particles, large area ordered interconnected Pt or Pt/Ag nanoparticles composite hollow hemispheres were generated. The fabricated Pt hollow hemispheres have flat bottoms and are flexible and robust enough to be easily folded. In addition to successfully solving the challenge about ordered structure construction of the hollow Pt or Pt/Ag nanoparticles composite hemispheres here, we also could finely control the wall thickness of these hemispheres easily by changing the sputtering time or current.Graphical abstractHighlights► We developed a new kind of steric hindrance colloidal microspheres approach. ► Ordered Pt hollow hemispheres were finely fabricated. ► The wall thickness of the Pt hollow hemispheres could be adjusted. ► Ordered Pt/Ag nanoparticles composite hollow hemispheres also could be obtained.
Co-reporter:Junyi Wei, Jianan Zhang, Yang Liu, Guiheng Xu, Zhimin Chen and Qun Xu
RSC Advances 2013 vol. 3(Issue 12) pp:3957-3962
Publication Date(Web):14 Jan 2013
DOI:10.1039/C3RA23040F
We report a facile and efficient method, via chemical polymerization of aniline in the presence of carbon nanofibers (CFs), to fabricate ordered whisker-like polyaniline/CFs nanocomposites. The morphology and microstructure of the obtained composites are characterized by FESEM, TEM, FTIR, Raman, XRD and UV-vis. As a result, PANI nanorods are vertically deposited on the wall of CFs. The composite had a high specific capacitance (427 F g−1) and a super long cycle life (a retention ratio of 90% after 3000 cycles).
Co-reporter:Leilei Lv, Qun Xu, Rui Ding, Li Qi, Hongyu Wang
Materials Letters 2013 Volume 111() pp:35-38
Publication Date(Web):15 November 2013
DOI:10.1016/j.matlet.2013.08.055
•Binary compound cobalt iron oxide (CoFe2O4) with broad potential window was synthesized.•CoFe2O4 exhibited a high specific capacitance (142 F g−1, 2 mV s−1) and a long cycling life (71.8% retention after 1000 cycles).•A hard template of Al2O3 derived from co-precipitating Al(NO3)3 precursor solutions created a highly porous morphology.A promising mesoporous cobalt iron oxide (CoFe2O4) electrode material for supercapacitors has been synthesized via a chemical co-precipitation method using aluminum nitrate (Al(NO3)3) as a precursor of aluminum oxide (Al2O3) hard template. The as-prepared CoFe2O4 materials were spherical-like nanoparticles with diameter of around 25 nm. Moreover, the as-prepared CoFe2O4 materials exhibited a high specific surface area (140.6 m2 g−1) and high porosity (0.23 cm3 g−1). The fabricated CoFe2O4 electrode showed typical pseudocapacitive behavior with a broad potential window (1.5 V), a high specific capacitance (142 F g−1, 2 mV s−1) and a long cycling life (71.8% retention after 1000 cycles).
Co-reporter:Dr. Jianan Zhang;Dr. Shaojun Guo;Junyi Wei; Wenfu Yan;Jianwei Fu;Shoupei Wang;Mingjing Cao;Zhimin Chen
Chemistry - A European Journal 2013 Volume 19( Issue 47) pp:16087-16092
Publication Date(Web):
DOI:10.1002/chem.201302416
Abstract
Pt-based nanostructures serving as anode catalysts for the methanol oxidation reaction (MOR) have been widely studied for many years. Nevertheless, challenging issues such as poor reaction kinetics and the short-term stability of the MOR are the main drawbacks of such catalysts and limit their applications. Herein, we have developed a facile approach to encapsulate Pt nanoparticles (NPs) inside the nanochannels of porous carbon nanotubes (CNTs; Pt-in-CNTs) as a new enhanced electrocatalytic material. The as-prepared CNTs offer simultaneously ordered diffusion channels for ions and a confinement effect for the NPs, which both facilitate the promotion of catalytic kinetics and avoid the Ostwald ripening of Pt NPs, thus leading to high activity and durable cycle life as an anode catalyst for MOR. This work provides a new approach for enhancing the stability and activity by optimizing the structure of the catalyst, and the Pt-in-CNTs represent the most durable catalysts ever reported for MOR.
Co-reporter:Xiaoli Zheng, Qun Xu, Jianbo Li, Lihua Li and Junyi Wei
RSC Advances 2012 vol. 2(Issue 28) pp:10632-10638
Publication Date(Web):11 Sep 2012
DOI:10.1039/C2RA21316H
A facile and green approach has been developed using supercritical CO2 as penetrant, expanding agent and antisolvent, and pyrene-polymers as a molecular wedge and modifier, leading to high-throughput graphene dispersions. Herein, two specially designed pyrene-polymers with a large planar aromatic group and two substituted polymer dangling chains have been employed to stabilize the graphene sheets, which show excellent solubility in aqueous and organic solvents. The morphology and quality of the exfoliated graphene sheets are studied by transmission electron microscope (TEM), atomic force microscopy (AFM), Raman, FTIR, and wide-scanning X-ray photoelectron spectroscopy (XPS), which reveal that large scale and high quality graphene flakes are obtained by the facile process. The supercritical CO2, pyrene-polymers and the solvent system have a significant influence on the exfoliation results. The pyrene-polymers attached to the graphene can further integrate graphene with other polymers to form new functional nanocomposites. This solution-based method combines high-throughput production and functionalization of graphene in one step, providing nanoscale building blocks for practical applications.
Co-reporter:Guiheng Xu, Nan Wang, Junyi Wei, Leilei Lv, Jianan Zhang, Zhimin Chen, and Qun Xu
Industrial & Engineering Chemistry Research 2012 Volume 51(Issue 44) pp:14390
Publication Date(Web):October 17, 2012
DOI:10.1021/ie301734f
We report a facile strategy to prepare graphene oxide (GO)/polyaniline (PANI) nanocomposite by in situ polymerization with the assistance of supercritical carbon dioxide (SC CO2). The morphology and chemical structure of the synthesized samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), FT-IR, Raman, and UV–vis spectrophotometry. As a result, PANI nanoparticles uniformly cover the GO sheets with the help of SC CO2, and the formation mechanism is suggested. The morphologies of GO/PANI nanocomposites can be controlled through adjusting the concentration of aniline. The GO/PANI nanocomposite exhibits better specific capacitance and cycle stability than pure PANI and GO owing to the synergistic effect of GO and PANI nanoparticles, making it promising application in electrochemical devices.
Co-reporter:Linghao He, Xiaoli Zheng, Qun Xu, Zhimin Chen, Jianwei Fu
Applied Surface Science 2012 Volume 258(Issue 10) pp:4614-4623
Publication Date(Web):1 March 2012
DOI:10.1016/j.apsusc.2012.01.040
Abstract
Carbon nanotubes (CNTs) and graphene nanosheets, as one-dimensional and two-dimensional carbon-based nanomaterials respectively, have different abilities to induce the polymer crystallization. In this study, hybrid materials, polyethylene (PE) decorating on CNTs and graphene oxide (GO), were prepared by a facile and efficient method using supercritical carbon dioxide (SC CO2) as anti-solvent. And the morphology and crystallization behavior of PE on CNTs and GO were investigated by transmission electron microscopy, Fourier transform infrared spectroscopy, Raman spectra, wide angle X-ray diffraction, and differential scanning calorimetry. Although both CNTs and GO could act as nucleating agents to induce PE epitaxial growth, CNTs were decorated by PE lamellar crystals forming nanohybrid “shish-kebab” (NHSK) structure, whereas GO sheets were only decorated with petal-like PE crystals. The varying morphologies of the nanohybrids depend on the PE epitaxy and the interactions between polymer chains and substrates. High surface curvature and the perfect ordered crystal structure of CNTs make PE crystals periodically grow on CNTs. While PE crystals grow and form multiple orientation-lamellae on GO due to the lattice matching and complex interactions between PE chains and GO. In addition, our experimental results show an interesting and evident stratification phenomenon for the PE/GO hybrid material, implying that GO decorated by PE have a screening function for the solvents. We anticipate that this work can widen the area of functionalization of carbon-based nanomaterials with a controlled means by an environmentally benign method, which are important for the functional design in nanodevice applications.
Co-reporter:Jianwei Fu, Minghuan Wang, Chao Zhang, Peng Zhang, Qun Xu
Materials Letters 2012 Volume 81() pp:215-218
Publication Date(Web):15 August 2012
DOI:10.1016/j.matlet.2012.04.152
Heteroatom-containing porous carbon nanospheres were fabricated by forming polyphosphazene nanospheres and carbonizing them with NaOH as activating agent. They were then examined as a material for hydrogen storage. N2 sorption and H2 sorption measurements showed that the carbon nanospheres possess a BET surface area of 1140 m2 g− 1, a total pore volume of 0.90 m3 g− 1, an ultramicropore volume of 0.30 m3 g− 1, a bimodal pore size distribution (3–5 nm and 0.6–0.8 nm diameter pores), and a gravimetric hydrogen uptake of 2.7 wt.% at 77 k and 1 atm.Highlights► Polyphosphazene nanospheres were used as carbon precursors. ► The carbon nanospheres possess a large surface area and a bimodal pore size distribution. ► Small amounts of heteroatoms such as N, O, P, and S were doped in carbon nanospheres. ► The carbon nanospheres exhibit a high hydrogen uptake of 2.7 wt.% at 77 k and 1 atm.
Co-reporter:Jianwei Fu, Zhimin Chen, Qun Xu, Jiafu Chen, Xiaobin Huang, Xiaozhen Tang
Carbon 2011 Volume 49(Issue 3) pp:1037-1039
Publication Date(Web):March 2011
DOI:10.1016/j.carbon.2010.10.050
Uniform porous carbon nanofibers with an average diameter of 90 nm were fabricated by forming polyphosphazene nanofibers and carbonizing them, without the need for any activation step. The structure and morphology of the carbon nanofibers were characterized by SEM, TEM, EDX, XRD, Raman spectrum and N2 adsorption. Results showed that the carbon nanofibers have a BET surface area of about 540 m2 g−1, a total pore volume of about 0.37 m3 g−1, and a narrow pore size distribution in the micropore range.Graphical abstractAn easy and cost-effective synthesis route to produce uniform porous carbon nanofibers was proposed, which involved the formation of polyphosphazene nanofibers and their subsequent carbonization. The resulting carbon nanofibers possessed a high BET surface area and a narrow pore size distribution in the micropore range.Research highlights► Polyphosphazene nanofibers were used as carbon precursors. ► The precursors could be easily synthesized in bulk quantities at room temperature. ► Any activation step was not used during the formation of pore structure.
Co-reporter:Qiuyan Yang, Jiafu Chen, Qun Xu, Linghao He, Zhimin Chen and Jianwei Fu
Soft Matter 2011 vol. 7(Issue 11) pp:5353-5359
Publication Date(Web):28 Apr 2011
DOI:10.1039/C1SM05041A
Spherical microstructures with core–shell features were assembled and stabilized by welding them in supercritical carbon dioxide (SC CO2). Hollow poly(styrene-co-divinylbenzene) (PS-co-DVB) capsules and polystyrene (PS) particles were used as building blocks and supporting cores, respectively. By adjusting the diameters of the PS “core”, the microstructure sizes can be adjusted simply from 2 to 19 μm. In addition, PS cores were selectively plastified to make the “satellite” capsule weld and even embed on their surface with the assistance of SC CO2. By varying a series of pressure (12 to 16 MPa), exposure time (2 to 6 h), and temperature (40, 50 °C) conditions, the welding or coalescence degrees of these PS-co-DVB capsules and PS cores were finely tuned. This is the first time that SC CO2 has been successfully applied to stabilize the spherical assembled microstructure.
Co-reporter:Jianwei Fu, Minghuan Wang, Shitao Wang, Xuzhe Wang, Hongfang Wang, Lei Hu, Qun Xu
Applied Surface Science 2011 Volume 257(Issue 16) pp:7129-7133
Publication Date(Web):1 June 2011
DOI:10.1016/j.apsusc.2011.03.069
Abstract
Poly(cyclotriphosphazene-co-4,4′-sulfonyldiphenol) (PZS) nanospheres with average diameter of 410 nm were synthesized rapidly at room temperature and then homogeneously decorated with Pd nanoparticles through an inorganic reaction in supercritical carbon dioxide–ethanol solution using PdCl2 as a metal precursor. The resultant Pd/PZS nanocomposites were morphologically and structurally characterized by means of scanning electron microscopy, transmission electron microscope equipped with energy-dispersive X-ray spectroscopy, and X-ray diffraction techniques. Characterization results showed that the Pd nanoparticles with good dispersibility could be well anchored onto the surfaces of the PZS nanospheres and the size of Pd nanoparticles could be controlled easily by varying the ethanol-reduction time.
Co-reporter:Zhimin Chen;Fengfeng Xue;Guannan Sun;Jiafu Chen
Journal of Applied Polymer Science 2011 Volume 119( Issue 4) pp:2393-2399
Publication Date(Web):
DOI:10.1002/app.32955
Abstract
Using emulsifier-free emulsion polymerization method, monodispersed crosslinked poly(styrene-co-methacrylic acid-co-ethylene glycol dimethacrylate) colloid microspheres were synthesized. The microspheres were treated in supercritical carbon dioxide (SCCO2) after they have self-assembled into ordered three-dimensional (3D) colloid arrays. The CO2 absorbed into the polymer microspheres enhances chain segments mobility and reduces the glass transition temperature (Tg) of polymer, which induce the microspheres coalesce at the relatively low temperature. The coalescence degree of microspheres was studied by varying the experimental temperature, pressure, and exposure time in SCCO2. The results were shown by scanning electron microscopy (SEM). Further, the lattice spacing of the assembled 3D colloid microspheres was calculated from the SEM images. It was illustrated that the coalescence degree enhanced with the increase of CO2 pressure; however, this tendency became weak when CO2 pressure reached a certain value. Extending exposure time in SCCO2 or elevating temperature can also increase coalescence degree, and the effect of temperature is more significant. It is believed that these results will make sense when the polymer microspheres are considered to be used as templates in SCCO2; meanwhile, it raises a new method about tuning the final morphology of the stabilized colloidal crystals and porous materials via controlling the coalescence degree with the assistance of SCCO2. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Co-reporter:Linghao He;Jing Sun;Xiaoli Zheng;Rui Song
Journal of Applied Polymer Science 2011 Volume 119( Issue 4) pp:1905-1913
Publication Date(Web):
DOI:10.1002/app.32907
Abstract
In this study, the poly(vinylidene fluoride) (PVDF)—multiwalled carbon nanotubes (MWNTs) composites have been prepared by solution casting in two different solvents: dimethyl sulfoxide (DMSO) and dimethylacetamide (DMAc). Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimeter (DSC) results showed that the crystal phases of PVDF are quite different in the two solvents. When DMSO is used as the solvent, the PVDF crystalline phases could be greatly alternated from α-form to β-form by the incorporation of MWNTs. While the crystalline structure of PVDF hardly change in the case of DMAc. The DSC and polarized optical microphotographs implied that MWNTs not only act as nucleating agents for PVDF but also confine the crystallization of PVDF. Besides, it was found that the storage modulus (E′) of the composites were significantly enhanced with an appropriate content of MWNTs. And when using DMSO as the solvent, one relaxation process emerges in the loss tan δ (loss factor) curves of the neat PVDF and PVDF/MWNTs composites, while it was not observed in the DMAc system. The obtained results revealed that varing solvents have different effects on the crystallization behavior of PVDF with the addition of MWNTs. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Co-reporter:Jiafu Chen;Yan Li;Fengfeng Xue;Zhimin Chen
Polymer Engineering & Science 2011 Volume 51( Issue 6) pp:1170-1177
Publication Date(Web):
DOI:10.1002/pen.21850
Abstract
Micron-sized, cross-linked polystyrene (PS) particles with different morphologies were prepared by the developed dispersion polymerization. By scanning electron microscope (SEM) observation, it was found that these PS particles had interesting shapes such as deformed sphere, hollow hemisphere and spheroid-like shape when initial monomer concentration, reaction time, and temperature and addition way of the reagent added in the third stage were different. The shape of the PS particles was changed from hollow hemisphere to spheroid-like shape with prolongation of the reaction time. It was remarkable that the rough surface of hollow-hemisphere-like PS particles became smooth and the hollow structure of smooth-hollow-hemisphere-like PS particles grew into solid structure at the same time. The formation mechanism behind these phenomena was discussed. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers
Co-reporter:Xiaoli Zheng, Qun Xu, Linghao He, Ning Yu, Shanshan Wang, Zhimin Chen, and JianWei Fu
The Journal of Physical Chemistry B 2011 Volume 115(Issue 19) pp:5815-5826
Publication Date(Web):April 26, 2011
DOI:10.1021/jp2018082
Graphene oxide (GO) sheets were noncovalently modified with an amphiphilic double-crystalline block copolymer, polyethylene-b-poly(ethylene oxide) (PE-b-PEO) with assistance of supercritical CO2 (SC CO2) in this work. The resulting PE-b-PEO/GO nanohybrids were characterized by transmission electron microscopy (TEM), wide-angle X-ray diffraction (WAXD), Fourier transform infrared spectroscopy (FTIR), and Raman spectra. Distinct morphologies of PE-b-PEO decorating on the surface of GO were obtained in different solvent systems and at different SC CO2 pressures. We found that the solvent system and the SC CO2 have significant influence on the crystallization, aggregation, or assembly behaviors of PE-b-PEO molecular chains on the GO sheets. The formation mechanism of the distinct nanohybrid structures is attributed to a relevant easy heteronucleation and the limited crystal growth of the block polymer on the surface of GO. The resulting modified GO sheets could find a broad spectrum of applications not only in producing graphene-based nanocomposites but also being used as a template to fabricate multifunctional structures due to the unique properties of PE-b-PEO. As a proof-of-concept, we further decorated the GO sheets with the as-prepared Au nanoparticles (Au NPs) and CdTe nanoparticles (CdTe NPs) with PE-b-PEO as the interlinker. Using the thiol-terminated PE-b-PEO as an interlinker, Au NPs can be densely assembled on the surface of GO via robust Au–S bonds. Furthermore, the photoluminescence quenching of CdTe NPs was more notable for PE-b-PEO/GO-CdTe hybrid compared to the GO-CdTe hybrid, suggesting that the electron transfer from the CdTe NPs to the GO sheets was enhanced with the PE-b-PEO interlinker. The availability of these affordable graphene-based multifunctional structures and their fundamental properties will open up new opportunities for nanoscience and nanotechnology and accelerate their applications.
Co-reporter:Guannan Sun;Zhimin Chen;Shanshan Wang;Linmei Li
Colloid and Polymer Science 2011 Volume 289( Issue 12) pp:1397-1406
Publication Date(Web):2011 August
DOI:10.1007/s00396-011-2470-4
This article presents a novel route to prepare hollow silica microspheres with well-defined wall thickness by using cross-linked polystyrene (PS) microspheres as templates with the assistance of supercritical carbon dioxide (SC-CO2). In this approach, the cross-linked PS templates can be firstly prepared via emulsifier-free polymerization method by using ethylene glycol dimethacrylate or divinylbenzene as cross-linkers. Then, the silica shell from the sol–gel process of tetraethyl orthosilicate (TEOS) which was penetrated into the PS template with the assistance of SC-CO2 was obtained. Finally, the hollow silica spheres were generated after calcinations at 600 °C for 4 h. The shell thickness of the hollow silica spheres could be finely tuned not only by adjusting the TEOS/PS ratio, which is the most frequently used method, but also by changing the pressure and aging time of the SC-CO2 treatment. Fourier transform infrared spectroscopy, transmission electron microscopy, and scanning electron microscope were used to characterize these hollow silica spheres.
Co-reporter:Ning Yu, Linghao He, Yuanyuan Ren, Qun Xu
Polymer 2011 Volume 52(Issue 2) pp:472-480
Publication Date(Web):21 January 2011
DOI:10.1016/j.polymer.2010.11.045
As a typical engineering plastic and high-crystallization polymer, polyoxymethylene (POM) has been successfully wrapped on single-walled carbon nanotubes (SWCNTs) using a simple supercritical carbon dioxide (SC CO2) antisolvent-induced polymer epitaxy method. The characterization results of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) reveal that the SWCNTs are coated by laminar POM with the thicknesses of a few nanometers. The polymer adsorption on CNTs via multiple weak molecular interactions of CH groups with CNTs has been identified with FTIR and Raman spectroscopy. The experimental results indicate that the decorating degree of POM on the surface of CNTs increases significantly with the increase of SC CO2 pressure, and accordingly the dispersion of SWCNT modified by POM at higher pressure are more excellent than that of obtained at lower pressure. Further the processing stability of POM/CNTs composites are investigated by differential scanning calorimetry and thermogravimetric analysis. The experimental results obtained show that their thermal stability behavior is closely related to surface properties of CNTs. Apparently, the composites with POM-decorating SWCNTs as the filler shows higher melting points compared to the POM composites with pristine SWCNTs as the filler. Therefore, we anticipate this work may lead to a controllable method making use of peculiar properties of SC CO2 to help to fabricate the functional CNTs-based nanocomposites containing highly crystalline thermoplastic materials such as POM.
Co-reporter:Ning Yu, Xiaoli Zheng, Qun Xu, and Linghao He
Macromolecules 2011 Volume 44(Issue 10) pp:3958-3965
Publication Date(Web):April 29, 2011
DOI:10.1021/ma200465a
As a typical double-crystalline diblock copolymer, polyethylene-b-poly(ethylene oxide) (PE-b-PEO) has been successfully modified on single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) using a simple supercritical carbon dioxide (SC CO2) antisolvent-induced polymer epitaxy method. The characterization results of transmission electron microscopy (TEM) demonstrated that the unique double-crystalline block copolymer PE-b-PEO can be periodically decorated along carbon nanotubes (CNTs), leading to a novel amphiphilic nanohybird structure. The effect of different solvents on the decorated patterns of PE-b-PEO on CNTs has been discussed in this work. We found that the selectivity of solvent to the segments of block copolymer played a decisive role on the morphology of PE-b-PEO assembling on CNTs. When 1,2-dichlorobenzene (DCB) or p-xylene was used as the solvent, PE-b-PEO formed periodic patterns on CNTs, where the nanotube-induced PE crystallization was critical to the formation of the novel regular nanohybird structure. When the solvent was switched to N,N-dimethylacetamide (DMAc), which was more selective for PEO, periodic patterns were not observed, and merely the thin polymer coatings were observed on CNTs. The experimental results indicated that the decorating degree of PE-b-PEO on the surface of CNTs increased significantly with the increase of SC CO2 pressure. FT-IR and Raman spectra indicated that there existed multiple weak molecular interactions between polymer chains and CNTs. Therefore, we anticipate this work may lead to a controllable method making use of peculiar properties of SC CO2 to help to fabricate the functional CNTs-based nanocomposties containing diblock copolymer with the various micromorphologies in the different organic solvents.
Co-reporter:Jianwei Fu, Qun Xu, Jiafu Chen, Zhimin Chen, Xiaobin Huang and Xiaozhen Tang
Chemical Communications 2010 vol. 46(Issue 35) pp:6563-6565
Publication Date(Web):16 Aug 2010
DOI:10.1039/C0CC01185A
Uniform carbon spheres with hollow core and porous shell structures were controllably fabricated through carbonizing fine core/shell particles of polystyrene/cross-linked poly(cyclotriphosphazene-co-4,4′-sulfonyldiphenol), obtained by a simple template approach.
Co-reporter:Jianwei Fu, Jiafu Chen, Zhimin Chen, Qun Xu, Xiaobin Huang and Xiaozhen Tang
New Journal of Chemistry 2010 vol. 34(Issue 4) pp:599-602
Publication Date(Web):05 Mar 2010
DOI:10.1039/B9NJ00774A
We report on the controlled preparation of cross-linked poly(cyclotriphosphazene-co-4,4′-sulfonyldiphenol) (PZS) nanotubes using Ag nanowires as sacrificial templates. The as-prepared PZS nanotubes have a good chemical stability in concentrated nitric acid and an initial 475 °C thermal decomposition temperature in air.
Co-reporter:Linghao He;Chengwu Hua;Rui Song
Polymer Composites 2010 Volume 31( Issue 5) pp:921-927
Publication Date(Web):
DOI:10.1002/pc.20876
Abstract
Composites were prepared by solution blending poly(vinylidene fluoride) (PVDF) and multi-walled carbon nanotubes (MWNTs). Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) results showed that the crystalline structure of PVDF was changed by the addition of MWNTs and a MWNTs-induced crystal transformation from α-phase to β-phase of PVDF was confirmed. With differential scanning calorimeter (DSC) and dynamic mechanic thermal analysis (DMA) techniques, thermal and mechanical properties of the composite films were examined. As the DSC results showed, addition of MWNTs would lead to the increased cooling crystallization temperature (Tc), implying that MWNTs nanoparticles could act as nucleating agents, which is further proved with the help of polarized optical microphotographs. On the other hand, the decreasing of Dd (degree of crystallinity) implied that the MWNTs networks can confine the crystallization of PVDF. Through the curve analysis of the dynamic mechanical measurements, it was found that the storage modulus (E′) is significantly enhanced, revealing that a strong interaction should exist between PVDF and MWNTs. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers
Co-reporter:Linghao He;Rui Song;Chengwu Hua
Polymer Composites 2010 Volume 31( Issue 5) pp:913-920
Publication Date(Web):
DOI:10.1002/pc.20875
Abstract
The morphology, nucleation, and crystallization of polyethylene/carbon nanotubes composites prepared by solution crystallization method of high density polyethylene on Multiwall Carbon Nanotubes (MWNTs) are studied. Transmission electron microscopy (TEM) results show that the center stems of MWNTs are decorated with lamellar crystals. The nonisothermal crystallization kinetics of pure PE and PE/MWNTs composites are investigated by differential scanning calorimetry at various cooling rates. It is found that the Avrami analysis modified by Jeziorny and Mo can describe the nonisothermal crystallization process of pure PE and PE/MWNTs very well. The difference in the value of exponent between PE and PE/MWNTs suggests that addition of the MWNTs influences the mechanism of nucleation and the growth of PE crystallites. On one hand, the increasing of temperature corresponding to the maximum rate of crystallization and the onset crystallization temperature and the study of the nucleation activity reveal that the inorganic component (MWNTs) can act as the nucleating agent to facilitate the crystallization of PE in the hybrids. On the other hand, the decreasing degree of crystallinity and the increasing of half-crystallization time imply that the MWNTs networks confine the crystallization of PE. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers
Co-reporter:Linghao He, Xiaoli Zheng and Qun Xu
The Journal of Physical Chemistry B 2010 Volume 114(Issue 16) pp:5257-5262
Publication Date(Web):April 7, 2010
DOI:10.1021/jp911621y
We report herein a typical piezoelectric polymer, poly(vinylidene fluoride) (PVDF) to be successfully wrapped on single-walled carbon nanotubes (SWCNTs) using a simple supercritical carbon dioxide (SC CO2) antisolvent-induced polymer epitaxy method. Our study focused on the effect of different solvents on the morphology of PVDF wrapping on SWCNTs. Three organic solvents, dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), and N,N-dimethylacetamide (DMAc) were chosen for PVDF. When DMSO was used as solvent, the decorating degree of PVDF on the surface of SWCNTs increases significantly with the increase of SC CO2 pressure, and nanocrystals wrapping on SWCNTs can be observed at high pressure. FTIR and Raman spectra indicated that there exist interactions between SWCNTs and PVDF chains. What’s more, FTIR results also show that there exists a transformation from the β-phase to the α-phase of PVDF in DMSO with the assistance of SC CO2, which is similar to the action of elongation/shear flow field. It indicated that the α-phase is the predominant form occurring on the surface of SWCNTs after treatment with SC CO2. And the helical structure on SWCNTs observed from the TEM image reflected the alternate trans- and gauche-bond conformation of the α-form. When DMF or DMAc was used as the solvent, although nanocrystal wrapping and helical structure was not visible, the samples had more excellent dispersion than that in DMSO. Particularly, for DMF, a typical network structure was observed, which is similar to a spider web. Therefore, this work supplies a clue that the various morphologies of nanohybrid structure can be obtained just by changing the solvent during the treatment process of SC CO2, and accordingly, the tailored nanohybrid structure are promising and important for functional design as a basic component in microfabrication and other fields.
Co-reporter:Xiaoli Zheng and Qun Xu
The Journal of Physical Chemistry B 2010 Volume 114(Issue 29) pp:9435-9444
Publication Date(Web):July 2, 2010
DOI:10.1021/jp103932b
In this work, we provided a comparison study of morphology and crystallization behavior of polyethylene (PE) and poly(ethylene oxide) (PEO) on single-walled carbon nanotubes (SWNTs) with assistance of supercritical CO2. The resulting polymer/SWNT nanohybrids were characterized by transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, Raman spectra, wide-angle X-ray diffraction, and differential scanning calorimetry. SWNT small bundles were decorated by PE lamellar crystals, forming nanohybrid “shish-kebab” (NHSK) structure, whereas SWNTs were only wrapped by a thin amorphous polymer coating in the case of PEO. The varying morphologies of the nanohybrids were found to depend on the molecular conformation and the interactions between polymer chains and SWNTs. Nonisothermal experiments showed that SWNTs provided heterogeneous nucleation sites for PE crystallization, while the NHSK structure hindered polymer chain diffusion and crystal growth. Also, SWNTs played antinucleation effect on PEO. In addition, the formation mechanism analysis indicated that PE chains preferred to form a homogeneous coating along the tube axis before proceeding to kebab crystal growth. The purpose of this work is to enlarge the area of theoretical understanding of introducing precisely hierarchical structures on carbon nanotubes, which are important for functional design in nanodevice applications.
Co-reporter:Aping Niu, Yujie Han, Jian Wu, Ning Yu and Qun Xu
The Journal of Physical Chemistry C 2010 Volume 114(Issue 29) pp:12728-12735
Publication Date(Web):July 6, 2010
DOI:10.1021/jp104720w
One-dimensional (1D) carbon nanomaterials wrapped by silver nanoparticles were fabricated via a facile and environmentally benign route with the assistance of supercritical carbon dioxide. Transmission electron microscopy, scanning electron microscopy, and energy-dispersive X-ray analysis revealed that carbon nanofibers (CNFs) were densely coated by silver nanoparticles under the optimized experimental condition. In the case of carbon nanotube/silver (CNT/Ag) nanohybrids, these silver nanoparticles on the surface of carbon nanotubes were predominantly spherical in shape with excellent dispersion, and their sizes were smaller than that on carbon nanofibers. The UV−vis spectra presented a surface plasmon resonance vibration band at 448 and 414 nm for CNFs and CNTs, respectively. X-ray diffraction analysis showed that the nanoparticles were of a face centered cubic structure. Some crucial factors, which affect the growing and arraying of Ag nanoparticles along the axis of 1D carbon nanomaterials, had been investigated. As examples for promising applications, the antibacterial activities of the as-prepared one-dimensional nanocomposites were also studied.
Co-reporter:XiaoLi Zheng;ZongPeng Li
Science China Chemistry 2010 Volume 53( Issue 7) pp:1525-1533
Publication Date(Web):2010 July
DOI:10.1007/s11426-010-3106-0
One-dimensional carbon nano-materials, in particular carbon nanotubes (CNTs) and carbon nanofibers (CNFs), are of scientific and technological interest due to their satisfactory properties and ability to serve as templates for directed assembly. In this work, linear high density polyethylene (PE) was periodically decorated on CNTs and CNFs using a supercritical carbon dioxide (scCO2)antisolvent-induced polymer epitaxy (SAIPE) method, leading to nano-hybrid shish-kebab (NHSK) structures. The formation mechanism of different morphologies of PE lamellae on CNTs and CNFs has been discussed. Palladium nanoparticles were synthesized and immobilized on the PE/CNF NHSK structure with the assistance of scCO2. The obtained hierarchical nano-hybrid architecture may find applications in microfabrication and other related fields.
Co-reporter:Zhimin Chen, Shijiang Li, Fengfeng Xue, Guannan Sun, Chengguo Luo, Jiafu Chen, Qun Xu
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2010 Volume 355(1–3) pp:45-52
Publication Date(Web):20 February 2010
DOI:10.1016/j.colsurfa.2009.11.030
Using the excellent transport properties of supercritical carbon dioxide, tetraethyl orthosilicate (TEOS) could be easily carried into the template of the cross-linked polystyrene (PS) microspheres. Through the sol–gel procedure, the TEOS penetrated into the PS microspheres was transferred into silica. After sintering these composite particles, hollow silica microspheres were obtained. Through the above method, the hollow titanium dioxide microspheres also could be synthesized. The formation mechanism of the hollow particles was discussed and the morphology of the hollow microspheres was characterized by transmission electron microscopy (TEM) and scanning electronic microscope (SEM).
Co-reporter:Zhimin Chen, Mingchuan Zhuo, Fengfeng Xue, Jiafu Chen and Qun Xu
Industrial & Engineering Chemistry Research 2009 Volume 48(Issue 7) pp:3441
Publication Date(Web):March 3, 2009
DOI:10.1021/ie801557y
Magnetically separable mesoporous silica microspheres with open pore systems have been synthesized in supercritical carbon dioxide (SC-CO2). In the experiments, using the excellent transport properties of supercritical carbon dioxide, an acetone solution containing iron(III) acetylacetonate [Fe(acac)3] was easily infiltrated into the mesopores of the microspheres. After thermal decomposition, the Fe(acac)3 was easily transformed into Fe3O4 nanoparticles. A comparison experiment verified that the carrying effect of Fe(acac)3 using SC-CO2 was better than that observed for the common method. The magnetic microspheres were characterized by transmission electron microscopy, energy-dispersive X-ray analysis (EDAX), powder X-ray diffraction, and nitrogen adsorption−desorption. The magnetically separable property of the microspheres was also tested.
Co-reporter:Aping Niu, Yan Li, Jiafu Chen, Qun Xu and Yanxia Cao
Industrial & Engineering Chemistry Research 2009 Volume 48(Issue 15) pp:7103-7109
Publication Date(Web):July 2, 2009
DOI:10.1021/ie900204y
Titania nanocrystals were prepared by a particular way: first, supercritical CO2 (SC CO2) carried precursor tetrabutyl titanate (TBT) into the confined space of polystyrene (PS) microspheres; second, hydrolysis of TBT was controlled by the confined space of PS microspheres, which had a restraining effect on the hydrolysis rate of TBT; finally, TiO2 nanocrystals were obtained by calcining PS@TiO2 composite microspheres. The products obtained after hydrolysis and calcination, that is, PS@TiO2 composite microspheres and the finally obtained TiO2 nanocrystals, were characterized by transmission electron microscope and scanning electron microscope, respectively. Further high-resolution transmission electron microscopy and X-ray diffraction (XRD) indicated that the obtained TiO2 nanocrystals had fine crystalline structure. Additionally, the XRD pattern verified the presence of anatase and rutile in TiO2. The nucleation mechanism of TiO2 nanocrystals in the confined space of PS microspheres was also proposed.
Co-reporter:Qiuyan Yang;Shufa Qin;Jiafu Chen;Wei Ni
Journal of Applied Polymer Science 2009 Volume 113( Issue 6) pp:4015-4022
Publication Date(Web):
DOI:10.1002/app.30476
Abstract
The physical modification of the dry leather using supercritical carbon dioxide (SC-CO2) was studied in this article. A series of loosening processes of the leather fibers were carried out by changing the experimental conditions such as experimental pressure, experimental temperature, and time. The samples were characterized by scanning electronic microscopy (SEM), Brunauer–Emmett–Teller (BET) and X-ray diffraction (XRD). SEM images show that samples were loosened by SC-CO2 and the leather fibers in micron size arrange more orderly after treatment. The BET surface area of treated samples increase from 1.67 m2/g to 6.33 m2/g with the changing of conditions. The optimal treatment conditions were determined. Moreover, XRD patterns indicate that aggregation structure of collagen fibers in the sample was altered by SC-CO2, and it can be found that the loosening of leather mostly happened in amorphous regions of collagen fibers. Besides, the percent breaking elongation of the samples was examined by means of a tensile analyzing test, and it indicates that the elongation at break of all the treated samples in SC-CO2 can increase to 128.2% compared with 95.9% of the original ones. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Co-reporter:Chengwu Hua;Zhimin Chen;Linghao He
Journal of Polymer Science Part B: Polymer Physics 2009 Volume 47( Issue 8) pp:784-792
Publication Date(Web):
DOI:10.1002/polb.21685
Abstract
The ring-banded spherulites in poly(ε-caprolactone) (PCL) solution-casting films in the absence and presence of multi-walled carbon nanotube (MWCNT) are studied by atomic force microscopy (AFM), polarized optical microscopy (POM), transmission electron microscopy (TEM), and scanning electronic microscopy (SEM). The results indicate that birefringent ring-banded spherulites of PCL can grow from solution below 50 °C, and the temperature is much lower than that from pure PCL melt. We also find out that the presence of MWCNT apparently widen the temperature range of forming ring-banded structure. Furthermore, the mechanism for the ring-banded structure forming is studied, and it is attributed to the twisting of lamellae crystals, and the driving force is suggested including the deflexion of lamellae bundles. In addition, effect of compressed CO2 on the morphology of PCL and PCL/MWCNT solution-casting film is also investigated, and the results reveal that both PCL and PCL/MWCNT films undergo recrystallization with the treatment of compressed CO2 and accordingly, the related properties can be adjusted. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 784–792, 2009
Co-reporter:Yan Li, Jiafu Chen, Qun Xu, Linghao He and Zhimin Chen
The Journal of Physical Chemistry C 2009 Volume 113(Issue 23) pp:10085-10089
Publication Date(Web):May 14, 2009
DOI:10.1021/jp901237r
An effective mechanism to prepare monodisperse carbon nanospheres with a regular round-ball-like shape is introduced. The route involves three steps: first, to synthesize monodisperse cross-linked polystyrene beads (CLPBs) by soap-free emulsion polymerization; second, to increase the cross-linking degree of CLPBs via Friedel−Crafts alkylation as a post-cross-linking reaction; third, to carbonize the reaction product. Both solid and hollow carbon spheres can be produced by adjusting the post-cross-linking reaction time. Fourier transform infrared spectra demonstrated the occurrence of a Friedel−Crafts alkylation reaction, and X-ray diffraction results showed that the carbon nanospheres are amorphous in structure. Typically, nitrogen adsorption/desorption measurements indicate that solid and hollow carbon nanospheres have a Brunauer−Emmett−Teller surface area as high as 498 and 451 m2/g, respectively. So it indicates that this method is novel in the field of preparation of carbon microspheres.
Co-reporter:Yan Li, Jiafu Chen, Aping Niu, Fengfeng Xue, Yanxia Cao, Qun Xu
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2009 Volume 342(1–3) pp:107-114
Publication Date(Web):15 June 2009
DOI:10.1016/j.colsurfa.2009.04.021
Hollow poly (styrene-co-divinylbenzene) (PS-DVB) particles in nanometer scale with variable cavity sizes were prepared by a facile method only including both synthesis of core–shell PS-DVB particles (CSPPs) with uncross-linked core and cross-linked shell by soap-free emulsion polymerization and dissolution of uncross-linked cores of CSPPs by tetrachloromethane. The TEM results indicated that the cavity size of hollow PS-DVB particles could be controlled by adjusting the content of DVB during the polymerization process. Further hollow TiO2 particles were successfully prepared using CSPPs with 20 wt% DVB as template with the assistance of supercritical CO2 (SCCO2). The formation mechanism behind these phenomena was proposed.
Co-reporter:Zhimin Chen, Fengfeng Xue, Jiafu Chen, Qun Xu
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2009 Volume 335(1–3) pp:16-22
Publication Date(Web):5 March 2009
DOI:10.1016/j.colsurfa.2008.10.021
Using “two-stage” dispersion polymerization method polystyrene (PS) microspheres with “hard shell and soft core” are synthesized. Through treating these cross-link particles with supercritical carbon dioxide (SC CO2), these microspheres were welded together. After ultrasonic treatment, these welded microspheres were successfully separated and the submicron-sized pits were engraved on the surfaces of these particles, which finally realized the transformation of these particles from isotropy to anisotropy. The transformation degree of these microspheres (size and the depth of the pits on the microspheres) could be adjusted by changing the temperature and pressure of SC CO2. The SEM results illustrated that the anisotropic degree of the microspheres enhanced with increasing the pressure of SC CO2 in certain range and then decreased. Elevating the temperature at the same pressure could greatly enhance the anisotropic degree of these microspheres. Slight changing the cross-link density of the shell could also have obvious effect on the transformation degree of the PS particles.
Co-reporter:Fan Zhang, Qun Xu, Hao Zhang and Zhiwei Zhang
The Journal of Physical Chemistry C 2009 Volume 113(Issue 43) pp:18531-18535
Publication Date(Web):October 7, 2009
DOI:10.1021/jp905660z
Polymer supermolecular structures have been built on carbon nanotubes (CNT) using induced crystallization in supercritical CO2 (SC CO2). CNTs are wrapped by strands of nanocrystals as a “pear-necklace” in multihelix patterns, “shish-kebab” structures, and “muscle fiber” in the case of PEG, PE, and fluorinated liquid crystal polymer (FLCP), respectively. A number of structural variables have been identified, including chain regularity, thermodynamic chain flexibility in solution, and orientation of crystal growth induced by CNTs, and the environmental factor in supercritical CO2 conditions. These tailored nanohybrid architectures are promising and important for functional design as basic components in microfabrication and other fields.
Co-reporter:Jianbo Li, Qun Xu, Jiguang Wang, Jianxia Jiao and Zhiwei Zhang
Industrial & Engineering Chemistry Research 2008 Volume 47(Issue 20) pp:7680
Publication Date(Web):September 12, 2008
DOI:10.1021/ie0711269
A green and efficient process to synthesize monolithic porous inorganic materials with hierarchical structure has been presented. By using wood cellular structure as a template and supercritical CO2 as a solvent and carrier, the morphology and pore or channel systems of wood templates could be replicated faithfully. The total BET (Brunauer−Emmett−Teller) surface area of the resulting silica material can reach 469 m2/g using poplar as the template. It is found that different pore structure data can be obtained with different wood cellular structures as the template. Meanwhile, the pore structure data of the product can be adjusted by changing the experimental conditions of the supercritical CO2 during the impregnation process.
Co-reporter:Shimin Li, Qun Xu, Jiafu Chen and Yiqun Guo
Industrial & Engineering Chemistry Research 2008 Volume 47(Issue 21) pp:8211-8217
Publication Date(Web):October 9, 2008
DOI:10.1021/ie800046h
Supercritical carbon dioxide (SC CO2) was used as a carrier/solvent for the “dry” alumination of mesoporous silica to prepare aluminum-containing mesoporous MCM-41. The effect of alumination on the structure and crystallinity of the materials was studied. In addition, the hydrothermal and thermal stability of this material have been investigated and compared with Al-MCM-41 prepared via conventional impregnation and direct hydrothermal synthesis. Irrespective of the preparation method, the surface area, pore diameter, pore volume, and crystallinity of Al-MCM-41 all decrease after hydrothermal and thermal treatments. However, Al-MCM-41 materials prepared with the assistance of SC CO2 possess better hydrothermal and thermal stability. This method allows for the incorporation of aluminum onto rather than into pores wall, without disintegration of the mesoporous structure, compared to Al-MCM-41 that has been prepared via impregnation and direct hydrothermal synthesis.
Co-reporter:Ayou Hao;Yuanyuan Geng;Zhanyong Lu;Long Yu
Journal of Applied Polymer Science 2008 Volume 109( Issue 4) pp:2679-2686
Publication Date(Web):
DOI:10.1002/app.27861
Abstract
Microcellular foaming of biodegradable and biocompatible PLA/starch composites in supercritical/compressed CO2 has been studied. The purpose of this study is to explore the potential application of this kind of materials in medical materials or drug containers. The rate of CO2 uptake and CO2 equilibrium concentration in PLA/starch composites were studied by performing sorption and desorption experiments. The effects of a series of variable factors, such as saturation time and saturation temperature on the foaming morphology were studied through SEM observation and density measurement. The experimental results show that, while keeping other variables unchanged, longer saturation time leads to reduced bulk foam densities and different saturation pressures result in different bulk foam densities. The crystallinity of PLA–starch sample was characterized by differential scanning calorimetry. It indicates that the foaming treatment with supercritical CO2 increased the crystallinity of PLA/starch composites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Co-reporter:Zhiwei Zhang, Qun Xu, Zhimin Chen and Jun Yue
Macromolecules 2008 Volume 41(Issue 8) pp:2868-2873
Publication Date(Web):March 20, 2008
DOI:10.1021/ma702739n
In this study, we develop a facile and efficient method for period-decorating carbon nanotubes (CNTs) using a supercritical (SC) CO2 antisolvent-induced polymer epitaxy (SAIPE) method. It helps the epitaxy growth of PE on CNTs under a series of suitable experimental conditions, forming a nanohybrid shish-kebab (NHSK) structure. With the variation of a series of experimental conditions or peripheral effect, such as different solvent, PE concentration, CNTs concentration and SC CO2 pressure, the NHSK structure, i.e., the size of the lamellae and the interval between them along the stem, can be varied. When p-xylene was used as the solvent for PE and single-walled CNT (SWCNT), the size of the lamellae can be adjusted from 80−120 to 125−250 nm with the change of the PE concentration. Using the same solvent p-xylene, with the change of SC CO2 pressure, the size of the lamellae can be changed from 125−250 to 300−400 nm. When dichlorobenzene (DCB) was used as the solvent for PE and SWCNT, with the increase of the SWCNT concentration, from 0.002 to 0.006 and 0.01 wt %, the size of the lamellae can be reduced from 305−420 to 280−400 and 85−200 nm. In comparison to the experimental result with p-xylene used as the solvent, it is found that the decorated CNTs have more excellent dispersion when DCB was used as the solvent. Our experimental results indicate that the SAIPE method is effective for both SWCNTs and multiwalled CNTs (MWCNTs). Therefore, this work not only provides a new route to periodically functionalize CNTs with a controllable and adjustable method, but also it can be anticipated to open a gateway for making use of peculiar properties of SC CO2 to help functionalize CNTs in an environmentally benign manner.
Co-reporter:Fan Zhang, Hao Zhang, Zhiwei Zhang, Zhimin Chen and Qun Xu
Macromolecules 2008 Volume 41(Issue 12) pp:4519-4523
Publication Date(Web):May 31, 2008
DOI:10.1021/ma800514a
Co-reporter:Jianxia Jiao;Limin Li;Takano Tsubasa
Colloid and Polymer Science 2008 Volume 286( Issue 13) pp:1485-1491
Publication Date(Web):2008 November
DOI:10.1007/s00396-008-1919-6
Titania–silica composite have been prepared using polyethylene glycol (PEG) with different molecular weights (Mw), PEG20000, PEG10000, and PEG2000, as template in supercritical carbon dioxide (SC CO2). The composite precursors were dissolved in SC CO2 and impregnated into PEG templates using SC CO2 as swelling agent and carrier. After removing the template by calcination at suitable temperature, the titania–silica composite were obtained. The composite were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and nitrogen sorption–desorption experiment. Photocatalytic activity of the samples has been investigated by photodegradation of methyl orange. Results indicate that there are many Si–O–Ti linkages in the TiO2/SiO2 composite; the PEG template has a significant influence on the structure of TiO2/SiO2. In addition, the TiO2/SiO2 prepared with PEG10000 exhibited high photocatalytic efficiency. So this work supplies a clue to control and obtain the TiO2/SiO2 composite with different photocatalytic reactivity with the aid of suitable PEG template in supercritical CO2.
Co-reporter:Cuiyu Yin, Jianbo Li, Qun Xu, Qi Peng, Yabei Liu, Xinyuan Shen
Carbohydrate Polymers 2007 Volume 67(Issue 2) pp:147-154
Publication Date(Web):22 January 2007
DOI:10.1016/j.carbpol.2006.05.010
Chemical modification of cotton cellulose in supercritical carbon dioxide has been studied and cellulose carbamate has been successfully synthesized. Compared with the conventional carbamate process, the supercritical method had remarkably increased the nitrogen content of the modified cellulose. The effects of impregnating pressure, esterification temperature and esterification time on the nitrogen content of the products were discussed. The modified cellulose was characterized by Fourier transform infrared spectroscopy (FTIR), NMR spectrometer, X-ray diffraction (XRD), and thermogravimetry (TG). In addition, the surface morphology of modified cellulose fibers was investigated using scanning electron micrographs (SEM).
Co-reporter:Jianxia Jiao, Qun Xu, Limin Li
Journal of Colloid and Interface Science 2007 Volume 316(Issue 2) pp:596-603
Publication Date(Web):15 December 2007
DOI:10.1016/j.jcis.2007.08.056
Titania–silica mesoporous composites have been prepared using polyethylene glycol (PEG) 20,000 as a template direction reagent with the assistance of supercritical carbon dioxide (SC CO2). For this preparation method, the composite precursors of tetrabutyl titanate (TBTT) and tetraethyl orthosilicate (TEOS) were dissolved in supercritical CO2 and impregnated into PEG 20,000 using SC CO2 as swelling agent and carrier. After removal of the PEG template by calcination in air at suitable temperatures, porous titania–silica composites were obtained. Effects of CO2 pressure and temperature have been studied on the impregnation ratio during the supercritical fluid condition. The composite products were characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD), FTIR spectroscopy, nitrogen sorption–desorption experiments, scanning electronic microscope (SEM), and transmission electron microscope (TEM). XRD and nitrogen sorption–desorption experimental results indicate that the titania–silica composite crystallized in anatase phase and has a preferable BET surface area up to 301.98 m2/g. It was also demonstrated that the microstructure and macroproperty of TiO2/SiO2 composites depend strongly on the experimental pressure during the impregnation process in SC CO2. At suitable CO2 pressure, silica even can be found in a single crystalline structure in nature by observation of TEM. At the same time, SEM indicates that the composite product existed in a spheric form or a cubic form inserted with many holes. So this work provides a new route to control and obtain the special micrography of TiO2/SiO2 composites with the aid of suitable polymer templates in supercritical CO2.
Co-reporter:Qi Peng;Dengfeng Sun;Zhengzhong Shao
Journal of Applied Polymer Science 2006 Volume 100(Issue 2) pp:1299-1305
Publication Date(Web):30 JAN 2006
DOI:10.1002/app.23408
Graft copolymerization of methyl methacrylate (MMA) onto Antheraea pernyi silk fibers, initiated by benzoyl peroxide in the supercritical CO2 was investigated. The grafting degree was determined as a function of impregnating pressure, impregnating time, monomer concentration, initiator concentration, and reaction time. The structural properties of MMA-grafted fiber were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. Grafted MMA was chemically bonded and/or physically adhered to the surfaces of the fibers. The grafted silk fibers exhibited two steps of weight loss according to the characteristic of each component as demonstrated by the thermogravimetric analysis. The water-retention values indicated that the hydrophobic nature of the fibers was improved. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1299–1305, 2006
Co-reporter:Jinge Li;Long Yu;Wei Ni;Qi Peng;Zhenzhong Hou
Journal of Applied Polymer Science 2006 Volume 100(Issue 4) pp:2901-2906
Publication Date(Web):9 FEB 2006
DOI:10.1002/app.23796
Microcellular foaming of biodegradable Bionolle in supercritical CO2 has been produced. The effects of a series of variable factors, such as saturation temperature, saturation pressure, and depressurization time and step on the foam structures and density, were studied through measurement of density and SEM observation. The experimental results show that higher saturation temperatures lead to an increase in bulk densities; and different depressurization time and step result in different product cell morphology. In addition, at some saturation temperature, the orientation of the cells can be found in the product morphology. XRD experimental results show that the foaming treatment with SC CO2 increased the crystallinity of Bionolle. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2901–2906, 2006
Co-reporter:Zhenzhong Hou;Qi Peng;Jianbo Li;Haijuan Fan;Shijun Zheng;Zhenzhong Hou;Qi Peng;Jianbo Li;Haijuan Fan;Shijun Zheng
Journal of Applied Polymer Science 2006 Volume 100(Issue 6) pp:4280-4285
Publication Date(Web):8 MAR 2006
DOI:10.1002/app.23857
The grafting of poly(acrylic acid) to polypropylene was realized with supercritical CO2 as a substrate swelling agent and a monomer/initiator carrier. The effects of different supercritical CO2-assisted impregnation conditions on the substrate mass increment and grafting efficiency were studied. The original isotactic polypropylene and the grafting product were characterized through IR spectroscopy, differential scanning calorimetry, and scanning electron microscopy. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4280–4285, 2006
Co-reporter:Zhenzhong Hou;Guangfa Zhang;Haijuan Fan;Jianbo Li;Shijun Zheng
Journal of Applied Polymer Science 2006 Volume 101(Issue 4) pp:2614-2618
Publication Date(Web):27 MAY 2006
DOI:10.1002/app.24220
The grafting of polyacrylamide to polypropylene was realized with supercritical carbon dioxide as a substrate-swelling agent and monomer/initiator carrier. The effects of supercritical carbon dioxide assisted impregnation and graft polymerization conditions on the grafting ratio were studied. The original polypropylene and grafting products were characterized with infrared spectroscopy, differential scanning calorimetry, and scanning electron microscopy. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2614–2618, 2006
Co-reporter:Haijuan Fan, Qun Xu, Yiqun Guo, Qi Peng, Zhenzhong Hou
Materials Science and Engineering: A 2006 Volume 422(1–2) pp:272-277
Publication Date(Web):25 April 2006
DOI:10.1016/j.msea.2006.02.008
Nanoporous ferric oxide has been prepared with nanoscale casting process using activated carbon template in supercritical carbon dioxide. The precursors with the cosolvent of acetone were dissolved in supercritical CO2, and then attached to activated carbon in the supercritical condition. After removal of the activated carbon template by calcinations in air at 873 K, the nanoporous Fe2O3 was obtained. Four factors were considered to study the effect on the coating ratio and yield. The structure and morphology of the products were characterized through nitrogen adsorption–desorption isotherms, thermal gravimetric analysis (TGA), wide-angle X-ray diffraction (WAXD) and transmission electron microscopy (TEM).
Co-reporter:Qun Xu, Jianbo Li, Qi Peng, Linlin Wu, Suping Li
Materials Science and Engineering: B 2006 Volume 127(2–3) pp:212-217
Publication Date(Web):25 February 2006
DOI:10.1016/j.mseb.2005.10.031
A novel and simple approach to synthesize the hollow porous silica fibers with hierarchical structure had been proposed, in which natural silk fiber was used as template with the aid of supercritical CO2. Supercritical CO2 can be used to proceed with coating, during which silica precursor (TEOS) dissolved in supercritical CO2 and the supercritical CO2 was in contact with the silk templates. After removal of silk templates by calcinations, the final silica fiber materials replicate not only macroscopic alignment structure along the silk direction, but also microscopic porous structure on the surface of silk. We have shown that it is possible to tune the diameter, wall thickness, and the porous structure of the tube-like silica fibers by varying the pressure and temperature of the supercritical CO2.
Co-reporter:Qun Xu;Yuan Zhao
Journal of Applied Polymer Science 2005 Volume 96(Issue 6) pp:2016-2020
Publication Date(Web):5 APR 2005
DOI:10.1002/app.21646
A blend of polystyrene and thermal polyurethane (PS/TPU) was prepared using supercritical (SC) CO2 as a substrate-swelling agent and monomer/initiator carrier. The SC CO2/styrene/TPU ternary system was studied. Virgin TPU and synthesized blends were characterized through differential scanning calorimetry, infrared spectroscopy, rheometric measurements, and SEM. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2016–2020, 2005
Co-reporter:Maizhi Pang;Qi Peng;Yu Jiang;Jianbo Li;Mingwei Zhu;Hongying Wang
Journal of Applied Polymer Science 2005 Volume 98(Issue 2) pp:831-837
Publication Date(Web):29 JUL 2005
DOI:10.1002/app.22159
There is increasing interest in the application of supercritical CO2 (SCCO2) in the preparation of polymer membranes. Membrane formation with SCCO2 as a nonsolvent is analogous to the conventional immersion precipitation process using an organic nonsolvent. Polylactide membranes were prepared with SCCO2 as the nonsolvent under different experimental conditions such as different polymer concentrations, different depressurization rates, and different nonsolvent compositions. The effects of these conditions on the cross-sectional structure were investigated through scanning electron microscopy. In addition, solvent-induced crystallization and CO2-induced crystallization were studied. The crystallinity of PLA membranes prepared with different solvents or at different pressures was characterized by wide-angle X-ray diffraction and differential scanning calorimetry. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 831–837, 2005
Co-reporter:Qi Peng;Hongyan Xu;Maizhi Pang;Jianbo Li;Dengfeng Sun
Journal of Applied Polymer Science 2005 Volume 98(Issue 2) pp:864-868
Publication Date(Web):29 JUL 2005
DOI:10.1002/app.22186
Monomer acrylic acid (AA) and initiator azo-bis(isobutyronitrile)were carried into Antheraea pernyi silk fibroin (SF) fibers using supercritical CO2 as a solvent and carrier, followed by free radical polymerization at a suitable temperature, resulting in PAA/SF blends. The binary system of CO2/AA and the ternary system of CO2/AA/AIBN systems were studied. Different impregnation conditions, such as time, pressure, and concentration of AA in the fluid phase on mass uptake, were studied. Fourier transform infrared spectroscopy and X-ray diffraction results confirmed that PAA was indeed present in the silk and that there were intermolecular hydrogen bonds between PAA and SF. According to thermogravimetry and DTG, blending with PAA could enhance the thermal stability of SF slightly. The water retention values indicated that the hydrophilic nature of the fibers was improved. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 864–868, 2005
Co-reporter:Qun Xu, Jinling He, Yuning Chang, Buxing Han, Yiqun Guo, Yunlai Su
Materials Science and Engineering: B 2005 Volume 123(Issue 1) pp:41-44
Publication Date(Web):15 November 2005
DOI:10.1016/j.mseb.2005.06.010
Supercritical carbon dioxide (SC CO2) was used as carriers/solvent for “dry” alumination of mesoporous silica to prepare Al-MCM-41. The effect of aluminum on the structure and crystallinity of the materials was studied. Further, styrene monomer was impregnated into MCM-41 and Al-MCM-41 with the assistance of SC CO2, and then was polymerized in the substrates to prepare the composite of PS/MCM-41 and PS/Al-MCM-41. The experimental results indicate crystallinity and the pore volume of the composites both decreased with the addition of PS.
Co-reporter:Qun Xu, Kunlun Ding, Liumin He, Jianbo Li, Yiqun Guo, Haijuan Fan
Materials Science and Engineering: B 2005 Volume 121(Issue 3) pp:266-271
Publication Date(Web):15 August 2005
DOI:10.1016/j.mseb.2005.04.008
Supercritical fluids can be used to proceed nanoscale casting, during which silica precursor dissolved in supercritical CO2 and the supercritical CO2 was in contact with the active carbon templates. After removal of active carbon templates by calcinations, microporous and mesoporous silica samples replicating not only mesostructures, but also macroscopic of active carbon molds were obtained and the product have better porous capacity and specific surface area. Here, we studied the influences of a variety of factors upon nanoscale casting using supercritical fluids (NC-SCF), and determined the best casting condition. Also, we compared nanoscale casting by using supercritical fluids to simple liquid casting and on the basis of these studies, a new mechanism about preparing nanoporous silica with supercritical CO2-assisted method and with simple liquid casting was proposed.
Co-reporter:Qun Xu;Yuning Chang
Journal of Applied Polymer Science 2004 Volume 93(Issue 2) pp:742-748
Publication Date(Web):23 APR 2004
DOI:10.1002/app.20539
Styrene and acrylic acid were impregnated into a series of polyamide products (nylon1212, nylon1010, nylon66, nylon6) using supercritical CO2 as the additive-carrier and substrate-swelling agent. The impregnation efficiency of low molecular weight additives into substrates is attributed to complicated interactions among the system: (1) loading of additives in substrates, (2) dissolving of additives in CO2 phase, (3) swelling and plasticizing of substrates by CO2. For the first time solubility parameter was introduced to discuss the impregnation efficiency. It was found that the relative solubility of additive in the polymer substrate and CO2 is a major factor governing the incorporated amount; yet swelling of the substrate and CO2-induced crystallization also contribute to the value. The study generalizes complex factors influencing the impregnation possibility of different systems. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 742–748, 2004
Co-reporter:Qun Xu;Xianwen Ren;Yuning Chang;Jingwu Wang;Long Yu;Katherine Dean
Journal of Applied Polymer Science 2004 Volume 94(Issue 2) pp:
Publication Date(Web):5 AUG 2004
DOI:10.1002/app.20726
Microcellular foaming of low-Tg biodegradable and biocompatible polycaprolactone (PCL) in supercritical CO2 has been studied. The purpose is to apply microcellular materials to drug containers and medical materials for artificial skin or bone. Effects of a series of variable factors on the foam structures, such as saturation temperature, saturation pressure, saturation time, and depressurization time were studied. The experimental results indicate that, while keeping other variables unchanged, higher saturation temperature leads to reduced bulk densities and different saturation pressures result in different nucleation processes. In addition, saturation time has a profound effect on the structure of the product. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 593–597, 2004
Co-reporter:Qun Xu;Yuning Chang;Qingxiang Zhao;Buxing Han;Minying Liu;Yudong Wang
Journal of Applied Polymer Science 2004 Volume 92(Issue 3) pp:2023-2029
Publication Date(Web):8 MAR 2004
DOI:10.1002/app.20152
Polystyrene/nylon 1212 blends were prepared with supercritical CO2 as the substrate swelling agent and monomer/initiator carrier. Original nylon 1212 and blends were characterized with differential scanning calorimetry (DSC), polarizing microscopy, wide-angle X-ray diffraction, and scanning electron microscopy (SEM). A novel phenomenon, CO2-induced epitaxy, was discovered, and its mechanism was deduced. Thermal analysis performed with DSC indicated that the polystyrene/nylon 1212 blends had thermal stability superior to that of virgin nylon 1212. The DSC and SEM measurements indicated that incorporated polystyrene could notably improve the mechanical performance of nylon 1212. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2023–2029, 2004
Co-reporter:Qun Xu;Maizhi Pang;Qi Peng;Jianbo Li;Yu Jiang
Journal of Applied Polymer Science 2004 Volume 94(Issue 5) pp:2158-2163
Publication Date(Web):1 OCT 2004
DOI:10.1002/app.21132
The application of supercritical carbon dioxide (SCCO2) has been attracting more and more attention, especially in the formation of polymer membranes. The membrane formation using SCCO2 is analogous to conventional immersion precipitation process by using organic nonsolvent. Polylactide (PLA) membranes were prepared by phase separation with SCCO2 as nonsolvent. Two kinds of solvents were used to study the effect of the solvent on the cross-section structure of the PLA membrane and the compatibility between the solvent and SCCO2 was studied. The effect of the solvent and the preconditioning on the morphology of the PLA membrane was also investigated through scanning electron microscope, wide-angle X-ray diffraction, and polarizing microscopy. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2158–2163, 2004
Co-reporter:Qun Xu;Buxing Han;Haike Yan
Journal of Applied Polymer Science 2003 Volume 88(Issue 7) pp:1876-1880
Publication Date(Web):28 FEB 2003
DOI:10.1002/app.11908
Precipitation polymerizations of acrylic acid (AA) in compressed carbon dioxide (65 bar) with different cosolvents, acetic acid, ethanol, and tetrahydrofuran, were studied. Analyses by viscosity measurement and differential scanning calorimetry indicate that the cosolvents have a pronounced effect on the properties of the product. Scanning electron microscopy shows that the products progress from microparticles to bicontinuous networks to fibers with the change of cosolvents and reaction conditions. Measurement of the volume expansion (ΔV%) of the liquid phase containing different cosolvents indicates that the miscibility of compressed CO2 with the liquid phase is dependent on the cosolvent. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1876–1880, 2003
Co-reporter:Buxing Han;Haike Yan;Haike Yan;Buxing Han
Journal of Applied Polymer Science 2003 Volume 88(Issue 10) pp:2427-2433
Publication Date(Web):17 MAR 2003
DOI:10.1002/app.11978
Precipitation polymerization of methyl methacrylate (MMA) in tetrahydrofuran (THF) with compressed CO2 as an antisolvent was carried out at 335 K up to 8.5 MPa, and the decomposition rate of the initiator, 2,2′-azobisisobutyronitrile (AIBN), was studied with UV/vis. Gel permeation chromatography (GPC) and differential scanning calorimetry (DSC) were used to determine the average molecular weights and glass transition temperature (Tg), and scanning electron micrography (SEM) was used to observe the morphologies of the product. The results showed that the average molecular weights of the polymer vary considerably with the volume expansion of the solution induced by compressed CO2. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2427–2433, 2003
Co-reporter:Yuning Chang;Minying Liu;Yudong Wang;Qingxiang Zhao
Journal of Applied Polymer Science 2003 Volume 90(Issue 8) pp:2040-2044
Publication Date(Web):22 SEP 2003
DOI:10.1002/app.12731
PAA/nylon1212 blend was prepared using supercritical CO2 as substrate-swelling agent and monomer/initiator carrier. Both supercritical CO2/nylon1212 binary system and SC CO2/monomer/nylon1212 ternary system have been studied. Virgin nylon1212 and blends were characterized through differential scanning calorimetry (DSC), infrared spectroscopy (IR), and scanning electron microscopy (SEM). © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2040–2044, 2003
Co-reporter:Qianqian Xin, Jianwei Fu, Zhonghui Chen, Shujun Liu, Ya Yan, Jianan Zhang, Qun Xu
Journal of Environmental Chemical Engineering (September 2015) Volume 3(Issue 3) pp:1637-1647
Publication Date(Web):1 September 2015
DOI:10.1016/j.jece.2015.06.012
•Polypyrrole nanofibers as an adsorbent could be facilely synthesized.•The adsorbent showed excellent adsorption capacity of 169.55 mg/g for MO.•The adsorbent exhibited a selective adsorption behavior towards different organic dyes.•The pseudo-second-order model could be better to describe the adsorption of MO.•The MO adsorption onto polypyrrole nanofibers was endothermic and spontaneous.The polypyrrole (PPy) nanofibers were synthesized by an oxidative template assembly route and evaluated as an adsorbent for the removal of a typical anionic dye (methyl orange, MO) from aqueous solution. The as-synthesized PPy nanofibers were characterized by scanning electron microscopy (SEM), transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and N2 sorption. The effects of contact time, initial MO concentration, temperature, and initial solution pH on the adsorption of MO onto PPy nanofibers have been investigated. Experimental results showed that the PPy nanofibers possessed excellent adsorption capacity for MO (169.55 mg/g) at 25 °C. The pseudo-second-order model could fit to the experimental data better comparing with the pseudo-first-order kinetic adsorption model. And isotherm data fitted well to the Langmuir isotherm model. Thermodynamic study revealed that the adsorption process was endothermic and spontaneous in nature. In addition, the possible adsorption mechanism was proposed based on the experimental results. And the selective adsorption behaviors of the polypyrrole nanofibers towards different organic dyes were explored and the re-use of adsorbate was tested.Download high-res image (258KB)Download full-size image
Co-reporter:Tao Xu, Yun Wang, Xiaofang Zhou, Xiaoli Zheng, Qun Xu, Zhimin Chen, Yumei Ren, Bo Yan
Applied Surface Science (1 May 2017) Volume 403() pp:
Publication Date(Web):1 May 2017
DOI:10.1016/j.apsusc.2017.01.242
•In this study we have successfully exfoliated ultrathin WO3·H2O nanosheets from tunsten acid(H2WO4) with supercritical CO2 (SC CO2).•A novel type II 2D ultrathin TiO2/WO3·H2O heterostructures were fabricated with the assistance of SC CO2.•The formation of TiO2/WO3·H2O heterostructures is beneficial to effective separation of the electron-hole pairs.•The photocurrent response and MO degradation of TiO2/WO3·H2O heterostructures exhibit significantly improvement.The recombination of photo-induced charges is one of the main issues to limit the large-scale applications in photocatalysis and photoelectrocatalysis. To improve the charge separation, we fabricate a novel type II 2D ultrathin TiO2/WO3·H2O heterostructures with the assistance of supercritical CO2 (SC CO2) in this work. The as-fabricated heterostructures possess high photocatalytic activity for the degradation of methyl orange(MO) and high photocurrent response under simulated solar light (AM 1.5). For the TiO2/WO3·H2O heterostructures, the MO solution could be degraded by 95.5% in 150 min, and the photocurrent density reaches to 6.5 μA cm−2, exhibiting a significant enhancement compared with pure TiO2 and WO3·H2O nanosheets.2D heterostructures of TiO2/WO3·H2O nanosheets have been successfully fabricated with assistance of supercritical CO2 (SC CO2). The formation of heterostructures is beneficial to effective separation of the electron-hole pairs, thus resulting in enhanced photocatalytic activity toward the high photocurrent under simulated solar light irradiation.
Co-reporter:Xiaodan Xu, Lu Cai, Xiaoli Zheng and Qun Xu
Physical Chemistry Chemical Physics 2017 - vol. 19(Issue 24) pp:NaN16070-16070
Publication Date(Web):2017/05/31
DOI:10.1039/C7CP01277B
In this work we carried out molecular dynamics (MD) simulations to explore the mechanism of solvent-exfoliation and stabilization of graphene in the presence of (compressed) carbon dioxide (cpCO2), p-xylene and pyrene–polyethylene glycol (Py–PEG) polymers. We studied the role of each component in graphene exfoliation and stabilization by setting different experimental variables. The simulation results show that the cpCO2 molecules played a “wedge” role in the exfoliation process, firstly wedging into the interlayer, and then helping solvent molecules to insert into the interlayer. The solvent molecules between the graphene sheets are the main reasons that graphene exfoliation is achieved. And the Py–PEG polymer chains mainly act as stabilizers to prevent the exfoliated graphene sheets from restacking. This work provides detailed theoretical clues to better understand the mechanism of exfoliation and stabilization of graphene.
Co-reporter:Shoupei Wang, Jianan Zhang, Pei Shang, Yuanyuan Li, Zhimin Chen and Qun Xu
Chemical Communications 2014 - vol. 50(Issue 81) pp:NaN12094-12094
Publication Date(Web):2014/08/14
DOI:10.1039/C4CC04832F
N-doped carbon spheres with hierarchical micropore-nanosheet networks (HPSCSs) were facilely fabricated by a one-step carbonization and activation process of N containing polymer spheres by KOH. With the synergy effect of the multiple structures, HPSCSs exhibit a very high specific capacitance of 407.9 F g−1 at 1 mV s−1 (1.2 times higher than that of porous carbon spheres) and a robust cycling stability for supercapacitors.
Co-reporter:Yuhang Qi, Nan Wang, Qun Xu, Hongxiang Li, Pengshang Zhou, Xin Lu and Guoqiang Zhao
Chemical Communications 2015 - vol. 51(Issue 31) pp:NaN6729-6729
Publication Date(Web):2015/02/09
DOI:10.1039/C5CC00106D
We show that bulk MoS2 can be efficiently exfoliated into ultrathin nanosheets in supercritical CO2 with ethanol as cosolvent. Moreover, such tailored MoS2 nanostructures, when they are directly used as labels for bioimaging, show excellent imaging effects with strong fluorescence and nontoxicity.
Co-reporter:Jianwei Fu, Qun Xu, Jiafu Chen, Zhimin Chen, Xiaobin Huang and Xiaozhen Tang
Chemical Communications 2010 - vol. 46(Issue 35) pp:NaN6565-6565
Publication Date(Web):2010/08/16
DOI:10.1039/C0CC01185A
Uniform carbon spheres with hollow core and porous shell structures were controllably fabricated through carbonizing fine core/shell particles of polystyrene/cross-linked poly(cyclotriphosphazene-co-4,4′-sulfonyldiphenol), obtained by a simple template approach.
Co-reporter:Guiheng Xu, Qun Xu, Anjun Qin, Jingtao Cheng, Nan Wang, Junyi Wei, Chengliang Zhang, Zhenzhong Yang and Ben Zhong Tang
Journal of Materials Chemistry A 2013 - vol. 1(Issue 9) pp:NaN1721-1721
Publication Date(Web):2013/01/23
DOI:10.1039/C3TC00827D
We report a facile method for the fabrication of a nanocomposite that consists of AIE-active poly(aroxycarbonyltriazole) PACT polymer uniformly decorated on polydivinylbenzene (PDVB) nanotubes in the form of nanoparticles via the supercritical carbon dioxide (SC CO2)-assisted method. The on/off fluorescence switching for organic vapor and solvent was demonstrated with PACT/PDVB nanocomposite films.
Co-reporter:Shanshan Xu, Hongxia Yang, Kaixi Wang, Bo Wang and Qun Xu
Physical Chemistry Chemical Physics 2014 - vol. 16(Issue 16) pp:
Publication Date(Web):
DOI:10.1039/C3CP54957G
Co-reporter:Jiafu Chen, Zhanlin Lang, Qun Xu, Jianan Zhang, Jianwei Fu and Zhimin Chen
Physical Chemistry Chemical Physics 2013 - vol. 15(Issue 41) pp:NaN17792-17792
Publication Date(Web):2013/09/02
DOI:10.1039/C3CP52736K
A simple and efficient method to produce discrete, hierarchical porous carbon hemispheres (CHs) with high uniformity has been successfully developed by constructing nanoreactors and using low crosslinked poly(styrene-co-divinylbenzene) (P(St-co-DVB)) capsules as precursors. The samples are characterized by scanning and transmission electron microscopy, Fourier transform infrared and Raman spectroscopy, X-ray diffraction, and N2 adsorption and desorption. Considering their application, the cyclic voltammetry and electrochemical impedance spectroscopy characterization are tested. The experimental results show that the achievement of discrete and perfect carbon hemispheres is dependent on the proper amount of DVB in the P(St-co-DVB) capsules, which can contribute to the ideal thickness or mechanical strength of the shells. When the amount of DVB is 35 wt% in the precursors, a high Brunauer–Emmett–Teller surface area of 676 m2 g−1 can be obtained for the carbon hemispheres, and the extremely large pore volume of 2.63 cm3 g−1 can also be achieved at the same time. The electrochemical test shows the carbon hemispheres have a higher specific capacitance of ca. 83 F g−1 at 10 mV s−1, compared to other carbon materials. So this method supplies a platform to extend the fabrication field of carbon materials and supplies more chances for the application of carbon materials including carbon hemispheres that are important components and substrates for supercapacitors.
Co-reporter:Huanan Yu, Dongdong Xu and Qun Xu
Chemical Communications 2015 - vol. 51(Issue 67) pp:NaN13200-13200
Publication Date(Web):2015/07/10
DOI:10.1039/C5CC04009D
A hierarchical meso- and microporous metal–organic framework (MOF) was facilely fabricated in an ionic liquid (IL)/supercritical CO2 (SC CO2)/surfactant emulsion system. Notably, CO2 exerts a dual effect during the synthesis; that is, CO2 droplets act as a template for the cores of nanospheres while CO2-swollen micelles induce mesopores on nanospheres.
