Co-reporter:Linhong Xiao, Linli Xu, Yuying Yang, Sheng Zhang, Yong Huang, Christopher W. Bielawski, and Jianxin Geng
ACS Omega June 2017? Volume 2(Issue 6) pp:2665-2665
Publication Date(Web):June 15, 2017
DOI:10.1021/acsomega.7b00397
We report the preparation of polymer nanofibers with enhanced flame retardancy by coaxial electrospinning polyamide 66 (PA 66) and nanoscale graphene hybridized with red phosphorus (NG–RP). Transmission electron microscopy and energy-dispersive X-ray spectroscopy revealed that the nanofibers contained a NG–RP-based core surrounded by a PA 66 shell. The flame-retardant characteristics of the nanofibers were investigated by thermal gravimetric analysis, micro combustion calorimetry, and a series of vertical flame tests. The encapsulation of the NG–RP not only enhanced the flame-retardant characteristics of the nanofibers, but also improved their mechanical properties while maintaining the color and luster of the polymer, making the resultant nanofibers appropriate for use in a wide range of applications.Topics: Fibers; Fire-resistant materials; Materials processing; Mechanical properties; Polyamides; Polymer morphology; Thermal properties;
Co-reporter:Linli Xu, Linhong Xiao, Pan Jia, Karel Goossens, Peng Liu, Hui Li, Chungui Cheng, Yong Huang, Christopher W. Bielawski, and Jianxin Geng
ACS Applied Materials & Interfaces August 9, 2017 Volume 9(Issue 31) pp:26392-26392
Publication Date(Web):July 14, 2017
DOI:10.1021/acsami.7b06282
High-performance flame-retardant materials are urgently needed to address outstanding issues that pertain to safety. Traditional flame retardants are toxic to the environment and/or lack the physical properties required for use in many contemporary applications. Here, we show that isocyanate-based polyimide (PI) foam, a flammable material, can exhibit unusually superior flame retardancy as well as other excellent properties, such as being lightweight and displaying high mechanical strength, by incorporating red phosphorus (RP)-hybridized graphene. The covalent bonds formed between the graphene platelets and the PI matrix provide the resultant PI foam with a specific Young’s modulus (83 kNm kg–1) that is comparable to or even higher than those displayed by state-of-the-art foams, including silica aerogels, polystyrene foams, and polyurethane foams. In addition, even a low content of the RP-hybridized graphene (2.2 wt %) results in an exceptionally higher limiting oxygen index (39.4) than those of traditional flame-retardant polymer-based materials (typically 20–30). The resultant PI foam also exhibits thermal insulation properties that are similar to that of air. Moreover, the RP-hybridized graphene is prepared using a one-step ball milling process in 100% yield, and does not require solvent or produce waste. The preparation of the flame-retardant PI foams can be scaled as the starting materials are commercially available and the techniques employed are industrially compatible.Keywords: compressive property; fire retardant; graphene; polyimide foam; red phosphorus; thermal conductivity;
Co-reporter:M. Imran;M. Ikram;S. Dilpazir;M. Nafees;S. Ali;J. Geng
Applied Nanoscience 2017 Volume 7( Issue 8) pp:747-752
Publication Date(Web):16 October 2017
DOI:10.1007/s13204-017-0618-3
The article investigates the effects of NiO (p-type) and TiO2 (n-type) nanoparticles (NPs) on the performance of poly(3-hexylthiophene) (P3HT) and (phenyl-C61-butyric acid methylester) (PCBM) based devices with an inverse geometry. Various weight ratios of these nanoparticles were mixed in the polymer solution using 1,2-dichlorobenzene as solvent. An optimal amount of NPs-doped active layer exhibited higher power conversion efficiency (PCE) of 3.85% as compared to the reference cell, which exhibited an efficiency of 3.40% under white light illumination intensity of 100 mW/cm2. Enhanced PCE originates from increased film roughness and light harvesting due to increased absorption range upon mixing an optimal amount of NPs in the organic-based active layer. Further addition of NiO and TiO2 concentration relative to PCBM resulted in significant agglomeration of nanoparticles leading to degraded device parameters.
Co-reporter:Linhong Xiao, Jinhua Sun, Libing Liu, Rong Hu, Huan Lu, Chungui Cheng, Yong Huang, Shu WangJianxin Geng
ACS Applied Materials & Interfaces 2017 Volume 9(Issue 6) pp:
Publication Date(Web):January 23, 2017
DOI:10.1021/acsami.6b14473
Surface modification of graphene is extremely important for applications. Here, we report a grafting-through method for grafting water-soluble polythiophenes onto reduced graphene oxide (RGO) sheets. As a result of tailoring of the side chains of the polythiophenes, the modified RGO sheets, that is, RGO-g-P3TOPA and RGO-g-P3TOPS, are positively and negatively charged, respectively. The grafted water-soluble polythiophenes provide the modified RGO sheets with good dispersibility in water and high photothermal conversion efficiencies (ca. 88%). Notably, the positively charged RGO-g-P3TOPA exhibits unprecedentedly excellent photothermal bactericidal activity, because the electrostatic attractions between RGO-g-P3TOPA and Escherichia coli (E. coli) bind them together, facilitating direct heat conduction through their interfaces: the minimum concentration of RGO-g-P3TOPA that kills 100% of E. coli is 2.5 μg mL–1, which is only 1/16th of that required for RGO-g-P3TOPS to exhibit a similar bactericidal activity. The direct heat conduction mechanism is supported by zeta-potential measurements and photothermal heating tests, in which the achieved temperature of the RGO-g-P3TOPA suspension (2.5 μg mL–1, 32 °C) that kills 100% of E. coli is found to be much lower than the thermoablation threshold of bacteria. Therefore, this research demonstrates a novel and superior method that combines photothermal heating effect and electrostatic attractions to efficiently kill bacteria.Keywords: covalent functionalization; electrostatic attraction; graphene; photothermal killing of bacteria; water-soluble conjugated polymers;
Co-reporter:Hui Li;Xing Liu;Siqi Qi;Linli Xu;Dr. Guosheng Shi; Yihong Ding;Dr. Xiaoying Yan; Yong Huang; Jianxin Geng
Angewandte Chemie International Edition 2017 Volume 56(Issue 45) pp:14090-14095
Publication Date(Web):2017/11/06
DOI:10.1002/anie.201707823
AbstractZeolites with molecular dimension pores are widely used in petrochemical and fine-chemical industries. While traditional solvothermal syntheses suffer from environmental, safety, and efficiency issues, the newly developed solvent-free synthesis is limited by zeolite crystal aggregation. Herein, we report well-dispersed and faceted silicalite ZSM-5 zeolite crystals obtained using a solvent-free synthesis facilitated by graphene oxide (GO). The selective interactions between the GO sheets and different facets, which are confirmed by molecular dynamics simulations, result in oriented growth of the ZSM-5 crystals along the c-axis. More importantly, the incorporation of GO sheets into the ZSM-5 crystals leads to the formation of mesopores. Consequently, the faceted ZSM-5 crystals exhibit hierarchical pore structures. This synthetic method is superior to conventional approaches because of the features of the ZSM-5 zeolite.
Co-reporter:Yu Wu, Pan Jia, Linli Xu, Zhangyan Chen, Linhong Xiao, Jinhua Sun, Jun Zhang, Yong Huang, Christopher W. BielawskiJianxin Geng
ACS Applied Materials & Interfaces 2017 Volume 9(Issue 5) pp:
Publication Date(Web):January 17, 2017
DOI:10.1021/acsami.6b14895
Here, we describe an in situ approach for growing polyepoxides from the surfaces of graphene oxide (GO) using a surface-initiated polymerization reaction. The polymerization methodology is facile and general as a broad range of epoxides carrying various functional groups have been successfully polymerized by simply adding GO powders in the epoxide monomers. The resultant polyepoxide grafted GO are found to show enhanced dispersibility in various common solvents and to exhibit increased d-spacing between the basal planes. In particular, grafting poly(2,3-epoxy-1-propanol) (PEP) to GO results in a composite (i.e., GO-g-PEP) that is dispersible in water and miscible with polyether block amide, i.e., Pebax MH 1657. Preliminary studies have indicated the membranes prepared using Pebax/GO-g-PEP composites exhibit enhanced CO2 permeabilities and selectivities in comparison to H2, O2, or N2. The excellent performance in gas separation is attributed to the layered structure of the GO-g-PEP sheets with enlarged d-spacing and the functional groups present on the PEP chains grafted to the surfaces of GO sheets.Keywords: gas separation; graphene oxide; graphene oxide-initiated polymerization; membranes; polyepoxides;
Co-reporter:Mushtaque A. Memon, Wei Bai, Jinhua Sun, Muhammad Imran, Shah Nawaz Phulpoto, Shouke Yan, Yong Huang, and Jianxin Geng
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 18) pp:11711
Publication Date(Web):April 25, 2016
DOI:10.1021/acsami.6b01879
Fabrication of hybridized structures is an effective strategy to promote the performances of graphene-based composites for energy storage/conversion applications. In this work, macroporous structured graphene thin films (MGTFs) are fabricated on various substrates including flexible graphene papers (GPs) through an ice-crystal-induced phase separation process. The MGTFs prepared on GPs (MGTF@GPs) are recognized with remarkable features such as interconnected macroporous configuration, sufficient exfoliation of the conductive RGO sheets, and good mechanical flexibility. As such, the flexible MGTF@GPs are demonstrated as a versatile conductive platform for depositing conducting polymers (CPs), e.g., polyaniline (PAn), polypyrrole, and polythiophene, through in situ electropolymerization. The contents of the CPs in the composite films are readily controlled by varying the electropolymerization time. Notably, electrodeposition of PAn leads to the formation of nanostructures of PAn nanofibers on the walls of the macroporous structured RGO framework (PAn@MGTF@GPs): thereafter, the PAn@MGTF@GPs display a unique structural feature that combine the nanostructures of PAn nanofibers and the macroporous structures of RGO sheets. Being used as binder-free electrodes for flexible supercapacitors, the PAn@MGTF@GPs exhibit excellent electrochemical performance, in particular a high areal specific capacity (538 mF cm–2), high cycling stability, and remarkable capacitive stability to deformation, due to the unique electrode structures.Keywords: conducting polymers; electropolymerization; flexible supercapacitors; graphene papers; macroporous structured graphene thin films
Co-reporter:Yangbin Ding, Wei Bai, Jinhua Sun, Yu Wu, Mushtaque A. Memon, Chao Wang, Chengbin Liu, Yong Huang, and Jianxin Geng
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 19) pp:12165
Publication Date(Web):April 26, 2016
DOI:10.1021/acsami.6b02164
The morphologies of transition metal oxides have decisive impact on the performance of their applications. Here, we report a new and facile strategy for in situ preparation of anatase TiO2 nanospindles in three-dimensional reduced graphene oxide (RGO) structure (3D TiO2@RGO) using cellulose as both an intermediate agent eliminating the negative effect of graphene oxide (GO) on the growth of TiO2 crystals and as a structure-directing agent for the shape-controlled synthesis of TiO2 crystals. High-resolution transmission electron microscopy and X-ray diffractometer analysis indicated that the spindle shape of TiO2 crystals was formed through the restriction of the growth of high energy {010} facets due to preferential adsorption of cellulose on these facets. Because of the 3D structure of the composite, the large aspect ratio of the TiO2 nanospindles, and the exposed high-energy {010} facets of the TiO2 crystals, the 3D TiO2@RGO(Ce 1.7) exhibited excellent capacitive performance as an electrode material for supercapacitors, with a high specific capacitance (ca. 397 F g–1), a high energy density (55.7 Wh kg–1), and a high power density (1327 W kg–1) on the basis of the masses of RGO and TiO2. These levels of capacitive performance far exceed those of previously reported TiO2-based composites.Keywords: anatase TiO2; cellulose; shape-controlled synthesis; supercapacitors; three-dimensional graphene composites
Co-reporter:Wenpeng Hou, Ning-Jiu Zhao, Dongli Meng, Jing Tang, Yi Zeng, Yu Wu, Yangziwan Weng, Chungui Cheng, Xiulai Xu, Yi Li, Jian-Ping Zhang, Yong Huang, Christopher W. Bielawski, and Jianxin Geng
ACS Nano 2016 Volume 10(Issue 5) pp:5189
Publication Date(Web):April 16, 2016
DOI:10.1021/acsnano.6b00673
The installation of heterojunctions on the surfaces of carbon nanotubes (CNTs) is an effective method for promoting the charge separation processes needed for CNT-based electronics and optoelectronics applications. Conjugated polymers are proven state-of-the-art candidates for modifying the surfaces of CNTs. However, all previous attempts to incorporate conjugated polymers to CNTs resulted in unordered interfaces. Herein we show that well-defined chains of regioregular poly(3-hexylthiophene) (P3HT) were successfully grown from the surfaces of multiwalled CNTs (MWNTs) using surface-initiated Kumada catalyst-transfer polycondensation. The polymerization was found to proceed in a controlled manner as chains of tunable lengths were prepared through variation of the initial monomer-to-initiator ratio. Moreover, it was determined that large-diameter MWNTs afforded highly ordered P3HT aggregates, which exhibited a markedly bathochromically shifted optical absorption due to a high grafting density induced planarization of the polymer chains. Using ultrafast spectroscopy, the heterojunctions formed between the MWNTs and P3HT were shown to effectively overcome the binding energy of excitons, leading to photoinduced electron transfer from P3HT to MWNTs. Finally, when used as prototype devices, the individual MWNT-g-P3HT core–shell structures exhibited excellent photoresponses under a low illumination density.Keywords: carbon nanotubes; charge separation; photoresponse; poly(3-hexylthiophene); surface-initiated Kumada catalyst-transfer polycondensation
Co-reporter:Jinhua Sun;Mushtaque A. Memon;Wei Bai;Linhong Xiao;Bin Zhang;Yongdong Jin;Yong Huang
Advanced Functional Materials 2015 Volume 25( Issue 27) pp:4334-4343
Publication Date(Web):
DOI:10.1002/adfm.201501733
Graphene sheets have been demonstrated to be the building blocks for various assembly structures, which eventually determine the macroscopic properties of graphene materials. As a new assembly structure, transparent macroporous graphene thin films (MGTFs) are not readily prepared due to the restacking tendency of graphene sheets during processing. Here, an ice crystal-induced phase separation process is proposed for preparation of transparent MGTFs. The ice crystal-induced phase separation process exhibits several unique features, including efficient prevention of graphene oxide restacking, easy control on the transparency of the MGTFs, and wide applicability to substrates. It is shown that the MGTFs can be used as porous scaffold with high conductivity for electrochemical deposition of various semiconductors and rare metal nanoparticles such as CdSe, ZnO, and Pt, as well as successive deposition of different materials. Notably, the macroporous structures bestow the MGTFs and the nanoparticle-decorated MGTFs (i.e., Pt@MGTF and CdSe@MGTF) enhanced performance as electrode for oxygen reduction reaction and photoelectrochemical H2 generation.
Co-reporter:Linli Xu, Shidong Jiang, Baopeng Li, Wenpeng Hou, Guoxing Li, Mushtaque A. Memon, Yong Huang, and Jianxin Geng
Chemistry of Materials 2015 Volume 27(Issue 12) pp:4358
Publication Date(Web):June 1, 2015
DOI:10.1021/acs.chemmater.5b00981
Close-celled aromatic polyimide (PI)/graphene foams with low density and improved flexibility were fabricated by thermal foaming of poly(amic ester)/graphene oxide (PAE/GO) precursor powders. The PAE/GO precursor powders were prepared by grafting GO nanosheets with PAE chains, which led to efficient dispersion of the GO nanosheets in PAE matrix. Incorporation of GO resulted in an enhanced foaming capability of the precursor, i.e., enlarged cell size and decreased foam density. Notably, a decrease of 50% in the foam density was obtained via the addition of only 2 wt % GO in the precursor. In the foaming process, the GO nanosheets functioned as a versatile agent that not only provided heterogeneous nucleation sites but also produced gaseous molecules. By analyzing the foaming mechanism, the excellent features of GO in heat transfer, gas barrier, and strength reinforcement also facilitated to obtain large and uniform cells in the foams. In addition, the PI/graphene foams exhibited a prominent flexibility and enhanced flexural strength, as an elastic-to-nonelastic conversion of the initial stage of the compressive stress–strain curves was observed by increasing the content of graphene in the PI matrix and an increase of 22.5% in flexural strength was obtained by addition of 0.5 wt % GO in the precursor.
Co-reporter:Jinhua Sun, Linhong Xiao, Shidong Jiang, Guoxing Li, Yong Huang, and Jianxin Geng
Chemistry of Materials 2015 Volume 27(Issue 13) pp:4594
Publication Date(Web):June 16, 2015
DOI:10.1021/acs.chemmater.5b00885
For the first time, a composite of fluorine-doped SnO2 and reduced graphene oxide (F-SnO2@RGO) was synthesized using a cheap F-containing Sn source, Sn(BF4)2, through a hydrothermal process. X-ray photoelectron spectroscopy and X-ray diffraction results identified that F was doped in the unit cells of the SnO2 nanocrystals, instead of only on the surfaces of the nanoparticles. F doping of SnO2 led to more uniform and higher loading of the F-SnO2 nanoparticles on the surfaces of RGO sheets, as well as enhanced electron transportation and Li ion diffusion in the composite. As a result, the F-SnO2@RGO composite exhibited a remarkably high specific capacity (1277 mA h g–1 after 100 cycles), a long-term cycling stability, and excellent high-rate capacity at large charge/discharge current densities as anode material for lithium ion batteries. The outstanding performance of the F-SnO2@RGO composite electrode could be ascribed to the combined features of the composite electrode that dealt with both the electrode dynamics (enhanced electron transportation and Li ion diffusion due to F doping) and the electrode structure (uniform decoration of the F-SnO2 nanoparticles on the surfaces of RGO sheets and the three-dimensional porous structures of the F-SnO2@RGO composite).
Co-reporter:Baopeng Li, Wenpeng Hou, Jinhua Sun, Shidong Jiang, Linli Xu, Guoxing Li, Mushtaque A. Memon, Jianhua Cao, Yong Huang, Christopher W. Bielawski, and Jianxin Geng
Macromolecules 2015 Volume 48(Issue 4) pp:994-1001
Publication Date(Web):February 10, 2015
DOI:10.1021/ma5026237
Surface functionalization of graphene oxide (GO) sheets using polymers has emerged as a subject of enormous scientific interest due to the wide applications of GO in polymer composites and functional graphene-based materials. In this study, we grafted GO sheets with polystyrene (PS) and poly(styrene–isoprene) (PSI) using GO itself as a cationic initiator for homopolymerization of styrene and copolymerization of styrene and isoprene. The resultant GO-g-PS and GO-g-PSI composites displayed enhanced dispersibility in common organic solvents. With increasing the loading of isoprene in the copolymerization reaction, the glass transition temperature of the obtained products gradually decreased, combining the increased roughness of the GO-g-PSI sheets compared with the GO-g-PS sheets, which indicated the increased phase separation between the PS and PI segments in the PSI layer. Therefore, the packing of the GO-g-PS sheets, as well as the GO-g-PSI sheets, was not as compact as that of the GO sheets, leaving gradually increased quantity of pores in the films prepared with GO-g-PS and GO-g-PSI. Capitalizing on these tunable characters, hybridized membranes prepared by depositing GO sheets, GO-g-PS sheets, and the GO-g-PSI sheets obtained with gradually increased loading of isoprene in the copolymerization on the surfaces of commercially available polytetrafluoroethylene membranes displayed gradually increased gas permeability.
Co-reporter:Dongli Meng, Shaojun Yang, Dianming Sun, Yi Zeng, Jinhua Sun, Yi Li, Shouke Yan, Yong Huang, Christopher W. Bielawski and Jianxin Geng
Chemical Science 2014 vol. 5(Issue 8) pp:3130-3134
Publication Date(Web):14 Apr 2014
DOI:10.1039/C4SC00598H
A composite prepared by grafting a conjugated polymer, poly(3-hexylthiophene) (P3HT), to the surface of graphene oxide was shown to result in a dual-fluorescent material with tunable photoluminescent properties. Capitalizing on these unique features, a new class of graphene-based sensors that enables the ratiometric fluorescence detection of amine-based pollutants was developed. Moreover, through a detailed spectroscopic study, the origin of the optical properties of the aforementioned composite was studied and was found to be due to electronic decoupling of the conjugated polymer from the GO. The methodology described herein effectively overcomes a long-standing challenge that has prevented graphene based composites from finding utility in sensing and related applications.
Co-reporter:Jamil Memon, Jinhua Sun, Dongli Meng, Wenzhu Ouyang, Mushtaque A. Memon, Yong Huang, Shouke Yan and Jianxin Geng
Journal of Materials Chemistry A 2014 vol. 2(Issue 14) pp:5060-5067
Publication Date(Web):15 Jan 2014
DOI:10.1039/C3TA14613H
Graphene oxide (GO) as a template for the morphology controllable synthesis of inorganic particles has recently attracted enormous attention. In this study, we report the synthesis of graphene/Ni–Al layered double hydroxide (LDH) nanowires by using GO and adjusting the loading of urea in hydrothermal reactions. Transmission electron microscopy observation demonstrates that the graphene/Ni–Al LDH nanowires are composed of nano-sized Ni–Al LDH sheets. This finding demonstrates a new assembly form of LDH materials. Symmetric supercapacitors have been prepared by using the graphene/Ni–Al LDH nanowires as an electrode material. Compared to other Ni–Al LDH materials, the graphene/Ni–Al LDH nanowires exhibit much better performance as an electrode material for supercapacitors, due to the preferential conductive behaviour of the nanowire structures and the conductive networks formed by the nanowires in the corresponding electrodes.
Co-reporter:Shaojun Yang, Dongli Meng, Jinhua Sun, Yan Huang, Yong Huang, and Jianxin Geng
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 10) pp:7686
Publication Date(Web):April 15, 2014
DOI:10.1021/am500973m
In this study, we prepared electrochemically active films of poly(3-hexylthiophene) grafted single-walled carbon nanotubes (SWNT-g-P3HT) by using a modified vacuum-assisted deposition approach, in which a SWNT-g-P3HT composite layer of various thicknesses was deposited on the top of a thin SWNT layer. Measurement of the optical and electrical properties of the SWNT-g-P3HT composite films demonstrated that the thickness of the SWNT-g-P3HT composite films was controllable. The data of transmission electron microscope observation and Raman spectroscopy indicated that the covalent grafting of P3HT onto the surfaces of SWNTs resulted in intimate and stable connectivity between the two components in the SWNT-g-P3HT composite. Capitalizing on these unique features, we successfully developed a new class of electrochemical sensors that used the SWNT-g-P3HT composite films deposited on an indium–tin oxide substrate as an electrochemical electrode for detection of metal ions. Significantly, such a SWNT-g-P3HT composite electrode showed advantages in selective, quantitative, and more sensitive detection of Ag+ ions.Keywords: composites; detection; films; ions; P3HT; SWNTs;
Co-reporter:Dongli Meng, Shaojun Yang, Liang Guo, Guoxing Li, Jiechao Ge, Yong Huang, Christopher W. Bielawski and Jianxin Geng
Chemical Communications 2014 vol. 50(Issue 92) pp:14345-14348
Publication Date(Web):24 Sep 2014
DOI:10.1039/C4CC06849A
Composites prepared by grafting poly(3-hexylthiophene) (P3HT) onto the surfaces of reduced graphene oxide (RGO) (RGO-g-P3HT) exhibit an enhanced photothermal effect due to photoinduced energy transfer from P3HT to RGO. A remote photo-controlled electrical switch was prepared using RGO-g-P3HT as a photothermal layer.
Co-reporter:Shaojun Yang, Dongli Meng, Jinhua Sun, Wenpeng Hou, Yangbin Ding, Shidong Jiang, Yan Huang, Yong Huang and Jianxin Geng
RSC Advances 2014 vol. 4(Issue 48) pp:25051-25056
Publication Date(Web):25 Apr 2014
DOI:10.1039/C4RA02228A
In this study, multi-walled carbon nanotubes (MWNTs) were covalently modified by grafting poly(3-hexylthiophene) (P3HT) on to their surfaces. The modified MWNTs (MWNT-g-P3HT) showed enhanced dispersibility in common solvents, such as THF. Due to the intimate interaction between the P3HT and MWNTs, the MWNT-g-P3HT showed improved miscibility with P3HT, and the composite of the MWNT-g-P3HT and P3HT (MWNT-g-P3HT@P3HT) was likely to form continuous films. Notably, the MWNT-g-P3HT@P3HT composite films demonstrated an enhanced electrochemical response for the quantitative detection of Hg2+ ions, due to the synergistic effect of the electrocatalytic properties from the MWNTs and P3HT.
Co-reporter:Junfei Liang, Zhi Cai, Lidong Li, Lin Guo and Jianxin Geng
RSC Advances 2014 vol. 4(Issue 10) pp:4843-4847
Publication Date(Web):09 Dec 2013
DOI:10.1039/C3RA45147J
Amine-functionalized graphene aerogel was prepared through gelation and in situ reduction of GO by using polyethylenimine, and subsequent freeze-drying of the resultant graphene hydrogel. Having a large specific surface area, continuous pore structures, and active chemical adsorbing sites, the graphene aerogel exhibited better properties in adsorbing formaldehyde.
Co-reporter:Chao Wang;Dongli Meng;Jinhua Sun;Jamil Memon;Yong Huang
Advanced Materials Interfaces 2014 Volume 1( Issue 4) pp:
Publication Date(Web):
DOI:10.1002/admi.201300150
Reduced graphene oxide (RGO) wrapped titanium dioxide nanocrystals (TiO2 NCs@RGO) with oxygen vacancies (Vo) and Ti3+ defects have been synthesized by electrostatically wrapping GO around TiO2 NCs followed by thermal annealing at 400 °C. Transmission electron microscope observations have shown that TiO2 NCs@RGO has a unique crystalline core/crystalline shell structure, which is different from the original amorphous TiO2 covered TiO2 NCs. Raman spectroscopy, X-ray photoelectron spectroscopy, and electron paramagnetic resonance have demonstrated that Vo-Ti3+ species are more readily formed in TiO2 NCs@RGO than in TiO2 NCs. As a result, TiO2 NCs@RGO exhibits enhanced optical absorption in a wide wavelength range from visible light to near IR and red-shifted absorption edge. In the photocatalytic degradation reaction of methyl orange, the photodegradation rate constant for TiO2 NCs@RGO is 2.4 times higher than that of TiO2 NCs. The enhanced photocatalytic performance can be attributed to the improved charge separation at the interface of TiO2 NCs and RGO layer and the enhanced optical absorption in visible light region due to the donor levels of the defects such as Vo-Ti3+ species. This work establishes a new method for preparing Vo defect contained TiO2 catalysts.
Co-reporter:Jinhua Sun, Linhong Xiao, Dongli Meng, Jianxin Geng and Yong Huang
Chemical Communications 2013 vol. 49(Issue 49) pp:5538-5540
Publication Date(Web):03 Apr 2013
DOI:10.1039/C3CC40563J
Composite films of chemically converted graphene (CCG) and water-soluble polythiophenes (P3TOPS and P3TOPA) were prepared by a LBL method using a suspension of negatively charged CCG–P3TOPS sheets and a solution of positively charged P3TOPA. The composite films show enhanced photoresponse due to photoinduced electron transfer from the polythiophenes to CCG.
Co-reporter:Wenzhu Ouyang, Jinhua Sun, Jamil Memon, Chao Wang, Jianxin Geng, Yong Huang
Carbon 2013 Volume 62() pp:501-509
Publication Date(Web):October 2013
DOI:10.1016/j.carbon.2013.06.049
Controlling the assembled structures of graphene has recently attracted enormous attention due to intriguing properties of the resultant structures. In this study, three-dimensional (3D) porous structures of reduced graphene oxide (RGO) with various ratios of RGO to cellulose have been fabricated by a scalable, but simple and efficient, approach that consists of ball milling assisted chemical reduction of GO, template shaping, coagulating, and lyophilization. The efficient mechanical shearing of ball milling and the hydrogen bond interactions between RGO and cellulose molecules contribute to the formation of a homogeneous RGO/cellulose hydrogel, improved thermal stability of the resultant composites, and enhanced crystallinity of the cellulose in the composites. The coagulation effect of cellulose maintains the RGO sheets in the 3D structures of cellulose; on the other hand, the RGO sheets facilitate the preservation of the 3D structures during freeze-drying, leading to the formation of 3D porous structures of RGO/cellulose composites. Benefiting from the continuous RGO network in the composites, the 3D porous structures of RGO(70)/cellulose(100) (GO:cellulose = 70:100 in weight) show an electrical conductivity of 15.28 S m−1. Moreover, the 3D porous structures show potential application in supercapacitors due to the fact that they provide high specific surface area and fast charge propagation.
Co-reporter:Jinhua Sun;Guangfeng Wu;Jianxin Geng
Polymer Journal 2013 45(8) pp:813-818
Publication Date(Web):2012-12-19
DOI:10.1038/pj.2012.224
Polymer films with holes or fractal-like structures whose size is on the micron scale are of great interest. In this study, fractal-like structures of insoluble polythiophene were prepared via CS2 vapor annealing of solid thermocleavable polythiophene films in the presence of high humidity and subsequent thermal curing. Atomic force microscope and transmission electron microscopy observations demonstrate that holes form during the initial stage of solvent vapor annealing (SVA), further developing into fractal-like structures with the coalescence of the individual holes. Meanwhile, the crystallinity of the films can also be improved. A mechanism that involves solvent-covered water droplets has been proposed to explain the formation of the holes and the fractal-like structures. This is the first report of the formation of holes and fractal-like structures from solid films of conjugated polymers via SVA. The fractal-like structures can be preserved during the conversion from thermocleavable polythiophene to insoluble polythiophene by thermal curing.
Co-reporter:Dongli Meng, Jinhua Sun, Shidong Jiang, Yi Zeng, Yi Li, Shouke Yan, Jianxin Geng and Yong Huang
Journal of Materials Chemistry A 2012 vol. 22(Issue 40) pp:21583-21591
Publication Date(Web):29 Aug 2012
DOI:10.1039/C2JM35317B
In this study, we have grafted poly(3-hexylthiophene) (P3HT) brushes on GO sheets via a silylation reaction of the surfaces of GO sheets and a succeeding “click” reaction (GO(C)/P3HT composite). Compared with pure P3HT and the blend of P3HT and GO, the GO(C)/P3HT composite shows a red-shifted optical absorption maximum because of increased conjugation length of the grafted P3HT, which might be due to the crowding of the P3HT chains grafted on GO sheets. For comparison, P3HT chains were also grafted on GO sheets via the amidation reaction of the carboxylic acid groups (GO(A)/P3HT composite). However, the GO(A)/P3HT composite doesn't show a red shift in the UV-visible spectrum. The overall fluorescence quenching in the GO(C)/P3HT composite includes both dynamic quenching and forming a non-fluorescent ground-state complex. Additionally, thermogravimetric analysis and X-ray photoelectron spectroscopy results demonstrate that the efficiency of grafting P3HT on GO sheets via the “click” reaction approach is higher than via the amidation reaction approach. Atomic force microscopy and transmission electron microscopy observations show that the GO(C)/P3HT composite sheets are much thicker than the GO(A)/P3HT composite sheets, due to the higher grafting efficiency of the “click” reaction approach. Therefore, this work opens a novel avenue to tuning the optical properties of conjugated polymers via surface grafting chemistry.
Co-reporter:Jinhua Sun, Dongli Meng, Shidong Jiang, Guangfeng Wu, Shouke Yan, Jianxin Geng and Yong Huang
Journal of Materials Chemistry A 2012 vol. 22(Issue 36) pp:18879-18886
Publication Date(Web):26 Jul 2012
DOI:10.1039/C2JM33900E
In this study, multiple-bilayered reduced graphene oxide (RGO)–porphyrin films have been prepared via fabrication of multiple-bilayered graphene oxide (GO)–porphyrin films and succeeding vapour reduction of the GO–porphyrin films. The layer-by-layer method, which takes advantage of the π–π and electrostatic interactions between GO sheets and porphyrin molecules, has been used to prepare the multiple-bilayered GO–porphyrin films. Three porphyrins have been used: positively charged, neutral, and negatively charged porphyrins. The changes of the transparency of the films with the number of the bilayers show that the multiple-bilayered structures of the films formed with the positively charged porphyrin is better controlled as compared to the films formed with the neutral and the negatively charged porphyrins. UV-visible and photoluminescence (PL) spectra show that GO quenches the PL of porphyrins in the multiple-bilayered GO–porphyrin films, indicating photoinduced electron transfer from porphyrins to GO; meanwhile, photoinduced electron transfer also occurs from porphyrins to RGO in the multiple-bilayered RGO–porphyrin films. Photocurrent response has been measured using the multiple-bilayered RGO–porphyrin films prepared on indium-tin oxide glass substrates as working electrodes in photoelectrochemical cells. The multiple-bilayered RGO–porphyrin films show enhanced photocurrent with respect to that of the porphyrins alone due to the fact that RGO sheets function as electron acceptors and form transportation paths for electrons in the multiple-bilayered films.
Co-reporter:Dongli Meng, Jinhua Sun, Shidong Jiang, Yi Zeng, Yi Li, Shouke Yan, Jianxin Geng and Yong Huang
Journal of Materials Chemistry A 2012 - vol. 22(Issue 40) pp:NaN21591-21591
Publication Date(Web):2012/08/29
DOI:10.1039/C2JM35317B
In this study, we have grafted poly(3-hexylthiophene) (P3HT) brushes on GO sheets via a silylation reaction of the surfaces of GO sheets and a succeeding “click” reaction (GO(C)/P3HT composite). Compared with pure P3HT and the blend of P3HT and GO, the GO(C)/P3HT composite shows a red-shifted optical absorption maximum because of increased conjugation length of the grafted P3HT, which might be due to the crowding of the P3HT chains grafted on GO sheets. For comparison, P3HT chains were also grafted on GO sheets via the amidation reaction of the carboxylic acid groups (GO(A)/P3HT composite). However, the GO(A)/P3HT composite doesn't show a red shift in the UV-visible spectrum. The overall fluorescence quenching in the GO(C)/P3HT composite includes both dynamic quenching and forming a non-fluorescent ground-state complex. Additionally, thermogravimetric analysis and X-ray photoelectron spectroscopy results demonstrate that the efficiency of grafting P3HT on GO sheets via the “click” reaction approach is higher than via the amidation reaction approach. Atomic force microscopy and transmission electron microscopy observations show that the GO(C)/P3HT composite sheets are much thicker than the GO(A)/P3HT composite sheets, due to the higher grafting efficiency of the “click” reaction approach. Therefore, this work opens a novel avenue to tuning the optical properties of conjugated polymers via surface grafting chemistry.
Co-reporter:Dongli Meng, Shaojun Yang, Liang Guo, Guoxing Li, Jiechao Ge, Yong Huang, Christopher W. Bielawski and Jianxin Geng
Chemical Communications 2014 - vol. 50(Issue 92) pp:NaN14348-14348
Publication Date(Web):2014/09/24
DOI:10.1039/C4CC06849A
Composites prepared by grafting poly(3-hexylthiophene) (P3HT) onto the surfaces of reduced graphene oxide (RGO) (RGO-g-P3HT) exhibit an enhanced photothermal effect due to photoinduced energy transfer from P3HT to RGO. A remote photo-controlled electrical switch was prepared using RGO-g-P3HT as a photothermal layer.
Co-reporter:Jinhua Sun, Linhong Xiao, Dongli Meng, Jianxin Geng and Yong Huang
Chemical Communications 2013 - vol. 49(Issue 49) pp:NaN5540-5540
Publication Date(Web):2013/04/03
DOI:10.1039/C3CC40563J
Composite films of chemically converted graphene (CCG) and water-soluble polythiophenes (P3TOPS and P3TOPA) were prepared by a LBL method using a suspension of negatively charged CCG–P3TOPS sheets and a solution of positively charged P3TOPA. The composite films show enhanced photoresponse due to photoinduced electron transfer from the polythiophenes to CCG.
Co-reporter:Jinhua Sun, Dongli Meng, Shidong Jiang, Guangfeng Wu, Shouke Yan, Jianxin Geng and Yong Huang
Journal of Materials Chemistry A 2012 - vol. 22(Issue 36) pp:NaN18886-18886
Publication Date(Web):2012/07/26
DOI:10.1039/C2JM33900E
In this study, multiple-bilayered reduced graphene oxide (RGO)–porphyrin films have been prepared via fabrication of multiple-bilayered graphene oxide (GO)–porphyrin films and succeeding vapour reduction of the GO–porphyrin films. The layer-by-layer method, which takes advantage of the π–π and electrostatic interactions between GO sheets and porphyrin molecules, has been used to prepare the multiple-bilayered GO–porphyrin films. Three porphyrins have been used: positively charged, neutral, and negatively charged porphyrins. The changes of the transparency of the films with the number of the bilayers show that the multiple-bilayered structures of the films formed with the positively charged porphyrin is better controlled as compared to the films formed with the neutral and the negatively charged porphyrins. UV-visible and photoluminescence (PL) spectra show that GO quenches the PL of porphyrins in the multiple-bilayered GO–porphyrin films, indicating photoinduced electron transfer from porphyrins to GO; meanwhile, photoinduced electron transfer also occurs from porphyrins to RGO in the multiple-bilayered RGO–porphyrin films. Photocurrent response has been measured using the multiple-bilayered RGO–porphyrin films prepared on indium-tin oxide glass substrates as working electrodes in photoelectrochemical cells. The multiple-bilayered RGO–porphyrin films show enhanced photocurrent with respect to that of the porphyrins alone due to the fact that RGO sheets function as electron acceptors and form transportation paths for electrons in the multiple-bilayered films.
Co-reporter:Jamil Memon, Jinhua Sun, Dongli Meng, Wenzhu Ouyang, Mushtaque A. Memon, Yong Huang, Shouke Yan and Jianxin Geng
Journal of Materials Chemistry A 2014 - vol. 2(Issue 14) pp:NaN5067-5067
Publication Date(Web):2014/01/15
DOI:10.1039/C3TA14613H
Graphene oxide (GO) as a template for the morphology controllable synthesis of inorganic particles has recently attracted enormous attention. In this study, we report the synthesis of graphene/Ni–Al layered double hydroxide (LDH) nanowires by using GO and adjusting the loading of urea in hydrothermal reactions. Transmission electron microscopy observation demonstrates that the graphene/Ni–Al LDH nanowires are composed of nano-sized Ni–Al LDH sheets. This finding demonstrates a new assembly form of LDH materials. Symmetric supercapacitors have been prepared by using the graphene/Ni–Al LDH nanowires as an electrode material. Compared to other Ni–Al LDH materials, the graphene/Ni–Al LDH nanowires exhibit much better performance as an electrode material for supercapacitors, due to the preferential conductive behaviour of the nanowire structures and the conductive networks formed by the nanowires in the corresponding electrodes.
Co-reporter:Dongli Meng, Shaojun Yang, Dianming Sun, Yi Zeng, Jinhua Sun, Yi Li, Shouke Yan, Yong Huang, Christopher W. Bielawski and Jianxin Geng
Chemical Science (2010-Present) 2014 - vol. 5(Issue 8) pp:NaN3134-3134
Publication Date(Web):2014/04/14
DOI:10.1039/C4SC00598H
A composite prepared by grafting a conjugated polymer, poly(3-hexylthiophene) (P3HT), to the surface of graphene oxide was shown to result in a dual-fluorescent material with tunable photoluminescent properties. Capitalizing on these unique features, a new class of graphene-based sensors that enables the ratiometric fluorescence detection of amine-based pollutants was developed. Moreover, through a detailed spectroscopic study, the origin of the optical properties of the aforementioned composite was studied and was found to be due to electronic decoupling of the conjugated polymer from the GO. The methodology described herein effectively overcomes a long-standing challenge that has prevented graphene based composites from finding utility in sensing and related applications.
![Poly[(1,3-dihydro-1,3-dioxo-2H-isoindole-2,5-diyl)carbonyl(1,3-dihydro-1,3-dioxo-2H-isoindole-5,2-diyl)-1,4-phenyleneoxy-1,4-phenylene]](http://img.cochemist.com/ccimg/25000/24991-11-5.png)
![Poly[(1,3-dihydro-1,3-dioxo-2H-isoindole-2,5-diyl)carbonyl(1,3-dihydro-1,3-dioxo-2H-isoindole-5,2-diyl)-1,4-phenyleneoxy-1,4-phenylene]](http://img.cochemist.com/ccimg/25000/24991-11-5_b.png)
