Co-reporter:Ping Li;Jing Li;Zhe Zhao;Zhengsong Fang;Meijia Yang;Zhongke Yuan;You Zhang;Qiang Zhang;Wei Hong;Dingshan Yu
Advanced Science 2017 Volume 4(Issue 8) pp:
Publication Date(Web):2017/08/01
DOI:10.1002/advs.201700003
Herein, a general strategy is proposed to boost the energy storage capability of pseudocapacitive materials (i.e., MnO2) to their theoretical limits in unconventional 1D fiber configuration by rationally designing bicontinuous porous Ni skeleton@metal wire “sheath–core” metallic scaffold as a versatile host. As a proof of concept, the 1D metallic scaffold supported-MnO2 fiber electrode is demonstrated. The proposed “sheath” design not only affords large electrode surface area with ordered macropores for large electrolyte-ion accessibility and high electroactive material loading, but also renders interconnected porous metallic skeleton for efficient electronic and ionic transport, while the metallic “core” functions as an extra current collector to promote long-distance electron transport and electron collection. Benefiting from all these merits, the optimized fiber electrode yields unprecedented specific areal capacitance of 1303.6 mF cm−2 (1278 F g−1 based on MnO2, approaching the theoretical value of 1370 F g−1) in liquid KOH and 847.22 mF cm−2 in polyvinyl alcohol (PVA)/KOH gel electrolyte, 2–350 times of previously reported fiber electrodes. The solid-state fiber micro-pseudocapacitors simultaneously achieve remarkable areal energy and power densities of 18.83 µWh cm−2 and 16.33 mW cm−2, greatly exceeding the existing symmetric fiber supercapacitors, together with long cycle life and high rate capability.
Co-reporter:Jing Liu;Minfeng Li;Yuzhao Yang;Lirong Xu;Jingjing Lin;Wei Hong
Advanced Functional Materials 2017 Volume 27(Issue 33) pp:
Publication Date(Web):2017/09/01
DOI:10.1002/adfm.201701674
Current fabrication methods for metal interconnects and contacts are generally based on conventional photoresist fabrication procedures that require expensive equipment and multiple material/time-consuming steps. In this work, a photopatternable polyimide is synthesized via the copolymerization of a functional diamine monomer with a 1,4-dihydropyridine side-chain which can decompose under UV irradiation into a pyridine group—a promising ligand for palladium ions. After the absorption of palladium ions, the electroless copper plating is carried out to form metal patterns of copper. Copper patterns with smooth boundaries are confirmed by scanning electron microscope and atomic force microscope. Robust interfacial bonding between the copper and the polyimide film is evidenced by Scotch tape adhesion tests. The photopatternable polyimide has the advantages of low Pd consumption, easy operation without expansive equipment. The linear thermal expansion coefficient of the photopatternable polyimide remains close to the one of copper wire, demonstrating the adaptability of the photopatternable polyimide for integrated circuit application. This work presents the approach of (i) the synthesis of a novel photopatternable polyimide and (ii) its application for making flexible conductive metal structures and patterned metal interconnects, which can be expected to have tremendous potential in the field of flexible electronics.
Co-reporter:Lu Sun;Meijia Yang;Jianfeng Huang;Dingshan Yu;Wei Hong
Advanced Functional Materials 2016 Volume 26( Issue 27) pp:4943-4950
Publication Date(Web):
DOI:10.1002/adfm.201600894
Graphitic carbon nitride (g-C3N4) has attracted tremendous attention in photocatalysis due to its extraordinary features, such as good thermal and chemical stability, metal-free composition, and easy preparation. However, the photocatalytic performance of g-C3N4 is still restricted by the limited surface area, inefficient visible light absorption, and high recombination rate of photoinduced charge carriers. Herein, a facile synthesis to produce freestanding g-C3N4 photonic crystals (PCs) by crack-free, highly ordered colloid crystals templating is reported. The PC structure succeeded from the silica opals induces bicontinuous framework, stronger optical absorption, and increase in the lifetime of photoexcited charge carriers compared to that of the bulk g-C3N4, while the chemical structure remains similar to that of the bulk g-C3N4. As such, the g-C3N4 PCs have a much higher photodegradation kinetic of methyl orange and photocatalytic hydrogen production rate which is nearly nine times the rate of bulk g-C3N4.
Co-reporter:Xiao-Feng Lin, Zi-Yan Zhang, Zhong-Ke Yuan, Jing Li, Xiao-Fen Xiao, Wei Hong, Xu-Dong Chen, Ding-Shan Yu
Chinese Chemical Letters 2016 Volume 27(Issue 8) pp:1259-1270
Publication Date(Web):August 2016
DOI:10.1016/j.cclet.2016.06.041
Due to the remarkable electronic, optical, thermal, and mechanical properties, graphene-based materials have shown great potential in a wide range of technique applications. Particularly, the high transparency, conductivity, flexibility, and abundance make graphene materials highly attractive for polymer solar cells (PSCs). Graphene-based materials have been regarded as one promising candidate used in various parts in PSCs not only as electrodes, but also as interfacial layers and active layers with an aim to boost the power conversion efficiency of the devices. In this review, we summarize the recent progress about the design and synthesis of graphene-based materials for efficient PSCs along with the related challenges and future perspectives.Graphene-based materials can be employed in various parts of polymer solar cells with extraordinary performance.
Co-reporter:Xiaofeng Lin, Yuzhao Yang, Li Nian, Hua Su, Jiemei Ou, Zhongke Yuan, Fangyan Xie, Wei Hong, Dingshan Yu, Mingqiu Zhang, Yuguang Ma, Xudong Chen
Nano Energy 2016 Volume 26() pp:216-223
Publication Date(Web):August 2016
DOI:10.1016/j.nanoen.2016.05.011
•Reported C-dots with amino groups as an interfacial modification layer for the first time.•The C-dots modification can result in decreased work function and smoothed surface of the metal oxides and thus enhance charge extraction efficiency for the cathode.•The luminescent down-shifting effect of C-dots can increases the utilization of near ultraviolet and blue-violet portions of sunlight.•The optimized device based on PTB7-Th:PC71BM achieves a maximum PCE of up to 10.24%, outperforming previously reported PSCs using carbon nano-materials as additives so far.Herein, we have demonstrated that rationally-designed carbon dots (C-dots) with amino groups, for the first time, were used as an efficient interfacial modification layer on the ZnO or AZO interlayers, greatly improving the device performance. The C-dots modifying showed decreased work function and smoothed surface of metal oxides, facilitating the enhancement of charge extraction efficiency and the decrease of recombination losses for the cathode. More importantly, the C-dots showed the luminescent down-shifting effect, beneficial for the increase of the light conversion for near ultraviolet and blue-violet portions of sunlight. As a result, by incorporating ZnO/C-dots as the interlayers, our designed inverted polymer solar cells with PTB7:PC71BM as the active layer obtained over 20% enhancement compared with the devices with pure ZnO (from 7.41% to 9.01%). Notably, a maximum PCE of up to 10.24% was achieved with the AZO/C-dots as the interlayers and PTB7-Th:PC71BM instead of PTB7:PC71BM as the active layer, and this efficiency outperforms all previously reported PSCs using carbon materials as additives in the active layer or the interface materials. Our PCE value is also higher than those of many previously reported bulk-heterojunction (BHJ) solar cells using the organic polymer modifier.
Co-reporter:Wei Hong, Yu Zhang, Lin Gan, Xudong Chen and Mingqiu Zhang
Journal of Materials Chemistry A 2015 vol. 3(Issue 24) pp:6185-6191
Publication Date(Web):14 May 2015
DOI:10.1039/C5TC00464K
Ordered arrays of Ag-capped colloidal crystals were fabricated and modified with conjugated polymers to evaluate the excitation and emission fluorescence enhancement due to localized surface plasmon resonance (LSPR). The maximum enhancement accrued on the maximum overlap between the excitation wavelength and LSPRs of the substrates. The observed fluorescence enhancement and lifetime measurement showed that the large enhancement came from a combination of greatly enhanced excitation and an increased radiative decay rate, leading to an associated enhancement of the quantum efficiency. Thus, such Ag nanostructured arrays fabricated by colloidal lithograph show great potential for biosensing and photovoltaic applications, and the excitation wavelength–LSPR-based fluorescence enhancement proves useful for understanding and optimizing metal-enhanced fluorescence.
Co-reporter:Yuzhao Yang, Jian Qing, Jiemei Ou, Xiaofeng Lin, Zhongke Yuan, Dingshan Yu, Xiang Zhou, Xudong Chen
Solar Energy 2015 Volume 122() pp:231-238
Publication Date(Web):December 2015
DOI:10.1016/j.solener.2015.08.016
•The location effects of nanowires on the performance of PSCs were studied.•Three kinds of plasmonic structures were designed to investigate location effects.•Steady state PL and TRPL were used to study the effects of pre-designed structures.•The optimized pre-designed plasmonic inverted PSC showed the PCE up to 4.05%.Plasmonics can improve the performance of polymer solar cells (PSCs) by localizing and concentrating light, and the location of the plasmonic metallic nanostructure in devices plays an important role in how to design high-performance plasmonic solar cells. Here, by varying the location of silver nanowires (Ag NWs) within the device architecture (at the interface between indium–tin–oxide and cathode buffer layer, cathode buffer layer and active layer, active layer and anode buffer layer, respectively), a systematic study on plasmonic effect on the properties of photovoltaic material was presented. The density of photogenerated excitons, the electron delocalization and the effective conjugation length of the photovoltaic material in our pre-designed plasmonic structures were increased, and the enhancements of plasmonic effects were effective in a broad spectral range. When the pre-designed plasmonic structures were incorporated into the inverted PSCs, short circuit current density (Jsc) for all the investigated structures showed increase. The optimal inverted device performance was achieved when the Ag NWs were located at the interface of indium–tin–oxide and cathode buffer layer. The power conversion efficiency of the optimized plasmonic inverted device reached 4.05% under AM1.5 illumination (100 mW/cm2), which was due to the enhancement of Jsc without reducing the open-circuit voltage and FF of the plasmonic inverted PSCs by introducing Ag NWs.
Co-reporter:Yu Zhang, Wei Hong, Minfeng Li, Zhe Zhao, Lin Gan, Jiemei Ou, Xudong Chen, Mingqiu Zhang
Journal of Physics and Chemistry of Solids 2015 Volume 85() pp:75-80
Publication Date(Web):October 2015
DOI:10.1016/j.jpcs.2015.05.003
•We study the metal surface plasmon-enhanced emission of conjugated polymer (poly[2,5-bis(3′,7′-dimethyloctyloxy)-1,4-phenylenevinylene], BDMO-PPV) in the process that silver metal substrates changed from isolated nano-particles to continuous metal film•The photoluminescence (PL) enhancement was mainly raised from coupling of BDMO-PPV excitons with localized surface plasmon (LSP) of Ag nano-particles when the thickness of deposited Ag film was smaller than 15 nm.•However, surface plasmon polaritons (SPPs) dominated the PL enhancement when the thickness of deposied Ag film reached 20 nm or thicker.Herein we report a symmetric study of metal surface plasmon-enhanced emission of conjugated polymer (poly[2,5-bis(3′,7′-dimethyloctyloxy)-1,4-phenylenevinylene], BDMO-PPV) in the process that silver metal substrates changed from isolated nano-particles to continuous metal film. It was found that photoluminescence (PL) enhancement was mainly raised from coupling of BDMO-PPV excitons with localized surface plasmon (LSP) of Ag nano-particles when the thickness of deposited Ag film was smaller than 15 nm. However, surface plasmon polaritons (SPPs) dominated the PL enhancement when the thickness of deposited Ag film reached 20 nm or thicker. Temperature dependent PL of BDMO-PPV on the silver substrates were also investigated in the range of 10–300 K. Bose–Einstein statistical factors were calculated to reveal the mechanistic aspects of the observed temperature dependent fluorescence enhancement on Ag nano-films with variable thickness.
Co-reporter:Yunyun Huang, Wensheng Lin, Kan Chen, Wenkai Zhang, Xudong Chen and Ming Qiu Zhang
Physical Chemistry Chemical Physics 2014 vol. 16(Issue 23) pp:11584-11589
Publication Date(Web):14 Mar 2014
DOI:10.1039/C4CP00773E
A water-processable blue fluorescent silver nanoparticle@graphene–polymer composite (Ag@G–pNIPAM) consisting of graphene coated with a thermally responsive poly-(N-isopropylacrylamide) (pNIPAM) shell is prepared. The pNIPAM shell swells or collapses as a function of temperature, serving as a means to trap silver nanoparticles in solution and get them sufficiently close to the graphene core to provide fluorescence enhancement based on the local surface plasmon resonance (LSPR) effect. The unique thermoresponsive properties and high enhancement ratio of the material should find application in solution fluorescence enhancers and a variety of biomedical applications, such as cellular uptake, sensing and imaging.
Co-reporter:Jiemei Ou, Yuzhao Yang, Zhongke Yuan, Yu Zhang, Lin Gan, Xudong Chen
Synthetic Metals 2014 Volume 195() pp:9-15
Publication Date(Web):September 2014
DOI:10.1016/j.synthmet.2014.05.014
•A simple method was used to fabricate a nanostructure for PL enhancement.•To enhance the single molecule fluorescence of P3HT ∼7 folds by silver nanocubes.•PL enhancement of P3HT was due to the radiative decay rates and enhanced local field.We investigate the enhancement of poly(3-hexylthiophene) (P3HT) single molecule fluorescence using silver-nanocube as substrates. Results show that the silver nanocube substrate enhances the single molecule fluorescence of P3HT by about 7 folds and effectively improves the photophysical stabilities of individual P3HT molecules by delaying the photobleaching process. We find that the increase of the radiative decay rates, resulted from the coupling between photogenerated excitons and surface plasmon, is directly related to the observed fluorescence enhancement of P3HT. The enhanced local field provided by the silver-nanocube substrate also contributes to fluorescence enhancement via coupling. This coupling depends on the overlap between the emission frequency of the fluorophore and the surface plasmon field provided by the substrate. As the emission wavelength of the fluorophore gets closer to the surface plasmon resonance of silver nanocubes, the coupling becomes stronger, leading to greater fluorescence enhancement.The single molecule fluorescence enhancement of poly(3-hexylthiophene) (P3HT) on silver-nanocubes film substrates is due to the coupling between photogenerated excitons and surface plasmon depending on the overlap between the emission frequency and surface plasmon field.
Co-reporter:Wenkai Zhang, Yujie Chen, Lin Gan, Jian Qing, Xiang Zhou, Yunyun Huang, Yuzhao Yang, Yu Zhang, Jiemei Ou, Xudong Chen, Ming Qiu Zhang
Journal of Physics and Chemistry of Solids 2014 Volume 75(Issue 12) pp:1340-1346
Publication Date(Web):December 2014
DOI:10.1016/j.jpcs.2014.07.013
•Emission of polyfluorene derivatives (PCFOz) is enhanced through LSPR coupling effect.•Ag/PCFOz show blueshifted narrow emission pattern due to LSPR-excitons coupling.•Both light absorption and radiative recombination rate have been enhanced.•The PL enhancement ratio increases with increasing temperature.Polyfluorene-based blue light-emitting devices suffer from the shortcomings of low stability, drastic loss of quantum yield and poor color purity. To find out the solution, we use silver nanoparticles for enhancement of photoluminescence of polyfluorene copolymer (PCFOz) through localized surface plasmon resonance (LSPR) coupling effect. The photoluminescence from PCFOz can be concentrated down to nanoscale, realizing a high spatial selectivity of the fluorescence enhancement process. PL emission of conjugated polymer is blueshifted about 8 nm from the peak emission of 433 nm for the neat PCFOz film to around 425 nm for the Ag/PCFOz composite film. The full width at half maximum of PCFOz is reduced from 88 to 60 nm. Absorbance spectra and time resolved photoluminescence measurements further demonstrate that both absorption intensity and recombination rate of PCFOz increase due to strong LSPR-excitons coupling. Optical properties of such plasmon-enhanced organic light emitters were also studied by temperature-dependent PL spectroscopy from 10 to 200 K. In comparison with bare PCFOz, the LSPR induced emission enhancement ratio significantly increases with increasing temperature. These results are believed to be important for the development of highly efficient blue organic light-emitting devices based on all-solution processing.
Co-reporter:Wenzhi Zhang;Mingqiu Zhang
Polymer Bulletin 2014 Volume 71( Issue 1) pp:243-260
Publication Date(Web):2014 January
DOI:10.1007/s00289-013-1058-1
Phase transition process in aqueous solutions of poly (vinyl methyl ether) (PVME)/poly (2-ethyl-2-oxazoline) (PEtOx) mixtures was investigated by elastic light scattering (ELS) spectroscopy. The two temperatures of phase transition in solutions during heating were identified, corresponding to different lower critical solution temperatures of PVME and PEtOx. The ELS spectra revealed the aggregation of molecular chains in the course of phase transition. It was found that PVME chains collapsed and aggregated during heating. Afterward, the PEtOx chains began to aggregate. In contrast, during cooling, the PEtOx aggregates were initially swelled and followed by partial dissociation. This was probably because that the PVME aggregates formed in solution might sterically hinder the further swelling and dissociation of the PEtOx aggregates. Subsequently, the aggregates of PVME chains and the independent PEtOx aggregates swelled and dissociated, while the conformation of molecular chains finally returned to its original state. In view of the phase transition behavior of PVME/PEtOx solutions, the mixtures of two thermosensitive polymers might be used to develop new polymeric materials possibly applied in fields such as drug delivery, biosensor, and bioseparation. Moreover, a model was proposed to describe the phase transition process.
Co-reporter:Yunyun Huang;Ming Qiu Zhang
Journal of Materials Science 2014 Volume 49( Issue 8) pp:3025-3033
Publication Date(Web):2014 April
DOI:10.1007/s10853-013-8001-6
Graphene films which are fabricated by simple dispensing method without surface modification exhibit reversible switching between superhydrophobicity and superhydrophilicity under alternative UV illumination and dark storage. Careful study of the mechanisms is conducted in view of surface geometry, microstructure, and chemical compositions, and focused on chemical compositions. Photo-induced chemisorption of hydrophilic radicals and water molecules on graphene is found to be responsible for the transition from original hydrophobicity to hydrophilicity, even superhydrophilicity, while replacement of water molecules by oxygen during storage in the dark environment induces the hydrophobicity recovery of graphene films from hydrophilic state. Appearance and disappearance of hydroxyl radicals are closely related to the lattice structure of graphene and energy supply. This wettability conversion is fully reversible. The outcomes not only reveal micro-processes involved in wettability conversion of graphene but also help to purposely design and produce devices from carbon materials with tailor-made tunable surface wettability according to our actual need.
Co-reporter:Wenkai Zhang, Yujie Chen, Chenglong Hu, Yanfeng Zhang, Xudong Chen and Ming Qiu Zhang
Journal of Materials Chemistry A 2013 vol. 1(Issue 6) pp:1265-1271
Publication Date(Web):07 Dec 2012
DOI:10.1039/C2TC00568A
This study demonstrates a novel light-emitting conjugated polymer (PCFOz) used to initiate excitation and propagation of surface plasmon polaritons (SPPs) in silver nanowires. Excitons in the polymer optically excited in close proximity to silver nanowires directly couple to the guided SPPs, and then propagate towards the wires' ends and light up. A tunable exciton–plasmon coupling is realized by varying the distance between PCFOz and Ag nanowires. Strongly efficient excitation of SPPs appears in the case of a spacer thickness of ∼10 nm. Moreover, photobleaching of the organic system is dramatically suppressed by separating the emitter and metal with a spacer, allowing at least 20 times improvement of photostability with a spacer thickness of 25 nm. Spectral dependence of exciton–plasmon coupling indicates that the nanowires' tips contain larger amount of red components. Study of emission decay dynamics demonstrates that the emission properties of PCFOz have been significantly modified by the proximity of Ag nanowires, generating more than 9-fold enhancement of PCFOz spontaneous emission. These results are believed to be important for the development of thin-film photonic–plasmonic waveguides, single photon source and various nanoscale fluorescence sensors.
Co-reporter:X. H. Zu;W. Y. Tang;G. B. Yi;J. Yang
Russian Journal of Physical Chemistry B 2013 Volume 7( Issue 4) pp:389-396
Publication Date(Web):2013 July
DOI:10.1134/S1990793113030159
In this paper, a new rhodamine B lauryl amine (RBL) lipophilic derivative was synthesized by amidation of phenyl carboxylic group of RB with lauryl amine, and then its optical properties were studied on different conditions, such as varied excitation wavelengths, different kinds of solvents, pH values, etc. The results show that the absorption and emission spectra are significant different with the different structures of RBL. The absorption intensity of RBL in solvents with weak acidic proton was stronger than that in aprotic solvent because the former one can form hydrogen bond and thus stabilize the opened form of RBL. The fluorescence emission of RBL in dichloromethane and ethanol was stronger than that in acetone, tetrahydrofuran and water. It indicated that most of RBL molecules were in opened form in dichloromethane and ethanol, but in closed form in acetone, tetrahydrofuran and water. Finally, the influence of pH values was studied, and found that the intensity and position of absorption and emission peaks were almost the same in the whole acidic range, but changed a lot in alkaline medium.
Co-reporter:Yunyun Huang, Yujie Chen, Chenglong Hu, Bin Zhang, Ting Shen, Xudong Chen and Ming Qiu Zhang
Journal of Materials Chemistry A 2012 vol. 22(Issue 22) pp:10999-11002
Publication Date(Web):25 Apr 2012
DOI:10.1039/C2JM31410J
A facile method for preparing graphene–polyaniline composite is proposed without the necessity of using graphene oxide. By adding CdS nanoparticles into the in situ polymerization system consisting of graphene and aniline monomers, a graphene–polyaniline composite with a well-bonded interface is yielded. It is found that the nano-CdS particles act as a ‘bridge’, connecting (i) PANI via the electrostatic force of attraction between the electron clouds of the sulfur and nitrogen atoms and (ii) graphene by π–π stacking. Taking advantage of the effective interfacial interactions, a large enhancement (∼400%) of the photoelectronic performance in the composite is observed. The work opens up a path for maintaining the original structure and properties of graphene during graphene–polymer composite manufacturing.
Co-reporter:Chenglong Hu, Xudong Chen, Jian Chen, Weihong Zhang and Ming Qiu Zhang
Soft Matter 2012 vol. 8(Issue 17) pp:4780-4787
Publication Date(Web):13 Mar 2012
DOI:10.1039/C2SM07299H
The present work proposed a facile approach to quantify macromolecular migration in micrometer thick polymer films. Using a polystyrene (PS)/poly(methyl methacrylate) (PMMA) binary film as the model material, depth profile analysis was conducted by confocal Raman microscopy (CRM). The results showed mutual diffusion of PS and PMMA molecules across the interface of the immiscible polymer pairs when the binary film had been annealed. In addition, both tracer and mutual diffusion coefficients were determined on the basis of the Fickian model, and the factors that influenced the diffusion behavior were discussed. It is believed that the characterization framework established by the authors has theoretical value and practical meaning.
Co-reporter:Bin Zhang, Yujie Chen, Yanfeng Zhang, Xudong Chen, Zhenguo Chi, Jin Yang, Jiemei Ou, Ming Qiu Zhang, Dehao Li, Dong Wang, Mingkai Liu and Juying Zhou
Physical Chemistry Chemical Physics 2012 vol. 14(Issue 13) pp:4640-4650
Publication Date(Web):13 Feb 2012
DOI:10.1039/C2CP23953A
In order to investigate the steric effect of aromatic pendant groups and the electrical bistability in nonconjugated polymers potentially for memory device applications, two π-stacked polymers with different steric structures are synthesized and characterized. They exhibit two conductivity states and can be switched from an initial low-conductivity (OFF) state to a high-conductivity (ON) state. Additionally, they demonstrate nonvolatile write-once-read-many-times (WORM) memory behavior with an ON/OFF current ratio up to 104, and flash memory behavior with an ON/OFF current ratio of approximately 105. Both steady-state and time-resolved fluorescence spectroscopies are used to examine the conformational change of the polymers responding to an applied external electrical voltage. The results provide useful information on different steric effects of pendant groups in polymer chains, resulting in various electrical behaviors. The possibility in realizing an “erasable” behavior through breaking π-stacked structures of pendant groups by a reversal of the electric field was also discussed on the basis of temperature-dependent fluorescence spectroscopy investigation. These results may thus offer a guideline for the design of practical polymer memory devices via tuning steric structure of π-stacked polymers.
Co-reporter:Kun Yang;Yu Zhao Yang;Cheng Long Hu;Yun Yun Huang;Wen Kai Zhang;Xu Dong Chen;Ming Qiu Zhang
Macromolecular Chemistry and Physics 2012 Volume 213( Issue 16) pp:1735-1741
Publication Date(Web):
DOI:10.1002/macp.201200090
Abstract
Resonance light scattering (RLS) technique was applied to study macromolecular entanglements in highly dilute poly(vinyl methyl ether) (PVME)/poly(ethylene oxide) (PEO) solution during phase transition process. Temperature dependences of RLS intensities of PVME, PEO and PVME/PEO solutions were recorded. In addition, simulated temperature dependence of RLS intensity of PVME/PEO solution was drawn supposing there was no interaction between PEO and PVME. Comparison between the measured with the simulated results indicated that there were obvious differences in RLS intensities and transition temperatures. The present work proved the existence of entanglements during phase separation in highly dilute solution. Moreover, a model was proposed to describe the entanglement behavior.
Co-reporter:Guoshan He, Jin Yang, Xindan Zheng, Qing Wu, Lihua Guo, Mingqiu Zhang, Xudong Chen
Polymer Testing 2012 Volume 31(Issue 1) pp:182-190
Publication Date(Web):February 2012
DOI:10.1016/j.polymertesting.2011.10.009
Hyperbranched polyethylene (HBPE)/linear polystyrene (PS)/chloroform (CF) solution was selected as a model system to investigate the effect of branching structure on entanglement and phase separation behavior in semi-dilute ternary polymer solutions. All the HBPE materials in this work were found to have similar chain architectures and the critical molecular weight was estimated to be 81.2 kDa. The results obtained by elastic light scattering and intrinsic fluorescence methods suggested that all ternary solutions exhibited UCST transition behavior upon cooling. Also, it was found that the increase in the molecular weight of PS led to increase in the phase separation rate, consistent with de Gennes prediction. However, the increase of molecular weight of HBPE did not monotonously reduce the compatibility of polymer components and the phase separation rate in ternary blends is as follows: medium molecular weight HBPE (HBPE-M) > high molecular weight HBPE (HBPE-H) > low molecular weight HBPE (HBPE-L). This abnormal behavior can be explained by the fact that, (i) for HBPE-L, no entanglements between HBPE chains occurred and the branching effect can be ignored, and (ii) for HBPE-M and HBPE-H, entanglement of HBPE chains can be formed, and the dilution of branches on entanglement of backbones should be taken into consideration, that is, the shorter the branches of HBPE, the higher the possibility of interpenetration of HBPE backbones between neighboring molecules and, consequently, the faster aggregation of HBPE during phase separation. Furthermore, a simple model based on decomposition reaction was proposed to quantitatively describe the phase separation kinetics and the apparent activation energies of phase separation were calculated to be −150.3 and −52.3 kJ/mol for HBPE-M/PS/CF and HBPE-H/PS/CF systems, respectively.
Co-reporter:Chenglong Hu;Yujie Chen; Xudong Chen;Bin Zhang;Jin Yang;Juying Zhou; Ming Qiu Zhang
Chemistry - A European Journal 2012 Volume 18( Issue 5) pp:1467-1475
Publication Date(Web):
DOI:10.1002/chem.201101769
Abstract
In this paper, the effect of the internal micro-magnetic field (IMMF) on the photocurrent property of conjugated polymer/inorganic semiconductor nanocomposites is reported and analyzed. By using the redox reaction, magnetic Fe3O4 nanoparticles were coated on the surface of highly active nanorods of conjugated polyaniline (PANI), forming an internal micro-magnetic electron donor (i.e., Fe3O4@PANI). After subsequent incorporation of CdS nanoparticles (serving as electron acceptors), the power conversion efficiency (PCE) of the system (Fe3O4@PANI-CdS) was found to be as high as 3.563 %, contrasting sharply with the value (1.135 %) of the hybrid without Fe3O4 (PANI-CdS). This obvious enhancement originated from the fact that the IMMF increased the number of singlet polaron pairs through field-dependent intersystem crossing (ISC), giving a positive contribution to the photocurrent generation. Additionally, the dependence of the photocurrent on the remnant magnetization of the Fe3O4@PANI-CdS nanocomposites was investigated. A percolation behavior was observed, which was due to the appearance of interpenetrating networks consisting of donor and acceptor phases, leading to the recombination of charge carriers through trapping. The outcomes of the present work might help to produce a new family of conjugated organic/inorganic semiconductor nanocomposites with designed optoelectronic performances.
Co-reporter:Wenzhi Zhang;Jin Yang;Mingqiu Zhang
Polymer Bulletin 2012 Volume 68( Issue 2) pp:425-440
Publication Date(Web):2012 January
DOI:10.1007/s00289-011-0554-4
By using elastic light scattering (ELS) spectroscopy, dependences of lower critical solution temperature (LCST) of poly(vinyl methyl ether) (PVME)/poly(ethylene glycol) (PEG) solutions on concentration (CPEG) and molecular weight of PEG were analyzed. It was found that the onset temperature of phase separation (Tp) decreased with increasing CPEG or molecular weight of PEG in the solutions. It indicated that PEG was competitive with PVME in complexing water molecules. The presence of PEG disturbed the hydration layer around PVME, facilitating the aggregation of PVME chains at lower temperature. Moreover, the ELS spectra revealed the aggregation and dissociation of molecular chains in PVME/PEG solutions during one heating and cooling cycle. PVME chains aggregated above the microphase transition temperature. With further increasing temperature, PVME aggregates started to contract, and then kept stable. During cooling, the chain aggregates were not immediately swelled but gradually swelled, and began to dissociate when the solution temperature was further decreased. Finally, the conformation of the molecular chains returned to its original state.
Co-reporter:Juying Zhou, Jin Yang, Chenglong Hu, Kun Yang, Bin Zhang and Xudong Chen
Soft Matter 2011 vol. 7(Issue 10) pp:5010-5019
Publication Date(Web):04 Apr 2011
DOI:10.1039/C0SM01418D
Helical junction-helix-wormlike transformation of syndiotactic polystyrene (sPS) conformations in a sPS/chloroform gel was investigated during melting process. The gel melting process involved a reversible dissociation of the network structure at low temperature and a reversible transformation process from helix to wormlike conformation at high temperature. The reaction order for the normal melting process adopted was 1. The quantitative description of the phase transformation kinetics for the melting process of sPS/chloroform gel was performed by resonance light scattering technique (RLS). Only the dissociation of the three helical junctions existed when the temperature was lower than 57 °C. As the rate-determining step, the transition from helix to wormlike conformation was identified when the temperature was higher than 57 °C. RLS proved to be an effective means for characterization of kinetic processes in polymer gels.
Co-reporter:Guibin Yi;Zhenghong Zhu;Fei Wang;Jin Yang;Yunwei Huang
Chinese Journal of Chemistry 2011 Volume 29( Issue 5) pp:1041-1048
Publication Date(Web):
DOI:10.1002/cjoc.201190177
Abstract
A thermally sensitive copolymer, poly(N-isopropylacrylamide-co-styrene) [P(NIPAM-co-St)] (Mn9.5×105 g/mol and Mw/Mn1.51) was synthesized by soap-free emulsion polymerization. The phase separation of the copolymer in water was investigated by Rayleigh scattering (RS) technique. The RS spectra revealed the transition of molecular conformation and the aggregation of molecular chains in the course of phase separation. The coil-to-globule and globule-to-coil transitions of P(NIPAM-co-St) chains were found in one heating-and-cooling cycle. By means of Avrami formula, apparent activation energy of phase separation of P(NIPAM-co-St) aqueous solutions was estimated. Moreover, a model was proposed to describe the phase separation process.
Co-reporter:Wei-ang Luo;Zhengfu Liao;Jin Yang;Xindan Zheng;Kancheng Mai
Macromolecular Chemistry and Physics 2011 Volume 212( Issue 11) pp:1176-1184
Publication Date(Web):
DOI:10.1002/macp.201000746
Co-reporter:Juying Zhou, Jin Yang, Xudong Chen, Weiang Luo, Wenzhi Zhang, Kun Yang, Bin Zhang
Journal of Molecular Structure 2011 Volume 987(1–3) pp:91-100
Publication Date(Web):22 February 2011
DOI:10.1016/j.molstruc.2010.11.065
The phase transformation of tetraethyleneglycol dodecyl ether (C12E4) solution was investigated by Rayleigh light scattering (RLS) technique. It was shown that the scattering spectra were very sensitive to the molecular motions of C12E4. For dilute solutions, phase transformation from micelles to vesicles was observed in a temperature jump process, and the vesicle formation process involves four stages: (I) micelle aggregation stage, (II) scission stage, (III) fusion stage and (IV) phase transition stage. The corresponding morphologies were confirmed by Atomic force microscopy (AFM) measurements and the vesicle radii were calculated from the form factors. For concentrated systems, the phase transformation temperatures were determined using the intensity ratio of two scattering peaks due to the appearance of peak shifts in scattering spectra. In this case, two processes can be found during the phase transformation, i.e., micelle aggregation and phase transformation from micelle aggregation to lamellar phase.
Co-reporter:Juying Zhou, Jin Yang, Kun Yang, Bin Zhang, Chenglong Hu, Xudong Chen
Polymer 2011 Volume 52(Issue 15) pp:3503-3511
Publication Date(Web):7 July 2011
DOI:10.1016/j.polymer.2011.05.020
Conformational behaviors of syndiotactic polystyrene (sPS) in chloroform were investigated by detecting its concentration dependence of intrinsic fluorescence in the range from 25 to −62 °C. For the dimer emission, the coexistence of T-shaped configuration with sandwich configuration was observed and the contribution of sandwich configuration increases with increasing sPS concentration in the system. In addition, three conformations are observed in sPS/CHCl3 systems: (I) coil phase; (II) coil-to-helix transformation; (III) helix-to-network transformation. The conformational ordering of polymer chain in super dilute sPS/CHCl3 systems during isothermal process indicated that micro-gel formed when the concentration was higher than 0.2 g L−1, and single helix formed at 0.09 ∼ 0.2 g L−1 proceeds through a unimolecular or self-organization mechanism and no helical aggregates were found. The helix was formed by clustering of several chain segments when the polymer concentration was below 0.09 g L−1. Moreover, a model was proposed to describe the elasticity of sPS/CHCl3 systems near and beyond the critical percolation concentration.
Co-reporter:Yunbo Li;Xiaoyan Zhang;Fangming Zhu
Colloid and Polymer Science 2011 Volume 289( Issue 7) pp:767-774
Publication Date(Web):2011 May
DOI:10.1007/s00396-011-2390-3
Complexation behaviour of cellulose derivative/surfactant mixtures in aqueous solution was investigated by nonlinear enhanced Rayleigh scattering (NERS). The NERS spectra of polymer solutions, including second-order scattering, third-order scattering, frequency doubling scattering and triplet frequency scattering were created using by spectrofluorometer. The results indicated that NERS intensity of cellulose derivative/surfactant systems changes differently with continuing addition of surfactant due to the complexation between cellulose derivative and surfactant. The critical micelle concentration of cellulose derivatives/surfactants system is easy to obtain. The change of NERS intensity reveals the complexation behaviour of cellulose derivative/surfactant and the aggregation state of polymer chains in evidence. Therefore, NERS had been successfully developed to study complexation behaviour of cellulose derivative/surfactant mixtures in solution.
Co-reporter:Jin Yang, Xindan Zheng, Bin Zhang, Ruowen Fu, and Xudong Chen
Macromolecules 2011 Volume 44(Issue 4) pp:1026-1033
Publication Date(Web):January 27, 2011
DOI:10.1021/ma102243u
The aggregation behaviors of an ABA block copolymer, polystyrene-b-poly(ethylene/butylene)-b-polystyrene triblock copolymer (SEBS), were investigated in methylene dichloride (selective solvent for PS block) and mixture of n-hexane and cyclohexane (selective solvent of PEB block), i.e., SEBS-(S) and SEBS-(EB) solution, respectively. Both static and dynamic light scattering showed that the conformational change of molecular chain underwent three stages in SEBS-(S) solution. By using steady-state and time-resolved fluorescence, it was concluded that, when the micellization process of SEBS-(S) solution occurred, PS segments was dramatically stretched during the aggregation of PEB block into micelle cores, resulting in the great decrease in the amount of intramolecular excimers. In the case of SEBS-(EB) solution, five stages were observed in dynamic light scattering result during the micellization, suggesting that further aggregation between micelles was induced by the bridging effect of the dangling outer block (PS). The steady-state fluorescence results indicated that the intermicellar aggregation would not lead to a dramatic decrease in interchain distance of PS block in micelle cores. Interestingly, the time-resolved fluorescence indicated that, for SEBS solutions, the conformation of PS block was completely homogeneous in its selective solvent but microheterogenous in the solvent selective for PEB block. Moreover, the activation energy of excimer association and dissociation in both SEBS solutions were also estimated, which can be considered as the key parameters for characterizing the comformation of macromolecular chains during the micellization process.
Co-reporter:Kun Yang, Xue Huan Wang, Xu Dong Chen, Ming Qiu Zhang
Polymer 2011 Volume 52(Issue 15) pp:3512-3517
Publication Date(Web):7 July 2011
DOI:10.1016/j.polymer.2011.05.018
To investigate the influence of molecular structure such as side chain on phase separation process in solution, naphthalene-labeled poly (octadecyl vinyl ether) (PODVE) with long side chains was synthesized by living cationic polymerization. Rayleigh Light scattering (RLS) and photoluminescence (PL) studies indicated that side chain played a dominant role in phase separation process in PODVE/dichloromethane system. According to the results of RLS and PL spectra, it was found that PODVE chains changed from expanded coils to collapsed globules and then aggregated. At C = 0.2 g/L, the long side chain of PODVE (102) separated out from nonpolar solvent below 7.2 °C, which directly caused phase separation in solution. In addition, the phase separation temperature slightly increased when the concentration of PODVE (102) solution varies from 0.05 g/L to 0.2 g/L, and more obviously (i.e., from 3.5 °C to 7.2 °C) as the molecular weight increases from 4300 to 10 200. The Activation energy of phase separation of the PODVE solution was −270.09 kJ/mol estimated by means of Avrami equation and Arrhenius formula.The conformational ordering of polymer chain naphthalene-labeled poly(octadecyl vinyl ether) chains in dichloromethane solution was studied by Rayleigh Light scattering technique during cooling process.
Co-reporter:Jin Yang, Xudong Chen, Ruowen Fu, Wei-ang Luo, Yunbo Li and Mingqiu Zhang
Physical Chemistry Chemical Physics 2010 vol. 12(Issue 9) pp:2238-2245
Publication Date(Web):19 Jan 2010
DOI:10.1039/B918069A
In this work, kinetics of phase separation in the blends of polystyrene (PS) and poly(vinyl methyl ether) (PVME) was investigated by a simple and sensitive method, i.e., resonance light scattering (RLS) spectroscopy. Owing to the aggregation of chromophores (phenyl rings) in the systems when phase separation occurred, RLS intensities were drastically enhanced and hence acted as a characteristic indicator. At the early stage of phase separation, two different RLS behaviors corresponding to spinodal decomposition (SD) and nucleation and growth (NG) were observed. The Cahn-Hilliard (C–H) linearization theory was found not applicable for kinetics analysis of the scattering data at λ < 346 nm due to RLS effect near the absorption band. Based on a decomposition reaction model, the apparent activation energy of SD phase separation was estimated by the Arrhenius equation. In view of its simplicity and sensitivity of measurement, affordability and availability of instrument, and wide application range of polymer blends, RLS proved to be an effective means for characterization of microstructural variation in polymer blends.
Co-reporter:Wei-ang Luo, Xudong Chen, Zhengfu Liao, Jin Yang, Kancheng Mai and Mingqiu Zhang
Physical Chemistry Chemical Physics 2010 vol. 12(Issue 18) pp:4686-4693
Publication Date(Web):19 Mar 2010
DOI:10.1039/B921435F
The dynamic process of cold crystallization of amorphous poly(trimethylene terephthalate) (PTT) was investigated with resonance light scattering (RLS). By using an enhanced scattering peak at 329 nm, which was in close proximity to the absorption band of PTT film, density fluctuation due to gradual transition from amorphous to crystalline with increasing temperature was monitored. Accordingly, molecular chains movement and structure evolution in PTT during cold crystallization, in particular, the information about each phase of crystallization, including induction, nucleation, nucleus growth and secondary crystallization, were thoroughly revealed. The experimental results indicated that the kinetics parameters measured by the RLS method were in good agreement with those obtained by differential scanning calorimetry (DSC) and fluorescence spectroscopy. In addition, the RLS method can tell more details of the movement and variation in fine structures than DSC and fluorescence techniques as a result of its significantly enhanced scattering signals, like the orientation fluctuations of rigid segments in the course of glass transition and crystallization induction.
Co-reporter:Wei-Ang Luo;Guobin Yi;Jin Yang;Zhengfu Liao;Kancheng Mai;Mingqiu Zhang
Journal of Applied Polymer Science 2010 Volume 115( Issue 2) pp:1015-1021
Publication Date(Web):
DOI:10.1002/app.31054
Abstract
The dynamic rheology and morphology of poly(trimethylene terephthalate) and maleic anhydride grafted poly(ethylene octene) composites were investigated. A specific viscoelastic phenomenon, that is, a second plateau, appeared at low frequencies and exhibited a certain dependence on the content of elastomer particles and the temperature. This phenomenon was attributed to the formation of an aggregation structure of rubber particles. The analyses of the dynamic viscoelastic functions suggested that the heterogeneity of the composites was enhanced as the particle content or temperature increased. The microstructural observation by scanning electron microscopy confirmed that maleic anhydride could react with the end groups of poly(trimethylene terephthalate) to form a stable interfacial layer and result in a smaller dispersed-phase particle size due to the reduced interface tension. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Co-reporter:Wen Zhi Zhang, Xu Dong Chen, Jin Yang, Wei-ang Luo and Ming Qiu Zhang
The Journal of Physical Chemistry B 2010 Volume 114(Issue 3) pp:1301-1306
Publication Date(Web):January 4, 2010
DOI:10.1021/jp909925v
The resonance light scattering (RLS) technique based on a conventional fluorescence spectrophotometer was used to quantitatively describe the aggregation and dissociation of polystyrene (PS) in cyclohexane solution during cyclic heating and cooling. Transitions in conformation of PS molecules and aggregation of PS chains in the course of phase separation were revealed. The results indicated that PS chains changed from random coils to collapsed globules and then aggregated when temperature decreased. In contrast, when the system is heated, the chain aggregates were initially swelled and followed by gradual dissociation. Subsequently, the conformation of PS chains returned to the original state. Kinetics of phase separation of the PS solution was analyzed, which allowed estimation of the apparent activation energy.
Co-reporter:Ling Zhang, Jing Su, Wenzhi Zhang, Ming Ding, Xudong Chen and Qing Wu
Langmuir 2010 Volume 26(Issue 8) pp:5801-5807
Publication Date(Web):December 21, 2009
DOI:10.1021/la903711e
The phase-transition behavior of unimolecular dendritic polyethylene amphiphiles with core−shell architecture aqueous solutions was investigated by a Rayleigh scattering (RS) technique. Dendritic polyethylene (DPE)-poly(oligo(ethylenegylcol) methacrylate) (POEGMA) with a DPE hydrophobic core and a POEGMA hydrophilic shell was synthesized by the atom-transfer radical polymerization (ATRP) of OEGMA using DPE terminated by the bromine group as a macroinitiator. The fluorescence measurements implied that DPE-POEGMA molecules in aqueous solutions existed as the unimolecular micelles. To understand the phase-transition behavior of dendritic polyethylene amphiphilic unimolecular micelles in aqueous solutions, the temperature dependence of the RS spectra of DPE-POEGMA aqueous solutions under the heating-and-cooling cycle indicated that the heating and cooling processes were reversible but hysteresis existed. The phase transition of DPE-POEGMA aqueous solutions decelerated with increasing levels of PEGylation. DPE-POEGMA exhibited a lower phase-transition temperature in D2O than in water.
Co-reporter:Xudong Chen, Mingqiu Zhang, Yujie Chen, Dingshan Yu, Baojun Li, Zhiqiu He, Guangji Li
Materials Chemistry and Physics 2009 Volume 118(Issue 1) pp:203-207
Publication Date(Web):15 November 2009
DOI:10.1016/j.matchemphys.2009.07.032
Organic nanowires based on p-hydroxybenzoic acid were synthesized in terms of hydrothermal method. Substrate that is necessary for other nanowires to grow up was no longer needed in the present case. The resultant rod-like nanowires 50–100 nm in diameter and 10–20 μm in length consist of coordinate structure established by complexation between zinc ions, acetoxyl groups and p-hydroxybenzoic acid's carboxyl and phenolic hydroxyl. Through careful observation with scanning electron microscope, it is known that formation of the nanowires experienced nucleation, growing and shaping stages, following vapor–liquid–solid mechanism. The synthetic route is simple, and easy to be monitored owing to the mild reaction conditions. The work might open up new opportunities for nanodevice fabrication with organic nanowires rather than conventional metal and semiconductor ones.
Co-reporter:Jin Yang, Xudong Chen, Yunbo Li, Weiang Luo, Ruowen Fu, Mingqiu Zhang
Polymer Testing 2009 Volume 28(Issue 2) pp:165-168
Publication Date(Web):April 2009
DOI:10.1016/j.polymertesting.2008.11.009
The synchronous scan spectra (SSS) technique was successfully applied to monitor the macromolecular chain motions near the glass transition temperature in polystyrene (PS) and poly (vinyl methyl ether) (PVME) films on a copper substrate. In SSS of PS and PVME films, two peaks at 467 nm and 473 nm, which correlated to the light source spectrum of the spectrofluorimeter, were used to characterize the glass transition of polymers. By monitoring the intensity of peaks at 467 and 473 nm in the spectra, the intensity-temperature curves exhibited kinks near the glass transition. The kinks have also been shown in plots of IR473/IR467vs. temperature, which implies the distinct fluctuation of SSS intensity distribution at the glass transition temperature of the polymer. As a spectroscopy measurement method with simplicity, rapidity and sensitivity, the SSS method was proved to be able to monitor the glass transition in polymers, which has been commonly measured by differential scanning calorimetry (DSC).
Co-reporter:Dingshan Yu, Yujie Chen, Baojun Li, Xudong Chen
Materials Letters 2009 Volume 63(Issue 27) pp:2317-2320
Publication Date(Web):15 November 2009
DOI:10.1016/j.matlet.2009.07.063
Well-defined PbS nanocubes have been synthesized at room temperature by a mild solution-based simple method in the presence of sulfonated polymer as both stabilizer and crystal growth modifier. The simple method avoids high temperature which is required in the preparation of cubic-shaped PbS nanocrystals by hydrothermal reaction. A growth mechanism of the PbS nanocubes in the mild solution was discussed. The as-prepared samples exhibit intense visible emission and weaker near-infrared emission. The samples can be readily dissolved by organic solvents to form stable colloids for further processing, assembly or applications.
Co-reporter:Jin Yang, Xudong Chen, Ruowen Fu, Yunbo Li, Wei-ang Luo, Mingqiu Zhang
Polymer Testing 2009 Volume 28(Issue 4) pp:456-460
Publication Date(Web):June 2009
DOI:10.1016/j.polymertesting.2009.03.005
Two-dimensional (2D) correlation resonance light scattering (RLS) spectroscopy has been successfully applied to investigate phase separation of polystyrene (PS)/poly (vinyl methyl ether) (PVME) film by using a conventional spectrofluorimeter. 2D synchronous correlation RLS spectrum indicates that the RLS peak intensity drastically increases with a rise in temperature due to aggregation of chromophores (i.e. phenyl rings) in PS particles in the course of phase separation. In addition, as concluded by 2D asynchronous correlation RLS spectrum, RLS has higher sensitivity than conventional light scattering. For RLS, the closer to the absorption band, the more sensitive it is to the aggregation during phase separation. By means of moving-window two-dimensional (MW2D) correlation spectrum based on autocorrelation calculations, the cloud point (370 K) was determined, which is in good agreement with the literature. On the other hand, time evolution of RLS intensity at various temperatures distinctly shows that phase separation of PS/PVME film involves two mechanisms, i.e. spinodal decomposition (SD) and nucleation and growth (NG). Accordingly, 2D correlation RLS proves to be a very simple and sensitive method to monitor phase separation in polymer blends and might supplement the existing characterization tools.
Co-reporter:Yong Hu;Xiong Fu;Xu-dong Chen;Jin Yang;Liang-sheng Yang
Polymer Bulletin 2009 Volume 62( Issue 4) pp:549-559
Publication Date(Web):2009 April
DOI:10.1007/s00289-008-0032-9
Resonance light scattering (RLS) spectra were used to study the formation of complexes of carboxymethyl cellulose (CMC) and polylactic acid (PLA) in a mixed solvent of 10% DMSO/90% H2O(V/V). The RLS results showed that the CMC and PLA could form a steady homogeneous complex due to the interaction of hydrogen bonding. With the increasing of CMC mass fraction in the complex, the observed durative enhancement RLS signal with two inflexion points indicated the forming of complexes and aggregation of complexes. The aggregation equilibrium and thermo stability of the complexes were also investigated based on RLS values.
Co-reporter:Wen Zhi Zhang, Xu Dong Chen, Wei-ang Luo, Jin Yang, Ming Qiu Zhang and Fang Ming Zhu
Macromolecules 2009 Volume 42(Issue 5) pp:1720-1725
Publication Date(Web):February 17, 2009
DOI:10.1021/ma802671a
Phase separation and its kinetics of poly (vinyl methyl ether) (PVME) aqueous solutions was investigated by Rayleigh scattering (RS) technique in this work. Concentration dependence of the lower critical solution temperature and time dependence of phase separation were collected, respectively. The RS spectra revealed the transition of molecular conformation and aggregation of molecular chains in the course of phase separation. It was found that upon heating PVME chains changed from expanded coils to collapsed globules and then aggregated. In contrast, during cooling, the chain aggregates were initially swelled and followed by gradual dissociation, while the conformation of molecular chains finally returned to its original state. By means of Avrami equation and Arrhenius formula, apparent activation energy of phase separation of PVME aqueous solutions was estimated. Moreover, a model was proposed to describe the phase separation process.
Co-reporter:Jin Yang;Ruowen Fu;Mingqiu Zhang;Haibin Chen;Jiasheng Wang
Journal of Applied Polymer Science 2008 Volume 109( Issue 6) pp:3452-3457
Publication Date(Web):
DOI:10.1002/app.28412
Abstract
Two grafted ethylene–octene copolymers [POEs; i.e., POE-g-maleic anhydried (MAH) and aminated POE (denoted by POE-g-NH2) were used as compatibilizers in immiscible blends of thermoplastic polyurethane (TPU) and POE. The effects of the compatibilizers on the dynamic rheological properties and morphologies of the TPU/POE blends were investigated. The characteristic rheological behaviors of the blends indicated that the strong interactions between the two phases were due to the compatibilization. Microstructural observation confirmed that the compatibilizers were located at the interface in the blends and formed a stable interfacial layer and smaller dispersed phase particle size. Compared with POE-g-MAH, POE-g-NH2 exhibited a better compatibilization effect in the TPU/POE blends. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Co-reporter:Wei-ang Luo, Yujie Chen, Xudong Chen, Zhengfu Liao, Kancheng Mai and Mingqiu Zhang
Macromolecules 2008 Volume 41(Issue 11) pp:3912-3918
Publication Date(Web):May 10, 2008
DOI:10.1021/ma8000059
Photoinduced energy transfer in poly(trimethylene terephthalate) (PTT) was investigated by examining its excitation wavelength and concentration dependences of fluorescence in solutions. Accordingly, critical quench concentration and critical trap formation concentration were identified. Besides, studies of temperature effect on photoluminescence (PL) behavior of amorphous PTT film from −183 to +177 °C revealed that both fluorescence and phosphorescence emissions at low temperature can be attributed to monomers and traps. Phosphorescence quenching originated from the discontinuous increase of nonradiative processes. The corresponding quenching activation energies were estimated to be 13.5 kJ/mol for monomer phosphorescence quenching and 17.2 kJ/mol for exciplex phosphorescence quenching, respectively. Furthermore, the PL method proved to be able to monitor molecular relaxations (including γ-, β-, and α-transitions) and cold crystallization in PTT film, which used to be measured by dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC), respectively.
Co-reporter:Yunbo Li, Xudong Chen, Mingqiu Zhang, Weiang Luo, Jin Yang and Fangming Zhu
Macromolecules 2008 Volume 41(Issue 13) pp:4873-4880
Publication Date(Web):2017-2-22
DOI:10.1021/ma702800p
On the basis of the relationship between macromolecular aggregate and resonance Rayleigh scattering (RRS) intensity, RRS spectra were utilized to monitor macromolecular aggregating process in poly(acrylic acid) (PAA). No probe and labeling were incorporated; RRS can reveal the macromolecule extension or contraction under external stimuli such as the changes in pH and ionic strength, as well as the addition of surfactant. Results indicated that the addition of base, acid and NaCl altered macromolecular phase behavior of PAA in aqueous solution due to electrostatic effect. Besides, sodium dodecyl sulfate (SDS) or cetyltrimethylammonium bromide (CTAB) interacted with PAA in solution to form polymer-surfactants complexes, inducing macromolecular chain aggregate. On the basis of the analysis of the results, two models were proposed in this work to explain the observed phenomena. RRS is a sensitive method to characterize the macromolecular aggregate.
Co-reporter:Wei-ang Luo, Zhengfu Liao, Jin Yan, Yunbo Li, Xudong Chen, Kancheng Mai and Mingqiu Zhang
Macromolecules 2008 Volume 41(Issue 20) pp:7513-7518
Publication Date(Web):September 26, 2008
DOI:10.1021/ma801119n
Dynamic processes of isothermally cold-crystallized poly(trimethylene terephthalate) (PTT) was investigated by fluorescence spectroscopy of its amorphous region. The key issue lay in the fact that the emission at 390 nm originating from the main chain phenylene ring in the amorphous phase was correlated to the cold-crystallization. A reduction in this emission peak intensity corresponded to a gradual transition of the phenylene ring in the amorphous to crystal region. Accordingly, molecular chain movement and structure evolution of PTT in the course of cold-crystallization were carefully revealed. The experimental results indicated that the kinetics parameters measured by the fluorescence spectroscopy method are in good agreement with those by differential scanning calorimetry (DSC). What is more, the former was capable of providing detailed information about structural variations during cold-crystallization, for example, molecule arrangement in induction phase.
Co-reporter:Xudong Chen, Yeping Dong, Li Fan, Dacheng Yang
Analytica Chimica Acta 2007 Volume 582(Issue 2) pp:281-287
Publication Date(Web):23 January 2007
DOI:10.1016/j.aca.2006.09.027
The fluorescence emitted by the functionalized ZnS nanocrystal at 440 nm could be efficiently enhanced or quenched when various peptides were added. The mechanism of the fluorescence enchancement and quenching of ZnS nanocrystals was discussed. The binding constant and numbers of binding sites was obtained from the Scatchard plot. The change of fluorescence intensity was in proportion to the concentration of peptides. The limits of detection were in range of 0.011–0.028 μg mL−1. Application results to synthetic samples showed simplicity, rapidity, high sensitivity and satisfactory reproducibility of the presented method. Measurements of real samples also give satisfactory results which were in good agreement with those obtained using high performance liquid chromatograph (HPLC) and liquid chromatograph–mass spectrograph (LC–MS) methods.
Co-reporter:Xudong Chen, Yeping Dong, Li Fan, Dacheng Yang, Mingqiu Zhang
Analytica Chimica Acta 2007 Volume 597(Issue 2) pp:300-305
Publication Date(Web):10 August 2007
DOI:10.1016/j.aca.2007.07.008
Resonance light scattering (RLS) of the functionalized ZnS nanocrystals–peptides system and its analytical application have been studied. The RLS intensity can be efficiently enhanced when various peptides were added. The mechanism of the RLS enhancement of ZnS nanocrystals was discussed. The change of RLS intensity was in proportion to the concentration of peptides. The limits of detection were in range of 2.8–5.7 ng mL−1. Application results to synthetic samples showed simplicity, rapidity, high sensitivity and satisfactory reproducibility of the presented method. Measurements of real samples also give satisfactory results which were in good agreement with those obtained using high performance liquid chromatography (HPLC) and liquid chromatography–mass spectrography (LC–MS) methods.
Co-reporter:Xu Dong Chen, Zhi Wang, Zheng Fu Liao, Yu Liang Mai, Ming Qiu Zhang
Polymer Testing 2007 Volume 26(Issue 2) pp:202-208
Publication Date(Web):April 2007
DOI:10.1016/j.polymertesting.2006.10.002
Photooxidation of polyurethane (PU) and its composites with anatase and rutile titanium dioxide nanoparticles induced by ultraviolet exposure was investigated in this work. Anatase was found to be a photosensitiser that accelerates photooxidation of PU, while rutile acted as an effective stabilizer retarding photooxidation of PU. With a rise in the TiO2 nanoparticle content, both photosensitivity of PU/anatase TiO2 nanocomposite and photostability of PU/rutile TiO2 nanocomposite increase. The photocatalytic degradation mechanism of PU and its nanocomposites are briefly discussed. The results are believed to facilitate proper application of TiO2 nanoparticles for different purposes.
Co-reporter:Xiong Fu;Rengui Wen;Xiaowei He;Xiaoya Shang
Journal of Polymer Research 2007 Volume 14( Issue 4) pp:297-304
Publication Date(Web):2007 August
DOI:10.1007/s10965-007-9110-1
In this paper, polyethylene-octene elastomer (POE) and starch blends were studied. The compatibility beyween POE and starch was improved by adding polyethylene-octene/maleic anhydride graft copolymer (POE-MA) as compatibilizer. The compatibilization reaction was followed by FTIR spectra. The morphology of the blends was investigated using scanning electron microscopy (SEM). It was found that the size of the starch phase increased with an increasing content of starch for the blends. The addition of POE-MA can lower the size of the starch phase in the POE matrix, and this was due to the formation of an ester carbonyl function group by the chemical reaction between the anhydride groups and hydroxyl groups on starch. This was reflected in the mechanical properties of the blends, the addition of POE-MA compatibilizer can improve the mechanical properties of POE/starch blends. The thermogravimetric analysis of POE/starch blends was also conducted.
Co-reporter:Bin Zhang, Yujie Chen, Yanfeng Zhang, Xudong Chen, Zhenguo Chi, Jin Yang, Jiemei Ou, Ming Qiu Zhang, Dehao Li, Dong Wang, Mingkai Liu and Juying Zhou
Physical Chemistry Chemical Physics 2012 - vol. 14(Issue 13) pp:NaN4650-4650
Publication Date(Web):2012/02/13
DOI:10.1039/C2CP23953A
In order to investigate the steric effect of aromatic pendant groups and the electrical bistability in nonconjugated polymers potentially for memory device applications, two π-stacked polymers with different steric structures are synthesized and characterized. They exhibit two conductivity states and can be switched from an initial low-conductivity (OFF) state to a high-conductivity (ON) state. Additionally, they demonstrate nonvolatile write-once-read-many-times (WORM) memory behavior with an ON/OFF current ratio up to 104, and flash memory behavior with an ON/OFF current ratio of approximately 105. Both steady-state and time-resolved fluorescence spectroscopies are used to examine the conformational change of the polymers responding to an applied external electrical voltage. The results provide useful information on different steric effects of pendant groups in polymer chains, resulting in various electrical behaviors. The possibility in realizing an “erasable” behavior through breaking π-stacked structures of pendant groups by a reversal of the electric field was also discussed on the basis of temperature-dependent fluorescence spectroscopy investigation. These results may thus offer a guideline for the design of practical polymer memory devices via tuning steric structure of π-stacked polymers.
Co-reporter:Wenkai Zhang, Yujie Chen, Chenglong Hu, Yanfeng Zhang, Xudong Chen and Ming Qiu Zhang
Journal of Materials Chemistry A 2013 - vol. 1(Issue 6) pp:NaN1271-1271
Publication Date(Web):2012/12/07
DOI:10.1039/C2TC00568A
This study demonstrates a novel light-emitting conjugated polymer (PCFOz) used to initiate excitation and propagation of surface plasmon polaritons (SPPs) in silver nanowires. Excitons in the polymer optically excited in close proximity to silver nanowires directly couple to the guided SPPs, and then propagate towards the wires' ends and light up. A tunable exciton–plasmon coupling is realized by varying the distance between PCFOz and Ag nanowires. Strongly efficient excitation of SPPs appears in the case of a spacer thickness of ∼10 nm. Moreover, photobleaching of the organic system is dramatically suppressed by separating the emitter and metal with a spacer, allowing at least 20 times improvement of photostability with a spacer thickness of 25 nm. Spectral dependence of exciton–plasmon coupling indicates that the nanowires' tips contain larger amount of red components. Study of emission decay dynamics demonstrates that the emission properties of PCFOz have been significantly modified by the proximity of Ag nanowires, generating more than 9-fold enhancement of PCFOz spontaneous emission. These results are believed to be important for the development of thin-film photonic–plasmonic waveguides, single photon source and various nanoscale fluorescence sensors.
Co-reporter:Yunyun Huang, Wensheng Lin, Kan Chen, Wenkai Zhang, Xudong Chen and Ming Qiu Zhang
Physical Chemistry Chemical Physics 2014 - vol. 16(Issue 23) pp:
Publication Date(Web):
DOI:10.1039/C4CP00773E
Co-reporter:Jin Yang, Xudong Chen, Ruowen Fu, Wei-ang Luo, Yunbo Li and Mingqiu Zhang
Physical Chemistry Chemical Physics 2010 - vol. 12(Issue 9) pp:NaN2245-2245
Publication Date(Web):2010/01/19
DOI:10.1039/B918069A
In this work, kinetics of phase separation in the blends of polystyrene (PS) and poly(vinyl methyl ether) (PVME) was investigated by a simple and sensitive method, i.e., resonance light scattering (RLS) spectroscopy. Owing to the aggregation of chromophores (phenyl rings) in the systems when phase separation occurred, RLS intensities were drastically enhanced and hence acted as a characteristic indicator. At the early stage of phase separation, two different RLS behaviors corresponding to spinodal decomposition (SD) and nucleation and growth (NG) were observed. The Cahn-Hilliard (C–H) linearization theory was found not applicable for kinetics analysis of the scattering data at λ < 346 nm due to RLS effect near the absorption band. Based on a decomposition reaction model, the apparent activation energy of SD phase separation was estimated by the Arrhenius equation. In view of its simplicity and sensitivity of measurement, affordability and availability of instrument, and wide application range of polymer blends, RLS proved to be an effective means for characterization of microstructural variation in polymer blends.
Co-reporter:Yunyun Huang, Yujie Chen, Chenglong Hu, Bin Zhang, Ting Shen, Xudong Chen and Ming Qiu Zhang
Journal of Materials Chemistry A 2012 - vol. 22(Issue 22) pp:
Publication Date(Web):
DOI:10.1039/C2JM31410J
Co-reporter:Wei-ang Luo, Xudong Chen, Zhengfu Liao, Jin Yang, Kancheng Mai and Mingqiu Zhang
Physical Chemistry Chemical Physics 2010 - vol. 12(Issue 18) pp:NaN4693-4693
Publication Date(Web):2010/03/19
DOI:10.1039/B921435F
The dynamic process of cold crystallization of amorphous poly(trimethylene terephthalate) (PTT) was investigated with resonance light scattering (RLS). By using an enhanced scattering peak at 329 nm, which was in close proximity to the absorption band of PTT film, density fluctuation due to gradual transition from amorphous to crystalline with increasing temperature was monitored. Accordingly, molecular chains movement and structure evolution in PTT during cold crystallization, in particular, the information about each phase of crystallization, including induction, nucleation, nucleus growth and secondary crystallization, were thoroughly revealed. The experimental results indicated that the kinetics parameters measured by the RLS method were in good agreement with those obtained by differential scanning calorimetry (DSC) and fluorescence spectroscopy. In addition, the RLS method can tell more details of the movement and variation in fine structures than DSC and fluorescence techniques as a result of its significantly enhanced scattering signals, like the orientation fluctuations of rigid segments in the course of glass transition and crystallization induction.
Co-reporter:Wei Hong, Yu Zhang, Lin Gan, Xudong Chen and Mingqiu Zhang
Journal of Materials Chemistry A 2015 - vol. 3(Issue 24) pp:NaN6191-6191
Publication Date(Web):2015/05/14
DOI:10.1039/C5TC00464K
Ordered arrays of Ag-capped colloidal crystals were fabricated and modified with conjugated polymers to evaluate the excitation and emission fluorescence enhancement due to localized surface plasmon resonance (LSPR). The maximum enhancement accrued on the maximum overlap between the excitation wavelength and LSPRs of the substrates. The observed fluorescence enhancement and lifetime measurement showed that the large enhancement came from a combination of greatly enhanced excitation and an increased radiative decay rate, leading to an associated enhancement of the quantum efficiency. Thus, such Ag nanostructured arrays fabricated by colloidal lithograph show great potential for biosensing and photovoltaic applications, and the excitation wavelength–LSPR-based fluorescence enhancement proves useful for understanding and optimizing metal-enhanced fluorescence.
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