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Tian C.,MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter | Ding C.,Xi'an Jiaotong University | Liu S.,CAS Institute of Physics | Yang S.,MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter | And 5 more authors.
ACS Nano | Year: 2011

Using three-dimensional finite-difference time-domain (FDTD) simulation, we described a systematic investigation on the electric field enhancement of the silver corrugated nanowires. The enhancement factor (EF) of surface-enhanced Raman scattering (SERS) for corrugated nanowires can be markedly increased by 1 or 2 orders of magnitude as compared with the smooth nanowires. Moreover, the EF can be further increased with nanoparticle attachment on the corrugated Ag nanowires owing to the coupling between the discrete plasmon state of the nanoparticles and continuum plasmon states of the corrugated nanowire or the crossed corrugated nanowires. The surface plasmonic field distribution of Ag nanowires can be effectively controlled by the polarization of the incident light. Raman spectrum measurements show that the relatively dense corrugated nanowires exhibit a relatively high reproducibility and SERS enhancement attributed to the elimination of polarization-dependent SERS-anisotropic enhancement via the overlapping of randomly distributed Ag nanowires. Such nanostructures as potential nanoantennas offer a route to optimize plasmon coupling for designing miniaturization integration. © 2011 American Chemical Society.

Deng S.,University of Maryland University College | Deng S.,Xiamen University | Zhang Y.,University of Maryland University College | Zhang Y.,MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter | And 7 more authors.
Nature Communications | Year: 2011

Covalent chemistry typically occurs randomly on the graphene lattice of a carbon nanotube because electrons are delocalized over thousands of atomic sites, and rapidly destroys the electrical and optical properties of the nanotube. Here we show that the Billups-Birch reductive alkylation, a variant of the nearly century-old Birch reduction, occurs on single-walled carbon nanotubes by defect activation and propagates exclusively from sp 3 defect sites, with an estimated probability more than 1,300 times higher than otherwise random bonding to the 'π-electron sea'. This mechanism quickly leads to confinement of the reaction fronts in the tubular direction. The confinement gives rise to a series of interesting phenomena, including clustered distributions of the functional groups and a constant propagation rate of 18 ±6 nm per reaction cycle that allows straightforward control of the spatial pattern of functional groups on the nanometre length scale. © 2011 Macmillan Publishers Limited. All rights reserved.

Tan S.,Xi'an Jiaotong University | Li J.,Xi'an Jiaotong University | Gao G.,Xi'an Jiaotong University | Li H.,CAS Institute of Chemistry | And 2 more authors.
Journal of Materials Chemistry | Year: 2012

Fluoropolymer containing unsaturation, an important intermediate for many reactions such as radical addition and Michael addition reaction, could be either utilized to synthesize fluoropolymer with desired functions or cured for rubber applications, which has rarely been investigated because of the absence of a synthetic strategy. A facile method to synthesize fluoropolymer with tunable unsaturation via controlled dehydrochlorination of commercially available poly(vinylidene fluoride-co-chlorotrifluoroethylene) (P(VDF-co-CTFE)) catalyzed by tertiary monoamines under mild conditions has been reported in this work. The resultant copolymers are carefully characterized with nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR), and thermal gravimetric analysis (TGA). It has been shown that the elimination could be well controlled by employing proper solvent, catalyst and reaction conditions. The typical side reactions catalyzed with amines, such as Michael addition reaction and main chain scission during the dehydrofluorination of fluoropolymer, could be avoided in the present reaction system. The kinetics results indicate that the elimination reaction is in a bi-molecular mechanism (E2), which is well recognized in strong base-catalyzed elimination of halogenated hydrocarbon. The concentration, alkalinity and steric bulk of the catalysts, the polarity and capability to absorb HCl acid of solvents, and the reaction time and temperature exhibit dominant influences on the dehydrochlorination of P(VDF-co-CTFE). The fluoropolymer containing unsaturation is readily cured with peroxide, and the crosslinked fluoropolymer exhibits excellent solvent resistance and mechanical properties. © 2012 The Royal Society of Chemistry.

Tan S.,Xi'an Jiaotong University | Li J.,Xi'an Jiaotong University | Zhang Z.,Xi'an Jiaotong University | Zhang Z.,MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter
Macromolecules | Year: 2011

ATRP has been recognized as a powerful tool to synthesize polymers with well-defined structures, narrow polydispersity, and controlled molecular weight in the past decades. Usually, it is believed that the typical side reactions (such as termination and chain transfer reactions) in typical radical polymerizations could be inhibited in ATRP for the persistent radical effect. More recently, some researchers did notice that some chain transfer reaction to N containing ligands happens in ATRP. However, the chain transfer constant (ktr/kp) in ATRP has never been able to be measured experimentally due to the difficulty of determining the precise composition of the resultant polymer. Therefore, the influence of chain transfer reaction onto ATRP has rarely been discussed. In this work, we provide a novel method to determine the competition between chain transfer reaction and initiation reaction of free radicals (ktr/ki) by analyzing the structure of grafting copolymers from poly(vinylidene fluoride-co- trichlorofluoride ethylene) P(VDF-co-CTFE). The perfect coincidence of experimental results with theoretical ones indicates that the method may help to understand the chain transfer reaction in ATRP as well as its influence on the chain end of resultant polymer. © 2011 American Chemical Society.

Li J.,Xi'an Jiaotong University | Tan S.,Xi'an Jiaotong University | Ding S.,Xi'an Jiaotong University | Li H.,CAS Institute of Chemistry | And 3 more authors.
Journal of Materials Chemistry | Year: 2012

In this work, we report a novel antiferroelectric-like performance at high poling fields obtained in poly(ethyl methacrylate) (PEMA) grafted poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)) series copolymers for application as high energy density and low loss capacitor dielectrics films. Compared with the pristine P(VDF-TrFE) random copolymer, an enhanced discharged energy density but a lowered energy loss has been observed as more PEMA is grafted. This novel antiferroelectric-like behavior at high poling field was explained by the crystalline impediment and polarization confinement effect induced by PEMA side chains. The highest discharged energy density of 14 J cm-3 and a low loss of 30% at 550 MV m-1 are achieved in the sample containing 22 wt% PEMA. This finding represents one of the effective routes to design potential dielectric polymer films for high energy storage applications. © The Royal Society of Chemistry 2012.

Li J.,Xi'an Jiaotong University | Hu X.,Xi'an Jiaotong University | Gao G.,Xi'an Jiaotong University | Ding S.,Xi'an Jiaotong University | And 4 more authors.
Journal of Materials Chemistry C | Year: 2013

For potential application in high energy storage capacitors with high energy density and low energy loss, three sets of poly(vinylidene fluoride-co-trifluoroethylene-co-chlorotrifluoroethylene) [P(VDF-TrFE-CTFE)] grafted with poly(methacrylic ester)s, including poly(methyl methacrylate) (PMMA), poly(ethyl methacrylate) (PEMA) and poly(butyl methacrylate) (PBMA) copolymers, are designed and investigated carefully. Due to their intermediate polarity, relatively high glass transition temperature, and excellent compatibility with PVDF chains, the poly(methacrylic ester) segments introduced could not only dramatically weaken the coupling interactions of oriented polar crystals, but could also accelerate the reversal switching of polar crystal domains along the applied electric field, which leads to well hindered remnant polarization. As a result, the displacement-electric field (D-E) hysteresis behaviors of the graft copolymers could be tuned from typical ferroelectric to either antiferroelectric or linear shape under high electric field. Meanwhile, significantly reduced energy loss and effectively improved energy discharging efficiency were obtained. Compared with PMMA and PBMA, PEMA with intermediate polarity and grafting length exhibits more suitable confinement of the F-P transition of P(VDF-TrFE-CTFE), and thus more desirable energy storage properties are observed in the resultant copolymers. These findings may help to deeply understand the ferroelectric nature of PVDF based fluoropolymers and design new energy storage capacitor materials with high discharged energy density and low energy loss. This journal is © 2013 The Royal Society of Chemistry.

Tan S.,Xi'an Jiaotong University | Liu E.,Xi'an Jiaotong University | Zhang Q.,Xi'an Jiaotong University | Zhang Z.,Xi'an Jiaotong University | Zhang Z.,MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter
Chemical Communications | Year: 2011

An environmentally friendly and controllable P(VDF-co-CTFE) hydrogenation route involving the transition-metal complex mediated radical chain transfer reaction is successfully developed to synthesize P(VDF-co-CTFE-co-TrFE). The typical transition metal catalysts of ATRP reaction could be applied in this process. © 2011 The Royal Society of Chemistry.

Wang S.,Xi'an Jiaotong University | Jing X.,Xi'an Jiaotong University | Jing X.,MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter | Wang Y.,Xi'an Jiaotong University | Si J.,Xi'an Jiaotong University
Polymer Degradation and Stability | Year: 2014

This work reports an aryl boron-containing phenolic resin (PR) exhibiting an extremely high thermal decomposition temperature and char yield and formed by reacting phenylboronic acid (PBA) with PR. DSC was used to study the curing behaviour of the PBA modified PR (PBPR). The structure and thermal properties of the cured PBPR were investigated by FTIR, XPS, 11B NMR and TGA. Phenylboronates were formed during the curing of PBPR, which reduced the distance between benzene rings. The TGA indicates that the temperature with the maximum decomposition rate increased for the cured PBPR by 56 C, and the charring yield increased by 13.4 per cent (800 C, nitrogen atmosphere) relative to PR. FTIR, XPS, XRD, 11B NMR and Raman analyses were used to study the structural evolution of the cured PBPR during pyrolysis. Boron oxide was formed during the char formation from the cleavage of B-C and B-O-C bonds via pyrolysis, which effectively avoided the release of volatile carbon oxides and retained the carbon. In addition, incorporating boron into the carbon lattice increases the crystallite height and decreases the interlayer spacing. These findings reveal that PBA exhibited obvious effects in improving the thermal stability and promoting the graphite crystallites of PR during carbonization. © 2013 Elsevier Ltd. All rights reserved.

Liu C.H.,MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter | Ding C.H.,Xi'an Jiaotong University
Wear | Year: 2010

In this study, HFIS304 coating comprising NiCr (80/20) matrix (60 wt%) combined with Cr2O3 (20 wt%), Ag (10 wt%) and eutectic BaF2/CaF2 (10 wt%) as solid self-lubricants additives has been successfully prepared by cold isostatic pressing and high-frequency induction sintering (HFIS) on a Ni-based superalloy rod. The microstructure of HFIS304 was fine and dense, the size of Cr2O3, BaF2/CaF2 particles was below 1 μm, and that of Ag particles about 1 μm. The tribological properties of HFIS304 composites against Inconel X-750 were examined. The wear resistance and friction coefficient of the HFIS304 were superior to that of the PS304 in the temperature range from room temperature to 600 °C. The improvement in wear resistance of the HFIS304 was discussed in the terms of its microstructural characteristics. Additionally, the model of high temperature self-lubricating particles was proposed. © 2009 Elsevier B.V. All rights reserved.

Yang G.,Xi'an Jiaotong University | Yan W.,Xi'an Jiaotong University | Zhang Q.,Xi'an Jiaotong University | Shen S.,Xi'an Jiaotong University | Ding S.,MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter
Nanoscale | Year: 2013

One dimensional core/shell nanostructures consisting of two different semiconductors with appropriate band alignment are promising for photocatalytic hydrogen production due to their efficient light harvesting and fast carrier transport. In this work, CdS/ZnO core/shell nanofibers were successfully synthesized by one-pot single-spinneret electrospinning. The ZnO layered structures (60 nm in thickness) were uniformly grown onto continuous CdS core fibers (220 nm in diameter and several micrometers in length). The as-fabricated CdS/ZnO core/shell nanofibers as nanoheterojunction photocatalysts exhibited excellent visible light photocatalytic activity and stability for hydrogen production. The possible formation mechanism of the CdS/ZnO core/shell nanofibers was also proposed based on the experimental observations. Moreover, the morphologies and components of the as-prepared nanofibers can be controlled easily by tuning the annealing temperature and Zn/Cd ratios of the precursor solution. © 2013 The Royal Society of Chemistry.

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