Showing papers by "Zhen Li published in 2011"
TL;DR: In this paper, the carbon nanotube (CNT) sponges in terms of oil absorption were studied and it was shown that the sorption capacity of CNT sponge is greater than 100 grams for many organics and oils with viscosities of 3-200 cP.
273 citations
TL;DR: In this article, liquid phase exfoliated graphene sheets were modified by oleic acid and dispersed in lubricant oils as additives, and the tribological properties of graphene-contained oils were investigated using a four-ball tribometer.
Abstract: Liquid phase exfoliated graphene sheets were modified by oleic acid and dispersed in lubricant oils as additives. The tribological behaviours of graphene-contained oils were investigated using a four-ball tribometer. The lubricant with optimized graphene concentrations of 0.02–0.06 wt% showed enhanced friction and anti-wear performance, with friction coefficient and wear scar diameter reduced by 17% and 14%, respectively.
263 citations
TL;DR: This work achieves 13.8% efficiency solar cells by combining carbon nanotubes and Si and doping with dilute HNO(3).
Abstract: Various approaches to improve the efficiency of solar cells have followed the integration of nanomaterials into Si-based photovoltaic devices. Here, we achieve 13.8% efficiency solar cells by combining carbon nanotubes and Si and doping with dilute HNO3. Acid infiltration of nanotube networks significantly boost the cell efficiency by reducing the internal resistance that improves fill factor and by forming photoelectrochemical units that enhance charge separation and transport. Compared to conventional Si cells, the fabrication process is greatly simplified, simply involving the transfer of a porous semiconductor-rich nanotube film onto an n-type crystalline Si wafer followed by acid infiltration.
240 citations
TL;DR: Flu-1, a new design strategy for the development of fluorescent turn-on chemodosimeters toward OCl(-) was proposed by the removal of the C=N isomerization, which exhibited the off-on response for OCl(-), sensitively and selectively.
222 citations
TL;DR: In this paper, a modified one-pot hydrothermal route was used to synthesize ultra-thin anatase TiO2 nanosheets with dominant {001} facets and controllable thickness (1.6-2.7 nm).
Abstract: Ultra-thin anatase TiO2 nanosheets with dominant {001} facets (∼82%) and controllable thickness (1.6–2.7 nm) were synthesized by using a modified one-pot hydrothermal route. As a morphology controlling agent, the concentration of hydrofluoric acid has a significant impact on the thickness of the as-synthesized TiO2 nanosheets. In addition, according to the XRD patterns and TEM images of the products on different reaction stages, the growth process of TiO2 nanosheets was clarified for the first time. We further measured the efficiency for H2 evolution of the ultra-thin anatase TiO2 nanosheets loaded with 1 wt% Pt from photochemical reduction of water in the presence of methanol as a scavenger. The TiO2 nanosheets exhibited a H2 evolution rate as high as 7381 μmol h−1 g−1 under UV-vis light irradiation, attributing to their exposed reactive {001} facets and high crystallinity.
190 citations
TL;DR: Experimental results show that the proposed watermarking method is comparable to, if not, better than SVD based method and several selected typical audioWatermarking methods, even in the presence of various common signal processing attacks.
160 citations
TL;DR: In this paper, the stability of surface structure under other ambient conditions might be one of the most critical issues for anatase TiO2 with exposed high-reactive {001} facets.
Abstract: Due to its great importance in fundamental research and practical applications, tailored synthesis of anatase TiO2 dominated with highly energetic {001} facets has been extensively studied during the past few years. However, clean (001) surface of anatase TiO2 has been evidenced to be unstable and usually tends to reconstruct under ultrahigh-vacuum conditions. Thus, the stability of surface structure under other ambient conditions might be one of the most critical issues for anatase TiO2 with exposed high-reactive {001} facets. In this study, the hydrothermal stability of {001} faceted anatase TiO2 was systematically investigated by using single-crystalline anatase TiO2 nanosheets with 80% {001} facets as a model starting material. Under hydrothermal conditions (200 °C in deionized water), anatase TiO2 nanosheets can grow into larger single crystals with a truncated bipyramidal shape through an oriented attachment process along the [001] crystallographic direction, driven by the minimization of surface en...
158 citations
TL;DR: In this paper, the authors reviewed some new design strategies for second-order NLO polymers, including dendronized polymers and hyperbranched polymers with the new concept of the "suitable isolation group".
155 citations
23 Oct 2011
TL;DR: Experimental results demonstrate that the proposed LWT-SVD method is not only robust to both general signal processing and desynchronization attacks but also outperform the selected previous studies.
Abstract: In this paper, a new and robust audio watermarking scheme based on lifting wavelet transform (LWT) and singular value decomposition (SVD) is proposed. Specifically, the watermark data is inserted in the LWT coefficients of the low frequency subband taking advantage of SVD and quantization index modulation (QIM). The use of QIM renders our scheme blind in nature. Furthermore, the synchronization code technique is also integrated with hybrid LWT-SVD audio watermarking. Experimental results demonstrate that the proposed LWT-SVD method is not only robust to both general signal processing and desynchronization attacks but also outperform the selected previous studies.
143 citations
TL;DR: Graphene oxide (GO) was found to effectively enhance the selectivity of aggregation-induced emission (AIE) biosensors, and a new method based on GO and AIE molecules was proposed to detect bovine serum albumin (BSA) with high sensitivity and selectivity.
141 citations
TL;DR: The Cu(2+) sensor could act as a new good probe toward hypochlorites with high sensitivity as low as 8.1 × 10(-7) M, providing a novel approach to develop new probes for oxidants.
TL;DR: In this article, a new disubstituted polyacetylene (P2) bearing pyridine moieties in the side chains was prepared conveniently through a postfunctional method, the strong green fluorescence of which could be completely quenched by Cu2+ ions at the concentration as low as 2.0 × 10−6 mol/L in diluted solutions.
Abstract: To develop sensitive and selective S2– chemosensors, a new disubstituted polyacetylene (P2) bearing pyridine moieties in the side chains was prepared conveniently through a postfunctional method, the strong green fluorescence of which could be completely quenched by Cu2+ ions at the concentration as low as 2.0 × 10–6 mol/L in diluted solutions. Based on the displacement strategy, by utilizing the much higher stability constant of the complex of S2– and Cu2+, the quenched fluorescence of the solution of P2 by Cu2+ ions could recover upon the addition of trace S2– anions, with the detection limit down to 5.0 × 10–7 mol/L. Moreover, no interference were observed from other anions, including SO32–, HSO3–, SO42–, ClO4–, I–, Br–, Cl–, F–, IO3–, HPO42–, PO43–, C2O42–, S2O32–, CO32–, AcO–, CN–, and P2O74–, making P2 a novel, sensitive, and selective sulfide probe.
TL;DR: In this article, the authors reported the enhanced photovoltaic properties in polycrystalline BiFeO3 (BFO) thin films with graphene as top electrodes The short circuit current density (Jsc) and open circuit voltage of the heterojunction were measured to be 25 µA/cm2 and 044 µV, respectively.
Abstract: We report the enhanced photovoltaic properties in polycrystalline BiFeO3 (BFO) thin films with graphene as top electrodes The short circuit current density (Jsc) and open circuit voltage of the heterojunction are measured to be 25 μA/cm2 and 044 V, respectively, much higher than the reported values for polycrystalline BFO with indium tin oxide (ITO) as top electrodes Influence of HNO3 treatment on the photovoltaic properties is studied, and a significant photocurrent density improvement from 25 μA/cm2 to 28 mA/cm2 is observed A metal-intrinsic semiconductor-metal model is proposed to explain the graphene induced enhancement comparing with traditional ITO
TL;DR: Two new highly selective colorimetric chemosensors for Hg(2+), based on azobenzene and highly selective Hg (2+)-promoted deprotection of a dithioacetal have been designed and synthesized.
Abstract: Two new highly selective colorimetric chemosensors for Hg(2+), based on azobenzene and highly selective Hg(2+)-promoted deprotection of a dithioacetal have been designed and synthesized. In the presence of as little as 20 mu m Hg(2+), the sensors change their color from light yellow to deep red, which can easily be observed by the naked eye. The underlying signaling mechanism is intramolecular charge transfer (ICT). The sensors have good selectivity for Hg(2+) with respect to several common alkali, alkaline earth, and transition metal ions. Furthermore, they can be used for in-the-field measurements by virtue of a dipstick approach without any additional equipment.
TL;DR: This study identifies miR-378-TOB2-cyclin D1 as a functional module to mediate the cross talk between Myc and Ras signaling in cellular transformation.
Abstract: The c-Myc transcription factor activates a cascade of downstream targets to form a complex transcriptional program that ultimately leads to cellular transformation. Although a large number of protein-encoding genes as well as non-coding RNAs were identified as Myc targets, only a few have been validated to be functionally important for c-Myc-driven transformation. Here, we identify a microRNA (miRNA), miR-378, as a novel target of the c-Myc oncoprotein that is able to cooperate with activated Ras or HER2 to promote cellular transformation. Mechanistically, miR-378 achieves this oncogenic effect, at least in part, by targeting and inhibiting the anti-proliferative BTG family member, TOB2, which is further elucidated as a candidate tumor suppressor to transcriptionally repress proto-oncogene cyclin D1. Therefore, our study identifies miR-378-TOB2-cyclin D1 as a functional module to mediate the cross talk between Myc and Ras signaling in cellular transformation.
TL;DR: Based on the protection reaction between ethanethiol and aldehyde, a novel fluorescent probe (2) for Hg2+ ions, with the simplest structure reported so far, was designed, which displayed high sensitivity and selectivity towards Hg 2+ and Ag+ over other metal ions with detectable fluorescent signals, due to distinct deprotection reaction of dithioacetal as discussed by the authors.
Abstract: Based on the protection reaction between ethanethiol and aldehyde, a novel fluorescent probe (2) for Hg2+ ions, with the simplest structure reported so far, was designed, which displayed high sensitivity and selectivity towards Hg2+ and Ag+ over other metal ions with detectable fluorescent signals, due to distinct deprotection reaction of dithioacetal. Compound 2 was further utilized to construct the chemical reaction-based conjugated polymer probes (P2 and P4) for Hg2+ ions. More importantly, the effect of the molecular weight of conjugated polymers on the sensitivity of the probes towards Hg2+ ions was carefully studied.
TL;DR: These robust near-infrared Au NCs show great potential in biolabeling, tracking, and imaging of other cells and diseases, especially in the diagnosis and treatment of chronic myeloid leukemia.
Abstract: Highly bright fluorescent gold nanoclusters (Au NCs) have been prepared by one-step reduction of aqueous precursor solution in the presence of multidentate thioether-terminated poly(methacrylic acid) (PTMP-PMAA). The fluorescence quantum yield of the resultant Au NCs is 4.8% higher than that of the similarly sized Au NCs prepared by the etching method (1.8–4.0%). These Au NCs show excellent photostability and have been successfully applied to label the hematopoietic cells first. The results show that Au NCs were endocytosed by the cancer cells significantly more than the normal cells, in comparison with control experiments labeled with fluorescent quantum dots (CdTe). The cytotoxicity experiments demonstrate the excellent biocompatibility of Au NCs, proven by a relatively lower cytotoxicity than CdTe. These robust near-infrared Au NCs show great potential in biolabeling, tracking, and imaging of other cells and diseases, especially in the diagnosis and treatment of chronic myeloid leukemia.
TL;DR: In this paper, the authors combined two planar nanostructures, graphene and CdSe nanobelts, to construct Schottky junction solar cells with open-circuit voltages of about 0.5 V and cell efficiencies on the order of 0.1%.
Abstract: We have combined two planar nanostructures, graphene and CdSe nanobelts, to construct Schottky junction solar cells with open-circuit voltages of about 0.5 V and cell efficiencies on the order of 0.1%. By covering transparent graphene or carbon nanotube (CNT) films on selected positions along macroscopically long CdSe nanobelts, we have demonstrated the fabrication of active solar cells with many different configurations and parallel connections from individual or multiple assembled nanobelts. The graphene-CdSe nanobelt solar cells reported here show a great flexibility in creating diverse device architectures, and might be scaled up for cell integration based on assembled nanobelt arrays and patterned graphene (or CNT) films.
TL;DR: By utilizing a displacement method, a macrocyclic compound 1, could report the presence of sulfide anion, with the detection limit of 7.0 × 10(-7) mol/L, making compound 1 a new, highly sensitive and selective sulfideAnion chemosensor.
Abstract: By utilizing a displacement method, a macrocyclic compound 1, could report the presence of sulfide anion, with the detection limit of 7.0 × 10−7 mol/L; moreover, no interference was observed from other anions, including SO32−, HSO3−, SO42−, ClO4−, I−, Br−, Cl−, F−, IO3−, HPO42−, PO43−, C2O42−, S2O32−, CO32−, AcO−, CN− and P2O74−, making compound 1 a new, highly sensitive and selective sulfide anion chemosensor.
TL;DR: A fast (in 10-40 s) flame synthesis of high quality few-layered graphene/graphite films, offering the advantages of simplicity, high efficiency, energy saving, low cost and the ability to extend to continuous and mass production of graphene.
TL;DR: In this paper, the authors used polarimetric SAR image for classification on and around the Dongkemadi glacier in the Qinghai-Tibetan plateau and found that this distinction can be achieved by target decomposition.
TL;DR: A simple fluorescence method for detection of cyanide sensitively and selectively based on the dissolution of polymer-coated gold nanoparticles by cyanide, which worked well in the above water samples, with a good linear correlation.
Abstract: We report a simple fluorescence method for detection of cyanide sensitively and selectively based on the dissolution of polymer-coated gold nanoparticles by cyanide. The lowest concentration for quantification of cyanide ions was 3.0×10(-7) M, and other common anions nearly have no influence. Furthermore, several real water samples spiked with cyanide, including local groundwater, tap water, boiled water, and lake water, were analyzed, and the experimental results demonstrated that our sensing system worked well in the above water samples, with a good linear correlation.
21 Mar 2011
TL;DR: This work details the authors' efforts to push the baseline of expression recognition performance on a realistic database with an ensemble of features comprising of Hierarchial Gaussianization, Scale Invariant Feature Transform and Optic Flow.
Abstract: This work details the authors' efforts to push the baseline of expression recognition performance on a realistic database. Both subject-dependent and subject-independent emotion recognition scenarios are addressed in this work. These two happen frequently in real life settings. The approach towards solving this problem involves face detection, followed by key point identification, then feature generation and then finally classification. An ensemble of features comprising of Hierarchial Gaussianization (HG), Scale Invariant Feature Transform (SIFT) and Optic Flow have been incorporated. In the classification stage we used SVMs. The classification task has been divided into person specific and person independent emotion recognition. Both manual labels and automatic algorithms for person verification have been attempted. They both give similar performance.
TL;DR: This work fabricated CNT sponge nanocomposites by directly infiltrating epoxy fluid into the CNT framework while maintaining the original network structure and CNT contact, with simultaneous improvement in mechanical and electrical properties.
Abstract: Fabrication of high-performance nanocomposites requires that the nanoscale fillers be dispersed uniformly and form a continuous network throughout the matrix. Direct infiltration of porous CNT sponges consisting of a three-dimensional nanotube scaffold may provide a possible solution to this challenge. Here, we fabricated CNT sponge nanocomposites by directly infiltrating epoxy fluid into the CNT framework while maintaining the original network structure and CNT contact, with simultaneous improvement in mechanical and electrical properties. The resulting composites have an isotropic structure with electrical resistivities of 10 to 30 Ω·cm along arbitrary directions, much higher than traditional composites by mixing random CNTs with epoxy matrix. We observed reversible resistance change in the sponge composites under compression at modest strains, which can be explained by tunneling conduction model, suggesting potential applications in electromechanical sensors.
TL;DR: In this paper, the effect of acetonitrile feeding amount on optical transmittance and electrical conductivity of N-doped carbon thin films (N-CFMs) on copper foils is investigated.
TL;DR: In this paper, the authors take advantage of well-developed technologies used for dispersing carbon nanotubes for the subsequent fabrication of nanocompositematerials, which is crucially important for their practical application.
Abstract: and so on.However,itisstillabigchallengetomakegraphenesoluble,ordispersewellinsolvents,includingorganicandaqueousmedia, due to aggregation and/or restacking effects,althoughthesolubilization/dispersionofgrapheneenablesthe processing of this material by solvent-assisted techni-ques for the subsequent fabrication of nanocompositematerials, which is crucially important for their practicalapplication.By taking advantage of well-developed technologiesused for dispersing carbon nanotubes,
TL;DR: Carbon thin films with blue emission were fabricated on various substrates by spin coating dodecylamine (DDA)-capped carbon nanoparticles (CNPs) in this paper.
Abstract: Carbon thin films with blue emission were fabricated on various substrates by spin coating dodecylamine (DDA)-capped carbon nanoparticles (CNPs).
TL;DR: Four new hyperbranched polytriazoles containing azo moieties, derived from different AB(2) -type monomers, were successfully prepared through the "click" chemistry reaction under copper(I) catalysis by modifying the synthetic route.
Abstract: In this paper, four new hyperbranched polytriazoles containing azo moieties, derived from different AB(2) -type monomers, were successfully prepared through the "click" chemistry reaction under copper(I) catalysis by modifying the synthetic route. The polymers were soluble in organic solvents and exhibited good second-order nonlinear optical (NLO) properties. Thanks to the self-assembly of perfluoroaromatic moieties in the periphery, HP2 showed the best NLO properties, with the d(33) value as high as 145.0 pm V(-1).
TL;DR: In this article, six AB 2 -type polytriazoles containing azo-chromophore moieties, derived from the same hyperbranched polymer intermediate, were successfully prepared through click reaction under copper(I) catalysis by modifying the synthetic route.
Abstract: In this article, according to the concept of "suitable isolation group," six new AB 2 -type polytriazoles containing azo-chromophore moieties, derived from the same hyperbranched polymer intermediate, were successfully prepared through click reaction under copper(I) catalysis by modifying the synthetic route, in which different isolation groups in different size were introduced to the periphery of the hyperbranched polymers as end-capping moieties. With the different end-capping groups, these hyperbranched polymers, P1-P6, exhibited different solubility and processability; also, their nonlinear optical properties were modified accordingly, realizing the adjustment of the properties of hyperbranched polymers through the structural design.
TL;DR: In this paper, the average velocity gradient (AVG) method is proposed to improve window sizes in feature tracking and to obtain the most suitable flow field, which is based on a cross-correlation algorithm that seeks offsets of the maximal correlation windows on repeated satellite images.
Abstract: Feature tracking is an efficient way to derive glacier velocity. It is based on a cross-correlation algorithm that seeks offsets of the maximal correlation windows on repeated satellite images. In this paper we demonstrate that different window sizes lead to different velocities. The averaged velocity gradient (AVG) method is proposed to improve window sizes in feature tracking and to obtain the most suitable flow field. The AVG method measures velocity variation between adjacent windows on the whole glacier in the image. Different window sizes lead to different AVG values, and the best-size window corresponds to the value where the AVG changes from abrupt to gradual. Using improved feature tracking, two flow fields of the same glacier are acquired with Advanced Land Observing Satellite (ALOS) optical and synthetic aperture radar (SAR) data, respectively. The advantages, application conditions, accuracy and disadvantages of the two kinds of data using the feature tracking method are discussed.