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Showing papers by "Zhen Li published in 2009"


Journal ArticleDOI
TL;DR: In this article, a synthetic route for silole functionalization is elaborated, through which a series of functionalized siloles are successfully prepared, and most of them show an opposite phenomenon of aggregation-induced emission (AIE).
Abstract: The synthesis of functionalized siloles has been a challenge because of the incompatibility of polar functional groups with the reactive intermediates in the conventional protocols for silole synthesis. In this work, a synthetic route for silole functionalization is elaborated, through which a series of functionalized siloles are successfully prepared. Whereas light emissions of traditional luminophores are often quenched by aggregation, most of the functionalized siloles show an exactly opposite phenomenon of aggregation-induced emission (AIE). The siloles are nonemissive when dissolved in their good solvents but become highly luminescent when aggregated in their poor solvents or in the solid state. Manipulation of the aggregation–deaggregation processes of the siloles enables them to play two seemly antagonistic roles and work as both excellent quenchers and efficient emitters. The AIE effect endows the siloles with multifaceted functionalities, including fluorescence quenching, pH sensing, explosive detection, and biological probing. The sensing processes are very sensitive (with detection limit down to 0.1 ppm) and highly selective (with capability of discriminating among different kinds of ions, explosives, proteins, DNAs, and RNAs). The siloles also serve as active layers in the fabrication of electroluminescent devices and as photosensitive films in the generation of fluorescence patterns.

303 citations


Journal ArticleDOI
TL;DR: In this paper, high quality graphene sheets have been prepared by a facile liquid phase exfoliation of worm-like graphite (WEG), and this approach combining with advances in large scale industry manufacturing of WEG could potentially lead to the development of new and more effective graphene products.
Abstract: High quality graphene sheets have been prepared by a facile liquid phase exfoliation of worm-like graphite (WEG). This approach combining with the advances in large scale industry manufacturing of WEG could potentially lead to the development of new and more effective graphene products.

189 citations


Proceedings ArticleDOI
01 Sep 2009
TL;DR: A new image representation to capture both the appearance and spatial information for image classification applications is proposed and it is justified that the traditional histogram representation and the spatial pyramid matching are special cases of the hierarchical Gaussianization.
Abstract: In this paper, we propose a new image representation to capture both the appearance and spatial information for image classification applications First, we model the feature vectors, from the whole corpus, from each image and at each individual patch, in a Bayesian hierarchical framework using mixtures of Gaussians After such a hierarchical Gaussianization, each image is represented by a Gaussian mixture model (GMM) for its appearance, and several Gaussian maps for its spatial layout Then we extract the appearance information from the GMM parameters, and the spatial information from global and local statistics over Gaussian maps Finally, we employ a supervised dimension reduction technique called DAP (discriminant attribute projection) to remove noise directions and to further enhance the discriminating power of our representation We justify that the traditional histogram representation and the spatial pyramid matching are special cases of our hierarchical Gaussianization We compare our new representation with other approaches in scene classification, object recognition and face recognition, and our performance ranks among the top in all three tasks

165 citations


Journal ArticleDOI
TL;DR: The obtained experimental results demonstrated that the attachment of aromatic rotors to luminophore moieties would lead to the decreased quantum yields, which confirmed that the AIEE phenomena were caused by the restriction of the intramolecular vibrational and rotational motions in an indirect manner.
Abstract: A series of new carbazole-based luminophores (1−12) were synthesized and well characterized, which demonstrated aggregation-induced emission enhancement (AIEE) properties. The obtained experimental results demonstrated that the attachment of aromatic rotors to luminophore moieties would lead to the decreased quantum yields (measured in diluted solutions); the more rotors attached, the smaller the quantum yields tested. This further confirmed that the AIEE phenomena were caused by the restriction of the intramolecular vibrational and rotational motions in an indirect manner.

165 citations


Journal ArticleDOI
TL;DR: A new rhodamine-based dye (I) was successfully developed as a colorimetric chemosensor for the sensitive detection of cyanide, with a detection limit as low as 0.013 ppm.
Abstract: By applying an indirect strategy, a new rhodamine-based dye (I) was successfully developed as a colorimetric chemosensor for the sensitive detection of cyanide. In the presence of copper ions, the colorless solution of compound I changed to magenta; however, upon the addition of trace cyanide, the magenta color faded to colorless immediately, with a detection limit as low as 0.013 ppm (ΔA = 0.054), much lower than the Maximum Contaminant Level for cyanide in drinking water (0.20 ppm) set by the US Environmental Protection Agency. Other anions, including Cl−, I−, IO3−, SO42−, NO2−, Br−, H2PO4−, F−, SCN−, HSO4−, and ClO4−, had nearly no influence on the probing behavior of dye I toward cyanide.

146 citations


Journal ArticleDOI
Zhong'an Li1, Gui Yu1, Pan Hu1, Cheng Ye1, Yunqi Liu1, Jingui Qin1, Zhen Li1 
TL;DR: In this article, azo-chromophore-containing hyperbranched polymers (HP1 and HP2) were constructed from AB2 mixtures using a synthetic procedure.
Abstract: By modifying the synthetic procedure, the previous reported impossible approach was successfully utilized to construct new azo-chromophore-containing hyperbranched polymers (HP1 and HP2) from AB2 m...

107 citations


Journal ArticleDOI
TL;DR: Novel data is provided indicating the BST2 protein expression is associated with the formation of bone metastases in human breast cancer, and it is believed that BST2 may be a potential biomarker in breast cancer with bone metastasis.
Abstract: Bone metastases are frequent complications of breast cancer. Recent literature implicates multiple chemokines in the formation of bone metastases in breast cancer. However, the molecular mechanism of metastatic bone disease in breast cancer remains unknown. We have recently made the novel observation of the BST2 protein expression in human breast cancer cell lines. The purpose of our present study is to investigate the expression and the role of BST2 in bone metastatic breast cancer. cDNA microarray analysis was used to compare the BST2 gene expression between a metastatic to bone human breast cancer cell line (MDA-231BO) and a primary human breast cancer cell line (MDA-231). The BST2 expression in one bone metastatic breast cancer and seven non-bone metastatic breast cancer cell lines were also determined using real-time RT-PCR and Western blot assays. We then employed tissue array to further study the BST2 expression in human breast cancer using array slides containing 20 independent breast cancer tumors that formed metastatic bone lesions, 30 non-metastasis-forming breast cancer tumors, and 8 normal breast tissues. In order to test the feasibility of utilizing BST2 as a serum marker for the presence of bone metastasis in breast cancer, we had measured the BST2 expression levels in human serums by using ELISA on 43 breast cancer patients with bone metastasis, 43 breast cancer patients without bone metastasis, and 14 normal healthy controls. The relationship between cell migration and proliferation and BST2 expression was also studied in a human breast recombinant model system using migration and FACS analysis. The microarray demonstrated over expression of the BST2 gene in the bone metastatic breast cancer cell line (MDA-231BO) compared to the primary human breast cancer cell line (MDA-231). The expression of the BST2 gene was significantly increased in the bone metastatic breast cancer cell lines and tumor tissues compared to non-bone metastatic breast cancer cell lines and tumor tissues by real time RT-PCR, Western blot and TMA. Furthermore, serum levels of BST2 measured by ELISA were also significantly higher among patients with breast cancer metastatic to bone compared to breast cancer patients without metastatic to bone (P < .0001). Most importantly, the breast cancer cell line that transfected with BST2 demonstrated increased BST2 expressions, which was associated with increased cancer cell migration and cell proliferation. These results provide novel data indicating the BST2 protein expression is associated with the formation of bone metastases in human breast cancer. We believe that BST2 may be a potential biomarker in breast cancer with bone metastasis.

103 citations


Journal ArticleDOI
TL;DR: A hybrid solar cell model composed of a heterojunction cell and a photoelectrochemical (PEC) cell has been proposed and characterized and a power conversion efficiency of 1.29%, higher than those reported for SiNW array-based PEC cells, has been obtained.
Abstract: A hybrid solar cell model composed of a heterojunction cell and a photoelectrochemical (PEC) cell has been proposed and characterized. In the hybrid cell, a thin film of double-walled carbon nanotubes forms a heterojunction with the silicon nanowire (SiNW) array and also functions as the transparent counter electrode of the PEC cell. The cell performance can be readily tuned by controlling the SiNW density. Under AM 1.5G illumination, a power conversion efficiency of 1.29%, higher than those reported for SiNW array-based PEC cells, has been obtained.

95 citations


Journal ArticleDOI
TL;DR: In this article, the effect of different reaction parameters on the structural and optical properties of CdSe nanowires has been investigated, and the results are compared with those reported in literature.
Abstract: Semiconductor nanowires prepared by wet chemical methods are a relatively new field of 1D electronic systems, where the dimensions can be controlled by changing the reaction parameters using solution chemistry. Here, the solution–liquid–solid approach where the nanowire growth is governed by low-melting-point catalyst particles, such as Bi nanocrystals, is presented. In particular, the focus is on the preparation and characterization of CdSe nanowires, a material which serves a prototype structure for many kinds of low dimensional semiconductor systems. To investigate the influence of different reaction parameters on the structural and optical properties of the nanowires, a comprehensive synthetic study is presented, and the results are compared with those reported in literature. How the interplay between different reaction parameters affects the diameter, length, crystal structure, and the optical properties of the resultant nanowires are demonstrated. The structural properties are mainly determined by competing reaction pathways, such as the growth of Bi nanocatalysts, the formation and catalytic growth of nanowires, and the formation and uncatalytic growth of quantum dots. Systematic variation of the reaction parameters (e.g., molecular precursors, concentration and concentration ratios, organic ligands, or reaction time, and temperature) enables control of the nanowire diameter from 6 to 33 nm, while their length can be adjusted between several tens of nanometers and tens of micrometers. The obtained CdSe nanowires exhibit an admixture of wurtzite (W) and zinc blende (ZB) structure, which is investigated by X-ray diffraction. The diameter-dependent band gaps of these nanowires can be varied between 650 and 700 nm while their fluorescence intensities are mainly governed by the Cd/Se precursor ratio and the ligands used.

94 citations


Journal ArticleDOI
Xinming Li1, Hongwei Zhu1, Jinquan Wei1, Kunlin Wang1, Eryang Xu1, Zhen Li1, Dehai Wu1 
TL;DR: In this article, the band gaps of self-assembled single-walled carbon nanotube (SWNT) films have been determined through curve fitting using the semi-empirical Tauc and Davis-Mott model, based on the measurement of optical absorption at the visible and near infrared range.
Abstract: The band gaps of self-assembled single-walled carbon nanotube (SWNT) films have been determined through curve fitting using the semi-empirical Tauc and Davis–Mott model, based on the measurement of optical absorption at the visible and near infrared range. This study provides a practicable option for the determination of band gaps for ultra-thin SWNT films or multi-walled carbon nanotube films whose vHs peaks cannot be well resolved in absorption spectra.

88 citations



Journal ArticleDOI
21 Sep 2009-Analyst
TL;DR: An azo-based dye (I) was designed for the detection of cyanide by utilizing a new indirect method and could give rise to visible red-to-yellow color change, making compound I a selective and sensitive cyanide chemosensor.
Abstract: An azo-based dye (I) was designed for the detection of cyanide by utilizing a new indirect method. In the presence of Cu(II), compound I could give rise to visible red-to-yellow color change. The resultant yellow solution could change to red immediately upon the addition of trace cyanide, with the detection limit of 0.15 ppm, but no changes were observed in the presence of other anions, including Cl−, I−, IO3−, SO42−, NO2−, Br−, H2PO4−, F−, SCN−, HSO4−, ClO4− and CN−, making compound I a selective and sensitive cyanide chemosensor.

Journal ArticleDOI
TL;DR: Two indole-based organic dyes were conveniently prepared and well characterized and utilized as dye sensitizers in dye-sensitized solar cells and demonstrated efficient photon-to-electron conversion properties.
Abstract: Two indole-based organic dyes were conveniently prepared and well characterized. The triphenylamine or carbazole moieties were bonded to the indole group acting as a potential electron donor, which can tune the HOMO and LUMO levels of the resultant dye, and another triphenylamine or carbazole group was linked to the pyrrole ring on the nitrogen atom, which was expected to suppress the aggregation of the dye in the solid state to some degree. These two dyes were utilized as dye sensitizers in dye-sensitized solar cells and demonstrated efficient photon-to-electron conversion properties.

Journal ArticleDOI
TL;DR: In this paper, surface-functionalized periodic mesoporous organosilica (PMO) hollow spheres are successfully synthesized by using a hybrid silica precursor, 1,2-bis(trimethoxysilyl)ethane (BTME), and five precursors with different functional groups (−SH, −NH2, −CN, −C═C, −benzene) as well as surfactants, fluorocarbon and cetyltrimethylammonium bromide, combining a new vesicle and liquid
Abstract: Surface-functionalized periodic mesoporous organosilica (PMO) hollow spheres are successfully synthesized by using a hybrid silica precursor, 1,2-bis(trimethoxysilyl)ethane (BTME), and five precursors with different functional groups (−SH, −NH2, −CN, −C═C, −benzene) as well as surfactants, fluorocarbon and cetyltrimethylammonium bromide, combining a new vesicle and liquid crystal “dual templating” technique. Different disruption effects on the final mesostructure are observed following the order of −SH from 3-mercaptopropyltrimethoxysilane (MPTMS) > −benzene from (trimethoxysilyl)benzene (TMSB) ∼ −C═C from vinyltrimethoxysilane (VTMS) > −NH2 from 3-aminopropyltriethoxysilane (APTES) > −CN from 3-cyanopropyltriethoxysilane (CPTES). The particle size, cavity size, and wall thickness of these hollow spheres can be adjusted by changing the amount of precursors or surfactants applied. In terms of providing better control over surface properties of products and giving more uniform surface coverage of functional...

Journal ArticleDOI
TL;DR: In this paper, the controlled synthesis of copper sulfide (CuS) nanoplate-based architectures in different solvents has been realized at low cost by simply reaction of Cu(NO3)2·3H2O and S under solvothermal conditions without the use of any template.


Journal ArticleDOI
TL;DR: In this article, a new hyperbranched polymer (HB-car), constructed fully by carbazole moieties, is successfully synthesized through a one-pot Suzuki coupling reaction.
Abstract: A new hyperbranched polymer (HB-car), constructed fully by carbazole moieties, is successfully synthesized through a one-pot Suzuki coupling reaction. The resultant polymer is well-characterized, and its hole-transporting ability is studied carefully. The device, in which HB-car is utilized as a hole-transporting layer and tris-(8-hydroxyquinoline) aluminum as an electron-emitting layer as well as electron-transporting layer, gives a much higher efficiency (3.05 cd A–1), than that of a poly(N-vinylcarbazole) based device (2.19 cd A–1) under similar experimental conditions. The remarkable performance is attributed to its low energy barrier and enhanced hole-drifting ability in the HB-car based device. In addition, for the first time, a field-effect transistor (FET) based on the hyperbranched polymer is fabricated, and the organic FET device shows that HB-car is a typical p-type FET material with a saturation mobility of 1 × 10–5 cm2 V–1 s–1, a threshold voltage of –47.1 V, and an on-to-off current ratio of 103.

Journal ArticleDOI
TL;DR: In this paper, the authors presented the preparation and characterization of ZnO/ZnS nanostructured materials through sulfuration conversion from znO nanorods by a simple chemical synthesis.

Journal ArticleDOI
TL;DR: In this article, a simple hydrothermal method and fabricated the ZnO/SiO 2 core/shell nanostructures through a sol-gel chemistry process successfully, the structure, morphology and composition of the products were determined by the techniques of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), energy dispersive x-ray spectroscope (EDS) and transmission electron microscope (TEM).

Journal ArticleDOI
TL;DR: In this article, X-ray powder diffraction (XRD) and transmission electron microscopy (TEM) were used to characterize CdS nanostructured materials by a chemical synthesis via the reaction of Cd(NO3)2·4H2O and various sulfur sources.

Journal ArticleDOI
Zhong'an Li1, Wenbo Wu1, Gui Yu1, Yunqi Liu1, Cheng Ye1, Jingui Qin1, Zhen Li1 
TL;DR: The obtained experimental results indicated that the utilization of "H"-type chromophores might be a promising choice to efficiently translate the large beta values of the organic Chromophores into high macroscopic NLO activities of polymers.
Abstract: For the first time, a series of dendronlike main-chain polyurethanes have been successfully designed and synthesized, in which different isolation groups with different sizes were introduced to modify the subtle structure of the used “H”-type chromophores, according the concept of “suitable isolation groups”. Thanks to the advantages of “H”-type chromophores and the introduced suitable isolation group, all of the polymers demonstrated large NLO effects, good processability, improved optical transparency, and thermal stability. The obtained experimental results indicated that the utilization of “H”-type chromophores might be a promising choice to efficiently translate the large β values of the organic chromophores into high macroscopic NLO activities of polymers.

Journal ArticleDOI
TL;DR: The organization and composition of endocrine islets were investigated in both embryonic and adult pancreas and found that beta-cells were generally located in the center and non-beta cells in the periphery; reminiscent of the "mantel-core" organization of islets of Langerhans in mammals.

Journal ArticleDOI
TL;DR: In this article, two dendronized nonlinear optical polyfluorenes were synthesized with high azo-chromophore loading density by the introduction of high generation chromophore dendrons on the side chains.
Abstract: Two new dendronized nonlinear optical (NLO) polyfluorenes were synthesized with high azo-chromophore loading density by the introduction of high generation chromophore dendrons on the side chains. Thanks to the advantages of Sharpless’ click chemistry reaction, the dendrons were conveniently bonded to the backbone of polyfluorene with the conversion of 100%, although they were really very bulky. The new-formed triazole rings in the dendrons acted as suitable isolation groups to minimize the strong dipole−dipole interactions among the polar chromophore moieties to improve NLO effects, according to the results obtained from UV−vis spectra and order parameters. All the polymers were well characterized and exhibited good solubility, high thermal ability, wide optical window, and large NLO effects (up to 106.0 pm/V). In addition, the tested NLO results of these dendronzied polymers demonstrated a deviation from the dipolar frustration that typically limits the NLO effect in conventional chromophore/polymer com...

Journal ArticleDOI
16 Jan 2009-Polymer
TL;DR: In this paper, a new disubstituted polyacetylene (P1) was utilized to sense α-amino acids based on a "turn-on" model, through an indirect approach.

Journal ArticleDOI
Zhong'an Li1, Wenbo Wu1, Cheng Ye1, Jingui Qin1, Zhen Li1 
TL;DR: Two new series of main-chain and side-chain second-order nonlinear optical polyurethanes have been successfully prepared, in which isolation groups with different sizes were introduced to adjust the NLO property of the resultant polymers, according to the concept of "suitable isolation groups".
Abstract: In this paper, two new series of main-chain and side-chain second-order nonlinear optical (NLO) polyurethanes have been successfully prepared, in which isolation groups with different sizes were introduced to adjust the NLO property of the resultant polymers, according to the concept of “suitable isolation groups”. The second harmonic generation (SHG) experiments demonstrated that all the polymers exhibited large second harmonic generation (SHG) coefficients of d33 values (up to 105.6 pm/V) with excellent thermal stability and film-forming ability, indicating that the introduction of isolation groups could alleviate the “nonlinearity−stability trade off” efficiently. In addition, for both main-chain and side-chain polymers, BOP acted as the suitable isolation group. It was also found that the positive influence of the linked suitable isolation spacer was more obvious in the main-chain polymers, in comparison with those in the side-chain polymers.

Journal ArticleDOI
TL;DR: The experimental results demonstrated that the alpha-amino acid selective nature of P1 over other analytes was relatively good, so the work reported here might open up a new avenue for developing new biosensors.
Abstract: For the first time, a conjugated fluorescent polymer was utilized to probe α-amino acids, sensitively and selectively, through a new approach. First the strong fluorescence of the prepared polyfluorene (P1) was quenched by trace copper ions, and then the quenched fluorescence was recovered upon the addition of α-amino acids, making P1 a new and sensitive biosensor toward α-amino acids. The experimental results demonstrated that the α-amino acid selective nature of P1 over other analytes was relatively good. Thus, the work reported here might open up a new avenue for developing new biosensors.

Journal ArticleDOI
TL;DR: A novel series of indole-based conjugated oligomers were synthesized by Wittig-Horner-Emmons olefination from the aryl-bridged bisindole aldehydes and the corresponding bisphosphonates and showed favorable properties.
Abstract: A novel series of indole-based conjugated oligomers were synthesized by Wittig−Horner−Emmons olefination from the aryl-bridged bisindole aldehydes and the corresponding bisphosphonates. The introduction of indole into the light-emitting materials made these oligmers exhibit favorable properties. They were thermally stable, and the UV−vis spectra of the oligomers could be modulated by the arylenevinylene units; their PL and EL spectra also showed similar properties that can be further modulated. The highest luminance achieved in a device with the configuration ITO/PEDOT:PSS/oligomer/Ba/Al was 2536 cd/m2 at 7.5 V for oligomer P6, and the highest external EL quantum efficiency of 0.39% and luminous efficiency of 0.97 cd/A were attained by oligomer P1.

Proceedings ArticleDOI
Tao Chen1, Kui Wu1, Kim-Hui Yap1, Zhen Li1, Flora S. Tsai1 
18 May 2009
TL;DR: A survey on mobile landmark recognition for information retrieval and techniques and algorithms used in the literatures, including content analysis of landmarks and classification methods for recognition, will be presented.
Abstract: The growing usage of mobile devices has led to proliferation of many mobile applications. A growing trend in mobile applications is centered on mobile landmark recognition. It is a new mobile application that recognizes a captured landmark using the mobile device and retrieves related information. This paper will present a survey on mobile landmark recognition for information retrieval. A general overview of existing mobile landmark recognition systems will be summarized. The techniques and algorithms used in the literatures, including content analysis of landmarks and classification methods for recognition, will be described.

Journal ArticleDOI
TL;DR: ZnO nanospindles are synthesized by PVP-assisted hydrothermal growth and ZnO@ZnS core-shell microspindles were successfully fabricated by sulfidation as mentioned in this paper via a facile chemical synthesis.

Journal ArticleDOI
TL;DR: New imidazole-functionalized disubstituted polyacetylene was synthesized by utilizing the postfunctional strategy and its ability to sense copper ions and α-amino acids by fluorescence quenching has been studied.
Abstract: New imidazole-functionalized disubstituted polyacetylene was synthesized by utilizing the postfunctional strategy. In addition, its ability to sense copper ions and α-amino acids by fluorescence quenching has been studied. The quenching of the fluorescence of the imidazole-functionalized disubstituted polyacetylene was observed at a very low level of Cu(2+) (7.0 × 10(-7) mol · L(-1) ). The fluorescent intensity decreased rapidly upon the increase of the concentration of the added solution of Cu(2+) . It was expected that the addition of α-amino acids to the solution of the polyacetylene/Cu(2+) complex could turn on the fluorescence of the polyacetylene, if α-amino acids could remove the copper ions from the complex. Glycine, was used for testing: upon the addition of glycine the quenched fluorescence of P1 turned on immediately. The detection limit was as low as 6.0 × 10(-5) mol · L(-1) .