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Showing papers by "Zhong Chen published in 2012"


Journal ArticleDOI
TL;DR: In this article, a stable titanate nanobelt (TNB) particle suspension was prepared by a hydrogen-bond-driven assembly of pre-hydrolysed fluoroalkylsilane (FAS) on its surface.
Abstract: A stable titanate nanobelt (TNB) particle suspension was prepared by a hydrogen-bond-driven assembly of pre-hydrolysed fluoroalkylsilane (FAS) on its surface. A one-step electrophoretic deposition was applied to fabricate a transparent cross-aligned superhydrophobic TNB/FAS film on a conducting glass substrate. By controlling the deposition time, we have shown the transition between a “sticky” hydrophobic state (high contact angle with strong adhesion) and a “sliding” superhydrophobic state (high contact angle with weak adhesion). The optical transmittance can reach as high as 80% throughout most of the visible light region of the spectrum. These coatings have also displayed high chemical stability and self-cleaning ability. Upon heating the hydrophobic coatings at 500 °C, the TNB coating transforms into a porous TiO2(B) structure with superhydrophilic behavior and could be used for anti-fogging applications. With this TiO2-based system, we have demonstrated three different wetting states: superhydrophobicity with weak adhesion, high hydrophobicity with strong adhesion, and superhydrophilicity with immediate water spreading. Moreover, this work has also demonstrated superhydrophobic TNB/FAS films with high chemical stability and good self-cleaning performance and superhydrophilic pore-like TiO2(B) films with rapid water spreading and excellent anti-fogging ability.

426 citations


Journal ArticleDOI
TL;DR: Monodisperse Gd(2) O(3) -embedded iron oxide (GdIO) nanoparticles can simultaneously enhance the local magnetic field intensities of each other under an external magnetic field and result in synergistic enhancement of T(1) and T( 2) effects.
Abstract: National Science Foundation of China [21021061, 81000662, 21222106, J1030415]; Fundamental Research Funds for the Central Universities [2010121012]; Program for New Century Excellent Talents in University [NCET-10-0709]

259 citations


Journal ArticleDOI
Xiaobo Qu1, Di Guo1, Bende Ning1, Yingkun Hou, Yulan Lin1, Shuhui Cai1, Zhong Chen1 
TL;DR: Simulation results on phantom and in vivo data indicate that the proposed patch-based directional wavelets method outperforms conventional compressed sensing MRI methods in preserving the edges and suppressing the noise.

240 citations


Journal ArticleDOI
TL;DR: In this paper, three-dimensional TiO2 microspheres with different hierarchical nanostructures were synthesized by the synergistic strategies of ultrafast electrochemical spark discharge spallation process followed by thermal treatment.
Abstract: Three-dimensional TiO2 microspheres with different hierarchical nanostructures were synthesized by the synergistic strategies of ultrafast electrochemical spark discharge spallation process followed by thermal treatment. The morphology, crystal structure, surface area, and photocatalytic activity of the hierarchical nanostructures were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, surface area analysis, and UV–vis spectroscopy respectively. The nanostructure of hierarchical microspheres undergoes three evolution steps, which includes the change from nanosheets into hybrid nanoflakes/nanoparticles and finally to nanoparticles as calcination temperature increases, in line with the predicable trend of increase in crystallinity and decrease in specific surface area. Compared to other forms of calcined TiO2 samples (nanosheets and nanoparticles), the hybrid TiO2 nanoflake/nanoparticle hierarchical porous structure exhibits a higher photocatalytic activity f...

157 citations


Journal ArticleDOI
TL;DR: These nanoparticles are uniform in size, stable against photosensitizer leaching, and highly efficient in photogenerating cytotoxic singlet oxygen under near-infrared (NIR) light.
Abstract: Lanthanide-doped upconversion nanoparticles (UCNPs) have attracted considerable attention for their application in biomedicine. Here, silica-coated NaGdF(4):Yb,Er/NaGdF(4) nanoparticles with a tetrasubstituted carboxy aluminum phthalocyanine (AlC(4)Pc) photosensitizer covalently incorporated inside the silica shells were prepared and applied in the photodynamic therapy (PDT) and magnetic resonance imaging (MRI) of cancer cells. These UCNP@SiO(2)(AlC(4)Pc) nanoparticles were uniform in size, stable against photosensitizer leaching, and highly efficient in photogenerating cytotoxic singlet oxygen under near-infrared (NIR) light. In vitro studies indicated that these nanoparticles could effectively kill cancer cells upon NIR irradiation. Moreover, the nanoparticles also demonstrated good MR contrast, both in aqueous solution and inside cells. This is the first time that NaGdF(4):Yb,Er/NaGdF(4) upconversion-nanocrystal-based multifunctional nanomaterials have been synthesized and applied in PDT. Our results show that these multifunctional nanoparticles are very promising for applications in versatile imaging diagnosis and as a therapy tool in biomedical engineering.

126 citations


Journal ArticleDOI
TL;DR: In this paper, a series of SnBi alloys with Bi concentration ranging from 3% to 70% have been studied by nanoindentation technique at room temperature and the constant strain rate (CSR) method was used to evaluate the elastic modulus, hardness and the creep stress exponent of the alloys.
Abstract: A series of SnBi alloys with Bi concentration ranging from 3% to 70% have been studied by nanoindentation technique at room temperature. Constant strain rate (CSR) method was used to evaluate the elastic modulus, hardness and the creep stress exponent of the alloys. SnBi solid solutions with Bi concentration up to 10 wt% show significantly higher modulus and hardness than pure Sn. Small amount of Bi precipitates inside Sn-rich phase effectively enhance the hardness and creep resistance of the alloy; while such distribution of Bi particles has no effect on the elastic response of the matrix. The strain rate–stress relationship of the SnBi alloys has been evaluated in the range from 90 to 450 MPa. Three stress regions dominated by different rate-controlling mechanisms exist for the SnBi alloys with Bi concentration greater than 10%. At the high stress region (>370 MPa), dislocation glide dominates the creep rate where the stress exponents are greater than 10. At the intermediate stress region (200–370 MPa), dislocation climb is the dominant creep mechanism with stress exponents around 5–8. When fine lamellar structure is the dominant constituent of the microstructure, phase boundary sliding is identified as the rate-controlling mechanism in the low stress region (

109 citations


Journal ArticleDOI
TL;DR: In this paper, an imidazole-functionalized graphene (G-IMD) was prepared from graphene oxide by a facile one-pot method, and the functionalized graphene not only showed improved organic compatibility but also could simultaneously play the roles of a cure accelerator and reinforcement for anhydride-cured epoxies.
Abstract: In this study, an imidazole-functionalized graphene (G-IMD) was prepared from graphene oxide by a facile one-pot method. The functionalized graphene not only showed improved organic compatibility but also could simultaneously play the roles of a cure accelerator and reinforcement for anhydride-cured epoxies. Our results showed that G-IMD could successfully catalyze the curing reaction without the addition of any routine accelerator. Thermal and mechanical properties of the epoxy–G-IMD nanocomposites were systematically studied at different filler loadings. Compared with neat epoxy resin, tensile strength and Young's modulus of the nanocomposites were enhanced by 97% and 12%, respectively, at only 0.4 wt% G-IMD loading. Dynamic mechanical analysis and electron microscopic results revealed that the drastic improvements in mechanical properties could be attributed to the homogeneous dispersion of G-IMD and covalent bonding at the interface, which effectively improved the efficiency of load transfer between the matrix and graphene.

89 citations


Journal ArticleDOI
TL;DR: In this paper, a bifunctional visible-light photocatalyst Ag-AgBr/TiO2 was synthesized by a facile one-pot method, which exhibited much superior visible light photocatalytic activities for ibuprofen (IBP) degradation and mineralization.
Abstract: A bifunctional visible-light photocatalyst Ag–AgBr/TiO2 was synthesized by a facile one-pot method. The three-component composite exhibited much superior visible-light photocatalytic activities for ibuprofen (IBP) degradation and mineralization as compared to single-component (TiO2) and two-component (Ag/TiO2, Ag–AgBr) systems, as well as the conventional Ag–AgBr/P25. After 6 h of white LED irradiation, 81% of organic carbon could be mineralized along with decreased aromaticity and toxicity of the IBP degradation products. Meanwhile, the synthesized Ag–AgBr/TiO2 exhibited much stronger antibacterial activities than TiO2 and conventional Ag–AgBr/P25 under white LED irradiation. More interestingly, the Ag–AgBr/TiO2 had novel antibacterial activities against E. coli in the dark as compared to other Ag–AgBr/semiconductor photocatalysts that have been reported. For the first time, the action spectrum of Ag–AgBr/TiO2 was investigated using different colors of LED to elucidate the roles of Ag nanoparticles and AgBr in its visible-light photocatalytic activity. It reveals that both AgBr and Ag nanoparticles were photoactive species contributing to the high photocatalytic performance. Among the various oxidative species (h+, ˙OH, O2˙− and 1O2), O2˙− was the predominant species involved in IBP degradation upon the Ag–AgBr/TiO2 under white LED irradiation. The visible-light photocatalytic mechanism of Ag–AgBr/TiO2 and factor contributing to its high photostability in water are proposed.

89 citations


Journal ArticleDOI
TL;DR: In this paper, two nanoindentation methods, i.e., constant load (CL) test and constant strain rate (CSR) test, were used to detect the creep of polycrystalline Tin (Sn) and single crystal Aluminium (Al).
Abstract: Creep properties of polycrystalline Tin (Sn) and single crystal Aluminium (Al) were studied by two nanoindentation methods, i.e., constant load (CL) test and constant strain rate (CSR) test. The indentation strain rate and stress were calculated as the analogies drawn from uniaxial creep analysis. The stress exponent was expressed as the slope of the strain rate–stress curves plotted in the double logarithm scale. Between the two testing methods, the CSR test was clearly shown to be able to detect the creep of Sn in the power-law region, where the grain size had little effect on the creep rate. However, it was found that steady-state creep could not be achieved in the CL test. This has imposed ambiguities in applying the creep analysis developed from conventional creep scheme. The creep displacement from CL test was found unrepeatable for multiple measurements. CL test also has a smaller accessible stress range than that from a CSR test. The gradual variation of the stress exponents, especially for the small grain Sn sample, during holding process in the CL test could be due to the participation of the other rate controlling mechanisms which were closely related to the non-steady-state creep behaviour.

80 citations


Journal ArticleDOI
TL;DR: The optimized Ag/AgX thin films exhibited excellent degradation performance under visible light because of localized surface plasmon resonance effect and the reaction time, solution pH, and concentration of halide anions on the morphology of the AgX photocatalysts has been studied.
Abstract: Dense and uniform silver halides AgX (X = Cl, Br, I) nanoparticles were successfully fabricated on layered titanate nanowired honeycomb (TNHC) thin films. The growth of AgX nanocrystals was carried...

77 citations


Journal ArticleDOI
TL;DR: In this article, a nanohybrid plasmonic photocatalyst, comprising Ag-AgX (X = Cl, Br, I) nanoparticles anchored on titanate nanotubes, was fabricated via a silver ion incorporation process followed by hydrogen halide injection and light-irradiation.
Abstract: A nanohybrid plasmonic photocatalyst, comprising Ag-AgX (X = Cl, Br, I) nanoparticles anchored on titanate nanotubes, was fabricated via a silver ion incorporation process followed by hydrogen halide injection and light-irradiation. The Ag-AgX-titanate nanotubes (Ag-AgX-TNT) hybrid with a high surface area could synergistically adsorb and degrade methylene blue (MB) under visible light, viz., the titanate nanotubes adsorb MB onto their surfaces, which aids the degradation of MB by Ag-AgX nanoparticles. The excellent degradation performance of Ag-AgX under visible light originated from its localized surface plasmonic resonance effect. Therefore, this integrated silver halides/titanate hybrid can efficiently degrade MB dye, and shows good potential for waste water treatment utilizing solar irradiation.

Journal ArticleDOI
TL;DR: In this article, the optical properties of the doped NaTaO3 powders were tuned by changing the molar ratio of Na and Ta in the initial reactants, which resulted in the highest band gap narrowing compared to the other synthesis conditions.

Journal ArticleDOI
TL;DR: In this article, a method to extend the absorption edge of photocatalyst to visible region by the surface plasmon effect of silver is described. But the method is limited to the case of titanate nanotubes.

Journal ArticleDOI
TL;DR: In this article, a solid solution photocatalyst, Na1−xLaxFe1−1−o3 (x up to 0.06), was prepared by the conventional solid-state method, and the photophysical properties of the samples were studied by various experimen.
Abstract: A solid solution photocatalyst, Na1–xLaxFe1–xTaxO3 (x up to 0.06), was prepared by the conventional solid-state method. The photophysical properties of the samples were studied by various experimen ...

Journal ArticleDOI
TL;DR: In this article, defect migration and formation in both cubic zirconia (c-ZrO2) and ZrOS under different electron and element chemical potentials using density functional theory.

Journal ArticleDOI
TL;DR: In this article, the current and temperature dependence of GaN-based high power blue light-emitting diodes were investigated and a set of temperature sensitive optical parameters (TSOPs) were identified that can provide a real-time solution for determining the junction temperature.
Abstract: We investigate the current and temperature dependence of GaN-based high power blue light-emitting diodes and identify a set of temperature sensitive optical parameters (TSOPs) that can provide a real-time solution for determining the junction temperature (Tj). The relationships among Tj, forward current and TSOPs, “center of mass” wavelength, and, in particular, full width at half maximum (FWHM) have been studied, and the relevant mathematic models have been developed. The analysis indicates that using FWHM may yield higher accuracy than using other parameters as TSOPs.

Journal ArticleDOI
TL;DR: In this article, the spatial variation of the external quantum efficiency (EQE) of InGaN light-emitting diodes is investigated, and two different types of EQE droop are examined in one single device, offering unambiguous analyses on the underlying material physics without the complications of processing variation.
Abstract: We investigate the spatial variation of the external quantum efficiency (EQE) of InGaN light-emitting diodes. Two different types of EQE droop are examined in one single device, offering unambiguous analyses on the underlying material physics without the complications of the processing variation. The interplays of microscopic defects, extended defects, and energy fluctuation dictate the mechanisms of the droop, which represents a common theme in various optoelectronic devices. The two droop types correspond to the two extreme situations of energy fluctuation that affects the carrier diffusion and recombination. The finding suggests ways for improving the device performance, depending on operation conditions.

Journal ArticleDOI
TL;DR: A dual-phase material (DP-160) comprising hydrated titanate (H2Ti3O7·xH2O) and anatase (TiO2) was synthesized in a low-temperature one-pot process in the presence of triethylamine (TEA) as the N-source.

Journal ArticleDOI
TL;DR: In this article, two possible mechanisms of sulfur poisoning of copper (Cu) surfaces: S adsorption and formation of Cu-S compounds were studied. And the authors predicted a new Cu−S phase diagram that not only describes the formation of compounds but also predicts a dependence of the transition temperature between clean and contaminated Cu surfaces on partial pressure ratio of H 2 and H 2 S (P H 2 /PH 2 S ).

Journal ArticleDOI
TL;DR: In this article, an understanding of the reaction mechanisms of EDTA and diethanolamine for producing solution-derived (K, Na)NbO3 (KNN) thin films with outstanding piezoelectric properties and low leakage current is developed.
Abstract: An understanding of the reaction mechanisms of ethylenediaminetetraacetic acid (EDTA) and diethanolamine (DEA) for producing solution-derived (K, Na)NbO3 (KNN) thin films with outstanding piezoelectric properties and low leakage current is developed. X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and nuclear magnetic resonance spectroscopy (NMR) were used to analyze the interactions among EDTA, DEA, and metal cations in both precursor solutions and amorphous films. XPS analyses showed that the oxidation states of potassium, niobium, and oxygen in KNN amorphous film were enhanced with addition of EDTA and DEA in the precursor solution, which shifted closer to the oxidation states in the perovskite phase of the resulting KNN oxide film. FTIR analyses indicated that EDTA and DEA formed dative bonds with the nonhydrated potassium and sodium acetate after pyrolysis process at 330 °C while NMR analyses showed that such interactions could have occurred in the precursor so...

Journal ArticleDOI
Yushan Chen1, Shuhui Cai1, Congbo Cai1, Xiaohong Cui1, Zhong Chen1 
TL;DR: The experimental results demonstrate that this pulse sequence can retain useful structural information, even when the field inhomogeneity is sufficiently severe to erase almost all spectral information with conventional one‐dimensional single‐quantum coherence techniques, and good solvent suppression can be achieved.
Abstract: National Natural Science Foundation (NNSF) of China [81171331, 10974164, 11174239, 11074209]; Fundamental Research Fund for the Central Universities [2010121101]

Journal ArticleDOI
TL;DR: In this article, a novel cationic quaternary chalcohalide nanobelts were found in Hg4In2Q3Cl8 (Q = S, Se, Te), obtained by solid-state reaction.
Abstract: Novel cationic quaternary chalcohalide nanobelts were found in Hg4In2Q3Cl8 (Q = S, Se, Te), obtained by solid-state reaction. Due to the effects of dimensional reduction, both theoretical and experimental results demonstrate that their bandgaps are remarkably increased compared to those of the zinc-blende structure HgQ (Q = S, Se, Te).

Journal ArticleDOI
TL;DR: In this article, the electrical-thermal-optical characteristics of AlGaInP yellow and InGaN/GaN blue LEDs under electrical stresses were studied and the relationship between ideality factor and radiative recombination was also established.
Abstract: The electrical-thermal-optical characteristics of AlGaInP yellow and InGaN/GaN blue LEDs under electrical stresses were studied. Since the increase of effective acceptor concentration on p-type side, the forward voltages of AlGaInP decrease after 3155 h aging. And the operating voltage of high forward bias expansion for InGaN/GaN is due to the increase of the series resistance. Compared with InGaN/GaN, AlGaInP LEDs display different trend for the relationship between optical output and ideality factors. The relationship between ideality factor and radiative recombination is also studied and established. The characteristic of different intermediate adhesive is compared during aging period based on transient thermal test.

Journal ArticleDOI
Jingjing Xu1, Shuhui Cai1, Xuejun Li1, Jiyang Dong1, Jun Ding1, Zhong Chen1 
TL;DR: This poster presents a probabilistic procedure to estimate the iron content of nanoporous nanoporous particles and reports the results show clear trends towards higher iron content in nanoporous materials.

Journal ArticleDOI
Jihong Zhang1, Yulin Gao1, Yijun Lu1, Lihong Zhu1, Ziquan Guo1, Chen Guolong1, Zhong Chen1 
TL;DR: In this article, the measurement of the junction temperature and the determination of the thermal resistance of the single-crystal-silicon solar cell under the dark and illuminating conditions, respectively, were reported.
Abstract: This paper reports the measurement of the junction temperature and the determination of the thermal resistance of the single-crystal-silicon solar cell under the dark and illuminating conditions, respectively. Under the dark condition, the solar cell is considered as a conventional p-n junction and is subject to a reverse current in order to measure its junction temperature and determine the thermal resistance. A white LED array is used as the light source to operate the solar cell in order to avoid the heating effect of the infrared light by the solar simulator. Furthermore, we thoroughly calculate the thermal dissipation power. The result demonstrates that the thermal resistance drops from 3.7 to 2.0 K/W with the increase of the irradiance from 89.6 to 194.3 $\hbox{W/m}^{2}$ . It is also found that the thermal resistance under the dark condition is much higher than that under the illuminating condition, which is attributed to the light effect on the thermal resistance.

Journal ArticleDOI
Meijin Lin1, Yanqin Lin1, Xi Chen1, Shuhui Cai1, Zhong Chen1 
TL;DR: A pulse sequence termed CT-iDH, which combines intermolecular double-quantum filter (iDQF) with a modified constant-time (CT) scheme, is designed to achieve fast acquisition of high-resolution intermolescular zero-quantity coherences (iZQCs) and interm Molecule double-Quantum coherence spectra without strong coupling artifacts.

Journal ArticleDOI
TL;DR: This paper aims to demonstrate the efforts towards in-situ applicability of EMMARM, as to provide real-time information about concrete mechanical properties such as E-modulus and compressive strength in the response of the immune system to E-worm infection.

Journal ArticleDOI
TL;DR: In this paper, the effect of oxygen concentration on the thermal stability of amorphous Ta-Ni thin film alloy was studied, where the films were deposited on Si substrates by co-sputtering of Ta and Ni targets.

Journal ArticleDOI
TL;DR: In this article, two types of amorphous thin films, namely Ta67.34Ni27.06O5.60 and Ta73.25Ni26.10O0.65, were employed to assess the diffusion barrier performance, and the samples were then annealed in vacuum for 30min at temperatures ranging from 500°C to 800°C.

Journal ArticleDOI
TL;DR: In this paper, the thermal and infrared properties of a vertical-electrode gallium-nitride light-emitting diode (GaN LED) were investigated using different heating mechanisms.
Abstract: The thermal and infrared properties of a vertical-electrode gallium-nitride light-emitting diode (GaN LED) are studied. Because infrared emissivity is a critical parameter for temperature measurements, the relationship between temperature and emissivity for a vertical-electrode GaN LED is investigated using different heating mechanisms; the result indicates a strong dependence between them. The temperature variation across the chip surface of a LED with a Si substrate increases from 2.9 to 8.4°C when the current changes from 100 to 900 mA with heat sink temperature of 45°C. Temperature nonuniformity may occur as a consequence of nonuniform joule heating, which is due to nonuniform current flow through the vertical-electrode LED. Around the electrode pad the spreading current is especially crowded.