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D Z Shen

Publications and source records attributed to D Z Shen.

9 recordsLinked to original sources
PubMed2006

A simple route to porous ZnO and ZnCdO nanowires.

Porous ZnO nanowires were obtained in an inexpensive and simple way by thermally oxidizing ZnSe nanowires in air. The morphologies of the precursor and resulted nanowires are almost identical. X-ray diffraction and energy-dispersive X-ray spectroscopy reveal that the zinc blende ZnSe nanowires were transformed into wurtzite ZnO nanowires after oxidation. Transmission electron microscope measurements indicate that the ZnO nanowires are polycrystalline and are composed of nanoparticles and nanopores. ZnCdO nanowires, which were seldom reported previously, have also been prepared in this way. Just like the ZnO nanowires, the ZnCdO nanowires also show the porous structure. Photoluminescence studies on both ZnO and ZnCdO nanowires show intense near-band edge emissions at room temperature. The transition from one kind of nanowires to another by simple thermal oxidization described in this paper may be applicable to some other compound semiconductors and may open a practical route to yield nanowires.

Journal Article↗
PubMed2005

Optical properties of ZnO and ZnO:In nanorods assembled by sol-gel method.

Self-assembled zinc oxide (ZnO) and indium-doping zinc oxide (ZnO:In) nanorod thin films were synthesized on quartz substrates without catalyst in aqueous solution by sol-gel method. The samples were characterized by x-ray diffraction (XRD), scanning electron microscope (SEM), Raman-scattering spectroscopy, room-temperature photoluminescence (PL) spectra, and temperature-dependent PL spectra measurements. XRD and Raman spectra illustrated that there were no single In2O3 phase in ZnO lattice after indium doping. The PL spectra of ZnO showed a strong UV emission band located at 394 nm and a very weak visible emission associated with deep-level defects. Indium incorporation induced the shift of optical band gap, quenching of the near-band-edge photoluminescence and enhanced LO mode multiphonon resonant Raman scattering in ZnO crystals at different temperatures. Abnormal temperature dependence of UV emission integrated intensity of ZnO and ZnO:In samples is observed. The local state emission peak of ZnO:In samples at 3.37 eV is observed in low-temperature PL spectra. The near-band-edge emission peak at room temperature was a mixture of excitons and impurity-related transitions for both of two samples.

Journal Article↗
PubMed2005

The optical properties of ZnO hexagonal prisms grown from poly (vinylpyrrolidone)-assisted electrochemical assembly onto Si (111) substrate.

ZnO hexagonal prisms have been grown from poly (vinylpyrrolidone)-assisted electrochemical assembly onto p-type Si (111) substrate. These ZnO prisms arrays are highly (0002) orientated. The (0001) end facets and {1010} side facets of the hexagonal prisms are well defined. The photoluminescence (PL) spectrum of these ZnO prisms shows an intense ultraviolet near band-gap emission with a full width at half maximum of 86 meV at room temperature. The low-temperature PL spectrum is split into well-resolved free and bound exciton emission lines. The temperature dependence of the exciton emission intensities shows a nonmonotonic decaying behavior, which can be explained by the existence of interfacial states.

Journal Article↗
PubMed2005

Effects of thermal annealing on the structural and optical properties of Mg(x)Zn(1-x)O nanocrystals.

Mg(x)Zn(1-x)O ternary alloy nanocrystals with hexagonal wurtzite structures were fabricated by using the sol-gel method. X-ray diffraction patterns, UV-vis absorption spectra, and photoluminescence spectra were used to characterize the structural and optical properties of the nanocrystals. For as-prepared nanocrystals, the band gap increases with increasing Mg content. Weak excitonic emission with strong deep-level emission related to oxygen vacancy and interface defects is observed in the photoluminescence spectra at room temperature. Thermal annealing in oxygen was used to decrease the number of defects and to improve the quality of the nanocrystals. In terms of XRD results, the grain sizes of nanocrystals increase with increasing annealing temperature and the lattice constants of alloy are smaller than those of pure ZnO. The band gap becomes narrower with increasing annealing temperature. For Mg(x)Zn(1-x)O nanocrystals (x=0.03-0.15) annealed at temperatures ranging from 500 to 1000 degrees C, intense near-band-edge (NBE) emissions and weak deep-level (DL) emissions are observed. Consequently, the quality of Mg(x)Zn(1-x)O nanocrystals can be improved by thermal annealing.

Journal Article↗
PubMed2005

Preparation of ZnO colloids by aggregation of the nanocrystal subunits.

Colloidal ZnO particles with narrow size distribution were prepared via a sol-gel process by base-catalyzed hydrolysis of zinc acetate. The morphology of ordered arrays of the particles was recorded by SEM. SEM also reveals that these uniform particles were composed of tiny ZnO subunits (singlets) sized of several nanometers. The size of the singlets, which is confirmed by X-ray diffraction and UV-vis absorption spectra, increases as the aging time is prolonged. The size-selective formation of colloids by aggregation of nanosized subunits is proposed to consist of two-stage growth by nucleation of nanosized crystalline primary particles and their subsequent aggregation into polycrystalline secondary colloids. The aggregates are all spherical because the internal rearrangement processes are fast enough. The ZnO colloids, i.e., the aggregates, tend to self-assemble into well-ordered hexagonal close-packed structures. Room-temperature photoluminescence was characterized for green and aged ZnO.

Journal Article↗
PubMed1994

Hypocholesterolemic effects of mixture Da Huai on experimental rats and treatment of a homozygous FH child.

This study observes the hypocholesterolemic effects of Mixture Da Huai--a drug of enhancing monocyte macrophage system--on experimental rats, and the treatment of a homozygous familial hypercholesterolemia (FH) child. The results show that TC, VLDL-C and LDL-C in Mixture Da Huai group were significantly reduced and HDL-C was significantly increased. Fractional clearance rates for 125I-GLC-LDL, and the 125I-GLD-LDL uptake of rat peritoneal macrophages were significantly increased. Excretions of total sterol and acidic sterol in feces were also increased. After treatment for 3 months, serum TC and LDL-C of a homozygous FH child were significantly decreased. Tendon and cutaneous xanthomas were limited. This study indicates that by promoting the monocyte macrophage system to degrade LDL, a promising prevention and treatment of hypercholesterolemia and atherosclerosis might be provided, especially in the treatment of homozygous FH.

Animals↗
PubMed1991

[Effect of acupuncture and moxibustion on antiobesity in the variation of plasma cyclic nucleotide and the function of vegetative nervous system].

The authors observed the changes of the obesity index, lipid index, the equilibrium indices of the vegetative nervous system (Y value) and the plasma cAMP of 46 cases of simple obese before and after acupuncture. Of 46 cases, 39 were of the non-sthenia of liver-Yang (group 1) and 7 of the sthenia of liver-Yang (group 2). It was found that the sympathetic nervous function of the patients in group 1 was markedly higher than the normal. In both of them, the lipid metabolism was abnormal and the content of cAMP in plasma was significantly lower than the normal. The marked effects were achieved on the cases which received one course of treatment (1 month) by acupuncture, the total effective rate being 84.8%. The acupuncture brought about not only antiobesity effect but biphase changes on the blood pressures and Y value as well, that is, acupuncture raised the blood pressures and Y value of the patients in group 1 but reduced the blood pressures and Y value of the patients in group 2. In addition, acupuncture brought about good regulation effect on lipid metabolism and plasma cAMP of patients. This suggests that the regulation effect of acupuncture on plasma cAMP of patients with simple obese might be an important link by which antiobesity effect may be achieved.

Acupuncture Therapy↗