Zhiping Yang

Changeable position of SPR peak of Ag nanoparticles embedded in mesoporous SiO2 glass by annealing treatment

Small Ag particles or clusters doped mesoporous SiO2 composite glass were prepared by the sol–gel process combined girradiation at room temperature and in ambient pressure. High-resolution transmission electron microscope (HRTEM) has revealed the existence of Ag nanoparticles and their growing through annealing treatments. With the particle size changing, an interesting reversible peak shift effect of the surface plasma resonance (SPR) was observed in the optical absorption measurement, which is explained as a comprehensive competitive result of both intrinsic property (size effect) and extrinsic influence from the matrix or the surrounding medium (interface interaction and its induced spill-out effect). # 2002 Elsevier Science B.V. All rights reserved.

Preparation of nanosized particles of FeNi and FeCo alloy in solution

FeNi and FeCo alloys of different compositions are prepared at room temperature in solution by surface catalysis or high-pressure inducement. Their sizes and morphologies are analyzed with X-ray diffraction (XRD), high-resolution transmission electron microscope (HRTEM) and X-ray photoelectron spectroscopy (XPS). The phase transformations of these alloys are similar to the reported phase diagrams of FeNi and FeCo alloys. HRTEM image of FeCo4 alloy shows the presence of rods. Their magnetic properties are studied. Surprisingly, the coercivity of FeCo4 alloy reaches as high as 718 Oe.

Synthesis of cobalt nanoparticles in ethanol hydrazine alkaline system (EHAS) at room temperature

Abstract Hydrazine, used as reducing agent in ethanol hydrazine alkaline system (EHAS) at room temperature, reduced cobalt salts (CoCl 2 ·6H 2 O or CoSO 4 ·7H 2 O) to FCC phase and HCP phase cobalt nanoparticles that were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetry (TG) and differential thermal analysis (DTA). After the nanoparticles were heated in argon at 200 °C for 2 h, the HCP phase cobalt nanoparticles grow more regular and larger, and the coercivity of the sample is increased from 480 to 680 Oe.

Gamma-irradiation-induced Ag/SiO2 composite films and their optical absorption properties

Abstract Small Ag particles or clusters dispersed mesoporous SiO 2 composite films were prepared by a new method: First the matrix SiO 2 films were prepared by sol–gel process combined with the dip-coating technique, then they were soaked in AgNO 3 solutions followed by irradiation of γ-ray at room temperature and in ambient pressure. The structures of these films were examined by X-ray diffraction (XRD), high-resolution transmission electron microscope (HRTEM), and optical absorption spectroscopy. It has been shown that the Ag particles grown within the porous SiO 2 films are very small, and they are isolated and dispersed from each other with very narrow size distributions. With increasing the soaking concentration and an additional annealing, an opposite peakshift effect of the surface plasmon resonance (SPR) was observed in the optical absorption measurements.

Optical absorption properties of Ag/SiO2 composite films induced by gamma irradiation

Mesoporous SiO2 composite films with small Ag particles or clusters dispersed in them were prepared by a new method: first the matrix SiO2 films were prepared by the sol?gel process combined with the dip-coating technique; then they were soaked in AgNO3 solutions; this was followed by irradiation with ?-rays at room temperature and ambient pressure. The structure of these films was examined by high-resolution transmission electron microscopy, and their optical absorption spectra were examined. It has been shown that the Ag particles grown within the porous SiO2 films are very small and are highly dispersed. On increasing the soaking concentration and subjecting the samples to an additional annealing, a different peak-shift effect for the surface plasmon resonance was observed in the optical absorption measurement. Possible mechanisms of this behaviour are discussed in this paper.