Structural and spectral properties of SnO2 nanocrystal prepared by microemulsion technique |
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| Authors: | JX Zhou MS Zhang JM Hong JL Fang Z Yin |
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| Institution: | (1) Department of Physics and Astronomy, Arizona State University, 85287-1504 Tempe, AZ, USA;(2) Institute of Microbiology, Immunology and Molecular Medicine, Tzu Chi University, 701, Sec. 3, Chung-Yang Rd., 970 Hualien, Taiwan, R.O.C;(3) Department of Pathology, Johns Hopkins Medical Institutions, 21231 Baltimore, MD, USA;(4) Department of Cellular Injury, Walter Reed Army Institute of Research, 20910-7500 Silver Spring, MD, USA;(5) Department of Medicine, Uniformed Services University of The Health Sciences, 20814-4799 Bethesda, MD, USA;(6) Department of Pharmacology, Uniformed Services University of The Health Sciences, 20814-4799 Bethesda, MD, USA |
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| Abstract: | Extrafine SnO2 nanocrystals as small as 2.4 nm were synthesized by the microemulsion method. The grain sizes and crystallization process were measured and investigated by X-ray diffraction. Two growth processes were proposed, and the activation energies of 4.3 and 23 KJ/mol were obtained for respective low-and fast-growth processes. TEM micrographs and the selected-area diffraction recorded their morphology and crystallization, well crystallized at about 773 K. All the IR modes measured by FT-IR spectrometer were assigned. The 616 cm-1 mode after annealing at 673 K showed fine crystallization. The temperature dependence of the Raman spectra shows that increase in intensity and decrease in linewidth of the 636 cm-1 mode with the increasing grain size indicate a phonon confinement effect. A new 330 cm-1 Raman mode originally inactive in bulk, was observed in the SnO2 nanocrystal by size effect. A low frequency mode at 76 cm-1 shifts to 38 cm-1 as the temperature goes up 873 K, which can be characterized to determine the SnO2 grain sizes. PACS 61.46.+w; 61.10.-i; 78.30.-j; 81.20.-n |
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