Polaron absorption in tungsten oxide nanoparticle aggregates

被引：46

作者：

Niklasson, GA ^{[1
]}

Klasson, J ^{[1
]}

Olsson, E ^{[1
]}

机构：

[1] Uppsala Univ, Angstrom Lab, Dept Mat Sci, SE-75121 Uppsala, Sweden

来源：

ELECTROCHIMICA ACTA | 2001年 / 46卷 / 13-14期

关键词：

nanoparticles; optical absorption; polaron; bandgap; tungsten oxide;

D O I：

10.1016/S0013-4686(01)00388-7

中图分类号：

O646 [电化学、电解、磁化学];

学科分类号：

081704 ;

摘要：

Small tungsten oxide nanoparticles were prepared from a heated tungsten filament, by gas evaporation in air at pressures between 1 and 9 Torr. Transmission electron microscopy showed that the median particle diameter increased with pressure during evaporation from 7 nm at 1 Torr to 21 nm at 9 Torr. X-ray diffraction measurements were in agreement with data for the monoclinic and triclinic structures of tungsten trioxide. Composition analysis by Rutherford backscattering spectrometry gave evidence for a substoichiometric composition of WO2.7 to WO2.8. Optical reflectance and transmittance of samples deposited on sapphire substrates were measured in the wavelength range of 0.2-10 mum. From these data the absorption coefficient of the particulate samples was obtained. A strong absorption peak in the near infrared was ascribed to polaron absorption. The peak wavelength consistently shifted towards longer wavelengths with increasing evaporation pressure. This is probably a particle size effect and may be connected to an observed bandgap widening with decreasing particle size. (C) 2001 Elsevier Science Ltd. All rights reserved.

引用

页码：1967 / 1971

页数：5

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