Use of diffuse reflectance spectroscopy for optical characterization of un-supported nanostructures

Abstract

Optical properties of un-supported or powdered nanostructures are frequently determined through UV-Vis absorption spectroscopy of their dispersed solutions in liquid media. Though the peak position of the absorption band of semiconductor nanostructures could be defined well from such measurements, precise determination of their band gap energies ( E g ) is difficult. However, using the Kubelka-Munk treatment on the diffuse reflectance spectra of such powdered semiconductor nanostructures, it is possible to extract their E g unambiguously. We discussed the advantages of using Diffuse Reflectance Spectroscopy (DRS) over UV-Vis absorption spectroscopy in powdered nanostructured materials. Un-doped and In-doped ZnO nanostructures of needle-like morphology, grown by a low-temperature hydrothermal technique are used for the optical studies. Possible sources of mistake in estimating E g from UV-Vis absorption spectra of dispersed samples are discussed.