Low-temperature photoluminescence of WO3 nanoparticles

In this paper we report the results on the study of the low-temperature photoluminescence of WO3 nanoparticles uncoated and coated by carbon. The photoluminescence spectra of WO3 nanoparticles at T = 15 K demonstrate the two sharp emission bands at 369 nm and 374 nm, respectively. The energy position, the small full width at half maximum (FWHM) of these bands and the strong quenching of the intensity with increasing temperature allowed us to attribute these emission bands to the radiative recombination of bound excitons. These excitons are localized on the donor states in the conduction band of WO3. The difference in the relative intensities of the bound exciton emission bands in the uncoated and the carbon coated WO3 nanoparticles is explained by the charge (electrons) transfer from the WO3 nanoparticles to the carbon coating layer.