Optical properties of ThO2-based nanoparticles

Thoria nanomaterials show great interest in different fields other than nuclear technology. In this work, optical characteristics of four types of thoria-based nanoparticles were evaluated. The ultraviolet-visible (UV-vis) absorption spectrum of the pure (undoped/uncapped) thoria nanoparticles was characterised by an intense peak at 222 nm, while the doped/capped thoria nanoparticles shown maximum absorption peaks at both 195/200 nm and 233 nm. Contrarily to the particle size, the band gap energy of the thoria nanoparticles decreased with the doping/capping process using arsenic (As-(III))/cysteine (Cyst). The room-temperature photoluminescence excitation spectra were featured by two bands located at 268 nm for both pure and As-doped thoria nanoparticles and at 352 nm for all thoria-based nanoparticles studied, recording the photoluminescence emission at 500 nm. The characteristic wavelengths of the photoluminescence emission spectra were at 325 and 385 nm for the pure and As-doped thoria nano particles, while only the band at 385/415 nm was noted for the Cyst-capped thoria nanoparticles, with slightly red shift depending on the excitation wavelength. (C) 2016 Elsevier B.V. All rights reserved.