Effects of precipitation temperature on the photochromic properties of h-MoO3

Hexagonal MoO3 powders were successfully precipitated at reaction temperatures ranging from 55 to 85 degrees C. The effects of the synthesis temperature on the crystal structure, crystallite size, morphology, optical properties, and photochromic properties were investigated. The MoO3 powders were characterized by X-ray diffractometer (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-vis diffuse reflectance spectrophotometer (UV-vis DRS), Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET) and X-ray photoelectron spectroscopy (XPS). The band gap energy of MoO3 varied from 3.14 to 3.20 eV, depending on the reaction temperature. The photochromic properties were determined after UV irradiation using the CIE Lab color system. The flower-like MoO3 crystals obtained at the highest reaction temperature exhibited the best photochromic properties, and hexagonal rod-shaped crystals were synthesized at lower temperatures. (C) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.