Photoinduced effects of monochromatic visible light with different wavelengths on realgar

Abstract

Realgar is a well-known light-sensitive material. Under illumination, realgar is oxidized into arsenolite and uzonite, and uzonite generates pararealgar. To further study the effect of light with different wavelengths on realgar, herein, the light-induced reaction of realgar under irradiation of four monochromatic visible lights, red light (628.0–648.0 nm), amber light (585.4–604.6 nm), green light (506.0–544.0 nm), and blue light (428.9–447.1 nm), have been studied by confocal Raman, X-ray diffraction, and ultraviolet–visible absorption spectroscopy. The results of Raman spectra show that the photoinduced effect of different monochromatic lights on realgar is different. Realgar is stable under red light but is sensitive to other visible lights like amber, green, and blue light. The light-induced reaction of realgar is the fastest under the green light. The effect of the blue light on realgar is complicated. Pararealgar, as the light-induced product of realgar, transforms into uzonite under the blue light, which is discussed based on the bandgap of pararealgar calculated using the density functional theory method.