Photo-controlled redox of hydrogen-terminated silicon nanowire established by the reversible color alteration of methylene blue

Abstract

The surface of hydrogen-terminated silicon nanowires was proved to be photo-active and redox-controllable under a visible light by the color alteration of methylene blue: colorless in dark and blue in light in the presence of H-SiNWs. The process of the redox reaction was monitored by a UV–vis spectrophotometry, showing a repeatable interconversion between methylene blue and lueco methylene blue within 2h under conditions of alternant dark and light environments. During the redox process, oxygen was proved necessary for the reversible color alteration of methylene blue. The high repeatability in dark-reduction and photo-oxidation of methylene blue demonstrates the catalytic activity of ultrafine hydrogen-terminated silicon nanowires. Finally, a possible mechanism is deduced.