Molybdenum Disulfide Flakes as Platforms for the Photoconversion of 4-Nitrothiophenol

Two-dimensional (2D) transition metal dichalcogenides (TMD) are of specific interest for a variety of applications when they present a semiconducting character. The band gap between the valence and the conducting band can be tuned and is dependent on the phase of the TMD flake, the number of layers, and how the flakes are chemically modified to impart new surface functionalities. We investigate the surface functionalization of molybdenum disulfide (MoS2) flakes with electron-acceptor 4-nitrothiophenol (NTP) and measure how the band gap of the flake is altered by the presence of this small organic molecule. The functionalized MoS2 surface with NTP is investigated with confocal and tip-enhanced Raman spectroscopy as well as with photoluminescence microscopy under 532 nm excitation. Photoconversion of NTP into dimercaptoazobenzene (DMAB) and aminothiophenol (ATP) is reported even under weak irradiation conditions, highlighting the potential of MoS2 for its photocatalytic properties. The intensity and spectral changes of the photoluminescence of modified MoS2 are indicative of the charge transfer character between MoS2 and NTP.