H 2 S is a toxic and corrosive gas, whose accurate detection at sub-ppm concentrations is of high practical importance in environmental, industrial, and health safety applications. Herein, we propose a chemiresistive sensor device that applies a composite of single-walled carbon nanotubes (SWCNTs) and brominated fullerene (C 60 Br 24 ) as a sensing component, which is capable of detecting 50 ppb H 2 S even at room temperature with an excellent response of 1.75% in a selective manner. In contrast, a poor gas response of pristine C 60 -based composites was found in control measurements. The experimental results are complemented by density functional theory calculations showing that C 60 Br 24 in contact with SWCNTs induces localized hole doping in the nanotubes, which is increased further when H 2 S adsorbs on C 60 Br 24 but decreases in the regions, where direct adsorption of H 2 S on the nanotubes takes place due to electron doping from the analyte. Accordingly, the heterogeneous chemical environment in the composite results in spatial fluctuations of hole density upon gas adsorption, hence influencing carrier transport and thus giving rise to chemiresistive sensing.

In this study, we evaluate the variation of the work function of phosphorene during thermal oxidation at different temperatures. The ultraviolet photoelectron spectroscopy results show an N-shaped behaviour that is explained by the oxidation process and the dangling-to-interstitial conversion at elevated temperatures. The exfoliation degree and x-ray photoelectron spectroscopy confirm the formation of native oxides in the top-most layer that passivates the material. Ex-situ XPS reveals the full oxidation of monolayers at temperatures higher than 140 °C, but few-layer phosphorene withstands the thermal oxidation even up to 200 °C with slight modifications of the A 2 g/A 1 g and A 2 g/B 2g vibrational mode ratios and a weak fluorescence in the Raman spectra of the heat-treated samples.