Phase-Dependent Dual Discrimination of MoSe 2 /MoO 3 Composites Toward N , N -Dimethylformamide and Triethylamine at Room Temperature.

Herein, we present, a chemiresistive-type gas sensor composed of two-dimensional 1T-2H phase MoSe 2 and MoO 3 . Mixed phase MoSe 2 and MoSe 2 /MoO 3 composites were synthesized via a facile hydrothermal method. The structure analysis using X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy revealed the formation of different phases of MoSe 2 at different temperatures. With increase in synthesis temperature from 180 to 200 °C, the relative percentage of 1T and 2H-MoSe 2 phases changed from 80 to 48%. On the other hand, at 220 °C, 2H-MoSe 2 was obtained as a major component. The gas sensing properties of individual MoSe 2 and composites were investigated at room temperature toward various analytes. The obtained results revealed that composites possess improved sensing features as compared with individual MoSe 2 or MoO 3 . Data also revealed that the composite with dominating 1T-phase exhibits relatively higher response (10%, at 10 ppm) for dimethylformamide (DMF) compared to triethylamine (TEA) (3%, at 10 ppm). In contrast, the composite with larger 2H-phase exhibited affinity toward TEA and had a relative response of about 2%. Therefore, selectivity of a sensor device can be tuned by an appropriately designed MoSe 2 /MoO 3 composite. These results signify the importance of MoO 3 -based composites with dual-phase MoSe 2 for successfully discriminating between DMF and TEA at room-temperature.