Vertical MoS₂ Nanosheets via Space-Confined CVD for Room Temperature Photo-Enhanced Highly Selective Triethylamine Sensing

The layered structure and atomic thinness of transition metal dichalcogenide (TMD) semiconductors make them attractive for various applications. By precise control of the morphology of these materials on the nanoscale, the material can be engineered for specific functional device applications. The present study represents a systematic growth procedure, wherein a space-confined chemical vapor deposition (CVD) route allowed us to synthesize vertically oriented molybdenum disulfide (MoS₂) nanosheets with high phase selectivity. While achieving control over the growth of vertical MoS₂ (V-MoS₂) within a single growth run has many challenges, we demonstrate vertical growth of MoO₂ and its subsequent transformation to either a MoO₂/MoS₂ core-shell structure or vertical MoS₂ nanosheets on a SiO₂/Si substrate, by modulating the sulfur concentration during the growth process. As a morphologically rich structure, the edge-enhanced MoS₂ flower-like structure offered high selectivity toward triethylamine (TEA) sensing over many other volatile organic chemicals (VOCs) studied. The VOC sensing study showed ultrahigh selectivity and sensitivity (9.35 ± 1.20) × 10^-4 ppm^-1 toward TEA under ultraviolet light exposure. The vertical MoS₂ nanosheets with enhanced hydrophobic property showed excellent ambient stability, suggesting its potential for the development of sensors for room-temperature triethylamine detection at the ppm level.