Defect-Selective Functionalization of 2D-WS₂ Nanofilms with Pt Nanoparticles for Enhanced Room-Temperature NO₂ Gas Sensing

We introduce a new approach for the fabrication of an ultrasensitive nitrogen dioxide (NO 2 ) gas sensor operating at room temperature. By using atomic layer deposition (ALD), Pt nanoparticles (NPs) can be selectively decorated on surface defects of tungsten disulfide (WS 2 ). Our study demonstrated that defect-selectively functionalized gas sensors with Pt NPs only at high-surface-energy sites, such as dangling bonds and grain boundaries, exhibit a greater enhancement in sensitivity than nonselectively functionalized sensors. Additionally, the sensing performances of WS 2 -based gas sensors were enhanced by controlling the particle size and varying the number of ALD cycles. Specifically, the gas response of Pt-functionalized WS 2 to 10 ppm of NO 2 was maximized at 150 cycles of ALD, resulting in a remarkable 10-fold increase (∼850%) compared to pristine WS 2, and almost complete recovery (∼93.2%) was achieved at 200 cycles. Furthermore, even at a very low concentration level of 100 ppb, the optimized Pt/WS 2 sensor showed excellent detection performance, with a response rate of 47%. Also, it exhibited excellent NO 2 gas selectivity and device stability. Our defect-selective functionalization method for improving the essential performance of gas sensors is expected to be applied to a wide range of functional materials, including Ru, Pd, SnO 2, and ZnO. This exhibits remarkable potential for practical applications in human health and environmental monitoring.