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

Abstract

We introduce a new approach for the fabrication of an ultrasensitive nitrogen dioxide (NO2) 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 (WS2). 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 WS2-based gas sensors were enhanced by controlling the particle size and varying the number of ALD cycles. Specifically, the gas response of Pt-functionalized WS2 to 10 ppm of NO2 was maximized at 150 cycles of ALD, resulting in a remarkable 10-fold increase (∼850%) compared to pristine WS2, 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/WS2 sensor showed excellent detection performance, with a response rate of 47%. Also, it exhibited excellent NO2 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, SnO2, and ZnO. This exhibits remarkable potential for practical applications in human health and environmental monitoring.