Layer-dependent gas sensing performance of APCVD-grown MoS2 toward NO2

Abstract

The controlled growth and layer-dependent properties of two-dimensional (2D) transition metal dichalcogenides (TMDs) are critical for their practical deployment in chemical sensing. In this work, we demonstrate the synthesis of mono-, bi-, and trilayer MoS<inf>2</inf> films via an ambient-pressure chemical vapor deposition (APCVD) route with precise control over nucleation density. Structural and spectroscopic analyses confirm uniform, crystalline layers with excellent spatial homogeneity. The gas sensing performance of the as-grown films toward NO<inf>2</inf> was systematically investigated, revealing that bilayer MoS<inf>2</inf> exhibited the highest sensitivity (∼ 40.6 at 100 ppm) compared to monolayer (∼ 32.5) and trilayer (∼ 23.6). The bilayer configuration offered an optimal balance of surface adsorption sites and electronic density of states, enabling fast response (∼ 1.25 min), recovery (∼ 1.45 min), and reliable detection down to 23 ppb. Furthermore, Au nanoparticle decoration on bilayer MoS<inf>2</inf> significantly enhanced sensitivity (up to ∼ 51.5) and improved kinetics owing to catalytic and charge-transfer effects. The fabricated devices are also characterized by excellent repeatability, long-term stability, and selectivity against interfering gases. This study highlights the critical role of MoS<inf>2</inf> thickness and noble metal functionalization in engineering next-generation room-temperature NO<inf>2</inf> sensors. © © 2026. Published by Elsevier B.V.