Peroxide-Induced Tuning of the Conductivity of Nanometer-Thick MoS₂ Films for Solid-State Sensors

Abstract

Applications of molybdenum disulfide (MoS2) in energy storage devices, solar cells, electrocatalysts, and sensors require good electrical conductivity. However, neither of the current ways to prepare conductive MoS2 (lithium intercalation and hydrothermal processes) is easily amenable to scale-up. A possible alternative pathway is the modulation of the electronic properties of the semiconducting form of MoS2 through structural defects. Here, we report the preparation of nanoscale conductive MoS2 flakes by treating exfoliated 2H-MoS2 with dilute aqueous hydrogen peroxide at room temperature. Sheet resistance measurements as well as Raman and photoelectron spectroscopy reveal the partial formation of hydrogen molybdenum bronze (HxMoO3) and substoichiometric MoO3–y, which help tune the conductivity of the nanometer-scale thin films without impacting the sulfur-to-molybdenum ratio. We have cast the material into thin film networks to fabricate highly stable chemiresistive pH sensors. Our work introduces a straightforward and safe way of preparing a conductive form of MoS2 and its application as a low-cost solid-state sensor.