TiO2-modified MoS2 monolayer films enable sensitive NH3 sensing at room temperature

Abstract

The research and development of high-performance NH₃ sensors are of great significance for environment monitoring and disease diagnosis applications. Two-dimensional (2D) MoS₂ nanomaterials have exhibited great potential for building room-temperature (RT) NH₃ sensors but still suffer from relatively low sensitivity. Herein, the TiO₂-modified monolayer MoS₂ films with controllable TiO₂ loading contents are fabricated by a facile approach. A remarkable enhancement in the RT NH₃ sensing performance is achieved after the n–n hetero-compositing of the TiO₂/MoS₂ system. The device with 95% surface coverage of TiO₂ shows enhanced sensor response, low detection limit (0.5 ppm), wide detection range (0.5–1000 ppm), good repeatability, and superior selectivity against other gases. In situ Kelvin potential force microscopy results revealed that the TiO₂ modification not only improved the surface reactivity of the sensing layers but also contributed to the NH₃ sensing performance by serving as the “gas-gating” layers that modulated the electron depletion layer and the conductivity of the MoS₂ films. Such an n–n hetero-compositing strategy can provide a simple and cost-effective approach for developing high-performance NH₃ sensors based on 2D semiconductors.