High Performance Room-Temperature Acetone Sensors Enabled by Fermi-Level Engineering in Au-Decorated n-Type SnS₂ Layers

Non-invasive monitoring of diabetes through exhaled acetone detection remains a challenging goal, as energy-demanding metal oxide sensors operate at elevated temperatures (>150°C). Here, we report on a room-temperature acetone sensor that harnesses interfacial Fermi-level modulation in gold nanoparticle (Au NP)-decorated n-type SnS₂ layers. In contrast with pristine SnS₂, which exhibits negative sensitivity due to indirect electron generation from acetone adsorption–induced band (E_D), Au NP decoration effectively repositions the Fermi level below the E_D. This realignment facilitates direct charge transfer between acetone molecules and the Au NP–SnS₂ interface, yielding a pronounced positive sensing response. The device exhibits excellent sensitivities of 910% at 7 ppm and 344% at 0.5 ppm under zero gate voltage, with additional tunability enabled through electrostatic gating. This study demonstrates a new material-engineering strategy for achieving low-power, room-temperature molecular diagnostics, advancing the integration of breath-based sensors into future medical and wearable device technologies.