Laser-Assisted Mo2C-Derived Patterned Oxide for Highly Selective Room Temperature Ammonia Sensor for Food Spoilage Monitoring.

The need for advanced gas sensors has risen for the detection of hazardous gases, breath analysis, and food industry applications. Transition metal carbides (TMCs), like Mo₂C, are novel gas-sensing materials attributed to high electronic conductivity and superior catalytic properties. Poor sensitivity and selectivity are big concerns in TMC-based sensors due to their low specific surface area and fewer reactive sites. Partial oxidation of Mo₂C offers the tuning of structural, chemical, and electronic properties. However, conventional techniques, annealing, and solution processing offer uncontrolled oxidation and lead to structural degradation. Herein, by using a temporally and spatially controlled picosecond (ps) pulsed laser, micropatterned Mo₂C-derived oxide (MoO₃) is developed at room temperature for highly efficient ammonia (NH₃) sensing. The uniformly decorated MoO₃ nanoclusters over Mo₂C function as active centers for better NH₃ interaction and formation of discrete Schottky barriers (SBs) between materials, tuning the charge carrier transportation. The MoO₃/Mo₂C sensor exhibited excellent selectivity toward NH₃ over other interfering gases like hydrogen, ethanol, and acetone. This sensor showed excellent sensitivity (351%/100 parts per billion (ppb) NH₃) and long-term stability. The Mo₂C laser-treated sensor has been successfully tested for monitoring food spoilage. Laser-assisted engineering will provide a new avenue for designing highly efficient gas sensors.