Gas Sensing of Laser-Produced Hybrid TiO₂-ZnO Nanomaterials under Room-Temperature Conditions

The preparation method can considerably affect the structural, morphological, and gas-sensing properties of mixed-oxide materials which often demonstrate superior photocatalytic and sensing performance in comparison with single-metal oxides. In this work, hybrids of semiconductor nanomaterials based on TiO₂ and ZnO were prepared by laser ablation of Zn and Ti plates in water and then tested as chemiresistive gas sensors towards volatile organics (2-propanol, acetaldehyde, ethanol, methanol) and ammonia. An infrared millisecond pulsed laser with energy 2.0 J/pulse and a repetition rate of 5 Hz was applied to Zn and Ti metal targets in different ablation sequences to produce two nano-hybrids (TiO₂/ZnO and ZnO/TiO₂). The surface chemistry, morphology, crystallinity, and phase composition of the prepared hybrids were found to tune their gas-sensing properties. Among all tested gases, sample TiO₂/ZnO showed selectivity to ethanol, while sample ZnO/TiO₂ sensed 2-propanol at room temperature, both with a detection limit of ~50 ppm. The response and recovery times were found to be 24 and 607 s for the TiO₂/ZnO sensor, and 54 and 50 s for its ZnO/TiO₂ counterpart, respectively, towards 100 ppm of the target gas at room temperature.