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