ZnSe/NiO heterostructure-based chemiresistive-type sensors for low-concentration NO₂ detection

Novel ZnSe/NiO heterostructure nanocomposites were successfully prepared by one-step hydrothermal method. The ZnSe/NiO-based sensor exhibits a response of ~ 96.47% to 8 × 10⁻⁶ NO₂ at 140 °C, which is significantly higher than those of intrinsic ZnSe-based (no response) and NiO-based (~ 19.65%) sensors. The theoretical detection limit (LOD) of the sensor is calculated to be 8.91 × 10⁻⁹, indicating that the sensor can be applied to detect the ultralow concentrations of NO₂. The effect of NiO content on the gas-sensing performance of the nanocomposites was investigated in detail. The optimal NiO content in the nanocomposite is determined to be 15.16% to achieve the highest response. The as-fabricated sensor also presents an excellent selectivity to several possible interferents such as methanol, ethanol, acetone, benzene, ammonia and formaldehyde. The enhanced sensing performance can be attributed to the formation of p–p heterostructures between ZnSe and NiO, which induces the charge transfer across the interfaces and yields more active sites.