NiO–ZnO Nanoheterojunction Networks for Room-Temperature Volatile Organic Compounds Sensing

摘要

Engineering of highly performing nanomaterials, capable of rapid detectionof trace concentrations of gas molecules at room temperature, is key to thedevelopment of the next generation of miniaturized chemical sensors. Here, ahighly performing nanoheterojunctions layout is presented for the rapid roomtemperaturechemical sensing of volatile organic compounds down to ten particlesper billion concentrations. The layout consists of a 3D network of nickeloxide–zinc oxide (NiO–ZnO) p–n semiconductors with grain size of ≈20 nmnanometers and a porosity of ≈98%. Notably, it is observed that the formationof the p–n heterojunctions by decoration of a ZnO nanoparticle networks withNiO increases the sensor response by more than four times while improvingthe lower limit of detection. Under solar light irradiation, the optimalNiO–ZnO nanoheterojunction networks demonstrate a strong and selectiveroom-temperature response to two important volatile organic compoundsutilized for breath analysis, namely acetone and ethanol. Furthermore, theseNiO–ZnO nanoheterojunctions show an inverse response to acetone fromthat observed for all others reducing gas molecules (i.e., ethanol, propane,and ethylbenzene). It is believed that these novel insights of the optoelectrochemicalproperties of ultraporous nanoheterojunction networks provideguidelines for the future design of low-power solid-state chemical sensors.