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

Abstract

Engineering of highly performing nanomaterials, capable of rapid detection of trace concentrations of gas molecules at room temperature, is key to the development of the next generation of miniaturized chemical sensors. Here, a highly performing nanoheterojunctions layout is presented for the rapid room‐temperature chemical sensing of volatile organic compounds down to ten particles per billion concentrations. The layout consists of a 3D network of nickel oxide–zinc oxide (NiO–ZnO) p–n semiconductors with grain size of ≈20 nm nanometers and a porosity of ≈98%. Notably, it is observed that the formation of the p–n heterojunctions by decoration of a ZnO nanoparticle networks with NiO increases the sensor response by more than four times while improving the lower limit of detection. Under solar light irradiation, the optimal NiO–ZnO nanoheterojunction networks demonstrate a strong and selective room‐temperature response to two important volatile organic compounds utilized for breath analysis, namely acetone and ethanol. Furthermore, these NiO–ZnO nanoheterojunctions show an inverse response to acetone from that observed for all others reducing gas molecules (i.e., ethanol, propane, and ethylbenzene). It is believed that these novel insights of the optoelectrochemical properties of ultraporous nanoheterojunction networks provide guidelines for the future design of low‐power solid‐state chemical sensors.

Exploring SnxTi1−xO2 Solid Solutions Grown onto Graphene Oxide (GO) as Selective Toluene Gas Sensors

“…Specifically, both samples conserve the highest sensitivity and goodness of sensor signal towards acetone molecules, rather than toluene gas. However, interestingly, the 32:1 TiO 2 /GO sample exhibits a "reversed" behavior in the case of small and polar molecules, such as acetone (Figure 5f), maybe caused by the interaction between the moisture adsorbed on the sensing material highly-hydrophilic surface [60] and the VOC molecules, and this is lost when the operating temperature is above the water condensation point, as reported by Tricoli et al [65]. Overall, the tailoring of titanium ions into tin dioxide matrix alongside with the integration of graphene oxide into the metal oxides could be exploited for the engineering of materials with higher sensing performances, especially in terms of selectivity to different VOC species.…”

ZnO‐Based Ultraviolet Photodetectors with Tunable Spectral Responses

“…Figure a–c depicts the X‐ray diffraction patterns of the ZnO thin films on glass substrates as a function of annealing temperatures. It is clear that the ZnO thin films are polycrystalline with diffraction peaks located at 31.9°, 34.5°, 36.3°, 56.7°, corresponding to the crystal planes of (100) (002) (101) (110), respectively . Obviously, the crystallinity was effectively enhanced with the increase of annealing temperature from 200 to 400 °C.…”

NH3 Sensor Based on 3D Hierarchical Flower-Shaped n-ZnO/p-NiO Heterostructures Yields Outstanding Sensing Capabilities at ppb Level

“…Up to now, many working groups tried to improve the gas sensing properties of ZnO-based gas sensors by construction p - n heterojunctions. For example, Chen et al reported the fabrication of ultraporous ZnO/NiO heterojunction networks using flame synthesis and aerosol self-assemble, and studied their gas sensitivity toward volatile organic compounds (VOC) gas [ 23 ]. The reported results demonstrated that the ZnO/NiO nanoparticle networks demonstrated excellent sensitivity to acetone and ethanol gas.…”