The UV Effect on the Chemiresistive Response of ZnO Nanostructures to Isopropanol and Benzene at PPM Concentrations in Mixture with Dry and Wet Air

Abstract

Towards the development of low-power miniature gas detectors, there is a high interest in the research of light-activated metal oxide gas sensors capable to operate at room temperature (RT). Herein, we study ZnO nanostructures grown by the electrochemical deposition method over Si/SiO2 substrates equipped by multiple Pt electrodes to serve as on-chip gas monitors and thoroughly estimate its chemiresistive performance upon exposing to two model VOCs, isopropanol and benzene, in a wide operating temperature range, from RT to 350 °C, and LED-powered UV illumination, 380 nm wavelength; the dry air and humid-enriched, 50 rel. %, air are employed as a background. We show that the UV activation allows one to get a distinctive chemiresistive signal of the ZnO sensor to isopropanol at RT regardless of the interfering presence of H2O vapors. On the contrary, the benzene vapors do not react with UV-illuminated ZnO at RT under dry air while the humidity’s appearance gives an opportunity to detect this gas. Still, both VOCs are well detected by the ZnO sensor under heating at a 200–350 °C range independently on additional UV exciting. We employ quantum chemical calculations to explain the differences between these two VOCs’ interactions with ZnO surface by a remarkable distinction of the binding energies characterizing single molecules, which is −0.44 eV in the case of isopropanol and −3.67 eV in the case of benzene. The full covering of a ZnO supercell by H2O molecules taken for the effect’s estimation shifts the binding energies to −0.50 eV and −0.72 eV, respectively. This theory insight supports the experimental observation that benzene could not react with ZnO surface at RT under employed LED UV without humidity’s presence, indifference to isopropanol.

UV-Light-Tunable p-/n-Type Chemiresistive Gas Sensors Based on Quasi-1D TiS3 Nanoribbons: Detection of Isopropanol at ppm Concentrations

“…In order to explore the possibility of selective detection of isopropanol, we exposed the TiS3 NW-based chip to benzene vapor, which is known to be more inert to interact with chemiresistive materials [83]. In the experiments utilizing the TiS3 NW sensors, we could only reliably register the chemiresistive response to 100 ppm concentration of benzene vapors.…”

“…The results of the LDA analysis are plotted in Figure 8d-i for various operation conditions. The points are the vector signals (resistance distributions) from the array while ellipses are built accounting for Gaussian distributions of in-class In order to explore the possibility of selective detection of isopropanol, we exposed the TiS 3 NW-based chip to benzene vapor, which is known to be more inert to interact with chemiresistive materials [83]. In the experiments utilizing the TiS 3 NW sensors, we could only reliably register the chemiresistive response to 100 ppm concentration of benzene vapors.…”

Preparation of ZnO Thick Films Activated with UV-LED for Efficient H2S Gas Sensing

“…Gas sensors based on ZnO nanostructures often require an external excitation to activate the surface of ZnO and thus accelerate the adsorption/desorption processes of gas molecules. Typically, this activation occurs at high temperatures, between 300 and 500 • C, where a metallic heater is responsible for raising the temperature, which requires advanced energy consumption, about 500 to 5000 mW [23]. Currently, other options to activate a gas sensor are the 2D and 3D microheaters, due to their low energy consumption, which is in the range of 10 to 80 mW and raise the temperature from 0 to 700 • C [24].…”

ZnO-based chemi-resistive sensors for CO2 detection: a review

“…ZnO exhibits high transparency in the visible and near-ultraviolet (UV) spectral regions and wide conductivity range, which is modified under photoreduction/oxidation conditions (Patil et al , 2011). The wide band gap ( E g = 3.37 eV) of ZnO, which falls into UV range (wavelength of 100–400 nm), makes it an appropriate material for exciting electron transitions at room temperature and, thus, a promising UV-activated gas sensor (Solomatin et al , 2021).…”