Visible Light-Induced Room-Temperature Formaldehyde Gas Sensor Based on Porous Three-Dimensional ZnO Nanorod Clusters with Rich Oxygen Vacancies

Abstract

Oxygen vacancy (V O ) is a kind of primary point defect that extensively exists in semiconductor metal oxides (SMOs). Owing to some of its inherent qualities, an artificial manipulation of V O content in one material has evolved into a hot research field, which is deemed to be capable of modulating band structures and surface characteristics of SMOs. Specific to the gas-sensing area, V O engineering of sensing materials has become an effective means in enhancing sensor response and inducing light-enhanced sensing. In this work, a high-efficiency microwave hydrothermal treatment was utilized to prepare a V O -rich ZnO sample without additional reagents. The X-ray photoelectron spectroscopy test revealed a significant increase in V O proportion, which was from 9.21% in commercial ZnO to 36.27% in synthesized V O -rich ZnO possessing three-dimensional and air-permeable microstructures. The subsequent UV–vis–NIR absorption and photoluminescence spectroscopy indicated an extension absorption in the visible region and band gap reduction of V O -rich ZnO. It turned out that the V O -rich ZnO-based sensor exhibited a considerable response of 63% toward 1 ppm HCHO at room temperature (RT, 25 °C) under visible light irradiation. Particularly, the response/recovery time was only 32/20 s for 1 ppm HCHO and further shortened to 10/5 s for 10 ppm HCHO, which was an excellent performance and comparable to most sensors working at high temperatures. The results in this work strongly suggested the availability of V O engineering and also provided a meaningful candidate for researchers to develop high-performance RT sensors detecting volatile organic compounds.

Surface-Catalyzed Zinc Oxide Nanorods and Interconnected Tetrapods as Efficient Methane Gas Sensing Platforms

“…The optical properties of the ZnO-NR and T-ZnO thin films were studied using UVvisible (UV-Vis) and photoluminescence (PL) spectroscopy at room temperature (Figure 4). ZnO possesses two emission peaks at room temperature, one at 375 nm, and the other between 480 and 560 nm [24,37]. The first emission peak at 375 nm occurs in the UV region and the second emission peak occurs in the green visible region, which is typically broader due to intrinsic defects present in the ZnO-NR and T-ZnO films [28].…”

Rapid and highly sensitive detection of formaldehyde gas via a polyoxometalate–CuBi 2O 4 composite gas sensor

“…Therefore, monitoring the existence of formaldehyde content in the environment is of critical importance. In recent years, metal oxide gas-sensing semiconductors have been used for detecting formaldehyde, and gas sensors constructed with such semiconductor materials have been continually explored [6][7][8]. However, as the existing formaldehyde gas sensors have the shortcomings of low gas response and poor selectivity [9], researchers have been exploring the development of new gassensing semiconductors.…”

UV-Induced Room-Temperature Ethylene Sensors Based on Ag-Decorated ZnO Nanoflowers for Fruit Ripeness Monitoring

“…Therefore, achieving high sensitivity and selectivity ethylene sensing has remained a significant challenge, owing to the relatively stable and low reactivity of ethylene gas. Recently, photoexcitation has been proposed to reduce the operation temperature of gas sensors even down to room temperature. , The sensing mechanism is generally explained based on the surface reaction between target gas and ionized surface oxygen induced by light illumination. − In material perspective, ZnO is one of the most promising materials for photoactivated gas sensors due to its prominent photonic and electronic properties. − Additionally, modification through doping with noble metal nanoparticles (NPs) such as palladium (Pd), platinum (Pt), , silver (Ag), and gold (Au), − can remarkably improve the response and selectivity of ZnO sensors. Among them, Ag NPs have been widely used in ZnO complexes due to their relatively low cost and excellent catalytic properties. − In particular, the presence of Ag NP catalysts can accelerate the adsorption of ambient oxygen on the metal oxide surface.…”