ZnO/NiO heterostructure-based microsensors used in formaldehyde detection at room temperature: Influence of the sensor operating voltage

Abstract

Recently the emissions of volatile organic compounds (VOCs) in the atmosphere have increased dramatically with rapid development of urbanization and industry. This led to a large decline in air quality around the world, which resulted in a heavy impact on human health. Therefore, new/cheap detection devices for VOCs are of high interest. Formaldehyde (FA) is a very toxic VOC, which damages the respiratory system even in the smallest doses and short exposure time. Zinc oxide (ZnO)/nickel oxide (NiO) heterostructures were synthesized using an economical route: firstly, NiO was prepared by liquid exfoliation technique and deposited by dip-coating on alumina ceramic transducers with two interdigital gold (Au) electrodes, followed by low—temperature hydrothermal growth of ZnO. The as-prepared sensors were characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM-EDAX), and X-Ray fluorescence (XRF). The response/recovery of ZnO/NiO heterostructure-based microsensors for formaldehyde was investigated at room temperature, in agreement with modern sensing requirements. The sensor operating voltage was varied between 1.5 and 5.0 V direct current (DC), to achieve the best sensor performance.

Cobalt- and Copper-Based Chemiresistors for Low Concentration Methane Detection, a Comparison Study

“…AFM measurements were carried out in non-contact mode [ 19 ] with XE-100 (Park Systems), using sharp tips (NCHR from Nanosensors), having less than 8 nm tip radius, ~125 µm length, ~30 µm mean width, thickness ~4 µm, ~42 N/m force constant and ~330 kHz resonance frequency. The XEI (v.1.8.0) image processing program developed by Park Systems was used for displaying the images and subsequent statistical data analysis.…”

“…The microstructure of the samples was investigated by SEM using a high-resolution microscope (FEI, Quanta 3D FEG). The analyses were performed in high vacuum mode at high accelerating voltages (30 kV), and the sensors were analyzed directly [ 19 , 20 , 21 , 22 ] (samples were immobilized on a double-sided carbon tape, without coating).…”

Chemiresistors with In2O3 Nanostructured Sensitive Films Used for Ozone Detection at Room Temperature

“…The state of the art regarding SMOX-based ozone sensors, comprised in Table 1, shows that other research groups obtained in some cases successful ozone detection in the ppb range but with higher working temperatures, which involves additional electronics necessary for the detection device, an impediment from the economical perspective [42][43][44][45][46] when mass-production is to be considered. Regarding sensor stability, it must be mentioned that sensing measurements were performed several months after sensor fabrication with excellent results (sensor response was ranged between 1.3 and 2.2), so the sensitive film is considered to be chemically stable.…”

“…The state of the art regarding SMOX-based ozone sensors, comprised in Table 1, shows that other research groups obtained in some cases successful ozone detection in the ppb range but with higher working temperatures, which involves additional electronics necessary for the detection device, an impediment from the economical perspective [42][43][44][45][46] when mass-production is to be considered.…”

Sensing Mechanism and Characterization of NO2 Gas Sensors Using Gold-Black NP-Decorated Ga2O3 Nanorod Sensing Membranes

“…In recent years, several materials have been used to fabricate gas sensors. Among them, metal oxide materials, such as zinc oxide (ZnO), , indium oxide (In 2 O 3 ), , tungsten trioxide (WO 3 ), , and gallium oxide (Ga 2 O 3 ), , have garnered significant attention due to their low cost, simple fabrication, small size, and ease manipulation. − In view of their considerable surface-to-volume ratio and more surface gas adsorption sites, nanomaterials and nanostructures are deliberately applied to the gas sensors to improve their performances. − In spite of the fact that homojunctions are formed between nanostructures to improve the sensitivity of gas sensors, , the formation of p–n heterojunctions between nanostructures can effectively promote the sensitivity and the resistance change. − Recently, to further enhance the performances of gas sensors by using an enhanced metal spillover phenomenon, the structures of metal-decorated metal oxide nanorods have been extensively studied and developed. − …”