In this paper, ultraviolet (UV) detecting performances of the n-i-p SiCN homojunction prepared on a p-type (100) silicon substrate under room and elevated temperatures were studied. We analyze the morphology and structure of the crystalline SiCN film on Si first and then examine responses of the sensors to UV light by measurement of photo/dark current ratio with and without the irradiation of a 254-nm UV light. The current ratios of the homojunction under -5 bias, with and without irradiation of a 254-nm UV light are 3180 and 135.65, respectively, at room temperature and 200°C. The results are comparable or better to the reported UV detectors based on 4H-SiC or AlGaN in room or high temperature.

Different structures of the cuprous oxide nanoparticles with cubic, truncated-octahedral and octahedral morphology were developed for sensing hydrogen peroxide. The structure and composition of the prepared cuprous oxide were examined by SEM, XRD, EDS, and TEM. The cyclic voltammetry and amperometric analysis were carried out to analyze the catalytic ability. The results indicate that the octahedral cuprous oxide nanoparticles (∼100 nm) with {111} facets have the best sensitivity of 28.0 μAmM⁻¹cm⁻², which is better than the reported hydrogen peroxide sensors in the linear range of 0.5–3mM. Selectivity of the sensor among hydrogen peroxide and interferents also has a superior performance.

Different nanostructures of tungsten oxide (WO3) can be hydrothermally synthesized by controlling the pH value through adding HCl solution. WO3 has a square plate-like structure when the mixture solution has a pH value of 1.0. At this pH, WO3 nanoplates are dispersed and did not formed clusters. Porous nickel oxide (NiO) spheres are also hydrothermally synthesized for decoration on the surface of WO3 nanoplates. Holes on the NiO spheres increase the surface area of the material and enhance the sensing performances of the sensor. By combining these two materials, the sensor with p-n-n junction is sensitive to ethanol and has a high sensitivity of 155%. The response and recovery times are also fast with good sensitivity and selectivity. It has a high potential for applying to ethanol sensing in industrial and medical areas.

An ammonia sensor based on a delay-line surface acoustic wave (SAW) device is developed in this study by coating the delay line area of the device with a nano-structured molybdenum disulfide (MoS₂) sensitive material. A SAW device of 122 MHz was designed and fabricated with a pair of interdigital transducers (IDTs) defined on a 128° y-cut LiNbO₃ substrate using photolithography technologies, and the aluminum IDT electrodes were deposited by a DC magnetron sputtering system. By adjusting the pH values of precursor solutions, molybdenum disulfide (MoS₂) nanospheres were prepared with various structures using a hydrothermal method. Finally, an NH₃ gas sensor with high sensitivity of 4878 Hz/ppm, operating at room temperature, was successfully obtained. The excellent sensitivity performance may be due to the efficient adsorption of NH₃ gas molecules on the surfaces of the nanoflower-like MoS₂, which has a larger specific surface area and provides more active sites, and results in a larger change in the resonant frequency of the device due to the mass loading effect.