An ultraviolet-enhanced (UV-enhanced) nitric oxide (NO) sensor based on silver-doped zinc oxide (ZnO) nanoflowers is developed using a low-cost hydrothermal method. The results indicate that silver (Ag) ions were doped into the ZnO nanostructure successfully, thus changing the morphology. In the high-resolution transmission electron microscopy images, we also found that some Ag ions were separated out onto the surface of the ZnO nanoflowers and that the Ag-doped and Ag nanoparticles improved the sensing property. The NO sensing property increased from 73.91 to 89.04% through the use of a UV light-emitting diode (UV-LED). The response time was approximately 120 s without the UV-LED, and the UV-enhanced Ag-doped ZnO nanoflower sensor exhibited a reduced response time (60 s). The best working temperature could be reduced from 200 to 150 °C using UV light illumination, and it was found that the NO response increased by 15.13% at 150 °C. The UV photoresponse of the Ag-doped ZnO nanoflowers and the mechanisms by which the improvement of NO sensing property occurred through the use of UV light illumination are discussed. The property of the gas sensor can be calibrated using a self-photoelectric effect under UV light illumination. These interesting UV-enhanced Ag-doped ZnO nanoflowers are viable candidates for practical applications.

In this investigation, gas sensors based on zinc oxide (ZnO) nanorods (NRs) with Co concentration were successfully fabricated and explored. A 100 nm-thick ZnO film was deposited as a seed layer onto Corning glass substrate via radio frequency (RF) magnetron sputtering technique. Then, Co-doped ZnO (CZO) NR arrays were grown by using a simple chemical bath deposition (CBD) method at 95 °C for 3 h and annealing at 450 °C, in which the Co-doping contents are 0, 5, and 10 mM. The surface-to-volume ratio of CZO NRs was higher than that of the pure ZnO structure. X-ray diffraction (XRD) results showed that the synthesised NRs were a single crystalline of the hexagonal wurtzite structure with uniform growth orientation of the c -axis. In addition, increasing ethanol (C ₂ H ₅ OH) response depends on O vacancy (V _O ) adsorption, which is measured via photoluminescence (PL) emission. Compared with pure ZnO NRs, the results showed that the CZO-5 (with 5 mM Co solution) NRs exhibited a superior sensitivity in C ₂ H ₅ OH gas applications and a fast response/recovery time. Meanwhile, the CZO-5 gas sensor presented a high response rate of 90.71% at 300 °C operating temperature when the concentration of ambient C ₂ H ₅ OH gas was 100 ppm.

The ultraviolet (UV) photodetectors with ZnO nanorods (NRs)/CdS thin film heterostructures on glass substrates have been fabricated and characterized. It can be seen that the UV photoresponsivity of such a device became higher as the ZnO NR length was increased in the investigation. With an incident wavelength of 350 nm and 5 V applied bias, the responsivity of photodetectors based on ZnO NR/CdS heterostructures with the ZnO NR length at 500, 350, and 200 nm and traditional CdS film were at 12.86, 3.83, 0.91, and 0.75 A/W, respectively. The measurement results of the fabricated photodetectors based on ZnO nanorods (NRs)/CdS heterostructures have shown a significant high sensitivity in the range of UV light, which can be useful for the application of UV detection.

We demonstrate that heterojunction photovoltaics based on hydrothermal-grown In2S3 on p-Si were fabricated and characterized in the paper. An n-type In2S3 nanoflake-based film with unique 'cross-linked network' structure was grown on the prepared p-type silicon substrate. It was found that the bandgap energy of such In2S3 film is 2.5 eV by optical absorption spectra. This unique nanostructure significantly enhances the surface area of the In2S3 films, leading to obtain lower reflectance spectra as the thickness of In2S3 film was increased. Additionally, such a nanostructure resulted in a closer spacing between the cross-linked In2S3 nanostructures and formed more direct conduction paths for electron transportation. Thus, the short-circuit current density (Jsc) was effectively improved by using a suitable thickness of In2S3. The power conversion efficiency (PCE, eta) of the AZO/In2S3/textured p-Si heterojunction solar cell with 100-nm-thick In2S3 film was 2.39%.

Sensitivity of the Micro Electro Mechanical System (MEMS) device ZnO nanosheets sensor and the Au doped ZnO nanosheets sensor has been investigated. The ZnO samples have been prepared using Hydrothermal synthesis at 90 °C. The prepared ZnO nanostructure is tested for structural morphology and crystallinity properties. The elemental analysis of the ZnO sample and Au–ZnO samples are tested by using Energy Dispersive X-ray Spectroscopy (EDS) spectrum analysis. MEMS device microheater is designed and prepared for testing the sensitivity of Ethanol gas. Thermal properties of the MEMS microheater is studied for better gas testing at different temperatures. Both the ZnO nanosheets sensor and Au doped ZnO nanosheets sensor are tested using Ethanol gas, and the gas concentrations are taken to be 15, 30, 45, and 60 ppm at 300 °C. The gas sensing response of pure ZnO nanosheets tested for ethanol gas at 60 ppm showed 20%, while the Au–ZnO nanosheets showed 35%, which is increased by 15% at similar operating conditions.

Gas sensing properties of pure ZnO and CuO layered ZnO nanostructures prepared on Micro Electro Mechanical system (MEMS) devices has been investigated. ZnO nanostructure is prepared using hydrothermal process and the structure deposited has rough surface with number of pores. CuO films (25 nm and 50 nm) are deposited on the ZnO nanostructure using RF sputtering process and the total thickness of 25 nm CuO layered ZnO is recorded about 3.30 μ m. For the sake of gas sensing working conditions, MEMS microheater thermal properties are also studied. CuO coated ZnO MEMS device is tested for H ₂ S gas at 200 °C temperature. Gas sensing properties of 25 nm thickness CuO on ZnO MEMS device sensor shown 42.5% of enhanced sensing response at 1 ppm when compared to pure ZnO sensor which only showed 23.2% response. The enhanced sensing response is due to the formation of CuO and ZnO heterojunctions. The sensor exhibited good sensitivity towards H ₂ S gas than other gases (SO ₂ , CO, NH ₃ and ethanol) at the operating temperature of 200 °C. A random repeatability test at 800 ppb H ₂ S gas concentration is done with 25 nm CuO layered ZnO which showed good repeating sensing results.