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In the present work, ZnO nanorods and Ag nanoparticles (NPs) decorated ZnO nanorods (NRs) were synthesized on a Si/SiO2 substrate by a simple chemical hydrothermal route. Various characterization techniques studied phase formation, surface morphology, and elemental composition of prepared samples. Gas sensing measurements for pristine ZnO and Ag/ZnO NRs have been carried out under a low detection limit (2–10 ppm). The highly crystalline nature of NRs aided in achieving a great sensing response. The ZnO NRs exhibit a sensing response of 934% towards 10 ppm NO2 at a working temperature of 180 °C. However, Ag/ZnO sensor gives the highest sensing response of 1075% for 10 ppm NO2 at a working temperature of 180 °C. The cause behind the increment of Ag/ZnO sensor response is explained via chemical and electronic models. These observations make an energy-efficient sensor for the detection of NO2 in the environment. [ABSTRACT FROM AUTHOR]

We demonstrate RF sputtered Ni-doped ZnO nanostructures for detection of extremely low concentration (1 ppm) of hydrogen gas at moderate operating temperature of 75 °C. Structural, morphological, electrical and hydrogen sensing behavior of the Ni-doped ZnO nanostructures strongly depends on doping concentration. Ni doping exceptionally enhances the sensing response and reduces the operating temperature of the sensor as compared to undoped ZnO. The major role of the Ni-doping is to create more active sites for chemisorbed oxygen on the surface of sensor and, correspondingly, to improve the sensing response. The 4 at% of Ni-doped ZnO exhibits the highest response (∼69%) for 1% H 2 at 150 °C, which are ∼1.5 times higher than for the undoped ZnO. This is ascribed to lowest activation energy ∼6.47 KJ/mol. Diminishing of the relative response was observed in 6% Ni- doped ZnO due to separation of NiO phase. [ABSTRACT FROM AUTHOR]

Hydrogen gas sensing response of RF sputtered nano-crystalline ZnO thin film is improved by \sim 34.73 % using swift heavy ion irradiation technique. X-ray diffraction reveals single crystalline wurtzite structure of ZnO thin films. Full width half maximum (FWHM) of (0002) diffraction peak is decreased with increase in ion fluences. However, at very high fluence 1\times 10^{13} ions/cm2, crystallinity is degraded while FWHM of diffraction peak increases. The ZnO films were grown under highly compressive stress, which was relaxed with incremental ion fluences up to 1\times 10^{13}$ ions/cm2. Cathodoluminenscence spectroscopy shows intense predominant peak around \sim 3.23$ eV, which indicates good optical quality of the films. As ion fluence increases, a blue shift appears in near band emission peak from 3.23 to 3.33 eV, which indicates that in-plane stress is decreased. Surface morphology shows generation of self-affine nanostructure and grain fragments as ion fluences were increased. Grain fragmentations had enhanced the surface reaction, and as a result, gas sensor’s relative response has improved. It was observed that the gas sensor’s sensitivity is strongly dependent on ion fluences and operating temperature. The sensitivity was enhanced from 66.68% to 89.84% with fluence variations from pristine to 1\times 10^{12} ions/cm2 at 175 °C operating temperature. [ABSTRACT FROM PUBLISHER]