In this paper, the ZnO target was synthesized by the solid-state reaction method and a nanostructured thin film was deposited by the RF (radio frequency) magnetron sputtering method on a Multi-Sensor-Platform. The obtained ZnO nanostructured film was investigated as the sensing material. Energy-Dispersive X-ray (EDX) analysis indicated the existence of La in the synthesized ZnO material. Scanning Electron Microscope (SEM) images of the film showed the grain sizes in the range of 20–40 nm. Sensor performance characteristics such as a dynamic response, response and recovery times, and ethanol detection range were investigated at 50–300 °C. A sensitivity was observed at extremely low concentrations of ethanol (0.7 ppm). The minimum response and recovery times of the sensor corresponding to 675 ppm ethanol vapor concentration at 250 °C were found to be 14 s and 61 s, respectively. The sensor showed a high response, good selectivity, fast response/recovery behavior, excellent repeatability toward ethanol vapor, and low sensitivity toward humidity. These characteristics enable the use of a ZnO based sensor for ethanol detecting applications.

The results of research works related to the study of thick-film multiwall carbon nanotube–tin oxide nanocomposite sensors of propylene glycol (PG), dimethylformamide (DMF) and formaldehyde (FA) vapors are presented in this paper. These sensors were derived using hydrothermal synthesis and sol–gel methods. Investigations of response–recovery characteristics in the 50–300 °C operating temperature range reveal that the optimal operating temperature for PG, DMF and FA vapor sensors, taking into account both high response and acceptable response and recovery times are about 200 and 220 °C, respectively. The dependence of the sensor response on gas concentration is linear in all cases. Minimal propylene glycol, dimethylformamide and formaldehyde gas concentrations, where the perceptible signal was noticed, were 13, 5 and 115 ppm, respectively.

This work presents a novel nanostructured material SnO2/multiwalled carbon nanotubes (MWCNTs) as a sensing film for the detection of acetone and ethanol vapors. The fabrication of SnO2/MWCNT chemoresistive sensors demonstrates a cost-effective hydrothermal method using a centrifugation technique. The material investigation of the synthesized SnO2/MWCNTs nanocomposite represents various techniques, such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray (EDX) elementary analysis, EDX mapping, and X-ray diffraction (XRD) analysis. The SnO2/MWCNTs sensor exhibits rapid response/recovery behavior toward acetone (53/5 s) and ethanol (86/3 s) while showing satisfactory values of responsiveness (Sact = 90.5 and Setn = 21, n = 100 ppm). The low detection limit of these vapors is assigned a concentration of 1 ppm, where discernible responses are elicited. Thus, the SnO2/MWCNTs sensor production efforts have yielded a high-end volatile organic compound (VOC) detector, highly suitable for human technological and engineering activity.

Ammonia has a wide range of applications in various branches of industry and technology; the detection of its low concentrations is a preventive method for ambient air quality pollution and a useful method for noninvasive diagnosis of kidney disease by monitoring in exhaled human breath. In this work, a high-performance ammonia sensor based on the Fe₂O₃/MWCNTs (multiwalled carbon nanotubes) material was produced by applying the e-beam deposition method. The morphology, composition, and chemical state of the Fe₂O₃/MWCNTs material were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), Raman spectroscopy (Raman), Fourier transform infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The gas-sensing behavior of the sensor to various concentrations of NH₃ was measured at 200 °C, representing excellent gas response and sophisticated performance parameters. The low detection limit of the Fe₂O₃/MWCNTs sensor was 3 ppm of NH₃, corresponding to the response value of 2.7. The promising values of the response and recovery times (40 and 25 s) confirmed the high speed of ammonia detection. Thus, the suggested Fe₂O₃/MWCNTs material that is sensitive to low concentrations of NH₃ can be successfully used in a new generation of ammonia alarm systems.

In this report, a Fe₂O₃:ZnO sputtering target and a nanograins-based sensor were developed for the room temperature (RT) detection of hydrogen peroxide vapor (HPV) using the solid-state reaction method and the radio frequency (RF) magnetron sputtering technique, respectively. The characterization of the synthesized sputtering target and the obtained nanostructured film was carried out by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy-dispersive X-ray (EDX) analyses. The SEM and TEM images of the film revealed its homogeneous granular structure, with a grain size of 10–30 nm and an interplanar spacing of Fe₂O₃ and ZnO, respectively. EDX spectroscopy presented the real concentrations of Zn in the target material and in the film (21.2 wt.% and 19.4 wt.%, respectively), with a uniform distribution of O, Al, Zn, and Fe elements in the e-mapped images of the Fe₂O₃:ZnO film. The gas sensing behavior was investigated in the temperature range of 25–250 °C with regards to the 1.5–56 ppm HPV concentrations, with and without ultraviolet (UV) irradiation. The presence of UV light on the Fe₂O₃:ZnO surface at RT reduced a low detection limit from 3 ppm to 1.5 ppm, which corresponded to a response value of 12, with the sensor’s response and recovery times of 91 s and 482 s, respectively. The obtained promising results are attributed to the improved characteristics of the Fe₂O₃:ZnO composite material, which will enable its use in multifunctional sensor systems and medical diagnostic devices.