Multi-walled carbon nanotubes (MWCNTs) without and with adsorbed silver nanoparticles (Ag-NPs), are used to detect acetone vapour. MWCNTs are grown on SiO2/Si substrates and silver (Ag) nanoparticles (NPs) are deposited onto some of these MWCNTs using electron beam evaporation method. The sensitivity of CNT based sensors (with and without NPs) increases with the concentration of acetone vapour (50 ppm to 800 ppm) while a substantial rise in sensitivity is obtained from MWCNTs with Ag NPs. Band diagrams of the MWCNTs, with and without NPs, are analyzed to understand the gas molecules adsorption phenomena. This study is the first to establish that such sensors can operate at 27 °C rather than the 180 °C–450 °C used elsewhere, thus offering significant advantages over existing methods. To investigate the sensors’ dependability, they’re exposed to three cycles of 50 ppm acetone gas. These tests show that the devices’ responses remain unchanged, indicating their reliability. The effects of humidity upon MWCNT acetone sensors within 100 ppm of acetone vapour are also studied and improved performance towards stability and response/recovery is observed for the sensors with Ag-NPs. Furthermore, higher selectivity is observed for the Ag-coated sensors for acetone against various target gases (acetone, ethanol, NO2, ammonia, and acetone with water).

Wide band gap semiconductors such as ZnO are characterized by unique optoelectronic properties, which have led to numerous applications in the field of sensors and optoelectronics. These components are commonly fabricated on rigid substrates. However, the same synthesis method cannot be used to fabricate these components on flexible substrates. In this work, we present a method to fabricate metal−semiconductor−metal ultraviolet photodetectors with ZnO nanorods on flexible substrates. It is observed that the overall characteristics of the fabricated ZnO nanorod photodetector are greatly enhanced by doping with gallium (Ga). The nanorods are grown on a flexible substrate (poly(ethylene 2,6-naphthalate)) at a low temperature of 80 °C. The performance of Ga-doped ZnO nanorods (GZO) shows a significant improvement in electrical measurements compared to pure ZnO nanorods. The photocurrent-to-dark current ratios of both ZnO and GZO nanorod-based photodetectors are approximately 8.5 and 570.2 under a 1 V bias, respectively. The dark current and photocurrent are substantially improved by the addition of the Ga dopant. Transient response measurements indicated that the GZO nanorod photodetectors are stable and reproducible, and no change in the current−voltage characteristics is noted after multiple bending cycles. These results indicate that Ga-doping can improve the ZnO nanorod optical and electric characteristics; this proposed method is useful for device fabrication on low-melting-point substrates to produce flexible costeffective devices.

In the past decades, a variety of morphologies and doping zinc oxide (ZnO) nanomaterials have attracted significant attention due to their outstanding properties for photodetectors (PDs). This perspective provides the state of recent advancements regarding the doping of ZnO-based PDs and discusses future directions of ZnO-based optoelectronic devices in order to provide a useful reference for those who are interested in PDs.

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Zinc oxide (ZnO)-based semiconductor is a promising application for ultraviolet photodetectors (UV PDs). The performance of ZnO UV PDs can be improved in two orientations: by reduction of the dark current and by increasing the photocurrent. In the study, we used two processes to prepare ZnO UV PDs: photochemical vapor deposition to fabricate silicon dioxide as an insulator layer and a radio frequency sputter system to prepare the ZnO film as an active layer. The results show that the silicon dioxide layer can reduce the dark current. Moreover, a large photo–dark current ratio of the metal–insulator–semiconductor (MIS) structured PD is 200 times than the metal–semiconductor–metal (MSM) structured PD. When the silicon dioxide thickness is 98 nm, we can significantly enhance the rejection ratio. The silicon dioxide layer can reduce the noise effect and enhance the device detectivity. These results indicate that the insertion of a silicon dioxide layer into ZnO PDs is potentially useful for practical applications.