Novel gas sensors with high sensing properties, simultaneously operating at room temperature are considerably more attractive owing to their low power consumption, high security and long-term stability. Till date, zinc oxide (ZnO) as semiconducting metal oxide is considered as the promising resistive-type gas sensing material, but elevated operating temperature becomes the bottleneck of its extensive applications in the field of real-time gas monitoring, especially in flammable and explosive gas atmosphere. In this respect, worldwide efforts have been devoted to reducing the operating temperature by means of multiple methods In this communication, room-temperature gas sensing properties of ZnO based gas sensors are comprehensively reviewed. Much more attention is particularly paid to the effective strategies that create room-temperature gas sensing of ZnO based gas sensors, mainly including surface modification, additive doping and light activation. Finally, some perspectives for future investigation on room-temperature gas-sensing materials are discussed as well.

Room-temperature gas sensing of ZnO-based gas sensor: A review

High-precision gas sensors operated at room temperature are attractive for various real-time gas monitoring applications, with advantages including low energy consumption, cost effectiveness and device miniaturization/flexibility. Studies on sensing materials, which play a key role in good gas sensing performance, are currently focused extensively on semiconducting metal oxide nanostructures (SMONs) used in the conventional resistance type gas sensors. This topical review highlights the designs and mechanisms of different SMONs with various patterns (e.g. nanoparticles, nanowires, nanosheets, nanorods, nanotubes, nanofilms, etc.) for gas sensors to detect various hazardous gases at room temperature. The key topics include (1) single phase SMONs including both n-type and p-type ones; (2) noble metal nanoparticle and metal ion modified SMONs; (3) composite oxides of SMONs; (4) composites of SMONs with carbon nanomaterials. Enhancement of the sensing performance of SMONs at room temperature can also be realized using a photo-activation effect such as ultraviolet light. SMON based mechanically flexible and wearable room temperature gas sensors are also discussed. Various mechanisms have been discussed for the enhanced sensing performance, which include redox reactions, heterojunction generation, formation of metal sulfides and the spillover effect. Finally, major challenges and prospects for the SMON based room temperature gas sensors are highlighted.

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Advances in designs and mechanisms of semiconducting metal oxide nanostructures for high-precision gas sensors operated at room temperature

Zinc oxide (ZnO) is an adaptable material that has distinctive properties, such as high-sensitivity, large specific area, non-toxicity, good compatibility and a high isoelectric point, which favours it to be considered with a few exceptions. It is the most desirable group of nanostructure as far as both structure and properties. The unique and tuneable properties of nanostructured ZnO shows excellent stability in chemically as well as thermally stable n-type semiconducting material with wide applications such as in luminescent material, supercapacitors, battery, solar cells, photocatalysis, biosensors, biomedical and biological applications in the form of bulk crystal, thin film and pellets. The nanosized materials exhibit higher dissolution rates as well as higher solubility when compared to the bulk materials. This review significantly focused on the current improvement in ZnO-based nanomaterials/composites/doped materials for the application in the field of energy storage and conversion devices and biological applications. Special deliberation has been paid on supercapacitors, Li-ion batteries, dye-sensitized solar cells, photocatalysis, biosensors, biomedical and biological applications. Finally, the benefits of ZnO-based materials for the utilizations in the field of energy and biological sciences are moreover consistently analysed.

https://iopscience.iop.org/article/10.1088/1361-6528/ab268a/pdf

A review on ZnO nanostructured materials: energy, environmental and biological applications.

Smart wound dressings for wound healing

Preparation of large-scale cupric oxide nanowires by thermal evaporation method

Room temperature ferromagnetism and gas sensing in ZnO nanostructures: Influence of intrinsic defects and Mn, Co, Cu doping

Design of multi-functional cotton gauze with antimicrobial and drug delivery properties.

Structural analysis of aerosol spray pyrolysis ZnO films exhibiting ultra low ozone detection limits at room temperature

In this work, photodegradation of a synthetic textile wastewater composed of a mixture of three reactive azo dyes (RO 122, RR 195 and RY 145) was performed using silver doped zinc oxide (Ag/ZnO) thin films. The photocatalyst preparation was conducted through sol-gel method and was characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDX) and ultraviolet-visible (UV–vis) spectroscopy. The photocatalytic activity of Ag/ZnO thin film was assessed by measuring the decolorization rate constant of the dyes mixture spectrophotometrically. The chemical structure of each dye influences the photodegradation rate either in mixture or in individual dyes solutions. Several parameters which influence photocatalytic degradation such as catalyst dose, dyes concentrations as well as addition of hydrogen peroxide as an electron acceptor have been studied. The results revealed that these parameters should be optimized to obtain the maximum photocatalytic degradation.

F. A. Mahmoud

Papers

Room temperature ferromagnetism and gas sensing in ZnO nanostructures: Influence of intrinsic defects and Mn, Co, Cu doping

Design of multi-functional cotton gauze with antimicrobial and drug delivery properties.

Structural analysis of aerosol spray pyrolysis ZnO films exhibiting ultra low ozone detection limits at room temperature

Enhanced photocatalytic degradation of textile wastewater using Ag/ZnO thin films

Preparation of Chitosan-grafted-Polyvinyl acetate Metal Nanocomposite for producing Multifunctional Textile Cotton Fabrics.