In this study we report the enhancement of UV photodetection and wavelength tunable light induced NO gas sensing at room temperature using Au-ZnO nanocomposites synthesized by a simple photochemical process Plasmonic Au-ZnO nanostructures with a size less than the incident wavelength have been found to exhibit a localized surface plasmon resonance (LSPR) that leads to a strong absorption, scattering and local field enhancement The photoresponse of Au-ZnO nanocomposite can be effectively enhanced by 80 times at 335 nm over control ZnO We also demonstrated Au-ZnO nanocomposite's application to wavelength tunable gas sensor operating at room temperature The sensing response of Au-ZnO nancomposite is enhanced both in UV and visible region, as compared to control ZnO The sensitivity is observed to be higher in the visible region due to the LSPR effect of Au NPs The selectivity is found to be higher for NO gas over CO and some other volatile organic compounds (VOCs), with a minimum detection limit of 01 ppb for Au-ZnO sensor at 335 nm

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Multifunctional Au-ZnO Plasmonic Nanostructures for Enhanced UV Photodetector and Room Temperature NO Sensing Devices

https://www.econstor.eu/bitstream/10419/244006/1/1693663112.pdf

Enhanced sensing performance of ZnO nanostructures-based gas sensors: A review

Detection of COVID-19: A review of the current literature and future perspectives.

Semiconductor photocatalysis, a sustainable and renewable technology, is deemed to be a new path to resolve environmental pollution and energy shortage. The development of effective photocatalysts, especially the metal-free photocatalysts, is a critical determinant of this technique. The recently emerged 2D material of black phosphorus with distinctive properties of tunable direct bandgap, ultrahigh charge mobility, fortified optical absorption, large specific surface area, and anisotropic structure has captured enormous attention since the first exfoliation of bulk black phosphorus into mono- or few layered phosphorene in 2014. In this article, the state-of-the-art preparation methods are first summarized for bulk black phosphorus, phosphorene, and black phosphorus quantum dot and then the fundamental structure and electronic and optical properties are analyzed to evaluate its feasibility as a metal-free photocatalyst. Various modifications on black phosphorus are also summarized to enhance its photocatalytic performance. Furthermore, the multifarious applications such as solar to energy conversion, organic removal, disinfection, nitrogen fixation, and photodynamic therapy are discussed and some of the future challenges and opportunities for black phosphorus research are proposed. This review reveals that the rising star of black phosphorus will be a multifunctional material in the postgraphene era.

Black Phosphorus, a Rising Star 2D Nanomaterial in the Post-Graphene Era: Synthesis, Properties, Modifications, and Photocatalysis Applications

Since the first suggestion, during the 1950s, that high-surface-area metal oxides could be used as conductometric gas sensors enormous efforts have been made to enhance both the selectivity and the sensitivity of such devices, and to reduce their operational power requirements. This development has involved the exploration of response mechanisms, the selection of the most appropriate oxide compositions, the fabrication of two-phase ‘hetero-structures’, the addition of metallic catalyst particles and the optimisation of the manner in which the materials are presented to the gas—the structure and the nanostructure of the sensing elements. Far more of the scientific literature has been devoted to seeking such improvements in metal oxide gas sensors than has been directed at all other solid-state gas sensors together. Recent progress in the research and development of metal oxide gas sensor technology is surveyed in this invited review. The advances that have been made are quite spectacular and the results of individual pieces of work are drawn together here so that trends can be seen. Emerging features include: the significance of n-type/p-type switching, the enhancement of sensing performance of materials through the incorporation of secondary components and the advantages of interrogating sensors with alternating current rather than direct current.

https://iopscience.iop.org/article/10.1088/1361-6501/aa7443/pdf

Progress in the development of semiconducting metal oxide gas sensors: a review

Volatile organic compound sensing using copper oxide thin films: Addressing the cross sensitivity issue

Rapid and real-time detection of heavy metals in water with a portable microsystem is a growing demand in the field of environmental monitoring, food safety, and future cyber-physical infrastructure. Here, we report a novel ultrasensitive pulse-driven capacitance-based lead ion sensor using self-assembled graphene oxide (GO) monolayer deposition strategy to recognize the heavy metal ions in water. The overall field-effect transistor (FET) structure consists of a thermally reduced graphene oxide (rGO) channel with a thin layer of Al2O3 passivation as a top gate combined with sputtered gold nanoparticles that link with the glutathione (GSH) probe to attract Pb2+ ions in water. Using a preprogrammed microcontroller, chemo-capacitance based detection of lead ions has been demonstrated with this FET sensor. With a rapid response (∼1–2 s) and negligible signal drift, a limit of detection (LOD) < 1 ppb and excellent selectivity (with a sensitivity to lead ions 1 order of magnitude higher than that of interfering...

Pulse-Driven Capacitive Lead Ion Detection with Reduced Graphene Oxide Field-Effect Transistor Integrated with an Analyzing Device for Rapid Water Quality Monitoring.

Using sol–gel synthesis, we have synthesized phase pure, porous, WO 3 thin film (thickness ∼70 nm) on optically flat quartz substrates. The deposited films were characterized in terms of their structure, microstructure, and gas sensing characteristics. We have investigated the NO 2 (0.2–50 ppm), CO (10–500 ppm), methane, and butane (50–500 ppm) sensing characteristics of the synthesized films. The low ppm NO 2 sensing characteristics of these films are found to be superior than most of the nano-structured WO 3 sensing elements reported in recent literatures. For higher test gas concentrations, we found these sensing elements are sensitive to carbon monoxide (>10 ppm), methane, and butane gases (>50 ppm). We demonstrated that exponential moving average feature extraction algorithm of the resistance transients in conjunction with pattern recognition analyses is one of the most viable approach to address the cross-sensitivity of WO 3 thin film NO 2 sensors towards other reducing gases.

NO2 sensing and selectivity characteristics of tungsten oxide thin films

ZnO nanobundles were grown via a nano-templating technique over a porous silica bed using an aqueous chemical route. The growth of nanobundles initiated from ZnO nano-seeds positioned at various levels over a nanoporous matrix of self-assembled polymethylsilsesquioxane nanoparticles. Bundles of different features like nanowires, nanorods and nanotubes with a high surface roughness were grown over these templates by a day-long incubation in an aqueous solution of hexamethylene tetra-amine and zinc nitrate. We envisage these ZnO nanostructures for sensitive hydrogen detection. Photoluminescence spectra indicate the nanotubes to be most sensitive towards H2. We observe high reconditionability, moderate sensitivity and a temperature dependent charge carrier reversal phenomenon.

Hydrogen sensing based on nanoporous silica-embedded ultra dense ZnO nanobundles

In the present work, a novel strategy has been adopted to develop highly sensitive and selective carbon monoxide (CO) gas sensor using ( x )NiFe 2 O 4 (spinel)–(1 −  x )La 0.8 Pb 0.2 Fe 0.8 Co 0.2 O 3 (perovskite) (0 ≤  x  ≤ 1) composite nano-powders. These powders were prepared through a citric acid mediated wet chemical pechini route. We have investigated the effect of the inclusion of perovskite phase in the spinel matrix to achieve high sensitivity, selectivity, lowering of the optimum temperature, rapid response and recovery time toward CO sensing. Improvement of these gas sensing parameters are essential to yield smart CO sensing system. We have demonstrated that optimized 25%NiFe 2 O 4 –75%La 0.8 Pb 0.2 Fe 0.8 Co 0.2 O 3 composite exhibits excellent sensitivity and selectivity toward CO sensing in operating temperatures ranging between 125 and 175 °C. The plausible reasons for the improvement in gas sensing parameters are discussed.

Arnab Maity

Papers

Volatile organic compound sensing using copper oxide thin films: Addressing the cross sensitivity issue

Pulse-Driven Capacitive Lead Ion Detection with Reduced Graphene Oxide Field-Effect Transistor Integrated with an Analyzing Device for Rapid Water Quality Monitoring.

NO2 sensing and selectivity characteristics of tungsten oxide thin films

Hydrogen sensing based on nanoporous silica-embedded ultra dense ZnO nanobundles

Engineered spinel–perovskite composite sensor for selective carbon monoxide gas sensing