New frontiers in the plant extract mediated biosynthesis of copper oxide (CuO) nanoparticles and their potential applications: A review.

2D and nanostructured metal sulfide materials are promising in the advancement of several gas sensing applications due to the abundant choice of materials with easily tunable electronic, optical, physical, and chemical properties. These applications are particularly attractive for gas sensing in environmental monitoring and breath analysis. This review gives a systematic description of various gas sensors based on 2D and nanostructured metal sulfide materials. Firstly, the crystal structures of metal sulfides are introduced. Secondly, the gas sensing mechanisms of different metal sulfides based on density functional theory analysis are summarised. Various gas-sensing concepts of metal sulfide-based devices, including chemiresistors, functionalized metal sulfides, Schottky junctions, heterojunctions, field-effect transistors, and optical and surface acoustic wave sensors, are compared and presented. It then discusses the extensive applications of metal sulfide-based sensors for different gas molecules, including volatile organic compounds (i.e., acetone, benzene, methane, formaldehyde, ethanol, and liquefied petroleum gas) and inorganic gas (i.e., CO2, O2, NH3, H2S, SO2, NOx, CH4, H2, and humidity). Finally, a strengths–weaknesses–opportunities–threats (SWOT) analysis is proposed for future development and commercialization in this field.

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Recent advances in 2D/nanostructured metal sulfide-based gas sensors: mechanisms, applications, and perspectives

Over the last couple of decades, the advancement in Microelectromechanical System (MEMS) devices is highly demanded for integrating the economically miniaturized sensors with fabricating technology. A sensor is a system that detects and responds to multiple physical inputs and converting them into analogue or digital forms. The sensor transforms these variations into a form which can be utilized as a marker to monitor the device variable. MEMS exhibits excellent feasibility in miniaturization sensors due to its small dimension, low power consumption, superior performance, and, batch-fabrication. This article presents the recent developments in standard actuation and sensing mechanisms that can serve MEMS-based devices, which is expected to revolutionize almost many product categories in the current era. The featured principles of actuating, sensing mechanisms and real-life applications have also been discussed. Proper understanding of the actuating and sensing mechanisms for the MEMS-based devices can play a vital role in effective selection for novel and complex application design.

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A Review of Actuation and Sensing Mechanisms in MEMS-Based Sensor Devices

Metal oxide nanoparticles have been widely utilized for the fabrication of functional gas sensors to determine various flammable, explosive, toxic, and harmful gases due to their advantages of low cost, fast response, and high sensitivity. However, metal oxide-based gas sensors reveal the shortcomings of high operating temperature, high power requirement, and low selectivity, which limited their rapid development in the fabrication of high-performance gas sensors. The combination of metal oxides with two-dimensional (2D) nanomaterials to construct a heterostructure can hybridize the advantages of each other and overcome their respective shortcomings, thereby improving the sensing performance of the fabricated gas sensors. In this review, we present recent advances in the fabrication of metal oxide-, 2D nanomaterials-, as well as 2D material/metal oxide composite-based gas sensors with highly sensitive and selective functions. To achieve this aim, we firstly introduce the working principles of various gas sensors, and then discuss the factors that could affect the sensitivity of gas sensors. After that, a lot of cases on the fabrication of gas sensors by using metal oxides, 2D materials, and 2D material/metal oxide composites are demonstrated. Finally, we summarize the current development and discuss potential research directions in this promising topic. We believe in this work is helpful for the readers in multidiscipline research fields like materials science, nanotechnology, chemical engineering, environmental science, and other related aspects.

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The Combination of Two-Dimensional Nanomaterials with Metal Oxide Nanoparticles for Gas Sensors: A Review

Abstract Three-dimensional inverse opal (3DIO) ZnO-Fe3O4 composite structure was prepared by a template method and the gas sensing property was investigated toward trace acetone which is an important biomarker of diabetes. The prepared 3DIO composite sensors have large surface area due to both macropores (larger than 100 nm) and mesoporous structure in skeleton, which make the inner surface accessible and provide more active sites to adsorb more oxygen species and target molecules. 3DIO ZnO-Fe3O4 composite sensor exhibits much higher response toward acetone relative to pure ZnO sensor. The optimal 3DIO sensor exhibited a detection limit as low as 100 ppb acetone and showed 40% response increase from 0.9 ppm (healthy humans) to 1.8 ppm (diabetics) which allow reliable diagnosis of diabetic patients by acetone monitoring.

Three-dimensional ordered ZnO-Fe3O4 inverse opal sensor toward trace concenration acetone detection

Acetone is a well-known volatile organic compound that is widely used in different industrial and domestic areas. However, it can have dangerous effects on human life and health. Thus, the realization of sensitive and selective sensors for recognition of acetone is highly important. Among different gas sensors, resistive gas sensors based on nanostructured metal oxide with high surface area, have been widely reported for successful detection of acetone gas, owing to their high sensitivity, fast dynamics, high stability, and low price. Herein, we discuss different aspects of metal oxide-based acetone gas sensors in pristine, composite, doped, and noble metal functionalized forms. Gas sensing mechanisms are also discussed. This review is an informative document for those who are working in the field of gas sensors.

https://www.mdpi.com/1424-8220/20/11/3096/pdf

Nanostructured Metal Oxide-Based Acetone Gas Sensors: A Review

Effect of Ag on the ZnO nanoparticles properties as an ethanol vapor sensor

A novel room temperature ethanol sensor based on PbS:SnS2 nanocomposite with enhanced ethanol sensing properties

High-detectivity near-infrared photodetector based on Ag2S nanocrystals

Vanadium pentoxide (V2O5) is a transition metal oxide with features such as high availability, good catalytic activity, unique electrical properties and high conductivity which are appropriate for gas sensing applications. In this review, we discuss different gas sensing aspects of V2O5 in pristine, doped, decorated and composite forms. Depending on its synthesis procedure, morphology, sensing temperature and surface conditions, the V2O5-based gas sensors show different responses to target gases. Herein, we have discussed the behavior of V2O5-based gas sensors to different gases and associated sensing mechanisms. This review paper can be a useful reference for the researchers who works in the field of gas sensors.

Hossein Roshan

Papers

Nanostructured Metal Oxide-Based Acetone Gas Sensors: A Review

Effect of Ag on the ZnO nanoparticles properties as an ethanol vapor sensor

A novel room temperature ethanol sensor based on PbS:SnS2 nanocomposite with enhanced ethanol sensing properties

High-detectivity near-infrared photodetector based on Ag2S nanocrystals

A Review of Nanostructured Resistive-Based Vanadium Oxide Gas Sensors