The employment of graphene for multifunctional uses has been a cornerstone in sensing technology. Due to its excellent electrochemical properties, graphene has been used in its pure and composite forms to detect target molecules over a wide range of surfaces. The adsorption process on the graphene-based sensors has been studied in terms of the change in resistance and capacitance values for various industrial and environmental applications. This paper highlights the performance of graphene-based sensors for detecting different kinds of domestic and industrial gases. These graphene-based gas sensors have achieved enhanced output in terms of sensitivity and working range due to specific experimental parameters, such as elevated temperature, presence of particular gas-specific layers and integration with specific nanomaterials that assist with the adsorption of gases. The presented research work has been classified based on the physical nature of graphene used in conjugation with other processed materials. The detection of five different types of gases, including carbon dioxide (CO2), ammonia (NH3), hydrogen sulphide (H2S), nitrogen dioxide (NO2) and ethanol (C2H5OH) has been shown in the paper. The challenges of the current graphene-based gas sensors and their possible remedies have also been showcased in the paper.

Currently, the gas sensor market is worth USD 2.33 billion. It is forecasted that the growth of compound annual rate value willing to be 8.7% within the length from 2021 to 2028. The commercial prospects of the semiconducting metal oxide-based gas sensor are limited due to high-temperature operation, higher power consumption, short-term stability, and sensitivity to humidity. Amongst all, tin oxide-based sensors are most commercialized owing to their tunable physicochemical properties. Moreover, the bottlenecks of elevated temperature operation, stability, and selectivity can be catered to by developing its hybrid nanocomposites with other organic and inorganic materials. The multi-interactions, surface functionalization, and formation of heterojunctions in SnO2 nanocomposites enhance their interaction with analyte molecules resulting in excellent sensing performances. This review aims to provide insights into various synthesis strategies to fabricate SnO2 and its hybrid nanocomposites. The advancements in physicochemical properties and structural chemistries are discussed in terms of various spectroscopic analyses. Further, the development in sensor devices using hybrid SnO2 nanoparticles and their sensing properties towards different gasses and VOCs are discussed. This review focuses on studies dealing with low and moderate-temperature gas detection through SnO2 based nanosystems. A comprehensive comparison and correlation of all the mentioned sensing results have been concluded to propose suitable conditions, hybrid SnO2 nanocomposite for superior gas sensing applications.

There is a constant need to maintain the quality of consumed food. In retrospect to the recent pandemic and other food-related problems, scientists have focused on the numbers of microorganisms that are present in different food items. As a result of changes in certain environmental factors such as temperature and humidity, there is a constant risk for the growth of harmful microorganisms, such as bacteria and fungi, in consumed food. This questions the edibility of the food items, and constant monitoring to avoid food poisoning-related diseases is required. Among the different nanomaterials used to develop sensors to detect microorganisms, graphene has been one of the primary materials due to its exceptional electromechanical properties. Graphene sensors are able to detect microorganisms in both a composite and non-composite manner, due to their excellent electrochemical characteristics such as their high aspect ratios, excellent charge transfer capacity and high electron mobility. The paper depicts the fabrication of some of these graphene-based sensors, and their utilization to detect bacteria, fungi and other microorganisms that are present in very small amounts in different food items. In addition to the classified manner of the graphene-based sensors, this paper also depicts some of the challenges that exist in current scenarios, and their possible remedies.

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