Graphene, a single, one-atom-thick sheet of carbon atoms arranged in a honeycomb lattice and the two-dimensional building block for carbon materials, has attracted great interest for a wide range of applications. Due to its superior properties such as thermo-electric conduction, surface area and mechanical strength, graphene materials have inspired huge interest in sensing of various chemical species. In this timely review, we discuss the recent advancement in the field of graphene based gas sensors with emphasis on the use of modified graphene materials. Further, insights of theoretical and experimental aspects associated with such systems are also discussed with significance on the sensitivity and selectivity of graphene towards various gas molecules. The first section introduces graphene, its synthesis methods and its physico-chemical properties. The second part focuses on the theoretical approaches that discuss the structural improvisations of graphene for its effective use as gas sensing materials. The third section discusses the applications of pristine and modified graphene materials in gas sensing applications. Various graphene modification methods are discussed including using dopants and defects, decoration with metal/metal oxide nanoparticles, and functionalization with polymers. Finally, a discussion on the future challenges and perspectives of this enticing field of graphene sensors for gas detection is provided.

Recent advances in graphene based gas sensors

Wearable electronics is expected to be one of the most active research areas in the next decade; therefore, nanomaterials possessing high carrier mobility, optical transparency, mechanical robustness and flexibility, lightweight, and environmental stability will be in immense demand. Graphene is one of the nanomaterials that fulfill all these requirements, along with other inherently unique properties and convenience to fabricate into different morphological nanostructures, from atomically thin single layers to nanoribbons. Graphene-based materials have also been investigated in sensor technologies, from chemical sensing to detection of cancer biomarkers. The progress of graphene-based flexible gas and chemical sensors in terms of material preparation, sensor fabrication, and their performance are reviewed here. The article provides a brief introduction to graphene-based materials and their potential applications in flexible and stretchable wearable electronic devices. The role of graphene in fabricating ...

Flexible Graphene-Based Wearable Gas and Chemical Sensors

Graphene-based gas/vapor sensors have attracted much attention in recent years due to their variety of structures, unique sensing performances, room-temperature working conditions, and tremendous application prospects, etc. Herein, we summarize recent advantages in graphene preparation, sensor construction, and sensing properties of various graphene-based gas/vapor sensors, such as NH3, NO2, H2, CO, SO2, H2S, as well as vapor of volatile organic compounds. The detection mechanisms pertaining to various gases are also discussed. In conclusion part, some existing problems which may hinder the sensor applications are presented. Several possible methods to solve these problems are proposed, for example, conceived solutions, hybrid nanostructures, multiple sensor arrays, and new recognition algorithm.

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A Review on Graphene-Based Gas/Vapor Sensors with Unique Properties and Potential Applications

Electrically–transduced sensors, with their simplicity and compatibility with standard electronic technologies, produce signals that can be efficiently acquired, processed, stored, and analyzed. Two dimensional (2D) nanomaterials, including graphene, phosphorene (BP), transition metal dichalcogenides (TMDCs), and others, have proven to be attractive for the fabrication of high–performance electrically-transduced chemical sensors due to their remarkable electronic and physical properties originating from their 2D structure. This review highlights the advances in electrically-transduced chemical sensing that rely on 2D materials. The structural components of such sensors are described, and the underlying operating principles for different types of architectures are discussed. The structural features, electronic properties, and surface chemistry of 2D nanostructures that dictate their sensing performance are reviewed. Key advances in the application of 2D materials, from both a historical and analytical pers...

Electrically-Transduced Chemical Sensors Based on Two-Dimensional Nanomaterials

Metal oxide/graphene nanocomposites are emerging as one of the promising candidate materials for developing high-performance gas sensors. Here, we demonstrate sensitive room-temperature H2S gas sensors based on SnO2 quantum wires that are anchored on reduced graphene oxide (rGO) nanosheets. Using a one-step colloidal synthesis strategy, the morphology-related quantum confinement of SnO2 can be well-controlled by tuning the reaction time, because of the steric hindrance effect of rGO. The as-synthesized SnO2 quantum wire/rGO nanocomposites are spin-coated onto ceramics substrates without further sintering to construct chemiresistive gas sensors. The optimal sensor response toward 50 ppm of H2S is 33 in 2 s, and it is fully reversible upon H2S release at 22 °C. In addition to the excellent gas adsorption of ultrathin SnO2 quantum wires, the superior sensing performance of SnO2 quantum wire/rGO nanocomposites can be attributed to the enhanced electron transport resulting from the favorable charge transfer of...

Sensitive Room-Temperature H2S Gas Sensors Employing SnO2 Quantum Wire/Reduced Graphene Oxide Nanocomposites

Abstract Polyphenylene sulfide (PPS) is a versatile material that gives extruded and molded components the ability to meet exceptionally demanding criteria. This semicrystalline engineering thermoplastic has outstanding thermal stability, superior toughness, inherent flame resistance, and excellent chemical resistance. It also has high mechanical strength, impact resistance, and dimensional stability as well as good electrical properties. The present review outlines the synthesis methods, characterizations, and electrical and dielectric properties of PPS composite. Its structural and morphological characteristics, studied for advanced applications such as photovoltaic cells, gas sensors, and supercapacitors, are in prospect. In the composite phase, the electric and dielectric properties of PPS are found to be improved.

Polyphenylene sulfide (PPS): state of the art and applications

A comprehensive study of effect of concentration, particle size and particle shape on thermal conductivity of titania/water based nanofluid

Solvent mixed spray pyrolysis technique has attracted a global interest in the synthesis of nanomaterials since reactions can be run in liquid state without further heating. Magnesium oxide (MgO) is a category of the practical semiconductor metal oxides, which is extensively used as catalyst and optical material. In the present study, MgO nanoparticles were successfully synthesized using a solvent mixed spray pyrolysis. The X-ray diffraction pattern confirmed the formation of MgO phase with an excellent crystalline structure. Debye-Scherrer equation is used for the determination of particle size, which was found to be 9.2 nm. Tunneling electron microscope analysis indicated that the as-synthesized particles are nanoparticles with an average particle size of 9 nm. Meanwhile, the ultraviolet-visible spectroscopy of the resulting product was evaluated to study its optical property via measurement of the band gap energy value.

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Synthesis of MgO Nanoparticles by Solvent Mixed Spray Pyrolysis Technique for Optical Investigation

A chemiresistive gas sensor based on few-layered graphene (FLG) has been fabricated and evaluated for carbon dioxide (CO2) and liquid petroleum gas (LPG) sensing. The electrochemical exfoliation method was used to synthesize FLG. The resulting sample of FLG was characterized by x-ray diffraction, Raman spectroscopy, atomic force microscopy, and transmission electron microscopy with selected-area diffraction. Ultraviolet–visible and fluorescence spectroscopy were employed to study the optical properties. Thermal behavior was analyzed through thermogravimetric–differential thermal analysis. The sensing response of the chemiresistor is defined as the ratio of resistance in gas to air at the stabilized resistance in air. The FLG chemiresistor exhibited good sensing response (3.83 for CO2, 0.92 for LPG), response time (11 s for CO2, 5 s for LPG), recovery time (14 s for CO2, 18 s for LPG), and resolution limit (3 ppm for CO2, 4 ppm for LPG), and excellent stability at room temperature. The gas sensing mechanism is discussed on the basis of marginal difference in Raman intensity and also by using defect chemistry through fluorescence measurements.

Kailash Nemade

Papers

Polyphenylene sulfide (PPS): state of the art and applications

A comprehensive study of effect of concentration, particle size and particle shape on thermal conductivity of titania/water based nanofluid

Synthesis of MgO Nanoparticles by Solvent Mixed Spray Pyrolysis Technique for Optical Investigation

Chemiresistive Gas Sensing by Few-Layered Graphene

Band gap engineering of CuS nanoparticles for artificial photosynthesis