International Journal of Research and Review DOI: https://doi.org/10.52403/ijrr.20210746 Vol.8; Issue: 7; July 2021 Website: www.ijrrjournal.com Short Communication E-ISSN: 2349-9788; P-ISSN: 2454-2237 International Journal of Research and Review (ijrrjournal.com) 332 Vol.8; Issue: 7; July 2021 Green Synthesis of SnO 2 /Carbon Quantum Dots Nanocomposite for Gas Sensing Application Hare Narayan Prajapati 1 , Pradeep Kumar Khiriya 2 , Gagan Kant Tripathi 3 , Priyavand Bundela 4 , Purnima Swarup Khare 5 1-5 School of Nanotechnology, Rajiv Gandhi Proudyogiki Vishwavidyalaya, Bhopal, Madhya Pradesh Corresponding Author: Hare Narayan Prajapati ABSTRACT SnO 2 /Carbon Quantum Dots (CQDs) were synthesized by a hydrothermal method using grape fruit juice. The nanocomposites (NC) were characterized by means of XRD and Gas sensing properties. The sensor devices were fabricated using SnO 2 /CQDs NC as sensing materials. The effect of the CQDs content on the gas-sensing responses and the gas-sensing selectivity was investigated. In this work, the gas sensor developed is exposed to carbon monoxide polluting gas like at different temperatures to determine the optimum operating temperatures which allow obtaining the highest sensitivity for gas. Keywords: Green synthesis, Grape fruit, SnO 2 nanoparticles, CQDs, Gas sensor INTRODUCTION Green synthesis is defined as the use of environmentally compatible materials such as bacteria, fungi and plants in the synthesis of nanoparticles [1] . These green and economical strategies are free of the short falls associated with conventional synthetic strategies, i.e. they are environment-friendly [2,3] . We have synthesized a carbon dot compositor with SnO 2 nanoparticles by green preparation method and gas sensors are widely used in hydrothermal processing [4] . They are one of the indispensable technologies in modern life. Materials which change their properties depending on ambient gases can be used as gas detection materials [5] . Optical or electrical signals can be used to detect gas concentrations. For an optical gas sensor, the color of the sensor varies with the concentration of gas detected [6] . For an electric gas sensor, the gas concentration can be detected either by changing the resistance of the sensor resulting from a reaction of the gas with chemisorbed oxygen on the surface of the sensing material, or by varying the output voltage by applying a temperature gradient provided by a chemical reaction to a thermoelectric sensing material [7] . Many transition metal oxides exhibit sensitivity towards oxidizing and reducing gases by varying their electrical properties: usually changes in the electrical conductance in response to environmental gases are monitored [8] . SnO 2 is currently the most widely used material for detecting of various gases due to its suitable physicochemical properties and lower cost compared to available materials for the similar applications [9] . It is sensitive to gas CO at moderate temperature. Because gas sensing procedures strongly rely on the surface chemical reactions, there is a relationship between the gas sensitivity and their surface chemical activities [10] . SnO 2 has a high reactivity to reduce gases at relatively low operating temperatures due to the easy adsorption of oxygen at its surface. The presence of a certain metal or oxides on the sensing material surface would improve its sensing properties to certain gases [11] . Carbon quantum dots (CQDs) have received much attention in recent past