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Electrochemical, chemiresistive and wearable sensors based on tin oxide (SnO2) were investigated for chemical sensing applications. There is an increased usage of SnO2 as modifier electrode materials because of its astonishing features of thermal stability, biocompatibility, excellent bandgap, cost effective and abundant availability. The surface of working electrode is modified by nanomaterials of SnO2 in combination with various metals, semiconductors and carbon derivatives for improved sensing performance. Various voltammetric and amperometric techniques were involved in studying the electrochemical properties and behaviour of the anlaytes at the surface of modified electrodes. This review focused on some recent works that provides an overview of the applications of SnO2 nanomaterials for the development of chemiresistive, electrochemical, and wearable sensors.

Multi-walled carbon nanotubes (MWCNTs) without and with adsorbed silver nanoparticles (Ag-NPs), are used to detect acetone vapour. MWCNTs are grown on SiO2/Si substrates and silver (Ag) nanoparticles (NPs) are deposited onto some of these MWCNTs using electron beam evaporation method. The sensitivity of CNT based sensors (with and without NPs) increases with the concentration of acetone vapour (50 ppm to 800 ppm) while a substantial rise in sensitivity is obtained from MWCNTs with Ag NPs. Band diagrams of the MWCNTs, with and without NPs, are analyzed to understand the gas molecules adsorption phenomena. This study is the first to establish that such sensors can operate at 27 °C rather than the 180 °C–450 °C used elsewhere, thus offering significant advantages over existing methods. To investigate the sensors’ dependability, they’re exposed to three cycles of 50 ppm acetone gas. These tests show that the devices’ responses remain unchanged, indicating their reliability. The effects of humidity upon MWCNT acetone sensors within 100 ppm of acetone vapour are also studied and improved performance towards stability and response/recovery is observed for the sensors with Ag-NPs. Furthermore, higher selectivity is observed for the Ag-coated sensors for acetone against various target gases (acetone, ethanol, NO2, ammonia, and acetone with water).

In the last three decades, a lot of scientific research has been carried out in the field of Carbon nanomaterials all over the world due to their significant electronic, optical, mechanical, chemical and thermal properties. The zero, one, two and three dimensional Carbon nanomaterials (i.e. fullerenes, Carbon nanotubes, Graphene, Carbon quantum dots, Carbon Nanohorns, Nanodiamonds, Carbon Nanofibres and Carbon black) have exhibited such inherent features that can be easily exploited in the development of advanced technology for sensing applications. The employment of nanomaterials within sensors has paved new way and opportunities for the detection of analytes or target molecules. Carbon nanomaterials based electrochemical biosensors have reported biocompatibility, better sensitivity, better selectivity and lower limits of detection to detect a wide range of chemical to biological molecules. In this paper, a comprehensive review has been made to cover recent developments in the field of Carbon based nanomaterials as electrochemical biosensors. The characteristic features of a variety of nanomaterials like fullerenes, Carbon nanotubes, Graphene, Carbon quantum dots, Carbon Nanohorns, Carbon Nanodiamonds, Carbon Nanofibres, Carbon black etc. have been discussed along with their synthesis methods. The recent application of all these nanomaterials as electrochemical biosensors for the detection of various biomolecules have been highlighted; the future prospects and possibilities in this field have been outlined.