There are various kinds of natural, chemical, and artificial species available in our surrounding environment, where some of them are essential while others are more harmful or less. The necessary gases/species like oxygen (O2), nitrogen (N2) and humidity should be maintained sufficiently in the global atmosphere while excess emission of hazardous or toxic gases can harm the living atmosphere. In this regard, the burning of fossil fuels (e.g., Coal, petroleum, and natural gas) are a significant concern for global air pollution. On burning, compounds containing carbon, nitrogen, and sulfur generate gaseous oxides by reacting with air. These toxic gases are harmful in the living atmosphere in parts per million (ppm) or even parts per billion (ppb). In addition, the leakage due to the explosion of lower hydrocarbons and hydrogen (H2) from fuels also promotes air pollution; 1/10 of lower explosion limit (LEL) is kept at an alarming level for each gas. In the present scenario, the increase of hazardous or toxic gases in the global environment is a major issue concerning the environment monitoring system where gas sensor shows the possible solution by detecting these toxic gases precisely.

A sensor is a device that detects/receives a physical or chemical stimulus and responds with an analytically helpful signal. In most cases, the sensor output is in the form of electrical or electronic. Sensors may be classified into two broad categories, i.e., (a) physical sensor and (b) chemical sensor. A chemical sensor can be defined as a device that transforms chemical information of the target species into a useful analytical signal. On the other hand, the physical sensor can be defined as a device that gives information about the physical property of the system to be investigated. A gas sensor is a family member of a chemical sensor, which detects and/or quantifies the presence of gases as well as the concentration of the gases in a fixed volume where dry air is generally used as a reference environment.

Numerous researches on gas sensing applications confirm that materials with favorable physical, chemical, structural, and electrical properties can be used to design gas sensors in various applications. Various materials, including semiconducting materials, semiconducting metal oxides, pure metals, solid electrolytes, organic materials (polymers and other semiconducting materials), ionic membranes, and ionic salts, are studied for gas sensing applications. 

Our research group on gas sensors works on fabrication and testing of humidity/gas sensors on various synthesized nanomaterials such as carbonaceous (Graphene, Graphene oxide, Carbon nanotubes), Transition metal dichalcogenides (TMDs), Transition metal carbides (MXenes), Metal-organic Frameworks (MOFs), nanofiller based polymer materials etc.