Isotherm Models and First-Principles Studies of Gas Adsorption in Graphene Field-Effect Transistors: A Review

Graphene has attracted a lot of attention in gas sensing applications for its high surface area ratio and unique chemical or physical gas adsorption ability. Being an important research method, theoretical calculations play a key role in both illustrating the gas sensing mechanism of graphene and improving the gas sensing performance of graphene-based sensors. This review discusses the application of adsorption isotherm theory and first-principles studies to graphene gas sensors. Different isotherm theories are presented, including Langmuir, Freundlich, BET, and Temkin isotherm models, and it is illustrated how to investigate the adsorption information from them. The first-principles analysis of graphene-based gas sensors is presented. In general, doping with transition metals and nonmetals can improve the sensitivity of graphene to gases. This review shows the significance of using theoretical calculations to design novel and efficient gas sensors. The theoretical results obtained so far can be of great help in designing novel and efficient graphene-based gas sensors.