Quartz crystal microbalance (QCM) is a mass-sensitive device, and has been attracting intensive attention in the field of gas sensor because of its many advantages such as high sensitivity, low cost, easy installation and inherent ability to monitor analytes in real time. Sensing material is a key issue for the range of application of QCM sensors. This paper reviews the current research status of sensing materials for specific gases, including polymers, supermolecules, ionic liquids, molecular liquids and nanomaterials. The current status and sensing mechanisms of QCM sensors using nanomaterials as sensing layer are introduced in detail. On the basis of the research status, a prospect is given of sensing materials. As a low-cost, easy operation, high-accuracy gas detection device, QCM would be more widely applied in the future.

Contents
1 Introduction
2 Polymers functionalized QCM sensors
2.1 Humidity detection
2.2 Agent stimulant detection
2.3 VOCs detection
3 Supermolecules functionalized QCM sensors
3.1 Inorganic gas pollutants detection
3.2 VOCs detection
4 Ionic liquids and molecular liquids functionalized QCM sensors
4.1 VOCs detection
4.2 Non-volatility compounds detection
5 Nanomaterials functionalized QCM sensors
5.1 Humidity detection
5.2 Inorganic gas pollutants detection
5.3 VOCs detection
5.4 HCN and agent stimulant detection
6 Conclusion and outlook