Rapid Liquid Recognition and Quality Inspection with Graphene Test Papers.

Electronic tongue is widely applied in liquid sensing for applications in various fields, such as environmental monitoring, healthcare, and food quality test. A rapid and simple liquid-sensing method can greatly facilitate the routine quality tests of liquids. Nanomaterials can help miniaturize sensing devices. In this work, a broad-spectrum liquid-sensing system is developed for rapid liquid recognition based on disposable graphene-polymer nanocomposite test paper prepared through ion-assisted filtration. Using this liquid-sensing system, a number of complex liquids are successfully recognized, including metal salt solutions and polymer solutions. The electronic tongue system is especially suitable for checking the quality of the foodstuff, including soft drinks, alcoholic liquor, and milk. The toxicants in these liquids can be readily detected. Furthermore, the novel material-structure design and liquid-detection method can be expanded to other chemical sensors, which can greatly enrich the chemical information collected from the electrical response of single chemiresistor platform.