Fluorescence quenching mechanism and the application of green carbon nanodots in the detection of heavy metal ions: a review

Abstract

Fluorescent carbon nanodots (CNDs) are renowned as a new family of zero-dimensional nanomaterials. In the current scenario, CNDs are considered an iconic research field because of their desirable fluorescent behavior, biocompatibility, the ease of functionalization, chemical inertness, and photostability. There are many ways to produce CNDs but natural renewable carbon sources can produce CNDs on a large scale. This can be a significant advantage for researchers to explore their versatile applications. Hitherto, CNDs have been scrutinized as a selective and sensitive fluorescent sensor for different heavy metal ions even at femtomolar ranges. This review overlooks all the previously provided information on the synthesis, properties, and application of CNDs. However, it focuses on the fluorescence-sensing mechanism of heavy metal ions using green-derived CNDs as the detection tool. We give a brief outline of green sources utilized in the CND synthesis, its properties, and the fluorescence mechanism of CNDs. Finally, we comprehensively summarize the quenching mechanism of heavy metal ions to illustrate the related green CND-based sensors. Furthermore, problems and possible solutions to overcome the future path of CNDs in this sensing field are discussed.