Design and applications of carbon dots-based ratiometric fluorescent probes: A review

Ratiometric fluorescence (FL) probes can eliminate the background interference and provide more accurate detection results than single emission intensity-based nanoprobes. Recently, carbon dots (CDs)-based ratiometric FL probes have received extensive research attention due to their excellent biocompatibility, water solubility, and multi-emission capabilities. In this review, we firstly summarize the construction strategies of CDs-based ratiometric FL probes, including physical mixing, nanohybrid, and dual-emitting CDs strategies. Additionally, we classify the sensing types of CDs-based ratiometric FL probes into five categories according to the difference in spectral variation caused by analytes: “single-response-ON”, “single-response-OFF”, “double-responses-ON”, “double-responses-OFF”, and “double-responses-Reverse” types. Finally, a thorough overview of CDs-based ratiometric FL probe applications in ions, molecules, pH, and temperature sensing is provided. We believe this review can show the latest research progress of CDs-based ratiometric FL sensing fields and provide perspectives on future developments for the construction of CDs-based ratiometric FL probes and their potential applications.