Dual-analyte detection of Pb2+ and L-cysteine using a ratiometric fluorescence probe based on carbon dots

The increasing presence of heavy metals and amino acids in environmental and pharmaceutical samples necessitates the development of effective and sensitive detection methods. Traditional analytical techniques often lack the specificity and sensitivity required for simultaneous detection of multiple analytes, leading to a need for novel approaches. In this study, we developed a ratiometric fluorescence probe based on a physical mixture of red and blue carbon dots (R/BCDs) for the selective detection of lead ions (Pb2+) and L-cysteine (L-Cys). The probe was synthesized through hydrothermal methods and characterized by various spectroscopic techniques. The R/BCDs probe exhibited a remarkable 11.6-fold fluorescence quenching in response to Pb2+, with a detection limit of 15 nM, while subsequent addition of L-Cys showed a 9.6-fold restored fluorescence signal, achieving a detection limit of 75 nM. Additionally, we demonstrated the feasibility of fabricating colorimetric test paper and hydrogels, enabling rapid on-site analysis. This dual-analyte detection capability was demonstrated through successful application in real water and pharmaceutical samples. The R/BCDs probe offers a novel, simple, and effective strategy for environmental monitoring and biological assessments, highlighting its potential for practical applications.