One step synthesis of red light-emitting carbon dots (R-CDs) with highly photoluminescence from O-phenylenediamine and 2,4-diaminophenol as fluorescent probes for detection of pH and Cr (VI)

In this study, a new type of red light-emitting carbon dots (R-CDs) that can selectively recognize Cr(VI) was prepared by using the strategy of 2,4-diaminophenol to enhance the fluorescence of O-phenylenediamine based carbon dots. The results showed that 2,4-diaminophenol increased the quantum yield (QY) of carbon quantum dots (CDs), and the QY of CDs increased from the original 8.7% to 20.1%(R-CDs). R-CDs show sensitivity to acidic conditions and maintain good linearity between pH = 1.00-4.00, making them useful for pH probes. Furthermore, the prepared R-CDs possess good solubility in water. They are responsive to changes in Cr(VI) concentrations in aqueous environments. R-CDs' quenching was linearly correlated with the Cr(VI) concentration within a range of 0-20 μM, with a lower detection limit of 66 nM. The detection mechanism is attributed to the formation of hydrogen bonds between Cr(VI) and R-CDs, resulting in the fluorescence quenching of R-CDs. R-CDs could be considered effective multifunctional fluorescent probes for pH and Cr(VI) in aqueous environments. This study will provide new R-CD design strategies that selectively identify specific target substances.