Red-Emitting Carbon Dots as a Dual Sensor for In³⁺ and Pd²⁺ in Water

We have demonstrated the synthesis, characterization, and application of nitrogen-doped red-emitting carbon dots (NRCDs) for dual sensing of indium (In³⁺) and palladium (Pd²⁺) in water. The detection of In³⁺ was associated with "turn-on" fluorescence response with a red shift, while in the presence of Pd²⁺, the fluorescence intensity of NRCDs was quenched to show a "turn-off" response. The interaction of NRCDs with the metal ions was investigated using ¹H nuclear magnetic resonance and Fourier-transform infrared spectroscopy studies. The synthesized nanoprobes possessed good biocompatibility and photostability and were found to be suitable candidates for bioimaging due to their emission profiles in the near-infrared (NIR) window. Applicability of the as-prepared NRCDs was demonstrated in the NIR region when they were loaded in vesicle membranes with and without cations and subjected to confocal imaging successfully.