Elucidating the Quenching Mechanism in Carbon Dot-Metal Interactions–Designing Sensitive and Selective Optical Probes

Abstract

Overexposure to metals has significant adverse effects on human and animal health coupled with nefarious consequences to the environment. Sensitive tools to measure low contaminant levels exist, but often come at a high cost and require tedious procedures. Thus, there exists a need for the development of affordable metal sensors that can offer high sensitivity and selectivity while being accessible on a global scale. Here, carbon dots, prepared in a one-pot synthesis using glutathione and formamide, have been developed as dual fluorescent metal sensing probes. Following extensive characterization of their physico-chemical properties, it is demonstrated that dual fluorescence can be exploited to build a robust ratiometric sensor with low-ppb detection sensitivity in water. This investigation shows that these optical probes are selective for Pb2+ and Hg2+ ions. Using steady-state and dynamic optical characterization techniques, coupled with hard and soft acid-base theory, the underlying reason for this selective behavior was identified. These findings shed light on the nature of metal-carbon dot interactions, which can be used to tailor their properties to target specific metal ions. Finally, these findings can be applicable to other fluorescent nanoparticle systems that are targeted for development as metal sensors.

Fluorescent Polymer Carbon Dots for the Sensitive–Selective Sensing of Fe3+Metal Ions and Cellular Imaging

“…The results prove that the lifetime of FPCDs does not significantly change after the addition of Fe 3+ ions, suggesting the occurrence of static quenching. 20,26,65 Thus, we concluded that both IFE and static quenching mechanisms are involved in the fluorescence quenching of FPCDs in the presence of Fe 3+ ions.…”

“…It is found that the excitation spectra of FPCDs and absorption spectra of Fe 3+ efficiently overlap, which clearly shows the possibility of IFE. ,, To further confirm the possibility of IFE, we obtained the fluorescence spectra of FPCDs by reducing their concentration (Figure S12). Results show that the PL intensity decreases with a decrease in the concentration of FPCDs, indicating the absence of any internal IFE. Again, we shifted the excitation wavelength far from the absorption of the quencher to minimize IFE.…”

A comprehensive review on multi-colored emissive carbon dots as fluorescent probes for the detection of pharmaceutical drugs in water

“…It can be of two types: oxidative PET and reductive PET. 159 The lowest unoccupied molecular orbitals (LUMO) of both the C-dots and quencher are involved in electron transfer in the case of the oxidative PET process. The reductive PET process involves electron transfer between the highest occupied molecular orbital (HOMO) of the C-dots and LUMO of the quencher molecules.…”

Intrinsic Blue Fluorescence of 2.0G PAMAM-DCM Polymer Dots and Its Applications for Fe3+ Sensing

“…Meanwhile, PCDs, as a fluorescence sensor, [26,27] show great applications in environmental sciences [28,29], chemical analysis [30], and biological fields [31][32][33]. In contrast to the instrumental detection of metal ions, PD fluorescence sensors are simple, portable, highly efficient, and fast-responding [34].…”