Porphyrin-based carbon dots as fluorescence probe for sensing of Fe sup(3+) ion and S sup(2-) anion in aqueous solution

Abstract

In this work, a facile bottom-up approach was employed to synthesize the porphyrin-citric acid-derived fluorescent carbon dots (Por-CA-CDs) using a single-step hydrothermal method. As-prepared Por-CA-CDs were well characterized using spectroscopic techniques such as FT-IR, high-resolution transmission electron microscopy, P-XRD, UV-Vis absorption, and photoluminescence spectroscopy. The synthesized Por-CA-CDs exhibited blue fluorescence with excellent photostability and diameter ranging from 2.4 to 6.4?nm. Por-CA-CDs show excitation-dependent emission behavior, with a quantum yield of 26 percent and were used for sensing of Fe sup(3+) and S sup(2-) ions in an aqueous solution. Por-CA-CDs demonstrated a robust and selective reaction to Fe sup(3+) compared to the other cations utilized in this investigation. The sensing capability of Por-CA-CDs with Fe sip(3+) ions was evaluated with fluorescence spectroscopy, and results show a "Turn-Off" emission mode upon binding of Fe sup(3+) with Por-CA-CDs. In metal ion sensing studies, the fluorescence intensity of Por-CA-CDs exhibited significant quenching upon the addition of Fe sup(3+) at concentrations ranging from 0 to 230 mu M, with a detection limit (LOD) of 3.2 x 10 sup(-8) M. The quenching efficiency and Stern-Volmer quenching constant were computed as 99.45 percent and 4.4 x 10 sup(6) M sup(-1), respectively. Interestingly, fluorescence of Por-CA-CDs can be regained with the addition of S sup(2-) (0-160 mu M) with LOD of 4.3 x 10 sup(-6) M and Stern-Volmer quenching constant of 6 x 10 sup(5) M sup(-1). Most importantly, the toxicity assay revealed good reliability for samples in deionized, tap, and river water, suggesting applications for Fe sup(3+) monitoring in complex environments.