Porphyrin-based carbon dots as fluorescence probe for sensing of Fe<sup>3+</sup> ion and S<sup>2-</sup> anion in aqueous solution
Creators: name: Khobrekar, Pritesh P.
name: Gawade, Vilas K.
name: Jadhav, Ratan W.
name: Bugde, Sandesh T.
name: Bhosale, Sheshanath V.
Publisher: name: Taylor & Francis
Year: 2024
Subjects: subject: Biophysics
subject: Biochemistry
subject: Physical Sciences not elsewhere classified
subject: Microbiology
subject: FOS: Biological sciences
subject: Pharmacology
subject: Biotechnology
subject: Environmental Sciences not elsewhere classified
subject: Chemical Sciences not elsewhere classified
subject: Marine Biology

description: 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% and were used for sensing of Fe<sup>3+</sup> and S<sup>2−</sup> ions in an aqueous solution. Por-CA-CDs demonstrated a robust and selective reaction to Fe<sup>3+</sup> compared to the other cations utilized in this investigation. The sensing capability of Por-CA-CDs with Fe<sup>3+</sup> ions was evaluated with fluorescence spectroscopy, and results show a “Turn-Off” emission mode upon binding of Fe<sup>3+</sup> 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+</sup> at concentrations ranging from 0 to 230 μM, with a detection limit (LOD) of 3.2 × 10<sup>−8</sup> M. The quenching efficiency and Stern-Volmer quenching constant were computed as 99.45% and 4.4 × 10<sup>6</sup> M<sup>−1</sup>, respectively. Interestingly, fluorescence of Por-CA-CDs can be regained with the addition of S<sup>2−</sup> (0-160 µM) with LOD of 4.3 × 10<sup>−6</sup> M and Stern-Volmer quenching constant of 6 × 10<sup>5</sup> M<sup>−1</sup>. Most importantly, the toxicity assay revealed good reliability for samples in deionized, tap, and river water, suggesting applications for Fe<sup>3+</sup> monitoring in complex environments. The porphyrin-functionalized highly fluorescent carbon dots (Por-CA-CQDs) was synthesized using a low-cost, eco-friendly, and single-step hydrothermal method with well-distributed size with an average size of 2.4 to 6.4 nm, containing several functional groups on the surface of the carbon core. The Por-CA-CQDs exhibited bright blue fluorescence with typical excitation-dependent emission behavior and an emission quantum yield of 26%. Moreover, Por-CA-CQDs used for detection of Fe<sup>3+</sup> in an aqueous solution with a fluorescence “Turn-Off” mode. The detection limit, quenching efficiency and Stern-Volmer quenching constant was calculated to be 3.2 × 10<sup>-6</sup> M, 99.45% and 4.4 × 10<sup>6</sup> M<sup>-1,</sup> respectively. Interestingly fluorescence of Por-CA-CDs can be regained with the addition of S<sup>2−</sup>.