Tagetes erecta as an organic precursor: synthesis of highly fluorescent CQDs for the micromolar tracing of ferric ions in human blood serum.

The present article illustrates the green synthesis of novel carbon quantum dots (CQDs) from biomass viz. Tagetes erecta (TE), and subsequently fabrication of a metal ion probe for the sensing of Fe 3+ in real samples. TE-derived CQDs (TE-CQDs) have been synthesized by a facile, eco-friendly, bottom-up hydrothermal approach using TE as a carbon source. The successful synthesis and proper phase formation of the envisaged material has been confirmed by various characterization techniques (Raman, XRD, XPS, TEM, and EDS). Notably, the green synthesized TE-CQDs show biocompatibility, good solubility in aqueous media, and non-toxicity. The as-synthesized TE-CQDs show an intense photoluminescence peak at 425 nm and exhibit excitation dependent photoluminescence behavior. The proposed TE-CQD-based probe offers a remarkable fluorescence (FL) quenching for Fe 3+ with high selectivity ( K q ∼ 10.022 × 10 13 M -1 s -1 ) and a sensitive/rapid response in a linear concentration range 0-90 μM (regression coefficient R 2 ∼ 0.99) for the detection of Fe 3+ . The limit of detection (LOD) of the probe for Fe 3+ has been found as 0.37 μM in the standard solution. It has further been applied for the detection of Fe 3+ in real samples (human blood serum) and displays good performance with LOD ∼ 0.36 μM. The proposed TE-CQD-based ion sensing probe has potential prospects to be used effectively in biological studies and clinical diagnosis.