Green synthesis of glowing carbon dots from Carica papaya waste pulp and their application as a label-freechemo probe for chromium detection in water

The work presents the facile green synthesis of blue luminescent C-dots (CDs) using papaya waste (Carica papaya) as a precursor. The as-synthesized CDS exhibit a quantum yield of 23.7% and are of size < 10 nm, while their polymerized architecture is confirmed by NMR spectroscopic analysis. The presence of various carbonyl and carboxyl surface groups confirmedthrough FT-IR is utilized for their surface modification with Ethylenediaminetetraacetic acid (EDTA) to detect chromium in water with high sensitivity and selectivity. The sensor demonstrated a fashioned decrease in fluorescence intensity on chromium (Cr (III), Cr (VI), Cr (III) + Cr (VI)) addition in a wide detection window of 10-1000 ppb. The theoretical detection (LOD, 3 s/sensitivity) and quantification (LOQ, 10 s/sensitivity) limits for total chromium were found to be 0.708 ppb and 2.4 ppb, respectively. The study presents fruit waste-derived and modified green CDS based chromium sensing platform for their potential integration with optical analyzers in water pollutants monitoring.