Solvent-engineered carbon dots from rice straw for selective fluorescent detection of Cr(VI) and Pb(II)

Lead (Pb (II)) and hexavalent chromium (Cr(VI)) are recognized as major water pollutants, posing significant environmental and health concerns due to their toxicity and persistence. To address the critical need for their detection in aqueous systems, carbon dots (CDs) are prepared using rice straw as the raw material. The extraction was performed using two solvents of different polarity i.e., ethanol and hexane. Both the extracts were utilised for the CDs preparation viz CDsheaxneand CDsEtOH. Transmission electron microscopy (TEM) analysis revealed that the average particle sizes of CDsHexane and CDsEtOH were 4.5 nm and 9.2 nm, respectively.FTIR analysis illustrates the presence of different kinds of functional groups such as hydroxyl, carbonyl, and carboxyl on CDs. The prepared CDsheaxneand CDsEtOH showed a fluorescent quenching response towards the detection of Cr(VI) and Pb(II). The quantitative analysis demonstrated a linear detection range of 1-10 mu M for both contaminants. The detection limits were determined to be 0.19 mu M and 10.94 mu M for CDsheaxne and CDsEtOH, respectively. Further validation through real sample analysis confirmed the practical applicability of these CDs in detecting these contaminants in water, and the recovery was found to be above 90 %. Thus, the synthesized fluorescent probes have been proven an efficient platform for the fluorescent sensing of aforementioned target analytes.