Valorization of cantaloupe waste for green microwave-driven synthesis of N-self doped CQDs as a fluorescence sensor for nizatidine in urine and pharmaceuticals. A step ahead for circular economy practice

In the current study, a fast, ecological, one -pot, and cost-efficient method was developed for the synthesis of nitrogen -doped carbon quantum dots (N-CQDs) using plant wastes. This method includes the treatment of cantaloupe seeds and mush by microwave for four -minutes as a re-cyclable, green, and cheap carbon and nitrogen source. The furnished N-CQDs show a fluorescence quantum yield of 13.15 %, excellent water solubility, and high stability. A full characterization of the plant waste -derived quantum dots revealed the self -doping with nitrogen. The synthesized N-CQDs have been applied as an efficient nanoprobe for fluorometric determination of nizatidine (NZT), a gastroprotective drug, at lambda ex/lambda em of 325/416 nm within the concentration range of 0.75-100.0 mu M and LOD of 0.24 mu M. The N-CQDs show excellent selectivity for NZT in the presence of various possibly co -existing substances. Excellent mean % recovery was achieved for the determination of NZT in capsules (101.97 +/- 0.91 %). Moreover, the N-CQDs were used for the determination of NZT in human urine within the concentration range of 2.5-100.0 mu M with LOD of 0.8 mu M, therefore it has been applied for monitoring the excretion profile of NZT in urine. The greenness of the proposed probe has been evaluated using two greenness software and metrics proving excellent greenness feature that is attributed to using a renewable and cheap plant waste product as a feedstock via low-energy/low-cost microwave -assisted synthesis, elimination of organic solvents and hazardous chemicals, and relying on a direct mix -and -read assay.