From carob to carbon dots: Sustainable synthesis of fluorescent nanosensor for sensitive secnidazole determination in pharmaceutical, biological, and environmental samples

• Rapid microwave synthesis of N-CNPs from carob fruit extrcat in six minutes. • N-CNPs enable secnidazole detection with a limit of 2.8 μM. • Excellent selectivity against various interfering substances. • Eco-friendly approach with high recovery rates in diverse matrices. • N-CNPs effectively monitor secnidazole elimination in human urine. A fast, one pot, eco-friendly, and affordable fluorescent nanoprobe for the antimicrobial drug secnidazole was created. Highly luminescent N-doped carbon nanoparticles (N-CNPs) were produced for the first time from carob fruit extract as a readily available precursor via microwave-assisted synthesis in about six minutes. The developed N-CNPs exhibited good stability and water solubility. EDX, TEM, XPS, XRD, Zeta potential analysis, UV-visible spectroscopy, Fourier transform infrared, and fluorescence spectroscopy were used to characterize the N-CNPs comprehensively. The furnished N-CNPs demonstrated outstanding capabilities as a fluorescence nanosensor for secnidazole detection at λ ex /λ em of 330/425 nm within a concentration range from 10.0 to 200.0 μM and a limit of detection of 2.8 μM. The fluorescence of the proposed N-CNPs was successfully quenched by secnidazole by the inner filter effect. The nanoprobes exhibit excellent secnidazole selectivity even when a variety of potentially interfering drugs, excipients, or ions are present. This approach was used to analyze secnidazole in pharmaceutical dosage forms with a recovery percentage of 99.52 ±1.37% for Fladazole tablets® and 101.6 ±1.92% for Cipazole tablets® and in tap and irrigation water with recovery percentages of 101.1±3.2% and 99.23±1.11%, respectively. Furthermore, the N-CNPs have been employed to monitor the urinary elimination of SNZ with a limit of detection of 6.95 μM. The use of an economical and sustainable plant as a substrate through microwave-assisted synthesis shows excellent greenness and blueness characteristics of the suggested probe as assessed by AGREE and ComplexGAPI, and BAGI, respectively.