Development of Sustainable Nitrogen‐Doped Carbon Quantum Dot Nanoprobe Using Red Onion for Ultrasensitive Estimation of Fluoride Ion in Human Saliva

A quick, eco‐friendly, and economical approach for the synthesis of self‐nitrogen doped carbon quantum dots (N‐CQDs) utilizing onion extract was created in the current study. This method used a microwave to heat an onion for 4 min, providing a sustainable source of carbon and nitrogen. The provided N‐CQDs exhibited great stability and a fluorescence quantum yield of 12.1% at λex/λem of 340/430 nm, respectively. The produced N‐CQDs served as a successful nanoprobe for fluoride measurement, within a concentration range of 20–300 ng/mL with a detection limit of 4.557 ng/mL. In the presence of several potentially conflicting medications, the N‐CQDs showed remarkable fluoride selectivity. For the assessment of water's fluoride content, a mean percentage recovery of 100.955 ± 0.416 was obtained. The N‐CQDs were employed to measure fluoride in human saliva within the 50–1000 ng/mL concentration range, with a limit of detection of 15.693 ng/mL. Making use of AGREE and complexGABI and complexMoGABI approach, the suggested probe's greenness was assessed. Its good greenness was ascribed to the use of a low‐cost plant, low‐energy consumption through microwave‐assisted synthesis, and avoiding dangerous chemicals and organic solvents. The blueness of the developed approach was assessed using the Blue Applicability Grade Index (BAGI).