Ciritcioglu, Ali ArdaElibol, ErdemGunaydin, ZehraDemirci, Tuna2025-10-112025-10-1120251572-38871875-8355https://doi.org/10.1007/s10930-025-10249-whttps://hdl.handle.net/20.500.12684/22074This study presents the development of a carbon quantum dot (CQD)-based fluorescence sensor for the accurate quantification of Folic Acid (FA). CQDs were synthesized from hazelnut husk using a solvothermal method and functionalized with silver ions to create an off-state fluorescence system. Upon mixing FA solutions, prepared from pure water and pharmaceutical tablets, with phosphate-buffered saline (PBS) and off-state CQDs, fluorescence emission was restored (on-state) in a concentration-dependent manner when excited at 360 nm. A strong linear relationship was observed between FA concentration and fluorescence intensity, with an R-2 value of approximate to 0.994. The samples were categorized into low (0.0376-0.7533 mu M) and high (0.7533-7.533 mu M) concentration groups for improved accuracy, achieving mean percentage errors of 0.70% and 1.85%, respectively, at concentrations as low as 0.565 mu M. This CQD-based sensor demonstrated rapid, cost-effective, and highly sensitive detection capabilities, making it a promising alternative for FA quantification in biomedical and nutritional applications. Furthermore, the use of sustainable raw materials, such as hazelnut husk, highlights the eco-friendly and practical advantages of this method over conventional techniques.en10.1007/s10930-025-10249-winfo:eu-repo/semantics/closedAccessCarbon quantum dotsFA detectionFluorescence sensorsHazelnut huskArticle443283296400563302-s2.0-86000487696WOS:001439521400001Q2Q4