Utilisation of Carbon Quantum Dots from Hazelnut Husk for Folic Acid (FA) Detection: An Innovative Approach

This 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 R² value of ≈ 0.994. The samples were categorized into low (0.0376–0.7533 µM) and high (0.7533–7.533 µM) concentration groups for improved accuracy, achieving mean percentage errors of 0.70% and 1.85%, respectively, at concentrations as low as 0.565 µM. 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.