Innovative nano sensors: boron quantum dots for precision detection of folic acid

Abstract

In this study, heavy-metal-free boron quantum dots (BQDs) were successfully synthesized via a one-pot solvothermal approach using boric acid dissolved in an optimized dimethylformamide (DMF) and monopropylene glycol (MPG) dual solvent system. To establish a highly selective “off-to-on” fluorometric nanosensor, the surfaces of the BQDs were tailored via silver (Ag) modification. The structural, chemical, and optical behaviors of the synthesized nanomaterials were comprehensively validated through HR-TEM, FT-IR, and UV-Vis characterizations. Under optimal conditions, the BQD-Ag sensor exhibited a constant photoluminescence (PL) emission peak within the 446–449 nm range. Benefiting from a rigid linear coordination geometry between the surface silver ions and the pteridine nitrogen of folic acid (FA), the sensor demonstrated outstanding sensitivity with a revised limit of detection (LOD) of 0.058 µM and a limit of quantification (LOQ) of 0.176 µM across a wide linear range. The practical reliability of the platform was successfully evaluated using complex real-world agricultural matrices, including parsley, red lentil, and green lentil. The method yielded exceptional reproducibility with relative standard deviations (%RSD) below 0.60% and satisfactory spike and recovery values ranging between 91.2% and 104.8%. Eliminating the need for hazardous heavy metals while preserving superior optical qualities, this sustainable BQD-based platform offers a cost-effective, precise, and robust alternative for potential biosensing, food safety regulations, and clinical diagnostics.