Mechanochemical Green Synthesis of Exfoliated Edge-Functionalized Boron Nitride Quantum Dots: Application to Vitamin C Sensing through Hybridization with Gold Electrodes.

Two-dimensional boron nitride quantum dots (2D BNQDs) with excellent chemical stability, high photoluminescence efficiency, and low toxicity are a new class of advanced materials for biosensing and bioimaging applications. To overcome the current challenge about the lack of facile, scalable, and reproducible synthesis approach of BNQDs, we introduce a green and facile approach based on mechanochemical exfoliation of bulk h-BN particles in ethanol. Few-layered hydroxylated-functionalized QDs with a thickness of 1-2 nm and a lateral dimension of 2-6 nm have been prepared. The synthesized nanocrystals exhibit a strong fluorescence emission at 407 and 425 nm with a quantum efficiency of ∼6.2%. Spectroscopic analyses determine that interactions between oxygen groups of the solvent with boron sites occur, which along with the mechanical forces, lead to efficient exfoliation of the hexagonal structure and surface functionalization with -OH groups. We also demonstrate that the orbital interaction between BNQDs and the gold surface results in a profound electrochemical catalytic activity toward oxidation of vitamin C. It is shown that the BNQD-modified screen-printed gold electrode exhibits a decreased onset oxidation potential for about 0.37 V/AgCl. In addition to high catalytic activity, electrochemical studies also reveal that this electrode allows selective and sensitive detection of vitamin C with a good response over a wide range from 0.80 μM to 5.0 mM with a detection limit of 0.45 μM (S/N = 3) and a sensitivity of 1.3 μA μM cm. Finally, the potential application of the hybrid sensor for detecting vitamin C in commercial drinks is demonstrated.