Observing Carbon Dots in Putative Boron Nitride Quantum Dots

Boron nitride quantum dots (BNQDs) have garnered a significant amount of attention in recent years due to their attractive optical properties, high stability, low toxicity, and good biocompatibility. However, our study reveals a critical mischaracterization in this field, demonstrating that some so-called BNQDs are, in fact, carbon dots (CDs) formed through the unintended carbonization of organic solvents during synthesis. Herein, we investigate the widely used combination of sonication and solvothermal conversion for BNQD preparation, using ethanol and <i>N</i>-methyl-2-pyrrolidone as solvents. Parallel syntheses are performed with and without BN bulk to produce the putative BNQDs and their corresponding CDs, respectively. Comprehensive characterizations, including optical properties and chemical compositions, reveal striking similarities between the BNQDs and the corresponding CDs. These similarities indicate that the presumed BNQDs are essentially CDs. This finding challenges the validity of numerous studies on BNQDs and calls for a critical re-evaluation of the synthesis-structure-property relationship in BN-based nanomaterials.