Synthesis of Black Phosphorene Quantum Dots from Red Phosphorus

Black phosphorene quantum dots (BPQDs) are most commonly derived from high-cost black phosphorus, while previous syntheses from the low-cost red phosphorus (P-red) allotrope are highly oxidised. Herein, we present an intrinsically scalable method to produce high quality BPQDs, by first ball-milling P-red to create nanocrystalline P-black and subsequent reductive etching using lithium electride solvated in liquid ammonia. The resultant similar to 25 nm BPQDs are crystalline with low oxygen content, and spontaneously soluble as individualized monolayers in tertiary amide solvents, as directly imaged by liquid-phase transmission electron microscopy. This new method presents a scalable route to producing quantities of high quality BPQDs for academic and industrial applications.