Black Phosphorus Synthesis via Ball Milling

When bulk black phosphorus (BP) is exfoliated into few layer sheets, termed “phosphorene,” it has desirable optoelectronic properties of a semiconductor with a unique layer-dependent direct bandgap. This work studies planetary ball milling parameters (PBM) for converting red phosphorus (RP) to BP and explores mixer and vibratory milling for novel means of exfoliation. The RP to BP conversion progress was studied with in-situ pressure monitoring and XRD. Synthesized bulk BP powder was dispersed in three solvents for exfoliation and characterized with TEM, Raman and UV-Vis spectroscopy. During PBM, the gradual transition from RP to BP occurred in less than 30 minutes at the highest milling intensity. With increased milling durations, conversion was observed at as low as 200 rpm. Raman characterization on the exfoliated BP solutions confirmed the preservation of the BP crystal structure while TEM imaging confirmed the presence of few layer BP flakes, indicating successful exfoliation through low energy milling. This work demonstrates industrially scalable milling techniques as a viable means to attain few layer BP