Tunable Colloidal Synthesis Enabling μ-ARPES on Individual Bismuth Nanocrystals.

Bismuth (Bi) nanomaterials are a promising platform for quantum and energy technologies due to strong spin-orbit coupling, high thermoelectric efficiency, and magnetoresistance. However, scalable and flexible synthesis of high-quality Bi nanostructures with fast research turnaround remains challenging. We report a controlled colloidal synthesis of Bi nanosheets with tunable lateral sizes (0.6-4.1 µm), hexagonal shape, and a layered single-crystalline structure along the {00l} planes. The Bi nanosheets exhibit excellent long-term structural stability and these colloidal nanostructures offer several key advantages: single-crystalline structure; tunability in size, shape, dimensionality, and doping; stability in solution, enabling solution-based processing; protection against oxidation by surface ligands; and cost-effective and scalable production. Here, we show that colloidal Bi nanosheets can even be directly investigated using techniques such as angle-resolved photoemission spectroscopy (ARPES). ARPES measurements on individual Bi nanosheets reveal a band structure in excellent agreement with DFT calculations, confirming high crystal quality and uniformity. Our findings demonstrate that colloidal-synthesized Bi nanosheets provide a scalable platform for producing and characterizing high-quality nanosheets, offering potential for integrations in advanced quantum, spintronic, and energy technologies.