# Tunable Colloidal Synthesis Enabling μ‐ARPES on Individual Bismuth Nanocrystals

## TL;DR

Researchers developed a scalable method to make high-quality bismuth nanosheets with tunable sizes and shapes, suitable for quantum and energy technologies.

## Contribution

A tunable colloidal synthesis method for bismuth nanosheets enabling direct μ-ARPES characterization of individual nanosheets.

## Key findings

- Bismuth nanosheets with tunable sizes (0.6–4.1 µm) and single-crystalline structure were synthesized.
- μ-ARPES measurements on individual nanosheets matched DFT calculations, confirming high crystal quality.
- The synthesis method is scalable, cost-effective, and produces stable nanosheets with excellent ambient stability.

## Abstract

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.

We report a highly 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 nanosheets feature high phase purity and excellent ambient stability. Remarkably, O2 promotes larger lateral growth with ultra‐smooth surfaces. This scalable, cost‐effective synthesis method yields high‐quality nanosheets, and μ‐ARPES measurements on individual nanosheets reveal a band structure in excellent agreement with DFT calculations, confirming high crystal quality and uniformity.