Atomic Scale Tracking of Single Layer Oxide Formation: Self-Peeling and Phase Transition in Solution

Area of Science:

• Materials Science
• Nanotechnology
• Chemistry

Background:

• Two-dimensional (2D) nanomaterials, such as indium oxide (In2O3) nanosheets, are crucial for advanced electronic and catalytic applications.
• Understanding the synthesis mechanisms at the atomic level is essential for controlling material properties and enabling scalable production.
• Previous studies have often lacked atomic-scale resolution to elucidate the intricate formation pathways of ultrathin nanosheets in solution.

Purpose of the Study:

• To investigate the atomic-scale formation process of indium oxide (In2O3) ultrathin nanosheets in solution using liquid phase transmission electron microscopy (TEM).
• To elucidate the phase transition pathway from precursor materials to the final In2O3 nanosheet structure.
• To identify the growth mechanisms and the role of capping agents in the formation of 2D nanomaterials.

Main Methods:

• Liquid phase transmission electron microscopy (TEM) for in situ atomic-scale observation of nanosheet formation.
• Density functional theory (DFT) calculations to investigate the role of oleylamine in the growth process.
• Analysis of phase transitions involving indium chloride trihydrate (InCl3·3H2O), indium hydroxide (In(OH)3), and indium oxide (In2O3).

Main Results:

• Observed the formation of In2O3 ultrathin nanosheets at atomic resolution in solution.
• Revealed a complex phase transition sequence: InCl3·3H2O → In(OH)3 → In2O3.
• Identified two distinct growth modes for the intermediate InCl3·3H2O nanosheet: layer-by-layer and strain-driven enation.
• Demonstrated that oleylamine facilitates the self-peeling process crucial for 2D growth.

Conclusions:

• The formation of In2O3 ultrathin nanosheets involves intricate phase transitions and distinct growth mechanisms.
• Oleylamine plays a critical role in enabling the self-peeling process, leading to the formation of 2D structures.
• These atomic-level insights advance the fundamental understanding of 2D nanomaterial synthesis in solution, guiding future material design.