Thermally Driven Solid-Phase Ion Exchange for In Situ Transition from Heterocore-Shell to Alloy Nanostructures.

Area of Science:

• Materials Science
• Nanotechnology
• Solid-State Chemistry

Background:

• Precise control over ion exchange reactions is crucial for synthesizing multielement nanostructures for applications in nanophotonics, semiconductors, photocatalysis, and batteries.
• Existing methods often regulate thermodynamic parameters but lack atomic-scale understanding of the dynamic ion exchange mechanism and microstructure evolution.

Purpose of the Study:

• To investigate the atomic-scale spatial rearrangement mechanism during ion exchange in heterocore-shell nanowire systems.
• To systematically analyze dynamic ion exchange behavior and correlated microstructure evolution.
• To provide a mechanistic understanding of solid-state ion kinetics and phase transition dynamics for designing functional nanomaterials.

Main Methods:

• In situ electron microscopy was employed to observe solid-state ion migration pathways.
• Quantitative analysis of formation processes and reaction kinetics under a uniform thermal field.
• Phase-field simulations were utilized to reconstruct divergent transport pathways and structural transformations.

Main Results:

• Thermal activation promotes Ag ion diffusion and bulk Te diffusion in Te_XSe_y@Se core-shell nanowires (NWs), leading to homogeneous Ag₂Se_xTe_1-x alloy formation via intracrystalline reorganization.
• Electron beam irradiation induces surface-dominated Ag ion diffusion, resulting in dual-core-shell architectures, contrasting with thermal effects.
• Achieved up to 5.5 mm migration distance with sufficient Ag supply, enabling centimeter-scale nanofilm formation.

Conclusions:

• The study deciphers divergent ion migration pathways and structural transformations driven by thermal versus electron beam stimuli.
• This mechanistic understanding provides a paradigm for interconverting between multiphase heterostructures and monophasic systems.
• Establishes a design framework for next-generation functional nanomaterials based on controlled ion exchange kinetics.