Complete miscibility of immiscible elements at the nanometre scale

Area of Science:

• Materials Science
• Nanotechnology
• Physical Chemistry

Background:

• Controlling material properties relies on understanding element mixing behavior.
• Nanomaterial element miscibility often differs significantly from bulk materials.
• Quantitative experimental data on nanoscale miscibility is limited.

Purpose of the Study:

• To investigate the evolution of gold (Au) and rhodium (Rh) miscibility in nanoparticles.
• To explore the effect of varying nanoparticle size (1-4 nm) and composition (15%-85% Au).

Main Methods:

• Synthesis of gold-rhodium nanoparticles across a range of sizes and compositions.
• Quantitative analysis using advanced electron microscopy techniques.
• Theoretical calculations to model and understand miscibility trends.

Main Results:

• Observed a transition from phase separation to alloying in nanoparticles as size decreased.
• Demonstrated complete miscibility of Au and Rh in nanoparticles smaller than 2 nm across all compositions.
• Identified particle size, composition, and potential surface adsorbates as key factors influencing miscibility.

Conclusions:

• Nanoparticle size is a critical determinant of element miscibility, overriding bulk immiscibility.
• Sub-2 nm nanoparticles exhibit unique alloying behavior, enabling complete miscibility of immiscible elements.
• Findings provide fundamental insights for designing novel alloyed nanomaterials with tailored properties.