Free silver nanoparticles doped by potassium: Work-function change in experiment and theory

Area of Science:

• Materials Science
• Surface Science
• Nanotechnology

Background:

• The work function (WF) of binary nanoparticles is crucial for understanding their electronic properties.
• Previous studies often faced challenges in accurately measuring WF for individual nanoparticles.
• The immiscibility of silver (Ag) and potassium (K) was a long-held assumption in metallurgy.

Purpose of the Study:

• To experimentally and theoretically investigate the composition-dependent work function of silver-potassium (Ag-K) nanoparticles.
• To determine the influence of potassium concentration on the work function of Ag-K nanoparticles.
• To elucidate the underlying mechanisms responsible for the observed work function changes.

Main Methods:

• Utilized synchrotron-based x-ray photoelectron spectroscopy (PES) for experimental measurements.
• Employed a microscopic jellium model for theoretical calculations.
• Produced Ag-K nanoparticles by exposing preformed Ag particles to potassium vapor.

Main Results:

• Experimentally observed a significant decrease in WF with increasing K concentration, dropping below the WF of pure K even at low K exposure.
• Theoretical modeling explored adsorption patterns with and without K diffusion.
• Results indicated that surface alloying, contrary to expectations of immiscibility, is essential for explaining the observed WF values.

Conclusions:

• The work function of Ag-K nanoparticles is highly sensitive to composition.
• Efficient surface alloying between Ag and K, despite their presumed immiscibility, is responsible for the measured WF.
• This finding challenges established knowledge regarding the behavior of these two metals in alloyed nanoparticles.