Photoemission core level binding energies from multiple sized nanoparticles on the same support: TiO₂(110)/Au

Area of Science:

• Surface Science
• Nanomaterials Science
• Physical Chemistry

Background:

• Understanding the electronic properties of nanoparticles is crucial for catalysis and electronics.
• Gold nanoparticles on reducible titanium dioxide (TiO2) are model systems for studying metal-support interactions.

Purpose of the Study:

• To demonstrate a novel method for measuring core level binding energies of size-varying nanoparticles on the same substrate.
• To investigate the influence of nanoparticle size and coverage on the electronic properties of gold (Au) on reduced TiO2(110).

Main Methods:

• Utilized in situ scanning tunneling microscopy (STM) and microfocused X-ray photoemission spectroscopy (XPS).
• Employed an STM tip-shadowing technique for controlled synthesis of patterned Au nanoparticles with varying sizes and coverages.
• Identified and imaged nanoparticle patterns using UV photoelectron emission microscopy.

Main Results:

• Investigated Au 4f core level binding energies as a function of Au nanoparticle coverage and size.
• Observed that a combination of initial and final state effects modifies binding energies with changing nanoparticle size.
• Found that binding energies for single Au atoms and small clusters are similar to high coverage, due to a cancellation of effects, and vary with coverage.

Conclusions:

• The observed binding energy variations are consistent with a Volmer-Weber nucleation-growth model.
• Electron transfer to the nanoparticles occurs at oxygen vacancies on the reduced TiO2 surface.
• The developed method enables detailed analysis of size-dependent electronic properties in nanoparticle systems.