Pt/Ag Solid Solution Alloy Nanoparticles in Miscibility Gaps Synthesized by Cosputtering onto Liquid Polymers

Area of Science:

• Materials Science
• Nanotechnology
• Physical Chemistry

Background:

• Alloy nanoparticles (NPs) offer unique properties compared to monometallic counterparts.
• Controlling the composition and size of bimetallic NPs is crucial for their applications.
• Previous studies on Pt/Au NPs showed a correlation between particle size and composition.

Purpose of the Study:

• To investigate the synthesis of platinum-silver (Pt/Ag) alloy NPs with controlled compositions.
• To understand the role of liquid polyethylene glycol (PEG) as a substrate during cosputtering.
• To compare the characteristics of Pt/Ag NPs formed on PEG with those formed on a traditional substrate.

Main Methods:

• Cosputtering of Platinum (Pt) and Silver (Ag) onto liquid polyethylene glycol (PEG, MW = 600).
• Varying sputtering currents (10–50 mA) to influence NP formation.
• Characterization of NP size, composition, and distribution using transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS).

Main Results:

• Pt/Ag NPs with mean sizes below 3 nm were successfully synthesized.
• Sputtering current adjustments significantly impacted NP composition and distribution, but not particle size.
• Pt/Ag NPs on PEG exhibited broader composition distributions and smaller sizes compared to NPs sputtered directly onto TEM grids.
• PEG was found to hinder NP and cluster aggregation, leading to smaller particle sizes and wider compositional ranges.

Conclusions:

• Liquid PEG acts as an effective medium to produce small, compositionally diverse Pt/Ag alloy NPs.
• The substrate plays a critical role in determining NP characteristics, contrasting with findings for Pt/Au systems.
• The composition of Pt/Ag NPs formed on PEG is primarily governed by random atomic combinations during sputtering and initial deposition.