Platinum-coated gold Nanoparticles are bimetallic core–shell nanostructures consisting of a spherical gold nanoparticle core encased in a platinum shell. The platinum shell can be deposited as a complete coating of controlled thickness, as discrete nanoparticles, or as a dendritic/porous structure—depending on the synthesis conditions and intended applications.

Optical Properties

Localized Surface Plasmon Resonance (LSPR)

Gold Nanoparticles exhibit a single LSPR peak in the visible region (typically 520–540 nm for 10–20 nm particles). Upon platinum coating, the LSPR peak undergoes characteristic changes:

Red-shift: The LSPR peak shifts to longer wavelengths

Broadening: The peak broadens due to damping from the platinum shell

Reduced intensity: The plasmon peak intensity decreases as the platinum shell thickness increases

The optical properties can be tuned by controlling the platinum shell thickness, enabling optimization for specific plasmonic and sensing applications.

Plasmon-Enhanced Catalysis

The most exciting aspect of AuNP@Pt NPs is plasmon-enhanced catalysis. When the gold core absorbs light at its LSPR wavelength, it generates hot electrons that can transfer to the platinum shell, enhancing catalytic activity. This enables chemical reactions to proceed under milder conditions or with higher efficiency under light irradiation.

Synthesis of Platinum-Coated Gold Nanoparticles

The synthesis of AuNP@Pt NPs typically follows a seed-mediated growth approach with platinum deposition onto pre-formed gold Nanoparticles.

Stage 1: Gold Nanosphere Synthesis

Gold Nanoparticles are synthesized using well-established methods, most commonly the Turkevich method (citrate reduction) or the Brust method (two-phase synthesis). The Turkevich method involves reducing chloroauric acid (HAuCl₄) with sodium citrate in aqueous solution, yielding highly monodisperse gold Nanoparticles with diameters ranging from 10 to 50 nm. The size can be controlled by adjusting the ratio of gold precursor to citrate.

Stage 2: Platinum Deposition

Platinum is deposited onto the gold nanosphere surface through reduction of a platinum precursor—typically chloroplatinic acid (H₂PtCl₆) or potassium tetrachloroplatinate (K₂PtCl₄)—in the presence of a reducing agent. The process typically involves:

Mixing gold Nanoparticles with a platinum precursor solution

Adding a reducing agent (sodium borohydride, ascorbic acid, or citric acid)

Allowing the reaction to proceed at controlled temperature and pH

Purifying the resulting AuNP@Pt NPs by centrifugation and washing

Key Properties and Advantages

AuNP@Pt NPs exhibit enhanced catalytic activity compared to pure platinum nanoparticles, attributed to electronic effects (the gold core modifies the electronic structure of the platinum shell, optimizing binding energies for reaction intermediates), strain effects (lattice mismatch between gold and platinum enhances catalytic activity), and bifunctional effects (the gold core can participate in certain reaction steps). The gold core also provides structural stability by preventing platinum dissolution under harsh conditions, preventing nanoparticle agglomeration and sintering, and maintaining stable catalytic performance over multiple cycles. Furthermore, the gold core enables plasmon-enhanced catalytic activity through visible light activation, hot electron transfer from the gold core to the platinum shell (reducing activation barriers), and localized heating from the photothermal effect of the gold core that accelerates reaction kinetics.

Applications

The primary application of AuNP@Pt NPs is electrocatalysis, where they have demonstrated exceptional promise as fuel cell catalysts: for the oxygen reduction reaction (ORR) , they exhibit higher mass activity than commercial Pt/C catalysts, enhanced stability, and reduced platinum loading; for methanol oxidation (MOR) , they offer enhanced CO tolerance, superior activity, and excellent stability for direct methanol fuel cells; for ethanol oxidation (EOR) , they provide high activity, resistance to poisoning, and potential for ethanol fuel cells; and for the hydrogen evolution reaction (HER) , they enable efficient hydrogen production from water electrolysis with reduced platinum loading and long-term stability. The gold core also enables plasmon-enhanced catalysis, where visible light activation drives reactions at lower temperatures with controlled selectivity. In SERS and sensing, AuNP@Pt NPs serve as sensitive substrates for chemical sensing, in situ reaction monitoring, and biosensing of DNA, proteins, and small molecules. In biomedical applications, they enable photothermal therapy (combining the gold core's photothermal properties with the platinum shell's catalytic functionality), drug delivery through functionalization of the platinum shell, biosensing of biomarkers, and antimicrobial activity via reactive oxygen species generation. Beyond electrochemistry, AuNP@Pt NPs are effective catalysts for hydrogenation, oxidation, and cross-coupling reactions. Compared to pure platinum nanoparticles, they offer several key advantages: reduced platinum loading (lowering cost), enhanced catalytic activity (due to electronic and strain effects), improved stability (the gold core prevents platinum dissolution and agglomeration), plasmon-enhanced catalysis, and multifunctionality—combining plasmonic and catalytic properties in a single nanostructure.

How to Buy?

BOT Bioparticles specializes in high-quality gold nanoparticles with precisely controlled sizes and surface modifications. For researchers interested in platinum-coated gold Nanoparticles, BOT Bioparticles offers professional custom synthesis and surface functionalization services to meet specific application requirements. Our technical team can assist with:

Gold nanosphere synthesis: Precise size control and characterization

Platinum deposition: Controlled deposition of platinum shells or nanoparticles

Surface functionalization: Custom modifications for specific applications

Characterization: TEM, UV-VIS, DLS, and other characterization techniques