Platinum-coated gold nanorods are bimetallic core–shell nanostructures consisting of a gold nanorod core encased in a platinum shell. The platinum shell can be deposited as a complete coating, discrete nanoparticles, or even site-selectively on specific regions of the nanorod.

Why Platinum?

Platinum offers several unique advantages:

Superior catalytic activity: Platinum is one of the most effective catalysts, enabling a wide range of chemical reactions. It is widely used in catalytic converters, fuel cells, and chemical synthesis.

Excellent stability: Platinum exhibits remarkable stability under reaction conditions, making it suitable for repeated catalytic cycles.

Electrocatalytic properties: Platinum is the benchmark catalyst for fuel cell reactions including oxygen reduction and methanol oxidation.

Plasmonic enhancement: The proximity of the plasmonic gold core to the platinum shell enables plasmon-mediated catalysis, where light absorption enhances the catalytic activity.

SERS activity: The platinum shell provides a surface for surface-enhanced Raman scattering (SERS), enabling in situ monitoring of catalytic reactions.

Synthesis of Platinum-Coated Gold Nanorods

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

Stage 1: Gold Nanorod Synthesis

Gold nanorods are first synthesized via the seed-mediated growth method. Tiny gold seed particles are generated using a strong reducing agent (sodium borohydride) and then added to a growth solution containing gold ions, ascorbic acid, and structure-directing surfactants—typically cetyltrimethylammonium bromide (CTAB). The surfactant directs anisotropic growth along the longitudinal axis, yielding rod-shaped nanoparticles with tunable aspect ratios.

Stage 2: Platinum Deposition

Platinum is deposited onto the gold nanorod 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 nanorods with a platinum precursor solution

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

Allowing the reaction to proceed at controlled temperature and pH

Purifying the resulting AuNR@Pt NPs by centrifugation

Key Properties and Advantages

Plasmon-Enhanced Catalysis

The most exciting property of AuNR@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.

The enhanced catalytic activity is attributed to:

LSPR-induced local heating: The photothermal effect of the gold core heats the platinum surface, accelerating reaction kinetics

Hot electron transfer: Energetic electrons from the gold core transfer to the platinum shell, reducing activation barriers

Enhanced electron density: The plasmonic effect increases the electron density at the platinum surface, promoting catalytic reactions

SERS Enhancement

The presence of platinum on the gold nanorod surface creates SERS activity. While platinum is not as strong a SERS substrate as gold or silver, the proximity to the gold surface enables sensitive detection of molecules adsorbed on the platinum surface. This makes AuNR@Pt NPs ideal for in situ monitoring of catalytic reactions.

Hydrogen Storage and Sensing

Platinum, like palladium, can absorb hydrogen, enabling hydrogen sensing applications. The absorption of hydrogen changes the refractive index and electrical properties of the platinum shell, which can be detected through LSPR shifts of the gold core.

Excellent Stability

The platinum shell provides excellent stability under reaction conditions, preventing degradation of the gold core and maintaining catalytic performance over multiple cycles. This is particularly valuable for industrial catalysis where stability is critical.

Biomedical Applications

Platinum-coated gold nanorods (AuNR@Pt NPs) have emerged as versatile platforms across a wide spectrum of applications, combining the excellent photothermal properties of the gold core with the catalytic functionality of the platinum shell. In biomedicine, they serve as effective photothermal agents for cancer therapy—achieving efficient heating under NIR laser irradiation and enabling targeted treatment combined with catalytic generation of therapeutic agents; the platinum shell also provides a platform for drug loading and delivery, including catalytic prodrug activation, stimuli-responsive controlled release, and multimodal therapy integrating chemotherapy, photothermal therapy, and catalytic therapy. As biosensing platforms, AuNR@Pt NPs enable SERS-based biomolecule detection, electrochemical biosensing leveraging platinum's electrocatalytic properties, and LSPR-based refractive index sensing. Their catalytic properties are also harnessed for antimicrobial applications through reactive oxygen species generation and combination photothermal–catalytic therapy. In catalysis, AuNR@Pt NPs have shown exceptional promise as electrocatalysts for fuel cells—demonstrating higher mass activity than commercial Pt/C catalysts for oxygen reduction, methanol oxidation, and ethanol oxidation, with the gold core enhancing stability and reducing platinum loading. They are also highly effective for the hydrogen evolution reaction, enabling efficient hydrogen production with minimized precious metal usage and excellent long-term stability. For methanol oxidation, they exhibit enhanced CO tolerance and superior activity compared to pure platinum. The plasmonic properties of the gold core enable plasmon-enhanced catalysis, where visible light activation drives reactions at lower temperatures with controlled selectivity. Finally, AuNR@Pt NPs serve as powerful platforms for SERS and sensing applications, enabling in situ reaction monitoring (detection of intermediates and products, mechanistic studies, and rapid optimization) as well as sensitive, selective, and rapid chemical sensing of various analytes.

Future Perspectives

The field of platinum-coated gold nanorods continues to advance rapidly. Key trends include:

Precision synthesis: Improved control over platinum shell thickness and morphology

Multifunctional platforms: Integration of catalysis, sensing, and therapy

Site-selective functionalization: Controlled platinum deposition for enhanced activity

Machine learning: Optimization of synthesis parameters and catalytic performance

Clinical translation: Exploring biomedical applications

Sustainable catalysis: Development of green synthesis methods and recyclable catalysts

How to Buy?

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

Gold nanorod synthesis: Precise control over aspect ratio and SPR

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