Silver-shelled gold nanoparticles are bimetallic core-shell nanospheres that combine a gold core with an outer silver shell. By controlling the dimensions of each metal layer, the particle composition and optical response can be tuned independently of total particle diameter.
These Au@Ag core-shell nanoparticles are useful for plasmonic studies, dissolution and nanotoxicology research, and single-particle elemental analysis. Their defined gold-to-silver ratio also makes them useful as highly characterized reference and tracer materials where both particle structure and elemental composition are important.
Looking for silver-shelled gold nanoparticles?
Our current catalog offering is a 20 nm citrate-stabilized Au@Ag nanosphere. Custom development is available for other particle dimensions, Au/Ag ratios, and surfaces.
Gold-Core/Silver-Shell Structure & Properties
Silver-shelled gold nanoparticles contain a spherical gold core surrounded by a continuous silver shell. The total particle diameter, gold-core diameter, and silver-shell thickness can be controlled during synthesis, allowing both the optical properties and elemental composition of the particle to be engineered.
The current catalog material has a nominal total diameter of 20 nm and is stabilized with sodium citrate in a 2 mM sodium citrate solution. It is provided at 1 mg/mL based on total metal content. Other core-shell dimensions can be developed on a custom basis.
Current catalog configuration
- Total diameter: 20 nm nominal
- Surface: Citrate
- Solvent: 2 mM sodium citrate solution
- Concentration: 1 mg/mL total metal content
How Core & Shell Dimensions Tune Optical Properties
Gold and silver have distinct plasmonic optical properties, and combining them in a core-shell structure produces an optical response that depends on both the gold-core diameter and silver-shell thickness. Changing these dimensions also changes the relative amount of each metal within the particle.
As a result, silver-shelled gold nanoparticles can have extinction spectra that differ from either solid gold or solid silver nanoparticles of the same total diameter.
Core-shell architecture therefore provides an additional optical design variable beyond total particle diameter alone. The spectra below compare Au@Ag core-shell particles with solid silver and solid gold nanoparticles of equivalent overall dimensions.
For more information about how composition, particle dimensions, and surrounding refractive index influence nanoparticle optical response, see The Science of Plasmonics and the Mie Theory Calculator.
Applications of Silver-Shelled Gold Nanoparticles
Plasmonics & Optical Research
The combination of gold and silver within a single particle provides control over plasmon resonance through both particle geometry and composition. Gold-core diameter, silver-shell thickness, and total particle size can therefore be adjusted to produce optical responses that differ from monometallic gold or silver nanoparticles.
These properties make Au@Ag particles useful for plasmonic studies where the relationship between particle architecture, elemental composition, and optical response is of interest. Silver-shelled gold nanoparticles have also been used in enhanced Raman spectroscopy platforms, including a study using Au, Ag, and Au@Ag particles on gold-coated zein nanophotonic structures.1
Explore Surface-Enhanced Spectroscopy: SERS & SEF and Nanomaterials for Optical Engineering for additional application context.
Nanotoxicology & Dissolution Studies
Silver nanoparticle fate and behavior can depend on particle size, surface chemistry, aggregation state, and dissolution. Bimetallic Au@Ag nanoparticles provide an additional way to investigate these processes because the silver shell and gold core can be tracked independently.
As the silver component changes or dissolves during an experiment, transmission electron microscopy can be used to examine changes in core-shell structure and locate the more persistent gold core. Elemental analysis by ICP-MS can also monitor changes in the silver-to-gold ratio, providing complementary information about particle dissolution, fate, and transport.
This dual-element architecture can therefore help distinguish changes to the silver component from movement or persistence of the underlying nanoparticle structure. For broader experimental considerations, see Nanotoxicology: Particle Selection.
Single-Particle ICP-MS & Reference Materials
Bimetallic nanoparticles can be used as standards or tracer materials in single-particle inductively coupled plasma mass spectrometry (SP-ICP-MS). Precisely controlled Au@Ag particles provide both a defined particle size and a defined elemental relationship within each particle.
Low particle-to-particle variation in the Au:Ag ratio is particularly useful when evaluating multi-element measurements. During dissolution studies, changes in the silver signal can be compared with the more stable gold component, providing an internal elemental reference as the particle changes.
Au@Ag core-shell particles have also been used in studies evaluating SP-ICP-MS analysis of complex mixtures containing monometallic gold, monometallic silver, and compositionally distinct bimetallic nanoparticles of equivalent overall size.2
For additional information about nanoparticle standards and measurement applications, see Reference Material Nanoparticles.
Representative Au@Ag Core-Shell Designs
The 20 nm material is the current standard catalog offering. The additional configurations below are retained as representative core-shell designs previously characterized by nanoComposix and illustrate how changing gold-core diameter and silver-shell thickness changes particle composition and optical response.
| Total Diameter | Core-Shell Design & Reference Properties |
|---|---|
| 20 nm | 7 nm gold core • 6.5 nm silver shell • 8% Au / 92% Ag by mass • plasmon resonance peak ≈ 400 nm |
| 60 nm | 30 nm gold core • 15 nm silver shell • 21% Au / 79% Ag by mass • plasmon resonance peak ≈ 430 nm |
| 80 nm | 50 nm gold core • 15 nm silver shell • 37% Au / 63% Ag by mass • plasmon resonance peak ≈ 490 nm |
Values above are retained as technical reference data for these characterized core-shell designs and should not be interpreted as a list of current standard catalog configurations. Refer to the individual product page and batch-specific Certificate of Analysis for current product specifications.
Custom Silver-Shelled Gold Nanoparticles
Core diameter, shell thickness, Au/Ag ratio, total particle size, and surface chemistry provide several independent variables for tailoring a bimetallic nanoparticle to a particular analytical or optical requirement.
If the standard 20 nm citrate material does not meet your needs, nanoComposix can evaluate custom Au@Ag nanoparticles with different dimensions, metal ratios, surfaces, or formulations through Custom Nanoparticle Development.
Need a different core size, shell thickness, Au/Ag ratio, or surface?
Talk with our technical team about designing silver-shelled gold nanoparticles around your optical, analytical, or reference-material requirements.
Selected Literature
- Ma, X.; Turasan, H.; Jia, F.; Seo, S.; Wang, Z.; Liu, G. L.; Kokini, J. L. A Novel Biodegradable ESERS (Enhanced SERS) Platform with Deposition of Au, Ag and Au/Ag Nanoparticles on Gold Coated Zein Nanophotonic Structures for the Detection of Food Analytes. Vibrational Spectroscopy 2020, 106, 103013.
- Merrifield, R. C.; Stephan, C.; Lead, J. R. Single-Particle Inductively Coupled Plasma Mass Spectroscopy Analysis of Size and Number Concentration in Mixtures of Monometallic and Bimetallic (Core-Shell) Nanoparticles. Talanta 2017, 162, 130–134.
Related silver-shelled gold nanoparticle resources