Gold nanoshells are plasmonic nanoparticles composed of a nanoscale silica core surrounded by a thin gold shell. Their core-shell architecture provides strong control over localized surface plasmon resonance (LSPR), allowing absorption and scattering to be tuned across the visible and near-infrared (NIR) spectrum.
This combination of tunable optical response, strong extinction, and flexible surface chemistry makes gold nanoshells useful in sensing, imaging, diagnostics, spectroscopy, and photothermal research.
Looking for gold nanoshells for your application?
Explore 150 nm gold nanoshells with surfaces for passive, covalent, or streptavidin-based conjugation, plus NHS-activated dried conjugation kits.
Tunable Optical Properties of Gold Nanoshells
The optical properties of gold nanoshells depend strongly on the relative dimensions of the silica core and gold shell. Increasing the core diameter relative to shell thickness generally shifts the LSPR toward longer wavelengths, providing a way to engineer nanoshell absorption and scattering for a desired spectral region.
Core-shell geometry also affects the balance between absorption and scattering. This tunability distinguishes nanoshells from solid spherical gold nanoparticles and enables optical responses extending well into the NIR.
Dark-field scattering from gold nanoshells.
Different nanoshell architectures can scatter different portions of the visible and near-infrared spectrum. Their strong plasmonic response makes them useful for dark-field imaging, optical sensing, Surface-Enhanced Raman Spectroscopy (SERS), and other applications where absorption or scattering is important.
Explore the underlying relationships between nanoparticle structure and optical response in Gold Nanoparticle Optical Properties.
Absorption, Scattering & Bichromic Color
Gold nanoshells can exhibit substantial absorption and scattering within the same particle. As a result, some formulations appear different depending on whether they are viewed in transmitted or reflected light. For example, a nanoshell dispersion may appear blue in transmission while scattered light appears red or rust-colored.
Learn more about how absorption and scattering create these effects in Plasmonic Color Engineering. You can also use the Mie Theory Calculator to explore how silica core diameter, gold shell thickness, and surrounding refractive index affect calculated nanoshell extinction, absorption, and scattering.
Custom Gold Nanoshells & LSPR Tuning
Core-shell geometry provides a direct way to engineer nanoshell optical response. Applications that require a different resonance wavelength, absorption-to-scattering balance, particle architecture, surface chemistry, or formulation may benefit from a custom nanoshell design.
Need a gold nanoshell tuned to your optical application?
Work with our technical team to develop nanoshells around your target LSPR, particle dimensions, surface chemistry, and formulation requirements.
Standard Gold Nanoshells & Conjugation Options
Current standard gold nanoshell products use a nominal 150 nm core-shell architecture and are offered with multiple surface options for biomolecule conjugation. Refer to the 150 nm Gold Nanoshells product page for current specifications, concentrations, and expected optical ranges.
| Surface | Best Suited For |
|---|---|
| Citrate | Passive adsorption of antibodies and other proteins onto the nanoshell surface. |
| Carboxyl | Covalent conjugation to primary amines using EDC/Sulfo-NHS chemistry. The 150 nm carboxyl nanoshell uses a lipoic-acid surface. |
| Streptavidin | High-affinity attachment of biotinylated antibodies, proteins, oligonucleotides, and other molecules. |
| NHS-Activated | Direct covalent attachment to primary amines without requiring the user to perform the EDC/Sulfo-NHS activation step. Available as a dried conjugation kit. |
Detailed particle-specific conjugation procedures are available in the nanoComposix Protocol Library.
Carboxyl Gold Nanoshell Surface Chemistry
Lipoic acid surface ligand.
The carboxyl-functionalized 150 nm nanoshell uses lipoic acid, which contains sulfur groups that bind strongly to the gold surface and a carboxylic acid group available for further functionalization.
Carboxyl groups can be activated using EDC/Sulfo-NHS chemistry and subsequently coupled to primary amines on antibodies or other biomolecules, forming an amide linkage.
Representative Surface Charge & Stability Data
The following data characterize the tested 150 nm carboxyl-functionalized nanoshell formulation. They illustrate how solution conditions can affect surface charge and colloidal behavior, but the specific response depends on particle formulation, concentration, buffer composition, and test conditions.
Surface Charge vs. pH
Representative zeta potential-pH response of carboxyl-functionalized 150 nm gold nanoshells.
The lipoic-acid carboxyl surface remains negatively charged across most of the tested pH range and approaches a more neutral surface under strongly acidic conditions as the carboxyl groups become protonated. Because zeta potential depends on the surrounding solution, pH-dependent measurements should always be interpreted together with ionic strength and formulation conditions.
See Zeta Potential Measurements for more information about surface charge and isoelectric behavior.
Salt Stability
Representative UV-Vis response of carboxyl-functionalized 150 nm gold nanoshells during a sodium chloride challenge.
Increasing ionic strength can screen electrostatic repulsion between particles and reduce colloidal stability. In this specific 10-minute sodium chloride challenge, the nanoshell spectra remained relatively stable below approximately 20 mM NaCl, while more pronounced spectral changes occurred at higher salt concentrations.
The decrease in the nanoshell plasmon signal and overall optical intensity observed under destabilizing conditions is consistent with aggregation and particle precipitation. This threshold is specific to the tested formulation and conditions rather than a universal salt-stability limit for gold nanoshells.
For more information on using UV-Vis and other methods to monitor dispersion stability, see Nanoparticle Characterization Techniques.
Gold Nanoshell Applications
Optical Sensing & Imaging
Strong scattering and tunable LSPR make gold nanoshells useful for optical imaging, SERS, refractive-index sensing, and other plasmonic technologies. Their optical response can be engineered around the wavelength range and absorption-to-scattering balance required by the system.
Biofunctionalized gold nanoshells have also been investigated as contrast agents for optical coherence tomography (OCT). Muñoz-Ortiz et al. used functionalized nanoshells to target molecular markers associated with infarcted myocardial tissue and enhance OCT imaging of damaged regions.
Diagnostics
Gold nanoshells can provide a strong visible reporter signal in lateral flow and other diagnostic formats. In a published PSA lateral flow study, 150 nm nanoshell labels produced a fivefold lower detection limit than 40 nm gold nanospheres in that assay.
For a broader discussion of when nanoshells may help address weak test-line signal, see Increasing Lateral Flow Assay Sensitivity.
Photothermal & Biomedical Research
Gold nanoshells with strong NIR absorption efficiently convert absorbed light into heat, which has driven extensive research into photothermal applications. Nanoshells have also been studied for biological imaging and other light-responsive biomedical systems.
Selected Gold Nanoshell Publications
- Srinivasan, B.; Nanus, D. M.; Erickson, D.; Mehta, S. “Highly Portable Quantitative Screening Test for Prostate-Specific Antigen at Point of Care”. Current Research in Biotechnology 2021, 3, 288–299.
- Muñoz-Ortiz, T.; Hu, J.; Ortgies, D. H.; et al. “Molecular Imaging of Infarcted Heart by Biofunctionalized Gold Nanoshells”. Advanced Healthcare Materials 2021, 10, 2002186.
- Gonzalez-Moa, M. J.; Van Dorst, B.; Lagatie, O.; et al. “Proof-of-Concept Rapid Diagnostic Test for Onchocerciasis: Exploring Peptide Biomarkers and the Use of Gold Nanoshells as Reporter Nanoparticles”. ACS Infectious Diseases 2018, 4, 912–917.
- Simón, M.; Jørgensen, J. T.; Norregaard, K.; Kjaer, A. “18F-FDG Positron Emission Tomography and Diffusion-Weighted Magnetic Resonance Imaging for Response Evaluation of Nanoparticle-Mediated Photothermal Therapy”. Scientific Reports 2020, 10, 7595.
Related gold nanoshell resources