Gold Nanostars

What Gold Nanostars are and Where they are used ?

Gold nanostars are branched gold nanoparticles with sharp tips that concentrate electromagnetic fields into intense plasmonic “hot spots.” By controlling their core and branch geometry, their localized surface plasmon resonance (LSPR) can be tuned from the visible to the near-infrared region.

Representation of the use of gold nanostars in photothermal research

Photothermal Research

Gold nanostars absorb near-infrared light and convert it into localized heat. Their sharp branches produce a “lightning-rod effect,” concentrating the electromagnetic field at the tips and enabling strong, tunable NIR absorption. This makes them well-suited for investigation as photothermal agents in cancer research. However, heating efficiency and selectivity depend on nanostar geometry and concentration, surface targeting, tissue depth, laser wavelength, power, and exposure time; these parameters must therefore be validated for each experimental model.
Schematic presentation of hot spots on gold nanostars

SERS and Trace Detection

The sharp tips of gold nanostars—and the narrow gaps formed when particles are brought close together—can generate intense electromagnetic “hot spots” that strongly enhance Raman signals. This makes gold nanostars useful as SERS substrates or nanotags for detecting low concentrations of DNA, proteins, exosomes, pathogens, and other biomarkers in early-detection and point-of-care research. Learn more about Gold Nanostars Hot Spots and Why They Matter.
Illustration of tunable plasmonics for gold nanostars

Tunable Plasmonics from the Visible to the Near-Infrared

The LSPR peak of a gold nanostar is governed by its core size and branch geometry, including branch length, width, aspect ratio, and tip sharpness. Our three standard products have LSPR peaks within the 800–1050 nm range, while custom geometries can be designed with peaks between 600 and 1100 nm to match a selected laser wavelength or optical imaging window. Their high surface area and functionalizable gold surface also support research into targeted delivery and controlled release, with SERS or other plasmonic signals enabling optical tracking and, in some systems, real-time release monitoring.
Representation of the use of gold nanostars in imaging and theranostic research

Imaging and Theranostics

The strong optical scattering and absorption of gold nanostars support their studies as contrast agents for dark-field microscopy and photoacoustic imaging, while their enhanced Raman signals enable SERS-based detection and particle tracking. Because a single nanostar platform can combine imaging with light-triggered localized heating, gold nanostars are also studied for theranostic applications that integrate diagnostic and therapeutic functions. Learn more about the diagnostic and therapeutic applications of Biocompatible Nano-Gold.

Peer-reviewed articles that used NanoBrand gold nanoparticles are listed on the Publications page.

Which Size and LSPR Peak for Your Application?

Match the LSPR peak to your excitation wavelength or optical imaging window. Across our three standard products, the peak shifts to longer wavelengths as the core diameter increases:

  • 30 nm: 800–850 nm
  • 60 nm: 900–950 nm
  • 90 nm: 1000–1050 nm

Confirm the final selection under your complete assay or imaging conditions, as surface conjugation and changes in the surrounding medium can shift the LSPR peak.

Product Core diameter Branch length LSPR peak Coating
Gold Nanostars 30 nm 30 nm 15 to 30 nm 800 to 850 nm PVP or chitosan
Gold Nanostars 60 nm 60 nm 20 to 40 nm 900 to 950 nm PVP or chitosan
Gold Nanostars 90 nm 90 nm 20 to 40 nm 1000 to 1050 nm PVP or chitosan

All three standard gold nanostar products are available at an optical density of 1. If your application requires an LSPR peak outside the specified ranges, custom nanostar geometries can be made to order, as described below the product listings. For spherical gold nanoparticles, the Citrate line offers sizes from 5 to 200 nm for general research applications, while the IVD-READY line is designed for conjugation in lateral-flow assays and biosensors.

Available Gold Nanostars Products:

Schematic representation of gold nanostars with chitosan and PVP surface coatings

PVP or Chitosan Coating in Reactant-Free Water

Each Gold Nanostars product is supplied with either a PVP or chitosan coating, which should be selected when ordering. PVP provides a nonionic, sterically stabilizing coating; PVP-coated nanostars may nevertheless exhibit a slightly negative measured zeta potential. Chitosan provides a pH‑dependent cationic coating: under typical assay conditions (acidic to near‑neutral pH), chitosan‑coated nanostars exhibit a positive surface charge that supports electrostatic binding of negatively charged species such as nucleic acids. As pH increases toward alkaline conditions, protonation decreases; the surface can drift toward weakly positive or near‑neutral, and colloidal stability may rely more on steric than electrostatic effects. Both coatings support colloidal stability and help preserve the branched nanostar morphology, while providing an interface for further functionalization. Uncoated nanostars are not offered because a stabilizing surface layer is needed to limit aggregation and morphological changes. Read Why did we choose not to sell them "bare".

The nanostars are dispersed in Milli-Q water with a resistivity of 18.2 MΩ·cm. No CTAB, CTAC, Tween surfactants, PBS, buffers or proprietary stabilizer mixtures are added to the final dispersion. Residual synthesis surfactants or buffers may also interfere with ligand exchange, analyte access, conjugation, or SERS measurements. Read Why stabilizing agents should be avoided.

Alternative polymers and biofunctional coatings are available upon request.

Representation of gold nanostars core diameter and branches length

Controlled Geometry and Lot-Specific Characterization

For each production lot, TEM images are analyzed to determine the average core diameter, branch length and size distribution. A volume-equivalent spherical diameter is then estimated using a defined geometric model to support particle-mass and concentration calculations.

Each order includes a lot-specific Certificate of Analysis and Safety Data Sheet. The CoA reports TEM images, the UV–Vis extinction spectrum, hydrodynamic diameter and zeta potential.

Lot-to-lot control of nanostar geometry helps maintain the LSPR peak within its specified wavelength range and supports reproducible performance across successive orders. Because final behavior can also depend on conjugation, medium composition and instrument settings, performance should be confirmed under the intended experimental conditions.

The nanostars are produced using a green-chemistry-inspired process designed to minimize the use of harsh reagents. View representative CoAs for the 800–850 nm product:

Our Nanoparticle Characterization Services, including high-resolution imaging and EDS analysis, are also available for customer-supplied samples.

Bottles containing three different gold nanostars products from NanoBrand

Standard Configurations, Custom Nanostars and Ordering

The three standard products are listed at optical density 1, with a PVP or a chitosan coating, in seven volumes from 5 ml to 125 ml. The price of each configuration appears on the product page and updates in the cart. Nanostars with a custom core diameter, LSPR peak position, concentration or coating are made to order.

  • Universities: 10% discount applicable to the purchase order
  • Returning customers: 5% discount added to the cart automatically
  • Products are manufactured in Canada and ship in 1–2 weeks for small orders and 2–3 weeks for large orders 
  • Custom nanostars: please send us the approximate core diameter or LSPR peak position, the surface coating, the concentration as OD or particles per ml, and the order volume
  • Bulk quantities: lead times are confirmed following review of the requested specifications, concentration, batch volume and characterization requirements

Frequently Asked Questions

What is the difference between gold nanostars and gold nanourchins?

Gold nanostars carry sharp, anisotropic branches on a central core. Gold nanourchins have a rounded, raspberry-like surface. Nanostars are chosen when a narrow, tunable near-infrared resonance and intense tip hot spots are needed; nanourchins suit broadband, rough-surface SERS and large-area substrates. The comparison is developed in What to choose: Gold Nanostars or Gold Nanourchins.

What are gold nanostar hot spots?

Hot spots are nanoscale regions where incident light generates exceptionally strong localized electromagnetic fields. In gold nanostars, they form primarily at sharp branch tips through the lightning-rod effect and within narrow gaps between adjacent particles through plasmonic coupling.

Molecules positioned within or near these regions can produce Raman signals many orders of magnitude stronger than conventional Raman scattering, forming the basis of nanostar-enabled SERS detection. Hot-spot intensity depends on several factors, including tip sharpness, branch geometry, excitation wavelength and the width of interparticle gaps; sharper tips and narrower, well-controlled gaps generally produce stronger field enhancement.

Read What are Gold Nanostars’ “hot spots”, and why do they matter?

Why are gold nanostars coated rather than sold bare?

Uncoated gold nanostars are susceptible to aggregation in high-ionic-strength and protein-rich media, uncontrolled biomolecule adsorption, and gradual tip rounding. Because their near-infrared LSPR depends strongly on branch geometry, tip reshaping can shift the LSPR toward shorter wavelengths and reduce the optical response associated with the nanostar tips.

PVP or chitosan coatings improve colloidal and morphological stability while providing a surface for subsequent functionalization with antibodies, peptides, oligonucleotides, or other ligands. Learn more about Why we chose not to sell bare gold nanostars.

How should gold nanostars be stored?

Store gold nanostars at 4–25 °C, protected from direct light, and do not freeze. Storage near 4 °C generally provides better long-term stability, while freezing may cause irreversible aggregation. Before use, gently invert the container to redisperse the particles without vigorous shaking.

During extended storage, the LSPR peak may shift slightly, often toward shorter wavelengths, while remaining within the specified range. Before a critical experiment, particularly after prolonged storage, record a fresh UV–Vis spectrum to confirm the peak position, intensity and line shape. See our guide to evaluating gold nanoparticle stability using UV–Vis spectroscopy.