Find answers to common questions about gold nanoparticles, including surface chemistry, thin-film processing, gold nanoshell optical properties, and gold nanorod selection and characterization.
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Gold Nanoparticle FAQs
- Do you offer bare or uncapped gold nanoparticles?
- Can gold nanoparticles be used for spin coating and thin-film deposition?
- How can I deposit a monolayer of gold nanoparticles?
- What is CTAB and why is its removal from gold nanorods important?
- Which gold nanorod wavelengths and surfaces are available?
- Why is the resonance wavelength of my gold nanorods different from the nominal wavelength?
- Why doesn't DLS match the TEM dimensions of my gold nanorods?
Gold Nanoparticles: General Questions
Do you offer bare or uncapped gold nanoparticles?
Stable colloidal nanoparticles require some form of surface stabilization. Without a stabilizing surface, attractive interactions between particles can lead to rapid aggregation.
For applications requiring subsequent ligand exchange or surface modification, citrate is often a useful starting surface because it is relatively easy to displace with molecules that bind more strongly to gold. Surface availability varies by particle size and product platform, so refer to the Gold Nanoparticle collection for current options.
If your application requires a different surface, solvent, concentration, or particle configuration, see our Custom Nanoparticle Development capabilities.
Gold Nanoparticle Processing
Can gold nanoparticles be used for spin coating and thin-film deposition?
Yes. Film formation depends on particle concentration, solvent properties, substrate chemistry, and deposition conditions. Increasing nanoparticle concentration or modifying the formulation can help achieve the particle density and coating behavior required for a particular process.
See Depositing Monolayers & Thin Films of Nanoparticles for an overview of spin coating, drop casting, dip coating, spray coating, and other deposition approaches. For application-specific solvent transfer or formulation requirements, see Custom Nanoparticle Development.
How can I deposit a monolayer of gold nanoparticles?
Several approaches can be used to assemble nanoparticles onto a surface, including electrostatic surface-mediated assembly, layer-by-layer deposition, and other controlled coating methods. Particle surface chemistry, substrate functionalization, concentration, solvent, and incubation conditions all influence surface coverage and particle organization.
Our nanoparticle thin-film and monolayer guide provides additional guidance on selecting a deposition approach.
Gold Nanorods
What is CTAB and why is its removal from gold nanorods important?
Cetyltrimethylammonium bromide (CTAB) is a cationic surfactant commonly used during gold nanorod synthesis because it helps direct anisotropic particle growth and stabilize the developing nanorods.
CTAB can create challenges for downstream applications because it is difficult to displace, can interfere with subsequent surface functionalization, and can produce undesirable biological interactions. Many commercially available gold nanorods are therefore supplied with CTAB remaining on the particle surface.
nanoComposix removes CTAB from our gold nanorods and replaces it with application-ready surface chemistries. This provides a cleaner starting material for ligand exchange, conjugation, sensing, biological research, and other applications where residual CTAB may interfere with performance.
Our CTAB-removal process was developed using analytical testing, including mass-spectrometry-based methods, to confirm removal of the synthesis surfactant. Current gold nanorods are available with citrate and, for select resonance wavelengths, PEG and PEG-carboxyl surfaces.
Explore current options in the Gold Nanorod collection.
Which gold nanorod wavelengths and surfaces are available?
Standard gold nanorods are currently available with longitudinal LSPR wavelengths centered at 650, 808, and 980 nm. Surface availability depends on the resonance wavelength:
| Resonance | Standard Surfaces |
|---|---|
| 650 nm | Citrate, PEG, PEG-Carboxyl |
| 808 nm | Citrate, PEG, PEG-Carboxyl |
| 980 nm | Citrate |
See the Gold Nanorod collection for current product configurations and specifications.
If your application requires a different resonance wavelength, particle geometry, surface chemistry, concentration, or formulation, see Custom Nanoparticle Development. For antibody, protein, nucleic acid, peptide, or other biomolecule functionalization, see Custom Conjugate Development & Manufacturing.
Why is the resonance wavelength of my gold nanorods different from the nominal wavelength?
The longitudinal LSPR of a gold nanorod is highly sensitive to particle dimensions and aspect ratio, so some variation in the exact peak position is expected within the product specification.
For current standard nanorods, the specification requires absorbance at the nominal wavelength to be greater than 90% of the peak absorbance. This approach accounts for small peak-position differences while controlling the optical response at the wavelength for which the product is designed.
Refer to the individual Gold Nanorod product page and batch-specific Certificate of Analysis for the applicable specification.
Why doesn't DLS match the TEM dimensions of my gold nanorods?
Dynamic light scattering (DLS) does not directly measure the length or width of a nanorod. It measures particle diffusion in solution and reports an equivalent hydrodynamic size, while transmission electron microscopy (TEM) directly measures the physical dimensions of individual rods.
Because gold nanorods are anisotropic, the DLS hydrodynamic diameter should not be interpreted as either the TEM length or thickness. DLS remains useful for monitoring dispersion quality because aggregation can produce a substantial increase in the measured hydrodynamic size.
For more information about the differences between these methods, see Nanoparticle Characterization Techniques.
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