Gold nanorods are anisotropic plasmonic nanoparticles whose optical properties can be tuned by controlling their length-to-width ratio, or aspect ratio. Unlike spherical gold nanoparticles, nanorods exhibit two localized surface plasmon resonance (LSPR) modes: a transverse mode across the short axis and a longitudinal mode along the long axis.
The longitudinal LSPR is particularly tunable and can be shifted from the visible into the near-infrared (NIR), making gold nanorods useful for sensing, imaging, spectroscopy, optical engineering, and photothermal research.
Looking for gold nanorods with a specific optical response?
Explore gold nanorods with standard resonance wavelengths at 650, 808, and 980 nm for sensing, imaging, spectroscopy, photothermal research, and optical applications.
Gold Nanorod Optical Properties & Aspect Ratio
Gold nanorod LSPR depends strongly on particle geometry. Increasing the aspect ratio generally shifts the longitudinal resonance toward longer wavelengths, while lower-aspect-ratio rods resonate at shorter wavelengths.
Current standard gold nanorods are available with longitudinal resonance wavelengths at 650, 808, and 980 nm.
| Longitudinal LSPR | Typical Aspect Ratio | Standard Surfaces |
|---|---|---|
| 650 nm | ~2.7 | Citrate, PEG, PEG-Carboxyl |
| 808 nm | ~4.1 | Citrate, PEG, PEG-Carboxyl |
| 980 nm | ~5.6 | Citrate |
Changing gold nanorod aspect ratio shifts the longitudinal LSPR across the visible and near-infrared spectrum.
Because nanorods provide strong control over resonance wavelength and absorption, they can be selected to match particular light sources, detection windows, or optical requirements. For more background on LSPR, absorption, and scattering, see Gold Nanoparticle Optical Properties.
Custom Gold Nanorods & LSPR Tuning
Gold nanorod dimensions can be engineered to shift the longitudinal LSPR beyond the standard catalog wavelengths. Custom development can also address particle dimensions, surface chemistry, formulation, concentration, and other application-specific requirements.
Gold nanorod geometry can be adjusted to target different longitudinal resonance wavelengths.
Need a different nanorod resonance?
Work with our technical team to develop gold nanorods around your target LSPR, particle dimensions, surface chemistry, and formulation requirements.
Gold Nanorod Surface Chemistry & Functionalization
The nanorod surface affects colloidal stability, solvent compatibility, biomolecule interactions, and downstream functionalization. Current standard surface options include citrate, PEG, and PEG-carboxyl, with availability depending on resonance wavelength.
| Surface | Typical Use |
|---|---|
| Citrate | A relatively displaceable surface for subsequent ligand exchange or functionalization with other molecules. |
| PEG | Provides steric stabilization for applications requiring greater stability in aqueous buffers and compatible polar solvents. |
| PEG-Carboxyl | Provides a carboxyl-functionalized surface for covalent coupling to molecules containing primary amines using EDC/Sulfo-NHS chemistry. |
Detailed particle-specific procedures are available in the nanoComposix Protocol Library.
If your project requires antibody, protein, nucleic acid, peptide, or other biomolecule attachment beyond a standard conjugation workflow, our Custom Conjugate Development & Manufacturing team can support conjugation chemistry, optimization, characterization, and scale-up.
Gold Nanorod Applications
Biosensing & Optical Sensing
The longitudinal LSPR of gold nanorods is sensitive to changes in the refractive index near the particle surface. Adsorption or binding of molecules can therefore produce measurable spectral shifts, making nanorods useful for label-free sensing, biosensors, and other plasmonic detection strategies.
The surface can also be functionalized with antibodies, proteins, oligonucleotides, peptides, or other recognition molecules to introduce target-specific interactions.
Photothermal Research
Gold nanorods absorb strongly near their longitudinal resonance and convert absorbed optical energy into heat. This behavior has motivated extensive research into photothermal systems, including studies that match nanorod LSPR to visible or NIR excitation wavelengths.
Photothermal performance depends on particle dimensions, concentration, excitation conditions, surface chemistry, and the surrounding environment. Biological applications should also consider the material-specific factors discussed in Gold Nanoparticle Safety & Toxicity Considerations.
Photoacoustic Imaging
Strong optical absorption also makes gold nanorods useful as contrast agents in photoacoustic imaging. Absorbed pulsed light produces localized thermoelastic expansion and generates acoustic waves that can be detected to form an image.
Nanorod geometry and resonance wavelength can be selected around the optical requirements of the imaging system, while surface functionalization can support application-specific targeting strategies.
Drug Delivery Research
Gold nanorods have also been investigated as functional components of drug-delivery systems. Surface ligands can provide targeting or biomolecule attachment, while the plasmonic response can support light-responsive approaches. Nanorods may also be incorporated into hybrid structures such as silica-coated or mesoporous particle systems.
For programs requiring application-specific particle architecture or functionalization, see Custom Nanoparticle Development and Custom Conjugate Development & Manufacturing.
Selected Gold Nanorod Publications
- Cao, J.; Sun, T.; Grattan, K. T. V. “Gold Nanorod-Based Localized Surface Plasmon Resonance Biosensors: A Review”. Sensors and Actuators B: Chemical 2014, 195, 332–351.
- Mayer, K. M.; Lee, S.; Liao, H.; et al. “A Label-Free Immunoassay Based Upon Localized Surface Plasmon Resonance of Gold Nanorods”. ACS Nano 2008, 2, 687–692.
- Chen, H.; Shao, L.; Ming, T.; et al. “Understanding the Photothermal Conversion Efficiency of Gold Nanocrystals”. Small 2010, 6, 2272–2280.
- Knights, O. B.; Ye, S.; Ingram, N.; Freear, S.; McLaughlan, J. R. “Optimising Gold Nanorods for Photoacoustic Imaging In Vitro”. Nanoscale Advances 2019, 1, 1472–1481.
- Zhang, Z.; Wang, L.; Wang, J.; et al. “Mesoporous Silica-Coated Gold Nanorods as a Light-Mediated Multifunctional Theranostic Platform”. Advanced Materials 2012, 24, 1418–1423.
Related gold nanorod resources