Plasmonics

NanoComposix fabricates a variety of optically efficient plasmonic nanoparticles with absorption and scattering spectra that can be tuned from 380–5000 nm. These nanoparticles have been used successfully in applications including diagnostics, photovoltaics, and photothermal therapeutics.

To read more about plasmonics please see our technology and knowledge base pages. To model the optical properties of plasmonic nanospheres of various materials, please see our Online Mie Theory Simulator.

Silver Nanospheres

Silver nanospheres with high optical efficiencies availabe in sizes ranging from 10 nm to 100 nm.

  • Resonant wavelength: 400–520 nm
  • Optical densities as high as 130 OD/cm
  • Ag mass concentration: 0.02 or 1 mg/mL
  • Available with citrate, tannic acid, PVP, or silica surfaces

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The optical properties of silver nanospheres are a function of the nanoparticle diameter. As the diameter increases, the peak extinction (scattering + absorption) shifts to longer wavelengths and broadens, and the nanoparticle albedo (a ratio of scattering to total extinction) increases (Figure 1). At diameters greater than 80 nm, a second peak becomes visible at shorter wavelengths than the primary peak. This secondary peak is due to a quadrupole resonance that has a different electron oscillation pattern than the primary dipole resonance.

Figure 1: (Left) Extinction (the sum of scattering and absorption) spectra of NanoXact silver nanoparticles with diameters ranging from 10–100 nm at mass concentrations of 0.02 mg/mL. BioPure nanoparticles have optical densities that are 50-times larger. (Right) Plot of silver nanosphere albedo (a ratio of scattering to total extinction) as a function of nanoparticle diameter.

Sprix Silver Nanoplates

Sprix silver nanoplates with high optical efficiencies and tunable optical resonances Available with diameters between 40 and 200 nm and thicknesses of ~10 nm.

  • Resonant wavelength: 550–1000 nm
  • Optical densities as high as 1000 OD/cm
  • Ag mass concentration: 0.02 or 1 mg/mL
  • Available with PVP, PVA, or silica surfaces

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The optical properties of silver nanoplates is a function of the aspect ratio (length:width), with plates with larger aspect ratios having peaks at longer wavelengths. By precisely controlling the plate diameter and thickness, the nanoplate’s optical resonance can be tuned to peak at specific wavelengths in the visible and near-IR spectral regions (Figure 4). This allows plates to be tuned to interact with specific laser lines, including 532 nm, 632.8 nm, 660 nm, 785 nm, 808 nm, and 1064 nm lasers.

Figure 2: (Left) Extinction spectra of silver nanoplates with varying aspect ratios. (Right) TEM image of silver nanoplates.

Sprix Silver Nanowires

High aspect ratio Sprix silver nanowires with diameters of <100 nm and lengths of 2–5 microns or 15–25 microns.

  • Resonant wavelength: 400 nm–10 microns
  • Ag mass concentration: 1 mg/mL
  • Available with PVP or silica surfaces

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Plasmonic silver nanowires support resonances in the mid to long range infrared, with wires with larger aspect ratios (a ratio of wire length:width) supporting resonances at longer wavelengths. Additionally, because Sprix wires have lengths longer than the wavelengths of visible light, visible light propagates through silver nanowires, and can couple through crossed nanowires, and to other nearby plasmonic nanoparticles (Figure 5).

 

Figure 3: (Left) White light dark field microscopy image of Sprix nanowires with lengths of 20 microns. Because the nanowires have lengths much longer than the wavelengths of visible light, they scatter all wavelengths of visible light and appear white/gold. (Right) Dark field microscopy image of Sprix nanowires with lengths of 4 microns. When illuminated with a red laser, the wires efficiently scatter the incident light and therefore appear red.

Gold Nanospheres

Gold nanospheres with high optical efficiencies availabe in sizes ranging from 10 nm to 100 nm.

  • Optical densities as high as 130 OD/cm
  • Ag mass concentration: 0.02 or 1 mg/mL
  • Available with citrate, tannic acid, PVP, or silica surfaces

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The optical properties of gold nanospheres is a function of the nanoparticle diameter. As the diameter increases, the peak plasmon resonance shifts to longer wavelengths and broadens, and the nanoparticle albedo (a ratio of scattering to total extinction) increases (Figure 6). Additionally, as the particles get larger, the particle scattering peak moves to longer wavelengths than the absorption peak (This can be observed by modeling different sized gold nanospheres using our Online Mie Theory Simulator).

Figure 4: (Left) Extinction (the sum of scattering and absorption) spectra of NanoXact gold nanoparticles with diameters ranging from 10 - 100 nm at mass concentrations of 0.05 mg/mL. BioPure nanoparticles have optical densities that are 20-times larger. (Right) Plot of gold nanosphere albedo (a ratio of scattering to total extinction) as a function of nanoparticle diameter.

Gold Nanoshells

Gold nanoshells are nanoscale silica cores surrounded by an ultra-thin gold shell that can be tuned to strongly absorb or scatter light at any wavelength in the visible and near-IR regions of the electromagnetic spectrum.

  • NanoXact (0.05 mg/mL) or BioPure (1 mg/mL) concentrations in water
  • Polyvinylpyrollidone (PVP) or Polyethylene Glycol (PEG) surface coatings
  • 800 nm resonant (120 nm silica core with a 15 nm gold shell)

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By changing the core/shell ratio the optical properties of gold nanoparticles can be tuned over a wide range of optical frequencies. The most common gold nanoshell has a 120 nm silica core, a 15 nm thick gold shell and a resonance at 800 nm (see UV-Visible spectrum below).  Particles with other core / shell dimensions or different surface capping agents are available on request.