Silver Nanoparticles

Silver nanoparticles are one of the most commonly utilized nanomaterials due to  their anti-microbial properties, high electrical conductivity, and unique optical properties.

NanoComposix's silver nanoparticle formulations are unaggregated solutions of high purity silver nanoparticles with a narrow size distribution.  Each nanoparticle batch has been extensively characterized and is provided with a detailed analytical report.

Silver Nanoparticle Products

Silver NanoPlates We are proud to offer Silver NanoPlates as our newest product line.  Our silver nanoplates have extremely high optical efficiencies, and can be tuned to interact with wavelengths ranging from 550 nm to 950 nm.

Silver Nanoparticle Optical Properties

Silver nanoparticles have unique optical properties because they support surface plasmons (see our plasmonics tutorial). At specific wavelengths of light the surface plasmons are driven into resonance and the silver nanopartices have a distinct color that is a function of their size, shape, and environment. The plasmon resonance of silver nanoparticles is responsible for their yellow color in solution. Any visible change to the color of the nanoparticles in solution typically indicates that the aggregation state of the nanoparticles has changed.

Quality Metrics

In addition to size and shape data obtained by TEM and aggregate size determined by DLS, a large amount of information can be obtained by quantifying the color of silver nanoparticles using UV-Visible spectroscopy. Changes in the optical properties are usually due to aggregation, photoactivity, or Ostwald's ripening, which typically manifest in the a UV-Visible spectrum as reduced peak height and increased peak width. By comparing the optical spectrum of the nanoparticle solution to the optical spectrum provided in each nanoComposix specification sheet, you can ensure that the nanoparticles have not changed over time and will have high confidence that the characteristics of the nanoparticle's remain the same as when they were purchased.

Dark Field Microscopy

Due to silver nanoparticle's unique optical properties, the scattering from individual nanoparticles larger than 40 nm can be imaged using a standard dark field microscope. Individual spherical silver nanoparticles will intensely scatter light, with smaller particles scattering blue light, and larger particles scattering green light. In fact, 40 nm diameter silver nanoparticles scatter more light per unit volume than any other form of matter. Under dark field microscopy, uniform spherical particles that are not aggregated on the slide will appear uniform and have the same color. Nanoparticles with different sizes and shapes will have many different colors and intensities.

Resuspended Dried Powders vs. Colloidal Suspensions

When dried powders of silver nanoparticles are resuspended in solution, the nanoparticles are typically aggregated into large clusters that cannot be broken up with any processing technique. Nanoparticles aggregates have a reduced surface area, larger effective mass, and different optical properties than monodisperse nanoparticles in solution. Thus, when comparing nanoparticles from different vendors it is critical to find out the hydrodynamic diameter (measured by DLS) of the nanoparticles to determine the degree of aggregation. For silver, the aggregation state can be determined by the color of the nanoparticles in solution. A dilute solution of individual silver nanoparticles will be a clear yellow in solution. If the silver nanoparticle solution is a dark grey, the nanoparticles are have irreversibly aggregated.

Silver Nanoparticle Concentration

When researching what nanoparticles to buy and use it is critical to be able to compare formulations from different suppliers.  There are a number of different ways that the concentrations are reported.  Here we provide tables converting our silver nanoparticle formulations into other commonly reported concentration units.

NanoXact Silver Nanoparticles

BioPure Silver Nanoparticles