Hi, my name is David Garcia and I'm the Characterization Services manager at nanoComposix.
Today, I'm going to be giving a brief overview of the instruments that we use to characterize
our nanomaterials. Every product we sell comes with a certificate of analysis. We use the
6 techniques that I'll be discussing to make all of these measurements, and everything
is a core part of our QC process and is why we pride ourselves on highly characterized
nanomaterials. If you're not buying a nanomaterial from us, but want your nanomaterials characterized,
we also offer these techniques as a service. For more information on each technique and
submitting a sample for analysis, please visit our Characterization Services page.
TEM is a technique that is used to image materials that are smaller than visible light and thus
cannot be seen on a conventional optical microscope. In a TEM, one side has an electron beam, and
the other side has a detector, in this case a CCD camera. In between is your sample, which
is dried down onto a grid. Nanoparticles absorb the incoming electrons, which creates shadows
where the particles are. From this data, you can learn about the particle's size, structure,
shape, and even crystallinity. TEM is a vital characterization technique
at nanoComposix that is used to quantify the base or grain particle size an important
metric that is featured on all of our certificate of analyses. If you also know the concentration
of your particles, you can combine the numbers to calculate things such as surface area and
particle concentration.
To understand how our particles absorb and scatter light, we use a UV-Vis spectrophotometer.
Not only do you learn optical properties, but the spectra from the UV-Vis measurements
can also be used to evaluate particle size, shape and concentration, whether or not your
particles are aggregated. To measure UV-Vis, a beam of light is shone
on a sample that is in line with a detector. The sample will interact uniquely with certain
portions of the broad-spectrum light sources, leaving behind an extinction spectrum that
is characteristic of that material. UV-Vis is a critical characteristic of all
our products, especially the extremely bright noble metal plasmonic particles. Due to the
relative ease of measurement and the multitude of information it gives,
it's also used here as a routine QC check.
For more information on UV-Vis, please see Parts 1 and 2 of our UV-Vis Tutorial video, available on our website.
Many of our products are used for in-vivo applications, so it's really important for
us to make sure they are free of bacterial contamination. We determine this by Endotoxin
Assay. An Endotoxin is a component of the cell wall of gram-negative bacteria that can
cause many health problems once it's in the blood stream, such as septic shock.
A special reagent isolated from horseshoe crab blood is added to a sample. If there's
endotoxin present, a series of clotting reactions will occur that causes the sample to become
turbid. The rate that it becomes turbid is proportional to the endotoxin content, and
this rate can be compared against a standard curve to calculate the endotoxin concentration.
ICP-MS is the most sensitive method we have to identify and measure the concentration
of metals. In an ICP-MS, super hot plasma is used to atomize samples creating ions.
A quadrupole mass analyzer filters these ions based upon their mass to charge ratio and
ions that pass through the filter hit a detector and are counted. This can be compared against
a serial dilution curve and extremely precise concentrations can be determined this way.
ICP-MS measurements are essential in determining the concentration of our products.
This in turn aids in the calculation of particle concentration and surface area.
DLS uses light scattering to determine the hydrodynamic diameter of a sample.
The hydrodynamic diameter is the size of the base particle plus the layers of ions, molecules
and covalently bound ligands on the surface that travel with the particle as it moves in solution.
A beam of light is shone on a dispersion of nanoparticles, which scatter
light to a detector that is offset at a high angle. The Brownian motion of the
particles creates a pattern of light at the detector that fluctuates at a rate that is a function of their size.
The DLS is similar to the UV-Vis in that it requires a similar sample prep and is a cuvette
style instrument. It's a quick way to verify changes in surface chemistry, and to monitor the stability of colloids.
Zeta Potential is another important characteristic of many colloidal systems and it is also measured
on the same instrument that we used to perform DLS.
In summary, the zeta potential is the electrostatic repulsion or attraction between particles
highly negative or highly positive zeta potentials indicate particles that are greatly
dispersed and stable, because they are repelled from each other.
Zeta is measured by applying an electric field to the electrodes of a cell containing a dispursed sample.
Particles migrate towards the electrode of opposite charge at a rate that is proportional
to their zeta potential. The rate of movement is calculated by the fluctuations in scattered
light as the particles pass through a 632 nm light source.
In addition to stability, monitoring the change in zeta potential over time can give you insight
into how the surface is changing over time.
And that concludes our segment on standard characterization services.
Please be sure to leave any comments or questions below, and check out our characterization services website
for more detailed information on each technique or for submitting a sample for analysis.
Thanks for watching!