Researchers at the University of Potsdam, Germany, are using a Zetasizer Nano
ZS from Malvern
Instruments to measure the dimensions and stability of gold nanoparticles
smaller than 5 nm in diameter.
Gold has long been considered as an inert element, but in nanoparticulate form
it can be very reactive. For particles under 5 nm the surface electrons increasingly
dominate the properties of the surface and consequently of the system. This
makes gold nanoparticles interesting for life science applications, in tagging
viruses and cells for example.
Sabine Kosmella and Joachim Koetz made the ultrafine nanoparticles in a one-step
reaction using gold chloride and an oligosaccharide-modified hyper-branched
polyethylenimine (PEI). The PEI is a polyelectrolyte that acts as a reducing
agent as well as a stabilising agent. To make the particles, a mixture of gold
chloride and PEI in solution is heated to 100 degC. This results in a dispersion
of gold nanoparticles, which turn the solution red.
With the Zetasizer Nano the researchers were able to show that the average
diameter of the particles was less than 5 nm and to determine the zeta potential
of the dispersion, an indicator of its stability.
"Being able to measure particle size is important for the determination
of the hydrodynamic radius of the particles including the polymer shell in comparison
to other methods like TEM, visualising the particle radius without polymer shell"
said Dr Kosmella.
The Zetasizer Nano ZS from Malvern Instruments enables the measurement of both
particle size, from 0.6nm to 6000 nm, and zeta potential in a single instrument.
The technology built into the system provides the sensitivity required for measuring
dilute proteins and polymers, as well as the ability to measure emulsions and
suspensions at high concentrations. It is the method of choice for nano-particle
applications from routine colloid size measurements to the investigation of
particulates at the leading edge of materials research. www.malvern.com/zetasizernano
Malvern, Malvern Instruments and Zetasizer are registered trademarks of Malvern