By Melbourne Centre for Nanofabrication
Particle characterisation is an important step in the study of nano-particulate systems. Measuring surface charge, or zeta potential, is necessary in the binding of materials as the zeta potential will determine what will adhere to it. There are three processes which aid in the study of particle size, molecular weight and zeta potential. Dynamic light scattering is used to measure particle and molecule size by measuring the diffusion of particles moving under Brownian motion and converting this to size. Static light scattering is used to measure the molecular weight of proteins and polymers by measuring the scattering intensity of the molecules. Laser doppler micro-electrophoresis is used to measure surface charge, or zeta potential. This involves applying an electric field to a solution of particles to excite them and cause them to move. Their velocity is measured and their surface charge calculated accordingly. The zeta sizer may be used in the study of organic and inorganic nanoparticles, ceramics, pigments and inks, emulsions and pharmaceuticals. MCN’s particle characterisation instrument is the Malvern Zetasizer Nano ZS. It is a combined particle sizer and zeta potential unit that can measure the hydrodynamic size of particles (0.6nm – 6µm), the zeta potential of particles in the size range of 5nm – 10µm, as well as estimate the molecular weight of polymers and proteins up to 2 x 10 7 Da with minimal sample volume. It is able to perform analysis and measurements of specimens in liquid suspensions while the system also features a fully automated titrator, allowing the measurement of zeta potential as a function of pH, conductivity or concentration of an additive.
