Particle diameter measurement of a nanoparticle composite - Using density gradient ultracentrifugation and dynamic light scattering

Thanks to progress in nanotechnology in recent years, it has become ever more important to determine the accurate diameter of nanoparticles. The most common method used for the measurement of the particle diameter of nanoparticles is dynamic light scattering (photo correlation method), but if the sample is a composite material, it would be possible to more accurately measure the particle diameter if the composite could be separated into single materials. In the experiment this time, we will report on the results of the measurement of the particle diameter of a composite comprised of three components with different densities using the density gradient centrifugation method to isolate the components.

Discussion

When using the normal pelleting and density gradient centrifugation / sedimentation velocity method,precipitation will occur with the particle size as the greatest separation factor, but in this experiment, the density gradient / centrifugal separation equilibrium method was used, in which the density will be the separation factor. Using a fixed angle rotor will make it possible to use greater centrifugal force, enabling separation within approximately 1/3 of the time that would be required when using a swing rotor. For recovery of the components forming a band in the middle layer of the tube, the tube side surface was punctured using a syringe to collect the material, which was measured using DelsaMax PRO. The components deposited on the bottom were collected by cutting the tube, and were measured using Multisizer 4. Based on the results of this experiment, we believe that the density gradient centrifugation / sedimentation equilibrium method is an extremely useful means of measuring the particle diameter of nanoparticle composite material samples