Investigation of quantum size colloids using the XL-I ultracentrifuge

Abstract

Quantum size colloids attract a steadily growing scientific and economical interest because of their size-dependent optical and electrical properties. It is shown that the fractionation in the analytical ultracentrifuge enables the characterization of individual species even in complicated mixtures. If an ultracentrifuge with combined UV-absorption and Rayleigh interference optics is used, dependence of the spectra as well as of extinction coefficients on the particle size can be examined. As it is also possible to monitor particle growth from its initial stages, the combined spectral and particle size information can lead to an understanding of the particle growth mechanism. This is demonstrated for model systems of aggregates of small individual particles and grown particles of the same size. Furthermore, sedimentation velocity experiments prove to be very useful for determining the effectiveness of reactions performed in “micellar nanoreactors” and for determining the extinction coefficient of one component in a complicated mixture.