3. Density Gradient Ultracentrifugation Technique

As a general, non-destructive, and scalable separation method, DGUC has recently been demonstrated as an efficient way of sorting colloidal nanoparticles according to their differences in chemical, structural, size, or morphology. After the introduction of basic concepts of density gradient ultracentrifugation, for the practical applications, there are various parameters to be considered. Nanoparticles will have different movement ways in different separation systems. In principle, particle movement characteristic in liquid media not only depends on the centrifugal force but also relies on the density, size, and shape of particle and the density and viscosity of the liquid medium and so on, while the gravity and intermolecular force can be ignored. In this chapter, typical parameters such as choice of gradient media, density gradient, rotor type, centrifugation speed, and time will be discussed.