Characterization of Nanoparticles by Light Scattering

Abstract

Metal oxide nanoparticles are increasingly being used to prepare new nanocrystaline materials. By controlling formulations of multicomponent metal oxides; crystal shape, structure and surface properties important in the design of new materials are gaining acceptance for many applications. Metal oxide composites are being used to design new electronic, magnetic and optical properties into material structures. Often these are formulated and processed in slurries or aqueous suspensions. A key parameter of controlling the design of such colloidal nanoparticle systems is their particle size. There are different methods by which a particle size can be obtained. Comparing stated dimensions from one method with those from another must be approached with caution: distributions in terms of volume, number or scattering intensity usually produce vastly differing results – despite expressing the exact same physical situation. Another fundamental colloidal characteristic is the zeta potential. This parameter effectively quantifies electrostatic stabilization, and can be used in formulation development to avoid instability as a result of particle-particle attraction.

Both size and zeta potential are easily measured by light scattering. Small amounts of aggregates are quickly detected by dynamic light scattering (DLS). The zeta potential is rapidly measured by electrophoretic light scattering (ELS). As an example of a typical metal oxide, data for TiO₂ nanoparticles are presented.

Light scattering is a versatile measurement technique and ideally suited as a metrology of choice for size and stability quantification of nano-sized materials.