Structure and dynamics: Static scattering of radiation and optical correlation techniques

The precise knowledge of size and shape of nanoobjects, either dispersed in a fluid phase or embedded in a solid matrix, is essential to assess structure/function relationships in all of the diverse application fields. Equally important is the characterization of the dynamical behavior in relation with the transport properties. This chapter provides a basic introduction to the static scattering techniques and the optical correlation techniques for the structural and dynamical characterization of nanostructured systems. The mathematical formalism will be kept to a minimum, in order to convey the main concepts without discouraging the not expert reader, while maintaining a rigorous approach to the pillars of the method. At the beginning of the chapter, we will briefly review the basics of a scattering experiment (either static or dynamic), through the definition of the independent variable, the momentum transfer vector. The first part of the chapter will then describe static scattering: we will introduce the effect of intraparticle and interparticle correlations, coded in the form factor and the structure factor, respectively, on the final scattering pattern. The contrast term will then be presented, to define precisely the information one can gather from and to select the most suitable radiation source for the experiment. The second part of the chapter will report on dynamic scattering and imaging techniques: we will first explain how dynamic information is contained in intensity fluctuations. We will then describe techniques based on the measurement and analysis of fluctuations of coherent and incoherent radiation. We will conclude by introducing recently developed techniques based on Imaging. For static and dynamic information, some examples will illustrate the application of these techniques to nanoparticle dispersions, to show the enormous potential for the structural and dynamical characterization on this size scale.