Microscopic techniques for the characterisation of metal-based nanoparticles

At the emerge of the nanotechnology in the second half of the 20th century, nanoscale-modified advanced materials appear to be the materials-of-choice, possessing remarkable properties. Such materials are known to exhibit novel and significantly enhanced physical, chemical, biological and mechanical properties. Most nanomaterials' unique physical properties originate from their increased specific surface area as the particle size decreases to nano-length scale, so-called surface-to-volume ratio, SA:V. Due to the particles' small size, the microscopy techniques that allow direct observation of the particulates and their simultaneous characterisation are scarce. Among them, electron microscopy methods, especially transmission electron microscopy (TEM), is the most widely used technique for characterisation of the nanoparticles size, shape, and homogeneity. Nevertheless, when applying the electron microscopy methods for the nanoparticles' characterisation, several limitations have to be considered, such as sample-preparation induced artefacts, time-consuming analyses and interpretation of the results, and especially small number of particles that can be analysed in such a manner. Therefore, a combination of several different experimental approaches is advised, which depends on the research task. In the following sections, the general background on the nanoparticle analysis and the limitations of the most common microscopic and spectroscopic techniques for characterisation of nanoscaled metal-based particulates' will be summarised.