ABSTRACT
Following the denition from the European Commission, all engineered particles <100 nm in diameter are nanoparticles (NPs) (https://europa.eu, 2011). By this denition, many “nanoproducts” exist on the market, in which nanoscaled particles are the main building blocks. From a more scientic viewpoint, nanomaterials are dened by the change of important physicochemical properties with decreasing crystal or particle size (Brune et al. 2006). Such signicant changes do not normally occur in particles >30 nm but mostly in particles <10 nm. The reasons for the changes in the material properties are the high surface/ volume ratio and the changes in the electronic band structure (quantum connement). The surface/volume ratio is not only a geometrical parameter that increases the reactivity per mass of a material but it also affects thermodynamic properties such as phase stability and equilibrium, including the melting temperature, homogeneity of the particles, and shape. Simultaneously, quantum connement occurs, and the electrical and optical properties including the chemical reactivity are changed. A third origin of changes at the nanosize are properties such as ferromagnetism or ferroelectricity; they both depend on the interaction potential between the atoms (exchange energy), which decreases with a decreasing number of atoms per particle. If the thermal energy is larger than the interaction energy, the material loses its ordered arrangement of magnetic moments and becomes paramagnetic. Such properties depend not only on the temperature but also on the observation time. This short list demonstrates that NPs are indeed very complex materials and that a large number of properties should differ from the bulk behavior if the size of the particles decreases. It is important to be able to predict
CONTENTS
16.1 Introduction ........................................................................................................................ 251 16.2 Physicochemical Properties of NPs ................................................................................. 252 16.3 Particle-Particle Interactions ...........................................................................................253 16.4 Protein Adsorption ............................................................................................................ 257 16.5 Particle Agglomeration ..................................................................................................... 259 16.6 Particle Transport .............................................................................................................. 260 16.7 Conclusions ......................................................................................................................... 263 Acknowledgments ......................................................................................................................264 References .....................................................................................................................................264
