This review describes recent efforts on the synthesis, dispersion and surface functionalization of the three dominating oxide nanoparticles used for photocatalytic, UV-blocking and sunscreen applications: titania, zinc oxide, and ceria. The gas phase and liquid phase synthesis is described briefly and examples are given of how weakly aggregated photocatalytic or UV-absorbing oxide nanoparticles with different composition, morphology and size can be generated. The principles of deagglomeration are reviewed and the specific challenges for nanoparticles highlighted. The stabilization of oxide nanoparticles in both aqueous and non-aqueous media requires a good understanding of the magnitude of the interparticle forces and the surface chemistry of the materials. Quantitative estimates of the Hamaker constants in various media and measurements of the isoelectric points for the different oxide nanoparticles are presented together with an overview of different additives used to prepare stable dispersions. The structural and chemical requirements and the various routes to produce transparent photocatalytic and nanoparticle-based UV-protecting coatings, and UV-blocking sunscreens are described and discussed.

Silica nanoparticles with different functionalities (amine, nitrile, phenyl and vinyl) have been synthesised via a two‐stage method and characterised in depth. Analysis by TEM, DLS and AFM has shown that the sizes of these synthetic nanoparticles are mainly in the range of 60‐100 nm. In addition, 13C and 29Si CP/MAS NMR spectroscopy has been used to provide evidence of the presence of the organic functional groups. Finally, zeta potential measurements have been used to determine the stability of the colloidal dispersions in each case. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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