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Hematite nanoparticles were synthesized for ultraviolet filtration application by the precipitation method followed by calcination at different temperatures. A range of crystallite sizes between 37 and 85 nm (as determined by the Scherrer formula) was obtained, according to the temperature used for the calcination. An increase in the absorbance with increasing crystallite size was observed over the whole ultraviolet B and A range. The experimental band gap was 2.94 eV for the sample calcined at 500 degrees C and 3.08 eV for the sample calcined at 300 degrees C. The in vitro sun protection factor and protection factor-ultraviolet A of a water-in-oil emulsion made with the sample calcined at 500 degrees C as active ingredient were 9.21 and 8.81, respectively, which is higher than the protection factor-ultraviolet A values obtained for titanium dioxide and zinc oxide at the same mass concentration. The emulsion was found to be photostable.

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Iron doped CeO2 nanoparticles with doping concentrations between 0 and 30 mol% were synthesized by the co-precipitation method for potential application as a pigmented ultraviolet filtration material. Each sample was calcined in air and in argon. The iron solubility limit in the CeO2 lattice was found to be between 10 and 20 mol%. Raman spectroscopy results revealed that both iron doping and argon calcination increase the concentration of oxygen vacancies in the CeO2 lattice. Iron doping causes a blue-shift of the absorbance spectrum, which can be linked to the decreased crystallite size, as obtained by XRD peak broadening using the Scherrer formula. The undoped samples showed weak ferromagnetic behaviour whereas the doped samples were all paramagnetic.

A sodium montmorillonite/ureasil-poly(oxyethylene) clay-polymer nanocomposite was prepared using the solgel reaction of a U-PEO hybrid precursor/clay mineral suspension, with the aim of developing a sorbent for the removal of cationic dyes from aqueous media. The structural characteristics of the nanocomposite were studied by FTIR, XRD, UV-Vis spectroscopy, and SAXS. The XRD results revealed intercalation of the U-PEO in the silicate interlayer spaces. FTIR spectra indicated the existence of strong interactions between methylene blue (MB) dye and the clay mineral silicate layers. Time-resolved SAXS measurements during MB adsorption showed a decrease of the montmorillonite (Mt) peak area and an increase of the half-height width of the peak, indicating that water uptake during dye adsorption caused a reduction of the Mt. crystallite size. UV-Vis adsorption experiments showed that the kinetics of MB adsorption followed a pseudo-first order process and that the steady state equilibrium adsorption capacity followed the Langmuir model. The results showed that the nanocomposite is potentially applicable as an adsorbent of dyes present in contaminated waters.