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Changes to the surface composition of hydroxyapatite were measured after incubations in water, in ethanol or in a mixed aqueous-alcoholic medium. Ethanol decreased the surface presence of calcium ions in direct proportion to its amount in the medium. Because of its lower polarity than that of water, ethanol also increased the interfacial energy, in response to which the surface relaxed by rearranging into a more disordered state, as indicated by the increase in the heterogeneity of both calcium and oxygen electronic states. Accordingly, the binding energy of core-level oxygen electrons consistently increased with the concentration of ethanol and was compensated for by the decrease of the corresponding binding energies in calcium atoms, attesting to the weakened ionic bonds at the interface. The weakened ionic bonds increased the metallicity of the calcium ion, which prompted the offset of the valence band edge determined by the Ca 4s electron energy state toward the Fermi level and the conduction band, thus shrinking the band gap and increasing the electrical conductivity of the surface. The surface energy reduction entailing the partial loss of the crystalline order at the surface predisposed the nanoparticles incubated in alcoholic media for diminished sorption of proteins, but also for an augmented osteogenic response. These results demonstrate that surface functionalization of materials for various physicochemical and biological effects could be achieved without the use of chemical ligands. Rather, more economical design techniques stemming from the repertoire of materials science and engineering could be employed with equally satisfactory outcomes. [Display omitted] • XPS was used to measure changes to the surface of HAp at deeper and terminal levels in response to incubation medium. • O 1s binding energy increased with the amount of ethanol in the medium, attesting to weakened ionic bonds at the interface. • Weakened ionic bonds increased the metallicity of calcium ion, which increased the electrical conductivity of the surface. • Ethanol decreases the surface presence of calcium ions on HAp in direct proportion to its amount. • Ethanol increases the interfacial energy and induces surface relaxation into a more disordered state. [ABSTRACT FROM AUTHOR]

Abstract: Nanostructured NiZn ferrites were synthesized using two different techniques: first, a precipitation procedure in the reverse micelles of a CTAB/1-hexanol/H2O microemulsion, and second, precipitation in a bulk aqueous solution. XRD measurements, magnetic measurements, TEM imaging, analytical measurements and thermal analyses were used in an attempt to reveal the chemical pathway that leads to the formation of NiZn ferrite in the microemulsion and in the bulk aqueous solution. It was found that reverse micelles do not act as inert nano-sized reactors that influence only morphological properties of the synthesized powders, but have a decisive influence on the identity of the final product when compared to the non-microemulsion procedure, and therefore present the molecular structures which are actively engaged in the chemical pathway according to which the herein presented room temperature synthesis of NiZn ferrite nanoparticles takes place. The influence of the initial pH on the chemical pathway of reverse-micellar synthesis and the morphology of the synthesized particles was discussed after initially it was found that the pH of the precipitation ought to be higher than 8 in order to obtain the desired ferrite as a final product. [Copyright &y& Elsevier]

Metals and metal oxides have subpar antibacterial activities compared to those of small-molecule antibiotics, yet there are hopes that with proper compositional and structural adjustments this gap might be bridged. In this study, titanium dioxide (TiO 2) nanoparticles were mechanically activated and combined with particulate silver through simple reduction process elicited by UV irradiation and assisted with the ultrasound. The resulting powders in various combinations (Ag vs. no Ag, activated vs. non-activated) were characterized using a range of experimental techniques and assessed for their antibacterial activities. The preparation procedure presented in this work prevails over the disadvantages of many chemical routes, most critically by avoiding the use of toxic substances. The mechanical activation did not reduce the particle size or crystallinity of TiO 2 nor did it consistently alter the bandgap, yet it enabled the doubling of the amount of silver incorporable into the material. Further, while both mechanical activation and the addition of silver in the amount not exceeding 0.5 wt% produced barely detectable structural changes in the material, they both augmented its antibacterial activity. The precursor TiO 2 powder produced no inhibition zone against any of the four bacterial species tested, while the mechanical activation of TiO 2 led to the formation of distinct inhibition zones against each of the four bacterial species tested. The addition of silver to activated TiO 2 further widened the inhibition zones and it also imparted the antibacterial activity to non-activated TiO 2. The boost in the antibacterial activity achieved by the short mechanical activation was of a similar magnitude as the boost obtained after the addition of silver. The antibacterial activity was not different for different species when no silver was added to the system. However, with the addition of silver, species selectivity was obtained, as the composites were more effective against the two Gram-negative species (Escherichia coli and Klebsiella pneumoniae) than against the two Gram-positive ones (Staphylococcus aureus and Bacillus subtilis). The antibacterial activity increased with the addition of silver in the broth assay, but it was mediocre compared to that detected in the agar assay, attesting to the poor dispersability of the powders and their best performance when the bacterial cells migrate to the composite surface than vice versa. The findings of this study give hope that with appropriate microstructural or compositional alterations, the antibacterial activity of metal oxide powders and inorganic materials in general can be made comparable to that of small-molecule antibiotics. [Display omitted] • The mechanical activation of TiO 2 as an prerequisite for antibacterial activity • Ag distribution over TiO 2 surface by ultrasonically-assisted chemical precipitation • Homogeneous Ag deposition onto TiO 2 at a low net concentration • The mechanical activation doubled the amount of Ag incorporable into TiO 2 • The mechanical activation and addition of Ag augmented TiO 2 antibacterial effect. [ABSTRACT FROM AUTHOR]