The effect of the addition of colloidal iridium oxide into sol-gel obtained titanium and ruthenium oxide coatings on titanium on their electrochemical properties.

Electrochemical properties of sol-gel processed Ti(0.6)Ir(0.4)O(2) and Ti(0.6)Ru(0.3)Ir(0.1)O(2) coatings on titanium substrate were investigated using cyclic voltammetry, polarization measurements and electrochemical impedance spectroscopy and compared to the properties of Ti(0.6)Ru(0.4)O(2) coating. The role of iridium oxide in the improvement of the electrocatalytic, capacitive and stability properties of titanium anodes activated by a RuO(2)-TiO(2) coating is discussed. The oxide sols were prepared by forced hydrolysis of the metal chlorides. The characterization by dynamic light scattering and X-ray diffraction showed that polydisperse oxide sols were obtained with the particles tending to form agglomerates. The presence of IrO(2) causes a suppression of the X-ray diffraction peaks of TiO(2) and RuO(2) in the sol-gel prepared Ti(0.6)Ir(0.4)O(2) and Ti(0.6)Ru(0.3)Ir(0.1)O(2) coatings. The IrO(2)-containing coatings had an enhanced charge storage ability and activity for the oxygen evolution reaction (OER) in comparison to Ti(0.6)Ru(0.4)O(2) coating. The voltammogram of the Ti(0.6)Ir(0.4)O(2)/Ti electrode showed well-resolved peaks related to Ir redox transitions, which are responsible for the enhanced charge storage ability of IrO(2)-containing coatings. Redox transitions of Ir were also registered in the high-frequency domain of the ac impedance spectra of the coatings as a semicircle with characteristics insensitive to the electrolyte composition and to the electrode potential prior to OER. However, the semicircle characteristics were different for the two IrO(2)-containing coatings, as well as at potentials outside the OER in comparison to those at which the OER occurs.

Comments on the authors' response to the comments on "Factors influencing the removal of divalent cations by hydroxyapatite", by Smiciklas et al.

Recently, Smiciklas et al. have responded to my comments on their article "Factors influencing the removal of divalent cations by hydroxyapatite". The authors' response, however, contains similar mistakes given in their article.

Influence of natural zeolitic tuff and organozeolites surface charge on sorption of ionizable fumonisin B(1).

Natural zeolitic tuff was modified with 2, 5 and 10mmol M(+)/100g of octadecyldimethylbenzyl ammonium (ODMBA) ions and the products were denoted as OZ-2, OZ-5 and OZ-10. The starting material and organozeolites were characterized by determination of the point of zero charge (pH(pzc)) and by thermal analysis. In vitro sorption of fumonisin B(1) (FB(1)) was studied for all sorbents at pH 3, 7 and 9. The pH(pzc) for the zeolitic tuff was 6.8+/-0.1, while the pH(pzc) for OZ-2, OZ-5 and OZ-10 pH(pzc) was 7.0+/-0.1. The curves pH(final)=f(pH(initial)) suggest that the surfaces of all sorbents are positively charged at pH 3 and uncharged at pH 7 and 9. High sorption of FB(1) by the zeolitic tuff in acidic solution suggests electrostatic interactions between the anionic FB(1) and the positively charged surface. At pH 7 and 9, adsorption of FB(1) is prevented because anionic FB(1) cannot be adsorbed at the uncharged surface. From the pH(pzc) for the organozeolites, it is possible that with lower amounts of ODMBA (OZ-2 and OZ-5), at pH 3, beside interactions between head groups of ODMBA and its alkyl chains and anionic FB(1), electrostatic interactions between positive uncovered surface and anionic FB(1) contribute to the sorption, while at pH 7 and 9 there is only the possibility for interactions between FB(1) and ODMBA. When the zeolitic surface was completely covered with ODMBA (OZ-10), FB(1) sorption was independent of the form of FB(1) suggesting only interactions between ODMBA and FB(1).

Opposite effects of nanocrystalline fullerene (C(60)) on tumour cell growth in vitro and in vivo and a possible role of immunosupression in the cancer-promoting activity of C(60).

In the present study, we compared the effects of nanocrystalline fullerene suspension (nanoC(60)) on tumour cell growth in vitro and in vivo. NanoC(60) suspension was prepared by solvent exchange using tetrahydrofuran to dissolve C(60). In vitro, nanoC(60) caused oxidative stress, mitochondrial depolarization and caspase activation, leading to apoptotic and necrotic death in mouse B16 melanoma cells. Biodistribution studies demonstrated that intraperitoneally injected radiolabeled (125I) nanoC(60) readily accumulated in the tumour tissue of mice subcutaneously inoculated with B16 cells. However, intraperitoneal administration of nanoC(60) over the course of two weeks starting from melanoma cell implantation not only failed to reduce, but significantly augmented tumour growth. The tumour-promoting effect of nanoC(60) was accompanied by a significant increase in splenocyte production of the immunoregulatory free radical nitric oxide (NO), as well as by a reduction in splenocyte proliferative responses to T- and B-cell mitogens ConcanavalinA and bacterial lipopolysaccharide, respectively. A negative correlation between NO production and splenocyte proliferation indicated a possible role of NO in reducing the proliferation of splenocytes from nanoC(60)-injected mice. These data demonstrate that nanoC(60), in contrast to its potent anticancer activity in vitro, can potentiate tumour growth in vivo, possibly by causing NO-dependent suppression of anticancer immune response.

Comments on "factors influencing the removal of divalent cations by hydroxyapatite".

Recently, Smiciklas et al. [I. Smiciklas, A. Onjia, S. Raicevic, Dj. Janackovic, M. Mitric, J. Hazard. Mater. 152 (2008) 876-884)] have reported on the effect of pH, contact time, initial metal concentration and presence of common competing cations on hydroxyapatite sorption properties towards Pb(2+), Cd(2+), Zn(2+) and Sr(2+) ions. However, application of some experimental procedures and methods, as well as the presentation and interpretation of some data is problematic or erroneous.

The influence of cationic impurities in silica on its crystallization and point of zero charge.

The influence of the heat treatment on the crystal structure change of five (two laboratory prepared and three commercial) silica powders were investigated. Silicas were heat treated in the temperature range from 150 to 1300 degrees C in air. Also, the influence of the washing procedure with 0.01 mol/L HCl in order to desorb cations present as impurities in silica samples, was studied. The change of the amorphous into the crystal structure (alpha-cristobalite) takes place in the range 1050-1300 degrees C, depending on the chemical purity of silica samples. Points of zero charge, pHpzc, of the same silica samples, ranging from 3.8 to 7.1, were also determined by batch equilibration method. It is shown that the desorption of cations from silica samples, i.e., increase in their purity, leads to a shift in pHpzc toward lower values.

An inverse gas chromatography study of the adsorption of organics on nickel- and copper-hexacyanoferrates at zero surface coverage.

The surface properties of Ni and Cu hexacyanoferrates were investigated by the inverse gas chromatography method. Retentions of 10 organic compounds were measured at zero surface coverage in the temperature range 80 to 95 degrees C. The gas/solid partition coefficients and the related thermodynamic data of adsorption (standard free energy change, standard state enthalpies, and entropy changes) also at zero surface coverage were determined. The dispersive component of free surface energy of both hexacyanoferrates, at investigated temperatures, was calculated. The surface acid/base properties were also evaluated using polar adsorbates and the results obtained indicate that nickel hexacyanoferrate is more acidic than copper hexacyanoferrate.