Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: KEGG:D01931 (TiO2)
 11,320 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Azelaic acid is an aliphatic dicarboxylic acid (HOOC-(CH2)7-COOH) which has recently been shown to have some practical therapeutic applications in skin diseases of different etiologies. It possesses diverse biological activities and its mechanisms of action are still under investigation. Azelaic acid, as disodium salt (C(9)2Na), at concentrations from 0.05 mM to 1.0 mM is capable of inhibiting significantly the hydroxylation of 1-tyrosine to 1-DOPA due to hydroxylradicals (HO.) produced by Fenton reaction. Similarly C(9)2Na significantly inhibits the heterogeneous photocatalytic oxidation of toluene to cresols, and the peroxidation of arachidonic acid (C20:4,n6), due to HO. formed by dissolved oxygen in the presence of UV-irradiated semiconductor TiO2 (photo-Fenton type reaction). C(9)2Na decomposition and its by-products formation are quantifiable only at high HO. concentrations. On the contrary, C(9)2Na is not a scavenger of O2-. generated by xanthine-xanthine oxidase system. Under the same experimental conditions, mannitol behaves like C(9)2Na. These data indicate that HO. scavenging capacity of C(9)2Na in vitro, and represent a useful tool for further investigations on the mechanisms of action of azelaic acid in biological systems.
 ...
PMID:Scavenging activity of azelaic acid on hydroxyl radicals "in vitro". 164 75

Many reactive metals are difficult to prepare in pure form without complicated and expensive procedures. Although titanium has many desirable properties (it is light, strong and corrosion-resistant), its use has been restricted because of its high processing cost. In the current pyrometallurgical process--the Kroll process--the titanium minerals rutile and ilmenite are carbochlorinated to remove oxygen, iron and other impurities, producing a TiCl4 vapour. This is then reduced to titanium metal by magnesium metal; the by-product MgCl2 is removed by vacuum distillation. The prediction that this process would be replaced by an electrochemical route has not been fulfilled; attempts involving the electro-deposition of titanium from ionic solutions have been hampered by difficulties in eliminating the redox cycling of multivalent titanium ions and in handling very reactive dendritic products. Here we report an electrochemical method for the direct reduction of solid TiO2, in which the oxygen is ionized, dissolved in a molten salt and discharged at the anode, leaving pure titanium at the cathode. The simplicity and rapidity of this process compared to conventional routes should result in reduced production costs and the approach should be applicable to a wide range of metal oxides.
 ...
PMID:Direct electrochemical reduction of titanium dioxide to titanium in molten calcium chloride 1101 88

The previously unknown titanium(IV)-containing mu-hydroxo dimeric heteropolytungstate (Bu4N)7[(PTiW11O39)2-OH] (TBA salt of H1) has been synthesized, starting from H5PTiW11O40, and characterized by elemental analysis, multinuclear (31P, 17O, 183W) NMR, IR, FAB-MS, cyclic voltammetry, and potentiometric titration. 31P NMR reveals that H1 (delta -12.76) readily forms in MeCN from the Keggin monomer (POM), PTiW11O40(5-) (2, delta -13.34), upon the addition of 1.5 equiv of H+, via the protonated species, P(TiOH)W11O39(4-) (H2, delta -13.44). The ratio of H1, 2, and H2, which are present in equilibrium in MeCN solution at 25 degrees C, depends on the concentration of both H+ and H2O. The Ti-O-Ti linkage readily reacts with nucleophilic reagents, such as H2O and ROH, to yield monomeric Keggin derivatives. mu-Hydroxo dimer H1 shows higher catalytic activity than 2 for thioether oxidation by hydrogen peroxide in acetonitrile. The reaction proceeds readily at room temperature and affords the corresponding sulfoxide and sulfone in ca. quantitative yield. The addition of H2O2 to H1 or H2 results in the formation of a peroxo complex, most likely the hydroperoxo complex P(TiOOH)W11O39(4-) (I), which has 31P NMR resonance at -12.43 ppm. The rate of the formation of I is higher from H2 than from H1. When H1 is used as a catalyst precursor, the rates of the thioether oxidation and peroxo complex formation increase with increasing H2O concentration, which favors the cleavage of H1 to H2. H2O2 in MeCN slowly converts 2 to another peroxotitanium complex, P(TiO2)W11O39(5-) (II), which has 31P NMR resonance at -12.98 ppm. Peroxo complexes I and II differ in their protonation state and interconvert fast on the 31P NMR time scale. Addition of 1 equiv of H+ completely converts II to I, while 1 equiv of OH- completely converts I to II. 31P NMR confirms that I is stable under turnover conditions (thioether, H2O2, MeCN). Contrary to two-phase systems such as dichloroethane/aqueous H2O2, no products resulting from the destruction of the Keggin POM were detected in MeCN in the presence of H2O2 (a 500-fold molar excess). The reactivity of I, generated in situ from II by adding 1 equiv of H+, toward organic sulfides under stoichiometric conditions was confirmed using both 31P NMR and UV-vis spectroscopy. This is a rare demonstration of the direct stoichiometric oxidation of an organic substrate by a titanium peroxo complex.
 ...
PMID:A dimeric titanium-containing polyoxometalate. Synthesis, characterization, and catalysis of H2O2-based thioether oxidation. 1119 77

Photocatalytic degradation (PCD) of aqueous paraquat was accelerated by the addition of either phosphate or sulfate salt. Attachment of these anions to the TiO2 surface possibly results in increased adsorption of the cationic paraquat species and in turn its photocatalysis rate. The same effect was obtained more consistently using the Nafion (an anionic polymer)-coated TiO2. Enhanced PCD of paraquat and some amine compounds was noted. However the anionic and neutral compounds were not affected significantly. Nafion proved to be stable against photocatalysis. It has been suggested that the degradation rate is larger for the cationic compounds with higher pK(B). For a phenol-paraquat-TiO2 system, paraquat degradation did not begin till near-complete phenol removal. Using the Nafion-coated TiO2, both phenol and paraquat degradations started simultaneously. Nevertheless, complete paraquat removal still took longer than phenol.
 ...
PMID:Enhanced photocatalytic activity of nafion-coated TiO2. 1134 18

In solution phase synthesis of nanoparticles, processes such as coarsening and aggregation can compete with nucleation and growth in modifying the particle size distribution in the system. We show that coarsening of ZnO and TiO2 nanoparticles in solution follows the Lifshitz-Slyozov-Wagner rate law for diffusion controlled coarsening originally derived for colloidal systems with micrometer-sized particles, where the average particle size cubed is proportional to time. The rate constant for growth of ZnO in propanol is in the range 10(-4)-10(-2) nm3 x s(-1) and is dependent on the precursor anion and temperature. The coarsening of TiO2 nanoparticles from aqueous Ti(IV) alkoxide solutions is slower due to the low solubility of TiO2 with the rate constant in the range 10(-5)-10(-3) nm3 x s(-1) for temperatures between 150 degrees C and 220 degrees C. Epitaxial attachment of TiO2 particles becomes significant at higher temperatures and longer times. We show that the dominant parameters controlling the coarsening kinetics are solvent, precursor salt, and temperature.
 ...
PMID:Coarsening of metal oxide nanoparticles. 1224 60

Composite ZnO/SnO2 catalyst has been studied for the sensitized degradation of dyes e.g. Eosin Y (2', 4', 5', 7'-tetrabromofluorescein disodium salt) in relation to efficient charge separation properties of the catalyst. Improved photocatalytic activity was observed in the case of ZnO/SnO2 composite catalyst compared to the catalytic activity of ZnO, SnO2 or TiO2 powder. The suppression of charge recombination in the composite ZnO/SnO2 catalyst led to higher catalytic activity for the degradation of Eosin Y. Degradation of Eosin follows concomitant formation of CO2 and formation of CO2 followed a pseudo-first-order rate. Photoelectrochemical cells constructed using SnO2, ZnO, ZnO/SnO2 sensitized with Eosin Y showed V(oc) of 175, 306, 512 mV/cm2 and I(sc) of 50, 70, 200 microA/cm2 respectively. A higher irreversible degradation of Eosin Y and higher V(oc) observed on composite ZnO/SnO2 than ZnO and SnO2 separately can be considered as a proof of enhanced charge separation of ZnO/SnO2 catalyst. Eosin Y showed a higher emission decreases on ZnO/SnO2 composite than on individual ZnO, SnO2 or TiO2 indicating dominance of the charge injection process. Photoinjected electrons are tunneled from ZnO to SnO2 particles accumulating injected electrons in the conduction bands allowing wider separation of excited carriers.
 ...
PMID:Composite tin and zinc oxide nanocrystalline particles for enhanced charge separation in sensitized degradation of dyes. 1236 41

In this work, the comparison of 4-chlorophenol (4-CP) degradation by two different AOT processes has been performed: a) a homogeneous system with Fe(III)-NTA (1:1 complex), b) a TiO2/Fe(III)-NTA heterogeneous system. In both cases, NTA appears to play a positive role in the photochemical reaction. In the homogeneous system, the iron salt is the only absorbing species and is proved to be able to photoinduce 4-CP degradation ([4-CP] = 0.1-0.2 mM, [FeNTA] = 0.3-0.9 mM, pH 4, lambda = 365 nm). The progress of the reaction was positively affected by the FeNTA concentration, and the reaction kept going even after the total disappearance of FeNTA. However, 4-CP complete degradation requires the presence of oxygen, otherwise the reaction stops. In the heterogeneous system ([4-CP] = 2.0 mM, [FeNTA] = 1.0-2.0 mM, [TiO2] = 0.1 and 1.0 g L(-1), pH 3, lambda = 300-400 nm), an important effect of the complex on the degradation extent and on the initial reaction rate can be seen, which overcomes the effect of non-complexed Fe(III). This behaviour is more important at the highest TiO2 concentration.
 ...
PMID:Degradation of 4-chlorophenol mediated by Fe(III)-NTA in homogeneous and heterogeneous systems. 1507 59

H2O2 generated and released from TiO2 photocatalysts to the gas phase was detected. A flow-through cell packed with TiO2-coated glass beads was irradiated with UV light, and the gas flowing out of the cell was flushed through a collecting solution containing 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulforic acid) diammonium salt (ABTS) and peroxidase. Oxidative coloration of ABTS was observed only in the absence of catalase, indicating the presence of H2O2 in the gas. The quantum yield of the H2O2 generation was estimated to be > 1 x 10(-7). The detected amount of H2O2 decreased as the TiO2 thickness decreased. H2O2 was not detected when dry air or nitrogen was used.
 ...
PMID:Detection of H2O2 released from TiO2 photocatalyst to air. 1511 53

One of the problems connected with wastewater treatment by the photocatalytic method in the presence of TiO2 suspension is necessity of the later catalyst separation. The method proposed by us for this purpose, consists in the usage of coagulation of TiO2 suspension with the aid of FeCl3, particularly in the cases when addition of the salt is used in order to intensification of the photocatalytic process. The effects of the TiO2 separation were studied from the mixtures, after photocatalytic Acid Orange 7 degradation, with dosage of FeCl3 at different stages of the process. The coagulation was carried out at different pH values as well as different FeCl3 concentrations. It was stated that nearly 100% of separation and simultaneously, nearly 100% of decolouration of the examined Acid Orange 7 solutions after their illumination in the presence of TiO2/FeCl3 and coagulation which was produced only by increasing of pH of the obtained mixtures, were nearly possible.
 ...
PMID:The separation of catalyst after photocatalytic reactions conducted in the presence of TiO2/FeCl3/UV. 1581 14

Batchwise heterogeneous photocatalytic oxidation of model wastewater (solutions of the azo dye "Acid Orange 7" in tap water) has been performed in a laboratory-scale stirred vessel reactor with non-submerged UV-A lamps using titanium dioxide "P25" as photocatalyst. Comparison to results of solar pilot-scale Plexiglass double-skin sheet reactor (DSSR) experiments indicates that the lab-scale method may predict area demand for technical-scale DSSR design. Characteristic UV-A fluences leading to TOC or COD reduction to e(-1) of the initial concentrations were determined in lab-scale stirred vessel experiments for treated effluents of seven different industrial branches, secondary municipal effluent and biologically treated greywater. Predicted areas for solar photocatalytic oxidation of these effluents in DSSRs yielding mineralization of 95% of organics in 100 m3 of the respective effluents for a TiO2 concentration of 2 g l(-1) and a sky and solar radiation of 3.9kWh m(-2) d(-1) within one day greatly varied from below 6,000 m2 (biologically treated lubricating oil refinery effluent) to more than 100,000 m2 (highly saline biologically treated effluent of chemical industry). Especially municipal and refinery effluents (except oil reclaiming) have been identified as promising candidates for reuse after solar photocatalytic oxidation. Mineralization efficiency was decreasing with increasing alkalinity of effluents. This was interpreted by competition of hydrogen carbonate anions with organics for binding sites on photocatalyst surface and by OH radical scavenging by hydrogen carbonate. Dependence on alkalinity was superimposed by salinity influence as some effluents with high alkalinity also exhibited high salt concentrations (especially chloride).
 ...
PMID:Solar photocatalytic oxidation of pretreated wastewaters: laboratory scale generation of design data for technical-scale double-skin sheet reactors. 1597 68


1 2 3 4 5 6 7 8 9 10 Next >>