Search results for "Oxide"

The Photocatalytic Activity of Novel, Substituted Porphyrin/TiO2-Based Composites

2010

Four novel porphyrins, 5-[3-(3-phenoxy)-propoxy]phenyl porphyrin, 5,15-di-[3-(3-phenoxy)-propoxy] phenyl porphyrin, 5,10,15-tri-[3-(3-phenoxy)-propoxy]phenyl porphyrin, 5,10,15,20-tetra-[3-(3-phenoxy)- propoxy]phenyl porphyrin, and their corresponding Cu(II) porphyrins, were synthesized and characterized spectroscopically. The photodegradation of 4-nitrophenol in aq. suspension was used to determine the photocatalytic activity of polycrystalline TiO2 samples which had been impregnated with the Cu(II) porphyrins, as sensitizers. The photocatalytic activity of the composite depends mainly on the amount of sensitizer on the TiO2 surface rather than the nature of the substituted porphyrins.

Untersuchungen zum oxidativen abbau nativer cellulose. I. Das anfangsstadium des heterogenen abbaus von alkalicellulose aus baumwolle und eine bezieh…

1973

Behandlung nativer Baumwollcellulose mit NaOH verschiedener Konzentration uber langere Zeiten unter Reinstickstoff vermindert den STAUDINGER-Index der Cellulose in CUOXAM und des daraus hergestellten Cellulosetrinitrats (CTN) in Aceton um einen erheblichen Betrag. Lichtstreuungsmessungen zeigen, das wahrend dieses Prozesses das Molekulargewicht erhalten bleibt, wahrend der Tragheitsradius abnimmt und der 2. Virialkoeffizient zunimmt. Die enge Molekulargewichtsverteilung des nativen Produkts bleibt hierbei erhalten. Schwache Sauerstoffzufuhr erhoht zunachst die Viskositat, um sie erst bei langerem Abbau zu erniedrigen. Diese Phanomene werden folgendermasen gedeutet : Die Cellulosemolekule li…

The electrochemistry of carbon monoxide reductive cyclotetramerization to squarate anion

1978

Abstract The electrochemical reduction, of carbon monoxide to C4O2−4 squarate anion is investigated. Particular attention is devoted to the influence that solvents, electrolytes, electrodes and carbon monoxide pressure have on the yields. The main feature appears to be that strictly controlled conditions are not necessary for cyclotetramerization. In dmf — Bu4NBr the following yields vs reacted CO and circulated charge were obtained with different cathodes: Pt(49%, 34%); Au(48%, 29%); Al(47%, 38%); stainless steel (36%, 33%); graphite (39%, 31%). A distinct influence of the supporting electrolyte (inorganic and tetraalkylammonium halides) was however observed.

ChemInform Abstract: First Synthesis of Chiral 3-Vinylindoles as 4π-Components for Diels- Alder Reactions.

2010

The first syntheses of chiral 3- and 2-vinylindoles bearing sulfoxide or (-)-menthyloxy functional groups at the β-vinyl positions by way of procedures based on the Horner-Wadsworth-Emmons and Wittig reactions, respectively, are described. Some Diels-Alder reactions demonstrating the 4π-reactivity of these compounds are reported.

Volatile Constituents ofTeucrium poliumL. from Turkey

1998

Abstract The volatile constituents obtained from the aerial parts of Teucrium polium were analyzed by GC and GC/MS. The oil was found to contain 37 components, of which 30 were identified. The major constituents were β-pinene (18.0%), β-caryophyllene (17.8%), α-pinene (12.0%), caryophyllene oxide (10.0%), myrcene (6.8%) and germacrene-D (5.3%)

The bleaching efficacy of carbamide peroxide gels containing potassium nitrate desensitizer

2020

Background To evaluate the bleaching efficacy of at-home carbamide peroxide (CP) gels in two concentrations, containing or not a desensitizing agent. Material and methods Forty incisors were divided into four groups (n=10), according to gel concentrations (10% or 22%), and presence or not of 3% potassium nitrate in the gel. A thin layer of gel was applied to the buccal surface of each tooth for 2h/day for 4 weeks. Bleaching efficacy was measured using a spectrophotometer, and ∆E*ab, ∆E00 and ∆WID were calculated. Measurements were performed at baseline, 7, 14, 21, 28, and 35 days following the first gel application. Data were analyzed by two-way RM-ANOVA and Tukey's test (α=0.05). Results R…

Smoking and Oxidative Stress: Vascular Damage

2007

Photochemistry of the H2O/CO System Revisited : The HXeOH···CO Complex in a Xenon Matrix

2017

We report on the complex of a noble-gas hydride HXeOH with carbon monoxide. This species is prepared via the annealing-induced H + Xe + OH···CO reaction in a xenon matrix, the OH···CO complexes being produced by VUV photolysis of the H2O···CO complexes. The H–Xe stretching mode of the HXeOH···CO complex absorbs at 1590.3 cm–1 and it is blue-shifted by 12.7 cm–1 from the H–Xe stretching band of HXeOH monomer. The observed blue shift indicates the stabilization of the H–Xe bond upon complexation, which is characteristic of complexes of noble-gas hydrides. The HXeOH···CO species is the first complex of a noble-gas hydride with carbon monoxide and the second observed complex of HXeOH. On the ba…

PtTe2: Potential new material for the growth of defect-free TeO2 single crystals

2008

Abstract The dissociation of Te–O bonds is the main drawback, which hampers the yield of large-sized paratellurite single crystals of high optical quality when using platinum crucibles. In this work, it is assumed that a catalytic dissociation process involves the intermediate formation of platinum tellurides, these ones being then responsible for entrapment of gas bubbles and black precipitates when growth proceeds. To alleviate this difficulty, we suggest that platinum ditelluride could be a chemically more appropriate compound instead of pure platinum. First experiments on direct transformation of platinum sheets into PtTe 2 under tellurium gas atmosphere are described, as well as the pr…

Titanium dioxide in dental enamel as a trace element and its variation with bleaching

2017

Background Titanium is a less studied trace element in dental enamel. Literature relates an increased Titanium concentration with a decreased enamel crystal domain size, which in turn is related to a higher color value. The aim of our study was to analyze the effect of tooth bleaching agents on its concentration in dental enamel by means of confocal Raman spectroscopy. Material and methods Human teeth were randomly distributed in six experimental groups (n=10) and submitted to different bleaching protocols according to the manufacturer´s instructions. Confocal Raman spectroscopy was carried out in order to identify and quantify the presence of titanium dioxide molecules in enamel prior to a…