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Chemicals, plastics and rubber industries

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Electron spin resonance studies on the oxidation mechanism of sterically hindered cyclic amines in Ti[O.sub.2] photocatalytic systems

Article Abstract:

The key species X in the formation process of 4,hydroxy-2,2,6,6-tetramethyl piperidine 1-oxyl (TEMPOL) from 4-hydroxy-2,2,6,6-tetramethylpiperidine (HTMP) in Ti[O.sub.2] photocatalytic system is examined on the basis of the changes of the formation rate with various additives. The experimental observations have indicated that the direct photocatalytic oxidation of HTMP followed by reaction with [O.sub.2] is the dominant process in the formation of TEMPOL radicals and the electrochemical measurements have shown that HTMP is oxidized at 0.7 V.

Industrial Organic Chemicals, Cyclic Crude and Intermediate Manufacturing, Heterocyclics NEC, Analysis, Oxidation-reduction reaction, Oxidation-reduction reactions, Heterocyclic aromatic compounds, Amines

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Direct detection of OH radicals diffused to the gas phase from the UV-irradiated photocatalytic Ti[O.sub.2] surfaces by means of laser-induced fluorescence spectroscopy

Article Abstract:

The laser-induced fluorescence (LIF) technique is used in the in situ detection of OH radicals diffused in the gas phase from the photocatalytic titanium dioxide (Ti[O.sub.2]) surfaces. The appearance of OD-LIF intensities after the exposure of [D.sub.2]O vapors over Ti[O.sub.2] powders and the decrease of the time-resolved signals of OH-LIF intensities with increased calcined temperatures of Ti[O.sub.2] powders have suggested that the exchangeable water at the Ti[O.sub.2] surface is the origin of the diffused OH radical.

Science & research, Research, Radicals (Chemistry)

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Adsorption and photocatalytic decomposition of amino acids in Ti[O.sub.2] photocatalytic systems

Article Abstract:

The adsorption and photodecomposition of amino acids on a Ti[O.sub.2] surface are examined by zeta potential measurements and [super 1]H NMR spectroscopy in Ti[O.sub.2] aqueous suspension systems. The calcined Ti[O.sub.2] without surface hydroxyl groups are used to verify the correlation of the surface hydroxyl groups with the photocatalysis of amino acids.

Usage, Observations, Nuclear magnetic resonance spectroscopy, Optical properties, Amino acids, Hydroxylation

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