UV illumination

When a question exists about whether the carving is ancient, an examination under uv illumination can be very helpful. For example, an aged marble surface exhibits, under a properly filtered mercury lamp, a mellow, brownish fluorescence, whereas a fresh surface, under the same conditions, appears purple. It is not uncommon that old carvings have been sharpened this is detectable with the microscope and under uv examination. 

PMMA-impregnated sol—gel-derived siUca gels have also been examined (54). Long-wave uv illumination was employed in addition to benzoyl peroxide for PMMA polymerization. This method prohibited the degradation of the siUca xerogel from moisture adsorption and desorption. Overall the material behaved more like bulk PMMA than bulk siUca, with the exception of hardness. 

The UV illumination of carefully selected solutions of 10 M Pu(IV) in 0.5 HClOb significantly increased the disproportionation rate and shifted the equilibrium in favor of Pu3, Pu022+, and acid. Those effects are shown in Fig. 2. 

Rajeshwar and co-workers performed photocatalytic underpotential deposition of Cd and Pb onto the surface of Se-modified Ti02 particles to prepare CdSe/Ti02 and PbSe/Ti02 composites [97, 98]. The Se-modified Ti02 particles were prepared themselves by UV illumination of titania particles in a Se(fV)-containing aqueous solution. The photocatalytic UPD of Cd and Pb on the bare Ti02 surface was found... 

The near-UV illuminated titanium dioxide (anatase) powder flow reactor, as well as the gas chromatographic methods for analysis of effluents, has been described in detail earlier [2]. The procedvu-es followed were substantially those of Luo and OUis [1], and Sauer et al. [2]. 

Hydrogen is readily formed in the near UV illumination of sols or suspensions of platinized TiO containing a sacrificial electron donor Figure 27 shows the... 

For the DRIFTS study, the Nafion-Ti02 slurries were sonicated for 2 hours, dried at ambient conditions for 5 hr, and ground with a pestle and mortar until a fine powder catalyst was formed. 30 mg of the resulting catalysts were placed on top of 80 mg of inert CaF2 powder (325 mesh, Alfa Aesar) in a DRIFTS cell s sample holder. The sample holder was enclosed by a dome with two IR transparent ZnSe windows and a third CaF2 window for UV illumination. For the ATR study, the Nafion-Ti02 slurries, which were sonicated for two hours, were cast directly on the surface of the ATR ZnSe crystal to form a continuous solid film. The films were enclosed with a stainless steel cover equipped with a CaF2 window for UV illumination. 

Figure 52.1. Single beam IR spectra of the Pl/Ti02 catalyst on the DRIFT cell before and after introducing ethanol, and during UV illumination.

Figure 52.2. Difference spectra of the Pt/Ti02 catalyst on the DRIFTS cell during UV illumination.

Figure 52.5. Difference spectra of a 1 1 Nafion Ti02 weight ratio catalyst on the DRIFTS cell during UV illumination. Difference spectra was obtained by subtracting the spectram at 0 min (i.e., before the reaction starts) from the subsequent spectra.

Some other studies showed that the combination of the three polymorphs with reduced crystallite size and high surface area can lead to the best photocatalysts for 4-chlorophenol degradation [37], or that particles in the dimension range 25-40 nm give the best performances [38]. Therefore, many elements contribute to the final photocatalytic activity and sometimes the increased contribution of one parameter can compensate for the decrease of another one. For example, better photocatalytic activity can be obtained even if the surface area decreases, with a concomitant increase in the crystallinity of the sample, which finally results in a higher number of electron-hole pairs formed on the surface by UV illumination and in their increased lifetime (slower recombination) [39]. Better crystallinity can be obtained with the use of ionic liquids during the synthesis [39], with a consequent increase of activity. 

HYDROZONE [Hydrogen peroxide ozone] A process for destroying organic wastes in aqueous streams by oxidation with a combination of hydrogen peroxide, ozone, and UV illumination. Developed by EA Technology, Chester, UK, in the 1980s. See also Ultrox. 

P. Pichat, M.N. Mozzanega, J. Disdier, J.M. Herrmann, Room temperature hydrogen production from aliphatic alcohols uv-illuminated Pt/Ti02 catalysts, Int.J. Hydrogen Energy 9 (1984) 397-403. 

Figure 5. Thermally stimulated current of poly-N-vinylcarbazole showing clear peak at 5°C. Peaks increase with the increase of UV illumination of the total light of the Hg lamp of Figure 3, at —150°C in vacuo 5—40 min. Collecting voltage 30V (Au +) heating rate 3.3°C/min. Films were cleaned prior to the measurement.

Fig. 9.21 In vivo images of MWCNTs-QDs (0.5 tg ml-1 in PBS) in mice injected at different body regions a) MWCNTs attached with CdSe/Zns quantum dots (emission of 600 nm) at middorsal location b) MWCNTs attached with CdSe/ZnS quantum dots at ventrolateral locations, the suspensions were diluted by PBS at various concentrations as indicated (A through E) c) MWCNTs attached with InGaP/ZnS quantum dots (emission of 680 nm, 0.25 jj,g ml-1 in PBS) in liver, kidney, and leg muscles. All images were taken successfully in 2 min under epi-UV illuminator with excitation of 435nm. (Shi et al. 2007). Published with permission from Wiley-VCH see Color Plates)...

Ghko, Y., Tryk, D.A., Hashimoto, K., and Fujishima, A. Autoxidation of acetaldehyde initiated by TiG2 photocatalysis under weak UV illumination, J. Phys. Chem. B, 102(15) 2699-2704, 1998. 

Equipment PCR machine, scintillation counter, tabletop centrifuge, temperature-controlled water baths, equipment for horizontal and vertical electrophoresis, UV-illuminator, phosphor imager, automatic DNA sequencer, vacuum dot-blot manifold (Schleicher and Schuell). PCR 0.5 ml hot-start mbes, aerosol resistant pipette rips, autoclaved Eppendorf tubes (all from Fischer Scientific, Brightwaters, NY) and glassware, diethyl pyrocarbonate (DEPC, Sigma)-treated solutions. 

Fig. 3.23 Efficiency under near UV illumination of a photoelectrochemical cell comprised of a titania nanotube array photoanode and Pt counter electrode. For the calculation of efficiency using equation (3.6.13), a two electrode geometry was used while for the calculation using equations (3.6.15a) and (3.6.16), a three electrode geometry was used.

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