UV/visible light irradiations

The diarylethene containing imidazo[4,5-f][l,10]phenanthroline has been synthesized but no examples of metal complexes are reported yet [76]. These ligands are sensitive to both light (UV/visible light irradiation) and chemical stimuli (alkali/ acid treatment). A reversible four-state molecular switch has been realized by a single molecule. 

Dentures require accurate fit, reasonable chewing efficiency, and lifelike appearance (189). The chewing efficiency of artificial dentures is one-sixth that of natural dentition (190). AcryHc resins are generally used as powder/Hquid formulations for denture base, bone cement, and related appHcations. Polymerization is achieved thermally using initiators photochemicaHy using photoactive chemicals and either uv or visible light irradiation and at ambient temperatures using initiator/activator systems. 

Bare CuOx-supported nanostructures showed some activity in H 2 production from methanol-water mixture under UV-visible irradiation [180]. Ni is also used as a dopant, and small amounts (1 wt.%) of this element in mesoporous titania guarantee good activity in water-methanol mixtures under UV-visible light [181]. Indium-tantalum oxide Ni-doped materials also provided photocatalysts with promising efficiencies for direct water splitting [182]. TiOz nanotubes doped with Ir and Co nanopartides were effective for visible light water splitting even in the absence of... 

Zou Z, Ye J, Arakawa H (2003) Photocatalytic water splitting into H2 and or O2 under UV and visible light irradiation with a semiconductor catalyst. Int J Hydrogen Energy 28 663-669... 

To secure the efficiency of the one electron transfer, electron acceptors like 9,10-dicyanoanthracene (DCA) or quinones in conjunction with UV or visible light irradiation are commonly employed. Although photosensitized reactions are usually associated with a singlet excited state (equations 4 and 5), some processes of this type can occur thermally in the dark. 

Photoinduced Changes in Phase Boundary Potentials. The photoinduced membrane potentials were measured by using PVC matrix liquid membranes in contact with a polypyrrole-coated Pt electrode [dibutyl phthalate (DBP) as the membrane solvent]. The polypyrrole layer allows to obtain a stable and sample-in-dependent potential drop between Pt and the PVC membrane. The phase boundary potential at the interface of a membrane containing ionophore and an aqueous RbCl or KCl solution could be reversibly altered by UV and visible light irradiation, as shown for ionophore 89 in Figure 23a,b. The values of the photoinduced potential... 

Figure 23. Photoresponse of the EMF induced by UV and visible light irradiation for membrane 89 in contact with (a) 0.1 M aqueous RbCI and (b) 0.1 M aqueous KCI. Membrane composition DBP/PVC = 2 1 wl/wt containing 1 mM of 89.

Several TTF derivatives with photoresponsive moieties have been described in recent years with a view to studying the interplay of photochromic and electrochemical properties. Uchida, Irie, and coworkers have reported TTF derivatives with diarylethene moieties such as 14.24 The corresponding open- and closed-isomers of 14 can be reversibly interconverted by UV and visible light irradiations. The results show that the open- and closed-isomers of 14 show different electrochemical responses. 

However, unlike photosynthesis in green plants, the titanium oxide photocatalyst does not absorb visible light and, therefore, it can make use of only 3-4% of solar photons that reach the Earth. Therefore, to address such enormous tasks, photocatalytic systems which are able to operate effectively and efficiently not only under ultraviolet (UV) but also under sunlight must be established. To this end, it is vital to design and develop unique titanium oxide photocatalysts which can absorb and operate with high efficiency under solar and/or visible-light irradiation [9-16]. 

This chapter deals with the design and development of such unique second-generation titanium oxide photocatalysts which absorb UV-visible light and operate effectively under visible and/or solar irradiation by applying an advanced metal ion-implantation method. 

The incorporation of a cationic azobenzene derivative, p-( a> -dimethyl-ethanolammonioethoxyj-azobenzene bromide, into nanoporous silica films and the photochemical reactions of the adsorbed dye were investigated. The nanoporous silica films were prepared from tetramethoxysilane and octadecyltrimethyl-ammonium chloride by the rapid solvent evaporation method which we have reported previously. The adsorption of the cationic azo dye was conducted by casting an ethanol solution of the dye onto the nanoporous silica films. Upon UV light irradiation, trans-azobenzene isomerized photochemically to the c/s-form and photochemically formed c/ s-form turned back to the frans-form upon visible light irradiation. The nanoporous silica films were proved to be an excellent reaction media to immobilize organic photocromic species. 

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