Surface photochromism

SURFACE PHOTOCHROMISM FOR REGULATION OF LIQUID-CRYSTAL ALIGNMENT... 

Introduction of photochemistry is particularly interesting since it enables us to acquire high density and fast accessible optical memories as well as new sights on molecular interactions in the LC phase. Here, photochemical approadies to regulate the LC orientation are briefly reviewed. Afterwards, our new findings on precise 3D control of the LC orientation by anisotropic surface photochromism will be introduced. 

Baranov A V, Bobovich Y S and Petrov V I 1993 Surface-enhanced resonance hyper-Raman (SERHR) spectroscopy of photochromic molecules J. Raman Spectrosc. 24 695-7... 

The color development of photochromic compounds can also be utili2ed as a diagnostic tool. The temperature dependence of the fa ding of 6-nitroindolinospiropyran served as the basis for a nondestmctive inspection technique for honeycomb aerospace stmctures (43). One surface of the stmcture to be exarnined was covered with a paint containing the photochromic compound and activated to a violet color with ultraviolet light. The other side of the stmcture was then heated. The transfer of heat through the honeycomb stmcture caused bleaching of the temperature-dependent photochromic compound. Defects in the honeycomb where heat transfer was inhibited could be detected as darker areas. 

Hellmann, J., Hamano, M., Karthaus, O., Ijiro, K., Shimomura, M. and Irie, M. (1998) Aggregation of dendrimers with a photochromic dithienylethene core group on the mica surface - atomic force microscopic imaging. Jpn. J. Appl. Phys., 37, L816-L819. 

M., Horiuchi, S., Tanaka, N., Tanigaki, N. and Hiraga, T. (2003) Addition of functional characteristics of organic photochromic dye to nano-structures by selective doping on a polymer surface. Jpn. J. Appl. Phys., 42, L983-L985. 

The present technique enables light-induced redox reaction UV light-induced oxidative dissolution and visible light-induced reductive deposition of silver nanoparticles. Reversible control of the particle size is therefore possible in principle. The reversible redox process can be applied to surface patterning and a photoelectrochemical actuator, besides the multicolor photochromism. 

The present photoelectrochemical deposition/dissolution method is applicable to reversible control of the particle size. A typical application taking advantage of the method is the multicolor photochromism. Additional applications include surface patterning and photoelectrochemical actuator. The patterning is possible by using a thiol-modified silver... 

When the initial concentration of the merocyanine form is lower than the CMC of the spiropyran form, the change in surface tension is gradual all through the progression of photoreaction. The value of Ajjq/Acqq remains constant during photoirradiation. Unfortunately, reversibility of this photochromism is poor and the micelle formation/dissociation cycle deteriorates rapidly. 

This investigation aims for the first time at the stabilization of photoisomers of photochromic dye molecules in molecular sieves by modification of the MCM-41 surface and covalent bonding of dye molecules. Diphenyldichlorosilane is utilized for pre-silylation to warrant an anchoring of the dyes exclusively inside the MCM-41 channel structure. 

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