Control mechanisms, luminescence

Xu, L. Lu, C. Zhang, Z. Yang, X. Hou, W. (2010). Various self-assembled three-dimensional hierarchical architectures of La2(Mo04)3 controlled synthesis, growth mechanisms, luminescence properties and adsorption activities. Nanoscale, 2., (May 2010) 995-1005, ISSN 2040-3364. 

Most of the luminescent systems mentioned appear to be. under some nerve control. Normally, a luminous flash is observed after mechanical or electrical stimulation of most of the aforementioned species. A number of these also exhibit a diurnal rhythm of luminescence. 

Abstract We describe mechanochromic and thermochromic photoluminescent liquid crystals. In particular, mechanochromic photoluminescent liquid crystals found recently, which are new stimuli-responsive materials are reported. For example, photoluminescent liquid crystals having bulky dendritic moieties with long alkyl chains change their photoluminescent colors by mechanical stimuli associated with isothermal phase transitions. The photoluminescent properties of molecular assemblies depend on their assembled structures. Therefore, controlling the structures of molecular assemblies with external stimuli leads to the development of stimuli-responsive luminescent materials. Mechanochromic photoluminescent properties are also observed for a photoluminescent metallomesogen and a liquid-crystalline polymer. We also show thermochromic photoluminescent liquid crystals based on origo-(/ -phenylenevinylene) and anthracene moieties and a thermochromic photoluminescent metallocomplex. 

A new probe of solvent accessibility of bound sensitizers has been described and tested for the particular case of a series of Ru" and Os photosensitizers bound to sodium lauryl sulphate micelles. The method depends upon the large solvent deuterium effect on excited-state lifetimes, and a correlation has been established between accessibility of bound complexes and hydrophobicity of the ligands. Luminescence properties of amphiphilic annelide-type complexes of ruthenium in micellar phases have been described. In the case of [4,4 -bis(nonadecyl)-2,2 -bipyridyl]bis-[4,4 -di-(10,13,16-trioxaundecyl)-2,2 -bipyridyl]ruthenium dichloride, intramicellar self-quenching effects have an influence on the excited-state lifetime, and the mechanism of self-quenching has been determined. Deactivation of [Ru(bipy)3] by [Co(EDTA)] has been studied in a micellar environment and found to occur by electron transfer at diffusion-controlled rates a stereoselective effect has been observed. ... 

The mechanism of reversible triplet-triplet energy transfer is used in a lightharvesting array constructed around a the Ru(bpy)3 " core and bearing one or three pyrenyl units in the periphery (27) [192], UV excitation of these systems yields a strong visible MLCT-based emission, with a lifetime of 2.9 and 9.0 ps respectively for the mono- and the tris-pyrene system. The equilibrium constant between the MLCT and the pyrene triplet, and therefore the triplet lifetimes, are modulated by the fractional contribution of each individual triplet molecule involved in the equilibrium. This approach allows for a synthetic control of the luminescence lifetime by simply changing the number of pyrenyl units. 

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