Solid quenching effects

State decarbonylation reaction in total synthesis was reported recently in the case of natnral prodnct (+)-herbetenolide, which farther illustrates the exquisite control that the solid state may exert on the chemical behavior of the otherwise highly promiscuous reactive intermediates. As word or caution, it should be mentioned that intramolecular quenching effects known to act in solution can also affect that reaction in the solid state. Recently reported examples include the well-known intramolecular P-phenyl and electron transfer quenching. ... 

In Figure 5, the normalized emission spectra of the two solid hybrid materials, GFP/SBA-15 and GFP/Aerosil , are reported. The shape of the emission profile for GFP/SBA-15 follows closely that of the GFP in buffer solution, whereas the photoemission intensity of GFP/Aerosil is one order of magnitude lower and slightly different in its tale shape (spectra at the actual intensities not reported). This reduction in intensity could be explained by a multilayer arrangement of the protein molecules on the amorphous nanoparticles, which would explain both the difference in emission spectra ("self-quenching effect") and the difference in adsorption amount shown above. 

The use of solid-phase micro-extraction (SPME) for the qualitative and quantitative determination of LAS in wastewater samples was investigated by Ceglarek et al. [7]. When examining the effect of salt addition on the extraction efficiency, NaCl, commonly used in SPME to improve extraction yields, turned out to be unsuitable because of the formation of [(NaCl) CiP clusters in the ESI-MS (prior to injection LAS was desorbed from the fibre by methanolAvater (50 50)), the formation of which were assumed to be responsible for the quantitative suppression of the LAS signals. These quenching effects were excluded when using ammonium acetate instead of NaCl. 

The PL quantum yield r)pl. While r]pl of many dyes is close to 100% in solution, in almost all cases that yields drops precipitously as the concentration of the dye increases. This well-known concentration quenching effect is due to the creation of nonradiative decay paths in concentrated solutions and in solid-state. These include nonradiative torsional quenching of the SE,148 fission of SEs to TEs in the case of rubrene (see Sec. 1.2 above), or dissociation of SEs to charge transfer excitons (CTEs), i.e., intermolecular polaron pairs, in most of the luminescent polymers and many small molecular films,20 24 29 32 or other nonradiative quenching of SEs by polarons or trapped charges.25,29 31 32 In view of these numerous nonradiative decay paths, the synthesis of films in which r]PL exceeds 20%, such as in some PPVs,149 exceeds 30%, as in some films of m-LPPP,85 and may be as high as 60%, as in diphenyl substituted polyacetylenes,95 96 is impressive. 

This behaviour is the total opposite of the concentration-quenching effect. Enhanced solid-state emission of a biphenylethene derivative 2... 

Steady-state and time-resolved studies of the excited properties of the [Ru(bpy)3] adsorbed on a variety of clay minerals have been carried out by some research groups in order to understand the adsorbed states of [Ru(bpy)3] more clearly (77-87). Habti et al. have reported nonexponential decay of the excited state of [Ru(bpy)3] adsorbed on a variety of clay minerals with different iron contents (78). From the effects of iron content on the decay profiles, they point out the quenching effect of the irons within the lattice of the minerals and the essentially immobile character of adsorbed [Ru(bpy)3] on the microsecond time scale. Each adsorbed probe ion is able to interact with a vCTy limited number of neighboring quencher ions around the adsorption sites. The total quenching probability for a particular probe is determined by the quencha- concentration in the solid and by the number of sohd particles in contact with the probe. They have also mentioned that the degree of swelling affects the quenching. 

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