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International Journal of Photoenergy
Volume 4 (2002), Issue 4, Pages 161-171
http://dx.doi.org/10.1155/S1110662X02000193

Liquid and frozen multilayers of decanol in zeolites as microreactors for direct and oxygen mediated triplet-triplet annihilation of porphyrin

1Centro de Quimica Estrutural, Complexo 1, Instituto Superior Tecnico, Lisbon Codex 1096, Portugal
2Russian Academy of Sciences, Institute of Biochemical Physics, Ulitsa Kosygina 4, Moscow 119991, Russia

Copyright © 2002 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The kinetics of triplet state decay and concomitant delayed fluorescence of tetraphenylporphyrin (TPP) incorporated into the multilayers of n-decanol adsorbed on the external surface of zeolites at different temperatures were studied by the laser flash photolysis via monitoring the emission and diffuse-reflectance. In deoxygenated samples, the kinetics of diffusion-controlled bimolecular triplet-triplet annihilation (TTA) has been used to probe the multilayers. A very large local concentration of reactants may be obtained using small bulk amounts. A fast TTA rate constant demonstrated the triplet energy migration in TPP assemblies formed at the liquid/solid interface. The TTA in aerated samples is mediated by molecular oxygen leading to 1O2 feedback—induced delayed fluorescence. Singlet oxygen works as an efficient mobile energy carrier between TPP triplets. The parameters of both TTA may be modified by multilayer, which acts as microreactor with supramolecular organization. The freezing of n-decanol results in dramatic apparent acceleration of both direct and 1O2 mediated TTA due to the increase in local TPP concentration because of displacement of TPP molecules into the residual liquid domains in polycrystalline matrix. The concentration of TPP in those microreactors can be three orders of magnitude larger than the solubility limit in a particular neat liquid solvent demonstrating the unique features of solid solution, which seems to be due to the presence of crystal/liquid interfaces.