| Laser beams have been widely used in many areas of laboratory experiments, industry, medicine and military. Despite the great contributions they brought to our society, they have also brought a potential hazard for human eyes and optical sensors. So there is significant interest for the development of "optical limiter", which strongly attenuates intense optical beams while exhibiting high transmittance for low-intensity ambient light levels, and therefore protects human eyes and optical sensors from intense laser pulses. The lack of appreciate nonlinear materials has been a significant barrier in the development of such devices.Metallophalocyanines(MPcs) are a kind of centrosymmetric planar organo-metallic molecules with an extensively delocalized two dimensional conjugated π-electron system which show a relatively large third order optical nonlmearity, varying upon central metal atom substitution and other factors. Other interesting properties of this molecule and many of its derivative products are their versatility, architectural flexibility and high environmental stability, which are very important requirements to implement photo-electronic applications. An important issue to be addressed for the successful application of MPc in optical area where will find interesting application is represented by their incorporation in a matrix to fabricate a solid state system. One of the practicing methods is sol-gel technique, which has been widely used to incorporate a variety of organic and organo-metallic molecules in inorganic host.This paper reports the successful preparation of MPc molecules doped silica gel glass composites obtained by sol-gel technique. The composites are transparent and homogeneous with required optical quality. The problem of doped MPc's dimerization is discussed and different kinds of solving methods are presented. The relationship between the composites' matrix and dopant component, structure and optical properties is studied. A series of important conclusions and creative achievements are obtained.Using pore structure measurement technique, the changes of pore structure of silica gel glass matrix under different sol-gel processing conditions are studied. It is found that changing of catalyst and solvent will influence the relatively reaction velocity of hydrolysis and polycondensation and therefore change the pore structure of resulted silica gel glass matrix. As the result, the ideal prescription for silica gel glass matrix is proposed. The ratio of tetraethyloxysilane (TEOS): ethanol: distilled water is 1: 3: 4. N-N' dimethyl formamide(DMF) was used as solvent and drying control chemical additive (DCCA) in a proportion of 0.3 DMF/ ethanol volume ratio. Drops of HF/HC1 mixture acid was added to promote hydrolysis (pH = 2). The so made silica gel glass has quasi-inkbottle shape and median pore size distribution of 5-8nm which is suitable for the doping and protection of MPc molecules.MPc molecules in matrix always have a strong tendency to dimerization that can badly affect the linear absorption spectrum, causing quench of dye fluorescence and change the yield of photochemical processes. It is a vital problem that worth more attention. If dye doped solid-state optical devices are ever to become practical, the issue of dimer formation must be resolved. Using UV/Vis absorption spectra, dimerization of different molecular structured MPcs is tracked along sol-gel process and co-related with the change of micro-environment in which doped MPc molecules existed. It is found that dimerization of doped MPc molecules is mainly affected by three factors. One is the structure characteristic of MPc molecule. The other is the change of chemical environment, including the decrease of ethanol /water ratio and quantity of remaining solvent, which promotes dimerization. The third is the formation of crosslinked silica network and micropores which can protect MPc molecules from colliding with each other and therefore suppress dimerization. In order to prepare composites with the least dimerizatio... |
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