1988 Volume 36 Issue 8 Pages 2742-2749
The effect of concentration of sodium dodecyl sulfate (SDS) on the efficiency of photooxidation of methyl orange (MO) sensitized with tetraphenylporphyrin (TPP) in SDS aqueous solution was investigated. Below the critical micelle concentration of SDS-TPP mixed solution (cmcmix), TPP was solubilized as an oligomer complex composed of one or plural TPP molecules and plural SDS ones; only the oligomer complex composed of one TPP molecule and plural SDS ones (TPPm-SDSs complex) among the oligomer complexes contributed to the efficient photooxidation of MO. Above the cmcmix, however, the reaction efficiency decreased with increase in the SDS concentration. Above the cmcmix, all the TPP molecules were not always solubilized without aggregating among themselves in the micellar phase and some of the TPP molecules were solubilized as TPPm-SDSs complexes in the aqueous phase. With increase in the SDS concentration, the TPPm-SDSs complexes were absorbed into the micelle and TPP monomer was increased in the micellar phase, where TPP had a lower reaction efficiency than TPP solubilized as a TPPm-SDSs complex due to the less polar environment in the micellar phase. Thus, above the cmcmix, the diminution of the reaction efficiency with increasing SDS concentration could be ascribed to the decrease in the amount of TPP monomer solubilized as a TPPm-SDSs complex.
