The controllable nanostructure and photocatalytic behaviour of 5,10,15,20-tetra-(3,4,5 trimethoxyphenyl) porphyrin through solvophobic supramolecular self-assembly

Abstract

In this study, the self-assembly of 5,10,15,20-tetra(3,4,5-trimethoxyphenyl)porphyrin (coded as: TTOP) in the mixture of tetrahydrofuran (THF) and H2O and the photocatalytic activity of resulting self-assembled aggregates toward the degradation of organic compounds were investigated. TTOP were well dispersed as monomers in THF, however, they stacked into aggregates upon the addition of water (20-90 percent). Depending on the THF/H2O mixture various nanostructures were observed. Microrods with an average width of 0.62 plus or minus 0.22 mu m and length of 10.17 plus or minus 2.04 mu m and the sphere-like particles with diameters ranging from 0.5 to 1.2 mu m were obtained in 70 percent water in THF. Nonetheless, the particles disappeared and rods turned to slabs with same length but much larger width (4.48 plus or minus 2.27 mu m) as 80 percent water in THF was used. The particles with irregular shapes, which connected into large aggregates, were obtained at 90 percent water in THF. These structures exhibited significant difference in photocatalytic ability for the degradation of dye (rohdamine B, RhB and methylene blue, MB). The rate constants of RhB degradation were 4.35.10-4 min-1, 1.13.10-3 min-1, 2.63.10-3 min-1, and 3.52.10-3 min-1 for the porphyrin monomers in THF and its aggregates states obtained by mixing of 70 percent, 80 percent, and 90 percent water in THF, respectively. The results indicated the important role of solvent in the formation and control the structures of porphyrin aggregates, which are crucial to an effective porphyrin-based photocatalyst.