Assessment of photosensitization performance and stability of host-guest MCM-41 composites from the direct observation of singlet oxygen formation and properties

Abstract

New heterogeneous porous materials based on 5,10,15,20-(tetraphenyl)porphyrin (H2TPP), 5,10,15,20-(tetra-N-methyl-4-pyridyl)porphyrin tetrachloride (H2TNMPyP), zinc(II) 5,10,15,20-(tetra-N-methyl-4-pyridyl)porphyrin tetrachloride (ZnTNMPyP), 5,10,15,20-(tetra-4-carboxyphenyl)porphyrin (H2TCPP) and zinc(II)5,10,15,20-(tetra-4-carboxyphenyl)porphyrin (ZnTCPP) have been incorporated into mesoporous silica MCM-41 from slow diffusion of solutions containing different concentrations of porphyrin chromophores. Successful incorporation of all porphyrins has been confirmed by UV-Vis spectroscopy and TGA. XRD patterns of these silica-based host-guest samples prove that the mesoporous structure of MCM-41 remains unchanged after encapsulation. The potential abilities of these photosensitizers to form singlet oxygen (1O[Formula: see text] at the solid state/air interface after light excitation were investigated. Despite the variable amount of encapsulated porphyrin derivatives (based on UV-vis assessment and chemical analysis), the phosphorescence intensity of 1O2 peak at 1270 nm remains relatively the same from one composite to the other meaning that the photosensitizers are mainly placed at the surface of the MCM-41 particles.