Nanostructured Glasses Based on Hybrid Silica Materials Incorporating a New Asymmetrical Phenyl-Substituted Porphyrin

Abstract

The new asymmetrical, phenyl substituted porphyrin structure, namely: 5,10,15-tris(3-hydroxy-phenyl)-20- (3,4-dimethoxy-phenyl)-21H,23H-porphyrin, along with the nanostructured glasses and silica-based nanoparticles embedded with this compound were synthetized and characterized as to be designated for potential use in construction of advanced optoelectronic devices or electrochemical sensors. This porphyrin was synthesized by a multicomponent Adler- Longo type reaction using two different substituted aldehydes, and next characterized by HPLC, TLC, MS, UV-vis, fluorescence spectroscopy, AFM, 1 H-NMR and 13 C-NMR analysis. The observed changes in UV-vis and emission spectra were also discussed in terms of various pH conditions. The series of novel porphyrin-silica nanomaterials have been prepared by using silica matrices obtained in two variable sol-gel processes, i.e. via the one step acid- or two steps acid- base-catalyzed hydrolysis and condensation of tetraethylorthosilicate. Especially, the hybrid monolithic glass nanomaterials obtained here via the one step acid-sol-gel procedure exhibited a high intensity of the emission spectra bands and, besides, a very sharp bathochromic shift in the red region towards 723 nm, thus making also these nanoparticles as the valuable source of potential second generation photosensitizers. In the atomic force microscopy (AFM) measurements this hybrid nanomaterials displayed the spherical and highly monodispersed particles of ultra low size (less than 70 nm and with an average height of 20 nm), controlled shape, high porosity, and superior stability as the potential water-insoluble photosensitizers.