Fluorescent porphyrins covalently bound to silica xerogel matrices

Chemical‐Bonding Assembly, Physical Characterization, and Photophysical Properties of Lanthanide Hybrids from a Functional Thiazole Bridge

“…From free ligand L1 (Figure 1a), the double peaks at 3384 (ν as-NH 2 ) and 3275 cm -1 (ν s-NH 2 ) are the unique vibrations of the NH 2 group. In Figure 1b, clear and strong evidence of nucleophilic attack of the amino group of the ligand over the isocyanate group (-N=C=O of the TESPIC molecule) is that the bands at 2268 and 859 cm -1 assigned to the normal and deformation vibrations of the isocyanate group disappear after a reaction time of 18 h. [23] At the same time, the band at 1667 cm -1 can be assigned to the C=O groups; this is proof of the formation of a -CONH group, which bonds the ligand to the propyl group of TESPIC. Additionally, two adjacent peaks at 2933 and 2882 cm -1 in Figure 1b are ν as (CH 2 ) and ν s (CH 2 ) of the three methylene groups of TESPIC.…”

Homogeneous and Heterogeneous Free-Based Porphyrins Incorporated to Silica Gel as Fluorescent Materials and Visible Light Catalysts Mimic Monooxygenases

“…Such results may be also interpreted in terms of the earlier described spectral investigations, which revealed the contrasting capabilities of HmP-IX and H 2 OEP aggregation in both the sol solution and sol-gel matrix, as well as differences in the formation of H-and J-type agglomerates in xerogel. Since the HmP in silica preserves the fluorescence, we can not preclude the formation of -CO-O-Si ester bridges with the siloxane network by HmP, because according to the other authors the covalent bond between the porphyrin molecules and the silica walls in the interior pores of the gel diminish the interaction of porphyrin molecules with silanol groups (Si-OH) and then the possibility of non-radiating decay of the fluorescent process of porphyrins (Garcia-Sanchez et al, 2009). Thus, the significant drop of the photocatalytic activity of the HmP-IX in silica may be attributed to its chemical binding with SiO 2 , probably hindering the undergoing intersystem passing from the singlet excited state of porphyrin to its triplet state, which is an important criterion for a photosensitizer and photochemical activation of dioxygen.…”

“…For HmP-IX porphyrine the intensity of the bands 345 and 425 nm is similar, which means that the concentrations of H-and J-aggregates are Textural characteristics of silica xerogel based on N 2 adsorption revealed the microporous character of adsorbent, however, apart from the micro-, the meso-and macropores were present in the silica structure with the pore size diameter: 17-3000 Å; therefore the accommodation of J-and H-dimers of porphyrines inside the gel structure is possible without steric obstacles. It must be emphasized that besides optical applications, the silica materials should have very small pore sizes and if the functionalized porphyrin systems are used as biocatalysts or chemical sensors, the passage of reagents and products in and out of the pores becomes really important (Garcia-Sanchez et al, 2009). Control of many operational factors involved in the hydrolysis and condensation during the sol-gel process is essential for achieving a proper balance between non-leaching of the entrapped bioactive porphyrins and their accessibility to the reagents.…”

Glucose biosensor based on covalent immobilization of enzyme in sol–gel composite film combined with Prussian blue/carbon nanotubes hybrid

“…As a particular silane coupling agent, 3-isocyanatopropyltriethoxysilane (ICPTES) has attracted increasing * Corresponding author. interest in the synthesis of SiO 2 -based organic-inorganic hybrid materials with polymers, such as CS (Biazzotto et al, 2000;Silva et al, 2005;Garcia-Sanchez et al, 2009;Kumbar et al, 2010). The good covalent coupling reactivity of the isocyanate group toward the amino group without severe conditions and the spontaneous sol-gel process of the triethoxysilane group allow the convenient preparation of covalently cross-linked organic-inorganic hybrid materials (Li et al, 2009).…”