Fluorescent porphyrins trapped in monolithic SiO2 gels

Thermo-Stability of Natural Products Based on Chlorophyll Species Embedded in Silica Xerogel

“…This result contrasts with the case of barley leaves, embedded in silica matrix, where a blue shift of 10 nm of the red emission peak was observed, when aging time was of 12 months [2]. This blue shift also was observed in samples of ortho-amino-substituted porphyrin H 2 T(o-NH 2 )PP, embedded in SiO 2 matrix [11]. This work reports biostability and thermostability of green leaves extract embedded in a silica matrix prepared by sol-gel method.…”

“…Thus, at this temperature, the sample presents a fraction of decomposition of the chlorophyll a in the PSII photosystem. Mainly, takes place a primary conversion of the chlorophyll in proteins as phaeophytene [11] [13].…”

Structural Comportment of Extract of <i>Bougainvillea xbuttiana</i> Flower Incorporated in Silica Xerogel Matrix

“…In particular for the PSII the chlorophyll variation indicate denaturation of these species, mainly, the primary conversion of chlorophyll to protein species, as phaeophytene [12] [21].…”

Fluorescent tetraruthenated porphyrins embedded in monolithic SiO2 gels by the sol–gel process

“…In this work, however, the gel-embedded tetraruthenated porphyrins present detectable fluorescence when excited in the LF band of [Ru II (bipy) 2 Cl + ] fragments, showing that the π * emitting state of the porphyrin center can be pumped either from a direct excitation, or by an intramolecular mechanism involving the peripheral [Ru II (bipy) 2 Cl + ] groups [2]. This is an important finding since fluorescence suppression upon incorporation into sol-gel matrices for porphyrins have been described as a result of the tight environment around the porphyrin and to the different polarity of the environment in the silane network [12]. For instance, this is particularly undesirable when the hybrid material is designed for photodynamic therapy.…”

“…However, some drawbacks found in this field are related to the low solubility of many porphyrins in polar solvents such as water and alcohols, which precludes their incorporation into silica gels [11]. This problem has been overcome by the attachment of chemical substituents such as -OH and -NH 2 in the peripheral groups of the macrocycles [12]. In other cases, porphyrin aggregation, fluorescence suppression upon aging, and demetallation of metallated porphyrins under acidic conditions of the sol-gel procedure were described, making necessary the choice of a suitable solvent mixture to solve these problems [13].…”