Comparative Study of the Optical and Textural Properties of Tetrapyrrole Macrocycles Trapped Within ZrO2, TiO2, and SiO2 Translucent Xerogels

Abstract

Abstract:The entrapping of physicochemical active molecules inside mesoporous networks is an appealing field of research due to the myriad of potential applications in optics, photocatalysis, chemical sensing, and medicine. One of the most important reasons for this success is the possibility of optimizing the properties that a free active species displays in solution but now trapped inside a solid substrate. Additionally it is possible to modulate the textural characteristics of substrates, such as pore size, specific surface area, polarity and chemical affinity of the surface, toward the physical or chemical adhesion of a variety of adsorbates. In the present document, two kinds of non-silicon metal alkoxides, Zr and Ti, are employed to prepare xerogels containing entrapped tetrapyrrolic species that could be inserted beforehand in analogue silica systems. The main goal is to develop efficient methods for trapping or binding tetrapyrrole macrocycles inside TiO2 and ZrO2 xerogels, while comparing the properties of these systems against those of the SiO2 analogues. Once the optimal synthesis conditions for obtaining translucent monolithic xerogels of ZrO2 and TiO2 networks were determined, it was confirmed that these substrates allowed the entrapment, in monomeric form, of macrocycles that commonly appear as aggregates within the SiO2 OPEN ACCESSMolecules 2015, 20 19464 network. From these experiments, it could be determined that the average pore diameters, specific surface areas, and water sorption capacities depicted by each one of these substrates, are a consequence of their own nature combined with the particular structure of the entrapped tetrapyrrole macrocycle. Furthermore, the establishment of covalent bonds between the intruding species and the pore walls leads to the obtainment of very similar pore sizes in the three different metal oxide (Ti, Zr, and Si) substrates as a consequence of the templating effect of the encapsulated species.

Chlorophyll a Covalently Bonded to Organo-Modified Translucent Silica Xerogels: Optimizing Fluorescence and Maximum Loading

“…In both sets of samples, the allyl or phenyl groups substituted the surface Si-OH groups and reduced their populations in the final xerogels. As was previously demonstrated, the rehydration process induces an evident NIR band pathway and intensities changes which help understanding the polar or non polar nature of the network [42]. The intensities of the peaks related to Si-OH groups interacting with physisorbed water and which appear at around 1428, 1900, and 2200 nm, suggest that, in the samples functionalized with allyl groups, these species have no great effect over water retention and rehydration processes, but there exists an important effect related to chlorophyll a concentration (Figure 6a).…”

Controllable Preparation of Monodisperse Mesoporous Silica from Microspheres to Microcapsules and Catalytic Loading of Au Nanoparticles

“…The development of advanced functional nanomaterials with size-controlled, structure-controlled nanopores remains one of the most vital fields in nanomaterials research. , More particularly, spherical mesoporous materials have attracted much attention due to their unique spherical shape, which shows the closed filling property and lowest surface energy . Among them, monodisperse spherical mesoporous silica materials (including hollow mesoporous microcapsule) have garnered intensive attention because of their distinctive advantages, such as, large specific surface area, controllable pore size, well-defined surface properties for modification, good carriers, and good biocompatibility, which grant them enormous potential in the fields of adsorption, catalysis, supports, , drug delivery, and sensor …”

“…1,2 More particularly, spherical mesoporous materials have attracted much attention due to their unique spherical shape, which shows the closed filling property and lowest surface energy. 3 Among them, monodisperse spherical mesoporous silica materials (including hollow mesoporous microcapsule) have garnered intensive attention because of their distinctive advantages, such as, large specific surface area, 4 controllable pore size, 5 well-defined surface properties for modification, 6 good carriers, 7 and good biocompatibility, 8 which grant them enormous potential in the fields of adsorption, 9 catalysis, supports, 10,11 drug delivery, 12 and sensor. 13 To date, it is a great challenge to design monodisperse mesoporous silica microspheres (M-MSMs) by a flexible and efficient method.…”

Characterization and Computation of Yb/TiO2 and Its Photocatalytic Degradation with Benzohydroxamic Acid

“…TiO 2 is considered to be one of the most promising and widely used semiconductor photocatalyst materials, primarily due to its chemical stability, unique optical properties, nontoxicity, strong oxidizing power, and low cost [ 1 ]. However, the largest obstacles to its use are the wide band gap (3.2 eV) and the easy recombination of photogenerated electron-hole pairs, which limit the use of solar light and reduce photon efficiency [ 2 ]. Therefore, improvement of photocatalytic activity has been a core topic in photocatalysis research field in recent years.…”