Fabrication and photophysical studies of phenosafranine and proflavine dyes encapsulated in mesoporous MCM-41 along with titanium dioxide nanoparticles

Photochemistry and Photophysics in Silica-Based Materials: Ultrafast and Single Molecule Spectroscopy Observation

“…When this dye is trapped within NaY and ZSM-5 supercages, its fluorescence decays are biexponential, with time constants of 0.48 and 1.42 ns (PHNS/NaY) and 0.13 and 0.55 ns (PHNS/ZSM-5), which are similar to those observed when silica nanoparticles were used, reflecting that this molecule mostly interacts with the zeolite surface . In both complexes, the presence of TiO 2 NPs causes a static emission quenching that is proportional to the TiO 2 concentration in the host. , When TiO 2 NPs are in MCM41 material, they also enable an EI process from the S 1 state of PHNS to the CB of the semiconductor . However, the ET reaction is more efficient in the MCM41-based complexes than in the zeolite-based ones since the encapsulation of the dye inside of the larger MCM41 pore allows greater contact with the TiO 2 NPs, thus producing faster EI processes. , Similar studies were reported for other dyes such as PF, Th + (Scheme ), and methylene blue (MB) (Scheme ) interacting with ZSM-5 and NaY zeolites and MCM41 materials. ,− The results show that the photophysical properties of these dyes are affected by the morphology and the composition of the host materials and the presence or absence of TiO 2 NPs. ,− In SBMs, the fluorescence of these molecules decay biexponentially; the short component is attributed to the molecules that exhibit strong interactions with the silica host, and the long one is due to molecules whose environment is similar to the solution. , The introduction of TiO 2 NPs inside these hosts produces a decrease in the fluorescence intensity attributed to the photosensitization of TiO 2 by caged dye molecules through the EI process. , …”

“…Some molecules can be protonated when they are encapsulated in SBMs. − The guest forms one or more cationic species depending on the available proton-acceptor groups and the acidity of the encapsulating material. − In these systems, intermolecular H-bonds may stabilize the encapsulated guest and increase its fluorescence lifetime.…”

“…The photosensitization of TiO 2 in cages or micro- and mesoporous materials has been used as a strategy for the formation of ET complexes. Several studies of the photophysical properties of PHNS (Scheme ) adsorbed on different zeolites and mesoporous materials that were photosensitized with TiO 2 NPs have been published. ,,− PHNS is an azine derivative that can behave as an electron A and D in both the ground and excited states, which makes it an important molecule in the field of ET. When this dye is trapped within NaY and ZSM-5 supercages, its fluorescence decays are biexponential, with time constants of 0.48 and 1.42 ns (PHNS/NaY) and 0.13 and 0.55 ns (PHNS/ZSM-5), which are similar to those observed when silica nanoparticles were used, reflecting that this molecule mostly interacts with the zeolite surface .…”

“…365,366 When TiO 2 NPs are in MCM41 material, they also enable an EI process from the S 1 state of PHNS to the CB of the semiconductor. 230 However, the ET reaction is more efficient in the MCM41-based complexes than in the zeolite-based ones since the encapsulation of the dye inside of the larger MCM41 pore allows greater contact with the TiO 2 NPs, thus producing faster EI processes. 230,366 Similar studies were reported for other dyes such as PF, Th + (Scheme 2), and methylene blue (MB) (Scheme 4) interacting with ZSM-5 and NaY zeolites and MCM41 materials.…”

Effectively CO 2 photoreduction to CH 4 by the synergistic effects of Ca and Ti on Ca-loaded TiSiMCM-41 mesoporous photocatalytic systems

“…TiO 2 -based nanomaterials, which are generally obtained by sol-gel, hydrothermal, and solvothermal methods, have a large BET surface area and strong adsorption ability, and are one of the most intensively studied and widely used [3][4][5][6]. These materials also have several advantages including higher oxidation potential, relatively inexpensive, abundance, non-toxicity, and chemically/thermally stable.…”