Photophysical Properties of [60]Fullerenes and Phthalocyanines Embedded in Ordered Mesoporous Silica Films Annealed at Various Temperatures

Abstract

The photophysical properties of fullerene and/or phthalocyanine dyes embedded in ordered mesoporous silica films and the influence of annealing temperature on the nature of the immobilized dye molecules has been investigated using photoluminescence (PL) and diffuse reflectance (DR) studies. The PL and DR studies show that fullerene (C60) and/or zinc phthalocyanine (ZnPc) molecules incorporated into transparent mesoporous silica films, via either sol-gel or grafting routes, exist predominantly in monomeric form. Careful choice of annealing temperature, between 25 and 225 degrees C, can further enhance monomeric dispersion. For C60-containing films, monomeric dispersion of fullerene was observed for annealing temperatures up to 175 degrees C for sol-gel derived films and 225 degrees C for grafted films. Both sol-gel and grafted ZnPc-containing films showed evidence of monodispersed phthalocyanine for annealing temperatures up to 225 degrees C. In general, annealing temperatures in the range 125-175 degrees C were found to yield optimal monodispersion of the dye molecules. When both C60 and ZnPc were incorporated into the silica films, no evidence of interaction between the dyes, i.e., charge-transfer transitions or the formation of fullerene/phthalocyanine charge-transfer complexes, was observed. This suggests that embedded fullerene and phthalocyanine molecules may be used for the preparation of solid-state optical limiters, based on reverse saturable absorption, where monomeric dispersion of the dye molecules is important.

Silica‐Based Mesoporous Organic–Inorganic Hybrid Materials

“…In a similar vein, but at significantly lower temperatures, Subbiah und Mokaya78 were able to insert fullerenes and zinc phthalocyanines into the channel system of mesoporous MCM‐41‐like silica films, either individually or both species together. In this case, the guest molecules were also well separated.…”

Multifunctional Nano‐Bioprobes Based on Rattle‐Structured Upconverting Luminescent Nanoparticles

“…From UV/Vis absorption spectra, amajority of monomers located at 669 nm and am inority of dimers at 611 nm were observed for ZnPc-COOH in DMF (Figure 4a). [9] In aqueous solution, ZnPc-COOH is apt to self-aggregate to form dimers or oligomers,resulting in aremarkable broadening and blueshift in the absorption. [9] Dimers or oligomers were dominant when ZnPc-COOH was loaded in UCNP@RS while more than half of monomers were maintained in UCNP@ROS-ZnPc-COOH, indicating the inhibition of ZnPc-COOH selfaggregation by organosilica framework owing to hydrophobic interactions and p-p overlapping.T he organosilica also provide as trong adsorption on ZnPc-COOH.…”

Multifunctional Nano‐Bioprobes Based on Rattle‐Structured Upconverting Luminescent Nanoparticles

“…From UV/Vis absorption spectra, a majority of monomers located at 669 nm and a minority of dimers at 611 nm were observed for ZnPc‐COOH in DMF (Figure 4 a). 9 In aqueous solution, ZnPc‐COOH is apt to self‐aggregate to form dimers or oligomers, resulting in a remarkable broadening and blue‐shift in the absorption 9. Dimers or oligomers were dominant when ZnPc‐COOH was loaded in UCNP@RS while more than half of monomers were maintained in UCNP@ROS‐ZnPc‐COOH, indicating the inhibition of ZnPc‐COOH self‐aggregation by organosilica framework owing to hydrophobic interactions and π–π overlapping.…”