Site-Specific Anchoring of a Flavonol Dye into Zeolite β Nanoparticles

Abstract

Microporous zeolite nanoparticles have been used as a host for the confinement of 3-hydroxyflavone (3-OHF), leading to stable fluorescent colloids that may constitute a first step in the development of future biomarkers. Prior to the dye inclusion, the host physicochemical properties (porosity and crystalline structure) have been extensively studied. In particular, conditions for obtaining a template-free host have been established. It has been shown that standard calcination procedures, required to reveal the micropores, cannot be straighforward applied since they leave a non-negligible concentration of template residues in the host. Afterward, structural and chemical characterization, as well as simulation of 3-OHF-loaded zeolite β colloids enabled to determine the presence and location of [(3-OHF)Al] chelates in the zeolite micropores. Characterization of the dye loading by independent techniques involving elemental analysis, pore volume, and crystalline structure investigations highlighted the determinant impact of prior calcination treatments and the presence in the zeolite micropores of trapped solvent molecules simultaneously with the dye.

Two‐Dye Core/Shell Zeolite Nanoparticles: A New Tool for Ratiometric pH Measurements

“…This value is significantly higher than the value (0.33) determined in ref. [32] for a sample undergoing the same calcination procedure, and thus suggests a correspondingly higher 3HF loading in the present study. Herein, zeolite-b was prepared using molecular silicate tetraethylorthosilicate (TEOS) as the silica precursor instead of commonly used colloidal silica.…”

“…After the insertion of the 3HF dye ([3HF@tfb ]) into the porous network of the zeolite, the corresponding values decrease to 424 m 2 g À1 and 0.124 cm 3 g. These results demonstrate the presence of a guest species in the zeolite matrix and actually, as described previously in ref. [32], the anchoring of the 3HF dye to the inorganic network through the structural aluminum atoms. The mesoporous volume (pore www.afm-journal.de diameter >20 Å ) is also affected, decreasing from 0.651 to 0.433 cm 3 g À1 , indicating the possible sorption of 3HF outside the microporous network of zeolite b nanocrystals.…”

“…Similarly to a previous investigation, [32] we performed wideangle X-ray diffraction (WAXRD) measurements (Fig. 4).…”

“…The [3HF@tfb ] sample exhibits a maximum signal around 400 nm which corresponds to the chelated form of 3HF. [32] The [3HF@tfb ]@[sFd@SiO 2 ]-A sample exhibits another inflexion point at the absorption maximum of fluorescein, i.e., at 490 nm, revealing the presence of the dye in the resulting nanoparticles. Moreover, quantitative difference of scattered light between these two samples could be explained by a difference in the number of particles present in solution (at equal mass concentration, i.e., 1 mg mL À1 ) due to the increase in particle diameter.…”

“…[30] In previous papers, we described the preparation of fluorescent zeolite nanoparticles involving 3-hydroxyflavone (3HF) as the guest dye and the zeolite b as the host matrix. [31,32] Combining the large pore size of zeolite b (0.73 nm, compatible with 1.13 nm  0.66 nm dimensions of planar 3HF) and the chelating ability of 3HF with structural aluminum atoms, [33] this host-guest system appears today as an interesting system for biological sensing applications.…”