Photochemistry of 2-(2‘-Hydroxyphenyl)benzothiazole Encapsulated in Nanosized Zeolites

Abstract

The in situ incorporation and characterization of 2-(2‘-hydroxyphenyl)benzothiazole (HBT) in the cages of nanosized FAU zeolites is reported. We demonstrate the advantage of using colloidal zeolite solutions to perform subpicosecond transient experiments on nanosized host/guest systems. FAU molecular sieve is prepared from precursor solutions containing as organic template only tetramethylammonium hydroxide (TMA) or both molecules HBT and TMA, using a hydrothermal treatment at 90 °C for 70 h. In situ dynamic light scattering investigations of the precursor solutions and the crystalline suspensions are performed with the original sample concentrations using a backscattering mode. The radius of the amorphous entities formed in the TMA-containing precursor solutions is about 25 nm, while that of the amorphous species in the HBT/TMA precursor solution is about 15 nm. The final particle size of FAU and HBT/FAU colloidal zeolites is 100 and 80 nm, respectively. The encapsulation of HBT with different concentrations into the large pore FAU molecular sieve host is confirmed by Raman, infrared, and 13C solid-state NMR spectroscopies. The spectroscopic data reveal that the HBT molecules are incorporated in the nanosized zeolite particles, thus leading to changes in the environment of the TMA ions as well as in the local atomic arrangements of the FAU structure. At high concentration of HBT, a large fraction of the sodalite cages are destroyed, and the HBT and TMA molecules are located in the subsequently formed cavities. Steady-state UV−vis spectra also reveal the presence of the keto HBT-conformers inside the FAU zeolite nanocrystals. Upon UV excitation, the HBT molecules occluded in the zeolite nanoparticles undergo ultrafast intermolecular proton transfer within 1.5 ps.

Femtochemistry of Guest Molecules Hosted in Colloidal Zeolites

“…The cumulative analysis gave an average particle radius with a reasonable distribution between the minimum and maximum particle sizes present in the sample. [9,29] For all three samples, TPA-MFI, HBT-MFI, and HBT-TPA-MFI, the mean size is approximately 70±90 nm. The polydispersity index is below 0.1, suggesting a monomodal particle size distribution in these samples.…”

Kompostite auf Basis von Zeolithen oder geordnet mesoporösen Oxiden für Anwendungen in der Photonik und Sensorik

“…Besonders geeignet sind in Zeolith-Nanopartikel eingelagerte fluoreszierende Farbstoffe [72,73], wenn deren Fluoreszenzsignal durch die nachzuweisenden Gase selektiv gequencht wird. Solche Fluoreszenzfarbstoff/Zeolith-Komposit-Systeme eignen sich beispielsweise als Biolabel [74], da sie in Zellen oder Makrophagen eingebaut werden können und beispielsweise, wie im Falle von Ru(bpy) 3…”

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

“…[26] In this respect, combining the possibility to synthesize nanosized zeolite particles with the optical properties of such dye-doped systems may offer new perspectives in developing multifunctional nanomaterials for biological applications. While a few papers have described the preparation of luminescent zeolite nanoparticles, [27][28][29] only one has shown their potential use as fluorescent biolabel. [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.…”