A new synthesis method for preparation of thin films and powders consisting of zeolite beta nanocrystals embedded in ordered mesoporous silica matrix is described. The final structures possessing bimodal porosity, i.e., high degree of mesophase order and spatially defined microporous zeolite nanocrystals are obtained via simultaneous solvent evaporation of preformed silica/surfactant/ethanol/nanosized zeolite beta assemblies. The films were characterized with grazing-incident diffraction (GID), nitrogen sorption based on gravimetric measurements with quartz crystal microbalance (QCM) devices, and transmission electron microscopy (TEM). It is shown that the incorporation of beta nanocrystals in the mesoporous silica matrix and the mesophase order itself can be controlled through the variation of the fractional amounts of the zeolite nanoparticles and silica/surfactant solutions. The HR-TEM measurements showed that the nanosized Beta microporous crystals are separated and at the same time connected through an ordered mesostructured matrix.

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.

Amorphous silica grains were subjected to a hydrothermal treatment to be transformed into closely packed ZSM-5 zeolite nanocrystalline bodies. Three synthesis approaches have been developed: (I) direct hydrothermal treatment of the amorphous silica grains in a ZSM-5 precursor solution; (II) impregnation of charge-reversed amorphous silica grains with 2-10 nm preorganized units followed by a hydrothermal treatment in a silica-free precursor synthesis solution; and (III) electrostatic adsorption of 50-nm sized ZSM-5 seeds on the amorphous silica grains followed by a hydrothermal treatment with a ZSM-5 precursor solution. The synthesized solids were characterized by X-ray diffraction, Raman spectroscopy, TG analysis, N 2 adsorption measurements, and scanning electron microscopy. The resulted zeolitic bodies are built of uniform closely packed nanocrystals and retain the size and morphological features of the initial amorphous silica grains. The crystallinity, the average size of crystallites, and the mechanical properties of the nanozeolite bodies depend strongly on the synthesis procedure. It was found that procedure II provides mechanically stable bodies built of closely packed nanocrystallites with a size of about 40 nm, which are very promising for the production of self-bonded nanozeolite structures.

AlPO4-18 layers were prepared on Si wafers via spin-coating or the Langmuir−Blodgett (LB) method using nanosized crystals. Multilayers were deposited by spin-coating, whereas the seeds assembled by the LB technique were monolayers. The seeded layers were not stable upon secondary growth under microwave radiation, and no films were formed on the supports. Dense AlPO4-18 films could be obtained by secondary growth after stabilization of the seed layers by adding prehydrolyzed tetraethylorthosilicate (TEOS) to the colloidal AlPO4-18 suspension prior to support seeding. The stabilized seed layers and the grown AlPO4-18 films were stable. The structure and the morphology of the films grown using the two types of seeded supports were similar, independent of the method used for seeding. The AlPO4-18 nanocrystals used for seeding showed very high water capacity with low temperatures of water removal when heated. The layers and films prepared are of potential interest for sensing, heat pump, and cooling machines applications.

No abstract

No abstract

No abstract

No abstract