Search

The process of formation of ultrasmall EMT-type zeolitefrom organic-template-freehomogeneous suspensions is presented. The formation of transparentuniform suspension utilizing sodium aluminate, sodium silicate, andsodium hydroxide under controlled mixing is found to be of primaryimportance to control the nucleation and growth process of EMT-typecrystals. The investigation of zeolite intermediates reveals the formationof uniformly sized gel particles (5–10 nm in size). The meanhydrodynamic diameter of the crystalline EMT-type zeolite correspondsto the size of the amorphous particles formed after preparation ofthe clear precursor suspension. Controlled formation of uniform precursorparticles predetermines, to great extent, the following nucleationand growth steps and, thus, the characteristicsof the ultimate product. The amorphous particles are transformed tosingle EMT-type crystals 6–15 nm in size at 303 K within 36h. Small changes in the initial composition or the preparation procedurelead to the formation of other sodalite-cage-containing zeolites.Thus, it is of critical importance to control the nucleation kineticsin order to obtain the EMT-type material as pure phase. Besides theEMT zeolite, the crystallization fields of other zeolites upon low-temperaturesynthesis conditions are studied. The careful control of gel chemistry,combined with slow nucleation kinetics at low temperature, can provideaccess to important nanoscale zeolites while avoiding the use of expensiveorganic templates. [ABSTRACT FROM AUTHOR]

EMT-type zeolite nanoparticles (EMT NPs) with particle size of 10-20 nm and external surface area of 200 m 2 /g have shown high selective affinity toward plasma protein (fibrinogen). Besides, the EMT NPs have demonstrated no adverse effect on blood coagulation hemostasis. Therefore, it was envisioned that the EMT NPs could inhibit possible β-amyloid (Aβ)-fibrinogen interactions that result in the formation of structurally abnormal clots, which are resistant to lysis, in cerebral vessels of patients with Alzheimer disease (AD). To evaluate this hypothesis, the clot formation and degradation of Aβ-fibrinogen in the presence and absence of the EMT zeolite NPs were assessed. The results clearly showed that the delay in clot dissolution was significantly reduced in the presence of zeolite NPs. By formation of protein corona, the EMT NPs showed a negligible reduction in their inhibitory strength. Docking of small molecules (Aβ-fibrinogen) introduced a novel potential inhibitory candidate. The zeolite NPs showed similar inhibitory effects on binding of fibrinogen to both Aβ(25-35) and/or Aβ(1-42). This indicates that the inhibitory strength of these NPs is independent of Aβ sequence, and it is suggested that the zeolite NPs adsorb fibrinogen and specifically obstruct their Aβ binding sites. Therefore, the zeolite NPs can be the safe and effective inhibitors in preventing Aβ-fibrinogen interaction and consequent cognitive damage.

The efficiency of zeolite X nanocrystals (FAU-type framework structure) containing different extra-framework cations (Li(+), Na(+), K(+), and Ca(2+)) in slowing the thermal oxidation of palm oil is reported. The oxidation study of palm oil is conducted in the presence of zeolite nanocrystals (0.5 wt %) at 150 °C. Several characterization techniques such as visual analysis, colorimetry, rheometry, total acid number (TAN), FT-IR spectroscopy, (1)H NMR spectroscopy, and Karl Fischer analyses are applied to follow the oxidative evolution of the oil. It was found that zeolite nanocrystals decelerate the oxidation of palm oil through stabilization of hydroperoxides, which are the primary oxidation product, and concurrently via adsorption of the secondary oxidation products (alcohols, aldehydes, ketones, carboxylic acids, and esters). In addition to the experimental results, periodic density functional theory (DFT) calculations are performed to elucidate further the oxidation process of the palm oil in the presence of zeolite nanocrystals. The DFT calculations show that the metal complexes formed with peroxides are more stable than the complexes with alkenes with the same ions. The peroxides captured in the zeolite X nanocrystals consequently decelerate further oxidation toward formation of acids. Unlike the monovalent alkali metal cations in the zeolite X nanocrystals (K(+), Na(+), and Li(+)), Ca(2+) reduced the acidity of the oil by neutralizing the acidic carboxylate compounds to COO(-)(Ca(2+))1/2 species.