Hussein Awala

Template-free nanosized faujasite-type zeolites

Nanosized faujasite (FAU) crystals have great potential as catalysts or adsorbents to more efficiently process present and forthcoming synthetic and renewable feedstocks in oil refining, petrochemistry and fine chemistry. Here, we report the rational design of template-free nanosized FAU zeolites with exceptional properties, including extremely small crystallites (10-15 nm) with a narrow particle size distribution, high crystalline yields (above 80%), micropore volumes (0.30 cm(3) g(-1)) comparable to their conventional counterparts (micrometre-sized crystals), Si/Al ratios adjustable between 1.1 and 2.1 (zeolites X or Y) and excellent thermal stability leading to superior catalytic performance in the dealkylation of a bulky molecule, 1,3,5-triisopropylbenzene, probing sites mostly located on the external surface of the nanosized crystals. Another important feature is their excellent colloidal stability, which facilitates a uniform dispersion on supports for applications in catalysis, sorption and thin-to-thick coatings.

Vapor Responsive One-Dimensional Photonic Crystals from Zeolite Nanoparticles and Metal Oxide Films for Optical Sensing

The preparation of responsive multilayered structures with quarter-wave design based on layer-by-layer deposition of sol-gel derived Nb2O5 films and spin-coated MEL type zeolite is demonstrated. The refractive indices (n) and thicknesses (d) of the layers are determined using non-linear curve fitting of the measured reflectance spectra. Besides, the surface and cross-sectional features of the multilayered structures are characterized by scanning electron microscopy (SEM). The quasi-omnidirectional photonic band for the multilayered structures is predicted theoretically, and confirmed experimentally by reflectance measurements at oblique incidence with polarized light. The sensing properties of the multilayered structures toward acetone are studied by measuring transmittance spectra prior and after vapor exposure. Furthermore, the potential of the one-dimensional photonic crystals based on the multilayered structure consisting of Nb2O5 and MEL type zeolite as a chemical sensor with optical read-out is discussed.

Zeolite Nanoparticles for Selective Sorption of Plasma Proteins

The affinity of zeolite nanoparticles (diameter of 8–12 nm) possessing high surface area and high pore volume towards human plasma proteins has been investigated. The protein composition (corona) of zeolite nanoparticles has been shown to be more dependent on the plasma protein concentrations and the type of zeolites than zeolite nanoparticles concentration. The number of proteins present in the corona of zeolite nanoparticles at 100% plasma (in vivo state) is less than with 10% plasma exposure. This could be due to a competition between the proteins to occupy the corona of the zeolite nanoparticles. Moreover, a high selective adsorption for apolipoprotein C-III (APOC-III) and fibrinogen on the zeolite nanoparticles at high plasma concentration (100%) was observed. While the zeolite nanoparticles exposed to low plasma concentration (10%) exhibited a high selective adsorption for immunoglobulin gamma (i.e. IGHG1, IGHG2 and IGHG4) proteins. The zeolite nanoparticles can potentially be used for selectively capture of APOC-III in order to reduce the activation of lipoprotein lipase inhibition during hypertriglyceridemia treatment. The zeolite nanoparticles can be adapted to hemophilic patients (hemophilia A (F-VIII deficient) and hemophilia B (F-IX deficient)) with a risk of bleeding, and thus might be potentially used in combination with the existing therapy.

Photonic Materials for Holographic Sensing

Holography is a practical approach to fabricating optical sensors for applications in the detection of chemical analytes and physical changes. Holographic sensors incorporate diffraction gratings within functionalized polymers or natural organic polymer matrices, that allow indirect optical measurements of physical and chemical stimuli. The advantages of holographic sensors over other optical sensors are the ability to produce three-dimensional (3D) images and amenability to mass manufacturing at low-cost. The aim of this chapter is to (1) describe the principle of operation of holographic sensors (2) describe the holographic recording techniques used for their fabrication (3) discuss approaches to preparing recording media and overview strategies of their functionalization in order to obtain stimuli responsive devices, and (4) highlight emerging applications in environmental sensing and point-of-care diagnostics. Particular emphasis is put on the photonic materials used for holographic sensors recording and the different approaches used for their functionalization with the view of how this can be used to improve sensors sensitivity, selectivity and response time. The main challenges in holographic sensors research and possible solutions to these challenges are outlined.

Properties of methylene blue in the presence of zeolite nanoparticles

The interactions between methylene blue (MB) and zeolite nanocrystals in water suspensions are investigated. The zeolite nanocrystals (diameter of 40–70 nm) with BEA-, LTL- and LTA-type framework structures with pore size of 7.3, 7.1 and 4.1 A, respectively, are chosen to evaluate their effect on the stabilization of the MB (7.0 × 16 A) in their pores and on the crystals surface. It is found that the MB molecules enter the channels of the LTL-type zeolite nanocrystals, while the BEA-type zeolite is partially filled by the MB due to the presence of organic agent (tetraethylammonium cations) in the channels. The highly hydrophilic surface of the LTA-type nanocrystals with pore size smaller than the size of MB is strongly modified, but no MB molecules in the LTA-zeolite channels are present due to pore size restriction. The UV-vis characterization of the suspensions containing zeolite nanocrystals and MB (samples LTL-MB, BEA-MB and LTA-MB) reveal a shift in the absorption maximum (581 nm) with 16.5 nm for BEA, 15.5 nm for LTL, and 13.5 nm for LTA zeolite crystals. The absorption maximum in the three suspensions shifts to shorter wavelengths (blue shift) with time, and only the LTA-MB sample returns to 581 nm after 8 minutes that corresponds to the original wavelength of the free MB molecule in water. The observed blue shift for samples BEA-MB and LTL-MB is explained with the penetration and stabilization of MB molecules in the zeolite pores. The zeolite nanocrystals in the presence of MB show high stability in water suspensions, which make them a promising matrix for preparation of water-soluble photopolymers. Photopolymers for full colors holography with expanded wavelength sensitivity range based on addition of more than one sensitizer (MB, erythrosine B and acriflavine stabilized in zeolite nanocrystals) are under development.

Ionothermal synthesis of FeAPO-5 in the presence of phosphorous acid

The ionothermal crystallization of FeAPO-5 molecular sieves in the presence of phosphorous acid (H3PO3) has been investigated. The use of H3PO3 enabled the formation of a metastable intermediate phase (FeNKX-2) that transforms into a more open-framework crystalline phase (FeAPO-5). The initial raw materials dissolved rapidly in the presence of the [bdmim]Cl polar ionic liquid, and the addition of the Fe3+ salt resulted in the crystallization of the FeNKX-2 intermediate. At this stage, the [bdmim]+ cation did not play the role of a pore filler for the FeNKX-2 crystalline structure. Consecutive phase transformation from the FeNKX-2 to the FeAPO-5 phase occurred under prolonged ionothermal treatment, and during this stage, the tetrahedral Fe3+ species was found to not only participate in the construction of the FeAPO-5 framework but also act as an intermediary electron-transfer medium. The fast crystallization of FeAPO-5 was explained by the presence of Fe3+ as an intermediate electron-transfer medium promoting the fast release of phosphorus nutrients (P5+) from the phosphite (P3+) reservoir that were further required for the crystallization of the FeAPO-5 molecular sieves. The use of ionic liquids as dual solvents and templates in combination with H3PO3 as an alternative phosphorus source thus opens the possibility to synthesize other microporous materials via a phase transformation approach.

Microfabricated test structures for thermal gas sensor

Microfabricated test structures are presented for the proof validation of a new chemical sensor concept. The proposed detection principle is based on time constant shift of a thermal device covered with zeolites when target species are adsorbed.

Inhibition of Palm Oil Oxidation by Zeolite Nanocrystals

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.

Effect of Extra-Framework Cations of LTL Nanozeolites to Inhibit Oil Oxidation

Lubricant oils take significant part in current health and environmental considerations since they are an integral and indispensable component of modern technology. Antioxidants are probably the most important additives used in oils because oxidative deterioration plays a major role in oil degradation. Zeolite nanoparticles (NPs) have been proven as another option as green antioxidants in oil formulation. The anti-oxidative behavior of zeolite NPs is obvious; however, the phenomenon is still under investigation. Herein, a study of the effect of extra-framework cations stabilized on Linde Type L (LTL) zeolite NPs (ca. 20 nm) on inhibition of oxidation in palm oil-based lubricant oil is reported. Hydrophilic LTL zeolites with a Si/Al ratio of 3.2 containing four different inorganic cations (Li+, Na+, K+, Ca2+) were applied. The oxidation of the lubricant oil was followed by visual observation, colorimetry, fourier transform infrared (FTIR) spectroscopy, 1H NMR spectroscopy, total acid number (TAN), and rheology analyses. The effect of extra-framework cations to slow down the rate of oil oxidation and to control the viscosity of oil is demonstrated. The degradation rate of the lubricant oil samples is decreased considerably as the polarizability of cation is increased with the presence of zeolite NPs. More importantly, the microporous zeolite NPs have a great influence in halting the steps that lead to the polymerization of the oils and thus increasing the lifetime of oils.

A Facile Route toward the Increase of Oxygen Content in Nanosized Zeolite by Insertion of Cerium and Fluorinated Compounds

Enriching oxygen content within nanosized zeolite X (as synthesized Na-X) by insertion of cerium (ion exchanged Ce-X) and functionalization with bromoperfluoro-n-octane (fluorinated F-X) is reported. The materials were fully characterized by powder X-ray diffraction (XRD), dynamic light scattering (DLS), zeta potential, thermogravimetric analysis (TGA), nitrogen adsorption, and nuclear magnetic resonance (19F NMR). The O2 adsorption in the zeolite samples at various concentrations (0 to 165 Torr) at −196 °C was studied by in situ FTIR. The modification of nanosized zeolites did not alter their colloidal stability, crystallinity, porosity, and particle size distribution. The inclusion of cerium and bromoperfluoro-n-octane considerably increase the oxygen capacity by 33% for samples Ce-X and F-X in comparison to the as-synthesized Na-X zeolite. Further, toxicity tests revealed that these materials are safe, which opens the door for their implementation in medical applications, where controlled delivery of oxygen is highly desirable.