Effects of Crystallinity in Spin‐On Pure‐Silica‐Zeolite MFI Low‐Dielectric‐Constant Films

Low‐dielectric‐constant (low‐κ) materials are a critical requirement for future generations of computer microprocessors. As a unique class of porous silicas, pure silica zeolites (PSZs) have been shown to be a promising low‐κ material with excellent mechanical strength (e.g., elastic modulus of 16–18 GPa) due to their crystalline nature. In the present study, we show for the first time that higher crystallinity of spin‐on PSZ MFI films leads to lower κ values and less moisture sensitivity—two critical properties of a porous low‐κ material. We have also advanced the two‐stage synthesis method to produce zeolite nanoparticles with high yield (77 %) and a small diameter (< 80 nm). A κ value of 1.6 is obtained from the silylated highly crystalline PSZ MFI film and the κ value only increases by 12.5 % after exposure to ambient conditions for a period of 24 h.     

Core–Shell Zeolite Microcomposites

Core–shell zeolite composites possessing a core and a shell of different zeolite structure types have been synthesized. A characteristic feature of the obtained composites is the relatively large single‐crystal core and the very thin polycrystalline shell. The incompatibility between the core crystals and the zeolite precursor mixture yielding the shell layer has been circumvented by the adsorption of nanoseeds on the core surface, which induced the crystallization of the shell. The pretreated core crystals are subsequently subjected to a continuous growth in a zeolite precursor mixture. The feasibility of this synthetic approach has been exemplified by the preparation of core–shell β‐zeolite–silicalite‐1 composites. The synthesized composites have been characterized using X‐ray diffraction, high‐resolution transmission electron microscopy, and scanning electron microscopy. The integrity of the shell layer has been tested via N₂‐adsorption measurements on materials comprising a calcined core (β‐zeolite) and a non‐calcined tetrapropylammonium (TPA)‐containing shell, the latter being non‐permeable for the N₂ molecules. These measurements have shown that 86 % of the β‐zeolite crystals are covered with a defect‐free TPA–silicalite‐1 shell after a single hydrothermal treatment, while after three consecutive crystallization steps this value reaches 99 %. The shell integrity of the calcined composite has been studied by the adsorption of butane, toluene, and 1,3,5‐trimethylbenzene, which confirmed the superior performance of the triple‐shell composites.     

Osteoconductive and Osteoinductive Properties of Zeolite MFI Coatings on Titanium Alloys

The use of zeolite MFI‐coated titanium alloy for bone cell growth and new bone formation in vitro is investigated. The corrosion‐resistant MFI coating is shown to be osteoconductive and to promote proliferation of human fetal osteoblasts (hFOBs) as compared to bare titanium alloy, Ti6Al4V. The zeolite crystal microstructure appears to facilitate osteoblast adhesion and induces osteointegration, as evaluated with microscopy. In addition, the zeolite promotes the differentiation of hFOBs into mature osteoblasts, as well as the production of a mineralized matrix at earlier times in culture compared to Ti6Al4V, indicating higher osteoinductive properties of the MFI coating than titanium alone. A significant increase in the expression of the bone morphogenetic protein (BMP‐2) gene is measured in hFOBs cultured on zeolite coatings compared to bare Ti6Al4V. This is the first report on highly corrosion‐resistant zeolite MFI coatings on Ti6A14V alloys with the potential to be used as a material of improved osteointegration appropriate for bone tissue regeneration.     

Tuning the Size and Shape of Zeolite L‐Based Inorganic–Organic Host–Guest Composites for Optical Antenna Systems

Fine tuning of the size of zeolite L crystals in a large range is possible by changing the composition of the starting gel for otherwise constant reaction conditions. We describe a convenient way to prepare different crystalline materials in the size range of 30 nm up to 3000 nm. Representative data on the morphology, the pore volume, the size distribution and the optical antenna system behavior for light harvesting and transport are reported. We have extended the investigations on energy migration in pyronine‐loaded zeolite L crystals as donor molecules, modified with oxonine as luminescent acceptors (traps) at the crystal ends. The preparation procedure reported and the extended zeolite materials now available lead to a large improvement of the energy migration efficiency.     

Tailored Mesoporosity Development in Zeolite Crystals by Partial Detemplation and Desilication

Partial detemplation of zeolites followed by desilication in alkaline medium is demonstrated as a powerful and elegant approach to design hierarchical zeolites with tailored degree of mesoporosity. This achievement, illustrated for large beta crystals, is based on the fact that the template‐containing zeolite is virtually inert to Si leaching upon treatment in aqueous NaOH solutions. Partial removal of the structure‐directing agent creates regions in the crystal susceptible to mesopore formation by subsequent desilication, while template‐containing regions are protected from silicon extraction. Variation of the calcination temperature in the range 230–550 °C determines the amount of template removed and enables control of the extent of mesopore formation in the zeolite (20–230 m² g^?1) upon alkaline treatment. The functionality of the introduced mesoporosity in the hierarchical beta crystals is demonstrated by the improved performance in the catalytic pyrolysis of low‐density polyethylene. The partial detemplation–desilication treatment enhances the tuning options of this demetallation method.     

Magnetic Multi‐Functional Nano Composites for Environmental Applications

A novel concept is proposed to synthesize a new class of composites featuring magnetic, molecular sieve and metallic nanoparticle properties. These multi‐functional materials have potential applications as recyclable catalysts, disinfectants and sorbents. The magnetic property enables effective separation of the spent composites from complex multiphase systems for regeneration and recycle, safe disposal of the waste and/or recovery of loaded valuable species. The zeolite molecular sieve provides a matrix which supports a remarkably new, simple, efficient and economical method to make stable, supported silver nanoparticles by silver ion exchange and controlled thermal reduction. The silver nanoparticles generated in this way have excellent properties such as high reactivity and good thermal stability without aggregation, which act as nano reactors for desired functionality in a wide range of applications. Magnetic component (Fe₃O₄), molecular sieve matrix (zeolite) and silver nanoparticles generated by ion exchange followed by controlled reduction, together form this unique novel composite with designed functions. It represents a practically operational, economical, sustainable and environmentally friendly new advanced functional material. This paper focuses on the novel synthesis and characterization of the composite, with an example of applications as sorbents for the removal of vapor‐phase mercury from the flue gas of coal‐fired power plants.     

Shape Selectivity in Adsorption of n‐ and Iso‐alkanes on a Zeotile‐2 Microporous/Mesoporous Hybrid and Mesoporous MCM‐48

The adsorption of linear and branched C5–C9 alkanes in the temperature range 50–250 °C on mesoporous MCM‐48 material and its microporous/mesoporous variant Zeotile‐2 at low surface coverage is investigated using the pulse chromatographic technique. On MCM‐48, the differences in adsorption between linear and branched alkanes are merely a result of differences in volatility, indicating that the MCM‐48 material does not present shape‐selective adsorption sites. On Zeotile‐2, there is a preferential adsorption of linear over branched alkanes. The difference arises from a difference in adsorption entropy rather than enthalpy. Upon their adsorption on Zeotile‐2 branched alkanes lose relatively more entropy than their linear isomers do. Zeolitic molecular pockets embedded in the walls of the mesoporous Zeotile‐2 impose steric constraints on the bulky isoalkanes. Zeotile‐2 combines adsorption properties from microporous and mesoporous materials. Compared to the nitrogen molecule, linear and branched C5–C9 alkanes are superior probes for investigating micropores and micropockets in hierarchical materials.     

Preparation of Hollow Zeolite Spheres and Three‐Dimensionally Ordered Macroporous Zeolite Monoliths with Functionalized Interiors

A novel and flexible strategy involving hydrothermal transformation of guest‐incorporated zeolite‐seeded mesoporous silica spheres was proposed to prepare guest‐encapsulated hollow zeolite spheres and three‐dimensionally (3D) ordered macroporous zeolite monoliths. The guest species that were pre‐incorporated into the mesopores of silica spheres could be spontaneously encapsulated inside the formed hollow zeolite shells by consuming silica nutrition of the original mesoporous silica cores during the hydrothermal process. A wide range of guest materials with a size ranging from nanometers to micrometers, e.g., Ag and PdO nanoparticles, and mesoporous spheres of carbon and polymer of micrometer size were successfully encapsulated into both discrete hollow zeolite spheres and 3D ordered macroporous zeolite monoliths. Such materials are expected to find a variety of applications such as catalysis, adsorption, and novel microreactors for their special structures with active species inside and zeolitic porous shell outside.     

Synthesis of ZSM‐5 Films and Monoliths with Bimodal Micro/Mesoscopic Structures

A route to synthesize ZSM‐5 crystals with a bimodal micro/mesoscopic pore system has been developed in this study; the successful incorporation of the mesopores within the ZSM‐5 structure was performed using tetrapropylammonium hydroxide (TPAOH)‐impregnated mesoporous materials containing carbon nanotubes in the pores, which were encapsulated in the ZSM‐5 crystals during a solid rearrangement process within the framework. Such mesoporous ZSM‐5 zeolites can be readily obtained as powders, thin films, or monoliths.     

Bioinspired Multifunctional Foam with Self‐Cleaning and Oil/Water Separation

Oil/water separation is a worldwide challenge. Learning from nature provides a promising approach for the construction of functional materials with oil/water separation. In this contribution, inspired by superhydrophobic self‐cleaning lotus leaves and porous biomaterials, a facile method is proposed to fabricate polyurethane foam with simultaneous superhydrophobicity and superoleophilicity. Due to its low density, light weight, and superhydrophobicity, the as‐prepared foam can float easily on water. Furthermore, the foam demonstrates super‐repellency towards corrosive liquids, self‐cleaning, and oil/water separation properties, possessing multifunction integration. We expect that this low‐cost process can be readily and widely adopted for the design of multifunctional foams for large‐area oil‐spill cleanup.     

Optically Functional Zeolites: Evaluation of UV and VUV Stimulated Photoluminescence Properties of Ce3+‐ and Tb3+‐doped Zeolite X

The optical properties of Tb³⁺/Ce³⁺ doped zeolites are elucidated with emphasis on ultraviolet (UV) and vacuum ultraviolet (VUV) excitation and luminescence. Ce³⁺ sensitized Tb³⁺ emission with quantum yields of 85 % may be obtained at 330 nm excitation. Low absorptivity at 254 nm due to low Ce³⁺ concentrations or low Ce³⁺/Tb³⁺ ratios, which are required for the suppression of UV components, restricts their applicability as phosphors for Hg‐based discharges, e.g., in conventional fluorescent lamps. Near band edge excitation at 172 nm revealed an immediate quantum yield of 50 % enabled by a zeolite → Ce³⁺ (5d¹) → Tb³⁺ (4f⁷5d¹) energy transfer channel, which may be exploited for the down‐conversion of the Xe₂ excimer emission.     

Copper‐Free Clickable Coatings

The copper‐catalyzed azide–alkyne 1,3‐dipolar cycloaddition (CuAAC) is extensively used for the functionalization of well‐defined polymeric materials. However, the necessity for copper, which is inherently toxic, limits the potential applications of these materials in the area of biology and biomedicine. Therefore, the first entirely copper‐free procedure for the synthesis of clickable coatings for the immobilization of functional molecules is reported. In the first step, azide‐functional coatings are prepared by thermal crosslinking of side‐chain azide‐functional polymers and dialkyne linkers. In a second step, three copper‐free click reactions (i.e., the Staudinger ligation, the dibenzocyclooctyne‐based strain‐promoted azide–alkyne [3+2] cycloaddition, and the methyl‐oxanorbornadiene‐based tandem cycloaddition?retro‐Diels?Alder (crDA) reaction) are used to functionalize the azide‐containing surfaces with fluorescent probes, allowing qualitative comparison with the traditional CuAAC.     

Porous Polymer Films with Gradient‐Refractive‐Index Structure for Broadband and Omnidirectional Antireflection Coatings

Porous polymer films that can be employed for broadband and omnidirectional antireflection coatings are successfully shown. These films form a gradient‐refractive‐index structure and are achieved by spin‐coating the solution of a polystyrene‐block‐poly(methyl methacrylate) (PS‐b‐PMMA)/PMMA blend onto an octadecyltrichlorosilane (OTS)‐modified glass substrate. Thus, a gradient distribution of PMMA domains in the vertical direction of the entire microphase‐separated film is obtained. After those PMMA domains are removed, a PS porous structure with an excellent gradient porosity ratio in the vertical direction of the film is formed. Glass substrates coated with such porous polymer film exhibit both broadband and omnidirectional antireflection properties because the refractive index increases gradually from the top to the bottom of the film. An excellent transmittance of >97% for both visible and near‐infrared (NIR) light is achieved in these gradient‐refractive‐index structures. When the incident angle is increased, the total transmittance for three different incident angles is improved dramatically. Meanwhile, the film possesses a color reproduction character in the visible light range.     

VEGF‐Functionalized Polyelectrolyte Multilayers as Proangiogenic Prosthetic Coatings

Stimulation of transprosthetic vascularization represents an interesting strategy in implantology to allow rapid tissue integration and finally to avoid prosthetic rejection. To achieve this goal, we modified the surface of porous titanium implants with polyelectrolyte multilayer (PEM) films functionalized with vascular endothelial growth factor (VEGF). Among the two PEM systems investigated, poly(L‐lysine)/poly(L‐glutamic acid) (PLL/PGA) and poly(allylamine hydrochloride)/poly(sodium 4‐styrenesulfonate) (PAH/PSS), the (PAH/PSS)₄ architecture was selected to functionalize porous titanium, both for its high efficiency to adsorb VEGF and for its biocompatibility toward endothelial cells. In an original way, we unambiguously demonstrated that VEGF adsorbed on (PAH/PSS)₄ maintains its bioactivity in vitro and stimulates endothelial cells proliferation. This effect was correlated with specific activation of intracellular signaling pathways induced by successive phosphorylation of the endothelial VEGF receptor VEGFR2 and mitogen‐activated protein kinases (MAPK) ERK1/2. By clearly demonstrating the proangiogenic activity of the VEGF‐PEM coating in vitro, the present study constitutes a first step toward in vivo application.     

Biocatalytic Nanoscale Coatings Through Biomimetic Layer‐by‐Layer Mineralization

Recent insight into the molecular mechanisms of biological mineral formation (biomineralization) has enabled biomimetic approaches for the synthesis of functional organic‐inorganic hybrid materials under mild reaction conditions. Here we describe a novel method for enzyme immobilization in thin (nanoscale) conformal mineral coatings using biomimetic layer‐by‐layer (LbL) mineralization. The method utilizes a multifunctional molecule comprised of a naturally‐occurring peptide, protamine (PA), covalently bound to the redox enzyme Glucose oxidase (GOx). PA mimics the mineralizing properties of biomolecules involved in silica biomineralization in diatoms, and its covalent attachment to GOx does not interfere with the catalytic activity. Highly efficient and stable incorporation of this modified enzyme (GOx‐PA) into nanoscale layers (～5–7 nm thickness) of Ti‐O and Si‐O is accomplished during protamine‐enabled LbL mineralization on silica spheres. Depending on the layer location of the enzyme and the type of mineral (silica or titania) within which the enzyme is incorporated, the resulting multilayer biocatalytic hybrid materials exhibit between 20–100% of the activity of the free enzyme in solution. Analyses of kinetic properties (V_max, K_M) of the immobilized enzyme, coupled with characterization of physical properties of the mineral‐bearing layers (thickness, porosity, pore size distribution), indicates that the catalytic activities of the synthesized hybrid nanoscale coatings are largely determined by substrate diffusion rather than enzyme functionality. The GOx‐PA immobilized in these nanoscale layers is substantially stabilized against heat‐induced denaturation and largely protected from proteolytic attack. The method for enzyme immobilization described here enables, for the first time, the high yield immobilization and stabilization of enzymes within continuous, conformal, and nanoscale coatings through biomimetic LbL mineralization. This approach will likely be applicable to a wide variety of surfaces and functional biomolecules. The ability to synthesize thin (nanoscale) conformal enzyme‐loaded layers is of interest for numerous applications, including enzyme‐based biofuel cells and biosensors.     

Synthesis and Characterization of a Composite Zeolite–Metglas Carbon Dioxide Sensor

The synthesis of a faujasite–Metglas composite material that can be used in gas‐sensing applications is presented. A continuous faujasite film was synthesized on a Metglas magnetoelastic strip using the secondary growth method. The ability of the new composite to remotely sense carbon dioxide in a nitrogen atmosphere at room temperature over a wide range of concentrations is demonstrated by monitoring the changes in the resonance frequency of the strip. The novel sensor combines the electromagnetic properties of the magnetoelastic material with the adsorption properties of the faujasite crystals. Experiments performed over a period of a few months showed that the composite sensor remained fully operational, thus indicating its long‐term stability. Furthermore, the present work demonstrates that a zeolite–Metglas composite can be used as a sensor of an analyte in a mixture as long as it adsorbs selectively larger amounts of the particular analyte than other compounds present in the mixture.     

Template‐Free Sol‐Gel Preparation of Superhydrophobic ORMOSIL Films for Double‐Wavelength Broadband Antireflective Coatings

A double‐layer double‐wavelength antireflective (AR) coating with 100% transmittance at both 1064 nm and 532 nm, which is very important in high power laser systems, is designed using thin film design software (TFCalc). The refractive indices for the bottom and top layers of the designed AR coating are about 1.30 and 1.14. A simple, template‐free sol‐gel route is proposed to prepare the superhydrophobic ORMOSIL (organically modified silicate) thin film, which has an ultralow refractive index, by silica particle surface modification using hexamethylisilazane (HMDS); this treatment decreases the refractive index of the silica thin film from 1.23 to 1.13. The formation mechanism of the ultralow refractive index thin film is proposed. The particle surface modification with HMDS significantly improves the hydrophobicity of the coated film; the water contact angle of the film increases from 23.4° to 160°. The bottom layer, which has a refractive index of 1.30, is prepared from acid‐catalyzed and base‐catalyzed mixed silica sol. A double‐layer silica AR coating is obtained with transmittances of 99.6% and 99.8% at 532 nm and 1064 nm, respectively.