Template Properties Research Articles

Synthesis and characterization of α-Fe2O3 mesoporous using SBA-15 silica as template and investigation of its catalytic activity for thermal decomposition of ammonium perchlorate particles

In this study, mesoporous α-Fe2O3 catalysts were synthesized from mesoporous silica SBA-15 as the hard template and iron nitrate as the iron oxide source via nanocasting strategy. In order to access the highest loading of iron oxide in the template pores, different weight ratios of Fe(NO3)3·9H2O/SBA-15 were used in the pore-filling step by two solvents process. The structural and textural properties of the SBA-15 template and α-Fe2O3-2.0 catalyst were characterized by means of X-ray diffraction, transmission electron microscopy and nitrogen adsorption–desorption techniques. The findings indicated that the resulting iron oxides are crystalline and to some extent, have negative replica structures of mesoporous SBA-15 template. The catalytic performance of mesoporous α-Fe2O3 towards thermal decomposition of ammonium perchlorate was evaluated by differential scanning calorimetry technique. The specific heat released from the AP decomposition in the presence of catalyst was improved by increasing the precursor to template weight ratio. Therefore, the specific resulting heat released from the composite of AP and mesoporous α-Fe2O3-2.0 (1110Jg−1) was ~3 folds of that for pure AP (423Jg−1).

Tuning of ZnO 1D nanostructures by atomic layer deposition and electrospinning for optical gas sensor applications

We explored for the first time the ability of a three-dimensional polyacrylonitrile/ZnO material—prepared by a combination of electrospinning and atomic layer deposition (ALD) as a new material with a large surface area—to enhance the performance of optical sensors for volatile organic compound (VOC) detection. The photoluminescence (PL) peak intensity of these one-dimensional nanostructures has been enhanced by a factor of 2000 compared to a flat Si substrate. In addition, a phase transition of the ZnO ALD coating from amorphous to crystalline has been observed due to the properties of a polyacrylonitrile nanofiber template: surface strain, roughness, and an increased number of nucleation sites in comparison with a flat Si substrate. The greatly improved PL performance of these nanostructured surfaces could produce exciting materials for implantation in VOC optical sensor applications.

Organic Hydrogel Templates for Tunable Mesoporous Silica Hybrid Materials

ABSTRACTPorous coatings at the surface of living cells have application in human cell transplantation by controlling the transport of biomolecules to and from the cells. Sol-gel-derived mesoporous silica materials are good candidates for such coatings, owing to their biocompatibility, facile solution-based synthesis conditions, and thin film formation. Diffusion and transport across the coating correlates to long-range microstructural properties, including pore size distribution, porosity, and pore morphology. Here, we investigated collagen-fibril matrices with known biocompatibility to serve as templating systems for directed silica deposition. Type 1 collagen oligomers derived from porcine skin are extensively characterized such that we can predict and customize the final collagen-fibril matrix with respect to fibril density, interfibril branching and viscoelasticity. We show that these matrices template and direct the deposition of mesoporous silica at the level of individual collagen fibrils. We varied the fibril density, silicic acid concentration, and time of exposure to silicifying solution and characterized the resulting hybrid materials by scanning electron microscopy, energy-dispersive x-ray spectroscopy, and rheology. Microstructural properties of the collagen-fibril template are preserved in the silica surface of hybrid materials. Results for three different collagen fibril densities, corresponding to shear storage moduli of 200 Pa, 1000 Pa, and 1600 Pa, indicate that increased fibril density increases the absolute amount of templated silica when all other silica synthesis conditions are kept constant. Additionally, mechanical properties of the hybrid material are dominated by the presence of the silica coating rather than the starting collagen matrix stiffness.

Improved silica–titania catalysts by chitin biotemplating

New silica–titania mesoporous catalysts with improved performance were achieved by combining surface and templating properties of α-chitin nanorods recovered from biomass with sol–gel and spray-drying processes.

Novel barium-organic incorporated iodometalates: do they have template properties for constructing rare heterotrimetallic hybrids?

New barium-organic derivatives are introduced as countercations in the iodocuprates and -argentates to yield novel hybrids with unique structural motifs and bonding modes, many of them also showing vivid fluorescence on exposure to UV light. The tetrahedral MX4/trigonal-coplanar MX3 unit in these hybrids [Ba2(DMSO)12Cu8I12] (1) and [Ba(tetraglyme)2]2[Ag8I12]·EtOH (7) can be replaced by the M'I4/M'I3 unit without compromising their basic structural motifs, thus leading to the formation of the rare mixed Cu-Ag iodometalates [Ba2(DMSO)12Cu4Ag4I12] (9) and [Ba(tetraglyme)2]2[CuAg7I12]·EtOH (10), respectively. In contrast, a breakdown in the structure-directing properties of these iodometalates was observed in the mixed Ag-Pb iodometalate [Ba(tetraglyme)2]2[Pb2Ag2I10]·2Me2CO (11), where the basic structure of the synthon [Ba(tetraglyme)2]2[Ag4I8] (8) was not retained due to the compulsory molecular rearrangement required as a result of replacing AgI4/AgI3 units with octahedral PbI6 units.

Experimental Study on the Mechanical Properties of Renewable Rubber Building Template

Discarded rubber is renewable resource, and the reasonable use of discarded rubber is conducive to protect environment and save energy. This paper designs rubber template with the thermoplastic elastomer which processed by waste rubber powder and plastic. The physical and mechanical properties of various materials are obtained, and the bearing capacity of renewable rubber building template is calculated and analyzed through mechanical test. The results indicate that the mechanical properties of 16mm renewable rubber building template are equal to 18mm plywood. The research establishes a preliminary foundation for the industrialization of rubber building template.

Self-Assembled Core-Shell Fe<sub>3</sub>O<sub>4</sub>@SiO<sub>2 </sub>Nanoparticles with High Magnetic Sensitivity from Electrospun Fibers

Nanofibers composed of the hydrophilic polymer polyvinylpyrrolidone K90 (PVP), cetyltrimethylammonium bromide (CTAB), tetraethyl orthosilicate (TEOS) and Fe3O4were fabricated using an electrospinning process. As a result of the templating and confinement properties of the nanfibers, silica coated magnetite (Fe3O4@SiO2) core-shell nanoparticles (NPs) with high magnetic sensitivity were spontaneously formed through molecular self-assembly when the fibers were added to 80% aqueous ethanol (PH=9.0). The typical saturation magnetization of the Fe3O4@SiO2composite particles is up to 43.8 emu/g, with superparamagnetic properties being observed at room temperature. Since the nanoparticles have high magnetic sensitivity and are preparedviaa facile and convenient strategy, they have much promise in a range of practical applications.

Large Magnetoresistance and Electrostatic Control of Magnetism in Ordered Mesoporous La1–xCaxMnO3 Thin Films

Ferroic nanomaterials have received much attention in recent times because of their potential for novel applications. Here, we report a facile bottom–up synthetic approach to the first ordered mesoporous mixed-valence manganese oxide. Continuous thin films of perovskite-type La0.68Ca0.30Mn1.02O3−δ have been prepared from common inorganic salt precursors by taking advantage of the superior templating properties of a polyisobutylene-block-poly(ethylene oxide) diblock copolymer. This novel solution-processed mesostructured material is well-defined at the nanometer and micrometer levels and behaves superparamagnetically above 230 K. Furthermore, it exhibits large magnetoresistance over a wide range of temperatures due to complex percolation pathways for electron transport imparted by the unique pore–solid architecture, and it is ferromagnetic metallic below 180 K. We also demonstrate reversible magnetization modulation of up to 8.5% by electrostatic charge carrier doping in the polymer-templated thin films. T...

Photocatalytic hydrogen production on Pt-loaded TiO2 inverse opals

TiO2 inverse opals present increased photocatalytic production of H2. TiO2 inverse opals with different pore size and TiO2 macroporous structures with disordered arrangement of the pores have been tested in the photocatalytic production of hydrogen in aqueous solution with a formate buffer as hole scavenger. TiO2 inverse opals belong to the family of metamaterials and exhibit unique catalytic properties arising from their peculiar interaction with light. To discriminate the effects of slow photons the hydrogen photoproduction experiments were carried out at two different wavelengths, at 365nm where the effect of slow photons is maximized, and at 254nm where it is negligible. The resulting hydrogen production rates suggest a strong effect of the slow light and of the polymer template used in the synthesis of the TiO2 powders. The chemical properties of the polymeric sacrificial template determine the crystalline phase of the sample and as a consequence affect the catalytic performances of the resulting TiO2 structures.

Influence of 3C–SiC/Si (111) template properties on the strain relaxation in thick GaN films

In this work, we study the influence of 3C–SiC/Si (111) template parameters (thickness, roughness and substrate miscut) on the GaN crystal quality and its strain state. For this, structures with an AlN nucleation layer and 1–4µm thick GaN layer have been grown by molecular beam epitaxy in order to select the best templates for the growth of thick GaN structures. Similar GaN structures have been grown directly on silicon for comparisons. The influence of the high silicon doping is confirmed on the enhancement of strain relaxation. Despite this limitation, a 5µm thick crack-free continuous GaN structure (with 1µm silicon doped) has been successfully grown on the best selected template. Furthermore, the growth by metal–organic chemical vapor deposition of structures with AlN and SiN inter-layers and thick continuous GaN layers on Si (111), 3C–SiC/Si (111) and SoPSiC (silicon on polycrystalline silicon carbide) has been achieved in order to show the relative benefit of each approach in terms of layer quality and strain state.

Templating Fullerenes by Domain Boundaries of a Nanoporous Network

We present a new templating approach that combines the templating properties of nanoporous networks with the dynamic properties and the lattice mismatch of domain boundaries. This templating approach allows for the inclusion of guests with different sizes without the need for a strict molecular design to tailor the nanoporous network. With this approach, nonperiodic patterns of functional molecules can be formed and studied. We show that domain boundaries in a trimesic acid network are preferred over pores within the network as adsorption sites for fullerenes by a factor of 100-200. Pristine fullerenes of different sizes and functionalized fullerenes were templated in this way.

Biochemical and Biophysical Properties of Positively Supercoiled DNA

Here we studied the biophysical and biochemical properties of the positively supercoiled DNA under different conditions. Large amount of positively supercoiled DNA is difficult to obtain compared to the natural-occurring negatively supercoiled DNA. Therefore, the biophysical and biochemical properties have not been fully explored. In this report we utilized Archaeoglobus fulgidus DNA reverse gyrase, which was expressed in E. coli strain BL21(DE3)/pLysS and purified using an optimized purification scheme, to convert the negatively supercoilied plasmid DNA to the positively supercoiled DNA. The positively supercoiled DNA was further purified by the CsCl-EB density-gradient centrifugation. After we obtained a few milligrams of the positively supercoiled DNA template, biochemical and biophysical properties were characterized using different techniques, such as UV melting, circular dichroism, AFM (atomic force microscope), fluorescence spectrometry, DNA topoisomerase assays, and etc. Our results are expected to provide the basis for the utilization of the (+) supercoiled DNA for future biomedical applications, such as the use of (+) supercoiled DNA templates for the screening of anti-gyrase antibiotics.

Pore size effect on the formation of polymer nanotubular structures within nanoporous templates

Nanotubular structures have recently received much attention due to their potential applications in biosensors, drug delivery systems, electronic devices, and many others. The layer-by-layer (LbL) deposition technique on 3-dimensional templates has been one of the most popular methods for the formation of nanotubular structures. Any size, shape, and composition template can be utilized and the desired amount of various materials can be readily incorporated within the thin film geometry with nanoscale control. Therefore, the morphological features of those materials can easily be tuned by varying the structural properties of templates. However, LbL deposition within a confined geometry actually shows somewhat different results due to the geometrical restriction, which is still not fully understood so far. In the present study, in order to investigate such a template effect on the LbL process, we utilized a cylindrical nanoporous anodic aluminum oxide (AAO) structure as a template for the LbL process, yielding polymer nanotube structures. By varying the pore size of the porous templates, we determined the LbL process within porous structures was strongly governed by the geometrical characteristics of the utilized templates.

Effects of annealing on structural and magnetic properties of template synthesized cobalt nanowires useful as data storage and nano devices

Cobalt nanowires of 100 nm diameter were synthesised electrochemically, in the pores of anodic alumina membrane (AAM). Electrochemical impedance spectroscopy was used to study the in situ growth of cobalt nanowires in the AAM. The structural and morphological characterization of template synthesized cobalt nanowires was done through X-ray diffractometer and scanning electron microscope, respectively. Effect of annealing on electrical and magnetic properties of cobalt nanowires was also investigated.

Effect of the polar modifiers on supercritical extraction efficiency for template removal from hexagonal mesoporous silica materials: Solubility parameter and polarity considerations

The introduction of polar modifiers usually can make supercritical CO2 extraction more attractive in various potential applications. In this work, modified supercritical CO2 extraction of the dodecylamine template has been performed on freshly synthesized mesoporous HMS materials with the use of 10 different polar modifiers. The effects of the polar modifiers on the extraction efficiencies of the amine template and structural properties of resultant HMS materials have been investigated in detail. Among the ten modifiers used, formic and acetic acids, water and methanol give reasonably high extraction efficiencies and the effects of the modifier identity on extraction efficiencies have been discussed in terms of solubility parameter and dipole moment of the modifiers. Methanol seems to be much better than the other modifiers for the SCCO2 extraction of dodecylamine from HMS materials since the resulted materials have well preserved highly ordered mesoporous structure and possessed much large specific surface area and pore volume as reflected by XRD spectra and nitrogen adsorption/desorption results.

Research Progress of Hollow Structural Materials Prepared <I>via</I> Templating Method

Hollow structural materials with low density and high surface area which can encapsulate small molecules, are widely used in environmental protection, drug delivery system, electronic and other fields. Because templating method is simple, and owns high repeat rate, good prediction and many other advantages, it is particularly interesting and frequently used to fabricate hollow structural materials with homogeneous, dense layers. Templating methods can be divided broadly into two classes according to the properties of templates used in synthesis, which can be called tra- ditional templating methods and self-templating methods, respectively. In this review, a comprehensive overview of the preparation of hollow structural materials via templating methods was provided. The progress of two traditional templating methods: hard templates and soft templates were firstly summarized. The research and development of hollow structural materials prepared via four self-templating methods: Ostwald ripening, Kirkendall effect, galvanic replacement and chemical etching were mainly reviewed and commented in the later. At last, perspective on the future research and development of hollow structural materials prepared by templating methods were also discussed.

Hole–Shell Microparticles from Controllably Evolved Double Emulsions

Polymeric core–shell microparticles with hollow interiors have great potential for use as microencapsulation systems for controlled load/release, active protection, and confined microreaction. Core–shell structures with solid shells provide effective encapsulation; however, transport of the encapsulated molecule through the shell is more difficult. Addition of holes to the shell can provide more versatility for the microparticles by facilitating mass transport through the shell based on the size or functional selectivity of the holes; this produces microparticles with porous shells for a myriad of uses including controlled capture of particles, controlled release of active molecules and small particles, and removal of pollutants. Additional uses for these microparticles can be achieved through finer control of the holes in the shell: for example, a single, defined hole can provide a very versatile structure for selectively capturing particles for classification and separation, or capturing cells for confined culture. Even more versatility can be obtained through control of the shape of the hollow core: for example, microparticles with a dimple-shaped core are useful for sizeselective capture of colloidal particles, whereas microparticles with a fishbowl-shaped core are more useful for loading objects such as cells and confining a microreaction. Finally, to make these structures fully functional, it is also desirable to control the interfacial properties of the core to enable precise interactions between encapsulated molecules and the solid shell. Colloidal-scale core–shell microparticles with a single hole in the shell are typically made with particle or emulsiontemplate methods: polymerization-induced buckling of silicon drops, freeze-drying solvent-swollen polymeric particles, self-assembly of phase-separated polymers, diffusion-induced escape of monomers or solvents from the microparticles during fabrication, selective polymerization of phase-separated drops, and other means to control the phase behavior of the templates. These microparticles provide excellent performance when sizes less than a few microns are required. By contrast, larger microparticles provide additional versatility when the size requirements are not constrained to very small particles. These microparticles are typically formed using emulsion drops as templates and have sizes of tens of micrometers or larger. Even finer control over the monodispersity of the microparticles is achieved using microfluidic techniques to produce the emulsion templates. The microparticle structure strongly depends on the configuration between the coredrop and shell-drop in the emulsion templates. With the shelldrop partially wetted on the core-drop, organic-biphasic Janus drops produce truncated-sphere-shaped microparticles. With completely wetted core–shell configurations, aqueousbiphasic drops and water-in-oil-in-water (W/O/W) double emulsions respectively produce bowl-shaped and fishbowlshaped microparticles. Surface modification of these microparticles was recently achieved by introducing functional nanoparticles such as SiO2 nanoparticles into the organic phase of the emulsion templates. Complete versatility of the microparticles requires accurate and independent control of the shape and size of both the single-hole and the hollow-core, as well as the functionality of the core surface; this requires precise control of the configurations and interfacial properties of the emulsion templates. However, techniques to achieve this sort of fine control do not exist. Herein, we report a versatile strategy for fabrication of highly controlled hole–shell microparticles with a hollow core and a single, precisely determined hole, and with simultaneous, independent control of the properties of the core interface. W/O/W double emulsions from capillary microfluidics were used as the initial templates for the microparticles. By controlling the composition of the organic middle phase, we varied the adhesion energy DF between the inner drop and outer phase to control the evolution of the emulsions from initial core-shell to the desired acorn-shaped configuration; this produces versatile emulsion templates for controllable fabrication of monodisperse hole-shell microparticles with advanced shapes. Further adjustment of the hole–shell structures can be achieved by changing the size and [*] Dr. W. Wang, M.-J. Zhang, Dr. R. Xie, Dr. X.-J. Ju, C. Yang, C.-L. Mou, Prof. L.-Y. Chu School of Chemical Engineering, Sichuan University Chengdu, Sichuan, 610065 (China) E-mail: chuly@scu.edu.cn Homepage: http://teacher.scu.edu.cn/ftp_teacher0/cly/

Template synthesis, structure and properties of 4-pyridinylboron-capped iron(II) clathrochelate precursors for Bubnov diallylation reaction

Direct template macrobicyclization of three aliphatic, aromatic and dichlorine-containing a-dioxime molecules with 4-pyridinylboronic acid on a Fe2 + ion as a matrix afforded the first macrobicyclic tris-dioximates with 4-pyridinyl apical substituents. The macrobicyclic complexes synthesized were characterized using elemental analysis, spectroscopic methods, X-ray crystallography and cyclic voltammetry.

Statistical Hiding Fuzzy Commitment Scheme for Securing Biometric Templates

2 Abstract — By considering the security flaws in cryptographic hash functions, any commitment scheme designed straight through hash function usage in general terms is insecure. In this paper, we develop a general fuzzy commitment scheme called an ordinary fuzzy commitment scheme (OFCS), in which many fuzzy commitment schemes with variety complexity assumptions is constructed. The scheme is provably statistical hiding (the advisory gets almost no statistically advantages about the secret message). The efficiency of our scheme offers different security assurance, and the trusted third party is not involved in the exchange of commitment. The characteristic of our scheme makes it useful for biometrics systems. If the biometrics template is compromised, then there is no way to use it directly again even in secure biometrics systems. This paper combines biometrics and OFCS to achieve biometric protection scheme using smart cards with renewability of protected biometrics template property.

Reusing models and properties in the analysis of similar interactive devices

The paper is concerned with the comparative analysis of interactive devices. It compares two devices by checking systematically a set of template properties that are designed to explore important interface characteristics. The two devices are designed to support similar tasks in a clinical setting. The devices differ as a result of judgements based on a range of considerations including software. Variations between designs are often relatively subtle and do not always become evident through even relatively thorough user testing. Notwithstanding their subtlety, these differences may be important to the safety or usability of the device. The illustrated approach uses formal techniques to provide the analysis. This means that similar analysis can be applied systematically.