Formation of Helically Structured Chitin/CaCO3 Hybrids through an Approach Inspired by the Biomineralization Processes of Crustacean Cuticles.

PubMed

Matsumura, Shunichi; Kajiyama, Satoshi; Nishimura, Tatsuya; Kato, Takashi

2015-10-01

Chitin/CaCO3 hybrids with helical structures are formed through a biomineralization-inspired crystallization process under ambient conditions. Liquid-crystalline chitin whiskers are used as helically ordered templates. The liquid-crystalline structures are stabilized by acidic polymer networks which interact with the chitin templates. The crystallization of CaCO3 is conducted by soaking the templates in the colloidal suspension of amorphous CaCO3 (ACC) at room temperature. At the initial stage of crystallization, ACC particles are introduced inside the templates, and they crystallize to CaCO3 nanocrystals. The acidic polymer networks induce CaCO3 crystallization. The characterization of the resultant hybrids reveals that they possess helical order and homogeneous hybrid structures of chitin and CaCO3 , which resemble the structure and composition of the exoskeleton of crustaceans. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Oriented Y-type hexagonal ferrite thin films prepared by chemical solution deposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Buršík, J., E-mail: bursik@iic.cas.cz; Kužel, R.; Knížek, K.

2013-07-15

Thin films of Ba{sub 2}Zn{sub 2}Fe{sub 12}O{sub 22} (Y) hexaferrite were prepared through the chemical solution deposition method on SrTiO{sub 3}(1 1 1) (ST) single crystal substrates using epitaxial SrFe{sub 12}O{sub 19} (M) hexaferrite thin layer as a seed template layer. The process of crystallization was mainly investigated by means of X-ray diffraction and atomic force microscopy. A detailed inspection revealed that growth of seed layer starts through the break-up of initially continuous film into isolated grains with expressive shape anisotropy and hexagonal habit. The vital parameters of the seed layer, i.e. thickness, substrate coverage, crystallization conditions and temperature rampmore » were optimized with the aim to obtain epitaxially crystallized Y phase. X-ray diffraction Pole figure measurements and Φ scans reveal perfect parallel in-plane alignment of SrTiO{sub 3} substrate and both hexaferrite phases. - Graphical abstract: XRD pole figure and AFM patterns of Ba{sub 2}Zn{sub 2}Fe{sub 12}O{sub 22} thin film epitaxially grown on SrTiO{sub 3}(1 1 1) single crystal using seeding layer templating. - Highlights: • Single phase Y-type hexagonal ferrite thin films were prepared by CSD method. • Seed M layer breaks into isolated single crystal islands and serves as a template. • Large seed grains grow by consuming the grains within the bulk of recoated film. • We explained the observed orientation relation of epitaxial domains. • Epitaxial growth on SrTiO{sub 3}(1 1 1) with relation (0 0 1){sub M,Y}//(1 1 1){sub ST}+[1 0 0]{sub M,Y}//[2 −1 −1]{sub ST}.« less

The effect of adding CTAB template in ZSM-5 synthesis

NASA Astrophysics Data System (ADS)

Widayat, Widayat; Annisa, Arianti Nuur

2017-11-01

In general, ZSM-5 synthesis is performed using a hydrothermal process that takes place at high temperature and high pressure (> 373 K,> 1 bar). The synthesis of ZSM-5 is influenced by the organic template used. The organic template serves as a determinant of the zeolite crystal structure formation. CTAB is an easily found organic template and the price is cheap so the production cost of ZSM-5 synthesis would be more efficient. In this research, ZSM-5 is synthesized by varying temperature and crystallization time. The result showed the optimal condition of ZSM-5 synthesis was at 363 K for the crystallization temperature with 8 hours of crystallization time. The crystalline product had 60.07% of crystallinity with an aluminosilicate composition of 72% w/w.

Fabrication of Au- and Ag–SiO{sub 2} inverse opals having both localized surface plasmon resonance and Bragg diffraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Erola, Markus O.A.; Philip, Anish; Ahmed, Tanzir

The inverse opal films of SiO{sub 2} containing metal nanoparticles can have both the localized surface plasmon resonance (LSPR) of metal nanoparticles and the Bragg diffraction of inverse opal crystals of SiO{sub 2}, which are very useful properties for applications, such as tunable photonic structures, catalysts and sensors. However, effective processes for fabrication of these films from colloidal particles have rarely been reported. In our study, two methods for preparation of inverse opal films of SiO{sub 2} with three different crystal sizes and containing gold or silver nanoparticles (NPs) via self-assembly using electrostatic interactions and capillary forces are reported. Themore » Bragg diffraction of inverse opal films of SiO{sub 2} in the presence and absence of the template was measured and predicted on the basis of with UV–vis spectroscopy and scanning electron microscopy. The preparation methods used provided good-quality inverse opal SiO{sub 2} films containing highly dispersed, plasmonic AuNPs or AgNPs and having both Bragg diffractions and LSPRs. - Graphical abstract: For syntheses of SiO{sub 2} inverse opals containing Au/Ag nanoparticles two approaches and three template sizes were employed. Self-assembly of template molecules and metal nanoparticles occurred using electrostatic interactions and capillary forces. Both the Bragg diffraction of the photonic crystal and the localized surface plasmon resonance of Au/Ag nanoparticles were detected. - Highlights: • Fabrication methods of silica inverse opals containing metal nanoparticles studied. • Three template sizes used to produce SiO{sub 2} inverse opals with Au/Ag nanoparticles. • PS templates with Au nanoparticles adsorbed used in formation of inverse opals. • Ag particles infiltrated in inverse opals with capillary and electrostatic forces. • Bragg diffractions of IOs and surface plasmon resonances of nanoparticles observed.« less

Advances in nanosized zeolites

NASA Astrophysics Data System (ADS)

Mintova, Svetlana; Gilson, Jean-Pierre; Valtchev, Valentin

2013-07-01

This review highlights recent developments in the synthesis of nanosized zeolites. The strategies available for their preparation (organic-template assisted, organic-template free, and alternative procedures) are discussed. Major breakthroughs achieved by the so-called zeolite crystal engineering and encompass items such as mastering and using the physicochemical properties of the precursor synthesis gel/suspension, optimizing the use of silicon and aluminium precursor sources, the rational use of organic templates and structure-directing inorganic cations, and careful adjustment of synthesis conditions (temperature, pressure, time, heating processes from conventional to microwave and sonication) are addressed. An on-going broad and deep fundamental understanding of the crystallization process, explaining the influence of all variables of this complex set of reactions, underpins an even more rational design of nanosized zeolites with exceptional properties. Finally, the advantages and limitations of these methods are addressed with particular attention to their industrial prospects and utilization in existing and advanced applications.

Single crystalline hollow metal-organic frameworks: a metal-organic polyhedron single crystal as a sacrificial template.

PubMed

Kim, Hyehyun; Oh, Minhak; Kim, Dongwook; Park, Jeongin; Seong, Junmo; Kwak, Sang Kyu; Lah, Myoung Soo

2015-02-28

Single crystalline hollow metal-organic frameworks (MOFs) with cavity dimensions on the order of several micrometers and hundreds of micrometers were prepared using a metal-organic polyhedron single crystal as a sacrificial hard template. The hollow nature of the MOF crystal was confirmed by scanning electron microscopy of the crystal sliced using a focused ion beam.

Inverse opal photonic crystals with photonic band gaps in the visible and near-infrared

NASA Astrophysics Data System (ADS)

Jarvis, Brandon C.; Gilleland, Cody L.; Renfro, Tim; Gutierrez, Jose; Parikh, Kunjal; Glosser, R.; Landon, Preston B.

2005-08-01

Colloidal silica spheres with 200nm, 250nm, and 290nm diameters were self-assembled with single crystal crystallites 4-5mm wide and 10-15mm long. Larger spheres with diameters between 1000-2300nm were self-assembled with single crystal crystallites up to 1.5mm wide and 2mm long. The silica opals self-assembled vertically along the [100] direction of the face centered cubic lattice resulting in self-templated opals. Inverse opal photonic crystals with a partial band gap possessing a maximum in the near infrared at 3.8μm were constructed from opal templates composed of 2300nm diameter spheres with chalcogenide Ge33As12Se55 (AMTIR-1), a transparent glass in the near infrared with high refractive index. Inverse gold and gold/ polypropylene composite photonic crystals were fabricated from synthetic opal templates composed of 200-290nm silica spheres. The reflectance spectra and electrical conductance of the resulting structures is presented. Gold was infiltrated into opal templates as gold chloride and heat converted to metallic gold. Opals partially infiltrated with gold were co-infiltrated with polypropylene plastic for mechanical support prior to removal of the silica template with hydrofluoric acid.

Low-Voltage Organic Single-Crystal Field-Effect Transistor with Steep Subthreshold Slope.

PubMed

Yang, Fangxu; Sun, Lingjie; Han, Jiangli; Li, Baili; Yu, Xi; Zhang, Xiaotao; Ren, Xiaochen; Hu, Wenping

2018-03-06

Anodization is a promising technique to form high- k dielectrics for low-power organic field-effect transistor (OFET) applications. However, the surface quality of the dielectric, which is mainly inherited from the metal electrode, can be improved further than other fabrication techniques, such as sol-gel. In this study, we applied the template stripping method to fabricate a low-power single-crystalline OFET based on the anodized AlO x dielectric. We found that the template stripping method largely improves the surface roughness of the deposited Al and allows for the formation of a high-quality AlO x high- k dielectric by anodization. The ultraflat AlO x /SAM dielectric combined with a single-crystal 2,6-diphenylanthracene (DPA) semiconductor produced a nearly defect-free interface with a steep subthreshold swing (SS) of 66 mV/decade. The current device is a promising candidate for future ultralow-power applications. Other than metal deposition, template stripping could provide a general approach to improve thin-film quality for many other types of materials and processes.

Synthesis of three-dimensionally ordered macro-/mesoporous Pt with high electrocatalytic activity by a dual-templating approach

NASA Astrophysics Data System (ADS)

Zhang, Chengwei; Yang, Hui; Sun, Tingting; Shan, Nannan; Chen, Jianfeng; Xu, Lianbin; Yan, Yushan

2014-01-01

Three dimensionally ordered macro-/mesoporous (3DOM/m) Pt catalysts are fabricated by chemical reduction employing a dual-templating synthesis approach combining both colloidal crystal (opal) templating (hard-templating) and lyotropic liquid crystal templating (soft-templating) techniques. The macropore walls of the prepared 3DOM/m Pt exhibit a uniform mesoporous structure composed of polycrystalline Pt nanoparticles. Both the size of the mesopores and Pt nanocrystallites are in the range of 3-5 nm. The 3DOM/m Pt catalyst shows a larger electrochemically active surface area (ECSA), and higher catalytic activity as well as better poisoning tolerance for methanol oxidation reaction (MOR) than the commercial Pt black catalyst.

Investigation of surface-modified solid lipid nanocontainers formulated with a heterolipid-templated homolipid.

PubMed

Attama, A A; Müller-Goymann, C C

2007-04-04

There is increasing interest in the search for improved drug delivery systems with greater versatility. Consequently, many drug delivery systems have been studied. In this study, surface-modified lipid nanocontainers were formulated with a homolipid from Capra hircus (goat fat) templated with a heterolipid (Phospholipon 90G) which was also the surface modifier. The solid lipid nanocontainers (SLN) were formulated by hot high pressure homogenisation using increasing concentrations of polysorbate 80 as the mobile surfactant. Prior to SLN preparation, the templated homolipid was formulated by fusion to obtain a homogeneous lipid matrix, which was characterized using differential scanning calorimetry (DSC), polarized light microscopy (PLM) and wide angle X-ray diffraction (WAXD) to obtain its thermal and crystal characteristics. Isothermal heat conduction microcalorimetry (IMC) and freeze-fracture transmission electron microscopy (FFTEM) studies were carried out on the templated homolipid and SLN containing 1.0% (w/w) of polysorbate 80 to study their in situ crystallization kinetics and morphology, respectively. The formulated SLN were also subjected to time-resolved DSC, WAXD and particle size analyses for one month. The thermal and crystal characteristics were compared with those of the bulk lipid matrix (templated homolipid). Result of the particle size analysis indicated that the particles size remained roughly within the lower nanometer range after one month. FFTEM micrograph of the lipid matrices revealed lamellar sheets for Phospholipon 90G and layered triglyceride structures for the homolipid and Phospholipon 90G-templated homolipid. FFTEM micrograph of SLN revealed anisometric structures. PLM of the templated homolipid did not show, but goat fat (homolipid) alone showed slight growth in crystals with time. WAXD and DSC studies revealed minor increase in crystallinity of the new lipid matrix after one month and DSC also detected templation of homolipid by the heterolipid noted by the disappearance of the lower melting peak of the homolipid. However, for the SLN, WAXD results showed low crystalline particles while DSC only showed a very little endothermic process after one month of storage at 20 degrees C. The implication of this finding is that progression of the SLN to highly ordered particles over time would not occur. This will be favourable for any incorporated drug as drug expulsion, due to increase in crystallinity, will not occur. Result obtained from analysis of the isothermal crystallization exotherms indicated that the templated homolipid and SLN1 containing 1.0% polysorbate 80 possess similar nucleation mechanisms and growth dimensions different from the pure homolipid. The SLN containing 0.5 and 1.0% polysorbate 80 possessed good properties and could prove to be good delivery systems for drugs for parenteral or ocular administration. The result of this study also shows a method of improving natural lipids for use in particulate drug delivery systems.

Inkjet-Printed Nanocavities on a Photonic Crystal Template.

PubMed

Brossard, Frederic S F; Pecunia, Vincenzo; Ramsay, Andrew J; Griffiths, Jonathan P; Hugues, Maxime; Sirringhaus, Henning

2017-12-01

The last decade has witnessed the rapid development of inkjet printing as an attractive bottom-up microfabrication technology due to its simplicity and potentially low cost. The wealth of printable materials has been key to its widespread adoption in organic optoelectronics and biotechnology. However, its implementation in nanophotonics has so far been limited by the coarse resolution of conventional inkjet-printing methods. In addition, the low refractive index of organic materials prevents the use of "soft-photonics" in applications where strong light confinement is required. This study introduces a hybrid approach for creating and fine tuning high-Q nanocavities, involving the local deposition of an organic ink on the surface of an inorganic 2D photonic crystal template using a commercially available high-resolution inkjet printer. The controllability of this approach is demonstrated by tuning the resonance of the printed nanocavities by the number of printer passes and by the fabrication of photonic crystal molecules with controllable splitting. The versatility of this method is evidenced by the realization of nanocavities obtained by surface deposition on a blank photonic crystal. A new method for a free-form, high-density, material-independent, and high-throughput fabrication technique is thus established with a manifold of opportunities in photonic applications. © 2017 Hitachi Cambridge Laboratory. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A simple template method for hierarchical dendrites of silver nanorods and their applications in catalysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gao Peng; Zhang Milin; Hou Hongwei

2008-03-04

A novel strategy has been put forward to prepare hierarchical dendrites of silver nanorods via a simple integration method using 'Devarda's template' as a reducing agent and architecture template with the assistance of ultrasonic waves, in which the template was firstly fabricated and employed. The individual silver dendrite is composed of a long central trunk with secondary branches, which preferentially grew in a parallel direction with a definite angle to the trunk. The results reveal that the dendrites are single crystalline in nature and interestingly prove that the silver single crystal has the preferential orientation in <1 1 1> directionmore » in normal conditions. The contrast experiments demonstrated that both 'Devarda's template' and the ultrasonic irradiation are necessary for building hierarchically silver dendrites in a water system. Moreover, the experimental results show that the dendrites of silver nanorods are the superior electrode materials for the electrochemical sensors to detect directly NO{sub 2}{sup -} in aqueous solution.« less

Synthesis of Mesoporous Single Crystal Co(OH)2 Nanoplate and Its Topotactic Conversion to Dual-Pore Mesoporous Single Crystal Co3O4.

PubMed

Jia, Bao-Rui; Qin, Ming-Li; Li, Shu-Mei; Zhang, Zi-Li; Lu, Hui-Feng; Chen, Peng-Qi; Wu, Hao-Yang; Lu, Xin; Zhang, Lin; Qu, Xuan-Hui

2016-06-22

A new class of mesoporous single crystalline (MSC) material, Co(OH)2 nanoplates, is synthesized by a soft template method, and it is topotactically converted to dual-pore MSC Co3O4. Most mesoporous materials derived from the soft template method are reported to be amorphous or polycrystallined; however, in our synthesis, Co(OH)2 seeds grow to form single crystals, with amphiphilic block copolymer F127 colloids as the pore producer. The single-crystalline nature of material can be kept during the conversion from Co(OH)2 to Co3O4, and special dual-pore MSC Co3O4 nanoplates can be obtained. As the anode of lithium-ion batteries, such dual-pore MSC Co3O4 nanoplates possess exceedingly high capacity as well as long cyclic performance (730 mAh g(-1) at 1 A g(-1) after the 350th cycle). The superior performance is because of the unique hierarchical mesoporous structure, which could significantly improve Li(+) diffusion kinetics, and the exposed highly active (111) crystal planes are in favor of the conversion reaction in the charge/discharge cycles.

Epitaxial growth of three dimensionally structured III-V photonic crystal via hydride vapor phase epitaxy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng, Qiye; Kim, Honggyu; Zhang, Runyu

2015-12-14

Three-dimensional (3D) photonic crystals are one class of materials where epitaxy, and the resultant attractive electronic properties, would enable new functionalities for optoelectronic devices. Here we utilize self-assembled colloidal templates to fabricate epitaxially grown single crystal 3D mesostructured GaxIn1-xP (GaInP) semiconductor photonic crystals using hydride vapor phase epitaxy (HVPE). The epitaxial relationship between the 3D GaInP and the substrate is preserved during the growth through the complex geometry of the template as confirmed by X-ray diffraction (XRD) and high resolution transmission electron microscopy. XRD reciprocal space mapping of the 3D epitaxial layer further demonstrates the film to be nearly fullymore » relaxed with a negligible strain gradient. Fourier transform infrared spectroscopy reflection measurement indicates the optical properties of the photonic crystal which agree with finite difference time domain simulations. This work extends the scope of the very few known methods for the fabrication of epitaxial III-V 3D mesostructured materials to the well-developed HVPE technique.« less

Epitaxial growth of three dimensionally structured III-V photonic crystal via hydride vapor phase epitaxy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng, Qiye; Kim, Honggyu; Zhang, Runyu

2015-12-14

Three-dimensional (3D) photonic crystals are one class of materials where epitaxy, and the resultant attractive electronic properties, would enable new functionalities for optoelectronic devices. Here we utilize self-assembled colloidal templates to fabricate epitaxially grown single crystal 3D mesostructured Ga{sub x}In{sub 1−x}P (GaInP) semiconductor photonic crystals using hydride vapor phase epitaxy (HVPE). The epitaxial relationship between the 3D GaInP and the substrate is preserved during the growth through the complex geometry of the template as confirmed by X-ray diffraction (XRD) and high resolution transmission electron microscopy. XRD reciprocal space mapping of the 3D epitaxial layer further demonstrates the film to bemore » nearly fully relaxed with a negligible strain gradient. Fourier transform infrared spectroscopy reflection measurement indicates the optical properties of the photonic crystal which agree with finite difference time domain simulations. This work extends the scope of the very few known methods for the fabrication of epitaxial III-V 3D mesostructured materials to the well-developed HVPE technique.« less

Ordered nanoparticle arrays formed on engineered chaperonin protein templates

NASA Technical Reports Server (NTRS)

McMillan, R. Andrew; Paavola, Chad D.; Howard, Jeanie; Chan, Suzanne L.; Zaluzec, Nestor J.; Trent, Jonathan D.

2002-01-01

Traditional methods for fabricating nanoscale arrays are usually based on lithographic techniques. Alternative new approaches rely on the use of nanoscale templates made of synthetic or biological materials. Some proteins, for example, have been used to form ordered two-dimensional arrays. Here, we fabricated nanoscale ordered arrays of metal and semiconductor quantum dots by binding preformed nanoparticles onto crystalline protein templates made from genetically engineered hollow double-ring structures called chaperonins. Using structural information as a guide, a thermostable recombinant chaperonin subunit was modified to assemble into chaperonins with either 3 nm or 9 nm apical pores surrounded by chemically reactive thiols. These engineered chaperonins were crystallized into two-dimensional templates up to 20 microm in diameter. The periodic solvent-exposed thiols within these crystalline templates were used to size-selectively bind and organize either gold (1.4, 5 or 10nm) or CdSe-ZnS semiconductor (4.5 nm) quantum dots into arrays. The order within the arrays was defined by the lattice of the underlying protein crystal. By combining the self-assembling properties of chaperonins with mutations guided by structural modelling, we demonstrate that quantum dots can be manipulated using modified chaperonins and organized into arrays for use in next-generation electronic and photonic devices.

Control of Orientation and Morphology of Crystals Grown Under Organic Templates

NASA Astrophysics Data System (ADS)

Stripe, Benjamin

Living creatures demonstrate an extraordinary ability to both grow and control the growth of inorganic crystals. These biominerals are found almost everywhere in nature from simple plants and plankton to our own teeth and bones. A great deal of research has been focused on how living creatures are able to achieve such control over the shape, size, orientation, and arrangement of these biominerals. Many studies have been done demonstrating the effects the presence of organic molecules can have on the morphology of nucleating inorganic crystals. These studies have led to the use of ordered arrays of biological molecules as templates to select the orientation of the crystals. Such experiments have had amazing success cataloging monolayers, orientations and morphologies of crystals grown beneath them. However, despite several decades of work, the exact mechanisms by which the orientation and morphology of crystals is selected by organic templates are still not known. The present study attempts to explain the complex interactions that take place at the template surface and decide the orientations and morphologies of the crystals that nucleate there. To do this, scanning electron microscopy (SEM), grazing incidence x-ray diffraction (GID), and x-ray reflectivity have been used to probe the templates and nucleating crystals in situ. The experiments described here seek to move beyond the well-studied two-component systems. In many of these two-component systems a single template and a single type of crystal are grown, and often many claims and comparisons are made about monolayer charge, crystal surface energies, stereochemical recognition, and lattice matches. However, almost all of the claims and comparisons are between systems that are different enough that assumptions about relative charge, strain, recognition, and lattice dynamics are either unfounded or poorly supported. To bridge this gap in the comparison of these different two-component systems the studies presented here are tunable three-component systems. These experiments allow for either continuously adjusting the template by means of two miscible monolayers or adjusting the growing crystals by incorporation of secondary ions. In either case, the idea is the same: we can more accurately compare two-component systems and isolate the controlling factor in the selection of orientation and morphology of the nucleating crystals. The results of these studies have shown that there is a complex interplay of charge, lattice parameters and kinetics. Despite this, we have been able to show that well-oriented growth of single non-dendritic crystals is limited to a fairly small range of surface charges and relative growth kinetics. Within this range, variations in the growing crystals can be seen based on changes in the average lattice parameters despite there being no evidence of direct epitaxy. Theories have evolved around the idea of stereochemical matching between the template and nucleating surface. These theories correlate the template molecular tilt to the orientation relative to the nucleation plane. However, these theories are not supported by the results presented in this manuscript. The data presented in this manuscript are suggestive of far more complex interfacial interactions involving an intermediary amorphous precursor, or possible networks of hydrated or hydrogen bonded ions than has been suggested in previous studies. Excitingly, it appears to be possible to control the selection of orientation using these multicomponent systems despite the complex interactions at the surface.

Rational design of mesoporous metals and related nanomaterials by a soft-template approach.

PubMed

Yamauchi, Yusuke; Kuroda, Kazuyuki

2008-04-07

We review recent developments in the preparation of mesoporous metals and related metal-based nanomaterials. Among the many types of mesoporous materials, mesoporous metals hold promise for a wide range of potential applications, such as in electronic devices, magnetic recording media, and metal catalysts, owing to their metallic frameworks. Mesoporous metals with highly ordered networks and narrow pore-size distributions have traditionally been produced by using mesoporous silica as a hard template. This method involves the formation of an original template followed by deposition of metals within the mesopores and subsequent removal of the template. Another synthetic method is the direct-template approach from lyotropic liquid crystals (LLCs) made of nonionic surfactants at high concentrations. Direct-template synthesis creates a novel avenue for the production of mesoporous metals as well as related metal-based nanomaterials. Many mesoporous metals have been prepared by the chemical or electrochemical reduction of metal salts dissolved in aqueous LLC domains. As a soft template, LLCs are more versatile and therefore more advantageous than hard templates. It is possible to produce various nanostructures (e.g., lamellar, 2D hexagonal (p6mm), and 3D cubic (Ia\\3d)), nanoparticles, and nanotubes simply by controlling the composition of the reaction bath.

PEG-nanotube liquid crystals as templates for construction of surfactant-free gold nanorods.

PubMed

Kameta, Naohiro; Shiroishi, Hidenobu

2018-05-03

Lyotropic liquid crystals, in which nanotubes coated with polyethylene glycol were aligned side-by-side in aqueous dispersions, acted as templates for the construction of surfactant-free gold nanorods with controllable diameters, functionalizable surfaces, and tunable optical properties.

An automated method for modeling proteins on known templates using distance geometry.

PubMed

Srinivasan, S; March, C J; Sudarsanam, S

1993-02-01

We present an automated method incorporated into a software package, FOLDER, to fold a protein sequence on a given three-dimensional (3D) template. Starting with the sequence alignment of a family of homologous proteins, tertiary structures are modeled using the known 3D structure of one member of the family as a template. Homologous interatomic distances from the template are used as constraints. For nonhomologous regions in the model protein, the lower and the upper bounds for the interatomic distances are imposed by steric constraints and the globular dimensions of the template, respectively. Distance geometry is used to embed an ensemble of structures consistent with these distance bounds. Structures are selected from this ensemble based on minimal distance error criteria, after a penalty function optimization step. These structures are then refined using energy optimization methods. The method is tested by simulating the alpha-chain of horse hemoglobin using the alpha-chain of human hemoglobin as the template and by comparing the generated models with the crystal structure of the alpha-chain of horse hemoglobin. We also test the packing efficiency of this method by reconstructing the atomic positions of the interior side chains beyond C beta atoms of a protein domain from a known 3D structure. In both test cases, models retain the template constraints and any additionally imposed constraints while the packing of the interior residues is optimized with no short contacts or bond deformations. To demonstrate the use of this method in simulating structures of proteins with nonhomologous disulfides, we construct a model of murine interleukin (IL)-4 using the NMR structure of human IL-4 as the template. The resulting geometry of the nonhomologous disulfide in the model structure for murine IL-4 is consistent with standard disulfide geometry.

Langmuir-Blodgett nanotemplates for protein crystallography.

PubMed

Pechkova, Eugenia; Nicolini, Claudio

2017-12-01

The new generation of synchrotrons and microfocused beamlines has enabled great progress in X-ray protein crystallography, resulting in new 3D atomic structures for proteins of high interest to the pharmaceutical industry and life sciences. It is, however, often still challenging to produce protein crystals of sufficient size and quality (order, intensity of diffraction, radiation stability). In this protocol, we provide instructions for performing the Langmuir-Blodgett (LB) nanotemplate method, a crystallization approach that can be used for any protein (including membrane proteins). We describe how to produce highly ordered 2D LB protein monolayers at the air-water interface and deposit them on glass slides. LB-film formation can be observed by surface-pressure measurements and Brewster angle microscopy (BAM), although its quality can be characterized by atomic force microscopy (AFM) and nanogravimetry. Such films are then used as a 2D template for triggering 3D protein crystal formation by hanging-drop vapor diffusion. The procedure for forming the 2D template takes a few minutes. Structural information about the protein reorganization in the LB film during the crystallization process on the nano level can be obtained using an in situ submicron GISAXS (grazing-incidence small-angle X-ray scattering) method. MicroGISAXS spectra, measured directly at the interface of the LB films and protein solution in real time, as described in this protocol, can be interpreted in terms of the buildup of layers, islands, or holes. In our experience, the obtained LB crystals take 1-10 d to prepare and they are more ordered and radiation stable as compared with those produced using other crystallization methods.

Two-Dimensional Fullerene Assembly from an Exfoliated van der Waals Template.

PubMed

Lee, Kihong; Choi, Bonnie; Plante, Ilan Jen-La; Paley, Maria V; Zhong, Xinjue; Crowther, Andrew C; Owen, Jonathan S; Zhu, Xiaoyang; Roy, Xavier

2018-05-22

Two-dimensional (2D) materials are commonly prepared by exfoliating bulk layered van der Waals crystals. The creation of synthetic 2D materials from bottom-up methods is an important challenge as their structural flexibility will enable chemists to tune the materials properties. A 2D material was assembled using C 60 as a polymerizable monomer. The C 60 building blocks are first assembled into a layered solid using a molecular cluster as structure director. The resulting hierarchical crystal is used as a template to polymerize its C 60 monolayers, which can be exfoliated down to 2D crystalline nanosheets. Derived from the parent template, the 2D structure is composed of a layer of inorganic cluster, sandwiched between two monolayers of polymerized C 60 . The nanosheets can be transferred onto solid substrates and depolymerized by heating. Electronic absorption spectroscopy reveals an optical gap of 0.25 eV, narrower than that of the bulk parent crystalline solid. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Blue-phase templated fabrication of three-dimensional nanostructures for photonic applications.

PubMed

Castles, F; Day, F V; Morris, S M; Ko, D-H; Gardiner, D J; Qasim, M M; Nosheen, S; Hands, P J W; Choi, S S; Friend, R H; Coles, H J

2012-05-13

A promising approach to the fabrication of materials with nanoscale features is the transfer of liquid-crystalline structure to polymers. However, this has not been achieved in systems with full three-dimensional periodicity. Here we demonstrate the fabrication of self-assembled three-dimensional nanostructures by polymer templating blue phase I, a chiral liquid crystal with cubic symmetry. Blue phase I was photopolymerized and the remaining liquid crystal removed to create a porous free-standing cast, which retains the chiral three-dimensional structure of the blue phase, yet contains no chiral additive molecules. The cast may in turn be used as a hard template for the fabrication of new materials. By refilling the cast with an achiral nematic liquid crystal, we created templated blue phases that have unprecedented thermal stability in the range -125 to 125 °C, and that act as both mirrorless lasers and switchable electro-optic devices. Blue-phase templated materials will facilitate advances in device architectures for photonics applications in particular.

A facile precursor route to highly loaded metal/ceramic nanofibers as a robust surface-enhanced Raman template

NASA Astrophysics Data System (ADS)

Park, Jay Hoon; Joo, Yong Lak

2017-09-01

We report silver (Ag)/ceramic nanofibers with highly robust and sensitive optical sensory capabilities that can withstand harsh conditions. These nanofibers are fabricated by first electrospinning solutions of poly vinyl alcohol (PVA) and metal precursor polymers, followed by subsequent series of heat treatment. The reported fabrication method demonstrate the effects of (i) the location of Ag crystals, (ii) crystal size and shape, and (iii) constituents of the ceramic matrix as surface-enhanced Raman spectroscopy (SERS) templates with 10-6 M 4-mercaptobenzoic acid (4-MBA). Notably, these silver/ceramic nanofibers preserved most of their highly sensitive localized surface plasmon resonance (LSPR) even under high temperature of 400 °C, in contrast to preformed Ag nanoparticles (NPs) in PVA nanofibers which lost most of its optical property presumably due to (i) Ag oxidation and (ii) loss of the matrix material. Among the ceramic substrates of ZrO2, Al2O3, and ZnO with silver crystals, we discovered that the ZnO substrate showed the most consistent and the strongest signal strength owing to the synergistic chemical and optical properties of the ZnO substrate. Moreover, the pure Ag nanofiber proved to be the best heat-resistant SERS template, owing to its (i) anisotropic morphology and (ii) thicker diameter when compared with other conventional Ag nanomaterials. These results demonstrated simple yet highly controllable fabrication of robust SERS templates, with potential applications in a catalytic sensory which is often exposed to harsh conditions.

Photonic band gap templating using optical interference lithography

NASA Astrophysics Data System (ADS)

Chan, Timothy Y. M.; Toader, Ovidiu; John, Sajeev

2005-04-01

We describe the properties of three families of inversion-symmetric, large photonic band-gap (PBG) template architectures defined by iso-intensity surfaces in four beam laser interference patterns. These templates can be fabricated by optical interference (holographic) lithography in a suitable polymer photo-resist. PBG materials can be synthesized from these templates using two stages of infiltration and inversion, first with silica and second with silicon. By considering point and space group symmetries to produce laser interference patterns with the smallest possible irreducible Brillouin zones, we obtain laser beam intensities, directions, and polarizations which generate a diamond-like (fcc) crystal, a novel body-centered cubic (bcc) architecture, and a simple-cubic (sc) structure. We obtain laser beam parameters that maximize the intensity contrasts of the interference patterns. This optimizes the robustness of the holographic lithography to inhomogeneity in the polymer photo-resist. When the optimized iso-intensity surface defines a silicon to air boundary (dielectric contrast of 11.9 to 1), the fcc, bcc, and sc crystals have PBG to center frequency ratios of 25%, 21%, and 11%, respectively. A full PBG forms for the diamond-like crystal when the refractive index contrast exceeds 1.97 to 1. We illustrate a noninversion symmetric PBG architecture that interpolates between a simple fcc structure and a diamond network structure. This crystal exhibits two distinct and complete photonic band gaps. We also describe a generalized class of tetragonal photonic crystals that interpolate between and extrapolate beyond the diamond-like crystal and the optimized bcc crystal. We demonstrate the extent to which the resulting PBG materials are robust against perturbations to the laser beam amplitudes and polarizations, and template inhomogeneity. The body centered cubic structure exhibits the maximum robustness overall.

Single-crystal gallium nitride nanotubes.

PubMed

Goldberger, Joshua; He, Rongrui; Zhang, Yanfeng; Lee, Sangkwon; Yan, Haoquan; Choi, Heon-Jin; Yang, Peidong

2003-04-10

Since the discovery of carbon nanotubes in 1991 (ref. 1), there have been significant research efforts to synthesize nanometre-scale tubular forms of various solids. The formation of tubular nanostructure generally requires a layered or anisotropic crystal structure. There are reports of nanotubes made from silica, alumina, silicon and metals that do not have a layered crystal structure; they are synthesized by using carbon nanotubes and porous membranes as templates, or by thin-film rolling. These nanotubes, however, are either amorphous, polycrystalline or exist only in ultrahigh vacuum. The growth of single-crystal semiconductor hollow nanotubes would be advantageous in potential nanoscale electronics, optoelectronics and biochemical-sensing applications. Here we report an 'epitaxial casting' approach for the synthesis of single-crystal GaN nanotubes with inner diameters of 30-200 nm and wall thicknesses of 5-50 nm. Hexagonal ZnO nanowires were used as templates for the epitaxial overgrowth of thin GaN layers in a chemical vapour deposition system. The ZnO nanowire templates were subsequently removed by thermal reduction and evaporation, resulting in ordered arrays of GaN nanotubes on the substrates. This templating process should be applicable to many other semiconductor systems.

Characterization of calcium carbonate crystals in pigeon yolk sacs with different incubation times.

PubMed

Song, Juan; Cheng, Haixia; Shen, Xinyu; Hu, Jingxiao; Tong, Hua

2014-05-01

Calcium carbonate crystals are known to form in the yolk sacs of fertile pigeon eggs at late stages of incubation. The composition and structure of these crystals were investigated, the crystallization environment was inspected, and the physical chemistry constants of the yolk fluid were determined through the incubation period. Polarized light microscopy was used to observe the generation and distribution of calcium carbonate crystals in the yolk sac. In addition, X-ray diffraction was employed to analyze the composition and crystal phase of the yolk sac. A decalcification and deproteination method was established to analyze the ultrastructure and composition of the crystals, as well as the internal relationship between inorganic and organic phases of the crystals. Additionally, scanning electron microscopy, transmission electron microscopy, X-ray energy dispersive spectroscopy, and Fourier transform infrared spectroscopy were used to evaluate the characteristics of the crystals. Our results demonstrated that the calcium carbonate crystals were mainly composed of vaterite and calcite, with vaterite being the major component. Vaterite, a type of biomaterial generated by an organic template control, presented as a concentric hierarchical spherical structure. The organic nature of the biomaterial prevented vaterite from transforming into calcite, which is more thermodynamically stable than vaterite. Additionally, the configuration, size, and aggregation of vaterite were also mediated by the organic template. This bio-vaterite was found during the incubation period and is valuable in calcium transport during embryonic development. Copyright © 2014 Elsevier Ltd. All rights reserved.

Macroporous ceramics by colloidal templating

NASA Astrophysics Data System (ADS)

Subramaniam, G.; Pine, David J.

2000-04-01

We describe a novel method of fabricating macroporous ceramics employing colloidal dispersion of ultrafine ceramic particles with latex particles as the templates. The colloidal particles form a particulate gel on drying and fill the voids of the ordered latex templates. Subsequent removal of the template by calcination results in the formation of an ordered macroporous ceramic. The process has significant advantages over the traditional sol-gel process employing alkoxide precursors. Most importantly, the much lower shrinkage compared to the sol-gel process enabled us to produce larger pieces of the sample. The larger shrinkage involved in the sol-gel process often results in small and fragile pieces of the macroporous material which has to be subsequently heat treated to induce crystallization. The ability to choose crystalline colloidal particles in our method obviates the need for heat treatment to achieve crystallinity. We have synthesized a variety of materials such as macroporous silica, titania, alumina and recently have also extended the approach to macroporous silicon which is not amenable to the sol-gel process.

Sacrificial template method of fabricating a nanotube

DOEpatents

Yang, Peidong [Berkeley, CA; He, Rongrui [Berkeley, CA; Goldberger, Joshua [Berkeley, CA; Fan, Rong [El Cerrito, CA; Wu, Yi-Ying [Albany, CA; Li, Deyu [Albany, CA; Majumdar, Arun [Orinda, CA

2007-05-01

Methods of fabricating uniform nanotubes are described in which nanotubes were synthesized as sheaths over nanowire templates, such as using a chemical vapor deposition process. For example, single-crystalline zinc oxide (ZnO) nanowires are utilized as templates over which gallium nitride (GaN) is epitaxially grown. The ZnO templates are then removed, such as by thermal reduction and evaporation. The completed single-crystalline GaN nanotubes preferably have inner diameters ranging from 30 nm to 200 nm, and wall thicknesses between 5 and 50 nm. Transmission electron microscopy studies show that the resultant nanotubes are single-crystalline with a wurtzite structure, and are oriented along the <001> direction. The present invention exemplifies single-crystalline nanotubes of materials with a non-layered crystal structure. Similar "epitaxial-casting" approaches could be used to produce arrays and single-crystalline nanotubes of other solid materials and semiconductors. Furthermore, the fabrication of multi-sheath nanotubes are described as well as nanotubes having multiple longitudinal segments.

Polymer-templated nucleation and crystal growth of perovskite films for solar cells with efficiency greater than 21%

NASA Astrophysics Data System (ADS)

Bi, Dongqin; Yi, Chenyi; Luo, Jingshan; Décoppet, Jean-David; Zhang, Fei; Zakeeruddin, Shaik Mohammed; Li, Xiong; Hagfeldt, Anders; Grätzel, Michael

2016-10-01

The past several years have witnessed the rapid emergence of a class of solar cells based on mixed organic-inorganic halide perovskites. Today’s state-of-the-art perovskite solar cells (PSCs) employ various methods to enhance nucleation and improve the smoothness of the perovskite films formed via solution processing. However, the lack of precise control over the crystallization process creates a risk of forming unwanted defects, for example, pinholes and grain boundaries. Here, we introduce an approach to prepare perovskite films of high electronic quality by using poly(methyl methacrylate) (PMMA) as a template to control nucleation and crystal growth. We obtain shiny smooth perovskite films of excellent electronic quality, as manifested by a remarkably long photoluminescence lifetime. We realize stable PSCs with excellent reproducibility showing a power conversion efficiency (PCE) of up to 21.6% and a certified PCE of 21.02% under standard AM 1.5G reporting conditions.

Interfacial Interaction in Anodic Aluminum Oxide Templates Modifies Morphology, Surface Area, and Crystallization of Polyamide-6 Nanofibers.

PubMed

Xue, Junhui; Xu, Yizhuang; Jin, Zhaoxia

2016-03-08

Here, we demonstrated that, when the precipitation process of polyamide-6 (PA6) solution happens in cylindrical channels of an anodized aluminum oxide membrane (AAO), interface interactions between a solid surface, solvent, non-solvent, and PA6 will influence the obtained polymer nanostructures, resulting in complex morphologies, increased surface area, and crystallization changes. With the enhancing interaction of PA6 and the AAO surface, the morphology of PA6 nanostructures changes from solid nanofibers, mesoporous, to bamboo-like, while at the same time, metastable γ-phase domains increase in these PA6 nanostructures. Brunauer-Emmett-Teller (BET) surface areas of solid, bamboo-like, and mesoporous PA6 nanofibers rise from 16, 20.9, to 25 m(2)/g. This study shows that interfacial interaction in AAO template fabrication can be used in manipulating the morphology and crystallization of one-dimensional polymer nanostructures. It also provides us a simple and novel method to create porous PA6 nanofibers with a large surface area.

In situ analysis of the organic framework in the prismatic layer of mollusc shell.

PubMed

Tong, Hua; Hu, Jiming; Ma, Wentao; Zhong, Guirong; Yao, Songnian; Cao, Nianxing

2002-06-01

A novel in situ analytic approach was constructed by means of ion sputtering, decalcification and deprotein techniques combining with scanning electron microscopy (SEM) and transmission electron microscope (TEM) ultrastructural analysis. The method was employed to determine the spatial distribution of the organic framework outside and the inner crystal and organic/inorganic interface spatial geometrical relationship in the prismatic layer of cristaris plicate (leach). The results show that there is a substructure of organic matrix in the intracrystalline region. The prismatic layer forms according to strict hierarchical configuration of regular pattern. Each unit of organic template of prismatic layer can uniquely determine the column crystal growth direction, spatial orientation and size. Cavity templates are responsible for supporting. limiting size and shape and determining the crystal growth spatial orientation, while the intracrystal organic matrix is responsible for providing nucleation point and inducing the nucleation process of calcite. The stereo hierarchical fabrication of prismatic layer was elucidated for the first time.

Size Controllable, Transparent, and Flexible 2D Silver Meshes Using Recrystallized Ice Crystals as Templates.

PubMed

Wu, Shuwang; Li, Linhai; Xue, Han; Liu, Kai; Fan, Qingrui; Bai, Guoying; Wang, Jianjun

2017-10-24

Ice templates have been widely utilized for the preparation of porous materials due to the obvious advantages, such as environmentally benign and applicable to a wide range of materials. However, it remains a challenge to have controlled pore size as well as dimension of the prepared porous materials with the conventional ice template, since it often employs the kinetically not-stable growing ice crystals as the template. For example, there is no report so far for the preparation of 2D metal meshes with tunable pore size based on the ice template, although facile and eco-friendly prepared metal meshes are highly desirable for wearable electronics. Here, we report the preparation of 2D silver meshes with tunable mesh size employing recrystallized ice crystals as templates. Ice recrystallization is a kinetically stable process; therefore, the grain size of recrystallized ice crystals can be easily tuned, e.g., by adding different salts and changing the annealing temperature. Consequently, the size and line width of silver meshes obtained after freeze-drying can be easily adjusted, which in turn varied the conductivity of the obtained 2D silver film. Moreover, the silver meshes are transparent and display stable conductivity after the repeated stretching and bending. It can be envisioned that this approach for the preparation of 2D conducting films is of practical importance for wearable electronics. Moreover, this study provides a generic approach for the fabrication of 2D meshes with a controllable pore size.

Morphology-controlled synthesis of Co{sub 3}O{sub 4} by one step template-free hydrothermal method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Keqing; Liu, Jiajia; Wen, Panyue

2015-07-15

Highlights: • Co{sub 3}O{sub 4} crystals had been synthesized by one step template-free hydrothermal method. • The H{sub 2}O{sub 2} plays a crucial role in morphological control of Co{sub 3}O{sub 4} nanostructures. • The morphology has significant effect on the optical property of Co{sub 3}O{sub 4}. - Abstract: We had developed a facile synthetic route of Co{sub 3}O{sub 4} crystals with different morphologies via one step template-free hydrothermal method. The phase and composition of the Co{sub 3}O{sub 4} were investigated by X-ray powder diffraction and Raman spectrum. The morphology and structure of the synthesized samples were characterized by scanning electronmore » microscopy and transmission electron microscopy. The H{sub 2}O{sub 2} played a crucial role in morphological control of Co{sub 3}O{sub 4} nanostructures. It only obtained Co-based precursor in the absence of H{sub 2}O{sub 2}. On the contrary, the Co{sub 3}O{sub 4} with different morphologies including nanoparticles, nano-discs and well-defined octahedral nanostructures were synthesized in the presence of H{sub 2}O{sub 2}. In addition, the optical property of the obtained Co{sub 3}O{sub 4} samples was investigated by UV–vis spectra.« less

Synthesis of non-siliceous mesoporous oxides.

PubMed

Gu, Dong; Schüth, Ferdi

2014-01-07

Mesoporous non-siliceous oxides have attracted great interest due to their unique properties and potential applications. Since the discovery of mesoporous silicates in 1990s, organic-inorganic assembly processes by using surfactants or block copolymers as soft templates have been considered as a feasible path for creating mesopores in metal oxides. However, the harsh sol-gel conditions and low thermal stabilities have limited the expansion of this method to various metal oxide species. Nanocasting, using ordered mesoporous silica or carbon as a hard template, has provided possibilities for preparing novel mesoporous materials with new structures, compositions and high thermal stabilities. This review concerns the synthesis, composition, and parameter control of mesoporous non-siliceous oxides. Four synthesis routes, i.e. soft-templating (surfactants or block copolymers as templates), hard-templating (mesoporous silicas or carbons as sacrificial templates), colloidal crystal templating (3-D ordered colloidal particles as a template), and super lattice routes, are summarized in this review. Mesoporous metal oxides with different compositions have different properties. Non-siliceous mesoporous oxides are comprehensively described, including a discussion of constituting elements, synthesis, and structures. General aspects concerning pore size control, atomic scale crystallinity, and phase control are also reviewed.

Abiotic ligation of DNA oligomers templated by their liquid crystal ordering

NASA Astrophysics Data System (ADS)

Fraccia, Tommaso P.; Smith, Gregory P.; Zanchetta, Giuliano; Paraboschi, Elvezia; Yi, Yougwooo; Walba, David M.; Dieci, Giorgio; Clark, Noel A.; Bellini, Tommaso

2015-03-01

It has been observed that concentrated solutions of short DNA oligomers develop liquid crystal ordering as the result of a hierarchically structured supramolecular self-assembly. In mixtures of oligomers with various degree of complementarity, liquid crystal microdomains are formed via the selective aggregation of those oligomers that have a sufficient degree of duplexing and propensity for physical polymerization. Here we show that such domains act as fluid and permeable microreactors in which the order-stabilized molecular contacts between duplex terminals serve as physical templates for their chemical ligation. In the presence of abiotic condensing agents, liquid crystal ordering markedly enhances ligation efficacy, thereby enhancing its own phase stability. The coupling between order-templated ligation and selectivity provided by supramolecular ordering enables an autocatalytic cycle favouring the growth of DNA chains, up to biologically relevant lengths, from few-base long oligomers. This finding suggests a novel scenario for the abiotic origin of nucleic acids.

A highly oriented hybrid microarray modified electrode fabricated by a template-free method for ultrasensitive electrochemical DNA recognition

NASA Astrophysics Data System (ADS)

Shi, Lei; Chu, Zhenyu; Dong, Xueliang; Jin, Wanqin; Dempsey, Eithne

2013-10-01

Highly oriented growth of a hybrid microarray was realized by a facile template-free method on gold substrates for the first time. The proposed formation mechanism involves an interfacial structure-directing force arising from self-assembled monolayers (SAMs) between gold substrates and hybrid crystals. Different SAMs and variable surface coverage of the assembled molecules play a critical role in the interfacial directing forces and influence the morphologies of hybrid films. A highly oriented hybrid microarray was formed on the highly aligned and vertical SAMs of 1,4-benzenedithiol molecules with rigid backbones, which afforded an intense structure-directing power for the oriented growth of hybrid crystals. Additionally, the density of the microarray could be adjusted by controlling the surface coverage of assembled molecules. Based on the hybrid microarray modified electrode with a large specific area (ca. 10 times its geometrical area), a label-free electrochemical DNA biosensor was constructed for the detection of an oligonucleotide fragment of the avian flu virus H5N1. The DNA biosensor displayed a significantly low detection limit of 5 pM (S/N = 3), a wide linear response from 10 pM to 10 nM, as well as excellent selectivity, good regeneration and high stability. We expect that the proposed template-free method can provide a new reference for the fabrication of a highly oriented hybrid array and the as-prepared microarray modified electrode will be a promising paradigm in constructing highly sensitive and selective biosensors.Highly oriented growth of a hybrid microarray was realized by a facile template-free method on gold substrates for the first time. The proposed formation mechanism involves an interfacial structure-directing force arising from self-assembled monolayers (SAMs) between gold substrates and hybrid crystals. Different SAMs and variable surface coverage of the assembled molecules play a critical role in the interfacial directing forces and influence the morphologies of hybrid films. A highly oriented hybrid microarray was formed on the highly aligned and vertical SAMs of 1,4-benzenedithiol molecules with rigid backbones, which afforded an intense structure-directing power for the oriented growth of hybrid crystals. Additionally, the density of the microarray could be adjusted by controlling the surface coverage of assembled molecules. Based on the hybrid microarray modified electrode with a large specific area (ca. 10 times its geometrical area), a label-free electrochemical DNA biosensor was constructed for the detection of an oligonucleotide fragment of the avian flu virus H5N1. The DNA biosensor displayed a significantly low detection limit of 5 pM (S/N = 3), a wide linear response from 10 pM to 10 nM, as well as excellent selectivity, good regeneration and high stability. We expect that the proposed template-free method can provide a new reference for the fabrication of a highly oriented hybrid array and the as-prepared microarray modified electrode will be a promising paradigm in constructing highly sensitive and selective biosensors. Electronic supplementary information (ESI) available: Four-probe method for determining the conductivity of the hybrid crystal (Fig. S1); stability comparisons of the hybrid films (Fig. S2); FESEM images of the hybrid microarray (Fig. S3); electrochemical characterizations of the hybrid films (Fig. S4); DFT simulations (Fig. S5); cross-sectional FESEM image of the hybrid microarray (Fig. S6); regeneration and stability tests of the DNA biosensor (Fig. S7). See DOI: 10.1039/c3nr03097k

Inverse opal photonic crystal of chalcogenide glass by solution processing.

PubMed

Kohoutek, Tomas; Orava, Jiri; Sawada, Tsutomu; Fudouzi, Hiroshi

2011-01-15

Chalcogenide opal and inverse opal photonic crystals were successfully fabricated by low-cost and low-temperature solution-based process, which is well developed in polymer films processing. Highly ordered silica colloidal crystal films were successfully infilled with nano-colloidal solution of the high refractive index As(30)S(70) chalcogenide glass by using spin-coating method. The silica/As-S opal film was etched in HF acid to dissolve the silica opal template and fabricate the inverse opal As-S photonic crystal. Both, the infilled silica/As-S opal film (Δn ~ 0.84 near λ=770 nm) and the inverse opal As-S photonic structure (Δn ~ 1.26 near λ=660 nm) had significantly enhanced reflectivity values and wider photonic bandgaps in comparison with the silica opal film template (Δn ~ 0.434 near λ=600 nm). The key aspects of opal film preparation by spin-coating of nano-colloidal chalcogenide glass solution are discussed. The solution fabricated "inorganic polymer" opal and the inverse opal structures exceed photonic properties of silica or any organic polymer opal film. The fabricated photonic structures are proposed for designing novel flexible colloidal crystal laser devices, photonic waveguides and chemical sensors. Copyright © 2010 Elsevier Inc. All rights reserved.

Organic-inorganic templates in biomineralization of shells, bone, teeth, and bacterial biofilms

NASA Astrophysics Data System (ADS)

de Stasio, Gelsomina Pupa

2005-03-01

Recent experiments with the Spectromicroscope for PHotoelectron Imaging of Nanostructure with X-rays (SPHINX)[1] on the biofilm formed by Fe-oxidizing bacteria in fresh, ground water, demonstrated that microbially extruded polysaccharide filaments provide the precipitation site for amorphous FeOOH filaments [2]. Upon aging the mineralized filaments crystallize to ferrihydrite (2-line FeOOH), with one curved pseudo-single crystal of akaganeite β-FeOOH), at the core of each filament. The crystals are only 2 nm wide and up to 10 micron long (aspect ratio 1:1000:1), and their structure and morphology is unprecedented. Furthermore, akaganeite should not form in fresh water, therefore a templation mechanism was hypothesized, and supported by SPHINX analysis of carbon XANES. The results indicate that after formation of the crystal fiber, the polysaccharide structure is also altered, and C1s spectra suggest that the COO^- group is involved in the templation mechanism. This was the first successful attempt to understand the organic-inorganic chemical interface in a biomineralized system. Many more templated biomineral systems can and will now be analyzed with this new approach. *Ultramicroscopy 99, 87-94 (2004). *Science 303, 1656-1658 (2004).

Porous Networks Through Colloidal Templates

NASA Astrophysics Data System (ADS)

Li, Qin; Retsch, Markus; Wang, Jianjun; Knoll, Wolfgang; Jonas, Ulrich

Porous networks represent a class of materials with interconnected voids with specific properties concerning adsorption, mass and heat transport, and spatial confinement, which lead to a wide range of applications ranging from oil recovery and water purification to tissue engineering. Porous networks with well-defined, highly ordered structure and periodicities around the wavelength of light can furthermore show very sophisticated optical properties. Such networks can be fabricated from a very large range of materials by infiltration of a sacrificial colloidal crystal template and subsequent removal of the template. The preparation procedures reported in the literature are discussed in this review and the resulting porous networks are presented with respect to the underlying material class. Furthermore, methods for hierarchical superstructure formation and functionalization of the network walls are discussed.

Templated Sphere Phase Liquid Crystals for Tunable Random Lasing

PubMed Central

Chen, Ziping; Hu, Dechun; Chen, Xingwu; Zeng, Deren; Lee, Yungjui; Chen, Xiaoxian; Lu, Jiangang

2017-01-01

A sphere phase liquid crystal (SPLC) composed of three-dimensional twist structures with disclinations among them exists between isotropic phase and blue phase in a very narrow temperature range, about several degrees centigrade. A low concentration polymer template is applied to improve the thermal stability of SPLCs and broadens the temperature range to more than 448 K. By template processing, a wavelength tunable random lasing is demonstrated with dye doped SPLC. With different polymer concentrations, the reconstructed SPLC random lasing may achieve more than 40 nm wavelength continuous shifting by electric field modulation. PMID:29140283

Spatially orthogonal chemical functionalization of a hierarchical pore network for catalytic cascade reactions

NASA Astrophysics Data System (ADS)

Parlett, Christopher M. A.; Isaacs, Mark A.; Beaumont, Simon K.; Bingham, Laura M.; Hondow, Nicole S.; Wilson, Karen; Lee, Adam F.

2016-02-01

The chemical functionality within porous architectures dictates their performance as heterogeneous catalysts; however, synthetic routes to control the spatial distribution of individual functions within porous solids are limited. Here we report the fabrication of spatially orthogonal bifunctional porous catalysts, through the stepwise template removal and chemical functionalization of an interconnected silica framework. Selective removal of polystyrene nanosphere templates from a lyotropic liquid crystal-templated silica sol-gel matrix, followed by extraction of the liquid crystal template, affords a hierarchical macroporous-mesoporous architecture. Decoupling of the individual template extractions allows independent functionalization of macropore and mesopore networks on the basis of chemical and/or size specificity. Spatial compartmentalization of, and directed molecular transport between, chemical functionalities affords control over the reaction sequence in catalytic cascades; herein illustrated by the Pd/Pt-catalysed oxidation of cinnamyl alcohol to cinnamic acid. We anticipate that our methodology will prompt further design of multifunctional materials comprising spatially compartmentalized functions.

An algorithm for automatic crystal identification in pixelated scintillation detectors using thin plate splines and Gaussian mixture models

NASA Astrophysics Data System (ADS)

Schellenberg, Graham; Stortz, Greg; Goertzen, Andrew L.

2016-02-01

A typical positron emission tomography detector is comprised of a scintillator crystal array coupled to a photodetector array or other position sensitive detector. Such detectors using light sharing to read out crystal elements require the creation of a crystal lookup table (CLUT) that maps the detector response to the crystal of interaction based on the x-y position of the event calculated through Anger-type logic. It is vital for system performance that these CLUTs be accurate so that the location of events can be accurately identified and so that crystal-specific corrections, such as energy windowing or time alignment, can be applied. While using manual segmentation of the flood image to create the CLUT is a simple and reliable approach, it is both tedious and time consuming for systems with large numbers of crystal elements. In this work we describe the development of an automated algorithm for CLUT generation that uses a Gaussian mixture model paired with thin plate splines (TPS) to iteratively fit a crystal layout template that includes the crystal numbering pattern. Starting from a region of stability, Gaussians are individually fit to data corresponding to crystal locations while simultaneously updating a TPS for predicting future Gaussian locations at the edge of a region of interest that grows as individual Gaussians converge to crystal locations. The algorithm was tested with flood image data collected from 16 detector modules, each consisting of a 409 crystal dual-layer offset LYSO crystal array readout by a 32 pixel SiPM array. For these detector flood images, depending on user defined input parameters, the algorithm runtime ranged between 17.5-82.5 s per detector on a single core of an Intel i7 processor. The method maintained an accuracy above 99.8% across all tests, with the majority of errors being localized to error prone corner regions. This method can be easily extended for use with other detector types through adjustment of the initial template model used.

The different conformations and crystal structures of dihydroergocristine

NASA Astrophysics Data System (ADS)

Mönch, B.; Kraus, W.; Köppen, R.; Emmerling, F.

2016-02-01

The identification of different forms of dihydroergocristine (DHEC) was carried out by crystallization from different organic solvents. DHEC was identified as potential template for molecularly imprinted polymers (MIPs) for the epimeric specific analysis of ergot alkaloids (EAs) in food. DHEC was crystallized from different solvents in order to mimic the typical MIP synthesis conditions. Four new solvatomorphs of DHEC were obtained. All solvatomorphs contain a water molecule in the crystal structure, whereas three compounds contain an additional solvent molecule. Based on the conformation of DHEC a comparison with typical EA molecules was possible. The analysis showed that DHEC is a suitable template for MIPs for EAs.

Direct electrodeposition of porous gold nanowire arrays for biosensing applications.

PubMed

Zhang, Xinyi; Li, Dan; Bourgeois, Laure; Wang, Huanting; Webley, Paul A

2009-02-02

Nanochannel alumina templates are used as templates for fabrication of porous gold nanowire arrays by a direct electrodeposition method. After modification with glucose oxidase, a porous gold nanowire-array electrode is shown to be an excellent electrochemical biosensor for the detection of glucose. The picture shows an SEM image of a nanowire array after removal of the alumina template by acid dissolution. We report the fabrication of porous gold nanowire arrays by means of a one-step electrodeposition method utilizing nanochannel alumina templates. The microstructure of gold nanowires depends strongly on the current density. The formation of porous gold nanowires is attributed to disperse crystallization under conditions of low nucleation rate. Interfacial electron transport through the porous gold nanowires is studied by electrochemical impedance spectroscopy. Cyclic voltammetric studies on the porous gold nanowire arrays reveal a low-potential electrocatalytic response towards hydrogen peroxide. The properties of the glucose oxidase modified porous gold nanowire array electrode are elucidated and compared with those of nonporous enzyme electrodes. The glucose oxidase modified porous gold nanowire-array electrode is shown to be an excellent electrochemical biosensor for the detection of glucose.

Tunable alumina 2D photonic-crystal structures via biomineralization of peacock tail feathers

NASA Astrophysics Data System (ADS)

Jiang, Yonggang; Wang, Rui; Feng, Lin; Li, Jian; An, Zhonglie; Zhang, Deyuan

2018-04-01

Peacock tail feathers with subtle periodic nanostructures exhibit diverse striking brilliancy, which can be applied as natural templates to fabricate artificial photonic crystals (PhCs) via a biomineralization method. Alumina photonic-crystal structures are successfully synthesized via an immersion and two-step calcination process. The lattice constants of the artificial PhCs are greatly reduced compared to their natural matrices. The lattice constants are tunable by modifying the final annealing conditions in the biomineralization process. The reflection spectra of the alumina photonic-crystal structures are measured, which is related to their material and structural parameters. This work suggests a facile fabrication process to construct alumina PhCs with a high-temperature resistance.

Manipulating the assembly of perovskites onto soft nanoimprinted titanium dioxide templates.

PubMed

Baca, Alfred J; Roberts, M Joseph; Stenger-Smith, John; Baldwin, Lawrence

2018-06-22

Soft nanoimprinted titanium dioxide (TiO 2 ) substrates decorated with methylammonium lead halide perovskite (MAPbI 3 ) crystals were fabricated by controlling the perovskite precursor concentration and volume during spin coat processing combined with the use of hydrophobic TiO 2 templates. The patterned growth was demonstrated with different perovskite crystallization methods. We investigated and successfully demonstrated the controlled assembly of two MAPbI 3 nanomaterials, one a nanocomposite formed between the perovskite and a hole conducting polymer poly(2,5-bis(N-methyl-N-hexylamino)phenylene vinylene) (BAMPPV), and a second formed from perovskite crystals using common solution based MAPbI 3 growth methods (1-step and 2-step processing). Both types of MAPbI 3 crystals were fabricated on hydrophobic TiO 2 nanotemplates composed of nanowells or grating patterns. Patterned areas as large as 100 μm × 100 μm were achieved. We examined and characterized the substrates using atomic force microscopy, scanning electron microscopy, x-ray diffraction, and energy dispersive spectroscopy. We present the optical properties (i.e. fluorescence and transmission) of soft nanoimprinted nanowells decorated with perovskites demonstrating the successful synthesis of MAPbI 3 perovskite nanocrystals. As an example of their use, we demonstrate a two terminal device and show photocurrent response of a perovskite patterned micro-grating. Our method is a nondestructive approach to nanopatterning perovskites, and produces patterned arrays that maintain their photo-electric properties. The results presented herein suggests an attractive route to developing nanopatterned and small area perovskite substrates for applications in photovoltaics, x-ray sensing/detection, image sensor arrays, and others.

Manipulating the assembly of perovskites onto soft nanoimprinted titanium dioxide templates

NASA Astrophysics Data System (ADS)

Baca, Alfred J.; Roberts, M. Joseph; Stenger-Smith, John; Baldwin, Lawrence

2018-06-01

Soft nanoimprinted titanium dioxide (TiO2) substrates decorated with methylammonium lead halide perovskite (MAPbI3) crystals were fabricated by controlling the perovskite precursor concentration and volume during spin coat processing combined with the use of hydrophobic TiO2 templates. The patterned growth was demonstrated with different perovskite crystallization methods. We investigated and successfully demonstrated the controlled assembly of two MAPbI3 nanomaterials, one a nanocomposite formed between the perovskite and a hole conducting polymer poly(2,5-bis(N-methyl-N-hexylamino)phenylene vinylene) (BAMPPV), and a second formed from perovskite crystals using common solution based MAPbI3 growth methods (1-step and 2-step processing). Both types of MAPbI3 crystals were fabricated on hydrophobic TiO2 nanotemplates composed of nanowells or grating patterns. Patterned areas as large as 100 μm × 100 μm were achieved. We examined and characterized the substrates using atomic force microscopy, scanning electron microscopy, x-ray diffraction, and energy dispersive spectroscopy. We present the optical properties (i.e. fluorescence and transmission) of soft nanoimprinted nanowells decorated with perovskites demonstrating the successful synthesis of MAPbI3 perovskite nanocrystals. As an example of their use, we demonstrate a two terminal device and show photocurrent response of a perovskite patterned micro-grating. Our method is a nondestructive approach to nanopatterning perovskites, and produces patterned arrays that maintain their photo-electric properties. The results presented herein suggests an attractive route to developing nanopatterned and small area perovskite substrates for applications in photovoltaics, x-ray sensing/detection, image sensor arrays, and others.

Hydroxyapatite-binding peptides for bone growth and inhibition

DOEpatents

Bertozzi, Carolyn R [Berkeley, CA; Song, Jie [Shrewsbury, MA; Lee, Seung-Wuk [Walnut Creek, CA

2011-09-20

Hydroxyapatite (HA)-binding peptides are selected using combinatorial phage library display. Pseudo-repetitive consensus amino acid sequences possessing periodic hydroxyl side chains in every two or three amino acid sequences are obtained. These sequences resemble the (Gly-Pro-Hyp).sub.x repeat of human type I collagen, a major component of extracellular matrices of natural bone. A consistent presence of basic amino acid residues is also observed. The peptides are synthesized by the solid-phase synthetic method and then used for template-driven HA-mineralization. Microscopy reveal that the peptides template the growth of polycrystalline HA crystals .about.40 nm in size.

Gold surface plasmon crystal structure based-on polystyrene template for biosensor application.

PubMed

Cheng, Min-Zhuo; Zhang, Jing; Bao, Dequan; Huang, Xiwei

2018-05-21

In this communication, we assembled ordered polystyrene (PS) microsphere array as a template with the drop-coating method, and the oxygen plasma was used to etch the template to adjust the spacing between the PS microspheres. Nano-triangular gold array and silver nano-pyramid array were obtained by ion beam sputtering to deposit precious metal gold and silver. We observed the surface morphology of Au and Au/Ag composite films by scanning electron microscope and characterized the films by X-ray diffraction and ultraviolet/visible light spectrophotometer. The results show that the etching time of oxygen plasma has an obvious effect in adjusting the spacing between PSs and has a significant effect on the morphology of Au structure. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Wide-band tunable photonic bandgap device and laser in dye-doped liquid crystal refilled cholesteric liquid crystal polymer template system

NASA Astrophysics Data System (ADS)

Lin, Jia-De; Lin, Hong-Lin; Lin, Hsin-Yu; Wei, Guan-Jhong; Lee, Chia-Rong

2017-02-01

The scientists in the field of liquid crystal (LC) have paid significant attention in the exploration of novel cholesteric LC (CLC) polymer template (simply called template) in recent years. The self-assembling nanostructural template with chirality can effectively overcome the limitation in the optical features of traditional CLCs, such as enhancement of reflectivity over 50%, multiple photonic bandgaps (PBGs), and changeable optical characteristics by flexibly replacing the refilling LC materials, and so on. This work fabricates two gradient-pitched CLC templates with two opposite handednesses, which are then merged as a spatially tunable and highly reflective CLC template sample. This sample can simultaneously reflect right- and left-circularly polarized lights and the tunable spectral range includes the entire visible region. By increasing the temperature of the template sample exceeding the clearing point of the refilling LC, the light scattering significantly decreases and the reflectance effectively increase to exceed 50% in the entire visible region. This device has a maximum reflectance over 85% and a wide-band spatial tunability in PBG between 400 nm and 800 nm which covers the entire visible region. Not only the sample can be employed as a wide-band spatially tunable filter, but also the system doping with two suitable laser dyes which emitted fluorescence can cover entire visible region can develop a low-threshold, mirror-less laser with a spatial tunability at spectral regions including blue to red region (from 484 nm to 634 nm) and simultaneous lasing emission of left- and right-circular polarizations.

Modeling Conformal Growth in Photonic Crystals and Comparing to Experiment

NASA Astrophysics Data System (ADS)

Brzezinski, Andrew; Chen, Ying-Chieh; Wiltzius, Pierre; Braun, Paul

2008-03-01

Conformal growth, e.g. atomic layer deposition (ALD), of materials such as silicon and TiO2 on three dimensional (3D) templates is important for making photonic crystals. However, reliable calculations of optical properties as a function of the conformal growth, such as the optical band structure, are hampered by difficultly in accurately assessing a deposited material's spatial distribution. A widely used approximation ignores ``pinch off'' of precursor gas and assumes complete template infilling. Another approximation results in non-uniform growth velocity by employing iso-intensity surfaces of the 3D interference pattern used to create the template. We have developed an accurate model of conformal growth in arbitrary 3D periodic structures, allowing for arbitrary surface orientation. Results are compared with the above approximations and with experimentally fabricated photonic crystals. We use an SU8 polymer template created by 4-beam interference lithography, onto which various amounts of TiO2 are grown by ALD. Characterization is performed by analysis of cross-sectional scanning electron micrographs and by solid angle resolved optical spectroscopy.

Automated identification and indexing of dislocations in crystal interfaces

DOE PAGES

Stukowski, Alexander; Bulatov, Vasily V.; Arsenlis, Athanasios

2012-10-31

Here, we present a computational method for identifying partial and interfacial dislocations in atomistic models of crystals with defects. Our automated algorithm is based on a discrete Burgers circuit integral over the elastic displacement field and is not limited to specific lattices or dislocation types. Dislocations in grain boundaries and other interfaces are identified by mapping atomic bonds from the dislocated interface to an ideal template configuration of the coherent interface to reveal incompatible displacements induced by dislocations and to determine their Burgers vectors. Additionally, the algorithm generates a continuous line representation of each dislocation segment in the crystal andmore » also identifies dislocation junctions.« less

RNA Crystallization

NASA Technical Reports Server (NTRS)

Golden, Barbara L.; Kundrot, Craig E.

2003-01-01

RNA molecules may be crystallized using variations of the methods developed for protein crystallography. As the technology has become available to syntheisize and purify RNA molecules in the quantities and with the quality that is required for crystallography, the field of RNA structure has exploded. The first consideration when crystallizing an RNA is the sequence, which may be varied in a rational way to enhance crystallizability or prevent formation of alternate structures. Once a sequence has been designed, the RNA may be synthesized chemically by solid-state synthesis, or it may be produced enzymatically using RNA polymerase and an appropriate DNA template. Purification of milligram quantities of RNA can be accomplished by HPLC or gel electrophoresis. As with proteins, crystallization of RNA is usually accomplished by vapor diffusion techniques. There are several considerations that are either unique to RNA crystallization or more important for RNA crystallization. Techniques for design, synthesis, purification, and crystallization of RNAs will be reviewed here.

Optimization of rotamers prior to template minimization improves stability predictions made by computational protein design.

PubMed

Davey, James A; Chica, Roberto A

2015-04-01

Computational protein design (CPD) predictions are highly dependent on the structure of the input template used. However, it is unclear how small differences in template geometry translate to large differences in stability prediction accuracy. Herein, we explored how structural changes to the input template affect the outcome of stability predictions by CPD. To do this, we prepared alternate templates by Rotamer Optimization followed by energy Minimization (ROM) and used them to recapitulate the stability of 84 protein G domain β1 mutant sequences. In the ROM process, side-chain rotamers for wild-type (WT) or mutant sequences are optimized on crystal or nuclear magnetic resonance (NMR) structures prior to template minimization, resulting in alternate structures termed ROM templates. We show that use of ROM templates prepared from sequences known to be stable results predominantly in improved prediction accuracy compared to using the minimized crystal or NMR structures. Conversely, ROM templates prepared from sequences that are less stable than the WT reduce prediction accuracy by increasing the number of false positives. These observed changes in prediction outcomes are attributed to differences in side-chain contacts made by rotamers in ROM templates. Finally, we show that ROM templates prepared from sequences that are unfolded or that adopt a nonnative fold result in the selective enrichment of sequences that are also unfolded or that adopt a nonnative fold, respectively. Our results demonstrate the existence of a rotamer bias caused by the input template that can be harnessed to skew predictions toward sequences displaying desired characteristics. © 2014 The Protein Society.

General method for the synthesis of hierarchical nanocrystal-based mesoporous materials.

PubMed

Rauda, Iris E; Buonsanti, Raffaella; Saldarriaga-Lopez, Laura C; Benjauthrit, Kanokraj; Schelhas, Laura T; Stefik, Morgan; Augustyn, Veronica; Ko, Jesse; Dunn, Bruce; Wiesner, Ulrich; Milliron, Delia J; Tolbert, Sarah H

2012-07-24

Block copolymer templating of inorganic materials is a robust method for the production of nanoporous materials. The method is limited, however, by the fact that the molecular inorganic precursors commonly used generally form amorphous porous materials that often cannot be crystallized with retention of porosity. To overcome this issue, here we present a general method for the production of templated mesoporous materials from preformed nanocrystal building blocks. The work takes advantage of recent synthetic advances that allow organic ligands to be stripped off of the surface of nanocrystals to produce soluble, charge-stabilized colloids. Nanocrystals then undergo evaporation-induced co-assembly with amphiphilic diblock copolymers to form a nanostructured inorganic/organic composite. Thermal degradation of the polymer template results in nanocrystal-based mesoporous materials. Here, we show that this method can be applied to nanocrystals with a broad range of compositions and sizes, and that assembly of nanocrystals can be carried out using a broad family of polymer templates. The resultant materials show disordered but homogeneous mesoporosity that can be tuned through the choice of template. The materials also show significant microporosity, formed by the agglomerated nanocrystals, and this porosity can be tuned by the nanocrystal size. We demonstrate through careful selection of the synthetic components that specifically designed nanostructured materials can be constructed. Because of the combination of open and interconnected porosity, high surface area, and compositional tunability, these materials are likely to find uses in a broad range of applications. For example, enhanced charge storage kinetics in nanoporous Mn(3)O(4) is demonstrated here.

Preparation of micro/nanostructure TiO2 spheres by controlling pollen as hard template and soft template.

PubMed

Yang, Xiaohui; Xu, Bin; Zhang, Xuehong; Song, Xiuqin; Chen, Rufen

2014-09-01

In this paper, micro/nanostructure TiO2 spheres were synthesized by a sunflower pollen induced and self-assembly mineralization process, in which a titania precursor and pollen reacted in one-pot at normal pressure. In this paper, the bio-template advantage, as hard and soft template is fully demonstrated. The superiority of our synthesis is that we not only can control pollen as hard template, but also can control it as soft template only by changing reactions temperature. Under 80 degrees C of water bath, TiO2 microspheres which replicated the morphology of pollen were prepared by controlling pollen as hard template. Under 100 degrees C, hierarchical TiO2 spheres with complicated morphology, different from pollen template, were synthesized by using pollen as soft template. At the same time, judicious choice of the amount of pollen affords the synthesis of hierarchical structures spheres with adjustable morphology and crystal structure. The morphology can be tuned from microspheres constructed from TiO2 nanorods to nanospheres constructed from TiO2 nanoparticles, and the crystal structure can be tuned from rutile to anatase. More over this anatase phase can be keep better even at high temperature of 1000 degrees C. The as-prepared micro/nano structure photocatalysts not only have high photocatalytic activities, but also have good separability and reuse performance.

Purification and Bicelle Crystallization for Structure Determination of the E. coli Outer Membrane Protein TamA.

PubMed

Gruss, Fabian; Hiller, Sebastian; Maier, Timm

2015-01-01

TamA is an Omp85 protein involved in autotransporter assembly in the outer membrane of Escherichia coli. It comprises a C-terminal 16-stranded transmembrane β-barrel as well as three periplasmic POTRA domains, and is a challenging target for structure determination. Here, we present a method for crystal structure determination of TamA, including recombinant expression in E. coli, detergent extraction, chromatographic purification, and bicelle crystallization in combination with seeding. As a result, crystals in space group P21212 are obtained, which diffract to 2.3 Å resolution. This protocol also serves as a template for structure determination of other outer membrane proteins, in particular of the Omp85 family.

Preferred orientations of laterally grown silicon films over amorphous substrates using the vapor-liquid-solid technique

NASA Astrophysics Data System (ADS)

LeBoeuf, J. L.; Brodusch, N.; Gauvin, R.; Quitoriano, N. J.

2014-12-01

A novel method has been optimized so that adhesion layers are no longer needed to reliably deposit patterned gold structures on amorphous substrates. Using this technique allows for the fabrication of amorphous oxide templates known as micro-crucibles, which confine a vapor-liquid-solid (VLS) catalyst of nominally pure gold to a specific geometry. Within these confined templates of amorphous materials, faceted silicon crystals have been grown laterally. The novel deposition technique, which enables the nominally pure gold catalyst, involves the undercutting of an initial chromium adhesion layer. Using electron backscatter diffraction it was found that silicon nucleated in these micro-crucibles were 30% single crystals, 45% potentially twinned crystals and 25% polycrystals for the experimental conditions used. Single, potentially twinned, and polycrystals all had an aversion to growth with the {1 0 0} surface parallel to the amorphous substrate. Closer analysis of grain boundaries of potentially twinned and polycrystalline samples revealed that the overwhelming majority of them were of the 60° Σ3 coherent twin boundary type. The large amount of coherent twin boundaries present in the grown, two-dimensional silicon crystals suggest that lateral VLS growth occurs very close to thermodynamic equilibrium. It is suggested that free energy fluctuations during growth or cooling, and impurities were the causes for this twinning.

Bottom-up Fabrication of Multilayer Stacks of 3D Photonic Crystals from Titanium Dioxide.

PubMed

Kubrin, Roman; Pasquarelli, Robert M; Waleczek, Martin; Lee, Hooi Sing; Zierold, Robert; do Rosário, Jefferson J; Dyachenko, Pavel N; Montero Moreno, Josep M; Petrov, Alexander Yu; Janssen, Rolf; Eich, Manfred; Nielsch, Kornelius; Schneider, Gerold A

2016-04-27

A strategy for stacking multiple ceramic 3D photonic crystals is developed. Periodically structured porous films are produced by vertical convective self-assembly of polystyrene (PS) microspheres. After infiltration of the opaline templates by atomic layer deposition (ALD) of titania and thermal decomposition of the polystyrene matrix, a ceramic 3D photonic crystal is formed. Further layers with different sizes of pores are deposited subsequently by repetition of the process. The influence of process parameters on morphology and photonic properties of double and triple stacks is systematically studied. Prolonged contact of amorphous titania films with warm water during self-assembly of the successive templates is found to result in exaggerated roughness of the surfaces re-exposed to ALD. Random scattering on rough internal surfaces disrupts ballistic transport of incident photons into deeper layers of the multistacks. Substantially smoother interfaces are obtained by calcination of the structure after each infiltration, which converts amorphous titania into the crystalline anatase before resuming the ALD infiltration. High quality triple stacks consisting of anatase inverse opals with different pore sizes are demonstrated for the first time. The elaborated fabrication method shows promise for various applications demanding broadband dielectric reflectors or titania photonic crystals with a long mean free path of photons.

Ordered mesoporous crystalline gamma-Al2O3 with variable architecture and porosity from a single hard template.

PubMed

Wu, Zhangxiong; Li, Qiang; Feng, Dan; Webley, Paul A; Zhao, Dongyuan

2010-09-01

In this paper, an efficient route is developed for controllable synthesis of ordered mesoporous alumina (OMA) materials with variable pore architectures and high mesoporosity, as well as crystalline framework. The route is based on the nanocasting pathway with bimodal mesoporous carbon as the hard template. In contrast to conventional reports, we first realize the possibility of creating two ordered mesopore architectures by using a single carbon hard template obtained from organic-organic self-assembly, which is also the first time such carbon materials are adopted to replicate ordered mesoporous materials. The mesopore architecture and surface property of the carbon template are rationally designed in order to obtain ordered alumina mesostructures. We found that the key factors rely on the unique bimodal mesopore architecture and surface functionalization of the carbon hard template. Namely, the bimodal mesopores (2.3 and 5.9 nm) and the surface functionalities make it possible to selectively load alumina into the small mesopores dominantly and/or with a layer of alumina coated on the inner surface of the large primary mesopores with different thicknesses until full loading is achieved. Thus, OMA materials with variable pore architectures (similar and reverse mesostructures relative to the carbon template) and controllable mesoporosity in a wide range are achieved. Meanwhile, in situ ammonia hydrolysis for conversion of the metal precursor to its hydroxide is helpful for easy crystallization (as low as approximately 500 degrees C). Well-crystallized alumina frameworks composed of gamma-Al(2)O(3) nanocrystals with sizes of 6-7 nm are obtained after burning out the carbon template at 600 degrees C, which is advantageous over soft-templated aluminas. The effects of synthesis factors are demonstrated and discussed relative to control experiments. Furthermore, our method is versatile enough to be used for general synthesis of other important but difficult-to-synthesize mesoporous metal oxides, such as magnesium oxide. We believe that the fundamentals in this research will provide new insights for rational synthesis of ordered mesoporous materials.

Patterned solid state growth of barium titanate crystals

NASA Astrophysics Data System (ADS)

Ugorek, Michael Stephen

An understanding of microstructure evolution in ceramic materials, including single crystal development and abnormal/enhanced grain growth should enable more controlled final ceramic element structures. In this study, two different approaches were used to control single crystal development in a patterned array. These two methods are: (1) patterned solid state growth in BaTiO 3 ceramics, and (2) metal-mediated single crystal growth in BaTiO 3. With the patterned solid state growth technique, optical photolithography was used to pattern dopants as well as [001] and [110] BaTiO3 single crystal template arrays with a 1000 microm line pattern array with 1000 microm spacings. These patterns were subsequently used to control the matrix grain growth evolution and single crystal development in BaTiO3. It was shown that the growth kinetics can be controlled by a small initial grain size, atmosphere conditions, and the introduction of a dopant at selective areas/interfaces. By using a PO2 of 1x10-5 atm during high temperature heat treatment, the matrix coarsening has been limited (to roughly 2 times the initial grain size), while retaining single crystal boundary motion up to 0.5 mm during growth for dwell times up to 9 h at 1300°C. The longitudinal and lateral growth rates were optimized at 10--15 microm/h at 1300°C in a PO2 of 1x10 -5 atm for single crystal growth with limited matrix coarsening. Using these conditions, a patterned microstructure in BaTiO3 was obtained. With the metal-mediated single crystal growth technique, a novel approach for fabricating 2-2 single crystal/polymer composites with a kerf < 5 microns was demonstrated. Surface templated grain growth was used to propagate a single crystal interface into a polycrystalline BaTiO3 or Ba(Zr0.05 Ti0.95)O3 matrix with lamellar nickel layers. The grain growth evolution and texture development were studied using both [001] and [110] BaTiO3 single crystals templates. By using a PO 2 of 1x10-11 atm during high temperature heat treatment, matrix coarsening was limited while enabling single crystal boundary motion up to 0.35 mm during growth between 1250°C and 1300°C with growth rates ˜ 3--4 microm/h for both single crystal orientations. By removing the inner electrodes, 2-2 single crystal (or ceramic) composites were prepared. The piezoelectric and dielectric properties of the composites of the two compositions were measured. The d33 and d31 of the composites were similar to the polycrystalline ceramic of the same composition.

Conductive layer for biaxially oriented semiconductor film growth

DOEpatents

Findikoglu, Alp T.; Matias, Vladimir

2007-10-30

A conductive layer for biaxially oriented semiconductor film growth and a thin film semiconductor structure such as, for example, a photodetector, a photovoltaic cell, or a light emitting diode (LED) that includes a crystallographically oriented semiconducting film disposed on the conductive layer. The thin film semiconductor structure includes: a substrate; a first electrode deposited on the substrate; and a semiconducting layer epitaxially deposited on the first electrode. The first electrode includes a template layer deposited on the substrate and a buffer layer epitaxially deposited on the template layer. The template layer includes a first metal nitride that is electrically conductive and has a rock salt crystal structure, and the buffer layer includes a second metal nitride that is electrically conductive. The semiconducting layer is epitaxially deposited on the buffer layer. A method of making such a thin film semiconductor structure is also described.

Diagnosing the Internal Architecture of Zeolite Ferrierite

PubMed Central

Schmidt, Joel E.; Hendriks, Frank C.; Lutz, Martin; Post, L. Christiaan; Fu, Donglong

2017-01-01

Abstract Large crystals of zeolite ferrierite (FER) are important model systems for spatially resolved catalysis and diffusion studies, though there is considerable variation in crystal habit depending on the chemical composition and employed synthesis conditions. A synergistic combination of techniques has been applied, including single crystal X‐ray diffraction, high‐temperature in situ confocal fluorescence microscopy, fluorescent probe molecules, wide‐field microscopy and atomic force microscopy to unravel the internal architecture of three distinct FER zeolites. Pyrolyzed template species can be used as markers for the 8‐membered ring direction as they are trapped in the terraced roof of the FER crystals. This happens as the materials grow in a layer‐by‐layer, defect‐free manner normal to the large crystal surface, and leads to a facile method to diagnose the pore system orientation, which avoids tedious single crystal X‐ray diffraction experiments. PMID:28809081

A novel fabrication of Cu{sub 2}O@Cu{sub 7}S{sub 4} core-shell micro/nanocrystals from Cu{sub 2}O temples and enhanced photocatalytic activities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Junqi, E-mail: sfmlab@163.com; Sun, Long; Yan, Ying

2016-08-15

Highlights: • The Cu{sub 2}O@Cu{sub 7}S{sub 4} core-shell crystals maintained the same morphology with template. • The crystals exhibit enhanced photocatalytic activity than the pure Cu{sub 2}O crystals. • The photocatalytic activity of different R crystals is diverse from each other. • A possible formation mechanism has been proposed. - Abstract: Uniform and monodispersed Cu{sub 2}O@Cu{sub 7}S{sub 4} core-shell micro/nanocrystals have been synthesized successfully at room temperature via a simple chemical etching reaction, using Cu{sub 2}O as sacrificial template. The structure and properties of the crystals were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM),more » X-ray photoelectron spectra (XPS). The photocatalytic activity of the Cu{sub 2}O@Cu{sub 7}S{sub 4} crystals was evaluated by photocatalytic decolorization of MeO (methyl orange) aqueous solution at ambient temperature under visible-light irradiation. The results show that the as-prepared Cu{sub 2}O@Cu{sub 7}S{sub 4} crystals revealed core-shell structure, which maintained the same morphology with corresponding template and were composed of cuboctahedron Cu{sub 7}S{sub 4} shell and active Cu{sub 2}O core. Due to the unique Cu{sub 2}O@Cu{sub 7}S{sub 4} core-shell structure, the crystals exhibit enhanced photocatalytic activity than that of the pure Cu{sub 2}O crystals, and the photocatalytic activity of different R crystals is diverse from each other. A possible formation mechanism has been proposed.« less

Shock-Induced phase transition of single crystal copper

NASA Astrophysics Data System (ADS)

Neogi, Anupam; Mitra, Nilanjan

2017-05-01

We have carried out a series of multi-million atoms non-equilibrium molecular dynamics simulations to investigate the effect of crystal orientation over the shock induced plasticity and phase transformation in single crystal copper. Crystallographic orientation of [100], [110] and [111] has been studied for various intensity of shock ranging from 1.0 km/s to 3.0 km/s. During shock wave propagation along <100> and <110>, a FCC-to-BCC phase transformation has been observed to occur behind the shock front at higher intensity of shock. Nucleated body centered phase is identified through common neighbor analysis, polyhedral matching template method, radial distribution function and also from the energetic of the particles.

Monolayer Colloidal Crystals by Modified Air-Water Interface Self-Assembly Approach

PubMed Central

Ye, Xin; Huang, Jin; Zeng, Yong; Sun, Lai-Xi; Geng, Feng; Liu, Hong-Jie; Wang, Feng-Rui; Jiang, Xiao-Dong; Wu, Wei-Dong; Zheng, Wan-Guo

2017-01-01

Hexagonally ordered arrays of polystyrene (PS) microspheres were prepared by a modified air-water self-assembly method. A detailed analysis of the air-water interface self-assembly process was conducted. Several parameters affect the quality of the monolayer colloidal crystals, i.e., the colloidal microsphere concentration on the latex, the surfactant concentration, the polystyrene microsphere diameter, the microsphere polydispersity, and the degree of sphericity of polystyrene microspheres. An abrupt change in surface tension was used to improve the quality of the monolayer colloidal crystal. Three typical microstructures, i.e., a cone, a pillar, and a binary structure were prepared by reactive-ion etching using a high-quality colloidal crystal mask. This study provides insight into the production of microsphere templates with flexible structures for large-area patterned materials. PMID:28946664

Light-assisted, templated self-assembly using a photonic-crystal slab.

PubMed

Jaquay, Eric; Martínez, Luis Javier; Mejia, Camilo A; Povinelli, Michelle L

2013-05-08

We experimentally demonstrate the technique of light-assisted, templated self-assembly (LATS). We excite a guided-resonance mode of a photonic-crystal slab with 1.55 μm laser light to create an array of optical traps. We demonstrate assembly of a square lattice of 520 nm diameter polystyrene particles spaced by 860 nm. Our results demonstrate how LATS can be used to fabricate reconfigurable structures with symmetries different from traditional colloidal self-assembly, which is limited by free energetic constraints.

Ultrathin Uniform Platinum Nanowires via a Facile Route Using an Inverse Hexagonal Surfactant Phase Template.

PubMed

Akbar, Samina; Boswell, Jacob; Worsley, Carys; Elliott, Joanne M; Squires, Adam M

2018-06-19

We present an attractive method for the fabrication of long, straight, highly crystalline, ultrathin platinum nanowires. The fabrication is simply achieved using an inverse hexagonal (H II ) lyotropic liquid crystal phase of the commercial surfactant phytantriol as a template. A platinum precursor dissolved within the cylindrical aqueous channels of the liquid crystal phase is chemically reduced by galvanic displacement using stainless steel. We demonstrate the production of nanowires using the H II phase in the phytantriol/water system which we obtain either by heating to 55 °C or at room temperature by the addition of a hydrophobic liquid, 9- cis-tricosene, to relieve packing frustration. The two sets of conditions produced high aspect nanowires with diameters of 2.5 and 1.7 nm, respectively, at least hundreds of nanometers in length, matching the size of the aqueous channels in which they grow. This versatile approach can be extended to produce highly uniform nanowires from a range of metals.

Template-mediated nano-crystallite networks in semiconducting polymers.

PubMed

Kwon, Sooncheol; Yu, Kilho; Kweon, Kyoungchun; Kim, Geunjin; Kim, Junghwan; Kim, Heejoo; Jo, Yong-Ryun; Kim, Bong-Joong; Kim, Jehan; Lee, Seoung Ho; Lee, Kwanghee

2014-06-18

Unlike typical inorganic semiconductors with a crystal structure, the charge dynamics of π-conjugated polymers (π-CPs) are severely limited by the presence of amorphous portions between the ordered crystalline regions. Thus, the formation of interconnected pathways along crystallites of π-CPs is desired to ensure highly efficient charge transport in printable electronics. Here we report the formation of nano-crystallite networks in π-CP films by employing novel template-mediated crystallization (TMC) via polaron formation and electrostatic interaction. The lateral and vertical charge transport of TMC-treated films increased by two orders of magnitude compared with pristine π-CPs. In particular, because of the unprecedented room temperature and solution-processing advantages of our TMC method, we achieve a field-effect mobility of 0.25 cm(2) V(-1) s(-1) using a plastic substrate, which corresponds to the highest value reported thus far. Because our findings can be applied to various π-conjugated semiconductors, our approach is universal and is expected to yield high-performance printable electronics.

LiCoO2 Concaved Cuboctahedrons from Symmetry-Controlled Topological Reactions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, H.; Wu, L.; Zhang, L.

2011-01-19

Morphology control of functional materials is generally performed by controlling the growth rates on selected orientations or faces. Here, we control particle morphology by 'crystal templating': by choosing appropriate precursor crystals and reaction conditions, we demonstrate that a material with rhombohedral symmetry - namely the layered, positive electrode material, LiCoO{sub 2} - can grow to form a quadruple-twinned crystal with overall cubic symmetry. The twinned crystals show an unusual, concaved-cuboctahedron morphology, with uniform particle sizes of 0.5-2 {micro}m. On the basis of a range of synthetic and analytical experiments, including solid-state NMR, X-ray powder diffraction analysis and HRTEM, we proposemore » that these twinned crystals form via selective dissolution and an ion-exchange reaction accompanied by oxidation of a parent crystal of CoO, a material with cubic symmetry. This template crystal serves to nucleate the growth of four LiCoO{sub 2} twin crystals and to convert a highly anisotropic, layered material into a pseudo-3-dimensional, isotropic material.« less

Preferred orientations of laterally grown silicon films over amorphous substrates using the vapor–liquid–solid technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

LeBoeuf, J. L., E-mail: jerome.leboeuf@mail.mcgill.ca; Brodusch, N.; Gauvin, R.

2014-12-28

A novel method has been optimized so that adhesion layers are no longer needed to reliably deposit patterned gold structures on amorphous substrates. Using this technique allows for the fabrication of amorphous oxide templates known as micro-crucibles, which confine a vapor–liquid–solid (VLS) catalyst of nominally pure gold to a specific geometry. Within these confined templates of amorphous materials, faceted silicon crystals have been grown laterally. The novel deposition technique, which enables the nominally pure gold catalyst, involves the undercutting of an initial chromium adhesion layer. Using electron backscatter diffraction it was found that silicon nucleated in these micro-crucibles were 30%more » single crystals, 45% potentially twinned crystals and 25% polycrystals for the experimental conditions used. Single, potentially twinned, and polycrystals all had an aversion to growth with the (1 0 0) surface parallel to the amorphous substrate. Closer analysis of grain boundaries of potentially twinned and polycrystalline samples revealed that the overwhelming majority of them were of the 60° Σ3 coherent twin boundary type. The large amount of coherent twin boundaries present in the grown, two-dimensional silicon crystals suggest that lateral VLS growth occurs very close to thermodynamic equilibrium. It is suggested that free energy fluctuations during growth or cooling, and impurities were the causes for this twinning.« less

Microstructural analysis in the depth direction of a heteroepitaxial AlN thick film grown on a trench-patterned template by nanobeam X-ray diffraction

NASA Astrophysics Data System (ADS)

Shida, K.; Takeuchi, S.; Tohei, T.; Miyake, H.; Hiramatsu, K.; Sumitani, K.; Imai, Y.; Kimura, S.; Sakai, A.

2018-04-01

This work quantitatively assessed the three-dimensional distribution of crystal lattice distortions in an epitaxial AlN thick film grown on a trench-patterned template, using nanobeam X-ray diffraction. Position-dependent ω-2θ-φ mapping clearly demonstrated local tilting, spacing and twisting of lattice planes as well as fluctuations in these phenomena on a sub-micrometer scale comparable to the pitch of the trench-and-terrace patterning. Analysis of the crystal lattice distortion in the depth direction was performed using a newly developed method in which the X-ray nanobeam diffracted from the sample surface to specific depths can be selectively detected by employing a Pt wire profiler. This technique generated depth-resolved ω-2θ-φ maps confirming that fluctuations in lattice plane tilting and spacing greatly depend on the dislocation distribution and the history of the AlN epitaxial growth on the trench-patterned structure. It was also found that both fluctuations were reduced on approaching the AlN surface and, in particular, were sharply reduced at specific depths in the terrace regions. These sharp reductions are attributed to the formation of sacrificial zones with degraded crystal quality around the trenches and possibly lead to raising the crystal quality near the surface of the AlN film.

Biomimetic and Aggregation-Driven Crystallization Route for Room-Temperature Material Synthesis: Growth of β-Ga2O3 Nanoparticles Using Peptide Assemblies as Nanoreactors

PubMed Central

Lee, Sang-Yup; Gao, Xueyun; Matsui, Hiroshi

2008-01-01

The room temperature synthesis of β-Ga2O3 nanocrystal was examined by coupling two biomimetic crystallization techniques, the enzymatic peptide nano-assembly templating and the aggregation-driven crystallization. The catalytic template of peptide assembly nucleated and mineralized primary β-Ga2O3 crystals, and then fused them to grow single-crystalline and monodisperse nanoparticles in the cavity of the peptide assembly at room temperature. In this work, the peptide assembly was exploited as a nano-reactor with an enzymatic functionality catalyzing the hydrolysis of gallium precursors. In addition, the characteristic ring-structure of peptide assembly is expected to provide an efficient dehydration pathway and the crystallization control over the surface tension, which are advantageous for the β-Ga2O3 crystal growth. This multifunctional peptide assembly could be applied for syntheses of a variety of nanomaterials that are kinetically difficult to grow at room temperature. PMID:17302413

Solvothermal synthesis and surface chemistry to control the size and morphology of nanoquartz

DOE PAGES

Sochalski-Kolbus, Lindsay M.; Wang, Hsiu-Wen; Rondinone, Adam Justin; ...

2015-09-29

In this paper, we report a solvothermal synthesis method that allows the crystallization of quartz to occur at a relatively low temperature of 300°C in the form of isolated nanosized euhedral crystals. Transmission electron microscopy (TEM) and small area electron diffraction (SAED) were used to confirm the phases present and their particle sizes, morphologies, and crystallinity of the products. In conclusion, the results show that it is possible to control the size and morphology of the nanoquartz from rough nanospheres to nanorods using fluoride, which templates the nanocrystals and moderates growth.

Development of highly porous crystalline titania photocatalysts

NASA Astrophysics Data System (ADS)

Marszewski, Michal

The objectives of this dissertation are the design, synthesis, and characterization of titania materials with surface area, porosity, crystallinity and doping tailored toward photocatalytic applications. Ultimately, the research should result in a strategy allowing the synthesis of titania with all these important features. The synthetic methods investigated in this research will include: i) soft-templating, ii) hard-templating, and iii) modified precursor strategy. Soft-templating strategy uses organic templates--either block copolymers or surfactants--that under specific conditions assemble into micelles, and later, these micelles are used to template the desired material around them. The resulting organic-inorganic composite is then calcined in air to remove the organic template and recover the final material with high surface area and large pore volume. This work explores 1) synthesis of titania materials in the presence of polymer templates, and the effects of different synthetic conditions on the structure of the resulting materials. Hard-templating, in contrast to soft-templating, uses inorganic templates. The hard template is introduced during the synthesis to cast its shape onto the fabricated material and removed afterwards, when the material has formed. The final material is an inverse replica of the hard template used, typically with a well-developed mesostructure. This work explores 1) hard templating synthesis of titania materials using silica and alumina, and 2) the effects of the template amount and type. The modified precursor strategy is a novel synthetic method, developed in this research, and designed specifically to achieve titania material with high surface area, large pore volume, high crystallinity, and possibly doping. The modified precursors are prepared by reacting generic titania precursors, such as titanium isopropoxide (TIPO), with organic acids, which results in substitution of some or all alkoxide groups in TIPO structure. The goal is to introduce new, easily carbonizable groups in TIPO structure so that the modified precursor can serve as titania and carbon precursor simultaneously. Subsequently, during carbonization in inert atmosphere, a carbon framework is formed that works as a scaffold, protecting titania during its crystallization. Afterwards, the carbon scaffold is removed by calcination in air. This work explores the modified precursor strategy by 1) preparing titania materials from TIPO modified with different carboxylic acids and 2) investigating the effect of the modifying acid on the properties of the carbon-titania composites and the final titania materials.

Computational Redesign of Thioredoxin Is Hypersensitive toward Minor Conformational Changes in the Backbone Template

PubMed Central

Christensen, Signe; Horowitz, Scott; Bardwell, James C.A.; Olsen, Johan G.; Willemoës, Martin; Lindorff-Larsen, Kresten; Ferkinghoff-Borg, Jesper; Hamelryck, Thomas; Winther, Jakob R.

2017-01-01

Despite the development of powerful computational tools, the full-sequence design of proteins still remains a challenging task. To investigate the limits and capabilities of computational tools, we conducted a study of the ability of the program Rosetta to predict sequences that recreate the authentic fold of thioredoxin. Focusing on the influence of conformational details in the template structures, we based our study on 8 experimentally determined template structures and generated 120 designs from each. For experimental evaluation, we chose six sequences from each of the eight templates by objective criteria. The 48 selected sequences were evaluated based on their progressive ability to (1) produce soluble protein in Escherichia coli and (2) yield stable monomeric protein, and (3) on the ability of the stable, soluble proteins to adopt the target fold. Of the 48 designs, we were able to synthesize 32, 20 of which resulted in soluble protein. Of these, only two were sufficiently stable to be purified. An X-ray crystal structure was solved for one of the designs, revealing a close resemblance to the target structure. We found a significant difference among the eight template structures to realize the above three criteria despite their high structural similarity. Thus, in order to improve the success rate of computational full-sequence design methods, we recommend that multiple template structures are used. Furthermore, this study shows that special care should be taken when optimizing the geometry of a structure prior to computational design when using a method that is based on rigid conformations. PMID:27659562

Computational Redesign of Thioredoxin Is Hypersensitive toward Minor Conformational Changes in the Backbone Template.

PubMed

Johansson, Kristoffer E; Tidemand Johansen, Nicolai; Christensen, Signe; Horowitz, Scott; Bardwell, James C A; Olsen, Johan G; Willemoës, Martin; Lindorff-Larsen, Kresten; Ferkinghoff-Borg, Jesper; Hamelryck, Thomas; Winther, Jakob R

2016-10-23

Despite the development of powerful computational tools, the full-sequence design of proteins still remains a challenging task. To investigate the limits and capabilities of computational tools, we conducted a study of the ability of the program Rosetta to predict sequences that recreate the authentic fold of thioredoxin. Focusing on the influence of conformational details in the template structures, we based our study on 8 experimentally determined template structures and generated 120 designs from each. For experimental evaluation, we chose six sequences from each of the eight templates by objective criteria. The 48 selected sequences were evaluated based on their progressive ability to (1) produce soluble protein in Escherichia coli and (2) yield stable monomeric protein, and (3) on the ability of the stable, soluble proteins to adopt the target fold. Of the 48 designs, we were able to synthesize 32, 20 of which resulted in soluble protein. Of these, only two were sufficiently stable to be purified. An X-ray crystal structure was solved for one of the designs, revealing a close resemblance to the target structure. We found a significant difference among the eight template structures to realize the above three criteria despite their high structural similarity. Thus, in order to improve the success rate of computational full-sequence design methods, we recommend that multiple template structures are used. Furthermore, this study shows that special care should be taken when optimizing the geometry of a structure prior to computational design when using a method that is based on rigid conformations. Copyright © 2016 Elsevier Ltd. All rights reserved.

Magnetic assembly and annealing of colloidal lattices and superlattices.

PubMed

Tierno, Pietro

2014-07-08

The ability to assemble mesoscopic colloidal lattices above a surface is important for fundamental studies related with nucleation and crystallization but also for a variety of technological applications in photonics and microengineering. Current techniques based on particle sedimentation above a lithographic template are limited by a slow deposition process and by the use of static templates, which make difficult to implement fast annealing procedures. Here it is demonstrated a method to realize and anneal a series of colloidal lattices displaying triangular, honeycomb, or kagome-like symmetry above a structure magnetic substrate. By using a binary mixture of particles, superlattices can be realized increasing further the variety and complexity of the colloidal patterns which can be produced.

One-pot synthesis and photoluminescence properties of core/porous-shell olive-like BaWO4 microstructure by a template-assisted hydrothermal method

NASA Astrophysics Data System (ADS)

Zhang, Suyue; Wang, Yunlong; Wang, Cuiping; Zhang, Hui; Shen, Yuhua; Xie, Anjian

2016-02-01

Core/porous-shell olive-like crystalline BaWO4 is synthesized by a combined simple hydrothermal method and soft template approach. The prepared product shows an olive-like shape with diameter of ˜2 μm, length of ˜4 μm, and the thickness of the shell of about 65 nm, which are orderly assembled by many nanoparticles. A possible formation mechanism of olive-like BaWO4 microstructure involving interfacial recognization of ions, nucleation, aggregation, in situ growth and Ostwald ripening process is proposed. Polyacrylic acid sodium (PAAS) as a template plays an important role in inducing the nucleation and growth of olive-like BaWO4 microcrystalline. Other shapes of BaWO4 microcrystalline are also fabricated by varying the concentration of PAAS and Ba2+. The olive-like product with a core-shell structure which exists a large number of pores on crystal surface shows excellent photoluminescence property, which have potentially applied prospects in fields such as light display systems etc.

Nanoplate-like tungsten trioxide (hydrate) films prepared by crystal-seed-assisted hydrothermal reaction

NASA Astrophysics Data System (ADS)

Wang, P.; Yang, L.; Dai, B.; Yang, Z.; Guo, S.; Zhu, J.

2017-07-01

Vertically-aligned WO3 nanoplates on transparent conducting fluorine-doped tin oxide (FTO) glass were prepared by a facile template-free crystal-seed-assisted hydrothermal method. The effects of the hydrothermal temperature and reaction time on the crystal structure and morphology of the products were investigated by XRD and SEM. The XRD results showed that the as-prepared thin films obtained below 150∘C comprised orthorhombic WO3 ṡ H2O and completely converted to monoclinic WO3 at 180∘C. It was also noted that there was a phase transformation from orthorhombic to monoclinic by increasing the reaction time from 1 to 12 h. SEM analysis revealed that WO3 thin films are composed of plate-like nanostructures.

Fabrication and Characterization of Three Dimensional Photonic Crystals Generated by Multibeam Interference Lithography

ERIC Educational Resources Information Center

Chen, Ying-Chieh

2009-01-01

Multibeam interference lithography is investigated as a manufacturing technique for three-dimensional photonic crystal templates. In this research, optimization of the optical setup and the photoresist initiation system leads to a significant improvement of the optical quality of the crystal, as characterized by normal incidence optical…

Template-assisted mineral formation via an amorphous liquid phase precursor route

NASA Astrophysics Data System (ADS)

Amos, Fairland F.

The search for alternative routes to synthesize inorganic materials has led to the biomimetic route of producing ceramics. In this method, materials are manufactured at ambient temperatures and in aqueous solutions with soluble additives and insoluble matrix, similar to the biological strategy for the formation of minerals by living organisms. Using this approach, an anionic polypeptide additive was used to induce an amorphous liquid-phase precursor to either calcium carbonate or calcium phosphate. This precursor was then templated on either organic or inorganic substrates. Non-equilibrium morphologies, such as two-dimensional calcium carbonate films, one-dimensional calcium carbonate mesostructures and "molten" calcium phosphate spherulites were produced, which are not typical of the traditional (additive-free) solution grown crystals in the laboratory. In the study of calcium carbonate, the amorphous calcium carbonate mineral formed via the liquid-phase precursor, either underwent a dissolution-recrystallization event or a pseudo-solid-state transformation to produce different morphologies and polymorphs of the mineral. Discrete or aggregate calcite crystals were formed via the dissolution of the amorphous phase to allow the reprecipitation of the stable crystal. Non-equilibrium morphologies, e.g., films, mesotubules and mesowires were templated using organic and inorganic substrates and compartments. These structures were generated via an amorphous solid to crystalline solid transformation. Single crystalline tablets and mesowires of aragonite, which are reported to be found only in nature as skeletal structures of marine organisms, such as mollusk nacre and echinoderm teeth, were successfully synthesized. These biomimetic structures were grown via the polymer-induced liquid-phase precursor route in the presence of magnesium. Only low magnesium-bearing calcite was formed in the absence of the polymer. A similar approach of using a polymeric additive was implemented in calcium phosphate. Spherulitic crystals and films, seemingly formed from a molten state, were produced. These structures served as nucleating surfaces for the radial formation of calcium oxalate minerals. The composite calcium phosphate-calcium oxalate assemblies are similar to the core-shell structures found in certain kidney stones.

Complementary effects of multi-protein components on biomineralization in vitro

PubMed Central

Ba, Xiaolan; Rafailovich, Miriam; Meng, Yizhi; Pernodet, Nadine; Wirick, Sue; Füredi-Milhofer, Helga; Qin, Yi-Xian; DiMasi, Elaine

2016-01-01

The extracellular matrix (ECM) is composed of mixed protein fibers whose precise composition affects biomineralization. New methods are needed to probe the interactions of these proteins with calcium phosphate mineral and with each other. Here we follow calcium phosphate mineralization on protein fibers self-assembled in vitro from solutions of fibronectin, elastin and their mixture. We probe the surface morphology and mechanical properties of the protein fibers during the early stages. The development of mineral crystals on the protein matrices is also investigated. In physiological mineralization solution, the elastic modulus of the fibers in the fibronectin-elastin mixture increases to a greater extent than that of the fibers from either pure protein. In the presence of fibronectin, longer exposure in the mineral solution leads to the formation of amorphous calcium phosphate particles templated along the self-assembled fibers, while elastin fibers only collect calcium without any mineral observed during early stage. TEM images confirm that small needle-shape crystals are confined inside elastin fibers which suppress the release of mineral outside the fibers during late stage, while hydroxyapatite crystals form when fibronectin is present. These results demonstrate complementary actions of the two ECM proteins fibronectin and elastin to collect cations and template mineral, respectively. PMID:20035875

Synthesis of Ammonia-Assisted Porous Nickel Ferrite (NiFe₂O₄) Nanostructures as an Electrode Material for Supercapacitors.

PubMed

Bhojane, Prateek; Sharma, Alfa; Pusty, Manojit; Kumar, Yogendra; Sen, Somaditya; Shirage, Parasharam

2017-02-01

In this work, we report a low cost, facile synthesis method for Nickel ferrite (NiFe₂O₄) nanostructures obtained by chemical bath deposition method for alternate transition metal oxide electrode material as a solution for clean energy. We developed a template free ammonia assisted method for obtaining porous structure which offering better supercapacitive performance of NiFe₂O₄ electrode material than previously reported for pure NiFe₂O₄. Here we explore the physical characterizations X-ray diffraction, FESEM, HRTEM performed to under-stand its crystal structure and morphology as well as the electrochemical measurements was performed to understand the electrochemical behaviour of the material. Here ammonia plays an important role in governing the structure/morphology of the material and enhances the electrochemical performance. The specific capacitance of 541 Fg⁻¹ is achieved at 2 mVs⁻¹ scan rate which is highest for the pure NiFe₂O₄ electrode material without using any addition of carbon based material, heterostructure or template based method.

Elimination-Fusion Self-Assembly of a Nanometer-Scale 72-Nucleus Silver Cluster Caging a Pair of [EuW10 O36 ]9- Polyoxometalates.

PubMed

Zhang, Shan-Shan; Su, Hai-Feng; Wang, Zhi; Wang, Xing-Po; Chen, Wen-Xian; Zhao, Quan-Qin; Tung, Chen-Ho; Sun, Di; Zheng, Lan-Sun

2018-02-06

The largest known polyoxometalate (POM)-templated silver-alkynyl cluster, [(EuW 10 O 36 ) 2 @Ag 72 (tBuC≡C) 48 Cl 2 ⋅4 BF 4 ] (SD/Ag20), was isolated under solvothermal conditions and structurally characterized. It was confirmed by single-crystal X-ray diffraction (SCXRD) as a {EuW 10 } 2 -in-{Ag 72 } clusters-in-cluster rod-like compound. The high-resolution electrospray ionization mass spectrometry (HR-ESI-MS) shows that such a double anion-templated cluster is assembled from a crucial single anion-templated Ag 42 intermediate in the solution. The crystallization of Ag 42 species (SD/Ag21), followed by SCXRD, gave an important clue about the assembly route of SD/Ag20 in solution: the Ag 42 cluster eliminates six silver atoms laterally, then fuses together at the vacant face to form the final Ag 72 cluster (elimination-fusion mechanism). The characteristic emission of [EuW 10 O 36 ] 9- is well maintained in SD/Ag20. This work not only provides a new method for the synthesis of larger silver clusters as well as the functional integration of the silver cluster and POMs, but also gives deep insights about the high-nuclear silver cluster assembly mechanism. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Highly crystalline inverse opal transition metal oxides via a combined assembly of soft and hard chemistries.

PubMed

Orilall, M Christopher; Abrams, Neal M; Lee, Jinwoo; DiSalvo, Francis J; Wiesner, Ulrich

2008-07-16

A combined assembly of soft and hard chemistries is employed to generate highly crystalline three-dimensionally ordered macroporous (3DOM) niobia (Nb2O5) and titania (TiO2) structures by colloidal crystal templating. Polystyrene spheres with sp2 hybridized carbon are used in a reverse-template infiltration technique based on the aqueous liquid phase deposition of the metal oxide in the interstitial spaces of a colloidal assembly. Heating under inert atmosphere as high as 900 degrees C converts the polymer into sturdy carbon that acts as a scaffold and keeps the macropores open while the oxides crystallize. Using X-ray diffraction it is demonstrated that for both oxides this approach leads to highly crystalline materials while heat treatments to lower temperatures commonly used for polymer colloidal templating, in particular for niobia, results in only weakly crystallized materials. Furthermore it is demonstrated that heat treatment directly to higher temperatures without generating the carbon scaffold leads to a collapse of the macrostructure. The approach should in principle be applicable to other 3DOM materials that require heat treatments to higher temperatures.

Characterization of photonic colloidal crystals in real and reciprocal space

NASA Astrophysics Data System (ADS)

Thijssen, J. H. J.

2007-05-01

In this thesis, we present experimental work on the characterization of photonic colloidal crystals in real and reciprocal space. Photonic crystals are structures in which the refractive index varies periodically in space on the length scale of the wavelength of light. Self-assembly of colloidal particles is a promising route towards three-dimensional (3-D) photonic crystals. However, fabrication of photonic band-gap materials remains challenging, so calculations that predict their optical properties are indispensable. Our photonic band-structure calculations on binary Laves phases have led to a proposed route towards photonic colloidal crystals with a band gap in the visible region. Furthermore, contrary to results in literature, we found that there is no photonic band gap for inverse BCT crystals. Finally, optical spectra of colloidal crystals were analyzed using band-structure calculations. Self-assembled photonic crystals are fabricated in multiple steps. Each of these steps can significantly affect the 3-D structure of the resulting crystal. X-rays are an excellent probe of the internal structure of photonic crystals, even if the refractive-index contrast is large. In Chapter 3, we demonstrate that an angular resolution of 0.002 mrad is achievable at a third-generation synchrotron using compound refractive optics. As a result, the position and the width of Bragg reflections in 2D diffraction patterns can be resolved, even for lattice spacings larger than a micrometer (corresponding to approximately 0.1 mrad). X-ray diffraction patterns and electron-microscopy images are used in Chapter 4 to determine the orientation of hexagonal layers in convective-assembly colloidal crystals. Quantitative analysis revealed that, in our samples, the layers were not exactly hexagonal and the stacking sequence was that of face-centered cubic (FCC) crystals, though stacking faults may have been present. In Chapter 5, binary colloidal crystals of organic spheres (polystyrene, PMMA) and/or inorganic spheres (silica) are introduced as promising templates for strongly photonic crystals. To prevent melting of the template, we used atomic layer deposition (ALD) to infiltrate polystyrene and PMMA templates with alumina, after which chemical vapor deposition (CVD) was used to further enhance the refractive-index contrast. Binary colloidal crystals of silica spheres can be infiltrated by CVD directly, but they often have a layer of colloidal fluid on top. Preliminary etching experiments demonstrated that it may be possible to etch silica templates with plasmas or with adhesive tape. As described in Chapter 6, sedimentation of colloidal silica spheres in an external, high-frequency electric field lead to mm-scale BCT crystals with up to 25 layers. In addition, electric fields were used as an external control to switch between BCT and close-packed (CP) crystal structures within seconds. We also developed two procedures to invert BCT crystals without loss of structure - colloidal particles were immobilized by diffusion-polymerization or photo-induced polymerization of the surrounding solvent. Some BCT crystals were even infiltrated with silicon using CVD. We demonstrate in Chapter 7 that X-ray diffraction can be used to determine the 3-D structure of such photonic colloidal crystals at the various stages of their fabrication. Excellent agreement was found with confocal and electron-microscopy images.

Biomimetic Photonic Crystals based on Diatom Algae Frustules

NASA Astrophysics Data System (ADS)

Mishler, Jonathan; Alverson, Andrew; Herzog, Joseph

2015-03-01

Diatom algae are unicellular, photosynthetic microorganisms with a unique external shell known as a frustule. Frustules, which are composed of amorphous silica, exhibit a unique periodic nano-patterning, distinguishing diatoms from other types of phytoplankton. Diatoms have been studied for their distinctive optical properties due to their resemblance of photonic crystals. In this regard, diatoms are not only considered for their applications as photonic crystals, but also for their use as biomimetic templates for artificially fabricated photonic crystals. Through the examination and measurement of the physical characteristics of many scanning electron microscope (SEM) images of diatom frustules, a biomimetic photonic crystal derived from diatom frustules can be recreated and modeled with the finite element method. In this approach, the average geometries of the diatom frustules are used to recreate a 2-dimensional photonic crystal, after which the electric field distribution and optical transmission through the photonic crystal are both measured. The optical transmission is then compared to the transmission spectra of a regular hexagonal photonic crystal, revealing the effects of diatom geometry on their optical properties. Finally, the dimensions of the photonic crystal are parametrically swept, allowing for further control over the transmission of light through the photonic crystal.

Ultrasensitive detection of nucleic acids and proteins using quartz crystal microbalance and surface plasmon resonance sensors based on target-triggering multiple signal amplification strategy.

PubMed

Sun, Wenbo; Song, Weiling; Guo, Xiaoyan; Wang, Zonghua

2017-07-25

In this study, quartz crystal microbalance (QCM) and surface plasmon resonance (SPR) sensors were combined with template enhanced hybridization processes (TEHP), rolling circle amplification (RCA) and biocatalytic precipitation (BCP) for ultrasensitive detection of DNA and protein. The DNA complementary to the aptamer was released by the specific binding of the aptamer to the target protein and then hybridized with the capture probe and the assistant DNA to form a ternary "Y" junction structure. The initiation chain was generated by the template-enhanced hybridization process which leaded to the rolling circle amplification reaction, and a large number of repeating unit sequences were formed. Hybridized with the enzyme-labeled probes, the biocatalytic precipitation reaction was further carried out, resulting in a large amount of insoluble precipitates and amplifying the detection signal. Under the optimum conditions, detection limits as low as 43 aM for target DNA and 53 aM for lysozyme were achieved. In addition, this method also showed good selectivity and sensitivity in human serum. Copyright © 2017 Elsevier B.V. All rights reserved.

Repurposing compact discs as master molds to fabricate high-performance organic nanowire field-effect transistors

NASA Astrophysics Data System (ADS)

Kim, Kyunghun; Cho, Jinhwi; Jhon, Heesauk; Jeon, Jongwook; Kang, Myounggon; Eon Park, Chan; Lee, Jihoon; An, Tae Kyu

2017-05-01

Organic field-effect transistors (OFETs) have been developed over the past few decades due to their potential applications in future electronics such as wearable and foldable electronics. As the electrical performance of OFETs has improved, patterning organic semiconducting crystals has become a key issue for their commercialization. However, conventional soft lithographic techniques have required the use of expensive processes to fabricate high-resolution master molds. In this study, we demonstrated a cost-effective method to prepare nanopatterned master molds for the fabrication of high-performance nanowire OFETs. We repurposed commercially available compact discs (CDs) as master molds because they already have linear nanopatterns on their surface. Flexible nanopatterned templates were replicated from the CDs using UV-imprint lithography. Subsequently, 6,13-bis-(triisopropylsilylethynyl) pentacene nanowires (NWs) were grown from the templates using a capillary force-assisted lithographic technique. The NW-based OFETs showed a high average field-effect mobility of 2.04 cm2 V-1 s-1. This result was attributed to the high crystallinity of the NWs and to their crystal orientation favorable for charge transport.

Unusually large unit cell of lipid bicontinuous cubic phase: towards nature's length scales

NASA Astrophysics Data System (ADS)

Kim, Hojun; Leal, Cecilia

Lipid bicontinuous cubic phases are of great interest for drug delivery, protein crystallization, biosensing, and templates for directing hard material assembly. Structural modulations of lipid mesophases regarding phase identity and unit cell size are often necessary to augment loading and gain pore size control. One important example is the need for unit cells large enough to guide the crystallization of bigger proteins without distortion of the templating phase. In nature, bicontinuous cubic constructs achieve unit cell dimensions as high as 300 nm. However, the largest unit cell of lipid mesophases synthesized in the lab is an order of magnitude lower. In fact, it has been predicted theoretically that lipid bicontinuous cubic phases of unit cell dimensions exceeding 30 nm could not exist, as high membrane fluctuations would damp liquid crystalline order. Here we report non-equilibrium assembly methods of synthesizing metastable bicontinuous cubic phases with unit cell dimensions as high as 70 nm. The phases are stable for very long periods and become increasingly ordered as time goes by without changes to unit cell dimensions. We acknowledge the funding source as a NIH.

C-Axis-Oriented Hydroxyapatite Film Grown Using ZnO Buffer Layer

NASA Astrophysics Data System (ADS)

Sakoishi, Yasuhiro; Iguchi, Ryo; Nishikawa, Hiroaki; Hontsu, Shigeki; Hayami, Takashi; Kusunoki, Masanobu

2013-11-01

A method of fabricating c-axis-oriented hydroxyapatite film on a quartz crystal microbalance (QCM) sensor was investigated. ZnO was used as a template to obtain a hexagonal hydroxyapatite crystal of uniaxial orientation. The ZnO was grown as a c-axis film on a Au/quartz with the surface structure of a QCM sensor. Under optimized conditions, hydroxyapatite was deposited by pulsed laser deposition. X-ray diffraction showed the hydroxyapatite film to be oriented along the c-axis. Because Au and ZnO are applied to many devices, the anisotropic properties of hydroxyapatite may be incorporated into these devices as well as QCM sensors.

Preparation of Three-Dimensional Graphene Foams Using Powder Metallurgy Templates.

PubMed

Sha, Junwei; Gao, Caitian; Lee, Seoung-Ki; Li, Yilun; Zhao, Naiqin; Tour, James M

2016-01-26

A simple and scalable method which combines traditional powder metallurgy and chemical vapor deposition is developed for the synthesis of mesoporous free-standing 3D graphene foams. The powder metallurgy templates for 3D graphene foams (PMT-GFs) consist of particle-like carbon shells which are connected by multilayered graphene that shows high specific surface area (1080 m(2) g(-1)), good crystallization, good electrical conductivity (13.8 S cm(-1)), and a mechanically robust structure. The PMT-GFs did not break under direct flushing with DI water, and they were able to recover after being compressed. These properties indicate promising applications of PMT-GFs for fields requiring 3D carbon frameworks such as in energy-based electrodes and mechanical dampening.

High nitrogen pressure solution growth of GaN

NASA Astrophysics Data System (ADS)

Bockowski, Michal

2014-10-01

Results of GaN growth from gallium solution under high nitrogen pressure are presented. Basic of the high nitrogen pressure solution (HNPS) growth method is described. A new approach of seeded growth, multi-feed seed (MFS) configuration, is demonstrated. The use of two kinds of seeds: free-standing hydride vapor phase epitaxy GaN (HVPE-GaN) obtained from metal organic chemical vapor deposition (MOCVD)-GaN/sapphire templates and free-standing HVPE-GaN obtained from the ammonothermally grown GaN crystals, is shown. Depending on the seeds’ structural quality, the differences in the structural properties of pressure grown material are demonstrated and analyzed. The role and influence of impurities, like oxygen and magnesium, on GaN crystals grown from gallium solution in the MFS configuration is presented. The properties of differently doped GaN crystals are discussed. An application of the pressure grown GaN crystals as substrates for electronic and optoelectronic devices is reported.

ZnO nanodisk based UV detectors with printed electrodes.

PubMed

Alenezi, Mohammad R; Alshammari, Abdullah S; Alzanki, Talal H; Jarowski, Peter; Henley, Simon John; Silva, S Ravi P

2014-04-08

The fabrication of highly functional materials for practical devices requires a deep understanding of the association between morphological and structural properties and applications. A controlled hydrothermal method to produce single crystal ZnO hexagonal nanodisks, nanorings, and nanoroses using a mixed solution of zinc sulfate (ZnSO4) and hexamethylenetetramine (HMTA) without the need of catalysts, substrates, or templates at low temperature (75 °C) is introduced. Metal-semiconductor-metal (MSM) ultraviolet (UV) detectors were fabricated based on individual and multiple single-crystal zinc oxide (ZnO) hexagonal nanodisks. High quality single crystal individual nanodisk devices were fabricated with inkjet-printed silver electrodes. The detectors fabricated show record photoresponsivity (3300 A/W) and external quantum efficiency (1.2 × 10(4)), which we attribute to the absence of grain boundaries in the single crystal ZnO nanodisk and the polarity of its exposed surface.

Light-assisted templated self assembly using photonic crystal slabs.

PubMed

Mejia, Camilo A; Dutt, Avik; Povinelli, Michelle L

2011-06-06

We explore a technique which we term light-assisted templated self-assembly. We calculate the optical forces on colloidal particles over a photonic crystal slab. We show that exciting a guided resonance mode of the slab yields a resonantly-enhanced, attractive optical force. We calculate the lateral optical forces above the slab and predict that stably trapped periodic patterns of particles are dependent on wavelength and polarization. Tuning the wavelength or polarization of the light source may thus allow the formation and reconfiguration of patterns. We expect that this technique may be used to design all-optically reconfigurable photonic devices.

Cloning, purification, crystallization and preliminary X-ray crystallographic analysis of SET/TAF-Iß δN from Homo sapiens.

PubMed

Xu, Zhen; Yang, Weili; Shi, Nuo; Gao, Yongxiang; Teng, Maikun; Niu, Liwen

2010-08-01

The histone chaperone SET encoded by the SET gene, which is also known as template-activating factor Iß (TAF-Iß), is a multifunctional molecule that is involved in many biological phenomena such as histone binding, nucleosome assembly, chromatin remodelling, replication, transcription and apoptosis. A truncated SET/TAF-Iß ΔN protein that lacked the first 22 residues of the N-terminus but contained the C-terminal acidic domain and an additional His6 tag at the C-terminus was overexpressed in Escherichia coli and crystallized by the hanging-drop vapour-diffusion method using sodium acetate as precipitant at 283 K. The crystals diffracted to 2.7 A resolution and belonged to space group P4(3)2(1)2.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ranieri, M.G.A., E-mail: gabi.ranieri@ig.com.br; Aguiar, E.C.; Cilense, M.

Highlights: • Bi{sub 4}Ti{sub 3}O{sub 12} thick films were obtained by SSR and PPM methods. • Both systems crystallize in an orthorhombic structure. • Textured characteristics were evidenced. • Grain morphology affects the P–E loops. - Abstract: Bismuth titanate powders (Bi{sub 4}Ti{sub 3}O{sub 12}-BIT) were fabricated by solid state reaction (SSR) and polymeric precursor method (PPM). From these powders, Bi{sub 4}Ti{sub 3}O{sub 12} pellets were obtained by tape-casting using plate-like templates particles prepared by a molten salt method. The BIT phase crystallizes in an orthorhombic structure type with space group Fmmm. Agglomeration of the particles, which affects the densification ofmore » the ceramic, electrical conduction and leakage current at high electric fields, was monitored by transmission electronic microscopy (TEM) analyses. FEG-SEM indicated that different shape of grains of BIT ceramics was influenced by the processing route. Both SSR and PPM methods lead to unsaturated P–E loops of BIT ceramics originating from the highly c-axis orientation and high conductivity which was affected by charge carriers flowing normally to the grain boundary of the crystal lattice.« less

Methods of using structures including catalytic materials disposed within porous zeolite materials to synthesize hydrocarbons

DOEpatents

Rollins, Harry W [Idaho Falls, ID; Petkovic, Lucia M [Idaho Falls, ID; Ginosar, Daniel M [Idaho Falls, ID

2011-02-01

Catalytic structures include a catalytic material disposed within a zeolite material. The catalytic material may be capable of catalyzing a formation of methanol from carbon monoxide and/or carbon dioxide, and the zeolite material may be capable of catalyzing a formation of hydrocarbon molecules from methanol. The catalytic material may include copper and zinc oxide. The zeolite material may include a first plurality of pores substantially defined by a crystal structure of the zeolite material and a second plurality of pores dispersed throughout the zeolite material. Systems for synthesizing hydrocarbon molecules also include catalytic structures. Methods for synthesizing hydrocarbon molecules include contacting hydrogen and at least one of carbon monoxide and carbon dioxide with such catalytic structures. Catalytic structures are fabricated by forming a zeolite material at least partially around a template structure, removing the template structure, and introducing a catalytic material into the zeolite material.

Functional materials based on nanocrystalline cellulose

NASA Astrophysics Data System (ADS)

Surov, O. V.; Voronova, M. I.; Zakharov, A. G.

2017-10-01

The data on the synthesis of functional materials based on nanocrystalline cellulose (NCC) published over the past 10 years are analyzed. The liquid-crystal properties of NCC suspensions, methods of investigation of NCC suspensions and films, conditions for preserving chiral nematic structure in the NCC films after removal of the solvent and features of templated sol-gel synthesis of functional materials based on NCC are considered. The bibliography includes 106 references.

Fabrication and characterization of cerium-doped barium titanate inverse opal by sol-gel method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jin Yi; Zhu Yihua; Yang Xiaoling

Cerium-doped barium titanate inverted opal was synthesized from barium acetate contained cerous acetate and tetrabutyl titanate in the interstitial spaces of a polystyrene (PS) opal. This procedure involves infiltration of precursors into the interstices of the PS opal template followed by hydrolytic polycondensation of the precursors to amorphous barium titanate and removal of the PS opal by calcination. The morphologies of opal and inverse opal were characterized by scanning electron microscope (SEM). The pores were characterized by mercury intrusion porosimetry (MIP). X-ray photoelectron spectroscopy (XPS) investigation showed the doping structure of cerium, barium and titanium. And powder X-ray diffraction allowsmore » one to observe the influence of doping degree on the grain size. The lattice parameters, crystal size and lattice strain were calculated by the Rietveld refinement method. The synthesis of cerium-doped barium titanate inverted opals provides an opportunity to electrically and optically engineer the photonic band structure and the possibility of developing tunable three-dimensional photonic crystal devices. - Graphical abstract: Cerium-doped barium titanate inverted opal was synthesized from barium acetate acid contained cerous acetate and tetrabutyl titanate in the interstitial spaces of a PS opal, which involves infiltration of precursors into the interstices of the PS opal template and removal of the PS opal by calcination.« less

Supercritical CO2/Co-solvents Extraction of Porogen and Surfactant to Obtain

NASA Astrophysics Data System (ADS)

Lubguban, Jorge

2005-03-01

A method of pore generation by supercritical CO2 (SCCO2)/co-solvents extraction for the preparation of nanoporous organosilicate thin films for ultralow dielectric constant materials is investigated. A nanohybrid film was prepared from poly (propylene glycol) (PPG) and poly(methylsilsesquioxane) (PMSSQ) whereby the PPG porogen are entrapped within the crosslinked PMSSQ matrix. Another set of thin films was produced by liquid crystal templating whereby non-ionic (polyoxyethylene 10 stearyl ether) (Brij76) and ionic (cetyltrimethylammonium bromide) (CTAB) surfactant were used as sacrificial templates in a tetraethoxy silane (TEOS) and methyltrimethoxy silane (MTMS) based matrix. These two types of films were treated with SCCO2/co-solvents to remove porogen and surfactant templates. As a comparison, porous structures generated by thermal decomposition were also evaluated. It is found that SCCO2/co-solvents treatment produced closely comparable results with thermal decomposition. The results were evident from Fourier Transform Infrared (FT- IR) spectroscopy and optical constants data obtained from variable angle spectroscopic ellipsometry (VASE).

Important property of polymer spheres for the preparation of three-dimensionally ordered macroporous (3DOM) metal oxides by the ethylene glycol method: the glass-transition temperature.

PubMed

Sadakane, Masahiro; Sasaki, Keisuke; Nakamura, Hiroki; Yamamoto, Takashi; Ninomiya, Wataru; Ueda, Wataru

2012-12-21

We demonstrate that the glass-transition temperature (T(g)) of a polymer sphere template is a crucial factor in the production of three-dimensionally ordered macroporous (3DOM) materials. Metal nitrate dissolved in ethylene glycol-methanol was infiltrated into the void of a face-centered, close-packed colloidal crystal of poly(methyl methacrylate) (PMMA)-based spheres. The metal nitrate reacts with EG to form a metal oxalate (or metal glycoxylate) solid (nitrate oxidation) in the void of the template when the metal nitrate-EG-PMMA composite is heated. Further heating converts metal oxalate to metal oxide and removes PMMA to form 3DOM materials. We investigated the effect of T(g) of PMMA templates and obtained clear evidence that the solidification temperature of the metal precursor solution (i.e., nitration oxidation temperature) should be lower than the T(g) of the polymer spheres to obtain a well-ordered 3DOM structure.

Hemispherical Brillouin zone imaging of a diamond-type biological photonic crystal

PubMed Central

Wilts, Bodo D.; Michielsen, Kristel; De Raedt, Hans; Stavenga, Doekele G.

2012-01-01

The brilliant structural body colours of many animals are created by three-dimensional biological photonic crystals that act as wavelength-specific reflectors. Here, we report a study on the vividly coloured scales of the diamond weevil, Entimus imperialis. Electron microscopy identified the chitin and air assemblies inside the scales as domains of a single-network diamond (Fd3m) photonic crystal. We visualized the topology of the first Brillouin zone (FBZ) by imaging scatterometry, and we reconstructed the complete photonic band structure diagram (PBSD) of the chitinous photonic crystal from reflectance spectra. Comparison with calculated PBSDs indeed showed a perfect overlap. The unique method of non-invasive hemispherical imaging of the FBZ provides key insights for the investigation of photonic crystals in the visible wavelength range. The characterized extremely large biophotonic nanostructures of E. imperialis are structurally optimized for high reflectance and may thus be well suited for use as a template for producing novel photonic devices, e.g. through biomimicry or direct infiltration from dielectric material. PMID:22188768

Structure of Hepatitis C Virus Polymerase in Complex with Primer-Template RNA

PubMed Central

Murakami, Eisuke; Lam, Angela M.; Grice, Rena L.; Du, Jinfa; Sofia, Michael J.; Furman, Philip A.; Otto, Michael J.

2012-01-01

The replication of the hepatitis C viral (HCV) genome is accomplished by the NS5B RNA-dependent RNA polymerase (RdRp), for which mechanistic understanding and structure-guided drug design efforts have been hampered by its propensity to crystallize in a closed, polymerization-incompetent state. The removal of an autoinhibitory β-hairpin loop from genotype 2a HCV NS5B increases de novo RNA synthesis by >100-fold, promotes RNA binding, and facilitated the determination of the first crystallographic structures of HCV polymerase in complex with RNA primer-template pairs. These crystal structures demonstrate the structural realignment required for primer-template recognition and elongation, provide new insights into HCV RNA synthesis at the molecular level, and may prove useful in the structure-based design of novel antiviral compounds. Additionally, our approach for obtaining the RNA primer-template-bound structure of HCV polymerase may be generally applicable to solving RNA-bound complexes for other viral RdRps that contain similar regulatory β-hairpin loops, including bovine viral diarrhea virus, dengue virus, and West Nile virus. PMID:22496223

Diatom-templated TiO2 with enhanced photocatalytic activity: biomimetics of photonic crystals

NASA Astrophysics Data System (ADS)

He, Jiao; Chen, Daomei; Li, Yongli; Shao, Junlong; Xie, Jiao; Sun, Yuejuan; Yan, Zhiying; Wang, Jiaqiang

2013-11-01

The siliceous frustules with sophisticated optical structure endow diatoms with superior solar light-harvesting abilities for effective photosynthesis. The preserved frustules of diatom ( Cocconeis placentula) cells, as biophotonic crystals, were thus employed as both hard templates and silicon resources to synthesize TiO2 photocatalyst. Characterizations by a combination of physicochemical techniques proved that the bio-inspired sample is TiO2-coated SiO2 with biogenic C self-doped in. It was found that the synthesized composites exhibited similar morphologies to the original diatom templates. In comparison with commercial Degussa P25 TiO2, the C-doped TiO2/SiO2 catalyst exhibited more light absorption in the visible region and higher photocatalytic efficiency for photodegradation of rhodamine B under visible light due to the biomorphic hierarchical structures, TiO2 coating and C-doping.

Optimizing Pt/TiO2 templates for textured PZT growth and MEMS devices

NASA Astrophysics Data System (ADS)

Potrepka, Daniel; Fox, Glenn; Sanchez, Luz; Polcawich, Ronald

2013-03-01

Crystallographic texture of lead zirconate titanate (PZT) thin films strongly influences piezoelectric properties used in MEMS applications. Textured growth can be achieved by relying on crystal growth habit and can also be initiated by the use of a seed-layer heteroepitaxial template. Template choice and the process used to form it determine structural quality, ultimately influencing performance and reliability of MEMS PZT devices such as switches, filters, and actuators. This study focuses on how 111-textured PZT is generated by a combination of crystal habit and templating mechanisms that occur in the PZT/bottom-electrode stack. The sequence begins with 0001-textured Ti deposited on thermally grown SiO2 on a Si wafer. The Ti is converted to 100-textured TiO2 (rutile) through thermal oxidation. Then 111-textured Pt can be grown to act as a template for 111-textured PZT. Ti and Pt are deposited by DC magnetron sputtering. TiO2 and Pt film textures and structure were optimized by variation of sputtering deposition times, temperatures and power levels, and post-deposition anneal conditions. The relationship between Ti, TiO2, and Pt texture and their impact on PZT growth will be presented. Also affiliated with U.S. Army Research Lab, Adelphi, MD 20783, USA

Photonic crystals at visible, x-ray, and terahertz frequencies

NASA Astrophysics Data System (ADS)

Prasad, Tushar

Photonic crystals are artificial structures with a periodically varying refractive index. This property allows photonic crystals to control the propagation of photons, making them desirable components for novel photonic devices. Photonic crystals are also termed as "semiconductors of light", since they control the flow of electromagnetic radiation similar to the way electrons are excited in a semiconductor crystal. The scale of periodicity in the refractive index determines the frequency (or wavelength) of the electromagnetic waves that can be manipulated. This thesis presents a detailed analysis of photonic crystals at visible, x-ray, and terahertz frequencies. Self-assembly and spin-coating methods are used to fabricate colloidal photonic crystals at visible frequencies. Their dispersion characteristics are examined through theoretical as well as experimental studies. Based on their peculiar dispersion property called the superprism effect, a sensor that can detect small quantities of chemical substances is designed. A photonic crystal that can manipulate x-rays is fabricated by using crystals of a non-toxic plant virus as templates. Calculations show that these metallized three-dimensional crystals can find utility in x-ray optical systems. Terahertz photonic crystal slabs are fabricated by standard lithographic and etching techniques. In-plane superprism effect and out-of-plane guided resonances are studied by terahertz time-domain spectroscopy, and verified by numerical simulations.

High-quality photonic crystals with a nearly complete band gap obtained by direct inversion of woodpile templates with titanium dioxide.

PubMed

Marichy, Catherine; Muller, Nicolas; Froufe-Pérez, Luis S; Scheffold, Frank

2016-02-25

Photonic crystal materials are based on a periodic modulation of the dielectric constant on length scales comparable to the wavelength of light. These materials can exhibit photonic band gaps; frequency regions for which the propagation of electromagnetic radiation is forbidden due to the depletion of the density of states. In order to exhibit a full band gap, 3D PCs must present a threshold refractive index contrast that depends on the crystal structure. In the case of the so-called woodpile photonic crystals this threshold is comparably low, approximately 1.9 for the direct structure. Therefore direct or inverted woodpiles made of high refractive index materials like silicon, germanium or titanium dioxide are sought after. Here we show that, by combining multiphoton lithography and atomic layer deposition, we can achieve a direct inversion of polymer templates into TiO2 based photonic crystals. The obtained structures show remarkable optical properties in the near-infrared region with almost perfect specular reflectance, a transmission dip close to the detection limit and a Bragg length comparable to the lattice constant.

Following DNA chain extension and protein conformational changes in crystals of a Y-family DNA polymerase via Raman crystallography.

PubMed

Espinoza-Herrera, Shirly J; Gaur, Vineet; Suo, Zucai; Carey, Paul R

2013-07-23

Y-Family DNA polymerases are known to bypass DNA lesions in vitro and in vivo. Sulfolobus solfataricus DNA polymerase (Dpo4) was chosen as a model Y-family enzyme for investigating the mechanism of DNA synthesis in single crystals. Crystals of Dpo4 in complexes with DNA (the binary complex) in the presence or absence of an incoming nucleotide were analyzed by Raman microscopy. (13)C- and (15)N-labeled d*CTP, or unlabeled dCTP, were soaked into the binary crystals with G as the templating base. In the presence of the catalytic metal ions, Mg(2+) and Mn(2+), nucleotide incorporation was detected by the disappearance of the triphosphate band of dCTP and the retention of *C modes in the crystal following soaking out of noncovalently bound C(or *C)TP. The addition of the second coded base, thymine, was observed by adding cognate dTTP to the crystal following a single d*CTP addition. Adding these two bases caused visible damage to the crystal that was possibly caused by protein and/or DNA conformational change within the crystal. When d*CTP is soaked into the Dpo4 crystal in the absence of Mn(2+) or Mg(2+), the primer extension reaction did not occur; instead, a ternary protein·template·d*CTP complex was formed. In the Raman difference spectra of both binary and ternary complexes, in addition to the modes of d(*C)CTP, features caused by ring modes from the template/primer bases being perturbed and from the DNA backbone appear, as well as features from perturbed peptide and amino acid side chain modes. These effects are more pronounced in the ternary complex than in the binary complex. Using standardized Raman intensities followed as a function of time, the C(*C)TP population in the crystal was maximal at ∼20 min. These remained unchanged in the ternary complex but declined in the binary complexes as chain incorporation occurred.

Inverse opal with an ultraviolet photonic gap

NASA Astrophysics Data System (ADS)

Ni, Peigen; Cheng, Bingying; Zhang, Daozhong

2002-03-01

Photonic crystals composed of TiO2 and air voids fabricated by the template method exhibit an ultraviolet photonic stop band (˜380 nm) in the Γ-L direction. Scanning electron microscopy images show that the inverse opal possesses face-centered-cubic symmetry with a lattice constant of 240 nm. The transmission spectra show that the change in transmittance is one order of magnitude in the gap, which is in accord with the reflection spectrum.

[Chitosan-collagen polymer induced remineralization of tooth hard tissue through self-growing methods].

PubMed

Xun, Ren; Jing, Yao; Qin, Du; Chuhang, Liao; Kun, Tian

2014-10-01

To modify biomacromolecules, such as chitosan and collagen, to synthesize a mineralized template that will induce self-growing remineralization of tooth enamel. Natural polycation polysaccharide chitosan was modified through phosphorylation to synthesize the polyanion derivative ofphosphorylated chitosan. Parent hydrogels com- bined with chitosan and collagen I were built through peptide binding reaction using genipin as a crosslinker. The gels self- assembled on the tooth's inert surface, which was stimulated by ultraviolet radiation. The bionic saliva provided mineralized ion, and then the hydroxyapatite assembled and grew in situ on the tooth. The functional group P04(3-) (3,446 cm(-1)) was grafted on chitosan as confirmed by the Fourier transform infrared spectroscopy. The porous polyelectrolyte complex hydrogel formed by the interaction between the polycation chitosan and the polyanion phosphorylated chitosan could induce hydroxyapatite crystal nucleation and growth on the hydrogel fiber surfaces. The neonatal crystal was hydroxyapatite as confirmed by X-ray diffraction and was tightly connected to the tooth. A continuous structure of column crystals with sizes ranging from 30 nm to 60 nm was observed. The structure was in parallel direction similar to the direction of the enamel rod, and its hardness was close to dentin. The parent hydrogels that were easily obtained and controlled could mimic the template of the enamel mineralization and induce a self-growing hydroxyapatite, which is an important step in the structural bionics of enamel.

Hydrothermal synthesis of free-template zeolite T from kaolin

NASA Astrophysics Data System (ADS)

Arshad, Sazmal E.; Yusslee, Eddy F.; Rahman, Md. Lutfor; Sarkar, Shaheen M.; Patuwan, Siti Z.

2017-12-01

Free-template zeolite T crystals were synthesized via hydrothermal synthesis by utilizing the activated kaolin as silica and alumina source, with the molar composition of 1 SiO2: 0.04 Al2O3: 0.26 Na2O: 0.09 K2O: 14 H2O. Observation of the formation of free-template zeolite crystals were done at temperature 90°C, 100 °C and 110 °C respectively. It was therefore determined that during the 120 h of the synthesis at 90 °C, zeolite T nucleated and formed a first competitive phase with zeolite L. As temperature increases to 100 °C, zeolite T presented itself as a major phase in the system at time 168 h. Subsequently, development of Zeolite T with second competitive phase of zeolite W was observed at temperature 110 °C. In this study, XRD and SEM instruments were used to monitor the behavior of zeolite T crystals with respect of temperature and time. By using natural resource of kaolin clay as a starting material, this paper hence aims to provide new findings in synthesis of zeolite T using low energy consumption and low production cost.

Structural colored gels for tunable soft photonic crystals.

PubMed

Harun-Ur-Rashid, Mohammad; Seki, Takahiro; Takeoka, Yukikazu

2009-01-01

A periodically ordered interconnecting porous structure can be embodied in chemical gels by using closest-packed colloidal crystals as templates. The interconnecting porosity not only provides a quick response but also endows the porous gels with structural color arising from coherent Bragg optical diffraction. The structural colors revealed by porous gels can be regulated by several techniques, and thus, it is feasible to obtain desirable, smart, soft materials. A well-known thermosensitive monomer, N-isopropylacrylamide (NIPA), and other minor monomers were used to fabricate various structural colored gels. The selection of minor monomers depended on the targeted properties. This review focuses on the synthesis of templates, structural colored porous gels, and the applications of structural colored gel as smart soft materials for tunable photonic crystals. (c) 2009 The Japan Chemical Journal Forum and Wiley Periodicals, Inc.

Fabrication of self-assembled photonic-crystal structures by centrifugation and spin coating

NASA Astrophysics Data System (ADS)

Xu, Yan; Schneider, Garrett J.; Wetzel, Eric D.; Prather, Dennis W.

2003-11-01

We have developed a simple, low-cost process for the fabrication of high-quality three-dimensional artificial-opal and inverse-opal photonic crystals. The process is based on the self-assembly of a template from a uniform suspension of polystyrene microspheres, which is sintered for added strength and subsequently back-filled with high-index material. The template formation is assisted by a combination of centrifugation and spin-annealing, which requires relatively short process times and inexpensive laboratory equipment. The process has been used to fabricate polycrystalline photonic crystals with photonic stop gaps in the mid-IR portion of the spectrum. Details of the fabrication process and fabricated samples will be presented. In addition, Fourier-transform IR reflection spectroscopy has been used to characterize the samples; the results are shown to be in excellent agreement with band structure diffraction calculations.

Photonic band gap in (Pb,La)(Zr,Ti)O3 inverse opals

NASA Astrophysics Data System (ADS)

Li, Bo; Zhou, Ji; Hao, Lifeng; Hu, Wei; Zong, Ruilong; Cai, Minmin; Fu, Min; Gui, Zhilun; Li, Longtu; Li, Qi

2003-05-01

(Pb,La)(Zr,Ti)O3 (PLZT) inverse opal photonic crystals were synthesized by a process of self-assembly in combination with a sol-gel technique. In this process, PLZT precursors were infiltrated into the interstices of the opal template assembled by monodisperse submicron polystyrene spheres, and then gelled in a humid environment. Polystyrene template was removed by calcining the specimen at a final temperature of 700 °C accompanied with the crystallization of perovskite phase in PLZT inverse opal network. Scanning electron microscope images show that the inverse opals possess a fcc structure with a lattice constant of 250 nm. A wide photonic band gap in the visible range is observed from transmission spectra of the sample. Such PLZT inverse opals as photonic crystals should be of importance in device applications.

Cross-linked lysozyme crystal templated synthesis of Au nanoparticles as high-performance recyclable catalysts.

PubMed

Liang, Miao; Wang, Libing; Liu, Xia; Qi, Wei; Su, Rongxin; Huang, Renliang; Yu, Yanjun; He, Zhimin

2013-06-21

Bio-nanomaterials fabricated using a bioinspired templating technique represent a novel class of composite materials with diverse applications in biomedical, electronic devices, drug delivery, and catalysis. In this study, Au nanoparticles (NPs) are synthesized within the solvent channels of cross-linked lysozyme crystals (CLLCs) in situ without the introduction of extra chemical reagents or physical treatments. The as-prepared AuNPs-in-protein crystal hybrid materials are characterized by light microscopy, transmission electron microscopy, x-ray diffraction, and Fourier-transform infrared spectroscopy analyses. Small AuNPs with narrow size distribution reveal the restriction effects of the porous structure in the lysozyme crystals. These composite materials are proven to be active heterogeneous catalysts for the reduction of 4-nitrophenol to 4-aminophenol. These catalysts can be easily recovered and reused at least 20 times because of the physical stability and macro-dimension of CLLCs. This work is the first to use CLLCs as a solid biotemplate for the preparation of recyclable high-performance catalysts.

Cross-linked lysozyme crystal templated synthesis of Au nanoparticles as high-performance recyclable catalysts

NASA Astrophysics Data System (ADS)

Liang, Miao; Wang, Libing; Liu, Xia; Qi, Wei; Su, Rongxin; Huang, Renliang; Yu, Yanjun; He, Zhimin

2013-06-01

Bio-nanomaterials fabricated using a bioinspired templating technique represent a novel class of composite materials with diverse applications in biomedical, electronic devices, drug delivery, and catalysis. In this study, Au nanoparticles (NPs) are synthesized within the solvent channels of cross-linked lysozyme crystals (CLLCs) in situ without the introduction of extra chemical reagents or physical treatments. The as-prepared AuNPs-in-protein crystal hybrid materials are characterized by light microscopy, transmission electron microscopy, x-ray diffraction, and Fourier-transform infrared spectroscopy analyses. Small AuNPs with narrow size distribution reveal the restriction effects of the porous structure in the lysozyme crystals. These composite materials are proven to be active heterogeneous catalysts for the reduction of 4-nitrophenol to 4-aminophenol. These catalysts can be easily recovered and reused at least 20 times because of the physical stability and macro-dimension of CLLCs. This work is the first to use CLLCs as a solid biotemplate for the preparation of recyclable high-performance catalysts.

Anisotropic growth of hydroxyapatite on the silk fibroin films

NASA Astrophysics Data System (ADS)

Li, Yucheng; Cai, Yurong; Kong, Xiangdong; Yao, Juming

2008-12-01

Bombyx mori silk fibroin is of practical interest for its excellent intrinsic properties utilizable in the biotechnological and biomedical fields. Here, the silk fibroin films were pretreated with different methods and then used as the template for the hydroxyapatite (HA) crystal growth. To study the effect of silk films' surface structure on the protein biomineralization, the films were immersed into 1.5 times simulated body fluid (1.5 × SBF) to induce the HA deposition at 37 °C. The results showed that an anisotropic growth of HA crystals was observed on the different films as judging from XRD, TEM and HRTEM data. This was thought that the positions and density of carboxyl groups, C dbnd O and amino groups on the surface of SF films may be different, which play the key effect on HA crystal growth.

Electrochemical synthesis of mesoporous gold films toward mesospace-stimulated optical properties

NASA Astrophysics Data System (ADS)

Li, Cuiling; Dag, Ömer; Dao, Thang Duy; Nagao, Tadaaki; Sakamoto, Yasuhiro; Kimura, Tatsuo; Terasaki, Osamu; Yamauchi, Yusuke

2015-03-01

Mesoporous gold (Au) films with tunable pores are expected to provide fascinating optical properties stimulated by the mesospaces, but they have not been realized yet because of the difficulty of controlling the Au crystal growth. Here, we report a reliable soft-templating method to fabricate mesoporous Au films using stable micelles of diblock copolymers, with electrochemical deposition advantageous for precise control of Au crystal growth. Strong field enhancement takes place around the center of the uniform mesopores as well as on the walls between the pores, leading to the enhanced light scattering as well as surface-enhanced Raman scattering (SERS), which is understandable, for example, from Babinet principles applied for the reverse system of nanoparticle ensembles.

Hydroxyapatite crystals biologically inspired on titanium by using an organic template based on the copolymer of acrylic acid and itaconic acid.

PubMed

Zhang, Chao; Li, Zhi-An; Cheng, Xiang-Rong; Xiao, Qun; Li, Hong-Bo

2010-01-01

Hydroxyapatite coating on metal implants is an effective method to enhance bioactive properties of the metal surface. We report here a method to coat the Ti-6Al-4V alloy with hydroxyapatite crystals. After alkaline/heat treatment, the spontaneous growth of organoapatite on titanium alloy surface involves sequential preadsorption of titanium isopropoxide (TIPO) and the copolymer of acrylic acid and itaconic acid on the metal, followed by exposure to simulated body fluid (SBF). The organoapatite characterization of the coating was carried out by scanning electron microscopy, energy dispersive spectrometer, and X-ray diffraction. The copolymer of acrylic acid and itaconic acid overlayer which is rich of carboxylate groups can lead to the deposition of needle-like and homogeneous HA on the surface after immersion in SBF.

Diamond Lattice Colloidal Crystals from Binary DNA-grafted Microspheres

NASA Astrophysics Data System (ADS)

Crocker, John; Wang, Yifan; Jenkins, Ian; McGinley, James; Sinno, Talid

Future optical materials promise to do for photonics what semiconductors did for electronics, but the challenge has long been in creating the structure they require regular, three-dimensional array of transparent microspheres arranged like the atoms in a diamond crystal. Here we demonstrate a simple approach for spontaneously growing double-diamond (or B32) crystals from a binary suspension of sub-micron polymer microspheres with synthetic DNA grafted to their surfaces. While diamond symmetry crystals have previously been grown from much smaller nanoparticles, none of those methods appear workable for the larger particles needed for photonic applications, whose size must be comparable to the wavelength of visible light. Intriguingly, matched simulations fail to nucleate or grow B32 crystals from suspension; nor have they been predicted on the basis of theoretical arguments. We conjecture that the B32 crystals may form via transformation from a precursor with a different lattice structure in the bulk or on its surface. The feasibility of converting our self-assembled crystals into diamond-symmetry photonic templates will be discussed. This finding suggests that still other unexpected microstructures may be accessible using this approach. US National Science Foundation, CBET- 1403237.

Topological defects in liquid crystals and molecular self-assembly (Conference Presentation)

NASA Astrophysics Data System (ADS)

Abbott, Nicholas L.

2017-02-01

Topological defects in liquid crystals (LCs) have been widely used to organize colloidal dispersions and template polymerizations, leading to a range of elastomers and gels with complex mechanical and optical properties. However, little is understood about molecular-level assembly processes within defects. This presentation will describe an experimental study that reveals that nanoscopic environments defined by LC topological defects can selectively trigger processes of molecular self-assembly. By using fluorescence microscopy, cryogenic transmission electron microscopy and super-resolution optical microscopy, key signatures of molecular self-assembly of amphiphilic molecules in topological defects are observed - including cooperativity, reversibility, and controlled growth of the molecular assemblies. By using polymerizable amphiphiles, we also demonstrate preservation of molecular assemblies templated by defects, including nanoscopic "o-rings" synthesized from "Saturn-ring" disclinations. Our results reveal that topological defects in LCs are a versatile class of three-dimensional, dynamic and reconfigurable templates that can direct processes of molecular self-assembly in a manner that is strongly analogous to other classes of macromolecular templates (e.g., polymer—surfactant complexes). Opportunities for the design of exquisitely responsive soft materials will be discussed using bacterial endotoxin as an example.

Fabrication of ordered arrays of micro- and nanoscale features with control over their shape and size via templated solid-state dewetting.

PubMed

Ye, Jongpil

2015-05-08

Templated solid-state dewetting of single-crystal films has been shown to be used to produce regular patterns of various shapes. However, the materials for which this patterning method is applicable, and the size range of the patterns produced are still limited. Here, it is shown that ordered arrays of micro- and nanoscale features can be produced with control over their shape and size via solid-state dewetting of patches patterned from single-crystal palladium and nickel films of different thicknesses and orientations. The shape and size characteristics of the patterns are found to be widely controllable with varying the shape, width, thickness, and orientation of the initial patches. The morphological evolution of the patches is also dependent on the film material, with different dewetting behaviors observed in palladium and nickel films. The mechanisms underlying the pattern formation are explained in terms of the influence on Rayleigh-like instability of the patch geometry and the surface energy anisotropy of the film material. This mechanistic understanding of pattern formation can be used to design patches for the precise fabrication of micro- and nanoscale structures with the desired shapes and feature sizes.

Fabrication of ordered arrays of micro- and nanoscale features with control over their shape and size via templated solid-state dewetting

PubMed Central

Ye, Jongpil

2015-01-01

Templated solid-state dewetting of single-crystal films has been shown to be used to produce regular patterns of various shapes. However, the materials for which this patterning method is applicable, and the size range of the patterns produced are still limited. Here, it is shown that ordered arrays of micro- and nanoscale features can be produced with control over their shape and size via solid-state dewetting of patches patterned from single-crystal palladium and nickel films of different thicknesses and orientations. The shape and size characteristics of the patterns are found to be widely controllable with varying the shape, width, thickness, and orientation of the initial patches. The morphological evolution of the patches is also dependent on the film material, with different dewetting behaviors observed in palladium and nickel films. The mechanisms underlying the pattern formation are explained in terms of the influence on Rayleigh-like instability of the patch geometry and the surface energy anisotropy of the film material. This mechanistic understanding of pattern formation can be used to design patches for the precise fabrication of micro- and nanoscale structures with the desired shapes and feature sizes. PMID:25951816

Engineered ZnO nanowire arrays using different nanopatterning techniques

NASA Astrophysics Data System (ADS)

Volk, János; Szabó, Zoltán; Erdélyi, Róbert; Khánh, Nguyen Q.

2012-02-01

The impact of various masking patterns and template layers on the wet chemically grown vertical ZnO nanowire arrays was investigated. The nanowires/nanorods were seeded at nucleation windows which were patterned in a mask layer using various techniques such as electron beam lithography, nanosphere photolithography, and atomic force microscope type nanolithography. The compared ZnO templates included single crystals, epitaxial layer, and textured polycrystalline films. Scanning electron microscopy revealed that the alignment and crystal orientation of the nanowires were dictated by the underlying seed layer, while their geometry can be tuned by the parameters of the certain nanopatterning technique and of the wet chemical process. The comparison of the alternative nanolithography techniques showed that using direct writing methods the diameter of the ordered ZnO nanowires can be as low as 30-40 nm at a density of 100- 1000 NW/μm2 in a very limited area (10 μm2-1 mm2). Nanosphere photolithography assisted growth, on the other hand, favors thicker nanopillars (~400 nm) and enables large-area, low-cost patterning (1-100 cm2). These alternative lowtemperature fabrication routes can be used for different novel optoelectronic devices, such as nanorod based ultraviolet photodiode, light emitting device, and waveguide laser.

Measuring the dielectric and optical response of millimeter-scale amorphous and hexagonal boron nitride films grown on epitaxial graphene.

PubMed

Rigosi, Albert F; Hill, Heather M; Glavin, Nicholas R; Pookpanratana, Sujitra J; Yang, Yanfei; Boosalis, Alexander G; Hu, Jiuning; Rice, Anthony; Allerman, Andrew A; Nguyen, Nhan V; Hacker, Christina A; Elmquist, Randolph E; Hight Walker, Angela R; Newell, David B

2018-01-01

Monolayer epitaxial graphene (EG), grown on the Si face of SiC, is an advantageous material for a variety of electronic and optical applications. EG forms as a single crystal over millimeter-scale areas and consequently, the large scale single crystal can be utilized as a template for growth of other materials. In this work, we present the use of EG as a template to form millimeter-scale amorphous and hexagonal boron nitride ( a -BN and h -BN) films. The a -BN is formed with pulsed laser deposition and the h -BN is grown with triethylboron (TEB) and NH 3 precursors, making it the first metal organic chemical vapor deposition (MOCVD) process of this growth type performed on epitaxial graphene. A variety of optical and non-optical characterization methods are used to determine the optical absorption and dielectric functions of the EG, a -BN, and h -BN within the energy range of 1 eV to 8.5 eV. Furthermore, we report the first ellipsometric observation of high-energy resonant excitons in EG from the 4H polytype of SiC and an analysis on the interactions within the EG and h -BN heterostructure.

Fabrication of 3D photonic crystals from chitosan that are responsive to organic solvents.

PubMed

Huang, Guanbo; Yin, Yibing; Pan, Zeng; Chen, Mingxi; Zhang, Lei; Liu, Yu; Zhang, Yongli; Gao, Jianping

2014-12-08

Inspired by photonic nanostructures in nature, such as the hair-like chaetae on the body of sea mice, inverse opal photonic crystals films were fabricated with chitosan, a kind of biomacromolecule found in nature. First, monodispersed polystyrene (PS) colloidal crystal templates with different particle sizes were prepared. The inverse opal films (IOFs) were fabricated through in situ cross-linking of the PS templates. The IOFs contain periodically ordered interconnecting pores that endow the films with photonic stop bands and structural colors, which are visible to the naked eye. The IOFs exhibit rapid reversible changes in their structural colors and reflectance peaks in response to alcohols and phenols. Possible mechanisms for the shifts in the IOF's reflectance peaks are proposed. The changes in the IOFs in response to alcohols and phenols provide a potential way to visually detect these organic solvents.

Insights into the Formation and Properties of Templated Dual Mesoporous Titania with Enhanced Photocatalytic Activity.

PubMed

Naboulsi, Issam; Lebeau, Bénédicte; Michelin, Laure; Carteret, Cédric; Vidal, Loic; Bonne, Magali; Blin, Jean-Luc

2017-01-25

The one pot synthesis of dual mesoporous titania (2.3 and 7.7 nm) has been achieved from a mixture of fluorinated and Pluronic surfactants. The small and large mesopore networks are templated, respectively, by a fluorinated-rich liquid crystal and a Pluronic-rich liquid crystal, which are in equilibrium. After calcination at 350 °C, the amorphous walls are transformed into semicrystalline anatase preserving the mesoporous structure. Results concerning the photodegradation of methyl orange using the calcined photocatalysts highlight that the kinetic rate constant (k) determined for the dual mesoporous titania is 2.6 times higher than the k value obtained for the monomodal ones.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mosley, Ralph T.; Edwards, Thomas E.; Murakami, Eisuke

The replication of the hepatitis C viral (HCV) genome is accomplished by the NS5B RNA-dependent RNA polymerase (RdRp), for which mechanistic understanding and structure-guided drug design efforts have been hampered by its propensity to crystallize in a closed, polymerization-incompetent state. The removal of an autoinhibitory {beta}-hairpin loop from genotype 2a HCV NS5B increases de novo RNA synthesis by >100-fold, promotes RNA binding, and facilitated the determination of the first crystallographic structures of HCV polymerase in complex with RNA primer-template pairs. These crystal structures demonstrate the structural realignment required for primer-template recognition and elongation, provide new insights into HCV RNA synthesismore » at the molecular level, and may prove useful in the structure-based design of novel antiviral compounds. Additionally, our approach for obtaining the RNA primer-template-bound structure of HCV polymerase may be generally applicable to solving RNA-bound complexes for other viral RdRps that contain similar regulatory {beta}-hairpin loops, including bovine viral diarrhea virus, dengue virus, and West Nile virus.« less

Hydrothermal synthesis of zinc oxide nanoparticles using rice as soft biotemplate.

PubMed

Ramimoghadam, Donya; Bin Hussein, Mohd Zobir; Taufiq-Yap, Yun Hin

2013-01-01

Rice as a renewable, abundant bio-resource with unique characteristics can be used as a bio-template to synthesize various functional nanomaterials. Therefore, the effect of uncooked rice flour as bio-template on physico-chemical properties, especially the morphology of zinc oxide nanostructures was investigated in this study. The ZnO particles were synthesized through hydrothermal-biotemplate method using zinc acetate-sodium hydroxide and uncooked rice flour at various ratios as precursors at 120°C for 18 hours. The results indicate that rice as a bio-template can be used to modify the shape and size of zinc oxide particles. Different morphologies, namely flake-, flower-, rose-, star- and rod-like structures were obtained with particle size at micro- and nanometer range. Pore size and texture of the resulting zinc oxide particles were found to be template-dependent and the resulting specific surface area enhanced compared to the zinc oxide synthesized without rice under the same conditions. However, optical property particularly the band gap energy is generally quite similar. Pure zinc oxide crystals were successfully synthesized using rice flour as biotemplate at various ratios of zinc salt to rice. The size- and shape-controlled capability of rice to assemble the ZnO particles can be employed for further useful practical applications.

Compact hybrid optoelectrical unit for image processing and recognition

NASA Astrophysics Data System (ADS)

Cheng, Gang; Jin, Guofan; Wu, Minxian; Liu, Haisong; He, Qingsheng; Yuan, ShiFu

1998-07-01

In this paper a compact opto-electric unit (CHOEU) for digital image processing and recognition is proposed. The central part of CHOEU is an incoherent optical correlator, which is realized with a SHARP QA-1200 8.4 inch active matrix TFT liquid crystal display panel which is used as two real-time spatial light modulators for both the input image and reference template. CHOEU can do two main processing works. One is digital filtering; the other is object matching. Using CHOEU an edge-detection operator is realized to extract the edges from the input images. Then the reprocessed images are sent into the object recognition unit for identifying the important targets. A novel template- matching method is proposed for gray-tome image recognition. A positive and negative cycle-encoding method is introduced to realize the absolute difference measurement pixel- matching on a correlator structure simply. The system has god fault-tolerance ability for rotation distortion, Gaussian noise disturbance or information losing. The experiments are given at the end of this paper.

Crystal nuclei templated nanostructured membranes prepared by solvent crystallization and polymer migration

NASA Astrophysics Data System (ADS)

Wang, Bo; Ji, Jing; Li, Kang

2016-09-01

Currently, production of porous polymeric membranes for filtration is predominated by the phase-separation process. However, this method has reached its technological limit, and there have been no significant breakthrough over the last decade. Here we show, using polyvinylidene fluoride as a sample polymer, a new concept of membrane manufacturing by combining oriented green solvent crystallization and polymer migration is able to obtain high performance membranes with pure water permeation flux substantially higher than those with similar pore size prepared by conventional phase-separation processes. The new manufacturing procedure is governed by fewer operating parameters and is, thus, easier to control with reproducible results. Apart from the high water permeation flux, the prepared membranes also show excellent stable flux after fouling and superior mechanical properties of high pressure load and better abrasion resistance. These findings demonstrate the promise of a new concept for green manufacturing nanostructured polymeric membranes with high performances.

Pharmaceutical polymorph control in a drug-mimetic supramolecular gel† †Electronic supplementary information (ESI) available: Synthetic and crystallographic experimental details, rheology, full crystallization and calculation details. See DOI: 10.1039/c6sc04126d Click here for additional data file.

PubMed Central

Foster, Jonathan A.; Damodaran, Krishna K.; Maurin, Antoine; Thompson, Hugh P. G.; Cameron, Gary J.; Bernal, Jenifer Cuesta

2017-01-01

We report the synthesis of a bis(urea) gelator designed to specifically mimic the chemical structure of the highly polymorphic drug substance ROY. Crystallization of ROY from toluene gels of this gelator results in the formation of the metastable red form instead of the thermodynamic yellow polymorph. In contrast, all other gels and solution control experiments give the yellow form. Conformational and crystal structure prediction methods have been used to propose the structure of the gel and show that the templation of the red form by the targeted gel results from conformational matching of the gelator to the ROY substrate coupled with overgrowth of ROY onto the local periodic structure of the gel fibres. PMID:28451150

Tilt Grain Boundary Topology Induced by Substrate Topography.

PubMed

Yu, Henry; Gupta, Nitant; Hu, Zhili; Wang, Kai; Srijanto, Bernadeta R; Xiao, Kai; Geohegan, David B; Yakobson, Boris I

2017-09-26

Synthesis of two-dimensional (2D) crystals is a topic of great current interest, since their chemical makeup, electronic, mechanical, catalytic, and optical properties are so diverse. A universal challenge, however, is the generally random formation of defects caused by various growth factors on flat surfaces. Here we show through theoretical analysis and experimental demonstration that nonplanar, curved-topography substrates permit the intentional and controllable creation of topological defects within 2D materials. We augment a common phase-field method by adding a geometric phase to track the crystal misorientation on a curved surface and to detect the formation of grain boundaries, especially when a growing monocrystal "catches its own tail" on a nontrivial topographical feature. It is specifically illustrated by simulated growth of a trigonal symmetry crystal on a conical-planar substrate, to match the experimental synthesis of WS 2 on silicon template, with satisfactory and in some cases remarkable agreement of theory predictions and experimental evidence.

Control of Partial Coalescence of Self-Assembled Metal Nano-Particles across Lyotropic Liquid Crystals Templates towards Long Range Meso-Porous Metal Frameworks Design

PubMed Central

Dumée, Ludovic F.; Lemoine, Jean-Baptiste; Ancel, Alice; Hameed, Nishar; He, Li; Kong, Lingxue

2015-01-01

The formation of purely metallic meso-porous metal thin films by partial interface coalescence of self-assembled metal nano-particles across aqueous solutions of Pluronics triblock lyotropic liquid crystals is demonstrated for the first time. Small angle X-ray scattering was used to study the influence of the thin film composition and processing conditions on the ordered structures. The structural characteristics of the meso-structures formed demonstrated to primarily rely on the lyotropic liquid crystal properties while the nature of the metal nano-particles used as well as the their diameters were found to affect the ordered structure formation. The impact of the annealing temperature on the nano-particle coalescence and efficiency at removing the templating lyotropic liquid crystals was also analysed. It is demonstrated that the lyotropic liquid crystal is rendered slightly less thermally stable, upon mixing with metal nano-particles and that low annealing temperatures are sufficient to form purely metallic frameworks with average pore size distributions smaller than 500 nm and porosity around 45% with potential application in sensing, catalysis, nanoscale heat exchange, and molecular separation. PMID:28347094

The effect of calcination temperature on the microstructure and photocatalytic activity of TiO2-based composite nanotubes prepared by an in situ template dissolution method

NASA Astrophysics Data System (ADS)

Fan, Jiajie; Zhao, Li; Yu, Jiaguo; Liu, Gang

2012-09-01

TiO2-based composite nanotubes, based on an in situ template dissolution method, were one-step fabricated in a mixed aqueous solution of ammonium hexafluorotitanate and boric acid using ZnO nanorods as templates, and then the samples were calcined at different temperatures. The photocatalytic activity of the samples was evaluated by photocatalytic decoloration of Methyl Orange (MO) aqueous solution at ambient temperature under UV light. The results showed that the prepared sample possessed nanoscale tubular morphology with a wall thickness of ca. 30-50 nm, inner diameters of ca. 50-150 nm and lengths of ca. 400-2000 nm. The calcined samples exhibited excellent stabilization of the anatase phase in a wide temperature range of 300-800 °C. The un-calcined and calcined samples possessed hierarchically macro-mesoporous structures. The sample calcined at 600 °C exhibited the highest photocatalytic activity, corresponding to the maximal formation rate of \\z.rad OH on the photocatalyst. This is attributed to the improvement of anatase TiO2 crystallization, the formation of multi-phase structures including anatase, cubic Zn2TiO4, hexagonal ZnTiO3 and cubic ZnTiO3, and the presence of hierarchically macro-mesoporous structures.

Novel Shape-Stabilized Phase Change Materials Composed of Polyethylene Glycol/Nonsurfactant-Templated Mesoporous Silica: Preparation and Thermal Properties

NASA Astrophysics Data System (ADS)

Chen, Yan; Zhu, Yingying; Wang, Jinbao; Lv, Mengjiao; Zhang, Xiongjie; Gao, Junkai; Zhang, Zijun; Lei, Hao

2017-12-01

A novel shape-stabilized phase change material (PEG/TAMS), fabricated using tannic acid-templated mesoporous silica (TAMS) as a support for polyethylene glycol, was developed for thermal energy storage. The method used to synthesize TAMS was simple, cost effective, environmentally friendly, and free of surfactant. The characterization results indicated that PEG was physically absorbed to TAMS and that TAMS had no influence on the crystal structure of PEG. According to the TGA thermograms, PEG/TAMS has excellent thermal stability and can be applied over a wide temperature range. Additionally, the differential scanning calorimetry results suggested that PEG/TAMS has good thermal properties and that its fusion and solidification enthalpies reached 114.7 J/g and 102.4 J/g, respectively. The results indicated that PEG/TAMS has great potential for practical applications.

Scalable solution-phase epitaxial growth of symmetry-mismatched heterostructures on two-dimensional crystal soft template.

PubMed

Lin, Zhaoyang; Yin, Anxiang; Mao, Jun; Xia, Yi; Kempf, Nicholas; He, Qiyuan; Wang, Yiliu; Chen, Chih-Yen; Zhang, Yanliang; Ozolins, Vidvuds; Ren, Zhifeng; Huang, Yu; Duan, Xiangfeng

2016-10-01

Epitaxial heterostructures with precisely controlled composition and electronic modulation are of central importance for electronics, optoelectronics, thermoelectrics, and catalysis. In general, epitaxial material growth requires identical or nearly identical crystal structures with small misfit in lattice symmetry and parameters and is typically achieved by vapor-phase depositions in vacuum. We report a scalable solution-phase growth of symmetry-mismatched PbSe/Bi 2 Se 3 epitaxial heterostructures by using two-dimensional (2D) Bi 2 Se 3 nanoplates as soft templates. The dangling bond-free surface of 2D Bi 2 Se 3 nanoplates guides the growth of PbSe crystal without requiring a one-to-one match in the atomic structure, which exerts minimal restriction on the epitaxial layer. With a layered structure and weak van der Waals interlayer interaction, the interface layer in the 2D Bi 2 Se 3 nanoplates can deform to accommodate incoming layer, thus functioning as a soft template for symmetry-mismatched epitaxial growth of cubic PbSe crystal on rhombohedral Bi 2 Se 3 nanoplates. We show that a solution chemistry approach can be readily used for the synthesis of gram-scale PbSe/Bi 2 Se 3 epitaxial heterostructures, in which the square PbSe (001) layer forms on the trigonal/hexagonal (0001) plane of Bi 2 Se 3 nanoplates. We further show that the resulted PbSe/Bi 2 Se 3 heterostructures can be readily processed into bulk pellet with considerably suppressed thermal conductivity (0.30 W/m·K at room temperature) while retaining respectable electrical conductivity, together delivering a thermoelectric figure of merit ZT three times higher than that of the pristine Bi 2 Se 3 nanoplates at 575 K. Our study demonstrates a unique epitaxy mode enabled by the 2D nanocrystal soft template via an affordable and scalable solution chemistry approach. It opens up new opportunities for the creation of diverse epitaxial heterostructures with highly disparate structures and functions.

Scalable solution-phase epitaxial growth of symmetry-mismatched heterostructures on two-dimensional crystal soft template

PubMed Central

Lin, Zhaoyang; Yin, Anxiang; Mao, Jun; Xia, Yi; Kempf, Nicholas; He, Qiyuan; Wang, Yiliu; Chen, Chih-Yen; Zhang, Yanliang; Ozolins, Vidvuds; Ren, Zhifeng; Huang, Yu; Duan, Xiangfeng

2016-01-01

Epitaxial heterostructures with precisely controlled composition and electronic modulation are of central importance for electronics, optoelectronics, thermoelectrics, and catalysis. In general, epitaxial material growth requires identical or nearly identical crystal structures with small misfit in lattice symmetry and parameters and is typically achieved by vapor-phase depositions in vacuum. We report a scalable solution-phase growth of symmetry-mismatched PbSe/Bi2Se3 epitaxial heterostructures by using two-dimensional (2D) Bi2Se3 nanoplates as soft templates. The dangling bond–free surface of 2D Bi2Se3 nanoplates guides the growth of PbSe crystal without requiring a one-to-one match in the atomic structure, which exerts minimal restriction on the epitaxial layer. With a layered structure and weak van der Waals interlayer interaction, the interface layer in the 2D Bi2Se3 nanoplates can deform to accommodate incoming layer, thus functioning as a soft template for symmetry-mismatched epitaxial growth of cubic PbSe crystal on rhombohedral Bi2Se3 nanoplates. We show that a solution chemistry approach can be readily used for the synthesis of gram-scale PbSe/Bi2Se3 epitaxial heterostructures, in which the square PbSe (001) layer forms on the trigonal/hexagonal (0001) plane of Bi2Se3 nanoplates. We further show that the resulted PbSe/Bi2Se3 heterostructures can be readily processed into bulk pellet with considerably suppressed thermal conductivity (0.30 W/m·K at room temperature) while retaining respectable electrical conductivity, together delivering a thermoelectric figure of merit ZT three times higher than that of the pristine Bi2Se3 nanoplates at 575 K. Our study demonstrates a unique epitaxy mode enabled by the 2D nanocrystal soft template via an affordable and scalable solution chemistry approach. It opens up new opportunities for the creation of diverse epitaxial heterostructures with highly disparate structures and functions. PMID:27730211

Crystallization Behavior of Poly(ethylene oxide) in Vertically Aligned Carbon Nanotube Array.

PubMed

Sheng, Jiadong; Zhou, Shenglin; Yang, Zhaohui; Zhang, Xiaohua

2018-03-27

We investigate the effect of the presence of vertically aligned multiwalled carbon nanotubes (CNTs) on the orientation of poly(ethylene oxide) (PEO) lamellae and PEO crystallinity. The high alignment of carbon nanotubes acting as templates probably governs the orientation of PEO lamellae. This templating effect might result in the lamella planes of PEO crystals oriented along a direction parallel to the long axis of the nanotubes. The presence of aligned carbon nanotubes also gives rise to the decreases in PEO crystallinity, crystallization temperature, and melting temperature due to the perturbation of carbon nanotubes to the crystallization of PEO. These effects have significant implications for controlling the orientation of PEO lamellae and decreasing the crystallinity of PEO and thickness of PEO lamellae, which have significant impacts on ion transport in PEO/CNT composite and the capacitive performance of PEO/CNT composite. Both the decreased PEO crystallinity and the orientation of PEO lamellae along the long axes of vertically aligned CNTs give rise to the decrease in the charge transfer resistance, which is associated with the improvements in the ion transport and capacitive performance of PEO/CNT composite.

Hemispherical cavities on silicon substrates: an overview of micro fabrication techniques

NASA Astrophysics Data System (ADS)

Poncelet, O.; Rasson, J.; Tuyaerts, R.; Coulombier, M.; Kotipalli, R.; Raskin, J.-P.; Francis, L. A.

2018-04-01

Hemispherical photonic crystals found in species like Papilio blumei and Cicendella chinensis have inspired new applications like anti-counterfeiting devices and gas sensors. In this work, we investigate and compare four different ways to micro fabricate such hemispherical cavities: using colloids as template, by wet (HNA) or dry (XeF2) isotropic etching of silicon and by electrochemical etching of silicon. The shape and the roughness of the obtained cavities have been discussed and the pros/cons for each method are highlighted.

Mesoporous inverse opal TiO2 film as light scattering layer for dye-sensitized solar cell.

PubMed

Jin, Mingshi; Kim, Sung Soo; Yoon, Minyoung; Li, Zhenghua; Lee, Yoon Yun; Kim, Ji Man

2012-01-01

The light harvesting efficiency of dye-sensitized solar cells was enhanced by using a scattering layer. Such as sphere type TiO2, inverse photonic crystal TiO2, hollow spherical TiO2. Among these materials, the TiO2 with inverse photonic crystal (IPC) structure, synthesized by self-assembly using spherical templates, has attracted much attention due to their photonic crystal characteristics and light scattering effects. However, when applied in the DSSCs, the surface area of IPC is very low that caused insufficient adsorption amount of dye molecules. In the present work, a scattering layer with mesoporous inverse photonic crystal (MIPC) TiO2 film was fabricated by the sol-gel reactions with surfactant-assisted sol-gel method using poly(methyl methacrylate) as the template and titanium (IV) isopropoxide as the TiO2 precursor. After removing the PMMA and surfactant, a highly ordered macroporous structure with mesopores were successfully obtained. The surface area and total pore volume of the MIPC were 82 m2/g and 0.31 cm3/g, respectively, which is much larger than those of the IPC. The DSSCs with the scattering layer of MIPC film exhibited 18 and 10% higher photo-conversion efficiency than those of cells only with a nano-crystalline TiO2 film and with scattering layer of IPC film. From UV-visible spectra of dye solutions, the MIPC film showed a higher amount of absorbed dye molecules than those of the reference and IPC films. Accordingly, an increase in the photo-current density through abundant adsorption of the dye, coupled with inherent light scattering ability can improve overall photo-conversion efficiency.

Observation of Quantum Confinement in Monodisperse Methylammonium Lead Halide Perovskite Nanocrystals Embedded in Mesoporous Silica.

PubMed

Malgras, Victor; Tominaka, Satoshi; Ryan, James W; Henzie, Joel; Takei, Toshiaki; Ohara, Koji; Yamauchi, Yusuke

2016-10-13

Hybrid organic-inorganic metal halide perovskites have fascinating electronic properties and have already been implemented in various devices. Although the behavior of bulk metal halide perovskites has been widely studied, the properties of perovskite nanocrystals are less well-understood because synthesizing them is still very challenging, in part because of stability. Here we demonstrate a simple and versatile method to grow monodisperse CH 3 NH 3 PbBr x I x-3 perovskite nanocrystals inside mesoporous silica templates. The size of the nanocrystal is governed by the pore size of the templates (3.3, 3.7, 4.2, 6.2, and 7.1 nm). In-depth structural analysis shows that the nanocrystals maintain the perovskite crystal structure, but it is slightly distorted. Quantum confinement was observed by tuning the size of the particles via the template. This approach provides an additional route to tune the optical bandgap of the nanocrystal. The level of quantum confinement was modeled taking into account the dimensions of the rod-shaped nanocrystals and their close packing inside the channels of the template. Photoluminescence measurements on CH 3 NH 3 PbBr clearly show a shift from green to blue as the pore size is decreased. Synthesizing perovskite nanostructures in templates improves their stability and enables tunable electronic properties via quantum confinement. These structures may be useful as reference materials for comparison with other perovskites, or as functional materials in all solid-state light-emitting diodes.

Recombinant viral RdRps can initiate RNA synthesis from circular templates

PubMed Central

RANJITH-KUMAR, C.T.; KAO, C.C.

2006-01-01

The crystal structure of the recombinant hepatitis C virus (HCV) RNA-dependent RNA polymerase (RdRp) revealed extensive interactions between the fingers and the thumb subdomains, resulting in a closed conformation with an established template channel that should specifically accept single-stranded templates. We made circularized RNA templates and found that they were efficiently used by the HCV RdRp to synthesize product RNAs that are significantly longer than the template, suggesting that RdRp could exist in an open conformation prior to template binding. RNA synthesis using circular RNA templates had properties similar to those previously documented for linear RNA, including a need for higher GTP concentration for initiation, usage of GTP analogs, sensitivity to salt, and involvement of active-site residues for product formation. Some products were resistant to challenge with the template competitor heparin, indicating that the elongation complexes remain bound to template and are competent for RNA synthesis. Other products were not elongated in the presence of heparin, indicating that the elongation complex was terminated. Lastly, recombinant RdRps from two other flaviviruses and from the Pseudomonas phage φ6 also could use circular RNA templates for RNA-dependent RNA synthesis, although the φ6 RdRp could only use circular RNAs made from the 3′-terminal sequence of the φ6 genome. PMID:16373481

Organic Single-Crystal Semiconductor Films on a Millimeter Domain Scale.

PubMed

Kwon, Sooncheol; Kim, Jehan; Kim, Geunjin; Yu, Kilho; Jo, Yong-Ryun; Kim, Bong-Joong; Kim, Junghwan; Kang, Hongkyu; Park, Byoungwook; Lee, Kwanghee

2015-11-18

Nucleation and growth processes can be effectively controlled in organic semiconductor films through a new concept of template-mediated molecular crystal seeds during the phase transition; the effective control of these processes ensures millimeter-scale crystal domains, as well as the performance of the resulting organic films with intrinsic hole mobility of 18 cm(2) V(-1) s(-1). © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Hierarchical templating in deposition of semi-covalently imprinted inverse opal polythiophene film for femtomolar determination of human serum albumin.

PubMed

Dabrowski, Marcin; Cieplak, Maciej; Sharma, Piyush Sindhu; Borowicz, Pawel; Noworyta, Krzysztof; Lisowski, Wojciech; D'Souza, Francis; Kuhn, Alexander; Kutner, Wlodzimierz

2017-08-15

Nanostructured artificial receptor materials with unprecedented hierarchical structure for determination of human serum albumin (HSA) are designed and fabricated. For that purpose a new hierarchical template is prepared. This template allowed for simultaneous structural control of the deposited molecularly imprinted polymer (MIP) film on three length scales. A colloidal crystal templating with optimized electrochemical polymerization of 2,3'-bithiophene enables deposition of an MIP film in the form of an inverse opal. Thickness of the deposited polymer film is precisely controlled with the number of current oscillations during potentiostatic deposition of the imprinted poly(2,3'-bithiophene) film. Prior immobilization of HSA on the colloidal crystal allows formation of molecularly imprinted cavities exclusively on the internal surface of the pores. Furthermore, all binding sites are located on the surface of the imprinted cavities at locations corresponding to positions of functional groups present on the surface of HSA molecules due to prior derivatization of HSA molecules with appropriate functional monomers. This synergistic strategy results in a material with superior recognition performance. Integration of the MIP film as a recognition unit with a sensitive extended-gate field-effect transistor (EG-FET) transducer leads to highly selective HSA determination in the femtomolar concentration range. Copyright © 2017 Elsevier B.V. All rights reserved.

Nacre-like calcium carbonate controlled by ionic liquid/graphene oxide composite template.

PubMed

Yao, Chengli; Xie, Anjian; Shen, Yuhua; Zhu, Jinmiao; Li, Hongying

2015-06-01

Nacre-like calcium carbonate nanostructures have been mediated by an ionic liquid (IL)-graphene oxide (GO) composite template. The resultant crystals were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, and X-ray powder diffractometry (XRD). The results showed that either 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM]BF4) or graphene oxide can act as a soft template for calcium carbonate formation with unusual morphologies. Based on the time-dependent morphology changes of calcium carbonate particles, it is concluded that nacre-like calcium carbonate nanostructures can be formed gradually utilizing [BMIM]BF4/GO composite template. During the process of calcium carbonate formation, [BMIM]BF4 acted not only as solvents but also as morphology templates for the fabrication of calcium carbonate materials with nacre-like morphology. Based on the observations, the possible mechanisms were also discussed. Copyright © 2015 Elsevier B.V. All rights reserved.

Porous silicon photonic crystals as hosts for polymers, biopolymers, and magnetic nanoparticles

NASA Astrophysics Data System (ADS)

Li, Yang Yang

This thesis describes the construction of one-dimensional photonic crystals of porous silicon by electrochemically etching and the use of these materials as hosts for polymers, biopolymers, and magnetic nanoparticles. The spectral features of the photonic crystals derive from a porosity gradient that is determined by the electrochemical etching parameters. Since the photonic crystals are constructed of a porous material, they can serve as hosts for other materials. The first chapter of the thesis provides an introduction to porous Si, templating techniques and the use of porous materials for controlled release of drugs. This latter section is added because much of the thesis work addresses the application of porous Si hosts for controlled release of drugs. In the second chapter, it is shown that the spectral properties of the porous Si photonic crystal template can be transferred to a variety of organic and biopolymers. It is demonstrated that these castings can be used as vapor sensors and as self-reporting, bioresorbable materials. If the template is not removed, porous Si polymer composites are formed. The third chapter discussed that by spray-coating a fine mist of polymer solution onto the porous Si film, robust and smooth micron-sized cylindrical photonic crystals suitable for bioassays can be prepared. The fourth chapter focuses on using porous Si photonic crystals as a host for magnetic nanoparticles. The magnetic nanoparticles in this work are found to adhere to the surface of the porous Si film as well to infiltrate the pore structure. In a demonstration of optical switching that may be useful for information display applications, flipping between the colored to dark sides by application of a magnetic field is found to occur at rates of as large as 175 Hz. As the host for soluble molecular species, porous Si photonic crystals can be impregnated from solution. The aggregates that form upon evaporation of solvent are found to scatter light from the resonant optical structure over a large solid angle. The spectrum of the scattered light provides a convenient means of monitoring the temporal release characteristics of the guest material. An application of the phenomenon is demonstrated for release of a drug (caffeine) into aqueous solution from a porous Si photonic crystal.

Directed-assembly of ordered nanoparticle arrays exploiting multiple adsorption mechanisms on a self-assembling biological template

NASA Astrophysics Data System (ADS)

Shindel, Matthew M.

Developing processes to fabricate inorganic architectures with designer functionalities at increasingly minute length-scales is of chief concern in the fields of nanotechnology and nanoscience. This enterprise requires assembly mechanisms with the capacity to tailor both the spatial arrangement and material composition of a system's constituent building blocks. To this end, significant advances can be made by turning to biology, as the natural world has evolved the ability to generate intricate nanostructures, which can potentially be employed as templates for inorganic nanosystems. We explore this biotemplating methodology using two-dimensional streptavidin crystals, investigating the ability of the protein lattice to direct the assembly of ordered metallic nanoparticle arrays. We demonstrate that the adsorption of nanoparticles on the protein monolayer can be induced through both electrostatic and molecular recognition (ligand-receptor) interactions. Furthermore, the dynamics of adsorption can be modulated through both environmental factors (e.g. pH), and by tailoring particle surface chemistry. When the characteristic nanoparticle size is on the order of the biotemplate's unit-cell dimension, electrostatically-mediated adsorption occurs in a site-specific manner. The nanoparticles exhibit a pronounced preference for adhering to the areas between protein molecules. The two-dimensional structure of the resultant nanoparticle ensemble consequently conforms to that of the underlying protein crystal. Through theoretical calculations, simulation and experiment, we show that interparticle spacing in the templated array is influenced by the screened-coulombic repulsion between particles, and can thus be tuned by controlling ionic strength during deposition. Templating ordered nanoparticle arrays via ligand-receptor mediated adsorption, and the constrained growth of metallic nanoparticles directly on the protein lattice from ionic precursors are also examined. Overall, this work demonstrates that the streptavidin crystal system possesses unique utility for nanoscale, directed-assembly applications.

Templated Solid-State Dewetting of Thin Silicon Films.

PubMed

Naffouti, Meher; David, Thomas; Benkouider, Abdelmalek; Favre, Luc; Delobbe, Anne; Ronda, Antoine; Berbezier, Isabelle; Abbarchi, Marco

2016-11-01

Thin film dewetting can be efficiently exploited for the implementation of functionalized surfaces over very large scales. Although the formation of sub-micrometer sized crystals via solid-state dewetting represents a viable method for the fabrication of quantum dots and optical meta-surfaces, there are several limitations related to the intrinsic features of dewetting in a crystalline medium. Disordered spatial organization, size, and shape fluctuations are relevant issues not properly addressed so far. This study reports on the deterministic nucleation and precise positioning of Si- and SiGe-based nanocrystals by templated solid-state dewetting of thin silicon films. The dewetting dynamics is guided by pattern size and shape taking full control over number, size, shape, and relative position of the particles (islands dimensions and relative distances are in the hundreds nm range and fluctuate ≈11% for the volumes and ≈5% for the positioning). © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Solution-phase synthesis of nanomaterials at low temperature

NASA Astrophysics Data System (ADS)

Zhu, Yongchun; Qian, Yitai

2009-01-01

This paper reviews the solution-phase synthesis of nanoparticles via some routes at low temperatures, such as room temperature route, wave-assisted synthesis (γ-irradiation route and sonochemical route), directly heating at low temperatures, and hydrothermal/solvothermal methods. A number of strategies were developed to control the shape, the size, as well as the dispersion of nanostructures. Using diethylamine or n-butylamine as solvent, semiconductor nanorods were yielded. By the hydrothermal treatment of amorphous colloids, Bi2S3 nanorods and Se nanowires were obtained. CdS nanowires were prepared in the presence of polyacrylamide. ZnS nanowires were obtained using liquid crystal. The polymer poly (vinyl acetate) tubule acted as both nanoreactor and template for the CdSe nanowire growth. Assisted by the surfactant of sodium dodecyl benzenesulfonate (SDBS), nickel nanobelts were synthesized. In addition, Ag nanowires, Te nanotubes and ZnO nanorod arrays could be prepared without adding any additives or templates.

Polymer-Templated LiFePO4/C Nanonetworks as High-Performance Cathode Materials for Lithium-Ion Batteries.

PubMed

Fischer, Michael G; Hua, Xiao; Wilts, Bodo D; Castillo-Martínez, Elizabeth; Steiner, Ullrich

2018-01-17

Lithium iron phosphate (LFP) is currently one of the main cathode materials used in lithium-ion batteries due to its safety, relatively low cost, and exceptional cycle life. To overcome its poor ionic and electrical conductivities, LFP is often nanostructured, and its surface is coated with conductive carbon (LFP/C). Here, we demonstrate a sol-gel based synthesis procedure that utilizes a block copolymer (BCP) as a templating agent and a homopolymer as an additional carbon source. The high-molecular-weight BCP produces self-assembled aggregates with the precursor-sol on the 10 nm scale, stabilizing the LFP structure during crystallization at high temperatures. This results in a LFP nanonetwork consisting of interconnected ∼10 nm-sized particles covered by a uniform carbon coating that displays a high rate performance and an excellent cycle life. Our "one-pot" method is facile and scalable for use in established battery production methodologies.

Enantioselective recognition at mesoporous chiral metal surfaces.

PubMed

Wattanakit, Chularat; Côme, Yémima Bon Saint; Lapeyre, Veronique; Bopp, Philippe A; Heim, Matthias; Yadnum, Sudarat; Nokbin, Somkiat; Warakulwit, Chompunuch; Limtrakul, Jumras; Kuhn, Alexander

2014-01-01

Chirality is widespread in natural systems, and artificial reproduction of chiral recognition is a major scientific challenge, especially owing to various potential applications ranging from catalysis to sensing and separation science. In this context, molecular imprinting is a well-known approach for generating materials with enantioselective properties, and it has been successfully employed using polymers. However, it is particularly difficult to synthesize chiral metal matrices by this method. Here we report the fabrication of a chirally imprinted mesoporous metal, obtained by the electrochemical reduction of platinum salts in the presence of a liquid crystal phase and chiral template molecules. The porous platinum retains a chiral character after removal of the template molecules. A matrix obtained in this way exhibits a large active surface area due to its mesoporosity, and also shows a significant discrimination between two enantiomers, when they are probed using such materials as electrodes.

Visible-light-assisted SLCs template synthesis of sea anemone-like Pd/PANI nanocomposites with high electrocatalytic activity for methane oxidation in acidic medium

NASA Astrophysics Data System (ADS)

Tan, De-Xin; Wang, Yan-Li

2018-03-01

Sea anemone-like palladium (Pd)/polyaniline (PANI) nanocomposites were synthesized via visible-light-assisted swollen liquid crystals (SLCs) template method. The resulting samples were characterized by transmission electron microscopy (TEM), selected area electron diffraction (SAED), energy dispersive spectrometer (EDS), x-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), ultraviolet-visible (UV–vis) absorption spectroscopy and Fourier transform infrared (FT-IR) spectroscopy, respectively. The electrocatalytic properties of Pd/PANI nanocomposites modified glass carbon electrode (GCE) for methane oxidation were investigated by cycle voltammetry (CV) and chronoamperometry. Those dispersed sea anemone-like Pd/PANI nanocomposites had an average diameter of 320 nm. The obtained Pd nanoparticles with an average diameter of about 45 nm were uniformly distributed in PANI matrix. Sea anemone-like Pd/PANI nanocomposites exhibited excellent electrocatalytic activity and stability for oxidation of methane (CH4).

The energetics of mesopore formation in zeolites with surfactants.

PubMed

Linares, Noemi; Jardim, Erika de Oliveira; Sachse, Alexander; Serrano, Elena; Garcia-Martinez, Javier

2018-05-02

Mesoporosity can be conveniently introduced in zeolites by treating them in basic surfactant solutions. The apparent activation energy involved in the formation of mesopores in USY via surfactant-templating was obtained through the combination of in situ synchrotron XRD and ex situ gas adsorption. Additionally, techniques such as pH measurements and TG/DTA were employed to determine the OH- evolution and the CTA+ uptake during the development of mesoporosity, providing information about the different steps involved. By combining both in situ and ex situ techniques, we have been able, for the first time, to determine the apparent activation energies of the different processes involved in the mesostructuring of USY zeolites, which are in the same order of magnitude (30 - 65 kJ mol-1) of those involved in the crystallization of zeolites. Hence, important mechanistic insights on the surfactant-templating method were obtained. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effects of C3+ ion irradiation on structural, electrical and magnetic properties of Ni nanotubes

NASA Astrophysics Data System (ADS)

Shlimas, D. I.; Kozlovskiy, A. L.; Zdorovets, M. V.; Kadyrzhanov, K. K.; Uglov, V. V.; Kenzhina, I. E.; Shumskaya, E. E.; Kaniukov, E. Y.

2018-03-01

Ion irradiation is an attractive method for obtaining nanostructures that can be used under extreme conditions. Also, it is possible to control the technological process that allows obtaining nanomaterials with new properties at ion irradiation. In this paper, we study the effect of irradiation with 28 MeV C3+ ions and fluences up to 5 × 1011 cm-2 on the structure and properties of template-synthesized nickel nanotubes with a length of 12 μm, with diameters of 400 nm, and a wall thickness of 100 nm. It is demonstrated that the main factor influencing the degradation of nanostructures under irradiation in PET template is the processes of mixing the material of nanostructures with the surrounding polymer. The influence of irradiation with various fluences on the crystal structure, electrical and magnetic properties of nickel nanotubes is studied.

Systems including catalysts in porous zeolite materials within a reactor for use in synthesizing hydrocarbons

DOEpatents

Rolllins, Harry W [Idaho Falls, ID; Petkovic, Lucia M [Idaho Falls, ID; Ginosar, Daniel M [Idaho Falls, ID

2012-07-24

Catalytic structures include a catalytic material disposed within a zeolite material. The catalytic material may be capable of catalyzing a formation of methanol from carbon monoxide and/or carbon dioxide, and the zeolite material may be capable of catalyzing a formation of hydrocarbon molecules from methanol. The catalytic material may include copper and zinc oxide. The zeolite material may include a first plurality of pores substantially defined by a crystal structure of the zeolite material and a second plurality of pores dispersed throughout the zeolite material. Systems for synthesizing hydrocarbon molecules also include catalytic structures. Methods for synthesizing hydrocarbon molecules include contacting hydrogen and at least one of carbon monoxide and carbon dioxide with such catalytic structures. Catalytic structures are fabricated by forming a zeolite material at least partially around a template structure, removing the template structure, and introducing a catalytic material into the zeolite material.

Nanoconfinement: an effective way to enhance PVDF piezoelectric properties.

PubMed

Cauda, Valentina; Stassi, Stefano; Bejtka, Katarzyna; Canavese, Giancarlo

2013-07-10

The dimensional confinement and oriented crystallization are both key factors in determining the piezoelectric properties of a polymeric nanostructured material. Here we prepare arrays of one-dimensional polymeric nanowires showing piezoelectric features by template-wetting two distinct polymers into anodic porous alumina (APA) membranes. In particular, poly(vinylidene fluoride), PVDF, and its copolymer poly(vinylidene fluoride-trifluoroethylene), PVTF, are obtained in commercially available APA, showing a final diameter of about 200 nm and several micrometers in length, reflecting the templating matrix features. We show that the crystallization of both polymers into a ferroelectric phase is directed by the nanotemplate confinement. Interestingly, the PVDF nanowires mainly crystallize into the β-phase in the nanoporous matrix, whereas the reference thin film of PVDF crystallizes in the α nonpolar phase. In the case of the PVTF nanowires, needle-like crystals oriented perpendicularly to the APA channel walls are observed, giving insight on the molecular orientation of the polymer within the nanowire structure. A remarkable piezoelectric behavior of both 1-D polymeric nanowires is observed, upon recording ferroelectric polarization, hysteresis, and displacement loops. In particular, an outstanding piezoelectric effect is observed for the PVDF nanowires with respect to the polymeric thin film, considering that no poling was carried out. Current versus voltage (I-V) characteristics showed a consistent switching behavior of the ferroelectric polar domains, thus revealing the importance of the confined and oriented crystallization of the polymer in monodimensional nanoarchitectures.

Propagation of biochirality: crossovers and nonclassical crystallization kinetics of aspartic acid in water.

PubMed

Lee, Tu; Lin, Yu Kun; Tsai, Ya Chung; Lee, Hung Lin

2013-11-01

All experimental procedures discussed could be treated as a screening tool for probing the existence of molecular association among the chiral molecules and the solvent system. The molecular association phases of a racemic conglomerate solution (CS) and a racemic compound solution (RCS), and the templating effect of aspartic acid solid surface were observed to minimize the chance of redissolving racemic conglomerate and racemic compound aspartic acid in water and reforming an RCS in crossovers experiments. Only 1 %wt% of l-aspartic acid was adequate enough to induce a transformation from a racemic compound aspartic acid to a racemic conglomerate aspartic acid. This would make the propagation of biochirality more feasible and sound. However, tetrapeptide, (l-aspartic acid)4 , failed to induce enantioseparation as templates purely by crystallization. Nonclassical crystallization theory was needed to take into account the existence of a CS. Fundamental parameters of the crystallization kinetics such as the induction time, interfacial energy, Gibbs energetic barrier, nucleation rate, and critical size of stable nuclei of: (i) racemic compound aspartic acid, (ii) racemic compound aspartic acid seeded with 1 %wt% l-aspartic acid, (iii) racemic conglomerate aspartic acid, and (iv) l-aspartic acid were evaluated and compared with different initial supersaturation ratios. Morphological studies of crystals grown from the crystallization kinetics were also carried out. © 2013 Wiley Periodicals, Inc.

Structural, crystal structure, Hirshfeld surface analysis and physicochemical studies of a new chlorocadmate template by 1-(2-hydroxyethyl)piperazine

NASA Astrophysics Data System (ADS)

Soudani, S.; Jeanneau, E.; Jelsch, C.; Lefebvre, F.; Ben Nasr, C.

2016-11-01

The synthesis, crystal structure and spectroscopic characterization of a new chlorocadmate template by the 1-(2-hydroxyethyl)piperazine ligand are reported. In the atomic arrangement, the CdCl5O entities are deployed in corrugated rows along the a-axis at y = 1/4 and y = 3/4 to form layers parallel to the (a,b) plane. In these crystals, piperazinediium cations are in a chair conformation and are inserted between these layers through Nsbnd H⋯Cl, Csbnd H⋯Cl, Osbnd H⋯Cl and Nsbnd H⋯O hydrogen bonds to form infinite three-dimensional network. Investigation of intermolecular interactions and crystal packing via Hirshfeld surface analysis reveals that H⋯Cl and Csbnd H⋯Hsbnd C intermolecular interactions are the most abundant contacts of the organic cation in the crystal packing. The crystal contacts enrichments reveals that, the Cd++ … Cl- salt bridges, the Cd⋯O complexation and Osbnd H⋯Cl- and Nsbnd H⋯Cl-strong H-bonds are the driving forces in the packing formation. The presence of twelve independent chloride anions and four organic cation in the asymmetric unit allowed comparing their contact propensities. The 13C and 15N CP-MAS NMR spectra are in agreement with the X-ray structure. Additional characterization of this compound has also been performed by IR spectroscopy.

Direct Writing of Three-Dimensional Macroporous Photonic Crystals on Pressure-Responsive Shape Memory Polymers.

PubMed

Fang, Yin; Ni, Yongliang; Leo, Sin-Yen; Wang, Bingchen; Basile, Vito; Taylor, Curtis; Jiang, Peng

2015-10-28

Here we report a single-step direct writing technology for making three-dimensional (3D) macroporous photonic crystal patterns on a new type of pressure-responsive shape memory polymer (SMP). This approach integrates two disparate fields that do not typically intersect: the well-established templating nanofabrication and shape memory materials. Periodic arrays of polymer macropores templated from self-assembled colloidal crystals are squeezed into disordered arrays in an unusual shape memory "cold" programming process. The recovery of the original macroporous photonic crystal lattices can be triggered by direct writing at ambient conditions using both macroscopic and nanoscopic tools, like a pencil or a nanoindenter. Interestingly, this shape memory disorder-order transition is reversible and the photonic crystal patterns can be erased and regenerated hundreds of times, promising the making of reconfigurable/rewritable nanooptical devices. Quantitative insights into the shape memory recovery of collapsed macropores induced by the lateral shear stresses in direct writing are gained through fundamental investigations on important process parameters, including the tip material, the critical pressure and writing speed for triggering the recovery of the deformed macropores, and the minimal feature size that can be directly written on the SMP membranes. Besides straightforward applications in photonic crystal devices, these smart mechanochromic SMPs that are sensitive to various mechanical stresses could render important technological applications ranging from chromogenic stress and impact sensors to rewritable high-density optical data storage media.

Anion Exchange in II-VI Semiconducting Nanostructures via Atomic Templating.

PubMed

Agarwal, Rahul; Krook, Nadia M; Ren, Ming-Liang; Tan, Liang Z; Liu, Wenjing; Rappe, Andrew M; Agarwal, Ritesh

2018-03-14

Controlled chemical transformation of nanostructures is a promising technique to obtain precisely designed novel materials, which are difficult to synthesize otherwise. We report high-temperature vapor-phase anion-exchange reactions to chemically transform II-VI semiconductor nanostructures (100-300 nm length scale) while retaining the single crystallinity, crystal structure, morphology, and even defect distribution of the parent material via atomic templating. The concept of atomic templating is employed to obtain kinetically controlled, thermodynamically metastable structural phases such as zincblende CdSe and CdS from zincblende CdTe upon complete chemical replacement of Te with Se or S. The underlying transformation mechanisms are explained through first-principles density functional theory calculations. Atomic templating is a unique path to independently tune materials' phase and composition at the nanoscale, allowing the synthesis of novel materials.

New developments in 3D liquid crystal elastomers scaffolds for tissue engineering: from physical template to responsive substrate

NASA Astrophysics Data System (ADS)

Prévôt, Marianne E.; Bergquist, Leah E.; Sharma, Anshul; Mori, Taizo; Gao, Yungxiang; Bera, Tanmay; Zhu, Chenhui; Leslie, Michelle T.; Cukelj, Richard; Korley, LaShanda T. J.; Freeman, Ernest J.; McDonough, Jennifer A.; Clements, Robert J.; Hegmann, Elda

2017-08-01

We report here on cell growth and proliferation within a 3D architecture created using smectic liquid crystal elastomers (LCEs) leading to a responsive scaffold for tissue engineering. The investigated LCE scaffolds exhibit biocompatibility, controlled degradability, with mechanical properties and morphologies that can match development of the extracellular matrix. Moreover, the synthetic pathway and scaffold design offer a versatility of processing, allowing modifications of the surface such as adjusting the hydrophilic/hydrophobic balance and the mobility of the LC moieties to enhance the biomaterial performance. First, we succeeded in generating LCEs whose mechanical properties mimic muscle tissue. In films, our LCEs showed cell adhesion, proliferation, and alignment. We also achieved creating 3D LCE structures using either metallic template or microsphere scaffolds. Finally, we recorded a four times higher cell proliferation capability in comparison to conventional porous films and, most importantly, anisotropic cell growth that highlights the tremendous effect of liquid crystal moieties within LCEs on the cell environment.

Tuning calcium carbonate growth through physical confinement and templating with amyloid-like polypeptide aggregates

NASA Astrophysics Data System (ADS)

Colaco, Martin Francis

The creation of useful composite materials requires precise control of the interface between the components in order to tune the overall shape and material properties. Despite the current research into nanotechnology, our ability to create materials with nanoscale precision is nascent. However, nature has a paradigm for the creation of finely structured composites under mild conditions called biomineralization. Through control of protein template assembly, solution conditions, and physical confinement, organisms are able to create useful optical and structural materials, such as bones, teeth, and mollusk shells. The objective of this thesis is to elucidate the importance of these various controls in synthetic systems to further our ability to create nanostructured materials. We begin by examining the formation of self-assembled monolayers (SAMs) of organosilanes on silica oxides. The formation of functionalized surfaces can help control the mineralization of amorphous or crystalline calcium carbonate. Long-chained organosilanes organize on surfaces to form dense, solid-like films, with the terminal groups determining the hydrophobicity and stereochemistry of the film. Our work has shown that uniform hydrophobic and hydrophilic films can be formed by using cleaned silica over glass or mica and through a vapor phase reaction over a liquid one. Additionally, we showed that mixed SAMs with phase-separated domains could be created through the selection of organosilanes and reaction conditions. We have built on these functionalized surfaces through the use of microfabrication and a gas permeable polymer to create three-dimensionally confined microcrystallizers. Other researchers have shown that one-dimensional confinement with a multi-functional surface (patterned with a small nucleating ordered region in a disordered SAM) can stabilize the creation of an amorphous calcium carbonate film before a single, large, micropatterned crystal is grown. Our work has determined that this methodology does not extend to three-dimensional confined systems, as the water has no method of escape. Through the addition of an insoluble hydroscopic polymer to our microreactors, amorphous calcium carbonate of controllable sizes can be grown. However, crystalline calcium carbonate cannot be grown without some type of templating. Studies of calcium carbonate templating have predominantly been performed on SAMs or in poorly characterized gels or protein films. The use of ordered protein or polypeptide aggregates for templating permits both geometry and charge surface density to be varied. We have studied the kinetics and final morphology of ordered aggregates of poly-L-glutamic acid and a copolymer of glutamic acid and alanine through experiments and simulations. Electrostatics, not structure, of the monomer appeared to be the dominating factor in the aggregation, as pH and salt concentration changes led to dramatic changes in the kinetics. Examining our experimental with existing models provided inconsistent results, so we developed a new model that yielded physically realistic rate constants, while generating better fits with longer lag phases and faster growths. However, despite the similarity of aggregation conditions, the two polypeptides yielded vastly different morphologies, with the PEA forming typical amyloid-like fibrils and PE forming larger, twisted lamellar aggregates. Templating with these aggregates also yielded dramatically different patterns. Polycrystalline rhombohedral calcite with smooth faces and edges grew on PEA fibrils, with minimal templating in evidence. However, on PE, numerous calcite crystals with triangular projections tracked the surface of the aggregate. The PE lamellae are characterized by extensive beta-sheet structure. In this conformation, the glutamic acid spacings on the surface of the aggregates can mimic the spacings of the carboxylates in the calcite lattice. In addition, the high negative charge density on the polypeptide surface led to a large number of nucleation sites. As the crystals grow, they impinge on each other but are limited to grow in one direction, perpendicular to the aggregate surface. Thus, the crystal structure propagates even at large length scales.

Protein purification and crystallization artifacts: The tale usually not told.

PubMed

Niedzialkowska, Ewa; Gasiorowska, Olga; Handing, Katarzyna B; Majorek, Karolina A; Porebski, Przemyslaw J; Shabalin, Ivan G; Zasadzinska, Ewelina; Cymborowski, Marcin; Minor, Wladek

2016-03-01

The misidentification of a protein sample, or contamination of a sample with the wrong protein, may be a potential reason for the non-reproducibility of experiments. This problem may occur in the process of heterologous overexpression and purification of recombinant proteins, as well as purification of proteins from natural sources. If the contaminated or misidentified sample is used for crystallization, in many cases the problem may not be detected until structures are determined. In the case of functional studies, the problem may not be detected for years. Here several procedures that can be successfully used for the identification of crystallized protein contaminants, including: (i) a lattice parameter search against known structures, (ii) sequence or fold identification from partially built models, and (iii) molecular replacement with common contaminants as search templates have been presented. A list of common contaminant structures to be used as alternative search models was provided. These methods were used to identify four cases of purification and crystallization artifacts. This report provides troubleshooting pointers for researchers facing difficulties in phasing or model building. © 2016 The Protein Society.

Nanoparticle guests in lyotropic liquid crystals

NASA Astrophysics Data System (ADS)

Dölle, Sarah; Park, Ji Hyun; Schymura, Stefan; Jo, Hyeran; Scalia, Giusy; Lagerwall, Jan P. F.

In this chapter we discuss the benefits, peculiarities and main challenges related to nanoparticle templating in lyotropic liquid crystals. We first give a brief bird's-eye view of the field, discussing different nanoparticles as well as different lyotropic hosts that have been explored, but then quickly focus on the dispersion of carbon nanotubes in surfactant-based lyotropic nematic phases. We discuss in some detail how the transfer of orientational order from liquid crystal host to nanoparticle guest can be verified and which degree of ordering can be expected, as well as the importance of choosing the right surfactant and its concentration for the stability of the nanoparticle suspension. We introduce a method for dispersing nanoparticles with an absolute minimum of stabilizing surfactant, based on dispersion below the Krafft temperature, and we discuss the peculiar phenomenon of filament formation in lyotropic nematic phases with a sufficient concentration of well-dispersed carbon nanotubes. Finally, we describe how the total surfactant concentration in micellar nematics can be greatly reduced by combining cat- and anionic surfactants, and we discuss how nanotubes can help in inducing the liquid crystal phase close to the isotropic-nematic boundary.

Crystalline structures, thermal properties and crystallizing mechanism of polyamide 6 nanotubes in confined space

NASA Astrophysics Data System (ADS)

Li, Xiaoru; Peng, Zhi; Yang, Chao; Han, Ping; Song, Guojun; Cong, Longliang

2016-09-01

The polyamide 6 (PA6) nanotubes were prepared by infiltrating the anodic aluminum oxide templates with polymer solution. Crystalline regions in the nanotube walls were detected by high-resolution transmission electron microscopy (HRTEM). X-ray diffraction (XRD), Fast Fourier Transform (FFT) and differential scanning calorimetry (DSC) techniques were employed to investigate crystallization, crystal faces and thermodynamics. It was found that the crystals were transformed from α-form in bulk to γ-form in nanotubes. It was made a detailed analysis in this article. Moreover, schematic diagram for the crystallizing mechanism of PA6 nanotubes was given to explain PA6 molecules how to crystallize in the nano-pores.

Reconfigurable Photonic Crystals Enabled by Multistimuli-Responsive Shape Memory Polymers Possessing Room Temperature Shape Processability.

PubMed

Fang, Yin; Leo, Sin-Yen; Ni, Yongliang; Wang, Junyu; Wang, Bingchen; Yu, Long; Dong, Zhe; Dai, Yuqiong; Basile, Vito; Taylor, Curtis; Jiang, Peng

2017-02-15

Traditional shape memory polymers (SMPs) are mostly thermoresponsive, and their applications in nano-optics are hindered by heat-demanding programming and recovery processes. By integrating a polyurethane-based shape memory copolymer with templating nanofabrication, reconfigurable/rewritable macroporous photonic crystals have been demonstrated. This SMP coupled with the unique macroporous structure enables unusual all-room-temperature shape memory cycles. "Cold" programming involving microscopic order-disorder transitions of the templated macropores is achieved by mechanically deforming the macroporous SMP membranes. The rapid recovery of the permanent, highly ordered photonic crystal structure from the temporary, disordered configuration can be triggered by multiple stimuli including a large variety of vapors and solvents, heat, and microwave radiation. Importantly, the striking chromogenic effects associated with these athermal and thermal processes render a sensitive and noninvasive optical methodology for quantitatively characterizing the intriguing nanoscopic shape memory effects. Some critical parameters/mechanisms that could significantly affect the final performance of SMP-based reconfigurable photonic crystals including strain recovery ratio, dynamics and reversibility of shape recovery, as well as capillary condensation of vapors in macropores, which play a crucial role in vapor-triggered recovery, can be evaluated using this new optical technology.

Engineering Strain for Improved III-Nitride Optoelectronic Device Performance

NASA Astrophysics Data System (ADS)

Van Den Broeck, Dennis Marnix

Due to growing environmental and economic concerns, renewable energy generation and high-efficiency lighting are becoming even more important in the scientific community. III-Nitride devices have been essential in production of high-brightness light-emitting diodes (LEDs) and are now entering the photovoltaic (PV) realm as the technology advances. InGaN/GaN multiple quantum well LEDs emitting in the blue/green region have emerged as promising candidates for next-generation lighting technologies. Due to the large lattice mismatch between InN and GaN, large electric fields exist within the quantum well layers and result in low rates of radiative recombination, especially for the green spectral region. This is commonly referred to as the "green gap" and results in poor external quantum efficiencies for light-emitting diodes and laser diodes. In order to mitigate the compressive stress of InGaN QWs, a novel growth technique is developed in order to grown thick, strain-relaxed In yGa1-yN templates for 0.08 < y < 0.11. By inserting 2 nm GaN interlayers into the growing InyGa1-yN film, and subsequently annealing the structure, "semibulk" InGaN templates were achieved with vastly superior crystal and optical properties than bulk InGaN films. These semibulk InGaN templates were then utilized as new templates for multiple quantum well active layers, effectively reducing the compressive strain in the InGaN wells due to the larger lattice constant of the InGaN template with respect to a GaN template. A zero-stress balance method was used in order to realize a strain-balanced multiple quantum well structure, which again showed improved optical characteristics when compared to fully-strain active regions. The semibulk InGaN template was then implemented into "strain-compensated" LED structures, where light emission was achieved with very little leakage current. Discussion of these strain-compensated devices compared to conventional LEDs is detailed.

Electrical conductivity studies of graphene wrapped nanocrystalline LiMnPO{sub 4} composite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheruku, Rajesh; D, Surya Bhaskaram; Govindaraj, G., E-mail: ggraj-7@yahoo.com

Nanocrystalline LiMnPO{sub 4} material was synthesized by template free sucrose assisted hydrothermal method. The material possesses the orthorhombic crystal structure with Pnma, space group having four formula units. The GO was prepared by the hummer’s method and it was reduced graphene oxide (rGO) with hydrazine hydrate in the presence of nitrogen atmosphere. LiMnPO{sub 4} material was wrapped by the rGO to increase its conductivity. The structural characterization was accomplished through X-ray diffraction, FT-IR and Raman spectroscopy. Morphology was identified by the SEM, Electrical characterization was done through impedance spectroscopy and the results were reported.

Did template-directed nucleation precede molecular replication?

NASA Technical Reports Server (NTRS)

Orgel, Leslie E.

1986-01-01

It is proposed that mononucleotides incorporated into the surfaces of microcrystals of inorganic phosphates such as hydroxyapatite can act as templates to assemble complementary mononucleotides from solution, and that the phosphate groups of the assembled nucleotides can facilitate nucleation of a second hydroxyapatite crystal. This would provide a mechanism of replication that is subject to natural selection. The possible role of a replicating system of this kind in the origins of life on the earth is discussed.

Tube Formation in Nanoscale Materials

PubMed Central

2008-01-01

The formation of tubular nanostructures normally requires layered, anisotropic, or pseudo-layered crystal structures, while inorganic compounds typically do not possess such structures, inorganic nanotubes thus have been a hot topic in the past decade. In this article, we review recent research activities on nanotubes fabrication and focus on three novel synthetic strategies for generating nanotubes from inorganic materials that do not have a layered structure. Specifically, thermal oxidation method based on gas–solid reaction to porous CuO nanotubes has been successfully established, semiconductor ZnS and Nb2O5nanotubes have been prepared by employing sacrificial template strategy based on liquid–solid reaction, and an in situ template method has been developed for the preparation of ZnO taper tubes through a chemical etching reaction. We have described the nanotube formation processes and illustrated the detailed key factors during their growth. The proposed mechanisms are presented for nanotube fabrication and the important pioneering studies are discussed on the rational design and fabrication of functional materials with tubular structures. It is the intention of this contribution to provide a brief account of these research activities. PMID:20592945

Ultrasonic-assisted synthesis of monodisperse single-crystalline silver nanoplates and gold nanorings.

PubMed

Jiang, Li-Ping; Xu, Shu; Zhu, Jian-Min; Zhang, Jian-Rong; Zhu, Jun-Jie; Chen, Hong-Yuan

2004-09-20

A simple sonochemical route was developed for the crystal growth of uniform silver nanoplates and ringlike gold nanocrystals in a N,N-dimethylformamide solution. The platelike structures were generated from the selective growth on different crystal planes in the presence of poly(vinylpyrrolidone) and the ultrasonic-assisted Ostwald ripening processes. The silver nanoplates in solution served as the templates for the synthesis of ringlike gold crystals via a displacement reaction. Both the silver nanoplates and gold nanorings were highly oriented single crystals with (111) planes as the basal planes. Copyright 2004 American Chemical Society

Silver nanoplates with ground or metastable structures obtained from template-free two-phase aqueous/organic synthesis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhelev, Doncho V., E-mail: dontcho.jelev@nih.gov; Zheleva, Tsvetanka S.

2014-01-28

Silver has unique electrical, catalytic, and plasmonic characteristics and has been widely sought for fabrication of nanostructures. The properties of silver nanostructures are intimately coupled to the structure of silver crystals. Two crystal structures are known for silver: the stable (ground) state cubic face centered 3C-Ag structure and the metastable hexagonal 4H-Ag structure. Recently, Chackraborty et al. [J. Phys.: Condens. Matter 23, 325401 (2011)] discovered a low density, highly reactive metastable hexagonal 2H-Ag structure accessible during electrodeposition of silver nanowires in porous anodic alumina templates. This 2H-Ag structure has enhanced electrical and catalytic characteristics. In the present work we reportmore » template-free synthesis of silver nanoplates with the metastable 2H-Ag crystal structure, which appears together with the ground 3C-Ag and the metastable 4H-Ag structures in a two-phase solution synthesis with citric acid as the capping agent. The capacity of citric acid to stabilize both the stable and the metastable structures is explained by its preferential binding to the close packed facets of Ag crystals, which are the (111) planes for 3C-Ag and the (0001) planes for 4H-Ag and 2H-Ag. Nanoplate morphology and structure are characterized using scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. The synthesized nanoplates have thickness from 15 to 17 nm and edge length from 1 to 10 μm. Transmission electron microscopy selected area electron diffraction is used to uniquely identify and distinguish between nanoplates with 2H-Ag or 4H-Ag or 3C-Ag structures.« less

Structural and optical properties of ZnO nanorods synthesized via template free approach

NASA Astrophysics Data System (ADS)

Kajal, Priyanka; D, Pooja; Jaggi, Neena

2016-06-01

In this paper, we report a novel method for synthesis of semiconducting ZnO nanorods using Zinc acetate dehydrate precursor in a methanol—de-ionized (1:5) mixture via template free approach. Scanning electron microscope (SEM) and transmission electron microscope (TEM) images of as synthesized nanorods revealed hexagonal symmetry of rods, whereas x-ray diffraction (XRD) analysis for structure and phase has shown high crystallinity with wurtzite crystal structure. The structural characterization by FT-IR analysis revealed presence of various groups on as synthesized ZnO nanorods, whereas the UV-Vis analysis has shown a blue shift in the absorption spectra as compared to bulk ZnO due to quantum confinement of charge carriers. Photoluminescence (PL) spectroscopy study has also been performed revealing a good degree of phosphorescence in the ZnO nanorods. Further, thermo gravimetric analysis (TGA) revealed that as synthesized nanorods by present method are highly stable at high temperature (1000 °C). This study provides an alternative, less expensive and a very simple method for the fabrication of ZnO nanorods in abundance, which can be further used for various sensing applications, in particular, gas sensing.

Positioning growth of NPB crystalline nanowires on the PTCDA nanocrystal template.

PubMed

Wang, Hong; Lin, Haiping; Fan, Xing; Ostendorp, Stefan; Wang, Yandong; Huang, Lizhen; Jiang, Lin; Li, Youyong; Wilde, Gerhard; Fuchs, Harald; Wang, Wenchong; Chi, Lifeng

2018-05-31

Non-planar organic molecules often form amorphous films via vapor phase deposition on surfaces. In this study, we demonstrate for the first time that direct crystalline growth of non-planar NPB is possible when the orientation of initially deposited molecules on a PTCDA nanocrystal template is controlled to make it analogous to the structure of the molecular crystal. The crystalline NPB nanowires can be further positioned by controlling the site-selective growth of PTCDA nanocrystal templates at pre-determined locations. Short channel bottom contact OFET array with the NPB nanowires directly grown on electrodes were subsequently fabricated. The hole mobility of NPB nanowires is improved by 40-fold in comparison to that of the amorphous films.

A Robust and Engineerable Self-Assembling Protein Template for the Synthesis and Patterning of Ordered Nanoparticle Arrays

NASA Technical Reports Server (NTRS)

McMillan, R. Andrew; Howard, Jeanie; Zaluzec, Nestor J.; Kagawa, Hiromi K.; Li, Yi-Fen; Paavola, Chad D.; Trent, Jonathan D.

2004-01-01

Self-assembling biomolecules that form highly ordered structures have attracted interest as potential alternatives to conventional lithographic processes for patterning materials. Here we introduce a general technique for patterning materials on the nanoscale using genetically modified protein cage structures called chaperonins that self-assemble into crystalline templates. Constrained chemical synthesis of transition metal nanoparticles is specific to templates genetically functionalized with poly-Histidine sequences. These arrays of materials are ordered by the nanoscale structure of the crystallized protein. This system may be easily adapted to pattern a variety of materials given the rapidly growing list of peptide sequences selected by screening for specificity for inorganic materials.

Crystal orientation of PEO confined within the nanorod templated by AAO nanochannels.

PubMed

Liu, Chien-Liang; Chen, Hsin-Lung

2018-06-18

The orientation of poly(ethylene oxide) (PEO) crystallites developed in the nanochannels of anodic aluminum oxide (AAO) membrane has been investigated. PEO was filled homogeneously into the nanochannels in the melt state, and the crystallization confined within the PEO nanorod thus formed was allowed to take place subsequently at different temperatures. The effects of PEO molecular weight (MPEO), crystallization temperature (Tc) and AAO channel diameter (DAAO) on the crystal orientation attained in the nanorod were revealed by 2-D wide angle X-ray scattering (WAXS) patterns. In the nanochannels with DAAO = 23 nm, the crystallites formed from PEO with the lowest MPEO (= 3400 g mol-1) were found to adopt a predominantly perpendicular orientation with the crystalline stems aligning normal to the channel axis irrespective of Tc (ranging from -40 to 20 °C). Increasing MPEO or decreasing Tc tended to induce the development of the tilt orientation characterized by the tilt of the (120) plane by 45° from the channel axis. In the case of the highest MPEO (= 95 000 g mol-1) studied, both perpendicular and tilt orientations coexisted irrespective of Tc. Coexistent orientation was always observed in the channels with a larger diameter (DAAO = 89 nm) irrespective of MPEO and Tc. Compared with the previous results of the crystal orientation attained in nanotubes templated by the preferential wetting of the channel walls by PEO, the window of the perpendicular crystal orientation in the nanorod was much narrower due to its weaker confinement effect imposed on the crystal growth than that set by the nanotube.

A chiral self-assembled monolayer derived from a resolving agent and its performance as a crystallization template for an organic compound from organic solvents.

PubMed

Bejarano-Villafuerte, Ángela; van der Meijden, Maarten W; Lingenfelder, Magalí; Wurst, Klaus; Kellogg, Richard M; Amabilino, David B

2012-12-07

A new chiral nonracemic thiol derived from a popular acidic resolving agent that incorporates a cyclic disubstituted phosphate group (phencyphos) has been prepared in enantiomerically pure form. The stereochemistry and absolute configuration were established by performing a single-crystal X-ray structural analysis of a synthetic intermediate. The thiol compound was used for the preparation of self-assembled monolayers (SAMs) on both monocrystalline and polycrystalline metallic gold, which have very different surface roughness. The monolayers were used to promote the nucleation and growth of crystals from nonaqueous solutions of an organic molecule (the parent phencyphos) of similar structure to the compound present in the monolayer. The template layers influence the nucleation and growth of the phencyphos crystals despite the lack of two-dimensional order in the surfaces. Heterogeneous nucleation of phencyphos takes place upon evaporation of either CHCl(3) or isopropanol solutions of the compound on the SAM surfaces, where the evaporation rate merely influences the size and homogeneity of the crystals. The roughness of the surface also plays an important role; the polycrystalline gold produces more homogeneous samples because of the greater number of nucleation sites. Clear evidence for nucleation and growth on the surfaces is shown by scanning electron microscopy. The variation in crystal form achieved by using different surfaces and solvents suggests that the layers are applicable for the preparation of organic crystals from organic solutions. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Hybridized Phosphate with Ultrathin Nanoslices and Single Crystal Microplatelets for High Performance Supercapacitors

PubMed Central

Zhao, Yufeng; Chen, Zhaoyang; Xiong, Ding-Bang; Qiao, Yuqing; Tang, Yongfu; Gao, Faming

2016-01-01

A novel hybridized phosphate is developed through a mild hydrothermal method to construct high performance asymmetric supercapacitor. Single layered (Ni,Co)3(PO4)2·8H2O nanoslices (∼1 nm) and single crystal (NH4)(Ni,Co)PO4·0.67H2O microplatelets are obtained through a template sacrificial method and dissolution recrystallization approach respectively in one step. This unique hybridized structure delivers a maximum specific capacitance of 1128 F g−1 at current density of 0.5 A g−1. The asymmetric supercapacitor (ASC) based on the hybrid exhibits a high energy density of 35.3 Wh kg−1 at low power density, and still holds 30.9 Wh kg−1 at 4400 W kg−1. Significantly, the ASC manifests very high cycling stability with 95.6% capacitance retention after 5000 cycles. Such excellent electrochemical performance could be attributed to the synergistic effect of the surface redox reaction from the ultrathin nanoslices and ion intercalation from the single crystal bulk structure. This material represents a novel kind of electrode material for the potential application in supercapacitors. PMID:26833204

Hybridized Phosphate with Ultrathin Nanoslices and Single Crystal Microplatelets for High Performance Supercapacitors

NASA Astrophysics Data System (ADS)

Zhao, Yufeng; Chen, Zhaoyang; Xiong, Ding-Bang; Qiao, Yuqing; Tang, Yongfu; Gao, Faming

2016-02-01

A novel hybridized phosphate is developed through a mild hydrothermal method to construct high performance asymmetric supercapacitor. Single layered (Ni,Co)3(PO4)2·8H2O nanoslices (˜1 nm) and single crystal (NH4)(Ni,Co)PO4·0.67H2O microplatelets are obtained through a template sacrificial method and dissolution recrystallization approach respectively in one step. This unique hybridized structure delivers a maximum specific capacitance of 1128 F g-1 at current density of 0.5 A g-1. The asymmetric supercapacitor (ASC) based on the hybrid exhibits a high energy density of 35.3 Wh kg-1 at low power density, and still holds 30.9 Wh kg-1 at 4400 W kg-1. Significantly, the ASC manifests very high cycling stability with 95.6% capacitance retention after 5000 cycles. Such excellent electrochemical performance could be attributed to the synergistic effect of the surface redox reaction from the ultrathin nanoslices and ion intercalation from the single crystal bulk structure. This material represents a novel kind of electrode material for the potential application in supercapacitors.

Influence of boric acid (H3BO3) concentration on the physical properties of electrochemical deposited nickel (Ni) nanowires

NASA Astrophysics Data System (ADS)

Kananathan, J.; Sofiah, A. G. N.; Samykano, M.; Ulakanathan, S.; Lah, N. A. C.; Harun, W. S. W.; Sudhakar, K.; Kadirgama, K.; Ngui, W. K.; Siregar, J. P.

2017-10-01

Authors have investigated the influence of the stabilizer (Boric Acid) concentration during the template-assisted electrochemical deposition of Nickel (Ni) nanowires in Anodic Alumina Oxide (AAO) templates. The synthesis was performed using Ni Sulfate Hexahydrate (NiSO4.6H2O) as metal salts and Boric Acid (H3BO3) as a stabilizer. The mixture of both solutions creates electrolyte and utilized for the electrochemical deposition of Ni nanowires. During the experiment, the boric acid concentration varied between 5 g/L, 37.5 g/L and 60 g/L with a deposition temperature of 80 °C (constant). After the electrochemical deposition process, AAO templates were cleaned with distilled water before dissolution in Sodium Hydroxide (NaOH) solution to obtain the freestanding Ni nanowires. Physical properties of the synthesized Ni nanowires were analyzed using Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive Spectroscopy (EDX) and X-ray Diffraction (XRD). The physical properties of obtained Ni nanowires has eloborated by taking into account the effect of boric acid concentration on the surface morphology, growth length, elemental composition and crystal orientation crystal of the synthesized nickel nanowires. The finding exposes that the boric acid concentration does not influence all aspects in the physicals properties of the synthesized Ni nanowires. The boric acid concentration did not affect the surface texture and crystal orientation. However, shorter Ni nanowires obtained as the concentration of boric acid increased.

Continuous mesoporous titania nanocrystals: their growth in confined space and scope for application.

PubMed

Dutta, Saikat; Bhaumik, Asim

2013-11-01

Enjoying the single lifestyle: With an overwhelming efficiency compared to thermally sintered preformed nanocrystals, mesoporous single crystals (MSCs) of TiO2 constitute a new class of semiconductor materials for low-cost solar power, solar fuel, photocatalysis, and energy storage applications. This Highlight explores the benefits of template-directed seed-mediated growth in the confined space of a preseeded mesoporous template, and possible research avenues for further improvements. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ion dynamics in nanocrystalline LiMnPO{sub 4} synthesised by novel template free hydrothermal approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vijayan, Lakshmi, E-mail: lakshmivijayan@gmail.com; Cheruku, Rajesh; Govindaraj, G.

A dense core rectangular shaped nanocrystalline LiMnPO{sub 4} material was synthesized by template free sucrose assisted hydrothermal synthesis. The material possess orthorhombic crystal structure with Pnma, space group having four formula units. The structural characterization was accomplished through X-ray diffraction, thermo gravimetry/differential thermal analysis. Morphology was identified by the SEM, VSM was used to verify the magnetic behavior of the material and electrical characterization was done through impedance spectroscopy and the results were reported.

3-Dimensional Colloidal Crystals From Hollow Spheres

NASA Astrophysics Data System (ADS)

Zhang, Jian; Work, William J.; Sanyal, Subrata; Lin, Keng-Hui; Yodh, A. G.

2000-03-01

We have succeeded in synthesizing submicron-sized, hollow PMMA spheres and self-assembling them into colloidal crystalline structures using the depletion force. The resulting structures can be used as templates to make high refractive-index contrast, porous, inorganic structures without the need to use calcination or chemical-etching. With the method of emulsion polymerization, we managed to coat a thin PMMA shell around a swellable P(MMA/MAA/EGDMA) core. After neutralization and heating above the glass transition temperature of PMMA, we obtained water-swollen hydrogel particles encapsulated in PMMA shells. These composite particles become hollow spheres after drying. We characterized the particles with both transmission electron microscopy (TEM) and dynamic light scattering (DLS). The TEM results confirmed that each sphere has a hollow core. The DLS results showed that our hollow spheres are submicron-sized, with a swelling ratio of at least 25%, and with a polydispersity less than 5%. We anticipate using this method in the near-future to encapsulate ferrofluid emulsion droplets and liquid crystal droplets.

Conductive indium-tin oxidenanowire and nanotube arrays made by electrochemically assisted deposition in template membranes: switching between wire and tube growth modes by surface chemical modification of the template

NASA Astrophysics Data System (ADS)

Kovtyukhova, Nina I.; Mallouk, Thomas E.

2011-04-01

Tin-doped indium hydroxide (InSnOH) nanowires (NWs) and nanotubes (NTs) were grown from acidic aqueous solutions of inorganic precursors in a simple one-step electrochemically assisted deposition (EAD) process inside Au-plugged anodic aluminium oxide and polycarbonatemembranes. When the membranes were used without any pre-treatment, InSnOH crystals nucleated on the both the Au-cathode and pore wall surfaces. By adjusting the surface chemistry of Au or the pore walls, it was possible to switch between NW and NT growth modes. InSnOH was converted into indiumtin oxide (ITO) by annealing the InSnOH-filled membranes at 300 °C. The resulting wires and tubes were characterized by field emission scanning electron microscopy, transmission electron microscopy, X-ray and electron diffraction, Auger electron spectroscopy and electrical conductivity measurements. InSnOH and ITO NWs and NTs consisted of ~25-50 nm in size crystalline grains with the cubic crystal structures of In(OH)3 and In2O3, respectively, and showed essentially the same morphological features as planar ITO films made by the same method. Separate tin oxide/hydroxide phases were not observed by any of the characterization methods. After heating in air at 600 °C, the ITO NWs had resistivity on the order of 10°Ω cm. EAD is an inexpensive and scalable solution-based technique, and allows one to grow dense arrays of vertically aligned, crystalline and conductive ITO NWs and NTs.

Well-crystallized mesoporous TiO2 shells for enhanced photocatalytic activity: prepared by carbon coating and silica-protected calcination.

PubMed

Zhang, Zewu; Zhou, Yuming; Zhang, Yiwei; Zhou, Shijian; Shi, Junjun; Kong, Jie; Zhang, Sicheng

2013-04-14

Mesoporous anatase-phase TiO2 hollow shells were successfully fabricated by the solvothermal and calcination process. This method involves preparation of SiO2@TiO2 core-shell colloidal templates, sequential deposition of carbon and then silica layers through solvothermal and sol-gel processes, crystallization of TiO2 by calcination and finally removal of the inner and outer silica to produce hollow anatase TiO2 shells. The prepared samples were characterized by transmission electron microscopy, X-ray diffraction, N2 adsorption-desorption isotherms and UV-vis absorption spectroscopy. The results show that a uniform carbon layer is coated on the core-shell particles through the solvothermal process. The combustion of carbon offers the space for the TiO2 to further grow into large crystal grains, and the outer silica layer serves as a barrier against the excessive growth of anatase TiO2 nanocrystals. Furthermore, the initial crystallization of TiO2 generated in the carbon coating step and the heat generated by the combustion of the carbon layer allow the crystallization of TiO2 at a relatively low temperature without changing the uniform structure. When used as photocatalysts for the oxidation decomposition of Rhodamine B in aqueous solution under UV irradiation, the hollow TiO2 shells showed enhanced catalytic activity. Moreover, the TiO2 hollow shells prepared with optimal crystallinity by this method showed a higher performance than commercial P25 TiO2.

Direct anisotropic growth of CdS nanocrystals in thermotropic liquid crystal templates for heterojunction optoelectronics.

PubMed

Yuan, Kai; Chen, Lie; Chen, Yiwang

2014-09-01

The direct growth of CdS nanocrystals in functional solid-state thermotropic liquid crystal (LC) small molecules and a conjugated LC polymer by in situ thermal decomposition of a single-source cadmium xanthate precursor to fabricate LC/CdS hybrid nanocomposites is described. The influence of thermal annealing temperature of the LC/CdS precursors upon the nanomorphology, photophysics, and optoelectronic properties of the LC/CdS nanocomposites is systematically studied. Steady-state PL and ultrafast emission dynamics studies show that the charge-transfer rates are strongly dependent on the thermal annealing temperature. Notably, annealing at liquid-crystal state temperature promotes a more organized nanomorphology of the LC/CdS nanocomposites with improved photophysics and optoelectronic properties. The results confirm that thermotropic LCs can be ideal candidates as organization templates for the control of organic/inorganic hybrid nanocomposites at the nanoscale level. The results also demonstrate that in situ growth of semiconducting nanocrystals in thermotropic LCs is a versatile route to hybrid organic/inorganic nanocomposites and optoelectronic devices. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Scalable salt-templated synthesis of two-dimensional transition metal oxides

PubMed Central

Xiao, Xu; Song, Huaibing; Lin, Shizhe; Zhou, Ying; Zhan, Xiaojun; Hu, Zhimi; Zhang, Qi; Sun, Jiyu; Yang, Bo; Li, Tianqi; Jiao, Liying; Zhou, Jun; Tang, Jiang; Gogotsi, Yury

2016-01-01

Two-dimensional atomic crystals, such as two-dimensional oxides, have attracted much attention in energy storage because nearly all of the atoms can be exposed to the electrolyte and involved in redox reactions. However, current strategies are largely limited to intrinsically layered compounds. Here we report a general strategy that uses the surfaces of water-soluble salt crystals as growth templates and is applicable to not only layered compounds but also various transition metal oxides, such as hexagonal-MoO3, MoO2, MnO and hexagonal-WO3. The planar growth is hypothesized to occur via a match between the crystal lattices of the salt and the growing oxide. Restacked two-dimensional hexagonal-MoO3 exhibits high pseudocapacitive performances (for example, 300 F cm−3 in an Al2(SO4)3 electrolyte). The synthesis of various two-dimensional transition metal oxides and the demonstration of high capacitance are expected to enable fundamental studies of dimensionality effects on their properties and facilitate their use in energy storage and other applications. PMID:27103200

Ordered three-dimensional interconnected nanoarchitectures in anodic porous alumina

PubMed Central

Martín, Jaime; Martín-González, Marisol; Fernández, Jose Francisco; Caballero-Calero, Olga

2014-01-01

Three-dimensional nanostructures combine properties of nanoscale materials with the advantages of being macro-sized pieces when the time comes to manipulate, measure their properties, or make a device. However, the amount of compounds with the ability to self-organize in ordered three-dimensional nanostructures is limited. Therefore, template-based fabrication strategies become the key approach towards three-dimensional nanostructures. Here we report the simple fabrication of a template based on anodic aluminum oxide, having a well-defined, ordered, tunable, homogeneous 3D nanotubular network in the sub 100 nm range. The three-dimensional templates are then employed to achieve three-dimensional, ordered nanowire-networks in Bi2Te3 and polystyrene. Lastly, we demonstrate the photonic crystal behavior of both the template and the polystyrene three-dimensional nanostructure. Our approach may establish the foundations for future high-throughput, cheap, photonic materials and devices made of simple commodity plastics, metals, and semiconductors. PMID:25342247

Centroid stabilization in alignment of FOA corner cube: designing of a matched filter

NASA Astrophysics Data System (ADS)

Awwal, Abdul; Wilhelmsen, Karl; Roberts, Randy; Leach, Richard; Miller Kamm, Victoria; Ngo, Tony; Lowe-Webb, Roger

2015-02-01

The current automation of image-based alignment of NIF high energy laser beams is providing the capability of executing multiple target shots per day. An important aspect of performing multiple shots in a day is to reduce additional time spent aligning specific beams due to perturbations in those beam images. One such alignment is beam centration through the second and third harmonic generating crystals in the final optics assembly (FOA), which employs two retro-reflecting corner cubes to represent the beam center. The FOA houses the frequency conversion crystals for third harmonic generation as the beams enters the target chamber. Beam-to-beam variations and systematic beam changes over time in the FOA corner-cube images can lead to a reduction in accuracy as well as increased convergence durations for the template based centroid detector. This work presents a systematic approach of maintaining FOA corner cube centroid templates so that stable position estimation is applied thereby leading to fast convergence of alignment control loops. In the matched filtering approach, a template is designed based on most recent images taken in the last 60 days. The results show that new filter reduces the divergence of the position estimation of FOA images.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Geyuan

My research projects are focused on application of photonics, optics and micro- fabrication technology in energy related fields. Photonic crystal fabrication research has the potential to help us generate and use light more efficiently. In order to fabricate active 3D woodpile photonic structure devices, a woodpile template is needed to enable the crystal growth process. We developed a silica woodpile template fabrication process based on two polymer transfer molding technique. A silica woodpile template is demonstrated to work with temperature up to 900 C. It provides a more economical way to explore making better 3D active woodpile photonic devices likemore » 3D photonic light emitting diodes (LED). Optical research on solar cell testing has the potential to make our energy generation more e cient and greener. PL imaging and LBIC mapping are used to measure CdTe solar cells with different back contacts. A strong correlation between PL image defects and LBIC map defects is observed. This opens up potential application for PL imaging in fast solar cell inspection. 2D laser IV scan shows its usage in 2D parameter mapping. We show its ability to generate important information about solar cell performance locally around PL image defects.« less

Cavity Pull Rod: Device to Promote Single Crystal Growth from the Melt

NASA Technical Reports Server (NTRS)

Goldsby, Jon (Inventor)

2017-01-01

A pull rod for use in producing a single crystal from a molten alloy is provided that includes an elongated rod having a first end and a second end, a first cavity defined at the first end and a second cavity defined at the first end and in communication with the first cavity. The first cavity receives the molten alloy and the second cavity vents a gas from the molten alloy to thereby template a single crystal when the pull rod is dipped into and extracted from the molten alloy.

High-resolution modeling of antibody structures by a combination of bioinformatics, expert knowledge, and molecular simulations.

PubMed

Shirai, Hiroki; Ikeda, Kazuyoshi; Yamashita, Kazuo; Tsuchiya, Yuko; Sarmiento, Jamica; Liang, Shide; Morokata, Tatsuaki; Mizuguchi, Kenji; Higo, Junichi; Standley, Daron M; Nakamura, Haruki

2014-08-01

In the second antibody modeling assessment, we used a semiautomated template-based structure modeling approach for 11 blinded antibody variable region (Fv) targets. The structural modeling method involved several steps, including template selection for framework and canonical structures of complementary determining regions (CDRs), homology modeling, energy minimization, and expert inspection. The submitted models for Fv modeling in Stage 1 had the lowest average backbone root mean square deviation (RMSD) (1.06 Å). Comparison to crystal structures showed the most accurate Fv models were generated for 4 out of 11 targets. We found that the successful modeling in Stage 1 mainly was due to expert-guided template selection for CDRs, especially for CDR-H3, based on our previously proposed empirical method (H3-rules) and the use of position specific scoring matrix-based scoring. Loop refinement using fragment assembly and multicanonical molecular dynamics (McMD) was applied to CDR-H3 loop modeling in Stage 2. Fragment assembly and McMD produced putative structural ensembles with low free energy values that were scored based on the OSCAR all-atom force field and conformation density in principal component analysis space, respectively, as well as the degree of consensus between the two sampling methods. The quality of 8 out of 10 targets improved as compared with Stage 1. For 4 out of 10 Stage-2 targets, our method generated top-scoring models with RMSD values of less than 1 Å. In this article, we discuss the strengths and weaknesses of our approach as well as possible directions for improvement to generate better predictions in the future. © 2014 Wiley Periodicals, Inc.

Self-assembled Multilayers of Silica Nanospheres for Defect Reduction in Non- and Semipolar Gallium Nitride Epitaxial Layers

PubMed Central

2015-01-01

Non- and semipolar GaN have great potential to improve the efficiency of light emitting devices due to much reduced internal electric fields. However, heteroepitaxial GaN growth in these crystal orientations suffers from very high dislocation and stacking faults densities. Here, we report a facile method to obtain low defect density non- and semipolar heteroepitaxial GaN via selective area epitaxy using self-assembled multilayers of silica nanospheres (MSN). Nonpolar (11–20) and semipolar (11–22) GaN layers with high crystal quality have been achieved by epitaxial integration of the MSN and a simple one-step overgrowth process, by which both dislocation and basal plane stacking fault densities can be significantly reduced. The underlying defect reduction mechanisms include epitaxial growth through the MSN covered template, island nucleation via nanogaps in the MSN, and lateral overgrowth and coalescence above the MSN. InGaN/GaN multiple quantum wells structures grown on a nonpolar GaN/MSN template show more than 30-fold increase in the luminescence intensity compared to a control sample without the MSN. This self-assembled MSN technique provides a new platform for epitaxial growth of nitride semiconductors and offers unique opportunities for improving the material quality of GaN grown on other orientations and foreign substrates or heteroepitaxial growth of other lattice-mismatched materials. PMID:27065755

FoldGPCR: structure prediction protocol for the transmembrane domain of G protein-coupled receptors from class A.

PubMed

Michino, Mayako; Chen, Jianhan; Stevens, Raymond C; Brooks, Charles L

2010-08-01

Building reliable structural models of G protein-coupled receptors (GPCRs) is a difficult task because of the paucity of suitable templates, low sequence identity, and the wide variety of ligand specificities within the superfamily. Template-based modeling is known to be the most successful method for protein structure prediction. However, refinement of homology models within 1-3 A C alpha RMSD of the native structure remains a major challenge. Here, we address this problem by developing a novel protocol (foldGPCR) for modeling the transmembrane (TM) region of GPCRs in complex with a ligand, aimed to accurately model the structural divergence between the template and target in the TM helices. The protocol is based on predicted conserved inter-residue contacts between the template and target, and exploits an all-atom implicit membrane force field. The placement of the ligand in the binding pocket is guided by biochemical data. The foldGPCR protocol is implemented by a stepwise hierarchical approach, in which the TM helical bundle and the ligand are assembled by simulated annealing trials in the first step, and the receptor-ligand complex is refined with replica exchange sampling in the second step. The protocol is applied to model the human beta(2)-adrenergic receptor (beta(2)AR) bound to carazolol, using contacts derived from the template structure of bovine rhodopsin. Comparison with the X-ray crystal structure of the beta(2)AR shows that our protocol is particularly successful in accurately capturing helix backbone irregularities and helix-helix packing interactions that distinguish rhodopsin from beta(2)AR. (c) 2010 Wiley-Liss, Inc.

The Preparation and Characterization of Natrolite Synthetized by Purified Attapulgite

NASA Astrophysics Data System (ADS)

Li, H. J.; Zhou, X. D.; Zhang, J. M.; Wu, X. Y.; Gao, H. B.

2017-06-01

This paper mainly researched the hydrothermal synthesis of Natrolite, using amorphous silicon source from the purified attapulgite. The effects of silicon source, silicon aluminum ratio, crystallization time and crystallization temperature on the synthesis of natrolite were investigated. The results showed that the optimal synthesis condition of natrolite was: Hydrothermal activated ATP with NaOH was silicon source, silicon aluminum ratio was 10:1, crystallization time lasted to 72h and crystallization temperature was 150°C, the template was removed by calcining 8 hours at 550°C. The structural formula of obtained natrolite is Na2Al2Si3O10•2H2O.

Dual exposure, two-photon, conformal phasemask lithography for three dimensional silicon inverse woodpile photonic crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shir, Daniel J.; Nelson, Erik C.; Chanda, Debashis

2010-01-01

The authors describe the fabrication and characterization of three dimensional silicon inverse woodpile photonic crystals. A dual exposure, two-photon, conformal phasemask technique is used to create high quality polymer woodpile structures over large areas with geometries that quantitatively match expectations based on optical simulations. Depositing silicon into these templates followed by the removal of the polymer results in silicon inverse woodpile photonic crystals for which calculations indicate a wide, complete photonic bandgap over a range of structural fill fractions. Spectroscopic measurements of normal incidence reflection from both the polymer and siliconphotonic crystals reveal good optical properties.

Studies on the formation of hierarchical zeolite T aggregates with well-defined morphology in different template systems

NASA Astrophysics Data System (ADS)

Yin, Xiaoyan; Chu, Naibo; Lu, Xuewei; Li, Zhongfang; Guo, Hong

2016-01-01

In this paper, the disk-like and pumpkin-like hierarchical zeolite T aggregates consisted of primary nano-grains have been hydrothermally synthesized with and without the aid of the second template. The first template is used with tetramethylammonium hydroxide (TMAOH) and the second template is used with triethanolamine (TEA) or polyving akohol (PVA). A combination of characterization techniques, including XRD, SEM, TEM and N2 adsorption-desorption to examine the crystal crystallinity, morphology and surface properties of hierarchical zeolite T aggregates. In the single-template preparation process, the two-step varying-temperature treatment has been used to improve the meso-porosity of zeolite T aggregates. In the double-template preparation process, the amounts of PVA or TEA on the crystallinity, morphology and meso-porosity of zeolite T aggregates have been studied. It has been proved that the interstitial voids between the primary grains of aggregates are the origin of additional mesopores of samples. The micro- and meso-porosities of samples prepared with and without the second template have been contrasted in detail at last. In particular, the sample synthesized with the addition of PVA presents a hierarchical pore structure with the highest Sext value of 122 m2/g and Vmeso value of 0.255 cm3/g.

Agarose template for the fabrication of macroporous metal oxide structures.

PubMed

Zhou, Jingfang; Zhou, Meifang; Caruso, Rachel A

2006-03-28

Agarose gels have been applied as templates for the formation of macroporous metal oxide structures. The preparation of the agarose template is extremely simple, and with variation of the agarose content, control over morphology is demonstrated: The average pore size decreases from 180 to 55 nm and the surface area increases from 238 to 271 m2 g(-1) with increasing agarose content in the gel. The gelling temperature was also found to influence the final template morphology. Conducting sol-gel chemistry within the template structure followed by removal of the template by heating to 450 degrees C gives porous inorganic oxides. The technique has been demonstrated for the oxides of titanium, zirconium, niobium, and tin. The final morphology of the metal oxide is homogeneous and results from a coating of the agarose structure. The pore diameter decreased and the specific surface area of the titanium dioxide materials increased from 28 to 66 m2 g(-1) as the agarose content in the template is increased from 0.5 to 5.0 wt%. The overall pore size and surface area are lower than the original gel due to shrinkage occurring with the sol-gel process, as well as crystallization and a loss of microporosity in the final material.

Materials with engineered mesoporosity for programmed mass transport

NASA Astrophysics Data System (ADS)

Gough, Dara V.

Transport in nanostructured materials is of great interest for scientists in various fields, including molecular sequestration, catalysis, artificial photosynthesis and energy storage. This thesis will present work on the transport of molecular and ionic species in mesoporous materials (materials with pore sizes between 2 and 50 nm). Initially, discussion will focus on the synthesis of mesoporous ZnS nanorattles and the size selected mass transport of small molecules through the mesopores. Discussion will then shift of exploration of cation exchange and electroless plating of metals to alter the mesoporous hollow sphere (MHS) materials and properties. The focus of discussion will then shift to the transport of ions into and out of a hierarchically structured gold electrode. Finally, a model gamma-bactiophage was developed to study the electromigration of charged molecules into and out of a confined geometry. A catalytically active biomolecular species was encapsulated within the central cavity of ZnS MHS. Both the activity of the encapsulated enzyme and the size-selective transport through the wall of the MHS were verified through the use of a common fluorogen, hydrogen peroxide, and sodium azide. Additionally, the protection of the enzyme was shown through size-selected blocking of a protease. The mesoporous hollow sphere system introduces size-selectivity to catalyzed chemical reactions; future work may include variations in pore sizes, and pore wall chemical functionalization. The pore size in ZnS mesoporous hollow spheres is controlled between 2.5 and 4.1 nm through swelling of the lyotropic liquid crystal template. The incorporation of a swelling agent is shown to linearly vary the hexagonal lyotropic liquid crystalline phase, which templates the mesopores, while allowing the high fidelity synthesis of mesoporous hollow spheres. Fluorescnently labeled ssDNA was utilized as a probe to explore the change in mesopore permeability afforded by the swollen template relative to the unswollen template. Electroless plating and cation exchange were explored as methods to vary the shell material of MHS. Mesoporous Ni MHS were obtained by the reduction of Ni2+ with dimethylamine borane onto a CML latex core. However, the resultant MHS were damaged due to core swelling during etch. To successfully obtain undeformed MHS, a silica core must be utilized; one possible route to explore, in order to reach this goal, is the surface chemistry/ligand effects on Ni2+. Cation exchange was performed in order to obtain CuS MHS; however, it proved an unsuccessful route to PbS, S and HgS. CdS-ZnS, Bi2S3 and Ag2S MHS were obtained only with significant defects. A novel hierarchically structured material, porous opal, was prepared using a colloidal crystal template and the dealloying of silver from gold and possed porosity on length scales range from 10s of nanometers (due to the colloidal crystal template) down to ca. 10 nm (due to dealloying). The transport properties of the material were studied using cyclic voltammetry and electrochemical impedance spectroscopy. The porous opal was found to posses enhanced charge transport properties relative to a unimodal porous gold film and a higher surface area than a gold opal. An equivalent circuit model was presented to explain the enhanced charge transport properties. A biomimetic system for studying the translocation of polymers through a channel and into a spherical cavity was developed based on inspiration from the gamma-bacteriophage. The nanocavity system was synthesized using two template length scales: 250 nm and 1.2 mum. Fabrication challenges that arose when using 1.2 mum colloidal templates were addressed, and the system was optimized for confinement studies of plasmid dsDNA.

On the Grand Challenges in Physical Petrology: the Multiphase Crossroads

NASA Astrophysics Data System (ADS)

Bergantz, G. W.

2014-12-01

Rapid progress in experimental, micro-analytical and textural analysis at the crystal scale has produced an unprecedented record of magmatic processes. However an obstacle to further progress is the lack of understanding of how mass, energy and momentum flux associated with crystal-rich, open-system events produces identifiable outcomes. Hence developing a physically-based understanding of magmatic systems linking micro-scale petrological observations with a physical template operating at the macro-scale presents a so-called "Grand Challenge." The essence of this challenge is that magmatic systems have characteristic length and feedback scales between those accessible by classical continuum and discrete methods. It has become increasingly obvious that the old-school continuum methods have limited resolution and power of explanation for multiphase (real) magma dynamics. This is, in part, because in crystal-rich systems the deformation is non-affine, and so the concept of constitutive behavior is less applicable and likely not even relevant, especially if one is interested in the emergent character of micro-scale processes. One expression of this is the cottage industry of proposing viscosity laws for magmas, which serves as "blunt force" de facto corrections for what is intrinsically multiphase behavior. Even in more fluid-rich systems many of these laws are not suitable for use in the very transport theories they aim to support. The alternative approach is the discrete method, where multiphase interactions are explicitly resolved. This is a daunting prospect given the numbers of crystals in magmas. But perhaps all crystals don't need to be modeled. I will demonstrate how discrete methods can recover critical state behavior, resolve crystal migration, the onset of visco-elastic behavior such as melt-present shear bands which sets the large-scale mixing volumes, some of the general morpho-dynamics that underlies purported rheological models, and transient controls on the emergence and dissipation of distinct thermodynamic states. As simulations with 106 - 107 crystals are now possible both the local, micro-scale crystal processes as well as the larger scale processes controlled by particle-particle-fluid interactions, can be simultaneously resolved.

Nano-honeycomb structured transparent electrode for enhanced light extraction from organic light-emitting diodes

NASA Astrophysics Data System (ADS)

Shi, Xiao-Bo; Qian, Min; Wang, Zhao-Kui; Liao, Liang-Sheng

2015-06-01

A universal nano-sphere lithography method has been developed to fabricate nano-structured transparent electrode, such as indium tin oxide (ITO), for light extraction from organic light-emitting diodes (OLEDs). Perforated SiO2 film made from a monolayer colloidal crystal of polystyrene spheres and tetraethyl orthosilicate sol-gel is used as a template. Ordered nano-honeycomb pits on the ITO electrode surface are obtained by chemical etching. The proposed method can be utilized to form large-area nano-structured ITO electrode. More than two folds' enhancement in both current efficiency and power efficiency has been achieved in a red phosphorescent OLED which was fabricated on the nano-structured ITO substrate.

Coupling of Ag Nanoparticle with Inverse Opal Photonic Crystals as a Novel Strategy for Upconversion Emission Enhancement of NaYF4: Yb(3+), Er(3+) Nanoparticles.

PubMed

Shao, Bo; Yang, Zhengwen; Wang, Yida; Li, Jun; Yang, Jianzhi; Qiu, Jianbei; Song, Zhiguo

2015-11-18

Rare-earth-ion-doped upconversion (UC) nanoparticles have generated considerable interest because of their potential application in solar cells, biological labeling, therapeutics, and imaging. However, the applications of UC nanoparticles were still limited because of their low emission efficiency. Photonic crystals and noble metal nanoparticles are applied extensively to enhance the UC emission of rare earth ions. In the present work, a novel substrate consisting of inverse opal photonic crystals and Ag nanoparticles was prepared by the template-assisted method, which was used to enhance the UC emission of NaYF4: Yb(3+), Er(3+) nanoparticles. The red or green UC emissions of NaYF4: Yb(3+), Er(3+) nanoparticles were selectively enhanced on the inverse opal substrates because of the Bragg reflection of the photonic band gap. Additionally, the UC emission enhancement of NaYF4: Yb(3+), Er(3+) nanoparticles induced by the coupling of metal nanoparticle plasmons and photonic crystal effects was realized on the Ag nanoparticles included in the inverse opal substrate. The present results demonstrated that coupling of Ag nanoparticle with inverse opal photonic crystals provides a useful strategy to enhance UC emission of rare-earth-ion-doped nanoparticles.

Preparation of core-shell CaCO3 capsules via Pickering emulsion templates.

PubMed

Wang, Xiaoli; Zhou, Weizheng; Cao, Jian; Liu, Weichang; Zhu, Shiping

2012-04-15

Micron size and food grade pristine CaCO(3) particles were used to stabilize an oil in water Pickering emulsion. The particles also acted as nucleation sites for the subsequent crystallization of CaCO(3) with the addition of CaCl(2) and CO(2) gas as precursors. After the controllable crystallization process, a dense CaCO(3) shell with a few microns in thickness was formed. The CaCO(3) shell was proven to be calcite without the presence of crystallization modifiers. The crystallization speed and the shell integrity were controlled by manipulating the addition of CaCl(2) amount during the different crystallization stages; therefore, the homogeneous nucleation in the bulk was almost inhibited, and the heterogeneous nucleation at the oil-water interface on pristine CaCO(3) particles was the main contribution to the growth of the shell. The encapsulated limonene flavor in CaCO(3) capsules showed a prolonged release in neutral water at 85°C, while a burst release at pH 2 water as expected. The method is a simple and scalable process for creating inorganic core-shell capsules and can be used for producing food grade capsules for controlling the flavor release or masking undesirable taste in mouth. Copyright © 2012 Elsevier Inc. All rights reserved.

Biomimetic piezoelectric quartz crystal sensor with chloramphenicol-imprinted polymer sensing layer.

PubMed

Ebarvia, Benilda S; Ubando, Isaiah E; Sevilla, Fortunato B

2015-11-01

The measurement of banned antibiotic like chloramphenicol is significant for customer protection and safety. The presence of residual antibiotics in foods and food products of animal origin could pose as health hazards and affect food quality for global acceptance. In this study, the potential of a chloramphenicol sensor based on molecularly imprinted polymer (MIP) coupled with a piezoelectric quartz crystal was explored. The MIP was prepared by precipitation polymerization at 60 °C. Methacrylic acid was used as monomer, trimethylolpropane trimethacrylate (TRIM) as crosslinker, and chloramphenicol as the template. Template removal on the resulting polymer was done by extraction using methanol-acetic acid. Characterization of the MIP and NIP were conducted by spectroscopic and microscopic methods. These further supported the imprinting and rebinding process of chloramphenicol to the polymer matrix. The chloramphenicol sensor was devised by spin-coating onto one side of the 10 MHz AT-cut quartz crystal the MIP suspension in polyvinylchloride-tetrahydrofuran (6:2:1 w/w/v) solution. Optimization of sensor response was performed by varying the type of cross-linker, amount of MIP sensing layer, curing time, and pH. The sensor exhibited good sensitivity of about 73 Hz/log (conc., µg mL(-1)) and good repeatability (rsd<10%). A linear relationship (r(2)=0.9901) between frequency shift and chloramphenicol concentration in the range of 1×10(-6) up to 1×10(-1) µg/mL was obtained. The sensor response was highly selective to chloramphenicol than with other compounds of similar chemical structures. Acceptable percent recovery was obtained for real sample analysis using the sensor. The proposed sensor could be a promising low cost and highly sensitive approach for residual chloramphenicol quantification in food products. Copyright © 2015 Elsevier B.V. All rights reserved.

Coordinative nanoporous polymers synthesized with hydrogen-bonded columnar liquid crystals.

PubMed

Ishihara, Shinsuke; Furuki, Yusuke; Hill, Jonathan P; Ariga, Katsuhiko; Takeoka, Shinji

2012-10-01

In this paper, we report the development of nanoporous polymer which demonstrates the coordination property toward zinc porphyrin. A hydrogen-bonded columnar liquid crystalline precursor composed of a triphenylene template and three equivalent of the surrounding dendric amphiphile bearing a pyridyl head group and a polymerizable aliphatic chain, was covalently fixed by photopolymerization, and then the subsequent selective removal of the template successively resulted in a nanoporous polymer in which the pore wall is modified with pyridyl groups. The nanoporous polymer reflected the conformation of template, and displayed considerable coordination ability of the pyridyl groups towards zinc porphyrin. The coordinative nanoporous polymer is promising as a nano-scaled scaffold for the organization of dyes into functional supramolecular architectures.

Calcite precipitates in Slovenian bottled waters.

PubMed

Stanič, Tamara Ferjan; Miler, Miloš; Brenčič, Mihael; Gosar, Mateja

2017-06-01

Storage of bottled waters in varying ambient conditions affects its characteristics. Different storage conditions cause changes in the initial chemical composition of bottled water which lead to the occurrence of precipitates with various morphologies. In order to assess the relationship between water composition, storage conditions and precipitate morphology, a study of four brands of Slovenian bottled water stored in PET bottles was carried out. Chemical analyses of the main ions and measurements of the physical properties of water samples were performed before and after storage of water samples at different ambient conditions. SEM/EDS analysis of precipitates was performed after elapsed storage time. The results show that the presence of Mg 2+ , SO 4 2- , SiO 2 , Al, Mn and other impurities such as K + , Na + , Ba and Sr in the water controlled precipitate morphology by inhibiting crystal growth and leading to elongated rhombohedral calcite crystal forms which exhibit furrowed surfaces and calcite rosettes. Different storage conditions, however, affected the number of crystallization nuclei and size of calcite crystals. Hollow calcite spheres composed of cleavage rhombohedrons formed in the water with variable storage conditions by a combination of evaporation and precipitation of water droplets during high temperatures or by the bubble templating method.

A pilot study of a heuristic algorithm for novel template identification from VA electronic medical record text.

PubMed

Redd, Andrew M; Gundlapalli, Adi V; Divita, Guy; Carter, Marjorie E; Tran, Le-Thuy; Samore, Matthew H

2017-07-01

Templates in text notes pose challenges for automated information extraction algorithms. We propose a method that identifies novel templates in plain text medical notes. The identification can then be used to either include or exclude templates when processing notes for information extraction. The two-module method is based on the framework of information foraging and addresses the hypothesis that documents containing templates and the templates within those documents can be identified by common features. The first module takes documents from the corpus and groups those with common templates. This is accomplished through a binned word count hierarchical clustering algorithm. The second module extracts the templates. It uses the groupings and performs a longest common subsequence (LCS) algorithm to obtain the constituent parts of the templates. The method was developed and tested on a random document corpus of 750 notes derived from a large database of US Department of Veterans Affairs (VA) electronic medical notes. The grouping module, using hierarchical clustering, identified 23 groups with 3 documents or more, consisting of 120 documents from the 750 documents in our test corpus. Of these, 18 groups had at least one common template that was present in all documents in the group for a positive predictive value of 78%. The LCS extraction module performed with 100% positive predictive value, 94% sensitivity, and 83% negative predictive value. The human review determined that in 4 groups the template covered the entire document, with the remaining 14 groups containing a common section template. Among documents with templates, the number of templates per document ranged from 1 to 14. The mean and median number of templates per group was 5.9 and 5, respectively. The grouping method was successful in finding like documents containing templates. Of the groups of documents containing templates, the LCS module was successful in deciphering text belonging to the template and text that was extraneous. Major obstacles to improved performance included documents composed of multiple templates, templates that included other templates embedded within them, and variants of templates. We demonstrate proof of concept of the grouping and extraction method of identifying templates in electronic medical records in this pilot study and propose methods to improve performance and scaling up. Published by Elsevier Inc.

A “dry and wet hybrid” lithography technique for multilevel replication templates: Applications to microfluidic neuron culture and two-phase global mixing

PubMed Central

Paul, Debjani; Saias, Laure; Pedinotti, Jean-Cedric; Chabert, Max; Magnifico, Sebastien; Pallandre, Antoine; De Lambert, Bertrand; Houdayer, Claude; Brugg, Bernard; Peyrin, Jean-Michel; Viovy, Jean-Louis

2011-01-01

A broad range of microfluidic applications, ranging from cell culture to protein crystallization, requires multilevel devices with different heights and feature sizes (from micrometers to millimeters). While state-of-the-art direct-writing techniques have been developed for creating complex three-dimensional shapes, replication molding from a multilevel template is still the preferred method for fast prototyping of microfluidic devices in the laboratory. Here, we report on a “dry and wet hybrid” technique to fabricate multilevel replication molds by combining SU-8 lithography with a dry film resist (Ordyl). We show that the two lithography protocols are chemically compatible with each other. Finally, we demonstrate the hybrid technique in two different microfluidic applications: (1) a neuron culture device with compartmentalization of different elements of a neuron and (2) a two-phase (gas-liquid) global micromixer for fast mixing of a small amount of a viscous liquid into a larger volume of a less viscous liquid. PMID:21559239

Molecular Dynamics Simulations of Cubic Phases in Pluronics Systems and Their Role in Templating Nanoparticles

NASA Astrophysics Data System (ADS)

Anderson, Joshua; Travesset, Alex; Lorenz, Chris

2007-03-01

We discuss molecular dynamics simulations aimed at predicting phase diagrams in Pluronic systems. Crystalline phases with cubic symmetries are particularly challenging to simulate. A general method that is able to obtain these phases is presented. As an example, we show our results for a system of ABA triblock polymers where each hydrophilic A block contains 10 beads and the hydrophobic block B contains 7 beads. These values match the ratio of PEO to PPO in Pluronic F127. Numerous simulation runs are carried out with differing initial conditions, which consistently produce textbook bcc and fcc lattices of micelles along with two other distorted bcc lattices. We find that the formation of a lattice is sensitive to the system's preparation and depends mainly on the kinetic temperature and equilibration time. Examination of the distorted lattices shows that they are related to the finite size of the simulation box. We conclude with some discussion on using these crystals as a template for nanoparticles or biomineralization.

In Situ High Temperature High Pressure MAS NMR Study on the Crystallization of AlPO 4 -5

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Zhenchao; Xu, Suochang; Hu, Mary Y.

2016-01-28

A damped oscillating crystallization process of AlPO4-5 at the presence of small amount of water is demonstrated by in situ high temperature high pressure multinuclear MAS NMR. Crystalline AlPO4-5 is formed from an intermediate semicrystalline phase via continuous rearrangement of the local structure of amorphous precursor gel. Activated water catalyzes the rearrangement via repeatedly hydrolysis and condensation reaction. Strong interactions between organic template and inorganic species facilitate the ordered rearrangement. During the crystallization process, excess water, phosphate, and aluminums are expelled from the precursor. The oscillating crystallization reflects mass transportation between the solid and liquid phase during the crystallization process.more » This crystallization process is also applicable to AlPO4-5 crystallized in the presence of a relatively large amount of water.« less

Angle-resolved reflection spectroscopy of high-quality PMMA opal crystal

NASA Astrophysics Data System (ADS)

Nemtsev, Ivan V.; Tambasov, Igor A.; Ivanenko, Alexander A.; Zyryanov, Victor Ya.

2018-02-01

PMMA opal crystal was prepared by a simple hybrid method, which includes sedimentation, meniscus formation and evaporation. We investigated three surfaces of this crystal by angle-resolved reflective light spectroscopy and SEM study. The angle-resolved reflective measurements were carried out in the 400-1100 nm range. We have determined the high-quality ordered surface of the crystal region. Narrow particle size distribution of the surface has been revealed. The average particle diameter obtained with SEM was nearly 361 nm. The most interesting result was that reflectivity of the surface turned out up to 98% at normal light incidence. Using a fit of dependences of the maximum reflectivity wavelength from an angle based on the Bragg-Snell law, the wavelength of maximum 0° reflectivity, the particle diameter and the fill factor have been determined. For the best surface maximum reflectivity wavelength of a 0° angle was estimated to be 869 nm. The particle diameter and fill factor were calculated as 372 nm and 0.8715, respectively. The diameter obtained by fitting is in excellent agreement with the particle diameter obtained with SEM. The reflectivity maximum is assumed to increase significantly when increasing the fill factor. We believe that using our simple approach to manufacture PMMA opal crystals will significantly increase the fabrication of high-quality photonic crystal templates and thin films.

Structure investigation of fluorinated aluminophosphate ULM-3 Al templated by 3-methylaminopropylamine

NASA Astrophysics Data System (ADS)

Zabukovec Logar, Natasa; Mali, Gregor; Rajic, Nevenka; Jevtic, Sanja; Rangus, Mojca; Golobic, Amalija; Kaucic, Venceslav

2010-05-01

A single-crystal X-ray diffraction analysis of an open-framework aluminophosphate ULM-3 Al prepared by 3-methylaminopropylamine (MAPA) as structure-directing agent revealed an orthorhombic Pcab symmetry ( a=9.9949(4) Å, b=15.8229(7) Å, c=18.1963(5) Å, R=0.0648, Z=8, unit cell formula [Al 24P 24O 96F 16·C 32H 112N 16]), which differs from the Pbc2 1 symmetry of the structural analogue prepared in the presence of 1,4-diaminobutane. The 27Al, 31P, 19F, 13C and 1H NMR investigations, which were performed to study in detail MAPA arrangement inside the framework as well as the interactions of MAPA with the aluminophosphate host, confirmed the crystal symmetry and the proposed hydrogen bonding scheme between the template and the framework.

Direct monolithic integration of vertical single crystalline octahedral molecular sieve nanowires on silicon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carretero-Genevrier, Adrian; Oro-Sole, Judith; Gazquez, Jaume

2013-12-13

We developed an original strategy to produce vertical epitaxial single crystalline manganese oxide octahedral molecular sieve (OMS) nanowires with tunable pore sizes and compositions on silicon substrates by using a chemical solution deposition approach. The nanowire growth mechanism involves the use of track-etched nanoporous polymer templates combined with the controlled growth of quartz thin films at the silicon surface, which allowed OMS nanowires to stabilize and crystallize. α-quartz thin films were obtained after thermal activated crystallization of the native amorphous silica surface layer assisted by Sr 2+- or Ba 2+-mediated heterogeneous catalysis in the air at 800 °C. These α-quartzmore » thin films work as a selective template for the epitaxial growth of randomly oriented vertical OMS nanowires. Furthermore, the combination of soft chemistry and epitaxial growth opens new opportunities for the effective integration of novel technological functional tunneled complex oxides nanomaterials on Si substrates.« less

Improved prediction of antibody VL–VH orientation

PubMed Central

Marze, Nicholas A.; Lyskov, Sergey; Gray, Jeffrey J.

2016-01-01

Antibodies are important immune molecules with high commercial value and therapeutic interest because of their ability to bind diverse antigens. Computational prediction of antibody structure can quickly reveal valuable information about the nature of these antigen-binding interactions, but only if the models are of sufficient quality. To achieve high model quality during complementarity-determining region (CDR) structural prediction, one must account for the VL–VH orientation. We developed a novel four-metric VL–VH orientation coordinate frame. Additionally, we extended the CDR grafting protocol in RosettaAntibody with a new method that diversifies VL–VH orientation by using 10 VL–VH orientation templates rather than a single one. We tested the multiple-template grafting protocol on two datasets of known antibody crystal structures. During the template-grafting phase, the new protocol improved the fraction of accurate VL–VH orientation predictions from only 26% (12/46) to 72% (33/46) of targets. After the full RosettaAntibody protocol, including CDR H3 remodeling and VL–VH re-orientation, the new protocol produced more candidate structures with accurate VL–VH orientation than the standard protocol in 43/46 targets (93%). The improved ability to predict VL–VH orientation will bolster predictions of other parts of the paratope, including the conformation of CDR H3, a grand challenge of antibody homology modeling. PMID:27276984

Computational study of textured ferroelectric polycrystals: Dielectric and piezoelectric properties of template-matrix composites

NASA Astrophysics Data System (ADS)

Zhou, Jie E.; Yan, Yongke; Priya, Shashank; Wang, Yu U.

2017-01-01

Quantitative relationships between processing, microstructure, and properties in textured ferroelectric polycrystals and the underlying responsible mechanisms are investigated by phase field modeling and computer simulation. This study focuses on three important aspects of textured ferroelectric ceramics: (i) grain microstructure evolution during templated grain growth processing, (ii) crystallographic texture development as a function of volume fraction and seed size of the templates, and (iii) dielectric and piezoelectric properties of the obtained template-matrix composites of textured polycrystals. Findings on the third aspect are presented here, while an accompanying paper of this work reports findings on the first two aspects. In this paper, the competing effects of crystallographic texture and template seed volume fraction on the dielectric and piezoelectric properties of ferroelectric polycrystals are investigated. The phase field model of ferroelectric composites consisting of template seeds embedded in matrix grains is developed to simulate domain evolution, polarization-electric field (P-E), and strain-electric field (ɛ-E) hysteresis loops. The coercive field, remnant polarization, dielectric permittivity, piezoelectric coefficient, and dissipation factor are studied as a function of grain texture and template seed volume fraction. It is found that, while crystallographic texture significantly improves the polycrystal properties towards those of single crystals, a higher volume fraction of template seeds tends to decrease the electromechanical properties, thus canceling the advantage of ferroelectric polycrystals textured by templated grain growth processing. This competing detrimental effect is shown to arise from the composite effect, where the template phase possesses material properties inferior to the matrix phase, causing mechanical clamping and charge accumulation at inter-phase interfaces between matrix and template inclusions. The computational results are compared with complementary experiments, where good agreement is obtained.

Robust fluoroscopic respiratory gating for lung cancer radiotherapy without implanted fiducial markers

NASA Astrophysics Data System (ADS)

Cui, Ying; Dy, Jennifer G.; Sharp, Greg C.; Alexander, Brian; Jiang, Steve B.

2007-02-01

For gated lung cancer radiotherapy, it is difficult to generate accurate gating signals due to the large uncertainties when using external surrogates and the risk of pneumothorax when using implanted fiducial markers. We have previously investigated and demonstrated the feasibility of generating gating signals using the correlation scores between the reference template image and the fluoroscopic images acquired during the treatment. In this paper, we present an in-depth study, aiming at the improvement of robustness of the algorithm and its validation using multiple sets of patient data. Three different template generating and matching methods have been developed and evaluated: (1) single template method, (2) multiple template method, and (3) template clustering method. Using the fluoroscopic data acquired during patient setup before each fraction of treatment, reference templates are built that represent the tumour position and shape in the gating window, which is assumed to be at the end-of-exhale phase. For the single template method, all the setup images within the gating window are averaged to generate a composite template. For the multiple template method, each setup image in the gating window is considered as a reference template and used to generate an ensemble of correlation scores. All the scores are then combined to generate the gating signal. For the template clustering method, clustering (grouping of similar objects together) is performed to reduce the large number of reference templates into a few representative ones. Each of these methods has been evaluated against the reference gating signal as manually determined by a radiation oncologist. Five patient datasets were used for evaluation. In each case, gated treatments were simulated at both 35% and 50% duty cycles. False positive, negative and total error rates were computed. Experiments show that the single template method is sensitive to noise; the multiple template and clustering methods are more robust to noise due to the smoothing effect of aggregation of correlation scores; and the clustering method results in the best performance in terms of computational efficiency and accuracy.

MgO NPs synthesis, capping and enhanced free radical effect on the bacteria and its cell morphology

NASA Astrophysics Data System (ADS)

Kushwaha, Amisha; Bagchi, T.

2018-05-01

Magnesium Oxide Nanoparticles (MgO NPs) commonly known as Magnesia is a white powder, hygroscopic material. MgO NPs were synthesized through four methods Co-precipitation method (Co-PM), Solution combustion (S-CoM) and Sol-gel method with starch (So-GSM) and CTAB (So-GCM), classified as template dependent and template independent method using magnesium nitrate hexahydrate (Mg(NO3).6H2O) as the precursor and comparative analysis was done through DLS. The order of hydrodynamic diameters of four different synthesis method of MgO NPs is Co-PM LA-MgO NPs> MgO NPs responding.

Supercritical-assistant liquid crystal template approach to synthesize mesoporous titania/multiwalled carbon nanotube composites with high visible-light driven photocatalytic performance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Chen; Li, Youji, E-mail: bcclyj@163.com; Xu, Peng

2014-12-15

Graphical abstract: We investigate the influence of mesoporous titania content upon the visible-light driven photocatalytic performance of MPT/MWCNTs in phenol degradation. - Highlights: • MPT/MWCNTs were fabricated by liquid-crystal template in supercritical CO{sub 2}. • MPT/MWCNTs show high visible-light driven photoactivity for phenol degradation. • MPT/MWCNTs also show high reusable photoactivity under visible irradiation. • MPT content can control visible-light driven photoactivity of MPT/MWCNTs. • MPT is not easily broken away from from MPT/MWCNT composites. - Abstract: Mesoporous titania (MPT) was deposited onto multiwalled carbon nanotubes (MWCNTs) by deposition of titanium sol containing liquid-crystal template with assistant of supercritical CO{submore » 2}. The products were characterized with various analytical techniques to determine their structural, morphological, optical absorption and photocatalytic properties. The results indicate that in photocatalytic degradation of phenol under visible light, the mixtures or composites of MPT and MWCNT show the high efficiency because of synergies between absorbing visible light, releasing electrons and facilitating transfer of charge carriers of MWCNTs and providing activated centers of MPT. Because of the mutual constraint between MPT and MWCNTs on the photocatalytic efficiency, the optimal loading of MPT in MPT/MWCNT-3 for phenol degradation is 48%. Because the intimate contact between MWCNTs and MPT is more beneficial to electron transformation, photoactivity of mixture is lower than that of composites with high reusable performance. The optimum conditions of phenol degradation were obtained.« less

Radio-nuclide mixture identification using medium energy resolution detectors

DOEpatents

Nelson, Karl Einar

2013-09-17

According to one embodiment, a method for identifying radio-nuclides includes receiving spectral data, extracting a feature set from the spectral data comparable to a plurality of templates in a template library, and using a branch and bound method to determine a probable template match based on the feature set and templates in the template library. In another embodiment, a device for identifying unknown radio-nuclides includes a processor, a multi-channel analyzer, and a memory operatively coupled to the processor, the memory having computer readable code stored thereon. The computer readable code is configured, when executed by the processor, to receive spectral data, to extract a feature set from the spectral data comparable to a plurality of templates in a template library, and to use a branch and bound method to determine a probable template match based on the feature set and templates in the template library.

Zn(II)-PEG 300 globules as soft template for the synthesis of hexagonal ZnO micronuts by the hydrothermal reaction method.

PubMed

Shi, Xixi; Pan, Lingling; Chen, Shuoping; Xiao, Yong; Liu, Qiaoyun; Yuan, Liangjie; Sun, Jutang; Cai, Lintao

2009-05-19

Hexagonal ZnO micronuts (HZMNs) have been successfully synthesized with the assistance of poly(ethylene glycol) (PEG) 300 via a hydrothermal method. The structure and morphology of the HZMNs were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and selected area electron diffraction (SAED). An individual ZnO micronut is revealed as twinned crystals. Time-dependent investigation shows that the growth of HZMNs involves a dissolution-recrystallization process followed by Ostwald ripening, in which is the first formed solid ZnO particles dissolve and transform to HZMNs with hollow structure. PEG 300 has been found to play a crucial role in the growth of this unique hollow structure. TEM observations show that the PEG chains aggregate to globules in water, which then have interaction with the dissolved zinc species to form the globules in a coiled state under hydrothermal conditions. These Zn(II)-PEG 300 globules act as soft template for the growth of HZMNs, and the possible growth mechanism is proposed. The room-temperature photoluminescence (PL) spectrum shows red emission around 612 nm with a full width at half-maximum (fwhm) only about 13 nm.

Hierarchical Metal–Organic Framework Hybrids: Perturbation-Assisted Nanofusion Synthesis

DOE PAGES

Yue, Yanfeng; Fulvio, Pasquale F.; Dai, Sheng

2015-12-04

Metal–organic frameworks (MOFs) represent a new family of microporous materials; however, microporous–mesoporous hierarchical MOF materials have been less investigated because of the lack of simple, reliable methods to introduce mesopores to the crystalline microporous particles. State-of-the-art MOF hierarchical materials have been prepared by ligand extension methods or by using a template, resulting in intrinsic mesopores of longer ligands or replicated pores from template agents, respectively. However, mesoporous MOF materials obtained through ligand extension often collapse in the absence of guest molecules, which dramatically reduces the size of the pore aperture. Although the template-directed strategy allows for the preparation of hierarchicalmore » materials with larger mesopores, the latter requires a template removal step, which may result in the collapse of the implemented mesopores. Recently, a general template-free synthesis of hierarchical microporous crystalline frameworks, such as MOFs and Prussian blue analogues (PBAs), has been reported. Our new method is based on the kinetically controlled precipitation (perturbation), with simultaneous condensation and redissolution of polymorphic nanocrystallites in the mother liquor. This method further eliminates the use of extended organic ligands and the micropores do not collapse upon removal of trapped guest solvent molecules, thus yielding hierarchical MOF materials with intriguing porosity in the gram scale. The hierarchical MOF materials prepared in this way exhibited exceptional properties when tested for the adsorption of large organic dyes over their corresponding microporous frameworks, due to the enhanced pore accessibility and electrolyte diffusion within the mesopores. As for PBAs, the pore size distribution of these materials can be tailored by changing the metals substituting Fe cations in the PB lattice. For these, the textural mesopores increased from approximately 10 nm for Cu analogue (mesoCuHCF), to 16 nm in Co substituted compound (mesoCoHCF), and to as large as 30 nm for the Ni derivative (mesoNiHCF). And while bulk PB and analogues have a higher capacitance than hierarchical analogues for Na-batteries, the increased accessibility to the microporous channels of PBAs allow for faster intercalated ion exchange and diffusion than in bulk PBA crystals. Therefore, hierarchical PBAs are promising candidates for electrodes in future electrochemical energy storage devices with faster charge–discharge rates than batteries, namely pseudocapacitors. Finally, this new synthetic method opens the possibility to prepare hierarchical materials having bimodal distribution of mesopores, and to tailor the structural properties of MOFs for different applications, including contrasting agents for MRI, and drug delivery.« less

Multi-template tensor-based morphometry: Application to analysis of Alzheimer's disease

PubMed Central

Koikkalainen, Juha; Lötjönen, Jyrki; Thurfjell, Lennart; Rueckert, Daniel; Waldemar, Gunhild; Soininen, Hilkka

2012-01-01

In this paper methods for using multiple templates in tensor-based morphometry (TBM) are presented and comparedtothe conventional single-template approach. TBM analysis requires non-rigid registrations which are often subject to registration errors. When using multiple templates and, therefore, multiple registrations, it can be assumed that the registration errors are averaged and eventually compensated. Four different methods are proposed for multi-template TBM. The methods were evaluated using magnetic resonance (MR) images of healthy controls, patients with stable or progressive mild cognitive impairment (MCI), and patients with Alzheimer's disease (AD) from the ADNI database (N=772). The performance of TBM features in classifying images was evaluated both quantitatively and qualitatively. Classification results show that the multi-template methods are statistically significantly better than the single-template method. The overall classification accuracy was 86.0% for the classification of control and AD subjects, and 72.1%for the classification of stable and progressive MCI subjects. The statistical group-level difference maps produced using multi-template TBM were smoother, formed larger continuous regions, and had larger t-values than the maps obtained with single-template TBM. PMID:21419228

Improving the efficiency of molecular replacement by utilizing a new iterative transform phasing algorithm

DOE Office of Scientific and Technical Information (OSTI.GOV)

He, Hongxing; Fang, Hengrui; Miller, Mitchell D.

2016-07-15

An iterative transform algorithm is proposed to improve the conventional molecular-replacement method for solving the phase problem in X-ray crystallography. Several examples of successful trial calculations carried out with real diffraction data are presented. An iterative transform method proposed previously for direct phasing of high-solvent-content protein crystals is employed for enhancing the molecular-replacement (MR) algorithm in protein crystallography. Target structures that are resistant to conventional MR due to insufficient similarity between the template and target structures might be tractable with this modified phasing method. Trial calculations involving three different structures are described to test and illustrate the methodology. The relationshipmore » of the approach to PHENIX Phaser-MR and MR-Rosetta is discussed.« less

Reducing the number of templates for aligned-spin compact binary coalescence gravitational wave searches using metric-agnostic template nudging

NASA Astrophysics Data System (ADS)

Indik, Nathaniel; Fehrmann, Henning; Harke, Franz; Krishnan, Badri; Nielsen, Alex B.

2018-06-01

Efficient multidimensional template placement is crucial in computationally intensive matched-filtering searches for gravitational waves (GWs). Here, we implement the neighboring cell algorithm (NCA) to improve the detection volume of an existing compact binary coalescence (CBC) template bank. This algorithm has already been successfully applied for a binary millisecond pulsar search in data from the Fermi satellite. It repositions templates from overdense regions to underdense regions and reduces the number of templates that would have been required by a stochastic method to achieve the same detection volume. Our method is readily generalizable to other CBC parameter spaces. Here we apply this method to the aligned-single-spin neutron star-black hole binary coalescence inspiral-merger-ringdown gravitational wave parameter space. We show that the template nudging algorithm can attain the equivalent effectualness of the stochastic method with 12% fewer templates.

Development of textured magnesium oxide templates and bicrystals using ion beam assisted deposition

NASA Astrophysics Data System (ADS)

Vallejo, Ronald N.

Recently, there has been an increased research effort in the deposition of near-single-crystal thin films on substrates that do not provide a template for epitaxial crystalline film growth. Ion beam assisted deposition (IBAD) has been demonstrated as one of the most promising methods to artificially control the texture in thin films. Biaxially textured MgO templates of 10 nm thickness were successfully fabricated on glass and silicon substrates without any buffer layers using IBAD. This work has shed insights on several issues. First, surface morphology ˜ 1 nm or better is only a necessary condition for textured IBAD-MgO, but not a sufficient condition. Additional surface preparation must be provided for nucleation and subsequent formation of the textured IBAD-MgO templates. Second, the role of buffer layer on IBAD-MgO texturing. It was found that the ion beam pre-exposure of the substrates prior to IBAD processing provided a sufficient condition for the nucleation and subsequent texture formation of the IBAD grown films. The ion pre-exposure replaced the need for buffer layers in silicon and glass substrates. Finally, by pre-exposing the substrates to Ar + ions, it was found that the ion beam modified the surface and improved the surface roughness of the glass substrates. Textured MgO epi templates were demonstrated for the first time on polymer based substrates (polyimide). This is a crucial step in the realization of epitaxial suspended devices. To achieve an epitaxial film on a sacrificial layer, an epitaxial template film must first be grown prior to subsequent film growth. The role of ion pre-exposure and buffer layer on texture formation was investigated in this part of the work. This thesis also presents groundbreaking results on the fabrication of bicrystal MgO films and bicrystal networks using ion beam assisted deposition. Highly oriented bicrystals, with a common (100) out-of-plane orientation and (110) in-plane orientations having a tilt angle of 45° and 20° have been successfully fabricated. This method has also been used to fabricate two dimensional bicrystal MgO networks in the micrometer scale. The same strategy can be applied to generate nanometer scale bicrystal networks of desired patterns.

Functional materials from cellulose-derived liquid-crystal templates.

PubMed

Giese, Michael; Blusch, Lina K; Khan, Mostofa K; MacLachlan, Mark J

2015-03-02

Cellulose nanocrystals (CNCs), known for more than 50 years, have attracted attention because of their unique properties such as high specific strength and modulus, high surface area, and fascinating optical properties. Just recently, however, their potential in supramolecular templating was identified by making use of their self-assembly behavior in aqueous dispersions in the presence of compatible precursors. The combination of the mesoporosity, photonic properties, and chiral nematic order of the materials, which are available as freestanding films, has led to a significant number of interesting and promising discoveries towards new functional materials. This Review summarizes the use of cellulose derivatives, especially CNCs, as novel templates and gives an overview of the recent developments toward new functional materials. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Viral assembly of oriented quantum dot nanowires

NASA Astrophysics Data System (ADS)

Mao, Chuanbin; Flynn, Christine E.; Hayhurst, Andrew; Sweeney, Rozamond; Qi, Jifa; Georgiou, George; Iverson, Brent; Belcher, Angela M.

2003-06-01

The highly organized structure of M13 bacteriophage was used as an evolved biological template for the nucleation and orientation of semiconductor nanowires. To create this organized template, peptides were selected by using a pIII phage display library for their ability to nucleate ZnS or CdS nanocrystals. The successful peptides were expressed as pVIII fusion proteins into the crystalline capsid of the virus. The engineered viruses were exposed to semiconductor precursor solutions, and the resultant nanocrystals that were templated along the viruses to form nanowires were extensively characterized by using high-resolution analytical electron microscopy and photoluminescence. ZnS nanocrystals were well crystallized on the viral capsid in a hexagonal wurtzite or a cubic zinc blende structure, depending on the peptide expressed on the viral capsid. Electron diffraction patterns showed single-crystal type behavior from a polynanocrystalline area of the nanowire formed, suggesting that the nanocrystals on the virus were preferentially oriented with their [001] perpendicular to the viral surface. Peptides that specifically directed CdS nanocrystal growth were also engineered into the viral capsid to create wurtzite CdS virus-based nanowires. Lastly, heterostructured nucleation was achieved with a dual-peptide virus engineered to express two distinct peptides within the same viral capsid. This work represents a genetically controlled biological synthesis route to a semiconductor nanoscale heterostructure.

Synthesis of functional ceramic supports by ice templating and atomic layer deposition

NASA Astrophysics Data System (ADS)

Klotz, Michaela; Weber, Matthieu; Deville, Sylvain; Oison, Didier; Iatsunskyi, Igor; Coy, Emerson; Bechelany, Mikhael

2018-05-01

In this work, we report an innovative route for the manufacturing of functional ceramic supports, by combining ice templating of yttria stabilized zirconia (YSZ) and atomic layer deposition (ALD) of Al2O3 processes. Ceramic YSZ monoliths are prepared using the ice-templating process, which is based on the controlled crystallization of water following a thermal gradient. Sublimation of the ice and the sintering of the material reveal the straight micrometer sized pores shaped by the ice crystal growth. The high temperature sintering allows for the ceramic materials to present excellent mechanical strength and porosities of 67%. Next, the conformality benefit of ALD is used to deposit an alumina coating at the surface of the YSZ pores, in order to obtain a functional material. The Al2O3 thin films obtained by ALD are 100 nm thick and conformally deposited within the macroporous ceramic supports, as shown by SEM and EDS analysis. Mercury intrusion experiments revealed a reduction of the entrance pore diameter, in line with the growth per cycle of 2 Å of the ALD process. In addition to the manufacture of the innovative ceramic nanomaterials, this article also describes the fine characterization of the coatings obtained using mercury intrusion, SEM and XRD analysis.

Viral assembly of oriented quantum dot nanowires.

PubMed

Mao, Chuanbin; Flynn, Christine E; Hayhurst, Andrew; Sweeney, Rozamond; Qi, Jifa; Georgiou, George; Iverson, Brent; Belcher, Angela M

2003-06-10

The highly organized structure of M13 bacteriophage was used as an evolved biological template for the nucleation and orientation of semiconductor nanowires. To create this organized template, peptides were selected by using a pIII phage display library for their ability to nucleate ZnS or CdS nanocrystals. The successful peptides were expressed as pVIII fusion proteins into the crystalline capsid of the virus. The engineered viruses were exposed to semiconductor precursor solutions, and the resultant nanocrystals that were templated along the viruses to form nanowires were extensively characterized by using high-resolution analytical electron microscopy and photoluminescence. ZnS nanocrystals were well crystallized on the viral capsid in a hexagonal wurtzite or a cubic zinc blende structure, depending on the peptide expressed on the viral capsid. Electron diffraction patterns showed single-crystal type behavior from a polynanocrystalline area of the nanowire formed, suggesting that the nanocrystals on the virus were preferentially oriented with their [001] perpendicular to the viral surface. Peptides that specifically directed CdS nanocrystal growth were also engineered into the viral capsid to create wurtzite CdS virus-based nanowires. Lastly, heterostructured nucleation was achieved with a dual-peptide virus engineered to express two distinct peptides within the same viral capsid. This work represents a genetically controlled biological synthesis route to a semiconductor nanoscale heterostructure.

A new photoactive Ru(II)tris(2,2'-bipyridine) templated Zn(II) benzene-1,4-dicarboxylate metal organic framework: structure and photophysical properties.

PubMed

Whittington, Christi L; Wojtas, Lukasz; Gao, Wen-Yang; Ma, Shengqian; Larsen, Randy W

2015-03-28

It has now been demonstrated that Ru(ii)tris(2,2'-bipyridine) (RuBpy) can be utilized to template the formation of new metal organic framework (MOF) materials containing crystallographically resolved RuBpy clusters with unique photophysical properties. Two such materials, RWLC-1 and RWLC-2, have now been reported from our laboratory and are composed of RuBpy encapsulated in MOFs composed of Zn(ii) ions and 1,3,5-tris(4-carboxyphenyl)benzene ligands (C. L. Whittington, L. Wojtas and R. W. Larsen, Inorg. Chem., 2014, 53, 160-166). Here, a third RuBpy templated photoactive MOF is described (RWLC-3) that is derived from the reaction between Zn(ii) ions and 1,4-dicarboxybenzene in the presence of RuBpy. Single Crystal X-ray diffraction studies determined the position of RuBpy cations within the crystal lattice. The RWLC-3 structure is described as a 2-fold interpenetrated pillared honeycomb network (bnb) containing crystallographically resolved RuBpy clusters. The two bnb networks are weakly interconnected. The encapsulated RuBpy exhibits two emission decay lifetimes (τ-fast = 120 ns, τ-slow = 453 ns) and a bathochromic shift in the steady state emission spectrum relative to RuBpy in ethanol.

Comparison of the properties of tonpilz transducers fabricated with 001 fiber-textured lead magnesium niobate-lead titanate ceramic and single crystals.

PubMed

Brosnan, Kristen H; Messing, Gary L; Markley, Douglas C; Meyer, Richard J

2009-11-01

Tonpilz transducers are fabricated from 001 fiber-textured 0.72Pb(Mg(1/3)Nb(2/3))O(3)-0.28PbTiO(3) (PMN-28PT) ceramics, obtained by the templated grain growth process, and PMN-28PT ceramic and Bridgman grown single crystals of the same composition. In-water characterization of single element transducers shows higher source levels, higher in-water coupling, and more usable bandwidth for the 81 vol % textured PMN-28PT device than for the ceramic PMN-28PT element. The 81 vol % textured PMN-28PT tonpilz element measured under large signals shows linearity in sound pressure levels up to 0.23 MV/m drive field but undergoes a phase transition due to a lowered transition temperature from the SrTiO(3) template particles. Although the textured ceramic performs well in this application, it could be further improved with compositional tailoring to raise the transition temperature and better processing to improve the texture quality. With these improvements textured piezoelectric ceramics will be viable options for medical ultrasound, actuators, and sonar applications because of their ease of processing, compositional homogeneity, and potentially lower cost than single crystal.

(C6N2H16)[Co(H2O)6](SO4)2.2H2O: A new hybrid material based on sulfate templated by diprotonated trans-1,4-diaminocyclohexane

NASA Astrophysics Data System (ADS)

Hamdi, N.; Ngopoh, F. A. I.; da Silva, I.; El Bali, B.; Lachkar, M.

2018-03-01

Employing trans-1,4-diaminocyclohexane (DACH) as template, the new hybrid sulphate (C6N2H16)[Co(H2O)6](SO4)2.2H2O was prepared in solution. Single-crystal X-ray diffraction analysis shows that it crystallizes in the monoclinic system (S.G.: P 21/n), with the following unit-cell parameters (Å,°): a = 6.2897(2), b = 12.3716(6), c = 13.1996(4), β = 98.091(3) V = 1016.89(7) Å3, Z = 4. Its 3D crystal structure is made upon isolated [Co(H2O)6] octahedra, regular [SO4] tetrahedra, protonated DACH and free H2O molecules, which interact through N-H···O and O-H···O hydrogen bonds. The Fourier transform infrared result exhibits bands corresponding to the vibrations of DACH, sulfate group and water molecules. The thermal decomposition of the phase consists mainly in the loss of the organic moiety and one sulfate group, leading thus to the formation of anhydrous cobalt sulfate.

Visual cluster analysis and pattern recognition template and methods

DOEpatents

Osbourn, Gordon Cecil; Martinez, Rubel Francisco

1999-01-01

A method of clustering using a novel template to define a region of influence. Using neighboring approximation methods, computation times can be significantly reduced. The template and method are applicable and improve pattern recognition techniques.

Targeting Neuroblastoma Cell Surface Proteins: Recommendations for Homology Modeling of hNET, ALK, and TrkB.

PubMed

Haddad, Yazan; Heger, Zbyněk; Adam, Vojtech

2017-01-01

Targeted therapy is a promising approach for treatment of neuroblastoma as evident from the large number of targeting agents employed in clinical practice today. In the absence of known crystal structures, researchers rely on homology modeling to construct template-based theoretical structures for drug design and testing. Here, we discuss three candidate cell surface proteins that are suitable for homology modeling: human norepinephrine transporter (hNET), anaplastic lymphoma kinase (ALK), and neurotrophic tyrosine kinase receptor 2 (NTRK2 or TrkB). When choosing templates, both sequence identity and structure quality are important for homology modeling and pose the first of many challenges in the modeling process. Homology modeling of hNET can be improved using template models of dopamine and serotonin transporters instead of the leucine transporter (LeuT). The extracellular domains of ALK and TrkB are yet to be exploited by homology modeling. There are several idiosyncrasies that require direct attention throughout the process of model construction, evaluation and refinement. Shifts/gaps in the alignment between the template and target, backbone outliers and side-chain rotamer outliers are among the main sources of physical errors in the structures. Low-conserved regions can be refined with loop modeling method. Residue hydrophobicity, accessibility to bound metals or glycosylation can aid in model refinement. We recommend resolving these idiosyncrasies as part of "good modeling practice" to obtain highest quality model. Decreasing physical errors in protein structures plays major role in the development of targeting agents and understanding of chemical interactions at the molecular level.

Mineral-Templated 3D Graphene Architectures for Energy-Efficient Electrodes.

PubMed

Zhang, Mingchao; Chen, Ke; Wang, Chunya; Jian, Muqiang; Yin, Zhe; Liu, Zhenglian; Hong, Guo; Liu, Zhongfan; Zhang, Yingying

2018-05-01

3D graphene networks have shown extraordinary promise for high-performance electrochemical devices. Herein, the chemical vapor deposition synthesis of a highly porous 3D graphene foam (3D-GF) using naturally abundant calcined Iceland crystal as the template is reported. Intriguingly, the Iceland crystal transforms to CaO monolith with evenly distributed micro/meso/macropores through the releasing of CO 2 at high temperature. Meanwhile, the hierarchical structure of the calcined template could be easily tuned under different calcination conditions. By precisely inheriting fine structure from the templates, the as-prepared 3D-GF possesses a tunable hierarchical porosity and low density. Thus, the hierarchical pores offer space for guest hybridization and provide an efficient pathway for ion/charge transport in typical energy conversion/storage systems. The 3D-GF skeleton electrode hybridized with Ni(OH) 2 /Co(OH) 2 through an optimal electrodeposition condition exhibits a high specific capacitance of 2922.2 F g -1 at a scan rate of 10 mV s -1 , and 2138.4 F g -1 at a discharge current density of 3.1 A g -1 . The hybrid 3D-GF symmetry supercapacitor shows a high energy density of 83.0 Wh kg -1 at a power density of 1011.3 W kg -1 and 31.4 Wh kg -1 at a high power density of 18 845.2 W kg -1 . The facile fabrication process enables the mass production of hierarchical porous 3D-GF for high-performance supercapacitors. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis of mesoporous SAPO-34 molecular sieves and their applications in dehydration of butanols and ethanol.

PubMed

Jun, Jong Won; Jeon, Jaewoo; Kim, Chul-Ung; Jeong, Kwang-Eun; Jeong, Soon-Yong; Jhung, Sung Hwa

2013-04-01

Microporous SAPO-34 molecular sieves were hydrothermally synthesized with microwave irradiation in the presence of tetraethylammonium hydroxide (TEAOH) as a template. SAPO-34 molecular sieves with mesoporosity were also prepared in the presence of carbon black as a hard template. By increasing the content of the carbon black template in the synthesis, the mesopore volume increased. Dehydration of alcohols (butanols and ethanol) was carried out with the synthesized SAPO-34 molecular sieves, and the lifetime of the catalysts for the dehydration reaction increased as the mesoporosity increased. Moreover, the performance of the microporous catalyst synthesized with microwave was better than that of the catalyst obtained with conventional electric heating. The relative performance of the catalytic dehydration may be explained by the mesoporosity and the crystal size. Therefore, it may be concluded that small-sized SAPO-34 molecular sieves with high mesoporosity can be produced efficiently with microwave irradiation in the presence of carbon black template, and the molecular sieves are effective in the stable dehydration of alcohols.

AlGaN/GaN high electron mobility transistor grown on GaN template substrate by molecule beam epitaxy system

NASA Astrophysics Data System (ADS)

Tsai, Jenn-Kai; Chen, Y. L.; Gau, M. H.; Pang, W. Y.; Hsu, Y. C.; Lo, Ikai; Hsieh, C. H.

2008-03-01

In this study, AlGaN/GaN high electron mobility transistor (HEMT) structure was grow on GaN template substrate radio frequency plasma assisted molecular beam epitaxy (MBE) equipped with an EPI UNI-Bulb nitrogen plasma source. The undoped GaN template substrate was grown on c-sapphire substrate by metal organic vapor phase epitaxy system (MOPVD). After growth of MOVPE and MBE, the samples are characterized by double crystal X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (SEM), atomic force microscopy (AFM), and Hall effect measurements. We found that the RMS roughness of template substrate play the major role in got the high value of mobility on AlGaN/GaN HEMT. When the roughness was lower than 0.77 nm in a 25 μm x 25 μm area, the mobility of HEMT at the temperature of 77 K was over 10000 cm^2/Vs.

Semi-polar (11-22) AlGaN on overgrown GaN on micro-rod templates: Simultaneous management of crystal quality improvement and cracking issue

NASA Astrophysics Data System (ADS)

Li, Z.; Jiu, L.; Gong, Y.; Wang, L.; Zhang, Y.; Bai, J.; Wang, T.

2017-02-01

Thick and crack-free semi-polar (11-22) AlGaN layers with various high Al compositions have been achieved by means of growth on the top of nearly but not yet fully coalesced GaN overgrown on micro-rod templates. The range of the Al composition of up to 55.7% was achieved, corresponding to an emission wavelength of up to 270 nm characterised by photoluminescence at room temperature. X-ray diffraction (XRD) measurements show greatly improved crystal quality as a result of lateral overgrowth compared to the AlGaN counterparts on standard planar substrates. The full width at half maximums of the XRD rocking curves measured along the [1-100]/[11-2-3] directions (the two typical orientations for characterizing the crystal quality of (11-22) AlGaN) are 0.2923°/0.2006° for 37.8% Al and 0.3825°/0.2064° for 55.7% Al, respectively, which have never been achieved previously. Our calculation based on reciprocal space mapping measurements has demonstrated significant strain relaxation in the AlGaN as a result of utilising the non-coalesced GaN underneath, contributing to the elimination of any cracks. The results presented have demonstrated that our overgrowth technique can effectively manage strain and improve crystal quality simultaneously.

Crystal Structure Prediction via Deep Learning.

PubMed

Ryan, Kevin; Lengyel, Jeff; Shatruk, Michael

2018-06-06

We demonstrate the application of deep neural networks as a machine-learning tool for the analysis of a large collection of crystallographic data contained in the crystal structure repositories. Using input data in the form of multi-perspective atomic fingerprints, which describe coordination topology around unique crystallographic sites, we show that the neural-network model can be trained to effectively distinguish chemical elements based on the topology of their crystallographic environment. The model also identifies structurally similar atomic sites in the entire dataset of ~50000 crystal structures, essentially uncovering trends that reflect the periodic table of elements. The trained model was used to analyze templates derived from the known binary and ternary crystal structures in order to predict the likelihood to form new compounds that could be generated by placing elements into these structural templates in combinatorial fashion. Statistical analysis of predictive performance of the neural-network model, which was applied to a test set of structures never seen by the model during training, indicates its ability to predict known elemental compositions with a high likelihood of success. In ~30% of cases, the known compositions were found among top-10 most likely candidates proposed by the model. These results suggest that the approach developed in this work can be used to effectively guide the synthetic efforts in the discovery of new materials, especially in the case of systems composed of 3 or more chemical elements.

Synthesis, structure and research on quasi-aromaticity of a new organically templated aluminoborate: [NH0.5C4H4NH0.5][AlB12O14(OH)12

NASA Astrophysics Data System (ADS)

Hu, HengBin; Chen, XiangYi; Deng, Song; Cai, Feng; Sun, YanQiong; Chen, YiPing

2012-02-01

By employing hydrothermal method, we identify a new organically templated aluminoborate [NH0.5C4H4NH0.5][AlB12O14(OH)12] which is structurally determined by single crystal X-ray diffraction and characterized by simulated and experimental IR, 2D IR COS (two-dimensional infrared correlation spectroscopy), NICS (nucleus-independent chemical shifts) and Mulliken charges calculations. Although the cluster anions [AlB12O14(OH)12]- is identical to the counterpart of compound reported by Lin et al. at 2008, we firstly bring up its quasi-aromaticity, discuss and confirm it by NICS, Mulliken charges calculations and magnetic-induced 2D IR COS, and conclude that three isolated and non-coplanar four-center six-electron π bonds of cluster could cooperate and interact with each other to form a closed conjugated large π orbital system, endowing the cluster anions with quasi-aromaticity. Thus, a one-dimensional chain is constructed by π-π stacked interaction between quasi-aromatic clusters and aromatic pyrazine along [1 0¯ 1] direction. The title compound crystallizes in monoclinic space group C2/c with a = 18.397(4), b = 12.0670(16), c = 11.075(2) Å, α = 90.00, β = 116.483(11), γ = 90.00°, Z = 4, V = 2200.6(7) Å, R = 0.0442 and wR = 0.1128 for 2689 observed reflections.

Soft-template construction of three-dimensionally ordered inverse opal structure from Li2FeSiO4/C composite nanofibers for high-rate lithium-ion batteries

NASA Astrophysics Data System (ADS)

Li, Donglin; Zhang, Wei; Sun, Ru; Yong, Hong-Tuan-Hua; Chen, Guangqi; Fan, Xiaoyong; Gou, Lei; Mao, Yiyang; Zhao, Kun; Tian, Miao

2016-06-01

Exploring a new method to fabricate small-sized nanofibers is essential to achieve superior performances for energy conversion and storage devices. Here, a novel soft-template strategy is developed to synthesize a three-dimensionally ordered macroporous (3DOM) architecture constructed from small-sized nanofibers. The effectiveness of a nanofiber-assembled three-dimensional inverse opal material as an electrode for high-rate lithium-ion batteries is demonstrated. The small-sized Li2FeSiO4/C composite nanofibers with a diameter of 20-30 nm are grown by employing a tri-block copolymer P123 as a structure directing agent. Accordingly, the macro-mesoporous hierarchical 3DOM architecture constructed from Li2FeSiO4/C nanofibers is further templated from P123 for the nanofibers and a polystyrene colloidal crystal array for the 3DOM architecture. We find that the thermal stability of the nanofiber morphology depends on the self-limited growth of Li2FeSiO4 nanocrystals in a crystalline-amorphous hybrid. As a cathode for a lithium-ion battery, the 3D hierarchical macro-mesoporous cathodes exhibit outstanding high-rate and ultralong-life performances with a capacity retention of 84% after 1500 cycles at 5 C in the voltage window of 1.5-4.5 V, which is greatly improved compared with a simple 3DOM Li2FeSiO4/C nanocomposite.Exploring a new method to fabricate small-sized nanofibers is essential to achieve superior performances for energy conversion and storage devices. Here, a novel soft-template strategy is developed to synthesize a three-dimensionally ordered macroporous (3DOM) architecture constructed from small-sized nanofibers. The effectiveness of a nanofiber-assembled three-dimensional inverse opal material as an electrode for high-rate lithium-ion batteries is demonstrated. The small-sized Li2FeSiO4/C composite nanofibers with a diameter of 20-30 nm are grown by employing a tri-block copolymer P123 as a structure directing agent. Accordingly, the macro-mesoporous hierarchical 3DOM architecture constructed from Li2FeSiO4/C nanofibers is further templated from P123 for the nanofibers and a polystyrene colloidal crystal array for the 3DOM architecture. We find that the thermal stability of the nanofiber morphology depends on the self-limited growth of Li2FeSiO4 nanocrystals in a crystalline-amorphous hybrid. As a cathode for a lithium-ion battery, the 3D hierarchical macro-mesoporous cathodes exhibit outstanding high-rate and ultralong-life performances with a capacity retention of 84% after 1500 cycles at 5 C in the voltage window of 1.5-4.5 V, which is greatly improved compared with a simple 3DOM Li2FeSiO4/C nanocomposite. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr07783d

Visual cluster analysis and pattern recognition template and methods

DOEpatents

Osbourn, G.C.; Martinez, R.F.

1999-05-04

A method of clustering using a novel template to define a region of influence is disclosed. Using neighboring approximation methods, computation times can be significantly reduced. The template and method are applicable and improve pattern recognition techniques. 30 figs.

Methanol conversion to light olefins over nanostructured CeAPSO-34 catalyst: Thermodynamic analysis of overall reactions and effect of template type on catalytic properties and performance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aghamohammadi, Sogand; Reactor and Catalysis Research Center; Haghighi, Mohammad, E-mail: haghighi@sut.ac.ir

2014-02-01

Graphical abstract: In this research nanostructured CeAPSO-34 was synthesized to explore the effect of TEAOH and morpholine on its physiochemical properties and MTO performance. Prepared catalysts were characterized with XRD, FESEM, BET, FTIR and NH3-TPD techniques. The results indicated that the nature of the template determines the physiochemical properties of CeAPSO-34 due to different rate of crystal growth. The catalyst obtained by using morpholine showed longer life time as well as sustaining light olefins selectivity at higher values. Furthermore, a comprehensive thermodynamic analysis of overall reactions network was carried out to address the major channels of methanol to olefins conversion.more » - Highlights: • Introduction of Ce into SAPO-34 framework. • Comparison of CeAPSO-34 synthesized using morpholine and TEAOH. • The nature of the template determines the physiochemical properties of CeAPSO-34. • Morpholine enhances catalyst lifetime in MTO process. • Presenting a complete reaction network for MTO process. - Abstract: TEAOH and morpholine were employed in synthesis of nanostructured CeAPSO-34 molecular sieve and used in methanol to olefins conversion. Prepared samples were characterized by XRD, FESEM, EDX, BET, FTIR and NH{sub 3}-TPD techniques. XRD patterns reflected the higher crystallinity of the catalyst synthesized with morpholine. The FESEM results indicated that the nature of the template determines the morphology of nanostructured CeAPSO-34 due to different rate of crystal growth. There was a meaningful difference in the strength of both strong and weak acid sites for CeAPSO-34 catalysts synthesized with TEAOH and morpholine templates. The catalyst synthesized with morpholine showed higher desorption temperature of both weak and strong acid sites evidenced by NH{sub 3}-TPD characterization. The catalyst obtained using morpholine template had the longer lifetime and sustained desired light olefins at higher values. A comprehensive thermodynamic analysis of overall reactions network was carried out to address the major channels of methanol to olefins conversion.« less

Processing of Nanosensors Using a Sacrificial Template Approach

NASA Technical Reports Server (NTRS)

Biaggi-Labiosa, Azlin M.; Hunter, Gary W.

2012-01-01

A new microsensor fabrication approach has been demonstrated based upon the use of nanostructures as templates. The fundamental idea is that existing nanostructures, such as carbon nano tubes or biological structures, have a material structure that can be used advantageously in order to provide new sensor systems but lack the advantages of some materials to, for example, operate at high temperatures. The approach is to start with a template using nanostructures such as a carbon nanotube. This template can then be coated by an oxide material with higher temperature capabilities. Upon heating in air, the carbon nanotube template is burned off, leaving only the metal oxide nanostructure. The resulting structure has a combination of the crystal structure and surface morphology of the carbon nanotube, combined with the material durability and hightemperature- sensing properties of the metal oxide. Further, since the metal oxide nanocrystals are deposited on the carbon nanotube, after burn-off what is left is a metal oxide porous nanostructure. This makes both the interior and the exterior of this nano structured sensor available for gas species detection. This, in effect, increases the surface area available for sensing, which has been shown in the past to significantly increase sensor performance.

X-ray Crystal Structure of Aristolochene Synthase from Aspergillus terreus and Evolution of Templates for the Cyclization of Farnesyl Diphosphate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shishova,E.; Di Costanzo, L.; Cane, D.

2007-01-01

Aristolochene synthase from Aspergillus terreus catalyzes the cyclization of the universal sesquiterpene precursor, farnesyl diphosphate, to form the bicyclic hydrocarbon aristolochene. The 2.2 {angstrom} resolution X-ray crystal structure of aristolochene synthase reveals a tetrameric quaternary structure in which each subunit adopts the {alpha}-helical class I terpene synthase fold with the active site in the 'open', solvent-exposed conformation. Intriguingly, the 2.15 {angstrom} resolution crystal structure of the complex with Mg{sup 2+}{sub 3}-pyrophosphate reveals ligand binding only to tetramer subunit D, which is stabilized in the 'closed' conformation required for catalysis. Tetramer assembly may hinder conformational changes required for the transition frommore » the inactive open conformation to the active closed conformation, thereby accounting for the attenuation of catalytic activity with an increase in enzyme concentration. In both conformations, but especially in the closed conformation, the active site contour is highly complementary in shape to that of aristolochene, and a catalytic function is proposed for the pyrophosphate anion based on its orientation with regard to the presumed binding mode of aristolochene. A similar active site contour is conserved in aristolochene synthase from Penicillium roqueforti despite the substantial divergent evolution of these two enzymes, while strikingly different active site contours are found in the sesquiterpene cyclases 5-epi-aristolochene synthase and trichodiene synthase. Thus, the terpenoid cyclase active site plays a critical role as a template in binding the flexible polyisoprenoid substrate in the proper conformation for catalysis. Across the greater family of terpenoid cyclases, this template is highly evolvable within a conserved {alpha}-helical fold for the synthesis of terpene natural products of diverse structure and stereochemistry.« less

Synthesis of CdS nanorods in soft template under gamma-irradiation.

PubMed

Zhao, Bing; Wang, Yanli; Zhang, Haijiao; Jiao, Zheng; Wang, Haobo; Ding, Guoji; Wu, Minghong

2009-02-01

CdS nano material which has a band gap of 2.42 eV at room temperature is a typical II-VII semiconductor having many commercial or potential applications, e.g., light-emitting diodes, solar cell and optoelectronic devices. In this paper, we use a new strategy to synthesize CdS nanorods. CdS nanorods were prepared in soft template under gamma-irradiation though the reaction of cadmium sulphide and thiacetamide (TAA). The formation process and characters of CdS nanorods was investigated in detail by transmission electron microscopy (TEM), electron diffraction (ED) pattern, X-ray powder diffraction (XRD), ultraviolet spectrophotometer (UV) and photoluminescence spectrophotometer (PL). In the experiment we proposed that the irradiation of gamma-ray accelerated the formation of S(2-) under acidic condition (pH = 3) and vinyl acetate (VAc) monomer formed pre-organized nano polymer tubules which were used as both templates and nanoreacters for the growth of CdS nanorods. In this process, we have obtained the CdS polycrystal nanorods with PVAc nano tubules and CdS single-crystal nanorods. The result of X-ray powder diffraction confirms that the crystal type of CdS nanorods is cubic F-43 m (216). The results from transmission electron microscopy and electron diffraction show that the concentrations of reactants and the dose rate of gamma-ray are key to produce appropriate CdS nanorods. Relatively low concentrations (Cd2+: 0.008-0.02 mol/L, Cd2+ : S(2-) = 1 : 2) of reactants and long time (1-2 d) of irradiation in low dose rate (6-14 Gy/min) are propitious to form CdS single-crystal nanorods with small diameter (less than 100 nm) and well length (2-5 microm). UV and PL characterizations show the sample have well optical properties.

Fabrication and Characterization of Vertically Aligned ZnO Nanorod Arrays via Inverted Monolayer Colloidal Crystals Mask

NASA Astrophysics Data System (ADS)

Chen, Cheng; Ding, Taotao; Qi, Zhiqiang; Zhang, Wei; Zhang, Jun; Xu, Juan; Chen, Jingwen; Dai, Jiangnan; Chen, Changqing

2018-04-01

The periodically ordered ZnO nanorod (NR) arrays have been successfully synthesized via a hydrothermal approach on the silicon substrates by templating of the TiO2 ring deriving from the polystyrene (PS) nanosphere monolayer colloidal crystals (MCC). With the inverted MCC mask, sol-gel-derived ZnO seeds could serve as the periodic nucleation positions for the site-specific growth of ZnO NRs. The large-scale patterned arrays of single ZnO NR with good side-orientation can be readily produced. According to the experimental results, the as-integrated ZnO NR arrays showed an excellent crystal quality and optical property, very suitable for optoelectronic applications such as stimulated emitters and ZnO photonic crystal devices.

Texturing of sodium bismuth titanate-barium titanate ceramics by templated grain growth

NASA Astrophysics Data System (ADS)

Yilmaz, Huseyin

2002-01-01

Sodium bismuth titanate modified with barium titanate, (Na1/2Bi 1/2)TiO3-BaTiO3 (NBT-BT), is a candidate lead-free piezoelectric material which has been shown to have comparatively high piezoelectric response. In this work, textured (Na1/2Bi1/2)TiO 3-BaTiO3 (5.5mol% BaTiO3) ceramics with <100> pc (where pc denotes the pseudocubic perovskite cell) orientation were fabricated by Templated Grain Growth (TGG) or Reactive Templated Grain Growth (RTGG) using anisotropically shaped template particles. In the case of TGG, molten salt synthesized SrTiO3 platelets were tape cast with a (Na1/2Bi1/2)TiO3-5.5mol%BaTiO3 powder and sintered at 1200°C for up to 12 hours. For the RTGG approach, Bi4Ti3O12 (BiT) platelets were tape cast with a Na2CO3, Bi2O3, TiO 2, and BaCO3 powder mixture and reactively sintered. The TGG approach using SrTiO3 templates gave stronger texture along [001] compared to the RTGG approach using BiT templates. The textured ceramics were characterized by X-ray and electron backscatter diffraction for the quality of texture. The texture function was quantified by the Lotgering factor, rocking curve, pole figures, inverse pole figures, and orientation imaging microscopy. Electrical and electromechanical property characterization of randomly oriented and <001>pc textured (Na1/2Bi1/2)TiO 3-5.5 mol% BaTiO3 rhombohedral ceramics showed 0.26% strain at 70 kV/cm, d33 coefficients over 500 pC/N have been obtained for highly textured samples (f ˜ 90%). The piezoelectric coefficient from Berlincourt was d33 ˜ 200 pC/N. The materials show considerable hysteresis. The presence of hysteresis in the unipolar-electric field curve is probably linked to the ferroelastic phase transition seen in the (Na 1/2Bi1/2)TiO3 system on cooling from high temperature at ˜520°C. The macroscopic physical properties (remanent polarization, dielectric constant, and piezoelectric coefficient) of random and textured ([001] pc) rhombohedral perovskites were estimated by linear averaging of single crystal data. However, the complete polarization, dielectric, and piezoelectric tensors are not available for NBT-BT single crystals. Therefore, the properties of lead based (PZT, 52/48) rhombohedral ferroelectric single domain-single crystals, whose properties (polarization, dielectric and piezoelectric) were computed using Landau-Ginsburg-Devonshire phenomenological theory (by Haun et. al.), were used in the calculations for random and textured cases. (Abstract shortened by UMI.)

Effect of silk sericin on morphology and structure of calcium carbonate crystal

NASA Astrophysics Data System (ADS)

Zhao, Rui-Bo; Han, Hua-Feng; Ding, Shao; Li, Ze-Hao; Kong, Xiang-Dong

2013-06-01

In this paper, silk sericin was employed to regulate the mineralization of calcium carbonate (CaCO3). CaCO3 composite particles were prepared by the precipitation reaction of sodium carbonate with calcium chloride solution in the presence of silk sericin. The as-prepared samples were collected at different reaction time to study the crystallization process of CaCO3 by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and X-ray diffraction (XRD). The results showed that silk sericin significantly affected the morphology and crystallographic polymorph of CaCO3. With increasing the reaction time, the crystal phase of CaCO3 transferred from calcite dominated to vaterite dominated mixtures, while the morphology of CaCO3 changed from disk-like calcite crystal to spherical vaterite crystal. These studies showed the potential of silk sericin used as a template molecule to control the growth of inorganic crystal.

A simple approach for large-area fabrication of Ag nanorings

NASA Astrophysics Data System (ADS)

Yuan, Zhi-hao; Zhou, Wei; Duan, Yue-qin; Bie, Li-jian

2008-02-01

A simple and low-cost method based on a two-step heat treatment of AgNO3/SiO2 film has been developed for fabricating metal Ag nanoring arrays. The as-prepared nanorings have an inner diameter of 70-250 nm and an average wall thickness (namely wire diameter) of approximately 30 nm with a number density of approximately 109 cm-2 on the surface of the SiO2 matrix. X-ray diffraction (XRD) results reveal that these nanorings exhibit a face-centered cubic crystal structure. Furthermore, a new growth mechanism, namely a molten metal bubble as a self-template, is tentatively proposed for Ag nanorings.

Energy transfer and visible-infrared quantum cutting photoluminescence modification in Tm-Yb codoped YPO(4) inverse opal photonic crystals.

PubMed

Wang, Siqin; Qiu, Jianbei; Wang, Qi; Zhou, Dacheng; Yang, Zhengwen

2015-08-01

YPO₄:  Tm, Yb inverse opal photonic crystals were successfully synthesized by the colloidal crystal templates method, and the visible-infrared quantum cutting (QC) photoluminescence properties of YPO₄:  Tm, Yb inverse opal photonic crystals were investigated. We obtained tetragonal phase YPO₄ in all the samples when the samples sintered at 950°C for 5 h. The visible emission intensity of Tm³⁺ decreased significantly when the photonic bandgap was located at 650 nm under 480 nm excitation. On the contrary, the QC emission intensity of Yb³⁺ was enhanced as compared with the no photonic bandgap sample. When the photonic bandgap was located at 480 nm, the Yb³⁺ and Tm³⁺ light-emitting intensity weakened at the same time. We demonstrated that the energy transfer between Tm³⁺ and Yb³⁺ is enhanced by the suppression of the red emission of Tm³⁺. Additionally, the mechanisms for the influence of the photonic bandgap on the energy transfer process of the Tm³⁺, Yb³⁺ codoped YPO₄ inverse opal are discussed.

Cluster self-organization of inorganic crystal-forming systems: Templated nanocluster precursors and self-assembly of framework MT structures of A/B,Zr silicates (A = Na, K; B = Ca, Sr)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ilyushin, G. D., E-mail: ilyushin@ns.crys.ras.ru

The basic concepts that are used to describe crystallization as a phenomenon of the hierarchical (cluster) self-organization of a chemical system are considered. The templation of theoretically possible nan-ocluster precursors composed of M octahedra and T tetrahedra by atoms of (A) alkaline and (B) alkaline earth metals is considered for the first time. A relationship between the A/B,M,T composition of templated nanocluster precursors with the composition of A/B,M silicates is established. The model that is developed is used to search for nanocluster precursors in framework MT structures of A/B,Zr silicates. Computer methods (TOPOS 4.0 program package) were used to performmore » complete 3D reconstruction of the self-assembly of all (four) structural types of A/B,Zr silicates (A = Na, K; B = Ca, Sr) with frameworks of the MT{sub 2}O{sub 7} type: nan-ocluster precursor S{sub 3}{sup 0}-primary chain S{sub 3}{sup 1}-microlayer S{sub 3}{sup 2}-microframework S{sub 3}{sup 3}. The invariant type of mono-cyclic nanocluster precursor M{sub 2}T{sub 4} (with the point symmetries 1-bar and 2), stabilized by one or two template cations (A and B), is determined. Bifurcations of the paths of evolution at the S{sub 3}{sup 1} level (structural branching point) are established for the self-assembly of the following frameworks: MT-1 in CaZrSi{sub 2}O{sub 7} (gittinsite, C2), MT-2 in SrZrSi{sub 2}O{sub 7} (P2{sub 1}/c); MT-3 in Na{sub 2}ZrSi{sub 2}O{sub 7} (parakeldyshite,), K{sub 2}ZrSi{sub 2}O{sub 7} (khibinskite, P2{sub 1}/b), and K{sub 2}ZrGe{sub 2}O{sub 7} (C2/c); and MT-4 in Na{sub 2}ZrSi{sub 2}O{sub 7} (H{sub 2}O)(C2/c), Na{sub 3}ScSi{sub 2}O{sub 7} (Pbnm), and K{sub 3}ScSi{sub 2}O{sub 7} (P6{sub 3}/mmc).« less

Discovery of a 2,4-Diamino-7-aminoalkoxy-quinazoline as a Potent and Selective Inhibitor of Histone Lysine Methyltransferase G9a†

PubMed Central

Liu, Feng; Chen, Xin; Allali-Hassani, Abdellah; Quinn, Amy M.; Wasney, Gregory A.; Dong, Aiping; Barsyte, Dalia; Kozieradzki, Ivona; Senisterra, Guillermo; Chau, Irene; Siarheyeva, Alena; Kireev, Dmitri B.; Jadhav, Ajit; Herold, J. Martin; Frye, Stephen V.; Arrowsmith, Cheryl H.; Brown, Peter J.; Simeonov, Anton; Vedadi, Masoud; Jin, Jian

2010-01-01

SAR exploration of the 2,4-diamino-6,7-dimethoxyquinazoline template led to the discovery of 8 (UNC0224) as a potent and selective G9a inhibitor. A high resolution X-ray crystal structure of the G9a-8 complex, the first co-crystal structure of G9a with a small molecule inhibitor, was obtained. The co-crystal structure validated our binding hypothesis and will enable structure-based design of novel inhibitors. 8 is a useful tool for investigating the biology of G9a and its roles in chromatin remodeling. PMID:19891491

A facile one-pot hydrothermal synthesis of β-MnO{sub 2} nanopincers and their catalytic degradation of methylene blue

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheng, Gao; Yu, Lin, E-mail: gych@gdut.edu.cn; Lin, Ting

2014-09-15

Branched β-MnO{sub 2} bipods with novel nanopincer morphology were prepared by a facile one-pot hydrothermal method via a redox reaction between NaClO{sub 3} and MnSO{sub 4} in sulfuric acid solution without using any surfactants or templates. The products were characterized in detail by various techniques including X-ray powder diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, surface area analyzer, field emission scanning electron microscopy and transmission electron microscopy. Results show that the obtained β-MnO{sub 2} nanopincers consist of two sharp nanorods with a diameter of 100–200 nm and a length of 1–2 μm. The concentration of H{sub 2}SO{sub 4} solution plays anmore » important role in controlling the crystal phase and morphology of the final product. A possible formation mechanism for the β-MnO{sub 2} nanopincers was proposed. Moreover, these β-MnO{sub 2} nanostructures exhibited better catalytic performance than the commercial MnO{sub 2} particles to decompose methyl blue (MB) in the presence of H{sub 2}O{sub 2}. - Graphical abstract: Branched β-MnO{sub 2} bipods with novel nanopincer morphology were prepared by a facile one-pot hydrothermal method through oxidizing MnSO{sub 4} with NaClO{sub 3} in H2SO{sub 4} condition without using any surfactants or templates. - Highlights: {sup •} Branched β-MnO{sub 2} nanopincers were prepared by a facile one-pot hydrothermal method. {sup •} Morphology and crystal phase of MnO{sub 2} were controlled by the H{sub 2}SO{sub 4} concentration. {sup •} A possible formation mechanism for the obtained β-MnO{sub 2} nanopincers was proposed. {sup •} The products showed great catalytic performance in degradation of methylene blue.« less

Real-Time Tracking by Double Templates Matching Based on Timed Motion History Image with HSV Feature

PubMed Central

Li, Zhiyong; Li, Pengfei; Yu, Xiaoping; Hashem, Mervat

2014-01-01

It is a challenge to represent the target appearance model for moving object tracking under complex environment. This study presents a novel method with appearance model described by double templates based on timed motion history image with HSV color histogram feature (tMHI-HSV). The main components include offline template and online template initialization, tMHI-HSV-based candidate patches feature histograms calculation, double templates matching (DTM) for object location, and templates updating. Firstly, we initialize the target object region and calculate its HSV color histogram feature as offline template and online template. Secondly, the tMHI-HSV is used to segment the motion region and calculate these candidate object patches' color histograms to represent their appearance models. Finally, we utilize the DTM method to trace the target and update the offline template and online template real-timely. The experimental results show that the proposed method can efficiently handle the scale variation and pose change of the rigid and nonrigid objects, even in illumination change and occlusion visual environment. PMID:24592185

The uncoupling of catalysis and translocation in the viral RNA-dependent RNA polymerase

PubMed Central

Shu, Bo; Gong, Peng

2017-01-01

ABSTRACT The nucleotide addition cycle of nucleic acid polymerases includes 2 major events: the pre-chemistry active site closure leading to the addition of one nucleotide to the product chain; the post-chemistry translocation step moving the polymerase active site one position downstream on its template. In viral RNA-dependent RNA polymerases (RdRPs), structural and biochemical evidences suggest that these 2 events are not tightly coupled, unlike the situation observed in A-family polymerases such as the bacteriophage T7 RNA polymerase. Recently, an RdRP translocation intermediate crystal structure of enterovirus 71 shed light on how translocation may be controlled by elements within RdRP catalytic motifs, and a series of poliovirus apo RdRP crystal structures explicitly suggest that a motif B loop may assist the movement of the template strand in late stages of transcription. Implications of RdRP catalysis-translocation uncoupling and the remaining challenges to further elucidate RdRP translocation mechanism are also discussed. PMID:28277928

Periodic Two-Dimensional GaAs and InGaAs Quantum Rings Grown on GaAs (001) by Droplet Epitaxy.

PubMed

Tung, Kar Hoo Patrick; Huang, Jian; Danner, Aaron

2016-06-01

Growth of ordered GaAs and InGaAs quantum rings (QRs) in a patterned SiO2 nanohole template by molecular beam epitaxy (MBE) using droplet epitaxy (DE) process is demonstrated. DE is an MBE growth technique used to fabricate quantum nanostructures of high crystal quality by supplying group III and group V elements in separate phases. In this work, ordered QRs grown on an ordered nanohole template are compared to self-assembled QRs grown with the same DE technique without the nanohole template. This study allows us to understand and compare the surface kinetics of Ga and InGa droplets when a template is present. It is found that template-grown GaAs QRs form clustered rings which can be attributed to low mobility of Ga droplets resulting in multiple nucleation sites for QR formation when As is supplied. However, the case of template-grown InGaAs QRs only one ring is formed per nanohole; no clustering is observed. The outer QR diameter is a close match to the nanohole template diameter. This can be attributed to more mobile InGa droplets, which coalesce from an Ostwald ripening to form a single large droplet before As is supplied. Thus, well-patterned InGaAs QRs are demonstrated and the kinetics of their growth are better understood which could potentially lead to improvements in the future devices that require the unique properties of patterned QRs.

A highly sensitive room temperature H2S gas sensor based on SnO2 multi-tube arrays bio-templated from insect bristles.

PubMed

Tian, Junlong; Pan, Feng; Xue, Ruiyang; Zhang, Wang; Fang, Xiaotian; Liu, Qinglei; Wang, Yuhua; Zhang, Zhijian; Zhang, Di

2015-05-07

A tin oxide multi-tube array (SMTA) with a parallel effect was fabricated through a simple and promising method combining chemosynthesis and biomimetic techniques; a biomimetic template was derived from the bristles on the wings of the Alpine Black Swallowtail butterfly (Papilio maackii). SnO2 tubes are hollow and porous structures with micro-pores regularly distributed on the wall. The morphology, the delicate microstructure and the crystal structure of this SMTA were characterized by super resolution digital microscopy, scanning electron microscopy, transmission electron microscopy and X-ray diffraction. The SMTA exhibits a high sensitivity to H2S gas at room temperature. It also exhibits a short response/recovery time, with an average value of 14/30 s at 5 ppm. In particular, heating is not required for the SMTA in the gas sensitivity measurement process. On the basis of these results, SMTA is proposed as a suitable new material for the design and fabrication of room-temperature H2S gas sensors.

Synthesis, characterization and solid-state properties of [Zn(Hdmmthiol)2]\\cdot2H2O complex

NASA Astrophysics Data System (ADS)

Dagdelen, Fethi; Aydogdu, Yildirim; Dey, Kamalendu; Biswas, Susobhan

2016-05-01

The zinc(II) complex with tridentate thiohydrazone ligand have been prepared by metal template reaction. The metal template reaction was used to prepare the zinc (II) complex with tridentate thiohydrazone ligand. The reaction of diacetylmonoxime and, morpholine N-thiohydrazidewith Zn(OAc)2 \\cdot2H2O under reflux yielded the formation of the [Zn(Hdmmthiol )2]\\cdot2H2O complex. The complex was characterized by a combination of protocols including elemental analysis, UV+vis, FT-IR, TG and PXRD. The temperature dependence of the electrical conductivity and the optical property of the [Zn(Hdmmthiol )2] \\cdot2H2O complex is called H2dammthiol was studied. Powder X-ray diffraction (PXRD) method was used to investigate the crystal structure of the sample. The zinc complex was shown to be a member of the triclinic system. The zinc complex was determined to have n-type conductivity as demonstrated in the hot probe measurements. The complex was determined to display direct optical transition with band gaps of 2.52eV as determined by the optical absorption analysis.

Facile controlled synthesis of micro/nanostructure MCrO 4 (M = Ba, Pb) by using Gemini surfactant C 12-PEG-C 12 as a soft template

NASA Astrophysics Data System (ADS)

Chang, Wengui; Shen, Yuhua; Xie, Anjian; Liu, Xue

2010-04-01

Gemini surfactants, double sodium α-sulfonic polyethylene glycol laurate (abbreviated C 12-PEG-C 12), were prepared and applied as soft templates in the controlled synthesis of BaCrO 4 and PbCrO 4 micro/nanocrystals. The template effects were investigated by adjusting the length of the spacer, using PEG400 and PEG4000, of the Gemini surfactant. The results indicated that the size and morphology of BaCrO 4 and PbCrO 4 micro/nanocrystals varied with the change in spacer length of C 12-PEG-C 12, suggesting that the different lengths of the polyethylene glycol group spacers in the Gemini surfactants played a key role in determining the size and shape of the MCrO 4 micro/nanoparticles. The dynamic process of the formation of the novel morphology BaCrO 4 crystals showed that the morphology grew from a round-bar polyhedron, to regular polyhedron, to approximate octahedron to a uniform pistachio nut shape. The growth mechanism of the BaCrO 4 micro/nanocrystals was explained that C 12-PEG-C 12 had a greater interfacial adsorption and would effectively control the shape evolution during the crystal growth, while PbCrO 4 could be explained that the Gemini surfactants can undergo liquid-crystalline phase transitions with long channels providing a soft template effect and derived the nanorods formation. Room temperature fluorescence spectra were studied and these showed that the pistachio-shaped BaCrO 4 microcrystals and PbCrO 4 nanorods possess photoactive luminescence properties with emission peaks at 470 and 549 nm, respectively.

Development of Total Knee Replacement Digital Templating Software

NASA Astrophysics Data System (ADS)

Yusof, Siti Fairuz; Sulaiman, Riza; Thian Seng, Lee; Mohd. Kassim, Abdul Yazid; Abdullah, Suhail; Yusof, Shahril; Omar, Masbah; Abdul Hamid, Hamzaini

In this study, by taking full advantage of digital X-ray and computer technology, we have developed a semi-automated procedure to template knee implants, by making use of digital templating method. Using this approach, a software system called OrthoKneeTMhas been designed and developed. The system is to be utilities as a study in the Department of Orthopaedic and Traumatology in medical faculty, UKM (FPUKM). OrthoKneeTMtemplating process employs uses a technique similar to those used by many surgeons, using acetate templates over X-ray films. Using template technique makes it easy to template various implant from every Implant manufacturers who have with a comprehensive database of templates. The templating functionality includes, template (knee) and manufactures templates (Smith & Nephew; and Zimmer). From an image of patient x-ray OrthoKneeTMtemplates help in quickly and easily reads to the approximate template size needed. The visual templating features then allow us quickly review multiple template sizes against the X-ray and thus obtain the nearly precise view of the implant size required. The system can assist by templating on one patient image and will generate reports that can accompany patient notes. The software system was implemented in Visual basic 6.0 Pro using the object-oriented techniques to manage the graphics and objects. The approaches for image scaling will be discussed. Several of measurement in orthopedic diagnosis process have been studied and added in this software as measurement tools features using mathematic theorem and equations. The study compared the results of the semi-automated (using digital templating) method to the conventional method to demonstrate the accuracy of the system.

Protein nanocrystallography: growth mechanism and atomic structure of crystals induced by nanotemplates.

PubMed

Pechkova, E; Vasile, F; Spera, R; Fiordoro, S; Nicolini, C

2005-11-01

Protein nanocrystallography, a new technology for crystal growth based on protein nanotemplates, has recently been shown to produce diffracting, stable and radiation-resistant lysozyme crystals. This article, by computing these lysozyme crystals' atomic structures, obtained by the diffraction patterns of microfocused synchrotron radiation, provides a possible mechanism for this increased stability, namely a significant decrease in water content accompanied by a minor but significant alpha-helix increase. These data are shown to be compatible with the circular dichroism and two-dimensional Fourier transform spectra of high-resolution H NMR of proteins dissolved from the same nanotemplate-based crystal versus those from a classical crystal. Finally, evidence for protein direct transfer from the nanotemplate to the drop and the participation of the template proteins in crystal nucleation and growth is provided by high-resolution NMR spectrometry and mass spectrometry. Furthermore, the lysozyme nanotemplate appears stable up to 523 K, as confirmed by a thermal denaturation study using spectropolarimetry. The overall data suggest that heat-proof lysozyme presence in the crystal provides a possible explanation of the crystal's resistance to synchrotron radiation.

Inhibition of Ice Growth and Recrystallization by Zirconium Acetate and Zirconium Acetate Hydroxide

PubMed Central

Mizrahy, Ortal; Bar-Dolev, Maya; Guy, Shlomit; Braslavsky, Ido

2013-01-01

The control over ice crystal growth, melting, and shaping is important in a variety of fields, including cell and food preservation and ice templating for the production of composite materials. Control over ice growth remains a challenge in industry, and the demand for new cryoprotectants is high. Naturally occurring cryoprotectants, such as antifreeze proteins (AFPs), present one solution for modulating ice crystal growth; however, the production of AFPs is expensive and inefficient. These obstacles can be overcome by identifying synthetic substitutes with similar AFP properties. Zirconium acetate (ZRA) was recently found to induce the formation of hexagonal cavities in materials prepared by ice templating. Here, we continue this line of study and examine the effects of ZRA and a related compound, zirconium acetate hydroxide (ZRAH), on ice growth, shaping, and recrystallization. We found that the growth rate of ice crystals was significantly reduced in the presence of ZRA and ZRAH, and that solutions containing these compounds display a small degree of thermal hysteresis, depending on the solution pH. The compounds were found to inhibit recrystallization in a manner similar to that observed in the presence of AFPs. The favorable properties of ZRA and ZRAH suggest tremendous potential utility in industrial applications. PMID:23555701

Bioinspired fabrication of hierarchically structured, pH-tunable photonic crystals with unique transition.

PubMed

Yang, Qingqing; Zhu, Shenmin; Peng, Wenhong; Yin, Chao; Wang, Wanlin; Gu, Jiajun; Zhang, Wang; Ma, Jun; Deng, Tao; Feng, Chuanliang; Zhang, Di

2013-06-25

We herein report a new class of photonic crystals with hierarchical structures, which are of color tunability over pH. The materials were fabricated through the deposition of polymethylacrylic acid (PMAA) onto a Morpho butterfly wing template by using a surface bonding and polymerization route. The amine groups of chitosan in Morpho butterfly wings provide reaction sites for the MAA monomer, resulting in hydrogen bonding between the template and MAA. Subsequent polymerization results in PMAA layers coating homogenously on the hierarchical photonic structures of the biotemplate. The pH-induced color change was detected by reflectance spectra as well as optical observation. A distinct U transition with pH was observed, demonstrating PMAA content-dependent properties. The appearance of the unique U transition results from electrostatic interaction between the -NH3(+) of chitosan and the -COO(-) groups of PMAA formed, leading to a special blue-shifted point at the pH value of the U transition, and the ionization of the two functional groups in the alkali and acid environment separately, resulting in a red shift. This work sets up a strategy for the design and fabrication of tunable photonic crystals with hierarchical structures, which provides a route for combining functional polymers with biotemplates for wide potential use in many fields.

Nanostructure templating using low temperature atomic layer deposition

DOEpatents

Grubbs, Robert K [Albuquerque, NM; Bogart, Gregory R [Corrales, NM; Rogers, John A [Champaign, IL

2011-12-20

Methods are described for making nanostructures that are mechanically, chemically and thermally stable at desired elevated temperatures, from nanostructure templates having a stability temperature that is less than the desired elevated temperature. The methods comprise depositing by atomic layer deposition (ALD) structural layers that are stable at the desired elevated temperatures, onto a template employing a graded temperature deposition scheme. At least one structural layer is deposited at an initial temperature that is less than or equal to the stability temperature of the template, and subsequent depositions made at incrementally increased deposition temperatures until the desired elevated temperature stability is achieved. Nanostructure templates include three dimensional (3D) polymeric templates having features on the order of 100 nm fabricated by proximity field nanopatterning (PnP) methods.

Growth and optical property characterization of textured barium titanate thin films for photonic applications

NASA Astrophysics Data System (ADS)

Dicken, Matthew J.; Diest, Kenneth; Park, Young-Bae; Atwater, Harry A.

2007-03-01

We have investigated the growth of barium titanate thin films on bulk crystalline and amorphous substrates utilizing biaxially oriented template layers. Ion beam-assisted deposition was used to grow thin, biaxially textured, magnesium oxide template layers on amorphous and silicon substrates. Growth of highly oriented barium titanate films on these template layers was achieved by molecular beam epitaxy using a layer-by-layer growth process. Barium titanate thin films were grown in molecular oxygen and in the presence of oxygen radicals produced by a 300 W radio frequency plasma. We used X-ray and in situ reflection high-energy electron diffraction (RHEED) to analyze the structural properties and show the predominantly c-oriented grains in the films. Variable angle spectroscopic ellipsometry was used to analyze and compare the optical properties of the thin films grown with and without oxygen plasma. We have shown that optical quality barium titanate thin films, which show bulk crystal-like properties, can be grown on any substrate through the use of biaxially oriented magnesium oxide template layers.

Highly mesoporous single-crystalline zeolite beta synthesized using a nonsurfactant cationic polymer as a dual-function template.

PubMed

Zhu, Jie; Zhu, Yihan; Zhu, Liangkui; Rigutto, Marcello; van der Made, Alexander; Yang, Chengguang; Pan, Shuxiang; Wang, Liang; Zhu, Longfeng; Jin, Yinying; Sun, Qi; Wu, Qinming; Meng, Xiangju; Zhang, Daliang; Han, Yu; Li, Jixue; Chu, Yueying; Zheng, Anmin; Qiu, Shilun; Zheng, Xiaoming; Xiao, Feng-Shou

2014-02-12

Mesoporous zeolites are useful solid catalysts for conversion of bulky molecules because they offer fast mass transfer along with size and shape selectivity. We report here the successful synthesis of mesoporous aluminosilicate zeolite Beta from a commercial cationic polymer that acts as a dual-function template to generate zeolitic micropores and mesopores simultaneously. This is the first demonstration of a single nonsurfactant polymer acting as such a template. Using high-resolution electron microscopy and tomography, we discovered that the resulting material (Beta-MS) has abundant and highly interconnected mesopores. More importantly, we demonstrated using a three-dimensional electron diffraction technique that each Beta-MS particle is a single crystal, whereas most previously reported mesoporous zeolites are comprised of nanosized zeolitic grains with random orientations. The use of nonsurfactant templates is essential to gaining single-crystalline mesoporous zeolites. The single-crystalline nature endows Beta-MS with better hydrothermal stability compared with surfactant-derived mesoporous zeolite Beta. Beta-MS also exhibited remarkably higher catalytic activity than did conventional zeolite Beta in acid-catalyzed reactions involving large molecules.

Crystallization and textural porosity of synthetic clay minerals.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carrado, K. A.; Csencsits, R.; Thiyagarajan, P.

2002-12-01

The crystallization of synthetic layered magnesium silicate hectorite clays from both silica sol and organosilane sources is compared. For the silica sol-derived clays, a templating method is employed wherein organic or polymeric molecules are included during clay crystallization that are then removed from the composites via calcination. The mechanism of silane-derived hectorite formation is followed by XRD, TGA, 29Si MAS NMR, and small angle X-ray scattering (SAXS), and results are compared to those obtained for the sol-derived hectorite. The mechanism appears to be similar but the rate is approximately doubled when the silane is used rather than silica sol. Analyticalmore » transmission electron microscopy (TEM) is exploited to glean structural morphology information towards resolving the nature of the resulting pore network structures. Results are compared with nitrogen adsorption-desorption isotherm behavior; dominant hysteresis loops are present in the type IV isotherms. Pore size distributions based on both the adsorption and desorption isotherms are compared. Small angle neutron scattering (SANS) experiments reveal that the average particle size increases as synthetic laponite < sol-derived hectorite < silane-derived hectorite < natural hectorite. Contrast matching SANS studies in aqueous and organic solvents are carried out to extract information about pore accessibility.« less

Silicon-based Porous Ceramics via Freeze Casting of Preceramic Polymers

NASA Astrophysics Data System (ADS)

Naviroj, Maninpat

Freeze casting is a technique for processing porous materials that has drawn significant attention for its effectiveness in producing a variety of tailorable pore structures for ceramics, metals, and polymers. With freeze casting, pores are generated based on a solidification process where ice crystals act as a sacrificial template which can eventually be sublimated to create pores. While the majority of freeze-casting studies have been performed using conventional ceramic suspensions, this work explores an alternative processing route by freeze casting with preceramic polymer solutions. Significant differences exist between freeze casting of a particulate suspension and a polymeric solution. These changes affect the processing method, solidification behavior, and pore structure, thereby introducing new challenges and possibilities for the freeze-casting technique. The first part of this study explored the processing requirements involved with freeze casting of preceramic polymers, along with methods to control the resulting pore structure. Solvent choice, freezing front velocity, and polymer concentration were used as processing variables to manipulate the pore structures. A total of seven organic solvents were freeze cast with a polymethylsiloxane preceramic polymer to produce ceramics with isotropic, dendritic, prismatic, and lamellar pore morphologies. Changes in freezing front velocity and polymer concentration were shown to influence pore size, shape, and connectivity. Differences between suspension- and solution-based samples freeze cast under equivalent conditions were also investigated. Certain solidification microstructures were strongly affected by the presence of suspended particles, creating differences between pore structures generated from the same solvents. Additionally, processing of solution-based samples were found to be the more facile technique. Compressive strength and water permeability of dendritic and lamellar structures were analyzed to determine functional differences between the pore structures. Results show that dendritic structures were up to 30 times stronger, while lamellar structures provided higher permeability constants. A change in freezing front velocity was shown to significantly affect permeability but not compressive strength. Finally, improved pore alignment along the freezing direction was achieved by controlling the nucleation and growth of solvent crystals through the use of a grain-selection template. Dendritic samples freeze cast with a template showed substantial increase in pore alignment, as determined by image analysis and permeability tests, with the permeability constant increasing by up to 6-fold when compared to a control sample.

Relative stability of the open and closed conformations of the active site loop of streptavidin

NASA Astrophysics Data System (ADS)

Ignacio J., General; Meirovitch, Hagai

2011-01-01

The eight-residue surface loop, 45-52 (Ser, Ala, Val, Gly, Asn, Ala, Glu, Ser), of the homotetrameric protein streptavidin has a "closed" conformation in the streptavidin-biotin complex, where the corresponding binding affinity is one of the strongest found in nature (ΔG ˜ -18 kcal/mol). However, in most of the crystal structures of apo (unbound) streptavidin, the loop conformation is "open" and typically exhibits partial disorder and high B-factors. Thus, it is plausible to assume that the loop structure is changed from open to closed upon binding of biotin, and the corresponding difference in free energy, ΔF = Fopen - Fclosed in the unbound protein, should therefore be considered in the total absolute free energy of binding. ΔF (which has generally been neglected) is calculated here using our "hypothetical scanning molecular-dynamics" (HSMD) method. We use a protein model in which only the atoms closest to the loop are considered (the "template") and they are fixed in the x-ray coordinates of the free protein; the x-ray conformation of the closed loop is attached to the same (unbound) template and both systems are capped with the same sphere of TIP3P water. Using the force field of the assisted model building with energy refinement (AMBER), we carry out two separate MD simulations (at temperature T = 300 K), starting from the open and closed conformations, where only the atoms of the loop and water are allowed to move (the template-water and template-loop interactions are considered). The absolute Fopen and Fclosed (of loop + water) are calculated from these trajectories, where the loop and water contributions are obtained by HSMD and a thermodynamic integration (TI) process, respectively. The combined HSMD-TI procedure leads to total (loop + water) ΔF = -27.1 ± 2.0 kcal/mol, where the entropy TΔS constitutes 34% of ΔF, meaning that the effect of S is significant and should not be ignored. Also, ΔS is positive, in accord with the high flexibility of the open loop observed in crystal structures, while the energy ΔE is unexpectedly negative, thus also adding to the stability of the open loop. The loop and the 250 capped water molecules are the largest system studied thus far, which constitutes a test for the efficiency of HSMD-TI; this efficiency and technical issues related to the implementation of the method are also discussed. Finally, the result for ΔF is a prediction that will be considered in the calculation of the absolute free energy of binding of biotin to streptavidin, which constitutes our next project.

Template-Framework Interactions in Tetraethylammonium-Directed Zeolite Synthesis

DOE PAGES

Schmidt, Joel E.; Fu, Donglong; Deem, Michael W.; ...

2016-11-22

Zeolites, having widespread applications in chemical industries, are often synthesized using organic templates. These can be cost-prohibitive, motivating investigations into their role in promoting crystallization. Herein, the relationship between framework structure, chemical composition, synthesis conditions and the conformation of the occluded, economical template tetraethylammonium (TEA +) has been systematically examined by experimental and computational means. The results show two distinct regimes of occluded conformer tendencies: 1) In frameworks with a large stabilization energy difference, only a single conformer was found (BEA, LTA and MFI). 2) In the frameworks with small stabilization energy differences (AEI, AFI, CHA and MOR), less thanmore » the interconversion of TEA + in solution, a heteroatom-dependent (Al, B, Co, Mn, Ti, Zn) distribution of conformers was observed. Our findings demonstrate that host–guest chemistry principles, including electrostatic interactions and coordination chemistry, are as important as ideal pore-filling.« less

Synthesis of ZSM-23/ZSM-22 intergrowth zeolite with a novel dual-template strategy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Bingchun, E-mail: wangbc@dicp.ac.cn; Graduate University of Chinese Academy of Sciences, Beijing 100049; Tian, Zhijian, E-mail: tianz@dicp.ac.cn

2009-12-15

ZSM-23/ZSM-22 intergrowth zeolite with fixed proportion of 60%ZSM-23/40%ZSM-22 has been synthesized with a novel dual-template strategy. The products were characterized by X-ray diffraction and scanning electron microscopy. Dimethylamine and diethylamine were used together as a dual-template system. The molar ratio of diethylamine to dimethylamine, which was changed with the type of aluminum source, was the key factor for the synthesis of intergrowth zeolites. A molar ratio of diethylamine to dimethylamine of 1:24 could result in an ZSM-23/ZSM-22 intergrowth zeolite if aluminum sulfate was used as aluminum source, whereas a molar ratio of diethylamine to dimethylamine of 1:12 was required tomore » get an ZSM-23/ZSM-22 intergrowth zeolite if sodium metaaluminate was used. Furthermore, fluoride anion could be involved in the process as a crystallization promoter.« less

Silicon crystallization in nanodot arrays organized by block copolymer lithography

NASA Astrophysics Data System (ADS)

Perego, Michele; Andreozzi, Andrea; Seguini, Gabriele; Schamm-Chardon, Sylvie; Castro, Celia; BenAssayag, Gerard

2014-12-01

Asymmetric polystyrene- b-polymethylmethacrylate (PS- b-PMMA) block copolymers are used to fabricate nanoporous PS templates with different pore diameter depending on the specific substrate neutralization protocol. The resulting polymeric templates are used as masks for the subsequent deposition of a thin ( h = 5 nm) amorphous Si layer by electron beam evaporation. After removal of the polymeric film and of the silicon excess, well-defined hexagonally packed amorphous Si nanodots are formed on the substrate. Their average diameter ( d < 20 nm), density (1.2 × 1011 cm-2), and lateral distribution closely mimic the original nanoporous template. Upon capping with SiO2 and high temperature annealing (1050 °C, N2), each amorphous Si nanodot rearranges in agglomerates of Si nanocrystals ( d < 4 nm). The average diameter and shape of these Si nanocrystals strongly depend on the size of the initial Si nanodot.

Up-conversion nanoparticles sensitized inverse opal photonic crystals enable efficient water purification under NIR irradiation

NASA Astrophysics Data System (ADS)

Zhang, Yuanyuan; Wang, Lili; Ma, Xiumei; Ren, Junfeng; Sun, Qinxing; Shi, Yongsheng; Li, Lin; Shi, Jinsheng

2018-03-01

A novel porous monolayer inverse opal (IO) structure was prepared by a simple sol-gel method combined with a self-assembly PS photonic crystal (PC) as template. By prolonging deposition time of PS spheres, three-dimensional multilayer TiO2 IOPC was also fabricated. Up-conversion nanoparticles (UCNPs) were selected to sensitize TiO2 IOPCs. Photocatalytic activity of as-prepared materials was investigated by disinfection of bacteria and organic pollutant degradation. Under NIR light irradiation, a large improvement in bacterial inactivation and photodegradation efficiency could be seen for NYF/TiO2 composites in comparison with other samples. As for monolayer NYF/TiO2, water disinfection of 100% inactivation of bacteria is realized within 11 h and kinetic constant of RhB degradation is 0.133 h-1, which is about 10 times higher than that of pure TiO2 IOPCs. Reasons of enhanced photocatalytic activity were systematically investigated and a possible mechanism for NIR-driven photocatalysis was reasonably proposed.

Near-Infrared Trigged Stimulus-Responsive Photonic Crystals with Hierarchical Structures.

PubMed

Lu, Tao; Pan, Hui; Ma, Jun; Li, Yao; Zhu, Shenmin; Zhang, Di

2017-10-04

Stimuli-responsive photonic crystals (PCs) trigged by light would provide a novel intuitive and quantitative method for noninvasive detection. Inspired by the flame-detecting aptitude of fire beetles and the hierarchical photonic structures of butterfly wings, we herein developed near-infrared stimuli-responsive PCs through coupling photothermal Fe 3 O 4 nanoparticles with thermoresponsive poly(N-isopropylacrylamide) (PNIPAM), with hierarchical photonic structured butterfly wing scales as the template. The nanoparticles within 10 s transferred near-infrared radiation into heat that triggered the phase transition of PNIPAM; this almost immediately posed an anticipated effect on the PNIPAM refractive index and resulted in a composite spectrum change of ∼26 nm, leading to the direct visual readout. It is noteworthy that the whole process is durable and stable mainly owing to the chemical bonding formed between PNIPAM and the biotemplate. We envision that this biologically inspired approach could be utilized in a broad range of applications and would have a great impact on various monitoring processes and medical sensing.

Investigation of partitionless growth of ɛ-Al60Sm11 phase in Al-10 at% Sm liquid

NASA Astrophysics Data System (ADS)

Sun, Yang; Ye, Zhuo; Zhang, Feng; Ding, Ze Jun; Wang, Cai-Zhuang; Kramer, Matthew J.; Ho, Kai-Ming

2018-01-01

Recent experiments on devitrification of Al90Sm10 amorphous alloys revealed an unusual polymorphic transformation to a complex cubic crystal structure called the ɛ-Al60Sm11 phase. Molecular dynamics simulations of the growth of the stoichiometric ɛ-phase seed in contact with an undercooled Al-10 at% Sm liquid are performed to elucidate the microscopic process of transformation. The as-grown crystal and undercooled liquid possess similar local order around Al atoms whereas a rigid network defined by the Sm sub-lattice develops during the growth. Using a template-cluster alignment method, we define an order parameter to characterize the structural evolution in the system. Estimates of the attachment rate is {R}{{a}}=8.70× {10}-4 Å-2 ns-1 and detachment rate is {R}{{d}}=3.83× {10}-4 Å-2 ns-1 at the interface between ɛ-Al60Sm11 and Al-10 at% Sm liquid at 800 K.

The crystal structure of an oligo(U):pre-mRNA duplex from a trypanosome RNA editing substrate

PubMed Central

Mooers, Blaine H.M.; Singh, Amritanshu

2011-01-01

Guide RNAs bind antiparallel to their target pre-mRNAs to form editing substrates in reaction cycles that insert or delete uridylates (Us) in most mitochondrial transcripts of trypanosomes. The 5′ end of each guide RNA has an anchor sequence that binds to the pre-mRNA by base-pair complementarity. The template sequence in the middle of the guide RNA directs the editing reactions. The 3′ ends of most guide RNAs have ∼15 contiguous Us that bind to the purine-rich unedited pre-mRNA upstream of the editing site. The resulting U-helix is rich in G·U wobble base pairs. To gain insights into the structure of the U-helix, we crystallized 8 bp of the U-helix in one editing substrate for the A6 mRNA of Trypanosoma brucei. The fragment provides three samples of the 5′-AGA-3′/5′-UUU-3′ base-pair triple. The fusion of two identical U-helices head-to-head promoted crystallization. We obtained X-ray diffraction data with a resolution limit of 1.37 Å. The U-helix had low and high twist angles before and after each G·U wobble base pair; this variation was partly due to shearing of the wobble base pairs as revealed in comparisons with a crystal structure of a 16-nt RNA with all Watson–Crick base pairs. Both crystal structures had wider major grooves at the junction between the poly(U) and polypurine tracts. This junction mimics the junction between the template helix and the U-helix in RNA-editing substrates and may be a site of major groove invasion by RNA editing proteins. PMID:21878548

GalaxyGPCRloop: Template-Based and Ab Initio Structure Sampling of the Extracellular Loops of G-Protein-Coupled Receptors.

PubMed

Won, Jonghun; Lee, Gyu Rie; Park, Hahnbeom; Seok, Chaok

2018-06-07

The second extracellular loops (ECL2s) of G-protein-coupled receptors (GPCRs) are often involved in GPCR functions, and their structures have important implications in drug discovery. However, structure prediction of ECL2 is difficult because of its long length and the structural diversity among different GPCRs. In this study, a new ECL2 conformational sampling method involving both template-based and ab initio sampling was developed. Inspired by the observation of similar ECL2 structures of closely related GPCRs, a template-based sampling method employing loop structure templates selected from the structure database was developed. A new metric for evaluating similarity of the target loop to templates was introduced for template selection. An ab initio loop sampling method was also developed to treat cases without highly similar templates. The ab initio method is based on the previously developed fragment assembly and loop closure method. A new sampling component that takes advantage of secondary structure prediction was added. In addition, a conserved disulfide bridge restraining ECL2 conformation was predicted and analytically incorporated into sampling, reducing the effective dimension of the conformational search space. The sampling method was combined with an existing energy function for comparison with previously reported loop structure prediction methods, and the benchmark test demonstrated outstanding performance.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Song, Jie; Viengkham, Malathong; Bertozzi, Carolyn R.

The controlled integration of organic and inorganic components confers natural bone with superior mechanical properties. Bone biogenesis is thought to occur by templated mineralization of hard apatite crystals by an elastic protein scaffold, a process we sought to emulate with synthetic biomimetic hydrogel polymers. Crosslinked polymethacrylamide and polymethacrylate hydrogels were functionalized with mineral-binding ligands and used to template the formation of hydroxyapatite. Strong adhesion between the organic and inorganic materials was achieved for hydrogels functionalized with either carboxylate or hydroxy ligands. The mineral-nucleating potential of hydroxyl groups identified here broadens the design parameters for synthetic bone-like composites and suggests amore » potential role for hydroxylated collagen proteins in bone mineralization.« less

Morphogenesis and crystallization of ZnS microspheres by a soft template-assisted hydrothermal route: synthesis, growth mechanism, and oxygen sensitivity.

PubMed

Yang, Liangbao; Han, Jun; Luo, Tao; Li, Minqiang; Huang, Jiarui; Meng, Fanli; Liu, Jinhuai

2009-01-05

Almost monodisperse ZnS microspheres have been synthesized on a large scale by a hydrothermal route, in which tungstosilicate acid (TSA) was used as a soft template. By controlling the reaction conditions, such as reaction temperature, pH value of the solutions, and the reaction medium, almost monodisperse microspheres can be synthesized. The structure of these microspheres is sensitive to the reaction conditions. The growth mechanism of these nearly monodisperse microspheres was examined. Oxygen sensing is realized from ZnS microspheres. The current through the ZnS microspheres under UV illumination increases as the oxygen concentration decreases.

Periodic assembly of nanoparticle arrays in disclinations of cholesteric liquid crystals.

PubMed

Li, Yunfeng; Prince, Elisabeth; Cho, Sangho; Salari, Alinaghi; Mosaddeghian Golestani, Youssef; Lavrentovich, Oleg D; Kumacheva, Eugenia

2017-02-28

An important goal of the modern soft matter science is to discover new self-assembly modalities to precisely control the placement of small particles in space. Spatial inhomogeneity of liquid crystals offers the capability to organize colloids in certain regions such as the cores of the topological defects. Here we report two self-assembly modes of nanoparticles in linear defects-disclinations in a lyotropic colloidal cholesteric liquid crystal: a continuous helicoidal thread and a periodic array of discrete beads. The beads form one-dimensional arrays with a periodicity that matches half a pitch of the cholesteric phase. The periodic assembly is governed by the anisotropic surface tension and elasticity at the interface of beads with the liquid crystal. This mode of self-assembly of nanoparticles in disclinations expands our ability to use topological defects in liquid crystals as templates for the organization of nanocolloids.

CHEMICAL SOLUTION DEPOSITION BASED OXIDE BUFFERS AND YBCO COATED CONDUCTORS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Paranthaman, Mariappan Parans

We have reviewed briefly the growth of buffer and high temperature superconducting oxide thin films using a chemical solution deposition (CSD) method. In the Rolling-Assisted Biaxially Textured Substrates (RABiTS) process, developed at Oak Ridge National Laboratory, utilizes the thermo mechanical processing to obtain the flexible, biaxially oriented copper, nickel or nickel-alloy substrates. Buffers and Rare Earth Barium Copper Oxide (REBCO) superconductors have been deposited epitaxially on the textured nickel alloy substrates. The starting substrate serves as a template for the REBCO layer, which has substantially fewer weak links. Buffer layers play a major role in fabricating the second generation REBCOmore » wire technology. The main purpose of the buffer layers is to provide a smooth, continuous and chemically inert surface for the growth of the REBCO film, while transferring the texture from the substrate to the superconductor layer. To achieve this, the buffer layers need to be epitaxial to the substrate, i.e. they have to nucleate and grow in the same bi-axial texture provided by the textured metal foil. The most commonly used RABiTS multi-layer architectures consist of a starting template of biaxially textured Ni-5 at.% W (Ni-W) substrate with a seed (first) layer of Yttrium Oxide (Y2O3), a barrier (second) layer of Yttria Stabilized Zirconia (YSZ), and a Cerium Oxide (CeO2) cap (third) layer. These three buffer layers are generally deposited using physical vapor deposition (PVD) techniques such as reactive sputtering. On top of the PVD template, REBCO film is then grown by a chemical solution deposition. This article reviews in detail about the list of oxide buffers and superconductor REBCO films grown epitaxially on single crystal and/or biaxially textured Ni-W substrates using a CSD method.« less

Synthesis of mesoporous zeolite single crystals with cheap porogens

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tao Haixiang; Li Changlin; Ren Jiawen

2011-07-15

Mesoporous zeolite (silicalite-1, ZSM-5, TS-1) single crystals have been successfully synthesized by adding soluble starch or sodium carboxymethyl cellulose (CMC) to a conventional zeolite synthesis system. The obtained samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen sorption analysis, {sup 27}Al magic angle spinning nuclear magnetic resonance ({sup 27}Al MAS NMR), temperature-programmed desorption of ammonia (NH{sub 3}-TPD) and ultraviolet-visible spectroscopy (UV-vis). The SEM images clearly show that all zeolite crystals possess the similar morphology with particle size of about 300 nm, the TEM images reveal that irregular intracrystalmore » pores are randomly distributed in the whole crystal. {sup 27}Al MAS NMR spectra indicate that nearly all of the Al atoms are in tetrahedral co-ordination in ZSM-5, UV-vis spectra confirm that nearly all of titanium atoms are incorporated into the framework of TS-1. The catalytic activity of meso-ZSM-5 in acetalization of cyclohexanone and meso-TS-1 in hydroxylation of phenol was also studied. The synthesis method reported in this paper is cost-effective and environmental friendly, can be easily expended to prepare other hierarchical structured zeolites. - Graphical abstract: Mesoporous zeolite single crystals were synthesized by using cheap porogens as template. Highlights: > Mesoporous zeolite (silicalite-1, ZSM-5, TS-1) single crystals were synthesized. > Soluble starch or sodium carboxymethyl cellulose (CMC) was used as porogens. > The mesoporous zeolites had connected mesopores although closed pores existed. > Higher catalytic activities were obtained.« less

Ultrathin SnO2 nanorods: template- and surfactant-free solution phase synthesis, growth mechanism, optical, gas-sensing, and surface adsorption properties.

PubMed

Xi, Guangcheng; Ye, Jinhua

2010-03-01

A novel template- and surfactant-free low temperature solution-phase method has been successfully developed for the controlled synthesis of ultrathin SnO(2) single-crystalline nanorods for the first time. The ultrathin SnO(2) single-crystalline nanorods are 2.0 +/- 0.5 nm in diameter, which is smaller than its exciton Bohr radius. The ultrathin SnO(2) nanorods show a high specific area (191.5 m(2) g(-1)). Such a thin SnO(2) single-crystalline nanorod is new in the family of SnO(2) nanostrucures and presents a strong quantum confinement effect. Its formation depends on the reaction temperature as well as on the concentration of the urea solution. A nonclassical crystallization process, Ostwald ripening process followed by an oriented attachment mechanism, is proposed based on the detailed observations from a time-dependent crystal evolution process. Importantly, such structured SnO(2) has shown a strong structure-induced enhancement of gas-sensing properties and has exhibited greatly enhanced gas-sensing property for the detection of ethanol than that of other structured SnO(2), such as the powders of nanobelts and microrods. Moreover, these ultrathin SnO(2) nanorods exhibit excellent ability to remove organic pollutant in wastewater by enormous surface adsorption. These properties are mainly attributed to its higher surface-to-volume ratio and ultrathin diameter. This work provides a novel low temperature, green, and inexpensive pathway to the synthesis of ultrathin nanorods, offering a new material form for sensors, solar cells, catalysts, water treatments, and other applications.

Impact of interaction range and curvature on crystal growth of particles confined to spherical surfaces.

PubMed

Paquay, Stefan; Both, Gert-Jan; van der Schoot, Paul

2017-07-01

When colloidal particles form a crystal phase on a spherical template, their packing is governed by the effective interaction between them and the elastic strain of bending the growing crystal. For example, if growth commences under appropriate conditions, and the isotropic crystal that forms reaches a critical size, growth continues via the incorporation of defects to alleviate elastic strain. Recently, it was experimentally found that, if defect formation is somehow not possible, the crystal instead continues growing in ribbons that protrude from the original crystal. Here we report on computer simulations in which we observe both the formation of ribbons at short interaction ranges and packings that incorporate defects if the interaction is longer-ranged. The ribbons only form above some critical crystal size, below which the nucleus is disk-shaped. We find that the scaling of the critical crystal size differs slightly from the one proposed in the literature, and we argue that this is because the actual morphology transition is caused by the competition between line tension and elastic stress, rather than the competition between chemical potential and elastic stress.

Impact of interaction range and curvature on crystal growth of particles confined to spherical surfaces

NASA Astrophysics Data System (ADS)

Paquay, Stefan; Both, Gert-Jan; van der Schoot, Paul

2017-07-01

When colloidal particles form a crystal phase on a spherical template, their packing is governed by the effective interaction between them and the elastic strain of bending the growing crystal. For example, if growth commences under appropriate conditions, and the isotropic crystal that forms reaches a critical size, growth continues via the incorporation of defects to alleviate elastic strain. Recently, it was experimentally found that, if defect formation is somehow not possible, the crystal instead continues growing in ribbons that protrude from the original crystal. Here we report on computer simulations in which we observe both the formation of ribbons at short interaction ranges and packings that incorporate defects if the interaction is longer-ranged. The ribbons only form above some critical crystal size, below which the nucleus is disk-shaped. We find that the scaling of the critical crystal size differs slightly from the one proposed in the literature, and we argue that this is because the actual morphology transition is caused by the competition between line tension and elastic stress, rather than the competition between chemical potential and elastic stress.

Comparison of Arterial Spin-labeling Perfusion Images at Different Spatial Normalization Methods Based on Voxel-based Statistical Analysis.

PubMed

Tani, Kazuki; Mio, Motohira; Toyofuku, Tatsuo; Kato, Shinichi; Masumoto, Tomoya; Ijichi, Tetsuya; Matsushima, Masatoshi; Morimoto, Shoichi; Hirata, Takumi

2017-01-01

Spatial normalization is a significant image pre-processing operation in statistical parametric mapping (SPM) analysis. The purpose of this study was to clarify the optimal method of spatial normalization for improving diagnostic accuracy in SPM analysis of arterial spin-labeling (ASL) perfusion images. We evaluated the SPM results of five spatial normalization methods obtained by comparing patients with Alzheimer's disease or normal pressure hydrocephalus complicated with dementia and cognitively healthy subjects. We used the following methods: 3DT1-conventional based on spatial normalization using anatomical images; 3DT1-DARTEL based on spatial normalization with DARTEL using anatomical images; 3DT1-conventional template and 3DT1-DARTEL template, created by averaging cognitively healthy subjects spatially normalized using the above methods; and ASL-DARTEL template created by averaging cognitively healthy subjects spatially normalized with DARTEL using ASL images only. Our results showed that ASL-DARTEL template was small compared with the other two templates. Our SPM results obtained with ASL-DARTEL template method were inaccurate. Also, there were no significant differences between 3DT1-conventional and 3DT1-DARTEL template methods. In contrast, the 3DT1-DARTEL method showed higher detection sensitivity, and precise anatomical location. Our SPM results suggest that we should perform spatial normalization with DARTEL using anatomical images.

Bio-inspired routes for synthesizing efficient nanoscale platinum electrocatalysts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cha, Jennifer N.; Wang, Joseph

2014-08-31

The overall objective of the proposed research is to use fundamental advances in bionanotechnology to design powerful platinum nanocrystal electrocatalysts for fuel cell applications. The new economically-viable, environmentally-friendly, bottom-up biochemical synthetic strategy will produce platinum nanocrystals with tailored size, shape and crystal orientation, hence leading to a maximum electrochemical reactivity. There are five specific aims to the proposed bio-inspired strategy for synthesizing efficient electrocatalytic platinum nanocrystals: (1) isolate peptides that both selectively bind particular crystal faces of platinum and promote the nucleation and growth of particular nanocrystal morphologies, (2) pattern nanoscale 2-dimensional arrays of platinum nucleating peptides from DNA scaffolds,more » (3) investigate the combined use of substrate patterned peptides and soluble peptides on nanocrystal morphology and growth (4) synthesize platinum crystals on planar and large-area carbon electrode supports, and (5) perform detailed characterization of the electrocatalytic behavior as a function of catalyst size, shape and morphology. Project Description and Impact: This bio-inspired collaborative research effort will address key challenges in designing powerful electrocatalysts for fuel cell applications by employing nucleic acid scaffolds in combination with peptides to perform specific, environmentally-friendly, simultaneous bottom-up biochemical synthesis and patterned assembly of highly uniform and efficient platinum nanocrystal catalysts. Bulk synthesis of nanoparticles usually produces a range of sizes, accessible catalytic sites, crystal morphologies, and orientations, all of which lead to inconsistent catalytic activities. In contrast, biological systems routinely demonstrate exquisite control over inorganic syntheses at neutral pH and ambient temperature and pressures. Because the orientation and arrangement of the templating biomolecules can be precisely controlled, the nanocrystals boast a defined shape, morphology, orientation and size and are synthesized at benign reaction conditions. Adapting the methods of biomineralization towards the synthesis of platinum nanocrystals will allow effective control at a molecular level of the synthesis of highly active metal electrocatalysts, with readily tailored properties, through tuning of the biochemical inputs. The proposed research will incorporate many facets of biomineralization by: (1) isolating peptides that selectively bind particular crystal faces of platinum (2) isolating peptides that promote the nucleation and growth of particular nanocrystal morphologies (3) using two-dimensional DNA scaffolds to control the spatial orientation and density of the platinum nucleating peptides, and (4) combining bio-templating and soluble peptides to control crystal nucleation, orientation, and morphology. The resulting platinum nanocrystals will be evaluated for their electrocatalytic behavior (on common carbon supports) to determine their optimal size, morphology and crystal structure. We expect that such rational biochemical design will lead to highly uniform and efficient platinum nanocrystal catalysts for fuel cell applications.« less

Effect of ionizing radiation on structural and conductive properties of copper nanotubes

NASA Astrophysics Data System (ADS)

Zdorovets, M. V.; Borgekov, D. B.; Kenzhina, I. E.; Kozlovskiy, A. L.

2018-01-01

The use of electron radiation is an effective tool for stimulating a controlled modification of structural and conductive properties of nanomaterials in modern materials science. The paper presents the results of studies of the influence of various types of radiation on structural and conductive properties of copper nanotubes obtained by electrochemical synthesis in pores of templates based on polyethylene terephthalate. Such methods as SEM, X-ray diffraction and EDS show that irradiation with a stream of high-energy electrons with doses of 50-250 kGy makes it possible to modify the crystal structure of nanotubes, increasing their conductivity and decreasing the resistance of nanostructures without destroying the structure.

Hierarchical photonic structured stimuli-responsive materials as high-performance colorimetric sensors

NASA Astrophysics Data System (ADS)

Lu, Tao; Zhu, Shenmin; Chen, Zhixin; Wang, Wanlin; Zhang, Wang; Zhang, Di

2016-05-01

Hierarchical photonic structures in nature are of special interest because they can be used as templates for fabrication of stimuli-responsive photonic crystals (PCs) with unique structures beyond man-made synthesis. The current stimuli-responsive PCs templated directly from natural PCs showed a very weak external stimuli response and poor durability due to the limitations of natural templates. Herein, we tackle this problem by chemically coating functional polymers, polyacrylamide, on butterfly wing scales which have hierarchical photonic structures. As a result of the combination of the strong water absorption properties of the polyacrylamide and the PC structures of the butterfly wing scales, the designed materials demonstrated excellent humidity responsive properties and a tremendous colour change. The colour change is induced by the refractive index change which is in turn due to the swollen nature of the polymer when the relative humidity changes. The butterfly wing scales also showed an excellent durability which is due to the chemical bonds formed between the polymer and wing scales. The synthesis strategy provides an avenue for the promising applications of stimuli-responsive PCs with hierarchical structures.Hierarchical photonic structures in nature are of special interest because they can be used as templates for fabrication of stimuli-responsive photonic crystals (PCs) with unique structures beyond man-made synthesis. The current stimuli-responsive PCs templated directly from natural PCs showed a very weak external stimuli response and poor durability due to the limitations of natural templates. Herein, we tackle this problem by chemically coating functional polymers, polyacrylamide, on butterfly wing scales which have hierarchical photonic structures. As a result of the combination of the strong water absorption properties of the polyacrylamide and the PC structures of the butterfly wing scales, the designed materials demonstrated excellent humidity responsive properties and a tremendous colour change. The colour change is induced by the refractive index change which is in turn due to the swollen nature of the polymer when the relative humidity changes. The butterfly wing scales also showed an excellent durability which is due to the chemical bonds formed between the polymer and wing scales. The synthesis strategy provides an avenue for the promising applications of stimuli-responsive PCs with hierarchical structures. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr01875k

Improving homology modeling of G-protein coupled receptors through multiple-template derived conserved inter-residue interactions

NASA Astrophysics Data System (ADS)

Chaudhari, Rajan; Heim, Andrew J.; Li, Zhijun

2015-05-01

Evidenced by the three-rounds of G-protein coupled receptors (GPCR) Dock competitions, improving homology modeling methods of helical transmembrane proteins including the GPCRs, based on templates of low sequence identity, remains an eminent challenge. Current approaches addressing this challenge adopt the philosophy of "modeling first, refinement next". In the present work, we developed an alternative modeling approach through the novel application of available multiple templates. First, conserved inter-residue interactions are derived from each additional template through conservation analysis of each template-target pairwise alignment. Then, these interactions are converted into distance restraints and incorporated in the homology modeling process. This approach was applied to modeling of the human β2 adrenergic receptor using the bovin rhodopsin and the human protease-activated receptor 1 as templates and improved model quality was demonstrated compared to the homology model generated by standard single-template and multiple-template methods. This method of "refined restraints first, modeling next", provides a fast and complementary way to the current modeling approaches. It allows rational identification and implementation of additional conserved distance restraints extracted from multiple templates and/or experimental data, and has the potential to be applicable to modeling of all helical transmembrane proteins.

Fibrillar films obtained from sodium soap fibers and polyelectrolyte multilayers.

PubMed

Zawko, Scott A; Schmidt, Christine E

2011-08-01

An objective of tissue engineering is to create synthetic polymer scaffolds with a fibrillar microstructure similar to the extracellular matrix. Here, we present a novel method for creating polymer fibers using the layer-by-layer method and sacrificial templates composed of sodium soap fibers. Soap fibers were prepared from neutralized fatty acids using a sodium chloride crystal dissolution method. Polyelectrolyte multilayers (PEMs) of polystyrene sulfonate and polyallylamine hydrochloride were deposited onto the soap fibers, crosslinked with glutaraldehyde, and then the soap fibers were leached with warm water and ethanol. The morphology of the resulting PEM structures was a dense network of fibers surrounded by a nonfibrillar matrix. Microscopy revealed that the PEM fibers were solid structures, presumably composed of polyelectrolytes complexed with residual fatty acids. These fibrillar PEM films were found to support the attachment of human dermal fibroblasts. Copyright © 2011 Wiley Periodicals, Inc.

A rational repeating template method for synthesis of 2D hexagonally ordered mesoporous precious metals.

PubMed

Takai, Azusa; Doi, Yoji; Yamauchi, Yusuke; Kuroda, Kazuyuki

2011-03-01

A repeating template method is presented for the synthesis of mesoporous metals with 2D hexagonal mesostructures. First, a silica replica (i.e., silica nanorods arranged periodically) is prepared by using 2D hexagonally ordered mesoporous carbon as the template. After that, the obtained silica replica is used as the second template for the preparation of mesoporous ruthenium. After the ruthenium species are introduced into the silica replica, the ruthenium species are then reduced by a vapor-infiltration method by using the reducing agent dimethylamine borane. After the ruthenium deposition, the silica is chemically removed. Analysis by transmission and scanning electron microscopies, a nitrogen-adsorption-desorption isotherm, and small-angle X-ray scattering revealed that the mesoporous ruthenium had a 2D hexagonal mesostructure, although the mesostructural ordering is decreased compared to that of the original mesoporous carbon template. This method is widely applicable to other metal systems. By changing the metal species introduced into the silica replica, several mesoporous metals (palladium and platinum) can be synthesized. Ordered mesoporous ruthenium and palladium, which are not easily attainable by the soft-templating methods, can be prepared. This study has overcome the composition variation limitations of the soft-templating method. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Molecular insights into the heterogeneous crystal growth of si methane hydrate.

PubMed

Vatamanu, Jenel; Kusalik, Peter G

2006-08-17

In this paper we report a successful molecular simulation study exploring the heterogeneous crystal growth of sI methane hydrate along its [001] crystallographic face. The molecular modeling of the crystal growth of methane hydrate has proven in the past to be very challenging, and a reasonable framework to overcome the difficulties related to the simulation of such systems is presented. Both the microscopic mechanisms of heterogeneous crystal growth as well as interfacial properties of methane hydrate are probed. In the presence of the appropriate crystal template, a strong tendency for water molecules to organize into cages around methane at the growing interface is observed; the interface also demonstrates a strong affinity for methane molecules. The maximum growth rate measured for a hydrate crystal is about 4 times higher than the value previously determined for ice I in a similar framework (Gulam Razul, M. S.; Hendry, J. G.; Kusalik, P. G. J. Chem. Phys. 2005, 123, 204722).

Photovoltaic panel extraction from very high-resolution aerial imagery using region-line primitive association analysis and template matching

NASA Astrophysics Data System (ADS)

Wang, Min; Cui, Qi; Sun, Yujie; Wang, Qiao

2018-07-01

In object-based image analysis (OBIA), object classification performance is jointly determined by image segmentation, sample or rule setting, and classifiers. Typically, as a crucial step to obtain object primitives, image segmentation quality significantly influences subsequent feature extraction and analyses. By contrast, template matching extracts specific objects from images and prevents shape defects caused by image segmentation. However, creating or editing templates is tedious and sometimes results in incomplete or inaccurate templates. In this study, we combine OBIA and template matching techniques to address these problems and aim for accurate photovoltaic panel (PVP) extraction from very high-resolution (VHR) aerial imagery. The proposed method is based on the previously proposed region-line primitive association framework, in which complementary information between region (segment) and line (straight line) primitives is utilized to achieve a more powerful performance than routine OBIA. Several novel concepts, including the mutual fitting ratio and best-fitting template based on region-line primitive association analyses, are proposed. Automatic template generation and matching method for PVP extraction from VHR imagery are designed for concept and model validation. Results show that the proposed method can successfully extract PVPs without any user-specified matching template or training sample. High user independency and accuracy are the main characteristics of the proposed method in comparison with routine OBIA and template matching techniques.

Enhanced photochemical catalysis of TiO2 inverse opals by modification with ZnO or Fe2O3 using ALD and the hydrothermal method

NASA Astrophysics Data System (ADS)

Liu, Jiatong; Sun, Cuifeng; Fu, Ming; Long, Jie; He, Dawei; Wang, Yongsheng

2018-02-01

The development of porous materials exhibiting photon regulation abilities for improved photoelectrochemical catalysis performance is always one of the important goals of solar energy harvesting. In this study, methods to improve the photocatalytic activity of TiO2 inverse opals were discussed. TiO2 inverse opals were prepared by atomic layer deposition (ALD) using colloidal crystal templates. In addition, TiO2 inverse opal heterostructures were fabricated using colloidal heterocrystals by repeated vertical deposition using different colloidal spheres. The hydrothermal method and ALD were used to prepare ZnO- or Fe2O3-modified TiO2 inverse opals on the internal surfaces of the TiO2 porous structures. Although the photonic reflection band was not significantly varied by oxide modification, the presence of Fe2O3 in the TiO2 inverse opals enhanced their visible absorption. The conformally modified oxides on the TiO2 inverse opals could also form energy barriers and avoid the recombination of electrons and holes. The fabrication of the TiO2 photonic crystal heterostructures and modification with ZnO or Fe2O3 can enhance the photocatalytic activity of TiO2 inverse opals.

Synthesis of highly efficient α-Fe{sub 2}O{sub 3} catalysts for CO oxidation derived from MIL-100(Fe)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cui, Lifeng; Zhao, Di; Yang, Yang

Mesoporous hollow α-Fe{sub 2}O{sub 3} bricks were synthesized via a hydrothermal method to create a precursor MIL-100(Fe) and a subsequent calcination process was applied to prepare the Fe{sub 2}O{sub 3} phase. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results showed the morphology of hollow α-Fe{sub 2}O{sub 3} bricks which inherited from the MIL-100(Fe) template. The catalytic activities of hollow α-Fe{sub 2}O{sub 3} bricks for CO oxidation are studied in this work. Due to better low temperature reduction behavior, mesoporous hollow α-Fe{sub 2}O{sub 3} bricks obtained at calcination temperature of 430 °C displayed high catalytic activity and excellent stabilitymore » with a complete CO conversion temperature (T{sub 100}) of 255 °C. - Graphical abstract: Synthesis of highly efficient α-Fe{sub 2}O{sub 3} catalysts for CO oxidation derived from MIL-100(Fe). - Highlights: • α-Fe{sub 2}O{sub 3} is prepared by the thermolysis of a MIL-100(Fe) template. • The morphology of hollow α-Fe{sub 2}O{sub 3} bricks is inherited from MIL-100(Fe) template. • α-Fe{sub 2}O{sub 3} obtained at calcined temperature of 430 °C displays high activity • Enhanced activity is attributed to crystal plane and reduction behavior.« less

Protein–DNA Interactions: The Story so Far and a New Method for Prediction

DOE PAGES

Jones, Susan; Thornton, Janet M.

2003-01-01

This review describes methods for the prediction of DNA binding function, and specifically summarizes a new method using 3D structural templates. The new method features the HTH motif that is found in approximately one-third of DNAbinding protein families. A library of 3D structural templates of HTH motifs was derived from proteins in the PDB. Templates were scanned against complete protein structures and the optimal superposition of a template on a structure calculated. Significance thresholds in terms of a minimum root mean squared deviation (rmsd) of an optimal superposition, and a minimum motif accessible surface area (ASA), have been calculated. Inmore » this way, it is possible to scan the template library against proteins of unknown function to make predictions about DNA-binding functionality.« less

Nanostructures of Indium Gallium Nitride Crystals Grown on Carbon Nanotubes.

PubMed

Park, Ji-Yeon; Man Song, Keun; Min, Yo-Sep; Choi, Chel-Jong; Seok Kim, Yoon; Lee, Sung-Nam

2015-11-16

Nanostructure (NS) InGaN crystals were grown on carbon nanotubes (CNTs) using metalorganic chemical vapor deposition. The NS-InGaN crystals, grown on a ~5-μm-long CNT/Si template, were estimated to be ~100-270 nm in size. Transmission electron microscope examinations revealed that single-crystalline InGaN NSs were formed with different crystal facets. The observed green (~500 nm) cathodoluminescence (CL) emission was consistent with the surface image of the NS-InGaN crystallites, indicating excellent optical properties of the InGaN NSs on CNTs. Moreover, the CL spectrum of InGaN NSs showed a broad emission band from 490 to 600 nm. Based on these results, we believe that InGaN NSs grown on CNTs could aid in overcoming the green gap in LED technologies.

Directed self-assembly of liquid crystalline blue-phases into ideal single-crystals

NASA Astrophysics Data System (ADS)

Martínez-González, Jose A.; Li, Xiao; Sadati, Monirosadat; Zhou, Ye; Zhang, Rui; Nealey, Paul F.; de Pablo, Juan J.

2017-06-01

Chiral nematic liquid crystals are known to form blue phases--liquid states of matter that exhibit ordered cubic arrangements of topological defects. Blue-phase specimens, however, are generally polycrystalline, consisting of randomly oriented domains that limit their performance in applications. A strategy that relies on nano-patterned substrates is presented here for preparation of stable, macroscopic single-crystal blue-phase materials. Different template designs are conceived to exert control over different planes of the blue-phase lattice orientation with respect to the underlying substrate. Experiments are then used to demonstrate that it is indeed possible to create stable single-crystal blue-phase domains with the desired orientation over large regions. These results provide a potential avenue to fully exploit the electro-optical properties of blue phases, which have been hindered by the existence of grain boundaries.

76 FR 4897 - Submission for OMB Review; OMB Control No. 3090-0291; FSRS Registration and Prime Awardee Entity...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-01-27

... methods for submitting multiple FFATA subaward reports: A batch upload template using Microsoft Excel, an... three methods for submitting multiple FFATA subaward reports: A batch upload template using Microsoft Excel, an XML report submission template and an XML web service. These methods do take advantage of the...

Sb-Te Phase-change Materials under Nanoscale Confinement

NASA Astrophysics Data System (ADS)

Ihalawela, Chandrasiri A.

Size, speed and efficiency are the major challenges of next generation nonvolatile memory (NVM), and phase-change memory (PCM) has captured a great attention due to its promising features. The key for PCM is rapid and reversible switching between amorphous and crystalline phases with optical or electrical excitation. The structural transition is associated with significant contrast in material properties which can be utilized in optical (CD, DVD, BD) and electronic (PCRAM) memory applications. Importantly, both the functionality and the success of PCM technology significantly depend on the core material and its properties. So investigating PC materials is crucial for the development of PCM technology to realized enhanced solutions. In regards to PC materials, Sb-Te binary plays a significant role as a basis to the well-known Ge-Sb-Te system. Unlike the conventional deposition methods (sputtering, evaporation), electrochemical deposition method is used due to its multiple advantages, such as conformality, via filling capability, etc. First, the controllable synthesis of Sb-Te thin films was studied for a wide range of compositions using this novel deposition method. Secondly, the solid electrolytic nature of stoichiometric Sb2Te3 was studied with respect to precious metals. With the understanding of 2D thin film synthesis, Sb-Te 1D nanowires (18 - 220 nm) were synthesized using templated electrodeposition, where nanoporous anodic aluminum oxide (AAO) was used as a template for the growth of nanowires. In order to gain the controllability over the deposition in high aspect ratio structures, growth mechanisms of both the thin films and nanowires were investigated. Systematic understanding gained thorough previous studies helped to formulate the ultimate goal of this dissertation. In this dissertation, the main objective is to understand the size effect of PC materials on their phase transition properties. The reduction of effective memory cell size in conjunction with multilevel cells could be promising to achieve high data densities. However the size reduction may result in changes in material properties. If phase transition properties of the materials are also tunable with respect to the size, then more attractive solutions could be realized. So we have reported the size effect on crystallization temperature of prototypical Sb2Te3 nanowires synthesized in AAO templates. Moreover, we have found that the reduction of nanowire size can elevate the crystallization temperature, which is crucial for data retention in PCM technology. Energy dispersive X-ray spectroscopy, X-ray diffraction, electron microscopy and electrical resistivity measurements were used to characterize the composition, structure, morphology, and phase transition properties of the materials. We believe that this dissertation will provide new insights into the size effect of PC materials in addition to the controllable synthesis of PC thin films and nanowires through the novel electrochemical method.

The RNA template channel of the RNA-dependent RNA polymerase as a target for development of antiviral therapy of multiple genera within a virus family.

PubMed

van der Linden, Lonneke; Vives-Adrián, Laia; Selisko, Barbara; Ferrer-Orta, Cristina; Liu, Xinran; Lanke, Kjerstin; Ulferts, Rachel; De Palma, Armando M; Tanchis, Federica; Goris, Nesya; Lefebvre, David; De Clercq, Kris; Leyssen, Pieter; Lacroix, Céline; Pürstinger, Gerhard; Coutard, Bruno; Canard, Bruno; Boehr, David D; Arnold, Jamie J; Cameron, Craig E; Verdaguer, Nuria; Neyts, Johan; van Kuppeveld, Frank J M

2015-03-01

The genus Enterovirus of the family Picornaviridae contains many important human pathogens (e.g., poliovirus, coxsackievirus, rhinovirus, and enterovirus 71) for which no antiviral drugs are available. The viral RNA-dependent RNA polymerase is an attractive target for antiviral therapy. Nucleoside-based inhibitors have broad-spectrum activity but often exhibit off-target effects. Most non-nucleoside inhibitors (NNIs) target surface cavities, which are structurally more flexible than the nucleotide-binding pocket, and hence have a more narrow spectrum of activity and are more prone to resistance development. Here, we report a novel NNI, GPC-N114 (2,2'-[(4-chloro-1,2-phenylene)bis(oxy)]bis(5-nitro-benzonitrile)) with broad-spectrum activity against enteroviruses and cardioviruses (another genus in the picornavirus family). Surprisingly, coxsackievirus B3 (CVB3) and poliovirus displayed a high genetic barrier to resistance against GPC-N114. By contrast, EMCV, a cardiovirus, rapidly acquired resistance due to mutations in 3Dpol. In vitro polymerase activity assays showed that GPC-N114 i) inhibited the elongation activity of recombinant CVB3 and EMCV 3Dpol, (ii) had reduced activity against EMCV 3Dpol with the resistance mutations, and (iii) was most efficient in inhibiting 3Dpol when added before the RNA template-primer duplex. Elucidation of a crystal structure of the inhibitor bound to CVB3 3Dpol confirmed the RNA-binding channel as the target for GPC-N114. Docking studies of the compound into the crystal structures of the compound-resistant EMCV 3Dpol mutants suggested that the resistant phenotype is due to subtle changes that interfere with the binding of GPC-N114 but not of the RNA template-primer. In conclusion, this study presents the first NNI that targets the RNA template channel of the picornavirus polymerase and identifies a new pocket that can be used for the design of broad-spectrum inhibitors. Moreover, this study provides important new insight into the plasticity of picornavirus polymerases at the template binding site.

The RNA Template Channel of the RNA-Dependent RNA Polymerase as a Target for Development of Antiviral Therapy of Multiple Genera within a Virus Family

PubMed Central

van der Linden, Lonneke; Vives-Adrián, Laia; Selisko, Barbara; Ferrer-Orta, Cristina; Liu, Xinran; Lanke, Kjerstin; Ulferts, Rachel; De Palma, Armando M.; Tanchis, Federica; Goris, Nesya; Lefebvre, David; De Clercq, Kris; Leyssen, Pieter; Lacroix, Céline; Pürstinger, Gerhard; Coutard, Bruno; Canard, Bruno; Boehr, David D.; Arnold, Jamie J.; Cameron, Craig E.; Verdaguer, Nuria

2015-01-01

The genus Enterovirus of the family Picornaviridae contains many important human pathogens (e.g., poliovirus, coxsackievirus, rhinovirus, and enterovirus 71) for which no antiviral drugs are available. The viral RNA-dependent RNA polymerase is an attractive target for antiviral therapy. Nucleoside-based inhibitors have broad-spectrum activity but often exhibit off-target effects. Most non-nucleoside inhibitors (NNIs) target surface cavities, which are structurally more flexible than the nucleotide-binding pocket, and hence have a more narrow spectrum of activity and are more prone to resistance development. Here, we report a novel NNI, GPC-N114 (2,2'-[(4-chloro-1,2-phenylene)bis(oxy)]bis(5-nitro-benzonitrile)) with broad-spectrum activity against enteroviruses and cardioviruses (another genus in the picornavirus family). Surprisingly, coxsackievirus B3 (CVB3) and poliovirus displayed a high genetic barrier to resistance against GPC-N114. By contrast, EMCV, a cardiovirus, rapidly acquired resistance due to mutations in 3Dpol. In vitro polymerase activity assays showed that GPC-N114 i) inhibited the elongation activity of recombinant CVB3 and EMCV 3Dpol, (ii) had reduced activity against EMCV 3Dpol with the resistance mutations, and (iii) was most efficient in inhibiting 3Dpol when added before the RNA template-primer duplex. Elucidation of a crystal structure of the inhibitor bound to CVB3 3Dpol confirmed the RNA-binding channel as the target for GPC-N114. Docking studies of the compound into the crystal structures of the compound-resistant EMCV 3Dpol mutants suggested that the resistant phenotype is due to subtle changes that interfere with the binding of GPC-N114 but not of the RNA template-primer. In conclusion, this study presents the first NNI that targets the RNA template channel of the picornavirus polymerase and identifies a new pocket that can be used for the design of broad-spectrum inhibitors. Moreover, this study provides important new insight into the plasticity of picornavirus polymerases at the template binding site. PMID:25799064

Creating Shape Templates for Patient Specific Biventricular Modeling in Congenital Heart Disease

PubMed Central

Gilbert, Kathleen; Farrar, Genevieve; Cowan, Brett R.; Suinesiaputra, Avan; Occleshaw, Christopher; Pontré, Beau; Perry, James; Hegde, Sanjeet; Marsden, Alison; Omens, Jeff; McCulloch, Andrew; Young, Alistair A.

2018-01-01

Survival rates for infants with congenital heart disease (CHD) are improving, resulting in a growing population of adults with CHD. However, the analysis of left and right ventricular function is very time-consuming owing to the variety of congenital morphologies. Efficient customization of patient geometry and function depends on high quality shape templates specifically designed for the application. In this paper, we combine a method for creating finite element shape templates with an interactive template customization to patient MRI examinations. This enables different templates to be chosen depending on patient morphology. To demonstrate this pipeline, a new biventricular template with 162 elements was created and tested in place of an existing 82-element template. The method was able to provide fast interactive biventricular analysis with 0.31 sec per edit response time. The new template was customized to 13 CHD patients with similar biventricular topology, showing improved performance over the previous template and good agreement with clinical indices. PMID:26736353

New immobilisation protocol for the template used in solid-phase synthesis of MIP nanoparticles

NASA Astrophysics Data System (ADS)

Chen, Lu; Muhammad, Turghun; Yakup, Burabiye; Piletsky, Sergey A.

2017-06-01

As a novel imprinting method, solid-phase synthesis has proven to be a promising approach to prepare polymer nanoparticles with specific recognition sites for a template molecule. In this method, imprinted polymer nanoparticles were synthesized using template immobilized on a solid support. Herein, preparation of immobilized templates on quartz chips through homogeneous route was reported as an efficient alternative strategy to heterogeneous one. The template molecule indole-3-butyric acid (IBA) was reacted with 3-aminopropyltriethoxysilane (APTES) to produce silylated template (IBA-APTES), and it was characterized by IR, 1H NMR and GC-MS. Then, the silylated template molecule was grafted onto the activated surfaces of quartz chip to prepare immobilized template (SiO2@IBA-APTES). The immobilization was confirmed by contact angle, XPS, UV and fluorescence measurement. Immobilization protocol has shown good reproducibility and stability of the immobilized template. MIP nanoparticles were prepared with high selectivity toward the molecule immobilized onto the solid surface. This provides a new approach for the development of molecularly imprinted nanoparticles.

Toward the Fabrication of Advanced Nanofiltration Membranes by Controlling Morphologies and Mesochannel Orientations of Hexagonal Lyotropic Liquid Crystals.

PubMed

Wang, Guang; Garvey, Christopher J; Zhao, Han; Huang, Kang; Kong, Lingxue

2017-07-21

Water scarcity has been recognized as one of the major threats to human activity, and, therefore, water purification technologies are increasingly drawing attention worldwide. Nanofiltration (NF) membrane technology has been proven to be an efficient and cost-effective way in terms of the size and continuity of the nanostructure. Using a template based on hexagonal lyotropic liquid crystals (LLCs) and partitioning monomer units within this structure for subsequent photo-polymerisation presents a unique path for the fabrication of NF membranes, potentially producing pores of uniform size, ranging from 1 to 5 nm, and large surface areas. The subsequent orientation of this pore network in a direction normal to a flat polymer film that provides ideal transport properties associated with continuous pores running through the membrane has been achieved by the orientation of hexagonal LLCs through various strategies. This review presents the current progresses on the strategies for structure retention from a hexagonal LLCs template and the up-to-date techniques used for the reorientation of mesochanels for continuity through the whole membrane.

Structural and functional engineering of one-dimensional nanostructures for device applications

NASA Astrophysics Data System (ADS)

Singh, Krishna Veer

Fabrication of 1-D nanostructures has been an area of keen interest due to their application in nanodevices. Carbon nanotubes (CNTs) and semiconducting nanorods are 1-D nanostructures of great importance. There are various challenges related to structural and functional aspects of these materials, which need to be addressed for their adaptation in devices. To this end, two approaches have been developed: (1) structural engineering of the nanorods and (2) functionalization of CNTs for device applications. In first approach, a new technique to produce single crystal semiconducting nanorods was developed. Single crystalline structure of nanorods is essential to obtain reproducible performance. The novel synthesis technique 'template assisted sonoelectrochemical deposition' was utilized to develop 'copper sulfide' and 'copper indium sulfide' nanorods. The use of sonoelectrochemical method resulted in the best deposition rate as compared to stirring-assisted and regular electrochemical deposition, respectively. Observed increase in the bulk electrolyte temperature, high acoustic pressure and shock waves generated from the collapse of bubbles could explain improved mass transport and reaction rate, which results in the formation of single crystal nanorods. Nanorods in the range of 50-200nm in diameter were synthesized and electrically characterized as p-type semiconductors. Excellent structural and repeatable electrical properties of the various nanorods developed by this technique make it suitable for developing nanorods for device applications. In addition, detailed statistical analysis of the polycarbonate templates (50-200 nm nominal pore size) used in electrodeposition provided a better understanding of template's as well as nanorods' structure. In the second approach, we functionally engineered single walled carbon nanotubes (SWNTs) with peptide nucleic acid (PNA) to form functional conjugates for molecular electronics. SWNT-PNA-SWNT conjugates were synthesized using carbodiimide chemistry. Also in this work, the electric transport measurements of SWNT-PNA conjugates are reported for the first time. Corresponding analysis reveals that these conjugates exhibit diodic behaviour and in some devices negative differential resistance (NDR) was also observed. The unique electrical and structural properties of these conjugates make them a potential candidate for application in CNT based nanodevices. Hence, this work demonstrates novel techniques to functionally and structurally engineer 1-D nanomaterials for device applications.

Lyotropic Liquid Crystal Phases from Anisotropic Nanomaterials

PubMed Central

Dierking, Ingo

2017-01-01

Liquid crystals are an integral part of a mature display technology, also establishing themselves in other applications, such as spatial light modulators, telecommunication technology, photonics, or sensors, just to name a few of the non-display applications. In recent years, there has been an increasing trend to add various nanomaterials to liquid crystals, which is motivated by several aspects of materials development. (i) addition of nanomaterials can change and thus tune the properties of the liquid crystal; (ii) novel functionalities can be added to the liquid crystal; and (iii) the self-organization of the liquid crystalline state can be exploited to template ordered structures or to transfer order onto dispersed nanomaterials. Much of the research effort has been concentrated on thermotropic systems, which change order as a function of temperature. Here we review the other side of the medal, the formation and properties of ordered, anisotropic fluid phases, liquid crystals, by addition of shape-anisotropic nanomaterials to isotropic liquids. Several classes of materials will be discussed, inorganic and mineral liquid crystals, viruses, nanotubes and nanorods, as well as graphene oxide. PMID:28974025

All-wurtzite ZnO/ZnSe hetero-nanohelix: formation, mechanics and luminescence

NASA Astrophysics Data System (ADS)

Sun, Luwei; Ye, Zhizhen; He, Haiping

2015-04-01

A unique all-wurtzite ZnO/ZnSe hetero-nanohelix is formed via growing wurtzite ZnSe nanoteeth on ZnO nanobelts through a one step thermal evaporation method. The microstructure and growth mechanism of the hetero-nanohelix are investigated in detail. The formation of metastable wurtzite ZnSe is attributed to the wurtzite ZnO template. Mechanical forces, thermal expansion and polar plane in hexagonal crystals are suggested to contribute to the bending of the nanohelix. A boomerang-like structural block is proposed to assemble the zigzag ZnO nanobelts. The incorporation of Se into ZnO results in a strong orange emission. The heterostructure of the ZnO/ZnSe nanohelix is confirmed by elemental mapping and luminescence imaging. The fabrication of such a hetero-nanohelix may provide insights into the growth mechanism of the rich family of ZnO-based nanostructures.A unique all-wurtzite ZnO/ZnSe hetero-nanohelix is formed via growing wurtzite ZnSe nanoteeth on ZnO nanobelts through a one step thermal evaporation method. The microstructure and growth mechanism of the hetero-nanohelix are investigated in detail. The formation of metastable wurtzite ZnSe is attributed to the wurtzite ZnO template. Mechanical forces, thermal expansion and polar plane in hexagonal crystals are suggested to contribute to the bending of the nanohelix. A boomerang-like structural block is proposed to assemble the zigzag ZnO nanobelts. The incorporation of Se into ZnO results in a strong orange emission. The heterostructure of the ZnO/ZnSe nanohelix is confirmed by elemental mapping and luminescence imaging. The fabrication of such a hetero-nanohelix may provide insights into the growth mechanism of the rich family of ZnO-based nanostructures. Electronic supplementary information (ESI) available: HRTEM image, EDS elemental mapping, XRD data, and calculation of bending mechanics. See DOI: 10.1039/c5nr00567a

Columnar and subsurface silicide growth with novel molecular beam epitaxy techniques

NASA Technical Reports Server (NTRS)

Fathauer, R. W.; George, T.; Pike, W. T.

1992-01-01

We have found novel growth modes for epitaxial CoSi2 at high temperatures coupled with Si-rich flux ratios or low deposition rates. In the first of these modes, codeposition of metal and Si at 600-800 C with excess Si leads to the formation of epitaxial silicide columns surrounded by single-crystal Si. During the initial stages of the deposition, the excess Si grows homoepitaxially in between the silicide, which forms islands, so that the lateral growth of the islands is confined. Once a template layer is established by this process, columns of silicide form as a result of selective epitaxy of silicide on silicide and Si on Si. This growth process allows nanometer control over silicide particles in three dimensions. In the second of these modes, a columnar silicide seed layer is used as a template to nucleate subsurface growth of CoSi2. With a 100 nm Si layer covering CoSi2 seeds, Co deposited at 800C and 0.01 nm/s diffuses down to grow on the buried seeds rather than nucleating surface silicide islands. For thicker Si caps or higher deposition rates, the surface concentration of Co exceeds the critical concentration for nucleation of islands, preventing this subsurface growth mode from occurring. Using this technique, single-crystal layers of CoSi2 buried under single-crystal Si caps have been grown.

Ordered macro-microporous metal-organic framework single crystals

NASA Astrophysics Data System (ADS)

Shen, Kui; Zhang, Lei; Chen, Xiaodong; Liu, Lingmei; Zhang, Daliang; Han, Yu; Chen, Junying; Long, Jilan; Luque, Rafael; Li, Yingwei; Chen, Banglin

2018-01-01

We constructed highly oriented and ordered macropores within metal-organic framework (MOF) single crystals, opening up the area of three-dimensional–ordered macro-microporous materials (that is, materials containing both macro- and micropores) in single-crystalline form. Our methodology relies on the strong shaping effects of a polystyrene nanosphere monolith template and a double-solvent–induced heterogeneous nucleation approach. This process synergistically enabled the in situ growth of MOFs within ordered voids, rendering a single crystal with oriented and ordered macro-microporous structure. The improved mass diffusion properties of such hierarchical frameworks, together with their robust single-crystalline nature, endow them with superior catalytic activity and recyclability for bulky-molecule reactions, as compared with conventional, polycrystalline hollow, and disordered macroporous ZIF-8.

Centroid stabilization for laser alignment to corner cubes: designing a matched filter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Awwal, Abdul A. S.; Bliss, Erlan; Brunton, Gordon

2016-11-08

Automation of image-based alignment of National Ignition Facility high energy laser beams is providing the capability of executing multiple target shots per day. One important alignment is beam centration through the second and third harmonic generating crystals in the final optics assembly (FOA), which employs two retroreflecting corner cubes as centering references for each beam. Beam-to-beam variations and systematic beam changes over time in the FOA corner cube images can lead to a reduction in accuracy as well as increased convergence durations for the template-based position detector. A systematic approach is described that maintains FOA corner cube templates and guaranteesmore » stable position estimation.« less

Centroid stabilization for laser alignment to corner cubes: designing a matched filter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Awwal, Abdul A. S.; Bliss, Erlan; Brunton, Gordon

2016-11-08

Automation of image-based alignment of NIF high energy laser beams is providing the capability of executing multiple target shots per day. One important alignment is beam centration through the second and third harmonic generating crystals in the final optics assembly (FOA), which employs two retro-reflecting corner cubes as centering references for each beam. Beam-to-beam variations and systematic beam changes over time in the FOA corner cube images can lead to a reduction in accuracy as well as increased convergence durations for the template-based position detector. A systematic approach is described that maintains FOA corner cube templates and guarantees stable positionmore » estimation.« less

Chitin: Formation of Helically Structured Chitin/CaCO3 Hybrids through an Approach Inspired by the Biomineralization Processes of Crustacean Cuticles (Small 38/2015).

PubMed

Matsumura, Shunichi; Kajiyama, Satoshi; Nishimura, Tatsuya; Kato, Takashi

2015-10-01

Biomineral-inspired hybrids forming helically ordered structures are developed by T. Kato and co-workers on page 5127. These helical hybrids consist of liquid-crystalline chitin and CaCO3 . They resemble the structures of crustacean cuticles such as the exoskeleton of a lobster or crayfish. These hybrids are formed through CaCO3 crystallization on the liquidcrystalline chitin templates. Polymer-stabilized amorphous CaCO3 is incorporated into the liquid-crystalline chitin templates. This approach is useful for the development of new hierarchical hybrid materials from abundant natural resources. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Bioimprinted QCM sensors for virus detection-screening of plant sap.

PubMed

Dickert, Franz L; Hayden, Oliver; Bindeus, Roland; Mann, Karl-J; Blaas, Dieter; Waigmann, Elisabeth

2004-04-01

Surface imprinting techniques on polymer-coated quartz-crystal microbalances (QCM) have been used to detect tobacco mosaic viruses (TMV) in aqueous media. Molecularly imprinted polymers (MIP), tailor-made by self organisation of monomers around a template (TMV), were generated directly on the gold electrodes. Imprinted trenches on the polymer surface mimicking the shape and surface functionality of the virus serve as recognition sites for re-adsorption after washing out of the template. The sensors are applicable to TMV detection ranging from 100 ng mL(-1) to 1 mg mL(-1) within minutes. Furthermore, direct measurements without time-consuming sample preparation are possible in complex matrices such as tobacco plant sap.

Nonenzymatic glucose detection by using a three-dimensionally ordered, macroporous platinum template.

PubMed

Song, Yan-Yan; Zhang, Dai; Gao, Wei; Xia, Xing-Hua

2005-03-18

A three-dimensionally ordered, macroporous, inverse-opal platinum film was synthesized electrochemically by the inverted colloidal-crystal template technique. The inverse-opal film that contains platinum nanoparticles showed improved electrocatalytic activity toward glucose oxidation with respect to the directly deposited platinum; this improvement is due to the interconnected porous structure and the greatly enhanced effective surface area. In addition, the inverse-opal Pt-film electrode responds more sensitively to glucose than to common interfering species of ascorbic acid, uric acid, and p-acetamidophenol due to their different electrochemical reaction mechanisms. Results showed that the ordered macroporous materials with enhanced selectivity and sensitivity are promising for fabrication of nonenzymatic glucose biosensors.

Mesoporous silica templated zirconia nanoparticles

NASA Astrophysics Data System (ADS)

Ballem, Mohamed A.; Córdoba, José M.; Odén, Magnus

2011-07-01

Nanoparticles of zirconium oxide (ZrO2) were synthesized by infiltration of a zirconia precursor (ZrOCl2·8H2O) into a SBA-15 mesoporous silica mold using a wet-impregnation technique. X-ray diffractometry and high-resolution transmission electron microscopy show formation of stable ZrO2 nanoparticles inside the silica pores after a thermal treatment at 550 °C. Subsequent leaching out of the silica template by NaOH resulted in well-dispersed ZrO2 nanoparticles with an average diameter of 4 nm. The formed single crystal nanoparticles are faceted with 110 surfaces termination suggesting it to be the preferred growth orientation. A growth model of these nanoparticles is also suggested.

Roles of aromatic side chains and template effects of the hydrophobic cavity of a self-assembled peptide nanoarchitecture for anisotropic growth of gold nanocrystals.

PubMed

Tomizaki, Kin-ya; Kishioka, Kohei; Kobayashi, Hiroki; Kobayashi, Akitsugu; Yamada, Naoki; Kataoka, Shunsuke; Imai, Takahito; Kasuno, Megumi

2015-11-15

Gold nanocrystals are promising as catalysts and for use in sensing/imaging systems, photonic/plasmonic devices, electronics, drug delivery systems, and for photothermal therapy due to their unique physical, chemical, and biocompatible properties. The use of various organic templates allows control of the size, shape, structure, surface modification and topology of gold nanocrystals; in particular, currently the synthesis of gold nanorods requires a cytotoxic surfactant to control morphology. To control the shape of gold nanocrystals, we previously demonstrated the de novo design and synthesis of a β-sheet-forming nonapeptide (RU006: Ac-AIAKAXKIA-NH2, X=L-2-naphthylalanine, Nal) and the fabrication of gold nanocrystals by mixing RU006 and HAuCl4 in water. The reaction afforded ultrathin gold nanoribbons 50-100 nm wide, several nanometers high, and microns long. To understand the mechanism underlying gold nanoribbon formation by the RU006 system, we here report (i) the effects of replacement of the Nal aromatic side chain in the RU006 sequence with other aromatic moieties, (ii) the electrochemical properties of aromatic side chains in the de novo designed template peptides to estimate the redox potential and number of electrons participating in the gold crystallization process, and (iii) the stoichiometry of the RU006 system for gold nanoribbon synthesis. Interestingly, RU006 bearing a naphthalene moiety (oxidation peak potential of 1.50 V vs Ag/Ag(+)) and an analog [Ant(6)]-RU006 bearing a bulky anthracene moiety (oxidation peak potential of 1.05 V vs Ag/Ag(+)) allowed the growth of anisotropic (ribbon-like) and isotropic (round) gold nanocrystals, respectively. This trend in morphology of gold nanocrystals was attributed to spatially-arranged hydrophobic cavities sufficiently large to accommodate the gold precursor and to allow directed crystal growth driven by cross-linking reactions among the naphthalene rings. Support for this mechanism was obtained by decreasing the mole fraction of [Ant(6)]-RU006 against the total concentration of [Ant(6)]-RU006 and [Phe(6)]-RU006: absorption spectra similar to that for RU006 were obtained. Differences in the redox properties of the anthracene and naphthalene moieties scarcely affected morphology. We propose that construction of an appropriate hydrophobic cavity is important for templating gold nanocrystal architectures by peptide self-assembly. This mechanism would be applicable for developing simple, low toxicity, mild synthetic methods for constructing metallic nanomaterials for therapeutic use. Copyright © 2015 Elsevier Ltd. All rights reserved.

Electroactive poly(vinylidene fluoride)-based structures for advanced applications.

PubMed

Ribeiro, Clarisse; Costa, Carlos M; Correia, Daniela M; Nunes-Pereira, João; Oliveira, Juliana; Martins, Pedro; Gonçalves, Renato; Cardoso, Vanessa F; Lanceros-Méndez, Senentxu

2018-04-01

Poly(vinylidene fluoride) (PVDF) and its copolymers are the polymers with the highest dielectric constants and electroactive responses, including piezoelectric, pyroelectric and ferroelectric effects. This semicrystalline polymer can crystallize in five different forms, each related to a different chain conformation. Of these different phases, the β phase is the one with the highest dipolar moment and the highest piezoelectric response; therefore, it is the most interesting for a diverse range of applications. Thus, a variety of processing methods have been developed to induce the formation of the polymer β phase. In addition, PVDF has the advantage of being easily processable, flexible and low-cost. In this protocol, we present a number of reproducible and effective methods to produce β-PVDF-based morphologies/structures in the form of dense films, porous films, 3D scaffolds, patterned structures, fibers and spheres. These structures can be fabricated by different processing techniques, including doctor blade, spin coating, printing technologies, non-solvent-induced phase separation (NIPS), temperature-induced phase separation (TIPS), solvent-casting particulate leaching, solvent-casting using a 3D nylon template, freeze extraction with a 3D poly(vinyl alcohol) (PVA) template, replica molding, and electrospinning or electrospray, with the fabrication method depending on the desired characteristics of the structure. The developed electroactive structures have shown potential to be used in a wide range of applications, including the formation of sensors and actuators, in biomedicine, for energy generation and storage, and as filtration membranes.

Autoclave method for rapid preparation of bacterial PCR-template DNA.

PubMed

Simmon, Keith E; Steadman, Dewey D; Durkin, Sarah; Baldwin, Amy; Jeffrey, Wade H; Sheridan, Peter; Horton, Rene; Shields, Malcolm S

2004-02-01

An autoclave method for preparing bacterial DNA for PCR template is presented, it eliminates the use of detergents, organic solvents, and mechanical cellular disruption approaches, thereby significantly reducing processing time and costs while increasing reproducibility. Bacteria are lysed by rapid heating and depressurization in an autoclave. The lysate, cleared by microcentrifugation, was either used directly in the PCR reaction, or concentrated by ultrafiltration. This approach was compared with seven established methods of DNA template preparation from four bacterial sources which included boiling Triton X-100 and SDS, bead beating, lysozyme/proteinase K, and CTAB lysis method components. Bacteria examined were Enterococcus and Escherichia coli, a natural marine bacterial community and an Antarctic cyanobacterial-mat. DNAs were tested for their suitability as PCR templates by repetitive element random amplified polymorphic DNA (RAPD) and denaturing gradient gel electrophoresis (DGGE) analysis. The autoclave method produced PCR amplifiable template comparable or superior to the other methods, with greater reproducibility, much shorter processing time, and at a significantly lower cost.

InP Nanoflag Growth from a Nanowire Template by in Situ Catalyst Manipulation.

PubMed

Kelrich, Alexander; Sorias, Ofir; Calahorra, Yonatan; Kauffmann, Yaron; Gladstone, Ran; Cohen, Shimon; Orenstein, Meir; Ritter, Dan

2016-04-13

Quasi-two-dimensional semiconductor materials are desirable for electronic, photonic, and energy conversion applications as well as fundamental science. We report on the synthesis of indium phosphide flag-like nanostructures by epitaxial growth on a nanowire template at 95% yield. The technique is based on in situ catalyst unpinning from the top of the nanowire and its induced migration along the nanowire sidewall. Investigation of the mechanism responsible for catalyst movement shows that its final position is determined by the structural defect density along the nanowire. The crystal structure of the "flagpole" nanowire is epitaxially transferred to the nanoflag. Pure wurtzite InP nanomembranes with just a single stacking fault originating from the defect in the flagpole that pinned the catalyst were obtained. Optical characterization shows efficient highly polarized photoluminescence at room temperature from a single nanoflag with up to 90% degree of linear polarization. Electric field intensity enhancement of the incident light was calculated to be 57, concentrated at the nanoflag tip. The presented growth method is general and thus can be employed for achieving similar nanostructures in other III-V semiconductor material systems with potential applications in active nanophotonics.

Synthesis of continuous boron nitride nanofibers by solution coating electrospun template fibers

NASA Astrophysics Data System (ADS)

Qiu, Yejun; Yu, Jie; Yin, Jing; Tan, Cuili; Zhou, Xiaosong; Bai, Xuedong; Wang, Enge

2009-08-01

Continuous boron nitride nanofibers (BNNFs) have been synthesized from boric oxide (B2O3) coatings deposited on stabilized electrospun polyacrylonitrile fibers (S-PANFs). The B2O3 overcoatings were prepared by impregnating the S-PANFs with B2O3 ethanol solutions. By successive heat treatments at 800 °C in NH3/O2 mixture, 1100 °C in pure NH3, and 1500 °C in N2, the S-PANFs were fully removed and the B2O3 coatings deflate to form solid fibers and transform into the BNNFs. The S-PANF template was fully removed by introducing O2 during nitridation, and thus resulted in the formation of the BNNFs. The diameter of the BNNFs can be effectively controlled by changing the mass concentration of the B2O3 solution, and diameters from 43 to 230 nm were obtained by changing the B2O3 mass concentration from 0.25% to 4.8%. The obtained BNNFs are crystallized with the (002) planes oriented in parallel to the fiber axis. This method provides a powerful tool for obtaining BNNFs with controllable diameters, especially extremely thin BNNFs.

Synthesis of continuous boron nitride nanofibers by solution coating electrospun template fibers.

PubMed

Qiu, Yejun; Yu, Jie; Yin, Jing; Tan, Cuili; Zhou, Xiaosong; Bai, Xuedong; Wang, Enge

2009-08-26

Continuous boron nitride nanofibers (BNNFs) have been synthesized from boric oxide (B(2)O(3)) coatings deposited on stabilized electrospun polyacrylonitrile fibers (S-PANFs). The B(2)O(3) overcoatings were prepared by impregnating the S-PANFs with B(2)O(3) ethanol solutions. By successive heat treatments at 800 degrees C in NH(3)/O(2) mixture, 1100 degrees C in pure NH(3), and 1500 degrees C in N(2), the S-PANFs were fully removed and the B(2)O(3) coatings deflate to form solid fibers and transform into the BNNFs. The S-PANF template was fully removed by introducing O(2) during nitridation, and thus resulted in the formation of the BNNFs. The diameter of the BNNFs can be effectively controlled by changing the mass concentration of the B(2)O(3) solution, and diameters from 43 to 230 nm were obtained by changing the B(2)O(3) mass concentration from 0.25% to 4.8%. The obtained BNNFs are crystallized with the (002) planes oriented in parallel to the fiber axis. This method provides a powerful tool for obtaining BNNFs with controllable diameters, especially extremely thin BNNFs.

Gravimetric antigen detection utilizing antibody-modified lipid bilayers.

PubMed

Larsson, Charlotte; Bramfeldt, Hanna; Wingren, Christer; Borrebaeck, Carl; Höök, Fredrik

2005-10-01

Lipid bilayers containing 5% nitrilotriacetic acid (NTA) lipids supported on SiO2 have been used as a template for immobilization of oligohistidine-tagged single-chained antibody fragments (scFvs) directed against cholera toxin. It was demonstrated that histidine-tagged scFvs could be equally efficiently coupled to an NTA-Ni2+-containing lipid bilayer from a purified sample as from an expression supernatant, thereby providing a coupling method that eliminates time-consuming protein prepurification steps. Irrespective of whether the coupling was made from the unpurified or purified antibody preparation, the template proved to be efficient for antigen (cholera toxin) detection, verified using quartz crystal microbalance with dissipation monitoring. In addition, via a secondary amplification step using lipid vesicles containing GM1 (the natural membrane receptor for cholera toxin), the detection limit of cholera toxin was less than 750 pM. To further strengthen the coupling of scFvs to the lipid bilayer, scFvs containing two histidine tags, instead of just one tag, were also evaluated. The increased coupling strength provided via the bivalent anchoring significantly reduced scFv displacement in complex solutions containing large amounts of histidine-containing proteins, verified via cholera toxin detection in serum.

Formation of gallium nitride templates and freestanding substrates by hydride vapor phase epitaxy for homoepitaxial growth of III-nitride devices

NASA Astrophysics Data System (ADS)

Williams, Adrian Daniel

Gallium nitride (GaN) is a direct wide band gap semiconductor currently under heavy development worldwide due to interest in its applications in ultra-violet optoelectronics, power electronics, devices operating in harsh environments (high temperature or corrorsive), etc. While a number of devices have been demonstrated with this material and its related alloys, the unavailability of GaN substrates is seen as one of the current major bottlenecks to both material quality and device performance. This dissertation is concerned with the synthesis of high quality GaN substrates by the hydride vapor phase epitaxy method (HVPE). In this work, the flow of growth precursors in a home-built HVPE reactor was modeled by the Navier-Stokes equation and solved by finite element analysis to promote uniformity of GaN on 2'' sapphire substrates. Kinetics of growth was studied and various regimes of growth were identified to establish a methodology for HVPE GaN growth, independent of reactor geometry. GaN templates as well as bulk substrates were fabricated in this work. Realization of freestanding GaN substrates was achieved through discovery of a natural stress-induced method of separating bulk GaN from sapphire via mechanical failure of a low-temperature GaN buffer layer. Such a process eliminates the need for pre- or post-processing of sapphire substrates, as is currently the standard. Stress in GaN-on-sapphire is discussed, with the dominant contributor identified as thermal stress due to thermal expansion coefficient mismatch between the two materials. This thermal stress is analyzed using Stoney's equation and conditions for crack-free growth of thick GaN substrates were identified. An etch-back process for planarizing GaN templates was also developed and successfully applied to rough GaN templates. The planarization of GaN has been mainly addressed by chemo-mechanical polishing (CMP) methods in the literature, with notable shortcomings including the inability to effectively planarize gallium-polar GaN, the preferred growth plane for devices. The process developed in this work bypasses the constraints of CMP, allowing for the planarization of all surfaces of GaN irrespective of crystal orientation. The GaN samples grown for this dissertation were studied by various techniques to characterize their structural, optical, and electrical properties.

Organized one dimensional nanomaterials: From preparations to applications

NASA Astrophysics Data System (ADS)

Wen, Xiaogang

This thesis is mainly concerned with the development of organized one dimensional (1D) nanomaterials and their applications. We have synthesized Ag2S, Cu2S nanowires, Fe2O3 nanobelt and nanowire arrays and ZnO nanobelt arrays from corresponding metal substrate respectively via gas solid reaction methods under different growth conditions. The effect of various parameters including temperature, reaction time, composition of gas, surface pre-oxidation, size of source materials etc. on the growth of metal oxide/sulfide 1D nanostructure have been studied systemically. The size and morphology of these 1D nanomaterials could be rationally controlled by adjusting the growth conditions. A tip growth mechanism has been confirmed based our results. The properties including PL, Raman, field effect transistors, and field emission of these materials have been measured. Cu(OH)2 nanoribbons have been synthesized by a solution solid reaction method using Cu and Cu2S nanowires as precursors. Cu(OH) 2 nanoribbons can form well-aligned arrays on Cu substrate. Low temperature facilitate the formation of Cu(OH)2 nanoribbon arrays. Reaction conditions affect the morphology, crystal structure, even composition of the products much. CuO nanorod arrays of several nm in diameter could be synthesis in changed condition. Cu(OH)2 nanoribbon arrays are good sacrifice template for synthesizing other Cu-based 1D nanomaterials. It has been converted to CuO, Cu2O, Cu8S9, Cu etc. 1D nanostructure through different physical and chemical reaction process. Au/Cu2S core/sheath nanowires have been synthesized in solution phase via a simple template-induced redox deposition process, after removing the Cu2S template, Au nanotubes have been formed. The photoelectrochemistry (PEC) properties of it have been studied. Ag dendritic nanostructures have been prepared via solution reaction. We have revealed that the stem, branch, and sub-branch grow along <100>, <111> and <100> directions, respectively. Such a preferential growth pattern along <100> and <111> alternately lead to the formation of the Ag nanodendrites. In another development, we have synthesized unltrathin Zn nanowires (<5nm) by a vapor transport method. Small molecules are induced into the gas phase as capping reagents. In this process, the small molecules serve as capping reagents or templates to confine the lateral growth and facilitate the formation of ultrathin 1D nanostructures. (Abstract shortened by UMI.)

A new template matching method based on contour information

NASA Astrophysics Data System (ADS)

Cai, Huiying; Zhu, Feng; Wu, Qingxiao; Li, Sicong

2014-11-01

Template matching is a significant approach in machine vision due to its effectiveness and robustness. However, most of the template matching methods are so time consuming that they can't be used to many real time applications. The closed contour matching method is a popular kind of template matching methods. This paper presents a new closed contour template matching method which is suitable for two dimensional objects. Coarse-to-fine searching strategy is used to improve the matching efficiency and a partial computation elimination scheme is proposed to further speed up the searching process. The method consists of offline model construction and online matching. In the process of model construction, triples and distance image are obtained from the template image. A certain number of triples which are composed by three points are created from the contour information that is extracted from the template image. The rule to select the three points is that the template contour is divided equally into three parts by these points. The distance image is obtained here by distance transform. Each point on the distance image represents the nearest distance between current point and the points on the template contour. During the process of matching, triples of the searching image are created with the same rule as the triples of the model. Through the similarity that is invariant to rotation, translation and scaling between triangles, the triples corresponding to the triples of the model are found. Then we can obtain the initial RST (rotation, translation and scaling) parameters mapping the searching contour to the template contour. In order to speed up the searching process, the points on the searching contour are sampled to reduce the number of the triples. To verify the RST parameters, the searching contour is projected into the distance image, and the mean distance can be computed rapidly by simple operations of addition and multiplication. In the fine searching process, the initial RST parameters are discrete to obtain the final accurate pose of the object. Experimental results show that the proposed method is reasonable and efficient, and can be used in many real time applications.

Site-specific colloidal crystal nucleation by template-enhanced particle transport

NASA Astrophysics Data System (ADS)

Mishra, Chandan K.; Sood, A. K.; Ganapathy, Rajesh

2016-10-01

The monomer surface mobility is the single most important parameter that decides the nucleation density and morphology of islands during thin-film growth. During template-assisted surface growth in particular, low surface mobilities can prevent monomers from reaching target sites and this results in a partial to complete loss of nucleation control. Whereas in atomic systems a broad range of surface mobilities can be readily accessed, for colloids, owing to their large size, this window is substantially narrow and therefore imposes severe restrictions in extending template-assisted growth techniques to steer their self-assembly. Here, we circumvented this fundamental limitation by designing templates with spatially varying feature sizes, in this case moiré patterns, which in the presence of short-range depletion attraction presented surface energy gradients for the diffusing colloids. The templates serve a dual purpose: first, directing the particles to target sites by enhancing their surface mean-free paths and second, dictating the size and symmetry of the growing crystallites. Using optical microscopy, we directly followed the nucleation and growth kinetics of colloidal islands on these surfaces at the single-particle level. We demonstrate nucleation control, with high fidelity, in a regime that has remained unaccessed in theoretical, numerical, and experimental studies on atoms and molecules as well. Our findings pave the way for fabricating nontrivial surface architectures composed of complex colloids and nanoparticles as well.

Catalyst- and template-free low-temperature in situ growth of n-type CdS nanowire on p-type CdTe film and p-n heterojunction properties

PubMed Central

Ma, Ligang; Liu, Wenchao; Cai, Hongling; Zhang, Fengming; Wu, Xiaoshan

2016-01-01

CdS is an important semiconductor used in optoelectronic devices. Simple techniques for growing CdS nanostructures are thus essential at a low cost. This study presents a novel method for growing single-crystal n-type CdS nanowires on p-type CdTe films by thermal annealing in an H2S/N2 mixed gas flow, which does not require the help of a catalyst or template. The formation process and growth mechanism of the nanowires are investigated. Well-dispersed whiskerlike CdS nanostructures are obtained at an appropriate annealing temperature and duration. We suggest that the stress-driving mechanism of nanowire formation may contribute to the growth of CdS nanowires, and that the evaporation of Te through the boundaries of the CdS grain seeds plays an important role in the sustainable growth of nanowire. In addition, CdS/CdTe heterojunction device is fabricated on Mo glass. The I-V characteristic of the heterojunction in dark shows typical rectifying diode behavior. The turn-on voltage can be regulated by annealing conditions. Meanwhile, the obvious photovoltaic effect is obtained on the in situ growth heterojunction prepared at low annealing temperature. Hence, this is a new fabricated method for CdTe-based materials in the field of energy conversion. PMID:27958306

Physicochemical and adsorptive characteristics of activated carbons from waste polyester textiles utilizing MgO template method.

PubMed

Xu, Zhihua; Zhang, Daofang; Yuan, Zhihang; Chen, Weifang; Zhang, Tianqi; Tian, Danqi; Deng, Haixuan

2017-10-01

Activated carbons with high specific surface areas were produced, utilizing waste polyester textiles as carbon precursor by magnesium oxide (MgO) template method. Magnesium chloride (MgCl 2 ), magnesium citrate (MgCi), and MgO were employed as MgO precursors to prepare activated carbons (AC-MgCl 2 , AC-MgCi, and AC-MgO). Thermogravimetry-differential scanning calorimetry was conducted to investigate the pore-forming mechanism, and N 2 adsorption/desorption isotherms, XRD, SEM-EDS, TEM, FTIR and pH pzc were achieved to analyze physicochemical characteristics of the samples. The specific surface areas of AC-MgCl 2 (1173 m 2 /g) and AC-MgCi (1336 m 2 /g) were much higher than that of AC-MgO (450 m 2 /g), and the pores sizes of which were micro-mesoporous, mesoporous, and macropores, respectively, due to the formation of MgO crystal with different sizes. All activated carbons had abundant acidic oxygen groups. In addition, batch adsorption experiments were carried out to investigate the adsorptive characteristics of the prepared activated carbons toward Cr(VI). The adsorption kinetics fitted well with the pseudo-second order, and the adsorptive capacity of AC-MgCl 2 (42.55 mg/g) was higher than those of AC-MgCi (40.93 mg/g) and AC-MgO (35.87 mg/g).

Self-assembled biomimetic antireflection coatings

NASA Astrophysics Data System (ADS)

Linn, Nicholas C.; Sun, Chih-Hung; Jiang, Peng; Jiang, Bin

2007-09-01

The authors report a simple self-assembly technique for fabricating antireflection coatings that mimic antireflective moth eyes. Wafer-scale, nonclose-packed colloidal crystals with remarkable large hexagonal domains are created by a spin-coating technology. The resulting polymer-embedded colloidal crystals exhibit highly ordered surface modulation and can be used directly as templates to cast poly(dimethylsiloxane) (PDMS) molds. Moth-eye antireflection coatings with adjustable reflectivity can then be molded against the PDMS master. The specular reflection of replicated nipple arrays matches the theoretical prediction using a thin-film multilayer model. These biomimetic films may find important technological application in optical coatings and solar cells.

Prediction of Protein Structure by Template-Based Modeling Combined with the UNRES Force Field.

PubMed

Krupa, Paweł; Mozolewska, Magdalena A; Joo, Keehyoung; Lee, Jooyoung; Czaplewski, Cezary; Liwo, Adam

2015-06-22

A new approach to the prediction of protein structures that uses distance and backbone virtual-bond dihedral angle restraints derived from template-based models and simulations with the united residue (UNRES) force field is proposed. The approach combines the accuracy and reliability of template-based methods for the segments of the target sequence with high similarity to those having known structures with the ability of UNRES to pack the domains correctly. Multiplexed replica-exchange molecular dynamics with restraints derived from template-based models of a given target, in which each restraint is weighted according to the accuracy of the prediction of the corresponding section of the molecule, is used to search the conformational space, and the weighted histogram analysis method and cluster analysis are applied to determine the families of the most probable conformations, from which candidate predictions are selected. To test the capability of the method to recover template-based models from restraints, five single-domain proteins with structures that have been well-predicted by template-based methods were used; it was found that the resulting structures were of the same quality as the best of the original models. To assess whether the new approach can improve template-based predictions with incorrectly predicted domain packing, four such targets were selected from the CASP10 targets; for three of them the new approach resulted in significantly better predictions compared with the original template-based models. The new approach can be used to predict the structures of proteins for which good templates can be found for sections of the sequence or an overall good template can be found for the entire sequence but the prediction quality is remarkably weaker in putative domain-linker regions.

Characterization of Anodic Aluminum Oxide Membrane with Variation of Crystallizing Temperature for pH Sensor.

PubMed

Yeo, Jin-Ho; Lee, Sung-Gap; Jo, Ye-Won; Jung, Hye-Rin

2015-11-01

We fabricated electrolyte-dielectric-metal (EDM) device incorporating a high-k Al2O3 sensing membrane from a porous anodic aluminum oxide (AAO) using a two step anodizing process for pH sensors. In order to change the properties of the AAO template, the crystallizing temperature was varied from 400 degrees C to 700 degrees C over 2 hours. The structural properties were observed by field emission scanning electron microscopy (FE-SEM). The pH sensitivity increased with an increase in the crystallizing temperature from 400 degrees C to 600 degrees C. However at 700 degrees C, deformation occurred. The porous AAO sensor with a crystallizing temperature of 600 degrees C displayed the good sensitivity and long-term stability and the values were 55.7 mV/pH and 0.16 mV/h, respectively.

Directed Self-Assembly of Liquid Crystalline Blue-Phases into Ideal Single-Crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martinez-Gonzalez, Jose A.; Li, Xiao; Sadati, Monirosadat

Chiral nematic liquid crystals are known to form blue phases—liquid states of matter that exhibit ordered cubic arrangements of topological defects. Blue-phase specimens, however, are generally polycrystalline, consisting of randomly oriented domains that limit their performance in applications. A strategy that relies on nano-patterned substrates is presented here for preparation of stable, macroscopic single-crystal blue-phase materials. Different template designs are conceived to exert control over different planes of the blue-phase lattice orientation with respect to the underlying substrate. Experiments are then used to demonstrate that it is indeed possible to create stable single-crystal blue-phase domains with the desired orientation overmore » large regions. Lastly, these results provide a potential avenue to fully exploit the electro-optical properties of blue phases, which have been hindered by the existence of grain boundaries.« less

Directed Self-Assembly of Liquid Crystalline Blue-Phases into Ideal Single-Crystals

DOE PAGES

Martinez-Gonzalez, Jose A.; Li, Xiao; Sadati, Monirosadat; ...

2017-06-16

Chiral nematic liquid crystals are known to form blue phases—liquid states of matter that exhibit ordered cubic arrangements of topological defects. Blue-phase specimens, however, are generally polycrystalline, consisting of randomly oriented domains that limit their performance in applications. A strategy that relies on nano-patterned substrates is presented here for preparation of stable, macroscopic single-crystal blue-phase materials. Different template designs are conceived to exert control over different planes of the blue-phase lattice orientation with respect to the underlying substrate. Experiments are then used to demonstrate that it is indeed possible to create stable single-crystal blue-phase domains with the desired orientation overmore » large regions. Lastly, these results provide a potential avenue to fully exploit the electro-optical properties of blue phases, which have been hindered by the existence of grain boundaries.« less

Biosynthesis of amorphous mesoporous aluminophosphates using yeast cells as templates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sifontes, Ángela B., E-mail: asifonte@ivic.gob.ve; González, Gema; Tovar, Leidy M.

2013-02-15

Graphical abstract: Display Omitted Highlights: ► Amorphous aluminophosphates can take place using yeast as template. ► A mesoporous material was obtained. ► The specific surface area after calcinations ranged between 176 and 214 m{sup 2} g{sup −1}. -- Abstract: In this study aluminophosphates have been synthesized from aluminum isopropoxide and phosphoric acid solutions using yeast cells as template. The physicochemical characterization was carried out by thermogravimetric analysis; X-ray diffraction; Fourier transform infrared; N{sub 2} adsorption–desorption isotherms; scanning electron microscopy; transmission electron microscopy and potentiometric titration with N-butylamine for determination of: thermal stability; crystalline structure; textural properties; morphology and surface acidity,more » respectively. The calcined powders consisted of an intimate mixture of amorphous and crystallized AlPO particles with sizes between 23 and 30 nm. The average pore size observed is 13–16 nm and the specific surface area after calcinations (at 650 °C) ranged between 176 and 214 m{sup 2} g{sup −1}.« less

Crystallographic observation of nonenzymatic RNA primer extension.

PubMed

Zhang, Wen; Walton, Travis; Li, Li; Szostak, Jack W

2018-05-31

The importance of genome replication has inspired detailed crystallographic studies of enzymatic DNA/RNA polymerization. In contrast, the mechanism of nonenzymatic polymerization is less well understood, despite its critical role in the origin of life. Here we report the direct observation of nonenzymatic RNA primer extension through time-resolved crystallography. We soaked crystals of an RNA primer-template-dGMP complex with guanosine-5'-phosphoro-2-aminoimidazolide for increasing times. At early times we see the activated ribonucleotides bound to the template, followed by formation of the imidazolium-bridged dinucleotide intermediate. At later times, we see a new phosphodiester bond forming between the primer and the incoming nucleotide. The intermediate is pre-organized because of the constraints of base-pairing with the template and hydrogen bonding between the imidazole amino group and both flanking phosphates. Our results provide atomic-resolution insight into the mechanism of nonenzymatic primer extension, and set the stage for further structural dissection and optimization of the RNA copying process. © 2018, Zhang et al.

A facile in situ self-assembly strategy for large-scale fabrication of CHS@MOF yolk/shell structure and its catalytic application in a flow system.

PubMed

Gao, Hongyi; Luan, Yi; Chaikittikul, Kullapat; Dong, Wenjun; Li, Jie; Zhang, Xiaowei; Jia, Dandan; Yang, Mu; Wang, Ge

2015-03-04

A hierarchical yolk/shell copper hydroxysulfates@MOF (CHS@MOF, where MOF = metal-organic frameworks) structure was fabricated from a homogeneous yolk/shell CHS template composed of an active shell and a stabilized core via a facile self-template strategy at room temperature. The active shell of the template served as the source of metal ion and was in situ transformed into a well-defined MOF crystal shell, and the relatively stabilized core retained its own nature during the formation of the MOF shell. The strategy of in situ transformation of CHS shell to MOF shell avoided the self-nucleation of MOF in the solution and complex multistep procedures. Furthermore, a flow reaction system using CHS@MOF as self-supported stationary-phase catalyst was developed, which demonstrated excellent catalytic performance for aldehyde acetalization with ethanol, and high yields and selectivities were achieved under mild conditions.

Visual cluster analysis and pattern recognition methods

DOEpatents

Osbourn, Gordon Cecil; Martinez, Rubel Francisco

2001-01-01

A method of clustering using a novel template to define a region of influence. Using neighboring approximation methods, computation times can be significantly reduced. The template and method are applicable and improve pattern recognition techniques.

University of Maryland MRSEC - Research: Seed 2

Science.gov Websites

Administration Committees Directory Research IRG 1 IRG 2 Seed 1 Seed 2 Seed 3 Highlights Publications Facilities MRSEC Templates Opportunities Search Home » Research » Seed 2 Seed 2: Synthesis and Exploration of Topological Insulators Figure 1 High quality single crystals of bismuth-based topological insulator grown at

Combinatorial selection of molecular conformations and supramolecular synthons in quercetin cocrystal landscapes: a route to ternary solids

PubMed Central

Dubey, Ritesh; Desiraju, Gautam R.

2015-01-01

The crystallization of 28 binary and ternary cocrystals of quercetin with dibasic coformers is analyzed in terms of a combinatorial selection from a solution of preferred molecular conformations and supramolecular synthons. The crystal structures are characterized by distinctive O—H⋯N and O—H⋯O based synthons and are classified as nonporous, porous and helical. Variability in molecular conformation and synthon structure led to an increase in the energetic and structural space around the crystallization event. This space is the crystal structure landscape of the compound and is explored by fine-tuning the experimental conditions of crystallization. In the landscape context, we develop a strategy for the isolation of ternary cocrystals with the use of auxiliary template molecules to reduce the molecular and supramolecular ‘confusion’ that is inherent in a molecule like quercetin. The absence of concomitant polymorphism in this study highlights the selectivity in conformation and synthon choice from the virtual combinatorial library in solution. PMID:26175900

Epitaxy: Programmable Atom Equivalents Versus Atoms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Mary X.; Seo, Soyoung E.; Gabrys, Paul A.

The programmability of DNA makes it an attractive structure-directing ligand for the assembly of nanoparticle superlattices in a manner that mimics many aspects of atomic crystallization. However, the synthesis of multilayer single crystals of defined size remains a challenge. Though previous studies considered lattice mismatch as the major limiting factor for multilayer assembly, thin film growth depends on many interlinked variables. Here, a more comprehensive approach is taken to study fundamental elements, such as the growth temperature and the thermodynamics of interfacial energetics, to achieve epitaxial growth of nanoparticle thin films. Under optimized equilibrium conditions, single crystal, multilayer thin filmsmore » can be synthesized over 500 × 500 μm2 areas on lithographically patterned templates. Importantly, these superlattices follow the same patterns of crystal growth demonstrated in thin film atomic deposition, allowing for these processes to be understood in the context of well-studied atomic epitaxy, and potentially enabling a nanoscale model to study fundamental crystallization processes.« less

Understanding Nanocalcification: A Role Suggested for Crystal Ghosts

PubMed Central

Bonucci, Ermanno

2014-01-01

The present survey deals with the initial stage of the calcification process in bone and other hard tissues, with special reference to the organic-inorganic relationship and the transformation that the early inorganic particles undergo as the process moves towards completion. Electron microscope studies clearly exclude the possibility that these particles might be crystalline structures, as often believed, by showing that they are, instead, organic-inorganic hybrids, each comprising a filamentous organic component (the crystal ghost) made up of acidic proteins. The hypothesis is suggested that the crystal ghosts bind and stabilize amorphous calcium phosphate and that their subsequent degradation allows the calcium phosphate, once released, to acquire a hydroxyapatite, crystal-like organization. A conclusive view of the mechanism of biological calcification cannot yet be proposed; even so, however, the role of crystal ghosts as a template of the structures usually called “crystallites” is a concept that has gathered increasing support and can no longer be disregarded. PMID:25056630

Segmented metallic nanostructures, homogeneous metallic nanostructures and methods for producing same

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wong, Stanislaus; Koenigsmann, Christopher

The present invention includes a method of producing a segmented 1D nanostructure. The method includes providing a vessel containing a template wherein on one side of the template is a first metal reagent solution and on the other side of the template is a reducing agent solution, wherein the template comprises at least one pore; allowing a first segment of a 1D nanostructure to grow within a pore of the template until a desired length is reached; replacing the first metal reagent solution with a second metal reagent solution; allowing a second segment of a 1D nanostructure to grow frommore » the first segment until a desired length is reached, wherein a segmented 1D nanostructure is produced.« less

iTemplate: A template-based eye movement data analysis approach.

PubMed

Xiao, Naiqi G; Lee, Kang

2018-02-08

Current eye movement data analysis methods rely on defining areas of interest (AOIs). Due to the fact that AOIs are created and modified manually, variances in their size, shape, and location are unavoidable. These variances affect not only the consistency of the AOI definitions, but also the validity of the eye movement analyses based on the AOIs. To reduce the variances in AOI creation and modification and achieve a procedure to process eye movement data with high precision and efficiency, we propose a template-based eye movement data analysis method. Using a linear transformation algorithm, this method registers the eye movement data from each individual stimulus to a template. Thus, users only need to create one set of AOIs for the template in order to analyze eye movement data, rather than creating a unique set of AOIs for all individual stimuli. This change greatly reduces the error caused by the variance from manually created AOIs and boosts the efficiency of the data analysis. Furthermore, this method can help researchers prepare eye movement data for some advanced analysis approaches, such as iMap. We have developed software (iTemplate) with a graphic user interface to make this analysis method available to researchers.

GalaxyTBM: template-based modeling by building a reliable core and refining unreliable local regions.

PubMed

Ko, Junsu; Park, Hahnbeom; Seok, Chaok

2012-08-10

Protein structures can be reliably predicted by template-based modeling (TBM) when experimental structures of homologous proteins are available. However, it is challenging to obtain structures more accurate than the single best templates by either combining information from multiple templates or by modeling regions that vary among templates or are not covered by any templates. We introduce GalaxyTBM, a new TBM method in which the more reliable core region is modeled first from multiple templates and less reliable, variable local regions, such as loops or termini, are then detected and re-modeled by an ab initio method. This TBM method is based on "Seok-server," which was tested in CASP9 and assessed to be amongst the top TBM servers. The accuracy of the initial core modeling is enhanced by focusing on more conserved regions in the multiple-template selection and multiple sequence alignment stages. Additional improvement is achieved by ab initio modeling of up to 3 unreliable local regions in the fixed framework of the core structure. Overall, GalaxyTBM reproduced the performance of Seok-server, with GalaxyTBM and Seok-server resulting in average GDT-TS of 68.1 and 68.4, respectively, when tested on 68 single-domain CASP9 TBM targets. For application to multi-domain proteins, GalaxyTBM must be combined with domain-splitting methods. Application of GalaxyTBM to CASP9 targets demonstrates that accurate protein structure prediction is possible by use of a multiple-template-based approach, and ab initio modeling of variable regions can further enhance the model quality.

Journal of Chemical Education: Software.

ERIC Educational Resources Information Center

Journal of Chemical Education, 1989

1989-01-01

"Spreadsheets in Physical Chemistry" contains reviewed and classroom tested Lotus 1-2-3 and SuperCalc IV templates and handouts designed for use in physical chemistry courses. The 21 templates keyed to Atkins' physical chemistry textbook, the 7 numerical methods templates, and the 10 simulation templates are discussed. (MVL)

Using Depletion Force to synthesize PBG crystals

NASA Astrophysics Data System (ADS)

Sanyal, Subrata; Zhang, Jian; Lin, Keng-Hui; Work, William J.; Yodh, A. G.

2000-03-01

Using the pathway of depletion-mediated crystallization, we have undertaken an exhaustive set of experiments in order to synthesize materials with novel optical and rheological properties, e.g., photonic bandgap (PBG) crystals. With the primary use of miceller depletion, we grow crystals of submicron-sized model colloidal (e.g., aqueous suspensions of polyballs or silica) particles from the walls of our sample microchambers, used for optical microscopy. Furthermore, the order of such crystals can be controlled by patterning one of the cell walls(K. H. Lin et al.), Manuscript under preparation (1999)., and after the formation of crystals the particles can be ``locked'' in their positions using chemical techniques(G. Pan et al.), Phys. Rev. Lett., 78, 3860 (1997); P. V. Braun (private communication).. The locked arrangements of particles serve as templates to fabricate(B. T. Holland et al.), Science, 281, 538 (1998); J. E. G. J. Wijnhoven et al., Science, 281, 802 (1998). microporous PBG materials. Experiments are underway to synthesize solid microspheres of high dielectric constant materials, and hollow microspheres, that can be arranged on patterned surfaces.

Ax(H3O)2-xMn5(HPO3)6 (A = Li, Na, K and NH4): open-framework manganese(ii) phosphites templated by mixed cationic species.

PubMed

Orive, Joseba; Fernández de Luis, Roberto; Fernández, Jesús Rodríguez; Lezama, Luis; Arriortua, María I

2016-07-26

Ax(H3O)2-xMn5(HPO3)6 (A = Li, x = 0.55 (1-Li); A = Na, x = 0.72 (2-Na); A = K, x = 0.30 (3-K); A = NH4, x = 0.59 (4-NH4)) phases were synthesized by employing mild hydrothermal conditions. 1-Li was studied by single crystal X-ray diffraction, while sodium, potassium and ammonium containing analogues were obtained as polycrystalline samples and characterized by powder X-ray diffraction. The four compounds were characterized by ICP-Q-MS, thermal analysis and XPS, IR, UV/Vis and EPR spectroscopy. Single crystal data indicate that 1-Li crystallizes in the P3[combining macron]c1 space group with lattice parameters a = 10.3764(1) Å and c = 9.4017(1) Å with Z = 2. The crystal structure of these phases is constituted by a three-dimensional [Mn(ii)5(HPO3)6](2-) anionic skeleton templated by alkali metal and ammonium cations together with protonated water molecules. Such an inorganic framework is formed by layers of edge-sharing MnO6 octahedra placed in the ab plane and joined along the c direction through phosphite pseudotetrahedra. The sheets display 12-membered ring channels parallel to the c-axis, ca. 5 Å in diameter, where the extraframework species display a strong disorder. EPR measurements point to the existence of short range ferromagnetic interactions around 12 K. Magnetic susceptibility and heat capacity measurements show that all the compounds exhibit long range antiferromagnetic order below circa 4 K, with a significant magnetocaloric effect around the Neel temperature.

Modeling IrisCode and its variants as convex polyhedral cones and its security implications.

PubMed

Kong, Adams Wai-Kin

2013-03-01

IrisCode, developed by Daugman, in 1993, is the most influential iris recognition algorithm. A thorough understanding of IrisCode is essential, because over 100 million persons have been enrolled by this algorithm and many biometric personal identification and template protection methods have been developed based on IrisCode. This paper indicates that a template produced by IrisCode or its variants is a convex polyhedral cone in a hyperspace. Its central ray, being a rough representation of the original biometric signal, can be computed by a simple algorithm, which can often be implemented in one Matlab command line. The central ray is an expected ray and also an optimal ray of an objective function on a group of distributions. This algorithm is derived from geometric properties of a convex polyhedral cone but does not rely on any prior knowledge (e.g., iris images). The experimental results show that biometric templates, including iris and palmprint templates, produced by different recognition methods can be matched through the central rays in their convex polyhedral cones and that templates protected by a method extended from IrisCode can be broken into. These experimental results indicate that, without a thorough security analysis, convex polyhedral cone templates cannot be assumed secure. Additionally, the simplicity of the algorithm implies that even junior hackers without knowledge of advanced image processing and biometric databases can still break into protected templates and reveal relationships among templates produced by different recognition methods.

Photoluminescent SBA-16 Rhombic Dodecahedral Particles: Assembly, Characterization, and ab Initio Modeling.

PubMed

Ruso, Juan M; Pardo, Victor; Sartuqui, Javier; Gravina, Noel; D'Elía, Noelia L; Pieroni, Olga I; Messina, Paula V

2015-06-17

Nowadays, the use of polyhedral instead of spherical particles as building blocks of engineering new materials has become an area of particular effort in the scientific community. Therefore, fabricating in a reproducible manner large amounts of uniform crystal-like particles is a huge challenge. In this work we report a low reagent-consuming binary surfactant templated method mediated by a hydrothermal treatment as a facile and controllable route for the synthesis of crystal-like rombdodecahedral particles exhibiting SBA-16 mesoporosity. It was determined that the hydrothermal treatment conditions were a key point upon the final material morphology, surface area, microporosity, wall thickness, and mesopore width. As a consequence of their internal mesoporosity order, rhombic dodecahedral synthesized particles exhibited highly efficient ultraviolet absorptions and photoluminescence emissions at room temperature. Conducting experimental and theoretical comparative studies allowed us to infer that the presence of intrinsic defects confined into an ordered mesoporous structure plays a very important role in semiconductor materials. The information presented here is expected to be useful, giving new, accurate information, for the construction of novel technological devices.

Molecular barcodes detect redundancy and contamination in hairpin-bisulfite PCR

PubMed Central

Miner, Brooks E.; Stöger, Reinhard J.; Burden, Alice F.; Laird, Charles D.; Hansen, R. Scott

2004-01-01

PCR amplification of limited amounts of DNA template carries an increased risk of product redundancy and contamination. We use molecular barcoding to label each genomic DNA template with an individual sequence tag prior to PCR amplification. In addition, we include molecular ‘batch-stamps’ that effectively label each genomic template with a sample ID and analysis date. This highly sensitive method identifies redundant and contaminant sequences and serves as a reliable method for positive identification of desired sequences; we can therefore capture accurately the genomic template diversity in the sample analyzed. Although our application described here involves the use of hairpin-bisulfite PCR for amplification of double-stranded DNA, the method can readily be adapted to single-strand PCR. Useful applications will include analyses of limited template DNA for biomedical, ancient DNA and forensic purposes. PMID:15459281

Enzymatic Production of Monoclonal Stoichiometric Single-Stranded DNA Oligonucleotides

PubMed Central

Ducani, Cosimo; Kaul, Corinna; Moche, Martin; Shih, William M.; Högberg, Björn

2013-01-01

Single-stranded oligonucleotides are important as research tools as probes for diagnostics and gene therapy. Today, production of oligonucleotides is done via solid-phase synthesis. However, the capabilities of current polymer chemistry are limited in comparison to what can be produced in biological systems. The errors in synthetic DNA increases with oligonucleotide length, and sequence diversity can often be a problem. Here, we present the Monoclonal Stoichiometric (MOSIC) method for enzymatic DNA oligonucleotide production. Using this method, we amplify oligonucleotides from clonal templates followed by digestion of a cutter-hairpin, resulting in pools of monoclonal oligonucleotides with precisely controlled relative stoichiometric ratios. We present data where MOSIC oligonucleotides, 14–378 nt long, were prepared either by in vitro rolling-circle amplification, or by amplification in Escherichia coli in the form of phagemid DNA. The formation of a DNA crystal and folding of DNA nanostructures confirmed the scalability, purity and stoichiometry of the produced oligonucleotides. PMID:23727986

Photoinduced silver nanoparticles/nanorings on plasmid DNA scaffolds.

PubMed

Liu, Jianhua; Zhang, Xiaoliang; Yu, Mei; Li, Songmei; Zhang, Jindan

2012-01-23

Biological scaffolds are being actively explored for the synthesis of nanomaterials with novel structures and unexpected properties. Toroidal plasmid DNA separated from the Bacillus host is applied as a sacrificial mold for the synthesis of silver nanoparticles and nanorings. The photoirradiation method is applied to reduce Ag(I) on the plasmid. The nanoparticles are obtained by varying the concentration of the Ag(I) ion solution and the exposure time of the plasmid-Ag(I) complex under UV light at 254 nm and room temperature. It is found that the plasmid serves not only as a template but also as a reductant to drive the silver nucleation and deposition. The resulting nanoparticles have a face-centered cubic (fcc) crystal structure and 20-30 nm average diameter. The detailed mechanism is discussed, and other metals or alloys could also be synthesized with this method. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

THTM: A template matching algorithm based on HOG descriptor and two-stage matching

NASA Astrophysics Data System (ADS)

Jiang, Yuanjie; Ruan, Li; Xiao, Limin; Liu, Xi; Yuan, Feng; Wang, Haitao

2018-04-01

We propose a novel method for template matching named THTM - a template matching algorithm based on HOG (histogram of gradient) and two-stage matching. We rely on the fast construction of HOG and the two-stage matching that jointly lead to a high accuracy approach for matching. TMTM give enough attention on HOG and creatively propose a twice-stage matching while traditional method only matches once. Our contribution is to apply HOG to template matching successfully and present two-stage matching, which is prominent to improve the matching accuracy based on HOG descriptor. We analyze key features of THTM and perform compared to other commonly used alternatives on a challenging real-world datasets. Experiments show that our method outperforms the comparison method.

Templated assembly of Co-Pt nanoparticles via thermal and laser-induced dewetting of bilayer metal films.

PubMed

Oh, Yong-Jun; Kim, Jung-Hwan; Thompson, Carl V; Ross, Caroline A

2013-01-07

Templated dewetting of a Co/Pt metal bilayer film on a topographic substrate was used to assemble arrays of Co-Pt alloy nanoparticles, with highly uniform particle size, shape and notably composition compared to nanoparticles formed on an untemplated substrate. Solid-state and liquid-state dewetting processes, using furnace annealing and laser irradiation respectively, were compared. Liquid state dewetting produced more uniform, conformal nanoparticles but they had a polycrystalline disordered fcc structure and relatively low magnetic coercivity. In contrast, solid state dewetting enabled formation of magnetically hard, ordered L1(0) Co-Pt single-crystal particles with coercivity >12 kOe. Furnace annealing converted the nanoparticles formed by liquid state dewetting into the L1(0) phase.

View-Invariant Gait Recognition Through Genetic Template Segmentation

NASA Astrophysics Data System (ADS)

Isaac, Ebenezer R. H. P.; Elias, Susan; Rajagopalan, Srinivasan; Easwarakumar, K. S.

2017-08-01

Template-based model-free approach provides by far the most successful solution to the gait recognition problem in literature. Recent work discusses how isolating the head and leg portion of the template increase the performance of a gait recognition system making it robust against covariates like clothing and carrying conditions. However, most involve a manual definition of the boundaries. The method we propose, the genetic template segmentation (GTS), employs the genetic algorithm to automate the boundary selection process. This method was tested on the GEI, GEnI and AEI templates. GEI seems to exhibit the best result when segmented with our approach. Experimental results depict that our approach significantly outperforms the existing implementations of view-invariant gait recognition.

A Modified Personalized Image-Based Drill Guide Template for Atlantoaxial Pedicle Screw Placement: A Clinical Study

PubMed Central

Jiang, Lianghai; Dong, Liang; Tan, Mingsheng; Qi, Yingna; Yang, Feng; Yi, Ping; Tang, Xiangsheng

2017-01-01

Background Atlantoaxial posterior pedicle screw fixation has been widely used for treatment of atlantoaxial instability (AAI). However, precise and safe insertion of atlantoaxial pedicle screws remains challenging. This study presents a modified drill guide template based on a previous template for atlantoaxial pedicle screw placement. Material/Methods Our study included 54 patients (34 males and 20 females) with AAI. All the patients underwent posterior atlantoaxial pedicle screw fixation: 25 patients underwent surgery with the use of a modified drill guide template (template group) and 29 patients underwent surgery via the conventional method (conventional group). In the template group, a modified drill guide template was designed for each patient. The modified drill guide template and intraoperative fluoroscopy were used for surgery in the template group, while only intraoperative fluoroscopy was used in the conventional group. Results Of the 54 patients, 52 (96.3%) completed the follow-up for more than 12 months. The template group had significantly lower intraoperative fluoroscopy frequency (p<0.001) and higher accuracy of screw insertion (p=0.045) than the conventional group. There were no significant differences in surgical duration, intraoperative blood loss, or improvement of neurological function between the 2 groups (p>0.05). Conclusions Based on the results of this study, it is feasible to use the modified drill guide template for atlantoaxial pedicle screw placement. Using the template can significantly lower the screw malposition rate and the frequency of intraoperative fluoroscopy. PMID:28301445

Fabrication of smooth patterned structures of refractory metals, semiconductors, and oxides via template stripping.

PubMed

Park, Jong Hyuk; Nagpal, Prashant; McPeak, Kevin M; Lindquist, Nathan C; Oh, Sang-Hyun; Norris, David J

2013-10-09

The template-stripping method can yield smooth patterned films without surface contamination. However, the process is typically limited to coinage metals such as silver and gold because other materials cannot be readily stripped from silicon templates due to strong adhesion. Herein, we report a more general template-stripping method that is applicable to a larger variety of materials, including refractory metals, semiconductors, and oxides. To address the adhesion issue, we introduce a thin gold layer between the template and the deposited materials. After peeling off the combined film from the template, the gold layer can be selectively removed via wet etching to reveal a smooth patterned structure of the desired material. Further, we demonstrate template-stripped multilayer structures that have potential applications for photovoltaics and solar absorbers. An entire patterned device, which can include a transparent conductor, semiconductor absorber, and back contact, can be fabricated. Since our approach can also produce many copies of the patterned structure with high fidelity by reusing the template, a low-cost and high-throughput process in micro- and nanofabrication is provided that is useful for electronics, plasmonics, and nanophotonics.

Fan fault diagnosis based on symmetrized dot pattern analysis and image matching

NASA Astrophysics Data System (ADS)

Xu, Xiaogang; Liu, Haixiao; Zhu, Hao; Wang, Songling

2016-07-01

To detect the mechanical failure of fans, a new diagnostic method based on the symmetrized dot pattern (SDP) analysis and image matching is proposed. Vibration signals of 13 kinds of running states are acquired on a centrifugal fan test bed and reconstructed by the SDP technique. The SDP pattern templates of each running state are established. An image matching method is performed to diagnose the fault. In order to improve the diagnostic accuracy, the single template, multiple templates and clustering fault templates are used to perform the image matching.

Platelets to rings: Influence of sodium dodecyl sulfate on Zn-Al layered double hydroxide morphology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yilmaz, Ceren; Unal, Ugur; Koc University, Chemistry Department, Rumelifeneri yolu, Sariyer 34450, Istanbul

2012-03-15

In the current study, influence of sodium dodecyl sulfate (SDS) on the crystallization of Zn-Al layered double hydroxide (LDH) was investigated. Depending on the SDS concentration coral-like and for the first time ring-like morphologies were obtained in a urea-hydrolysis method. It was revealed that the surfactant level in the starting solution plays an important role in the morphology. Concentration of surfactant equal to or above the anion exchange capacity of the LDH is influential in creating different morphologies. Another important parameter was the critical micelle concentration (CMC) of the surfactant. Surfactant concentrations well above CMC value resulted in ring-like structures.more » The crystallization mechanism was discussed. - Graphical abstract: Dependence of ZnAl LDH Morphology on SDS concentration. Highlights: Black-Right-Pointing-Pointer In-situ intercalation of SDS in ZnAl LDH was achieved via urea hydrolysis method. Black-Right-Pointing-Pointer Morphology of ZnAl LDH intercalated with SDS depended on the SDS concentration. Black-Right-Pointing-Pointer Ring like morphology for SDS intercalated ZnAl LDH was obtained for the first time. Black-Right-Pointing-Pointer Growth mechanism was discussed. Black-Right-Pointing-Pointer Template assisted growth of ZnAl LDH was proposed.« less

Growth of raspberry-, prism- and flower-like ZnO particles using template-free low-temperature hydrothermal method and their application as humidity sensors

NASA Astrophysics Data System (ADS)

Pál, Edit; Hornok, Viktória; Kun, Robert; Chernyshev, Vladimir; Seemann, Torben; Dékány, Imre; Busse, Matthias

2012-08-01

Zinc oxide particles with different morphologies were prepared by hydrothermal method at 60-90 °C. The structure formation was controlled by the addition rate and temperature of hydrolyzing agent, while the particles size (10 nm-2.5 μm) was influenced by the preparation (hydrothermal) temperature. Scanning electron microscopy studies showed that raspberry-, prism- and flower-like ZnO particles were prepared, whose average size decreased with increasing reaction temperature. X-ray diffraction investigations confirmed that ZnO particles with hexagonal crystal structure formed in all syntheses. The raspberry-, prism- and flower-like ZnO particles showed a weak UV-emission in the range of 390-395 nm and strong visible emission with a maximum at 586, 593 and 598 nm, respectively. Morphology effect on electrical and water vapour sensing properties of ZnO samples was investigated by impedance spectroscopy and quartz crystal microbalance, respectively. The absolute impedance of raspberry-, prism- and flower-like ZnO particles was found to be strong dependent on the morphology. Space-charge-limited conductivity transport mechanism was proved by the oscillatory behaviour of impedance. Humidity sensor tests also revealed morphology and specific surface area dependency on the sensitivity and water vapour adsorption property.

Fabrication of SrTiO3 nanotubes via an isomorphic conversion strategy

NASA Astrophysics Data System (ADS)

Yang, Dong; Zou, Xiaoyan; Tong, Zhenwei; Nan, Yanhu; Ding, Fei; Jiang, Zhongyi

2018-02-01

One-dimensional nanotubes have attracted enormous attention due to their specific structure and excellent performance since the carbon nanotube was prepared. In this study, the open-ended SrTiO3 nanotubes (STNTs) have been fabricated for the first time via an isomorphic conversion strategy using the protonated titanate nanotubes (HTNTs) as the precursor and template under the hydrothermal treatment. The as-prepared STNTs consist of uniform and continuous multilayers, having inner and outer diameters about 8.0 and 13 nm. The STNT formation involves the exchange of Sr2+ ions with H+ ions in HTNTs and then in situ growth of cubic SrTiO3 crystals by the templating of HTNT frameworks. It is found that the diffusion process of Sr2+ ions plays a critical role in controlling the nanotube morphology of SrTiO3 crystals. In addition, the SrTiO3 nanotubes exhibit high photocatalytic activity for the Cr(VI) reduction, which can reduce nearly 100% Cr(VI) within 6 h under simulated sunlight irradiation. The current strategy may be broadly applicable for fabricating the nanotubes from raw materials without 2D layered nanostructure. [Figure not available: see fulltext.

Synthesis, crystal structures and luminescent properties of two 4 d-4 f Ln-Ag heterometallic coordination polymers based on anion template

NASA Astrophysics Data System (ADS)

Fan, Le-Qing; Chen, Yuan; Wu, Ji-Huai; Huang, Yun-Fang

2011-04-01

Two new 4 d-4 f Ln-Ag heterometallic coordination polymers, {[ Ln3Ag 5(IN) 10(H 2O) 7]·4(ClO 4)·4(H 2O)} n ( Ln=Eu ( 1) and Sm ( 2), HIN=isonicotinic acid), have been synthesized under hydrothermal conditions by reactions of Ln2O 3, AgNO 3, HIN and HClO 4, and characterized by elemental analysis, IR, thermal analysis and single-crystal X-ray diffraction. It is proved that HClO 4 not only adjusts the pH value of the reaction mixture, but also acts as anion template. The structure determination reveals that 1 and 2 are isostructural and feature a novel two-dimensional (2D) layered hetrometallic structure constructed from one-dimensional Ln-carboxylate chains and pillared Ag(IN) 2 units. The 2D layers are further interlinked through Ag⋯Ag and Ag⋯O(ClO 4-) multiple weak interactions, which form a rare Ag-ClO 4 ribbon in lanthanide-transition metal coordination polymers, to give rise to a three-dimensional supramolecular architecture. Moreover, the luminescent properties of these two compounds have also been investigated at room temperature.

Colloidal crystal templated molecular imprinted polymer for the detection of 2-butoxyethanol in water contaminated by hydraulic fracturing.

PubMed

Dai, Jingjing; Vu, Danh; Nagel, Susan; Lin, Chung-Ho; Fidalgo de Cortalezzi, Maria

2017-12-06

The authors describe a molecularly imprinted polymer (MIP) that enables detection of 2-butoxyethanol (2BE), a pollutant associated with hydraulic fracturing contamination. Detection is based on a combination of a colloidal crystal templating and a molecular imprinting. The MIPs are shown to display higher binding capacity for 2BE compared to non-imprinted films (NIPs), with imprinting efficiencies of ∼ 2. The tests rely on the optical effects that are displayed by the uniformly ordered porous structure of the material. The reflectance spectra of the polymer films have characteristic Bragg peaks whose location varies with the concentration of 2BE. Peaks undergo longwave red shifts up to 50 nm on exposure of the MIP to 2BE in concentrations in the range from 1 ppb to 100 ppm. This allows for quantitative estimates of the 2BE concentrations present in aqueous solutions. The material is intended for use in the early detection of contamination at hydraulic fracturing sites. Graphical abstract Molecularly imprinted polymers (MIPs) sensor with the sensing ability on reflectance spectra responding to the presence of 2-butoxyethanol (2BE) for early detection of hydraulic fracking contamination.

Crystal Structure of the Oligomeric Form of Lassa Virus Matrix Protein Z.

PubMed

Hastie, Kathryn M; Zandonatti, Michelle; Liu, Tong; Li, Sheng; Woods, Virgil L; Saphire, Erica Ollmann

2016-05-01

The arenavirus matrix protein Z is highly multifunctional and occurs in both monomeric and oligomeric forms. The crystal structure of a dodecamer of Z from Lassa virus, presented here, illustrates a ring-like structure with a highly basic center. Mutagenesis demonstrates that the dimeric interface within the dodecamer and a Lys-Trp-Lys triad at the center of the ring are important for oligomerization. This structure provides an additional template to explore the many functions of Z. The arenavirus Lassa virus causes hundreds of thousands of infections each year, many of which develop into fatal hemorrhagic fever. The arenavirus matrix protein Z is multifunctional, with at least four distinct roles. Z exists in both monomeric and oligomeric forms, each of which likely serves a specific function in the viral life cycle. Here we present the dodecameric form of Lassa virus Z and demonstrate that Z forms a "wreath" with a highly basic center. This structure and that of monomeric Z now provide a pair of critical templates by which the multiple roles of Z in the viral life cycle may be interpreted. Copyright © 2016, American Society for Microbiology. All Rights Reserved.

Nanowire-templated lateral epitaxial growth of non-polar group III nitrides

DOEpatents

Wang, George T [Albuquerque, NM; Li, Qiming [Albuquerque, NM; Creighton, J Randall [Albuquerque, NM

2010-03-02

A method for growing high quality, nonpolar Group III nitrides using lateral growth from Group III nitride nanowires. The method of nanowire-templated lateral epitaxial growth (NTLEG) employs crystallographically aligned, substantially vertical Group III nitride nanowire arrays grown by metal-catalyzed metal-organic chemical vapor deposition (MOCVD) as templates for the lateral growth and coalescence of virtually crack-free Group III nitride films. This method requires no patterning or separate nitride growth step.

Assessing the applicability of template-based protein docking in the twilight zone.

PubMed

Negroni, Jacopo; Mosca, Roberto; Aloy, Patrick

2014-09-02

The structural modeling of protein interactions in the absence of close homologous templates is a challenging task. Recently, template-based docking methods have emerged to exploit local structural similarities to help ab-initio protocols provide reliable 3D models for protein interactions. In this work, we critically assess the performance of template-based docking in the twilight zone. Our results show that, while it is possible to find templates for nearly all known interactions, the quality of the obtained models is rather limited. We can increase the precision of the models at expenses of coverage, but it drastically reduces the potential applicability of the method, as illustrated by the whole-interactome modeling of nine organisms. Template-based docking is likely to play an important role in the structural characterization of the interaction space, but we still need to improve the repertoire of structural templates onto which we can reliably model protein complexes. Copyright © 2014 Elsevier Ltd. All rights reserved.

Microparticles Produced by the Hydrogel Template Method for Sustained Drug Delivery

PubMed Central

Lu, Ying; Sturek, Michael; Park, Kinam

2014-01-01

Polymeric microparticles have been used widely for sustained drug delivery. Current methods of microparticle production can be improved by making homogeneous particles in size and shape, increasing the drug loading, and controlling the initial burst release. In the current study, the hydrogel template method was used to produce homogeneous poly(lactide-co-glycolide) (PLGA) microparticles and to examine formulation and process-related parameters. Poly(vinyl alcohol) (PVA) was used to make hydrogel templates. The parameters examined include PVA molecular weight, type of PLGA (as characterized by lactide content, inherent viscosity), polymer concentration, drug concentration and composition of solvent system. Three model compounds studied were risperidone, methylprednisolone acetate and paclitaxel. The ability of the hydrogel template method to produce microparticles with good conformity to template was dependent on molecular weight of PVA and viscosity of the PLGA solution. Drug loading and encapsulation efficiency were found to be influenced by PLGA lactide content, polymer concentration and composition of the solvent system. The drug loading and encapsulation efficiency were 28.7% and 82% for risperidone, 31.5% and 90% for methylprednisolone acetate, and 32.2 % and 92 % for paclitaxel, respectively. For all three drugs, release was sustained for weeks, and the in vitro release profile of risperidone was comparable to that of microparticles prepared using the conventional emulsion method. The hydrogel template method provides a new approach of manipulating microparticles. PMID:24333903

DOE Office of Scientific and Technical Information (OSTI.GOV)

Campbell, W; Miften, M; Jones, B

Purpose: Pancreatic SBRT relies on extremely accurate delivery of ablative radiation doses to the target, and intra-fractional tracking of fiducial markers can facilitate improvements in dose delivery. However, this requires algorithms that are able to find fiducial markers with high speed and accuracy. The purpose of this study was to develop a novel marker tracking algorithm that is robust against many of the common errors seen with traditional template matching techniques. Methods: Using CBCT projection images, a method was developed to create detailed template images of fiducial marker clusters without prior knowledge of the number of markers, their positions, ormore » their orientations. Briefly, the method (i) enhances markers in projection images, (ii) stabilizes the cluster’s position, (iii) reconstructs the cluster in 3D, and (iv) precomputes a set of static template images dependent on gantry angle. Furthermore, breathing data were used to produce 4D reconstructions of clusters, yielding dynamic template images dependent on gantry angle and breathing amplitude. To test these two approaches, static and dynamic templates were used to track the motion of marker clusters in more than 66,000 projection images from 75 CBCT scans of 15 pancreatic SBRT patients. Results: For both static and dynamic templates, the new technique was able to locate marker clusters present in projection images 100% of the time. The algorithm was also able to correctly locate markers in several instances where only some of the markers were visible due to insufficient field-of-view. In cases where clusters exhibited deformation and/or rotation during breathing, dynamic templates resulted in cross-correlation scores up to 70% higher than static templates. Conclusion: Patient-specific templates provided complete tracking of fiducial marker clusters in CBCT scans, and dynamic templates helped to provide higher cross-correlation scores for deforming/rotating clusters. This novel algorithm provides an extremely accurate method to detect fiducial markers during treatment. Research funding provided by Varian Medical Systems to Miften and Jones.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zahn, Karl E.; Averill, April; Wallace, Susan S.

5-Hydroxycytosine (5-OHC) is a stable oxidation product of cytosine associated with an increased frequency of C {yields} T transition mutations. When this lesion escapes recognition by the base excision repair pathway and persists to serve as a templating base during DNA synthesis, replicative DNA polymerases often misincorporate dAMP at the primer terminus, which can lead to fixation of mutations and subsequent disease. To characterize the dynamics of DNA synthesis opposite 5-OHC, we initiated a comparison of unmodified dCMP to 5-OHC, 5-fluorocytosine (5-FC), and 5-methylcytosine (5-MEC) in which these bases act as templates in the active site of RB69 gp43, amore » high-fidelity DNA polymerase sharing homology with human replicative DNA polymerases. This study presents the first crystal structure of any DNA polymerase binding this physiologically important premutagenic DNA lesion, showing that while dGMP is stabilized by 5-OHC through normal Watson-Crick base pairing, incorporation of dAMP leads to unstacking and instability in the template. Furthermore, the electronegativity of the C5 substituent appears to be important in the miscoding potential of these cytosine-like templates. While dAMP is incorporated opposite 5-OHC {approx}5 times more efficiently than opposite unmodified dCMP, an elevated level of incorporation is also observed opposite 5-FC but not 5-MEC. Taken together, these data imply that the nonuniform templating by 5-OHC is due to weakened stacking capabilities, which allows dAMP incorporation to proceed in a manner similar to that observed opposite abasic sites.« less

Low-template methods yield limited extra information for PowerPlex® Fusion 6C profiling.

PubMed

Duijs, Francisca; van de Merwe, Linda; Sijen, Titia; Benschop, Corina C G

2018-06-01

Advances in autosomal DNA profiling systems enable analyzing increased numbers of short tandem repeat (STR) loci in one reaction. Increasing the number of STR loci increases the amount of information that may be obtained from a (crime scene) sample. In this study, we examined whether even more allelic information can be obtained by applying low-template methods. To this aim, the performance of the PowerPlex® Fusion 6C STR typing system was assessed when increasing the number of PCR cycles or enhancing the capillary electrophoresis (CE) injection settings. Results show that applying these low-template methods yields limited extra information and comes at cost of more background noise. In addition, the gain in detection of alleles was much smaller when compared to the gain when applying low-template methods to the 15-loci AmpFLSTR® NGM™ system. Consequently, the PowerPlex® Fusion 6C STR typing system was implemented using standard settings only; low-template methods were not implemented for our routine forensic casework. Copyright © 2018 Elsevier B.V. All rights reserved.

Synthesis and Characterization of CuFe 2O 4 Nano/Submicron Wire–Carbon Nanotube Composites as Binder-free Anodes for Li-Ion Batteries

DOE PAGES

Wang, Lei; Bock, David C.; Li, Jing; ...

2018-02-20

Here, a series of one-dimensional CuFe 2O 4 nano/sub-micron wires possessing different diameters, crystal phases, and crystal sizes have been successfully generated using a facile template-assisted co precipitation reaction at room temperature, followed by a short post-annealing process. The diameter and the crystal structure of the resulting CuFe 2O4 (CFO) wires were judiciously tuned by varying the pore size of the template and the post-annealing temperature, respectively. Carbon nanotubes (CNTs) were incorporated to generate CFO-CNT binder-free anodes, and multiple characterization techniques were employed with the goal of delineating the relationships between electrochemical behavior and the properties of both the CFOmore » wires (crystal phase, wire diameter, crystal size) and the electrode architecture (binder-free vs. conventionally prepared approaches). The study reveals several notable findings. First, the crystal phase (cubic or tetragonal) did not influence the electrochemical behavior in this CFO system. Second, regarding crystallite size and wire diameter, CFO wires with larger crystallite sizes exhibit improved cycling stability, while wires possessing smaller diameters exhibiting higher capacities. Finally, the electrochemical behavior is strongly influenced by the electrode architecture, with CFO-CNT binder-free electrodes demonstrating significantly higher capacities and cycling stability compared to conventionally prepared coatings. The mechanism(s) associated with the high capacities under low current density but limited electrochemical reversibility of CFO electrodes under high current density were probed via x-ray absorption spectroscopy (XAS) mapping with sub-micron spatial resolution for the first time. Results suggest that the capacity of the binder-free electrodes under high rate is limited by the irreversible formation of Cu 0, as well as limited reduction of Fe 3+, to Fe 2+ not Fe 0. The results (1) shed fundamental insight into the reversibility of CuFe 2O 4 materials cycled at high current density and (2) demonstrate that a synergistic effort to control both active material morphology and electrode architecture is an effective strategy for optimizing electrochemical behavior.« less

Synthesis and Characterization of CuFe 2O 4 Nano/Submicron Wire–Carbon Nanotube Composites as Binder-free Anodes for Li-Ion Batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Lei; Bock, David C.; Li, Jing

Here, a series of one-dimensional CuFe 2O 4 nano/sub-micron wires possessing different diameters, crystal phases, and crystal sizes have been successfully generated using a facile template-assisted co precipitation reaction at room temperature, followed by a short post-annealing process. The diameter and the crystal structure of the resulting CuFe 2O4 (CFO) wires were judiciously tuned by varying the pore size of the template and the post-annealing temperature, respectively. Carbon nanotubes (CNTs) were incorporated to generate CFO-CNT binder-free anodes, and multiple characterization techniques were employed with the goal of delineating the relationships between electrochemical behavior and the properties of both the CFOmore » wires (crystal phase, wire diameter, crystal size) and the electrode architecture (binder-free vs. conventionally prepared approaches). The study reveals several notable findings. First, the crystal phase (cubic or tetragonal) did not influence the electrochemical behavior in this CFO system. Second, regarding crystallite size and wire diameter, CFO wires with larger crystallite sizes exhibit improved cycling stability, while wires possessing smaller diameters exhibiting higher capacities. Finally, the electrochemical behavior is strongly influenced by the electrode architecture, with CFO-CNT binder-free electrodes demonstrating significantly higher capacities and cycling stability compared to conventionally prepared coatings. The mechanism(s) associated with the high capacities under low current density but limited electrochemical reversibility of CFO electrodes under high current density were probed via x-ray absorption spectroscopy (XAS) mapping with sub-micron spatial resolution for the first time. Results suggest that the capacity of the binder-free electrodes under high rate is limited by the irreversible formation of Cu 0, as well as limited reduction of Fe 3+, to Fe 2+ not Fe 0. The results (1) shed fundamental insight into the reversibility of CuFe 2O 4 materials cycled at high current density and (2) demonstrate that a synergistic effort to control both active material morphology and electrode architecture is an effective strategy for optimizing electrochemical behavior.« less

The Structure of a High Fidelity DNA Polymerase Bound to a Mismatched Nucleotide Reveals an “Ajar” Intermediate Conformation in the Nucleotide Selection Mechanism*

PubMed Central

Wu, Eugene Y.; Beese, Lorena S.

2011-01-01

To achieve accurate DNA synthesis, DNA polymerases must rapidly sample and discriminate against incorrect nucleotides. Here we report the crystal structure of a high fidelity DNA polymerase I bound to DNA primer-template caught in the act of binding a mismatched (dG:dTTP) nucleoside triphosphate. The polymerase adopts a conformation in between the previously established “open” and “closed” states. In this “ajar” conformation, the template base has moved into the insertion site but misaligns an incorrect nucleotide relative to the primer terminus. The displacement of a conserved active site tyrosine in the insertion site by the template base is accommodated by a distinctive kink in the polymerase O helix, resulting in a partially open ternary complex. We suggest that the ajar conformation allows the template to probe incoming nucleotides for complementarity before closure of the enzyme around the substrate. Based on solution fluorescence, kinetics, and crystallographic analyses of wild-type and mutant polymerases reported here, we present a three-state reaction pathway in which nucleotides either pass through this intermediate conformation to the closed conformation and catalysis or are misaligned within the intermediate, leading to destabilization of the closed conformation. PMID:21454515

Thermal annealing studies of GeTe-Sb2Te3 alloys with multiple interfaces

NASA Astrophysics Data System (ADS)

Bragaglia, Valeria; Mio, Antonio M.; Calarco, Raffaella

2017-08-01

A high degree of vacancy ordering is obtained by annealing amorphous GeTe-Sb2Te3 (GST) alloys deposited on a crystalline substrate, which acts as a template for the crystallization. Under annealing the material evolves from amorphous to disordered rocksalt, to ordered rocksalt with vacancies arranged into (111) oriented layers, and finally converts into the stable trigonal phase. The role of the interface in respect to the formation of an ordered crystalline phase is studied by comparing the transformation stages of crystalline GST with and without a capping layer. The capping layer offers another crystallization interface, which harms the overall crystalline quality.

A Stochastic Point Cloud Sampling Method for Multi-Template Protein Comparative Modeling.

PubMed

Li, Jilong; Cheng, Jianlin

2016-05-10

Generating tertiary structural models for a target protein from the known structure of its homologous template proteins and their pairwise sequence alignment is a key step in protein comparative modeling. Here, we developed a new stochastic point cloud sampling method, called MTMG, for multi-template protein model generation. The method first superposes the backbones of template structures, and the Cα atoms of the superposed templates form a point cloud for each position of a target protein, which are represented by a three-dimensional multivariate normal distribution. MTMG stochastically resamples the positions for Cα atoms of the residues whose positions are uncertain from the distribution, and accepts or rejects new position according to a simulated annealing protocol, which effectively removes atomic clashes commonly encountered in multi-template comparative modeling. We benchmarked MTMG on 1,033 sequence alignments generated for CASP9, CASP10 and CASP11 targets, respectively. Using multiple templates with MTMG improves the GDT-TS score and TM-score of structural models by 2.96-6.37% and 2.42-5.19% on the three datasets over using single templates. MTMG's performance was comparable to Modeller in terms of GDT-TS score, TM-score, and GDT-HA score, while the average RMSD was improved by a new sampling approach. The MTMG software is freely available at: http://sysbio.rnet.missouri.edu/multicom_toolbox/mtmg.html.

A Stochastic Point Cloud Sampling Method for Multi-Template Protein Comparative Modeling

PubMed Central

Li, Jilong; Cheng, Jianlin

2016-01-01

Generating tertiary structural models for a target protein from the known structure of its homologous template proteins and their pairwise sequence alignment is a key step in protein comparative modeling. Here, we developed a new stochastic point cloud sampling method, called MTMG, for multi-template protein model generation. The method first superposes the backbones of template structures, and the Cα atoms of the superposed templates form a point cloud for each position of a target protein, which are represented by a three-dimensional multivariate normal distribution. MTMG stochastically resamples the positions for Cα atoms of the residues whose positions are uncertain from the distribution, and accepts or rejects new position according to a simulated annealing protocol, which effectively removes atomic clashes commonly encountered in multi-template comparative modeling. We benchmarked MTMG on 1,033 sequence alignments generated for CASP9, CASP10 and CASP11 targets, respectively. Using multiple templates with MTMG improves the GDT-TS score and TM-score of structural models by 2.96–6.37% and 2.42–5.19% on the three datasets over using single templates. MTMG’s performance was comparable to Modeller in terms of GDT-TS score, TM-score, and GDT-HA score, while the average RMSD was improved by a new sampling approach. The MTMG software is freely available at: http://sysbio.rnet.missouri.edu/multicom_toolbox/mtmg.html. PMID:27161489

Controlling macro- and mesostructures with hierarchical porosity through combined hard and soft templating.

PubMed

Petkovich, Nicholas D; Stein, Andreas

2013-05-07

Rigid, porous objects and surfactants serve as powerful templates for the formation of mesoporous and macroporous materials. When both types of template are combined in a single synthesis, materials with intricate architectures and hierarchical porosity can be obtained. In this tutorial review, we explain how to conduct syntheses with both soft and hard templates; moreover, we describe methods to control the final structure present in the templated material. Much of the foundation for multiple templating lies in the study of materials made with only one type of template. To establish a foundation in this area, a description of hard and soft templating is given, delving into the templates available and the steps required for effective templating. This leads into an extended discussion about materials templated with both hard and soft templates. Through the use of recent examples in the literature, we aim to show the diversity of structures possible through multiple templating and the advantages these structures can provide for a wide range of applications. An emphasis is placed on how various factors-such as the type of template, type of precursor, heat-treatment temperature, confinement within a small space, and template-template interactions-impact morphology.

A bifacial quantum dot-sensitized solar cell with all-cadmium sulfide photoanode

NASA Astrophysics Data System (ADS)

Ma, Chunqing; Tang, Qunwei; Liu, Danyang; Zhao, Zhiyuan; He, Benlin; Chen, Haiyan; Yu, Liangmin

2015-02-01

Pursuit of a high power conversion efficiency and reduction of electricity-generation cost has been a persistent objective for quantum dot-sensitized solar cells (QDSSCs). We present here the fabrication of a QDSSC comprising a nanoflower-structured CdS anode, a liquid electrolyte having S2-/Sn2- redox couples, and a transparent CoSe counter electrode. Nanoflower-structured CdS anodes are prepared by a successive ionic layer adsorption and reaction (SILAR) method and subsequently hydrothermal strategy free of any surfactant or template. The CdS nanoparticles synthesized by a SILAR method act as "seed crystal" for growth of CdS nanoflowers. The average electron lifetime is markedly elevated in nanoflower-structured CdS anode in comparison with CdS nanoparticle or nanoporous CdS microsphere anode. Herein, we study the effect of synthesis method on CdS morphology and solar cell's photovoltaic performance, showing a power conversion efficiency of 1.67% and 1.17% for nanoflower-structured CdS QDSSC under front and rear irradiations, respectively.

Synthesis and characterization of pure strontium apatite particles and nanoporous scaffold prepared by dextrose-templated method

NASA Astrophysics Data System (ADS)

Ma, Xiaoyu; Liu, Yongjia; Zhu, Bangshang

2018-02-01

Strontium shows an increasing interest on bone formation and bone resorption prevention. Here, pure apatite strontium (Ap-SrOH) [Sr5(PO4)3(OH), strontium hydroxyapatite] particles were prepared by the precipitation method using Sr(NO3)2 · 6H2O and (NH4)2HPO4 as reagents. Scanning electron microscope, transmission electron microscope combined with electron diffraction, X-ray diffraction, Fourier transform infrared spectra (FTIR), variable temperature FTIR and thermo gravimetric analysis were employed to evaluate the crystalline structure, chemical composition, and thermal stability of the Ap-SrOH particles. The results show that phase pure Ap-SrOH particles were prepared by wet precipitation. The obtained Ap-SrOH particles are single crystal in phase structure, they have hexagonal fusiform shape, and their size is about 30-180 nm in diameter, and 0.4-2.5 μm in length. The cell MTT assay evaluations indicate that Ap-SrOH particles have very low cytotoxicity. Furthermore, nanoporous Ap-SrOH scaffolds were synthesized by anhydrous dextrose template method. After mixed 5-10 wt% of anhydrous dextrose with Ap-SrOH particles, pressed into discs, and sintered in microwave muffle furnace at 600 °C, the scaffolds with both nanoporous and nanotopography were formed. Cell culture of MC3T3-E1 osteoblasts in vitro show cells grow well on nanoporous Ap-SrOH scaffold. Therefore, Ap-SrOH particles and their nanoporous scaffolds are promising biomaterials for bone repairing and bone disease (e.g. osteoporosis) healing.

A Template for Open Inquiry: Using Questions to Encourage and Support Inquiry in Earth and Space Science

ERIC Educational Resources Information Center

Hermann, Ronald S.; Miranda, Rommel J.

2010-01-01

This article provides an instructional approach to helping students generate open-inquiry research questions, which the authors call the "open-inquiry question template." This template was created based on their experience teaching high school science and preservice university methods courses. To help teachers implement this template, they…

Fast template matching with polynomials.

PubMed

Omachi, Shinichiro; Omachi, Masako

2007-08-01

Template matching is widely used for many applications in image and signal processing. This paper proposes a novel template matching algorithm, called algebraic template matching. Given a template and an input image, algebraic template matching efficiently calculates similarities between the template and the partial images of the input image, for various widths and heights. The partial image most similar to the template image is detected from the input image for any location, width, and height. In the proposed algorithm, a polynomial that approximates the template image is used to match the input image instead of the template image. The proposed algorithm is effective especially when the width and height of the template image differ from the partial image to be matched. An algorithm using the Legendre polynomial is proposed for efficient approximation of the template image. This algorithm not only reduces computational costs, but also improves the quality of the approximated image. It is shown theoretically and experimentally that the computational cost of the proposed algorithm is much smaller than the existing methods.

Template based rotation: A method for functional connectivity analysis with a priori templates☆

PubMed Central

Schultz, Aaron P.; Chhatwal, Jasmeer P.; Huijbers, Willem; Hedden, Trey; van Dijk, Koene R.A.; McLaren, Donald G.; Ward, Andrew M.; Wigman, Sarah; Sperling, Reisa A.

2014-01-01

Functional connectivity magnetic resonance imaging (fcMRI) is a powerful tool for understanding the network level organization of the brain in research settings and is increasingly being used to study large-scale neuronal network degeneration in clinical trial settings. Presently, a variety of techniques, including seed-based correlation analysis and group independent components analysis (with either dual regression or back projection) are commonly employed to compute functional connectivity metrics. In the present report, we introduce template based rotation,1 a novel analytic approach optimized for use with a priori network parcellations, which may be particularly useful in clinical trial settings. Template based rotation was designed to leverage the stable spatial patterns of intrinsic connectivity derived from out-of-sample datasets by mapping data from novel sessions onto the previously defined a priori templates. We first demonstrate the feasibility of using previously defined a priori templates in connectivity analyses, and then compare the performance of template based rotation to seed based and dual regression methods by applying these analytic approaches to an fMRI dataset of normal young and elderly subjects. We observed that template based rotation and dual regression are approximately equivalent in detecting fcMRI differences between young and old subjects, demonstrating similar effect sizes for group differences and similar reliability metrics across 12 cortical networks. Both template based rotation and dual-regression demonstrated larger effect sizes and comparable reliabilities as compared to seed based correlation analysis, though all three methods yielded similar patterns of network differences. When performing inter-network and sub-network connectivity analyses, we observed that template based rotation offered greater flexibility, larger group differences, and more stable connectivity estimates as compared to dual regression and seed based analyses. This flexibility owes to the reduced spatial and temporal orthogonality constraints of template based rotation as compared to dual regression. These results suggest that template based rotation can provide a useful alternative to existing fcMRI analytic methods, particularly in clinical trial settings where predefined outcome measures and conserved network descriptions across groups are at a premium. PMID:25150630

The effect of pigeon yolk sac fluid on the growth behavior of calcium carbonate crystals.

PubMed

Song, Juan; Cheng, Haixia; Shen, Xinyu; Tong, Hua

2015-03-01

Previous experiments have proved that thermodynamically unstable calcium carbonate vaterite can exist for long periods in the yolk sac of a pigeon embryo. The aim of this article was to demonstrate the effect of in vitro mineralization of yolk sac fluid on calcium carbonate by direct precipitation. Experiments were conducted using pigeon yolk sac fluid and using lecithin extracted from pigeon yolk sac fluid as a control to investigate the regulating effects of the organic components in the embryo on the formation of the calcium carbonate precipitate. Multiple characterization methods were employed to study the various morphological patterns, sizes, crystal growth, and crystal phase transformations of the calcium carbonate precipitates as regulated by the yolk sac fluid extracted at different stages of incubation. The experimental results demonstrate that as the incubation proceeds towards the later stages, the composition and environmental features of the yolk sac fluid become more favorable for the formation of relatively unstable calcium carbonate phases with high energies of the vaterite state. The experiments conducted with extracted lecithin as the template for crystal growth yielded similar results. A large amount of organic molecules with polar functional groups carried by the yolk sac fluid have strong effects and can both initially induce the crystallization and regulate the aggregation of calcium carbonate. Furthermore, this regulation process is found to be closely related to the lecithin contained in yolk sac fluid. These observations confirm the changes in yolk sac fluid composition during incubation have significant effects on the production of vaterite, which implicates the calcium transport during embryo growth. © 2015 Poultry Science Association Inc.

Synthesis and characterization of Gd-doped magnetite nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Honghu; Iowa State Univ., Ames, IA; Malik, Vikash

There has been rising interest in the synthesis of magnetite nanoparticles due to their importance in biomedical and technological applications. Tunable magnetic properties of magnetite nanoparticles to meet specific requirements will greatly expand the spectrum of applications. Tremendous efforts have been devoted to studying and controlling the size, shape and magnetic properties of magnetite nanoparticles. We investigate gadolinium (Gd) doping to influence the growth process as well as magnetic properties of magnetite nanocrystals via a simple co-precipitation method under mild conditions in aqueous media. Gd doping was found to affect the growth process leading to synthesis of controllable particle sizesmore » under the conditions tested (0–10 at% Gd 3+). Typically, undoped and 5 at% Gd-doped magnetite nanoparticles were found to have crystal sizes of about 18 and 44 nm, respectively, supported by X-ray diffraction and transmission electron microscopy. These results showed that Gd-doped nanoparticles retained the magnetite crystal structure, with Gd 3+ randomly incorporated in the crystal lattice, probably in the octahedral sites. The composition of 5 at% Gd-doped magnetite was Fe (3-x)Gd xO 4 (x=0.085±0.002), as determined by inductively coupled plasma mass spectrometry. 5 at% Gd-doped nanoparticles exhibited ferrimagnetic properties with small coercivity (~65 Oe) and slightly decreased magnetization at 260 K in contrast to the undoped, superparamagnetic magnetite nanoparticles. Templation by the bacterial biomineralization protein Mms6 did not appear to affect the growth of the Gd-doped magnetite particles synthesized by this method.« less

Synthesis and characterization of Gd-doped magnetite nanoparticles

DOE PAGES

Zhang, Honghu; Iowa State Univ., Ames, IA; Malik, Vikash; ...

2016-10-04

There has been rising interest in the synthesis of magnetite nanoparticles due to their importance in biomedical and technological applications. Tunable magnetic properties of magnetite nanoparticles to meet specific requirements will greatly expand the spectrum of applications. Tremendous efforts have been devoted to studying and controlling the size, shape and magnetic properties of magnetite nanoparticles. We investigate gadolinium (Gd) doping to influence the growth process as well as magnetic properties of magnetite nanocrystals via a simple co-precipitation method under mild conditions in aqueous media. Gd doping was found to affect the growth process leading to synthesis of controllable particle sizesmore » under the conditions tested (0–10 at% Gd 3+). Typically, undoped and 5 at% Gd-doped magnetite nanoparticles were found to have crystal sizes of about 18 and 44 nm, respectively, supported by X-ray diffraction and transmission electron microscopy. These results showed that Gd-doped nanoparticles retained the magnetite crystal structure, with Gd 3+ randomly incorporated in the crystal lattice, probably in the octahedral sites. The composition of 5 at% Gd-doped magnetite was Fe (3-x)Gd xO 4 (x=0.085±0.002), as determined by inductively coupled plasma mass spectrometry. 5 at% Gd-doped nanoparticles exhibited ferrimagnetic properties with small coercivity (~65 Oe) and slightly decreased magnetization at 260 K in contrast to the undoped, superparamagnetic magnetite nanoparticles. Templation by the bacterial biomineralization protein Mms6 did not appear to affect the growth of the Gd-doped magnetite particles synthesized by this method.« less

Magnetic properties of GdMnO3 nanoparticles embedded in mesoporous silica

NASA Astrophysics Data System (ADS)

Tajiri, Takayuki; Mito, Masaki; Deguchi, Hiroyuki; Kohno, Atsushi

2018-05-01

Perovskite manganite GdMnO3 nanoparticles were synthesized using mesoporous silica as a template, and their magnetic properties and crystal structure were investigated. Powder X-ray diffraction data indicated successful synthesis of the GdMnO3 nanoparticles, with mean particle sizes of 13.9 and 20.9 nm. The lattice constants for the nanoparticles were slightly different from those for the bulk material and varied with the particle size. The magnetic transition temperatures for the nanoparticles were higher than those of the bulk crystal. The synthesized GdMnO3 nanoparticles exhibited superparamagnetic behaviors: The blocking temperature, coercive field, and transition temperature depended on the particle size. Magnetic measurements and crystal structure analysis suggest that the changes in the magnetic properties for GdMnO3 nanoparticles can be attributed to the modulation of the crystallographic structure.

Topology-Scaling Identification of Layered Solids and Stable Exfoliated 2D Materials.

PubMed

Ashton, Michael; Paul, Joshua; Sinnott, Susan B; Hennig, Richard G

2017-03-10

The Materials Project crystal structure database has been searched for materials possessing layered motifs in their crystal structures using a topology-scaling algorithm. The algorithm identifies and measures the sizes of bonded atomic clusters in a structure's unit cell, and determines their scaling with cell size. The search yielded 826 stable layered materials that are considered as candidates for the formation of two-dimensional monolayers via exfoliation. Density-functional theory was used to calculate the exfoliation energy of each material and 680 monolayers emerge with exfoliation energies below those of already-existent two-dimensional materials. The crystal structures of these two-dimensional materials provide templates for future theoretical searches of stable two-dimensional materials. The optimized structures and other calculated data for all 826 monolayers are provided at our database (https://materialsweb.org).

Metal-Organic Framework (MOF) Nanorods, Nanotubes, and Nanowires.

PubMed

Arbulu, Roberto C; Jiang, Ying-Bing; Peterson, Eric J; Qin, Yang

2018-05-14

New mechanisms for the controlled growth of one-dimensional (1D) metal-organic framework (MOF) nano- and superstructures under size-confinement and surface-directing effects have been discovered. Through applying interfacial synthesis templated by track-etched polycarbonate (PCTE) membranes, congruent polycrystalline zeolitic imidazolate framework-8 (ZIF-8) solid nanorods and hollow nanotubes were found to form within 100 nm membrane pores, while single crystalline ZIF-8 nanowires grew inside 30 nm pores, all of which possess large aspect ratios up to 60 and show preferential crystal orientation with the {100} planes aligned parallel to the long axis of the pore. Our findings provide a generalizable method for controlling size, morphology, and lattice orientation of MOF nanomaterials. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis and Photocatalytic Property of ZnO/TiO2 Inverse Opals Films with Controllable Composition and Topology

NASA Astrophysics Data System (ADS)

Xu, Jiao; Yang, Bei-fang; Fu, Zheng-ping; Wen, Mei-wang; Zhao, Yong-xun

2012-04-01

A novel method to fabricate composition- and topology-controlled ZnO/TiO2 inverse opals (IO) films using a positive sacrificial ZnO IO template has been developed. This method includes a two-step process, preparation of ZnO IO by a simple electrochemical deposition using a self-assembly polystyrene colloidal crystal template and preparation of ZnO/TiO2 IO by a liquid phase deposition (LPD) process at room temperature. The composition and topology of ZnO/TiO2 IO can be easily controlled by changing the duration of the LPD. After 20 min LPD process, a ZnO/TiO2 composite IO with non-close-packed face-centered cubic air sphere array was obtained. Prolonging the duration to 60 min, a pure TiO2 IO (TIO-LPD60) with obviously thickened walls was formed. The formation mechanism for the compositional and topological variation was discussed. A preliminary study on UV photocatalytic property of the samples for degradation of methylene blue reveals that the composition and topology significantly influenced the photocatalytic activity of the IO film. The ZnO/TiO2 composite IO demonstrates a higher degree of activity than both pure ZnO and pure TiO2 IO, although they have a similar IO wall thickness. Moreover, with increasing IO wall thickness from ~52 nm to ~90 nm, TIO-LPD60 exhibits the highest level of photocatalytic performance.

Fabrication of Smooth Patterned Structures of Refractory Metals, Semiconductors, and Oxides via Template Stripping

PubMed Central

2013-01-01

The template-stripping method can yield smooth patterned films without surface contamination. However, the process is typically limited to coinage metals such as silver and gold because other materials cannot be readily stripped from silicon templates due to strong adhesion. Herein, we report a more general template-stripping method that is applicable to a larger variety of materials, including refractory metals, semiconductors, and oxides. To address the adhesion issue, we introduce a thin gold layer between the template and the deposited materials. After peeling off the combined film from the template, the gold layer can be selectively removed via wet etching to reveal a smooth patterned structure of the desired material. Further, we demonstrate template-stripped multilayer structures that have potential applications for photovoltaics and solar absorbers. An entire patterned device, which can include a transparent conductor, semiconductor absorber, and back contact, can be fabricated. Since our approach can also produce many copies of the patterned structure with high fidelity by reusing the template, a low-cost and high-throughput process in micro- and nanofabrication is provided that is useful for electronics, plasmonics, and nanophotonics. PMID:24001174

Estimating B1+ in the breast at 7 T using a generic template.

PubMed

van Rijssel, Michael J; Pluim, Josien P W; Luijten, Peter R; Gilhuijs, Kenneth G A; Raaijmakers, Alexander J E; Klomp, Dennis W J

2018-05-01

Dynamic contrast-enhanced MRI is the workhorse of breast MRI, where the diagnosis of lesions is largely based on the enhancement curve shape. However, this curve shape is biased by RF transmit (B 1 + ) field inhomogeneities. B 1 + field information is required in order to correct these. The use of a generic, coil-specific B 1 + template is proposed and tested. Finite-difference time-domain simulations for B 1 + were performed for healthy female volunteers with a wide range of breast anatomies. A generic B 1 + template was constructed by averaging simulations based on four volunteers. Three-dimensional B 1 + maps were acquired in 15 other volunteers. Root mean square error (RMSE) metrics were calculated between individual simulations and the template, and between individual measurements and the template. The agreement between the proposed template approach and a B 1 + mapping method was compared against the agreement between acquisition and reacquisition using the same mapping protocol. RMSE values (% of nominal flip angle) comparing individual simulations with the template were in the range 2.00-4.01%, with mean 2.68%. RMSE values comparing individual measurements with the template were in the range8.1-16%, with mean 11.7%. The agreement between the proposed template approach and a B 1 + mapping method was only slightly worse than the agreement between two consecutive acquisitions using the same mapping protocol in one volunteer: the range of agreement increased from ±16% of the nominal angle for repeated measurement to ±22% for the B 1 + template. With local RF transmit coils, intersubject differences in B 1 + fields of the breast are comparable to the accuracy of B 1 + mapping methods, even at 7 T. Consequently, a single generic B 1 + template suits subjects over a wide range of breast anatomies, eliminating the need for a time-consuming B 1 + mapping protocol. © 2018 The Authors. NMR in Biomedicine published by John Wiley & Sons Ltd.

Estimating B 1 + in the breast at 7 T using a generic template

PubMed Central

Pluim, Josien P. W.; Luijten, Peter R.; Gilhuijs, Kenneth G. A.; Raaijmakers, Alexander J. E.; Klomp, Dennis W. J.

2018-01-01

Dynamic contrast‐enhanced MRI is the workhorse of breast MRI, where the diagnosis of lesions is largely based on the enhancement curve shape. However, this curve shape is biased by RF transmit (B 1 +) field inhomogeneities. B 1 + field information is required in order to correct these. The use of a generic, coil‐specific B 1 + template is proposed and tested. Finite‐difference time‐domain simulations for B 1 + were performed for healthy female volunteers with a wide range of breast anatomies. A generic B 1 + template was constructed by averaging simulations based on four volunteers. Three‐dimensional B 1 + maps were acquired in 15 other volunteers. Root mean square error (RMSE) metrics were calculated between individual simulations and the template, and between individual measurements and the template. The agreement between the proposed template approach and a B 1 + mapping method was compared against the agreement between acquisition and reacquisition using the same mapping protocol. RMSE values (% of nominal flip angle) comparing individual simulations with the template were in the range 2.00‐4.01%, with mean 2.68%. RMSE values comparing individual measurements with the template were in the range8.1‐16%, with mean 11.7%. The agreement between the proposed template approach and a B 1 + mapping method was only slightly worse than the agreement between two consecutive acquisitions using the same mapping protocol in one volunteer: the range of agreement increased from ±16% of the nominal angle for repeated measurement to ±22% for the B 1 + template. With local RF transmit coils, intersubject differences in B 1 + fields of the breast are comparable to the accuracy of B 1 + mapping methods, even at 7 T. Consequently, a single generic B 1 + template suits subjects over a wide range of breast anatomies, eliminating the need for a time‐consuming B 1 + mapping protocol. PMID:29570887

Sodium Chloride Crystal-Induced SERS Platform for Controlled Highly Sensitive Detection of Illicit Drugs.

PubMed

Yu, Borong; Li, Pan; Zhou, Binbin; Tang, Xianghu; Li, Shaofei; Yang, Liangbao

2018-04-03

A sodium chloride crystal-driven spontaneous 'hot spot' structure was demonstrated as a SERS-active platform, to get reproducible SERS signals, and eliminate the need for mapping large areas, in comparison with solution phase testing. During the process of solvent evaporation, the crystals produced induced silver aggregates to assemble around themselves. The micro-scale crystals can also act as a template to obtain an optical position, such that the assembled hot area is conveniently located during SERS measurements. More importantly, the chloride ions added in colloids can also replace the citrate and on the surface of the silver sol, and further decrease the background interference. High quality SERS spectra from heroin, methamphetamine (MAMP), and cocaine have been obtained on the crystal-driven hot spot structure with high sensitivity and credible reproducibility. This approach can not only bring the nanoparticles to form plasmonic hot spots in a controlled way, and thus provide high sensitivity, but also potentially be explored as an active substrate for label-free detection of other illicit drugs or additives. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Covalently Connecting Crystal Grains with Polyvinylammonium Carbochain Backbone To Suppress Grain Boundaries for Long-Term Stable Perovskite Solar Cells.

PubMed

Li, Han; Liang, Chao; Liu, Yingliang; Zhang, Yiqiang; Tong, Jincheng; Zuo, Weiwei; Xu, Shengang; Shao, Guosheng; Cao, Shaokui

2017-02-22

Grain boundaries act as rapid pathways for nonradiative carrier recombination, anion migration, and water corrosion, leading to low efficiency and poor stability of organometal halide perovskite solar cells (PSCs). In this work, the strategy suppressing the crystal grain boundaries is applied to improve the photovoltaic performance, especially moisture-resistant stability, with polyvinylammonium carbochain backbone covalently connecting the perovskite crystal grains. This cationic polyelectrolyte additive serves as nucleation sites and template for crystal growth of MAPbI 3 and afterward the immobilized adjacent crystal grains grow into the continuous compact, pinhole-free perovskite layer. As a result, the unsealed PSC devices, which are fabricated under low-temperature fabrication protocol with a proper content of polymer additive PVAm·HI, currently exhibit the maximum efficiency of 16.3%. Remarkably, these unsealed devices follow an "outside-in" corrosion mechanism and respectively retain 92% and 80% of the initial PCE value after being exposed under ambient environment for 50 days and 100 days, indicating the superiority of carbochain polymer additives in solving the long-term stability problem of PSCs.

Biological Niches within Human Calcified Aortic Valves: Towards Understanding of the Pathological Biomineralization Process

PubMed Central

Cottignoli, Valentina; Agrosì, Giovanna; Familiari, Giuseppe; Salvador, Loris

2015-01-01

Despite recent advances, mineralization site, its microarchitecture, and composition in calcific heart valve remain poorly understood. A multiscale investigation, using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectrometry (EDS), from micrometre up to nanometre, was conducted on human severely calcified aortic and mitral valves, to provide new insights into calcification process. Our aim was to evaluate the spatial relationship existing between bioapatite crystals, their local growing microenvironment, and the presence of a hierarchical architecture. Here we detected the presence of bioapatite crystals in two different mineralization sites that suggest the action of two different growth processes: a pathological crystallization process that occurs in biological niches and is ascribed to a purely physicochemical process and a matrix-mediated mineralized process in which the extracellular matrix acts as the template for a site-directed nanocrystals nucleation. Different shapes of bioapatite crystallization were observed at micrometer scale in each microenvironment but at the nanoscale level crystals appear to be made up by the same subunits. PMID:26509159

Crystallization and preliminary crystallographic analysis of poly(3-hydroxybutyrate) depolymerase from Bacillus thuringiensis.

PubMed

Wang, Yung Lin; Lin, Yi Ting; Chen, Chia Lin; Shaw, Gwo Chyuan; Liaw, Shwu Huey

2014-10-01

Poly[(R)-3-hydroxybutyrate] (PHB) is a microbial biopolymer that has been commercialized as biodegradable plastics. The key enzyme for the degradation is PHB depolymerase (PhaZ). A new intracellular PhaZ from Bacillus thuringiensis (BtPhaZ) has been screened for potential applications in polymer biodegradation. Recombinant BtPhaZ was crystallized using 25% polyethylene glycol 3350, 0.2 M ammonium acetate, 0.1 M bis-tris pH 6.5 at 288 K. The crystals belonged to space group P1, with unit-cell parameters a = 42.97, b = 83.23, c = 85.50 Å, α = 73.45, β = 82.83, γ = 83.49°. An X-ray diffraction data set was collected to 1.42 Å resolution with an Rmerge of 6.4%. Unexpectedly, a molecular-replacement solution was obtained using the crystal structure of Streptomyces lividans chloroperoxidase as a template, which shares 24% sequence identity to BtPhaZ. This is the first crystal structure of an intracellular poly(3-hydroxybutyrate) depolymerase.

Spinous TiO₂ and Au@TiO₂ octahedral nanocages: amorphisity-to-crystallinity transition-driven surface structural construction and photocatalytic study.

PubMed

Li, Jie; Zu, Lianhai; Li, Ying; Jin, Chao; Qin, Yao; Shi, Donglu; Yang, Jinhu

2014-07-15

Novel spinous TiO2 and Au@TiO2 octahedral nanocages have been prepared through a well-designed three-step strategy including templated TiO2 wet coating, subsequent structural ripening and final template removal or transformation. The strategy is built on an amorphisity-to-crystallinity transition-driven surface structural construction, which emphasizes the critical steps of crystallization-controlled TiO2 coating and consequent structural ripening. The influence of some key parameters, such as coating temperature, ripening temperature and ripening time, on the structure and morphology of the spinous TiO2 and Au@TiO2 nanocages have been investigated. In addition, in photocatalytic measurements, the prepared spinous TiO2-based nanocages exhibit enhanced photocatalytic efficiency relative to spinousless TiO2-based nanocages as well as P-25, owing to their structure advantages resulting from spinous surfaces. The photocatalytic activity of these TiO2 based photocatalysts has been systematically studied through the corresponding ·OH radical measurements. The synthetic strategy may work as a general method, through similarly designing, to realize surface structure engineering for various materials such as metals, hydroxide and other oxides besides TiO2. Copyright © 2014 Elsevier Inc. All rights reserved.

Synthesis of 5/7-, 5/8- and 5/9-bicyclic lactam templates as constraints for external beta-turns.

PubMed

Duggan, Heather M E; Hitchcock, Peter B; Young, Douglas W

2005-06-21

The 5/7-, 5/8- and 5/9-bicyclic lactams 3, 17, 5 and 6 have been synthesised as single diastereoisomers by a route involving ring closing olefin metathesis. The X-ray crystal structure of the amino acid hydrochloride has been carried out and compared to that of the saturated external beta-turn constraint 18.

Synthesis and Characterization of Functional Mesostructures Using Colloidal Crystal Templating

DTIC Science & Technology

2004-01-01

fluorescent probes in aqueous polymer solutions . Khoury and co-workers measured the diffusion coefficient of several fluorescein-labeled proteins in...diffraction naq refractive index of the aqueous solution phase xvii ni refractive index of component i ngel refractive index of the hydrogel...phase Tg glass transition temperature α angle of diffraction φaq volume fraction of the aqueous solution phase φi volume fraction of

Amine templating effect absent in uranyl sulfates synthesized with 1,4-n-butyldiamine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jouffret, Laurent J., E-mail: ljouffret@nd.edu; Wylie, Ernest M.; Burns, Peter C.

2013-01-15

Two new uranyl sulfates, (C{sub 4}H{sub 14}N{sub 2})[(UO{sub 2}){sub 2}(SO{sub 4}){sub 3}(H{sub 2}O)]{center_dot}2H{sub 2}O (NDUS2) and (C{sub 4}H{sub 14}N{sub 2})[(UO{sub 2})(SO{sub 4}){sub 2}(H{sub 2}O)]{center_dot}2H{sub 2}O (NDUS3), were synthesized and their crystal structures determined. NDUS2 was obtained in highly acidic media heat-treated at 373 K and subsequently maintained at 278 K until crystals formed after two months. NDUS3 results from the degradation of NDUS2 over the course of a few days. NDUS2 and NDUS3 crystallize in the monoclinic space group P2{sub 1}/n, a=10.9075(4) A, b=10.4513(4) A, c=17.7881(7) A, {beta}=97.908(2) Degree-Sign , V=2008.52(13) A{sup 3}, Z=4, at 140 K and a=8.8570(4) A,more » b=7.3299(3) A, c=20.4260(9) A, {beta}=95.140(2) Degree-Sign , V=1320.74(10) A{sup 3}, Z=4, at 140 K, respectively. The compounds contain interlayer 1,4-n-butyldiammonium cations that charge-balance the anionic structural units. - Graphical abstract: Amine templating effect absent in uranyl sulfates synthesized with 1,4-diaminobutane, as shown by the synthesis of two new uranyl sulfates, (C{sub 4}H{sub 14}N{sub 2})[(UO{sub 2}){sub 2}(SO{sub 4}){sub 3}(H{sub 2}O)]{center_dot}2H{sub 2}O (NDUS2) and (C{sub 4}H{sub 14}N{sub 2})[(UO{sub 2})(SO{sub 4}){sub 2}(H{sub 2}O)]{center_dot}2H{sub 2}O (NDUS3). Highlights: Black-Right-Pointing-Pointer Two layered uranyl sulfates were synthesized. Black-Right-Pointing-Pointer Amine molecules are located in the interlayers of the compounds. Black-Right-Pointing-Pointer No templating effect of the amine was observed. Black-Right-Pointing-Pointer Amine molecules are only charge balancing cations in the structures.« less

Sea urchin skeleton: Structure, composition, and application as a template for biomimetic materials

NASA Astrophysics Data System (ADS)

Shapkin, Nikolay P.; Khalchenko, Irina G.; Panasenko, Alexander E.; Drozdov, Anatoly L.

2017-07-01

SEM and optical microscopy, chemical and EDX analysis, XRD, and FT-IR spectroscopy of three sea urchins skeletons (tests) show that the test is a spongy stereom, consisting of calcite with high content of magnesium. The tests are composed of mineral-organic composite of calcite-magnesite crystals, coated with organic film, containing silicon in form of polyphenylsiloxane. In the test of sea urchin pore spaces are linked into united system of regular structure with structure motive period about 20 um. This developed three-dimensional structure was used as a template for polymer material based on polyferrofenilsiloxane [OSiC6H5OH]x[OSiC6H5O]y[OFeO]z, which is chemically similar to the native film, coating sea urchins skeleton.

New anion-templated 3D heterobimetallic open frameworks based on lanthanide-carboxylate layers and copper pillars

NASA Astrophysics Data System (ADS)

Li, Yun-Wu; Wang, Yong-Hui; Li, Yang-Guang; Wang, En-Bo

2008-06-01

A series of new three-dimensional (3D) lanthanide-transition metal (4 f-3 d) heterobimetallic open frameworks, [ Ln2(1,2-bdc) 2(H 2O) 2 Cu(inic) 2](ClO 4) ( Ln=Eu (1), Tb (2), Nd (3) and Sm (4); 1,2-bdc=1,2-benzenedicarboxylate; Hinic=isonicotinic acid) have been hydrothermally synthesized and characterized by elemental analysis, IR, TG and single-crystal X-ray diffraction analysis. Compounds 1-4 are isostructural. They possess a new anion-templated 3D heterobimetallic open framework, which is observed for the first time in the { Ln/ TM/bdc/inic} ( TM=transition metal) system. Compounds 1 and 2 exhibit the characteristic fluorescent properties of Eu(III) and Tb(III), respectively.

Light-assisted, templated self-assembly of gold nanoparticle chains.

PubMed

Jaquay, Eric; Martínez, Luis Javier; Huang, Ningfeng; Mejia, Camilo A; Sarkar, Debarghya; Povinelli, Michelle L

2014-09-10

We experimentally demonstrate the technique of light-assisted, templated self-assembly (LATS) to trap and assemble 200 nm diameter gold nanoparticles. We excite a guided-resonance mode of a photonic-crystal slab with 1.55 μm laser light to create an array of optical traps. Unlike our previous demonstration of LATS with polystyrene particles, we find that the interparticle interactions play a significant role in the resulting particle patterns. Despite a two-dimensionally periodic intensity profile in the slab, the particles form one-dimensional chains whose orientations can be controlled by the incident polarization of the light. The formation of chains can be understood in terms of a competition between the gradient force due to the excitation of the mode in the slab and optical binding between particles.

Ligand exchange and MIP-based paraoxon memories onto QCM sensor

NASA Astrophysics Data System (ADS)

Birlik Özkütük, Ebru; Emir Diltemiz, Sibel; Özalp, Elif; Uzun, Lokman; Ersöz, Arzu

2015-04-01

In this study, we have aimed to prepare quartz crystal microbalance (QCM) sensor using paraoxon-imprinted particles. Firstly, methacryloyl antipyrine (MAAP)-based metal-chelate-coordinated pre-complex has been prepared and used for paraoxon templation. Then, paraoxon-imprinted nanofilms were formed on QCM sensor after modification of the gold surfaces with allyl mercaptan. By this way, specific and selective memories, which depend on metal-chelate interactions between Eu(III) ions and template, for paraoxon molecules have been obtained on the electrode surface. QCM sensor has characterized using AFM and ellipsometer. The detection limit and the affinity constant have found to be 0.09 μM and 5.71 × 103 M-1 for MAAP-Eu paraoxon-based nanofilm, respectively. The specificity of the QCM sensor has shown using parathion as a competitor molecule.

Site-Specific Colloidal Crystal Nucleation by Template-enhanced Particle Transport

NASA Astrophysics Data System (ADS)

Mishra, Chandan K.; Sood, A. K.; Ganapathy, Rajesh

The deliberate positioning of nano- and microstructures on surfaces is often a prerequisite for fabricating functional devices. While template-assisted nucleation is a promising route to self-assemble these structures, its success hinges on particles reaching target sites prior to nucleation and for nano/microscale particles, this is hampered by their small surface mobilities. We tailored surface features, which in the presence of attractive depletion interactions not only directed micrometer-sized colloids to specific sites but also subsequently guided their growth into ordered crystalline arrays of well-defined size and symmetry. By following the nucleation kinetics with single-particle resolution, we demonstrate control over nucleation density in a growth regime that has hitherto remained inaccessible. Our findings pave the way towards realizing non-trivial surface architectures composed of complex colloids/nanoparticles as well.

Surface-enhanced Raman scattering on periodic metal nanotips with tunable sharpness.

PubMed

Linn, Nicholas C; Sun, Chih-Hung; Arya, Ajay; Jiang, Peng; Jiang, Bin

2009-06-03

This paper reports on a scalable bottom-up technology for producing periodic gold nanotips with tunable sharpness as surface-enhanced Raman scattering (SERS) substrates. Inverted silicon pyramidal pits, which are templated from non-close-packed colloidal crystals prepared by a spin-coating technology, are used as structural templates to replicate arrays of polymer nanopyramids with nanoscale sharp tips. The deposition of a thin layer of gold on the polymer nanopyramids leads to the formation of SERS-active substrates with a high enhancement factor (up to 10(8)). The thickness of the deposited metal determines the sharpness of the nanotips and the resulting Raman enhancement factor. Finite-element electromagnetic modeling shows that the nanotips can significantly enhance the local electromagnetic field and the sharpness of nanotips greatly affects the SERS enhancement.

Synthesis and Characterization of Pure Copper Nanostructures Using Wood Inherent Architecture as a Natural Template

NASA Astrophysics Data System (ADS)

Dong, Youming; Wang, Kaili; Tan, Yi; Wang, Qingchun; Li, Jianzhang; Mark, Hughes; Zhang, Shifeng

2018-04-01

The inherent sophisticated structure of wood inspires researchers to use it as a natural template for synthesizing functional nanoparticles. In this study, pure copper nanoparticles were synthesized using poplar wood as a natural inexpensive and renewable template. The crystal structure and morphologies of the copper nanoparticles were characterized by X-ray diffraction and field emission scanning electron microscopy. The optical properties, antibacterial properties, and stability of the hybrid wood materials were also tested. Due to the hierarchical and anisotropic structure and electron-rich components of wood, pure copper nanoparticles with high stability were synthesized with fcc structure and uniform sizes and then assembled into corncob-like copper deposits along the wood cell lumina. The products of nanoparticles depended strongly on the initial OH- concentration. With an increase in OH- concentration, Cu2O gradually decreased and Cu remained. Due to the restrictions inherent in wood structure, the derived Cu nanoparticles showed similar grain size in spite of increased Cu2+ concentration. This combination of Cu nanostructures and wood exhibited remarkable optical and antibacterial properties.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kirouac, Kevin N.; Ling, Hong; UWO)

Human DNA polymerase iota (pol iota) is a unique member of Y-family polymerases, which preferentially misincorporates nucleotides opposite thymines (T) and halts replication at T bases. The structural basis of the high error rates remains elusive. We present three crystal structures of pol complexed with DNA containing a thymine base, paired with correct or incorrect incoming nucleotides. A narrowed active site supports a pyrimidine to pyrimidine mismatch and excludes Watson-Crick base pairing by pol. The template thymine remains in an anti conformation irrespective of incoming nucleotides. Incoming ddATP adopts a syn conformation with reduced base stacking, whereas incorrect dGTP andmore » dTTP maintain anti conformations with normal base stacking. Further stabilization of dGTP by H-bonding with Gln59 of the finger domain explains the preferential T to G mismatch. A template 'U-turn' is stabilized by pol and the methyl group of the thymine template, revealing the structural basis of T stalling. Our structural and domain-swapping experiments indicate that the finger domain is responsible for pol's high error rates on pyrimidines and determines the incorporation specificity.« less

Confining metal-halide perovskites in nanoporous thin films

PubMed Central

Demchyshyn, Stepan; Roemer, Janina Melanie; Groiß, Heiko; Heilbrunner, Herwig; Ulbricht, Christoph; Apaydin, Dogukan; Böhm, Anton; Rütt, Uta; Bertram, Florian; Hesser, Günter; Scharber, Markus Clark; Sariciftci, Niyazi Serdar; Nickel, Bert; Bauer, Siegfried; Głowacki, Eric Daniel; Kaltenbrunner, Martin

2017-01-01

Controlling the size and shape of semiconducting nanocrystals advances nanoelectronics and photonics. Quantum-confined, inexpensive, solution-derived metal halide perovskites offer narrowband, color-pure emitters as integral parts of next-generation displays and optoelectronic devices. We use nanoporous silicon and alumina thin films as templates for the growth of perovskite nanocrystallites directly within device-relevant architectures without the use of colloidal stabilization. We find significantly blue-shifted photoluminescence emission by reducing the pore size; normally infrared-emitting materials become visibly red, and green-emitting materials become cyan and blue. Confining perovskite nanocrystals within porous oxide thin films drastically increases photoluminescence stability because the templates auspiciously serve as encapsulation. We quantify the template-induced size of the perovskite crystals in nanoporous silicon with microfocus high-energy x-ray depth profiling in transmission geometry, verifying the growth of perovskite nanocrystals throughout the entire thickness of the nanoporous films. Low-voltage electroluminescent diodes with narrow, blue-shifted emission fabricated from nanocrystalline perovskites grown in embedded nanoporous alumina thin films substantiate our general concept for next-generation photonic devices. PMID:28798959

Structural basis for inhibition of DNA replication by aphidicolin

DOE PAGES

Baranovskiy, A. G.; Babayeva, N. D.; Suwa, Y.; ...

2014-11-27

Natural tetracyclic diterpenoid aphidicolin is a potent and specific inhibitor of B-family DNA polymerases, haltering replication and possessing a strong antimitotic activity in human cancer cell lines. Clinical trials revealed limitations of aphidicolin as an antitumor drug because of its low solubility and fast clearance from human plasma. The absence of structural information hampered the improvement of aphidicolin-like inhibitors: more than 50 modifications have been generated so far, but all have lost the inhibitory and antitumor properties. Here we report the crystal structure of the catalytic core of human DNA polymerase α (Pol α) in the ternary complex with anmore » RNA-primed DNA template and aphidicolin. The inhibitor blocks binding of dCTP by docking at the Pol α active site and by rotating the template guanine. The structure provides a plausible mechanism for the selectivity of aphidicolin incorporation opposite template guanine and explains why previous modifications of aphidicolin failed to improve its affinity for Pol α. With new structural information, aphidicolin becomes an attractive lead compound for the design of novel derivatives with enhanced inhibitory properties for B-family DNA polymerases.« less

Fully Tunable Silicon Nanowire Arrays Fabricated by Soft Nanoparticle Templating.

PubMed

Rey, By Marcel; Elnathan, Roey; Ditcovski, Ran; Geisel, Karen; Zanini, Michele; Fernandez-Rodriguez, Miguel-Angel; Naik, Vikrant V; Frutiger, Andreas; Richtering, Walter; Ellenbogen, Tal; Voelcker, Nicolas H; Isa, Lucio

2016-01-13

We demonstrate a fabrication breakthrough to produce large-area arrays of vertically aligned silicon nanowires (VA-SiNWs) with full tunability of the geometry of the single nanowires and of the whole array, paving the way toward advanced programmable designs of nanowire platforms. At the core of our fabrication route, termed "Soft Nanoparticle Templating", is the conversion of gradually compressed self-assembled monolayers of soft nanoparticles (microgels) at a water-oil interface into customized lithographical masks to create VA-SiNW arrays by means of metal-assisted chemical etching (MACE). This combination of bottom-up and top-down techniques affords excellent control of nanowire etching site locations, enabling independent control of nanowire spacing, diameter and height in a single fabrication route. We demonstrate the fabrication of centimeter-scale two-dimensional gradient photonic crystals exhibiting continuously varying structural colors across the entire visible spectrum on a single silicon substrate, and the formation of tunable optical cavities supported by the VA-SiNWs, as unambiguously demonstrated through numerical simulations. Finally, Soft Nanoparticle Templating is combined with optical lithography to create hierarchical and programmable VA-SiNW patterns.

High-performance flexible surface-enhanced Raman scattering substrates fabricated by depositing Ag nanoislands on the dragonfly wing

NASA Astrophysics Data System (ADS)

Wang, Yuhong; Wang, Mingli; Shen, Lin; Sun, Xin; Shi, Guochao; Ma, Wanli; Yan, Xiaoya

2018-04-01

Natural dragonfly wing (DW), as a template, was deposited on noble metal sliver (Ag) nanoislands by magnetron sputtering to fabricate a flexible, low-cost, large-scale and environment-friendly surface-enhanced Raman scattering (SERS) substrate (Ag/DW substrate). Generally, materials with regular surface nanostructures are chosen for the templates, the selection of our new material with irregular surface nanostructures for substrates provides a new idea for the preparation of high-performance SERS-active substrates and many biomimetic materials. The optimum sputtering time of metal Ag was also investigated at which the prepared SERS-active substrates revealed remarkable SERS activities to 4-aminothiophenol (4-ATP) and crystal violet (CV). Even more surprisingly, the Ag/DW substrate with such an irregular template had reached the enhancement factor (EF) of ∼1.05 × 105 and the detection limit of 10-10 M to 4-ATP. The 3D finite-different time-domain (3D-FDTD) simulation illustrated that the "hot spots" between neighbouring Ag nanoislands at the top of pillars played a most important role in generating electromagnetic (EM) enhancement and strengthening Raman signals.

Synthesis of Mesoporous α-Fe2O3 Nanoparticles by Non-ionic Soft Template and Their Applications to Heavy Oil Upgrading

NASA Astrophysics Data System (ADS)

Park, Chulwoo; Jung, Jinhwan; Lee, Chul Wee; Cho, Joungmo

2016-12-01

This paper reports the synthetic route of 3-D network shape α-Fe2O3 from aqueous solutions of iron precursor using a non-ionic polymeric soft-template, Pluronic P123. During the synthesis of α-Fe2O3, particle sizes, crystal phases and morphologies were significantly influenced by pH, concentrations of precursor and template. The unique shape of worm-like hematite was obtained only when a starting solution was prepared by a weakly basic pH condition and a very specific composition of constituents. The synthesized nanocrystal at this condition had a narrow pore size distribution and high surface area compared to the bulk α-Fe2O3 or the one synthesized from lower pH conditions. The hydrocracking performance was tested over the synthesized iron oxide catalysts with different morphologies. The worm-like shape of iron oxide showed a superior performance, including overall yield of liquid fuel product and coke formation, over the hydrocracking of heavy petroleum oil.

Synthesis of Mesoporous α-Fe2O3 Nanoparticles by Non-ionic Soft Template and Their Applications to Heavy Oil Upgrading

PubMed Central

Park, Chulwoo; Jung, Jinhwan; Lee, Chul Wee; Cho, Joungmo

2016-01-01

This paper reports the synthetic route of 3-D network shape α-Fe2O3 from aqueous solutions of iron precursor using a non-ionic polymeric soft-template, Pluronic P123. During the synthesis of α-Fe2O3, particle sizes, crystal phases and morphologies were significantly influenced by pH, concentrations of precursor and template. The unique shape of worm-like hematite was obtained only when a starting solution was prepared by a weakly basic pH condition and a very specific composition of constituents. The synthesized nanocrystal at this condition had a narrow pore size distribution and high surface area compared to the bulk α-Fe2O3 or the one synthesized from lower pH conditions. The hydrocracking performance was tested over the synthesized iron oxide catalysts with different morphologies. The worm-like shape of iron oxide showed a superior performance, including overall yield of liquid fuel product and coke formation, over the hydrocracking of heavy petroleum oil. PMID:27966663

Synthesis of Mesoporous α-Fe2O3 Nanoparticles by Non-ionic Soft Template and Their Applications to Heavy Oil Upgrading.

PubMed

Park, Chulwoo; Jung, Jinhwan; Lee, Chul Wee; Cho, Joungmo

2016-12-14

This paper reports the synthetic route of 3-D network shape α-Fe 2 O 3 from aqueous solutions of iron precursor using a non-ionic polymeric soft-template, Pluronic P123. During the synthesis of α-Fe 2 O 3 , particle sizes, crystal phases and morphologies were significantly influenced by pH, concentrations of precursor and template. The unique shape of worm-like hematite was obtained only when a starting solution was prepared by a weakly basic pH condition and a very specific composition of constituents. The synthesized nanocrystal at this condition had a narrow pore size distribution and high surface area compared to the bulk α-Fe 2 O 3 or the one synthesized from lower pH conditions. The hydrocracking performance was tested over the synthesized iron oxide catalysts with different morphologies. The worm-like shape of iron oxide showed a superior performance, including overall yield of liquid fuel product and coke formation, over the hydrocracking of heavy petroleum oil.

In Situ Synthesis of Metal Nanoparticle Embedded Hybrid Soft Nanomaterials.

PubMed

Divya, Kizhmuri P; Miroshnikov, Mikhail; Dutta, Debjit; Vemula, Praveen Kumar; Ajayan, Pulickel M; John, George

2016-09-20

The allure of integrating the tunable properties of soft nanomaterials with the unique optical and electronic properties of metal nanoparticles has led to the development of organic-inorganic hybrid nanomaterials. A promising method for the synthesis of such organic-inorganic hybrid nanomaterials is afforded by the in situ generation of metal nanoparticles within a host organic template. Due to their tunable surface morphology and porosity, soft organic materials such as gels, liquid crystals, and polymers that are derived from various synthetic or natural compounds can act as templates for the synthesis of metal nanoparticles of different shapes and sizes. This method provides stabilization to the metal nanoparticles by the organic soft material and advantageously precludes the use of external reducing or capping agents in many instances. In this Account, we exemplify the green chemistry approach for synthesizing these materials, both in the choice of gelators as soft material frameworks and in the reduction mechanisms that generate the metal nanoparticles. Established herein is the core design principle centered on conceiving multifaceted amphiphilic soft materials that possess the ability to self-assemble and reduce metal ions into nanoparticles. Furthermore, these soft materials stabilize the in situ generated metal nanoparticles and retain their self-assembly ability to generate metal nanoparticle embedded homogeneous organic-inorganic hybrid materials. We discuss a remarkable example of vegetable-based drying oils as host templates for metal ions, resulting in the synthesis of novel hybrid nanomaterials. The synthesis of metal nanoparticles via polymers and self-assembled materials fabricated via cardanol (a bioorganic monomer derived from cashew nut shell liquid) are also explored in this Account. The organic-inorganic hybrid structures were characterized by several techniques such as UV-visible spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Utilization of silver nanoparticle-based hybrid nanomaterials as an antimicrobial material is another illustration of the advantage of hybrid nanomaterials. We envision that the results summarized in this Account will help the scientific community to design and develop diverse organic-inorganic hybrid materials using environmentally benign methods and that these materials will yield advanced properties that have multifaceted applications in various research fields.

Effects of 99mTc-TRODAT-1 drug template on image quantitative analysis

PubMed Central

Yang, Bang-Hung; Chou, Yuan-Hwa; Wang, Shyh-Jen; Chen, Jyh-Cheng

2018-01-01

99mTc-TRODAT-1 is a type of drug that can bind to dopamine transporters in living organisms and is often used in SPCT imaging for observation of changes in the activity uptake of dopamine in the striatum. Therefore, it is currently widely used in studies on clinical diagnosis of Parkinson’s disease (PD) and movement-related disorders. In conventional 99mTc-TRODAT-1 SPECT image evaluation, visual inspection or manual selection of ROI for semiquantitative analysis is mainly used to observe and evaluate the degree of striatal defects. However, these methods are dependent on the subjective opinions of observers, which lead to human errors, have shortcomings such as long duration, increased effort, and have low reproducibility. To solve this problem, this study aimed to establish an automatic semiquantitative analytical method for 99mTc-TRODAT-1. This method combines three drug templates (one built-in SPECT template in SPM software and two self-generated MRI-based and HMPAO-based TRODAT-1 templates) for the semiquantitative analysis of the striatal phantom and clinical images. At the same time, the results of automatic analysis of the three templates were compared with results from a conventional manual analysis for examining the feasibility of automatic analysis and the effects of drug templates on automatic semiquantitative analysis results. After comparison, it was found that the MRI-based TRODAT-1 template generated from MRI images is the most suitable template for 99mTc-TRODAT-1 automatic semiquantitative analysis. PMID:29543874

A real-time TV logo tracking method using template matching

NASA Astrophysics Data System (ADS)

Li, Zhi; Sang, Xinzhu; Yan, Binbin; Leng, Junmin

2012-11-01

A fast and accurate TV Logo detection method is presented based on real-time image filtering, noise eliminating and recognition of image features including edge and gray level information. It is important to accurately extract the optical template using the time averaging method from the sample video stream, and then different templates are used to match different logos in separated video streams with different resolution based on the topology features of logos. 12 video streams with different logos are used to verify the proposed method, and the experimental result demonstrates that the achieved accuracy can be up to 99%.

Templated and template-free fabrication strategies for zero-dimensional hollow MOF superstructures.

PubMed

Kim, Hyehyun; Lah, Myoung Soo

2017-05-16

Various fabrication strategies for hollow metal-organic framework (MOF) superstructures are reviewed and classified using various types of external templates and their properties. Hollow MOF superstructures have also been prepared without external templates, wherein unstable intermediates obtained during reactions convert to the final hollow MOF superstructures. Many hollow MOF superstructures have been fabricated using hard templates. After the core-shell core@MOF structure was prepared using a hard template, the core was selectively etched to generate a hollow MOF superstructure. Another approach for generating hollow superstructures is to use a solid reactant as a sacrificial template; this method requires no additional etching process. Soft templates such as discontinuous liquid/emulsion droplets and gas bubbles in a continuous soft phase have also been employed to prepare hollow MOF superstructures.

Morphology-preserving chemical conversion of bioorganic and inorganic templates

NASA Astrophysics Data System (ADS)

Vernon, Jonathan Paul

The generation of nanostructured assemblies with complex (three-dimensional, 3D) self-assembled morphologies and with complex (multicomponent) tailorable inorganic compositions is of considerable technological and scientific interest. This dissertation demonstrates self-assembled 3D organic templates of biogenic origin can be converted into replicas comprised of numerous other functional nanocrystalline inorganic materials. Nature provides a spectacular variety of biologically-assembled 3D organic structures with intricate, hierarchical (macro-to-micro-to-nanoscale) morphologies. Such processing on readily-available structurally complex templates provides a framework for chemical conversion of synthetic organic templates and, potentially, production of organic/inorganic composites. Four specific research thrusts are detailed in this document. First, chemical conversion of a nanostructured bioorganic template into a multicomponent oxide compound (tetragonal BaTiO3) via SSG coating and subsequent morphology-preserving microwave hydrothermal processing is demonstrated. Second, morphology-preserving chemical conversion of bioorganic templates into hierarchical photoluminescent microparticles is demonstrated to reveal both the dramatic change in properties such processing can provide, and the potential utility of chemically transformed templates in anti-counterfeiting / authentication applications. Third, determination of the reaction mechanism(s) for morphology-preserving microwave hydrothermal conversion of TiO2 to BaTiO3, through Au inert markers on single crystal rutile titania, is detailed. Finally, utilization of constructive coating techniques (SSG) and moderate temperature (< 500°C) heat treatments to modify and replicate structural color is coupled with deconstructive focused ion beam microsurgery to prepare samples for microscale structure interrogation. Specifically, the effects of coating thickness and composition on reflection spectra of structurally colored templates are examined. Also, the effects of the replacement of natural material with higher index of refraction inorganic materials on optical properties are discussed. The three processing research thrusts constituting chapters 1, 2 and 4 take advantage of moderate temperature processing to ensure nanocrystalline materials, either for shape preservation or to prevent scattering in optical applications. The research thrust detailed in chapter 3 examines hydrothermal conversion of TiO2 to BaTiO3, not only to identify the reaction mechanism(s) involved in hydrothermal conversion under morphology-preserving conditions, but also to introduce inert marker experiments to the field of microwave hydrothermal processing.

Enhanced photocatalytic performance of mesoporous TiO{sub 2} coated SBA-15 nanocomposites fabricated through a novel approach: supercritical deposition aided by liquid-crystal template

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Chen; Lin, Xiao; Li, Youji, E-mail: bcclyj@163.com

2016-03-15

Highlights: • Highly uniform mesoporous TiO{sub 2} nanopartices were coated SBA-15. • MT showed smaller crystallite size, higher hydroxyl content and surface area. • MT/SBA-15 show enhanced photocatalytic activity and high reused activity. • The optimum MT loading rate and calcination temperature were obtained to be 15% and 400 °C, respectively. • Photocatalytic behaviors are discussed in terms of the Langmuir–Hinshelwood model. - Abstract: Mesoporous TiO2 coated SBA-15 (MT@S) nanocomposites were fabricated through supercritical CO{sub 2} deposition aided by liquid-crystal template. The as-prepared samples were characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, diffuse reflectance spectroscopy and so on. Themore » results reveal that MT uniformly deposited onto silica with titania incorporated in SBA-15 channels, showed smaller crystallite size, higher hydroxyl content and surface area than nonporous TiO{sub 2} coated SBA-15 (NT@S) obtained by a similar route without template. With TiO{sub 2} loading ratio of 15 wt% and calcination temperature of 400 °C, 15%MT@S-400 showed the enhanced degradation efficiency for azo dyes (methylene blue, methyl orange, and rhodamine B) and phenol in comparsion with 15%NT@S-400, due to those improved textural and physicochemical properties. Meanwhile, the reused MT@S also showed high photoactivity. Additionally, the effects of MT content and calcination temperature have been examined as operational parameters. Photocatalytic reactions followed pseudo-first-order kinetics and are discussed in terms of the Langmuir–Hinshelwood model.« less

SU-E-J-108: Template Matching Based On Multiple Templates Can Improve the Tumor Tracking Performance When There Is Large Tumor Deformation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shi, X; Lin, J; Diwanji, T

2014-06-01

Purpose: Recently, template matching has been shown to be able to track tumor motion on cine-MRI images. However, artifacts such as deformation, rotation, and/or out-of-plane movement could seriously degrade the performance of this technique. In this work, we demonstrate the utility of multiple templates derived from different phases of tumor motion in reducing the negative effects of artifacts and improving the accuracy of template matching methods. Methods: Data from 2 patients with large tumors and significant tumor deformation were analyzed from a group of 12 patients from an earlier study. Cine-MRI (200 frames) imaging was performed while the patients weremore » instructed to breathe normally. Ground truth tumor position was established on each frame manually by a radiation oncologist. Tumor positions were also automatically determined using template matching with either single or multiple (5) templates. The tracking errors, defined as the absolute differences in tumor positions determined by the manual and automated methods, when using either single or multiple templates were compared in both the AP and SI directions, respectively. Results: Using multiple templates reduced the tracking error of template matching. In the SI direction where the tumor movement and deformation were significant, the mean tracking error decreased from 1.94 mm to 0.91 mm (Patient 1) and from 6.61 mm to 2.06 mm (Patient 2). In the AP direction where the tumor movement was small, the reduction of the mean tracking error was significant in Patient 1 (from 3.36 mm to 1.04 mm), but not in Patient 2 ( from 3.86 mm to 3.80 mm). Conclusion: This study shows the effectiveness of using multiple templates in improving the performance of template matching when artifacts like large tumor deformation or out-of-plane motion exists. Accurate tumor tracking capabilities can be integrated with MRI guided radiation therapy systems. This work was supported in part by grants from NIH/NCI CA 124766 and Varian Medical Systems, Palo Alto, CA.« less

Template optimization and transfer in perceptual learning.

PubMed

Kurki, Ilmari; Hyvärinen, Aapo; Saarinen, Jussi

2016-08-01

We studied how learning changes the processing of a low-level Gabor stimulus, using a classification-image method (psychophysical reverse correlation) and a task where observers discriminated between slight differences in the phase (relative alignment) of a target Gabor in visual noise. The method estimates the internal "template" that describes how the visual system weights the input information for decisions. One popular idea has been that learning makes the template more like an ideal Bayesian weighting; however, the evidence has been indirect. We used a new regression technique to directly estimate the template weight change and to test whether the direction of reweighting is significantly different from an optimal learning strategy. The subjects trained the task for six daily sessions, and we tested the transfer of training to a target in an orthogonal orientation. Strong learning and partial transfer were observed. We tested whether task precision (difficulty) had an effect on template change and transfer: Observers trained in either a high-precision (small, 60° phase difference) or a low-precision task (180°). Task precision did not have an effect on the amount of template change or transfer, suggesting that task precision per se does not determine whether learning generalizes. Classification images show that training made observers use more task-relevant features and unlearn some irrelevant features. The transfer templates resembled partially optimized versions of templates in training sessions. The template change direction resembles ideal learning significantly but not completely. The amount of template change was highly correlated with the amount of learning.

One New Method to Generate 3-Dimensional Virtual Mannequin

NASA Astrophysics Data System (ADS)

Xiu-jin, Shi; Zhi-jun, Wang; Jia-jin, Le

The personal virtual mannequin is very important in electronic made to measure (eMTM) system. There is one new easy method to generate personal virtual mannequin. First, the characteristic information of customer's body is got from two photos. Secondly, some human body part templates corresponding with the customer are selected from the templates library. Thirdly, these templates are modified and assembled according to certain rules to generate a personalized 3-dimensional human, and then the virtual mannequin is realized. Experimental result shows that the method is easy and feasible.

A novel approach for fabricating NiO hollow spheres for gas sensors

NASA Astrophysics Data System (ADS)

Kuang, Chengwei; Zeng, Wen; Ye, Hong; Li, Yanqiong

2018-03-01

Hollow spheres are usually fabricated by hard template methods or soft template methods with soft surfactants, which is quiet tedious and time-consuming. In this paper, NiO hollow spheres with fluffy surface were successfully synthesized by a facile hydrothermal method and subsequent calcination, where bubbles acted as the template. NiO hollow spheres exhibited excellent gas sensing performances, which results from its hollow structure and high specific surface area. In addition, a possible evolution mechanism of NiO hollow spheres was proposed based on experimental results.

A Fast Approach to Automatic Detection of Brain Lesions

PubMed Central

Koley, Subhranil; Chakraborty, Chandan; Mainero, Caterina; Fischl, Bruce; Aganj, Iman

2017-01-01

Template matching is a popular approach to computer-aided detection of brain lesions from magnetic resonance (MR) images. The outcomes are often sufficient for localizing lesions and assisting clinicians in diagnosis. However, processing large MR volumes with three-dimensional (3D) templates is demanding in terms of computational resources, hence the importance of the reduction of computational complexity of template matching, particularly in situations in which time is crucial (e.g. emergent stroke). In view of this, we make use of 3D Gaussian templates with varying radii and propose a new method to compute the normalized cross-correlation coefficient as a similarity metric between the MR volume and the template to detect brain lesions. Contrary to the conventional fast Fourier transform (FFT) based approach, whose runtime grows as O(N logN) with the number of voxels, the proposed method computes the cross-correlation in O(N). We show through our experiments that the proposed method outperforms the FFT approach in terms of computational time, and retains comparable accuracy. PMID:29082383

Tubular structured hierarchical mesoporous titania material derived from natural cellulosic substances and application as photocatalyst for degradation of methylene blue

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Haiqing; Liu, Xiaoyan; Huang, Jianguo, E-mail: jghuang@zju.edu.cn

Graphical abstract: Bio-inspired, tubular structured hierarchical mesoporous titania material with high photocatalytic activity under UV light was fabricated employing natural cellulosic substance (cotton) as hard template and cetyltrimethylammonium bromide (CTAB) surfactant as soft template using a one-pot sol-gel method. Highlights: {yields} Tubular structured mesoporous titania material was fabricated by sol-gel method. {yields} The titania material faithfully recorded the hierarchical structure of the template substrate (cotton). {yields} The titania material exhibited high photocatalytic activity in decomposition of methylene blue. -- Abstract: Bio-inspired, tubular structured hierarchical mesoporous titania material was designed and fabricated employing natural cellulosic substance (cotton) as hard template andmore » cetyltrimethylammonium bromide (CTAB) surfactant as soft template by one-pot sol-gel method. The tubular structured hierarchical mesoporous titania material processes large specific surface area (40.23 m{sup 2}/g) and shows high photocatalytic activity in the photodegradation of methylene blue under UV light irradiation.« less

Accurate and Simple Screw Insertion Procedure With Patient-Specific Screw Guide Templates for Posterior C1-C2 Fixation.

PubMed

Sugawara, Taku; Higashiyama, Naoki; Kaneyama, Shuichi; Sumi, Masatoshi

2017-03-15

Prospective clinical trial of the screw insertion method for posterior C1-C2 fixation utilizing the patient-specific screw guide template technique. To evaluate the efficacy of this method for insertion of C1 lateral mass screws (LMS), C2 pedicle screws (PS), and C2 laminar screws (LS). Posterior C1LMS and C2PS fixation, also known as the Goel-Harms method, can achieve immediate rigid fixation and high fusion rate, but the screw insertion carries the risk of injury to neuronal and vascular structures. Dissection of venous plexus and C2 nerve root to confirm the insertion point of the C1LMS may also cause problems. We have developed an intraoperative screw guiding method using patient-specific laminar templates. Preoperative bone images of computed tomography (CT) were analyzed using three-dimensional (3D)/multiplanar imaging software to plan the trajectories of the screws. Plastic templates with screw guiding structures were created for each lamina using 3D design and printing technology. Three types of templates were made for precise multistep guidance, and all templates were specially designed to fit and lock on the lamina during the procedure. Surgery was performed using this patient-specific screw guide template system, and placement of the screws was postoperatively evaluated using CT. Twelve patients with C1-C2 instability were treated with a total of 48 screws (24 C1LMS, 20 C2PS, 4 C2LS). Intraoperatively, each template was found to exactly fit and lock on the lamina and screw insertion was completed successfully without dissection of the venous plexus and C2 nerve root. Postoperative CT showed no cortical violation by the screws, and mean deviation of the screws from the planned trajectories was 0.70 ± 0.42 mm. The multistep, patient-specific screw guide template system is useful for intraoperative screw navigation in posterior C1-C2 fixation. This simple and economical method can improve the accuracy of screw insertion, and reduce operation time and radiation exposure of posterior C1-C2 fixation surgery. 3.

RNA 3D Structure Modeling by Combination of Template-Based Method ModeRNA, Template-Free Folding with SimRNA, and Refinement with QRNAS.

PubMed

Piatkowski, Pawel; Kasprzak, Joanna M; Kumar, Deepak; Magnus, Marcin; Chojnowski, Grzegorz; Bujnicki, Janusz M

2016-01-01

RNA encompasses an essential part of all known forms of life. The functions of many RNA molecules are dependent on their ability to form complex three-dimensional (3D) structures. However, experimental determination of RNA 3D structures is laborious and challenging, and therefore, the majority of known RNAs remain structurally uncharacterized. To address this problem, computational structure prediction methods were developed that either utilize information derived from known structures of other RNA molecules (by way of template-based modeling) or attempt to simulate the physical process of RNA structure formation (by way of template-free modeling). All computational methods suffer from various limitations that make theoretical models less reliable than high-resolution experimentally determined structures. This chapter provides a protocol for computational modeling of RNA 3D structure that overcomes major limitations by combining two complementary approaches: template-based modeling that is capable of predicting global architectures based on similarity to other molecules but often fails to predict local unique features, and template-free modeling that can predict the local folding, but is limited to modeling the structure of relatively small molecules. Here, we combine the use of a template-based method ModeRNA with a template-free method SimRNA. ModeRNA requires a sequence alignment of the target RNA sequence to be modeled with a template of the known structure; it generates a model that predicts the structure of a conserved core and provides a starting point for modeling of variable regions. SimRNA can be used to fold small RNAs (<80 nt) without any additional structural information, and to refold parts of models for larger RNAs that have a correctly modeled core. ModeRNA can be either downloaded, compiled and run locally or run through a web interface at http://genesilico.pl/modernaserver/ . SimRNA is currently available to download for local use as a precompiled software package at http://genesilico.pl/software/stand-alone/simrna and as a web server at http://genesilico.pl/SimRNAweb . For model optimization we use QRNAS, available at http://genesilico.pl/qrnas .

[Elaboration of the SPM template for the standardization of SPECT images with 123I-Ioflupane].

PubMed

García-Gómez, F J; García-Solís, D; Luis-Simón, F J; Marín-Oyaga, V A; Carrillo, F; Mir, P; Vázquez-Albertino, R J

2013-01-01

Statistical parametric mapping (SPM) is a widely used produced for normalization of functional images. This study has aimed to develop a normalization template of (123)I-Ioflupane SPECT-imaging DaTSCAN(®), GE Healthcare), not available in SPM5, and to validate it compared to other quantification methods. In order to write the template we retrospectively selected 26 subjects who had no evidence of nigrostriatal degeneration and whose age distribution was similar to that of the patients in the usual practice of our Department: 2 subjects (7.6%) were < 35 years, 9 between 35-65 years (34.6%) and 15 > 65 years (57.7%). All the studies were normalized with the T1-template available in SPM5 and an average image of the value was obtained for each voxel. For validation we analyzed 60 patients: 30 with idiopathic Parkinson's disease patients (iPD) with right involvement (66.83±12.20 years) and 30 with essential tremor patients (ET) (67.27±8.33 years). Specific uptake rates (SUR) of different striatal regions were compared after image normalization with our template and the application of a semiautomated VOIs-map created with Analyze v9.0 ((©)BIR, Mayo Clinic), against two quantification methods: a) manual adjustment of a ROIs-map drawn in Analyze, and b) semi-automated method (HERMES-BRASS) with normalization and implementation of VOIs-map. No statistically significant differences in the iPD/ET discriminatory capacity between the three methods analyzed were observed (p<0,001). The correlation of SUR after normalization with our «template» was higher than that obtained by method b) (R>0,871, p<0,001). This difference was greater in patients with PD. Our study demonstrates the efficacy of our SPM «template» for (123)I-Ioflupane SPECT-imaging, obtained from normalization with «T1-template». Copyright © 2012 Elsevier España, S.L. and SEMNIM. All rights reserved.

Deconstructing the Polymerase Chain Reaction: Understanding and Correcting Bias Associated with Primer Degeneracies and Primer-Template Mismatches

PubMed Central

Green, Stefan J.; Venkatramanan, Raghavee; Naqib, Ankur

2015-01-01

The polymerase chain reaction (PCR) is sensitive to mismatches between primer and template, and mismatches can lead to inefficient amplification of targeted regions of DNA template. In PCRs in which a degenerate primer pool is employed, each primer can behave differently. Therefore, inefficiencies due to different primer melting temperatures within a degenerate primer pool, in addition to mismatches between primer binding sites and primers, can lead to a distortion of the true relative abundance of targets in the original DNA pool. A theoretical analysis indicated that a combination of primer-template and primer-amplicon interactions during PCR cycles 3–12 is potentially responsible for this distortion. To test this hypothesis, we developed a novel amplification strategy, entitled “Polymerase-exonuclease (PEX) PCR”, in which primer-template interactions and primer-amplicon interactions are separated. The PEX PCR method substantially and significantly improved the evenness of recovery of sequences from a mock community of known composition, and allowed for amplification of templates with introduced mismatches near the 3’ end of the primer annealing sites. When the PEX PCR method was applied to genomic DNA extracted from complex environmental samples, a significant shift in the observed microbial community was detected. Furthermore, the PEX PCR method provides a mechanism to identify which primers in a primer pool are annealing to target gDNA. Primer utilization patterns revealed that at high annealing temperatures in the PEX PCR method, perfect match annealing predominates, while at lower annealing temperatures, primers with up to four mismatches with templates can contribute substantially to amplification. The PEX PCR method is simple to perform, is limited to PCR mixes and a single exonuclease step which can be performed without reaction cleanup, and is recommended for reactions in which degenerate primer pools are used or when mismatches between primers and template are possible. PMID:25996930

Toward a practical template-based approach to semiquantitative SPECT myocardial perfusion imaging.

PubMed

Hughes, Tyler; Celler, Anna

2012-03-01

Our template-based quantitative perfusion single photon emission computed tomography (SPECT) method (T-QPS) performs semiquantitative analysis for myocardial perfusion imaging (MPI) without the use of normal databases. However, in its current form, T-QPS requires extensive calculations, which limits its clinical application. In the interest of clinical feasibility, the authors examine the trade-off between accuracy and processing time as the method is simplified. The T-QPS method uses the reconstructed SPECT image of the patient to create a 3D digital template of his∕her healthy heart. This template is then projected, reconstructed, and sampled into the bulls-eye map domain. A ratio of the patient and template images produces a final corrected image in which a threshold is applied to identify perfusion defects. In principle, the template should be constructed with the heart and all extracardiac activity, and the projection step should include primary and scatter components; however, this leads to lengthy calculations. In an attempt to shorten the processing time, the authors analyzed the performance of four template (T) generation methods: T(P-HRT), T(PS-HRT), T(P-HRTBKG), and T(PS-HRTBKG), where P and S represent primary and scattered photons included in the projection step, respectively; and HRT and HRTBKG represent template constructed with the heart only and the heart with background activity, respectively. Forty-eight thorax phantoms and 21 randomly selected patient studies were analyzed using each approach. All studies used GE's Infinia Hawkeye SPECT∕CT system and followed a standard cardiac acquisition protocol. Approximate processing times for the T(P-HRT), T(PS-HRT), T(P-HRTBKG), and T(PS-HRTBKG) methods were less than a minute, 2-3 h, less than a minute and 3-4 h, respectively. In both the simulation and patient studies, a significant reduction in the quality of perfusion defect definition was exhibited by the T(P-HRT) method relative to the other three methods. The optimal method with respect to perfusion defect definition and processing time was T(P-HRTBKG) with a sensitivity, specificity, and accuracy in spatially defining the perfusion defects (simulation study) of 80%, 84%, and 83%, respectively. The T-QPS method using T(P-HRTBKG) leads to accurate and fast semiquantitative analysis of SPECT MPI, without the use of normal databases.

Effect of coccolith polysaccharides isolated from the coccolithophorid, Emiliania huxleyi, on calcite crystal formation in in vitro CaCO3 crystallization.

PubMed

Kayano, Keisuke; Saruwatari, Kazuko; Kogure, Toshihiro; Shiraiwa, Yoshihiro

2011-02-01

Marine coccolithophorids (Haptophyceae) produce calcified scales "coccoliths" which are composed of CaCO(3) and coccolith polysaccharides (CP) in the coccolith vesicles. CP was previously reported to be composed of uronic acids and sulfated residues, etc. attached to the polymannose main chain. Although anionic polymers are generally known to play key roles in biomineralization process, there is no experimental data how CP contributes to calcite crystal formation in the coccolithophorids. CP used was isolated from the most abundant coccolithophorid, Emiliania huxleyi. CaCO(3) crystallization experiment was performed on agar template layered onto a plastic plate that was dipped in the CaCO(3) crystallization solution. The typical rhombohedral calcite crystals were formed in the absence of CP. CaCO(3) crystals formed on the naked plastic plate were obviously changed to stick-like shapes when CP was present in the solution. EBSD analysis proved that the crystal is calcite of which c-axis was elongated. CP in the solution stimulated the formation of tabular crystals with flat edge in the agarose gel. SEM and FIB-TEM observations showed that the calcite crystals were formed in the gel. The formation of crystals without flat edge was stimulated when CP was preliminarily added in the gel. These observations suggest that CP has two functions: namely, one is to elongate the calcite crystal along c-axis and another is to induce tabular calcite crystal formation in the agarose gel. Thus, CP may function for the formation of highly elaborate species-specific structures of coccoliths in coccolithophorids.

A striking mobility improvement of C60 OFET by inserting diindenoperylene layer between C60 and SiO2 gate insulator

NASA Astrophysics Data System (ADS)

Yang, Jin-peng; Yonezawa, Keiichiro; Hinderhofer, Alexander; Bussolotti, Fabio; Kera, Satoshi; Ueno, Nobuo

2014-09-01

Gap states in organic semiconductors play a crucial role in determining Energy-Level Alignment and in many cases they act as charge trapping centers to result in serious lowering of charge mobility. Thus origin of gap states has gained increasing attention in order to realize higher mobility organic devises [1-4]. Bussolotti et al. have demonstrated recently that gap states in a pentacene thin film increase even by exposing the film to inert gas and confirmed that the gas exposure mediates structural defects in the film thus gap states [4]. The results have also indicated that preparation of highly-ordered organic thin film is necessary to improve the device performance, namely to decrease trapping states. To improve the ordering of molecule in the film, deposition of a template molecular underlayer is one of the simplest methods to increase the domain size of overlayer film and its crystallinity, and thus we expect improvement of the charge mobility [5]. Hinderhofer et al. reported recently that diindenoperylene (DIP; Figure 1a) could be used as a template layer to grow highly ordered and oriented C60 film with its (111) plane parallel to the SiO2 substrate [6]. Considering the hole mobility of DIP single crystal, which is quite low (~0.005 cm2 V-1S-1 at room temperature [7]), it is expected for the DIP template C60 thin film system that lower drain current would be achieved to improve the on/off ratios based on n type C60 transistor and its electron mobility (especially on the negative Vgs region, compared to PEN modified C60 transistors [8]).

Multiple template-based fluoroscopic tracking of lung tumor mass without implanted fiducial markers

NASA Astrophysics Data System (ADS)

Cui, Ying; Dy, Jennifer G.; Sharp, Gregory C.; Alexander, Brian; Jiang, Steve B.

2007-10-01

Precise lung tumor localization in real time is particularly important for some motion management techniques, such as respiratory gating or beam tracking with a dynamic multi-leaf collimator, due to the reduced clinical tumor volume (CTV) to planning target volume (PTV) margin and/or the escalated dose. There might be large uncertainties in deriving tumor position from external respiratory surrogates. While tracking implanted fiducial markers has sufficient accuracy, this procedure may not be widely accepted due to the risk of pneumothorax. Previously, we have developed a technique to generate gating signals from fluoroscopic images without implanted fiducial markers using a template matching method (Berbeco et al 2005 Phys. Med. Biol. 50 4481-90, Cui et al 2007 Phys. Med. Biol. 52 741-55). In this paper, we present an extension of this method to multiple-template matching for directly tracking the lung tumor mass in fluoroscopy video. The basic idea is as follows: (i) during the patient setup session, a pair of orthogonal fluoroscopic image sequences are taken and processed off-line to generate a set of reference templates that correspond to different breathing phases and tumor positions; (ii) during treatment delivery, fluoroscopic images are continuously acquired and processed; (iii) the similarity between each reference template and the processed incoming image is calculated; (iv) the tumor position in the incoming image is then estimated by combining the tumor centroid coordinates in reference templates with proper weights based on the measured similarities. With different handling of image processing and similarity calculation, two such multiple-template tracking techniques have been developed: one based on motion-enhanced templates and Pearson's correlation score while the other based on eigen templates and mean-squared error. The developed techniques have been tested on six sequences of fluoroscopic images from six lung cancer patients against the reference tumor positions manually determined by a radiation oncologist. The tumor centroid coordinates automatically detected using both methods agree well with the manually marked reference locations. The eigenspace tracking method performs slightly better than the motion-enhanced method, with average localization errors less than 2 pixels (1 mm) and the error at a 95% confidence level of about 2-4 pixels (1-2 mm). This work demonstrates the feasibility of direct tracking of a lung tumor mass in fluoroscopic images without implanted fiducial markers using multiple reference templates.

Synthesis, structure and luminescence of novel co-crystals based on bispyridyl-substituted α,β-unsaturated ketones with coformers

NASA Astrophysics Data System (ADS)

Li, Hong-Juan; Wang, Lei; Zhao, Juan-Juan; Sun, Ju-Feng; Sun, Ji-Liang; Wang, Chun-Hua; Hou, Gui-Ge

2015-01-01

Based on 2,6-bis((pyridin-4-yl)methylene)cyclohexanone (A) and N-methyl-3,5-bis((pyridin-4-yl)methylene)-4-piperidone (B) with coformers, three novel macrocyclic co-crystals, (A)ṡ(resorcinol) (1), (A)ṡ(1,3,5-benzenetriol) (2), (B)2ṡ(1,3,5-benzenetriol)2 (3) and three chain co-crystals, (A)ṡ(hydroquinone) (4), (A)ṡ(isophthalic acid) (5), (B)ṡ(isophthalic acid) (6) have been synthesized and structurally characterized by IR, 1H NMR and X-ray crystal structure analysis. Structural analysis indicates that four-component macrocycles in 1-3 are generated from "clip-like" resorcinol templates and building blocks, while 4-6 show infinite H-bonding chains. In addition, the luminescent properties of A, B and 1-6 are investigated primarily in the solid state. Compared with free building blocks, 1-6 are blue-shifted 55-60 nm with decreasing emission intensities in spite of the enhancement in 6. The change of luminescent properties might be caused mainly by incorporation of coformers into co-crystals, including H-bonds, molecular conformations, arranging dispositions and π-π characteristics. It might have potential applications for crystal engineering to construct patentable crystals with interesting luminescent properties.

Ferritin-Templated Quantum-Dots for Quantum Logic Gates

NASA Technical Reports Server (NTRS)

Choi, Sang H.; Kim, Jae-Woo; Chu, Sang-Hyon; Park, Yeonjoon; King, Glen C.; Lillehei, Peter T.; Kim, Seon-Jeong; Elliott, James R.

2005-01-01

Quantum logic gates (QLGs) or other logic systems are based on quantum-dots (QD) with a stringent requirement of size uniformity. The QD are widely known building units for QLGs. The size control of QD is a critical issue in quantum-dot fabrication. The work presented here offers a new method to develop quantum-dots using a bio-template, called ferritin, that ensures QD production in uniform size of nano-scale proportion. The bio-template for uniform yield of QD is based on a ferritin protein that allows reconstitution of core material through the reduction and chelation processes. One of the biggest challenges for developing QLG is the requirement of ordered and uniform size of QD for arrays on a substrate with nanometer precision. The QD development by bio-template includes the electrochemical/chemical reconsitution of ferritins with different core materials, such as iron, cobalt, manganese, platinum, and nickel. The other bio-template method used in our laboratory is dendrimers, precisely defined chemical structures. With ferritin-templated QD, we fabricated the heptagonshaped patterned array via direct nano manipulation of the ferritin molecules with a tip of atomic force microscope (AFM). We also designed various nanofabrication methods of QD arrays using a wide range manipulation techniques. The precise control of the ferritin-templated QD for a patterned arrangement are offered by various methods, such as a site-specific immobilization of thiolated ferritins through local oxidation using the AFM tip, ferritin arrays induced by gold nanoparticle manipulation, thiolated ferritin positioning by shaving method, etc. In the signal measurements, the current-voltage curve is obtained by measuring the current through the ferritin, between the tip and the substrate for potential sweeping or at constant potential. The measured resistance near zero bias was 1.8 teraohm for single holoferritin and 5.7 teraohm for single apoferritin, respectively.

Template-Based 3D Reconstruction of Non-rigid Deformable Object from Monocular Video

NASA Astrophysics Data System (ADS)

Liu, Yang; Peng, Xiaodong; Zhou, Wugen; Liu, Bo; Gerndt, Andreas

2018-06-01

In this paper, we propose a template-based 3D surface reconstruction system of non-rigid deformable objects from monocular video sequence. Firstly, we generate a semi-dense template of the target object with structure from motion method using a subsequence video. This video can be captured by rigid moving camera orienting the static target object or by a static camera observing the rigid moving target object. Then, with the reference template mesh as input and based on the framework of classical template-based methods, we solve an energy minimization problem to get the correspondence between the template and every frame to get the time-varying mesh to present the deformation of objects. The energy terms combine photometric cost, temporal and spatial smoothness cost as well as as-rigid-as-possible cost which can enable elastic deformation. In this paper, an easy and controllable solution to generate the semi-dense template for complex objects is presented. Besides, we use an effective iterative Schur based linear solver for the energy minimization problem. The experimental evaluation presents qualitative deformation objects reconstruction results with real sequences. Compare against the results with other templates as input, the reconstructions based on our template have more accurate and detailed results for certain regions. The experimental results show that the linear solver we used performs better efficiency compared to traditional conjugate gradient based solver.

Optimized Periocular Template Selection for Human Recognition

PubMed Central

Sa, Pankaj K.; Majhi, Banshidhar

2013-01-01

A novel approach for selecting a rectangular template around periocular region optimally potential for human recognition is proposed. A comparatively larger template of periocular image than the optimal one can be slightly more potent for recognition, but the larger template heavily slows down the biometric system by making feature extraction computationally intensive and increasing the database size. A smaller template, on the contrary, cannot yield desirable recognition though the smaller template performs faster due to low computation for feature extraction. These two contradictory objectives (namely, (a) to minimize the size of periocular template and (b) to maximize the recognition through the template) are aimed to be optimized through the proposed research. This paper proposes four different approaches for dynamic optimal template selection from periocular region. The proposed methods are tested on publicly available unconstrained UBIRISv2 and FERET databases and satisfactory results have been achieved. Thus obtained template can be used for recognition of individuals in an organization and can be generalized to recognize every citizen of a nation. PMID:23984370

Synthesis of parallel and antiparallel core-shell triangular nanoparticles

NASA Astrophysics Data System (ADS)

Bhattacharjee, Gourab; Satpati, Biswarup

2018-04-01

Core-shell triangular nanoparticles were synthesized by seed mediated growth. Using triangular gold (Au) nanoparticle as template, we have grown silver (Ag) shellto get core-shell nanoparticle. Here by changing the chemistry we have grown two types of core-shell structures where core and shell is having same symmetry and also having opposite symmetry. Both core and core-shell nanoparticles were characterized using transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX) to know the crystal structure and composition of these synthesized core-shell nanoparticles. From diffraction pattern analysis and energy filtered TEM (EFTEM) we have confirmed the crystal facet in core is responsible for such two dimensional growth of core-shell nanostructures.

Magnetophotonic crystals based on yttrium-iron-garnet infiltrated opals: Magnetization-induced second-harmonic generation

NASA Astrophysics Data System (ADS)

Murzina, T. V.; Kim, E. M.; Kapra, R. V.; Moshnina, I. V.; Aktsipetrov, O. A.; Kurdyukov, D. A.; Kaplan, S. F.; Golubev, V. G.; Bader, M. A.; Marowsky, G.

2006-01-01

Three-dimensional magnetophotonic crystals (MPCs) based on artificial opals infiltrated by yttrium iron garnet (YIG) are fabricated and their structural, optical, and nonlinear optical properties are studied. The formation of the crystalline YIG inside the opal matrix is checked by x-ray analysis. Two templates are used for the infiltration by YIG: bare opals and those covered by a thin platinum film. Optical second-harmonic generation (SHG) technique is used to study the magnetization-induced nonlinear-optical properties of the composed MPCs. A high nonlinear magneto-optical Kerr effect in the SHG intensity is observed at the edge of the photonic band gap of the MPCs.

A dataset for preparing pristine graphene-palladium nanocomposites using swollen liquid crystal templates

NASA Astrophysics Data System (ADS)

Vats, Tripti; Siril, Prem Felix

2017-12-01

Pristine graphene (G) has not received much attention as a catalyst support, presumably due to its relative inertness as compared to reduced graphene oxide (RGO). In the present work, we used swollen liquid crystals (SLCs) as nano-reactors for graphene-palladium nanocomposites synthesis. The 'soft' confinement of SLCs directs the growth of palladium (Pd) nanoparticles over the G sheets. In this dataset we include all the parameters and details of different techniques used for the characterization of G, SLCs and synthesized G-Pd nanocomposites. The synthesized G-palladium nanocomposites (Pd-G) exhibited improved catalytic activity compared with Pd-RGO and Pd nanoparticles, in the hydrogenation of nitrophenols and C-C coupling reactions.

Preparation of silica stabilized biological templates for the production of metal and layered nanoparticles

DOEpatents

Culver, James N; Royston, Elizabeth; Brown, Adam; Harris, Michael

2013-02-26

The present invention relates to a system and method providing for increased silica growth on a bio-template, wherein the bio-template is pretreated with aniline to produce a uniform silica attractive surface and yielding a significant silica layers of at least 10 nm, and more preferably at least 20 nm in thickness, thereby providing for a high degree of stability to the bio-template.

Replication of patterned thin-film structures for use in plasmonics and metamaterials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Norris, David J; Han, Sang Eon; Bhan, Aditya

The present invention provides templating methods for replicating patterned metal films from a template substrate such as for use in plasmonic devices and metamaterials. Advantageously, the template substrate is reusable and can provide plural copies of the structure of the template substrate. Because high-quality substrates that are inherently smooth and flat are available, patterned metal films in accordance with the present invention can advantageously provide surfaces that replicate the surface characteristics of the template substrate both in the patterned regions and in the unpatterned regions.

The Role of Standardized and Study-specific Human Brain Diffusion Tensor Templates in Inter-subject Spatial Normalization

PubMed Central

Zhang, Shengwei; Arfanakis, Konstantinos

2012-01-01

Purpose To investigate the effect of standardized and study-specific human brain diffusion tensor templates on the accuracy of spatial normalization, without ignoring the important roles of data quality and registration algorithm effectiveness. Materials and Methods Two groups of diffusion tensor imaging (DTI) datasets, with and without visible artifacts, were normalized to two standardized diffusion tensor templates (IIT2, ICBM81) as well as study-specific templates, using three registration approaches. The accuracy of inter-subject spatial normalization was compared across templates, using the most effective registration technique for each template and group of data. Results It was demonstrated that, for DTI data with visible artifacts, the study-specific template resulted in significantly higher spatial normalization accuracy than standardized templates. However, for data without visible artifacts, the study-specific template and the standardized template of higher quality (IIT2) resulted in similar normalization accuracy. Conclusion For DTI data with visible artifacts, a carefully constructed study-specific template may achieve higher normalization accuracy than that of standardized templates. However, as DTI data quality improves, a high-quality standardized template may be more advantageous than a study-specific template, since in addition to high normalization accuracy, it provides a standard reference across studies, as well as automated localization/segmentation when accompanied by anatomical labels. PMID:23034880

Purification, crystallization and preliminary X-ray study of the fungal laccase from Cerrena maxima

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lyashenko, Andrey V.; Zhukhlistova, Nadegda E.; Gabdoulkhakov, Azat G.

2006-10-01

The crystallization and preliminary X-ray structure at 1.9 Å resolution of the fungal laccase from C. maxima are presented. Laccases are members of the blue multi-copper oxidase family that oxidize substrate molecules by accepting electrons at a mononuclear copper centre and transferring them to a trinuclear centre. Dioxygen binds to the trinuclear centre and, following the transfer of four electrons, is reduced to two molecules of water. Crystals of the laccase from Cerrena maxima have been obtained and X-ray data were collected to 1.9 Å resolution using synchrotron radiation. A preliminary analysis shows that the enzyme has the typical laccasemore » structure and several carbohydrate sites have been identified. The carbohydrate chains appear to be involved in stabilization of the intermolecular contacts in the crystal structure, thus promoting the formation of well ordered crystals of the enzyme. Here, the results of an X-ray crystallographic study on the laccase from the fungus Cerrena maxima are reported. Crystals that diffract well to a resolution of at least 1.9 Å (R factor = 18.953%; R{sub free} = 23.835; r.m.s.d. bond lengths, 0.06 Å; r.m.s.d. bond angles, 1.07°) have been obtained despite the presence of glycan moieties. The overall spatial organization of C. maxima laccase and the structure of its copper-containing active centre have been determined by the molecular-replacement method using the laccase from Trametes versicolor (Piontek et al., 2002 ▶) as a structural template. In addition, four glycan-binding sites were identified and the 1.9 Å X-ray data were used to determine the previously unknown primary structure of this protein. The identity (calculated from sequence alignment) between the C. maxima laccase and the T. versicolor laccase is about 87%. Tyr196 and Tyr372 show significant extra density at the ortho positions and this has been interpreted in terms of NO{sub 2} substituents.« less

Assembly of large-area, highly ordered, crack-free inverse opal films

PubMed Central

Hatton, Benjamin; Mishchenko, Lidiya; Davis, Stan; Sandhage, Kenneth H.; Aizenberg, Joanna

2010-01-01

Whereas considerable interest exists in self-assembly of well-ordered, porous “inverse opal” structures for optical, electronic, and (bio)chemical applications, uncontrolled defect formation has limited the scale-up and practicality of such approaches. Here we demonstrate a new method for assembling highly ordered, crack-free inverse opal films over a centimeter scale. Multilayered composite colloidal crystal films have been generated via evaporative deposition of polymeric colloidal spheres suspended within a hydrolyzed silicate sol-gel precursor solution. The coassembly of a sacrificial colloidal template with a matrix material avoids the need for liquid infiltration into the preassembled colloidal crystal and minimizes the associated cracking and inhomogeneities of the resulting inverse opal films. We discuss the underlying mechanisms that may account for the formation of large-area defect-free films, their unique preferential growth along the 〈110〉 direction and unusual fracture behavior. We demonstrate that this coassembly approach allows the fabrication of hierarchical structures not achievable by conventional methods, such as multilayered films and deposition onto patterned or curved surfaces. These robust SiO2 inverse opals can be transformed into various materials that retain the morphology and order of the original films, as exemplified by the reactive conversion into Si or TiO2 replicas. We show that colloidal coassembly is available for a range of organometallic sol-gel and polymer matrix precursors, and represents a simple, low-cost, scalable method for generating high-quality, chemically tailorable inverse opal films for a variety of applications. PMID:20484675

Location of early aftershocks of the 2004 Mid-Niigata Prefecture Earthquake (M = 6.8) in central Japan using seismogram envelopes as templates

NASA Astrophysics Data System (ADS)

Kosuga, M.

2013-12-01

The location of early aftershocks is very important to obtain information of mainshock fault, however, it is often difficult due to the long-lasting coda wave of mainshock and successive occurrence of afterrshocks. To overcome this difficulty, we developed a method of location using seismogram envelopes as templates, and applied the method to the early aftershock sequence of the 2004 Mid-Niigata Prefecture (Chuetsu) Earthquake (M = 6.8) in central Japan. The location method composes of three processes. The first process is the calculation of cross-correlation coefficients between a continuous (target) and template envelopes. We prepare envelopes by taking the logarithm of root-mean-squared amplitude of band-pass filtered seismograms. We perform the calculation by shifting the time window to obtain a set of cross-correlation values for each template. The second process is the event detection (selection of template) and magnitude estimate. We search for the events in descending order of cross-correlation in a time window excluding the dead times around the previously detected events. Magnitude is calculated by the amplitude ratio of target and template envelopes. The third process is the relative event location to the selected template. We applied this method to the Chuetsu earthquake, a large inland earthquake with extensive aftershock activity. The number of detected events depends on the number of templates, frequency range, and the threshold value of cross-correlation. We set the threshold as 0.5 by referring to the histogram of cross-correlation. During a period of one-hour from the mainshock, we could detect more events than the JMA catalog. The location of events is generally near the catalog location. Though we should improve the methods of relative location and magnitude estimate, we conclude that the proposed method works adequately even just after the mainshock of large inland earthquake. Acknowledgement: We thank JMA, NIED, and the University of Tokyo for providing arrival time data, and waveform data. This work was supported by JSPS KAKENHI Grant Number 23540487.

Toward Optimizing VEMP: Calculating VEMP Inhibition Depth With a Generic Template.

PubMed

Noij, Kimberley S; van Tilburg, Mark J; Herrmann, Barbara S; Marciniak, Piotr; Rauch, Steven D; Guinan, John J

2018-04-05

Cervical vestibular evoked myogenic potentials (cVEMP) indirectly reveal the response of the saccule to acoustic stimuli through the inhibition of sternocleidomastoid muscle electromyographic response. VEMP inhibition depth (VEMPid) is a recently developed metric that estimates the percentage of saccular inhibition. VEMPid provides both normalization and better accuracy at low response levels than amplitude-normalized cVEMPs. Hopefully, VEMPid will aid in the clinical assessment of patients with vestibulopatholgy. To calculate VEMPid a template is needed. In the original method, a subject's own cVEMP was used as the template, but this method can be problematic in patients who do not have robust cVEMP responses. We hypothesize that a "generic" template, created by assembling cVEMPs from healthy subjects, can be used to compute VEMPid, which would facilitate the use of VEMPid in subjects with pathological conditions. A generic template was created by averaging cVEMP responses from 6 normal subjects. To compare VEMPid calculations using a generic versus a subject-specific template, cVEMPs were obtained in 40 healthy subjects using 500, 750, and 1000 Hz tonebursts at sound levels ranging from 98 to 123 dB peSPL. VEMPids were calculated both with the generic template and with the subject's own template. The ability of both templates to determine whether a cVEMP was present or not was compared with receiver operating characteristic curves. No significant differences were found between VEMPid calculations using a generic template versus using a subject-specific template for all frequencies and sound levels. Based on the receiver operating characteristic curves, the subject-specific and generic template did an equally good job at determining threshold. Within limits, the shape of the generic template did not affect these results. A generic template can be used instead of a subject-specific template to calculate VEMPid. Compared with cVEMP normalized by electromyographic amplitudes, VEMPid is advantageous because it averages zero when there is no sound stimulus and it allows the accumulating VEMPid value to be shown during data acquisition as a guide to deciding when enough data has been collected.

Color Tunable and Upconversion Luminescence in Yb-Tm Co-Doped Yttrium Phosphate Inverse Opal Photonic Crystals.

PubMed

Wang, Siqin; Qiu, Jianbei; Wang, Qi; Zhou, Dacheng; Yang, Zhengwen

2016-04-01

For this paper, YPO4: Tm, Yb inverse opals with the photonic band gaps at 475 nm and 655 nm were prepared by polystyrene colloidal crystal templates. We investigated the influence of photonic band gaps on the Tm-Yb upconversion emission which was in the YPO4: Tm Yb inverse opal photonic crystals. Comparing with the reference sample, significant suppression of both the blue and red upconversion luminescence of Tm3+ ions were observed in the inverse opals. The color purity of the blue emission was improved in the inverse opal by the suppression of red upconversion emission. Additionally, mechanism of upconversion emission in the inverse opal was discussed. We believe that the present work will be valuable for not only the foundational study of upconversion emission modification but also the development of new optical devices in upconversion lighting and display.

Pure rhombohedral Bi1-x EuxPO4 nano-/micro-structures: fast synthesis, shape evolution and luminescence properties.

PubMed

Yu, Dongyan; Liang, Yujun; Zhang, Mengfei; Li, Guogang; Yan, Chunjie

2016-02-01

BiPO4 and Eu-doped BiPO4 crystals were synthesized via a simple precipitation route at room temperature, employing Bi(NO3)3 and (NH4)2HPO4 as the reactants, Eu2O3 as the dopant and citric acid as a template. X-ray powder diffraction analyses showed that pure rhombohedral BiPO4 form was obtained, and was the preferential orientation growth of the crystal. Field emission scanning electron microscope observations showed that the concentration of Bi(3+) obviously changed the products' morphologies from nanosphere, hollow sphere to hexagonal prism. The acidity of the solution and the contents of citric acid and Eu(3+) ion tailored the size of the final crystals. Effects of concentration of Eu(3+) ion on the luminescence emission intensity were also investigated. Copyright © 2015 John Wiley & Sons, Ltd.

Crystallization and preliminary X-ray analysis of Leishmania major glyoxalase I

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ariza, Antonio; Vickers, Tim J.; Greig, Neil

2005-08-01

The detoxification enzyme glyoxalase I from L. major has been crystallized. Preliminary molecular-replacement calculations indicate the presence of three glyoxalase I dimers in the asymmetric unit. Glyoxalase I (GLO1) is a putative drug target for trypanosomatids, which are pathogenic protozoa that include the causative agents of leishmaniasis. Significant sequence and functional differences between Leishmania major and human GLO1 suggest that it may make a suitable template for rational inhibitor design. L. major GLO1 was crystallized in two forms: the first is extremely disordered and does not diffract, while the second, an orthorhombic form, produces diffraction to 2.0 Å. Molecular-replacement calculationsmore » indicate that there are three GLO1 dimers in the asymmetric unit, which take up a helical arrangement with their molecular dyads arranged approximately perpendicular to the c axis. Further analysis of these data are under way.« less

A putative siderophore-interacting protein from the marine bacterium Shewanella frigidimarina NCIMB 400: cloning, expression, purification, crystallization and X-ray diffraction analysis

PubMed Central

Trindade, Inês B.; Fonseca, Bruno M.; Matias, Pedro M.; Louro, Ricardo O.; Moe, Elin

2016-01-01

Siderophore-binding proteins (SIPs) perform a key role in iron acquisition in multiple organisms. In the genome of the marine bacterium Shewanella frigidimarina NCIMB 400, the gene tagged as SFRI_RS12295 encodes a protein from this family. Here, the cloning, expression, purification and crystallization of this protein are reported, together with its preliminary X-ray crystallographic analysis to 1.35 Å resolution. The SIP crystals belonged to the monoclinic space group P21, with unit-cell parameters a = 48.04, b = 78.31, c = 67.71 Å, α = 90, β = 99.94, γ = 90°, and are predicted to contain two molecules per asymmetric unit. Structure determination by molecular replacement and the use of previously determined ∼2 Å resolution SIP structures with ∼30% sequence identity as templates are ongoing. PMID:27599855

The Role Of Painleve II In Predicting New Liquid Crystal Self-Assembly Mechanisms

NASA Astrophysics Data System (ADS)

Troy, William C.

2018-01-01

We prove the existence of a new class of solutions, called shadow kinks, of the Painleve II equation {d2 w}/{dz2}=2w3 +zw+α,} where {α < 0} is a constant. Shadow kinks are sign changing solutions which satisfy { w(z) ˜ -{√ {-z/2}} as z \\to - ∞} and w(z) ˜ -{α}/{z} as z \\to ∞. These solutions play a critical role in the prediction of a new class of topological defects, one dimensional shadow kinks and two dimensional shadow vortices, in light-matter interaction experiments on nematic liquid crystals. These new defects are physically important since it has recently been shown ( Wang et al. in Nat Mater 15:106-112, 2016) that topological defects are a "template for molecular self-assembly" in liquid crystals. Connections with the modified KdV equation are also discussed.

Discovery and X-ray crystallographic analysis of a spiropiperidine iminohydantoin inhibitor of beta-secretase.

PubMed

Barrow, James C; Stauffer, Shaun R; Rittle, Kenneth E; Ngo, Phung L; Yang, ZhiQiang; Selnick, Harold G; Graham, Samuel L; Munshi, Sanjeev; McGaughey, Georgia B; Holloway, M Katharine; Simon, Adam J; Price, Eric A; Sankaranarayanan, Sethu; Colussi, Dennis; Tugusheva, Katherine; Lai, Ming-Tain; Espeseth, Amy S; Xu, Min; Huang, Qian; Wolfe, Abigail; Pietrak, Beth; Zuck, Paul; Levorse, Dorothy A; Hazuda, Daria; Vacca, Joseph P

2008-10-23

A high-throughput screen at 100 microM inhibitor concentration for the BACE-1 enzyme revealed a novel spiropiperidine iminohydantoin aspartyl protease inhibitor template. An X-ray cocrystal structure with BACE-1 revealed a novel mode of binding whereby the inhibitor interacts with the catalytic aspartates via bridging water molecules. Using the crystal structure as a guide, potent compounds with good brain penetration were designed.

High-Performance Substrates for SERS Detection via Microphotonic Photopolymer Characterization and Coating With Functionalized Hydrogels

DTIC Science & Technology

2006-11-26

with controlled micro and nanostructure for highly selective, high sensitivity assays. The process was modeled and a procedure for fabricating SERS...small volumes with controlled micro and nanostructure for highly selective, high sensitivity assays. We proved the feasibility of the technique and...films templated by colloidal crystals. The control over the film structure allowed optimizing their performance for potential sensor applications. The

From synthetic montroseite VOOH to topochemical paramontroseite VO2 and their applications in aqueous lithium ion batteries.

PubMed

Xu, Yang; Zheng, Lei; Xie, Yi

2010-11-28

Synthetic montroseite VOOH has been successfully prepared via a simple template-free hydrothermal route on a large scale for the first time-after sixty years of delay. The as-obtained sample shows a hierarchical morphology of urchin-like nanoarchitecture with hollow interiors consisting of well-crystalline nanorods standing vertically on the shell surface. Time-dependent experiments illustrated that these hierarchical hollow nanourchins were formed through the hydrolysis-driven Kirkendall effect coupled with a new-phased vanadium oxyhydroxide V(10)O(14)(OH)(2) precursor templated approach. Meanwhile, the as-obtained VOOH hollow nanourchins could convert topochemically to paramontroseite VO(2) without altering the size and original appearance during the annealing process due to the extreme structural similarity revealed by crystal structure analysis. Furthermore, the improved electrochemical performance of both montroseite VOOH and paramontroseite VO(2) hierarchical hollow structures toward Li uptake and release verifies their potential applications as anode materials in aqueous lithium ion batteries. These improved electrochemical properties could be ascribed to the synergetic effect of the microscopic tunneled crystal structure and macroscopic hollow morphological features, which provide the easy infiltration of electrolyte, short diffusion lengths for lithium ions and electron transport as well as sufficient void space to buffer the volume change.

Polarization switching behavior of one-axis-oriented lead zirconate titanate films fabricated on metal oxide nanosheet layer

NASA Astrophysics Data System (ADS)

Uchida, Hiroshi; Ichinose, Daichi; Shiraishi, Takahisa; Shima, Hiromi; Kiguchi, Takanori; Akama, Akihiko; Nishida, Ken; Konno, Toyohiko J.; Funakubo, Hiroshi

2017-10-01

For the application of electronic devices using ferroelectric/piezoelectric components, one-axis-oriented tetragonal Pb(Zr0.40Ti0.60)O3 (PZT) films with thicknesses of up to 1 µm were fabricated with the aid of a Ca2Nb3O10 nanosheet (ns-CN) template for preferential crystal growth for evaluating their polarization switching behavior. The ns-CN template was supported on ubiquitous silicon (Si) wafer by a simple dip coating technique, followed by the repetitive chemical solution deposition (CSD) of PZT films. The PZT films were grown successfully with preferential crystal orientation of PZT(100) up to the thickness of 1020 nm. The (100)-oriented PZT film with ∼1 µm thickness exhibited unique polarization behavior of ferroelectric polarization, i.e., a marked increase in remanent polarization (P r) up to approximately 40 µC/cm2 induced by domain switching under high electric field, whereas the film with a lower thickness showed only a lower P r of approximately 11 µC/cm2 even under a high electric field. The ferroelectric property of the (100)-oriented PZT film after domain switching on ns-CN/Pt/Si can be comparable to those of (001)/(100)-oriented epitaxial PZT films.

Facile synthesis of pristine graphene-palladium nanocomposites with extraordinary catalytic activities using swollen liquid crystals

NASA Astrophysics Data System (ADS)

Vats, T.; Dutt, S.; Kumar, R.; Siril, P. F.

2016-09-01

Amazing conductivity, perfect honeycomb sp2 arrangement and the high theoretical surface area make pristine graphene as one of the best materials suited for application as catalyst supports. Unfortunately, the low reactivity of the material makes the formation of nanocomposite with inorganic materials difficult. Here we report an easy approach to synthesize nanocomposites of pristine graphene with palladium (Pd-G) using swollen liquid crystals (SLCs) as a soft template. The SLC template gives the control to deposit very small Pd particles of uniform size on G as well as RGO. The synthesized nanocomposite (Pd-G) exhibited exceptionally better catalytic activity compared with Pd-RGO nanocomposite in the hydrogenation of nitrophenols and microwave assisted C-C coupling reactions. The catalytic activity of Pd-G nanocomposite during nitrophenol reduction reaction was sixteen times higher than Pd nanoparticles and more than double than Pd-RGO nanocomposite. The exceptionally high activity of pristine graphene supported catalysts in the organic reactions is explained on the basis of its better pi interacting property compared to partially reduced RGO. The Pd-G nanocomposite showed exceptional stability under the reaction conditions as it could be recycled upto a minimum of 15 cycles for the C-C coupling reactions without any loss in activity.

Cadmium (II) macrocyclic Schiff-base complexes containing piperazine moiety: Synthesis, spectroscopic, X-ray structure, theoretical and antibacterial studies

NASA Astrophysics Data System (ADS)

Keypour, Hassan; Mahmoudabadi, Masoumeh; Shooshtari, Amir; Bayat, Mehdi; Mohsenzadeh, Fariba; Gable, Robert William

2018-03-01

The new Cd(II) macrocyclic Schiff-base complexes were prepared via the metal templated [1 + 1] cyclocondensation of 2,2'-(piperazine-1,4-diylbis (methylene))dianiline (A) and 2,6-pyridinedicarbaldehyde or 2,6-diacetylpyridine. The products were characterized by elemental analysis, mass spectrometry and spectroscopic methods such as: FT-IR, 1H and 13C-NMR, the crystal structure of [CdL1(ClO4)2](CH3CN) (1) complex was also obtained by single-crystal X-ray crystallography. The complexes were tested for in vitro antibacterial properties against some bacteria. The complexes had antibacterial properties and in some cases were active even more than standards. The geometries of the [CdLn (ClO4)2], (n = 1,2) complexes have been optimized at the BP86/def2-SVP level of theory. Also the nature of Cd←Ln (n = 1, 2) bonds in [CdLn (ClO4)2], (n = 1,2) complexes are studied with the help of NBO and Energy decomposition analysis (EDA). Results showed that the nature of metal-ligand bond in the complexes is slightly more electrostatic with a contribution of about 52% in total interaction energy.

Novel combination of near-field s-SNOM microscopy with peak-force tapping for nano-chemical and nano-mechanical material characterization with sub-20 nm spatial resolution

NASA Astrophysics Data System (ADS)

Wagner, Martin; Carneiro, Karina; Habelitz, Stefan; Mueller, Thomas; BNS Team; UCSF Team

Heterogeneity in material systems requires methods for nanoscale chemical identification. Scattering scanning near-field microscopy (s-SNOM) is chemically sensitive in the infrared fingerprint region while providing down to 10 nm spatial resolution. This technique detects material specific tip-scattering in an atomic force microscope. Here, we present the first combination of s-SNOM with peak-force tapping (PFT), a valuable AFM technique that allows precise force control between tip and sample down to 10s of pN. The latter is essential for imaging fragile samples, but allows also quantitative extraction of nano-mechanical properties, e.g. the modulus. PFT can further be complemented by KPFM or conductive AFM for nano-electrical mapping, allowing access to nanoscale optical, mechanical and electrical information in a single instrument. We will address several questions ranging from graphene plasmonics to material distributions in polymers. We highlight a biological application where dental amelogenin protein was studied via s-SNOM to learn about its self-assembly into nanoribbons. At the same time PFT allows to track crystallization to distinguish protein from apatite crystals for which amelogenin is supposed to act as a template.

One-pot pseudomorphic crystallization of mesoporous porous silica to hierarchical porous zeolites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xing, Jun-Ling; Jiang, Shu-Hua; Pang, Jun-Ling

2015-09-15

Hierarchically porous silica with mesopore and zeolitic micropore was synthesized via pseudomorphic crystallization under high-temperature hydrothermal treatment in the presence of cetyltrimethylammonium tosylate and tetrapropylammonium ions. A combined characterization using small-angle X-ray diffraction (XRD), nitrogen adsorption, high-resolution transmission electron microscopy (TEM), thermogravimetric analysis (TG), and elemental analysis showed that dual templates, CTA{sup +} and TPA{sup +} molecules, can work in a cooperative manner to synthesize mesoporous zeolite in a one-pot system by precisely tuning the reaction conditions, such as reaction time and temperature, and type and amount of heterometal atoms. It is found that the presence of Ti precursor ismore » critical to the successful synthesis of such nanostructure. It not only retards the nucleation and growth of crystalline MFI domains, but also acts as nano-binder or nano-glue to favor the assembly of zeolite nanoblocks. - Graphical abstract: Display Omitted - Highlights: • A facile method to synthesize mesoporous zeolites with hierarchical porosity was presented. • It gives a new insight into keeping the balance between mesoscopic and molecular ordering in hierarchical porous materials. • A new understanding on the solid–solid transformation mechanism for the synthesis of titanosilicate zeolites was proposed.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Qi; Cheng, Xiaolin; Univ. of Tennessee, Knoxville, TN

Although Elvitegravir (EVG) is a newly developed antiretrovirals drug to treat the acquired immunodeficiency syndrome (AIDS), drug resistance has already been found in clinic, such as E92Q/N155H and Q148H/G140S. Several structural investigations have already been reported to reveal the molecular mechanism of the drug resistance. As full length crystal structure for HIV-1 integrase is still unsolved, we use in this paper the crystal structure of the full length prototype foamy virus (PFV) in complex with virus DNA and inhibitor Elvitegravir as a template to construct the wild type and E92Q/N155H mutant system of HIV-1 integrase. Molecular dynamic simulations was usedmore » to revel the binding mode and the drug resistance of the EVG ligand in E92Q/N155H. Several important interactions were discovered between the mutated residues and the residues in the active site of the E92Q/N155H double mutant pattern, and cross correlation and clustering methods were used for detailed analysis. The results from the MD simulation studies will be used to guide the experimental efforts of developing novel inhibitors against drug-resistant HIV integrase mutants.« less

Template protection and its implementation in 3D face recognition systems

NASA Astrophysics Data System (ADS)

Zhou, Xuebing

2007-04-01

As biometric recognition systems are widely applied in various application areas, security and privacy risks have recently attracted the attention of the biometric community. Template protection techniques prevent stored reference data from revealing private biometric information and enhance the security of biometrics systems against attacks such as identity theft and cross matching. This paper concentrates on a template protection algorithm that merges methods from cryptography, error correction coding and biometrics. The key component of the algorithm is to convert biometric templates into binary vectors. It is shown that the binary vectors should be robust, uniformly distributed, statistically independent and collision-free so that authentication performance can be optimized and information leakage can be avoided. Depending on statistical character of the biometric template, different approaches for transforming biometric templates into compact binary vectors are presented. The proposed methods are integrated into a 3D face recognition system and tested on the 3D facial images of the FRGC database. It is shown that the resulting binary vectors provide an authentication performance that is similar to the original 3D face templates. A high security level is achieved with reasonable false acceptance and false rejection rates of the system, based on an efficient statistical analysis. The algorithm estimates the statistical character of biometric templates from a number of biometric samples in the enrollment database. For the FRGC 3D face database, the small distinction of robustness and discriminative power between the classification results under the assumption of uniquely distributed templates and the ones under the assumption of Gaussian distributed templates is shown in our tests.

Georeferencing the Large-Scale Aerial Photographs of a Great Lakes Coastal Wetland: A Modified Photogrammetric Method

USGS Publications Warehouse

Murphy, Marilyn K.; Kowalski, Kurt P.; Grapentine, Joel L.

2010-01-01

The geocontrol template method was developed to georeference multiple, overlapping analog aerial photographs without reliance upon conventionally obtained horizontal ground control. The method was tested as part of a long-term wetland habitat restoration project at a Lake Erie coastal wetland complex in the U.S. Fish and Wildlife Service Ottawa National Wildlife Refuge. As in most coastal wetlands, annually identifiable ground-control features required to georeference photo-interpreted data are difficult to find. The geocontrol template method relies on the following four components: (a) an uncontrolled aerial photo mosaic of the study area, (b) global positioning system (GPS) derived horizontal coordinates of each photo’s principal point, (c) a geocontrol template created by the transfer of fiducial markings and calculated principal points to clear acetate from individual photographs arranged in a mosaic, and (d) the root-mean-square-error testing of the system to ensure an acceptable level of planimetric accuracy. Once created for a study area, the geocontrol template can be registered in geographic information system (GIS) software to facilitate interpretation of multiple images without individual image registration. The geocontrol template enables precise georeferencing of single images within larger blocks of photographs using a repeatable and consistent method.

Conformal spinel/layered heterostructures of Co3O4 shells grown on single-crystal Li-rich nanoplates for high-performance lithium-ion batteries

NASA Astrophysics Data System (ADS)

Xin, Yue; Lan, Xiwei; Chang, Peng; Huang, Yaqun; Wang, Libin; Hu, Xianluo

2018-07-01

Lithium-rich layered materials have received much attention because of their high specific capacity and high energy density. Unfortunately, they suffer from irreversible capacity loss, low initial Coulombic efficiency and poor cyclability. Here we report a facile co-precipitation method to synthesize uniform single-crystal Li-rich Li[Li0.2Mn0.54Ni0.13Co0.13]O2 nanoplates without using any template. Subsequently, a Co3O4 shell is in situ grown on the Li-rich nanoplates through a hydrothermal method, leading to spinel/layered heterostructures. The electrode made of conformal heterostructured Li-rich/Co3O4 nanoplates delivers a high discharge capacity of 296 mA h g-1 at 0.1 C with an initial Coulombic efficiency of 84%. The capacity retention reaches 83.2% with a discharge capacity of 223 mA h g-1 after 160 cycles at 0.2 C during the potential window ranging from 2.0 to 4.8 V. The enhanced electrochemical performance of the resulting Li-rich/Co3O4 nanoplates benefits from the unique conformal heterostructure as well as the electrochemically active LixCoOy generated between the reaction of Co3O4 shells and the extracted Li2O during charging/discharging processes.

Template-based structure modeling of protein-protein interactions

PubMed Central

Szilagyi, Andras; Zhang, Yang

2014-01-01

The structure of protein-protein complexes can be constructed by using the known structure of other protein complexes as a template. The complex structure templates are generally detected either by homology-based sequence alignments or, given the structure of monomer components, by structure-based comparisons. Critical improvements have been made in recent years by utilizing interface recognition and by recombining monomer and complex template libraries. Encouraging progress has also been witnessed in genome-wide applications of template-based modeling, with modeling accuracy comparable to high-throughput experimental data. Nevertheless, bottlenecks exist due to the incompleteness of the proteinprotein complex structure library and the lack of methods for distant homologous template identification and full-length complex structure refinement. PMID:24721449

Resolving the Framework Position of Organic Structure-Directing Agents in Hierarchical Zeolites via Polarized Stimulated Raman Scattering.

PubMed

Fleury, Guillaume; Steele, Julian A; Gerber, Iann C; Jolibois, F; Puech, P; Muraoka, Koki; Keoh, Sye Hoe; Chaikittisilp, Watcharop; Okubo, Tatsuya; Roeffaers, Maarten B J

2018-04-05

The direct synthesis of hierarchically intergrown silicalite-1 can be achieved using a specific diquaternary ammonium agent. However, the location of these molecules in the zeolite framework, which is critical to understand the formation of the material, remains unclear. Where traditional characterization tools have previously failed, herein we use polarized stimulated Raman scattering (SRS) microscopy to resolve molecular organization inside few-micron-sized crystals. Through a combination of experiment and first-principles calculations, our investigation reveals the preferential location of the templating agent inside the linear pores of the MFI framework. Besides illustrating the attractiveness of SRS microscopy in the field of material science to study and spatially resolve local molecular distribution as well as orientation, these results can be exploited in the design of new templating agents for the preparation of hierarchical zeolites.

Asymmetric synthesis using chiral-encoded metal

NASA Astrophysics Data System (ADS)

Yutthalekha, Thittaya; Wattanakit, Chularat; Lapeyre, Veronique; Nokbin, Somkiat; Warakulwit, Chompunuch; Limtrakul, Jumras; Kuhn, Alexander

2016-08-01

The synthesis of chiral compounds is of crucial importance in many areas of society and science, including medicine, biology, chemistry, biotechnology and agriculture. Thus, there is a fundamental interest in developing new approaches for the selective production of enantiomers. Here we report the use of mesoporous metal structures with encoded geometric chiral information for inducing asymmetry in the electrochemical synthesis of mandelic acid as a model molecule. The chiral-encoded mesoporous metal, obtained by the electrochemical reduction of platinum salts in the presence of a liquid crystal phase and the chiral template molecule, perfectly retains the chiral information after removal of the template. Starting from a prochiral compound we demonstrate enantiomeric excess of the (R)-enantiomer when using (R)-imprinted electrodes and vice versa for the (S)-imprinted ones. Moreover, changing the amount of chiral cavities in the material allows tuning the enantioselectivity.

Fabrication of mesoporous cerium dioxide films by cathodic electrodeposition.

PubMed

Kim, Young-Soo; Lee, Jin-Kyu; Ahn, Jae-Hoon; Park, Eun-Kyung; Kim, Gil-Pyo; Baeck, Sung-Hyeon

2007-11-01

Mesoporous cerium dioxide (Ceria, CeO2) thin films have been successfully electrodeposited onto ITO-coated glass substrates from an aqueous solution of cerium nitrate using CTAB (Cetyltrimethylammonium Bromide) as a templating agent. The synthesized films underwent detailed characterizations. The crystallinity of synthesized CeO2 film was confirmed by XRD analysis and HR-TEM analysis, and surface morphology was investigated by SEM analysis. The presence of mesoporosity in fabricated films was confirmed by TEM and small angle X-ray analysis. As-synthesized film was observed from XRD analysis and HR-TEM image to have well-crystallized structure of cubic phase CeO2. Transmission electron microscopy and small angle X-ray analysis revealed the presence of uniform mesoporosity with a well-ordered lamellar phase in the CeO2 films electrodeposited with CTAB templating.

Production of morphology-controllable porous hyaluronic acid particles using a spray-drying method.

PubMed

Iskandar, Ferry; Nandiyanto, Asep Bayu Dani; Widiyastuti, W; Young, Lee Sin; Okuyama, Kikuo; Gradon, Leon

2009-05-01

Hyaluronic acid (HA) porous particles with controllable porosity and pore size, ranging from 100 to 300 nm, were successfully prepared using a colloidal templating and spray-drying method. HA powder and polystyrene latex (PSL) particles, which were used as the precursor and templating agent, respectively, were mixed in aqueous solution and spray-dried using a two-fluid nozzle system to produce HA and PSL composite particles. Water was evaporated during spray-drying using heated air with a temperature of 120 degrees C. This simple process was completed within several seconds. The prepared particles were collected and washed with an organic solvent to dissolve the PSL templating agent. The porosity and pore size of the resulting particles were easily controlled by changing the initial mass ratio of precursor to templating agent, i.e., HA to PSL, and by altering the size of the PSL template particles.

Incorporating User Input in Template-Based Segmentation

PubMed Central

Vidal, Camille; Beggs, Dale; Younes, Laurent; Jain, Sanjay K.; Jedynak, Bruno

2015-01-01

We present a simple and elegant method to incorporate user input in a template-based segmentation method for diseased organs. The user provides a partial segmentation of the organ of interest, which is used to guide the template towards its target. The user also highlights some elements of the background that should be excluded from the final segmentation. We derive by likelihood maximization a registration algorithm from a simple statistical image model in which the user labels are modeled as Bernoulli random variables. The resulting registration algorithm minimizes the sum of square differences between the binary template and the user labels, while preventing the template from shrinking, and penalizing for the inclusion of background elements into the final segmentation. We assess the performance of the proposed algorithm on synthetic images in which the amount of user annotation is controlled. We demonstrate our algorithm on the segmentation of the lungs of Mycobacterium tuberculosis infected mice from μCT images. PMID:26146532

Structure-Based Predictions of Activity Cliffs

PubMed Central

Husby, Jarmila; Bottegoni, Giovanni; Kufareva, Irina; Abagyan, Ruben; Cavalli, Andrea

2015-01-01

In drug discovery, it is generally accepted that neighboring molecules in a given descriptors' space display similar activities. However, even in regions that provide strong predictability, structurally similar molecules can occasionally display large differences in potency. In QSAR jargon, these discontinuities in the activity landscape are known as ‘activity cliffs’. In this study, we assessed the reliability of ligand docking and virtual ligand screening schemes in predicting activity cliffs. We performed our calculations on a diverse, independently collected database of cliff-forming co-crystals. Starting from ideal situations, which allowed us to establish our baseline, we progressively moved toward simulating more realistic scenarios. Ensemble- and template-docking achieved a significant level of accuracy, suggesting that, despite the well-known limitations of empirical scoring schemes, activity cliffs can be accurately predicted by advanced structure-based methods. PMID:25918827