bluuebunny/crossref_metadata_2025 huggingface dataset:
Electric field pulse assisted covalent immobilization and hybridization of DNA in the nanosecond time scale
Authors: Fixe F. , Branz H.M. , Prazeres D.M.F. , Chu V. , Conde J.P.
Published: June 2019

A single, square, voltage pulse is used to accelerate both the immobilization kinetics of DNA molecules on a functionalized thin film silicon dioxide surface and the hybridization of complementary DNA strands to immobilized DNA molecules. The voltage pulse is applied to an integrated thin-film metal electrode beneath the functionalized surface. The duration and magnitude of the voltage pulse are compatible with silicon microelectronics circuits. During immobilization, covalent thiol bonding to the functionalized surface occurs during a single pulse lasting only 100 ns. Hybridization to the immobilized complementary strand occurs during 100 μs pulses.
Mems Tactile Sensors for Surgical Instruments
Authors: Rebello Keith J. , Lebouitz Kyle S. , Migliuolo Michele
Published: June 2019

The development of sophisticated endoscopic tools and the recent introduction of robotics are expanding the applications of minimally invasive surgery. The lack of tactile feedback in the currently available endoscopic and robotic telemanipulation systems however represents a significant limitation. A need has arisen for the development of surgical instruments having integrated sensors. Current efforts to integrate sensors into or onto surgical tools has focused on fabrication of sensors on silicon, polyimide, or some other substrate and then attaching the sensors to a tool by hand or machine with epoxy, tape, or some other glue layer. Attaching the sensor in this manner has certain deficiencies. In particular, this method of attaching sensors to a surgical tool limits the sensors size, increases its thickness, and further constrains where the sensor can be placed. A method of fabricating tactile sensors on surgical instruments that addresses these deficiencies is discussed.
Transimpedance Mode CMOS Microelectrode Array For In-Vitro Neuronal Activity Recording
Authors: Wegman Jacob S. , Dwarka Amar , Holzer Matthew , Lye Whye-Kei , Reed Michael L. , Herzog Erik , Blalock Travis N.
Published: June 2019

A CMOS integrated microelectrode array (IMA) utilizing a low-inpedance transimpedance input has been developed. The design uses a three-stage amplifier, including a transimpedance input stage, buffer, and multiplexor. The input stage presents a low impedance which provides bias for the neural input and maximizes the current transfer into the circuit. The amplifiers are replicated in an 8x8 array, enabling measurement of a network of 64 neurons invitro. The chip was post-processed to provide a bio-compatible gold interface between the electrodes and the neurons. Simulations and experimental results demonstrate the functionality of the new design. Additional measurements are underway to provide experimental confirmation of the system with in-vitro neurons.
Fabrication of Nanoscale Hydrophobic Regions on Anodic Alumina for Selective Adhesion of Biologic Molecules
Authors: Lin Xiefan , Ham Anthony S. W. , Villani Natalie A. , Lye Whye-Kei , Huang Qiyu , Lawrence Michael B. , Helmke Brian P. , Reed Michael L.
Published: June 2019

Studies of selective adhesion of biological molecules provide a path for understanding fundamental cellular properties. A useful technique is to use patterned substrates, where the pattern of interest has the same length scale as the molecular bonding sites of a cell, in the tens of nanometer range. We employ electrochemical methods to grow anodic alumina, which has a naturally ordered pore structure (interpore spacing of 40 to 400 nm) controlled by the anodization potential. We have also developed methods to selectively fill the alumina pores with materials with contrasting properties. Gold, for example, is electrochemically plated into the pores, and the excess material is removed by backsputter etching. The result is a patterned surface with closely separated islands of Au, surrounded by hydrophilic alumina. The pore spacing, which is determined by fabrication parameters, is hypothesized to have a direct effect on the spatial density of adhesion sites. By attaching adhesive molecules to the Au islands, we are able to observe and study cell rolling and adhesion phenomena. Through the measurements it is possible to estimate the length scale of receptor clusters on the cell surface. This information is useful in understanding mechanisms of leukocytes adhesion to endothelial cells as well as the effect of adhesion molecules adaptation on transmission of extracellular forces. The method also has applications in tissue engineering, drug and gene delivery, cell signaling and biocompatibility design.
Monitoring of stem cell proliferation and differentiation using a permittivity-responsive biointerface
Authors: Bagnaninchi P.O. , Dikeakos M. , Veres T. , Tabrizian M.
Published: June 2019

The main approach of in-vitro bone engineering is based on the use of stem cells cultured in microporous scaffolds. In order to quickly and non-destructively assess the different steps of bone formation, we have proposed the use of a permittivity-responsive sensor to monitor the microporous scaffold, which in this instance acts as a biointerface. The aim of this study is to monitor and characterize the growth and differentiation of cells in the microporous biointerface through CP measurements. Measurements are performed throughout the entire process of the cells' culture, growth and differentiation using a dielectric probe and a vector network analyser under sterile conditions. This concept of a permittivity-responsive biointerface will lead to sensitive biosensors especially adapted for use in tissue engineering.
Oblique-Incidence Reflectivity Difference and Fluorescence Imaging of Oligonucleotide and IgG Protein Microarrays
Authors: Landry James P. , Zhu X. D. , Guo X. W. , Gregg J. P.
Published: June 2019

We have constructed an oblique-incidence reflectivity difference (OI-RD) microscope for fluorescent label-free imaging of DNA and protein microarrays on standard glass substrates. Using both OI-RD and fluorescence images, we demonstrate a difference in wetting behavior of labeled and unlabeled IgG protein molecules deposited on an aldehyde-derivatized glass surface. The potential of fluorescent labeling agents to influence the properties of proteins highlights the need for label-free microarray detection techniques to supplement existing fluorescence methods. We also present OI-RD images of an oligonucleotide microarray after printing and washing procedures to demonstrate the use of OI-RD for non-destructive monitoring of changes in the optical properties of microarrays during processing.
Quantum Dot Bioconjugates as Energy Donors in Fluorescence Resonance Energy Transfer Assays
Authors: Clapp Aaron R. , Medintz Igor L. , Matthew Mauro J. , Mattoussi Hedi
Published: June 2019

Luminescent CdSe-ZnS core-shell quantum dot (QD) bioconjugates were used as energy donors in fluorescent resonance energy transfer (FRET) binding assays. The QDs were coated with saturating amounts of genetically engineered maltose binding protein (MBP) using a noncovalent immobilization process, and Cy3 organic dyes covalently attached at a specific sequence to MBP were used as energy acceptor molecules. Energy transfer efficiency was measured as a function of the MBP-Cy3/QD molar ratio for two different donor fluorescence emissions (different QD core sizes). Apparent donor-acceptor distances were determined from these FRET studies, and the measured distances are consistent with QD-protein conjugate dimensions previously determined from structural studies.
Structural and Initial Optical Characterization of Basalia Spicules in the Glass SpongeEuplectella
Authors: Sundar Vikram C. , Grazul John , Aizenberg Joanna
Published: June 2019

We report on the structural properties of siliceous spicules, found in the hexactinellid spongeEuplectella. Selective chemical etching ofEuplectellaspicules in bleach reveals the presence of a striated arrangement of silica spheres (∼50-200 nm in diameter) placed radially around a central, high-organic content cylindrical region. Complementary etching experiments with HF indicate a graded variation of silica content in these shells. The presence of such a multi-layered and variable-composition structure affords these spicules not only with enhanced structural integrity but could also be reflected in their optical properties. Qualitative, index-matched, refractive index measurements are shown to support this expectation.
Sea Urchin Mineralized Tissue
Authors: Stock S.R. , Ignatiev K. , Carlo F. De , Stock M.K. , Veis A.
Published: June 2019

Sea urchin ossicles are structural analogs of mammalian bones and serve as a model biomineral system. Sea urchins employ as wide a range of composite reinforcement strategies as are seen in engineering composites, and, studied as materials, teeth (and other ossicles) from different echinoid families illustrate combinations of reinforcement parameters and toughening mechanisms providing good functionality. Studying ossicles from different sea urchin families, therefore, is one method of probing the composite design space available to sea urchins, and this offers important guidance for engineering of structural tissue. This report is part of a larger multi-mode x-ray investigation employing microCT, both synchrotron and laboratory sources, phase contrast radiography and transmission microbeam diffraction mapping; voxels (volume elements) approaching 1 μm3can be interrogated noninvasively in millimeter sized samples. Only microCT results are presented below; these focus on sea urchin lanterns (jaw structure) and spines of a variety of sea urchin types and serve to illustrate how this sort of integrated approach might be applied to bone.
Formation of Complex Non-Equilibrium Morphologies of Calcite via Biomimetic Processing
Authors: Kim Yi-yeoun , Gower Laurie B.
Published: June 2019

Our biomimetic approach for fabricating organic-inorganic composites with structures similar to biominerals is based on a novel mineralization process, called the Polymer-Induced-Liquid-Precursor (PILP) process. This process enables the deposition of non-equilibrium mineral morphologies of calcite under low-temperature and aqueous-based conditions [1], including patterned thin films of calcite. We have recently found that when a surplus of acidic polymer is added, the patterned mineral films act as a secondary template for directing new crystal outgrowths, which form into complex morphologies of calcite with time, such as fibrous mats and “horsetails”. Two interdependent factors, the polymer and Ca-ion concentration, which change the local solution environment over time, appear to modulate the creation of these different structures. Such observations may provide clues for unraveling the long-standing mystery of how biological systems fabricate their sophisticated and complex morphologies.
Colloidal Preparation of γ-Fe2O3@Au [core@shell] Nanoparticles
Authors: Fang Jiye , He Jibao , Shin Eun Young , Grimm Deborah , O'Connor Charles J. , Jun Moo-Jin
Published: June 2019

γ-Fe2O3@Au core-shell nanoparticles were prepared through a combined route, in which high temperature organic solution synthesis and colloidal microemulsion techniques were successively applied. High magnification of TEM reveals the core-shell structure. The presence of Au on the surface of as-prepared particles is also confirmed by UV-Vis absorption. The magnetic core-shell nanoparticles offer a promising application in bio- and medical systems.
Peg-Containing Surfactants Enhance the Ultrasonic Permeabilizability of Liposomes
Authors: Lin Hung-Yin , Thomas James L.
Published: June 2019

The susceptibility of phosphatidylcholine liposomes to rupture by ultrasound was investigated. The liposomes were treated with (or had incorporated) a surface active dopant. The dopants studied here all contain polymers or oligomers of ethylene glycol as their hydrophilic “headgroup” component. All dopants strongly increased the ultrasonic permeabilizability of liposomes, as measured by the rate of release of a self-quenching fluorescent dye, at concentrations that caused no increase in permeability in the absence of ultrasound. The surface active dopants reached maximal effectiveness at about 1% of their critical micelle concentrations (CMCs). Using the roughly inverse relationship between CMC and membrane partition coefficient, we estimate that these maximally effective concentrations correspond approximately to the onset of headgroup contact among the surfactants in the membrane. Two surfactants, a PEG-lipid and a Pluronic triblock polymer, can be irreversibly incorporated into liposomes to give formulations that could in principle be used as drug delivery vehicles. The Pluronic polymer offers the possibility of additional temperature responsivity, owing to its highly temperaturedependent CMC.
Chromophore Binding to In-vitro Engineered Bio-mimetic Surfaces
Authors: Kinsella Joseph M. , Ivanisevic Albena
Published: June 2019

The research presented here aims to mimic the highly specialized local environment of the retina and to exploit the principles that govern its function, in order to construct functional optical interfaces that can be used as biotransducers. In the retina, a chromophore isomerizes and the protein to which it binds changes shape. In this proof-of-concept experiment we engineer an artificial surface to mimic the physiochemical environment of the retina and the key reaction of the visual cycle. We immobilized small peptides on silicon and assessed changes in their surface properties upon chromophore binding via AFM. Our observations suggest that when binding occurs it is accompanied by conformational changes of the surface-anchored peptide.
Poly-β-Cyclodextrins: Multifunctional Polymer Support for the Hydrolysis and Removal of Methyl Parathion
Authors: Lee Yongwoo , Singh Alok
Published: June 2019

Microparticles (32-53 μm) of cross-linked poly-β-Cyclodextrin (PCD) having a bifunctional hexyl spacer were prepared. PCD served as an insoluble robust matrix, which is chemically inert in acidic and basic media while preserving accessibility of pesticide methyl parathion (MPT) and its hydrolysis product p-nitrophenol (p-NP) to cyclodextrin cavities. The multi-utility of PCD was demonstrated as a stable biomaterial for adsorption of MPT and p-NP through inclusion phenomena and as a single unit system suitable for casting alternate enzyme/polyelectrolyte multilayers.
Biosynthesis of Silver Nanoparticles
Authors: Naik Rajesh R. , Stringer Sarah J. , Johnson Jay M. , Stone Morley O.
Published: June 2019

The use of biomolecules in the creation of inorganic materials offers an alternative to conventional synthetic methods. Biomolecules are currently used to control nucleation and growth of inorganic nanoparticles. Here we demonstrate the formation of silver nanoparticles in the presence of silver-binding peptides. Examination of the silver nanoparticles by transmission electron microscopy revealed a variety of crystal morphologies such as hexagons, triangles and spheres. The peptides serve to reduce the silver ions in the aqueous solution to metallic silver as well as control crystal growth. The nucleation property of peptides can be used as tool for bottom-up fabrication.
Tailor-Made Nanostructured Ion Selective MCM-48 Membranes
Authors: Chowdhury Sankhanilay Roy , Schmuhl Riaan , Keizer Klaas , Berg Albert van den , ten Elshof Johan E. , Blank Dave H.A.
Published: June 2019

Mesoporous templated MCM-48 silica was prepared using a C16 surfactant as template. The MCM-48 powders and thin films were characterized by different techniques. Two types of porous supports were used, namely macroporous á-alumina and silicon microsieves. The supported MCM-48 layers were applied as liquid permeable membranes in pressure-driven nanofiltration and electric field-mediated ion transport experiments.
Hierarchically Structured Silica Monoliths
Authors: Hüsing Nicola , Raab Christina , Torma Viktoria
Published: June 2019

Large monoliths with periodic mesopores in a macroporous web-like network structure are prepared using a diol-modified silane as silica precursor and lyotropic liquid crystalline phases of surfactants in water as structure-directing agents. The surfactant concentration is varied from 5 to 40wt%. Highly porous materials are synthesized applying two different drying procedures: supercritical drying with CO2 or ethanol, in addition to ambient pressure drying including surfactant expulsion via silanisation treatments with trimethylchlorosilane or hexamethyl disilazane. The monolithic materials show a very unique macro- and mesostructure which is characterized by N2-sorption measurements, small-angle X-ray scattering (SAXS), transmission electron microscopy (TEM) and scanning electron microscopy (SEM).
Self-assembly PbSe Nanoparticles into Nanorings
Authors: Zhou Weilie L. , He Jibao , Fang Jiye , Huynh Tuyet-Anh , Kennedy Trevor J. , Stokes Kevin L. , O'Connor Charles J.
Published: June 2019

In this presentation, we report the self-assembly of monolayer and multilayer nanorings of PbSe nanoparticles. PbSe nanoparticles were synthesized by using a high temperature precipitation method. The nanoparticles are about 5 nm and appeared as truncated octahedral enclosed by the {100} and {111} crystal facets of fcc structure. The large area monodisperse self-assembly nanoarrays were obtained by dropping the high concentration solution of PbSe nanoparticles on the carbon grid. The nanoparticles are hexagonal close packed and oriented randomly in the nanoarrays. By diluting the solution for large area self-assembly, self-assembly of monolayer and multilayer nanorings can be achieved. The nanoring formation is determined by hydrodynamics, surface effects, and interaction between the nanoparticles and carbon grid.
Palladium Nanowire Thin Films via Template Growth
Authors: Wang Donghai , Johnson David T. , McCaughey Byron F. , Hampsey J. Eric , He Jibao , Lu Yunfeng
Published: June 2019

Palladium nanowires have been electrodeposited into mesoporous silica thin film templates. Palladium continually grows and fills silica mesopores starting from a bottom conductive substrate, providing a ready and efficient route to fabricate a macroscopic palladium nanowire thin films for potentially use in fuel cells, electrodes, sensors, and other applications. X-ray diffraction (XRD) and transmission electron microscopy (TEM) indicate it is possible to create different nanowire morphology such as bundles and swirling mesostructure based on the template pore structure.
Stable Nanocapsules Formed from Headgroup Polymerization of Natural Phospholipids
Authors: Lawson Glenn E. , Singh Alok
Published: June 2019

Formation of lipid based hollow, spherical nanocapsules is reported. N-acylphosphotidylethanolamine (egg) derivatives equipped with divinylbenzoyl functionality in their headgroup region were synthesized to explore their polymerization behavior in vesicles. Polymerizable phospholipids alone produced vesicles as an aqueous dispersion and produced stable nanocapsules upon polymerization at room temperature. These structures survived a redispersed cycle following lyophilization and maintained their structural integrity in non-aqueous solvent.
Interface-dependence of Nucleation and Self-Assembly of Ultrathin Iron Oxide Films
Authors: Ketteler Guido , Ranke Wolfgang
Published: June 2019

The interface-dependence of heteroepitaxial growth of iron oxide films is investigated by scanning tunneling microscopy (STM) and low-energy electron diffraction (LEED). We show that the different chemical affinity to the metal substrate (Ru vs. Pt) and the step density (basal vs. vicinal Pt) significantly influence nucleation, heteroepitaxial crystal growth, and adhesion. Repeated Fe deposition-oxidation cycles lead to a Stranski-Krastanov growth mode on all substrates. On Ru(0001), metastable FeO(111) layers with strongly expanded lattice constants with a thickness up to 4 monolayers (ML) can be obtained by one-minute oxidation of the corresponding amount of Fe. Homogeneous nucleation of self-assembled, periodic Fe304(111) nanodomains embedded in an ultrathin FeO(111) film occurs on Ru(0001) in ∼4 ML thick FeO(111) films. Nucleation of Fe304(111) islands below 4 ML on Ru(0001) occurs preferentially at substrate step edges while on Pt(111), no influence of surface defects was observed. On a vicinal Pt substrate, the terrace width and step height triplicates under influence of the wetting FeO(111) film. Differences in the growth behavior are discussed in terms of the involved surface and interface free energies.
Substrate Dependent Bonding of Chemisorbed 1,1'-Biphenyl-4,4'-Dimethanethiol
Authors: Caruso A.N. , Rajesekaran R. , Redepenning J. , Losovyj Ya.B. , Dowben P. A.
Published: June 2019

We compare the adsorption of 1,1'-biphenyl-4,4'-dimethanethiol (BPDMT) on gold and cobalt surfaces. The molecular orbitals, identified from combined photoemission and inverse photoemission studies, exhibit shifts in binding energies with different deposition methods and substrates. These shifts indicate that this potential molecular dielectric exhibits stronger bonding to cobalt surfaces than gold surfaces.
Self-Assembled Organic-Inorganic Silica Hybrids From Polyviologens
Authors: Gray Graham M. , Hay John N.
Published: June 2019

Polyviologens (bipyridinium polymers) are effective catalysts for the polymerisation of silicic acid at room temperature and neutral pH. Variations in the alkylene spacer length and the associated counter ion appear to have little, if any, effect upon the rate of polymerisation as measured by the colorimetric molybdosilicate method. The resultant hybrid materials are amorphous aggregates of roughly spherical particles typically less than 0.1μm in diameter.
Towards Monodomains of Self-Organized Comb-Shaped Polymeric Supramolecules
Authors: Ikkala Olli , Brinke Gerrit ten
Published: June 2019

We have previously shown that hierarchical self-organization is achieved upon physically bonding amphiphilic molecules to diblock copolymers. Here we discuss the effect of imposed shear flow to achieve overall alignment of the locally self-organized structures. We will first present shear aligned polystyrene-block-poly(4-vinyl pyridine) diblock copolymers (PS-b-P4VP), where pentadecyl phenol (PDP) has been hydrogen bonded to the pyridines. Depending on the selected molecular weights, eg. hexagonal arrangement of PS cylinders in the lamellar matrix of P4VP(PDP) can be obtained with high overall order of both structures. This is a template to obtain discrete PS nanorods, which have P4VP corona once the PDP molecules have been cleaved off by a solvent treatment. Selecting a relatively high molecular weight PS block and a short P4VP block leads to mesoporous materials with emptied cylinders with P4VP brushes at the walls. The glassy state of the PS matrix prevents the pores from collapsing. The pyridine groups of PS-b-P4VP can be protonated using eg. toluene sulphonic acid and the resulting polymeric salt has been complexed using PDP. The weight fractions have been selected so that the polyelectrolyte/amphiphile complex self-organizes into cylindrical domains with hexagonal packing. Shear alignment leads to high overall order. SAXS in combination with structural models suggests that within the cylinders there are parallel self-organized layers. The conductivity is anisotropic. We will also discuss dielectric reflectors based on self-organized block polyelectrolytes consisting PS-b-P4VP where DBSA has been complexed to P4VP. In this case, plasticization due to the oligomeric side chains promotes a facile structure formation at long periodicities in comparison to concepts based on eg. blends of high molecular weight polymers and block copolymers. Finally, plasticized comb-shaped supramolecules based on rigid conjugated poly(p-pyridine) are discussed. Even gentle shearing leads to highly aligned lamellar structures, which show efficient polarized photoluminescence.
The Preparation of Large Scale Monolayers of Gold Nanoparticles on Modified Silicon Substrates using a Controlled Pulling Method
Authors: Tilley Richard , Saito Satoshi , Mastui Isao
Published: June 2019

The preparation of large scale monolayers of dodecanethiol coated nanoparticles on modified silicon substrates for use in storage media is reported. The formation of nanoparticle monolayers was accomplished by vertically pulling various modified silicon substrates at controlled speeds from nanoparticle solutions. The silicon substrates investigated had silanol and hydrogen terminated surfaces, surfaces chemically modified by (CH3) 3SiNHSi(CH3) 3 and (CH3O) 3Si(CH2)2(CF2) 7CF3 and a silicon substrate coated with amorphous carbon. All of these substrates have different surface polarities and a wide variation in monolayer coverage was obtained. The effect of the substrate pulling speed and solvent were also investigated.
Effects of Laterally and Vertically Neighboring Quantum Dots on Formation of a New Quantum Dot
Authors: Yang Bo , Tewary Vinod K.
Published: June 2019

We apply the elastic-energy-release rate (EERR) to identify the favored location of quantum dot (QD) formation in the presence of a laterally or vertically neighboring grown QD on a linear anisotropic elastic substrate. The EERR is defined as the relaxation energy per unit volume of QD growth. Numerical results for InAs QDs on a GaAs(001) substrate are reported. It is shown that the presence of a laterally neighboring QD inhibits the driving force for the formation of a new QD. In contrast, the presence of a buried (vertically) neighboring QD enhances the driving force for the formation of a new QD at its favorable location.

(Publication of the National Institute of Standards and Technology, an agency of the US Government; not subject to copyright.)
Structure of Self-assembled Magnetic FePtCu Nanoparticles Arrays
Authors: Sun Xiangcheng , Harrell J.W. , Nikles D. E. , Sun K. , Wang L. M. , Li J. , Wang Z. L.
Published: June 2019

In this study, a series of FexPtyCu100-x-y nanoparticles were chemically synthesized by solution-phase reduction of platinum and copper reagents and thermal decomposition of iron pentacarbonyl in the presence of stabilizers oleic acid and oleyl amine. As-prepared particles had a chemically disordered face-centered cubic (fcc) lattice with an average diameter of 3.5 nm. The particle size, and the corresponding size distribution were controlled by varying the organic surfactant (oleic acids, etc.), its concentration, and the reaction temperature. These particles were well dispersed in hydrocarbon solvents and self-assembled into two or three dimensions particles arrays with a variety of closepacking arrangements. Domain of monolayers, bilayers and multilayers of particles arrays were frequently detected in TEM specimens. Both cubic close-packed (ccp) and honeycomb arrays were also uniquely observed. It was also demonstrated that the controlled organic surfactant layer (organic capping) play a crucial role in determining assembly dimensions and symmetry as well as particle packing arrays.
Surface patterns of tetragonal phase FePt thin films from Pt@Fe2O3 core-shell nanoparticles using combined Langmuir-Blodgett and soft lithographic techniques
Authors: Guo Qijie , Teng Xiaowei , Yang Hong
Published: June 2019

We present the fabrication of micron-sized patterns of FePt thin films from Pt@Fe2O3 coreshell nanoparticles. In a typical procedure, Pt@Fe2O3 core-shell nanoparticles were spread and formed a Langmuir film using water as the subphase. This film was lifted onto polydimethylsiloxane (PDMS) stamps with micron-sized patterns of lines, dots and wells, and transferred onto silicon wafers using microcontact printing (ν-CP). The patterns of Pt@Fe2O3 core-shell nanoparticles were converted into face-centered tetragonal phase FePt alloy at enhanced temperatures in the presence of 5% hydrogen. Scanning electron microscopy (SEM), atomic force microscopy (AFM), powder X-ray diffraction (PXRD) and superconducting quantum interference device (SQUID) magnetometer were used to characterize the patterns and the properties of the final FePt alloy films.
Electro-optical and Morphological Properties of Bragg Transmission Gratings Written In Holographic Polymer Dispersed Liquid Crystals by Thiol-ene Photopolymerization
Authors: Natarajan L. V. , Tondiglia V. P. , Sutherland R. L. , Tomlin D. , Bunning T. J.
Published: June 2019

Holographic Bragg transmission gratings formed via the anisotropic phase separation of nanosized LC droplets (H-PDLC) were fabricated using thiol-ene photopolymerization. Using coherent UV laser light and a single prism, electrically switchable transmission gratings in the Bragg regime were written. The performance of the thiol-ene-based gratings were compared with those of multifunctional acrylate-based gratings written under similar conditions. Optical and electro-optical measurements suggest that thiol-ene polymers offer promise as hosts for improved H-PDLC performance. Interesting differences in the diffraction efficiencies for s– and p-probe beams are noted for the two matrices. Morphology studies by TEM and SEM exhibit striking differences in droplet shape and uniformity. These differences are speculated to be due to differences in polymer MW growth due to the step-growth propagation mechanism for thiol-enes as compared to the chain-growth propagation mechanism in multifunctional acrylates. The response times of the thiol-ene gratings were ten times slower than those of acrylates.
Magnetic Properties of La1-xSrxMnO3 Nanocrystals Embedded in A Mesoporous Silicate
Authors: Kohiki Shigemi , Ishida Yoshihisa , Nogami Sinichiro , Shimooka Hirokazu , Tajiri Takayuki , Deguchi Hiroyuki , Mitome Masanori , Oku Masaoki
Published: June 2019

We have prepared the diluted assemblies of La1-xSrxMnO3 (x = 0, 0.05, 0.15 and 0.175) nanocrystals (ø ∼ 2∼3 nm) embedded in amorphous SiO2 to clarify the nano-magnetism of both the antiferromagnetic and ferromagnetic La1-xSrxMnO3. All the samples of x = 0, 0.05, 0.15, and 0.175 exhibited superparamagnetism with the blocking temperature of ∼40 K. Except the hump at ∼40 K, the antiferromagnetic x = 0 and 0.05 samples showed simply paramagnetic-like characteristics in both the temperature dependent dc and ac susceptibilities. The ferromagnetic x = 0.15 and 0.175 samples demonstrated complicated characteristics in the temperature dependent susceptibilities. The samples indicated antiferromagnetic and ferromagnetic behavior above ∼50 K and ∼100 K, respectively. The field dependent magnetization is consistent with the predictions of systems having randomly oriented and noninteracting fine particles (ø ∼2∼3 nm). For the ferromagnetic La1-xSrxMnO3 nanocrystals, the antiferromagnetism at crystal surfaces suppressed largely the ferromagnetism in bulk.
Normal Incidence Intersubband Transitions in InGaAs/GaAs Quantum Dots With Non-monotonic Shift
Authors: Hussein M. L. , Ma W. Q. , Salamo G.J.
Published: June 2019

Multiple layers of self assembled In0.3Ga0.7As quantum dots of different size were grown on GaAs (100) using molecular beam epitaxy. Fourier-transform infrared spectroscopy shows absorption in the long-wavelength infrared region (8–10 νm) under normal incidence. The absorbance peak shift with dot size was investigated and revealed non-monotonic behavior of intersubband transitions. The optical absorption coefficient was calculated to be in order of 3.8×103 cm-2.
Synthesis and Electronic Properties of Single-Crystalline Indium Nitride Nanowires
Authors: Tang Tao , Han Song , Jin Wu , Liu Xiaolei , Li Chao , Zhang Daihua , Zhou Chongwu
Published: June 2019

InN nanowires were synthesized and characterized using a variety of techniques. A two-zone chemical vapor deposition technique was employed to operate the vapor generation and the nanowire growth at differential temperatures, leading to high-quality products and growth rates as high as 4–10 μm/hour. The as-grown nanowires showed highly single-crystalline structures and precisely controlled diameters by using monodispersed gold clusters as the catalyst. Devices consisting of single nanowires have been fabricated to explore their electronic transport properties. The temperature dependence of the conductance revealed thermal emission as the dominating transport mechanism.
Large Scale Production of Carbon Nanotube Transistors: A Generic Platform for Chemical Sensors
Authors: Gabriel Jean-Christophe P.
Published: June 2019

We report our work on the fabrication of nanotube-based field effect transistors (NTFET). Nanotubes were grown by chemical vapor deposition using various approaches, including a new formulation of nanotube growth catalysts that were directly patterned using UV lithography. We also report NTFETs based on randomly oriented nanotube networks that have a modulation of one. Finally, we report that a systematical and statistical characterization of millions of devices has led to the development of a robust process that may be useful in large scale production of reproducible, nanotube-based FETs, which, in turn, can be used as a generic platform for chemical sensors.
Quantum Dot-Organic Oligomer Nanostructures: Electronic Excitation Migration and Optical Memory Design
Authors: Javier Artjay , Yun C. Steven , Strouse Geoffrey F.
Published: June 2019

Energy, in the form of an electronic excitation, can be directed within an inorganicorganic composite of semiconductor quantum dots and organic oligomers by manipulating the structural conformations of the organic component or the size of the inorganic component. Continuous-wave and time-resolved photoluminescence studies indicate that weak electromagnetic resonant coupling between discrete intra-chain and inter-chain excitations of the oligomer and quantum dot excitations can be used to produce a potentially useful optical display material. Thin film blends demonstrate a thermally-induced luminescence-detected chainmelting phenomenon that has the potential for writable optical memory.
Synthesis of Gold Nanoshells and Their Use in Sensing Applications
Authors: Sun Yugang , Xia Younan
Published: June 2019

A general approach involved template-engaged, galvanic replacement reactions has been developed to prepare metallic nanostructures with hollow interiors by reacting solutions of appropriate salts with metallic solid nanoparticles. The reaction between aqueous chloroauric acid and silver nanoparticles was used as a typical example to demonstrate the synthesis of gold nanoshells. The morphology, void space, and wall thickness of these hollow structures were all determined by the silver templates, which were completely converted into soluble species during the replacement reaction. The extinction peaks of these gold nanoshells were considerably redshifted as compared to solid gold colloids having approximately the same dimensions. In addition, the surface plasmon resonance of gold nanoshells exhibited a much more sensitive response toward environmental changes even when compared with solid colloids with a mean size much smaller than that of gold nanoshells.
Preparation of Inks with Monodisperse Colloidal Silica and their Self-Assembly in a Ink-Jet Printed Droplet
Authors: Ko Hwa-Young , Shin Hyunjung , Moon Jooho
Published: June 2019

Semispherical self assemblies of colloids have been fabricated on a substrate using inkjet printing with an ink of submicron-sized monodisperse silica particles. Colloidal silica has been prepared by Stöber process. The shape and monodispersity of the synthesized colloidal particles were observed by scanning electron microscopy (SEM) and laser light scattering particle analyzer. Simple test patterns on various substrates (silicon wafer, Cu foil, and Mylar film) were printed with commercial HP printer. It was found that the uniformity and spatial extent of the self-assembled colloidal silica within a dot were significantly influenced by the contact angle between ink and substrates. Ink droplets printed on the hydrophobic Mylar film maintain a higher contact angle as compared to the hydrophilic substrates such as Si wafer. Slower evaporation and high capillary stress exerted on the ink droplet allow hemispherical colloidal aggregates with an ordered internal structure on Mylar film.
Selfassembling around Templates – Creating Nano Dots and Pits for Chemical Sensing –
Authors: Dickert Franz L. , Lieberzeit Peter A. , Hayden Oliver , Bindeus Roland , Mann Karl-Jürgen , Haderspöck Claudia
Published: June 2019

Nano- and micro-structured materials are a powerful tool in the development of chemical sensors. Surface imprinting of different biogenous species into pre-polymerized, highly crosslinked reaction mixtures (polyurethanes, polystyrenes, sol-gel materials etc.) yields selfassembled structures that are optimized to re-incorporate the template particle. Surface properties are tuned both on the micrometer as well as the molecular scale, as selectivity studies suggest the formation of strongly adapted interaction networks between the polymer and the species used for imprinting.
Catalytic Growth of Semiconducting ZnO Nanowires by Reactive Evaporation Process
Authors: Park Joodong , Choi Han-Ho , Singh Rajiv K.
Published: June 2019

Reactive evaporation process was introduced as a simple technique for the fabrication of aligned ZnO nanowires on a Si (100) surface. Single crystalline ZnO nanowire arrays were successfully synthesized on Au coated Si substrates via a VLS growth mechanism. The diameter of ZnO nanowires were observed to vary from 40 nm to 150 nm and the ratio of length to diameter was observed to be larger than 30. The diameter of ZnO nanowires was controlled by changing the processing temperature and by the thickness of Au catalyst film. Green emission induced from singly ionized oxygen vacancies was generated from ZnO nanowires with the excitonic emission in UV range. Higher intensity of the green emission was observed in thinner nanowires, which is attributed to their higher surface-to-volume ratio. Aligned structure formation and size control of ZnO nanowires could provide the potential for various nano-scale device applications.
Growth and Characterization of Cobalt-filled Carbon Nanotubes Prepared by a Simple Catalytic Method
Authors: Ma Xicheng , Cai Yuanhua , Li Xia , Lun Ning , Wen Shulin
Published: June 2019

High-quality cobalt-filled carbon nanotubes (CNTs) were prepared in situ in the decomposition of benzene over Co/silica-gel nano-scale catalysts. Unlike the previous reports, the catalysts needn't be pre-reduced prior to the forming of Co-filled CNTs, thus the advantage of this method is that Co-filled CNTs can be produced in one step, at a relatively low cost. Transmission electron microscopy (TEM) investigation showed that the products contained abundance of CNTs and most of them were filled with metallic nanoparticles or nanorods. High-resolution TEM (HRTEM), selected area electron diffraction (SAED) patterns and energy dispersive X-ray spectroscopy (EDS) confirmed the presence of Co inside the nanotubes. The encapsulated Co was further identified always as high temperature alpha-Co phase with fcc structure, which frequently consists of twinned boundaries and stacking faults. Based on the experimental results, a possible growth mechanism of the Co-filled CNTs was proposed.
Mirrorless Lasing in Liquid Crystalline Photonic Bandgap Materials
Authors: Cao Wenyi , Muñoz Antonio , Palffy-Muhoray Peter , Taheri Bahman
Published: June 2019

Liquid crystals (LC) are promising photonic bandgap (PBG) materials. Certain LC phases have spatially modulated ground states and effectively form self-assembled PBG structures. These structures can also be made permanent by photopolymerization. Typically, LCs respond readily to applied fields, enabling modulation and switching of the bandgap. Since classical light propagation is forbidden, fluorescent emission in the band gap can lead to population inversion and stimulated emission at the band edges. Mirrorless lasing experiments provide an effective probe of the bandgap. We discuss the underlying physics, and present the results of mirrorless lasing in a variety of cholesteric LC materials, including recent results of photon counting statistics and 3-D lasing in the cholesteric blue phase.
Nano-wire field-effect transistor in etched ion tracks of flexible polymer foils
Authors: Chen Jie , Klaumünzer S. , Könenkamp R.
Published: June 2019

We have used irradiation by fast heavy ions and subsequent etching to prepare cylindrical channels in polymer/metal/polymer stacks. These channels were subsequently filled with insulator and semiconductor material, and then provided with suitable metallic contacts, to obtain a vertical field-effect transistor device. Preparation and first electronic results on this new device are reported. Typically 107 to 108 transistors per cm2 with a diameter of ∼100 nm can be obtained in this technique. The fabrication does not require lithography on the scale of a single transistor, and is suitable for large-area applications. The embedding in a soft polymer matrix results in a robust arrangement, whose electronic characteristics are largely insensitive to mechanical stress. At the present stage of development the smallest dimension of a single transistor grown by this technique is ∼50 nm. Further reduction of the device dimensions appears possible and, with it, observation of single electron effects in these devices.
Formation ofWell-defined Nanocolumns by Ion Tracking Lithography
Authors: Felter T.E. , Musket R. G. , Macaulay J. , Contolini R. J. , Searson P. C.
Published: June 2019

Low dimensional systems on the nanometer scale afford a wealth of interesting possibilities including highly anisotropic behavior and quantum effects. Nanocolumns permit electrical and mechanical contact, yet benefit from two confined dimensions. This confinement leads to new optical, mechanical, electrical, chemical, and magnetic properties. We construct nanocolumn arrays with precise definition and independent control of diameter, length, orientation, areal density and composition so that geometry can be directly correlated to the quantum physical property of interest. The precision and control are products of the fabrication technique that we use. The process starts with an ion of sufficient energy to “track” a dielectric such as a film applied uniformly onto a substrate. The energy loss of the ion alters chemical bonding in the dielectric along the ion's straight trajectory. A suitable etchant quickly dissolves the latent tracks leaving high aspect ratio holes of small diameter (∼10nm) penetrating a film as thick as several microns. These small holes are interesting and useful in their own right and can be made to any desired size by continuing the etching process. Moreover, they serve as molds for electrochemical filling. After this electrodeposition, the mold material can be removed leaving the columns firmly attached to the substrate at the desired orientation. A variety of structures can be envisioned with these techniques. As examples, we have created arrays of Ni and of Pt nanocolumns (∼ 60 nm diameter and ∼ 600 nm long) oriented perpendicular to the substrate. The high aspect ratio and small diameter of the columns enables easy observation of quantum behavior, namely efficient electron field emission and Fowler Nordheim behavior.
Effect of Annealing on the Characteristics of Silicon Implanted Nano/trap Crystal Memories
Authors: Kalkur T.S. , Cramer Nick , Philofsky Elliott , Kammerdiner Lee
Published: June 2019

In this paper we are presenting the results of silicon nano-trap memory fabricated by implanting high dose silicon into gate oxide of thickness 30 nm. The gate oxide was grown by dry oxidation. Capacitance versus voltage characteristics of MOS (metal oxide silicon) structures with silicon implanted samples annealed in nitrogen environment at a temperature of 950 °C show a memory window depending on the applied DC bias voltage. A memory window of 3V was obtained for an applied bias voltage of ± 10V. Annealing of the MOS structures in a furnace at a temperature of 800 °C for 30 minutes in oxygen resulted in complete loss or collapse of the memory window. Annealing the samples rapid thermally in oxygen environment at 800 oC for 30 seconds, resulted in a memory window of about 2 Volts for an applied voltage of ± 14V.
Energy transport in metal nanoparticle plasmon waveguides
Authors: Maier Stefan A. , Kik Pieter G. , Sweatlock Luke A. , Atwater Harry A. , Penninkhof J. J. , Polman A. , Meltzer Sheffer , Harel Elad , Requicha Ari A.G. , Koel Bruce E.
Published: June 2019

We investigate the optical properties of arrays of closely spaced metal nanoparticles in view of their potential to guide electromagnetic energy with a lateral mode confinement below the diffraction limit of light. Finite-difference time-domain simulations of short arrays of noble metal nanospheres show that electromagnetic pulses at optical frequencies can propagate along the arrays due to near-field interactions between plasmon-polariton modes of adjacent nanoparticles. Near-field microscopy enables the study of energy transport in these plasmon waveguides and shows experimental evidence for energy propagation over a distance of 0.5 νm for plasmon waveguides consisting of spheroidal silver particles fabricated using electron beam lithography.
Ion Beam Synthesis and Optical Properties of Zn and Zno Nanocrystals in Sio2 and Caf2 Substrates
Authors: Liu Y.C. , Mu R. , Xu H.Y. , Lu Y.M. , Shen D.Z. , Fan X.W. , Henderson D. O. , White C.W.
Published: June 2019

Ion implantation was used to inject zinc ions into crystalline CaF2 and amorphous SiO2 substrates. Zn or ZnO nanoparticles were formed after annealing in a reducing (4% H2 + 96%Ar) or an oxidizing (10%O2 + 90% Ar ) atmosphere, respectively. When the sample was annealed in a reducing atmosphere, the absorption band at ∼ 5.3 eV for zinc implanted into SiO2 was attributed to zinc metal colloids. The absorption peak observed in the 4.3 – 4.7 eV region was due to the formation of ZnO nanocrystals, after the sample was annealed in an oxidizing environment. Both X-ray diffraction (XRD) and X-ray photospectroscopy (XPS) were used to confirm ZnO nanocrystal formation. For zinc implanted into CaF2, the as-formed ZnO nanocrystals were aligned with their [002] axes parallel to the [111] axis of the CaF2. Photoluminescence (PL) spectra showed UV and green emission from the zinc-implanted silica samples annealed under an oxygen atmosphere; however, no green emission was observed for ZnO formed in a CaF2 substrate. An additional emission was observed at ∼ 420 nm which might be due to F centers in CaF2 created by ion beam damage.
A Comparative Study on the Differences in the Evolutions of Thin Film Morphologies of Co-Al Binary System: Molecular Dynamics Study
Authors: Kim Sang-Pil , Lee Seung-Cheol , Lee Kwang-Ryeol , Lee Kyu-Hwan , Chung Yong-Chae
Published: June 2019

The morphology evolution of thin films was studied by molecular dynamics simulation. In this simulation four deposition and substrate elements combinations were used: Al on Al(001), Al on Co(001), Co on Co(001), Co on Al(001). The Al thin film was always grown by layer-bylayer mode regardless of substrates used. On the other hand, thin films formed by Co deposition depended on substrates used.While Co thin films on the Co substrates were grown by the island mode, a 3 monolayer (ML) thickness of CoAl surface compound was initially formed on Al substrate, before pure Co thin film growth occurred. In addition to the study on morphologies, the degrees of mixing of atoms in the interface were studied quantitatively. No surface mixing and a sharp interface were observed when Co was used as a substrate regardless of deposited atoms. On the contrary, a large amount of surface mixing or compound formation was observed when Al was used as a substrate.