bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimization of Biosensing Microcantilever Devices
Authors: Zhang Xuan , Yang Mo , Ozkan Cengiz S.
Published: June 2019

Optimization of piezoresistive microcantilevers for biosensing applications has been studied using finite element analysis. Models have been described for predicting the static behavior of cantilevers with elastic and piezoresistive layers for analyte-receptor binding. The high-sensitivity cantilevers can be used to detect changes in surface stress due to the binding and hybridization of biomolecules. Chemo-mechanical binding forces have been analyzed to understand the issues of saturation over the cantilever surface. The introduction of stress concentration regions during cantilever fabrication has also been discussed which enhances the detection sensitivity through increased surface stress.
Micromachined magnetic ultrasound transducer in post-processed CMOS
Authors: Viswanathan Rohit , Jankowski Nicholas , Lye Whye-Kei , Dufrenoy Gregory Petit , Harrison Michael J. , Hossack John A. , Blalock Travis N. , Reed Michael L.
Published: June 2019

This paper presents a novel MEMS Ultrasound Electro-Magnetic transducer. With advances in CMOS MEMS fabrication processes [2] we can explore and build miniature devices which could only be designed till a few years back. As our understanding in MEMS evolved, we explored the use of Electro-Magnetism as an effective way to produce ultrasound waves. Thus we can use a highly efficient and inexpensive fabrication technique to fabricate transducers with a fairly good capability to produce and detect ultrasound waves.

The transducer consists of 2 concentric spiral coils, one carrying an AC current (which is tethered to the substrate at one end and free to vibrate at the other, also called the “Flapper”) and other coil carrying DC current (enveloping the inner coil, fixed and called “Stator”). The force arising from the interaction of the coupled magnetic fields induces a mechanical vibration of the flapper structure. The transducer serves as an actuator or a sensor (where we simply apply a pressure force on the flapper and note the frequency response of the flapper).

The current mode helps to associate the transducer with front-end electronics, which is one of the most critical components of ultrasound imaging systems

Advantages of this approach as compared to traditional PZT ceramics and capacitative micromachined devices are explored.

Different dimensions of the transducer to accommodate the limitations in the processes are explored and a comparison of the parameters is presented.

Potential uses and future challenges are discussed.
Combinatorial Peptide Libraries for Selecting Inorganic-Binding Proteins: A Step in Molecular Biomimetics
Authors: Tamerler C. , Dinçer S. , Heidel D. , Karagûler N. , Sarikaya M.
Published: June 2019

Proteins, one of the building blocks in organisms, not only control the assembly in biological systems but also provide most of their complex functions. It may be possible to assemble materials for practical technological applications utilizing the unique advantages provided by proteins. Here we discuss molecular biomimetic pathways in the quest for imitating biology at the molecular scale via protein engineering. We use combinatorial biology protocols to select short polypeptides that have affinity to inorganic materials and use them in assembling novel hybrid materials. We give an overview of some of the recent developments of molecular engineering towards this goal. Inorganic surface specific proteins were identified by using cell surface and phage display technologies. Examples of metal and metal oxide specific polypeptides were represented with an emphasis on certain level of specificities. The recognition and self assembling characteristics of these inorganic-binding proteins would be employed in develeopment of hybrid multifunctional materials for novel bio- and nano-technological applications.
Modelling Carbon Nanotube Based Bio-Nano Systems: A Molecular Dynamics Study
Authors: Kong Yong , Cui Daxiang , Ozkan Cengiz S. , Gao Huajian
Published: June 2019

Molecular dynamics simulations were performed to study dynamics of carbon nanotube (CNT) interacting with biological molecules (DNA oligonucleotide and protein polypeptide) in an aqueous environment. Our results showed that an oligonucleotide or a polypeptide could be spontaneously inserted into a CNT, provided that the tube size is large enough and the oligonucleotide/polypeptide is appropriately aligned with CNT. The van der Waals and hydrophobic forces were found to be important for the insertion process, with the former playing a more dominant role in the CNT-oligonucleotide and CNT-polypeptide interaction. We discussed temperature effect on the filling process and found that higher temperature can accelerate encapsulation of biological molecules. Our study has general implications on filling nanoporous materials with water solutes of molecular cluster or nanoparticles. The encapsulated CNT-oligonucleotide/polypeptide or other CNT based bio-nano-complex can be further exploited for applications such as molecular electronics, sensors, electronic DNA sequencing, and nanotechnology of gene/drug delivery systems.
Bio-Inspired Morphogens and Biomimetic Biomaterials for Regenerative Medicine
Authors: Reddi A. Hari
Published: June 2019

Regenerative medicine is the science of design and manufacture of parts for functional restoration of damaged tissues due to cancer, disease and trauma. Morphogenesis is the developmental cascade of pattern formation, body plan establishment and differentiation of tissues culminating in adult form. Regeneration in general, recapitulates in parts, embryonic morphogenesis. Thus, the principles of morphogenesis can be applied to tissue engineering for regenerative medicine and surgery. The threekey ingredients for tissue engineering and regenerative medicine are inductive morphogens, responding stem cells, and extracellular matrix materials. Therefore bioactive morphogens can be integrated into materials for functional restoration by tissue engineering. A morphogen is a morphogenetic protein signal that acts on responding stem cells. Bone morphogenesis is induced by bone morphogenetic proteins (BMPs). BMPs play a role in pattern formation, cell differentiation, maintenance and regeneration of tissues. BMPs are pleiotropic and act on chemotaxis, mitosis and differentiation of progenitor stem cells. There are nearly twenty BMPs in the human genome. BMPs have actions beyond bone in development of teeth, heart, kidney, eye, skin, and brain. Thus, BMPs may be called body morphogenetic proteins. Stem cells are primordial cells with unlimited replicative potential and can be programmed by morphogens such as BMPs. Extracellular matrix is the native scaffolding material that can be used to deliver morphogens such as BMPs for tissue engineering of bone. Biomimetic materials are typically synthetic, polymeric structures that mimic extracellular matrix scaffolding by presenting the cellular binding sites found within collagens, fibronectin, proteoglycans and glycoproteins. Materials that mimic extracellular matrix scaffolding such as BMPs bind to collagens I&IV, heparan sulfate and heparin. BMPs bound to collagen acts as a composite biomaterial to initiate bone formation and the shape can be molded by an appropriate template. In addition to including BMPs in a carrier matrix, the geometry of the carrier matrix is critical for optimal tissue engineering. For example: collagen particles smaller than 44μm are feeble in bone induction compared to the coarse (420μm) particles. Gene therapy approaches using genes for morphogenesis such as BMPs allows a sustained, prolonged secretion of gene products. Thus, morphogens integrated into biomaterials may be useful in regenerative medicine.
Carbon Nanofiber Surface Roughness Increases Osteoblast Adhesion
Authors: Ellison Karen S. , Price Rachel L. , Haberstroh Karen M. , Webster Thomas J.
Published: June 2019

The present study demonstrated for the first time desirable cytocompatibility properties of carbon nanofibers pertinent for bone prosthetic applications. Specifically, osteoblast (boneforming cells), fibroblast (cells contributing to callus formation and fibrous encapsulation events that result in implant loosening), chondrocyte (cartilage-forming cells), and smooth muscle cell (for comparison purposes) adhesion were determined on carbon nanofibers in the present in vitro study. Results provided evidence that nanometer dimension carbon fibers promoted select osteoblast adhesion, in contrast to the performance of conventional carbon fibers. Moreover, adhesion of other cells was not influenced by carbon fiber dimensions. To determine properties that selectively enhanced osteoblast adhesion, similar cell adhesion assays were performed on poly-lactic-co-glycolic (PLGA) casts of carbon fiber compacts previously tested. Compared to PLGA casts of conventional carbon fibers, results provided the first evidence of enhanced select osteoblast adhesion on PLGA casts of nanophase carbon fibers. The summation of these results demonstrate that due to a high degree of nanometer surface roughness, carbon fibers and PLGA with nanometer surface dimensions may be optimal materials to selectively increase osteoblast adhesion necessary for successful orthopedic implant applications.
Development of Elastic Protein-based Polymers as Materials for Acoustic Absorption
Authors: Urry Dan W. , Xu J. , Wang Weijun , Hayes Larry , Prochazka Frederic , Parker Timothy M.
Published: June 2019

Elastic protein-based polymers comprised of repeating pentapeptide sequences, (GXGXP)n, exhibit mechanical resonances that have been observed to date with frequency maxima near 5 MHz and 3 kHz. Because the 3 kHz resonance is in the middle of the acoustic frequency range, the purpose here is to substantiate the relevance of the 3 kHz resonance to acoustic absorption and to demonstrate means of improving mechanical properties for the sound absorption application. Previously reported loss factor data in the 100 Hz to 10 kHz range is substantiated by relevant but distinctly different measurements of loss shear modulus and loss permittivity. Furthermore cross-linking approaches are reported that result in increased elastic moduli by an order of magnitude to 4 × 106 Pa at 20% strain and increased break stress by two orders of magnitude to 1.3 × 107 Pa while exhibiting break stain values of several hundred per cent.
Photoelectric Response of Self Assembled Films of Bacterio-Rhodopsin Purple Membrane Integrated on Silicon
Authors: Ricceri D. , Scicolone G. , Di Marco O. , Conoci S. , Pignataro B. , Coffa S.
Published: June 2019

Bacterio-rhodopsin purple membrane (PM) thin films have been prepared by selfassembling (SA) technique. Morphological properties of the layers were inspected by Scanning Electron Microscopy (SEM) and Scanning Force Microscopy (SFM) highlighting the presence of densely packed PM films. Reflectance Uv-vis spectra on these films revealed the typical bR absorption at 570 nm. By using a tungsten lamp illuminations (250-350 mW) chopped at 0.5Hz, photoelectric responses were detected. Differential (light-on and light-off) photocurrent signals of up to 1 μA/cm2 were obtained upon light exposure.
Lipid Membranes: Biological Inspiration for Micro and Nano Encapsulation Technologies, Especially Drug Delivery
Authors: Needham David
Published: June 2019

Our approach to biologically inspired materials and materials systems recognizes biology (at all scale levels) as a series ofproductsthat fulfill particular functions. It then links material composition and structure tofunctionthroughpropertiesand therefore attempts to bring mechanism to processes andfunctionsof biology. As an example of this approach we have focused on the lipid bilayer membranes of blood cells, like erythrocytes and neutrophils, as a bioinspired material system for drug delivery leading to the creation of waxy, nano capsules called liposomes that can be triggered to release their drug by hyperthermia. Thus, while Nature's encapsulation technology provides the inspiration, the mechanism of drug release is non-natural. The necessary design parameters for the required functions of drug encapsulation, i.e. drug retention, circulation half life, and eventual thermally-triggered drug release, were obtained through extensive experimentation and modeling of artificial lipid vesicles by us and others, with much of the mechanical and thermomechanical properties, molecular exchange, andin vitroperformance investigated by a direct micropipet manipulation technique. With respect to cancer chemotherapy, the unmet need for primary solid tumors is to deliver more drug to the tumor tissue thereby reducing the tumor size (debulking) while at the same time reducing toxic side effects. It is with these criteria in mind that we developed the temperature-triggered liposome for the treatment of solid tumors. This paper then, describes this liposome development and its performancein vivo, where, in some cases, the temperature-triggered release of drug directly in the blood stream and tumor resulted in complete tumor regression. What this example also shows is that through material property measurement and modeling, new insights into Nature's functions and designs can be discovered in areverse engineeringprocess from which new products can then beforward engineeredto solve engineering and product problems in health, technology, and the environment.
Direct Observation of Calcium Oxalate Monohydrate Precipitation at Phospholipid Monolayers with Brewster Angle Microscopy
Authors: Benítez Isa O. , Backov Rénal , Khan Saeed R. , Talham Daniel R.
Published: June 2019

The precipitation of calcium oxalate monohydrate (COM) at phospholipid monolayers has been observed in-situ by Brewster angle microscopy (BAM). A monolayer of 1,2-dipalmitoylsn-glycero-3-phosphocholine (DPPC) compressed to a LC state over a calcium oxalate subphase shows the growth of COM as very bright spots. The identity of COM was confirmed in a transferred film by scanning electron microscopy. BAM can also be used to determine where COM precipitates when the monolayer has two phases at equilibrium. Monolayers of DPPC and 1,2-dipalmitoyl-sn-glycero-3-[phospho-rac-(1-glycerol)] (DPPG) crystallize COM at phase boundaries. In addition, phase separated binary phospholipid mixtures of DPPC and 1,2-dimiristoyl-sn-glycero-3-phosphocholine (DMPC) have been prepared and monitored by BAM. The crystal growth in this case is confined to domains of DPPC due to its ability to form a liquid condensed phase.
Dextran Grafted Silicon Substrates: Preparation, Characterization And Biomedical Applications
Authors: Ombelli Michela , Eckmann David M. , Composto Russell J.
Published: June 2019

Biodevices used in the cardiovascular system suffer from well-known problems associated with surface-induced gas embolism and thrombosis. In order to improve the biocompatibility of these devices, biomimetic coatings show good promise. We recently synthesized a coating layer of dextran, a relatively simple and well characterized neutral polysaccharide, with the purpose of mimicking the cells' glycocalyx layer, that prevents non-specific cells-protein interactions. Systematic physical chemical characterization was performed on coatings obtained both from commonly used polydisperse dextrans and low-dispersity dextrans in the 1-100 kDalton molecular weight range.

We have combined standard surface analysis techniques, such as ellipsometry, contact angle measurements and AFM, with less traditional vibrational spectroscopy techniques in the characterization of our biomimetic coatings. FTIR, micro-FTIR and micro-Raman spectroscopies were utilized to correlate the conformational and molecular aspects of the grafted poly- and monodisperse dextran chains to their attractive biological properties.
Cytocompatibility and Material Properties of Poly-carbonate Urethane/Carbon Nanofiber Composites for Neural Applications
Authors: McKenzie Janice L. , Waid Michael C. , Shi Riyi , Webster Thomas J.
Published: June 2019

Carbon nanofibers possess excellent conductivity properties, which may be beneficial in the design of more effective neural prostheses, however, limited evidence on their cytocompatibility properties exists. The objective of the present in vitro study was to determine cytocompatibility and material properties of formulations containing carbon nanofibers to predict the gliotic scar tissue response. Poly-carbonate urethane was combined with carbon nanofibers in varying weight percentages to provide a supportive matrix with beneficial bulk electrical and mechanical properties. The substrates were tested for mechanical properties and conductivity. Astrocytes (glial scar tissue-forming cells) were seeded onto the substrates for adhesion. Results provided the first evidence that astrocytes preferentially adhered to the composite material that contained the lowest weight percentage of carbon nanofibers. Positive interactions with neurons, and, at the same time, limited astrocyte functions leading to decreased gliotic scar tissue formation are essential for increased neuronal implant efficacy.
Enhanced Osteoblast Adhesion on a Novel Hydroxyapatite Coating
Authors: Sato Michiko , Slamovich Elliott B. , Webster Thomas J.
Published: June 2019

Plasma spray deposition of hydroxyapatite (HA) onto a titanium implant involves high temperatures that may alter HA crystallinity and induce cracks in the coating. For this reason, the objective of this study was to design a novel HA coating material and method. Titanium was coated with HA, titania, and Poly (dl-lactic-glycolic acid) (PLGA) using sol-gel processing. The biocompatibility of the HA coating in the present study was compared to that of a plasmasprayed HA coating. Results of this study showed that osteoblast adhesion was promoted more in the HA coating proposed in this study than on the plasma-sprayed HA coating. In addition, hydrothermal treatment of the coating appeared to improve the biocompatibility of the HA coating. Since osteoblast adhesion is a necessary requirement for increased bonding of an implant to juxtaposed bone, these results support that hydrothermally sol-gel processed HA may be an optimal implant coating material and method.
Cytocompatibility of Carbon Nanofiber Materials for Neural Applications
Authors: McKenzie Janice L. , Waid Michael C. , Shi Riyi , Webster Thomas J.
Published: June 2019

Since the cytocompatibility of carbon nanofibers with respect to neural applications remains largely uninvestigated, the objective of the present in vitro study was to determine cytocompatibility properties of formulations containing carbon nanofibers. Carbon fiber substrates were prepared from four different types of carbon fibers, two with nanoscale diameters (nanophase, or less than or equal to 100 nm) and two with conventional diameters (or greater than 200 nm). Within these two categories, both a high and a low surface energy fiber were investigated and tested. Astrocytes (glial scar tissue-forming cells) and pheochromocytoma cells (PC-12; neuronal-like cells) were seeded separately onto the substrates. Results provided the first evidence that astrocytes preferentially adhered on the carbon fiber that had the largest diameter and the lowest surface energy. PC-12 cells exhibited the most neurites on the carbon fiber with nanodimensions and low surface energy. These results may indicate that PC-12 cells prefer nanoscale carbon fibers while astrocytes prefer conventional scale fibers. A composite was formed from poly-carbonate urethane and the 60 nm carbon fiber. Composite substrates were thus formed using different weight percentages of this fiber in the polymer matrix. Increased astrocyte adherence and PC-12 neurite density corresponded to decreasing amounts of the carbon nanofibers in the poly-carbonate urethane matrices. Controlling carbon fiber diameter may be an approach for increasing implant contact with neurons and decreasing scar tissue formation.
Monodisperse Mesoporous Microparticles Prepared by Evaporation-Induced Self Assembly Within Aerosols
Authors: Rathod Shailendra , Rama Rao G. V. , Andrzejewski Brett , López Gabriel P. , Ward Timothy L. , Brinker C. Jeffrey , Datye Abhaya K.
Published: June 2019

Evaporation induced self assembly (EISA) within microdroplets produced by a vibrating orifice aerosol generator (VOAG) has been used to produce monodisperse mesoporous silica particles. This process exploits the concentration of evaporating droplets to induce the organization of various amphiphilic molecules, effectively partitioning the silica precursor (TEOS) to the hydrophilic regions of the structure. Promotion of silica condensation, followed by removal of the surfactant, provides ordered spherical mesoporous particles. Using the VOAG we have produced highly monodisperse particles in the 5 to 10 μm diameter range. The cationic surfactant CTAB typically leads to hexagonal mesostructure with mean pore size of about 2 nm and specific surface area around 900 m2/g. We have also shown that the pore size in CTABtemplated particles can be increased to 3.8 nm by incorporating trimethylbenzene as a swelling agent. The TMB prefentially locates inside and swells the hydrophobic regions of the surfactant mesostructure. Pore size can also be varied by the choice of amphiphile. Hexagonally ordered particles have been produced using the nonionic surfactant Brij-58 and block copolymer F127. These powders possessed mean pore size 2.8 nm and 6.9 nm, respectively. The uptake of alkyl pyridinium chloride molecules have recently been measured, revealing an uptake capacity that is explained by surface adsorption (as opposed to simple pore infiltration). Kinetics of the uptake process are still be analyzed.
Novel Structure of Fullerenes and Endohedral Fullerenes
Authors: Wang Chun-Ru , Bai Chun-Li , Shinohara Hisanori
Published: June 2019

By using Krätschmer-Huffman synthesis and HPLC separation method we have isolated a series of novel fullerenes and endohedral fullerenes. Various spectroscopic techniques, e.g., MS, NMR, UV-vis-NIR, TEM, X-ray diffraction spectrometry etc., were adopted to characterize the isolated fullerenes. Several fullerenes were revealed to hold novel structures and electronic properties. For examples, C80(D5d) was isolated and characterized to have an ellipsoidal structure which is in fact one of the shortest SW-nanotubes; The isolation of Sc2@C66 breaks the well-known isolated-pentagon-rule (IPR) for the first time, which shows that the unconventional fullerenes may be dramatically stabilized through encaging metal atoms; Sc2C2@C84 is a novel molecular endohedral fullerene in which the Sc2C2 cluster rotates rapidly along the main C2 axis of C84(D2d). This fullerene is predicted to be a molecular magnet and may be used as nano-switcher in electronics.
Electrostatic Self-assembly of Metal and Semiconductor Nanoparticles in Polyelectrolytes: Assembly Dynamics, and Electrochemical Behavior
Authors: Markarian Mariezabel , Jaber Jad , Xin Yan , Ghannoum Sara , Halaoui Lara I.
Published: June 2019

The electrostatic self-assembly of hetero-nanostructured multilayers of metal and semiconductor nanoparticles in polyelectrolytes, the self-assembly dynamics, and electrochemistry at the assembled films is reported. Polyacrylate-capped Pt (=2.5 ± 0.6 nm) and Q-CdS nanoparticles (=3.6 ± 0.5 nm) were assembled in poly(diallyldimethylammonium chloride). The nanoparticle assembly dynamics is shown to be a function of the nanoparticle solution ionic strength and its composition. Electrochemical studies at Pt nanoparticles in PDDA reveal that charge hopping is feasible through the nanocomposite film, and that the catalytic activity of the nanoparticles is retained in the assembled structures.
Synthesis, Characterization, and Applications of Organic-Inorganic Hybrid Mesoporous Silica Prepared by Microwave Heating
Authors: Chung Jinseong , Whaseung Ahn Dongjun-Kim , Ahn Whaseung , Cheong Wonjo
Published: June 2019

Organic-inorganic hybrid mesoporous materials containing homogeneously distributed ethane group in silica framework were prepared using 1,2 bis(trimethoxysilyl) ethane (BTME) as a precursor and alkyltrimethylammonium chloride/bromide surfactant as a template. Characterization of the materials was performed using XRD, TEM/SEM, 29Si– / 13C– NMR, and N2-adsorption. Hydrothermal synthesis assisted by microwave heating produced a 1-3 micronsized hybrid material with spherical morphology in substantially reduced time. Bifunctional materials containing BTME and either aminopropyl- or mercaptopropy- group within the same silica framework were also prepared with or without the presence of a swelling agent, mesitylene. Mn-salen complex tethering on the hybrid material produced a catalyst with a somewhat enhanced performance in cyclohexene etherification using TBHP as an oxidant. Testing of the hybrid material as a reverse phase HPLC column material after C18 surface-functionalization demonstrated a promising result, which warrants further optimization of synthesis parameters.
Ordered Mesoporous Silica Films Synthesized from Vapor Phase
Authors: Tanaka Shunsuke , Nishiyama Norikazu , Egashira Yasuyuki , Oku Yoshiaki , Ueyama Korekazu
Published: June 2019

A novel synthesis route for mesostructured silica films is reported. Nano-phase transition from lamellar phase of surfactant to hexagonal phase of silica-surfactant nanocomposite was found under vapor infiltration. Vapor infiltration was performed using HCl as catalyst source and tetraethoxysilane (TEOS) as framework source. Highly ordered mesostructured silica films are obtained using alkyltrimethylammonium bromide CnTAB (the carbon number in the alkyl chain; n = 8, 10, 12, 14, 16, 18) as templating agent. The d values of the mesostructured silica films increase with increasing the length of the alkyl chain and are controllable by the synthetic temperature. The vapor infiltration synthesis is a simpler process compared to conventional sol-gel techniques and attractive for mass production of a variety of organic-inorganic composite materials and inorganic porous materials. This novel synthetic method provides opportunities for the creation of new materials technologies.
Continuous Flow Hyper-Polarized 129Xe-Mas Nmr Studies of Microporous Materials.
Authors: Nossov Andrei , Guenneau Flavien , Springuel-Huet Marie-Anne , Montouillout Valérie , Cognec Jean-Pierre , Knott Benno , Engelke Frank , Gédéon Antoine , Fernandez Christian
Published: June 2019

A Magic Angle Spinning (MAS) NMR probe has been designed allowing the in-situ measurements of NMR spectra of working catalyst. The probe was built following the original design of M. Hunger [Hunger, 1995 #2]. It allows the magic angle spinning of powder samples up to 3.5 kHz, under gas flowing conditions, and at temperatures up to 573K.
Formation Study of Nanocomposite Thin Films of Ferrite Dispersed in a Silica Matrix Prepared by sol-Gel Process
Authors: D. S. Mohallem Nelcy , Seara Luciana M.
Published: June 2019

Magnetic nanocomposite thin films formed by cobalt ferrite dispersed in silica matrix were prepared by sol-gel process using tetraethylorthosilicate (TEOS) as a precursor of silica, and metallic nitrates as precursors of the ferrite. The films were prepared with 5–50 wt. % ferrite contents and deposited on substrate using the dip-coating process. The films obtained were adherent, transparent, homogeneous and free of microcracks, with thickness between 30 and 500 nm. The films obtained presented crystalline CoFe2O4 phases dispersed in SiO2 amorphous matrix and saturation magnetization of approximately 9 emu/g considering the composite mass and 30 emu/g considering the ferrite mass.
Periodic Mesoporous SiCO Glasses with Cubic Symmetry Stable at 1000°C
Authors: Blum Raphaël , Goletto Valérie , Toury Bérangére , Babonneau Florence
Published: June 2019

A periodic mesoporous organosilica (PMO) with cubic Pm3n structure has been prepared from bis(trimethoxysilyl)ethane and cetytriethylammonium chloride. The sample has been heat treated under argon up to 1000°C, and the pyrolysis intermediates were analysed by X-ray diffraction using synchrotron radiation, multinuclear solid state NMR (29Si, 13C and 1H) and N2 adsorption-desorption experiments. The cubic Pm3n structure is retained after pyrolysis at 1000°C. The sample is a SiCO glass with mixed SiCxO4-x units (x = 0, 1, 2) and a very large surface area of 730 m2/g.
Micron to Sub-Micron Sized Highly Ordered Mesoporous Silica Particles Prepared Using a High Energy Ball Milling Process
Authors: Hampsey J. Eric , De Castro Claudio L. , McCaughey Byron F. , Wang Donghai , Mitchell Brian S. , Lu Yunfeng
Published: June 2019

Highly ordered mesoporous silica particles with sizes in the micron to sub-micron range are of great interest due to their applications as catalysts and filler materials. Currently, mesoporous silica particles are synthesized using large amounts of solvent, which is impractical for large scale-up in industry. This paper reports on a high-energy ball milling process that has been employed to create micron to sub-micron sized mesoporous silica particles starting from a silica xerogel prepared by a surfactant self-assembly sol-gel process. We have studied the effect of parameters such as milling media (e.g., zirconia, stainless steel, and steel centered nylon balls), milling time, the presence of surfactants during milling, particle size, and pore structure. Results from transmission electron microscopy (TEM), scanning electron microscopy (SEM), Xray diffraction (XRD), and nitrogen adsorption demonstrate the feasibility of producing large quantities of mesostructured particles by a simple milling process.
Synthesis of Phenol/Furfural Polymer Nanotubes
Authors: Uota Masafumi , Fujikawa Daisuke , Mohri Shinji , Kuroki Masako , Kaikake Katsuya , Yada Mitsunori , Machida Masato , Kijima Tsuyoshi
Published: June 2019

The first synthesis of phenol-furfural polymer nanotubes of 2–3nm hollow diameter is demonstrated as well as those with a hexagonal mesostructure. These nanopolymers were obtained by the templating method using a two-step reaction. At the first step, phenol and furfural were moderately reacted into cooligomers in the presence of NaOH. The resulting cooligomeric species were fully anionized and then reacted with additional phenol and alkyl trimetyl ammonium bromide at 40-80°C. The major phase for the 80°C product obtained at low concentration of surfactant was identified as nanotubular polymers of 1.9-3 nm inside and 6 nm outside diameters depending on the chain length of surfactant. In contrast, hexagonal mesostructured polymers characterized by a definite XRD peak occurred preferentially in the reaction using high surfactant-concentrations.
Silver-Polyimide Nanocomposite Membranes: Self-Generated Highly Reflective Flexible Mirrored Surfaces
Authors: Southward R. E. , Pevzner M. , Thompson D.W.
Published: June 2019

The synthesis of reflective silvered polyimide films by a single-stage auto-metallization process entailing the (hexafluoroacetylacetonato)silver(I) complex dissolved in solutions of poly(amic acid)s and polyimides formed from 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropanedianhydride (6FDA) and 2,2-bis(4-(4-aminophenoxy)hexafluoropropane (4-BDAF) is described. Heating cast silver(I)-poly(amic acid)/polyimide films effects silver(I) reduction and nanoaggregation giving reflective films for Ag concentrations from 6-10 wt %. A6% silver film gives specular reflectivies greater than 80%. Films prepared from the soluble fully imidized form of 6FDA/4-BDAF were less reflective.
Synthesis of Smart Mesoporous Materials
Authors: Rao G.V.Rama , Fu Qiang , Ista Linnea K. , Xu Huifang , Balamurugan S. , Sklar Larry A. , Ward Timothy L. , López Gabriel P.
Published: June 2019

This study details development of hybrid mesoporous materials in which molecular transport through mesopores can be precisely controlled and reversibly modulated. Mesoporous silica materials formed by surfactant templating were modified by surface initiated atom transfer radical polymerization of poly(N-isopropyl acrylamide) (PNIPAAm) a stimuli responsive polymer (SRP) within the porous network. Thermo gravimetric analysis and FTIR spectroscopy were used to confirm the presence of PNIPAAm on the silica surface. Nitrogen porosimetry, transmission electron microscopy and X-ray diffraction analyses confirmed that polymerization occurred uniformly within the porous network. Uptake and release of fluorescent dyes from the particles was monitored by spectrofluorimetry and scanning laser confocal microscopy. Results suggest that the presence of PNIPAAm, a SRP, in the porous network can be used to modulate the transport of aqueous solutes. At low temperature, (e.g., room temperature) the PNIPAAm is hydrated and extended and inhibits transport of analytes; at higher temperatures (e.g., 50°C) it is hydrophobic and is collapsed within the pore network, thus allowing solute diffusion into or out of the mesoporous silica. The transition form hydrophilic to hydrophobic state on polymer grafted mesoporous membranes was determined by contact angle measurements. This work has implications for the development of materials for the selective control of transport of molecular solutes in a variety of applications.
Dynamics and Rheology of GlassyMicellar Block Polyelectrolytes
Authors: Grandjean Julien , Mourchid Ahmed
Published: June 2019

Micellar solutions of polystyrene-poly(acrylic acid) block copolymers are studied in the jammed regime. Increasing attraction between soft spheres, both the rheology and dynamic light scattering show a re-entrant liquid to glass transition. The dynamics was also investigated at an attraction strength above the re-entrant transition line. Increasing concentration of sticky soft spheres in this region, the particle dynamics shows a remarkable extended logarithmic decay. The theoretical predictions of mode coupling theory agree well with our results.
Synthesis of Carbon Microcoils and Nanocoils on Various Substrates
Authors: Einarsson Erik , Jiao Jun , Prado Josie , Coia George M. , Love Logan
Published: June 2019

This research investigates the role of the substrate in the synthesis of carbon coils. Coils were produced on tungsten, titanium, and glassy carbon substrates via chemical vapor deposition (CVD) of acetylene (C2H2) on electrochemically deposited nickel at 800°C, but the growth varied among the samples. Coils were also produced on pure nickel by the same CVD method. Using tungsten as a substrate, carbon coils intermixed with thin carbon nanotubes were produced in high-yield from nickel particle clusters. On the titanium substrate, carbon coils were synthesized in small, high-yield patches with few co-produced carbon nanotubes. Synthesis from nickel clusters on glassy carbon usually resulted in amorphous carbon, but sparse, low-yield coil growth was observed. Carbon coils were also synthesized when pure nickel wire was used without a separate substrate. These results indicate the nickel catalyst controls the production of carbon coils, but the substrate has some effect on the yield. Carbon coils synthesized were either microcoils, which have diameters of a few microns, or nanocoils, which have diameters of one or two hundred nanometers.
Growth of Zinc Oxide Nanorods in Alocohol Solution
Authors: Yang Richard D. , Li Yuntao , Sue Hung-Jue
Published: June 2019

Zinc oxide (ZnO) nanorods have been grown by hydrolyzing Zn(OAc)2•2H2O in methanol solution. Nanoparticles in sizes ranging from 2 to 4 nm were first obtained at low concentration. The growth kinetics was monitored by UV-vis absorption spectroscopy. The precursor was then concentrated by 10 folds and refluxed at 60°C for 24 hours to form ZnO nanorods with an aspect ratio of 12. Ligand adsorption growth model was proposed to explain the anisotropic growth.
Toward Elimination of Solvents in Micro/Nanofabrication: Solventless Polymerization and Its Applications
Authors: Gu Hongwei , Fu Degang , Xu Chenjie , Tang Jun , Xie Jie , Xu Bing
Published: June 2019

Here we report a solventless polymerization process, which involves adding catalysts on the surface of a solid substrate and polymerizing volatile monomers at the gas/solid interface. It provides an alternative to other thin-film-making processes and may lead to reduce or eliminate the use of solvents in micro/nanofabrication. On silicon or silicon dioxide substrates, solventless produced thin films show improved smoothness inside microchannels, and suits reactive ion etching (RIE) process. In addition, this process offers a simple route to generate microstructures that are inaccessible in the presence of solvent, and provides a simple and fast protocol to screen catalysts in a parallel mode.
Theoretical Study on Tunnel Magnetoresistance Oscillation Due to Coulomb Blockade in Nanoscale Magnetic Tunnel Junction
Authors: Takemura Yasushi , Shirakashi Jun-ichi
Published: June 2019

In a small magnetic tunnel junction (MTJ) whose charging energy is larger than a thermal energy, the tunnel magnetoresistance (TMR) is enhanced by the Coulomb blockade. Transport properties in a double MTJ were theoretically studied by using the Monte Carlo method. The temperature dependence of current-voltage and TMR characteristics indicated that a small junction with 5 nm electrodes exhibited the Coulomb blockade at 300 K. It was also found that the background charge changed the threshold voltage of the Coulomb blockade. In asymmetric double tunnel junctions, the current-voltage characteristic exhibited a Coulomb staircase and the voltage dependence of the TMR ratio oscillated.
Synthesis and characterization of Pd nano-pillar arrays in the metal hydride switchable mirror
Authors: Vece M. Di , Kelly J.J.
Published: June 2019

A method is suggested for improving the switching characteristics of the metal-hydride mirror by enhancing hydrogen transport in the active film. Nano-pillars of palladium, which has a high diffusion coefficient for hydrogen, are introduced into the active layer and should serve as a “highway” for the rapid introduction of hydrogen. A palladium nano-pillar array is made by electrodeposition in the pores of a polycarbonate membrane. The membrane is dissolved and the active layer (an yttrium-magnesium alloy) is evaporated on the palladium nanostructures. Improved kinetics has not been shown conclusively and is still the subject of research.
Chemical Sensors Based on Individual In2O3 Nanowires
Authors: Zhang Daihua , Li Chao , Liu Xiaolei , Han Song , Tang Tao , Zhou Chongwu
Published: June 2019

Single crystalline In2O3 nanowires were synthesized and then utilized to construct field effect transistors (FETs) consisting of individual nanowires. Chemical sensors based on these In2O3 nanowire FETs have been demonstrated. Upon exposure to gaseous molecules such as NO2 and NH3, the electrical conductance of the In2O3 nanowire FETs are found to dramatically decrease rapidly, accompanied by substantial shifts in threshold gate voltage. Our In2O3 nanowire sensors exhibit significantly improved sensitivity, as well as shortened response times compared to most existing solid-state gas sensors. In addition, ultraviolet (UV) light is found to be able to greatly enhance the surface molecular desorption kinetics and serve as a “gas cleanser” for the In2O3 nanowire chemical sensors. It has been demonstrated that the recovery time of our devices can be shortened to ∼30 s by illuminating the devices with UV light in vacuum.
Growth and Optical Properties of GaP, GaP@GaN and GaN@GaP Core-shell Nanowires
Authors: Lin Hung-Min , Yang Jian , Chen Yong-Lin , Liu Yau-Chung , Yin Kai-Min , Kai Ji-Jung , Chen Fu-Rong , Chen Li-Chyong , Chen Yang-Fang , Chen Chia-Chun
Published: June 2019

High-quality GaP, GaP@GaN and GaN@GaP nanowires were grown by a convenient vapor deposition technique. The wire-like and two-layers structures of GaP@GaN and GaN@GaP core-shell nanowires were clearly resolved using X-ray powder diffraction and high-resolution transmission electron microscopy (HRTEM) and their growth directions were identified. Photoluminescence intensity of GaP@GaN nanowires increased as temperature increased. The result was interpreted by the piezoelectric effect induced from lattice mismatch between two semiconductor layers. An unexpected peak at 386 cm-1 was found in the Raman spectra of GaN@GaP and assigned to a surface phonon mode due to the interface. Detailed synthetic conditions and possible growth mechanisms of those nanowires were proposed.
Atomic Ordering in Self-assembled Epitaxial and Endotaxial Compound and Element Semiconductor Quantum Dot Structures: The First Review
Authors: Möck Peter
Published: June 2019

Although the main international research thrust on self-assembled epitaxial semiconductor quantum dots is currently being directed towards random alloy quantum dots, the suggestion is made that atomically ordered quantum dots which are grown by either epitaxy or endotaxy may in addition to their larger quantum confinement potentials possess superior long term structural stability. Such atomically ordered quantum dots should, therefore, be superior to random alloy quantum dots as far as prospective device applications are concerned. The basis for this suggestion is simple thermodynamic considerations. These considerations seem to explain our transmission electron microscopical observations of epitaxially grown atomically ordered In(Sb,As), (In,Ga)Sb, (Cd,Zn)Se, (Cd,Mn,Zn)Se quantum dots and Pb(Se,Te) quantum dot predecessor islands. Atomic ordering in (In,Ga)P quantum dot structures, as recently observed by other authors, does not seem to contradict our thermodynamic considerations. Endotaxially grown atomically ordered (In,Si,As) and (Sn,Si) quantum dots in Si matrices are briefly discussed as an even more unconventional approach to nanostructures with applications in electronics, photonics, information storage, and sensing.
From helical nanowires, nanocrosses to aligned micro-carbon fibers
Authors: Zhang Hai-Feng , Wang Chong-Min , Young James S. , Coleman James E. , Wang Lai-Sheng
Published: June 2019

We successfully synthesized helical core-shell crystalline SiC/SiO2 nanowires, core-shell crystalline SiC/C nano-crosses and well-aligned core-shell crystalline SiC/C fibers by using a chemical vapor deposition technique. For the helical crystalline SiC/SiO2 nanowires, the SiC core typically has diameters of 10-40 nm with a helical periodicity of 40-80 nm and is covered by a uniform layer of 30-60 nm thick amorphous SiO2. Detailed structural characterizations suggested that the growth of this novel structure was induced by screw dislocations on the nanometer scale. For the core-shell nanocrosses, the crystalline SiC core typically has diameters of 10 to 40 nm and is covered by a uniform layer of 80-110 nm graphitic carbon. The wellaligned SiC/C fibers were shown to be formed by two sequential steps: catalytic SiC growth and graphitic carbon nano-sheets coating. The helical nanowires and core-shell nanocrosses may have potential applications in nano-electronics. The formation mechanism of the carbon fibers suggested that fabrication of field emission filament carbon nano-fibers may be realized by using the aligned crystalline nanowires as templates.
Growth and Characterization of ZnO Nanowires
Authors: Baxter Jason B. , Bessems Ron E.M.W. , Aydil Eray S.
Published: June 2019

Single crystal ZnO nanowires were grown by chemical vapor deposition using monodisperse 5 nm or 20 nm diameter gold nanoparticle catalysts to control the nanowire diameter and location. The nanowires reach several microns in length and grow only from the gold nanoparticles. The nanowires have narrowly dispersed diameters, albeit significantly larger than the diameter of the gold particles used for catalyzing the growth. The nanowires grow in the [ 0 1 10 ] or [ 1 1 10 ] directions normal to the lowest energy planes in ZnO. ZnO nanowires emit in the near ultraviolet region of the electromagnetic spectrum upon excitation with highenergy photons or electrons. Electron diffraction and absence of luminescence associated with oxygen vacancies indicate high quality crystalline ZnO nanowires. Cathodoluminescence e mission along the entire length of the wire is consistent with a lack of non-radiative recombination sites associated with defects, lending further support for the high quality of these nanowires.
Nanoscale Surface Patterning
Authors: Yu Meng , Ivanisevic Albena
Published: June 2019

We present a methodology based on Dip-Pen Nanolithography 1 to fabricate nanoscale surface patterns composed of polyelectrolytes. Two widely used polymers Poly(diallyldimethylammonium chloride) (PDDA) and Poly(sodium 4-styrenesulfonate) PSS were chosen as the DPN “inks”. Patterns were created and evaluated on silicon oxide surfaces using an Atomic Force Microscope (AFM). To compare the polymer packing and the height of the nanopatterns, additional fabrication was performed using microcontact printing. We were able to generate structures with better polymer packing using DPN and control the height of the polymer structures more reproducibly compared to microcontact printing.
Generating Nanoscale Arrays Using Self-Organized Porous-Alumina Ion Implantation Masks
Authors: Rehn L. E. , Birtcher R. C. , Kestel B. J. , Baldo P. M. , Hiller J. , McCormick A.W.
Published: June 2019

Starting from two-step anodizing recipes available in the literature, we fabricated selfsupporting ordered ion-implantation masks that are several mm2 in area and 1-4 νm thick. SEM micrographs reveal self-organized structures with straight open pores, 25-150 nm in diameter, extending completely through the mask. As reported previously, the pore diameter and spacing depend critically upon the anodization parameters, e.g., type of acid and its molality, the applied voltage and the solution temperature. Ion-milling procedures were developed for opening the bottoms of the anodized pores. These masks appear quite robust during exposure to ion beams of 1-MeV He, Ne, and Kr. The steps necessary to fabricate the implantation masks, including opening the pores, are briefly described. Here we present new results obtained with a mask fabricated with pore dimensions as small as 25 nm in diameter, i.e., at the limit of what is technically feasible. Measurements are reported of the angular dependence of the transmitted ion current; these results are consistent with the physical dimensions of the opened pores. TEM images of a partial array obtained by implantation through the 25-nm pores are also shown.
The Luminescent Properties of Ion-Implantation-Fabricated SiO2:nc-Si Nanostructures Annealed at High Temperatures
Authors: Tetelbaum David I. , Gorshkov Oleg N. , Kasatkin Alexandr P. , Burdov Vladimir A. , Trushin Sergey A. , Mikhaylov Alexey N. , Gaponova Daria M.
Published: June 2019

The influence of the Si+ implantation dose and postimplantation annealing temperature on the photoluminescence (PL) intensity of silicon nanoinclusions in an SiO2 matrix was experimentally investigated. The way that the PL varied with dose and annealing temperature was explained on the basis of a model which takes into account the Ostwald ripening of nanocrystals and effect of the quantum dot size on the rate of radiative recombination.