bluuebunny/crossref_metadata_2025 huggingface dataset:
Transition Metal Doped ZnO for Spintronics
Authors: Pearton Stephen J. , Norton D. P. , Ivill M. P. , Hebard A. F. , Chen W. M. , Buyanova I. A. , Zavada J. M.
Published: April 2011

ZnO is a very promising material for spintronics applications, with many groups reporting room temperature ferromagnetism in films doped with transition metals during growth or by ion implantation. In films doped with Mn during PLD, we find an inverse correlation between magnetization and electron density as controlled by Sn doping. The saturation magnetization and coercivity of the implanted single-phase films were both strong functions of the initial anneal temperature, suggesting that carrier concentration alone cannot account for the magnetic properties of ZnO:Mn and factors such as crystalline quality and residual defects play a role. Plausible mechanisms for the ferromagnetism include the bound magnetic polaron model or exchange is mediated by carriers in a spin-spilt impurity band derived from extended donor orbitals. Spin-dependent phenomena in ZnO may lead to devices with new or enhanced functionality, such as polarized solid-state light sources and sensitive biological and chemical sensors.
Improvement of Turn-Off Characteristics in ZnOTFT's by Introducing Hydrogen During MOCVD Growth
Authors: Jo Jungyol , Seo Ogweon , Choi Hyoshik , Jun Chan Bong
Published: April 2011

Advantages of ZnO:

High Mobility < 10 cm2Vsec, enables larger pixel opening, safer operation compared to TFT-LCD based on amorphous Si.High current driving TFT, high speed data transfer.High optical transparency, direct, wide bandgap.Stable against water and oxygen, because already oxidized.
Effect of Processing Conditions on Electrical and Magnetic Properties of Pb(Zr, Ti)O3 CoFe2O4 Multilayers Thin Films
Authors: Ortega Nora Patricia , Bhattacharya P. , Katiyar Ram S , Majumder S B , Takeuchi I , Dutta P. , Sheehra M S , Kumar Ashok
Published: April 2011

The multilayers of ferroelectric (FE) Pb(Zr, Ti)O3 (PZT) and ferromagnetic (FM) CoFe2O4 (CFO) thin films with 3, 5, and 9 layers having configurations PZT/CFO (PC) and CFO/PZT (CP) were fabricated by pulsed laser deposition technique. We have investigated the effect of inter-diffusion at the interface of multilayers (MLs) and reversing the order of FE and FM layers in the multilayers configuration on the electrical/magnetic properties. The TEM of the films showed that the layer structure was not maintained and the inter-diffusion of the CFO into PZT and vice verse were observed at the interface of MLs. Both the PC and CP configurations of multilayer films exhibited pseudo FE hysteresis loop and proper FM hysteresis loops at room temperature. Reversing the multilayer configuration from CP to PC resulted in increasing the pseudo remanent polarization, however this behavior was not observed in magnetic properties. The frequency and temperature dependences of the impedance and modulus spectroscopy of the multilayer PC and CP films were studied in the ranges of 102 to 106 Hz and 200 to 650 K respectively. The electrical response of all multilayer films investigated could be resolved into two contributions. We attributed these to the grain and grain boundary effects in impedance and modulus formalism. We found that the difference between the grain and grain boundary capacitive effect decreased due to increase of the number of layers.
Influence of Thermal Treatment on YBa2Cu3O7-x Thick Films Prepared by Electrophoretic Deposition on Ni and Ag Substrates
Authors: Dusoulier Laurent , Denis Samuel , Dirickx Michel , Vanderbemden Philippe , Ausloos Marcel , Cloots Rudi , Vertruyen Bénédicte
Published: April 2011

We have studied the sintering parameters of YBa2Cu3O7-x (YBCO) coatings produced by electrophoretic deposition (EPD) on Ag and Ni substrates. The maximal sintering temperature is ∼ 930°C due to partial melting and chemical contamination for Ag and Ni substrates respectively. Increasing the sintering duration does not improve significantly the densification. When Ar sintering atmosphere is used, the coating density is strongly increased on Ag substrates while adhesion is poor on Ni substrates. The Ar-sintered YBCO coating deposited on planar Ag substrate displays a significant magnetic shielding effect for low frequency applied magnetic induction.
Critical Currents of Overdoped Co-evaporated YBCO Coated Conductors
Authors: Hänisch Jens , Storer Jonathan , Sheehan Chris , Coulter Yates , Matias Vladimir
Published: April 2011

Coated conductor samples, prepared by reactive co-evaporation, are investigated with respect to the hole-doping dependence of the critical current density. The samples are annealed in an atmosphere of variable oxygen content after which critical currents, critical temperature and the c-axis lattice spacing are measured. The lattice spacing increases with decreasing oxygen content, consistent with literature data. These co-evaporated samples show hole overdoped behavior with respect to the maximum Tc. The achievable range of hole doping in these samples seems to depend on surface coverage. Both self-field and in-field Jc at 75.5 K have a maximum in the overdoped region but at less than maximum oxygen content. The reason for the overdoping of these samples is discussed briefly in terms of Y-Ba disorder.
Evaluation and Testing of Organometallic Precursor for Copper Direct-Write
Authors: Majumder Prodyut , Tiwari Manish , Megaridis Constantine , McAndrew James , Xu Mindi , Belot John , Takoudis Christos G
Published: April 2011

A capillary bridge printing technique has been used to deposit copper interconnects using homogeneous solutions of a Cu(II) precursor in a series of low boiling primary alcohols. The rheological properties of the solutions have been measured first to determine their printability. The as-printed lines with subsequent annealing at relatively low temperatures (∼200 °C), in order to evaporate the volatile solvents and facilitate dissociation of the precursor deposit, produced conducting interconnects. The precursor has been demonstrated to be self-reducing and requires no reducing environment (e.g. H2) thus making the interconnect formation easier. Moreover, successful decomposition of the precursor into metallic Cu at such low temperatures holds promise for applications involving flexible polymer substrates.
On-chip Detection of Chemiluminescent Biomolecules Using an Integrated Thin Film Silicon Photodiode
Authors: Pereira A. , Pimentel A. , Chu V. , Prazeres D. M. F. , Conde J. P.
Published: April 2011

A hydrogenated amorphous silicon photodetector on a glass substrate is used for the integrated, real-time detection of chemiluminescent reactions in solution. The light emission at 425 nm resulting from the horseradish peroxidase-catalyzed oxidation of luminol is detected by a p-i-n amorphous silicon photodiode operated at zero bias. The limit of detection of the present device is in the range of nanomole of horseradish peroxidase per liter.
Dielectrophoretic Microfluidic Switching for Lab on a Chip Applications
Authors: Wang Lisen , Lee Abraham Philip
Published: April 2011

Dielectrophoresis switching with vertical microelectrodes in the side wall of microchannel have been designed, fabricated and tested. A set of interdigitated electrodes in the side wall of the microchannels is used for the generation of non-uniform electrical field to introduce DEP force to repel or attract beads/cells to the sidewalls. A countering DEP force is generated from another set of electrodes patterning on the opposing side walls. These DEP forces can be adjusted by the voltage and frequency applied. By manipulating the coupled DEP forces, the particles flowing through the microchannel can be positioned at different equilibrium points along the width direction and continue to flow into different outlets. The objects of interest can be switched to desired channel outlets in the flow with no need of any moving parts and the down-stream channel can be more than three outlets. Experimental results for switching cells to two outlets and polystyrene microbeads to five outlets have been achieved. The effect of the geometry and flow rate on the performance of the switching was studied and an analytical solution for the optimal design and operation of DEP electrode arrays has been derived from the proposed model.
High Performance Photo-curable Polymers and Oligomers Based on Novel Ring-opening Reactions of Oxetanes
Authors: Nishikubo Tadatomi , Kudo Hiroto
Published: April 2011

We found new reactionsof oxetanes with many reagents such as acyl chlorides, silyl chlorides, phosphonyl chlorides, alkyl chlorides, aryl esters, thio esters, phosphonic acids, carboxylic acids, thiols, and phenols using suitable quaternary onium salts or crown ether complexes as catalysts. More recently, we also found an anionic ring-opening polymerization of certain oxetane monomers such as (3-methyl-3-hydroxymethyl)oxetane and (3-ethyl-3-hydroxymethyl)oxetane, which have hydroxyl groups, catalyzed by potassium tert-butoxide and 18-crown-6-ether complex, and an anionic ring-opening alternating co-polymerization of oxetane monomers with cyclic carboxylic anhydrides. These reaction systems have also been applied to the synthesis of new functional polymers. In this article, we would like to introduce the application of these reaction systems for the synthesis of high performance new photo-curable polymers and oligomers containing pendant or terminal (meth)acryloyl groups.
Discovery and Development of OMNiMIPs: One MoNomer Molecularly Imprinted Polymers
Authors: Spivak David A. , Sibrian-Vazquez Martha , Houck Stephen
Published: April 2011

There is enormous potential for the analytical applications of molecularly imprinted polymers (MIPs); for example, the imprinted polymer sites can function as the molecular recognition element of sensors, immunoassays, and separation media. However, difficulties with formulation variables and the need for empirical optimization have inhibited the widespread use of MIPs by the general scientific community. While investigating new crosslinkers for molecular imprinting, we have recently discovered a much simpler approach to MIP formation which utilizes a single crosslinking monomer, NOBE (N, Obismethacryloyl ethanolamine) in addition to template, solvent and initiator (shown in Scheme 1). We have given this molecular imprinting method the acronym “OMNiMIPs” which stands for one monomer molecularly imprinted polymers. This new formulation eliminates variables such as choice of functional monomer (FM) and crosslinker (XL), the ratio of functional monomer to crosslinker (FM/XL), and the ratio of functional monomer to template which normally complicates MIP design. The affects of OMNiMIP performance variables toward molecular recognition indicate significant differences between these new materials and traditional MIPs formulated with ethyleneglycol dimethacrylate (EGDMA) and methacrylic acid (MAA). These differences and the utility of OMNiMIPs will be discussed.
Fabrication and Optical Characterization of Silicon Carbide Nanofibers
Authors: Khan Saima , Khan Aurangzeb , Kordesch Martin E.
Published: April 2011

Silicon Carbide (SiC) nanofibers were synthesized from SiC powder dispersed in polyethylene oxide (PEO) solution in Chloroform using the electrospinning technique. The as-spun fibers were then annealed at 1000ËC to 7 hours. The average diameter of the annealed fibers is 500 nm while the length of the annealed fibers is about 50 Âµm. The fibers were characterized using scanning electron microscope (SEM), X-ray diffraction (XRD) and Cathodoluminescence (CL). PL spectra from the annealed SiC fibers show a broad emission in the red-infrared spectral regime. The main peak is centered at 774 nm while the shoulder on the left is at 740 nm
Characterization of Electromechanical Transduction in Polyelectrolyte Gels for Mechanical Sensor Applications
Authors: Prudnikova Katsiaryna , Utz Marcel
Published: April 2011

We report a new experimental method for the characterization of the electromechanical properties of polyelectrolyte gels (PG). PGs have been studied extensively, but with limited success, as mechanical actuators. However, they are also promising as potentially biocompatible mechanical sensors. In order to integrate them into actual devices, their electromechanical transduction properties need to be characterized in a reproducible manner.

We have therefore developed a technique to measure the mechanically induced change in electrostatic potential in PGs. The polyelectrolyte gel is subjected to a well-defined pressure gradient by placing a thin, flat sample on a substrate with integrated concentric Platinum electrodes and indenting it with a spherical indenter. The potential values at the electrodes are measured using a MOSFET operational amplifier circuit with an input impedance of 1014 Ù and an effective dynamic range better than 16 bit. This method can be directly used to quantify electromechanical coupling in polyelectrolyte gels.
Effects of Al2O3 Nanopowder Filler Size on Glassy Polymeric Carbon Electrical Transport Behavior
Authors: Chhay Bopha , Minamisawa Renato Amaral , ILA Daryush
Published: April 2011

Glassy polymeric carbon (GPC) has a unique graphite micro-fibril structure that attributes singular properties to the material. The addition of nanoparticles in the GPC matrix to improve its properties has been the focus of recent studies for spacecraft coating applications. We report the effects of Al2O3 nanoparticles dispersed in GPC on the electrical properties. The fabrication process to produce homogenous samples and the electrical measurements are fully described. In addition, the chemical structure characterization was evaluated using Raman spectroscopy.
The study of Thermal Resistant Enhancement of Siloxane-Modified LED Transparent Encapsulants
Authors: Chen Kai-Chi , Hsu Chia-Wen , Li Hsun-Tien
Published: April 2011

Thermal resistant property of siloxane-modified epoxy compositions designed for long-term and high temperature storage was investigated. In this study, we developed two siloxane-modified epoxy compositions to improve the thermal stability of current epoxy encapsulants. One composition contained silicone epoxy, and the other one was cyclic aliphatic siloxane dianhydride.

We selected triglycidyl ether terminated Phenylmethylsiloxnae-co-dimethylsiloxne (GT-1000), which was compatible with the diglycidyl ether of bisphenol A epoxy (Epon-828), to partial replaced the epoxy resin and was cured by liquid anhydride (MHHPA). In the mean time, we also synthesized 5, 5'-(1, 1, 3, 3-tetramethyl disiloxane-1, 3-dilyl)-bis-norborane-2, 3-dicarboxylic anhydride (A1) as a co-curing agent to cure Epon-828.

The thermal resistance was studied by measuring the increase of yellow index (ΔYI) after thermal treatments. In 110 °C storage experiment for 1000 h, the ΔYI of GT-1000 0.2 equivalent was 1.51, whereas Epon-828/MHHPA (Comp 1) was 6.74. Moreover, The ΔYI of the composition with higher equivalent GT-1000 was only 2.15 after 2000 hours thermal aging. In the cyclic aliphatic siloxane dianhydride co-curing compositions, when A1 was 0.05 and 0.1 equivalent, the ΔYI was 2.28 and 0.72 after 1000 h, respectively. Compared with Comp 1, both GT-1000 and A1 were effective for thermal resistance.

In IR-reflow test, the ΔYI of GT-1000/Epon-828/MHHPA= 0.5/0.5/1 was 0.65 and that of Epon-828/MHHPA was 1.49 after 260 °C for 10 seconds. The results revealed that either the siloxane-modified epoxy or siloxane-modified curing agent had excellent thermal resistant property for high performance LED applications.
Phase Separation in Al2O3 Sol-gel System Incorporated with High Molecular Weight Poly(ethylene oxide)
Authors: Tokudome Yasuaki , Nakanishi Kazuki , Fujita Koji , Miura Kiyotaka , Hirao Kazuyuki
Published: April 2011

Pure alumina monoliths with well-defined macropores and mesostructured skeleton have been synthesized via a spontaneous route from the aqueous and ethanolic solution of aluminum salts in the presence of propylene oxide and high molecular weight poly(ethylene oxide)(PEO). The addition of propylene oxide to the starting solution controls the gelation, while the addition of PEO induces the phase separation. Appropriate choice of the starting composition, with which the phase separation and gelation concur, produces large-dimension (10mm×10mm×10mm), bicontinuous macroporous Al2O3 monoliths. The mean size of the continuously connected pores is controlled in the micrometer range, depending on the PEO concentration and polarity of the solution. On the other hand, micropores and mesopores, originated from the interstices among primary particles, exhibit median pore size of about 2.6 nm and the BET surface area as high as 396 m2/g after dried temperature at 40 °C.
Comparison of Different Reversed-Phase Packing Materials Based on Higher Organic Hybrid Particles
Authors: Lawrence Nicole L. , Wyndham Kevin D. , Glose Kenneth H. , Cook Jim T. , Brousmiche Darryl W. , Iraneta Pamela C. , Alden Bonnie A. , Boissel Cheryl A. , Walter Thomas H.
Published: April 2011

As part of our ongoing exploration into the field of hybrid organic/inorganic particles as HPLC packing materials, we have recently evaluated the use of porous particles synthesized from the co-condensation of ethylene-bridged alkoxysilanes with tetraethoxysilane [1,2]. By employing 4-100 mol% of hybrid organic/inorganic groups (i.e., O1.5SiCH2CH2SiO1.5) to 96-0 mol% inorganic groups (i.e., SiO2), novel hybrid particles have been prepared and shown to be excellent materials for the preparation of efficient and chemically resilient reversed-phase packing materials.
Polymer Composite Reinforced with Nanodiamonds and Clay
Authors: Karbushev Valeriy V. , Konstantinov Ivan , Semakov Alexander , Parsamyan Irina , Kulichikhin Valery , Popov Vladimir
Published: April 2011

Polymer/clay and polymer/nanodiamond composites were prepared via solution dispersion, melt processing and new so-called colloid-deposition techniques. The following polymers have been used as matrices: hydroxypropylcellulose, polysulfone and styrene-acrylonitrile copolymer. For estimation of particles distribution in polymer matrices the optical microscopy, SEM and TEM methods were used. The X-ray results demonstrate that at least at some compositions, the technique employed was successful to intercalate the clay structure. It was found that particles addition (at small concentration) to polymeric liquids leads to decrease of viscosity. Tensile testing showed considerable improvements of mechanical properties.
Mesoporous Hybrid Thin Films: Building Blocks for Complex Materials with Spatial Organization
Authors: Soler-Illia Galo J. , Angelomé Paula C. , Fuertes M. Cecilia , Wolosiuk Alejandro , Bilmes Sara A. , López-Alcaraz Francisco Javier , Míguez Hernán
Published: April 2011

Mesoporous Hybrid Thin Films (MHTF) of a variety of compositions and embedded organic functions are produced by combining sol-gel synthesis, template self-assembly and surface modification. One-pot or post-grafting strategies permit to modify the pore surface behavior. Highly controlled MHTF issued from a reproducible and modular synthesis can be used as building blocks for more complex structures, presenting order at larger scales, and novel properties derived from this multiscale order. Multilayer stacks of MHTF presenting specific and different functions and frameworks located in a well-defined position have been produced by combining sequential film deposition, selective functionalization and dissolution. These systems present new properties such as localized chemistry or modulable photonic crystal behavior.
Hybrid Nanoparticles Prepared by In-situ and Post-synthetic Surface Modification of Lanthanide-Based Nanoparticles with Phosphonic Acid Derivatives
Authors: Rill Christoph , Ivanovici Sorin , Kickelbick Guido
Published: April 2011

The use of various phosphonic acid derivatives – some of which contain polymerizable groups – as surface modifying agents for nanoparticles was studied both in-situ during the synthesis of lanthanide-based (Ln = Nd, Eu, Yb) nanoparticles at room temperature as well as in a separate step after the particle preparation by a hydrothermal method. In the single-pot in-situ method the phosphonic acid esters served as growth-limiting agent during particle formation leading to small nanoparticles with a size of only a few nanometers as determined by dynamic light scattering as well as transmission electron and atomic force microscopy. Free phosphonic acids as well as their silyl esters were used to modify the hydrothermally prepared neodymium hydroxide nanorods which had diameters of approx. 20 nm and a length ranging up to a few micrometers. The surface modification was confirmed by infrared spectroscopy and thermogravimetric analysis.
Metal Oxide Nanocrystals: Building Blocks for Mesostructures and Precursors for Metal Nitrides
Authors: Niederberger Markus , Buha Jelena , Djerdj Igor
Published: April 2011

Sol-gel routes to metal oxide nanoparticles in organic solvents under exclusion of water represent a valuable alternative to aqueous methods. In comparison to the complex aqueous chemistry, nonaqueous processes offer the possibility to better understand and to control the reaction pathways on a molecular level, enabling the synthesis of nanomaterials with high crystallinity and well-defined and uniform particle morphologies. The manifold role of the organic species in providing the oxygen for the oxide formation and in controlling the crystal growth and the assembly properties makes it possible to tailor the morphological, structural and compositional characteristics of the final inorganic products.

In addition to metal oxides with nearly spherical crystallite sizes in the range of just a few nanometers, also more complex morphologies such as nanowire bundles, nanorods or lamellar organic-inorganic hybrids of varying hierarchical complexity can be achieved in one step and without the use of any surfactants. The spherical nanocrystallites are on the one hand versatile building blocks for the fabrication of fully crystalline and ordered mesoporous materials and on the other hand suitable precursors for the synthesis of metal nitride nanoparticles.

This proceeding provides an overview of the various oxidic nanoparticles synthesized via the nonaqueous and surfactant-free sol-gel approach, summarizes the most frequently found formation mechanisms, and offers some insight into the crystallization pathway of nanoparticles. Furthermore, the use of metal oxide nanoparticles as nanobuilding blocks for the preparation of nano- and mesostructures as well as their transformation into metal nitride nanocrystals will be discussed.
Mechanical Behavior of Functional Hybrid Coating Based on Anisotropic Iron Oxide Nanoparticles
Authors: Chemin Nicolas , Rozes Laurence , Chanéac Corinne , Cassaignon Sophie , Jolivet Jean-Pierre , Barthel Etienne , Bourhis Eric Le , Sanchez Clément
Published: April 2011

Functional hybrid coatings have been elaborated from a polymer matrix incorporating iron oxide nanoparticles. Stable aqueous suspensions of goethite (α-FeOOH) nanorods, obtained by controlled precipitation of Fe3+ ions, were introduced in 2-hydroxyethyl methacrylate (HEMA). The films were spin-coated on glass substrates from the solutions prior to a UV light induced free radical polymerization step. Nanoindentation tests were carried out to investigate the mechanical properties of the hybrid coatings. Swelling measurements and Fourier Transformed Infrared Spectroscopy (FTIR) were used to characterize the interface between the iron oxide nanoparticles and the PHEMA matrix. Cross-sectional scanning electron microscopy (SEM) and transmission electron microscopy (TEM) was performed to evaluate the dispersion state of the iron oxide particles through the matrix. From a mechanical point of view, iron oxide nanorods yield to a strong reinforcement effect of PHEMA (increase in modulus and hardness by a factor 2 with 5%vol goethite nanoparticles). Origins of such reinforcement are attributed to the existence of highly favourable interactions at the goethite-PHEMA interface combined with a homogeneous dispersion of the particles. The nature of these interactions and evidences of there influence on the mechanical behaviour of the nanohybrid coatings are reported.
Fabrication of enamel-mimicking mineralization composite coating induced by electrolytic deposition (ELD) system
Authors: Fan Yuwei , Wang Rizhi , Moradian-Oldak Janet
Published: April 2011

Mature tooth enamel does not remodel nor self-repairs after damage. Therefore, in vitro formation of a uniquely ordered composite similar to enamel is of particular interest. In this study we applied a newly developed electrolytic deposition (ELD) system to promote the amelogenin nano-chain self-assembly and simultaneous calcium phosphate crystallization. Composite coatings of amelogenin-calcium phosphate were prepared on a cathode substrate (Si wafer), from an initial pH of 4-5, and calcium and phosphorus containing solution at room temperature. The effects of a recombinant full-length amelogenin (rP172) and truncated protein without the C-terminal (rP148) on the growth and morphology of the calcium phosphate nano-composite were investigated. A potentiostat was used to control the electrochemical parameters.Following the application of electric current, the local pH around the cathode was increased and resulted in the self-assembly of amelogenin that occurred simultaneously with calcium phosphate mineralization. Transmission and scanning electron micrographs of assembled rp172 amelogenin collected from the 25mM sodium phosphate solution during electrodeposition showed uniform nanospheres and nano-chains structures, while the rP148 formed irregular aggregates. SEM observation of the surface of the nano-composite after electrodeposition, revealed organized nano-rod structures in the presence of rP172, while only nano-sized spherical aggregates were seen in the presence of rP148. ATR-IR confirmed that the mineral phases were mainly octacalcium phosphate, but apatite and amorphous calcium phosphate were also present. Nanoindentation was tested on rP172 and rP148 composite coating. The rP172 composite coating exhibited higher elastic modulus and hardness than rP148 composite. The fracture toughness of rP172 composite was comparable to mature enamel. We therefore conclude that the 24 amino acid hydrophilic C-terminal of amelogenin is essential for the self-assembly, and therefore, for calcium phosphate crystal organization. The new electro-deposition system is effective for fabrication of amelogenin/apatite composites with defined organized structures.
Novel Vapor Phase biodegradable coatings for controlled drug delivery systems
Authors: Arjunan Arul Chakkaravarthi , Gupta Sushant , Singh Rajiv K , Singh Deepika , Opalko Jeff
Published: April 2011

The synthesis of nano-functionalized drug particles or drug particles with nanoscale biodegradable polymeric coatings has wider ranging applications in sustained release drug delivery systems. An important area of application includes delivery of drugs, such as proteins, peptides, and glucocorticoids via the inhalation process. The advantages of this method include, rapid absorption by the body and lack of metabolic degradation effects which is typically by some drugs during oral delivery. Here we discuss the novel pulsed laser and pulsed electron method to synthesize nanoscale biodegradable coatings of poly lactic acid (PLA) onto antiasthmatic drugs. In pulsed laser method a pulsed excimer laser ablates a thin layer of polymer which is deposited onto 1 -5 micron drug particles which are fluidized in the gas chamber. The control of the thickness, conformation and the chemistry of the nanoscale coating process will be discussed in detail. Applications of this methodology to delivery of anti asthamtic drugs and insulin will be discussed. The effect of polymer coating chemistry, molecular weight, hydrophobicity, and thickness on the sustained release characteristics will be discussed. A unique method for depositing the PLA films, pulsed electron beam deposition (PED) was used to deposit the films. This technique was tried done to overcome the difficulties like low absorption co-efficient of UV-laser. Method proved to be promising for producing smooth films and offers a better thickness control of the deposition. The RMS roughness and other morphological characteristics of PED deposited films were superior over the conventional laser ablated films.
A Combinatorial Approach Towards Functionalizing Copolymers with Effector Molecules that Attenuate Cyto-inflammatory Responses at the Biotic-abiotic Interface
Authors: Pierstorff Erik , Krucoff Max , Ho Dean
Published: April 2011

Functionalized copolymers offer the opportunity for tailored biology, where specific functionalities within these materials can be rapidly engineered on demand. Embedding effector molecules, for example, into these copolymers transforms an otherwise inactive component into a functional matrix for envisioned in vivo applications such as suppression of cellular inflammation/stress or immuno-regulatory implant coating, etc. Furthermore, our ability to utilize these copolymers in both a vesicular/planar configuration, coupled with their versatility in block composition empowers opportunities of utilizing vesicle-encapsulated effector molecules as dedicated drug delivery vehicles with targeting capabilities, or as modalities to replenish exhausted effector molecule stores within planar copolymer thin films. As such, these copolymeric membrane materials may potentially impact multiple medically-relevant fields in both scientific and technological contexts.

An important element empowering this transition is the examination of the bio-inert properties of these materials. This includes the interrogation of the stress response of macrophages to the chemical/topographical stimuli presented by these materials. We have previously developed copolymers as neural implant coatings functionalized with a glucocorticoid anti-inflammatory Dexamethasone (Dex) using Langmuir-Blodgett deposition. This technology successfully suppressed, to a significant degree, RAW264.7 macrophage transcriptional machinery of several cytokines including TNFα, Il-6, and Il-12 analyzed using real time PCR (RT-PCR). These findings offered insight into both bio-abio material fabrication, as well as analysis of stress specific gene program activation which may be used to generate principles for optimizing neural implant biocompatibility and chronicity by attenuating innate immune responses.

This study has broadened the range of applications of this material via its integration with a combination of intracellular signaling agonists (e.g. Liver X receptor-α/β (LXR α/β)) that function as non-steroidal anti-inflammatories to block transcriptional machinery associated with cell stress among other disorders. Here we demonstrate both planar encapsulation of an additional effector in the form of a robust, cell permeable LXRα/β agonist 3-((4-Methoxyphenyl)amino)-4-phenyl-1-(phenylmethyl)-1H-pyrrole-2, 5-dione using a crosslinked copolymer thin film. In addition, we investigated the underlying mechanisms of the attenuation of cellular inflammation via RT-PCR analysis of the resultant inhibition of lipopolysaccharide (LPS)-stimulated secretion of proinflammatory cytokine in murine macrophages. These advancements may potentially result in multi-functional nanoscale thin films that are chronically active, and can suppress cellular inflammation as implant coatings or bio-inert vesicular carriers of a non-steroidal pharmacological system.
Conductimetric Detection of Protein and Cancer Cells with Oxide Nanosensors
Authors: Goud Janagama , Raj P. Markondeya , Liu Jin , Iyer Mahadevan , Wang Z. L. , Tummala Rao
Published: April 2011

Semiconducting oxides are widely known and commercially applied for their gas sensing properties. However, biochemical sensing has mostly depended on optical and electrochemical techniques that are more cumbersome. This work investigates the biosensing characteristics of ZnO nanobelts and ZnO thin films. Zinc oxide thin film sensors showed changes in conductivity after protein functionalization with rabbit IgG and hybridization with anti-rabbit IgG. Conductivity changes were also measured after coating the oxides with MCF-7 cancer cells and its antibodies. In another set of experiments, ZnO nanobelts showed systematic conductivity changes with rabbit IgG protein hybridization. The experimental results in this paper indicate that the conductimetric properties of nano and thin film oxides can be sensitized to protein and cancer cell hybridization reactions. This technique can also be applied to certain other pathogen proteins or toxic proteins from the environment leading to low-cost miniaturized wireless biosensors.
Mercury Detection with Ag Nanoparticles Reduced on Si Thin Films
Authors: Kalkan A. Kaan
Published: April 2011

A surface plasmon resonance mercury sensor was demonstrated by electroless reduction of silver nanoparticles on amorphous silicon thin films. Unlike the previous Ag/Au nanoparticle - Hg interaction investigations, which monitored the blue shift of the dipolar plasmon band of well-dispersed nanoparticles, the present work reveals and explores the red shift of the symmetric hybrid plasmon mode of the interacting nanoparticles in response to Hg vapor exposure. Sensitivity to Hg was explored with varying nanoparticle size, which could be controlled by the immersion time associated with the reduction process. The recovery of the hybrid plasmon band after the Hg exposure was also monitored which was observed to be slower than the recovery of the dipolar plasmon band for noninteracting particles.
A Novel Efficient, Iodide-Free Redox Mediator for Dye-Sensitized Solar Cells
Authors: Zhang Zhipan , Chen Peter. Chaoyu , Zakeeruddin Shaik Mohammed , Moser Jacques-Edouard , Grätzel Michael
Published: April 2011

A stable organic molecular radical, 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO), has been electrochemically studied and employed as a new redox mediator in nanocrystalline TiO2 dye-sensitized solar cells (DSCs) when it is doped with nitrosonium tetrafluoroborate (NOBF4). Reasonable photocurrents can be achieved despite of driving force of only 0.2 eV for the TEMPO/TEMPO+ system as compared to 0.6 eV for the iodide/triiodide redox system. Judicious selections of a 5 µm photoanode made from TiO2 mesoscopic particles (60 nm in diameter) and an organic sensitizer with high molar extinction coefficient yield an overall power conversion of 5.0 % under AM 1.5 illumination at 100 mW cm-2 and an incident photon-to-current conversion efficiencies (IPCE) in excess of 50 %.
Ion Beam Assisted Square Spiral Photonic Crystal Fabrication
Authors: Sorge Jason , Summers Mark , Fleischauer Michael , Tabunshchyk Kyrylo , Kovalenko Andriy , Brett Michael
Published: April 2011

Photonic crystals currently hold exciting potential in waveguiding applications with the ability to greatly reduce waveguide bend radii, allowing for the realization of photonic networks with increased complexity and device density. Square spiral photonic crystals are comprised of periodic arrays of slanted cylindrical columns with periodic abrupt 90° changes in the column growth direction. The abrupt changes produce elbows which correspond to points in the three-dimensional diamond lattice, which are commonly referred to as diamond:n photonic crystal structures based on the nth nearest neighbor lattice point between column arms. The diamond:n structures are characterized by four parameters: column separation, spiral pitch, column diameter, and column growth angle. These structures have been shown theoretically to have a three-dimensional relative bandgap of approximately 15% for a direct silicon diamond:1 structure and approximately 24% for an inverse silicon diamond:5 structure with circular column cross sections. Silicon square spiral photonic crystals can be grown by a single-step thin film deposition process known as glancing angle deposition (GLAD), which utilizes rotation of lithographically patterned substrates and advanced control algorithms. While using GLAD to grow square spiral photonic crystals in a single-step process is desirable, it does have inherent limitations. Physical vapor deposited films deposited at oblique incidence angles form columns with angle ≤ 60° relative to the substrate normal. This deviates from the optimal diamond:1 and diamond:5 structures which require film growth angles of approximately 64° and 74°, respectively. Here we present SEM images of periodic silicon square spiral films grown with a vapor source incidence angle of 85° that indicate an average column tilt angle of 57˚ for films grown with the basic GLAD process and an average column tilt angle between 61˚ and 65˚ using an ion-assisted GLAD process. Photonic simulations indicating that square spiral films with complete three-dimensional photonic bandgaps are only achievable via ion-assisted GLAD are also presented.
Three-Dimensional Electromagnetic Metamaterials with Non-Maxwellian Effective Fields
Authors: Shin Jonghwa , Shen Jung-Tsung , Fan Shanhui
Published: April 2011

It is commonly assumed that the long-wavelength limit of a metamaterial can always be described in terms of effective permeability and permittivity tensors. Here we report that this assumption is not necessary–there exists a new class of metamaterial consisting of several interlocking disconnected metal networks, for which the effective long-wavelength theory is local, but the effective field is non-Maxwellian, and possesses much more internal degrees of freedom than effective Maxwellian fields in a local homogeneous medium.
Theory of Thermal Emissivity and Enhanced Absorption in Sub-wavelength Metallo-Dielectric Photonic Crystals
Authors: Biswas Rana , Puscasu Irina , Pralle Martin , McNeal Martin , Greenwald Anton , Daly James , Johnson Edward , Neginhal Srinivas , Ding Changgeng
Published: April 2011

Metallo-dielectric photonic crystals are sharp thermal emitters at infrared wavelengths, and are being employed in sensors. We describe the theory of thermal emission and enhanced absorption in these photonic crystals using a scattering matrix approach, where Maxwell's equations are solved in Fourier space. A sub-wavelength hole array in a metal layer is coupled to a two-dimensional photonic crystal of the same periodicity in these metallo-dielectric photonic crystals. The sub-wavelength hole array has an enhanced transmission mode that couples to a weakly guided mode of the photonic crystal having similar modal character. The transmissive mode of the hole array is absorbed by the photonic crystal to create a sharp absorption and reflective minimum. The enhanced absorption is investigated in different lattice symmetries.
Picosecond Polarisation Detector for Infrared and Terahertz Radiation
Authors: Weber Wolfgang , Kiermaier Josef , Danilov Sergey N. , Schuh Dieter , Gerl Christian , Wegscheider Werner , Bougeard Dominique , Abstreiter Gerhard , Prettl Wilhelm , Ganichev Sergey D.
Published: April 2011

We report on a room temperature detector of infrared/terahertz laser radiation allowing to measure and characterized the radiation polarization state with picosecond time resolution.
Selection of Optimum Nonlinear Crystals for Efficient Parametric Generation and Sensitive Detection of Monochromatic ns THz Pulses
Authors: Ding Yujie J.
Published: April 2011

We report our recent progress made on the development of widely-tunable monochromatic THz sources. They have been realized based on difference-frequency generation (DFG) in GaSe, ZnGeP2, and GaP crystals, respectively. Using a GaSe crystal, the output wavelength was tuned continuously in the range from 66.5 µm to 5664 µm (from 150 cm-1 to 1.77 cm-1) with the peak power reaching 389 W. Such a high peak power corresponds to a conversion efficiency of about 0.1% (a photon conversion efficiency of 19%). A further optimization on the THz beam parameter may result in an output peak power of a few kW. Within the range of 100-250 µm the output peak powers were higher than 100 W. We have also investigated THz frequency upconversion in GaSe, ZnGeP2, and GaP crystals. Such a parametric process has a potential for detecting THz pulses at room temperature or just using a thermoelectric cooler. The minimum detectable energy per pulse was measured to be 245 pJ, which corresponds to a noise equivalent energy of 77.5 . A further optimization of the process can reduce this value down to 1 .
Alternative Catalysts For Si-Technology Compatible Growth Of Si Nanowires
Authors: Iacopi Francesca , Vereecken Philippe M , Schaekers Marc , Caymax Matty , Moelans Nele , Blanpain Bart , Detavernier Christophe , D'Haen Jan , Griffiths Hefin
Published: April 2011

The use of Au nanoparticles as catalysts for growth of Si nanowires poses fundamental reliability concerns for applications in Si semiconductor technology. In this work we show that the choice of catalysts can be broadened when the need for catalytic precursor dissociation is eliminated. However, the requirements for selective deposition in a gas phase transport -limited regime become stringent. When competing deposition of amorphous Si can bury the particles faster than the incubation time for VLS growth, no nanowire growth will be initiated. We show that the use of a catalyst such as In, already in a liquid form at the growth temperature, is effective. Therefore, the choice of VLS catalysts among the low melting point metals from the III, IV and V groups is suggested.
Zero Valley Splitting at Zero Magnetic Field for Strained Si/SiGe Quantum Wells
Authors: Lee Seungwon , von Allmen Paul
Published: April 2011

The electronic structure for a strained silicon quantum well grown on a tilted SiGe substrate is calculated using an empirical tight-binding method. For a zero substrate tilt angle the two lowest minima of the conduction band define a non-zero valley splitting at the center of the Brillouin zone. A finite tilt angle for the substrate results in displacing the two lowest conduction band minima to finite k0 and -k0 in the Brillouin zone with equal energy. The vanishing of the valley splitting for quantum wells grown on tilted substrates is found to be a direct consequence of the periodicity of the steps at the interfaces between the quantum well and the buffer materials.
Phonon Spectra and Thermodynamic Properties Of Crystalline Nanowires
Authors: Ilic Dušan , Vucenovic Siniša , Jacimovski Stevo , Zoric Vojkan , Šetrajcic Jovan
Published: April 2011

Phonon spectra and allowed phonon states, as well as thermodynamic characteristics of nanowires of simple cubic crystalline structure, are analyzed using the method of two-time dependent Green's functions, adjusted to bounded crystalline structures. Poles of Green's functions, defining phonon spectra, can be found by solving of the secular equation. For different boundary parameters, this problem is presented graphically. The presence of boundaries as well as the change of boundary parameters leads to appearance of new properties of low dimensional structures (thin film and nanowire). The most important feature is that beside allowed energy zones (which are continuous as in the bulk structure), zones of forbidden states appear. Different values of boundary parameters lead to appearance of lower and upper energy gaps, or dispersion branches spreading out of bulk energy zone. The correlation with spectra of phonons in corresponding unbounded structures is maintained in the work. Determination of phonon spectra and allowed phonon energies has great importance for kinetic and thermodynamic properties of semiconductive nanostructures and devices. The temperature behavior of nanowire thermal capacitance is compared to that of bulk structures. It is shown that at extremely low temperature nanowire thermal capacitance is considerably lower than the thermal capacitance of bulk sample. It was discussed what are the consequences of this fact to the thermal, conducting and superconducting properties of materials.
Platinum Nanostructure Growth Using Self-Assembled Fluorocarbon Structure
Authors: Lee Sang Hwui , Liu Zhengchun , McMahon J. Jay , Lu Jian-Qiang
Published: April 2011

We report on a novel approach to grow platinum (Pt) nanostructure using a self-assembled fluorocarbon structure as a template. A ring-type structure of fluorocarbon residues forms during the reactive ion etching (RIE) of SiO2 using trifluoromethane (CHF3) and oxygen as etching gases. Typical dimensions of the ring-type fluorocarbon structure are found to be ∼50 nm in diameter, ∼10 nm in wall thickness, and ∼50 nm in height in this study. Platinum nanostructure up to 100 nm in height and 50 nm in diameter are grown on the template using a low-cost thin film sputter coater for 3 minutes. The morphology and growth mechanism of fluorocarbon structure and platinum nanostructure are discussed. This work provides a simple approach to platinum nanostructure growth for a fuel-cell application.
Modeling the Carrier Mobility in Nanowire Channel FET
Authors: Prost Werner , Blekker Kai , Do Quoc-Thai , Regolin Ingo , Müller Sven , Stichtenoth Daniel , Wegener Katharina , Ronning Carsten , Tegude Franz-Josef
Published: April 2011

We report on the extraction of carrier type, and mobility in semiconductor nanowires by adopting experimental nanowire field-effect transistor device data to a long channel MISFET device model. Numerous field-effect transistors were fabricated using n-InAs nanowires of a diameter of 50 nm as a channel. The I-V data of devices were analyzed at low to medium drain current in order to reduce the effect of extrinsic resistances. The gate capacitance is determined by an electro-static field simulation tool. The carrier mobility remains as the only parameter to fit experimental to modeled device data. The electron mobility in n-InAs nanowires is evaluated to µ = 13,000 cm2/Vs while for comparison n-ZnO nanowires exhibit a mobility of 800 cm2/Vs.
Carbon Nanotube Free-Standing Film of Pt/MWNTs as a Bifunctional Component in Hydrogen Proton Exchange Membrane Fuel Cells
Authors: Tang Jason M. , Jensen Kurt , Larsen Paul , Li Wenzhen , Itkis Mikhail E. , Yan Yushan , Haddon Robert C.
Published: April 2011

Conventional fuel cell architecture on one side of the membrane electrode assembly consists of a carbon backing layer, hydrophobic microporous layer (MPL), and a catalyst layer, which is in contact with the solid proton exchange membrane. Pt nanoparticles are deposited onto multi-walled carbon nanotubes (Pt/MWNTs) and a free-standing film of Pt/MWNTs is fabricated to act as the MPL and the catalyst layer in hydrogen fuel cells. The free-standing film of Pt/MWNTs condenses two functions into one bifunctional layer that simplifies the fuel cell fabrication procedure. Fuel cell polarization performance improves when using the free-standing film of Pt/MWNTs without the MPL resulting in a higher peak performance of 1.2 W/cm2 in comparison with 1.0 W/cm2 when in the presence of a MPL.
Carbon Nanotube Based Electrically Conductive and Optically Transparent Thin Films
Authors: Li Zhongrui , Dervishi Enkeleda , Saini Viney , Biris Alexandru R. , Lupu Dan , Xu Yang , Biris Alexandru Sorin
Published: April 2011

Highly electrically conductive and optically transparent thin films were fabricated on conventional glass substrates using different purified carbon nanotubes, single-wall (SWNT), double-wall (DWNT), and multi-wall (MWNT) carbon nanotubes. The starting carbon nanotube materials were first made into homogenous solution with either sodium cholate or dimethylformamide. Two different fabrication approaches, airbrushing and membrane filtration methods, were used and compared. The chemical modification of thionyl chloride was employed to further improve the optical and electric performance of the SWNT films. Additionally, the temperature dependence of the resistance measured on carbon nanotube networks has been investigated.