bluuebunny/crossref_metadata_2025_split huggingface dataset:
First-principles Study of Adsorption Energetics of Alkanethiols on GaAs(001)
Authors: Voznyy Oleksandr , Dubowski Jan J. 
Published: April 2011

ABSTRACTAdsorption of alkanethiols on GaAs (001) surface under low coverage conditions was studied using density functional calculations in a periodic supercell approach. The study of physisorbed precursor and transition to chemisorption revealed that hydrogen atoms stay on the surface upon S-H bond cleavage and significantly affect desorption products and energies, in agreement with available experimental data. Binding of thiols to GaAs is found to be comparable or stronger than that of thiols to noble metals surfaces. Calculated thiolate-surface binding energies are found to be higher for Ga-rich than for As-rich surfaces, and are strongly dependent on surface reconstruction, adsorption site and coverage. This dependence is explained by the violation or fulfillment of electron counting rule, rehybridization of surface atom orbitals and strain relaxation upon addition of extra electrons brought by adsorption.
Design of a Novel Electrically Conducting Biocompatible Polymer with Degradable Linkages for Biomedical Applications
Authors: Guimard Nathalie Kathryn , Sessler Jonathan L. , Schmidt Christine E. 
Published: April 2011

ABSTRACTUpon the discovery of the first conducting polymer in 1976, the replacement of metal-based semiconductors in many applications with conducting polymers was inevitable. Perhaps more surprisingly these materials showed promise in many biomedical applications. The finding that electrical fields and charges modulate shape, size, and proliferation of a number of cell types including nerve and bone, has prompted biomedical engineers to focus on the development of conducting polymer scaffolds for tissue regeneration and neural probes. A number of polymers have been studied for these applications, including polypyrrole (PPy), polythiophene, and polyaniline. One serious limitation to the use of conducting polymers in biological systems is their inability to degrade. Therefore, it has been proposed to design and synthesize a biocompatible, biodegradable, semiconducting polymer, which could broaden the scope of applications for conducting polymers. For instance, these unique polymers could potentially be implemented in temporary tissue and neural scaffolds, drug delivery, short-term electrodes, and tethers between nanotubes. Therefore, the goal of this investigation is to synthesize a polymer that is degradable, while maintaining conductivity. Initially, the incorporation of pyrrole oligomers into a biodegradable polymer was attempted; however, to overcome difficulties associated with the instability of these oligopyrroles, a novel polymer design has been proposed which incorporates thiophene oligomers. Oligothiophenes (OTs) are apt to be more conductive than oligopyrroles due to a smaller band gap between the valence and conductance bands. Additionally, OTs share many of the advantageous properties of oligopyrroles, including cell compatibility, but are more stable. The proposed novel co-polymer consists of quaterthiophene oligomers tethered together by aliphatic ester linkages, which would potentially render the co-polymer conductive by means of inter and intra chain oligo overlap and degradable via cleavage of the ester bond by esterases in the body. The synthesis of the novel copolymer, poly-dialcohol dimethyl quaterthiophene-co-adipic acid (PAMQAA) has been completed successfully and corroborated by NMR and MALDI. Initial characterization indicates PAMQAA has the following properties: Mw = 11,240-64,080 g/mol, PI = 1.2-1.4, degradation temperature = ∼160°C. Currently PAMQAA is being characterized to assess its Tg, Tm, conductivity, degradability, and biocompatability. Polymer modifications could allow further optimization of properties, such as the rate of degradation and conductivity, to target better the application of interest.
Integration of Biomolecules with Inorganic Ferroelectrics: A Novel Approach to Nanoscale Devices
Authors: Reiss Brian , Auciello Orlando , Ocola Leonidas E. , Firestone Millicent Anne 
Published: April 2011

ABSTRACTIn this work, we investigate the feasibility of using a surface-tethered heptapeptide sequence as the basis for a ferroelectric-actuated component in a nanofluidic device. The fluorescently-labeled peptide sequence, (CISLLHSTC) is shown by fluorescence microscopy to selectively coat the PZT patterned channel floors. The peptide binding strength to PZT is determined over a range of flow rates in the patterned channel by imaging the fluorescence intensity of the coated channel and monitoring the output spectroscopically. The peptide is found to be stripped from the PZT at flow rates exceeding 5mL/h. Initial results demonstrating the possibility of covalently integrating the short peptide sequence to larger biological components such as antibodies are also presented.
Development of Novel Nanostructured Tissue Engineering Scaffold Materials through Self-assembly for Bed-side Orthopedic Applications
Authors: Zhang Lijie , Ramsaywack Sharwatie , Fenniri Hicham , Webster Thomas J. 
Published: April 2011

ABSTRACTThe objective of the current study was to utilize a natural self-assembled organic biomaterial (helical rosette nanotubes (HRNs)) to improve bone growth necessary for orthopedic implant applications. The DNA base pair building blocks of HRNs can self-assemble through 18 H-bonds to form a supermacrocycle in water which then stack to form a nanotube 3.5 nm in diameter and several μm in length. The nanometric features and ability to place diverse amino acid side chains on HRNs make them intriguing materials for orthopedic applications. In this study, HRNs are combined with a biocompatible hydrogel matrix in order to obtain more robust scaffolds. Bone cell experiments in vitro demonstrated that the novel HRNs with hydrogels could greatly enhance osteoblast (bone-forming cell) adhesion even at a very low concentration (close to 0.001mg/ml). Morphology of the HRNs with hydrogel scaffolds was characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM) and atomic force microscopy (AFM). Results showed that there were bundles of nanotubes in the HRNs with hydrogel scaffolds. Therefore, considering the good biocompatibility and nano bone-like structure of these scaffolds, the nanostructured hydrogel matrix with HRNs have the potential to serve as novel bone building agents for “on-the-site” orthopedic applications.
Detection of Respiratory Viruses with Plastic High Throughput Screening Devices
Authors: Zhao Zhengshan , Diaz-Quijada Gerardo A. , Peytavi Régis , LeBlanc Éric , Frenette Johanne , Boivin Guy , Zoval Jim V. , Madou Marc , Dumoulin Michel M. , Veres Teodor , Bergeron Michel G. 
Published: April 2011

ABSTRACTMicroarrays have become one of the most convenient tools for high throughput screening and have catalyzed major advances in genomics and proteomics. Other important applications can be found in medical diagnostics, detection of biothreats, drug discovery, etc. Integration of microarrays with microfluidic devices can be highly advantageous in terms of portability, shorter analysis time and lower consumption of expensive biological analytes. Since fabrication of microfluidic devices using traditional materials such as glass is rather expensive, there is a high interest in employing polymeric materials as a low cost alternative suitable for mass production. We present proof-of-concept DNA arrays on a plastic platform for the detection of four important respiratory pathogens: Influenza A virus, respiratory syncytial virus, human enterovirus, and human metapneumovirus.This was accomplished by amplifying the genetic material from the viruses and simultaneously labeling the amplicons with a fluorescent dye (Cy3) via a highly sensitive multiplex Reverse Transcription Polymerase Chain Reaction (RT-PCR). The resultant RT-PCR product was hybridized, without further purification, with an array of specific oligonucleotide probes (20 mers) that had been covalently bound to a plastic substrate. Results indicate a high signal to background ratio that is comparable to commercially available microarray glass slides. In addition, 5 minute hybridization on this plastic substrate has been demonstrated using a centrifugal microfluidic platform, paving the way to a rapid medical diagnostic device for point-of-care use that is based on a low-cost portable Micro-Total-Analysis-System (μ-TAS).
Ge/Si self-assembled Islands for Photonics Applications
Authors: Boucaud Philippe , El Kurdi Moustafa , Li Xiang , Sauvage Sébastien , Checoury Xavier , David Sylvain , Yam Navy , Fossard Frédéric , Bouchier Daniel , Fishman Guy 
Published: April 2011

ABSTRACTWe first present an analysis of the band line-up in the case of SiGe/Si quantum wells and in the case of SiGe/Si self-assembled islands. The conduction and valence band diagrams are obtained from a 30 band k.p Hamiltonian which allows to describe simultaneously conduction and valence band states. The strain field is obtained from a microscopic valence force field theory. The band edge alignment is strongly dependent on the input parameters for this heterosystem. We determine the average valence band offset from photoluminescence measurements of heterostructures grown on relaxed SiGe buffer layers. A type II band line-up is calculated for all Ge compositions in the case of two-dimensional quantum wells and SiGe/Si self-assembled islands. The 30-band formalism allows the determination of the near-infrared interband recombination energy as a function of the self-assembled island structural parameters. We then present recent results obtained by embedding SiGe/Si self-assembled islands in two-dimensional photonic crystals. The photoluminescence of GeSi islands acts as an internal probe to characterize the optical properties of silicon-based two-dimensional photonic crystals designed for the near-infrared spectral range. Cavities, defect-free photonic crystals operated at the second Bragg order and two-dimensional photonic crystals fabricated on top of one-dimensional Bragg mirrors (2D + 1D) are described. We show that, in the case of 2D +1D structures, we can control the quality factor of optical modes at the second Bragg order by matching the resonance conditions and controlling the thickness of the layers. Photonic crystals with pure Ge layers are finally described.
Luminescence in Multilayers of SiGe Nanocrystals Embedded in SiO2
Authors: Avella Manual , Prieto Ángel Carmelo , Jiménez Juan , Rodríguez Andrés , Sangrador Jesús , Rodríguez Tomás , Ortiz María Isabel , Ballesteros Carmen , Kling Andreas 
Published: April 2011

ABSTRACTLuminescent multilayers of SiGe nanocrystals embedded in an oxide matrix have been fabricated by Low Pressure Chemical Vapour Deposition of a-SiGe and SiO2 in a single run followed by a Rapid Thermal Annealing treatment. The diameter of the nanoparticles, the oxide interlayer thickness and the annealing conditions have been investigated in order to get the maximum intensity of the luminescence. The structures with small nanoparticles (3-4.5 nm) separated by thick oxide barriers (≈35 nm) annealed at 900 °C for 60 s yield the maximum intensity. These samples exhibit luminescence from 80 K to room temperature. An additional treatment at 450 °C in forming gas further increases the intensity of this luminescence.
Laser Crystallization of Silicon Thin Films Using Photo Absorption Layer Formed by Spin Coating of Carbon Particles
Authors: Andoh Nobuyuki , Maki Masato , Sameshima Toshiyuki , Sano Naoki 
Published: April 2011

ABSTRACTWe report crystallization of amorphous silicon films 50∼1400 nm thick formed on glass substrates by irradiation of an infrared semiconductor laser. Carbon particles with a mean diameter of 200 nm were uniformly coated on the silicon films as the optical absorption layer. Samples were irradiated with a 940-nm continuous wave (CW) semiconductor laser with a power of 20 W. A high optical absorbance 76.5% at 940 nm of the carbon particles layers resulted in annealing of silicon films by heat diffusion from the carbon particle layers. After removing the carbon particles layer, Raman scattering spectral measurements were carried out. A high scattering intensity and a sharp crystalline silicon phonon band were observed. The analysis of Raman spectra revealed a crystalline volume ratio almost 1.0. The analysis of the optical reflectivity spectra also revealed that the silicon films were crystallized in the whole thickness by the present method.
Nonlinear Optical Properties of Si Nanocrystals
Authors: Spano Rita , Cazzanelli Massimo , Daldosso Nicola , Gaburro Zeno , Ferraioli Luigi , Tartara Luca , Yu Jin , Degiorgio Vittorio , Hernandez Sergi , Lebour Youcef , Pellegrino Paolo , Garrido Blas , Jordana Emmanuel , Fedeli Jean Marc , Pavesi Lorenzo 
Published: April 2011

ABSTRACTA systematic study of nonlinear optical properties of silicon nanocrystals (Si-nc) grown by plasma enhanced chemical vapor deposition (PECVD) is reported. Nonlinear optical refraction and absorption have been measured by z-scan technique at three different time regimes and at different wavelengths to investigate both the thermal and electronic responses. For this purpose three different laser sources have been used. Different behaviors, as expected from the theory, for different pump pulse durations are observed.
Mn-incorporated ZnSe and CdSe 1-dimensional Nanostructures
Authors: Hwang Seonoh , Lee Jinyoung , Lee Hyunju , Yoon Sangwon , Park Jeunghee 
Published: April 2011

ABSTRACTNovel Mn-incorporated ZnSe and CdSe 1-dimensionl nanostructures; straight nanowires, zigzagged nanobelts, and nanohooks, were first synthesized using chemical vapor deposition method. The Mn content reaches up to 40%. They all consisted of single-crystalline wurtzite structure for all Mn content. The structure has been thoroughly investigated by high-resolution transmission electron microscopy images as well as energy-dispersive X-ray fluorescence spectroscopy. The X-ray diffraction pattern confirms the formation of the wurtzite structure, even for 40% Mn incorporation. The lattice constants of Mn-doped ZnSe and CdSe 1-D nanostructures are expanded and reduced, respectively, by the Mn doping. The Mn2+ emission at 2.1 eV, originating from the d-d (4T1 → 6A1) transition, confirms the effective paramagnetic Mn2+ doping at tetrahedral coordinate sites. These Mn-incorporated nanostructures exhibit a paramagnetic behavior.
Patterned Carbon Nanotube Thin-Film Transistors with Transfer-Print Assembly
Authors: Sangwan Vinod. K. , Hines D. R. , Ballarotto V. W. , Esen G. , Fuhrer M. S. , Williams E. D. 
Published: April 2011

ABSTRACTConditions for the transfer printing of patterned carbon nanotube (CNT) films, along with a Au-gate, a poly methylmethacrylate (PMMA) dielectric layer and Au source-drain electrodes have been developed for the fabrication of thin-film transistors on a polyethylene terephthalate (PET) substrate. Chemical vapor deposition (CVD) grown CNTs were patterned using a photolithographic method.Transfer printing was used to fabricate devices having both top gate and bottom gate configurations. Replacement of the SiO2 dielectric with PMMA correlates with a decreased hysteresis in the transconductance behavior. Encapsulation of the CNTs between the polymeric substrate and dielectric layer yields ambipolar behavior. Variations in device performance are also observed as a function of CNT film density and channel length, suggesting changing contributions of the metallic and semiconducting CNTs to the transport mechanism.
Single Walled Carbon Nanotube Analysis by Photoluminescence and Raman Microscopy: Rapid, Robust Acquisition and Simulation of Quantum and Chiral Maps to Ease Structural Assignments
Authors: Gilmore Adam Matthew , Adar Fran , Lee Eunah , Kaminski Ray , Whitley Andrew 
Published: April 2011

ABSTRACTThis paper describes improved methods for both data acquisition and analysis that are pertinent to interpreting the structural composition of single-walled carbon nanotube (SWNT) mixtures and suspensions.Rapid data acquisition of photoluminescence is made possible with a specially configured spectrofluorometer which uses a liquid nitrogen-cooled InGaAs array detector, imaging spectrograph, excitation reference photodiode and tunable xenon excitation source to collect seamless, instrument-corrected, excitation-emission quantum maps. The preferred instrument configuration with the InGaAs array can generate a quantum map with both high S/N levels and spectral resolution in only seconds to minutes; previous single-channel InGaAs photodiode and photomultiplier detector measurements took hours to days. The standard spectral range for excitation and emission is from 250 nm to 1700 nm with an option to extend to 2200 nm. Robust analysis of the quantum maps is facilitated by a custom global analysis program (US Patent Pending) which incorporates a powerful ‘double-convolution integral’ DCI algorithm to simultaneously model the excitation and emission spectral bands for each SWNT species. The patented DCI algorithm reduces the number of free fitting parameters for the spectral simulation by up to a factor of 1000 compared to conventional 2 D spectral simulators. The global analysis yields quantitative information on the chirality and diameter parameters of SWNT species in a given mixture. Together the acquisition hardware and analysis software constitute significant developments with respect to enhanced sensitivity and statistical significance for quantifying the components of complex SWNT mixtures.Raman maps of SWNT's were collected from dispersions plated onto substrates such as silicon plates using multiple excitation wavelengths. Identification of the chirality of the tubes was made using the Kataura plot. In many instances single lines in the radial breathing mode region were recorded indicating the presence of a single tube. The implication for this observation is that there is more than adequate sensitivity to detect and identify single-walled tubes. More recently Raman excitation on an AFM using a gold-coated tip to induce surface enhancement has been achieved. In this configuration it will be possible to map the topology of the tubes using detailed information on their structural composition.
Covalent Bond Formation in Defected Nanopeapods Induces Local Deformations on Nanotube Walls
Authors: Yumura Takashi , Kertesz Miklos 
Published: April 2011

ABSTRACTProperties of defected nanopeapods, in which a defected C60 cage with a C1–C59 topology is encapsulated inside a (10,10) single walled carbon nanotube, have been analyzed using density functional theory (DFT) calculations. When new CC bonds are formed between the defected C60 and the nanotube, the CC network of the nanotube is perturbed near the binding site, and has butadiene and quinonoid perturbations. Such geometrical changes could play an important role in the selective functionalizations of carbon nanotubes.
Carbon Nanotube - Silicon Heterojunction Hyperspectral Photocurrent Response
Authors: Kuo Teng-fang , Straus Daniel A. , Tzolov Marian , Xu Jimmy 
Published: April 2011

ABSTRACTCarbon nanotubes (CNT) have been studied intensively for explorations of their unique electrical and mechanic properties in many applications. However, direct and functional integration of carbon nanotubes with silicon to form an electronically functional structure or device has remained a great challenge. Whereas vertically aligned bundles of nanotubes have been grown previously on silicon, the integration is mechanical, rather than electronical, in nature and the application of such mechanical integration is rather limited. In this work, we report on electronically functional integration of carbon nanotube with silicon, i.e., the formation of an electronic heterojunction by controlled growth of vertical and highly ordered array of ‘carbon nanotube - silicon’ (CNTS) heterojunctions of uniform diameter, length, and alignment. Moreover, we examine it as a hyperspectral photodiode. From the measured spectral dependence of the photocurrent, one may also extract the band gap of the nanotubes, which we find to be in agreement with that determined from conductance measurements. Mechanism of the infrared photocurrent response is elucidated by the current-voltage (I-V) and radiation intensity-photoresponse measurements. The linear intensity dependence of the photoresponse in the absorption ranges of Silicon and CNTs and the measured I-V characteristics all suggest that the photocurrent responses corresponding to the Silicon and CNT bands both originate from the intrinsic functionality of the heterojunction.
Molecular-Wetting Control by Ultrasmooth Pentacene Buffer for High-crystallinity Organic Field-Effect Transistors
Authors: Itaka Kenji , Yamashiro Mitsugu , Yamaguchi Jun , Haemori Masamitsu , Yaginuma Seiichiro , Matsumoto Yuji , Koinuma Hideomi 
Published: April 2011

ABSTRACTOrganic thin film devices are of interest for a variety of forthcoming ubiquitous electronics applications. In order to build ubiquitous high-performance devices, it is necessary to fabricate crystalline thin films of various organic materials onto “ubiquitous substrates” that are dictated by applications. However, many organic thin films crystallize only on a limited selection of substrates. Unfortunately, promising organic molecules, which have a large overlap of pi-orbitals between molecules, cannot migrate freely on a substrate because of stronger cohesion between molecules than interaction between the molecule and the substrate. Therefore, enhancement of the molecule-substrate interaction, i.e. ‘molecular wettability’ should promote crystallization. We found that an ultrasmooth monolayer of pentacene (C22H14), which can be grown on many general dielectric substrates, changes the molecular wettability of a substrate for other poorly wettable organic materials. We also demonstrate that a field effect transistor (FET) using a crystalline C60 thin film on a pentacene-buffered substrate can have a mobility of 4.9 cm2/Vs, which is 5-fold higher than that of C60 FETs without the buffer. Molecular wetting-controlled substrates can thus offer a general solution to the fabrication of high-performance crystalline plastic and molecular electronics.
Self Organization in Thin Films of a Substituted Perylene Imide with a Twisted Aromatic Core
Authors: Graaf Harald , Mattheus Christine C , Schlettwein Derck 
Published: April 2011

ABSTRACTThe aromatic core of perylene bisimides can be twisted by chemical substitution with chlorine in the bay-position. An example for this strategy is 1,6,7,10-tetra-chloro-N,N'-dimethyl-perylene-tetracarboxylic-bisimide, Cl4MePTCDI. This twisting leads to a decrease in directed intermolecular interactions, which causes a decrease in the electronic coupling of the molecules, interesting to be investigated in thin films of this molecular semiconductor. An amorphous solid phase was formed by physical vapor deposition. This amorphous phase showed the tendency to crystallize under ambient conditions as apparent von optical microscopy at the films. The crystallized phase was investigated by atomic force microscopy AFM and optical methods, where a formation of weak excimers was found.
Dependency of Nonvolatile Memory Behavior on Curing Temperature for Au Nanocrystals Embedded in PVK
Authors: Han Beyong-il , Lee Chang-Kyu , Kwon Jong-Sung , Na In-Chul , Park Jea-gun , Kim Young-Min 
Published: April 2011

ABSTRACTA bistable effects of Au nano-crystals embedded in poly(N-vinylcarbazole) (PVK) were observed. Subsequently we investigated dependency of the nonvolatile memory behavior on curing temperature for the Au nano-crystals embedded in the PVK. For the study, in the devices of different curing temperatures we measured current-voltage characteristics for the devices and investigated the formation of the Au nano-crystals using cross sectional transmission electron microscopy (TEM). The nonvolatile memory behavior depends on the curing temperature, which is attributed to the suitable formation of the Au nano-crystal.