bluuebunny/crossref_metadata_2025_split huggingface dataset:
Size-Dependent Mechanical Properties of Polymer-nanowires Fabricated by Two-photon Lithography
Authors: Shoji Satoru , Nakanishi Sana , Hamano Tomoki , Kawata Satoshi 
Published: August 2010

AbstractTwo-photon lithography allows us to fabricate arbitrary three-dimensional structures with micro/nano-spatial resolution. The intrinsic three-dimensional spatial resolution of two-photon lithography is a promising tool for developing a variety of novel photonic and mechanical nano-devices. In addition, two-photon lithography makes it possible to study the properties of polymers of micro/nano-meter dimension [1-4]. In this presentation, we show the evidence that the elasticity and the transition temperature of polymers start to show size-dependent characteristics when the size of the polymer decreases down to a few hundreds of nanometers. We fabricated free-standing polymer nano-wires in the shape of coil spring by two-photon lithography, and measured the elasticity of the nano-wires by applying a mechanical tension onto the springs through laser trapping technique under temperature control. From the stretching length of the spring generated by a certain optical force, the spring constant of the spring and the shear modulus of polymer were calculated from simple Hook’s law. The material we used is a compound of methyl-methacrylate, dipentaerythritol hexaacrylate, benzil, and 2-benzyl-2-(dimethylamino)-4’-morpholino-butyrophenone. We scanned a light spot of a Ti:Sapphire laser at 780 nm with a pulse width of 80 fs focused by a 1.4 NA microscope objective to shape the polymer nano-wires suspended by a thick pillar. We observed that the elasticity of the polymer, which is usually an invariable coefficient, changes according to the thickness of the polymer wire. Furthermore, we changed the temperature of the entire polymer structures from -20 to 40 °C with measuring the elasticity of the springs. We observed phase transition of polymer wires with a rapid change of the share modulus, which also shows a size-dependent behavior. Recently, the similar experimental results, i.e. the drop of the glass transition temperature, were also reported in thin polymer nano-films. Our result is a clear evidence of such a nano size-effect of mechanical properties in polymers confirmed from free-standing polymer nanostructures. [1]S. Nakanishi, H. Yoshikawa, S. Shoji, Z. Sekkat, and S. Kawata, J. Phys. Chem. B 112, 3586-3589 (2008). [2] S. Nakanishi, S. Shoji, S. Kawata, and H.-B. Sun, Appl. Phys. Lett. 91, 063112 (2007). [3]H. Ishitobi, S. Shoji, T. Hiramatsu, H.-B. Sun, Z. Sekkat, and S. Kawata, Opt. Express 16, 14106-14114 (2008). [4]S. Kawata, H.-B. Sun, T. Tanaka, and K. Takada, Nature, 412, 697 (2001).
Elastic Properties of Mimetically Synthesized Model Nanoporous Carbon
Authors: Mi Xi , Shi Yunfeng 
Published: August 2010

AbstractActivated carbon is widely used for its attractive diffusion, adsorption and reaction properties. However, its mechanical behavior has received much less attention. We present a molecular dynamics simulation study on the elastic properties of activated carbon with nanometer-sized pores. The nanoporous carbon sample is composed of curved and defected graphene sheets, which is synthesized using quench molecular dynamics (QMD) method [1]. One unique feature of the current model is the mechanical stability, thus the bulk modulus, Young’s modulus, shear modulus and Poisson’s ratio can be obtained from simulated mechanical tests. By varying the density of the nanoporous carbon model, it was further found that the bulk modulus vs. density relation follows Gibson-Ashby type power law with exponents of 2.80 at low densities and 1.65 at high densities.
Ultra-fast Time-Resolved Electron Diffraction of Strongly Driven Phase Transitions on Silicon Surfaces
Authors: Möllenbeck Simone , Hanisch-Blicharski Anja , Schneider Paul , Ligges Manuel , Zhou Ping , Kammler Martin , Krenzer Boris , Horn-von Hoegen Michael 
Published: August 2010

AbstractThe dynamics of strongly driven phase transitions at surfaces are studied by ultra-fast time-resolved reflection high energy electron diffraction. The surfaces are excited by an intense fs-laser pulse (pump) and probed by an ultra-short electron pulse with variable time delay. The order-disorder phase transition from a c(4×2) to a (2×1) of the bare Si(001) surface shows a transient decrease of the intensity of the c(4×2) spots which recovers on a time scale of a few hundred picoseconds indicating the excitation of the phase transition. On Si(111) a monolayer of Indium induces a (4×1) reconstruction which undergoes a Peierls like phase transition to a (8×“2”) reconstruction below 100 K. Upon laser excitation at a temperature of 40 K the phase transition was strongly driven. The (8×“2”)-diffraction spots instantaneously disappears, while the intensity of the (4×1)-spots increases. This increase of the (4×1) spot intensity excludes an explanation by the Debye-Waller-Effect and is evidence for a true structural phase transition at a surface.
Ultrafast All-optical Switching and Laser Action in Rotaxane
Authors: Mroz Marta M. , Perissinotto Stefano , Virgili Tersilla , Salerno Marco , Sforazzini Giuseppe , Anderson Harry L. , Lanzani Guglielmo 
Published: August 2010

AbstractLinear and non-linear optical properties of conjugated polymers are often masked by the inter-chain network in solid state. The formation of aggregates may trap excitons, reduce oscillator strength and modify relaxation processes. The control of the inter-chain interaction is the main reason for developing “threaded” polymers, where supra-molecular encapsulation should reduce aggregation. Here, we investigate the influence of the encapsulation with β-cyclodextrin (β-CD) macrocycles on the photophysics of the polyfluorene-alt-biphenylene (PFBP) using femtosecond non-linear spectroscopy. Upon threading we observe enhancement of the stimulated emission (SE) in the visible range and reduction of the charge absorption. These phenomena are ascribed to the reduced inter-chain interaction. In more isolated chains the dynamics of intra and inter-chain charge states are distinguished. In addition, we performed three-beam experiments in which a first pulse (pump) creates singlet excited states; a second (push) pulse re-excite the singlet state and a broadband probe pulse detects the induced changes in transmission. This technique shows: (i) charges are generated from higher lying singlet states also in isolated chains (ii) ultrafast optical gain switching is possible in threaded chain. Finally, we demonstrate that ASE occurs in films of threaded polymers and lasing can be achieved with much lower threshold than the neat polymer chain in the DFB configuration. All our findings point out the potential role of rotaxanes in photonics, as amplifiers and reopen the route to the electrically pumped organic lasers and all-optical logic devices.
Short-pulse Laser Induced Transient Structure Formation and Ablation Studied with Time-resolved Coherent XUV-scattering
Authors: Sokolowski-Tinten Klaus , Barty Anton , Boutet Sebastien , Shymanovich Uladzimir , Chapman Henry , Bogan Mike , Marchesini Stefano , Hau-Riege Stefan , Stojanovic Nikola , Bonse Jörn , Rosandi Yudi , Urbassek Herbert M. , Tobey Ra'anan , Ehrke Henri , Cavalleri Andrea , Düsterer Stefan , Redlin Harald , Frank Matthias , Bajt Sasa , Schulz Joachim , Seibert Marvin , Hajdu Janos , Treusch Rolf , Bostedt Christoph , Hoener M. , Möeller Thomas 
Published: August 2010

AbstractThe structural dynamics of short-pulse laser irradiated surfaces and nano-structures has been studied with nm spatial and ultrafast temporal resolution by means of single-shot coherent XUV-scattering techniques. The experiments allowed us to time-resolve the formation of laser-induced periodic surface structures, and to follow the expansion and disintegration of nano-objects during laser ablation.
The Role of Thermal and Electronic Pressure in the Picosecond Acoustic Response of Femtosecond Laser-excited Solids
Authors: Shymanovich Uladzimir , Nicoul Matthieu , Kähle Stefan , Lu Wei , Tarsevitch Alexander , Zhou Ping , Wietler Tobias , Horn-von Hoegen Michael , von der Linde Dietrich , Sokolowski-Tinten Klaus 
Published: August 2010

AbstractUltrafast time-resolved X-ray diffraction has been used to study the dynamics of coherent acoustic phonons in fs laser-excited Ge and Au, with the particular goal to clarify the interplay of the electronic and thermal pressure contributions. For semiconductors it is usually assumed that the electronic pressure is the dominant driving force. Our measurements reveal that in Ge the relative strength of the electronic pressure decreases with increasing laser fluence. Only for low fluences the electronic pressure dominates, while at high fluences the thermal pressure exceeds the electronic pressure. For the case of Au the data are well described within the established theoretical framework using the known values for those material parameters which determine the laser-induced pressure, namely the energy relaxation time and the electronic and lattice Grüneisen parameters.
Synthesis of LNF Nano Particles for Fuel Cell Applications
Authors: Bateni Reza , Nasirpour Maryan , Kesler Olivera 
Published: August 2010

AbstractThe aim of the present work is to understand the effect of different parameters such as the molar ratio of metallic ions to fuel in sol-gel solution, pH of the solution, and calcining temperature on the efficiency of the combustion synthesis technique in preparing submicron lanthanum nickel ferrite using metal nitrate-citrate/glycine mixtures. Scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS) was used to evaluate the powder morphology and elemental composition. The crystal structure of the calcined powders was evaluated by X-ray diffraction (XRD) and the thermal characteristics of the LNF precursors were examined by thermo-gravimetric analysis (TGA) in air, to identify suitable processing conditions. It was found that by increasing the molar ratio of fuel to metallic ions in the precursor solution, calcining could take place at lower temperatures. However, by increasing the molar ratio of fuel to metallic ions, the yield of the combustion process was decreased. Furthermore, the pH value of the precursor solution did not have any influence on the process efficiency over the range examined.
Modification of Aluminium Surface Using Picosecond Laser for Printing Applications
Authors: Ansari Imtiyaz Ahmed , Watkins Kennith G. , Sharp Martin C. , Hutchinson Richard , Potts Rodney 
Published: August 2010

AbstractUltrafast picosecond laser pulses of wavelength of 1064nm have allowed the surface modification of anodised aluminium plate for potential industrial application. The interaction of the laser with the substrate created a hydrophilic surface, giving a contact angle of less than 10 degrees. On examination under a Scanning Electron Microscope (SEM), it was observed that these surfaces have an interesting ‘lotus-leaf’ like structure. It has been found that these laser processed hydrophilic surfaces revert with time. The potential for application in the printing industry is strong due to the reusability and sustainability of the process materials; initial trials confirm this. This technology would offer extra advantages as a non-chemical process without the need for developer, thereby reducing the overall cost and time of printing.
Quantitative Kelvin Probe Force Microscopy
Authors: Baumgart Christine , Helm Manfred , Schmidt Heidemarie 
Published: August 2010

AbstractIn this paper we report on the investigation of electrostatic forces between a conductive probe and semiconducting materials by means of Kelvin probe force microscopy measurements. Due to the formation of an asymmetric electric dipole at the semiconductor surface, the measured KPFM bias is related with the energy difference between Fermi energy and respective band edge. Quantitative Kelvin probe force microscopy measurements on semiconductors, namely on a conventional dynamic random-access memory cell and on a cross-sectionally prepared Si epilayer structure, are presented.
The Development of Silicon Carbide Based Electrode Devices for Central Nervous System Biomedical Implants
Authors: Frewin Christopher , Oliveros Alexandra , Locke Christopher , Filonova Irina , Rogers Justin , Weeber Edwin , Saddow Stephen E. 
Published: August 2010

AbstractBrain machine interface (BMI) technology has been demonstrated to be a therapeutic solution for assisting people suffering from damage to the central nervous system (CNS), but BMI devices using implantable neural prosthetics have experienced difficulties in that they are recognized by glial cells as being foreign material, which leads to an immune response cascade process called gliosis. One material, cubic silicon carbide (3C-SiC), may provide an excellent solution for the generation of an implantable neural prosthetic interface component of a BMI system. We have recently reported on the biocompatibility of 3C-SiC with immortalized cells, and have extended this work by demonstrating neural cell action potential instigation via an electrode type device. Biocompatibility assessment of 3C-SiC was accomplished using in vitro methodology. 96 hour MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assays were performed to determine neural cell viability. Atomic force microscopy (AFM) was used to quantify attached cell morphology and determine lamellipodia/ filopodia interaction with the surface of the semiconductor. It was seen that neurons show excellent viability, cell morphology, and good lamellipodia/ filopodia permissiveness when interacting with 3C-SiC. A neuronal activation device (NAD), based on the planar Michigan microelectrode probe, was constructed from 3C-SiC with the goal of activating an action potential within a neuron. In order to illicit an action potential, neurons were seeded on the NAD device and then they were subjected to a biphasic square pulse signal. Successful action potential activation was recorded through the use of Rhod-2, a Ca2+ sensitive fluorescent dye. Based on these results, 3C-SiC may be an excellent material platform for neural prosthetics.
Endothelial Cell Attachment and Proliferation Studies on Modified Metal Stent Surfaces
Authors: Davè Vipul , Buensuceso Charito , Colter David , Zhao Jonathon , Falotico Robert 
Published: August 2010

AbstractFlat coupons prepared from cobalt chromium alloy (CoCr) were modified using different methods (low energy excimer laser processing, electron beam irradiation, and immobilized covalently-bound heparin coating). Human coronary artery endothelial cell (HCAEC) attachment and growth kinetics were investigated on unmodified and modified metal surfaces. Results showed that HCAEC attach to unmodified CoCr coupons and surface-modified CoCr coupons. No change in cell number was observed when cells were grown on CoCr coupons and heparin coated coupons throughout the 72h study period. A decrease in cell number was observed for excimer treated coupons. HCAEC seeding on CoCr stents indicated that cells attached and proliferated on the stents over a ten day study period. This research showed that physical modifications did not improve cell proliferation. Very few non-viable cells were observed for unmodified and surface bound heparin coupons, and cells attached to the surface up to 72h. This shows that heparin can be coated on a stent surface to provide anti-thrombotic properties without any negative effect on cell attachment and proliferation. In vitro screening method of testing endothelial cell attachment and proliferation on modified metal stent surfaces can be used to gain insight for developing next generation drug eluting stents with improved endothelialization behavior.
Semiconductor Quantum Dots for Cell Imaging
Authors: Aguilar Zoraida Pascual , Xu Hengyi , Jones Ben , Dixon John , Wang Andrew 
Published: August 2010

AbstractNanotechnology is currently undergoing unprecedented development in various fields. There has been a widespread interest in the application of nanomaterials in medicine with its promise of improving imaging, diagnostics, and therapy. The recent advances in engineering and technology have led to the development of new nanoscale platforms such as quantum dots, gold nanocrystals, superparamagnetic nanocrystals, and other semiconductor nanoparticles. Literature on the applications of quantum dots in life sciences has recently increased in number. This may have led to predictions that nanotechnology in life sciences research will contribute $3.4 billion by 2010 while institutions have predicted that the market for nanotechnology and corresponding products will reach $1 trillion in 2012 (1).Ocean NanoTech is at the height of developmental stages of nanoparticle production for biological applications. Ocean’s high quantum-yield quantum dots (QDs) is currently being tested and used for cell imaging, as wells as for the detection of proteins, DNA, whole cells, and whole organisms. Imaging of cells involves conjugation of QDs to highly sensitive and specific antibody to form QD˜Ab conjugates that attach to specific protein target on the cell surface. Attachment of the QD˜Ab on the cell surface allows imaging of the cell under a fluorescence microscope. QD based imaging can be used in a multiplex immunoassay detection of several types of cells (or microorganisms) in a single sample when several size tunable quantum dots are used as reporter probes.We report the QD imaging of breast cancer cells. Using the breast cancer cell line SK-BR3, which expresses high levels of her2 antigens on the cell surface, anti-her2 were conjugated to Ocean’s quantum dots, QSH620. To eliminate non-specific binding of the QD˜20Ab Ocean’s super blocking buffer BBB and BBG were used. Preliminary results of in vitro studies indicated that QD based systems can be used to image cells. We anticipate that this system can be transferred to in vivo detection.
Encapsulation of BSA within Gelatin Nanoparticles-laden Biopolymer Film
Authors: Zhang Jin , Zhu Jesse , Akhter Kazi Farida , Thomas Anu Alice 
Published: August 2010

AbstractThis research project aims at the development of new biopolymer nanocomposites which enable to act as a critical component to next generation medical device. In this paper, we developed an in situ method to encapsulate model protein, bovine serum albumin (BSA), within gelatin nanoparticles (NPs). The results demonstrate that the average diameter of the BSA-containing gelatin NPs is approximately 180 nm±10 nm. They can absorb up to 70% of water. The gelatin- nanoencapuslated BSA afterwards were loaded in the biopolymer film with thickness around 150 μm composed of poly(2-hydroxyethyl methacrylate) (pHEMA) through the photopolymerization. The release kinetics of BSA from the nanoparticles and the nanoparticle-laden p(HEMA) were studied through UV-Vis spectrometry, respectively. The releasing concentration of BSA increased with time (t), and about 80% of the encapsulated BSA was released in 80 hrs; while, the releasing profile of BSA from the gelatin nanoparticles-loaded hydrogel can be monitored up to10 days. These studies show that the gelatin nanoparticles are able to encapsulate water-soluble protein. The hydrogel film, pHEMA, enable to further prolong the releasing profile for the water soluble protein. It is expected that this new biodegradable polymer nanocomposites can be an alternative materials for consisting of implant medical device for protein therapy.
Photoluminescent Nanofibers for Solid-State Lighting Applications
Authors: Davis Lynn , Han Li , Hoertz Paul , Guzan Kim , Mills Karmann C. , Walls Howard J. , Walker Teri A. , Magnus-Aryitey Damaris 
Published: August 2010

AbstractPhotoluminescent nanofibers (PLN) can be formed by combining electrospun polymeric nanofibers and luminescent particles such as quantum dots (QD). The physical properties of PLNs are dependent upon many different nanoscale parameters associated with the nanofiber, the luminescent particles, and their interactions. By understanding and manipulating these properties, the performance of the resulting optical structure can be tailored for desired end-use applications. For example, the quantum efficiency of quantum dots in the PLN structure depends upon multiple parameters including quantum dot chemistry, the method of forming the PLN nanocomposites, and preventing agglomeration of the quantum dot particles. This is especially important in solution-based electrospinning environments where some common solvents may have a detrimental effect on the performance of the PLN. With the proper control of these parameters, high quantum efficiencies can be readily obtained for PLNs. Achieving high quantum efficiencies is critical in applications such as solid-state lighting where PLNs can be an effective secondary conversion material for producing white light. Methods of optimizing the performance of PLNs through nanoscale manipulation of the nanofiber are discussed along with guidelines for tailoring the performance of nanofibers and quantum dots for application-specific requirements.
Electrospun Nanofiber Networks for Electronics and Optics
Authors: Tanioka Akihiko , Matsumoto Hidetoshi , Tsuboi Kazuma 
Published: August 2010

AbstractIn this paper, we report on the preparation and applications of nanofiber networks, particularly in the area of optelectronics. The major topics are (i) carbon nanotubes grown on carbon nanofibers for a field emitter, (ii) dye-sensitized ZnO nanowires grown on carbon nanofibers for a photoelectrochemical cell, (iii) nanofiber coatings for coloring, and (iv) nanofiber coatings on gold substrate for surface plasmon resonance. The results presented here reveal the potential use of nanofiber networks for various optoelectronic devices.
Thin Film Silicon Photovoltaic Technology – From Innovation to Commercialization
Authors: Guha Subhendu , Yang Jeffrey 
Published: August 2010

AbstractThe last decade has witnessed tremendous progress in the science and technology of thin film silicon (amorphous and nanocrystalline) photovoltaic. The shipment of solar panels using this technology was about 200 MW in 2009; based on announcement of new or expanded production capacity, the shipment is projected to grow ten-times in the next 3-5 years. The key factor that will determine the wide-scale acceptance of the products will be the cost of solar electricity achieved using this technology. Efficiency of solar modules and throughput of production equipment will play a key role. In this paper, we discuss our roadmap to improve the product efficiency and machine throughput.
Advanced Light Trapping in Thin-film Silicon Solar Cells
Authors: Zeman Miro , Isabella Olindo , Jaeger Klaus , Santbergen Rudi , Liang Renrong , Solntsev Serge , Krc Janez 
Published: August 2010

AbstractPhoton management is one of the key issues for improving the performance of thin-film silicon solar cells. An important part of the photon management is light trapping that helps to confine photons inside the thin absorber layers. At present light trapping is accomplished by the employment of the refractive-index matching layers at the front side and the high-reflective layers at the back contact of the solar cells and scattering of light at randomly surface-textured interfaces. In this article key issues and potential of light management in thin-film silicon solar cells are addressed. Novel approaches for light trapping are presented such as i) surface textures based on periodic diffraction gratings and modulated surface morphologies for enhanced scattering and anti-reflection, ii) metal nano-particles introducing plasmonic scattering, and iii) one-dimensional photonic-crystal-like structures for back reflectors.