Here, we report results of our simulations studies on modeling the collagen-hydroxyapatite (HAP) interface in bone and influence of these interactions on mechanical behavior of collagen through molecular dynamics and steered molecular dynamics (SMD). Models of hexagonal HAP (10-10) and (0001) surface, and collagen with and without telopeptides were built to investigate the mechanical response of collagen in the proximity of mineral. The collagen molecule was pulled normal and parallel to the (0001) surface of hydroxyapatite. Water molecules were found have an important impact on deformation behavior of collagen in the proximity of HAP due to their large interaction energy with both collagen and HAP. Collagen appears stiffer at small displacement when pulled normal to HAP surface. At large displacement, collagen pulled parallel to HAP surface is stiffer. This difference in mechanical response of collagen pulled in parallel and perpendicular direction results from a difference in deformation mechanism of collagen. Further, the collagen molecule pulled in the proximity of HAP, parallel to surface, showed marked improvement in stiffness compared to absence of HAP. Furthermore, the deformation behavior of collagen not only depends on the presence or absence of HAP and direction of pulling, but also on the type of mineral surface in the proximity. The collagen pulled parallel to (10-10) and (0001) surfaces showed characteristically different type of load-displacement response. In addition, here we also report simulations on 300 nm length of collagen molecule indicating the role of length of model on the observed response in terms of both the magnitude of modulus obtained as well as the mechanisms of response of collagen to loading.

A Ag-Au(1-D)-CeO2 catalyst was prepared by precipitation method using Ag-Au nanowires and Ce(NO3)3·6H2O as precursors. The catalytic activity of the catalysts was evaluated in a steam reforming of methanol (SRM) reaction from 250 to 475 °C. 100 % of methanol conversion was observed at 450 °C together with high H2 selectivity. This study evidenced that the use of 1-D metallic nanostructures could be used as an active phase on a CeO2 matrix for steam reforming of methanol for H2 generation to be used as fuel.

The ground state electronic structures of the actinide oxides AO, A2O3 and AO2 (A=U, Np, Pu, Am, Cm, Bk, Cf) are determined from first-principles calculations using the self-interaction corrected local spin-density approximation. Our study reveals a strong link between preferred oxidation number and degree of localization. The ionic nature of the actinide oxides emerges from the fact that those oxides where the ground state is calculated to be metallic do not exist in nature, as the corresponding delocalized f-states favour the accommodation of additional O atoms into the crystal lattice.

Chalcopyrite Cu(In,Ga)S2 is a promising absorber in thin film solar cells, although the comparable high band gaps so far do not correspond to equivalent high open circuit voltages. We have performed photoluminescence studies on CdS passivated absorber layers deposited on Mo coated soda lime glass. From spectrally and spatially resolved (≤ 1μm) room temperature photoluminescence measurements we have extracted the local splitting of quasi- Fermi levels (EFn-EFp) and local absorption (A(ω)) particularly in the sub bandgap-regime via Planck's generalized law. We observe a substantial negative correlation coefficient between the local sub bandgap/defect absorption and the local (EFn-EFp), which we interpret in terms of the recombination of photogenerated minority carriers (here electrons) via sub bandgap states/deep defects. Moreover we have correlated local PL yields with corresponding values at neighbor sites versus distance (increment analysis). As we find lateral correlation distances in the vicinity of average grain sizes we conclude grains with PL yield and according different splitting of (EFn-EFp) to be independent from one another and be laterally distributed randomly.

Hydrogen is commonly introduced into silicon solar cells to reduce the deleterious effects of defects and to increase cell efficiency. When hydrogen is introduced into multicrystalline Si that is often used for the fabrication of solar cells, the H atoms become trapped by carbon impurities to produce defect structures known at H2*(C). These defects act as both a source and a sink for hydrogen in H-related defect reactions. IR spectroscopy has been used to determine what H- and C-related defects are formed in multicrystalline Si when the carbon concentration is varied. A process that is used by industry to introduce hydrogen into Si solar cells is the post-deposition annealing of a hydrogen-rich SiNx layer. The H2*(C) defects provide a strategy for estimating the concentration and penetration depth of the hydrogen that is introduced by this method.

ZnO-ZnS-CdS heterostructure photocatalysts for water splitting were designed and prepared by a wet chemistry method. It was found that ZnO-ZnS-CdS heterostructures are highly active photocatalysts for H2 evolution under simulated solar light irradiation in an aqueous solution containing SO32- and S2- ions as sacrificial reagents. H2 evolution with (ZnO)2-(ZnS)1-(CdS)1 heterostructure reaches up to 2790 μmol h−1 g−1. The photoexcited electrons in the ZnO-ZnS-CdS heterostructures have a much longer lifetime (>225 ns) than that of the sole ZnO, ZnS, and CdS (<65 ns). The favorable interface processes of the heterostructures make a significant contribution to high photocatalytic H2 evolution rate.

Ferritic/martensitic steels are attractive materials for use as components in nuclear reactors because of their high strength and good swelling resistance. Grain boundary specific phenomena (such as segregation, voiding, cracking, etc) are prevalent in these materials so grain boundary character is of primary importance. Certain types of boundaries are more susceptible to thermal creep damage whereas others tend to resist damage. If more damage resistant boundaries can be introduced into the structures, this will result in steel that is more resistant to the processes of degradation that prevail in high-temperature environments. We have characterized the grain boundary structure in HT9 steel by electron backscatter diffraction to identify boundaries that are resistant to degradation and those that are more susceptible to damage in extreme environments. It is found that intergranular damage is mitigated by a high fraction of low energy boundaries, and certain kinds of grain boundaries are more favored by intergranular cracks.

The pollution caused by heavy metals is one of the major environmental problems that is imperative to be solved. New technologies, easy to implement and to adapt to any system, deserve special attention and are a focus of this work the ability of Chlorella sp. and E. coli genetically engineered with mice metallothionein I, both immobilized in alginate of calcium to remove Cd(II) and Pb(II) from aqueous solutions was investigated in batch assays for the treatment of diluted aqueous solutions. The kinetics, sorption capacities and sorption percentage were determined. The influence of metal concentration in solution is discussed in the terms of Langmuir isotherm and constants. Sorption capacities increased with increasing metal concentration in solution. For solution containing 300 mg/L of metal, the observed uptake capacities were 94.941±1.094 mgCd/gChlorella. , 24.076±2.292 mgCd/gE.coli and 239.17±2.478 mgPb/gChlorella , 37.952±4.245 mgPb/gE.coli . The Langmuir constants to Chlorella sp. were qmax=285.72(mgPb/g), b=0.0276(l/mgPb), qmax=103.65(mgCd/g) and b=0.0005(l/mgCd) while to E. coli were qmax=28.141(mgPb/g), b=0.113(l/mgPb), qmax=24.272(mgCd/g) and b =0.019(l/mgCd). The biomass of the algae showed to have better capacity of metallic sorption that the biomass of the bacteria genetically engineering. The study proved that microorganisms biomass is a suitable material for the removal of the studied heavy metals ions from aqueous solutions, achieving removal efficiencies higher than 90%, and could be considered as a potential material for treating effluent polluted with Cd(II) and Pb(II) ions.

The conductivity of amorphous/nanocrystalline hydrogenated silicon thin films (a/nc-Si:H) deposited in a dual chamber co-deposition system exhibits a non-monotonic dependence on the nanocrystal concentration. Optical absorption measurements derived from the constant photocurrent method (CPM) and preliminary electron spin resonance (ESR) data for similarly prepared materials are reported. The optical absorption spectra, in particular the subgap absorption, are found to be independent of nanocrystalline density for relatively small crystal fractions (< 4%). For films with a higher crystalline content, the absorption spectra indicate broader Urbach slopes and higher midgap absorption. The ESR spectra show an approximately constant defect density across all of the films. These data are interpreted in terms of a model involving electron donation from the nanocrystals into the amorphous material.

We describe our efforts to control the grain boundary alignment in polycrystalline thin films of silicon by using a biaxially textured template layer of CaF2 for photovoltaic device applications. We have chosen CaF2 as a candidate material due to its close lattice match with silicon and its suitability as an ion beam assisted deposition (IBAD) material. We show that the CaF2 aligns biaxially at a thickness of ~10 nm and, with the addition of an epitaxial CaF2 layer, has an in-plane texture of ~15°. Deposition of a subsequent layer of Si aligns on the template layer with an in-plane texture of 10.8°. The additional improvement of in-plane texture is similar to the behavior observed in more fully characterized IBAD materials systems. A germanium buffer layer is used to assist in the epitaxial deposition of Si on CaF2 template layers and single crystal substrates. These experiments confirm that an IBAD template can be used to biaxially orient polycrystalline Si.

Silicon nanowires (Si NWs) were grown directly on transparent conductive oxide layers using a single pump down process in a plasma enhanced chemical vapour deposition (PECVD) system. Layers of ITO and SnO2 on glass substrates were exposed to a hydrogen plasma leading to the reduction of the oxide and to the agglomeration of the metal into catalyst droplets of a few tens of nanometers diameter. The diameter and the density of the nanowires depend on the catalysts droplets size and density, we studied step by step the evolution of the surface prior to and at the initial stage of the nanowire growth. The catalyst droplets size and distribution were essentially investigated through Scanning Electron Microscopy (SEM).

RNA- and DNA-mediation or templating of materials has been used to synthesize nanometer scale wires, and CdS nanoparticles. However, RNA and DNA have the potential to act as catalysts, which could be valuable tools in the search for new routes to materials synthesis. RNA has the ability to catalyze splicing and cutting of other RNA molecules. Catalytic activity has been extended to more general classes of reactions for both RNA and DNA using in vitro selection methods. However, catalytic activity in materials synthesis is a more recent idea that has not yet found great application. The first example of RNA-mediated evolutionary materials synthesis is discussed with specific data examples that show incompatibility of reagents in the solvent system utilized. The hydrophobic reagent Pd2(DBA)3, used as a metal precursor, was observed to spontaneously form nanostructures composed of Pd2(DBA)3 or Pd(DBA)3 rather than palladium nanoparticles, as originally reported 1. A case study of this materials synthesis example is described including the complimentary use of multi-length scale techniques including transmission electron microscopy (TEM), selected area electron diffraction (SAED), scanning TEM (STEM), electron energy loss spectroscopy (EELS), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and optical microscopy (OM). This example raises important questions regarding the extent to which non-aqueous solvents should be used in nucleic acid-mediated processes, the nature of selections in enzyme and materials development, and the requirement for chemical compatibility of the precursor molecules. The importance of good characterization tools at every stage of an in vitro selection is illustrated with concrete examples given. In order to look at the way forward for nucleic acid-mediated materials synthesis, an examination of the chemical interaction of nucleic acids with various precursors is considered. Application of density functional theory calculations provides one means to predict reactivity and compatibility. The repertoire of chemical interactions in the nucleic acids is considered vis-à-vis common metals and metal chalcogenides. The case is made for the need for water-soluble syntheses and well-controlled kinetics in order to achieve the control that is theoretically possible using nucleic-acids as a synthetic tool.

We report on a novel light sensing scheme based on a silicon/fullerene-derivative hetero-junction that allows the realization of optoelectronic devices for the detection of near to mid infrared radiation. Despite the absent absorption of silicon and the fullerene-derivative for wavelengths beyond 1.1 µm and 0.72 µm, respectively, a hetero-junction of these materials absorbs and generates a photo-current due to absorption in the near to mid infrared. This photo-current is caused by an interfacial absorption mechanism [1].

Besides its scientific relevance, the simple fabrication process of the hetero-junction (e.g. the fullerene-derivative is deposited by spin-coating on Si) as well as its compatibility with the established and rather cheap CMOS technology makes the presented hybrid approach a promising candidate for widespread applications.

In this paper a double pi'n/pin a-SiC:H voltage and optical bias controlled device is presented and it behavior as image and color sensor, optical amplifier and multiplex/demultiplex device discussed. The sensing element structure (single or tandem) and the light source properties (wavelength, intensity and frequency) are correlated with the sensor output characteristics (light-to-dark sensivity, resolution, linearity, bit rate and S/N ratio). Depending on the application, different readout techniques are used. When a low power monochromatic scanner readout the generated carriers the transducer recognize a color pattern projected on it acting as a color and image sensor. Scan speeds up to 104 lines per second are achieved without degradation in the resolution. If the photocurrent generated by different monochromatic pulsed channels is readout directly, the information is multiplexed or demultiplexed. It is possible to decode the information from three simultaneous color channels without bit errors at bit rates per channel higher than 4000bps. Finally, when triggered by appropriated light, it can amplify or suppress the generated photocurrent working as an optical amplifier. An electrical model is presented to support the sensing methodologies. Experimental and simulated results show that the tandem devices act as charge transfer systems. They filter, store, amplify and transport the photogenerated carriers, keeping its memory (color, intensity and frequency) without adding any optical pre-amplifier or optical filter as in the standard p-i-n cells.

Microfluidic mixing was applied to conventional acid pasting process to re-crystallize organic nanocrystals of Titanyl phthalocyanine (TiOPc). TiOPc nanocrystals were re-crystallized in a two step process. Seed particles were prepared by mixing TiOPc, dissolved in concentrated sulfuric acid with deionized water using high speed microchannel mixers. Seed particles were then subjected to post-precipitation treatment to achieve final crystalline product. Effects of seed preparation conditions, such as mixing efficiency (mixer type) and mixing temperature on the structure of final product were studied. Time evolution of optical absorption spectra was examined with a view to elucidate structure evolution during early stages of seed formation process.

Supported polyoxide catalysts on the base of Mo and W, as well as natural Kazakhstan's clays were tested in the process of oxidative conversion of propane and propane-butane mixture. The influence of reaction temperature, contact time, composition and percentage of the active component of catalyst were determined. The important petrochemical products - acetone (500-550°) and acetaldehyde (300-350°) were the main liquid products of reaction on natural Kazakhstan's clays and also on clays modified by Mo, Bi, Cr and Ga ions.

Thermoelectric (TE) effects as a coupling between heat and charge transfer can be described on a classical level in the framework of the Onsager theory. Under isotropic and steady state conditions the conservation equations can be combined to obtain a thermal energy balance containing the temperature distribution as target function. Besides the temperature the balance equation contains material properties represented by the Seebeck coefficient S, the electrical and thermal conductivities σ and κ, respectively. For the sake of simplicity, a 1D scheme has been chosen for the analytical and numerical treatment. Performance investigations are often done within the framework of the Constant Properties Model (CPM) or based on temperature dependent material properties. In the 1D steady state, there is an alternative approach available based on spatial material profiles. Following the approach by Müller and co-workers, the temperature profile T(x) is calculated numerically within a model-free setup directly from the 1D thermal energy balance, e.g., based on continuous monotonous gradient functions for all material profiles, and independent and free variability of the material parameters S(x), σ(x), and κ(x) is assumed initially. Doing so, the optimum electrical current density can be determined from the maximum of the global performance parameter (power output P or efficiency η). We present analytical results for the performance optimization calculating P and η with linear material profiles for S(x), a constant electrical and thermal conductivity, fixed TE element length L and fixed boundary temperatures.

The usage of organic materials in the manufacture of electronic polymer memory devices is on the rise. Polymer memory devices are fabricated by depositing a blend (an admixture of organic polymer, small molecules and nanoparticles) between two metal electrodes. The primary aim is to produce devices that exhibit two distinct electrical conductance states when a voltage is applied. These two states can be viewed as the realisation of non-volatile memory. This is an interesting development; however, there are a number of theories that have been proposed to explain the observed electrical behaviour. We have proposed a model that is based on electric dipole formation in the polymer matrix. Here, we investigate further the proposed model by deliberately creating electric dipoles in a polymer matrix using electron donors (8-Hydroxyquinoline, Tetrathiafulvalene and Bis(ethylenedithio)tetrathiafulvalene) and electron acceptors (7,7,8,8-Tetracyanoquinodimethane, Tetracyanoethylene and Fullerene) small molecules.

Two types of structures were investigated (i) a metal/blend of polymer and small molecules/metal (MOM), device and (ii) a metal/insulator/blend of small molecules and polymer/semiconductor (MIS) architecture. A blend of polymer and small organic molecules was prepared in methanol and spin-coated onto a glass substrate marked with thin aluminium (Al) tracks; a top Al contact was then evaporated onto the blend after drying - this resulted in a metal-organic-metal structure. The MIS structures consisted of an ohmic bottom Al contact, p-type Si, a polymer blend (two small organic molecules and insulating polymer), followed by polyvinyl acetate and finally a top, circular Al electrode. In-depth FTIR studies were carried out to understand the observed electrical behaviour. An electrical analysis of these structures was performed using an HP4140B picoammeter and an HP 4192A impedance analyser at a frequency of 1 MHz.

In this paper we present results on the use of a multilayered a-SiC:H heterostructure as a wavelength-division demultiplexing device (WDM) for the visible light spectrum. The WDM device is a glass/ITO/a-SiC:H (p-i-n)/ a-SiC:H(-p) /Si:H(-i)/SiC:H (-n)/ITO heterostructure in which the generated photocurrent at different values of the applied bias can be assigned to the different optical signals.

The device was characterized through spectral response measurements, under different electrical bias. Demonstration of the device functionality for WDM applications was done with three different input channels covering wavelengths within the visible range. The recovery of the input channels is explained using the photocurrent spectral dependence on the applied voltage. The influence of the optical power density was also analysed.

An electrical model, supported by a numerical simulation explains the device operation. Short range optical communications constitute the major application field, however other applications are also foreseen.

Chemical mechanical planarization (CMP) pads require conditioning to maintain the surfaces yielding optimal performance. However, conditioning not only regenerates the pad surface but also wears away the pad material and slurry transport grooves. Non-optimized conditioning may result in non-uniform pad profiles, limiting the productive lifetimes of pads. A new approach to conditioning uses closed-loop control (CLC) of conditioning sweep to enable uniform groove depth removal across the pad, throughout pad life. A sensor integrated into the conditioning arm enables the pad stack thickness to be monitored in situ and in real time. Feedback from the thickness sensor is used to modify pad conditioner dwell times across the pad surface, correcting for drifts in the pad profile that may arise as the pad and disk age. Pad profile CLC enables uniform reduction in groove depth with continued conditioning, providing longer consumables lifetimes and reduced operating costs.