We report the observation of an ultrafast (~ 430 fs) charge transfer processat the interface between a single-walled carbon nanotube (SWNT) wrapped by asemi-conducting polymer, poly(3-hexylthiophene) (P3HT), creating freepolarons on both materials. The addition of excess P3HT as a surroundingnetwork allows these free polarons to be long-lived at room temperature. Ourresults suggest that SWNT-P3HT blends incorporating only 1% fractions ofSWNTs can achieve a charge separation efficiency comparable to aconventional 60:40 P3HT-fullerene blend, provided small-diameter tubes areembedded in an excess P3HT matrix.

The spreading of a smectic nanodrop (8CB liquid crystal) on a solid surface was investigated by direct and real time imaging using the Surface Enhanced Ellipsometric Contrast (SEEC) microscopy [1-2]. The spreading ends with two molecular terraces (made of one monolayer and a bilayer). Two different behaviors were observed. In the first one the upper layer stays dense while shrinking. At the end of the process, the last molecules to disappear are located at the center of the initial disk. In the second one, nucleation and growth of holes is observed in the upper layer, in addition to shrinking. A model is proposed to describe the time evolution of the late stage structure. This model gives exact solutions of the kinetic equations, it covers strongly layered liquids such as smectic liquid crystals, it introduces the two dimensional Laplace pressure as an essential motor for spreading and it takes into account the liquid/gas transition in the surface layer that was consistently reported in experiments with 8CB. This model is in remarkable agreement with the experimental data and can explain the two observed behaviors [3].

The self-assembled block copolymer films with poly (ethylene oxide) (PEO) and hydrophobic polymetharylate (PMA) with azobenzene mesogen in the side chain, denoted as PEOm-b-PMA(Az)n, were used as the template to prepare hexagonally ordered silica nanorod arrays by immersing the template films in the silicate precursor containing tetraetoxysilane (TEOS). The diameter and the center-to-center distance of the SiO2 nanorod arrays were controlled by selecting the block copolymer with different PEO volume fraction. In addition, the contact angles of different kinds’ solvents for the SiO2 nanorod arrays were characterized. We further found, the diameter and the period distance of silica nanorods are very important factors for controlling the contact angle of different kind’s solvents on the surface of the SiO2 nanorod arrays.

The development of synthetic materials with inherent bone properties would allow the safe restoration of bone function and reduce current risks associated with the use of grafts. This study investigated the development of bacterial cellulose–hydroxyapatite composite (CdHA-BC) as a potential bone substitute material. Composites of bacterial cellulose (BC) and oxidized, degradable, cellulose (OBC) were mineralized by sequential incubation in calcium chloride and aqueous sodium phosphate to form a calcium deficient hydroxyapatite (CdHA). The CdHA produced in BC and OBC is similar in morphology and chemistry to the hydroxyapatite found in natural bone. The formation of CdHA is supported by XRD, and EDS results. The CdHA-BC and CdHA-OBC composites degrade in a simulated aqueous physiological environment.

We present a general method for investigating the energetics of small impurity-vacancy clusters in crystalline materials. We use a combination of molecular dynamics and Monte Carlo methods to locate low energy configurations of the bubbles, from which the binding energies of various point defects can be determined. This method is applied to case of hydrogen bubbles in alpha-iron. Clusters with ratios of up to 10 hydrogen atoms to a vacancy are studied. We find that hydrogen does help to stabilize voids in alpha-iron, but that hydrogen is quite weakly bound to these voids. Ratios of up to approximately 4 can be supported at low temperatures.

Polycrystalline silicon thin films were formed from the amorphous silicon thin film by the pulsed rapid thermal annealing process enhanced with a thin nickel seed layer through the vertical crystallization mechanism. In this paper, authors presented the results on the material properties of the crystallized film. The dopant and film thickness effects were also investigated. It has been demonstrated that a 2 μm thick amorphous silicon n+-i-p+ diode structure could be transformed into polycrystalline stack with a 4-pulse 1 sec 850°C heating and 5 sec cooling cycle process.

Hydrogels with their tunable properties are attractive candidates for developing tissue engineering scaffolds for various applications (including bone and cartilage). The current work involved studying the synergistic effect of basic fibroblast growth factor (bFGF) and platelet derived growth factor BB (PDGF-BB) entrapped within injectable porous gels for bone regeneration applications. An in situ gelling system was developed using bacterial polysaccharides gellan and xanthan gum by temperature and ionic gelation with Ca+2. After the initial characterization of the hydrogels, a dual growth factor release system was developed wherein growth factors were encapsulated within chitosan nanoparticles embedded in the gels as well as directly within the gel. The hydrogel structure was characterized by SEM and TEM and in vitro growth factor release studies showed a slow release profile in PBS. Further, human fetal osteoblasts were entrapped within the hydrogel and a 21 day osteoblast differentiation study was conducted. An improvement in osteoblast total protein synthesis and collagen content was observed by day 21 compared to control gels without growth factors. Although further evaluation regarding mechanical properties and expression of osteogenic differentiation marker genes will be necessary, the present study suggests that injectable scaffolds can be used for the delivery of multiple growth promoting agents to support osteoblast differentiation.

In this contribution 1, 2 and 3-dimensional simulations of micromorph silicon solar cells are presented. In order to simulate solar cells with rough interfaces, the surface topographies were measured via atomic force microscopy (AFM) and transferred into the commercial software Sentaurus TCAD (Synopsys). The model of the structure includes layer thicknesses and optoelectronic parameters like complex refractive index and defect structure. Results of the space resolved optical generation rates by using of the optical solver Raytracer are presented. The space resolved optical generation rate inside the semiconductor layers depends on the structure of the transparent conductive oxides (TCO) interface. In this contribution the influence of different optical generation rates on the electrical characteristics of the solar cell device are investigated. Furthermore, the optical and electrical results of the 1D, 2D and 3D structures, which have equal layer thicknesses and optoelectronic parameters, are compared.

Multiwall Carbon Nanotubes (MWCNT) align by coupling to the liquid crystals’ (LC) nematic director in LC/MWCNT dispersions. This coupling is so strong that the LC molecules act as molecular motors to reorient the MWCNTs when an electric field is applied across oriented electro optic cells. On the other hand, MWCNTs also improve the LC order and modify the crystal phase of LCs. We investigate the physical reasons for those strong effects by studying the molecular interactions between a host LC and MWCNTs. It has been predicted theoretically that the aromatic rings could stack with their π orbitals in 4-Cyano-4’-pentylbiphenyl (5CB) and MWCNT nanocomposites. Experimentally 5CB modifies the MWCNTs Raman breathing modes in the same nanocomposites. In turn, we look for evidence of this interaction between MWCNTs and LCs at the 5CB molecules. Using FTIR spectroscopy we found that the modes corresponding to 5CB aromatic rings vibrations are affected in the presence of MWCNTs which confirms that π-π stacking of 5CB’s biphenyl rigid core to the carbon rings on the MWCNTs’ surface may indeed be major mechanism for MWCNT/LC nematic coupling. It shows also that the Raman breathing mode effects on MWCNTs can be due to this π-π stacking interaction with 5CB. Further investigations of the MWCNTs interactions with 5CB can lead to developing of a complete model of this phenomenon and help applications for electro optic cells, nanoswitches, new crystal forms for optics, communication technology and others.

The effectiveness of using hydroxyapatite (HAP) as a consolidant for carbonate stones was evaluated. HAP was chosen as a consolidating agent since it is notably less soluble than calcite and has a similar crystal structure and a close lattice match to it. Among possible methods for forming HAP, the reaction between the calcite of the stone and a solution of diammonium hydrogen phosphate (DAP) in mild conditions was chosen. Indiana Limestone samples, artificially damaged by heating to 300°C for 1 hour, were treated with a 1 molar DAP solution by partial immersion and capillary absorption for 48 hours or by brushing until apparent refusal and wrapping with a plastic film for 48 hours. After washing in deionized water for 3 days and drying under a fan at room temperature until constant weight, the improvements in dynamic elastic modulus and tensile strength were evaluated. The formation of calcium phosphate phases was observed by scanning electron microscopy (SEM) and the phase characterization performed by energy dispersive X-ray spectroscopy (EDS) and electron back-scattered diffraction (EBSD). The water absorption modification after the consolidating treatment was then assessed. Results show that treated samples experienced significant increases in dynamic elastic modulus and tensile strength, as a consequence of crack reduction and pore filling consequent to HAP deposition at grain boundaries. The sorptivity of the treated samples is reduced by 26-44% (based on treatment technique), so that water and water vapor exchanges with the environment are not blocked.

Rhenium-oxide-modified supported iridium nanoparticles on silica catalyzes direct hydrogenolysis of glycerol to 1,3-propanediol in an aqueous media. The selectivity to 1,3-propanediol at an initial stage reaches 67%. The yield of 1,3-propanediol reaches 38% at 81% conversion of glycerol. The characterization of catalyst shows that oxidized Re clusters are formed on Ir metal particles. The synergy between Ir metal and ReOx clusters enables the catalytic activity.

Zinc oxide is a promising semiconductor film for active devices on flexible substrates, and synthesis routes using nanoparticle inks enable greater variety of applications. We introduce and characterize a two-step transient laser annealing process to create fully densified zinc oxide films from nanoparticle ink precursors. A low temperature sub-millisecond calcining step to remove solvent and organic stabilizing ligands was followed by a high-temperature pulsed laser sintering step to form densified 50-100 nm thin films with resistivities of 10-1 to 10-3 Ω-cm. Film microstructures can be varied between crystalline and amorphous without significant film damage by adjusting the fluence of the high-temperature sintering step. These processes would be compatible with a variety of nanoparticle species, deposition methods, and patterning methods, including roll-to-roll processing paradigms.

We report first principles modeling of partially hydrogenated graphene, with a variety of hydrogen induced superstructures. The dependence of the optical gap on hydrogen content and coverage is examined, to assess the best configurations suitable for optoelectronic applications. Electron and optical DFT LDA gaps in the range between 0.2 and 1.5 eV were obtained for low hydrogen coverage. For such systems, hydrogen clustering (by saturating neighbouring C dangling bonds at the opposite sides of the graphene sheet) is energetically most favourable and generally produces larger gap. More homogeneous H distribution one-side bonded to C-host atoms is, in contrast, less energetically favourable or even structurally unstable and generally produces smaller gap. In addition, ordering of hydrogen was observed at 50% of H, that offers a possibility of transforming 2D graphene to an array of 1D nanowires Calculated linear optical anisotropy and nonlinear second harmonic generation (this will be discussed in a forthcoming paper) indicate these are not only gap sensitive, but can provide an access to microscopic details of the 2D nano-sheets such as symmetry, hydrogen induced structure, degree of hydrogenation, chemical bonding and many others, all promising for device application. The approach developed can be used for graphene/ graphane single layer or bilayer, formed on top of various substrates, where experimental geometries may not provide conditions for complete hydrogenation of the 2D nano-sheet(s).

The growth of ZnSe and CdTe thin films by close spaced sublimation is examined. The investigations show that ZnSe films deposited on glass substrates are polycrystalline and exhibit wurtzite-zinc-blende polytypism. The CdTe films grown on glass/SnO2/ZnSe are polycrystalline and have an f.c.c. zinc-blende structure as in the case of a glass/SnO2/CdS buffer layer. The electric and photovoltaic parameters of ZnSe/CdTe solar cells depend on the ZnSe film thickness. Furthermore, it is shown for the first time that the best photovoltaic parameters are achieved using a Zn buffer layer at the interface between ZnSe and CdTe.

The carrier concentration and electronic transport properties in Bi2-xSbxTe3 alloy can be tuned by varying the Bi to Sb ratio, for high thermoelectric figure of merit. The concentration of intrinsic antisite defects in these alloys is also known to change with Bi to Sb ratio. Here we report the thermoelectric figure of merit of Sn doped Bi0.5Sb1.5Te3 alloy. Different atomic percentages of Sn was substituted at Bi/Sb site in Bi0.5Sb1.5Te3 alloy, synthesized by planetary ball milling. The electrical conductivity decreases with increasing Sn doping but for higher Sn content the electrical conductivity increases compared to undoped alloy. The Seebeck coefficient changes in accordance to electrical conductivity, resulting in small decrease in power factor for highest Sn doping. The lattice thermal conductivity shows a systematic decrease, with increasing Sn concentration resulting in a significant thermal conductivity reduction. Hence an increase in thermoelectric figure of merit could be achieved for the highest Sn (3at%) doping in Bi0.5Sb1.5Te3 alloy as compared to undoped alloy.

Experiments and analysis have been conducted to characterize flow separators used in applications where heated fluid passes between layers of solid material such as in the manufacturing of gelatinous materials. The Biot number of the configuration is the key parameter, and must be taken into account when optimizing performance. It is shown that most prior work was for low Biot number systems, and the particular configurations under consideration operate at high Biot number. Existing designs developed for lower Biot number (such as membrane filter spacers) are shown to perform poorly for this application. An experimental apparatus was designed and fabricated to quantitatively assess pressure drop through the system using different separation strategies. These results were compared with a simplified two-term model based on the physics of viscous drag in these devices. Channels without separators behave like classical Poiseuille flow. Channels with separators can be modeled with a two-term equation: a baseline Poiseuille term and a form drag term. A variety of separator designs are compared and their overall performance is discussed. We also illustrate the high sensitivity to gap height in all configurations.

The hydrogenated amorphous silicon (a-Si:H) single-junction thin-film solar cells were fabricated on SnO2:F-coated glasses by plasma-enhanced chemical vapor deposition (PECVD) system. The boron-doped amorphous silicon carbide (a-SiC:H) was served as the window layer (p-layer) and the undoped a-SiC:H was used as a buffer layer (b-layer). The optimization of the p/b/i/n thin-films in a-Si:H solar cells have been carried out and discussed. Considering the effects of light absorption, electron-hole extraction and light-induced degradation, the thicknesses of p, b, n and i layers have been optimized. The optimal a-Si:H thin-film solar cell having an efficiency of 9.46% was achieved, with VOC=906 mV, JSC=14.42 mA/cm2 and FF=72.36%.