Methods of improving low-cost Cu2O|ZnO heterojunction diodes fabricated through galvanostatic deposition of Cu2O are presented. Improved processing parameters responsible for maximizing built-in voltage (Vbi) are determined. The relationship between pH, deposition current, temperature, and diode quality is analyzed and a process window for optimal Cu2O deposition on ZnO is obtained with a pH range between 12.0 and 12.1 and a current density range which is determined by the effect of both pH and deposition current (Jdep) on grain size. The pH window is found to be narrower than previously reported1 and much narrower than the processing window for the deposition of Cu2O films. A two-step approach deposition based on the use of different Jdep is presented for the first time. A Vbi of 0.6 V is achieved, which is the highest reported for cells produced using low temperature processing routes involving electrodeposition and reactive sputtering.

We apply a living polymerization theory to describe cooperative string-like particle rearrangement clusters observed in simulations of a coarse-grained polymer melt. The theory quantitatively describes the interrelation between the average string length L, configurational entropy S conf, and the order parameter for string assembly Φ without free parameters. Combining this theory with the Adam-Gibbs (AG) model allows us to predict the relaxation time τ in a lower temperature T range than accessible by current simulations. In particular, the combined theories suggest a return to Arrhenius behavior near T g and a low T residual entropy, thus avoiding a Kauzmann ‘entropy crisis’.

A number of drug carrier systems such as liposomes, polymeric-nanoparticles, microparticles, polymeric micelles have been investigated for intracellular delivery. Among these liposomes are the potential drug vehicles for efficient cytosolic delivery. They have an adhesive property for cell membrane to encapsulate the drug or protein effectively and showing the enhanced absorption rate. One of the problems could be the difficulty of incorporation of the drug or protein into cell. Therefore many studies of the drug carriers have been developed to enhance the intracellular delivery of materials. Here we propose the novel method to improve the intracellular uptaking by using freeze concentration. Solutes are excluded from ice crystallization and concentrated in the remaining solution during freezing by freezing concentration. We have reported that polymeric cryoprotectant which is carboxylated poly-L-lysine was adsorbed on to the cell membrane during freezing and caused effective freeze concentration. In this study we investigated that delivery of protein effectively taking place by liposome as a carrier agent. It was successfully delivered protein to L929 cells via freeze concentration using polymeric cryoprotectant as a novel drug delivery.

We have studied the electrochemical reduction of CO2 using Cu2O nanoparticles deposited on planar electrodes. Nanoparticles are prepared in aqueous solution by chemical reduction of CuCl2 using ascorbic acid with polyethylene glycol surfactant. The particles are then re-suspended in ethanol with added Nafion binder and brush-coated onto glassy carbon substrates. The CO2 electroreduction activity is measured in KHCO3 electrolyte under flowing CO2 using a two-compartment electrochemical cell. Product formation rates are determined using gas chromatography; major gas phase products include CO, H2, C2H4, and CH4, while liquid phase products include C2H5OH and 1-C3H5OH. The observed product distribution agrees with results obtained previously using similar Cu2O particles deposited on carbon fiber paper supports, as well as Cu2O catalysts prepared by electrodeposition or thermal oxidation. In particular, the catalysts produce a much higher ratio of C2H4 to CH4 than observed using polycrystalline Cu foil. The potential dependence of the formation rates for hydrocarbon and alcohol products is roughly two times greater than for H2 and CO formation. Both XRD and SEM measurements confirm the Cu2O nanoparticles undergo at least partial reduction to Cu metal under CO2 reduction conditions, accompanied by significant surface morphological changes. Thus the kinetic results are consistent with current models that the increased C2H4/CH4 ratio is due to the presence of a more open atomic structure on the freshly reduced Cu surfaces.

Excitation of multiple Er3+ ions upon absorption of a single high-energy photon increases Er-related emission at 1.5 μm, and therefore enhances UV/visible-to-IR photon conversion efficiency. Here we investigate this effect for layers of Er-doped SiO2 sensitized with silicon nanocrystals by measuring the quantum yield of 1.5 µm Er-related emission. We demonstrate dramatic increase of the emission commencing for excitation energies above a certain threshold value, as the number of Er3+ ions excited upon absorption of a single incoming photon increases. By comparing differently prepared materials, we show that the actual value of this threshold energy and the rate of the observed increase of the quantum yield depend on sample characteristics – the size of Si nanocrystals and the ratio of Er3+ ions and nanocrystals concentrations.

In this paper we experimentally demonstrate the use of near-ultraviolet steady state illumination to increase the spectral sensitivity of a double a-SiC/Si pi’n/pin photodiode beyond the visible spectrum (400 nm-880 nm). The concept is extended to implement a one by four wavelength division multiplexer with channel separation in the visible/near infrared range. Optoelectronic characterization of the device is presented and shows the feasibility of tailoring the wavelength and bandwidth of a polychromatic mixture. Several monochromatic pulsed lights in the VIS/NIR range, separately or in a polychromatic mixture illuminated the device. Independent tuning of the wavelengths is performed by steady state 390 nm optical bias superimposed from front and back sides. Results show that, front background enhances the light-to-dark sensitivity of the medium, long and infrared wavelength channels, and quench strongly the shorter wavelengths. Back background has the opposite effect; it only enhances the channel magnitude in short wavelength range and strongly reduces it in the long ones. This nonlinearity provides the possibility for selective tuning a specific wavelength. A capacitive optoelectronic model supports the experimental results. A numerical simulation is presented.

Raman scattering of Si nanowires (NWs) presents antenna effects. The electromagnetic resonance depends on the electromagnetic coupling of the system laser/NW/substrate. The antenna effect of the Raman signal was measured in individual NWs deposited on different substrates, and also free standing NWs in air. The one phonon Raman band in NWs can reach high intensities depending on the system configuration; values of Raman intensity per unit volume more than a few hundred times with respect to bulk substrate can be obtained.

We present a physically justified formalism for the calculation of defect formation energies in UO2. The accessible ranges of chemical potentials of the two components U and O are calculated using the U-O experimental phase diagram and a constraint on the formation energies of vacancies. We then apply this formalism to the DFT+U investigation of the monovacancies and monointerstitials in UO2.

The results of the most stable charge states of these defects are consistent with a strongly ionic system. Calculations predict similarly low formation energies for $V_U^{4 - }$ and $I_O^{2 - }$ in hyperstoichiometric UO2.

Osteochondral (OC) tissue is comprised of articular cartilage, the subchondral bone and the central cartilage-bone interface. To facilitate proper regeneration, an equally complex and multiphasic matrix must be used. Although mono-phasic and bi-phasic matrices were previously applied, they failed to establish the OC interface upon regeneration. In this study, we designed and developed a novel matrix with increasing pore volume from one end to other, along the matrix length. For this matrix polylactide-co-glycolide (PLGA) 85:15 microspheres were combined with a water-soluble porogen in a layer-by-layer fashion and thermally sintered. The resulting matrix was then porogen-leached to form a gradiently-porous structured matrix. The formation of this gradient pore structure was established using Micro-Computed Tomography (μCT) scanning. A biodegradable hydrogel was infiltrated into the structure to form a unique OC matrix where the microsphere and hydrogel phases co-exist with opposing gradients. When the individual phases are associated with osteogenic and chondrogenic growth factors, the structureinduced factor delivery might provide the spatially controlled factor delivery necessary to regenerate osteochondral tissue structure. Overall, we designed a gradient matrix system that is expected to support osteochondral tissue engineering while forming a seamless interface between the cartilage and the bone matrix.

Solute trapping of vacancies in a Ni host lattice is a first step to understanding how solute additions may effect ordering phase transformation in Ni-based alloys. Minor additions of solutes (<3 wt.%) may not have an appreciable effect on the thermodynamics of phase stability but strong binding between the vacancy and solute may significantly alter the kinetics of phase transformations. In this work vacancy-solute binding energies are calculated for multiple elements (Cr, Fe, Mn, Si, Ti, Nb, Ta, Cu, Al, Mo) in a pure Ni face-centered cubic lattice. These elements are common in corrosion-resistant Ni-based alloys. Binding enthalpies for the first four nearest-neighbor vacancy-solute pairs are reported for all elements. The results of this study show that Si, Ti, Nb and Ta bind to vacancies in the first nearest-neighbor position. Alloys containing these solute additions may experience delayed phase transformation due to vacancy trapping that slows diffusion.

Two n+-i-p 6H-SiC diode families with P+ ion implanted emitter have been processed with all identical steps except the post implantation annealing: 1300°C/20min without C-cap has been compared with 1950°C/10min with C-cap. The analysis of the temperature dependence of the reverse current at low voltage (-100V) in the temperature range 27-290°C shows the dominance of a periphery current which is due to generation centers with number and activation energy dependent on the post implantation annealing process. The analysis of the temperature dependence of the forward current shows two ideality factor n region, one with n = 1.9/2 at low voltage and the other one with 1 < n < 2 without passing through 1 for increasing voltages. For both the diode families the current with n = 1.9/2 is a periphery current due to recombination centers with a thermal activation energy near the 6H-SiC mid gap. In the forward current region of 1 < n < 2, the two diode families show different ideality factor values which could be attributed to a different post implantation annealing defect activation.

In this communication, we report our efforts to develop amorphous silicon carbide (a-SiC) thin film photoelectrodes integrated with Si solar cells to form a monolithic, hybrid photovoltaic (PV)/a-SiC device capable of water splitting using sunlight as the only energy source. The main photoelectrochemical (PEC) properties of both the a-SiC photoelectrode and complete hybrid device fabricated by the plasma enhanced chemical vapor deposition (PECVD) technique at low temperature (≤ 200°C) are discussed. The surface modification with metal nanoparticles, which is critical to PEC performances of the hybrid device, is also described. We show that, with the an a-SiC photoelectrode of p-i-n configuration and a high performance silicon heterojunction solar cell as driver, the photocurrent of the hybrid PV/a-SiC device has reached ∼5 mA/cm2. Additionally, the durability of such device has reached ∼800 hours in acidic electrolyte. Finally, we describe a roadmap for achieving the solar-to-hydrogen efficiency of >10% by optimizing the device configuration.

A series of Ce3+ doped Ca8La2(PO4)6O2 phosphors with tunable emission were successfully synthesized by traditional solid state reaction. The crystal structure and photoluminescence properties were studied through X-ray diffraction, photoluminescence excitation and emission spectra. The results indicated that Ca8La2(PO4)6O2:Ce3+ exhibited color-tunable emission due to the 5d-4f transitions of Ce3+ ions under different wavelength excitation. The optimal doping content of Ce3+ ions in Ca8La2(PO4)6O2 was found to be 5 mol%. The site-selective photoluminescence property and the reason for red-shift of the emission band along with Ce3+ content and the excitation wavelength were also studied in detail.

This study demonstrates the potential application of glass particles doped with Zn+2 (GZn) as antimicrobial additives and atoxic of the HDPE and LLDPE polymers. Toxicity tests indicated the absence of toxicity in human cells. Microbiological tests proved the antimicrobial effect of GZn pure compound and of the additives polymeric compounds (HDPE/GZn and LLDPE/GZn). Have also indicated that with percentages of GZn higher than 2.00 wt% and a time of 4 hours the bactericidal performance is excellent and equal for both polymeric compounds.

We theoretically and experimentally investigate a novel modulation concept on silicon (Si) based on the combination of quantum confinement and plasmon enhancement effects. We experimentally study the suitability of Ge/SiGe quantum wells (QWs) on Si as the active material for a plasmon-enhanced optical modulator. We demonstrate that in QW structures absorption and modulation of light with transverse magnetic (TM) polarization are greatly enhanced due to favorable selection rules. Later, we theoretically study the plasmon propagation at the metal-Ge/SiGe QW interface. We design a novel Ge/SiGe QW structure that allows maximized overlap between the plasmonic mode and the underlying Ge/SiGe QWs.

In order to analyze the C-14 inventory and leaching rate for safety evaluation of transuranic waste disposal, it is necessary to establish an analytical method that can measure C-14 with sufficient precision [1]. Oxidative decomposition of organic compounds containing C-14 is carried out to absorb carbon dioxide (CO2) in an alkaline solution, which is mixed with a liquid scintillation cocktail, and the amount C-14 is quantified by measuring a beta ray spectrum with a liquid scintillation counter. It has been difficult to completely decompose carbon compounds in a sample, even to CO2, by using conventional oxidizing agents. In the work described here, we improved the method of oxidative decomposition used to completely decompose carbon compounds using peroxydisulfuric acid (K2S2O8). When C-14 in the form of CO2 was absorbed in a sodium hydroxide (NaOH) aqueous solution, only 80% of the actually used quantity was detected. Total organic carbon measurements showed that the entire quantity of CO2 was absorbed by NaOH. When NaOH aqueous solution was used, it was found that only the analytical value was 80%. The entire quantity of the actually used carbon could be measured by absorbing the CO2 in Carbo-Sorb®. An anion form and a neutral molecule exist in the organic compound released from activated metals. In order to identify organic compounds efficiently, fractionation into an anion and a neutral molecule and separation by high performance liquid chromatography (HPLC) are necessary. Here, we propose the combined use of an ion exchange resin and HPLC as an improved technique for identification of the chemical species.

The double-network (DN) hydrogel concept developed by J.P. Gong and Y. Osada builds upon interpenetrating networks by combining brittle and ductile components to have significantly enhanced fracture properties. The generality of the DN effect was tested by creating biopolymer-based hydrogels of methacrylated chondroitin sulfate (MCS) and polyacrylamide (PAAm) and extended upon creating DNs of MCS and poly(N,N dimethyl acrylamide) (PDMAAm), verifying that DNs were not limited to the original combination of poly(2-acrylamido-2-methylpropanesulfonic acid) (PAMPS)/polyacrylamide (PAAm). Further, the mechanical properties were varied by changing the monomer concentrations, cross-linker concentrations and the addition of cross-linking groups through copolymerizations of MCS and poly(ethylene glycol) diacrylate (PEGDA). Overall, this work demonstrates that a broad range of mechanical properties achievable through DN effect under tension and compression, generally independent of the swelling degree, which is fundamentally different behavior than possible with single networks.

The sub-threshold electron transport properties of amorphous (a-) germanium telluride (GeTe) phase change material (PCM) ultra-thin films are investigated by using ab initio molecular dynamics, density function theory, and Green’s function simulations. The simulation results reproduce the trends in measured electron transport properties, e.g. current-voltage curve, intra-bandgap donor-like and acceptor-like defect states, and p-type conductivity. The underlying physical mechanism of electron transport in ultra-scaled a-PCM is unraveled. We find that, though the current-voltage curve of the ultra-scaled a-PCM resembles that of the bulk a-PCM, their physical origins are different. Unlike the electron transport in bulk a-PCM, which is governed by the Poole-Frenkel effect, the electron transport in ultra-scaled a-PCM is largely dominated by tunneling transport via intra-bandgap donor-like and acceptor-like defect states.

This work demonstrates wafer bonding using initiated chemical vapor deposition (iCVD) poly(glycidylmethacrylate) (PGMA) thin films, and studies the impact of surface treatment to manipulate adhesion energy between polymer film and silicon substrate. Substrates were modified with organosilanes or nitrogen plasma prior to iCVD and bonding. Adhesion was characterized by measuring critical energy release rate (Gc) using a 4-point bend technique. Results demonstrate a correlation between substrate surface energy and polymer-substrate adhesion energy where, depending on the functional group, close to an order of magnitude variation in adhesion energy was observed. These results point to minimal covalent interaction between polymer and substrate for these samples. Exposing the bonded wafers to a thermal anneal step led to an improved grafting of PGMA to substrate. For grafted films, the sample failure mode shifted from adhesive to cohesive, with drastic increase in Gc. These findings demonstrate that the adhesion energy and failure mode of iCVD-PGMA bonded wafers can be manipulated through surface functionalization and thermal treatment, which enable both temporary and permanent chip-bonding applications using iCVD polymer films as adhesives.