The present study details facile synthesis of hollow Cu2O nanospheres decorated with Ag nanoparticles using a simple surfactant technique for enhanced photocatalytic activity. The morphology and structure is studied via XRD and SEM. Cu2O hollow nanospheres with a diameter of 500-800 nm were synthesized via Ostwald ripening using CuSO4 aqueous solution. The catalytic activity of Cu2O is studied in the presence of UV and visible light using Methyl Orange (MO) as a model pollutant. Ag decorated Cu2O particles showed a 49% increase in photocatalytic activity over the undecorated Cu2O. The improved photocatalytic activity is achieved by surface plasmon resonance effects in the silver nanoparticles, allowing utilization of the lower energy portion of the solar spectrum.

Topology optimization is a systematic, computational approach to the design of structure, defined as the layout of materials (and pores) across a domain. Typically employed at the component-level scale, topology optimization is increasingly being used to design the architecture of high performance materials. The resulting design problem is posed as an optimization problem with governing unit cell and upscaling mechanics embedded in the formulation, and solved with formal mathematical programming. This paper will describe recent advances in topology optimization, including incorporation of manufacturing processes and objectives governed by nonlinear mechanics and multiple physics, and demonstrate their application to the design of cellular materials. Optimized material architectures are shown to (computationally) approach theoretical bounds when available, and can be used to generate estimations of bounds when such bounds are unknown.

In the new DR-A in-situ diffusion experiment at Mont Terri, a perturbation (replacement of the initial synthetic porewater in the borehole with a high-salinity solution) has been induced to study the effects on solute transport and retention, and more importantly, to test the predictive capability of reactive transport codes. Reactive transport modeling is being performed by different teams (IDAEA-CSIC, PSI, Univ. Bern, Univ. British Columbia, Lawrence Berkeley Natl. Lab.). Initial modeling results using the CrunchFlow code and focusing on Cs+ behavior are reported here.

We present a new approach to prepare Transmission Electron Microscopy (TEM) nanowire (NW) samples that addresses the core drawbacks of conventional techniques, which are based on mechanical polishing. The proposed method is time efficient and uses XeF2 isotropic and selective dry etching of Si to remove the host substrate from the NWs, after their embedding into a poly(methyl-methacrylate) (PMMA) matrix. Scanning electron microscopy (SEM) data suggest that NWs were grown through the gaps between the parasitic layer islands and that the stems are in direct contact with the Si substrate. This technique does not adversely affect the NWs and offers a convenient means of transferring the GaAs NWs onto other surfaces for post-process TEM analysis. It also offers excellent potential to facilitate their integration into device fabrication via a bottom-up approach, using the PMMA layer as a transfer medium.

In this work, we report the synthesis of all-conjugated donor-acceptor block copolymers via a externally initiated Kumada catalyst-transfer polycondensation (KCTP) method. In the first step, electron acceptor blocks, poly(naphthalene diimide)s (PNDIs), were prepared via the Stille coupling polycondensation. Then, P3HT blocks were polymerized by KCTP initiated by Ni(COD)2 activated PNDI complexes. Therefore, a series of ABA (P3HTs were initiated from both ends of PNDI) and AB-type (P3HT was initiated from one end of PNDI) block copolymers were successfully synthesized. Before fabrication of all-polymer solar cells, the morphologies and crystalline behaviors of the block copolymers were extensively investigated as a function of thermal annealing and the main chain composition of PNDI block. As a control, the crystalline behaviors of the physical blends of P3HT and PNDIs were also reported. Finally, all-polymer solar cells were fabricated by using the block copolymers as the single active component or as surfactants. A PCE of 0.11 % with Voc=0.46 V, Jsc=0.50 mA/cm2, and FF=0.46 was recorded by using the donor-acceptor all-conjugated block copolymer as the single active component.

The paper reports on the fabrication of electrical isolation for planar AlGaN/GaN high electron mobility transistor using Al double-implantation. The implantation was performed using Al+ ions with energies of 800 keV and 300 keV with doses of 1.5×1013 ion/cm2 and 1×1013 ion/cm2, respectively. Electrical measurements have shown that after implantation the sheet resistance was 1.8×1011 Ω/□ and increased to 1.17×1014 Ω/□ and 3.29×1012 Ω/□ after annealing at 400°C and 600°C respectively. Annealing at 800°C decreased the sheet resistance to 1.38×108 Ω/□. Characterization by XRD, Raman and photoluminescence spectroscopy give evidence that implantation damages the crystal lattice, yielding insulating properties. It has been demonstrated that the isolation is stable up to 600°C.

A hierarchy of nanostructured-ZnO was fabricated on the electrospun nanofibers by atomic layer deposition (ALD) and hydrothermal growth, subsequently. Firstly, we produced poly(acrylonitrile) (PAN) nanofibers via electrospinning, then ALD process provided a highly uniform and conformal coating of polycrystalline ZnO with a precise control on the thickness (50 nm). In the last step, this ZnO coating depicting dominant oxygen vacancies and significant grain boundaries was used as a seed on which single crystalline ZnO nanoneedles (average diameter and length of ∼25 nm and ∼600 nm, respectively) with high optical quality were hydrothermally grown. The detailed morphological and structural studies were performed on the resulting nanofibers, and the photocatalytic activity (PCA) was tested with reference to the degradation of methylene blue. The results of PCA were discussed in conjunction with photoluminescence response. The nanoneedle structures supported the vectorial transport of photo-charge carriers, which is crucial for high catalytic activity. The enhanced PCA, structural stability and reusability of the PAN/ZnO nanoneedles indicated that this hierarchical structure is a potential candidate for waste water treatment.

Scanning probe microscopy, having the capability of nano-positioning and nanomanipulation, enables the characterization of material properties at a very small scale. In our previous work, the investigation of localized electrochemical reactions in Si3N4-TiC ceramic nanocomposites had been demonstrated using a single conductive scanning probe in a scanning impedance microscope (SIM). The results have provided experimental evidence that links the relations among microstructural heterogeneity, electrochemical property, and sintering behavior of spark plasma sintered ceramics. This single-probe SIM measurement gave through-body electrochemical information of specific surface feature of interest; however, the characterization of across-surface material properties in nanoscale is still much desired and unavailable.

To further investigate the heterogeneity of materials, we have designed and developed a dual-electrode scanning probe (DESP), which is capable of localized electrochemical characterization across the surface of a material. These probes were designed based on computer simulation and iterations, and fabricated using common semiconductor processing techniques. The span of two probes (electrodes) in our first prototypes was 10∼15 microns, which can be further reduced with optimized parameters. The DESP probes have been evaluated on Si3N4-TiC nanocomposites to demonstrate their functionality in topography scanning and in-situ impedance measurement. The impedance spectroscopy revealed two distinct impedance patterns for measurements across TiC-rich and Si3N4-rich surface regions. The design, fabrication, and evaluation of DESP were discussed in addition to the analysis of Si3N4-TiC nanocomposites.

Metal nanoparticle–decorated graphene oxides are promising materials for use in various optoelectronic applications because of their unique plasmonic properties. In this paper, a simple, environmentally friendly method for the synthesis of gold nanoparticle–decorated graphene oxide that can be used to improve the efficiency of organic photovoltaic devices (OPVs) is reported. Here, the amino acid glycine is empolyed as an environmentally friendly reducing reagent for the reduction of gold ions in the graphene oxide solutions. Furthermore, these nanocomposites are empolyed as the anode buffer layer in OPVs to trigger surface plasmonic resonance, which improved the efficiency of the OPVs. The results indicate that such nanomaterials appear to have great potential for application in OPVs.

The thermoluminiscent properties of MEH-PPV and MDMO-PPV conjugated polymers were studied in order to verify if they are suitable for use as TL dosimeter. The dose response that was analyzed cover the wide dose range 0.34-5.44 kGy. The measured glow curves show complex structures which were evaluated with kinetic parameters based on the MO (Mix Order) model together with the CGCD (Computerized Glow Curve Deconvolution) homemade program which is useful to understand the mechanisms responsible for TL emission.

Polysilsesquioxane passivation layers were used to passivate bottom gate a-InGaZnO (a-IGZO) thin film transistors (TFT). The a-IGZO TFTs passivated with polysilsesquioxane showed highly stable behavior during positive bias stress, negative bias stress, and negative bias illumination stress. A voltage threshold shift of up to 0.1 V, less than -0.1 V and -2.3 V for positive bias stress, negative bias stress, and negative bias illumination stress, respectively. We also report the effect of reactive ion etching (RIE) on the electrical characteristics of a-InGaZnO (a-IGZO) thin-film transistors (TFT) passivated with the polysilsesquioxane-based passivation layers. We show how post-annealing treatment using two different atmosphere conditions: under O2 ambient and combination of N2 and O2 ambient (20% O2), can be performed to recover the initial characteristics. Furthermore, we present a highly stable novel polysilsesquioxane photosensitive passivation material that can be used to completely circumvent the reactive ion etching effects.

The performance of commercially available silicon carbide (SiC) power devices is limited due to inherently high density of screw dislocations (SD), which are necessary for maintaining polytype during boule growth and commercially viable growth rates. The NASA Glenn Research Center (GRC) has recently proposed a new bulk growth process based on axial fiber growth (parallel to the c-axis) followed by lateral expansion (perpendicular to the c-axis) for producing multi-faceted m-plane SiC boules that can potentially produce wafers with as few as one SD per wafer. In order to implement this novel growth technique, the lateral homoepitaxial growth expansion of a SiC fiber without introducing a significant number of additional defects is critical. Lateral expansion is being investigated by hot wall chemical vapor deposition (HWCVD) growth of 6H-SiC a/m-plane seed crystals (0.8mm x 0.5mm x 15mm) designed to replicate axially grown SiC single crystal fibers. The post-growth crystals exhibit hexagonal morphology with approximately 1500 μm (1.5 mm) of total lateral expansion. Preliminary analysis by synchrotron white beam x-ray topography (SWBXT) confirms that the growth was homoepitaxial, matching the polytype of the respective underlying region of the seed crystal. Axial and transverse sections from the as-grown crystal samples were characterized in detail by a combination of SWBXT, transmission electron microscopy (TEM) and Raman spectroscopy to map defect types and distribution. X-ray diffraction analysis indicates the seed crystal contained stacking disorders and this appears to have been reproduced in the lateral growth sections. Analysis of the relative intensity for folded transverse acoustic (FTA) and optical (FTO) modes on the Raman spectra indicate the existence of stacking faults (SFs). Further, the density of stacking faults is higher in the seed than in the grown crystal. Bundles of dislocations are observed propagating from the seed in m-axis lateral directions. Contrast extinction analysis of these dislocation lines reveals they are edge type basal plane dislocations that track the growth direction. Polytype phase transition and stacking faults were observed by high-resolution TEM (HRTEM), in agreement with SWBXT and Raman scattering.

We investigated the photovoltaic (PV) parameters of a planar hetero-junction solar cell with di-[4-(N,Nditolyl-amino)-phenyl] cyclohexane (TAPC) as donor (D) and C60 as acceptor (A), upon exposing the acceptor side to oxygen and moisture. We found that for the same time of exposure, even minor oxygen amounts lead to more detrimental results compared to moisture. We argue that the photo-conversion efficiency (PCE) decreases due to creation of recombination centers at the interface, which induce losses in exciton diffusion and charge generation. Under the same conditions, we also registered a direct connection between the cell PV parameters’ decay and a C60 thin-film conductivity loss.

The tube-length distribution in the semiconducting single-wall carbon nanotube (s-SWCNT) ink extracted by the electric-field-induced layer formation (ELF) method was characterized by atomic force microscopy, which revealed that the nonionic surfactant Brij 700 adopted in ELF causes the significant and homogeneous shortening of SWCNTs compared with sodium cholate that is frequently used for the dispersion of SWCNTs as an ionic surfactant. It was found that the shortened s-SWCNTs in the semiconducting ink positively effect on the uniformity of performance among the s-SWCNT thin-film transistors.

Catalyst-free vapor phase transport was applied for the growth of ZnO nanoemitters. A single-crystalline ZnO:Al seed layer was deposited and used as a pseudo-catalyst. The desired morphology of nanostructures can be achieved by means of modifying the growth rates of crystal planes via adjustment in the growth conditions. The field emission characteristics of ZnO nanoemitters satisfied the Fowler-Nordheim relationship. The high aspect ratio of nanoemitters had a low turn-on electric field of 0.18 MV/m at emission current density of 0.1 μA/cm2. A stable electron emission with a variation of less than 14% was measured.

C-14 contained in Hull waste is one of the most important radionuclides in the safety assessment of transuranic (TRU) waste disposal. For more realistic safety assessment, it is important to clarify the release mechanism and chemical species of C-14 from Hull waste. In this research, leaching tests were conducted using an irradiated Zry cladding tube from a boiling-water reactor (BWR) to obtain leaching data and to investigate the relationship between Zry metal corrosion and C-14 release behavior. Both organic and inorganic C-14 compounds existed in the the liquid phase, and some C-14 moved to the gaseous phase. The release rate of C-14 obtained from the BWR cladding tube after two-year leaching tests was lower than the release rate from a pressurize water reactor (PWR) cladding tube. It is considered that the BWR cladding tube used in this test did not easily corrode since it used a comparatively new material. The release rate of C-14 was slightly lower as compared with the corrosion rate of unirradiated Zry. This is thought to be the result of improved corrosion resistance conferred by neutron irradiation, which encouraged the dissolution of grain boundary precipitation elements, such as Fe, Cr, and Ni, into the crystal grains. The leaching tests will be continued for 10 years.

A new route for atom-economical synthesis of functional polymers was developed. Oxidative polycoupling of 3,5-dimethyl-1-phenylpyrazole with 4,4’-(α,ω-alkylenedioxy) bis(diphenylacetylene)s and 1,2-diphenyl-1,2-bis[4-(phenylethynyl)phenyl]ethene, respectively, were catalyzed by [Cp*RhCl2]2, 1,2,3,4-tetraphenylcyclopenta-1,3-diene and copper(II) acetate in dimethylformamide under stoichiometric imbalance conditions, affording soluble poly(pyrazolylnaphthalene)s in satisfactory yields (isolation yield up to 82%) with high molecular weights (M w up to 35700). All the polymers were thermally stable, losing little of their weight at high temperatures of 323–422 oC. They possessed good film-forming property and their thin solid films showed high refractive indices (RI = 1.747–1.593) in a wide wavelength region of 400−1000 nm. The polymer carrying tetraphenylethene unit displayed a phenomenon of aggregation-induced emission and showed enhanced light emission in the aggregated state.

Morphology of the active layer in bulk heterojunction P3HT:PCBM organic solar cell was studied using Monte Carlo (MC) and coarse-grained dynamics simulations. While coarse-grained molecular dynamics allow us to quickly estimate the P3HT:PCBM interfacial energy of bilayer structure as a function of underlying layer thickness, bridging the dimension and time gap between dynamics simulations and experiment is computationally expensive and therefore not viable. Using MC technique with input from dynamics simulations allowed us to speed up the calculation and obtain final morphological information based on energetics and entropy, and at the same time retained the physics fidelity in-built in our validated coarse-grained model. The final structure gives phase separated domains with dimension of approximately 12 nm, on par with reported experimental result. The method can be applied to other organic photovoltaics systems to predict active layer morphology relevant for device performance or 3-dimensional device modelling at continuum level.