We demonstrate the potential of spectroscopic ellipsometry for the investigation of the chain segment density profile and layer thickness during the temperature-induced, reversible collapse−expansion transition of poly(N-isopropylacrylamide) (PNIPAM) grafted layers with variable grafting densities in aqueous systems. To obtain a quantitative description of the thickness of our swollen PNIPAM layers, various models were implemented to fit the ellipsometric data. From the ellipsometry results, the density and thickness variation accompanying the collapse transition across the lower critical solution temperature (LCST) was characterized. The collapse can be adequately explained by considering the PNIPAM film to consist of two layers: (i) a dense layer near the surface and (ii) a more diluted layer with a gradient density profile on the side of the film exposed to the solvent.

KNbO3 thick films were deposited on (100)c SrRuO3//(100)SrTiO3 substrates at 240 °C for 3 h by hydrothermal method. Film thickness increased linearly with increasing the deposition number of times and 130 μm thickness was achieved by the 6 time deposition. XRD analysis showed the growth of epitaxial orthorhombic films with the mixture orientation of (100), (010) and (001). Cross-sectional SEM observation showed that the 130 μm-thick film was dense and no obvious voids inside the film. In addition, the crystal structure change along film thickness direction was not detected from the cross-sectional Raman spectral observation.

One of the methods to grow nanoscale three-dimensional (3D) Au patterns is to perform local electron-beam-induced deposition (EBID) using the Me2Au(acac) precursor inside the chamber of a scanning electron microscope (SEM). However, due to the organometallic nature of the chemical, the concentration of the metallic constituent in the as-deposited structure is dramatically low, at around 10 at. % of Au. Ex-situ post-annealing of Me2Au(acac) EBIDs is a very promising purification approach, resulting in an Au content of > 92 at. % after annealing at 600 °C. However, in most of the cases it also distorts the geometrical shape of the heat-treated structure, preserving of which is essential for the application. In this paper we present a systematic study of the dependence between the annealing parameters and resulting purity in combination with the shape of the Au structure. Optimized heat treatment conditions for the creation of well-purified high aspect ratio Au pillar array are presented; and for planar continuous structures, the importance of the parameter height to area ratio is identified.

The introduction of nanotechnology in early classroom pedagogy is becoming a high priority in education. However, the concepts of nanotechnology can be difficult to conceptualize due to the esoteric nature of the subject. Inquiry-based nanotechnology modules are one way to help visualize nanomaterials to deliver the concepts of nanotechnology. We present the implementation and effectiveness of a newly developed module tying existing light and energy curriculum in middle school to nanoparticles, introducing the concept of a photocatalyst and energy. The module is part of a five year teacher professional development program in the Alabama Black Belt through a Math Science Partnership award from NSF (0832129) to increase students’ interests at the middle school level for pursuing continued math and science education and creative research activities in the future. Students impacted by the program are from low income rural communities where it is critical in preparing the next generation scientists and engineers for our nation’s future energy challenges.

Highly monodispersed ZnO nanoparticles (NPs) have been synthesized in polyol medium. The control on crystal size was attempted at 180°C by monitoring the heating rate of reacting solutions and the cooling rate (quenching) at the end of the reaction time. The possibility to promote crystal growth by heterogeneous nucleation was also evaluated; in this approach, pre-synthesized 5-nm pure ZnO nanocrystals were used as seeds in fresh Zn-polyol solutions at suitable seeds/ZnO w/w ratios. As-synthesized samples were characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM), Fourier Transform Infrared spectroscopy (FT-IR), Absorbance (UV-vis) and Photoluminescence spectroscopy (PL). XRD measurements confirmed the formation of well crystallized ZnO-wurtzite with absence of secondary phases in both seeds and grown crystals. FT-IR analyses evidenced the presence of organic moieties on the surface of the nanoparticles that are associated to the functional groups of polyol by-products; these adsorbed species would have prevented particles from aggregation. PL measurements (excitation wavelength 345 nm) reveled that a tuning in the emission bands of ZnO NPs can be achieved through synthesis conditions and crystal size. HRTEM measurements evidenced the formation of bare ZnO NPs of 2 nm, 6 nm, 20 nm and clusters of small nanocrystals.

Ordering types in the disordered structure of amorphous materials and structural changes which occur at glass-liquid transition are discussed revealing medium range order and reduction of topological signature of bonding system.

The metallic nickel (Ni) deposited on an n-Si substrate with resistivity of 4 – 6 Ω∙cm was oxidized by the ultra-violet (UV) oxidation technique to form a p-NiO/n-Si heterojunction diode. The rectifying current-voltage (I-V) characteristic confirmed formation of a pn junction. The capacitance-voltage (C-V) characteristic further identified an abrupt p+n junction between NiO and n-Si. The photocurrent increased with the increased wavelength of laser under illumination of the diode. The voltage-dependent photocurrent suggests that the carriers generated in the depletion region of Si was effectively collected but not outside the depletion region. A low diffusion length of holes was attributed to Ni diffusion in Si caused by the substrate heating during the UV oxidation.

We have examined the properties of helium bubbles in Fe using two different Fe-He potentials. The atomic configurations and formation energies of different He-vacancy complexes are determined and their stability in the region of nearby collision cascades is investigated. The results show that the optimal He to Fe vacancy ratio increases from about 1:1 for approximately 5 vacancies up to about 4:1 for 36 vacancies. Collision cascades initiated near the complex show that Fe vacancies produced by the cascades readily become part of the He-vacancy complexes. The energy barrier for an isolated He interstitial to diffuse was found to be 0.06 eV. Thus a possible mechanism for He bubble growth would be the addition of vacancies during a radiation event followed by the subsequent accumulation of mobile He interstitials produced by the corresponding nuclear reaction.

The Fukushima Daiichi nuclear power station accident and restoration works have produced significant volume of radioactive waste. The waste has very different characteristics from usual radioactive waste produced in nuclear power stations and it requires extensive research and development for management of the waste. R&D works such as analysis of the waste properties, hydrogen generation by radiolysis and diffusion in a storage vessel and corrosion of storage vessels, etc. have been performed for characterization and safe storage of the waste. The detailed R&D plan for processing and disposal waste will be established by the end of FY2012.

In the last decades many techniques have been proposed to manufacture thin (<50µm) silicon solar cells. The main issues in manufacturing thin solar cells are the unavailability of a reliable method to produce thin silicon foils with contained material losses (kerf-losses) and the difficulties in handling and processing such fragile foils. A way to solve both issues is to grow an epitaxial foil on top of a weak sintered porous silicon layer. The porous silicon layer is formed by electrochemical etching on a thick silicon substrate and then annealed to close the top surface. This surface is employed as seed layer for the epitaxial growth of a silicon layer which can be partially processed while attached on the substrate that provides mechanical support. Afterward, the foil can be bonded on glass, detached and further processed at module level. The efficiency of the final solar cell will depend on the quality of the epitaxial layer which, in turn, depends on the seed layer smoothness.

Several parameters can be adjusted to change the morphology and, hence, the properties of the porous layer, both in the porous silicon formation and the succeeding thermal treatment. This work focuses on the effect of the parameters that control the porous silicon formation on the structure of the porous silicon layer after annealing and, more specifically, on the roughness of the top surface. The reported analysis shows how the roughness of the seed layer can be reduced to improve the quality of the epitaxial growth.

Thin silicate nanoplatelets, derived from the exfoliation of natural Sodium montmorillonite (Na+-MMT) clays, show an unexpected antimicrobial property. A physical trapping mechanism has been proposed because the clay nanoplatelets can indiscriminately inhibit the growth of a broad spectrum of bacteria, including drug-resistant species such as methicillin-resistance S. aureus (MRSA) and silver ion-resistant E. coli. The ability to generate singlet oxygen species was first observed for the clay platelets that showed a high-aspect-ratio geometric shape and the presence of surface ionic charges. By comparison, the pristine clay with a multilayered structure failed to generate any singlet oxygen species. The ability to emit singlet oxygen species provides direct evidence for the antimicrobial ability of clay through a non-chemical mechanism, which opens the potential for medical use.

The report presents the results of research and development on cementation technology of liquid radioactive waste (LRW) generated in spent nuclear fuel reprocessing in Experimental Demonstration Center (EDC) at the Mountain Chemical Combine, Russian Federation.

Papers in this Volume were published in print format as an Appendix of Volume 1617

http://journals.cambridge.org/issue_MRS Online Proceedings Library/OPL1617no-1

In this study the strain states in alternating multilayers of an extrinsic O2− ion conductor yttria stabilized zirconia (YSZ) and an insulator RE2O3 (RE = Er, Y) are investigated as a function of the layer thickness. Multilayers with narrow columnar crystallites and coherent phase boundaries were grown by pulsed laser deposition (PLD). A detailed strain analysis is performed by X-Ray Diffraction XRD, measuring distinct reflections in and perpendicular to the interface planes. Because of small columnar crystallites in the layers, the interfacial strain decays by shear with increasing distance from the interface. The extent of the strained interface regions in the YSZ layers is estimated from XRD data. By using a quantitative analytical model based on the pressure dependence of the free migration enthalpy for vacancies the results are compared to former published experimental data on O2− ion conductivity and diffusion.

Energy storage is a key technology for establishing a stand-alone renewable energy system. Current energy-storage technologies are, however, not suitable for such an energy system. They are cost ineffective and/or are with low energy-conversion efficiency. Hydrogen generation and storage from water by sunlight is one of these technologies. In this study, a simple concept of hydrogen generation from water by using sunlight, “concentrated photovoltaic electrochemical cell (CPEC)” is proposed. It is experimentally shown that the CPEC operates stably and achieves conversion efficiency from light to hydrogen energy of over 12%.

The study of high quality YBa2Cu3O7-x (YBCO) based superconducting films is a fundamental issue to be addressed when dealing with the realization of efficient coated conductors with large current carrying capacity. In this perspective the investigation of innovative buffer layers structures able to allow epitaxial YBCO film grow on metallic substrates and to prevent contamination and degradation issues holds a central role.

In this work we thoroughly study the properties of YBCO films grown by means of pulsed lasers deposition on CeO2 template on both bare MgO single crystal and MgO-homoepitaxial/MgO single crystal substrates. Due to its high chemical and temperature stability the MgO reduces the oxygen diffusion effects. On the other hand, the CeO2 layer, pulsed laser deposited, prevents the YBCO film from metallic contamination and facilitates its epitaxial growth. Morphology and crystalline structure of buffer layers and superconductors film are investigated by using scanning electron microscopy (SEM), X-ray and electrons back-scattered diffraction techniques (XRD and EBSD).

YBCO films show good critical temperature values (Tc > 87K) with sharp transitions. These encouraging results make our structures promising candidates in the realization of high quality YBCO based coated conductors.

Epitaxial rhombohedral Pb(Zr0.65Ti0.35)O3films with (100) and (110)/(10-1) and (111)/(11-1) orientations were grown on various kinds of singlecrystal substrates having different thermal expansion coefficient. Volume fractions of (110) and (111) orientations in respective (110)/(10-1) and (111)/(11-1)-oriented films were almost linearly increased with increasing thermal strain, ε thermal, applied to the films that wasgenerated under the cooling process after the deposition from the growth temperature to the Curie temperature.Observed saturationpolarization (P sat)was changed linearly with the volume fractions of (110) and (111) orientations, in the same manner asthe volume fractions of (001) and (101) orientations in (001)/(100) and (101)/(110) oriented tetragonal Pb(Zr,Ti)O3 filmsreported previously. These results showed that the volume fraction of the non-180o domains Pb(Zr,Ti)O3films of both tetragonal and rhombohedral symmetriescan be manipulated by ε thermal, which brings possibly to control the P sat value.

Localized surface plasmon resonance (LSPR) is a label-free biosensing technique employing plasmonic nanostructures to detect local refractive index change induced by biomolecules in the vicinity of these nanostructures. In analogy to surface plasmon resonance (SPR) sensor in a cuvette, LSPR is resistant to bulk refractive index fluctuation yet remains comparably sensitive for biosensing purpose. LSPR has the advantage over SPR in that the overall system size is smaller, and not affected by normal temperature fluctuations during measurement. However, mass production of a cheap but effective LSPR substrate remains challenging. In this paper, a self-assembly gold nanoisland structure was synthesized on transparent glass substrate by a simple two-step deposition-growth process. The first step involved depositing an ultra thin film of gold with nominal thickness of 5 nm by thermal evaporation at 1× 10-7 torr. Then the gold coated substrate was placed into a high temperature oven and annealed at 450°C for 10 hours. By first observation, the annealed substrate turned from pale green to dark pink. Upon scanning with atomic force microscopy, it was revealed that nanoislands of about 100 nm to 150 nm wide with average height of 60 nm were formed. Optical extinction measurements showed that the absorption peak was about 560 nm with fullwidth-half-maximum of 100 nm, so dark pink color was observed. For the biosensing demonstration, Bovine serum albumin (BSA) and Anti-BSA bio-affinity interaction was measured using the self-assembly gold nanoisland LSPR sensor. Anti-BSA was functionalized onto the sensing site and BSA of known concentrations, i.e. 1 ug/ml was injected. The results showed LSPR spectral intensity change of 650 counts at the resonance slope of 634 nm. With standard deviation of spectral intensity fluctuation at 7 counts, the detection limit of BSA was estimated at about 0.5 nM which was comparable with that of LSPR systems with more elaborate nanostructures. The limit of detection of the present system can be further improved by implementing phase measurement and further nanostructure improvement.

We have investigated the effects of two different strain-relief bilayer shell structures on the luminescent properties of colloidal CdSe quantum dots (QDs). CdSe QDs with a strain-compensated ZnS/ZnCdS bilayer shell were synthesized using the successive ion layer adsorption and reaction technique and their crystallinity of was examined by X-ray diffraction. The QDs enjoyed the benefits of excellent exciton confinement by the ZnS intermediate shell and strain compensation by the ZnCdS outer shell. The resulting CdSe/ZnS/ZnCdS QDs exhibited 40% stronger photoluminescence and a smaller peak redshift upon shell growth compared to conventional CdSe/ZnCdS/ZnS core/shell/shell QDs with an intermediate lattice adaptor. CdSe/ZnS/ZnCdS QD light-emitting diodes (LEDs) had a luminance of 558 cd/m2 at 20 mA/cm2, 28% higher than that of CdSe/ZnCdS/ZnS QD-LEDs. The former also had better spectral purity. These results suggest that nanocrystal shells may be strain-engineered in a different way to achieve QDs of high crystalline and optical quality well suited for full-color display applications.

In order to achieve waste heat recovery using thermoelectric systems, thermoelectric materials showing high conversion efficiency over wide temperature range and high resistance against oxidation are indispensable. A silicide material with good n-type thermoelectric properties and oxidation resistance has been discovered. The composition and crystal structure of the silicide are found out Mn3Si4Al2 (abbreviated as 342 phase) and hexagonal CrSi2 structure, respectively. Element substitution of Mn with 3d transition metals is succeeded. Enhancement of Seebeck coefficient is observed in a Cr-substituted sample. The maximum dimensionless thermoelectric figure of merit ZT is 0.3 at 573 K in air for the Mn2.7Cr0.3Si4Al2 sample. Electrical resistivity of the Mn3Si4Al2 bulk sample holds constant value for 48 h at 873 K in air. This is due to formation of oxide passive layer on the surface of the bulk sample. The 342 phase is a promising n-type material with a good oxidation resistance in the middle temperature range of 500-800 K.