The results of correlated electron paramagnetic resonance (EPR) and photoluminescence (PL) study of obliquely deposited porous SiOx films after step-by-step 15 min annealing within 105 min in vacuum at 950°C are presented. The low intensity symmetrical and featureless EPR line with a g-value g=2.0044 and a linewidth of 0.77 mT has been detected in as-sputtered films and attributed to dangling bonds (DB) of silicon atoms in amorphous SiOx domains with x=0.8. Successive annealing results in decreasing this line and the appearance of an intense EPR line with g=2.0025, linewidth of 0.11 mT and a hyperfine doublet with 1.6 mT splitting. According to the parameters this spectrum has been attributed to the EX center, a hole delocalized over four non-bridging oxygen atoms grouped around a Si vacancy in SiO2. The impact of chemical treatment before annealing and duration of anneals on the defect system, and a correlation of the PL intensity with decreasing of the DB EPR signal are discussed.

Hybrid magnetic/plasmonic nanoparticles possess properties originating from each individual material. Such properties are beneficial for biological applications including bio-imaging, targeted drug delivery, in vivo diagnosis and therapy. Limitations regarding their stability and toxicity, however, challenge their safe use. Here, the one-step flame synthesis of composite SiO2-coated Ag/Fe2O3 nanoparticles is demonstrated. The hermetic SiO2 coating does not influence the morphology, the superparamagnetic properties of the iron oxide particles and the plasmonic optical properties of the silver particles. Therefore, the hybrid SiO2-coated Ag/Fe2O3 nanoparticles exhibit desired properties for their employment in bio-applications.

The national interest in science, technology, engineering and mathematics (STEM) has called attention to P-12 education, the STEM pipeline. Education of teachers is a primary influence on the education of children in the classroom. While high school (and often middle school) teachers are versed in the content of a particular aspect of STEM (e.g. Mathematics or Chemistry), elementary teachers, on the other end of the pipeline, are educated as generalists, with a primary goal of setting the foundations for future learning.

In 2004, a team of STEM and education faculty at St. Catherine University (SCU) was called together, united by their interest in improving STEM education for all students at SCU, particularly women. Combining the content expertise of the biology, chemistry, physics/engineering, and mathematics departments with the methods expertise of the education department, the team designed courses that made STEM concepts more engaging and relevant to students. In 2010, the STEM Certificate was solidified and required of all elementary education students. It is comprised of three interdisciplinary, team-taught, lab based courses that are open to all undergraduate majors at the institution. Each course is centered on one discipline (i.e. biology, chemistry, or engineering/physics). Chemistry of Life is the chemistry-focused course. The course was designed to include a capstone project. As an introduction to materials science, nanoscience was selected as the theme for the projects. The topic allowed for socially relevant and also highly interdisciplinary projects. Students working in teams of three or four, designed projects, determined how to measure and obtain data, and analyzed and interpreted results. A content and confidence assessment given to students before and after the projects showed an increase in both their understanding of nanomaterials and their confidence in conducting a nanoscience project.

Cationic liposome (CL) is a promising vector for nucleic acid therapy. In the present study, we investigated the effect of high hydrostatic pressure (HHP) treatment to lipoplex on the lipoplex-based antisense oligodeoxynucleotides (AS-ODNs) delivery in order to improve the transfection efficacy of lipoplex. Cationic liposome consisting of DOTMA and DOPE was used. AS-ODNs were designed to inhibit the expression of firefly luciferase. The complexes of CL and AS-ODN were prepared at various C/A ratios and then pressurized hydrostatically at various atmospheres (∼10,000 atm) for 10 min (HHP treatment). After removal of pressure, the pressurized lipoplexes were used. The lipoplex with and without the HHP treatment was transferred into HeLa cells expressing firefly luciferase transiently. The luciferase activity using the HHP-treated lipoplex was decreased compared to that of the non-pressurized lipoplex. Also, for HEK293 cells expressing luciferase stably, the lipoplex with the HHP treatment could effectively suppress the luciferase expression. In order to elucidate relationship between the structure and the transfection efficiency of the HHP-treated lipoplex, the properties of the HHPtreated lipoplex were examined by various physicochemical analyses. The different physicochemical properties between the lipoplexes with and without HHP treatment were showed, suggesting that the nature of lipoplex was changed by the HHP treatment. We believe that this change of lipoplex properties by the HHP treatment affected the efficiency of gene suppression. This HHP treatment for lipoplex appears to be a promising contribution to gene and oligonucleotide delivery.

Cluster dynamics (CD) modeling has been used to estimate the long-term evolution of point defect (PD) clusters. However, previous studies have often simplified the governing equations by assuming the maximum size of mobile self-interstitial atom (SIA) clusters and by ignoring the one-dimensional (1D) reaction kinetics of SIA loops. They have also conducted parameter fittings, such as the clustered fraction and the maximum size of clusters produced by collision cascade, to reproduce experimental data. In this study, in addition to modeling the 1D motion of SIA loops in the framework of the production bias model (PBM), reaction rates associated with carbon impurity atoms present in alpha iron were formulated to consider the trapping effect of one-dimensionally migrating SIA loops by a vacancy-carbon (V-C) complex that was shown to have strong bindings with SIA loops by previous atomistic simulations. Calculations results for neutron-irradiated alpha iron showed that the developed CD model can successfully reproduce the saturation trend of the number density of immobile SIA loops in contrast to the prediction using a model without the trapping effect.

High resolution Schottky barrier detectors for alpha particles have been fabricated on 20 μm n-type 4H-SiC epitaxial layers. Schottky barrier contact structure was accomplished by deposition of 10 nm nickel on the Si face of the epilayers. The detectors were characterized for structural, electrical, and spectroscopic properties. Scanning electron microscopy and Nomarski optical microscopy revealed a micropipe density lower than 1 cm-2. The current-voltage (I-V) characteristics of the device exhibited very low leakage current of the order of 6.5 pA at an operating bias of 90 V. C-V measurements revealed a typical effective doping concentrations of 2.4 × 1014 cm-3 in these epilayers. The detectors were evaluated for alpha particles detection using a 241Am source. An energy resolution of ∼0.98% for 5.48 MeV alpha particles was observed. The separate contribution of charge carrier drift and diffusion to the total charge collection efficiency has been calculated in these detectors following a drift-diffusion model. Detailed electronic noise analysis in terms of equivalent noise charge (ENC) was carried out to study the effect of various noise components that contribute to the total electronic noise in the detection system. Effect of shaping time, presence of source and bias on the ENC has been studied in details.

Non-stoichiometric and impurity doped titanium dioxide materials are good candidates for use in high temperature thermoelectric devices. Nanolayers of non-stoichiometric (TiO2-x) thin films were deposited on Al-foil by atomic layer deposition growth method. X-ray diffraction experiments showed anatase phase for these nanolayers. This crystal structure was maintained even after an annealing treatment of 600 °C for 60 minutes under an O2 pressure of ∼ 10 psi. This investigation presents for the first time how Al-foil can be functionalized by manipulating the Seebeck coefficient of these TiO2-x nanolayers.

The effect of γ-radiation on the mechanical properties of model UK intermediate and high level nuclear waste glasses was studied up to a dose of 8 MGy. It was determined that γ-irradiation up to this dose had no measurable effect upon the Young’s modulus, shear modulus, Poisson’s ratio, indentation hardness, or indentation fracture toughness. The absence of measurable radiation induced changes in mechanical properties was attributed to redox mediated healing of electron-hole pairs generated by γ-irradiation by multivalent transition metal ions, in particular the Fe3+ - Fe2+ couple.

Ordered one dimensional polypyrrole conducting polymer structure as a shell over TiO2 nanotube arrays at the core were formed by pulsed current electropolymerization. TiO2 nanotubes with rippled wall structure are designed by action of water in the anodizing medium. This provides open tube structure supporting short diffusion length and increased accessibility of ions involved in redox transition for energy storage. Electrochemical properties evaluated by cyclic voltammetry and electrochemical impedance spectroscopy show specific capacitance of 34-44 mF.cm-2 and extremely low bulk and charge transfer resistances.

We report on the fabrication of various high quality GaS nanostructures (angular nanobelts, nanowedges and nanotubes) and In2S3 nanostructures (tapered nanorods, nanobelts and nanowires) by catalyst assisted thermal evaporation process. The morphology and structures of the products were controlled by temperature and position of the substrates with respect to the source material. The morphologies of GaS and In2S3 nanostructures were examined by X-ray diffraction (XRD), scanning electron microscope (SEM), high-resolution transmission electron microscope (HRTEM), and energy dispersive spectroscopy (EDS). The optical and electronic properties of the synthesized materials were investigated in order to obtain a better fundamental understanding of the structure-property relationships in these materials which can be extended to other layered sulfide materials systems.

We review basic ideas behind state-of-the-art techniques for first-principles theoretical simulations of the phase stabilities and properties of alloys. We concentrate on methods that allow for an efficient treatment of compositional and thermal disorder effects. In particular, we present novel approach to evaluate free energy for strongly anharmonic systems. Theoretical tools are then employed in studies of two materials systems relevant for nuclear energy applications: Fe-Cr and Zr-based alloys. In particular, we investigate the effect of hydrostatic pressure and multicomponent alloying on the mixing enthalpy of Fe-Cr alloys, and show that in the ferromagnetic state both of them reduce the alloy stability at low Cr concentration. For Zr-Nb alloys, we demonstrate how microscopic parameters calculated from first-principles can be used in higher-level models.

An investigation on composite geopolymeric binders, based on alkali activated fly ash (PFA) substituted with low-alumina calcium aluminate cement (CAC), was carried out using a Factorial experimental design in which the factors and levels were: %Na2O, 8-12%; modulus of the solution Ms=SiO2/Na2O =0 - 2, 10-30 wt% of CAC and fineness of PFA (D90) from 161.8 to 6.46 microns. The contribution of each factor was estimated with the 28-day compressive strength as the response variable. The curing temperature was 24h@60°C, and then at 20°C until mechanical testing. The specimens were also characterized by XRD and SEM. The results showed that the grinding modified the morphology of the PFA without changing the crystallographic or chemical characteristics as detected by XRD; and improved the mechanical properties of the geopolymers. The strength increased notably with the Ms up to 1, and reduced for Ms >1; the strength increased with the %Na2O and %CAC. Electron microscopy showed a higher densification at smaller PFA particle size, and the CAC addition promoted the formation of zeolite and Na2O-Al2O3-SiO2-H2O products.

As produced, raw carbon nanotubes are not soluble in many solvents necessary for printing applications. Standard methods for circumventing this problem involve sidewall functionalization and surfactants. Sidewall functionalization invariably destroys the π-network that gives carbon nanotubes their useful electronic properties, while surfactants deposit an insulating layer onto the carbon nanotube surface that must be washed off to regain the desired properties. Non-covalent functionalization offers the possibility to achieve solubility without destroying the π-network, but published methods have resulted in relatively low concentrations or substandard electronic performance. We have developed a scalable method to non-covalently functionalize long (> 3 μm) carbon nanotubes with simple pyrene derivatives. This method produces highly dispersed solutions with concentrations as high as 2.5 g/l that can be used to produce conductive coatings with sheet resistance as low as 350 Ω/sq with 85% transmittance at 550 nm without post-deposition washing or doping treatments. The functionalized carbon nanotubes can be formulated into solutions that can be printed by ink-jet deposition, Aerosol-Jet® deposition, screen printing, and spray coating for printed electronics fabrication, and the solutions are stable for months without signs of bundling.

The specimen-size dependence of yield stress of nanocrystalline copper with average grain size (d) of 360 nm has been investigated through uniaxial compression tests of micrometer-size pillars fabricated via the focused ion beam method. The yield stress decreases with the decrease in the micropillar size while the yield stress is almost constant for larger micropillars. The critical specimen size (t) is approximately 12.5 μm, correspoinding to the critical (t/d) value, (t/d)*, of 35, which is much larger than that for coarse-grained copper polycrystals.

We investigate the dynamic behavior under uniaxial stress loading conditions of heterogeneous mixtures of Ti/Al/B via impact simulations on simulated microstructures. We simulate a range of Al concentrations at a constant theoretical material density (TMD) to determine their effects on the mechanical response of a realistic microstructure to impact conditions. We also study particle-level effects such as mixing, extreme deformation, and hot spot formation due to void collapse, as a function of microstructure. Our goal is to shed light on the possible meso-scale phenomena that makes a certain mixture more reactive than others of variable Al composition.

Remoras (echeneid fish) reversibly attach and detach to marine hosts, almost instantaneously, to “hitchhike” and feed. The adhesion mechanisms that they use are remarkably insensitive to substrate topology and quite different from the latching and suction cup-based systems associated with other species at similar length scales. Remora adhesion is also anisotropic; drag forces induced by the swimming host increase adhesive strength, while rapid detachment occurs when the remora reverses this shear load. In this work, an investigation of the adhesive system’s functional morphology and tissue properties was carried out initially through dissection and x-ray microtomographic analyses. Resulting finite element models of these components have provided new insights into the adaptive, hierarchical nature of the mechanisms and a path toward a wide range of engineering applications.

We review some recent results related to the steady-state and transient electron transport that occurs within bulk wurtzite zinc oxide. We employ three-valley Monte Carlo simulations of the electron transport within this material for the purposes of this analysis. Using these results, we devise a means of rendering transparent the electron drift velocity enhancement offered by transient electron transport over steady-state electron transport. A comparison, with results corresponding to gallium nitride, indium nitride, and aluminum nitride, is provided. The device implications of these results are then presented.

Pyrochemical reprocessing of nuclear fuels, in which electrochemical separation of actinides and fission products is mediated by a molten alkali chloride salt (typically a LiCl-KCl eutectic) is of interest for future nuclear energy cycles. A key challenge in the management of pyrochemical reprocessing wastes is decontamination and recycling of the molten salt medium to remove entrained actinides and radioactive lanthanide fission products. Since pyrochlore oxides are promising candidates for the immobilisation of lanthanides and actinides, we sought to use the “problematic” molten salt to our advantage as a reaction medium for low temperature synthesis of titanate pyrochlores. Through control of reaction time and temperature, we demonstrated the synthesis of lanthanide pyrochlores at temperatures as low as 700 °C in 1 h, compared to 1350 °C in 36 h for conventional solid state synthesis. The importance of this study is in demonstrating the potential feasibility for decontamination of pyrochemical reprocessing wastes by simple addition of TiO2 to form lanthanide and actinide pyrochlores by rapid molten salt assisted reaction at moderate temperature.

During the last years carbon-based nanostructures (such as, fullerenes, carbon nanotubes and graphene) have been object of intense investigations. The great interest in these nanostructures can be attributed to their remarkable electrical and mechanical properties. Their inorganic equivalent structures do exist and are based on boron nitride (BN) motifs. BN fullerenes, nanotubes and single layers have been already synthesized. Recently, the fracture patterns of single layer graphene and multi-walled carbon nanotubes under stress have been studied by theoretical and experimental methods. In this work we investigated the fracturing process of defective carbon and boron nitride nanotubes under similar stress conditions. We have carried out fully atomistic molecular reactive molecular dynamics simulations using the ReaxFF force field. The similarities and differences between carbon and boron nitride fracture patterns are addressed.

The photoluminescence, its temperature dependences, as well as structural characteristics obtained by the method of Scanning electronic microscopy (SEM) have been studied in ZnO:Ag nanorods prepared by the ultrasonic spray pyrolysis (USP). PL spectra of ZnO:Ag NRs in the temperature range from 10 K to 300 K are investigated. Three types of PL bands have been revealed: i) the near-band-edge (NBE) emission, ii) defect related emission and iii) IR emission. It is shown that IR emission corresponds to the second-order diffraction of near-band-edge (NBE) emission bands. The study of NBE PL temperature dependences reveals that the acceptor bound exciton (ABE) and its second-order diffraction peak disappeared at the temperature higher than 200 K. The attenuation of the ABE peak intensity is ascribed to the thermal dissociation of ABE with appearing a free exciton (FE). The PL bands, related to the LO phonon replica of FE and its second-order diffraction, dominate in the PL spectra at room temperature that testify on the high quality of ZnO:Ag films prepared by the USP technology.