A Ga0.8Fe1.2O3 epitaxial thin film was fabricated on a SrTiO3(111) substrate using pulsed laser deposition. The film is c-axis-oriented and has multiple in-plane domains. In-plane magnetization measurements show that it exhibits ferrimagnetic behavior with a Curie temperature (TC) of 290 K. The insulating film exhibits hopping conduction with a resistivity (ρ) of 4 × 105 Ωcm at 300 K. The ρ value is four orders lower than that of a BiFeO3 film, probably owing to the formation of multiple in-plane domains in the Ga0.8Fe1.2O3 film. Positive magnetoresistance with a maximum value of 3.5% near TC was observed, suggesting that antiferromagnetic interaction between Fe3+ ions decreases carrier transfer between the ions.

The National Alliance for Broader Impacts (NABI) seeks to foster a community of practice that increases individual and institutional capacity for, and engagement in, broader impact (BI) activities and scholarship. NABI currently has 537 individual members representing more than 210 institutions and organizations who are part of the growing network of professionals. The National Science Foundation (NSF) evaluates all proposals on their intellectual merit and their broader impacts. Many investigators grapple with how to articulate and effectively engage broad audiences in materials science and STEM. Here, we describe the effort of NABI to address BI challenges, present the NABI document Broader Impacts, Guiding Principles and Questions for National Science Foundation Principal Investigators and Proposal Reviewers; highlight the impacts of NABI as a catalyst for building BI capacity; and provide an example of assessing an innovative program’s BI.

A comparative study of ferroelectric and non-ferroelectric-gated organic field-effect transistors (FETs) have been carried out by using a small molecule semiconductor 6,13 bis(triisopropylsilylethynyl) pentacene (TIPS-pentacene) to understand the fundamental aspects of carrier transport in FET architectures. Temperature-dependent current-voltage characteristics from non-ferroelectric dielectric-gated FETs show a clear activated transport, independent of the dielectric constant. While using the ferroelectric dielectric polymer poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE), where the dielectric constant may be tuned by changing the temperature, a negative temperature coefficient of the carrier mobility is observed beyond 200 K. The polarization fluctuation dominant transport inherent to a ferroelectric dielectric in conjunction with the discrete nature of traps in TIPS-pentacene results in an effective de-trapping of the shallow trap states into more mobile states.

ZnO1-xTex thin films were deposited by DC reactive magnetron co-sputtering using pure Zn and Te targets. Te atomic concentration in the films ranged from x=0 to 0.33 by adjusting the applied power on the targets or varying the cathode-substrate distance. Chemical composition and crystalline structure were determined by RBS experiments and X-ray Diffraction, respectively. For low Te atomic concentrations (x≤0.04) the deposited ZnO1-xTex films showed a crystalline structure ZnO wurtzite type however, for increasing Te concentration significant broadening and decreasing intensities of the main peaks belonging to pure ZnO films together with some weak peaks characteristic of crystalline Trizinc Tellurate salt have appeared. For the highest x values some non-identified weak peaks beside to some others peaks corresponding to the crystalline phases mentioned above as well as, a broad band probably associated to amorphous TeO2 phase were observed. A preliminary optical characterization of the samples point out the possibility of different electronic transitions within the ZnO band gap.

In this study, Ni based ferrite nanomaterials were synthesized using sol-gel method for solar thermochemical splitting of CO2 using a thermogravimetric analyzer. To synthesize the ferrite materials, the corresponding metal precursors were dissolved in ethanol (with required molar ratios). After achieving the dissolution, propylene oxide (PO) was added to achieve the gel formation. Freshly synthesized gels were aged, dried, and calcined by heating up to 600°C in air. Powder x-ray diffractometer (XRD), BET surface area, as well as scanning (SEM) and transmission (TEM) electron microscopy characterized the calcined powders. The sol-gel derived ferrites were further tested towards their thermal reduction and CO2 splitting ability using a high temperature thermogravimetric analyzer (TGA).

Microelectrodes have attracted great interest for electroanalysis because of their unique properties, such as nonlinear diffusion, increased rate of mass transport and reduced capacitance, which allows a fast response. In this work, we created a porous nanocomposite of boron doped diamond (BDD) deposited on carbon nanotubes – reduced graphene oxide (CNTs – RGO) by Hot Filament Chemical Vapor Deposition (HFCVD) technique. The resulting material yielded porous BDD microelectrodes. On the first step, we have grown the CNTs on carbon fiber (CF) surface by Thermal CVD in a tubular reactor. Camphor solution and Fe-Co were carbon and catalyst source, respectively. For exfoliation, CNTs were treated by hydrogen plasma and oxygen plasma. We applied a seeding solution containing nanodiamond dispersed in KCl aqueous solution. Diamond nanoparticles interact with oxygen-containing groups on CNTs, promoting an efficient seeding. We deposited BDD films in an HFCVD reactor using methane/hydrogen gas mixtures. For doping, a partial hydrogen flow bubbled in a closed vessel containing a solution of boron oxide dissolved in methanol. The microelectrodes were characterized by Raman Scattering Spectroscopy, Scanning Electron Microscopy with Field Emission Gun and Cyclic Voltammetry. The crystalline quality of CNTs and BDD doping level were studied by Raman analysis. SEM micrographs showed that nanocomposite presented high porosity. Electrochemical analysis showed that the deposition of BDD on CNTs-RGO increased the electrochemical response of the microelectrode. Besides, this electrode presented a low capacitive current in comparison with BDD grown on flat substrates. Further, the porous BDD nanocomposite showed itself to be promising in electroanalysis.

Large numbers of high quality graphene transistors were fabricated by chemical vapor deposition and packaged into a standard electronics assembly, enabling the readout of graphene properties on the benchtop. After chemical functionalization, these sensors demonstrate sensitivity into the pM range to inflammation (IL6) and Zika virus (ZIKV NS1) biomarkers. Signal-to-noise ratio (SNR) of graphene biosensors is over an order of magnitude greater than established diagnostic and biophysical assays, namely ELISA and BLI respectively. High precision measurements of protein kinetics captured using this technology, commercially available as the AGILE R100, are comparable to both clinical diagnostic and state-of-the-art biomolecule characterization tools. These results demonstrate that graphene-based platforms are highly attractive biological sensors for next generation diagnostics.

We report on the preparation of conjugated polymer nanofibers via template-synthesis. A femtosecond laser machined fused silica template, with a micro-patterned array of high-aspect ratio surface nanopores, was first spin-coated with a polyvinyl alcohol (PVA) solution to form a water-soluble release layer. The PVA-lined template was then coated with a conjugated poly(3-hexylselenophene) (P3HS) – solvent solution. The solvent was allowed to dissipate, and the resulting {template / PVA liner / conjugated P3HS film} stack was then submerged in water to dissolve the PVA and release the conjugated polymer film from the template. The resulting conjugated polymer film exhibits an array of micro-patterned polymer nanofibers that constitute a negative replica of the PVA-lined template. The nanofibers come arranged in a vertical architecture that spans over the surface of the supporting film.

Carbon based materials have long been investigated as anodes for lithium ion batteries. Among these materials, porous carbon holds several advantages such as high stability, high specific surface area, and excellent cycling capability. To further enhance the energy storage performance, ceramic nanomaterials have been combined with carbon based materials as hybrid anodes for enhanced specific capacity. The use of metal oxide ceramic nanomaterials could enhance the surface electrochemical reactivity thus leads to the increasing of capacity retention at higher number of cycles. In this research, we synthesized ceria (CeO2) nano-particles on porous carbon to form inorganic-organic hybrid composites as an anode material for Li-ion battery. The high redox potential of ceria is expected to increase the specific capacity and energy density of the system. The electrochemical performance was determined by a battery analyzer. It is observed that the specific capacity could be improved by 77% using hybrid composites anode. The material morphology, crystal structure, and thermal stability were characterized by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), X-Ray Diffraction (XRD), and Thermogravimetric Analysis (TGA).

Long half-life biologically active fission products, such as technetium-99, present particular problems for the disposal of spent nuclear fuel (SNF). Technetium is present in relatively high concentrations in fuel (approx. 1kg tonne-1 SNF) and has very high mobility in oxidizing environments. Technetium is therefore generally removed from SNF either by solvent extraction and reduction, during the PUREX process, or by sorption via ion exchange processes. Historically technetium has been disposed of via dilution and dispersion in the sea but stringent regulations now mean that the preferred long term option is immobilization in a highly stable and durable matrix. In this contribution we have looked at the synthesis of fluorite derivative crystalline host phases based on the zirconolite structure. Samples have been characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDX), thermo-gravimetric analysis (TG), and mass spectroscopy (MS). We have used Mo as an inactive surrogate for Tc.

We present the optical and electrical properties of ITO and AZO films fabricated directly on silicon substrates under several growth and annealing temperatures, as well as their potential performance when used as low emissivity coatings in hybrid photovoltaic-thermal systems. We use broadband spectroscopic ellipsometry measurements (from 300 nm to 20 μm) to obtain a consistent model for the permittivity of each of the films. The best performance is found using the properties of the ITO film grown at 250 °C, with a state of the art resistivity of 0.2 mΩ-cm and an optimized thickness of 75 nm which leads to an estimated 50% increase in the extracted power compared to a standard diffused silicon solar cell. The Hall mobility and resistivity measurements of all the films are also provided, complementing and supporting the observed optical properties.

This paper highlights experimental and theoretical efforts dedicated to developing plasmonic-enhanced electrodes for the photo-electrochemical ethanol oxidation reaction (EOR) at room temperature in alkaline media. However, decoupling the electrocatalytic dark response from the plasmon-enhanced improvement presents a difficult challenge. To understand the plasmonic-enhancement of the photo-electrochemical EOR, multiple Au-Fe2O3 were fabricated and evaluated in parallel with discrete dipole approximation (DDA) modeling. Different Au-Fe2O3 were synthesized with Au nanoparticles located at variable positions within and/or on the Fe2O3 layer(s). The configurations investigated include thin film, embedded, surface and sandwich layered electrodes to facilitate optimal electrode design considerations for plasmonic-enhancement. The design strategies and configurations were guided by DDA simulations to assess absorption, scattering, and near-field enhancements within or near the semiconductor band edge, as well as the solution/electrode interface. For the different Fe2O3 loadings and Au nanoparticle sizes/distributions considered, it is determined that the Au-Fe2O3 surface configurations significantly enhanced the EOR in terms of a large positive current density enhancement, an increased photo-voltage and a lower onset potential relative to the other electrode designs.

Electrochemical Impedance Spectroscopy (EIS), is a confirmed tool for investigation of electrode/electrolyte interfaces and surface-modified electrodes. In the present work, we apply this approaching way to obtain a deeper insight into the electrochemical oxidation mechanism of the glucose in alkaline media. We studied the EIS response of gold nanoparticles embedded in carbon paste and use it as an electrode for the electro-oxidation of glucose. The results were compared with those of a polycrystalline gold electrode. In order to determine the polarization potentials for EIS tests, cyclic voltammetry is first conducted in 0.3 M KOH with 10 mM glucose, recorded at a scan rate of 1 mVs-1. Three polarization potentials were chosen, corresponding to: the open circuit potential (OCP), glucose oxidation and gold oxide formation respectively.