We investigated the connectivity of high-energy random grain boundaries through fractal analyses of specimens with different grain boundary (GB) microstructures in BFe10-1-1 copper–nickel alloy. It was found that the profile of maximum random boundary network possesses a fractal nature and more than one fractal dimension can exist. The fraction of special boundaries and grain size homogeneity can play an important role on GB character distribution. Here, GB microstructures are combined with quantitative materials structure–property relationship models to predict intergranular corrosion properties. The experimental results are accurately consistent with the theoretical predictions.

The advancement of lead-free piezoelectric nanogenerators (PENGs) for flexible electronics necessitates designing more efficient systems for improved energy storage capacity. In this light, the effects of patterning BaTiO3 nanotubes within PENG on the electromechanical properties of the device were investigated. The PENGs comprised a sandwich structure of Ti–BaTiO3–graphite–Ti encapsulated in polydimethylsiloxane. Four patterns of vertically aligned BaTiO3 nanotubes were synthesized via the hydrothermal conversion of selectively-anodized TiO2 nanotubes. The highest output voltage reached up to 1.9 V. Decreasing the nanotube array spacing and pattern diameter increased the lateral displacement of BaTiO3 therefore, increasing the output voltage of the device.

The authors report the microwave-assisted hydrothermal synthesis of α-La(IO3)3 nanocrystals doped with Yb3+ and Er3+ ions, along with their structural and optical characterizations. 50-nm-sized α-La0.9−xYb0.1Erx(IO3)3 nanocrystals with x = 0.005, 0.01, and 0.02 were synthesized and dispersed in ethylene glycol. The as-obtained suspensions exhibit both second harmonic generation (SHG) signal and up-conversion photoluminescence (UC-PL) without interplay between the two signals under near-infrared resonant excitation. The relative intensity of SHG and UC-PL emission can be modulated according to the excitation wavelength. The most intense UC-PL signal is obtained from a 980-nm excitation, thanks to the sensitization of Er3+ by Yb3+.

Two thiophene-based semiconductors, a vapor-deposited small molecule and an amorphous polymer, as well as pentacene for comparison, show potential in enhancing the thermoelectric properties of tellurium (Te) nanowires. For vapor-deposited films, Te nanostructures form directly on glass substrates or organic semiconductor films. The resulting Te power factor (S2σ) was enhanced from 36 to 45 W/mK2 (56 for pentacene) because the bilayer provides an enhancement in Seebeck (S) without compromising conductivity (σ). For solution deposited polymer blends, we obtained power factors from a Te nanowire network that alone would not have sufficient connectivity (up to 0.1 µW/mK2). While the organics are unoptimized, they are prototypical materials for further development.

Spider dragline silk is a self-assembling protein that rivals many engineering fibers in strength, extensibility, and toughness, making it a versatile biocompatible material. Here, atomistic-level structures of wildtype MaSp1 protein from the Nephila clavipes spider dragline silk sequences, obtained using an in silico approach based on replica exchange molecular dynamics and explicit water, are subjected to nanomechanical testing and released preceding failure. We approximate the relaxation time from an exponential decay function, and identify permanent changes in secondary structure. Our work provides fundamental insights into the time-dependent properties of silk and possibly other protein materials.

The relationship between the oscillatory force and the depth-response during dynamic indentation was analyzed mathematically and investigated experimentally in ultrafine-grained Al–Zn alloys processed by high-pressure torsion. We have shown for the first time that the phase shift between the local oscillatory force and depth signal, caused by the internal friction, is correlated to the strain-rate sensitivity, which is a key parameter indicating the ductility of materials. This correlation enables a new application of dynamic nanoindentation for studying the rate-dependent deformation-mechanisms of materials from a novel aspect.

We report here a successful fabrication of three-dimensional (3D) photoelectrodes fully coated with hydrothermally formed TiO2 nanotubes on multi-layered Ti mesh with significantly increased surface area. A near-vertical array of ~8 nm diameter nanotubes of TiO2 was also produced on the metallic surface of folded Ti mesh electrode. The multi-layered mesh was used as a 3D highly conductive electrode, as this architecture intuitively allows for light passage, reflections, and smooth water flow for possible continuous operation of water splitting reaction. By virtue of substantially increased surface area and more efficient light usage, significantly increased photocurrent densities were obtained.

Solid state batteries are an emerging alternative to traditional liquid electrolyte cells that provide potential for safe and high-energy density power sources. This report describes a self-forming, solid state battery based on the Li/I2 couple using an LiI-rich LiI(3-hydroxypropionitrile)2 electrolyte (LiI–LiI(HPN)2). As the negative and positive active materials are generated in situ, the solid electrolyte–current collector interfaces play a critical role in determining the electrochemical response of the battery. Herein, we report the investigation of solid electrolyte–current collector interfaces with a self-forming LiI–LiI(HPN)2 solid electrolyte and the role of varying interface design in reducing resistance during cycling.

Quantum dots (QDs) are increasingly employed in biologic imaging applications; however, anecdotal reports suggest difficulties in QD bioconjugation. Further, the stability of commercial QDs during bioconjugation has not been systematically evaluated. Thus, we examined fluorescence losses resulting from aggregation and declining photoluminescence quantum yield (QY) for commercial CdSe/ZnS QD products from four different vendors. QDs were most stable in the aqueous media in which they were supplied. The largest QY declines were observed during centrifugal filtration, whereas the largest declines in colloidal stability occurred in 2-(N-morpholino)ethanesulfonic acid (MES) buffer. These results enable optimization of bioconjugation protocols.

In in vitro separate compartment model of neuronal cells and extracellular iron oxide nanoparticles (IONs)–amyloid complexes, a traversing proton-induced Coulomb nanoradiator effect (CNR) was found to break up the ION–amyloid fibrils and to induce redox changes in the IONs. We found that the CNR effect caused the conversion of redox-active iron (II) into redox-inactive iron (III) as well as the disruption of the ION–amyloid fibrils without significantly damaging normal neuronal cells. Our observations suggest a non-invasive redox inactivation and β-amyloidolyis-based therapy of neurotoxic Aβ plaque involving a traversing proton Coulomb nanochelator that would not substantially impact normal neuronal cells.

Significant α-phase growth confinement in Grade 4 titanium (Ti) and substantial β-phase refinement in Grade 7 Ti were observed during high-temperature annealing. The mechanism for each observation was identified through detailed microstructural investigation assisted with phase diagram analyses. The former observation was due to the pinning effect of Fe-stabilized grain boundary (GB) β-Ti phases in Grade 4 Ti. The latter observation resulted from the redistribution of Fe and, palladium (Pd) in particular, in Fe-stabilized and Pd-containing GB β-Ti phases in Grade 7 Ti. Pd was found to exist mainly in two forms in cold-rolled Grade 7 Ti, i.e. Fe-stabilized GB β-Ti phases and an occasionally observed orthorhombic Ti88Pd9Fe3 phase. The latter is close to the Ti2Pd3 intermetallic phase in terms of the crystal structure.

Using in situ indentation, we show that highly localized and well-defined mechanical deformation can be coupled with structural and electronic characterization in the scanning tunneling microscope. Dislocations induced in Ni(100) were topographically imaged and probed by scanning tunneling spectroscopy to assess their effect on local surface electronic structure. Compared with undamaged terraces, dislocation regions exhibited a significant increase in local density of states near the Fermi level, and enhanced reactivity toward oxidation. In the context of the d-band electronic structure model, we suggest that the undercoordination of atoms and residual strain resulting from plastic deformation serve to locally accelerate adsorption-driven chemical reactions with species such as molecular oxygen.

A non-precious metal catalytic system of Fe-doped Ta2O5 is developed by pulsed laser deposition toward efficient oxygen evolution reaction (OER). The optimal Fe concentration is determined to be 5 at.% for optimized OER activity via a series of electrochemical characterizations. The 5 at.% Fe-doped Ta2O5 nanolayer possesses a low onset overpotential of 0.22 V, an overpotential of 0.38 V at 10 mA/cm2 and a Tafel slope of 54 mV/dec. Comprehensive first-principles calculations attribute the enhanced OER activity to the substitutional FeTa dopants, which generate a new active OER site on surface and simultaneously accelerate electron transfer over oxygens.

The hydrobaric effect on photoactivity of titanium dioxide (TiO2) fabricated by cathodic deposition in an aqueous solution was evaluated in this study. When the applied pressure was increased to 35 MPa, the water-splitting performance was improved by almost fourfold of the performance of the TiO2 prepared at atmospheric pressure. The surface states effect was significant in the deposited TiO2, which was exploited to affect the charges recombination of TiO2, and thereby enhance the resultant photoelectrochemical water-splitting performance. The hydrobaric cathodic deposition could be extended to fabrication of other metal oxides to eliminate the negative influence from the high-temperature process.

The structure of polymer networks in hydrogels determines the properties. In this study, we investigated the structure of a charge-balanced polyampholyte, poly(4-vinylbenzenesulfonate-co-[3-(methacryloylamino) propyl] trimethylammonium chloride). From as-prepared samples, nanoscale globules were visualized in polyampholyte hydrogels for the first time. The impact of dialyses processes on polymer structures were also studied. In deionized water, salt ions are leached out, thus polymer chains undergo zipping process to form cellular structure with micrometer-thick polymer walls that allow mechanical toughness to the hydrogel. Samples dialyzed in 6 M potassium hydroxide solution did not show such cellular structure, as in the case of as-prepared samples.

In this paper, a simple evolution equation for dislocation densities moving on a slip plane is proven. This equation gives the time evolution of dislocation density at a general field point on the slip plane, due to the approach of new dislocations and tilting of dislocations already at the field point. This equation is fully consistent with Acharya's evolution equation and Hochrainer et al.’s “continuous dislocation dynamics” (CDD) theory. However, it is shown that the variable of dislocation curvature in CDD is unnecessary if one considers one-dimensional flux divergence along the dislocation velocity direction.

The present work demonstrates controllable directive radiation of a dipolar emitter coupled to a substrate-supported dielectric nanowire antenna. Nanoactuators, transparent-conducting oxides, and graphene are integrated into the substrate, respectively, to establish tunable antenna platforms in visible, near-infrared (IR), and far-IR frequency regimes. We exploit the substrate-induced interference effects and tunability mechanisms in each antenna system to achieve directive radiation with real-time steering capability. The design and modeling are rigorously carried out using an efficient and accurate semi-analytical framework based on transition matrix formulation. Each configuration is optimized to achieve maximal steering range while attaining a proper gain. Owing to subwavelength footprint, enhanced directionality, real-time tunability, and fairly simple geometry, the proposed platforms are ideal candidates for nanoantenna synthesis.

CuInS2 (CIS) quantum dots (QDs) with different diameters were prepared and their optical properties were studied. The optical band gap of QDs, as estimated by absorption spectrum, was found to decrease with increase in size. The stokes shift between absorption and photoluminescence peaks was observed to be larger (>100 meV) in all the three samples. This shows that the defect states available in the forbidden gap dominates the recombination mechanism. The variation in the emission peak with QD size, however, indicates that the relaxation dynamics in CIS QDs involves both excitonic level as well as the defect states.