The generalized gradient approximation (GGA) often fails to correctly describe the electronic structure and thermochemistry of transition metal oxides and is commonly improved using an inexpensive correction term with a scaling parameter U. The authors tune U to reproduce experimental vanadium oxide redox energetics with a localized basis and a GGA functional. The value for U is found to be significantly lower than what is generally reported with plane-wave bases, with the uncorrected GGA results being already in reasonable agreement with experiments. This computational set-up is used to calculate interstitial and substitutional insertion energies of main group metals in vanadium pentoxide and interstitial doping is found to be thermodynamically favored.

Si-TiN alloys are attractive for use as negative electrodes in Li-ion cells because of the high conductivity, low electrolyte reactivity, and thermal stability of TiN. Here it is shown that Si-TiN alloys with high Si content can surprisingly be made by simply ball milling Si and Ti powders in N2(g); a reaction not predicted by thermodynamics. This offers a low-cost and simple method of synthesizing these attractive materials. The resulting alloys have smaller grain sizes than Si-TiN made by ball milling Si and TiN directly, giving them high thermal stability and improved cycling characteristics in Li cells.

We have studied the effect of hydrostatic pressure on the confined exciton in a spherical core–shell quantum dot. Using a simple variational approach under the framework of effective mass approximation, we have computed the excitonic binding energy as a function of the shell thickness under the applied hydrostatic pressure. Our results show that the ground state binding energy of exciton depends greatly on the shell thickness, which tends to the two-dimensional limit of 4RX, when the ratio a/b tends to unity. The numerical calculations also suggest that the applied hydrostatic pressure favors the attraction between electrons and holes so the excitonic binding energy increases when pressure increases.

The local-density approximation (LDA)-1/2 technique has been successfully applied to surmount current limitations in density-functional theory to determine excited-states properties of solids via LDAs to the exchange-correlation functional. The main task to properly apply this technique is to choose the “cut-off” radius to truncate the long-ranged self-energy function, originated by the procedure of removing the spurious self-energy of electrons (and/or holes). The usual procedure is by choosing an extreme of the variation of the band gap as a function of this cutoff. This work examines the relationship between that cut-off parameter and the electronegativity difference between cation and anion in binary compounds calculated self-consistently with LDA-1/2.

Modeling static and dynamic contact angles is a great challenge in studying wetting and de-wetting. We propose a new slip boundary model based on the Navier–Stokes equations, and establish a realistic continuum approach to simulate the contact line dynamics in 3-D. To validate our model, a water droplet interacting with micrometer-sized patterns of a hybrid hydro-phobic/-philic surface is studied numerically and compared with experimental measurements. Good agreement has been observed with four pillar spacings in the static, receding, and advancing modes. Moreover, details of the droplet–surface interaction are revealed, i.e., penetrations, sagging, local, and global contact angles.

Tin oxide (SnO2) hollow spheres modified with titanium dioxide (TiO2) nanowires (NWs) synthesized by sequential hydrothermal reactions were investigated as photoanodes for dye-sensitized solar cells. Not only does the hydrothermal treatment form numerous short TiO2 NWs on the surface of SnO2 spheres, but also passivates the surface of SnO2. Consequently, the specific surface area of the photoanode and dye loading are almost doubled, at the same time the surface defects and charge recombination are both appreciably reduced. As a result, the short-circuit photocurrent density and open-circuit photovoltage both greatly increased. The power conversion efficiency of the solar cells increases from 0.4% to 2.9%.

Several structure–property relationships are reported in large-area MoS2 thin films to understand the effect of sulfur vacancies along with complementary first-principles calculations. X-ray diffraction and reflectivity measurements demonstrated that sputtered MoS2 followed by a high-temperature sulfurization produced sharp film–substrate interface along with high crystalline order. Spectroscopic and transport measurements showed that removal of sulfur vacancies promoted A–B excitons, strong in-plane Raman modes, a sharp increase in dc resistivity, and strong photo-conducting behavior. We have clearly demonstrated that a hybrid method using magnetron sputtering can provide high-quality few-layer transition metal dichalcogenide films.

This paper reports the molecular organization and mechanical properties of electrospun, post-drawn polyacrylonitrile (PAN) nanofibers. Without post-drawing, the polymer chain was kinked and oriented in hexagonal crystalline structures. Immediate post-drawing in the semi-solid state disrupted the crystal structures and chain kink at maximum draw ratio. Structural re-orientation at maximum draw resulted in a 500% increase in Young's modulus and a 100% increase in ultimate tensile strength. By applying post-drawing to electrospinning it may be possible to obtain PAN fibers and PAN-derived carbon fibers with enhanced mechanical properties compared to available fabrication technologies.

Three different hydrothermally grown carbonaceous materials and their molybdenum chalcogenides derived from glucose (HTC, HTC–MoO2, HTC–MoS2) were investigated to evaluate their potential as Li-ion battery anodes. All tested materials exhibited good cycling performance at a current density of 100 mA/g and showed high coulombic efficiency, >98%, after the 50th cycle. Reversible charge capacities of HTC, HTC–MoO2, and HTC–MoS2 were 296, 266, and 484 mAh/g, respectively, after 50 successive cycles. This study demonstrated that the HTC–MoS2 showed the highest reversible charge capacity which promises to be a good candidate for an environmentally friendly anode material for Li-ion batteries.

Aluminum-doped zinc oxide films were prepared by atomic layer deposition using diethylzinc, trimethylaluminum, and water. High-purity water was used with low vacuum. The effect of growth temperature on characteristics of the films was investigated. The crystallinity was improved as growth temperature was increased from 180 to 235 °C, with the grain sizes increasing from 32.830 to 47.020 nm. The films possessed high transparency with a 95% transmission window blue shifted with growth temperature. This shift was seen in the energy-band gaps which changed from 3.46 to 3.68 eV, leading to a decreased resistivity from 1.52 × 10−5 to 1.28 × 10−5 Ω cm.

We observed the formation of dominant shear bands in model ZrCuAl metallic glass (MG) nanowires (18-nm-long) in molecular dynamics simulations, which implies size-independent incipient plasticity in MG materials. The MG nanowires were prepared using the simulated casting technique to ensure proper relaxation of sample surfaces. Under uniaxial compression, shear bands initiate at the surfaces and lead to reduced icosahedral short-range order. The shear band formation is sensitive to sample thermal history, which calls for careful consideration of sample preparation effects in both experimental and numerical studies of size effect in MG samples.

Two new organic dyes, WS-2.1 and WS-2.2—derivatives of the known dye WS-2—are computationally designed using a recently developed approach with a broad absorption peak at around 775 nm in acetonitrile for WS-2.2 versus 610 nm for WS-2. The red shift includes a significant contribution due to vibrations and is not reproduced by standard computational methods. The oxidation and reduction potentials of the dye render it well suited for use in dye-sensitized solar cells.

We report an easy way to assemble porous one-dimensional (1D) Ni2P nanowires through phosphatization of a Ni(SO4)0.3(OH)1.4 nanobelt precursor. The peculiar synthetic process endows the Ni2P nanowires with large surface area, hierarchical porous structure and the ability to form closely connected network for transporting both electrons and electrolytes, which in conjunction with the high intrinsic electrocatalytic activity make it an excellent low-cost counter electrode material for dye-sensitized solar cells (DSSCs). Indeed, the first investigation of such novel counter electrode for DSSC presented superb photovoltaic performance rivaling the conventional Pt counter electrode.

Cardiac progenitor cells (CPCs) are a promising candidate for cardiac regeneration, and the interaction between CPCs and their microenvironment can influence their regenerative response. Notch signaling plays a key role in cell fate decisions in the developing and adult heart. Here, we investigated the effect of three-dimensional (3D) spheroid culture, as a model of the 3D microenvironment, on Notch in fetal and adult human CPCs, under room air (20%) and physiological (5%) oxygen tension. Notch signaling is enhanced in 3D spheroids; spheroid culture under 5% O2 further increases Notch signaling enhancement, and might ultimately improve the regenerative potential of CPCs.

Metatronics, or metamaterial-inspired optical nanocircuitry, has provided a powerful toolset to tailor and implement modular quasi-static circuit functionalities in the optical regime. So far, these concepts have been mostly limited to linear operations, while many of the relevant operations in integrated circuits require nonlinear responses. In this work, we introduce nonlinear infrared nanocircuit elements exploiting large quantum conductance driven by photon-assisted tunneling and enhanced by hybrid plasmonic nanojunctions. Based on these concepts, we present infrared lumped nanocircuit mixers and switches for second-harmonic generation, and wide-spectrum self-amplitude modulators based on nanorods.

Nuclear translocation of Yes-associated-protein (YAP) in single cells serves as a key sensor of matrix stiffness. On two-dimensional (2D) polyacrylamide (PA) hydrogels, we found that nuclear YAP localization in epithelial clusters increases with gel stiffness and reduces with cell density. To measure YAP activity in 3D-like confinement of tunable stiffness, we fabricated PA-based microchannels. Here, narrower channels enhanced nuclear YAP localization even in softer extracellular matrix and denser epithelial clusters, both of which reduced YAP activation in 2D. Thus, the presented hydrogel microchannel-based platform may reveal new mechanosensitive cellular signatures in 3D-like settings, which cannot be captured on standard 2D hydrogels.

The design of π-conjugated molecules and polymers has driven the increase in efficiency of bulk heterojunction organic photovoltaic devices from <1% to over 12%. The pathways to generation of free charge carriers are still being uncovered. By focusing on blends of conjugated polymers with fullerenes, recent work has highlighted the impact of the design of donor–acceptor polymers on optoelectronic properties and phase-separated morphologies. This morphology of the active layer is largely controlled by processing conditions, such as use of processing additives. Developing a deep understanding of the impact of polymer chemistry and processing at the laboratory scale is key to translating the technology of organic photovoltaics from the research scale to large-area modules.

We report an epitaxy growth and characterization of InAs photodetector (PD) on virtual Ge/Si and GaP/Si substrates. The effect of different types of the virtual substrate on the structure and performance of the InAs PD was studied. Although the lattice mismatch between InAs and Si is large (11.6%), close to 100% relaxation of InAs was achieved on both virtual substrates. A higher surface roughness was observed in the InAs layer grown GaP/Si as compared with that of Ge/Si. InAs PD with room temperature blackbody specific detectivity of ~5 × 108 cm·Hz1/2/W is achieved in photovoltaic mode on both types of virtual substrate.

Partial aging of AA6060 aluminum alloys is known to result in a microstructure characterized by needle-shaped Si/Mg-rich precipitates. These precipitates belong to the non-equilibrium β″ phase and are coherent with the face-centered cubic Al lattice, despite of which they can cause considerable hardening. We have investigated the interaction between these β″ precipitates and dislocations using a unique combination of modeling and experimental observations. Dislocation-precipitate interactions are simulated using dislocation dynamics (DD) parameterized with atomistic simulations. The elastic fields due to the precipitates are described by a decay law fitted to high-resolution transmission electron microscopy measurements. These fields are subsequently used in DD to study the strength of individual precipitates as a function of size and dislocation character. Our results can be used to parameterize crystal plasticity models to calculate the strength of AA6060 at the macroscopic level.

In the recent years, several investigators are incorporating nanotechnology, one of the most powerful trendsetters in material research, to conventional polymer prepregs to enhance mechanical properties of composite strucutures. The current paper outlines the role of nanotechnology in reinforcing resin and challenges for fabricating nanomaterial reinforced prepregs. As delamination is the most critical problem for composite materials, the current study only focuses the application nanotechnology as a possible solution to alleviate delamination problems in laminated composites. The importance of nanoengineered prepregs is discussed in a viewpoint of improvement in interlaminar properties of the laminated composite materials.