Low-cost, earth-abundant magnetocaloric materials (MCMs) are required for energy-efficient, green, and affordable magnetic cooling technology. We investigated the magnetic and magnetocaloric properties of rare-earth-free Fe75−xCrxAl25 (19≤x≤25) arc-melted alloys. The Curie temperature (Tc) of these alloys could be tuned from 220 K up to room temperature by Cr additions. The relative cooling power/US$ was found to be superior to other promising MCMs. Fe50Cr25Al25 ball-milled powders, with an average particle size of ~25 nm, were used to prepare magnetic fluid. Maximum cooling (ΔT) of 5.4°C was observed for Fe50Cr25Al25-based fluids.

A computational model for the evaluation of the thermomechanical effects that give rise to the catastrophic optical damage of laser diodes has been devised. The model traces the progressive deterioration of the device running in continuous wave conditions. The local heating of the active layer locally leads to the onset of the plastic regime. As a result, dislocations and threads of dislocations grow across the active layers and lead to rapidly growing temperatures in the quantum well. The poor power dissipation under these conditions has been identified as the key factor driving the final degradation of the laser.

Gold nanoparticles (GNPs) of ~8 nm in diameter were used for the detection of organochlorine endosulfan pesticide (ESP) as colorimetric sensor and the design of GNP-based chemical sensor for its quantitative estimation has also been proposed. The original wine red color of GNPs changes into various shades of blue after the addition of different concentrations of ESP solutions. A GNP-based sensing electrode has been used for designing of ESP detection chemical sensor at ambient temperature. The response and sensitivity of ESP sensor parameters are obtained from their recovery curves of the change in resistance versus time.

Due to the lack of an effective and noninvasive screening tool, the early diagnosis of colorectal cancer (CRC) is currently difficult. For the early diagnosis of CRC, we have developed Fe3O4-Dye800-single chain fragment variable (ScFv)egfr/vegfr nanoprobes. ScFvegfr/vegfr (ScFv2) conjugated onto Fe3O4 nanoprobes efficiently recognized CRC tumors in vitro and in vivo. Near-infrared fluorescence imaging modalities such as Dye800 were utilized simultaneously with magnetic resonance to enhance detection efficiency. Fe3O4-Dye800-ScFv2 successfully detected tiny CRC tumors; the synergistic ScFv2 successfully enhanced CRC targeting. Thus, Fe3O4-Dye800-ScFv2 nanoprobes may represent a new molecular imaging strategy for the early detection of CRC.

Phase-change materials (PCMs) have important applications in optical and electronic storage devices. Ge2Sb2Te5 (GST) is a prototypical phase-change material (PCM) employed in state-of-the-art storage-class memories. In this work, we investigate crystallization of GST at temperatures 600–800 K by ab initio molecular dynamics. We consider large models containing 900 atoms, which enable us to investigate finite-size effects by comparison with smaller models. We use the metadynamics method to accelerate the formation of a large nucleus and then study the growth of the nucleus by unbiased simulations. The calculated crystal growth speed and its temperature-dependent behavior are in line with recent experimental work.

Magnetic tunnel junction can produce highly configurable molecular spintronics devices. This paper highlights a rather subtle attribute of magnetic tunnel junction fabrication that can lead to the very pronounced impact on magnetic properties of molecular spintronics device. We conducted magnetic studies to observe the effect of depositing ~5 nm Tantalum (Ta) on the top of a magnetic tunnel junction. We investigated the effect of Ta by using characterization techniques like ferromagnetic resonance, magnetometry, and polarized neutron reflectometry. Bridging paramagnetic molecules between the two ferromagnetic electrodes of magnetic tunnel junctions with and without Ta top layer produced the very different magnetic response.

Frequency-dependence and magnitude of second harmonic generation (SHG) from ~4 × 105 nm2 molybdenum disulfide (MoS2) monolayers was examined in presence of single 150 nm plasmonic gold@silica shell@core nanoantenna monomer and dimers. Quantitative agreement between discrete dipole approximation-calculated fields and measured SHG enhancements was found. SHG from MoS2 was enhanced up to 1.88 × upon deposition of a plasmonic nanoantenna-dimer with 170 nm gap, reaching maximal normalized SHG conversion efficiency of 0.0250%/W. Pump losses attributable to plasmonic damping, e.g., scattering and/or hot-electron injection into MoS2, were apparent. Linear and nonlinear optical activity of MoS2 and nanoantenna controls were compared with literature values.

The influence of the content of trifluoroacetate (TFA), in the precursor solution, on the critical current density (Jc) of YBa2Cu3O7−x (YBCO) superconducting films was investigated. We found that a TFA/Ba ratio of 0.68 is optimal to obtain high-performance YBCO films. Using this optimal solution, we then developed an ultraviolet (UV) light soaking technique to prepare YBCO films. This resulted in the constituent elements being uniformly distributed in the films, and this then enabled enhanced Jc. The addition of water vapor during the UV soaking process decreased the content of carbon residue in the films, and further increased the Jc of the resulting YBCO films.

The goal of this study was to perform in situ electrochemical polymerization of poly(3,4-ethylenedioxythiophene) (PEDOT) in peripheral nerves to create a soft, precisely located injectable conductive polymer electrode for bi-directional communication. Intraneural PEDOT polymerization was performed to target both outer and inner fascicles via custom fabricated 3D printed cuff electrodes and monomer injection strategies using a combination electrode-cannula system. Electrochemistry, histology, and laser light sheet microscopy revealed the presence of PEDOT at specified locations inside of peripheral nerve. This work demonstrates the potential for using in situ PEDOT electrodeposition as an injectable electrode for recording and stimulation of peripheral nerves.

The selectivity of catalyst is an essential factor in direct methanol fuel cells (DMFCs) and plays an important role to improve their performance. To this end, platinum (Pt)-based low-cost trimetallic catalysts have been developed. The catalyst comprising ultra-low Pt-decorated NiCu bimetallic alloys nanoparticles fabricated on reduced graphene oxide (rGO). The series of Pt-NiCu/rGO nanocomposites were synthesized with different compositions to obtain the optimal conditioned material. The electrochemical results showed good performance for the electro-oxidation of methanol at anodic end of DMFCs. These outcomes opened up a broad avenue for developing lower cost-active catalysts with better performance for DMFCs.

Lead halide perovskite solar cells (PSCs) with a structure of glass/FTO/TiO2/CH3NH3PbI3 with single-walled carbon nanotubes (SWNT) as the transparent top electrodes, followed by polymethyl methacrylate (PMMA) over-coating were fabricated. The SWNT-based PSCs do not require expensive metal electrodes and hole-transporting materials yet produce a decent power conversion efficiency of 11.8%, owing to the densifying effect of SWNTs by PMMA. The resulting devices demonstrate reduced hysteresis, improved stability, and increased power conversion efficiency.

We investigate the two-photon absorption characteristics of hemicyanine dyes that exhibit a one-photon absorption at around 500 nm. The dyes exhibited two-photon-induced fluorescence upon irradiation with an Yb-doped femtosecond fiber laser operating at 1030 nm. Among the dyes, 4-[4-[4-(dimethylamino)phenyl]-1,3-butadienyl]-1-ethyl-pyridinium perchlorate exhibited the most efficient two-photon-induced fluorescence at 1030 nm. Since these dyes possess cationic moiety, the dyes accumulated in the mitochondria of a living cell. Two-photon images of mitochondria were obtained by staining living HEK293 cells with these dyes. When 4-[4-[4-(dimethylamino)phenyl]-1,3-butadienyl]-1-ethyl-pyridinium perchlorate was employed, a two-photon-induced fluorescence image could be obtained even when a 3 mW fiber laser beam was used as the excitation source.

The use of copper hydroxyphosphate (Cu2PO4OH), also called libethenite, as a near-infrared (NIR) absorbing additive has been investigated. Samples were synthesized by using a hydrothermal treatment or simple wet chemical processing, which was later easily upscaled. All synthesized samples showed a strong absorption in the NIR region. Trials were conducted to produce laser-marked plastic plates and security IR ink printing tests. It was found that when incorporated in plastic and ink formulation, Cu2PO4OH added good NIR absorption properties without influencing other finished product properties too much, which confirms that it is a suitable additive that can be readily manufactured at room temperature and without pressured equipment.

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.

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.

We show that the optical response of ultrathin metallic films of finite lateral size and thickness can feature peculiar magneto-optical effects resulting from the spatial confinement of the electron motion. In particular, the frequency dependence of the magnetic permeability of the film exhibits a sharp resonance structure shifting to the red as the film aspect ratio increases. The films can also be negatively refractive in the IR frequency range under proper tuning. We show that these magneto-optical properties can be controlled by adjusting the film chemical composition, plasmonic material quality, the aspect ratio, and the surroundings of the film.

Melt electrospinning is a facile fabrication technique that can be utilized in the creation of microfibers without the use of solvent and with good control over feature placement. The available thermal energy of the melt electrospinning technique is often only utilized in the formation of the polymer melt but can also be used to thermodynamically drive chemical reactions. In this study, hybrid perovskite microcrystallites are synthesized in the polymer melt and electrospun to form composite microfibers. Unique hybrid perovskite microstructures were studied, elucidating mechanisms of formation at work in the polymer melt.

Lateral memristors consisting of planar Ag electrodes (with sub-micrometer separation) supported on thin films of amorphous zinc-tin-oxide have been characterized. After an initial filament-forming process, each device exhibited volatile, resistive switching. In the low resistance state, the transport mechanism and conductance depended on prior activity and on the imposed current limit, mimicking biologic synaptic plasticity. Microscopic observations performed on each device revealed nanoscale filaments between the electrodes. These filaments were subject to Rayleigh instability and exhibited relaxation times determined by their effective radii. The relaxation times and on:off resistance ratios suggest suitability for threshold switching selector devices.

A novel process for Boron doping of ultrananocrystalline diamond (UNCD) films, using thermal diffusion, is described. Hall measurements show an increase in carrier concentration from 1013 to 1020 cm−3. Ultraviolet Photoelectron Spectroscopy and x-ray Photoelectron Spectroscopy show a band gap of 4.4 eV, a work function of 5.1 eV and a Fermi level at 2.0 eV above the valence band. Boron atoms distribution through UNCD films, was measured by Secondary Ion Mass Spectrometry, revealing Boron atoms diffusivity of about 10−14 cm2/s. Raman spectroscopy and x-ray Diffraction analysis revealed that UNCD films did not suffer graphitization nor structural damage during annealing.

The thermal conductivities (κ) of bulk and thin-film α-Al2O3 are calculated from first principles using both the local density approximation (LDA) and the generalized gradient approximation (GGA) to exchange and correlation. The room temperature single-crystal LDA value ~39 W/m K agrees well with the experimental values ~35–39 W/m K, whereas the GGA values are much smaller ~26 W/m K. Throughout the temperature range, LDA is found to slightly overestimate κ, whereas GGA strongly underestimates it. We calculate the κ of crystalline α-Al2O3 thin films and observe a maximum of 79% reduction for 10 nm thickness.