This work presents a facile in-situ electrodeposition approach to integrate the amorphous-dominant NiFeSn5 catalyst with trace nanocrystalline domains onto Ni foam, serving as a self-supported bifunctional catalyst for high-efficiency overall water splitting (OWS). Sn incorporation can optimize the electron density of NiFe (oxy) hydroxide to facilitate the in-situ generation of high-valence active centers, which synergistically interact with Sn species to boost the intrinsic activity. The optimized NiFeSn5 catalyst exhibits low overpotentials of 248 mV for oxygen evolution reaction (OER) at 100 mA cm-2 and 117 mV for hydrogen evolution reaction (HER) at 10 mA cm-2 in 1 M KOH. Furthermore, when configuring as a symmetrical NiFeSn5||NiFeSn5 electrolyzer, it only requires a low operating voltage of as low as 1.54 V at 10 mA cm-2, maintaining a remarkable durability at 100 mA cm-2 over 120 h. This work provides a novel insight into modulating dynamic active-site formation, and establishes a versatile and scalable platform for the exploration of highly-active bifunctional electrocatalysts.

The commercial application of hydrogen production is heavily subjected to the expensive and complex fabrication of required bifunctional catalysts integrated with good oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) activity. Herein, a simple one-spot hydrothermal technique is advocated to simplify the synthesis of NiS/FeS/NiFeOOH heterostructure (denoted as NiFeS) and achieve exceptional bifunctional electrocatalyst for water splitting. Such NiFeS heterostructure reveals multi-synergistic heterointerfaces with chemical coupling to provide more accessible active sites, regulate electronic structure of the active center and enhance interfacial charge transfer, enabling a significant contribution in improving the catalysis. Therefore, the OER overpotential of NiFeS catalyst is only 249 mV to supply 100 mA cm(-2) current density, and the overpotential for HER reaches to 153 mV at 10 mA cm(-2). When constructed into a lab-made electrode system, it confirms a remarkable cell voltage of only 1.51 V at 10 mA cm(-2) for water splitting, along with an exceptional durability up to 100 h at 100 mA cm(-2). This study gives a novel insight into heterostructure engineering for the construction of bifunctional electrocatalysts.

Cordierite ceramic is usually used for diesel particulate filter owing to its excellent low thermal expansion coefficient and high thermal shock resistance properties. However, the co-exited intermediate spinel phase can deteriorate the thermal and mechanical performances of cordierite ceramic product, because the spinel phase has much higher thermal expansion coefficient comparing to that of cordierite. In this study, two methods are utilized to reduce the spinel impurity in the cordierite ceramic. On the one hand, rational reaction resources were introduced to decrease spinel production. The formation of intermediate spinel phase is systematically researched by X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman characterizations and the results clarified the preference of path "Enstatite + Mullite & RARR; Cordierite" for less spinel production in comparison to path "Enstatite + Al2O3 & RARR; Cordierite + Spinel." Additionally, MgO was introduced as fluxing agent to promote liquid-phase sintering, thus facilitating the conversion of spinel. On the other hand, the sintering schedule was improved by introducing a holding temperature gradient to promote the diffusion of Si4+ and further promote the conversion of spinel into cordierite. With these methods, the residual spinel phase is minimized, the resulting high-purity cordierite has a 47% reduction in the thermal expansion coefficient from 3.07 x 10-6/K to 1.63 x 10-6/K compared to the original cordierite sample.

High-purity, nano-sized (Ti0.2Zr0.2Nb0.2Mo0.2Hf0.2)B-2 (TZNMH) diboride powders were successfully synthesized via a combined flocculation precipitation and boro/carbothermal reduction method. Then, the solid solution formation, thermal radiation performance and mechanical properties of TZNMH were investigated. It is found that high entropy effect endows TZNMH ceramic with outstanding near-blackbody radiation performance in the UV-Vis-NIR region, with a thermal emissivity >= 95%. This is because high entropy induces robust intraband transition. A dense and single-phase TZNMH ceramic was obtained by spark plasma sintering with high hardness (HV0.1 =31.6 GPa) which remained above 30 GPa even after 60 h exposure at 1800 degrees C in Ar environment. This high hardness of TZNMH ceramic is believed to arise from the strong hybridization between metals and boron, as revealed by density functional theory calculations. This study demonstrates that high-entropy boride ceramics can be used as ideal high-temperature structural component with high thermal emissivity.

Surface-enhanced Raman scattering (SERS) spectroscopy has attracted increasing attention due to its high spectral reproducibility and unique selectivity to target molecules. Here, a facile approach is proposed to prepare Ag nanoparticles modified ZnO nanorod arrays (Ag/ZnO NR arrays). Ag nanoparticles were densely decorated on the surface of ZnO nanorods through silver mirror reaction and subsequent seed-assisted electrodeposition. The prepared Ag/ZnO NR arrays can be used as a sensitive, uniform, and repeatable SERS substrate for the rapid detection of organic dye molecules and biomolecules with concentrations higher than the corresponding limits of detection (LODs). The LODs for rhodamine 6G (R6G), 4-aminothiophenol (PATP) and adenine are calculated to be 1.0 × 10−13 M, 1.6 × 10−12 M and 3 × 10−11 M, respectively. The enhancement factor (EF) of the SERS substrate is estimated to be as high as ~2.7 × 108 when detecting 10−10 M R6G. Particularly, the as-synthesized substrate exhibits high selectivity to multiple components. In addition, the fabricated Ag/ZnO NR arrays can be recycled due to their superior self-cleaning ability and can realize photocatalytic degradation of R6G in water within 1 h driven by UV light, showing that the three-dimensional recyclable SERS substrates have wide applications in environmental pollution monitoring and biomedical analysis.

Thermal rectification (TR) phenomena in carbon nanotubes (CNTs) have been previously foreseen through theoretical predictions; however, its experimental realization in bulk CNT arrays remains relatively unexplored. Herein, we have synthesized vertically aligned carbon nanotube (VACNT) arrays of similar to 4.5 mm in length on a 4-inch silicon wafer by a combined bubble-assisted chemical vapor deposition method. By integrating these VACNT arrays with SnZn alloys, we have successfully developed devices capable of functioning across a wide temperature range spanning from 200 degrees C to 400 degrees C. Notably, the thermal boundary resistances (TBR) between the VACNTs and SnZn alloy exhibit pronounced dependence on the alloy's composition, exhibiting variations ranging from 0.12 cm(2)KW(-1) to 1.12 cm(2)KW(-1). Of particular significance, the TBRs of Sn50Zn50/VACNT compounds in the forward direction were found to fall within the range of 0.63-0.98 cm(2)KW(-1) in the temperature range from120 degrees C to 180 degrees C, while in the backward direction, they exhibited values in the range of 0.13-0.34 cm(2)KW(-1). These contrasting TBR values highlight a marked thermal rectification performance with a substantial TR coefficient between 0.49 and 0.66. Our comprehensive investigation sheds valuable insights into the TR effects within VACNTs and metal/alloy interfaces, presenting a promising avenue for the development of future thermal logic circuits and thermal transistors.

This study presents an analysis of the characterization and crystal structure of a series of materials, namely ZrW2-xMoxO8 (0 & LE; x & LE; 1). The isotropic coefficient of thermal expansion of these materials exhibited a systematic and progressive approach from negative values to zero thermal expansion, which is dependent on the increasing value of x. The range of the linear coefficient of thermal expansion, & alpha;l, for the entire series was observed to be between-8.44 x 10-6/& DEG;C and approximately-4.0 x 10-6/& DEG;C. In-situ X-ray diffraction and In-situ Raman spectroscopy were used to study the different structures of ZrW2-xMoxO8 (0 & LE; x & LE; 1), elucidating the changing rule of the thermal expansion coefficient and the mechanism of the ordered-disordered phase transition. According to Rietveld refinement results, Mo doping causes a decrease in the lattice parameters of the entire system and slows down the transverse motion of the bridge oxygen atoms in the small cell volume, which reduces the negative thermal expansion. As the interaction between W (Mo) and a single coordination oxygen atom weakened, the phase transition temperature decreased. This is because the W(Mo)1O4 and W(Mo)2O4 polyhedron can be flipped more easily via the "ratchet" process due to the lower electronegativity of the Mo atom (2.16 Pauling) compared to that of the W atom (2.36 Pauling). Furthermore, the impact of Mo substitution for W sites on the electronic structure was initially reported through X-ray photoelectron spectroscopy.

Here, a universal strategy for the controllable synthesis of three dimensional (3D) hierarchical Ag/ZnO hybrid arrays based on the urchin-like ZnO-nanorod array template is presented. The urchin-like ZnO-nanorod arrays are first achieved by electrodepositing a high density of ZnO-nanorods onto the surface of highly hexagonally arranged arrays of polystyrene (PS) microspheres, and then Ag-nanoparticles (Ag-NPs) are assembled onto the surface of each ZnO-nanorod via photochemical reaction, ion sputtering, galvanic cell reaction deposition and electrochemical deposition, forming the ordered hierarchical Ag/ZnO hybrid arrays. The urchin-like Ag/ZnO hybrid arrays with well-ordered hierarchical morphology and high density 'hot spots' located in the sub-10 nm gaps between neighboring Ag-NPs on both the same ZnO-nanorod and neighboring ZnO-nanorods can be directly utilized as hybrid surface-enhanced Raman scattering (SERS) substrates with high SERS activity. This work provides a strategy for the rational assembly of well-ordered hierarchical noble metal/semiconductor hybrid arrays, which may open up many opportunities in areas such as catalysis, SERS, and biosensing.

Thermal rectifier is a device with the higher heat transport capacity in one direction than the backward one, being similar to the electrical diode working for the control of the electrical current. In this work, we report a new thermal rectifier based on the flexible macroscopic polydimethylsiloxane ( PDMS) film with asymmetric cone-shape holes embedded with micrometer sized graphite powder ( denoted as PDMS@graphite). The PDMS@graphite shows thermal rectification behavior with an extracted thermal rectification coefficient of 1.1326 +/- 0.009 under 129.8 K temperature bias, and this value can be further modulated by changing the asymmetric ratio of the cone-shape interface in the PDMS@graphite film. Two underlying mechanisms are invited to explain the thermal rectification effect in the PDMS@graphite system. The one is the opposite temperature dependence of thermal conductivity for PDMS and graphite powder. The other one is the different temperature dependent thermal conductivity of the asymmetric cone-shape graphite in PDMS@graphite film in the forward and backward heating direction when applying the same temperature bias, which can be demonstrated in the COMOSL theoretical simulated temperature distributions for the PDMS@graphite. The as-fabricated flexible macroscopic PDMS@graphite composite film thermal rectifier may provide the potential applications in thermal control and management. (C) 2017 Elsevier Ltd. All rights reserved.

Active control of heat flow is one of the important concepts in phononic devices, among which thermal diode is a fundamental building block. The long-standing bottleneck is the relevant experiments lagging far behind theoretical results. In this paper, we experimentally demonstrated considerable thermal rectification in the Y-junction carbon nanotube (CNT) bundle with suspended thermal bridge method. The thermal rectification ratio is up to -8.3%+/- 0.5% with a relatively low temperature difference (Delta T= 4K). Molecular dynamics simulation results show that asymmetric phonon transmission in different (forward and backward) directions is responsible for the thermal rectification observed in the asymmetric CNT structure. (C) 2018 Elsevier Ltd. All rights reserved.

Here we report a low-cost synthetic approach for the direct fabrication of large-area Au nanourchin arrays on indium tin oxide (ITO) via a facile galvanic-cell-reaction-driven deposition in an aqueous solution of chloroauric acid and poly(vinyl pyrrolidone) (PVP). The homogeneous Au nanourchins are composed of abundant sharp nanotips, which can served as nanoantennas and increase the local electromagnetic field enhancement dramatically. Finite element theoretical calculations confirm the strong electromagnetic field can be created around the sharp nanotips and located in the nanogaps between adjacent tips of the Au nanourchins. In addition, the interparticle nanogaps between the neighboring Au nanourchins may create additional hotspots, which can induce the higher electromagnetic field intensity. By using rhodamine 6G as a test molecule, the large-area Au nanourchin arrays on ITO exhibit active, uniform, and reproducible surface-enhanced Raman scattering (SERS) effect. To trial their practical application, the Au nanourchin arrays are utilized as SERS substrates to detect 3,3’,4,4’-tetrachlorobiphenyl (PCB-77) one congener of polychlorinated biphenyls (PCBs) as a notorious class of persistent organic pollutants. The characteristic Raman peaks can be still identified when the concentration of PCB-77 is down to 5 × 10−6 M.

Large-scale flexible films with one side consisting of ordered Ag-NPs@ZnO-nanorods/PAN-nanopillar arrays were used as recyclable SERS substrates.

In this paper, single crystalline copper nanowires (CuNWs) have been electrochemically grown through anodic aluminum oxide template. The environmental stability of the as-obtained CuNWs in both 40% relative humidity (RH) atmosphere and 0.1 m NaOH aqueous solution has been subsequently studied. In 40% RH atmosphere, a uniform compact Cu2O layer is formed as a function of exposure time following the logarithmic law and epitaxially covers the CuNW surfaces. It is also found that the oxide layers on CuNWs are sequentially grown when subjected to the cyclic voltammetry measurement in 0.1 m NaOH solution. An epitaxially homogeneous Cu2O layer is initially formed over the surface of the CuNW substrates by solid-state reaction (SSR). Subsequently, the conversion of Cu2O into epitaxial CuO based on the SSR takes place with the increase of applied potential. This CuO layer is partially dissolved in the solution forming Cu(OH)(2), which then redeposited on the CuNW surfaces (i.e., dissolutionredeposition (DR) process) giving rise to a mixed polycrystalline CuO/Cu(OH)(2) layer. The further increase of applied potential allows the complete oxidation of Cu2O into CuO to form a dual-layer structure (i.e., CuO inner layer and Cu(OH)(2) outer layer) with random orientations through an enhanced DR process.

This article demonstrates a controllable and low-cost fabrication approach to large-scale flexible films with one side consisting of ordered and vertically aligned Ag-nanoplates assembled PAN-nanopillar arrays with high-density and uniform hot spots.

A series of Pb(Zr1-xTix)O-3 multilayer films alternatively stacked by Pb(Zr0.52Ti0.48)O-3 and Pb(Zr0.35Ti0.65)O-3 layers have been deposited on corning glass by magnetron sputtering. The films demonstrate pure perovskite structure and good crystallinity. A large tetragonality (c/a) of similar to 1.061 and a shift of similar to 0.08 eV for optical bandgap were investigated at layer engineered films. In addition, these samples exhibited a wild tunable electro-optic behavior from tens to similar to 250.2 pm/V, as well as fast switching time of down to a few microseconds. The giant EO coefficient was attribute the strain-polarization coupling effect and also comparable to that of epitaxial (001) single crystal PZT thin films. The combination of high transparency, large EO effect, fast switching time, and huge phase transition temperature in PZT-based thin films show the potential on electro-optics from laser to information telecommunication. (C) 2017 Elsevier B.V. All rights reserved.

High quality epitaxial BiFeO3 (BFO) thin films have been grown on (001) SrTiO3 substrate by magnetron sputtering. Both a-axis and c-axis BFO orientations were studied. Prism coupler results reveal that the c-axis and a-axis refractive indices of the BFO thin films were 2.721 and 2.653 at 632.8 nm; the corresponding propagation losses were 4.3 and 4.6 dB/cm, respectively. An electro-optic (EO) modulator based on such BFO film has been demonstrated with a fast switching time t = 3.8 μs at 632.8 nm for the a-axis orientation and t = 3.4 μs for the c-axis orientation. Moreover, these BFO films gave the Pockels coefficient reff = 19.3 pm/V for the c-axis orientation and reff = 15.9 pm/V for the a-axis orientation at 632.8 nm. Such an anisotropic refractive index and linear EO behaviors are attributed to the epitaxial strain and stripe domain structure in the BFO thin films with mixed phases. This study illustrates the suitability of the BFO thin films for EO modulators and optical switches beyond their current extensive spintronic and memory applications.

High-density plasmonic Ag nanoparticles (Ag-NPs) have been synthesized on a three-dimensional framework of natural basil seeds as the inexpensive substrates for surface-enhanced Raman scattering (SERS). The Ag-NPs decorated basil seeds (denoted as Ag-NPs@basil-seeds) are dipped into the analyte solution for rapid detection of methyl parathion in orange juice. Alternatively, they are incorporated into a microfluidic chip for online measurement of melamine in milk. The porous basil seeds can absorb trace melamine into the micro-cavity in the seeds, which load the melamine molecules into the gap where high-density "hot spots" appear under laser excitation. Hence the Ag-NPs@basil-seeds not only separate and pre-concentrate the trace analyte but also expose the analyte into the strong plasmonic field. This unique feature can eliminate the pre-treatment of analyte prior to SERS detection, and improve the sensitivity of the sensor. (C) 2015 Elsevier B.V. All rights reserved.

This study demonstrated a simple method for gold (Au) catalyzed atmospheric pressure chemical vapor deposition (CVD) of tower-like germanium (Ge) nanostructures (denoted as Ge nanotowers) on silicon substrate. The Ge nanotowers have quasi- hexagonal cross-section with a diameter gradually decreasing from the bottom to the top end and sawtooth-faceted sidewalls. The Ge nanotowers are formed in a competitive growth process involving an Au-catalyzed axial growth and lateral growth, which can be controlled by the varied reagent vapor pressure in the CVD growth. The relationship between CVD growth kinetics and the complex morphologies was carefully examined for Ge nanostructures ranging from cylindrical and tapered nanowires to moniliform-shaped and sawtooth faceted hexagonal nanotowers in different deposition zones. The resultant complex Ge nanotowers not only enrich the family of Ge-based nanostructures, but also have potentials as building blocks for Ge-based functional nanodevices.

A novel curved focal plane extreme ultraviolet (EUV) detector array designed for a moon-based EUV camera is demonstrated. The curved focal plane detector array operating in a pulse-counting mode consists of a curved microchannel plate (MCP) stack and an induced charge wedge-strip anode (WSA). The curved MCP is fabricated by firstly thermally slumping of the MCPs, and then followed by optical polishing and core glass etching. By using this technology, curved MCPs with a length-to-diameter (L/D) ratio of 80:1 and a radius of curvature of 150 mm have been successfully achieved. The performance of the curved MCP detector is fully characterized in terms of the background noise, pulse height distribution, gain, image linearity and spatial resolution. It is measured that a spatial resolution of 7.13 lp/mm can be achieved with a background noise of less than 0.3 counts/cm2⋅s. The characterization results indicate that the curved focal plane detector can fulfill the requirements of the moon-based EUV camera.