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Concentrated water-in-salt electrolytes (WiSEs) are used in aqueous batteries and to control electrochemical reactions for fuel production. The hydrogen evolution reaction is a parasitic reaction at the negative electrode that limits cell voltage in WiSE batteries and leads to self-discharge, and affects selectivity for electrosynthesis. Mitigating and modulating these processes is hampered by a limited fundamental understanding of HER kinetics in WiSEs. Here, we quantitatively assess how thermodynamics, kinetics, and interface layers control the apparent HER activities in 20 m LiTFSI. When the LiTFSI concentration is increased from 1 to 20 m, an increase in proton activity causes a positive shift in the HER equilibrium potential of 71 mV. The exchange current density, i o , derived from the HER branch for 20 m LiTFSI in 98% purity (0.56 ± 0.05 μA/cm Pt 2 ), however, is 8 times lower than for 20 m LiTFSI in 99.95% (4.7 ± 0.2 μA/cm Pt 2 ) and 32 times lower than for 1 m LiTFSI in 98% purity (18 ± 1 μA/cm Pt 2 ), demonstrating that the WiSE's impurities and concentration are both central in significantly suppressing HER kinetics. The ability and applicability of the reported methods are extended by examining additional WiSEs formulations made of acetates and nitrates.

A cation exchange strategy is proposed to convert layered Ti 3 C 2 -Na-TiO 2 MXene nanofibers into Ti 3 C 2 -Co-TiO 2 MXene nanoparticle arrays with open-layered 3D structure and numerous heterogeneous interfaces, which deliver excellent oxygen evolution reaction (OER) activity.

Constructing the strong interaction between the matrix and the active centers dominates the design of high-performance electromagnetic wave (EMW) absorption materials. However, the interaction-relevant absorption mechanism is still unclear, and the design of ultrahigh reflection loss ( R L < -80 dB) absorbers remains a great challenge. Herein, CoFe-based Prussian blue (PB) nanocubes are coprecipitated on the surface of ultrathin CoAl-LDH nanoplates with the assistance of unsaturated coordination sites. During the subsequent pyrolysis process, CoAl-LDH serves as a "ligand" providing a Co source and reacts with Fe or C in the CoFe-PB "host" to form stable CoFe alloys or CoC x species. As a result, strong reactions emerged between the CoAl-LDH matrix and the active CoFe-CoC x @NC centers. Based on the experimental results, the CoAl/CoFe-CoC x @NC hierarchical heterostructure delivers good dielectric losses (dipolar polarization, interface polarization, and conductive loss), magnetic losses (eddy current loss, natural resonance, and exchange resonance), and impedance matching, resulting in a remarkable EMW absorption performance with a reflection loss ( R L ) value of -82.1 dB at a matching thickness of 3.8 mm. Theoretical results (commercial CST) identify that the strong interaction between the 2D CoAl-LDH "ligand" and 2D CoFe-CoC x "host" promotes a robust heterointerface among the nanoparticles, nanosheets, and nanoplates, which extremely contribute to the dielectric loss. Meanwhile, the coupling effect of nanosheets and nanoplates greatly contributes to the matching performance. This work provides an aggressive strategy for the effect of ligands and hosts on high-performance EMW absorption.

Refractory carbides are attractive candidates for support materials in heterogeneous catalysis because of their high thermal, chemical, and mechanical stability. However, the industrial applications of refractory carbides, especially silicon carbide (SiC), are greatly hampered by their low surface area and harsh synthetic conditions, typically have a very limited surface area (<200 m 2 g -1 ), and are prepared in a high-temperature environment (>1,400 °C) that lasts for several or even tens of hours. Based on Le Chatelier's principle, we theoretically proposed and experimentally verified that a low-pressure carbothermal reduction (CR) strategy was capable of synthesizing high-surface area SiC (569.9 m 2 g -1 ) at a lower temperature and a faster rate (∼1,300 °C, 50 Pa, 30 s). Such high-surface area SiC possesses excellent thermal stability and antioxidant capacity since it maintained stability under a water-saturated airflow at 650 °C for 100 h. Furthermore, we demonstrated the feasibility of our strategy for scale-up production of high-surface area SiC (460.6 m 2 g -1 ), with a yield larger than 12 g in one experiment, by virtue of an industrial viable vacuum sintering furnace. Importantly, our strategy is  also applicable to the rapid synthesis of refractory metal carbides (NbC, Mo 2 C, TaC, WC) and even their emerging high-entropy carbides (VNbMoTaWC 5 , TiVNbTaWC 5 ). Therefore, our low-pressure CR method provides an alternative strategy, not merely limited to temperature and time items, to regulate the synthesis and facilitate the upcoming industrial applications of carbide-based advanced functional materials.

Cryogenic electron microscopy is one of the fastest and most robust methods for capturing high-resolution images of proteins, but stringent sample preparation, imaging conditions, and in situ radiation damage inflicted during data acquisition directly affect the resolution and ability to capture dynamic details, thereby limiting its broader utilization and adoption for protein studies. We addressed these drawbacks by introducing synthesized giant carbon nano-test tubes (GCNTTs) as radiation-insulating materials that lessen the irradiation impact on the protein during data acquisition, physical molecular concentrators that localize the proteins within a nanoscale field of view, and vessels that create a microenvironment for solution-phase imaging. High-resolution electron microscopy images of single and aggregated hemoglobin molecules within GCNTTs in both solid and solution states were acquired. Subsequent scanning transmission electron microscopy, small-angle neutron scattering, and fluorescence studies demonstrated that the GCNTT vessel protected the hemoglobin molecules from electron irradiation-, light-, or heat-induced denaturation. To demonstrate the robustness of GCNTT as an imaging platform that could potentially augment the study of proteins, we demonstrated the robustness of the GCNTT technique to image an alternative protein, d-fructose dehydrogenase, after cyclic voltammetry experiments to review encapsulation and binding insights. Given the simplicity of the material synthesis, sample preparation, and imaging technique, GCNTT is a promising imaging companion for high-resolution, single, and dynamic protein studies under electron microscopy.

Compared to traditional electric double-layer capacitors, redox-enhanced electrochemical capacitors (redox-ECs) show increased energy density and steadier power output thanks to the use of redox-active electrolytes. The aim of this study is to understand the electrochemical mechanisms of the aqueous pentyl viologen/bromide dual redox system at the interface of an ordered mesoporous carbon (CMK-8) and improve the device performance. Cells with CMK-8 carbon electrodes were investigated in several configurations using different charging rates and potential windows. The pentyl viologen electrochemistry shows a mixed behavior between solution-based diffusion and adsorption phenomena, with the reversible formation of an adsorbed layer. The extension of the voltage window allows for full reduction of the viologen molecules during charge and a consequent increase in the specific discharge energy delivered by the cell. Investigation of the mechanism indicates that a 1.5 V charging voltage with a 0.5 A g -1 charging rate and fast discharge rate produces the best overall performance.

The molecules feeding life's emergence are thought to have been provided through the hydrothermal interactions of convecting carbonic ocean waters with minerals comprising the early Hadean oceanic crust. Few laboratory experiments have simulated ancient hydrothermal conditions to test this conjecture. We used the JPL hydrothermal flow reactor to investigate CO 2 reduction in simulated ancient alkaline convective systems over 3 days (T = 120°C, P  = 100 bar, pH = 11). H 2 -rich hydrothermal simulant and CO 2 -rich ocean simulant solutions were periodically driven in 4-h cycles through synthetic mafic and ultramafic substrates and Fe>Ni sulfides. The resulting reductants included micromoles of HS - and formate accompanied possibly by micromoles of acetate and intermittent minor bursts of methane as ascertained by isotopic labeling. The formate concentrations directly correlated with the CO 2 input as well as with millimoles of Mg 2 + ions, whereas the acetate did not. Also, tens of micromoles of methane were drawn continuously from the reactor materials during what appeared to be the onset of serpentinization. These results support the hypothesis that formate may have been delivered directly to a branch of an emerging acetyl coenzyme-A pathway, thus obviating the need for the very first hydrogenation of CO 2 to be made in a hydrothermal mound. Another feed to early metabolism could have been methane, likely mostly leached from primary CH 4 present in the original Hadean crust or emanating from the mantle. That a small volume of methane was produced sporadically from the 13 CO 2 -feed, perhaps from transient occlusions, echoes the mixed results and interpretations from other laboratories. As serpentinization and hydrothermal leaching can occur wherever an ocean convects within anhydrous olivine- and sulfide-rich crust, these results may be generalized to other wet rocky planets and moons in our solar system and beyond.

The chemical reactivity and/or the diffusion of Ag atoms or ions during thermal processing can cause irreversible structural damage, hindering the application of Ag nanowires (NWs) in transparent conducting films and other applications that make use of the material's nanoscale properties. Here, we describe a simple and effective method for growing monolayer SnO 2 on the surface of Ag nanowires under ambient conditions, which protects the Ag nanowires from chemical and structural damage. Our results show that Sn 2+ and Ag atoms undergo a redox reaction in the presence of water. First-principle simulations suggest a reasonable mechanism for SnO 2 formation, showing that the interfacial polarization of the silver by the SnO 2 can significantly reduce the affinity of Ag to O 2 , thereby greatly reducing the oxidation of the silver. The corresponding values (for example, before coating: 17.2 Ω/sq at 86.4%, after coating: 19.0 Ω/sq at 86.6%) show that the deposition of monolayer SnO 2 enables the preservation of high transparency and conductivity of Ag. In sharp contrast to the large-scale degradation of pure Ag-NW films including the significant reduction of its electrical conductivity when subjected to a series of harsh corrosion environments, monolayer SnO 2 coated Ag-NW films survive structurally and retain their electrical conductivity. Consequently, the thermal, electrical, and chemical stability properties we report here, and the simplicity of the technology used to achieve them, are among the very best reported for transparent conductor materials to date.

Metallic nanostructures exhibit a strong plasmon resonance at a wavelength whose value is sensitive to the charge density in the nanostructure, its size, shape, interparticle coupling, and the dielectric properties of its surrounding medium. Here we use UV-visible transmission and reflectance spectroscopy to track the shifts of the plasmon resonance in an array of gold nanoparticles buried under metal-oxide layers of varying thickness produced using atomic layer deposition (ALD) and then coated with bulk layers of one of three metals: aluminum, silver, or gold. A significant shift in the plasmon resonance was observed and a precise value of ω p , the plasmon frequency of the gold comprising the nanoparticles, was determined by modeling the composite of gold nanoparticles and metal-oxide layer as an optically homogeneous film of core-shell particles bounded by two substrates: one of quartz and the other being one of the aforementioned metals, then using a Maxwell-Garnett effective medium expression to extract ω p for the gold nanoparticles before and after coating with the bulk metals. Under illumination, the change in the charge density of the gold nanoparticles per particle determined from the change in the values of ω p is found to be some 50-fold greater than what traditional electrostatic contact electrification models compute based on the work function difference of the two conductive materials. Moreover, when using bulk gold as the capping layer, which should have resulted in a negligible charge exchange between the gold nanoparticles and the bulk gold, a significant charge transfer from the bulk gold layer to the nanoparticles was observed as with the other metals. We explain these observations in terms of the "plasmoelectric effect", recently described by Atwater and co-workers, in which the gold nanoparticles modify their charge density to allow their resonant wavelength to match that of the incident light, thereby achieving, a lower value of the chemical potential due to the entropy increase resulting from the conversion of the plasmon's energy to heat. We conclude that even the act of registering the spectrum of nanoparticles is at times sufficient to alter their charge densities and hence their UV-visible spectra.

We present a sensitive and quantitative protein detection assay that can efficiently distinguish between specific and nonspecific target binding. Our technique combines dual affinity reagents with surface-enhanced Raman spectroscopy (SERS) and chemometric analysis. We link one Raman reporter-tagged affinity reagent to gold nanoparticles and another to a gold film, such that protein-binding events create a "hot spot" with strong SERS spectra from both Raman reporter molecules. Any signal generated in this context is indicative of recognition by both affinity labels, whereas signals generated by nonspecific binding lack one or the other label, enabling us to efficiently distinguish true from false positives. We show that the number of hot spots per unit area of our substrate offers a quantitative measure of analyte concentration and demonstrate that this dual-label, SERS-linked aptasensor assay can sensitively and selectively detect human α-thrombin in 1% human serum with a limit of detection of 86 pM., Competing Interests: The authors declare no conflict of interest.

Research in electric double-layer capacitors (EDLCs) and rechargeable batteries is converging to target systems that have battery-level energy density and capacitor-level cycling stability and power density. This research direction has been facilitated by the use of redox-active electrolytes that add faradaic charge storage to increase energy density of the EDLCs. Aqueous redox-enhanced electrochemical capacitors (redox ECs) have, however, performed poorly due to cross-diffusion of soluble redox couples, reduced cycle life, and low operating voltages. In this manuscript, we propose that these challenges can be simultaneously met by mechanistically designing a liquid-to-solid phase transition of oxidized catholyte (or reduced anolyte) with confinement in the pores of electrodes. Here we demonstrate the realization of this approach with the use of bromide catholyte and tetrabutylammonium cation that induces reversible solid-state complexation of Br 2 /Br 3 - . This mechanism solves the inherent cross-diffusion issue of redox ECs and has the added benefit of greatly stabilizing the reactive bromine generated during charging. Based on this new mechanistic insight on the utilization of solid-state bromine storage in redox ECs, we developed a dual-redox EC consisting of a bromide catholyte and an ethyl viologen anolyte with the addition of tetrabutylammonium bromide. In comparison to aqueous and organic electric double-layer capacitors, this system enhances energy by factors of ca. 11 and 3.5, respectively, with a specific energy of ∼64 W·h/kg at 1 A/g, a maximum power density >3 kW/kg, and cycling stability over 7000 cycles.

Janus nanoparticles (JNPs) offer unique features, including the precisely controlled distribution of compositions, surface charges, dipole moments, modular and combined functionalities, which enable excellent applications that are unavailable to their symmetrical counterparts. Assemblies of NPs exhibit coupled optical, electronic and magnetic properties that are different from single NPs. Herein, we report a new class of double-layered plasmonic-magnetic vesicle assembled from Janus amphiphilic Au-Fe 3 O 4 NPs grafted with polymer brushes of different hydrophilicity on Au and Fe 3 O 4 surfaces separately. Like liposomes, the vesicle shell is composed of two layers of Au-Fe 3 O 4 NPs in opposite direction, and the orientation of Au or Fe 3 O 4 in the shell can be well controlled by exploiting the amphiphilic property of the two types of polymers., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Short-chain polyphosphate (polyP) is released from platelets upon platelet activation, but it is not clear if it contributes to thrombosis. PolyP has increased propensity to clot blood with increased polymer length and when localized onto particles, but it is unknown whether spatial localization of short-chain polyP can accelerate clotting of flowing blood. Here, numerical simulations predicted the effect of localization of polyP on clotting under flow, and this was tested in vitro using microfluidics. Synthetic polyP was more effective at triggering clotting of flowing blood plasma when localized on a surface than when solubilized in solution or when localized as nanoparticles, accelerating clotting at 10-200 fold lower concentrations, particularly at low to sub-physiological shear rates typical of where thrombosis occurs in large veins or valves. Thus, sub-micromolar concentrations of short-chain polyP can accelerate clotting of flowing blood plasma under flow at low to sub-physiological shear rates. However, a physiological mechanism for the localization of polyP to platelet or vascular surfaces remains unknown., Competing Interests: S.A.S., D.K., G.D.S., and J.H.M. are co-inventors on pending patent applications covering potential medical uses of SNP-polyP. A.J.D. and Y.L. are co-inventors on a pending patent application related to the therapeutic usage and delivery of NP-polyP. D.K., G.D.S., and J.H.M. declare competing financial interests in this work. The remaining authors declare no competing financial interests.

A plasmonic liquid junction photovoltaic cell with greatly improved power conversion efficiency is described. When illuminated with simulated sunlight, the device (Au-TiO 2 /V 3+ (0.018 M), V 2+ (0.182 M)/Pt) reproducibly and sustainably produces an V OC of 0.50 V and a J SC of 0.5 mA cm -2 , corresponding to a power conversion efficiency of 0.095%.

Gratings have been widely investigated both theoretically and experimentally as surface-enhanced Raman spectroscopy (SERS) substrates, exhibiting, under appropriate circumstances, increased far-field extinctions and near-field intensities over those of an appropriately equivalent number of isolated particles. When the grating order transitions from evanescent to radiative, narrow resonance peaks are observed in the extinction spectrum whose properties can be manipulated by controlling the grating's geometric parameters. Here we report the application of the architectural principles of grating fabrication using a square two-dimensional array of gold-coated nanostructures that achieves SERS enhancements of 10(7) uniformly over areas of square centimeters. The high-performance grating substrates were fabricated using commonly available foundry-based techniques that have been chosen for their applicability to large-scale wafer processing. Additionally, we restricted ourselves to a parametric regime that optimizes SERS performance in a repeatable and reproducible manner.

The performance of redox-enhanced electrochemical capacitors (redox ECs) is substantially improved when oxidized catholyte (bromide) and reduced anolyte (viologen) are retained within the porous electrodes through reversible counterion-induced solid complexation. Investigation of the mechanism illustrates design principles and identifies pentyl viologen/bromide (PV/Br) as a new high-performance electrolyte. The symmetric PV/Br redox EC produces a specific energy of 48.5 W·h/kgdry at 0.5 A/gdry (0.44 kW/kgdry) with 99.7% Coulombic efficiency, maintains stability over 10 000 cycles, and functions identically when operated with reversed polarity.

Developing electrode materials with high-energy densities is important for the development of lithium-ion batteries. Here, we demonstrate a mesoporous molybdenum dioxide material with abnormal lithium-storage sites, which exhibits a discharge capacity of 1,814 mAh g(-1) for the first cycle, more than twice its theoretical value, and maintains its initial capacity after 50 cycles. Contrary to previous reports, we find that a mechanism for the high and reversible lithium-storage capacity of the mesoporous molybdenum dioxide electrode is not based on a conversion reaction. Insight into the electrochemical results, obtained by in situ X-ray absorption, scanning transmission electron microscopy analysis combined with electron energy loss spectroscopy and computational modelling indicates that the nanoscale pore engineering of this transition metal oxide enables an unexpected electrochemical mass storage reaction mechanism, and may provide a strategy for the design of cation storage materials for battery systems.

Plasmonic metal/semiconductor heterostructures show promise for visible-light-driven photocatalysis. Gold nanorods (AuNRs) semi-coated with TiO2 are expected to be ideally structured systems for hydrogen evolution. Synthesizing such structures by wet-chemistry methods, however, has proved challenging. Here we report the bottom-up synthesis of AuNR/TiO2 nanodumbbells (NDs) with spatially separated Au/TiO2 regions, whose structures are governed by the NRs' diameter, and the higher curvature and lower density of CnTAB surfactant at the NRs' tips than on their lateral surfaces, as well as the morphology's dependence on concentration, and alkyl chain length of CnTAB. The NDs show plasmon-enhanced H2 evolution under visible and near-infrared light.

Identification and characterization of catalytic active sites are the prerequisites for an atomic-level understanding of the catalytic mechanism and rational design of high-performance heterogeneous catalysts. Indirect evidence in recent reports suggests that platinum (Pt) single atoms are exceptionally active catalytic sites. We demonstrate that infrared spectroscopy can be a fast and convenient characterization method with which to directly distinguish and quantify Pt single atoms from nanoparticles. In addition, we directly observe that only Pt nanoparticles show activity for carbon monoxide (CO) oxidation and water-gas shift at low temperatures, whereas Pt single atoms behave as spectators. The lack of catalytic activity of Pt single atoms can be partly attributed to the strong binding of CO molecules., (Copyright © 2015, American Association for the Advancement of Science.)

We report a new electrochemical capacitor with an aqueous KI-KOH electrolyte that exhibits a higher specific energy and power than the state-of-the-art nonaqueous electrochemical capacitors. In addition to electrical double layer capacitance, redox reactions in this device contribute to charge storage at both positive and negative electrodes via a catholyte of IOx-/I- couple and a redox couple of H2O/Had, respectively. Here, we, for the first time, report utilizing IOx-/I- redox couple for the positive electrode, which pins the positive electrode potential to be 0.4-0.5 V vs Ag/AgCl. With the positive electrode potential pinned, we can polarize the cell to 1.6 V without breaking down the aqueous electrolyte so that the negative electrode potential could reach -1.1 V vs Ag/AgCl in the basic electrolyte, greatly enhancing energy storage. Both mass spectroscopy and Raman spectrometry confirm the formation of IO3- ions (+5) from I- (-1) after charging. Based on the total mass of electrodes and electrolyte in a practically relevant cell configuration, the device exhibits a maximum specific energy of 7.1 Wh/kg, operates between -20 and 50 °C, provides a maximum specific power of 6222 W/kg, and has a stable cycling life with 93% retention of the peak specific energy after 14,000 cycles.

Zeolites are crystalline inorganic solids with microporous structures, having widespread applications in the fields of catalysis, separation, adsorption, microelectronics, and medical diagnosis. A major drawback of zeolites is the mass transfer limitation due to the small size of the micropores (less than 1 nm). Numerous efforts have been dedicated to integrating mesopores with the microporous zeolite structures by using templating and/or destructive approaches. Here we provide a new strategy for hierarchical pore size zeolite synthesis, without using supramolecular or hard templates. The branching epitaxial growth behavior, as a result of aluminum-zoning, contributes to the formation of the hierarchical porous zeolite structures.

We have developed a facile procedure that can create asymmetrical building blocks by uniformly deforming nanospheres into C(∞v) symmetry at low cost and high quality. Concave polystyrene@carbon (PS@C) core-shell nanospheres were produced by a very simple microwave-assisted alcohol thermal treatment of spherical PS@C nanoparticles. The dimensions and ratio of the concave part can be precisely controlled by temperature and solvents. The concavity is created by varying the alcohol-thermal treatment to tune the swelling properties that lead to the mechanical deformation of the PS@C core-shell structure. The driving force is attributed to the significant volume increase that occurs upon polystyrene core swelling with the incorporation of solvent. We propose a mechanism adapted from published models for the depression of soft capsules. An extrapolation from this model predicts that the rigid shell is used to generate a cavity in the unbuckled shell, which is experimentally confirmed. This swelling and deformation route is flexible and should be applicable to other polymeric nanoparticles to produce asymmetrical nanoparticles.

Electrochemical double-layer capacitors exhibit high power and long cycle life but have low specific energy compared with batteries, limiting applications. Redox-enhanced capacitors increase specific energy by using redox-active electrolytes that are oxidized at the positive electrode and reduced at the negative electrode during charging. Here we report characteristics of several redox electrolytes to illustrate operational/self-discharge mechanisms and the design rules for high performance. We discover a methyl viologen (MV)/bromide electrolyte that delivers a high specific energy of ∼14 Wh kg(-1) based on the mass of electrodes and electrolyte, without the use of an ion-selective membrane separator. Substituting heptyl viologen for MV increases stability, with no degradation over 20,000 cycles. Self-discharge is low, due to adsorption of the redox couples in the charged state to the activated carbon, and comparable to cells with inert electrolyte. An electrochemical model reproduces experiments and predicts that 30-50 Wh kg(-1) is possible with optimization.

A high-yielding synthesis of a series of polyimide dendrimers, including decacyclene- and perylene-containing dendrimer D6, in which two types of polyimide dyes are present, is reported. In these constructs, the branching unit is represented by trisphenylamine, and the solubilizing chains by N-9-heptadecanyl-substituted perylene diimides. The photophysical properties of the dendrimers have been studied by absorption, steady-state, and time-resolved emission spectroscopy and pump-probe transient absorption spectroscopy. Photoinduced charge-separated (CS) states are formed on the femtosecond timescale upon visible excitation. In particular, in D6, two different CS states can be formed, involving different subunits that decays independently with different lifetimes (ca. 10-100 ps)., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

We present a silica nanoparticle (SNP) functionalized with polyphosphate (polyP) that accelerates the natural clotting process of the body. SNPs initiate the contact pathway of the blood-clotting system; short-chain polyP accelerates the common pathway by the rapid formation of thrombin, which enhances the overall blood-clotting system, both by accelerating fibrin generation and by facilitating the regulatory anticoagulation mechanisms essential for hemostasis. Analysis of the clotting properties of bare SNPs, bare polyP, and polyP-functionalized SNPs in plasma demonstrated that the attachment of polyP to SNPs to form polyP-SNPs creates a substantially enhanced synergistic effect that lowers clotting time and increases thrombin production at low concentrations. PolyP-SNP even retains its clotting function at ambient temperature. The polyP-SNP system has the potential to significantly improve trauma-treatment protocols and outcomes in hospital and prehospital settings., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The optical resonances of plasmonic nanostructures depend critically on the geometrical details of the absorber. We show that this unique property of plasmons can potentially be used to create panchromatic absorbers covering most of the useful solar spectrum, by measuring the light-to-hydrogen conversion capabilities of a series multielectrode photocatalytic devices, based on functionalized gold nanorods of appropriately chosen aspect ratios. Judiciously combining nanorods of various aspect ratios almost doubles the H2 production of the device over what is optimally possible with a device using gold nanorods of a single aspect ratio (all other key parameters being equal). The estimated quantum efficiency (absorbed photons-to-hydrogen) averaged over the entire solar spectrum of the best performing plasmonic multielectrode array was approximately 0.1%, and the measured H2 production rate for all of the devices was found to be approximately proportional to the hot electron generation. The device was monitored continuously for over 200 hr of operation without measurable diminution in the rate.

Constructing nanoparticles into well-defined structures at mesoscale and larger to create novel functional materials remains a challenge. Inspired by atomic epitaxial growth, we propose an "epitaxial assembly" method to form two-dimensional nanoparticle arrays (2D NAs) directly onto desired materials. As an illustration, we employ a series of surfactant-capped nanoparticles as the "artificial atoms" and layered hybrid perovskite (LHP) materials as the substrates and obtain 2D NAs in a large area with few defects. This method is universal for nanoparticles with different shapes, sizes, and compositions and for LHP substrates with different metallic cores. Raman spectroscopic and X-ray diffraction data support our hypothesis of epitaxial assembly. The novel method offers new insights into the controllable assembly of complex functional materials and may push the development of materials science at the mesoscale.

Plasmonic nanosystems have recently been shown to be capable of functioning as photovoltaics and of carrying out redox photochemistry, purportedly using the energetic electrons and holes created following plasmonic decay as charge carriers. Although such devices currently have low efficiency, they already manifest a number of favorable characteristics, such as their tunability over the entire solar spectrum and a remarkable resistance to photocorrosion. Here, we report a plasmonic photovoltaic using a 25 μm thick electrolytic liquid junction which supports the iodide/triiodide (I-/I3-) redox couple. The device produces photocurrent densities in excess of 40 μA cm(-2), an open circuit voltage (Voc) of ∼0.24 V and a fill factor of ∼0.5 using AM 1.5 G solar radiation at 100 mW cm(-2). The photocurrent and the power conversion efficiency are primarily limited by the low light absorption in the 2-D gold nanoparticle arrays. The use of a liquid junction greatly reduces dielectric breakdown in the oxide layers utilized, which must be very thin for optimal performance, leading to a great improvement in the long-term stability of the cell's performance.

We describe a general approach for the synthesis of micro-/nanostructured metal chalcogenides from elemental precursors. The excellent solubility of sulfur, selenium, and tellurium in phosphonium ionic liquids promotes fast reactions between chalcogens and various metal powders upon microwave heating, giving crystalline products. This approach is green, universal, and scalable.

An acetylcholinesterase-immobilized sensor unit was successfully prepared by encapsulating the enzyme within hybrid mesoporous silica membranes (F127-MST). Through a novel combination with tetracyanoquinodimethane, both acetylcholine and organophosphorus pesticides were successfully detected with high sensitivity. Furthermore, we manufactured the working prototype of an enzyme sensor with this sensor unit for detecting dichlorvos, aldicarb and parathion. At present, the detection limit in this working prototype either equaled or surpassed that of others. Also, we have the advantage of increased stability of the enzyme against the outer environment by encapsulation of the enzymes into a silica nanospace. Consequently, acetylcholinesterase immobilized in F127-MST is a practical sensor with high sensitivity, reusability, and storage stability.

The Li-S system offers a tantalizing battery for electric vehicles and renewable energy storage due to its high theoretical capacity of 1675 mAh g(-1) and its employment of abundant and available materials. One major challenge in this system stems from the formation of soluble polysulfides during the reduction of S8, the active cathode material, during discharge. The ability to deploy this system hinges on the ability to control the behavior of these polysulfides by containing them in the cathode and allowing for further redox. Here, we exploit the high surface areas and good electrical conductivity of mesoporous carbons (MC) to achieve high sulfur utilization while functionalizing the MC with sulfur (S-MC) in order to modify the surface chemistry and attract polysulfides to the carbon material. S-MC materials show enhanced capacity and cyclability trending as a function of sulfur functionality, specifically a 50% enhancement in discharge capacity is observed at high cycles (60-100 cycles). Impedance spectroscopy suggests that the S-MC materials exhibit a lower charge-transfer resistance compared with MC materials which allows for more efficient electrochemistry with species in solution at the cathode. Isothermal titration calorimetry shows that the change in surface chemistry from unfunctionalized to S-functionalized carbons results in an increased affinity of the polysulfide intermediates for the S-MC materials, which is the likely cause for enhanced cyclability.

For the first time, we demonstrate that orthorhombic V2O5 can exhibit superior electrochemical performance in sodium ion batteries when uniformly coated inside nanoporous carbon. The encapsulated V2O5 shows a specific capacity as high as 276 mAh/g, while the whole nanocomposite exhibits a capacity of 170 mAh/g. The V2O5/C composite was fabricated by a novel ambient hydrolysis deposition that features sequential water vapor adsorption in nanoporous carbon, followed by a hydrolysis reaction, exclusively inside the nanopores. The unique structure of the nanocomposite significantly enhances the capacity as well as the rate performance of orthorhombic V2O5 where the composite retains a capacity of over 90 mAh/g at a current rate of 640 mA/g. Furthermore, by calculating, we also revealed that a large portion of the sodium-ion storage, particularly at high current rates, is due to the V2O5 pseudocapacitance.

The conversion of sunlight into electricity by photovoltaics is currently a mature science and the foundation of a lucrative industry. In conventional excitonic solar cells, electron-hole pairs are generated by light absorption in a semiconductor and separated by the "built in" potential resulting from charge transfer accompanying Fermi-level equalization either at a p-n or a Schottky junction, followed by carrier collection at appropriate electrodes. Here we report a stable, wholly plasmonic photovoltaic device in which photon absorption and carrier generation take place exclusively in the plasmonic metal. The field established at a metal-semiconductor Schottky junction separates charges. The negative carriers are high-energy (hot) electrons produced immediately following the plasmon's dephasing. Some of the carriers are energetic enough to clear the Schottky barrier or quantum mechanically tunnel through it, thereby producing the output photocurrent. Short circuit photocurrent densities in the range 70-120 μA cm(-2) were obtained for simulated one-sun AM1.5 illumination with devices based on arrays of parallel gold nanorods, conformally coated with 10 nm TiO2 films and fashioned with a Ti metal collector. For the device with short circuit currents of 120 μA cm(-2), the internal quantum efficiency is ∼2.75%, and its wavelength response tracks the absorption spectrum of the transverse plasmon of the gold nanorods indicating that the absorbed photon-to-electron conversion process resulted exclusively in the Au, with the TiO2 playing a negligible role in charge carrier production. Devices fabricated with 50 nm TiO2 layers had open-circuit voltages as high as 210 mV, short circuit current densities of 26 μA cm(-2), and a fill factor of 0.3. For these devices, the TiO2 contributed a very small but measurable fraction of the charge carriers.

An approach based on a solution-based synthesis that produces a thermally stable Ag/oxide/S₂ Te₃ -Te metal-semiconductor heterostructure is described. With this approach, a figure of merit of zT = 1.0 at 460 K is achieved, a record for a heterostructured material made using wet chemistry. Combining experiments and theory shows that the large increase in the material's Seebeck coefficient results from hot carrier filtering., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Because of microbial resistance to conventional antibiotics, there is increasing interest in silver, including silver nanoparticles (nano-Ag), in antimicrobial applications. However, questions remain regarding the relative roles of nano-Ag particles, versus Ag(+) ions released from nano-Ag dissolution, in imparting bacterial toxicity. Here, we developed a novel nano-Ag that, based on its cysteine cap, was expected to dissolve slowly and thus potentially allow for differentiating nanoparticle, versus ionic, effects of Ag. The nano-Ag was systematically tested for its differential toxicity to Escherichia coli and Pseudomonas aeruginosa. Bacterial growth, reactive oxygen species (ROS) generation, particle dissolution, cellular electron transfer activity, and cell membrane damage and potential were evaluated. In minimal growth medium, E. coli and P. aeruginosa growth were slowed at 100 mg L(-1) (0.93 mM) and 5 mg L(-1) (0.046 mM), respectively; P. aeruginosa was completely inhibited at and above 10 mg L(-1) (0.093 mM). For both strains, toxicity was associated with ROS and cell membrane damage. Based on comparisons to AgNO3 exposures, toxicity from nano-Ag was due to Ag(+) ions and not intact nano-Ag, even though nanoparticle dissolution was less than 2% in minimal growth medium. Because of their stability and slow Ag(+) ion release, the cysteine-capped nano-Ag particles here are useful to antimicrobial applications. Additionally, our systematic approach to evaluating toxicity, membrane damage, and ROS generation can be applied with other nanomaterials and bacteria.

We present a rapid microwave-assisted solid-state approach to prepare complex platinum-group metal oxides with the formula La2BaMO5 (M = Pd, Pt). While conventional furnace-based preparations of these compounds take several days and often require oxidizing conditions, the microwave-assisted pathway enables the target compounds to be obtained with high phase purity in about 20 min of reaction time in air without the multiple regrindings that are required of conventional solid-state synthesis. These complex oxides are stable in various atmospheres up to 1000 °C unlike the simple noble metal oxides, which are reduced even at room temperature. Density functional theory-based calculations have been employed to establish the stability of these complex oxides and to understand the electronic structure origins of the stability, most notably the influence of electropositive cations. It is shown that the presence of electropositive ions in the oxide crystal structure "softens" the oxygen anion and results in more covalent (Pd/Pt)-O interactions.

We present a rapid microwave-assisted sol-gel approach to Pd-substituted LnFeO3 (Ln = Y, La) for applications in C-C coupling reactions. These materials could be prepared in household microwave ovens in less than 15 minutes of reaction time with the final materials displaying well-defined structure and morphology. Phase evolution was studied using time-dependent microwave heatings and then compared with the results obtained from thermogravimetric analyses. Materials were confirmed to be phase pure by laboratory and synchrotron X-ray diffraction. Substituted Pd is ionic as shown by the binding energy shift from X-ray photoelectron spectroscopy. The short heating periods required for phase purity allow these materials less time for sintering as compared to conventional solid state preparation methods, making relatively high surface areas achievable. These materials have been successfully used as catalyst precursor materials for C-C coupling reactions in which the active species is Pd(0). Pd-substituted LnFeO3 (Ln = Y, La) provides Pd(0) in solution which can be complexed by the ligand SPhos, allowing for aryl chloride coupling.

Simple organic cooperative assembly of triazine molecules leads to three-dimensional macroscopic assemblies of low-dimensional graphitic carbon nitrides (g-CNs), for example, nanoparticles, nanotubes, and nanosheets. The approach enables the characterization of the cooperative properties and photocatalytic activities of low-dimensional g-CN materials in hydrogen evolution reactions from water under visible light., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Delafossite CuCrO2 and spinel CuCr2O4 with mesoporous structures have been successfully synthesized using nanocasting methods based on a KIT-6 template. The functional activity of the mesoporous materials was evaluated in applications as heterogeneous catalysts. The activity for photocatalytic hydrogen production of the delafossite structures with different morphologies was characterized and the oxidation state changes associated with photocorrosion of Cu(+) investigated using electron energy loss spectroscopy (EELS). Mg(2+) doping was found to facilitate the casting of ordered structures for CuCrO2 and improves the photocorrosion resistance of delafossite structures. The mesoporous spinel CuCr2O4 nanostructures were found to be active for low temperature CO oxidation.

Half-Heusler thermoelectrics offer the possibility to choose from a variety of non-toxic and earth-abundant elements. TiNiSn is of particular interest and - with its relatively high electrical conductivity and Seebeck coefficient - allows for optimization of its thermoelectric figure of merit, reaching values of up to 1 in heavily-doped and/or phase-segregated systems. In this contribution, we used an energy- and time-efficient process involving solid-state preparation in a commercial microwave oven and a fast consolidation technique, Spark Plasma Sintering, to prepare a series of Ni-rich TiNi1+xSn with small deviations from the half-Heusler composition. Spark Plasma Sintering plays an important role in the process by being a part of the synthesis of the material rather than solely a densification technique. Synchrotron powder X-ray diffraction and microprobe data confirm the presence of a secondary TiNi2Sn full-Heusler phase within the half-Heusler matrix. We observe a clear correlation between the amount of full-Heusler phase and the lattice thermal conductivity of the samples, resulting in decreasing total thermal conductivity with increasing TiNi2Sn fraction. This trend shows that phonons are scattered effectively as a result of the microstructure of the materials with full-Heusler inclusions in the size range of microns to tens of microns. The best performing samples with around 5% of TiNi2Sn phase exhibit maximum figures of merit of almost 0.6 between 750 K and 800 K which is an increase of ca. 35% compared to the zT of the parent compound TiNiSn.

Efficient and cost-effective conversion of solar energy to useful chemicals and fuels could lead to a significant reduction in fossil hydrocarbon use. Artificial systems that use solar energy to produce chemicals have been reported for more than a century. However the most efficient devices demonstrated, based on traditionally fabricated compound semiconductors, have extremely short working lifetimes due to photocorrosion by the electrolyte. Here we report a stable, scalable design and molecular level fabrication strategy to create photoelectrochemically active heterostructure (PAH) units consisting of an efficient semiconductor light absorber in contact with oxidation and reduction electrocatalysts and otherwise protected by alumina. The functional heterostructures are fabricated by layer-by-layer, template-directed, electrochemical synthesis in porous anodic aluminum oxide membranes to produce high density arrays of electronically autonomous, nanostructured, corrosion resistant, photoactive units (~10(9)-10(10) PAHs per cm(2)). Each PAH unit is isolated from its neighbor by the transparent electrically insulating oxide cellular enclosure that makes the overall assembly fault tolerant. When illuminated with visible light, the free floating devices have been demonstrated to produce hydrogen at a stable rate for over 24 h in corrosive hydroiodic acid electrolyte with light as the only input. The quantum efficiency (averaged over the solar spectrum) for absorbed photons-to-hydrogen conversion was 7.4% and solar-to-hydrogen energy efficiency of incident light was 0.9%. The fabrication approach is scalable for commercial manufacturing and readily adaptable to a variety of earth abundant semiconductors which might otherwise be unstable as photoelectrocatalysts.

Polycrystalline Nd2Ru2O7 samples have been prepared and examined using a combination of structural, magnetic, and electrical and thermal transport studies. Analysis of synchrotron x-ray and neutron diffraction patterns suggests some site disorder on the A-site in the pyrochlore sublattice: Ru substitutes on the Nd-site up to 7.0(3)%, regardless of the different preparative conditions explored. Intrinsic magnetic and electrical transport properties have been measured. Ru 4d spins order antiferromagnetically at 143 K, as seen both in the susceptibility and in the specific heat, and there is a corresponding change in the electrical resistivity. The onset of a second antiferromagnetic ordering transition seen below 5 K is attributed to ordering of Nd 4f spins. Nd2Ru2O7 is an electrical insulator, and this behaviour is believed to be independent of the Ru-antisite disorder on the Nd-site. The electrical properties of Nd2Ru2O7 are presented in the light of data published on all A2Ru2O7 pyrochlores, and we emphasize the special structural role that Bi(3+) ions on the A-site play in driving metallic behaviour. High-temperature thermoelectric properties have also been measured. When considered in the context of known thermoelectric materials with useful figures-of-merit, it is clear that Nd2Ru2O7 has excessively high electrical resistivity which prevents it from being an effective thermoelectric. A method for screening candidate thermoelectrics is suggested.

Solar conversion to electricity or to fuels based on electron-hole pair production in semiconductors is a highly evolved scientific and commercial enterprise. Recently, it has been posited that charge carriers either directly transferred from the plasmonic structure to a neighbouring semiconductor (such as TiO₂) or to a photocatalyst, or induced by energy transfer in a neighbouring medium, could augment photoconversion processes, potentially leading to an entire new paradigm in harvesting photons for practical use. The strong dependence of the wavelength at which the local surface plasmon can be excited on the nanostructure makes it possible, in principle, to design plasmonic devices that can harvest photons over the entire solar spectrum and beyond. So far, however, most such systems show rather small photocatalytic activity in the visible as compared with the ultraviolet. Here, we report an efficient, autonomous solar water-splitting device based on a gold nanorod array in which essentially all charge carriers involved in the oxidation and reduction steps arise from the hot electrons resulting from the excitation of surface plasmons in the nanostructured gold. Each nanorod functions without external wiring, producing 5 × 10(13) H₂ molecules per cm(2) per s under 1 sun illumination (AM 1.5 and 100 mW cm(-2)), with unprecedented long-term operational stability.

Nanostructured Schottky inorganic-organic solar cells provide overall power conversion efficiencies exceeding 3%, with extremely large short-circuit photocurrents. The device EQE faithfully tracks the absorptance of the CdSe nanorods, and the IQE is approximately constant over the entire visible spectrum as opposed to a p-n junction hybrid solar cell fabricated with a highly absorbing organic polymer., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

We describe an inkjet printing assisted cooperative-assembly method for high-throughput generation of catalyst libraries (multicomponent mesoporous metal oxides) at a rate of 1,000,000-formulations/hour with up to eight-component compositions. The compositions and mesostructures of the libraries can be well-controlled and continuously varied. Fast identification of an inexpensive and efficient quaternary catalyst for photocatalytic hydrogen evolution is achieved via a multidimensional group testing strategy to reduce the number of performance validation experiments (25,000-fold reduction over an exhaustive one-by-one search).

We report a plasmonic water splitting cell in which 95% of the effective charge carriers derive from surface plasmon decay to hot electrons, as evidenced by fuel production efficiencies up to 20-fold higher at visible, as compared to UV, wavelengths. The cell functions by illuminating a dense array of aligned gold nanorods capped with TiO(2), forming a Schottky metal/semiconductor interface which collects and conducts the hot electrons to an unilluminated platinum counter-electrode where hydrogen gas evolves. The resultant positive charges in the Au nanorods function as holes and are extracted by an oxidation catalyst which electrocatalytically oxidizes water to oxygen gas.