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A cation exchange strategy is proposed to convert layered Ti3C2–Na–TiO2 MXene nanofibers into Ti3C2–Co–TiO2 MXene nanoparticle arrays with 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 (

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.

The construction of heterostructures with engineered phases and interfaces is crucial to essentially reform the oxygen evolution reaction (OER) in water splitting. Herein, a fine ion exchange route combined subsequent...

A cation exchange strategy is proposed to convert layered Ti

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 addition of redox-active molecules into electrochemical-capacitor electrolytes provides increased specific energy density. Here we illustrate the underlying operational mechanisms and design pr...

Great effort has recently been made to develop unique nanomaterials with superior reflection loss (RL), thin thickness, wide bandwidth and low density to improve their efficiency in electromagnetic (EM) microwave absorption, while maintaining a simple manufacturing process. The use of traditional nanomaterials with magnetic loss or dielectric loss, of course, not only makes the last requirement hard to meet but also restricts the thickness of absorber, and limits mass production. Recently, some promising nanomaterials with excellent conduction loss and polarization loss have been explored which promise to enable unique nanostructures with multiple reflections and interfacial polarization. Herein, we discuss the EM microwave absorption theory. Then, we review recent achievements in manufacturing EM microwave absorption materials, particularly focusing on the unique and key factors in design and control of structures and components. In addition, current challenges are presented, and prospects for future development in this rapidly blossoming field are discussed.

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

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 c...

Understanding the role of the morphology and particle–particle interactions on the plasmonic properties is of significant importance for the development of nanomaterials with excellent optical properties. However, the preparation of precisely defined nanomaterials with sizes that span a large range and their controllable self-assembly still remain a great challenge. Here, a multistep seed-mediated method has been established for preparing uniform Ag nanocubes over a broad size range from nanoscale (50 nm) to microscale (1400 nm) and with different hierarchical nanostructures range from “zero-dimension” (“0D”) to “three-dimension” (“3D”). The influence of the size and the interactions between the Ag nanocubes on their surface-enhanced Raman scattering (SERS) properties have been systematically and quantitatively investigated. It is demonstrated through experiments and finite-difference time-domain (FDTD) calculations that the SERS activity is dependent on the matching of the nanocube size to the excitation wavelength. The optimal combinations are 80, 110 and 130 nm nanocubes with respect to 532, 638 and 785 nm excitation wavelength, respectively. Furthermore, the Raman enhancement of the Ag nanocube hierarchical nanostructures increases rapidly from “0D” to “3D”, due to the extra increase of the hot spots that is attributed to the out-of-plane plasmonic coupling realized in the “3D” hierarchical nanostructures. This work clearly illustrates the quantitative role of the size and dimension of Ag nanocubes on their SERS properties and provides fundamental information for the design of advanced nanomaterials with higher SERS sensitivity.

Manganese oxides are promising water oxidation catalysts that have attracted great interest in the fuel cell industry. Previous studies have investigated differences in electrode activity based on the phases of MnO2 involved determining structures and composition ex-situ. Here we compare two preparations of MnO2 films, with differing catalytic activities as prepared, and observe morphological changes as a function of increasingly oxidizing potentials using in-operando Raman spectroscopy. We find that the Raman spectra of the films, both as-deposited and in solution, can be modelled as a binary mixture of amorphous manganese oxide and pure-phase cryptomelane that develop greater cryptomelane (α-MnO2) character as the oxidizing potential increases in 1M KOH. Analyzing the Raman spectra using classical least squares fitting, we determine that both films converge on a cryptomelane score of approximately 0.25; concurrently their catalytic activities improve. These results suggest that significant variations in electrocatalytic activity arise from short range ordering in the catalyst that is not easily determined using ex-situ structure determination.

Carbon-based anode materials hold a promising future for sodium-ion batteries (SIBs) due to their natural abundance and low cost of development. In spite of carbon's important role in the commercialization of lithium-ion batteries (LIBs), further exploration is necessary in order to find high-performance, high-rate carbon anode materials for SIBs. A honeycomb-like, nitrogen-rich (17.72 at%), hierarchically porous, and highly disordered carbonaceous material (N-HC) with an expanded interlayer distance (0.44 nm in average) is synthesized by spray drying and subsequent pyrolysis under flowing NH3. The hierarchically porous structure and rich nitrogen doping result in a large specific surface area (722 m2 g−1), more defects and active sites, and greater functional interface accessibility for the active porous carbonaceous material and electrolyte. When N-HC is used as the anode material for SIBs, the batteries display favorable discharge capacities (255.9 mA h g−1 in the 3000th cycle at 500 mA g−1) and good capacitive-energy-storage behavior (67% at a scan rate of 0.5 mV s−1) with excellent high-rate performance and ultra-stable cyclability over 10,000 cycles at 5000 mA g−1. Our results show that the combination of the hierarchically porous structure and nitrogen doping leads to improved energy storage by increasing the capacitive energy storage, which enhances the high-rate performance of N-HC. To further enhance the performance of the material, an electrical pretreatment is employed to increase the initial Coulombic efficiency of N-HC to 79.5%, a record high for an SIB cell. A full cell with an N-HC anode and a Na3V2(PO4)3/C cathode shows a high capacity with a favorable cyclability (238.7 mA h g−1 after 100 cycles at 100 mA g−1 and a capacity retention of 95.3% compared to the second cycle).

We report a simple one-pot solvothermal method of a FeS2/CNT (carbon nanotube) neural network nanostructure composite (FeS2/CNT-NN) that exhibits outstanding electrochemical performance as a sodium-ion battery anode. In these composites, uniform microspheres assembled from FeS2 nanoparticles act as “somas” and CNTs act as “neurites”. The weight ratio of FeS2 to CNTs affects not only the composite morphology, but also the sodium-ion storage performance. By optimizing this ratio, we achieve stable capacities up to 394 mA h g−1 after 400 cycles at 200 mA g−1. Most impressively, when the current densities are increased, excellent capacity and stability are maintained. At 1 A g−1 to 22 A g−1, surprisingly high capacities of 309 mA h g−1 to 254 mA h g−1 are maintained after 1800 cycles and 8400 cycles, respectively. The excellent electrochemical performance has been found to originate from the unique neural network structure, which offers high surface area and small FeS2 particle size for sufficient sodiation and desodiation, and enough room and mechanical integrity for volume expansion. Pseudocapacitance has also been found to dominate in the redox reactions, accounting for the outstanding rate and cycling performance. The excellent charge-discharge performance shows that FeS2/CNT-NN composites are promising candidates for rechargeable sodium-ion batteries.

A critical bottleneck in the development of aqueous electrochemical energy storage systems is the lack of viable complete cell designs. We report a metal-free, bipolar pouch cell designed with carbon black/polyethylene composite film (CBPE) current collectors as a practical cell architecture. The light-weight, corrosion-resistant CBPE provides stable operation in a variety of aqueous electrolytes over a ∼2.5 V potential range. Because CBPE is heat-sealable, it serves simultaneously as both the pouch cell packaging and seal in addition to its use as a current collector. Although this non-metallic composite has a low electrical conductivity relative to metal foils, current travels only a short distance in the through-plane direction of the current collector in the bipolar cell configuration. This shorter path length lowers the effective electrical resistance, making the design suitable for high-power applications. We test the cell architecture using an aqueous ZnBr2 battery chemistry and incorporate tetrabutylammonium cations to improve the intrinsic low Coulombic efficiency and fast self-discharge of non-flow ZnBr2 cells. These devices demonstrate a cell-level energy density of 50 W h L−1 at a 10C rate (0.5 kW L−1), with less than 1% capacity loss over 500 cycles. A large-area (>6 cm2) 4-cell stack is built to illustrate that the pouch cells are scalable to practical dimensions and stackable without sacrificing performance. The device operates in the range of 6–7 V and has an internal self-balancing mechanism that prevents any individual cell in the stack from overcharging. The results thus demonstrate both a conceptually new cell architecture that is broadly applicable to many aqueous electrolyte chemistries and a specific high-performance example thereof.

Redox-enhanced electrochemical capacitors (redox ECs) are a class of augmented electric double-layer capacitors utilizing reversible redox reactions of soluble redox couples in the electrolyte. These systems offer increased energy density, efficient power delivery, and simple construction. In this Perspective, we provide an overview of the emerging field of redox ECs, including the current status, advantages, and outstanding problems confronting their development. Our discussion is primarily focused on operating mechanisms and how they affect performance. We also provide a perspective on the advantage of dual-redox ECs and how to improve them based on fundamental design principles including self-discharge suppression strategies. Finally, we comment on best practices for device characterization, suggest performance-reporting protocols for redox ECs, and examine future directions for the field.

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 Br2/Br3–. This mechanism solves the inherent cross-diffusion i...

While silver and gold have been the dominant plasmonic metals used for surface-enhanced Raman spectroscopy (SERS) since the field’s inception. We argue that virtually any metal, when appropriately nanostructured as a grating, has the potential to be an efficient SERS substrate. This conclusion provides the basis for making SERS a general tool for studying surface processes and catalysis and allows SERS substrates to be routinely based on earth-abundant, low-cost, and chemically interesting metals. We illustrate the above premise by producing highly performing SERS substrates using aluminum, nickel, and copper in addition to silver and gold as benchmarks. All five metals were found to yield high SERS intensities. The approximately three orders enhancement variation among the five substrates based on differing metals is ascribed mainly to local field effects associated with individual grating elements. This conclusion is supported by local field calculations. This suggests that the largest contribution to t...

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-Fe3 O4 NPs grafted with polymer brushes of different hydrophilicity on Au and Fe3 O4 surfaces separately. Like liposomes, the vesicle shell is composed of two layers of Au-Fe3 O4 NPs in opposite direction, and the orientation of Au or Fe3 O4 in the shell can be well controlled by exploiting the amphiphilic property of the two types of polymers.

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

SiC oxidizes and is structurally unstable at temperatures above 1000 ​°C in a water-containing oxidative gaseous environment. Herein, we explore the hydrothermal stability of high-surface-area mesoporous SiC (m-SiC) prepared using Pluronic F-127 as structure directing agent, with and without boron doping as synthesized by a magnesiothermic reduction method (700 ​°C for 12 ​h). Under hydrothermal treatment at 800 ​°C in a water-saturated air stream, the undoped m-SiC is completely oxidized and reduced to amorphous SiO2. Lightly doped boron-substituted m-SiC (m-BxSiC, B/Si ​= ​0.04) is significantly more stable and retains the structural characteristics of m-SiC. m-BxSiC shows significant (300 ​°C) catalytic performance (CO conversion, HC conversion, and NO oxidation), better Pt dispersibility, and retention of a smaller Pt particle size. Studies of hierarchically porous m-BxSiC/PS prepared with F-127 and polystyrene dual templating further confirmed the enhancement by boron doping of the 800 ​°C hydrothermal stability and the 300 ​°C catalytic activity.

A large (40 mm ϕ) composite membrane with mesoporous silica nanotubes (F127MST) was coated with a thin carbon layer (1–2 graphene sheets) by carrying out chemical vapor deposition (CVD) using acetylene, and the obtained carbon-coated F127MST (C/F127MST) was used directly as an electrode. After evaluating the electrical conductivity inside the continuous mesopore network, the enzyme bilirubin oxidase (BOD) was loaded into the mesopores of C/F127MST to form BOD–C/F127MST. Indeed, this loading procedure was effective and achieved direct electron transfer between the enzymes and electrodes. The loading also was found to enhance the stability of stored BOD (it was stable for 15 days) and could be used to control the enzymatic reaction by varying the electric potential. We therefore consider BOD–C/F127MST to be a promising candidate as an effective bioelectrode in various fields.

AgPd alloy nanoparticles deposited on carbon nitride have been synthesized by a facile one-step reduction method and exhibit high catalytic activity at near room temperature (30 °C) for formic acid dehydrogenation, both under visible light and in darkness. The study proves that using the synergistic combination of alloying effects and metal-support interactions greatly enhances the catalytic activity of Pd-based nanocatalysts for hydrogen generation.

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 lithium-ion batteries (LIBs)/sodium-ion batteries (SIBs) with high energy density is vital to meet increasingly demanding requirements for energy storage. The initial Coulombic efficiency (ICE) of LIBs and SIBs anode materials, which is associated with the amount of redundant cathode materials in full cells, is a key parameter for the improvement of energy density in batteries. Generally, the low ICE of anode materials is compensated by additional loading of cathode materials in current commercial LIBs. Nevertheless, because the specific capacity of common lithium-metal oxide cathodes is lower than that of anodes, an excessive amount of cathode materials (10%–15% for graphite anode material) must be added to overcome the insufficient ICE of anode materials, which leads to an appreciable reduction of energy density. Specifically, the reduction is about 5%–20% of total available capacity in commercial graphite electrodes; and, it can even be as high as 15–50% for next-generation high-capacity anode materials (such as Si and Sn). Much work has been devoted to exploring anode materials with high ICE in LIBs/SIBs; however, to the best of our knowledge, there does not yet exist a comprehensive review. Herein, we provide an overview of ICE of anode materials both in LIBs and SIBs. In this review, we first discuss the current understanding of the association between ICE and energy density. This is followed by a detailed assessment of the reasons of the initial capacity loss (low ICE) for various types of anode materials. A summary is then given of the growing number of methods and related fundamental mechanisms being used to enhance ICE. We conclude with a perspective on the current challenges and promising research directions that might lead to further improvements of the ICE and the fabrication of higher-energy-density batteries.

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.

One model for the emergence of life posits that ancient, low temperature, submarine alkaline hydrothermal vents, partly composed of iron-sulfides, were capable of catalyzing the synthesis of prebiotic organic molecules from CO2, H2 and CH4. Specifically, hydrothermal mackinawite (FeIIS) and greigite (FeIIFeIII2S4) have been highlighted in previous studies as analogs of the active centers of hydrogenase, ferredoxin, acetyl coenzyme-A synthase and carbon monoxide dehydrogenase featured in the biochemistry of certain autotrophic prokaryotes that occupy the base of the evolutionary tree. Despite the proposed importance of iron sulfide minerals and clusters in the synthesis of abiotic organic molecules, the mechanisms for the formation of these sulfides from solution and their preservation under the anoxic and low temperature (below 100 °C) conditions expected in off-axis submarine alkaline vent systems is not well understood ( Bourdoiseau et al., 2011 , Rickard and Luther, 2007 ). To rectify this, single hydrothermal chimneys were precipitated using a unique apparatus to simulate growth at hydrothermal vents of moderate temperature under supposed Hadean ocean-bottom conditions. Iron sulfide phases were observed through Raman spectroscopy at growth temperatures ranging from 40° to 80 °C. Fe(III)-containing mackinawite is confirmed to be present with mackinawite and greigite, supporting an FeIII-mackinawite intermediate mechanism for the transformation of mackinawite to greigite below 100 °C. Raman spectroscopy of the chimneys revealed a maximum yield of greigite at 75 °C. These results suggest abiotic production of catalytically active mackinawite and greigite are possible under early Earth hydrothermal conditions as well as on other wet, rocky worlds geochemically similar to the Earth.

We propose a nanostructured Mn-doped V2O5 lithium-ion battery cathode material that facilitates cathodic charge transport. The synthesis strategy uses a layered compound, vanadium(III) jarosite, as the precursor, in which the Mn2+ ions are doped uniformly between the vanadium oxide crystal layers. Through a two-step transformation, the vanadium jarosite was converted into Mn2+-doped V2O5. The resulting aliovalent doping of the larger Mn cations in the modified V2O5 structure increases the cell volume, which facilitates diffusion of Li+ ions, and introduces oxygen vacancies that improve the electronic conductivity. Comparison of the electrochemical performance in Li-ion batteries of undoped and the Mn2+-doped V2O5 hierarchical structure made from layered vanadium jarosite confirms that the Mn-doping improves ion transport to give a high cathodic columbic capacity (253 mAhg–1 at 1C, 86% of the theoretical value, 294 mAhg–1) and excellent cycling stability.

Comparing active site reactivity Noble metal nanoparticles often exhibit behaviors distinct from atomic and bulk versions of the same material. Gold and platinum dispersed on metal oxide supports, for example, show remarkable low-temperature reactivity for carbon monoxide (CO) oxidation by oxygen or water. Ding et al. used infrared spectroscopy to identify CO adsorbed on isolated platinum atoms or nanoparticles dispersed on zeolite and oxide supports. Temperature-programmed desorption studies showed that CO reacted at much lower temperatures when adsorbed on nanoparticles versus on isolated metal atoms. Science , this issue p. 189

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 on the negative electrode, 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 spectrometry 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 to 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.

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).

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.

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 ωp, 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 extrac...

We report nickel oxide encapsulated nitrogen-rich carbon hollow spheres with multiporosity, where micropores increase the number of active sites to store redox ions and mesopores enhance the ionic diffusivity of encapsulated nickel oxide, which lead to high capacitance and robust cycle life. Moreover, a high-performance full capacitor showing excellent energy and power densities is realized.

We report utilization of graphitic carbon nitride (g-CN) as an electrocatalyst for dye-sensitized solar cells (DSSCs). Crystalline poly(triazine imide) based g-CN was synthesized via a modified ionothermal method, and deposited onto the counter electrodes along with a conductive additive and a sacrificial polymer binder. The resulting DSSCs exhibited a power conversion efficiency (7.8%) comparable to that of conventional Pt catalyst (7.9%), confirming the excellent catalytic activity of poly(triazine imide) g-CN as a non-precious metal electrocatalyst.

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.