Search

Electrochemical CO2 reduction (EC-CO2R) has seen a resurgence in interest over the past several years; however, the means of analyzing catalytically produced products continues to rely on decades-old methods such as gas chromatography, high-performance liquid chromatography, and nuclear magnetic resonance. Real-time analysis of the gaseous and liquid products of this reaction is highly desirable; however, few analytical techniques have been developed thus far to meet this need. Here, we demonstrate the first use of selected-ion flow-tube mass spectrometry (SIFT-MS) as an analytical tool capable of measuring in real time both the gas- and liquid-phase products of EC-CO2R in aqueous solution. SIFT-MS uses well-understood ion–molecule reactions to enable the analysis of similar multicomponent mixtures by preventing substantial fragmentation of the analyte. We lay out the framework in which to evaluate the tool's capabilities and show that the C1–C3 hydrocarbon, alcohol, and aldehyde products of CO2R should be quantitatively detectable.

Semiconductor compounds are widely used for photocatalytic hydrogen production applications, where photogenerated electron-hole pairs are exploited to induce catalysis. Recently, powders of a metallic oxide (Sr1-xNbO3, 0.033+δ and find that their bandgaps are ∼4.1 eV. Surprisingly, the carrier density of the conducting phase exceeds 1022 cm-3 and the carrier mobility is only 2.47 cm2 V-1 s-1. Contrary to earlier reports, the visible light absorption at 1.8 eV (∼688 nm) is due to the plasmon resonance, arising from the large carrier density. We propose that the hot electron and hole carriers excited via Landau damping (during the plasmon decay) are responsible for the photocatalytic property of this material under visible light irradiation.

Large polarons have been of significant recent technological interest as they screen and protect electrons from point-scattering centers. Anatase TiO 2 is a model system for studying large polarons as they can be studied systematically over a wide range of temperature and carrier density. The electronic and magneto transport properties of reduced anatase TiO 2 epitaxial thin films are analyzed considering various polaronic effects. Unexpectedly, with increasing carrier concentration, the mobility increases, which rarely happens in common metallic systems. We find that the screening of the electron-phonon (e-ph) coupling by excess carriers is necessary to explain this unusual dependence. We also find that the magnetoresistance could be decomposed into a linear and a quadratic component, separately characterizing the carrier transport and trapping as a function of temperature, respectively. The various transport behaviors could be organized into a single phase diagram, which clarifies the evolution of large polaron in this material.

With the rise in nosocomial infections worldwide, research on materials with an intrinsic ability to inhibit biofilm formation has been generating a great deal of interest. In the present work, we describe how thin film material libraries generated by pulsed laser deposition can be used for simultaneously screening several novel metal oxide mixtures that inhibit biofilm formation in a common human pathogen, Salmonella enterica serovar Typhimurium. We discovered that in a material library constructed using two metal oxides, the net effect on biofilm formation can be modeled as an addition of the activities of the individual oxides weighted to their relative composition at that particular point on the library. In contrast, for similar material libraries constructed using three metal oxides, there was a nonlinear relation between the amount of dominant metal oxide and the formation of Salmonella biofilms. This nonlinearity resulted in several useful metal oxide combinations that were not expected from the weighted average predictions. Our novel application will lead to the discovery of additional alternatives for creating antimicrobial surfaces.

Copper oxides have been of considerable interest as electrocatalysts for CO 2 reduction (CO2R) in aqueous electrolytes. However, their role as an active catalyst in reducing the required overpotential and improving the selectivity of reaction compared with that of polycrystalline copper remains controversial. Here, we introduce the use of selected-ion flow tube mass spectrometry, in concert with chronopotentiometry, in situ Raman spectroscopy, and computational modeling, to investigate CO2R on Cu 2 O nanoneedles, Cu 2 O nanocrystals, and Cu 2 O nanoparticles. We show experimentally that the selective formation of gaseous C 2 products (i.e., ethylene) in CO2R is preceded by the reduction of the copper oxide (Cu 2 OR) surface to metallic copper. On the basis of density functional theory modeling, CO2R products are not formed as long as Cu 2 O is present at the surface because Cu 2 OR is kinetically and energetically more favorable than CO2R.

Herein, we report a systematic study of water contact angle (WCA) of rare-earth oxide thin-films. These ultra-smooth and epitaxial thin-films were grown using pulsed laser deposition and then characterized using X-Ray diffraction (XRD), Rutherford backscattering spectroscopy (RBS), and atomic force microscopy (AFM). Through both the traditional sessile drop and the novel f-d method, we found that the films were intrinsically hydrophilic (WCA < 10°) just after being removed from the growth chamber, but their WCAs evolved with an exposure to the atmosphere with time to reach their eventual saturation values near 90° (but always stay 'technically' hydrophilic). X-Ray photoelectron spectroscopy analysis was used to further investigate qualitatively the nature of hydrocarbon contamination on the freshly prepared as well as the environmentally exposed REO thin-film samples as a function of the exposure time after they were removed from the deposition chamber. A clear correlation between the carbon coverage of the surface and the increase in WCA was observed for all of the rare-earth films, indicating the extrinsic nature of the surface wetting properties of these films and having no relation to the electronic configuration of the rare-earth atoms as proposed by Azimi et al.

This corrects the article DOI: 10.1038/nmat5009.

Non-volatile memories will play a decisive role in the next generation of digital technology. Flash memories are currently the key player in the field, yet they fail to meet the commercial demands of scalability and endurance. Resistive memory devices, and in particular memories based on low-cost, solution-processable and chemically tunable organic materials, are promising alternatives explored by the industry. However, to date, they have been lacking the performance and mechanistic understanding required for commercial translation. Here we report a resistive memory device based on a spin-coated active layer of a transition-metal complex, which shows high reproducibility (∼350 devices), fast switching (≤30 ns), excellent endurance (∼10 12  cycles), stability (>10 6  s) and scalability (down to ∼60 nm 2 ). In situ Raman and ultraviolet-visible spectroscopy alongside spectroelectrochemistry and quantum chemical calculations demonstrate that the redox state of the ligands determines the switching states of the device whereas the counterions control the hysteresis. This insight may accelerate the technological deployment of organic resistive memories.

Plasmonics has attracted tremendous interests for its ability to confine light into subwavelength dimensions, creating novel devices with unprecedented functionalities. New plasmonic materials are actively being searched, especially those with tunable plasmons and low loss in the visible-ultraviolet range. Such plasmons commonly occur in metals, but many metals have high plasmonic loss in the optical range, a main issue in current plasmonic research. Here, we discover an anomalous form of tunable correlated plasmons in a Mott-like insulating oxide from the Sr 1-x Nb 1-y O 3+δ family. These correlated plasmons have multiple plasmon frequencies and low loss in the visible-ultraviolet range. Supported by theoretical calculations, these plasmons arise from the nanometre-spaced confinement of extra oxygen planes that enhances the unscreened Coulomb interactions among charges. The correlated plasmons are tunable: they diminish as extra oxygen plane density or film thickness decreases. Our results open a path for plasmonics research in previously untapped insulating and strongly-correlated materials.

Strongly correlated electronic systems such as Transition Metal Oxides often possess various mid-gap states originating from intrinsic defects in these materials. In this paper, we investigate an extremely sharp Photoluminescence (PL) transition originating from such defect states in two widely used perovskites, LaAlO3 and SrTiO3. A detailed study of the PL as a function of temperature and magnetic field has been conducted to understand the behavior and origin of the transition involved. The temperature dependence of the PL peak position for SrTiO3 is observed to be opposite to that in LaAlO3. Our results reveal the presence of a spin/orbital character in these transitions which is evident from the splitting of these defect energy levels under a high magnetic field. These PL transitions have the potential for enabling non-contact thermal and field sensors.