Fe plays a critical, but not yet understood, role in enhancing the activity of the Ni-based oxygen evolution reaction (OER) electrocatalysts. We report electrochemical, in situ electrical, photoelectron spectroscopy, and X-ray diffraction measurements on Ni1–xFex(OH)2/Ni1–xFexOOH thin films to investigate the changes in electronic properties, OER activity, and structure as a result of Fe inclusion. We developed a simple method for purification of KOH electrolyte that uses precipitated bulk Ni(OH)2 to absorb Fe impurities. Cyclic voltammetry on rigorously Fe-free Ni(OH)2/NiOOH reveals new Ni redox features and no significant OER current until >400 mV overpotential, different from previous reports which were likely affected by Fe impurities. We show through controlled crystallization that β-NiOOH is less active for OER than the disordered γ-NiOOH starting material and that previous reports of increased activity for β-NiOOH are due to incorporation of Fe-impurities during the crystallization process. Through...

Nickel–Iron Oxyhydroxide Oxygen-Evolution Electrocatalysts: The Role of Intentional and Incidental Iron Incorporation

We have derived the general solution of a wave equation describing the dynamics of two-layer viscoelastic polymer materials of arbitrary thickness deposited on solid (quartz) surfaces in a fluid environment. Within the Voight model of viscoelastic element, we calculate the acoustic response of the system to an applied shear stress, i.e. we find the shift of the quartz generator resonance frequency and of the dissipation factor, and show that it strongly depends on the viscous loading of the adsorbed layers and on the shear storage and loss moduli of the overlayers. These results can readily be applied to quartz crystal acoustical measurements of the viscoelasticity of polymers which conserve their shape under the shear deformations and do not flow, and layered structures such as protein films adsorbed from solution onto the surface of self-assembled monolayers.

https://iopscience.iop.org/article/10.1238/Physica.Regular.059a00391/pdf

Viscoelastic Acoustic Response of Layered Polymer Films at Fluid-Solid Interfaces: Continuum Mechanics Approach

The gas sensors fabricated by using conducting polymers such as polyaniline (PAni), polypyrrole (PPy) and poly (3,4-ethylenedioxythiophene) (PEDOT) as the active layers have been reviewed. This review discusses the sensing mechanism and configurations of the sensors. The factors that affect the performances of the gas sensors are also addressed. The disadvantages of the sensors and a brief prospect in this research field are discussed at the end of the review.

/pdf/gas-sensors-based-on-conducting-polymers-4l6i49715q.pdf

Gas Sensors Based on Conducting Polymers

Membranes with unprecedented solvent permeance and high retention of dissolved solutes are needed to reduce the energy consumed by separations in organic liquids We used controlled interfacial polymerization to form free-standing polyamide nanofilms less than 10 nanometers in thickness, and incorporated them as separating layers in composite membranes Manipulation of nanofilm morphology by control of interfacial reaction conditions enabled the creation of smooth or crumpled textures; the nanofilms were sufficiently rigid that the crumpled textures could withstand pressurized filtration, resulting in increased permeable area Composite membranes comprising crumpled nanofilms on alumina supports provided high retention of solutes, with acetonitrile permeances up to 112 liters per square meter per hour per bar This is more than two orders of magnitude higher than permeances of commercially available membranes with equivalent solute retention

http://science.sciencemag.org/content/sci/348/6241/1347.full.pdf

Sub–10 nm polyamide nanofilms with ultrafast solvent transport for molecular separation

Protein adhesion plays a major role in determining the biocompatibility of materials. The first stage of implant integration is the adhesion of protein followed by cell attachment. Surface modification of implants (surface chemistry and topography) to induce and control protein and cell adhesion is currently of great interest. This communication presents data on protein adsorption (bovine serum albumin and fibrinogen) onto model hydrophobic (CH3) and hydrophilic (OH) surfaces, investigated using a quartz crystal microbalance (QCM) and grazing angle infrared spectroscopy. Our data suggest that albumin undergoes adsorption via a single step whereas fibrinogen adsorption is a more complex, multistage process. Albumin has a stronger affinity toward the CH3 compared to OH terminated surface. In contrast, fibrinogen adheres more rapidly to both surfaces, having a slightly higher affinity toward the hydrophobic surface. Conformational assessment of the adsorbed proteins by grazing angle infrared spectroscopy (GA...

Interpretation of Protein Adsorption: Surface-Induced Conformational Changes

Wird eine Fremdschicht auf eine zu Dickenscherungsschwingungen angeregte Schwingquarzplatte aufgebracht, so andert sich die Eigenfrequenz der Platte infolge Vergroserung der schwingenden Masse. Da die Frequenzanderung eines Schwingquarzes sehr genau vermessen werden kann, ergibt sich daraus eine sehr empfindliche Methode zur Wagung dunner Schichten. Massenbelegung der Fremdschicht und Frequenzanderung sind einander proportional. Die Proportionalitatskonstante last sich aus der Eigenfrequenz des Schwingquarzes berechnen, so das eine empirische Eichung bei der Schichtwagung mit Schwingquarzen entfallt. Die Genauigkeit des Schichtwageverfahrens ist in erster Linie durch die Temperaturabhangigkeit der Quarzeigenfrequenz begrenzt und betragt bei 1° C zugelassener Temperaturschwankung etwa ±4 · 10−9 g · cm−2. Das entspricht einer mittleren Dicke von 0,4 A bei der Dichte ϱ=1 g · cm−3. Das Verfahren wurde auch zur direkten Wagung einer Masse ausgenutzt (Mikrowagung). Dabei lies sich eine Genauigkeit von 10−10g erreichen.

Verwendung von Schwingquarzen zur Wägung dünner Schichten und zur Mikrowägung

Es wurde ein Mesverfahren beschrieben, das es gestattet, Schwingungsamplituden schwingender Platten mit extrem hoher Genauigkeit zu messen. Alle drei Komponenten der Plattenschwingung lassen sich mit diesem Verfahren getrennt messen. Das Verfahren beruht auf der Modulation eines schmalen Lichtbundels an einer schwingenden Kante. Bei den vorgelegten Messungen wurde mit einem AmplitudenauflosungsvermogenΔa≈1A. gearbeitet. Die Auflosungsgrenze ist jedoch nur durch das Signal/Rausch-Verhaltnis begrenzt, so das bei Verwendung von Beleuchtungsquellen groserer Leuchtdichte ein AmplitudenauflosungsvermogenΔa<10−10 cm erreichbar ist. Das Mesverfahren wurde zur Untersuchung der Schwingungsbilder dunner Schwingquarzplatten angewendet. Aus diesen Messungen wurden Beispiele angefuhrt, die den Einflus der Elektrodenmasse und der Plattenberandung auf die Schwingungsfigur zeigen.

Messung von Plattenschwingungen sehr kleiner Amplitude durch Lichtstrommodulation

The visible and ultraviolet radiation emitted from electron bombarded metal targets was investigated for normal and oblique electron incidence in the range of primary energiesE=6⋯40 keV. For normal incidence the observed spectra could be separated in transition radiation and bremsstrahlung because of their different energy dependences. When silver targets were bombarded at oblique incidence a third radiation was observed which is peaking nearλ=3500 A (half widthΔ λ=200⋯300 A). For grazing indicence (α=0,5° against the target surface) under UHV conditions the peak intensity is 100 times greater than transition radiation at normal incidence. Due to the wavelenght, the dependence on the angle of incidence, and the strong dependence on surface contaminations this radiation is assumed to be caused by surface plasmon excitation in the silver target.

Transition Radiation, Bremsstrahlung und Plasmastrahlung

A surface of a metal hit by electrons emits a radiation. Its spectrum covers the range of visible light and the ultra violett. This radiation was first observed byLilienfeld. We found that this radiation is not attributed to surface contaminations since it is also emitted from extremly clean metal surfaces. Spectrum, polarization, intensity, and temperature dependence of the radiation emitted by several metals were investigated. These measurements indicate that the Lilienfeld radiation can be interpreted as the transition radiation predicted byGinsburg andFrank. The possibilities of excitation of bremsstrahlung and plasma radiation are discussed.

Über die an Metallen durch Elektronen ausgelöste sichtbare und ultraviolette Strahlung

The transition (Lilienfeld) radiation emitted by an electron incident on a metal is studied for W, Ta, Mo, Ti, Pt, Ag, Ni, Al, Cu, and Cs. The radiation is found to be independent of the target temperature and gas pressure. The radiation is almost completely plane polarized, and forms a continuum. The radiation intensity is measured as functions of the target metal, emission angle, wavelength, electron energy, and current density. (T.F.H.)

G. Sauerbrey

Papers

Verwendung von Schwingquarzen zur Wägung dünner Schichten und zur Mikrowägung

Messung von Plattenschwingungen sehr kleiner Amplitude durch Lichtstrommodulation

Transition Radiation, Bremsstrahlung und Plasmastrahlung

Über die an Metallen durch Elektronen ausgelöste sichtbare und ultraviolette Strahlung

Experimental Detection of Transition Radiation