Diversity of solitary electron holes operating with non-perturbative trapping

Hans Schamel; Debraj Mandal; Devendra Sharma

doi:10.1063/5.0007941

Direct imaging of charge transfer

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100165860 ◽

1996 ◽

Vol 54 ◽

pp. 680-681

Author(s):

Yimei Zhu ◽

J. Tafto

Keyword(s):

Charge Transfer ◽

Electron Diffraction ◽

Scattering Amplitude ◽

High Temperature Superconductors ◽

Charge Carriers ◽

Image Charge ◽

Net Charge ◽

Long Time ◽

Electron Holes ◽

First Time

The electron holes confined to the CuO2-plane are the charge carriers in high-temperature superconductors, and thus, the distribution of charge plays a key role in determining their superconducting properties. While it has been known for a long time that in principle, electron diffraction at low angles is very sensitive to charge transfer, we, for the first time, show that under a proper TEM imaging condition, it is possible to directly image charge in crystals with a large unit cell. We apply this new way of studying charge distribution to the technologically important Bi2Sr2Ca1Cu2O8+δ superconductors.Charged particles interact with the electrostatic potential, and thus, for small scattering angles, the incident particle sees a nuclei that is screened by the electron cloud. Hence, the scattering amplitude mainly is determined by the net charge of the ion. Comparing with the high Z neutral Bi atom, we note that the scattering amplitude of the hole or an electron is larger at small scattering angles. This is in stark contrast to the displacements which contribute negligibly to the electron diffraction pattern at small angles because of the short g-vectors.

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Doping Effect in Nickel Oxide

Defect and Diffusion Forum ◽

10.4028/www.scientific.net/ddf.289-292.775 ◽

2009 ◽

Vol 289-292 ◽

pp. 775-782 ◽

Cited By ~ 1

Author(s):

Zbigniew Jurasz ◽

Krzysztof Adamaszek ◽

Romuald Janik ◽

Zbigniew Grzesik ◽

Stanisław Mrowec

Keyword(s):

Activation Energy ◽

Nickel Oxide ◽

High Temperatures ◽

Oxygen Pressure ◽

Pressure Dependence ◽

Oxidation Rate ◽

Doping Effect ◽

Self Diffusion ◽

Electron Holes ◽

Influence Of Impurities

Detailed investigations of nonstoichiometry as well as chemical and self-diffusion in nickel oxide have shown that doubly ionised cation vacancies and electron holes are the predominant defects in this material. The present work is an attempt to demonstrate that aliovalent impurities (Cr, Al, Na and Li) may considerably influence the concentration of these defects and, consequently, the oxidation rate of nickel at high temperatures. It has been shown that small amounts of tri-valent impurities (Cr, Al) bring about an increase of the oxidation rate, while mono-valent ones (Li, Na) decrease the rate of oxidation. These phenomena may satisfactorily be explained in terms of a doping effect. All experiments have been carried out as a function of temperature (1373-1673 K) and oxygen pressure (1-105 Pa) and consequently, it was possible to determine the influence of impurities not only on the oxidation rate but also on the activation energy of reaction and its pressure dependence. The results of these investigations could again be elucidated in terms of doping effect.

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Application of BiOX Photocatalysts in Remediation of Persistent Organic Pollutants

Catalysts ◽

10.3390/catal8120604 ◽

2018 ◽

Vol 8 (12) ◽

pp. 604 ◽

Cited By ~ 8

Author(s):

Robert Arthur ◽

John Ahern ◽

Howard Patterson

Keyword(s):

Photocatalytic Degradation ◽

Organic Pollutants ◽

Persistent Organic Pollutants ◽

Radical Scavenging ◽

Flow Chemistry ◽

Active Species ◽

Effective Strategies ◽

Degradation Of Dyes ◽

Bismuth Oxyhalides ◽

Electron Holes

Bismuth oxyhalides have recently gained attention for their promise as photocatalysts. Due to their layered structure, these materials present fascinating and highly desirable physicochemical properties including visible light photocatalytic capability and improved charge separation. While bismuth oxyhalides have been rigorously evaluated for the photocatalytic degradation of dyes and many synthesis strategies have been employed to enhance this property, relatively little work has been done to test them against pharmaceuticals and pesticides. These persistent organic pollutants are identified as emerging concerns by the EPA and effective strategies must be developed to combat them. Here, we review recent work directed at characterizing the nature of the interactions between bismuth oxyhalides and persistent organic pollutants using techniques including LC-MS/MS for the determination of photocatalytic degradation intermediates and radical scavenging to determine active species during photocatalytic degradation. The reported investigations indicate that the high activity of bismuth oxyhalides for the breakdown of persistent organic pollutants from water can be largely attributed to the strong oxidizing power of electron holes in the valence band. Unlike conventional catalysts like TiO2, these catalysts can also function in ambient solar conditions. This suggests a much wider potential use for these materials as green catalysts for industrial photocatalytic transformation, particularly in flow chemistry applications.

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Radiation in the neighbourhood of a double layer

Annales Geophysicae ◽

10.5194/angeo-32-677-2014 ◽

2014 ◽

Vol 32 (6) ◽

pp. 677-687 ◽

Cited By ~ 7

Author(s):

R. Pottelette ◽

M. Berthomier ◽

J. Pickett

Keyword(s):

Phase Space ◽

Electron Distribution ◽

Electron Distribution Function ◽

Source Region ◽

Double Layers ◽

Small Scale ◽

High Time Resolution ◽

Local Electron ◽

Nonlinear Phase ◽

Electron Holes

Abstract. In the auroral kilometric radiation (AKR) source region, acceleration layers narrow in altitude and associated with parallel field-aligned potential drops of several kV can be identified by using both particles and wave-field high time-resolution measurements from the Fast Auroral SnapshoT explorer spacecraft (FAST). These so-called double layers (DLs) are recorded around density enhancements in the auroral cavity, where the enhancement can be at the edge of the cavity or even within the cavity at a small scale. Once immersed in the plasma, DLs necessarily accelerate particles along the magnetic field lines, thereby generating locally strong turbulent processes leading to the formation of nonlinear phase space holes. The FAST data reveal the asymmetric character of the turbulence: the regions located on the high-potential side of the DLs are characterized by the presence of electron holes, while on the low-potential side, ion holes are recorded. The existence of these nonlinear phase space holes may affect the AKR radiation pattern in the neighbourhood of a DL where the electron distribution function is drastically different from a horseshoe shape. We present some observations which illustrate the systematic generation of elementary radiation events occurring significantly above the local electron gyrofrequency in the presence of electron holes. These fine-scale AKR radiators are associated with a local electron distribution which presents a pronounced beam-like shape.

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Brief Communication: The double layer in the separatrix region during magnetic reconnection

Nonlinear Processes in Geophysics ◽

10.5194/npg-22-167-2015 ◽

2015 ◽

Vol 22 (2) ◽

pp. 167-171

Author(s):

J. Guo ◽

B. Yu

Keyword(s):

Electron Beam ◽

Magnetic Reconnection ◽

Double Layer ◽

Particle In Cell ◽

Acoustic Instability ◽

Ion Acoustic ◽

Evolution Stage ◽

Spatial Size ◽

Electron Holes ◽

Observation Results

Abstract. With two-dimensional (2-D) particle-in-cell (PIC) simulations we investigate the evolution of the double layer (DL) driven by magnetic reconnection. Our results show that an electron beam can be generated in the separatrix region as magnetic reconnection proceeds. This electron beam could trigger the ion-acoustic instability; as a result, a DL accompanied with electron holes (EHs) can be found during the nonlinear evolution stage of this instability. The spatial size of the DL is about 10 Debye lengths. This DL propagates along the magnetic field at a velocity of about the ion-acoustic speed, which is consistent with the observation results.

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Nonlinear Alfvén waves, discontinuities, proton perpendicular acceleration, and magnetic holes/decreases in interplanetary space and the magnetosphere: intermediate shocks?

Nonlinear Processes in Geophysics ◽

10.5194/npg-12-321-2005 ◽

2005 ◽

Vol 12 (3) ◽

pp. 321-336 ◽

Cited By ~ 64

Author(s):

B. T. Tsurutani ◽

G. S. Lakhina ◽

J. S. Pickett ◽

F. L. Guarnieri ◽

N. Lin ◽

...

Keyword(s):

Interplanetary Space ◽

Alfven Waves ◽

Alfven Wave ◽

Alfvén Waves ◽

Reverse Shock ◽

Propagating Waves ◽

Mirror Mode ◽

Interaction Regions ◽

Electron Holes ◽

Proton Cyclotron

Abstract. Alfvén waves, discontinuities, proton perpendicular acceleration and magnetic decreases (MDs) in interplanetary space are shown to be interrelated. Discontinuities are the phase-steepened edges of Alfvén waves. Magnetic decreases are caused by a diamagnetic effect from perpendicularly accelerated (to the magnetic field) protons. The ion acceleration is associated with the dissipation of phase-steepened Alfvén waves, presumably through the Ponderomotive Force. Proton perpendicular heating, through instabilities, lead to the generation of both proton cyclotron waves and mirror mode structures. Electromagnetic and electrostatic electron waves are detected as well. The Alfvén waves are thus found to be both dispersive and dissipative, conditions indicting that they may be intermediate shocks. The resultant "turbulence" created by the Alfvén wave dissipation is quite complex. There are both propagating (waves) and nonpropagating (mirror mode structures and MDs) byproducts. Arguments are presented to indicate that similar processes associated with Alfvén waves are occurring in the magnetosphere. In the magnetosphere, the "turbulence" is even further complicated by the damping of obliquely propagating proton cyclotron waves and the formation of electron holes, a form of solitary waves. Interplanetary Alfvén waves are shown to rapidly phase-steepen at a distance of 1AU from the Sun. A steepening rate of ~35 times per wavelength is indicated by Cluster-ACE measurements. Interplanetary (reverse) shock compression of Alfvén waves is noted to cause the rapid formation of MDs on the sunward side of corotating interaction regions (CIRs). Although much has been learned about the Alfvén wave phase-steepening processfrom space plasma observations, many facets are still not understood. Several of these topics are discussed for the interested researcher. Computer simulations and theoretical developments will be particularly useful in making further progress in this exciting new area.

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Ag–Au Core–Shell Triangular Nanoprisms for Improving p-g-C3N4 Photocatalytic Hydrogen Production

Nanomaterials ◽

10.3390/nano11123347 ◽

2021 ◽

Vol 11 (12) ◽

pp. 3347

Author(s):

Yali Guo ◽

Anzhou Xu ◽

Juan Hou ◽

Qingcui Liu ◽

Hailong Li ◽

...

Keyword(s):

Hydrogen Production ◽

Self Assembly ◽

Rational Design ◽

Photogenerated Electron ◽

Core Shell ◽

Co Catalyst ◽

Replacement Method ◽

Assembly Method ◽

Free Replacement ◽

Electron Holes

Ag–Au core–shell triangular nanoprisms (Ag@Au TNPs) have aroused extensive research interest in the field of hydrogen evolution reaction (HER) due to their strong plasmon effect and stability. Here, Ag@Au TNPs were fabricated by the galvanic-free replacement method. Then, we loaded them on protonated g-C3N4 nanoprisms (P–CN) by the electrostatic self-assembly method as an efficient plasmonic photocatalyst for HER. The hydrogen production rate of Ag@Au TNPs/P–CN (4.52 mmol/g/h) is 4.1 times higher than that of P–CN (1.11 mmol/g/h) under simulated sunlight irradiation, making it the most competitive material for water splitting. The formed Schottky junction helps to trap the hot electrons generated from Ag@Au TNPs, and the well-preserved tips of the Ag@Au TNPs can effectively generate an electromagnetic field to inhibit the photogenerated electron–holes pairs recombination. This study suggests that the rational design of Ag@Au TNPs by the galvanic-free replacement method is an effective co-catalyst for HER and boosting the additional combination of plasmonic metals and catalyst metals for the enhancement to HER.

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Switching Between Enantiomers by Combining Chromoselective Photocatalysis and Biocatalysis

10.26434/chemrxiv.13521527.v1 ◽

2021 ◽

Author(s):

Luca Schmermund ◽

Susanne Reischauer ◽

Sarah Bierbaumer ◽

Christoph Winkler ◽

Alba Diaz-Rodriguez ◽

...

Keyword(s):

Photocatalytic Oxidation ◽

Green Light ◽

Light Irradiation ◽

Thermal Processes ◽

Rhodococcus Ruber ◽

Oxidation Potentials ◽

Enzymatic Cascades ◽

Electron Holes ◽

External Stimuli ◽

Generate Electron

<a></a><a></a><a></a><a></a><a></a><a>Controlling the selectivity of a chemical reaction with external stimuli is common in thermal processes, but rare in visible-light photocatalysis. Here we show that the redox potential of a carbon nitride photocatalyst (CN-OA-m) can be tuned by changing the irradiation wavelength to generate electron holes with different oxidation potentials. This tuning was the key to realizing photo-chemo-enzymatic cascades that give either the (S)- or the (R)-enantiomer of phenylethanol. In combination with an unspecific peroxygenase from Agrocybe aegerita, green light irradiation of CN-OA-m led to the enantioselective hydroxylation of ethylbenzene to (R)-1-phenylethanol (99% ee). In contrast, blue light irradiation triggered the photocatalytic oxidation of ethylbenzene to acetophenone, which in turn was enantioselectively reduced with an alcohol dehydrogenase from Rhodococcus ruber to form (S)-1-phenylethanol (93% ee).</a><a></a>

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