1,064 research outputs found
Robust surface electronic properties of topological insulators: Bi2Te3 films grown by molecular beam epitaxy
The surface electronic properties of the important topological insulator
Bi2Te3 are shown to be robust under an extended surface preparation procedure
which includes exposure to atmosphere and subsequent cleaning and
recrystallization by an optimized in-situ sputter-anneal procedure under ultra
high vacuum conditions. Clear Dirac-cone features are displayed in
high-resolution angle-resolved photoemission spectra from the resulting
samples, indicating remarkable insensitivity of the topological surface state
to cleaning-induced surface roughness.Comment: 3 pages, 3 figure
Electronic structure and magnetic properties of epitaxial FeRh(001) ultra-thin films on W(100)
Epitaxial FeRh(100) films (CsCl structure, thick), prepared
{\it in-situ} on a W(100) single crystal substrate, have been investigated via
valence band and core level photoemission. The presence of the
temperature-induced, first-order, antiferromagnetic to ferromagnetic
(AF FM) transition in these films has been verified via linear
dichroism in photoemission from the Fe 3 levels. Core level spectra indicate
a large moment on the Fe atom, practically unchanged in the FM and AF phases.
Judging from the valence band spectra, the metamagnetic transition takes place
without substantial modification of the electronic structure. In the FM phase,
the spin-resolved spectra compare satisfactorily to the calculated
spin-polarized bulk band structure.Comment: 7 pages, 5 figure
Infiltrated carbon foam composites
An infiltrated carbon foam composite and method for making the composite is described. The infiltrated carbon foam composite may include a carbonized carbon aerogel in cells of a carbon foam body and a resin is infiltrated into the carbon foam body filling the cells of the carbon foam body and spaces around the carbonized carbon aerogel. The infiltrated carbon foam composites may be useful for mid-density ablative thermal protection systems
Room temperature high frequency transport of Dirac fermions in epitaxially grown Sb_2Te_3 based topological insulators
We report on the observation of photogalvanic effects in epitaxially grown
Sb_2Te_3 three-dimensional (3D) topological insulators (TI). We show that
asymmetric scattering of Dirac electrons driven back and forth by the terahertz
electric field results in a dc electric current. Due to the "symmetry
filtration" the dc current is generated in the surface electrons only and
provides an opto-electronic access to probe the electric transport in TI,
surface domains orientation and details of electron scattering even in 3D TI at
room temperature where conventional surface electron transport is usually
hindered by the high carrier density in the bulk
Cascade kinetics in an enzyme-loaded aqueous two-phase system
Macromolecular crowding plays a critical role in the kinetics of enzymatic reactions. Dynamic compartmentalization of biological components in living cells due to liquid–liquid phase separation represents an important cell regulatory mechanism that can increase enzyme concentration locally and influence the diffusion of substrates. In the present study, we probed partitioning of two enzymes (horseradish-peroxidase and urate-oxidase) in a poly(ethylene glycol)–dextran aqueous two-phase system (ATPS) as a function of salt concentration and ion position in the Hofmeister series. Moreover, we investigated enzymatic cascade reactions and their kinetics within the ATPS, which revealed a strong influence of the ion hydration stemming from the background electrolyte on the partitioning coefficients of proteins following the Hofmeister series. As a result, we were able to realize cross-partitioning of two enzymes because of different protein net charges at a chosen pH. Our study reveals a strong dependency of the enzyme activity on the substrate type and crowding agent interaction on the final kinetics of enzymatic reactions in the ATPS and therefore provides substantial implications en route toward dynamic regulation of reactivity in synthetic protocells
Multifunctional Role of Magnetic Nanoparticles in Efficient Microalgae Separation and Catalytic Hydrothermal Liquefaction
In this work, the
efficiency of extracting algae from culture medium
using magnetic nanoparticles (MNPs), converting the algal/particle
slurry to biocrude using hydrothermal liquefaction (HTL), and successfully
recycling the MNPs from the char phase was fully demonstrated for
the first time. MNPs were synthesized by coprecipitation and used
to extract algae from aqueous phase at a separation efficiency (SE)
of 99%. The SE was optimized at pH 4. Liquefaction of algal/MNPs slurry
gave a biocrude yield of 37.1% while algae only yielded 23.2%. The
percentage areas in the GC-MS chromatogram corresponding to hydrocarbons
(HCs) in Zn-ferrite catalyzed and uncatalyzed biocrude were 46.5%
and 19.9%, respectively, while the percentage areas of heptadecane
from Zn-ferrite catalyzed and uncatalyzed biocrude were 37.8% and
10%, respectively. Furthermore, the percentage area of heteroatom
compounds in biocrude reduced substantially when liquefaction was
done in the presence of Zn/Mg ferrites. The nanoparticles were recovered
from biochar by sonication and recycled at a SE of 96.1%. Recycling
of MNPs for magnetic separation of algae and catalytic HTL could lower
the cost of microalgae harvesting and improve the yield and quality
of biocrude. This could potentially reduce the cost of advanced biofuel
processing from microalgae, making them more affordable in comparison
to petroleum-derived fuels
Direct observation of the band gap transition in atomically thin ReS
ReS is considered as a promising candidate for novel electronic and
sensor applications. The low crystal symmetry of the van der Waals compound
ReS leads to a highly anisotropic optical, vibrational, and transport
behavior. However, the details of the electronic band structure of this
fascinating material are still largely unexplored. We present a
momentum-resolved study of the electronic structure of monolayer, bilayer, and
bulk ReS using k-space photoemission microscopy in combination with
first-principles calculations. We demonstrate that the valence electrons in
bulk ReS are - contrary to assumptions in recent literature - significantly
delocalized across the van der Waals gap. Furthermore, we directly observe the
evolution of the valence band dispersion as a function of the number of layers,
revealing a significantly increased effective electron mass in single-layer
crystals. We also find that only bilayer ReS has a direct band gap. Our
results establish bilayer ReS as a advantageous building block for
two-dimensional devices and van der Waals heterostructures
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