Abstract
Monolayer transition metal dichalcogenides (TMD) have numerous potential applications in ultrathin electronics and photonics. The exposure of TMD-based devices to light generates ...photo-carriers resulting in an enhanced conductivity, which can be effectively used, e.g., in photodetectors. If the photo-enhanced conductivity persists after removal of the irradiation, the effect is known as persistent photoconductivity (PPC). Here we show that ultraviolet light (λ = 365 nm) exposure induces an extremely long-living giant PPC (GPPC) in monolayer MoS
2
(ML-MoS
2
) field-effect transistors (FET) with a time constant of ~30 days. Furthermore, this effect leads to a large enhancement of the conductivity up to a factor of 10
7
. In contrast to previous studies in which the origin of the PPC was attributed to extrinsic reasons such as trapped charges in the substrate or adsorbates, we show that the GPPC arises mainly from the intrinsic properties of ML-MoS
2
such as lattice defects that induce a large number of localized states in the forbidden gap. This finding is supported by a detailed experimental and theoretical study of the electric transport in TMD based FETs as well as by characterization of ML-MoS
2
with scanning tunneling spectroscopy, high-resolution transmission electron microscopy, and photoluminescence measurements. The obtained results provide a basis for the defect-based engineering of the electronic and optical properties of TMDs for device applications.
Plasmonic biosensing has emerged as the most sensitive label-free technique to detect various molecular species in solutions and has already proved crucial in drug discovery, food safety and studies ...of bio-reactions. This technique relies on surface plasmon resonances in ~50 nm metallic films and the possibility to functionalize the surface of the metal in order to achieve selectivity. At the same time, most metals corrode in bio-solutions, which reduces the quality factor and darkness of plasmonic resonances and thus the sensitivity. Furthermore, functionalization itself might have a detrimental effect on the quality of the surface, also reducing sensitivity. Here we demonstrate that the use of graphene and other layered materials for passivation and functionalization broadens the range of metals which can be used for plasmonic biosensing and increases the sensitivity by 3-4 orders of magnitude, as it guarantees stability of a metal in liquid and preserves the plasmonic resonances under biofunctionalization. We use this approach to detect low molecular weight HT-2 toxins (crucial for food safety), achieving phase sensitivity~0.5 fg/mL, three orders of magnitude higher than previously reported. This proves that layered materials provide a new platform for surface plasmon resonance biosensing, paving the way for compact biosensors for point of care testing.
Self-assembled monolayers (SAMs) of 1,1′-biphenyl-4-thiol (H–(C6H4)2–SH) on Au(111) were prepared from solution or via vapor deposition in ultrahigh vacuum and characterized by scanning tunneling ...microscopy (STM), low-energy electron diffraction (LEED), and X-ray photoelectron spectroscopy (XPS). In contrast to the typically observed for densely packed alkane-thiol SAMs on Au(111) (√3 × √3)R30° structure, the densely packed aromatic biphenylthiol SAMs prepared by both methods exhibit an unusual hexagonal (2 × 2) structure. Upon annealing at 100 °C, this structure evolves into the (2 × 7√3) structure resulting in the formation of highly ordered pinstripes oriented along the ⟨1 −1 0⟩ directions. Lower density SAMs, prepared by vapor deposition in vacuum, show mixed structures comprising the hexagonal (2 × 2) structure and two rectangular arrangements with the unit cells of (3√3 × 9) and (2√3 × 8). An extinction of the (3√3 × 9) structure in the favor of the (2√3 × 8) structure is observed upon annealing at temperatures of ∼100 °C.
In the framework of the CALPHAD method, the thermodynamic assessment of the Cu–Ti–Hf system has been performed for the first time. This assessment considers the existence of homogeneity regions for ...Cu
3
Ti
2
, Cu
4
Ti
3
, CuTi, Cu
5
Hf, Cu
51
Hf
14
, and Cu
10
Hf
7
compounds and the formation of a continuous solid solution of Cu(Ti, Hf)
2
(γ-phase) in the ternary system. The thermodynamic assessments of the boundary binary systems and data on phase transformations and mixing enthalpy of melts in the ternary system became the basis for calculations. The Compound Energy Formalism was used to model the thermodynamic properties of intermetallic compounds with a homogeneity region. The associated solution model was used to describe the complex temperature dependence of the thermodynamic properties of melts from the temperature at which equilibrium melts exist to the glass-formation temperature. Upon the calculations, isothermal sections, vertical sections, projections of the liquidus and solidus surfaces, and reaction scheme of the phase diagram were presented. The liquid phase participates in eleven four-phase invariant reactions occurring in the temperature range 1138–1541 K. The diagrams of metastable phase transformations involving supercooled Cu–Ti–Hf melts and boundary solid solutions based on pure components were calculated. It is shown that supercooled melts in wide concentration ranges are thermodynamically stable in relation to boundary solid solutions based on pure components. The concentration region of glass formation for Cu–Ti–Hf melts by liquid quenching, predicted by the relative position of the
T
0
L
/
ϕ
and
x
0
L
/
ϕ
lines, is
x
Cu
≈ 0.16–0.80.
The Ukrainian Phase Diagrams and Thermodynamics Commission has been a member of the Alloy Phase Diagram International Commission (APDIC) for almost thirty years (since 1994). APDIC unites 18 member ...organizations involving 26 countries. The main tasks of APDIC are the exchange of scientific information and coordination of the activities of the international scientific community, mainly in the field of state diagrams and phase thermodynamics. The annual report of the Ukrainian Commission on the results of the activities of Ukrainian scientists in this field in 2021 was presented at the APDIC meeting on May 27, 2022. This information is presented in a table, collecting data on the systems studied and the result obtained and containing a list of references to published papers. Scientists from the Frantsevich Institute for Problems of Materials Science (National Academy of Sciences of Ukraine, Kyiv), Taras Shevchenko National University of Kyiv (Ministry of Education and Science of Ukraine, Kyiv), and Donbas State Engineering Academy (Ministry of Education and Science of Ukraine, Kramatorsk) provided relevant information to the Ukrainian Commission.
Electron‐induced chemical lithography combined with self‐assembled monolayers and multivalent chelators for high‐affinity capturing of His‐tagged proteins are used to obtain specific, stable, highly ...parallel, and functional protein micro‐ and nanoarrays on solid substrates. The functionality of the generated large‐area protein arrays is shown in situ via specific, homogeneous, oriented and reversible immobilization of His6‐tagged 20S proteasome and fluorescence labelled His10‐tagged maltose binding proteins.
The main tasks of the international scientific organization Alloy Phase Diagram International Commission (APDIC), which unites 18 member organizations involving 26 countries, are the exchange of ...information and coordination of the activities of the international scientific community, mainly in the field of phase diagrams and thermodynamics. The Ukrainian Phase Diagrams and Thermodynamics Commission has been a member of APDIC since 1994. The annual report of the Ukrainian Commission on the results of the activities of Ukrainian scientists in this field in 2020 was presented at the APDIC meeting on June 18, 2021, which was held online due to the coronavirus pandemic. This information is presented in a table, collecting data on the studied systems and obtained result and containing a list of references to published papers. Scientists from the Frantsevich Institute for Problems of Materials Science (National Academy of Sciences of Ukraine, Kyiv), Taras Shevchenko National University of Kyiv (Ministry of Education and Science of Ukraine, Kyiv), and Donbas State Engineering Academy (Ministry of Education and Science of Ukraine, Kramatorsk) provided relevant information to the Ukrainian Commission.
•The thermodynamic description of the Cu–Fe–Ni system has been updated.•The new experimental data have been used to refine thermodynamic model of the system.•The four-sublattice model has been ...adopted to predict the equilibria involving the ordered L12 phase.•A significant improvement in comparison with the previous assessments has been achieved.•The liquidus and solidus projections have been presented.
The thermodynamic description of the Cu–Fe–Ni system has been updated considering the newly available experimental data, as well as compatibility of the present modeling with those used for the Cu and Fe systems. All of the experimental data available in the literature have been critically reviewed, and the inconsistent information has been excluded. The thermodynamic parameters have been evaluated in order to properly describe the thermodynamic properties of the liquid phase and miscibility gap in the solid state. A significant improvement in comparison with the previous thermodynamic descriptions has been achieved. Additionally, for the ordered L12 phase the four-sublattice model has been adopted to predict the ternary phase equilibria involving this phase. A set of thermodynamic parameters for the phases is given.
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