Search

An inverse patchy colloid (IPC) refers to a particle having patches that are mutually repulsive while the bare particle–patch interactions are attractive. We model a system of charged IPCs with a s...

We consider a double-layer structure consisting of a bilayer graphene sheet and a two-dimensional electron gas, isolated in a very thin GaAs quantum well. The collective excitations are determined from the zeroes of the dynamical dielectric function within the random-phase approximation, taking into account the temperature effects. Numerical calculations present that two plasmon modes exist in the system, similar to those in other double-layer structures. While the optical mode continues in the interband single-particle excitation area, the acoustic mode only crosses the intraband single-particle excitation boundary and disappears. Also, our investigations show that plasmon properties in the system are affected significantly by most of the chosen factors. Plasmon frequency increases as the separation increases while the increase in carrier density decreases noticeably these frequencies. Temperature affects plasmon characters similarly to but more weakly than that does in monolayer grapheme—two-dimensional electron gas double-layer structures. Finally, the temperature can increase the effects of some other parameters on plasmon properties of the system, so this factor should be taken into account in calculations to improve the model for better results.

The application of electrochemical potentials to surfaces is an easy and direct way to alter surface charge density, the structure of the electrochemical double layer, and the presence of electrochemically activated species. On such electrified interfaces the formation of biofilms is reduced. Here we investigate how applied potentials alter the colonization of surfaces by the marine bacterium Cobetia marina and the marine diatom Navicula perminuta. Different constant potentials between -0.8 and 0.6 V as well as regular switching between two potentials were investigated, and their influence on the attachment of the two biofilm-forming microorganisms on gold-coated working electrodes was quantified. Reduced bacteria and diatom attachment were found when negative potentials and alternating potentials were applied. The results are discussed on the basis of the electrochemical processes occurring at the working electrode in artificial seawater as revealed by cyclic voltammetry.

Diffusiophoresis of a charge regulated spherical polyelectrolyte nanogel (PE) due to an externally imposed ionic concentration gradient is considered. The immobile charge density of the nanogel develops through the association/dissociation reactions of their inorganic functional groups. The nanogel is ion and fluid permeable with dielectric permittivity different from that of the surrounding electrolyte medium. This difference in dielectric permittivity creates an ion partitioning due to the difference in self energy of ions. The Nernst–Planck equation for ion transport and the Poisson equation (PNP) for the electric field are modified to take into account the ion partitioning effects. The diffusiophoresis mechanism is governed by the electrophoresis generated by the induced electric field and chemiphoresis develops due to the mitigation of counterions across the double layer of the nanogel. In addition, the convection dominated double layer polarization and the counterion condensation as well as the electroosmotic flow created by the gel immobile charge play a role in the diffusiophoresis. All these effects are incorporated through the modified PNP equations coupled with the Navier–Stokes equations. The governing equations in their full form are solved numerically through a control volume approach. Present computed solutions for the limiting cases are in good agreement with the existing solutions based on the first-order perturbation analysis. In order to illustrate the diffusiophoresis mechanism we have measured the induced electric field and effective charge density of the PE and analyzed its dependence on several electrokinetic parameters. The contribution due to chemiphoresis is low for PE compared to a rigid colloid. For a highly permeable PE the diffusiophoretic velocity increases and approaches a saturation for higher range of the PE fixed charge density. The ion partitioning effect depletes counterions in PE to manifests its diffusiophoretic velocity. The diffusiophoretic velocity of PE for pH > IEP is higher than the case for which pH

External magnetic fields affect various electrochemical processes and can be used to enhance the efficiency of the electrochemical water splitting reaction. However, the driving forces behind this effect are poorly understood due to the analytical challenges of the available interface-sensitive techniques. Here, we present a set-up based on magneto- and electro-optical probing, which allows to juxtapose the magnetic properties of the electrode with the electrochemical current densities in situ at various applied potentials and magnetic fields. On the example of an archetypal hydrogen evolution catalyst, Pt (in a form of Co/Pt superlattice), we provide evidence that a magnetic field acts on the electrochemical double layer affecting the local concentration gradient of hydroxide ions, which simultaneously affects the magneto-optical and magnetocurrent response.

Two-dimensional systems that host one-dimensional helical states are exciting from the perspective of scalable topological quantum computation when coupled with a superconductor. Graphene is particularly promising for its high electronic quality, versatility in van der Waals heterostructures and its electron and hole-like degenerate 0$th$ Landau level. Here, we study a compact double layer graphene SQUID (superconducting quantum interference device), where the superconducting loop is reduced to the superconducting contacts, connecting two parallel graphene Josephson junctions. Despite the small size of the SQUID, it is fully tunable by independent gate control of the Fermi energies in both layers. Furthermore, both Josephson junctions show a skewed current phase relationship, indicating the presence of superconducting modes with high transparency. In the quantum Hall regime we measure a well defined conductance plateau of 2$e^2/h$ an indicative of counter propagating edge channels in the two layers. Our work opens a way for engineering topological superconductivity by coupling helical edge states, from graphene's electron-hole degenerate 0$th$ Landau level via superconducting contacts., 38 pages, 12 figures

Relevant fundamentals of the electrochemical double layer and supercapacitors utilizing the interfacial capacitance as well as superficial redox processes at the electrode/solution interface are briefly reviewed. Experimental methods for the determination of the capacity of electrochemical double layers, of charge storage electrode materials for supercapacitors, and of supercapacitors are discussed and compared. Intrinsic limitations and pitfalls are indicated; popular errors, misconceptions, and mistakes are evaluated. The suitability of available methods is discussed, and practical recommendations are provided.

The operation of dye-sensitized solar cells and quantum dot-sensitized solar cells (QDSSCs) depends strongly on the photoanode material employed. This is addressed in the present work by developing photoanodes based on a double-layer TiO2 inverse opal material with different interconnected pore sizes in the bottom and upper layers for use in QDSSCs. The proposed photoanode material leads to better infiltration of the sensitizers and the hole transporting material through the entire depth of the TiO2 layer. Double-layer TiO2 inverse opal-based QDSSCs are demonstrated to facilitate the greater absorbance of quantum dots and obtain higher photocurrent and power conversion efficiency than QDSSCs adopting single-layer TiO2 inverse opal photoanodes. Various QDSSCs employing double-layer TiO2 inverse opal photoanodes with different pore sizes in the layers are tested. The CdS/CdSe co-sensitized solar cell adopting the optimum photoanode configuration and thickness provided the highest QDSSC conversion efficiency of 5.79%.

Analysis of electrostatic floating potential fluctuations associated with multiple anodic double layer revealed a complexity dynamic coexisting with chaotic behavior. These externally controllable nonequilibrium quasi-stationary multiple anodic double layers were created in a cold cathode dc discharge setup in front of an extra anode which was used to supplement additional ionization. Despite the fact that chaos and complexity dynamics are often defined with entirely different properties, this study provides scenarios under which both can exist simultaneously. A stable multiple double-layer structure consisting of four successive double layers, each with positive and negative charged particles arranged in opposite sheets, was created when the anode potential exceeds a certain threshold value for a minimum gas breakdown bias between cathode and ground. After the stable multiple double layers was created, it was further controlled externally by varying the cathode bias between minimum gas breakdown bias of − 335 V and − 610 V at a pressure of 0.3 mbar for studying its advanced stages. With increase in cathode bias, multiple anodic double-layer structure advances towards the anode surface with the collapse of innermost layer due to the arrival of more energetic electrons in the anode zone. This process results from the self-organization and re-organization of charged particles in each double layer mediated by energetic electrons. The process continued until all the double layers disappeared and only an intense anode glow remained at anode for higher values of cathode bias. The chaotic dynamics of the system was studied at every stage by analyzing the corresponding floating potential fluctuations using FFT, phase space trajectories and nonlinear technique such as Lyapunov exponent, time-delay reconstruction etc. The analysis revealed the onset of chaos beyond − 410 V was triggered by the collapse of double layers. Estimation of correlation dimension, autocorrelation function and Hurst exponent unfolded the complexity features such as self-similarity and longtime dependence in the fluctuations. The value of correlation dimension reaches the maximum with an increase in cathode bias. Estimation of Hurst exponent using rescaled range analysis technique with values of H between 0.5 and 1 and algebraic decay of autocorrelation function provide signatures of long-range temporal correlations in the chaotic fluctuations and underlines the coexistence of complexity behavior.

In this study, thermal resistance of a double-layer micro-channel heat sink (DL-MCHS) with different ratio of upper and bottom channel heights in outlet (α=HU/HB) and the angle of channel inclinati...

In the design of photocathode, the internal electric field could be formed due to the graded Al compositional [Formula: see text] nanostructure, which can improve the top surface emission probability of carriers. In this paper, [Formula: see text] nanostructure array photocathode composed of two sub-layers is presented. Based on the finite element method, the influence of graded geometrical parameters on their optoelectronic characteristics is investigated. The results show that when the thickness of the sublayer is equal, the difference of the Al composition between the two sublayers of nanostructure is larger, the sub-layers are less, and the quantum efficiency is higher. The light capture ability of the photocathode can be enhanced by increasing the thickness and the array spacing of the first sublayer. Compared with the hexagonal cross-section structure, the light trapping effect and spectral response of the circular cross-section structure are better.

The method of regularised stokeslets is widely used to model microscale biological propulsion. The method is usually implemented with only the single-layer potential, the double-layer potential being neglected, despite this formulation often not being justified a priori due to nonrigid surface deformation. We describe a meshless approach enabling the inclusion of the double layer which is applied to several Stokes flow problems in which neglect of the double layer is not strictly valid: the drag on a spherical droplet with partial-slip boundary condition, swimming velocity and rate of working of a force-free spherical squirmer, and trajectory, swimmer-generated flow and rate of working of undulatory swimmers of varying slenderness. The resistance problem is solved accurately with modest discretisation on a notebook computer with the inclusion of the double layer ranging from no-slip to free-slip limits, the neglect of the double-layer potential results in up to 24% error, confirming the importance of the double layer in applications such as nanofluidics, in which partial slip may occur. The squirming swimmer problem is also solved for both velocity and rate of working to within a small percent error when the double-layer potential is included, but the error in the rate of working is above 250% when the double layer is neglected. The undulating swimmer problem by contrast produces a very similar value of the velocity and rate of working for both slender and nonslender swimmers, whether or not the double layer is included, which may be due to the deformation’s `locally rigid body’ nature, providing empirical evidence that its neglect may be reasonable in many problems of interest. The inclusion of the double layer enables us to confirm robustly that slenderness provides major advantages in efficient motility despite minimal qualitative changes to the flow field and force distribution.

The micro-channel heat dissipation system has minor specifications and good thermal conductivity per unit, which is the best choice for heat dissipation of micro-chips. By optimizing the cross sect...

Electrolytic diffusiophoresis is the movement of colloidal particles in response to a concentration gradient of an electrolyte. The diffusiophoretic velocity vDP is typically predicted through the relation vDP = DDP ∇log cs, where DDP is the diffusiophoretic mobility and cs is the concentration of the electrolyte. The logarithmic dependence of vDP on cs may suggest that the strength of diffusiophoretic motion is insensitive to the magnitude of the electrolyte concentration. In this article, we emphasize that DDP is intimately coupled with cs for all electrolyte concentrations. For dilute electrolytes, the finite double layer thickness effects are significant such that DDP decreases with a decrease in cs. In contrast, for concentrated electrolytes, charge screening could result in a decrease in DDP with an increase in cs. Therefore, we predict a maximum in DDP with cs for moderate electrolyte concentrations. We also show that for typical colloids and electrolytes , where Ds is the solute ambipolar diffusivity. To validate our model, we conduct microfluidic experiments with a wide range of electrolyte concentrations. The experimental data also reveals a maximum in DDP with cs, in agreement with our predictions. Our results have important implications in the broad areas of electrokinetics, lab-on-a-chip, active colloidal transport and biophysics.

Contemporary spintronics devices, notably GMR and TMR-sensors with high linear ranges, stand to benefit from large bias fields in excess of 1T that have been observed in exchange-coupled double layers using rare earth-transition metal ferrimagnets as pinning layers. However, before exploiting the strong coupling the reversal process must be understood at the scales of the smallest devices, where it would be effective. Little is known about these processes to-date, owing to the technical difficulty of imaging magnetic structures smaller than 20nm in fields of several Tesla. Here we image the nanoscale magnetic structures of a double layer comprising a polycrystalline Co/Pt-multilayer (Co/Pt) which is strongly exchange-coupled to an amorphous and magnetically-hard ferrimagnetic TbFe alloy layer. High resolution magnetic force microscopy provides snapshots of the magnetic structures along various applied fields between 0 and 7T as the magnetization reversal takes place. In contrast to a magnetization reversa...

The quartz crystal microbalance (QCM) has been used to study how the interfacial layer of an ionic liquid dissolved in a polar oil at low weight percentages responds to changes in applied potential. The changes in surface composition at the QCM gold surface depend on both the magnitude and sign of the applied potential. The time-resolved response indicates that the relaxation kinetics are limited by the diffusion of ions in the interfacial region and not in the bulk, since there is no concentration dependence. The measured mass changes cannot be explained only in terms of simple ion exchange; the relative molecular volumes of the ions and the density changes in response to ion exclusion must be considered. The relaxation behavior of the potential between the electrodes upon disconnecting the applied potential is more complex than that observed for pure ionic liquids, but a measure of the surface charge can be extracted from the exponential decay when the rapid initial potential drop is accounted for. The adsorbed film at the gold surface consists predominantly of ionic liquid despite the low concentration, which is unsurprising given the surtactant-like structures of (some of) the ionic liquid ions. Changes in response to potential correspond to changes in the relative numbers of cations and anions, rather than a change in the oil composition. No evidence for an electric field induced change in viscosity is observed. This work shows conclusively that electric potentials can be used to control the surface composition, even in an oil-based system, and paves the way for other ion solvent studies.

In this study, double-layer coatings of graphene oxide (GO)-poly(vinyl pyrrolidone) (PVP) (PGO) were deposited on the micro-textured Ti6Al4V substrates by electrophoretic deposition. Results revealed that the combination of micro-dimples and bi-layer PGO coatings significantly reduced the friction coefficient of textured Ti6Al4V from 0.5 to

Nanobubbles have electrically charged interfaces; hence, the diffused double layer theory can be applied to explain the behavior of nanobubbles in different electrolytic solutions. In this research, oxygen nanobubbles were generated in NaCl solutions of different concentrations, and bubble size and ζ potentials were measured just after the generation and after 1 week. The measured data and diffused double layer theory were used to compute the surface charge density, the potential due to the surface charge, and the interaction energy between bubbles. With the increased NaCl concentration, bubble size, surface charge density, and the number of negative charges increased, while the magnitude of ζ potential/surface potential, double layer thickness, internal pressure, and the electrostatic repulsion force decreased. The same trend was observed after 1 week. The net total energy calculation for the 0.001 M NaCl solution showed that the bubble repulsion for an intermediate separation distance had a 6.99 × 10

Double layer coating with variations in layer thickness on radar absorbent material (RAM), and Polyaniline dobed by DBSA as a dielectric material has been successfully synthesized. As well as Barium M-Hexaferrite doped by Zn2+ at x=0.9 as magnetic material successfully synthesized. Polyaniline has been synthesized by polymerization method and Barium M-Hexaferrite has been synthesized by solid state method. Characterization results obtained the conductivity of Polyaniline and Barium M-Hexaferrite respectively 4.4 × 10-1 S/m and 2.09 × 10-3 S/m, both of which are in range of semiconductor materials conductivity. The presence of Zn2+ doping successfully reduced hard magnetic properties of Barium M-Hexaferrite to be soft magnetic, with coercivity field (Hc) equals 0.0181 Tesla. Based on research that has been done, represent that double layer design with variations PANi : PANi + BaM (3:1) has maximum reflection loss value about -29,6003 dB, and 96.69% of energy absorbed. Whereas in variation of PANi: PANi + BaM (3: 1) has minimum reflection loss value about -15.2937 dB, and 82.21% of energy absorbed. In addition, the coating thickness variations also affect the absorption band width, with the most effective absorption peaks in “D” variation with bandwidth equals 1.81 GHz in range of frequency 8 to 9.81 GHz.

A double-layer liquid crystal (LC) lens array with composited dielectric layer is proposed. In our design, a spatially non-uniform electric field is generated between the strip electrodes, ...

Microarray technology plays an important role in detecting the sequence of the genome. In the production of microarrays, the formation of a homogeneous and uniform spot due to biodroplet pining is of great importance. In this work, using the molecular dynamics simulation method, it is possible to create homogeneous spots on the surface of graphene-based surfaces. Hence, the behavior of five different types of DNA including homogeneous sequences of adenine, cytosine, guanine, and thymine as well as heterogeneous sequence of bases in the water droplets, was subjected to a double-layer graphene substrate with a pillar structure. The results showed that double layer graphene with pillar pattern are successful in pinning of biodroplet and this substrate leads to the differnet placement of Oligonucleotide probes. Also, the results of wettability demonstrated that the formation of hydrogen bond between a single strand and water molecules reduces the spreading and increases the contact angle and height of biodroplet containing oligonucleotides with respect to the water droplet without oligonucleotides on the surface of the double layer graphene in pillar pattern. The results of the simulation of single-stranded DNA after equilibration showed that single strand of adenine and heterogeneous single strands had the least folding compared to other single strands, and the single strand of adenine produced the most stable structure. Hence, single-stranded adenine is stretched more compared to other single strands, which is due to the lack of tendency of this single strand for internal hydrogen bonds and regular spiral structure resulting from a strong internal π-π stacking interaction. As a result, single strand of adenine is more accessible to detect target single strands for use in microarrays.

The comparison and analysis for the preparation of related performance indicators of the thermal protection such as the ablation resistance performance, thermal stability at high temperature and reflection ability of the heat ray of kaolin double-layer coated flexible composites were carried on. Because of the 2 d stratified structure of kaolin, and at the same time it processes the higher refractoriness, excellent resistance to the elevated temperature, the certain heat insulation and the reflection performance of the heat ray, the adequate padding of kaolin can improve the prepared thermal protection ability of double-layer coating of flexible composites.

Direct growth of large area uniform high quality graphene films on insulating substrates is very important for graphene-based devices. Here we report a facile approach to directly fabricate uniform and large area bi-layer graphene films on MgO(100) substrates by chemical vapor deposition, without the aid of any metal catalysts. Raman spectroscopy, X-ray photoelectron spectroscopy, atomic force microscopy are used to characterize the synthesized graphene films. Raman mapping indicates that the graphene films are large area uniformity. The mobility of these directly grown graphene films is 130 cm2/(VS) and they may have potential applications in electronic devices, sensors, conductive films, etc.

In recent years, smart waterflooding has gained increased attention as an emerging EOR technology both for carbonate and sandstone reservoirs which would offset the need for utilization of toxic or expensive chemicals. Wettability alteration is one of the main mechanisms in smart waterflooding to improve oil recovery. Most previous studies showed that the rock wettability alteration toward water wetting conditions would help to recover oil. In this study, wettability alteration is investigated for a dolomite rock using the sessile drop method. The effects of monovalent and divalent cationic (K+ and Mg2+) and anionic (Cl− and SO42−) brines are discerned for different combination of various salts and concentrations of less than 5000 ppm. The experimental results showed that wettability would profoundly be changed for low salinity water in the presence of MgSO4 and KCl. The resultant findings are based on wettability alteration index (WAI) for different solutions and concentrations. It was found that KCl and MgSO4 can alter wettability up to 90% from strongly oil-wet to profoundly water-wet state within the range of investigated salt concentrations in this study. It was also found that double layer expansion and action of SO42− as a catalyst were the prevailing mechanisms in the process of wettability alteration.

A photoresponsive double-layer hydrogel has been developed, in which light-sensitive cinnamic moieties are grafted onto a polyacrylamide network to produce a photoresponsive layer and pure polyacrylamide formed the supporting layer. Ag nanoparticles were dispersed using in situ reduction on the photoresponsive layer to act as the catalyst. The as-fabricated hydrogel exhibits a shape memory effect and controllable catalytic behavior under an external light stimulus. When exposed to ultraviolet (UV) light at λ > 260 nm, the resulting cycloaddition of cinnamic moieties not only fix the hydrogel’s temporary shape, but also greatly slow down the catalytic reaction rate. After irradiated with UV light at λ < 260 nm, however, the newly formed crosslinking points are reversibly cleaved. This results in the shape recovery of the hydrogel to its permanent shape. At the same time, the catalytic reaction was greatly accelerated because of the facile diffusion of the reactants into the hydrogel.

TiO2 is an attractive electrode material in fast charging/discharging supercapacitors because of its high specific surface area. However, the low capacitance of TiO2 nanotubes as-anodized in the cl...

High power capability of the hybrid charge storage device Na-ion capacitor (NIC) is fabricated using battery type TiS2 as an insertion host with the double layer forming activated carbon (AC) as supercapacitor component. Earlier, it is presumed that Na/TiS2 system is considered as impractical energy storage system. TiS2 single crystals are synthesized and exhibit the reversible insertion of ~0.62 mol. Na. AC/TiS2 assembly is delivering the maximum energy density of ~38 Wh kg−1. One of the important aspects of this NIC is high power capability, which outperformed its analogue Li-ion capacitor fabricated under similar circumstances. Ministry of Education (MOE) Nanyang Technological University National Research Foundation (NRF) Accepted version This work was financially supported by NTU-HUJ Create Phase II which is a joint research programme between the Hebrew University of Jerusalem (HUJ, Israel) and Nanyang Technological University (NTU, Singapore) with CREATE (Campus for Research Excellence and Technological Enterprise) funding from National Research Foundation of Singapore (NRF, Singapore). Also, thank the financial support from the Ministry of Education - Singapore (MOE TIER 2 funding MOE2015-T2-1-046). VA thanks the financial support from the Science & Engineering Research Board (SERB), a statutory body of the Department of Science &Technology, Govt. of India through Ramanujan Fellowship (SB/S2/RJN-088/2016).

First-principles predictions play an important role in understanding chemistry at the electrochemical interface. Electronic structure calculations are straightforward for vacuum interfaces, but do not easily account for the interfacial fields and solvation that fundamentally change the nature of electrochemical reactions. Prevalent techniques for first-principles prediction of electrochemical processes range from expensive explicit solvation using ab initio molecular dynamics, through a hierarchy of continuum solvation techniques, to neglecting solvation and interfacial field effects entirely. Currently, no single approach reliably captures all relevant effects of the electrochemical double layer in first-principles calculations. This review systematically lays out the relation between all major approaches to first-principles electrochemistry, including the key approximations and their consequences for accuracy and computational cost. Focusing on ab initio methods for thermodynamic properties of aqueous interfaces, we first outline general considerations for modeling electrochemical interfaces, including solvent and electrolyte dynamics and electrification. We then present the specifics of various explicit and implicit models of the solvent and electrolyte. Finally, we discuss the compromise between computational efficiency and accuracy, and identify key outstanding challenges and future opportunities in the wide range of techniques for first-principles electrochemistry.

Based on a mean-field description of thermodynamic cyclic voltammograms (CVs), we analyze here in full generality, how CV peak positions and shapes are related to the underlying interface energetics, in particular when also including electrostatic double layer (DL) effects. We show in particular, how non-Nernstian behaviour is related to capacitive DL charging, and how this relates to common adsorbate-centered interpretations such as a changed adsorption energetics due to dipole-field interactions and the electrosorption valency – the number of exchanged electrons upon electrosorption per adsorbate. Using Ag(111) in halide-containing solutions as test case, we demonstrate that DL effects can introduce peak shifts that are already explained by rationalizing the interaction of isolated adsorbates with the interfacial fields, while alterations of the peak shape are mainly driven by the coverage-dependence of the adsorbate dipoles. In addition, we analyze in detail how changing the experimental conditions such as the ion concentrations in the solvent but also of the background electrolyte can affect the CV peaks via their impact on the potential drop in the DL and the DL capacitance, respectively. These results suggest new routes to analyze experimental CVs and use of those for a detailed assessment of the accuracy of atomistic models of electrified interfaces e.g. with and without explicitly treated interfacial solvent and/or approximate implicit solvent models.

Superfluidity has been predicted and now observed in a number of different electron-hole double-layer semiconductor heterostructures. In some of the heterostructures, such as GaAs and Ge-Si electron-hole double quantum wells, there is a strong mismatch between the electron and hole effective masses. We systematically investigate the sensitivity to unequal masses of the superfluid properties and the self-consistent screening of the electron-hole pairing interaction. We find that the superfluid properties are insensitive to mass imbalance in the low density BEC regime of strongly-coupled boson-like electron-hole pairs. At higher densities, in the BEC-BCS crossover regime of fermionic pairs, we find that mass imbalance between electrons and holes weakens the superfluidity and expands the density range for the BEC-BCS crossover regime. This permits screening to kill the superfluid at a lower density than for equal masses.

In this work, motivated by the fabrication of an AlSb monolayer, we have focused on the electronic, mechanical and optical properties of AlSb and InSb monolayers with double-layer honeycomb structures, employing the density functional theory approach. The phonon band structure and cohesive energy confirm the stability of the XSb (X = Al and In) monolayers. The mechanical properties reveal that the XSb monolayers have a brittle nature. Using the GGA + SOC (HSE + SOC) functionals, the bandgap of the AlSb monolayer is predicted to be direct, while InSb has a metallic character using both functionals. We find that XSb (X = Al, In) two-dimensional bodies can absorb ultraviolet light. The present findings suggest several applications of AlSb and InSb monolayers in novel optical and electronic usages.

Dielectric properties of nano-confined water are important in several areas of science, i.e., it is relevant in the dielectric double layer that exists in practically all heterogeneous fluid-based systems. Molecular dynamics simulations are used to predict the in-plane dielectric properties of confined water in planar channels of width ranging from sub-nanometer to bulk. Because of suppressed rotational degrees of freedom near the confining walls, the dipole of the water molecules tends to be aligned parallel to the walls, which results in a strongly enhanced in-plane dielectric constant (epsilon (parallel to)) reaching values of about 120 for channels with height 8 angstrom < h < 10 angstrom. With the increase in the width of the channel, we predict that epsilon (parallel to) decreases nonlinearly and reaches the bulk value for h > 70 angstrom. A stratified continuum model is proposed that reproduces the h > 10 angstrom dependence of epsilon (parallel to). For sub-nanometer height channels, abnormal behavior of epsilon (parallel to) is found with two orders of magnitude reduction of epsilon (parallel to) around h similar to 7.5 angstrom, which is attributed to the formation of a particular ice phase that exhibits long-time (similar to mu s) stable ferroelectricity. This is of particular importance for the understanding of the influence of confined water on the functioning of biological systems.

Adsorption of two organic pollutants (2-nitrophenol: 2-NRP and ketoprofen: KTP) on activated carbon produced from wastes deriving from a winery industry is investigated in the paper. Experimental data retrieved at T = 298–328 K indicate that, in the investigated equilibrium concentrations, a saturation phenomenon is reached for ketoprofen, while for 2-nitrophenol steeper curves are observed. For both the adsorbates, an increase in temperature determines a reduction of adsorption capacity. A modelling analysis via statistic physics models demonstrates that a double layer model is perfectly suitable to describe the adsorption mechanisms of both the investigated adsorbates. In light of the number of bonded molecules per adsorption site, the inclination of both the molecules upon adsorption is described. The obtained results suggest that they are adsorbed via both parallel and non parallel orientations, depending on the systems and temperature. Adsorption capacity variation is controlled by the number of bonded molecules per adsorption site and the density of receptor sites. Adsorption energy results show that physical interactions are responsible of the adsorption of both the pollutants. Finally, the results demonstrate that our adsorbent has an outstanding adsorption capacity which makes it promising for water depollution.

Quantum Boltzmann formalism is employed to study the transport properties of strongly-coupled double layer systems that enable the formation of interlayer excitons and exciton condensation. The importance of exciton formation, dissociation, and condensation is highlighted in the context of thermoelectric power generation, and this mathematical inquiry provides an alternative methodology to calculate the thermoelectric efficiency given the conditions of exciton formation. The Onsager relation for the Coulomb drag resistivity is shown to be valid even when exciton condensation is present. In addition, it is found that the traditional thermoelectric figure of merit is no longer sufficient to predict the efficiency of thermoelectric power generation in the presented situations. This inquiry offers insights for designing double layer systems, including their interlayer interactions, with enhanced thermoelectric energy conversion efficiency.

We study the solvation and electrostatic properties of bare gold (Au) nanoparticles (NPs) of 1-2 nm in size in aqueous electrolyte solutions of sodium salts of various anions with large physicochemical diversity (Cl-, BF4-, PF6-, Nip-(nitrophenolate), 3- and 4-valent hexacyanoferrate (HCF)) using nonpolarizable, classical molecular dynamics computer simulations. We find a substantial facet selectivity in the adsorption structure and spatial distribution of the ions at the Au-NPs: while sodium and some of the anions (e.g., Cl-, HCF3-) adsorb more at the `edgy' (100) and (110) facets of the NPs, where the water hydration structure is more disordered, other ions (e.g., BF4-, PF6-, Nip-) prefer to adsorb strongly on the extended and rather flat (111) facets. In particular, Nip-, which features an aromatic ring in its chemical structure, adsorbs strongly and perturbs the first water monolayer structure on the NP (111) facets substantially. Moreover, we calculate adsorptions, radially-resolved electrostatic potentials, as well as the far-field effective electrostatic surface charges and potentials by mapping the long-range decay of the calculated electrostatic potential distribution onto the standard Debye-Hückel form. We show how the extrapolation of these values to other ionic strengths can be performed by an analytical Adsorption-Grahame relation between effective surface charge and potential. We find for all salts negative effective surface potentials in the range from -10 mV for NaCl down to about -80 mV for NaNip, consistent with typical experimental ranges for the zeta-potential. We discuss how these values depend on the surface definition and compare them to the explicitly calculated electrostatic potentials near the NP surface, which are highly oscillatory in the ± 0.5 V range.

By using Monte Carlo simulations, we investigated a triangle double-layer graphene nanoisland with mixed-spin (3/2, 2) configuration. We focused on the effects of crystal-fields, exchange couplings, longitudinal magnetic fields, and temperature on the magnetic properties of the system. Various curves of magnetization, susceptibility, and internal energy as a function of temperature were obtained. We plotted the phase diagrams of blocking temperature in the different parameter planes. We found that increasing |Jab/JZ|,Jbb/JZ, and h/JZ or weakening |Db/JZ| is beneficial to improving the TB/JZ, but the TB/JZ is very insensitive to changes in the Da/JZ and Jaa/JZ. In addition, it is worth noting that the system can exhibit abundant multiple-loops hysteresis behaviors for certain physical parameters, such as triple, quadruple, quintuple, septuple hysteresis loops.

The interactions of a fast-moving charged particle with two parallel layers, each containing a two-dimensional electron gas (2DEG), which are separated by an insulating material, are investigated b...

Using ethylenediaminetetraacetic acid (EDTA) as a chelating agent and urea as a directional template, we report an effective method for the synthesis of porous strontium hydroxyapatite (SrHAp) microspheres employing homogeneous precipitation. More importantly, we can easily control the pore size (d) of porous SrHAp microspheres through the elaborate choice of reaction temperature (T) at atmospheric pressure. The experimental results show that the d of porous SrHAp microspheres rises gradually with the increase of T. In addition, with the increase of reaction time at the same T, the d of the microspheres remained unchanged, but the diameter of porous SrHAp microspheres gradually increased, and remained unchanged after 36 h. According to the Laplace equation, Kelvin equation and Clapeyron equation, the relationship of d and T is deduced as follows: . The experimental data (T, d) agreed with it. In particular, based on the unique role of EDTA and CO2 bubbles (urea hydrolysis) in the preparation of porous SrHAp microspheres, the self-assembly pore-forming mechanism of foam boundary templates was proposed. First, urea was hydrolyzed to produce CO2 bubbles (foam boundary template) and OH−, and EDTASr (EDTA chelates strontium ions) and H3O+ (acidic system) formed a liquid film-chelating ion electronic double layer (LFCIEDL) on the surface of CO2 bubbles, which not only chelated and located Sr2+, but also formed a stable foam boundary template. Secondly, Sr2+, H2PO4− and OH− were homogeneously nucleated in the Plateau borders among the bubbles. After that, along the bubble liquid film surface, Sr2+ is orientationally released from the outer edge to the inner. SrHAp lamellae were formed by self-assembly method, then they were interconnected. In addition, OH− produced by urea hydrolysis continuously provides power for self-assembly oriented growth. Finally OH− completely destroys the LFCIEDL on the surface of the bubble, causing the bubble to break, and the porous SrHAp microspheres are formed.

In this paper, the authors combine spin-polarized scanning tunneling microscopy measurements with density functional theory calculations to unravel the magnetic ground state of a Mn double layer on the W(001) surface. The Mn surface layer forms a checkerboard antiferromagnetic state while the subsurface Mn layer appears to be magnetically dead due to strong hybridization with the W substrate

Condensation of spatially indirect excitons, with the electrons and holes confined in two separate layers, has recently been observed in two different double layer heterostructures. High transition temperatures were reported in a double Transition Metal Dichalcogenide (TMD) monolayer system. We briefly review electron-hole double layer systems that have been proposed as candidates for this interesting phenomenon. We investigate the double TMD system WSe 2 /hBN/MoSe 2 , using a mean-field approach that includes multiband effects due to the spin-orbit coupling and self-consistent screening of the electron-hole Coulomb interaction. We demonstrate that the transition temperature observed in the double TMD monolayers, which is remarkably high relative to the other systems, is the result of (i) the large electron and hole effective masses in TMDs, (ii) the large TMD band gaps, and (iii) the presence of multiple superfluid condensates in the TMD system. The net effect is that the superfluidity is strong across a wide range of densities, which leads to high transition temperatures that extend as high as T B K T = 150 K.