Characteristics Of Monolayers Research Articles

Non-Classical Euler Buckling and Brazier Instability in Cylindrical Liquid Droplets.

Crystalline monolayers prevalent in nature and technology possess elusive elastic properties with important implications in fundamental physics, biology, and nanotechnology. Leveraging the recently discovered shape transitions of oil-in-water emulsion droplets, upon which these droplets adopt cylindrical shapes and elongate, we investigate the elastic characteristics of the crystalline monolayers covering their interfaces. To unravel the conditions governing Euler buckling and Brazier kink formation in these cylindrical tubular interfacial crystals, we strain the elongating cylindrical droplets within confining microfluidic wells. Our experiments unveil a nonclassical relation between the Young's modulus and the bending modulus of these crystals. Intriguingly, this relation varies with the radius of the cylindrical crystal, presenting a nonclassical mechanism for tuning of elasticity in nanotechnology applications.

Exploring optoelectronic and thermal characteristics of Janus MoSeTe and WSeTe monolayers under mechanical strain

This paper reveals the effect of external strain on the electronic, thermal and optical properties of Janus MSeTe (M=Mo, W) using first principles. Phonon spectrum calculations confirm the dynamic stability of the system. Biaxial stretching can effectively modulate its thermal properties. Uniaxial, biaxial and shear strains modulate the band structure, structural parameters, averaged differential charge density and optical properties of the MSeTe system to different degrees. The increase of compressive and shear strains leads to a gradual decrease of the band gap and triggers a semiconductor-metal phase transition at the critical point. The intrinsic system exhibits strong light absorption in the visible and ultraviolet regions, while strain induces a redshift of the light-absorbing edge, which enhances the response to the infrared and visible wavelength bands. These findings provide a theoretical basis and application potential for the design of optoelectronic devices and thermoelectric materials.

A Review on Investigating the Interactions between Nanoparticles and the Pulmonary Surfactant Monolayer with Coarse-Grained Molecular Dynamics Method.

Pulmonary drug delivery has garnered significant attention due to its targeted local lung action, minimal toxic side effects, and high drug utilization. However, the physicochemical properties of inhaled nanoparticles (NPs) used as drug carriers can influence their interactions with the pulmonary surfactant (PS) monolayer, potentially altering the fate of the NPs and impairing the biophysical function of the PS monolayer. Thus, the objective of this review is to summarize how the physicochemical properties of NPs affect their interactions with the PS monolayer. Initially, the definition and properties of NPs, as well as the composition and characteristics of the PS monolayer, are introduced. Subsequently, the coarse-grained molecular dynamics (CGMD) simulation method for studying the interactions between NPs and the PS monolayer is presented. Finally, the implications of the hydrophobicity, size, shape, surface charge, surface modification, and aggregation of NPs on their interactions with the PS monolayer and on the composition of biomolecular corona are discussed. In conclusion, gaining a deeper understanding of the effects of the physicochemical properties of NPs on their interactions with the PS monolayer will contribute to the development of safer and more effective nanomedicines for pulmonary drug delivery.

Interfacial rheology of polyelectrolyte microgel monolayers: Correlation between mechanical properties and phase behavior at oil-water interfaces

Microgels are confined to fluid interfaces in numerous applications, yet many aspects of the microgel-covered interface remain unclear. In this work, we use interfacial shear and dilatational rheology to study the effects of electrostatics on the mechanical characteristics of polyelectrolyte microgel monolayers at oil-water interfaces as a function of the microgel interfacial concentration. We find a clear correlation between the influence of charges on the mechanical properties of the monolayers and the influence of charges on their two-dimensional phase behavior. At lower microgel interfacial concentrations, the moduli of uncharged monolayers are larger than those of charged monolayers. Consistent with our previous findings on the phase behavior, here, the mechanical response of the interfacial layer is controlled by in-plane interactions of the microgels within the interface. At higher microgel interfacial concentrations, the moduli of charged monolayers are larger than those of uncharged monolayers. The mechanical response becomes dominated by out-of-plane interactions between the fractions of the adsorbed microgels further from the interface. Evidently, electrostatic interactions do not contribute directly to the mechanical response of the interfacial layer, that is, through charge repulsion, but indirectly through the difference in the swelling properties of uncharged and charged microgels. These results advance our understanding of how the charge-dependent microstructure of the interfacial layer affects its mechanical properties, which is not only important from a fundamental point of view but is also relevant to applications where polyelectrolyte microgels are used as responsive emulsion stabilizers.

Impacts of DCM-linked gating pore currents on the electrophysiological characteristics of hiPSC-CM monolayers

BackgroundVariants of the SCN5A gene, which encodes the NaV1.5 cardiac sodium channel, have been linked to arrhythmic disorders associated with dilated cardiomyopathy (DCM). However, the precise pathological mechanisms remain elusive. The present study aimed to elucidate the pathophysiological consequences of the DCM-linked Nav1.5/R219H variant, which is known to generate a gating pore current, using patient-specific human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) cultured in monolayers. MethodsVentricular- and atrial-like hiPSC-CM monolayers were generated from DCM patients carrying the R219H SCN5A variant as well as from healthy control individuals. CRISPR-corrected hiPSC-CMs served as isogenic controls. Simultaneous optical mapping of action potentials (APs) and calcium transients (CaTs) was employed to measure conduction velocities (CVs) and AP durations (APDs) and served as markers of electrical excitability. Calcium handling was evaluated by assessing CaT uptake (half-time to peak), recapture (tau of decay), and durations (TD50 and TD80). A multi-electrode array (MEA) analysis was conducted on hiPSC-CM monolayers to measure field potential (FP) parameters, including corrected Fridericia FP durations (FPDc). ResultsOur results revealed that CVs were significantly reduced by more than 50 % in both ventricular- and atrial-like hiPSC-CM monolayers carrying the R219H variant compared to the control group. APDs were also prolonged in the R219H group compared to the control and CRISPR-corrected groups. CaT uptake, reuptake, and duration were also markedly delayed in the R219H group compared to the control and CRISPR-corrected groups in both the ventricular- and the atrial-like hiPSC-CM monolayers. Lastly, the MEA data revealed a notably prolonged FPDc in the ventricular- and atrial-like hiPSC-CMs carrying the R219H variant compared to the control and isogenic control groups. ConclusionsThese findings highlight the impact of the gating pore current on AP propagation and calcium homeostasis within a functional syncytium environment and offer valuable insights into the potential mechanisms underlying DCM pathophysiology.

Adsorption characteristics of Ni cluster Modified-InN monolayer for indoor noxious gases (CH2O, C6H6, and NH3)

With the continuous enhancement of people's health awareness and the pursuit of high-quality life, the noxious gases generated after the renovation of new houses are receiving more attention. The gas sensing properties of InN monolayer modified with Ni clusters (1–3 Ni atoms) on CH2O, C6H6, and NH3 were analyzed based on DFT calculations, including the adsorption energy, charge transfer, density of states, bandgap structure, molecular orbitals, electrostatic potential, and desorption time investigation of gas adsorption systems. Moreover, different numbers of Ni atoms were introduced and their adsorption energies were analyzed. The results showed that the intrinsic InN and Ni–InN were suitable materials for gas sensors, while Ni2–InN and Ni3–InN were more suitable as adsorbents for clearing these three gases. The change in conductivity upon gas adsorption provides a theoretical basis for identifying the concentration of mixed gases of CH2O, C6H6, and NH3.

Piezoelectric characteristics of doped β-Ga2O3 monolayer: a first-principles study

Two-dimensional (2D) piezoelectric materials have been widely concerned because of their important applications in nano-piezoelectric generators. Finding two-dimensional materials with large piezoelectric effects is still a great challenge. In this work, the inversion center of the β-Ga2O3 monolayer was broken by substitutional doping. Not only the in-plane piezoelectric effect but also the uncommon out-of-plane piezoelectric effect is induced in the doped β-Ga2O3 monolayer. In addition, we analyzed the cause of the piezoelectric effects from their electronic properties. The values of out-of-plane (in-plane) piezoelectric coefficient for Cu-doped and Al-doped β-Ga2O3 reach −4.04 (3.95) pm/V and −2.91 (0.37) pm/V, respectively. The results are comparable with those of the commonly used bulk piezoelectric materials such as α-quartz (d11 = 2.3 pm V−1), AlN (d33 = 5.1 pm V−1), and GaN (d33 = 3.1 pm V−1), even though they are both two-dimensional structures. Our study shows a great potential application of doped β-Ga2O3 monolayer in micro and nano-electromechanical devices such as smart wearables, sensors, energy converters, and micro energy collectors.

Pd-Adsorbed SiN3 Monolayer as a Promising Gas Scavenger for SF6 Partial Discharge Decomposition Components: Insights from the First-Principles Study.

Gas-insulated switchgear (GIS) equipment must be protected by detecting and eliminating the toxic SF6 partial discharge decomposition components. This study employs first-principles calculations to thoroughly investigate the interaction between a Pd-adsorbed SiN3 monolayer (Pd-SiN3) and four typical SF6 decomposition gases (H2S, SO2, SOF2, and SO2F2). The study also investigates the associated geometric, electrical, and optical characteristics along with the sensing sensitivity and desorption efficiency. The ab initio molecular dynamics (AIMD) simulations demonstrated the favorable stability of the Pd-SiN3 monolayer. Furthermore, the Pd-SiN3 monolayer exhibited strong chemisorption behavior toward H2S, SO2, SOF2, and SO2F2 gases because of the higher adsorption energies of -2.717, -2.917, -2.457, and -2.025 eV, respectively. Furthermore, significant changes occur in the electronic and optical characteristics of the Pd-SiN3 monolayer following the adsorption of these gases, resulting in remarkable sensitivity of the Pd-SiN3 monolayer in relation to electrical conductivity and optical absorption. Meanwhile, all of these gas adsorption systems exhibited extremely long recovery times. The aforementioned theoretical findings suggest that the Pd-SiN3 monolayer has the potential to be an effective gas scavenger for the storage or removal of the SF6 decomposition components. Additionally, it might function as a reliable one-time sensor for detecting these gases. The results potentially provide valuable theoretical guidance for maintaining the normal operation of the SF6 insulation devices.

Combined DFT and MD simulation approach for the investigation of intrinsic material properties of T-phase Rb2Se monolayer

Two-dimensional monolayers are a prime class of materials due to their extensive spectrum of applications. In the present study, the material characteristics of the 1T-Rb2Se monolayer are investigated and analysed by employing the first-principles DFT calculations. The computations of structural, electronic, bonding nature, dynamical, optical, thermoelectric, and elastic properties of the theoretically predicted 1T-Rb2Se monolayer are effectuated. The 1T-Rb2Se monolayer displays a semiconducting nature with the energy gap quantified using various exchange-correlational potentials. The phonon and CPMD was deployed for the conclusions on the dynamical and thermal stabilities. With indirect band gap and good thermal response, the material will have possible applications in photovoltaics and thermoelectrics. Positive Poisson's ratio and elastic tensors validates the elastic strength of the monolayer. The effective masses of charge carriers and its relative ratio are determined from the energy band paraboloids with the deformation potentials for the accuracy of the relaxation time. The 1T-Rb2Se is electronically, ionically, dynamically, thermally, and elastically stable that confirms its feasibility for experimental studies.

First-principles insight into a Nb-embedded PdSe2 monolayer for dissolved gas sensing in oil-immersed transformers of a regional power grid

As the integration of renewable energy into the regional urban power grid, guaranteeing the safety of oil-immersed transformers emerges as a top priority. Dissolved gas analysis by nanomaterial-based gas sensor is a workable technique to evaluate the operation status of the oil-immersed transformers. This work purposes Nb-embedded PdSe2 (Nb-PdSe2) monolayer as a potential gas sensor upon C2H2 and C2H4, two typical dissolved gases, using the first-principles theory. One Se atom of the pristine PdSe2 monolayer is substituted by one Nb atom to establish the Nb-PdSe2 configuration, which is spontaneous at room temperature with binding energy of −1.81 eV. The adsorption characteristic of Nb-PdSe2 monolayer upon two gas species is analyzed and compared with other metal-doped TMDs. The analysis of electronic property reveals the favorable change in the bandgap of Nb-PdSe2 monolayer as well as the Nb-C bonding nature, leading to the strong sensing response of −99.99% and −99.87% in C2H2 and C2H4 systems using the frontier molecular orbital theory. These findings uncover the strong potential of Nb-PdSe2 monolayer as a resistive gas sensor upon two gases, which would be helpful to explore novel PdSe2-based gas sensor for application in some other fields.

Effect of two-dimensional non-local screening on characteristics of transition metal dichalcogenide monolayers

On the basis of the theory developed for the dielectric function of atomic thin layer insulating materials (Cudazzo et al 2011 Phys. Rev. B 84 085406), some characteristics of transition metal dichalcogenide monolayers are calculated in the framework of variational method. This method initially was designed to work for very weak or strong magnetic fields, but it is also in very good agreement with the numerical results obtained for intermediate magnetic fields. The expressions of the energy and effective radius of the ground impurity state, depending on the effective screening parameter of the problem, are obtained both without and with magnetic fields.

Effect of growth temperature on the microstructure and properties of epitaxial MoS2 monolayers grown by metalorganic chemical vapor deposition

Metalorganic chemical vapor deposition (MOCVD) is a promising technique for wafer-scale synthesis of MoS2 monolayers for 2D field-effect transistors (2D-FETs) and related devices. Epitaxial growth of MoS2 on sapphire provides films that are crystallographically well-oriented but typically contain low-angle grain boundaries (e.g., mirror twins), voids, and other defects depending on growth conditions and substrate characteristics. In this study, we investigate microstructure, optical properties, and field-effect characteristics of wafer-scale MoS2 monolayers grown by MOCVD on c-plane sapphire over a narrow window of growth temperatures (900–1000 °C). The density of low-angle grain boundaries in the MoS2 monolayer was found to decrease dramatically from 50% areal coverage for films grown at 900 °C to 5% at 1000 °C. This decrease in low-angle grain boundary density is correlated with an increase in the room-temperature photoluminescence intensity of A excitons and a decrease in the full-width-half maximum (FWHM) of the Raman A1g peak, which are typically indicative of a general reduction in defects in MoS2. However, the best transport properties (e.g., mean field-effect mobility mFE = 17.3 cm2/V s) were obtained in MoS2 monolayers grown at an intermediate temperature of 950 °C. It was found that as the growth temperature increased, small regions bound by high-angle boundaries begin to appear within the monolayer and increase in areal coverage, from ∼2% at 900 °C to ∼5% at 950 °C to ∼10% at 1000 °C. The growth temperature of 950 °C, therefore, provides an intermediate condition where the combined effects of low-angle and high-angle boundaries are minimized. The results of this study provide guidance on MOCVD growth and characterization that can be used to further optimize the performance of MoS2 2D-FETs.

Strain effect on the electronic and optical properties of anisotropic Au2Te monolayer

In this article, the strain effect on the electronic and optical properties of Au2Te monolayer is investigated based on first-principles calculations. The band gap responds monotonically to uniaxial strain, and it increases (decreases) from 1.13 (1.51) eV to 1.45 (1.13) eV for applying strain along the x (y) direction from -5% to +5%. The band gap varies in a parabolic trend for the applied biaxial strain, and both compressive and stretch strains increase the band gap. The indirect bandgap characteristic of Au2Te monolayer is maintained under both uniaxial and biaxial strains. In addition, the light absorption edge blueshift (redshift) with the increasing (decreasing) strain-induced band gap. Notably, the optical response is more sensitive to biaxial strain than uniaxial strain. These tunable properties endow the anisotropic Au2Te monolayer as a promising 2D semiconductor for anisotropic optoelectronic devices.

Transition metal doped 2D SiC (TM=Ag, Pd and Rh) as a potential candidate for NOx (x = 1,2) and NH3 sensing

To control the nitrogen oxide emissions in large power plants, accurate monitoring NOx and NH3 gases at the outlet of the selective catalytic reduction system is vital to determine the degree of NOx reaction and adjust the amount of injected NH3. In this study, transition-metal (TM) atoms (Ag, Pd and Rh) doped 2D graphene-like SiC monolayers have been designed based on first-principles calculations. The adsorption and detection characteristics of TM-doped 2D SiC monolayers for NOx (x = 1, 2) and NH3 were systematically investigated. It is found that TM-doped 2D SiC monolayers exhibit strong potential in developing chemical sensors capable of detecting NO, NO2 and NH3. With the decoration of TM atoms in SiC monolayers, the adsorption ability of NO, NO2 and NH3 could be enhanced ascribed to the increased adsorption energy and electrical conductivity. In addition, the TM-SiC monolayers exhibit desirable thermostability at 298 K, 498 K and 798 K. By comparing the variations in atom-to-atom distances, plane-averaged charge density differences, charge transfers, density of states, energy gap variation and the recovery times of TM-doped SiC before and after adsorbed NOx and NH3, we found that Pd-SiC, Ag-SiC and Rh-SiC are optimal for the detection and recovery of NO, NO2 and NH3 gases with adsorption energies − 1.82 eV, − 2.17 eV, − 1.10 eV, respectively.

Detailed investigations on stability and optoelectronic characteristics of the 1T-PdS2 monolayer

In this work, detailed theoretical elucidation on the structural stability and optoelectronic characteristics of the 1T-PdS2 monolayer is provided using density functional theory (DFT). The dynamical and mechanical stabilities of the structure are assessed through the analysis of phonon dispersion spectra and the Born-Huang stability criterion. The value of Young’s modulus comes out to be 68.75 Nm−1, which demonstrates high flexibility of the structure. Further, thermal stability of the structure is investigated using Ab-initio molecular dynamics simulations. The first-principle calculations by GGA + SOC (GGA + U) methods reveal that the monolayer is an indirect bandgap semiconductor having bandgap 1.14 eV (1.173 eV). The dielectric function displays its highest peak in the energy range 1.5–2 eV, whereas the maximum absorption coefficient lies in the ultraviolet region. Furthermore, the impact of vacancy defects are also investigated on the optoelectronic characteristics of the monolayer. The bandgap changes from indirect nature to direct one and reduces from 1.17 eV to 0.25 eV and 0.43 eV under single palladium and sulphur vacancies, respectively. The optical parameters also show enhancement with the introduction of these vacancies. The computational analysis reveals that 1T-PdS2 monolayer possesses advantageous attributes, making it a viable material for different optoelectronic applications.

Ultralow thermal conductivity of W-Janus bilayers (WXY: X, Y = S, Se, and Te) for thermoelectric devices.

Lattice thermal conductivity (κ) in tungsten dichalcogenide Janus (WXY, where X, Y = S, Se, and Te) monolayers and heterostructures (HSs) have been investigated using ab initio DFT simulations. Tungsten-based Janus monolayers show semiconducting behavior with the bandgap in the semiconducting range for WSSe (1.70 eV), WSTe (1.26 eV), and WSeTe (1.34 eV). When Janus monolayers are stacked to form HSs with weak van der Waals (vdW) interactions, the bandgap reduces to 0.19 eV, 0.40 eV, and 0.24 eV, respectively, for WSeTe/WSTe, WSSe/WSTe, and WSSe/WSeTe HSs. Thermal vibrational characteristics of Janus monolayers are modified when these are stacked in 2D HSs with the introduction of interlayer hybrid phonon modes. Large longitudinal-transverse optical (LO-TO) splitting is noticed at the Brillouin zone-center (Γ-point): 135 cm-1, 140 cm-1, and 150 cm-1 for WSeTe/WSTe, WSSe/WSeTe and WSSe/WSTe HSs, respectively. Thermal conductivity calculations show ultra-low κ values for WSeTe/WSTe (0.01 W m-1 K-1), WSSe/WSTe (0.02 W m-1 K-1) and WSSe/WSeTe HS (0.004 W m-1 K-1) at 300 K. The results can be attributed to the hybrid phonon modes with frequencies very close to acoustic modes at the gamma point, low Debye temperature (θD) and specific heat capacity. Our results highlight the possible applications of these HSs in designing thermoelectric interfaces at the nanoscale.

The electronic structure, optical properties, and phonon transport of a VBi monolayer in the rock-salt phase using the first-principles method

The structural, electric, and optical characteristics of the rock salt (RS) VBi monolayer are studied, together with the phonon transport, using first-principles simulations based on density functional theory (DFT). In addition to its unique electronic properties, the (RS) VBi monolayer also displayed a broad absorption spectrum ranging from visible light to the ultraviolet region. Furthermore, its convergent phonon scattering rate was found to be reduced. These findings highlight the potential of further theoretical and experimental investigations into the electronic structure, optical characteristics of the VBi monolayer. The experimental outcomes have shown that the monolayer of (RS) VBi possesses the characteristic of being a half-metal. In the case of the spin-up configuration, the material exhibited metallic properties as the energy levels intersected the Fermi level. On the other hand, for the spin-down configuration, a gap in energy appeared on both sides of the Fermi level, resulting in the formation of a semiconductor. This is indicated by the presence of a gap between the conduction band and the valence band, with the total energy gap of the compound being determined by the combined magnitude of both gaps. The specific energy gap of the (RS) VBi monolayer was measured to be 0.55 eV, which is half the size of a typical metal's energy gap (0.3 eV). Moreover, the (RS) VBi monolayer exhibited a magnetic moment per unit cell equivalent to 2µB, demonstrating a strong polarization at the Fermi level due to its half-metal nature.

Characteristics of Langmuir monomolecular monolayers formed by the novel oil blends

Abstract The aim of this work was to assess the physical properties of Langmuir monolayers of three new oil blends “RBWg” (obtained by mixing rapeseed oil, black cumin oil, and wheat germ oil), “REp” (rapeseed oil and evening primrose oil), and “CRb” (camelina oil and rice bran oil), as well as to characterize the molecular dynamics of their protons using low-field nuclear magnetic resonance (LF NMR) method. The studied blends are rich in oleic acid (C18:1), linolenic acid (C18:2), and α-linolenic acid (18:3). The chromatographically determined ratio of n6 to n3 fatty acids was found to be in the range of 5.18–5.27. The appropriate n6/n3 fatty acid ratio was also confirmed by FT-IR analysis. The spin–lattice relaxation rate (R 1) and spin–spin relaxation time (R 2) measured by LF NMR method were similar for the RBWg and REp blends but different from the third oil blend (CRb), which indicates lower proton mobility in CRb. The observed changes in the properties of monolayers of oil blends suggest that the refined rice bran oil in the CRb blend also significantly changes the viscoelastic properties of this blend. The results obtained in this study provide a theoretical basis for the development of a well-balanced approach to using oils in food production technology.

Modulation of magnetic and optical properties for GeS monolayer

The layered structure of GeS exhibits commendable thermal stability and holds significant promise in the realms of optoelectronics and ion batteries. But its application is limited as dilute magnetic semiconductor. Therefore, this study delves into the impact of 3d transition metal (TM = V, Cr, and Mn) doping on the magnetic and optical characteristics of two-dimensional GeS monolayer through a first-principles calculation method grounded in density functional theory. The findings elucidate that all doping systems lead to a reduction in the band gap, with the V-doped system exhibiting the most significant diminishment. After doping process, magnetic coupling emerges between the electrons in the TM-3d state and those in the S-3p state, resulting in the manifestation of magnetic semiconductor characterized by magnetic moments of 3 μB, 4 μB, and 5 μB, respectively. Comparative analysis with the pristine GeS monolayer, it reveals enhancements in optical absorptivity and refractive index within both the infrared and visible spectra of the doped systems. Notably, the V-doped system showcases superior optical properties due to its narrower band gap, facilitating more efficient electron transitions to the conduction band. Consequently, TM (TM = V, Cr, and Mn)-doped GeS monolayer hold promising potential in the realms of spintronics and optoelectronics.

Sensitive Detection of Biomolecular Adsorption by a Low-Density Surfactant Layer Using Sum-Frequency Vibrational Spectroscopy.

Small molecules or proteins interact with a biomembrane in various ways for molecular recognition, structure stabilization, and transmembrane signaling. In this study, 1,2-dipalmitoyl-3-trimethylammonium-propane (DPTAP), having a choline group, was used to investigate this interaction by using sum-frequency vibrational spectroscopy. The sum-frequency spectrum characteristic of a neat monolayer changed to that of a bare air/water interface at a larger molecular area of the DPTAP molecules due to local laser heating. Upon introduction of the aromatic molecules in the subphase at around 120 Å2 per molecule, the sum-frequency signal suddenly reappeared due to molecular adhesion, and this was utilized to probe the adsorption of the aromatic ring molecules in the water subphase to the choline headgroup of the DPTAP by cation-π interaction. The onset concentrations of this sum-frequency signal change allowed a comparison of the relative interaction strengths between different aromatic molecules. A zwitterionic surfactant molecule (DPPC) was found to interact weakly compared to the cationic DPTAP molecule.