Monolayer Phase Research Articles

Dynamic three dimensional environment for efficient and large scale generation of smooth muscle cells from hiPSCs

BackgroundChronic ischemic limb disease often leads to amputation, which remains a significant clinical problem. Smooth-muscle cells (SMCs) are crucially involved in the development and progression of many cardiovascular diseases, but studies with primary human SMCs have been limited by a lack of availability. Here, we evaluated the efficiency of two novel protocols for differentiating human induced-pluripotent stem cells (hiPSCs) into SMCs and assessed their potency for the treatment of ischemic limb disease.MethodshiPSCs were differentiated into SMCs via a conventional two-dimensional (2D) protocol that was conducted entirely with cell monolayers, or via two protocols that consisted of an initial five-day three-dimensional (3D) spheroid phase followed by a six-day 2D monolayer phase (3D + 2D differentiation). The 3D phases were conducted in shaker flasks on an orbital shaker (the 3D + 2D shaker protocol) or in a PBS bioreactor (the 3D + 2D bioreactor protocol). Differentiation efficiency was evaluated via the expression of SMC markers (smooth-muscle actin [SMA], smooth muscle protein 22 [SM22], and Calponin-1), and the biological activity of the differentiated hiPSC-SMCs was evaluated via in-vitro assessments of migration (scratch assay), contraction in response to the treatment with a prostaglandin H2 analog (U46619), and tube formation on Geltrex, as well as in-vivo measurements of perfusion (fluorescence angiography) and vessel density in the limbs of mice that were treated with hiPSC-SMCs after experimentally induced hind-limb ischemia (HLI).ResultsBoth 3D + 2D protocols yielded > 5.6 × 107 hiPSC-SMCs/differentiation, which was ~ nine-fold more than that produced via 2D differentiation, and flow cytometry analyses confirmed that > 98% of the 3D + 2D-differentiated hiPSC-SMCs expressed SMA, > 81% expressed SM22, and > 89% expressed Calponin-1. hiPSC-SMCs obtained via the 3D + 2D shaker protocol also displayed typical SMC-like migratory, contraction, and tube-formation activity in-vitro and significantly improved measurements of perfusion, vessel density, and SMA-positive arterial density in the ischemic limb of mouse HLI model.ConclusionsOur dynamic 3D + 2D protocols produced an exceptionally high yield of hiPSC-SMCs. Transplantation of these hiPSC-SMCs results in significantly improved recovery of ischemic limb after ischemic injury in mice.

First-principles study of the electron and phonon transport properties in monolayer boron monosulfide

Abstract Motivated by the excellent electronic properties of theoretical proposed monolayer boron monosulfides (BS) binary materials, which belong to a light-element member of the group IIIA chalcogenides family, we have investigated the electron and phonon transport properties of three monolayer phases of BS (α, β and γ) using first-principles and Boltzmann transport theory methods. The calculated electronic structures show that α- and β-BS are semiconductors with indirect bandgaps of 4.01 eV and 3.87 eV, respectively, whereas the γ-BS is a semiconductor with a direct bandgap of 2.97 eV. Additionally, due to their light carrier effective masses, superior high carrier mobilities are observed, thus bringing high Seebeck coefficients. We also find that due to the absence of imaginary phonon frequencies, the three monolayer phases of BS show dynamical stability. The phonon group velocity and relaxation time are also calculated to analyze the phonon thermal conductivity. We find that strong phonon scattering makes γ-BS monolayer possess extremely low phonon thermal conductivity (1.2 and 2.7 Wm−1K−1 along the x and y directions at 300 K, respectively), whereas α- and β-BS monolayers show a relatively high phonon thermal conductivity. Therefore, the highest predicted ZT value of 1.7 ( n -type) at 700 K is obtained for monolayer γ-BS along the x direction. However, α- and β-BS monolayers have extremely low ZT values. Our results reveal that the γ-BS monolayer has wider promising applications in high performance thermoelectric material than α- and β-BS monolayers.

Disappearance of Odd-Even Effects at the Substrate Interface of n-Alkanes.

The physical and chemical properties of organic compounds having alkyl chains are frequently influenced by the parity of the chain length, which is known as the odd-even effect. Understanding the molecular origin of this phenomenon is particularly important for designing materials used in organic thin-film devices. In this work, we focus on thin films of n-alkanes as the simplest model to study the odd-even effect at the substrate interface and analyze the aggregation structure using p-polarized multiple-angle incidence resolution spectrometry in combination with grazing incidence X-ray diffraction. The spectroscopic analysis shows a pronounced odd-even alternation of the molecular tilt angles in the multilayer films. In addition, high-resolution Brewster-angle transmission spectroscopy reveals that the conformation of the methyl group highly depends on whether the carbon number is even or odd. In contrast to the multilayer films, the odd-even effects do not appear in the monolayer films. We demonstrate that, in other words, the interlayer interactions of the molecules are responsible for the odd-even effects. This study also highlights the first identification of the monolayer phase of n-alkanes by using grazing incidence X-ray diffraction in combination with high-resolution infrared spectroscopy. These results not only reveal the molecular origin for the odd-even effect of n-alkanes but also provide analytical techniques for discussing the monolayer structure of various alkylated compounds on a functional group basis.

Strain-modulated intercalated phases of Pb monolayer with dual periodicity in SiC(0001)-graphene interface

Intercalation of metal atoms at the SiC(0001)-graphene (Gr) interface can provide confined 2D metal layers with interesting electronic properties. The intercalated Pb monolayer (ML) has shown the coexistence of the Gr(10 × 10)-moiré and a stripe phase, which still lacks understanding. Using density functional theory calculation and thermal annealing with ab initio molecular dynamics as motivated by experiment, we have studied the formation energy of Gr/Pb/SiC(0001) for different Pb coverages. Near the coverage of a Pb(111)-like ML mimicking the (10 × 10)-moiré, we find a slightly more stable stripe structure, where one half of the structure has compressive strain with Pb occupying the Si-top sites and the other half has tensile strain with Pb off the Si-top sites. This stripe structure along the Gr zigzag direction has a periodicity of 2.3 nm across the [1 2¯ 10] direction agreeing with the previous observations using scanning tunneling microscopy. Analysis with electron density difference and density of states show the tensile region has a more metallic character than the compressive region, while both are dominated by charge transfer from Pb ML to SiC(0001). The small energy difference between the stripe and Pb(111)-like structures means the two phases are almost degenerate and can coexist, which explains the experimental observations.

Optical anisotropy and surface phases of cholesterol derivative monolayer at air–water interface

Cholesterol and its derivatives play crucial roles in regulating processes of biological membranes. Langmuir monolayer can mimic a bio-membrane which can be used to investigate the molecular interaction governing the important physical phenomena. The cholesterol derivative exhibiting mesophases (CHLC molecules) was synthesized and spread at the air–water (A/W) interface to investigate the surface behavior. The monolayer exhibited a variety of surface phases such as gas, liquid expanded (LE), low density liquid like (L1) and liquid condensed (L2) phases. Treating the CHLC molecules to be rod-like, the average tilt of the molecules with respect to the surface normal in these phases are found to be different. The tilt angle decreases systematically from LE to L2 phase. The optical anisotropy of the ultrathin Langmuir-Blodgett (LB) films of CHLC molecules in these phases was measured using the surface plasmon resonance (SPR) spectroscopy. The high tilted molecules in the ultrathin LB film displayed a high value of optical anisotropy. The ultrathin film of CHLC molecules at different interfaces was investigated using Brewster angle microscopy, X-ray reflectivity (XRR), SPR spectroscopy and atomic force microscopy. This study is useful for the systems where the physical phenomena are governed by tilt of the molecules.

PH-dependent self-assembly of an acid derivative of cholesterol at interfaces

Understanding and control over the self-assembly of molecules is desirable in many physico-chemical processes. Functional groups responsive to a pH change offer immense scope in driving selective molecular self-assembly. pH-dependent self-assembly of an aromatic acid derivative of cholesterol, 4-(6-(cholest-5-ene-3-yloxy)-5-(oxopentyloxy)) benzoic acid, ChBA, is investigated at the air-aqueous interface and characterized using different interface-sensitive techniques. Evidence for the presence of unstable films of ChBA at the air-water interface or for pH < 10 emerges from the surface pressure – area per molecule isotherm, surface pressure relaxation, and Brewster angle microscopy studies. In contrast, for pH > 10.6, ChBA forms a relatively stable film with a higher magnitude of the collapse pressure (45 mN/m). The compressional moduli and the textures obtained using Brewster angle microscopy reveal the presence of two phases (L1 and L2), which are also highly stable with temperature. The surface topography of ChBA films transferred from the air-water interface reveals the presence of multilayers of different thicknesses, for film transferred at pH 11 reveals primarily a uniform and homogenous monolayer. Based on the dependence of the collapse pressure with pH, the surface pKa of ChBA is estimated to be about 10.6. Our studies show that the undissociated ChBA spontaneously forms multilayers, whereas partially or fully dissociated ChBA forms distinct and ordered monolayer phases, highlighting the role of electrostatic interactions.

Interfacial Enrichment of Lauric Acid Assisted by Long-Chain Fatty Acids, Acidity and Salinity at Sea Spray Aerosol Surfaces.

Surfactant monolayers at sea spray aerosol (SSA) surfaces regulate various atmospheric processes including gas transfer, cloud interactions, and radiative properties. Most experimental studies of SSA employ a simplified surfactant mixture of long-chain fatty acids (LCFAs) as a proxy for the sea surface microlayer or SSA surface. However, medium-chain fatty acids (MCFAs) make up nearly 30% of the FA fraction in nascent SSA. Given that LCFA monolayers are easily disrupted upon the introduction of chemical heterogeneity (such as mixed chain lengths), simple FA proxies are unlikely to represent realistic SSA interfaces. Integrating experimental and computational techniques, we characterize the impact that partially soluble MCFAs have on the properties of atmospherically relevant LCFA mixtures. We explore the extent to which the MCFA lauric acid (LA) is surface stabilized by varying acidity, salinity, and monolayer composition. We also discuss the impacts of pH on LCFA-assisted LA retention, where the presence of LCFAs may shift the surface-adsorption equilibria of laurate─the conjugate base─toward higher surface activities. Molecular dynamic simulations suggest a mechanism for the enhanced surface retention of laurate. We conclude that increased FA heterogeneity at SSA surfaces promotes surface activity of soluble FA species, altering monolayer phase behavior and impacting climate-relevant atmospheric processes.

Line tension and line entropy associated with the monolayer/trilayer boundary of smectic liquid crystal at the air-water interface.

Molecularly thin films of the smectic liquid crystal 4'-octyl-4-biphenylcarbonitrile (8CB) at the air-water interface phase separate into regions with different numbers of layers, in analogy with freestanding smectic liquid crystalline films. This paper reports the line tension associated with the boundary of coexisting trilayer and monolayer phases of in Langmuir films of 8CB at the air-water interface as a function of temperature and humidity and infers information on the boundary profile between the coexisting phases. Two complementary techniques are used to characterize the 8CB thin films: surface pressure-area isotherm and Brewster angle microscopy (BAM). We determine the line tension by stretching isolated domains from their equilibrium circular shape and analyzing the free relaxation with a hydrodynamic model. Then, we interpret the line tension vs temperature data in terms of an excess line entropy for the domain boundary, which requires careful consideration of the thermodynamics of inhomogeneous monolayer systems.

Friction Force Mapping of Molecular Ordering and Mesoscopic Phase Transformations in Layered-Crystalline Organic Semiconductor Films.

It is critical to understand molecular ordering processes in small-molecule organic semiconductor (OSC) films in optimizing electronic device applications, although it is difficult to observe and investigate the ordering characteristics at a mesoscopic or device scale. Here, we report that friction force microscopy (FFM) allows visualizing the ordering transformation process from a thermodynamically metastable phase to a stable phase at a mesoscopic scale. We utilized 2-octyl-benzothieno[3,2-b]naphtho[2,3-b]thiophene (2-C8-BTNT) as a typical highly layered-crystalline OSC. We found that the friction force between an AFM tip and spin-coated OSC films significantly depends on whether local film states are in metastable monolayer phase or stable bilayer-type herringbone (b-LHB) phase that exhibits high carrier mobility. The formation of the stable b-LHB phase leads to lower friction than the metastable monolayer phase, clearly visualizing the molecular order. Force map (Fmap) analysis indicates that the lower friction in the b-LHB phase should be associated with the reduction of interfacial adhesion force. Notably, the observed results demonstrate that the spin-coated thin film changes from continuous film with the monolayer phase to rugged microcrystal grains with the b-LHB phase when left at ambient conditions. By contrast, an appropriate post-thermal annealing process facilitates the phase transformation without inducing such morphological changes. The technique provides a unique and effective tool for revealing the relationship between processing conditions and device performance in polycrystalline OSC films.

Ammonium ion removal from aqueous solutions in the presence of organic compounds, using biochar from banana leaves. Competitive isotherm models

BackgroundIndustrial, e.g. food industrial and domestic wastewaters contain huge amount of compounds causing eutrophication, and should be removed with high cost during wastewater treatment. However, these compounds could be utilized as fertilizers too. Biochar can remove a wide range of pollutants from water, such as ammonium, which can be found in relatively high concentration in dairy wastewaters. However, adsorption performance may be affected by the presence of other wastewater pollutants. Thus, this study aims to determine the efficiency of biochar as an adsorbent of ammonium in aqueous solutions in the presence of some selected organic compounds of typical dairy wastewaters such as bovine serum albumin (BSA), lactose, and acetic acid. Methods: The biochar was produced from banana leaves at 300 °C, modified with NaOH, and characterized by Scanning Electron Microscope – Energy Dispersive X-Ray Spectroscopy (SEM-EDX), Fourier-transform infrared spectra (FTIR) analysis, and specific surface area measurements. Batch experiments were carried out to investigate the ammonium adsorption capacity and the ion competitive adsorption mechanism. Significant Findings: Results show that the surface structure of the biochar derived from banana leaves is different from other biochars previously studied; although the specific surface area is not very considerable and despite having nitrogen within the elemental composition, the biochar studied is capable of adsorbing 2.60 mg NH4+/m2, the highest ammonium removal in 2 h occurs at pH 9 and 500 mg biochar dose. Langmuir model in the monolayer phase analysis fits better for all scenarios and the maximum NH4+ adsorption capacity was 0.97 mg/g without organic compounds. In the multilayer adsorption phase, the isotherm model that best fits the data obtained is the Harkins-Jura model without organic compounds. The presence of organic compounds in the aqueous solution significantly impacts the adsorption of ammonium by biochar since it improves the adsorption capacity (1.132 mg/g BSA, 0.975 mg/g lactose, and 1.874 mg/g acetic acid). The Aranovich-Donohue isotherm model fitted the data obtained during ion competitive adsorption experiments well.

Significant improvement in structural, electronic, optical and thermoelectric properties of PdTe2 in bulk and monolayer phase: A G0W0+BSE approach

Using first principles calculations structural, electronic, thermoelectric and optical properties of PdTe2 in bulk and monolayer were investigated. The calculated lattice parameters with different exchange correlation functionals show that the results obtained with addition of van der Waals corrections (vdW-DFC09x) are very well matched with the results obtained experimental. For correct prediction of electronic band gap, G0W0 approximation is used and the calculated band structure reveal that PdTe2 in bulk form has metallic nature as attained in experimental studies. In addition, the electronic band gap results with G0W0 approximation depicted that PdTe2 in monolayer phase is a semiconductor material with a direct band gap of 1.12 eV. The optical spectra have been calculated via many-body perturbation theory (MBPT) by solving Bethe-Salpeter equation (BSE) (G0W0+BSE). Ultimately, the results of optical spectra demonstrated that PdTe2 in monolayer phase has strong optical absorption within visible light wavelengths than the bulk phase which is good for solar cell applications. Thermoelectric (TE) properties of PdTe2 in bulk and monolayer structures have been studied using BoltzTraP code. The TE properties calculations indicated that better performance can be obtained by reducing the dimensionality of materials. The figure of merit was found to be above unity for monolayer phase. This paper successfully exploited the enhancement of the figure of merit values with the monolayer structure of PdTe2 material.

Photoinduced Electronic and Spin Topological Phase Transitions in Monolayer Bismuth.

Ultrathin bismuth exhibits rich physics including strong spin-orbit coupling, ferroelectricity, nontrivial topology, and light-induced structural dynamics. We use abinitio calculations to show that light can induce structural transitions to four transient phases in bismuth monolayers. These light-induced phases exhibit nontrivial topological character, which we illustrate using the recently introduced concept of spin bands and spin-resolved Wilson loops. Specifically, we find that the topology changes via the closing of the electron and spin band gaps during photoinduced structural phase transitions, leading to distinct edge states. Our study provides strategies to tailor electronic and spin topology via ultrafast control of photoexcited carriers and associated structural dynamics.

Structural Order and Thermal Behavior of Ph-BTBT-10 Monolayer Phases

Structural Order and Thermal Behavior of Ph-BTBT-10 Monolayer Phases

MoS2 2D-polymorphs as Li-/Na-ion batteries: 1T' vs 2H phases

In this study, we compare the performance of two phases of MoS2 monolayers: 1T' and 2H, about their ability to adsorb lithium and sodium ions. Employing the density functional theory and molecular dynamics, we include the ion concentration to analyze the electronic structure, ion kinetics, and battery performance. The pristine 2H-MoS2 monolayer is the ground state. However, the charge transfer effects above a critical ion concentration yield a stability change, where the 1T'-MoS2 monolayer with adsorbed ions becomes more stable than the 2H counterpart. The diffusion of ions onto the 1T' monolayer is anisotropic, being more efficient at ion adsorption than the 2H phase. Finally, we calculate the open circuit voltage and specific capacity, confirming that the 1T'-MoS2 phase has great potential for developing lithium/sodium ion batteries.

Coexistence of a spin–valley-coupled Dirac semimetal and robust quantum spin Hall state with significant Rashba spin-splitting in a halogenated BiAs film

We predict multiple topological phases in a d-ClBiAsI monolayer through first-principles calculations. It harbors an exceptionally uncommon spin–valley-coupled Dirac semimetal (svc-DSM) state under modest tensile strain.

Two-dimensional fullerene-based monolayer materials assembled by C80 and Sc3N@C80.

Construction of two-dimensional (2D) materials using fullerenes as building blocks has attracted particular attention, primarily due to their ability to integrate desired functionalities into devices. However, realization of stable 2D phases of polymerized fullerenes remains a big challenge. Here, we propose two stable 2D monolayer phases with covalently bridged C80 cages, namely α-C80-2D and β-C80-2D, which are semiconductors with strong absorption in the long wave range and appreciable carrier mobility, respectively. The high stability originates from the bond energy released by the [2+2] cycloaddition polymerization of C80 is greater than the deformation energy of a cage. Starting from α-C80-2D, endohedral incorporation of the Sc3N molecule into each C80 cage leads to 2D semiconductors of α-Sc3N@C80-2D and α'-Sc3N@C80-2D, which possess exceptional stability and diverse physical properties, including unique electronic band structures, strong optical absorption in the visible (VIS) to near-infrared (NIR) regime, and anisotropic optical characteristics. Remarkably, a temperature-induced order-disorder transition in the α-Sc3N@C80-2D phase has been observed at elevated temperatures above 600 K. These findings expand the family of 2D carbon materials and provide useful clue for the potential applications of fullerene-assembled monolayer networks.

An investigation of the 2D Rb2O monolayer intrinsic properties from a theoretical perspective using DFT

In this research, Density Functional Theory (DFT) was employed to investigate the 1T phase of the Rb2O monolayer. The structural, electronic, optical, and thermal properties were studied utilizing the WIEN2k software. The band gaps found using GGA, LDA, mBJ, and hybrid correlation were 0.52 eV, 0.49 eV, 1.52 eV, and 1.17 eV. The phonon dispersion curve is implemented to assess the Rb2O monolayer's dynamical stability. The thermal stability is assessed using the Car-Parrinello Molecular Dynamics (CPMD) code of Quantum espresso. The absorption coefficient attains its peak value of 35.74 cm−1 at 9.72 eV. Based on the optical property results, the Rb2O monolayer shows promise in designing photovoltaic devices. At 400K, the Figure of merit found to be 0.85 which indicates that the Rb2O monolayer can be used for waste heat recovery systems. The excitonic effects are ascertained by the effective masses of the holes and electrons.

Photoinduced phases in jacutingaite monolayer

Photoinduced phases in jacutingaite monolayer

Topological phases of monolayer and bilayer depleted Lieb lattices

Existence of nontrivial topological phases in a tight binding Haldane-like model on the depleted Lieb lattice is reported. This two-band model is formulated by considering the nearest-neighbor (NN), next-NN (NNN) and next-NNN hopping terms along with complex phase which breaks the time reversal symmetry of this semi-metallic system. Topological feature of this model is studied along with the presence of sublattice symmetry breaking staggered onsite energy. Combined effect of these two broken symmetries is found crucial for an additional transition between nontrivial and trivial phases. System exhibits two types of phase transitions, say, between two nontrivial phases and nontrivial to trivial phases. Nonzero Chern numbers, existence of Hall plateau and symmetry protected edge states confirm the presence of the nontrivial phases. This two-band system hosts four different types of phases where two are topological. Additionally topological properties of stacked bilayer of the depleted Lieb lattices is also studied with similar Haldane-like Hamiltonian. This four-band system is found to host Chern insulating phases, with higher values of Chern numbers supported by in-gap edge states.

Monolayers of amino acid-type amphiphiles

The monolayer characteristics of selected N-alkanoyl substituted α-amino acid are studied with the objective to demonstrate the specific effect of the chemical structure of the polar head group which is highlighted with the D- and L-enantiomers of the following selected examples: R-alanine, R-serine, R-threonine, R-allo-threonine, and R-aspartic acid (R = C16, C18). The thermodynamic effect of the head group variation is studied. Experimental π-A isotherms of the N-tetradecyl-L-alanine monolayers show similar behavior as those of usual amphiphiles. The -CH3-group in R-alanine with the simplest head group structure is substituted by a -CH2-OH group in R-serine and serine methylester and by a -CH- CH3-OH group in R-threonine (or allo-threonine) and threonine methylester. The introduction of the methyl group in 3-position of serine (serine to 3-methyl-serine = threonine) shifts the characteristic temperatures by >20 K to lower values determined for N-C16-Dl-serine. The formation of the corresponding methylester decreases these temperatures by 15 K for serine with the shorter (C16) alkyl chain and only by ∼5 K for threonine with the longer chain (C18). The π–A curves of the enantiomeric and racemic allo-forms show similar features to those of N-stearoyl-threonine. The absolute T0-values (disappearance of the LE/LC-transition) are 4–5 K larger compared with the corresponding N-stearoyl-threonines, but the ΔT0 between the enantiomeric (D) and the racemic (DL) forms is only slightly larger than that of N-stearoyl-threonine.Monolayers of different N-alkanoyl substituted α-amino acid amphiphiles have been mesoscopically characterized. Substantial topological differences are observable at the condensed phase domains of several amino acid amphiphiles, such as, N-palmitoyl aspartic acid, N-palmitoyl- or N-stearoyl serine methyl ester, N-stearoyltyrosine, N-palmitoyl or N-myristoyl alanine. Many fascinating domain shapes are found, but always the curvatures of the two enantiomeric forms are directed in an opposite sense. The domain shape of the 1:1 racemic mixtures is usually different, but very often oppositely curved texture elements are observable.GIXD is used to study the characteristic features of the lattice structure of condensed monolayer phases on the Angstrom scale. Specific for all structures is the large tilt angle with respect to the surface normal, which decreases only marginally by compression. The large size of the head groups and strong interactions between them dominate the monolayer structure. As presented for NC16 and N-C18-threonine, N-C16-DL -serine, N-C16-L -serine, NC16 DL -serine-ME, NC16 L -serine-ME, NC18 DL -threonine-ME, and NC18 L -threonine-ME the enantiomers form an oblique lattice structure (3 diffraction peaks), whereas two peaks are observed for the racemates forming NNN tilted orthorhombic structures. A complete phase diagram of mixed monolayers of the D- and L-enantiomers of N-stearoyl-threonine with two eutectic points at xD ≈ 0.25 and xD ≈ 0.75 is proposed.The quantum chemical semiempirical PM3 method is applied to calculate the thermodynamic and structural parameters of clusterization in finite and infinite clusters for N-alkanoyl-substituted alanine with n = 8–17 carbon atoms in the chain at the air/water interface with the aim to obtain a new theoretical verification of the experimental results.