Journal articles on the topic 'Monolayer'
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1
Białkowska, Katarzyna, Małgorzata Bobrowska-Hägerstrand, and Henry Hägerstrand. "Expansion of Phosphatidylcholine and Phosphatidylserine/Phosphatidylcholine Monolayers by Differently Charged Amphiphiles." Zeitschrift für Naturforschung C 56, no. 9-10 (October 1, 2001): 826–30. http://dx.doi.org/10.1515/znc-2001-9-1024.
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Abstract Monolayer Technique, Nonionic Detergent, Erythrocyte Shape The degree and time-course of expansion of palmitoyloleoylphosphatidylcholine (PC) and bovine brain phosphatidylserine (PS)/PC (75:25, mol/mol) monolayers at 32 mN/m caused by differently charged amphiphiles (detergents) added to the sub-phase buffer (pH 7.4, 22 °C) were followed. Amphiphiles were added to the sub-phase at a concentration/monolayer area corresponding to the concentration/erythrocytes surface area where sphero-echinocytic or sphero-stomatocytic shapes are induced (0.46-14.6 μᴍ). Nonionic, cationic and anionic am phiphiles expanded the PS/PC monolayer significantly more (1.7-4.2 times) than the PC monolayer. A zwitterionic amphiphile expanded both monolayers to a similar extent. The initial rate of monolayer-expansion was higher for all amphiphiles (1.7-20.4 times) in the PS/PC monolayer than in the PC monolayer.It is suggested that hydrophobic interactions govern the intercalation of amphiphiles into monolayers, and that monolayer packing, modulated by phospholipid head group interactions and alkyl chain saturation, strongly influence amphiphile intercalation. A possible relation between the monolayer-expanding effect of amphiphiles and their effect on erythrocyte shape is discussed.
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Lu, L., H. Cui, W. Li, H. Zhang, and S. Xi. "Study of the mechanism for controlled crystallization of BaF2 under two kinds of monolayers." Journal of Materials Research 16, no. 8 (August 2001): 2415–20. http://dx.doi.org/10.1557/jmr.2001.0331.
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Controlled crystallization of BaF2 under two different kinds of monolayers, octadecylamine [CH3(CH2)17NH2] and hexadecanol [CH3(CH2)14CH2OH], has been studied by using x-ray diffraction (XRD) and scanning electron microscope. It was found that the monolayer headgroup, the degree of ionization of the headgroup, etc., had a complicated effect on the selectivity of monolayers for crystal and on the morphology and orientation of crystals grown under the compressed monolayers. At pH = 7.0, XRD analysis showed that (100)-oriented BaF2 crystals were formed under the octadecylamine monolayer, while several kinds of crystals were found under the hexadecanol monolayer. In comparison, at pH = 8.5, both (100)-oriented BaF2 and (111)-oriented Ba(NO3)2 crystals were obtained under the monolayer of octadecylamine. However, crystals formed under hexadecanol monolayer consist of BaF2, Ba(NO3)2, etc. The detailed mechanism for crystallization was discussed in terms of the specific interaction and lattice matching between the monolayer headgroup and the nucleating species.
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Takeshita, Naoki, Masanari Okuno, and Taka-aki Ishibashi. "Molecular conformation of DPPC phospholipid Langmuir and Langmuir–Blodgett monolayers studied by heterodyne-detected vibrational sum frequency generation spectroscopy." Physical Chemistry Chemical Physics 19, no. 3 (2017): 2060–66. http://dx.doi.org/10.1039/c6cp07800a.
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Heterodyne-detected vibrational sum frequency generation spectroscopy was used to investigate molecular structures of DPPC monolayers on water (Langmuir monolayer) and monolayers on a fused silica substrate (Langmuir-Blodgett [LB] monolayer).
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Zhang, Bo, Tomas Mikysek, Veronika Cicmancova, Stanislav Slang, Roman Svoboda, Petr Kutalek, and Tomas Wagner. "2D GeSe2 amorphous monolayer." Pure and Applied Chemistry 91, no. 11 (November 26, 2019): 1787–96. http://dx.doi.org/10.1515/pac-2019-0501.
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Abstract In this paper, GeSe2 thin film and glass ingot were prepared in a layered structure. Subsequently, the 2D amorphous monolayers were achieved from layered thin film and layered glass ingot. The thicknesses of monolayers from thin film range from 1.5 nm to 5 nm. And the thickness of monolayer from glass ingot is 7 μm. The fast cooling of material results in the formation of self-assembled monolayers. In the case of thin film, layers are connected with “bridge”. After doping of Ag, the precipitation of nano particles exfoliates the adjacent monolayers which can be further dispersed by etching of Ag particles. In the case of glass ingot, the composition changes at 1 % between adjacent monolayers, according to EDX (energy-dispersive X-ray spectroscopy) spectra. And the glass 2D monolayer can be mechanically peeled off from the glass ingot.
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Baker, MV, and J. Landau. "Self Assembled Alkanethiolate Monolayers as Thin Insulating Films." Australian Journal of Chemistry 48, no. 6 (1995): 1201. http://dx.doi.org/10.1071/ch9951201.
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Simple devices that contain alkanethiolate monolayers sandwiched between conducting films were prepared by fixing a gold film to the surface of an alkanethiolate monolayer (on a gold substrate) with silver paint. These devices, and similar devices that did not contain alkanethiolate monolayers, were tested as resistors in d.c . circuits. The devices that contained octadecanethiolate monolayers had resistances of approximately 1012 Ω, 10 orders of magnitude higher than the resistance of devices that contained no monolayers. Sulfur- terminated alkanethiolate monolayers were prepared by treatment of carboxylic acid-terminated monolayers with vapours of thionyl chloride followed by vapours of hexane-1,6-dithiol. Attempts to use the sulfur-containing groups at the surface of this monolayer as 'molecular glue' to attach a flexible gold film to the surface of the monolayer were unsuccessful.
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Kajiyama, Tisato. "Novel Concepts of the Aggregation Structure of Organic Monolayers on the Surface of Water." MRS Bulletin 20, no. 6 (June 1995): 32–38. http://dx.doi.org/10.1557/s0883769400036952.
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Langmuir-Blodgett (LB) films have been applied to molecular electronics, nonlinear optics, and biosensors. Their useful properties can be accessed by using a defect-free monolayer—the precursor of LB films. In order to prepare a defect-free or defect-diminished monolayer, it is necessary to estimate the molecular arrangements and structural defects in the monolayer. The actual structure of monolayers on the surface of water have been proposed on the basis of recent morphological and structural studies. Molecular-aggregation processes or monolayer-formation processes do not always match the general concept concluded from surface pressure-area (π-A) isotherms. Therefore, a universal understanding has not been reached. Here we present a novel and systematic classification for the aggregation structure of monolayers on the water surface and also demonstrate how to prepare defect-diminished monolayers.
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Pires, Cristiana L., Catarina Praça, Patrícia A. T. Martins, Ana L. M. Batista de Carvalho, Lino Ferreira, Maria Paula M. Marques, and Maria João Moreno. "Re-Use of Caco-2 Monolayers in Permeability Assays—Validation Regarding Cell Monolayer Integrity." Pharmaceutics 13, no. 10 (September 26, 2021): 1563. http://dx.doi.org/10.3390/pharmaceutics13101563.
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Caco-2 monolayers are a common in vitro model used to evaluate human intestinal absorption. The reference protocol requires 21 days post-seeding to establish a stable and confluent cell monolayer, which is used in a single permeability assay during the period of monolayer stability (up to day 30). In this work, we characterize variations in the tightness of the cell monolayer over the stable time interval and evaluate the conditions required for their re-use in permeability assays. The monolayer integrity was assessed through TEER measurements and permeability of the paracellular marker Lucifer Yellow (LY), complemented with nuclei and ZO-1 staining for morphological studies and the presence of tight junctions. Over 150 permeability assays were performed, which showed that manipulation of the cell monolayer in the permeability assay may contribute significantly to the flux of LY, leading to Papp values that are dependent on the sampling duration. The assay also leads to a small decrease in the cell monolayer TEER, which is fully recovered when cell monolayers are incubated with culture media for two full days. When this procedure is followed, the cell monolayers may be used for permeability assays on days 22, 25, and 28, triplicating the throughput of this important assay.
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Palada, C., P. Schouten, and C. Lemckert. "Testing the effectiveness of monolayers under wind and wave conditions." Water Science and Technology 65, no. 6 (March 1, 2012): 1137–41. http://dx.doi.org/10.2166/wst.2012.959.
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Monolayers are highly desirable for their evaporation reducing capabilities due to their relatively minimal cost and ease of application. Despite these positive attributes, monolayers have consistently failed to perform effectively due to the harsh wind and wave conditions prevalent across real-world water reserves. An exhaustive and consistent study testing the influence of wind and wave combinations on monolayer performance has yet to be presented in the literature. To remedy this, the effect of simultaneous wind and wave conditions on a benchmark high-performance monolayer (octadecanol suspension, CH3(CH2)16CH2OH) has been analysed. Subjected only to waves, the monolayer remained intact due to its innate ability to compress and expand. However, the constant simultaneous application of wind and waves caused the monolayer to break up and gather down-wind where it volatilised over time. At wind speeds above 1.3 m s−1 the monolayer was completely ineffective. For wind speeds below this threshold, the monolayer had an influence on the evaporation rate dependent on wind speed. From these results a series of application protocols can now be developed for the optimised deployment of monolayers in real-world water reserves. This will be of interest to private, commercial and government organisations involved in the storage and management of water resources.
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Cheng, Wei-Ying, Huei-Ru Fuh, and Ching-Ray Chang. "First-Principles Study for Gas Sensing of Defective SnSe2 Monolayers." Applied Sciences 10, no. 5 (February 29, 2020): 1623. http://dx.doi.org/10.3390/app10051623.
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We report the interaction between gas molecules (NO2 and NH3) and the SnSe2 monolayers with vacancy and dopants (O and N) for potential applications as gas sensors. Compared with the gas molecular adsorbed on pristine SnSe2 monolayer, the Se-vacancy SnSe2 monolayer obviously enhances sensitivity to NO2 adsorption. The O-doped SnSe2 monolayer shows similar sensitivity to the pristine SnSe2 monolayer when adsorbing NO2 molecule. However, only the N-doped SnSe2 monolayer represents a visible enhancement for NO2 and NH3 adsorption. This work reveals that the selectivity and sensitivity of SnSe2-based gas sensors could be improved by introducing the vacancy or dopants.
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Cott, G. R. "Modulation of bioelectric properties across alveolar type II cells by substratum." American Journal of Physiology-Cell Physiology 257, no. 4 (October 1, 1989): C678—C688. http://dx.doi.org/10.1152/ajpcell.1989.257.4.c678.
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Rat alveolar type II cells were cultured on collagen-coated filters (CCF) and human amnionic basement membrane (ABM) to determine the effect of culture substratum on the development of monolayer bioelectric properties. Monolayers cultured on both substrata rapidly developed bioelectric properties with similar time courses, monolayer capacitance values (approximately 1 muF/cm2), current-voltage relationships, and responses to stimulants and inhibitors of active ion transport. Increasing seeding densities tended to increase monolayer bioelectric properties regardless of culture substratum. Monolayers cultured on ABM had higher resistance values (491 vs. 291 omega.cm2) and lower short-circuit currents (2.85 vs. 4.51 muA/cm2) than monolayers with similar cell densities cultured on CCF. These differences in monolayer bioelectric properties were not due to differences in substratum resistance or capacitance effects. The relationships between monolayer bioelectric properties were also affected by the culture substratum. In additional experiments, cells cultured on contracted gels formed monolayers with high short-circuit currents (9.25 muA/cm2). Cell morphology varied depending on the culture substratum, with cells cultured on contracted gels appearing the most cuboidal, whereas the flattest and most attenuated cells were those cultured on ABM. On the basis of these observations, we conclude that culture substratum significantly affects the development of bioelectric properties across alveolar type II cell monolayers. In vivo the bioelectric properties across the alveolar epithelium may also vary with changes in cellular substratum or cell density (e.g., after acute lung injury) and possibly with cell morphology (e.g., alveolar type I vs. alveolar type II cells).
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Pittaway, P., M. Herzig, N. Stuckey, and K. Larsen. "Biodegradation of artificial monolayers applied to water storages to reduce evaporative loss." Water Science and Technology 72, no. 8 (July 7, 2015): 1334–40. http://dx.doi.org/10.2166/wst.2015.348.
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Repeat applications of an artificial monolayer to the interfacial boundary layer of large agricultural water storages during periods of high evaporative demand remains the most commercially feasible water conservation strategy. However, the interfacial boundary layer (or microlayer) is ecologically distinct from subsurface water, and repeat monolayer applications may adversely affect microlayer processes. In this study, the natural cleansing mechanisms operating within the microlayer were investigated to compare the biodegradability of two fatty alcohol (C16OH and C18OH) and one glycol ether (C18E1) monolayer compound. The C16OH and C18OH compounds were more susceptible to microbial degradation, but the C18E1 compound was most susceptible to indirect photodegradation. On clean water the surface pressure and evaporation reduction achieved with a compressed C18E1 monolayer was superior to the C18OH monolayer, but on brown water the surface pressure dropped rapidly. These results suggest artificial monolayers are readily degraded by the synergy between photo and microbial degradation. The residence time of C18OH and C18E1 monolayers on clear water is sufficient for cost-effective water conservation. However, the susceptibility of C18E1 to photodegradation indicates the application of this monolayer to brown water may not be cost-effective.
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Iritani, Kohei. "Fabrication of monolayer with aggregation-induced emission at the air/water interface." Impact 2022, no. 3 (June 30, 2022): 21–23. http://dx.doi.org/10.21820/23987073.2022.3.21.
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Existing methods for producing transparent fluorescent materials are adequate for small scale production but unsuitable for larger scales. Assistant Professor Kohei Iritani and his team at the Department of Applied Chemistry, School of Engineering, Tokyo University of Technology, Japan, are working to develop 2D monolayers to overcome this. These monolayers are formed by the self-assembly of organic molecules at the solid/liquid or air/water interface and monolayers with the aggregation-induced emission (AIE) effect have the potential to be used as transparent fluorescent materials. The researchers have been successful in synthesising various AIE molecules and have made attempts to form a monolayer using the Langmuir-Blodgett (LB) trough. The team established a method whereby if a monolayer could not be obtained, feedback was given to the molecular design and a process of trial and error was repeatedly performed while new molecules were synthesised. This led to the construction of a fluorescence monolayer that can be transferred to a glass substrate while maintaining fluorescence emission. In their work to construct a monolayer with AIE effect at the air/water interface the researchers are seeking to suppress intramolecular motion using a flat surface of water as a substrate and make it emit fluorescence by forming a monolayer.
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Wasserman, Stephen R., Hans Biebuyck, and George M. Whitesides. "Monolayers of 11-trichlorosilylundecyl thioacetate: A system that promotes adhesion between silicon dioxide and evaporated gold." Journal of Materials Research 4, no. 4 (August 1989): 886–92. http://dx.doi.org/10.1557/jmr.1989.0886.
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The use of sulfur-containing organic monolayer films improves adhesion between gold and silicon dioxide. The structures of these monolayers were analyzed using contact angle, ellipsometry, and XPS. The zone of adhesive failure was at or near the gold-monolayer interface.
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Lv, Ming-Hao, Chang-Ming Li, and Wei-Feng Sun. "Spin-Orbit Coupling and Spin-Polarized Electronic Structures of Janus Vanadium-Dichalcogenide Monolayers: First-Principles Calculations." Nanomaterials 12, no. 3 (January 24, 2022): 382. http://dx.doi.org/10.3390/nano12030382.
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Phonon and spintronic structures of monolayered Janus vanadium-dichalcogenide compounds are calculated by the first-principles schemes of pseudopotential plane-wave based on spin-density functional theory, to study dynamic structural stability and electronic spin-splitting due to spin-orbit coupling (SOC) and spin polarization. Geometry optimizations and phonon-dispersion spectra demonstrate that vanadium-dichalcogenide monolayers possess a high enough cohesive energy, while VSTe and VTe2 monolayers specially possess a relatively higher in-plane elastic coefficient and represent a dynamically stable structure without any virtual frequency of atomic vibration modes. Atomic population charges and electron density differences demonstrate that V–Te covalent bonds cause a high electrostatic potential gradient perpendicular to layer-plane internal VSTe and VSeTe monolayers. The spin polarization of vanadium 3d-orbital component causes a pronounced energetic spin-splitting of electronic-states near the Fermi level, leading to a semimetal band-structure and increasing optoelectronic band-gap. Rashba spin-splitting around G point in Brillouin zone can be specifically introduced into Janus VSeTe monolayer by strong chalcogen SOC together with a high intrinsic electric field (potential gradient) perpendicular to layer-plane. The vertical splitting of band-edge at K point can be enhanced by a stronger SOC of the chalcogen elements with larger atom numbers for constituting Janus V-dichalcogenide monolayers. The collinear spin-polarization causes the band-edge spin-splitting across Fermi level and leads to a ferrimagnetic order in layer-plane between V and chalcogen cations with higher α and β spin densities, respectively, which accounts for a large net spin as manifested more apparently in VSeTe monolayer. In a conclusion for Janus vanadium-dichalcogenide monolayers, the significant Rashba splitting with an enhanced K-point vertical splitting can be effectively introduced by a strong SOC in VSeTe monolayer, which simultaneously represents the largest net spin of 1.64 (ћ/2) per unit cell. The present study provides a normative scheme for first-principles electronic structure calculations of spintronic low-dimensional materials, and suggests a prospective extension of two-dimensional compound materials applied to spintronics.
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Şologan, Maria, Cristina Cantarutti, Silvia Bidoggia, Stefano Polizzi, Paolo Pengo, and Lucia Pasquato. "Routes to the preparation of mixed monolayers of fluorinated and hydrogenated alkanethiolates grafted on the surface of gold nanoparticles." Faraday Discussions 191 (2016): 527–43. http://dx.doi.org/10.1039/c6fd00016a.
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The use of binary blends of hydrogenated and fluorinated alkanethiolates represents an interesting approach to the construction of anisotropic hybrid organic–inorganic nanoparticles since the fluorinated and hydrogenated components are expected to self-sort on the nanoparticle surface because of their reciprocal phobicity. These mixed monolayers are therefore strongly non-ideal binary systems. The synthetic routes we explored to achieve mixed monolayer gold nanoparticles displaying hydrogenated and fluorinated ligands clearly show that the final monolayer composition is a non-linear function of the initial reaction mixture. Our data suggest that, under certain geometrical constraints, nucleation and growth of fluorinated domains could be the initial event in the formation of these mixed monolayers. The onset of domain formation depends on the structure of the fluorinated and hydrogenated species. The solubility of the mixed monolayer nanoparticles displayed a marked discontinuity as a function of the monolayer composition. When the fluorinated component content is small, the nanoparticle systems are fully soluble in chloroform, at intermediate content the nanoparticles become soluble in hexane and eventually they become soluble in fluorinated solvents only. The ranges of monolayer compositions in which the solubility transitions are observed depend on the nature of the thiols composing the monolayer.
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Kramer, R. H. "Extracellular matrix interactions with the apical surface of vascular endothelial cells." Journal of Cell Science 76, no. 1 (June 1, 1985): 1–16. http://dx.doi.org/10.1242/jcs.76.1.1.
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Cultured aortic endothelial cells, like their in vivo counterparts, form highly organized, confluent monolayers of polarized epithelioid cells that secrete, exclusively at their basal surface, an extracellular matrix to which they then attach. The influence of isolated subendothelial matrix preparations on cell polarity and monolayer organization was studied by presenting fragments of the matrix to confluent bovine aortic endothelial cell cultures. The matrix particles were immediately bound to the apical aspect of the cell monolayer and induced rapid reorganization of the monolayer into cells with a fibroblastoid morphology. To determine if fibronectin, the major glycoprotein of the subendothelial matrix, could be involved in the observed apical cell surface-matrix interactions, latex beads or small discs of Nucleopore filters were coated with the glycoprotein and presented to confluent monolayers. In a fashion similar to that observed with matrix fragments, materials coated with fibronectin caused focal reorganization of the cell layer. After contact with the coated beads, the underlying endothelial cells flowed upward and spread over the entire bead, forming a canopy of confluent cells that draped the particle. Contact of confluent monolayers with the coated filters induced similar behaviour, except that monolayer reorganization into the fibroblastoid phenotype was followed by emigration of the majority of underlying cells through the pores to the upper filter surface, where they formed a new organized cell monolayer with the typical endothelial cell morphology. Thus contact of the apical surface of endothelial cells with structures to which they adhere initiates a rapid disruption of the organized cell monolayer, followed immediately by a concerted effort of the local population to re-establish both cell polarity and monolayer contiguity. The expression of this behaviour may be important during tissue remodeling that occurs in neovascularization and during interactions with thromboemboli.
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Wijers, C. M. J., and O. Voskoboynikov. "Optical Reflection from a Monolayer of Embedded Nano-Objects Covered by a Thick Capping Layer." Advanced Materials Research 31 (November 2007): 52–55. http://dx.doi.org/10.4028/www.scientific.net/amr.31.52.
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In a hybrid discrete-continuum description the optical response of a capped monolayer of nano-objects has been determined. The monolayer emits a summation of partial plane waves obeying traditional reflection and transmission, enabling solution of the monolayer dipole strength. For thick capping layers the resulting reflection coefficients could be approximated by analytical expressions. These results have been used to investigate the feasibility of experimental detection of the optical response of nano-object monolayers.
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Williams, Ian, and Todd M. Squires. "Evolution and mechanics of mixed phospholipid fibrinogen monolayers." Journal of The Royal Society Interface 15, no. 141 (April 2018): 20170895. http://dx.doi.org/10.1098/rsif.2017.0895.
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All mammals depend on lung surfactant (LS) to reduce surface tension at the alveolar interface and facilitate respiration. The inactivation of LS in acute respiratory distress syndrome (ARDS) is generally accompanied by elevated levels of fibrinogen and other blood plasma proteins in the alveolar space. Motivated by the mechanical role fibrinogen may play in LS inactivation, we measure the interfacial rheology of mixed monolayers of fibrinogen and dipalmitoylphosphatidylcholine (DPPC), the main constituent of LS, and compare these to the single species monolayers. We find DPPC to be ineffective at displacing preadsorbed fibrinogen, which gives the resulting mixed monolayer a strongly elastic shear response. By contrast, how effectively a pre-existing DPPC monolayer prevents fibrinogen adsorption depends upon its surface pressure. At low DPPC surface pressures, fibrinogen penetrates DPPC monolayers, imparting a mixed viscoelastic shear response. At higher initial DPPC surface pressures, this response becomes increasingly viscous-dominated, and the monolayer retains a more fluid, DPPC-like character. Fluorescence microscopy reveals that the mixed monolayers exhibit qualitatively different morphologies. Fibrinogen has a strong, albeit preparation-dependent, mechanical effect on phospholipid monolayers, which may contribute to LS inactivation and disorders such as ARDS.
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Vi, Vo T. T., Cuong Q. Nguyen, Bui D. Hoi, Huynh V. Phuc, Chuong V. Nguyen, and Nguyen N. Hieu. "Chemical functionalization of SnAs monolayer: a first-principles study of SnAsX (X = Cl, Br, and I) monolayers." Journal of Physics D: Applied Physics 55, no. 50 (November 3, 2022): 505302. http://dx.doi.org/10.1088/1361-6463/ac9e07.
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Abstract Chemical functionalization is one of the effective methods to tune the electronic properties of two-dimensional (2D) nanostructures. In this paper, we study the structural, electronic properties, and carrier mobilities of 2D SnAs monolayer functionalized by chlorine, bromine, and iodine, namely SnAsX (X = Cl, Br, and I), by means of density functional theory. The obtained results show that the 2D SnAsX are energetically, dynamically, and mechanically stable. While the 2D pristine SnAs monolayer exhibits metallic characteristics, SnAsX monolayers are direct semiconductors with direct band gaps. The influence of spin–orbit coupling on the electronic characteristics of SnAsX is significant, especially in the case of SnAsI monolayer. The direct–indirect gap transitions are found in all three SnAsX monolayers when the biaxial strain is applied. Meanwhile, the effects of external electric fields on the electronic characteristics of SnAsX are insignificant. Our calculated results indicate that SnAsX monolayers have very high electron mobility and their transport characteristics are directionally isotropic along the investigated transport directions.
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Sammak, P. J., L. E. Hinman, P. O. Tran, M. D. Sjaastad, and T. E. Machen. "How do injured cells communicate with the surviving cell monolayer?" Journal of Cell Science 110, no. 4 (February 15, 1997): 465–75. http://dx.doi.org/10.1242/jcs.110.4.465.
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Mechanically scratching cell monolayers relieves contact inhibition and induces surviving cells near the wound edge to move and proliferate. The present work was designed to test whether surviving cells passively respond to newly available space, or whether cells are actively stimulated by signals from injured cells nearby. We monitored intracellular free Ca2+ ([Ca2+]i) while scratching confluent monolayers of bovine pulmonary endothelial cells and mouse mammary epithelial cells. Within seconds after wounding, a transient elevation of [Ca2+]i was observed in surviving cells. In endothelial cells, the [Ca2+]i elevation propagated into the monolayer for a distance of 10 to 12 cell rows at a speed of 20 to 28 microm/second. The amplitude of the wave of [Ca2+]i was reduced as it propagated into the monolayer, but the velocity of the wave was nearly constant. Cells that experienced the [Ca2+]i elevation had intact plasma membranes, and survived for over 24 hours post wounding. Removing extracellular Ca2+ decreased the amplitude by two-thirds and reduced the propagation rate by half, suggesting that Ca2+ influx contributed to the increased [Ca2+]i. To determine how [Ca2+]i waves were stimulated, we blocked extracellular communication by fluid perfusion or intercellular communication by breaks in the monolayer. In bovine pulmonary artery endothelial cultures, the [Ca2+]i wave passed over breaks in the monolayer, and was prevented from traveling upstream in a perfusion chamber. Conditioned media from injured cells also elevated [Ca2+]i in unwounded reporter cultures. In mouse mammary epithelial monolayers with established cell-cell contacts, the [Ca2+]i wave passed over breaks in the monolayer, but was only partially prevented from traveling upstream during perfusion. These experiments showed that mechanical wounds lead to long distance, [Ca2+]i-dependent communication between the injured cells and the surviving cell monolayer through at least two mechanisms: first, extracellular release of a chemical stimulus from wounded cells that diffused to neighboring cells (present in both monolayers); second, transmission of an intercellular signal through cell-cell junctions (present in the mammary epithelial monolayers). Thus, mechanical injury provided a direct, chemical stimulus to nearby cells which have not themselves been damaged.
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Barnoud, Jonathan, Laura Urbini, and Luca Monticelli. "C 60 fullerene promotes lung monolayer collapse." Journal of The Royal Society Interface 12, no. 104 (March 2015): 20140931. http://dx.doi.org/10.1098/rsif.2014.0931.
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Airborne nanometre-sized pollutants are responsible for various respiratory diseases. Such pollutants can reach the gas-exchange surface in the alveoli, which is lined with a monolayer of lung surfactant. The relationship between physiological effects of pollutants and molecular-level interactions is largely unknown. Here, we determine the effects of carbon nanoparticles on the properties of a model of lung monolayer using molecular simulations. We simulate phase-separated lipid monolayers in the presence of a model pollutant nanoparticle, C 60 fullerene. In the absence of nanoparticles, the monolayers collapse only at very low surface tensions (around 0 mN m −1 ). In the presence of nanoparticles, instead, monolayer collapse is observed at significantly higher surface tensions (up to ca 10 mN m −1 ). Collapse at higher tensions is related to lower mechanical rigidity of the monolayer. It is possible that similar mechanisms operate on lung surfactant in vivo , which suggests that health effects of airborne carbon nanoparticles may be mediated by alterations of the mechanical properties of lung surfactant.
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Rubio, Ramón G., Eduardo Guzmán, Francisco Ortega, and Libero Liggieri. "Monolayers of Cholesterol and Cholesteryl Stearate at the Water/Vapor Interface: A Physico-Chemical Study of Components of the Meibum Layer." Colloids and Interfaces 5, no. 2 (May 20, 2021): 30. http://dx.doi.org/10.3390/colloids5020030.
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Langmuir monolayers containing different amounts of cholesterol and cholesteryl stearate were studied at two different temperatures (24 °C and 35 °C). The main goal was to contribute towards the understanding of how the variations in the chemical composition may affect the physico-chemical properties of these specific lipid monolayers. The model mixture was chosen considering that cholesteryl esters are present in cell membranes and some other biological systems, including human tear lipids. Therefore, an investigation into the effect of the lipid monolayer composition on their interfacial properties may elucidate some of the fundamental reasons for the deficiencies in cell membranes and tear film functioning in vivo. The experimental results have shown that the molar ratio of the mixture plays a crucial role in the modulation of the Langmuir film properties. The condensing effects of the cholesterol and the interactions between the lipids in the monolayer were the main factors altering the monolayer response to dilatational deformation. The modification of the mixture compositions leads to significant changes in the Langmuir films and the mechanical performance, altering the ability of the monolayer to reduce the surface tension and the viscoelastic properties of the monolayers. This suggests that subtle modifications of the biomembrane composition may significantly alter its physiological function.
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Yu, Yawei, Xiao Xie, Xiaobiao Liu, Jia Li, François M. Peeters, and Linyang Li. "Two-dimensional semimetal states in transition metal trichlorides: A first-principles study." Applied Physics Letters 121, no. 11 (September 12, 2022): 112405. http://dx.doi.org/10.1063/5.0105605.
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The two-dimensional (2D) transition metal trihalide (TMX3, X = Cl, Br, I) family has attracted considerable attention in recent years due to the realization of CrCl3, CrBr3, and CrI3 monolayers. Up to now, the main focus of the theoretically predicted TMX3 monolayers has been on the Chern insulator states, which can realize the quantum anomalous Hall effect. Here, using first-principles calculations, we theoretically demonstrate that the stable OsCl3 monolayer has a ferromagnetic ground state and a spin-polarized Dirac point without spin–orbit coupling (SOC), which disappears in the band structure of a Janus OsBr1.5Cl1.5 monolayer. We find that OsCl3 exhibits in-plane magnetization when SOC is included. By manipulating the magnetization direction along the C2 symmetry axis of the OsCl3 structure, a gapless half-Dirac semimetal state with SOC can be achieved, which is different from the gapped Chern insulator state. Both semimetal states of OsCl3 monolayer without and with SOC exhibit a linear half-Dirac point (twofold degenerate) with high Fermi velocities. The achievement of the 2D semimetal state with SOC is expected to be found in other TMX3 monolayers, and we confirm it in a TiCl3 monolayer. This provides a different perspective to study the band structure with SOC of the 2D TMX3 family.
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Galli-Resta, Lucia, Elena Novelli, and Alessandro Viegi. "Dynamic microtubule-dependent interactions position homotypic neurones in regular monolayered arrays during retinal development." Development 129, no. 16 (August 15, 2002): 3803–14. http://dx.doi.org/10.1242/dev.129.16.3803.
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In the vertebrate retina cell layers support serial processing, while monolayered arrays of homotypic neurones tile each layer to allow parallel processing. How neurones form layers and arrays is still largely unknown. We show that monolayered retinal arrays are dynamic structures based on dendritic interactions between the array cells. The analysis of three developing retinal arrays shows that these become regular as a net of dendritic processes links neighbouring array cells. Molecular or pharmacological perturbations of microtubules within dendrites lead to a stereotyped and reversible disruption of array organization: array cells lose their regular spacing and the arrangement in a monolayer. This leads to a micro-mechanical explanation of how monolayers of regularly spaced ‘like-cells’ are formed.
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Razinkov, Vladimir I., Grigory B. Melikyan, Richard M. Epand, Raquel F. Epand, and Fredric S. Cohen. "Effects of Spontaneous Bilayer Curvature on Influenza Virus–mediated Fusion Pores." Journal of General Physiology 112, no. 4 (October 1, 1998): 409–22. http://dx.doi.org/10.1085/jgp.112.4.409.
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Cells expressing the hemagglutinin protein of influenza virus were fused to planar bilayer membranes containing the fluorescent lipid probes octadecylrhodamine (R18) or indocarbocyanine (DiI) to investigate whether spontaneous curvature of each monolayer of a target membrane affects the growth of fusion pores. R18 and DiI lowered the transition temperatures for formation of an inverted hexagonal phase, indicating that these probes facilitate the formation of negative curvature structures. The probes are known to translocate from one monolayer of a bilayer membrane to the other in a voltage-dependent manner. The spontaneous curvature of the cis monolayer (facing the cells) or the trans monolayer could therefore be made more negative through control of the polarity of voltage across the planar membrane. Electrical admittance measurements showed that the open times of flickering fusion pores were shorter when probes were in trans monolayers and longer when in cis monolayers compared with times when probe was symmetrically distributed. Open times were the same for probe symmetrically distributed as when probes were not present. Thus, open times were a function of the asymmetry of the spontaneous curvature between the trans and cis monolayers. Enriching the cis monolayer with a negative curvature probe reduced the probability that a small pore would fully enlarge, whereas enriching the trans monolayer promoted enlargement. Lysophosphatidylcholine has positive spontaneous curvature and does not translocate. When lysophosphatidylcholine was placed in trans leaflets of planar membranes, closing of fusion pores was rare. The effects of the negative and positive spontaneous curvature probes do not support the hypothesis that a flickering pore closes from an open state within a hemifusion diaphragm (essentially a “flat” structure). Rather, such effects support the hypothesis that the membrane surrounding the open pore forms a three-dimensional hourglass shape from which the pore flickers shut.
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Horiuchi, Takashi, Kazuya Matsunaga, Masatoshi Banno, Yusuke Nakano, Kohei Nishimura, Chika Hanzawa, Kei-ichi Miyamoto, Shinsuke Nomura, and Yuji Ohta. "HPMCs Induce Greater Intercellular Delocalization of Tight Junction-Associated Proteins Due to a Higher Susceptibility to H2O2 Compared with HUVECs." Peritoneal Dialysis International: Journal of the International Society for Peritoneal Dialysis 29, no. 2 (March 2009): 217–26. http://dx.doi.org/10.1177/089686080902900217.
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Background Reactive oxygen species (ROS) have been speculated as possible inducers of structural or functional changes that lead to a hyperpermeable state in patients on long-term peritoneal dialysis. This study aimed to compare localization of tight junction-associated proteins (TJPs), which relate to solute permeability characteristics, between human peritoneal mesothelial cell (HPMC) monolayers and human umbilical vein endothelial cell (HUVEC) monolayers under oxidative stress. Methods HPMCs and HUVECs were cultured on a polymer mesh until transepithelial electrical resistance reached a plateau. Solute permeation tests were conducted using FITC-labeled dextrans. Localization of TJPs was observed under a confocal laser scanning microscope. These experiments were carried out with/without 0.1 mmol/L H2O2. In addition, ROS production as well as the amounts of intracellular reductive glutathione (GSH) and oxidative glutathione were measured. Results When the monolayers were exposed to 0.1 mmol/L H2O2/medium for 2 hours, the HPMC monolayer revealed a significant reduction in transepithelial electrical resistance (from 32.5 ± 3.4 to 17.4 ± 4.9 Ω cm ) with delocalization of TJPs, particularly occludins. The HUVEC monolayer remained stable and exhibited an unremarkable change in TJP organization. Compared to the HUVEC monolayer, the HPMC monolayer exhibited two- to threefold higher 2′,7′–dichlorofluorescein intensities that increased in a dose-dependent manner. HUVECs contained approximately 2.5-times more GSH than HPMCs. This supported the lesser production of ROS when exposed to 0.1 mmol/L H2O2 for 24 hours. HUVECs used 8.03 nmol/mg GSH protein to maintain TJP localization, while only 3.75 nmol/mg GSH protein was available for the HPMCs. Conclusion The HUVEC monolayer, which was less permeable to middle-to-high molecular weight solutes, was more tolerant against ROS stress than the HPMC monolayer. Availability of intracellular GSH is an important issue in maintaining the integrity of the mesothelium.
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Martínez, Hector, Enrique Chacón, Pedro Tarazona, and Fernando Bresme. "The intrinsic interfacial structure of ionic surfactant monolayers at water–oil and water–vapour interfaces." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 467, no. 2131 (February 16, 2011): 1939–58. http://dx.doi.org/10.1098/rspa.2010.0516.
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Using computer simulations, we investigate the interfacial structure of sodium dodecyl sulphate (SDS) monolayers adsorbed at the water surface and water–oil interfaces. Using an algorithm that removes the averaging effect of the capillary waves, we obtain a detailed view of the solvation structure of water around the monolayer. We investigate surface concentrations between 45 and 33 Å 2 per surfactant, which are near experimental conditions corresponding to the critical micellar concentration and the formation of Newton black films. The surfactants induce a layering structure in water, which disappears at approximately 1 nm from the monolayer plane. The water molecules exhibit a preferred orientation with the dipoles pointing towards the monolayer. The orientational order decays slowly, but it does not influence the hydrogen bond structure of water, which is significantly disrupted in the interfacial region only. These structural changes are qualitatively the same in SDS–water and oil–SDS–water interfaces. In the latter case, we find a small degree of penetration of oil in the monolayer (between 0.2 and 0.25 molecules per SDS). This small penetration has a measurable effect on the monolayer, which increases its thickness by approximately 10 per cent. The bending modulus of the SDS monolayers is of the order of the thermal energy, k B T .
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Tim, Beata, Monika Rojewska, and Krystyna Prochaska. "Effect of Silica Microparticles on Interactions in Mono- and Multicomponent Membranes." International Journal of Molecular Sciences 23, no. 21 (October 24, 2022): 12822. http://dx.doi.org/10.3390/ijms232112822.
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Advancing our understanding of the mechanism of the interaction between inhaled pollutant microparticles and cell membrane components is useful to study the impact of fine particulate matter on human health. In this paper, we focus on the effect of cholesterol (Chol) molecules on the surface properties of a model membrane in the presence of silica microparticles (MPs). Mixed monolayers containing phospholipid-dipalmitoylphosphatidylcholine (DPPC), Chol and silica particle dispersions (MPs; 0.033% w/w, 0.33% w/w and 0.83% w/w) were formed and studied using the Langmuir monolayer technique complemented by Brewster Angle Microscopy (BAM) images. It was shown that Chol caused a condensation of the DPPC monolayer, which influenced the penetration of MPs and their interactions with the model membrane. The relaxation experiments of the lipid–MP monolayer proved that the presence of Chol molecules in the monolayer led to the formation of lipid and MP complexes. Strong interactions between Chol and MPs contributed to the formation of more stable monolayers. The presented results can be useful to better comprehend the interaction between particulate materials and the lipid components of biomembranes.
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Li, Fang-Qiang, Yang Zhang, and Sheng-Li Zhang. "Defects and Strain Engineering of Structural, Elastic, and Electronic Properties of Boron-Phosphide Monolayer: A Hybrid Density Functional Theory Study." Nanomaterials 11, no. 6 (May 25, 2021): 1395. http://dx.doi.org/10.3390/nano11061395.
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Defects and in-plane strain have significant effects on the electronic properties of two-dimensional nanostructures. However, due to the influence of substrate and environmental conditions, defects and strain are inevitable during the growth or processing. In this study, hybrid density functional theory was employed to systematically investigate the electronic properties of boron-phosphide monolayers tuned by the in-plane biaxial strain and defects. Four types of defects were considered: B-vacancy (B_v), P-vacancy (P_v), double vacancy (D_v), and Stone–Wales (S-W). Charge density difference and Bader charge analysis were performed to characterize the structural properties of defective monolayers. All of these defects could result in the boron-phosphide monolayer being much softer with anisotropic in-plane Young’s modulus, which is different from the isotropic modulus of the pure layer. The calculated electronic structures show that the P_v, D_v, and S-W defective monolayers are indirect band gap semiconductors, while the B_v defective system is metallic, which is different from the direct band gap of the pure boron-phosphide monolayer. In addition, the in-plane biaxial strain can monotonically tune the band gap of the boron-phosphide monolayer. The band gap increases with the increasing tension strain, while it decreases as the compression strain increases. Our results suggest that the defects and in-plane strain are effective for tuning the electronic properties of the boron-phosphide monolayer, which could motivate further studies to exploit the promising application in electronics and optoelectronics based on the boron-phosphide monolayer.
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Dong, Sha, Xiaoli Sun, and Zhiguo Wang. "Trapping polysulfide on two-dimensional molybdenum disulfide for Li–S batteries through phase selection with optimized binding." Beilstein Journal of Nanotechnology 10 (March 26, 2019): 774–80. http://dx.doi.org/10.3762/bjnano.10.77.
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Introducing anchoring materials into cathodes for Li–S batteries has been demonstrated as an effective way to overcome the shuttle effect and enhance the cycling stability. In this work, the anchoring effects of 2H-MoS2 and 1T'-MoS2 monolayers for Li–S batteries were investigated by using density functional theory calculations. It was found that the binding energies of Li2S x absorbed on 1T'-MoS2 monolayer are in the range of 0.31–2.94 eV, which is much higher than on the 2H-phase. The 1T'-MoS2 monolayer shows stronger trapping ability for Li2S x than the 2H-MoS2 monolayer. The 1T'-MoS2 monolayer can be used as effective anchoring material in cathodes for Li–S batteries.
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Mishra, Suryakant, and Debkumar Bhowmick. "Asymmetric Magnetoelectrochemistry: An Efficient Method to Grow Enantiopure Self-Assemble Monolayer." Magnetochemistry 6, no. 3 (September 1, 2020): 37. http://dx.doi.org/10.3390/magnetochemistry6030037.
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In this work, we are presenting magnetic field dependent electrochemical method to grow enantiopure monolayer. Thiol gold monolayer formation by redox reaction is studied on gold coated ferromagnetic surface. Infrared and photoemission spectroscopies are used to probe the quality of the monolayers, grown using different direction of magnetization of surface. Commercially available chiral molecules, L-cysteine along with dsDNA are used as control molecules for the measurements. Since it is established by aligning the electron spin within the surface, it helps to adsorb specific enantiomer of molecules, we have shown how direction of the magnet helps to grow good quality monolayer. Potential application of this work is in improving quality of monolayer and chiral separation.
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HASHIMOTO, YUICHI, KUNIHARU IJIRO, TETSURO SAWADAISHI, and MASATSUGU SHIMOMURA. "ELECTRIC CONDUCTIVITY OF NUCLEIC ACID POLYMER MONOLAYER." International Journal of Nanoscience 01, no. 05n06 (October 2002): 707–11. http://dx.doi.org/10.1142/s0219581x02000930.
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We investigated electric conductivities of poly nucleic acid-amphiphile polyion complex monolayers. The polyion complex monolayers were prepared by spreading of dialkylammonium salt on aqueous solutions of various poly nucleic acids. The complex monolayers were compressed at the air–water interface and transferred on comb-shaped Au-electrode substrates by vertical lifting method. I–T plots of the complex monolayers, which were measured under applying direct voltage, suggested that the complex monolayers were dielectric substances. The I–V plots indicated that the conductivity of the monolayer depended on the species of poly nucleic acids. Based on the ac impedance analysis of those monolayers, the bulk resistance of those monolayers was estimated from the complex impedance plane plots.
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Dickie, Adam J., Ashok K. Kakkar, and Michael A. Whitehead. "Molecular modelling of self-assembled alkynyl monolayer structures Unnatural symmetry units, surface bonding, and topochemical polymerization1." Canadian Journal of Chemistry 81, no. 11 (November 1, 2003): 1228–40. http://dx.doi.org/10.1139/v03-110.
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Geometric modelling techniques are used to map the potential energies of packing for self-assembled alkyl- and phenyl-backboned monolayers across a range of intermolecular separations. Natural packing distances of 4.24.4 Å produce less stable, more isotropic monolayers because of repulsive interchain contacts. Optimizations at unnatural surface densities found thin films of lower energy and higher symmetry existed at increased chainchain separations. Head-group bonding is therefore identified as a force for controlling monolayer order. Analysis of the natural monolayer structures on a silicon dioxide surface determined the favourable head-group structures, and allowed the topochemical polymerization of p-bis(butadiynyl)benzene monolayers to be rationalized.Key words: self-assembled monolayers, molecular modelling studies, repeating symmetry units, thin-film order, topochemical polymerization.
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Santiago, Jecksan R., E. Barry Troughton, Richard A. Dennis, and Phillip E. Russell. "Atomic Force Microscopy Studies of Microstructure and Properties of Self Assembled Monolayers." Microscopy and Microanalysis 4, S2 (July 1998): 308–9. http://dx.doi.org/10.1017/s1431927600021668.
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Ex-situ and in-situ studies were performed for self-assembled monolayers (SAMs) formation on mica. The behavior of two surfactants [octadecylphosphonic acid (OPA) and dodecylphosphonic acid (DPA)] in two different solutions [ethanol or tetrahydrofuran (THF)] were studied at different concentrations. A cross section analysis of the monolayer images at partial coverage showed thickness of 1.8 nm, 0.7 nm, and 1.0 nm for OPA, DPA and mixed OPA/DPA, respectively. These values are similar to the ones presented by Xiao and those expected for a monolayer of mixed surfactants as proposed by Whitesides. Since the topography of a monolayer resembles the substrate, the presence of the monolayer at full coverage was determinated by force-distance curve measurements. It was observed that the solvent had the ability to re-dissolve the OPA monolayer, suggesting that the bonding is of a physisorption nature.
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Elkins, Amy L., John G. Eley, Merrill C. Miller III, Iris H. Hall, Anup Sood, and Bernard Spielvogel. "Transepithelial Transport and Metabolism of Boronated Dipeptides Across Caco-2 and HCT-8 Cell Monolayers." Metal-Based Drugs 3, no. 6 (January 1, 1996): 277–86. http://dx.doi.org/10.1155/mbd.1996.277.
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Oral delivery of proteins and peptides as therapeutic agents is problematic due to their low bioavailability. This study examined the effect of boronation on the transepithelial transport and metabolism of three glycine-phenylalanine dipeptides in Caco-2 and HCT-8 cell monolayers. The three dipeptides exhibited passive transport characteristics in the monolayer systems. However, metabolism of the boronated dipeptides did occur, but to a lesser extent than the non-boronated glycine-phenylalanine dipeptide. The same metabolic scheme was seen in both cell monolayer system, but greater metabolism was seen in the HCT-8 cell monolayers.
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Martín, Santiago, Luz M. Ballesteros, Alejandro González-Orive, Hugo Oliva, Santiago Marqués-González, Matteo Lorenzoni, Richard J. Nichols, Francesc Pérez-Murano, Paul J. Low, and Pilar Cea. "Towards a metallic top contact electrode in molecular electronic devices exhibiting a large surface coverage by photoreduction of silver cations." Journal of Materials Chemistry C 4, no. 38 (2016): 9036–43. http://dx.doi.org/10.1039/c6tc03319a.
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Bae, Jeonghwan, and Youngdong Yoo. "A Novel Carbon-Assisted Chemical Vapor Deposition Growth of Large-Area Uniform Monolayer MoS2 and WS2." Nanomaterials 11, no. 9 (September 17, 2021): 2423. http://dx.doi.org/10.3390/nano11092423.
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Monolayer MoS2 can be used for various applications such as flexible optoelectronics and electronics due to its exceptional optical and electronic properties. For these applications, large-area synthesis of high-quality monolayer MoS2 is highly desirable. However, the conventional chemical vapor deposition (CVD) method using MoO3 and S powder has shown limitations in synthesizing high-quality monolayer MoS2 over a large area on a substrate. In this study, we present a novel carbon cloth-assisted CVD method for large-area uniform synthesis of high-quality monolayer MoS2. While the conventional CVD method produces thick MoS2 films in the center of the substrate and forms MoS2 monolayers at the edge of the thick MoS2 films, our carbon cloth-assisted CVD method uniformly grows high-quality monolayer MoS2 in the center of the substrate. The as-synthesized monolayer MoS2 was characterized in detail by Raman/photoluminescence spectroscopy, atomic force microscopy, and transmission electron microscopy. We reveal the growth process of monolayer MoS2 initiated from MoS2 seeds by synthesizing monolayer MoS2 with varying reaction times. In addition, we show that the CVD method employing carbon powder also produces uniform monolayer MoS2 without forming thick MoS2 films in the center of the substrate. This confirms that the large-area growth of monolayer MoS2 using the carbon cloth-assisted CVD method is mainly due to reducing properties of the carbon material, rather than the effect of covering the carbon cloth. Furthermore, we demonstrate that our carbon cloth-assisted CVD method is generally applicable to large-area uniform synthesis of other monolayer transition metal dichalcogenides, including monolayer WS2.
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Yuan, Cailei, Yingjie Cao, Xingfang Luo, Ting Yu, Zhenping Huang, Bo Xu, Yong Yang, Qinliang Li, Gang Gu, and Wen Lei. "Monolayer-by-monolayer stacked pyramid-like MoS2nanodots on monolayered MoS2flakes with enhanced photoluminescence." Nanoscale 7, no. 41 (2015): 17468–72. http://dx.doi.org/10.1039/c5nr05363c.
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Park, Yeseul, and Jin-Won Park. "Specific Detection of PE-Included Vesicles Using Cyclic Voltammetry." Applied Sciences 11, no. 8 (April 19, 2021): 3660. http://dx.doi.org/10.3390/app11083660.
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The binding between cinnamycin and the phosphatidylethanolamine (PE)-included vesicles was monitored using cyclic voltammetry (CV) measurements and interpreted in terms of the composition of the vesicles and the monolayer binding site. The monolayer was composed of pure 11-mercapto-1-undecanol (MUD) to 90% MUD/10% 16-mercaptohexadecanoic acid (MHA) on a gold surface. Cinnamycin was immobilized on each monolayer. The vesicles, prepared at the desired ratio of the phospholipids, were injected on the cinnamycin-immobilized surface. CV experiments were performed for each step. For the pure-dipalmitoylphosphatidyl-choline (DPPC) vesicles on all of monolayers and the DPPC/dipalmitoylphosphatidyl-ethanolamine (DPPE) vesicles on the pure-MUD monolayer, the electric property of the surface was little changed. However, the vesicles made with 90% DPPC/10% DPPE on the monolayer prepared with 99% MUD/1% MHA to 90% MUD/10% MHA showed a consistent decrease in the CV response. Additionally, in the 95% DPPC/5% DPPE vesicles and the 99.5% MUD/0.5% MHA monolayer, variances in the responses were observed.
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Gómez, A. Santos, and A. L. González. "Far Field Optical Properties of a Monolayer of SiO2 Spheres and Small Au Nanoparticles." MRS Advances 3, no. 64 (2018): 3917–23. http://dx.doi.org/10.1557/adv.2019.128.
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ABSTRACTHere, we present a numerical study of the far field optical response of a monolayer composed by an hexagonal closed packed array of SiO2 spheres with a single Au NP at each interstitial position. The Optical Efficiencies, Reflection, Transmission and Absorption at normal incidence, were calculated using Discrete Dipole Approximation model extended to periodic targets. In order to consider different amounts of loads of Au NPs per unit of area in the monolayer, we have fixed the diameter of Au NPs (9 nm) and varied the diameter of the SiO2 spheres. The numerical calculations indicate that Au-SiO2 composite monolayers can absorb and scatter the incident electromagnetic wave, as the load of Au NPs increases the monolayer becomes less transparent to light and the spectra are red-shifted. The profile of the absorption spectrum of the Au-SiO2 composite monolayer is very similar to that of a Au NPs monolayer (composite monolayer without the Silica spheres) but less intense, presumably because the Silica spheres screen the coupling of the Localized Surface Plasmons of Au NPs.
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Pittaway, Pamela A., and Tania R. van den Ancker. "Properties of natural microlayers on Australian freshwater storages and their potential to interact with artificial monolayers." Marine and Freshwater Research 61, no. 10 (2010): 1083. http://dx.doi.org/10.1071/mf09159.
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Microlayers are natural surface films derived from hydrophobic organic compounds that form on most lakes and streams. Holarctic brown-water lakes have been most commonly studied, with Australian research limited to marine microlayers. Artificial monolayers based on long-chain fatty alcohols have been applied to freshwater storages to reduce evaporative loss. As a water conservation strategy, monolayer technology was not widely adopted because of variable field performance. However, the role of natural microlayers in reducing monolayer performance has not previously been investigated. In the present study, microlayer and subsurface samples from six water storages in Queensland were characterised for water-quality indices, including biochemical oxygen demand, permanganate index and ultraviolet light absorbance. Microlayer enrichment in south-eastern Queensland is comparable to or higher than that in holarctic lakes. The results indicated that microlayer compounds have the potential to disrupt monolayers in at least the following three ways: as substrates for microbes capable of degrading monolayer compounds, as chromophores accelerating photodegradation, and as impurities disrupting the molecular packing required to reduce evaporative loss. The knowledge gained from studying natural microlayers can also be used to benchmark novel monolayer compounds, to minimise their environmental impact on freshwater ecosystems.
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Barzyk, Wanda, Ewa Rogalska, and Katarzyna Więcław-Czapla. "Penetration of Milk-Derived Antimicrobial Peptides into Phospholipid Monolayers as Model Biomembranes." Biochemistry Research International 2013 (2013): 1–16. http://dx.doi.org/10.1155/2013/914540.
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Three antimicrobial peptides derived from bovine milk proteins were examined with regard to penetration into insoluble monolayers formed with 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) or 1,2-dipalmitoyl-sn-glycero-3-phospho-rac-(1-glycerol) sodium salt (DPPG). Effects on surface pressure (Π) and electric surface potential (ΔV) were measured,Πwith a platinum Wilhelmy plate andΔVwith a vibrating plate. The penetration measurements were performed under stationary diffusion conditions and upon the compression of the monolayers. The two type measurements showed greatly different effects of the peptide-lipid interactions. Results of the stationary penetration show that the peptide interactions with DPPC monolayer are weak, repulsive, and nonspecific while the interactions with DPPG monolayer are significant, attractive, and specific. These results are in accord with the fact that antimicrobial peptides disrupt bacteria membranes (negative) while no significant effect on the host membranes (neutral) is observed. No such discrimination was revealed from the compression isotherms. The latter indicate that squeezing the penetrant out of the monolayer upon compression does not allow for establishing the penetration equilibrium, so the monolayer remains supersaturated with the penetrant and shows an under-equilibrium orientation within the entire compression range, practically.
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Hu, Yao Bo, Fu Sheng Pan, and Jing Feng Wang. "Selective Deposition of Titanium Dioxide Thin Film on Glass Monolayers by Impregnating Method." Materials Science Forum 610-613 (January 2009): 147–54. http://dx.doi.org/10.4028/www.scientific.net/msf.610-613.147.
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Titanium dioxide (TiO2) thin film was fabricated on the surface of glass monolayers at room temperature, using KH-550 as self-assembled monolayers (SAMs). The TiO2 gel precursor was characterized with differential scanning calorimetry – thermogravimetry (DSC-TG), and the TiO2 powder was analyzed with X-ray diffraction (XRD). The TiO2 thin film was tested with X-ray fluorescence spectroscopy (XRF). With the application of atomic force microscope (AFM) the surface topography of siloxane layer and TiO2 film were studied. Their hydrophilicities were measured. The transmittance of TiO2 film was detected by using dual beam ultraviolet - visible spectrophotometer. The results show that the TiO2 thin film is in monolayer with nanometer level, the deposition is the anatase structure. TiO2 is deposited on the surface instead of channel or gap of siloxane, the hydrophilicities of TiO2 monolayer film are perfect, and TiO2 monolayer film has a good transmissivity in the visible light area.
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Kewalramani, Sumit, Kyungil Kim, Guennadi Evmenenko, Paul Zschack, Evguenia Karapetrova, Jianming Bai, and Pulak Dutta. "Mechanisms for species-selective oriented crystal growth at organic templates." Journal of Materials Research 22, no. 10 (October 2007): 2785–90. http://dx.doi.org/10.1557/jmr.2007.0347.
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Langmuir monolayers floating on supersaturated aqueous subphases can act as templates for the growth of oriented inorganic films—a “bioinspired” nucleation process. We have performed in situ grazing incidence x-ray diffraction studies of the selective nucleation of BaClF and BaF2 under fatty acid monolayers. The arrangement of the fatty acid headgroups, the monolayer charge, and ion-specific effects all play important roles in selecting the inorganic species. When the monolayer is in a neutral state, both BaClF and BaF2 nucleate at the interface and are well aligned, but when the monolayer headgroup is deprotonated, only oriented BaF2 grows at the interface. We also observe an enhanced alignment of BaF2 crystals during growth from highly supersaturated solutions, presumably due to reorganization of preformed crystals at the organic template. These results show that a delicate interplay between multiple factors governs the oriented growth of inorganic films at organic templates.
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PENG, QING, JARED CREAN, ALBERT K. DEARDEN, CHEN HUANG, XIAODONG WEN, STÉPHANE P. A. BORDAS, and SUVRANU DE. "DEFECT ENGINEERING OF 2D MONATOMIC-LAYER MATERIALS." Modern Physics Letters B 27, no. 23 (September 9, 2013): 1330017. http://dx.doi.org/10.1142/s0217984913300172.
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Atomic-thick monolayer two-dimensional materials present advantageous properties compared to their bulk counterparts. The properties and behavior of these monolayers can be modified by introducing defects, namely defect engineering. In this paper, we review a group of common two-dimensional crystals, including graphene, graphyne, graphdiyne, graphn-yne, silicene, germanene, hexagonal boron nitride monolayers and MoS2monolayers, focusing on the effect of the defect engineering on these two-dimensional monolayer materials. Defect engineering leads to the discovery of potentially exotic properties that make the field of two-dimensional crystals fertile for future investigations and emerging technological applications with precisely tailored properties.
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Pak, Sangyeon, Jungmoon Lim, John Hong, and SeungNam Cha. "Enhanced Hydrogen Evolution Reaction in Surface Functionalized MoS2 Monolayers." Catalysts 11, no. 1 (January 6, 2021): 70. http://dx.doi.org/10.3390/catal11010070.
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Monolayered, semiconducting MoS2 and their transition metal dichalcogenides (TMDCs) families are promising and low-cost materials for hydrogen generation through electrolytes (HER, hydrogen evolution reaction) due to their high activities and electrochemical stability during the reaction. However, there is still a lack of understanding in identifying the underlying mechanism responsible for improving the electrocatalytic properties of theses monolayers. In this work, we investigated the significance of controlling carrier densities in a MoS2 monolayer and in turn the corresponding electrocatalytic behaviors in relation to the energy band structure of MoS2. Surface functionalization was employed to achieve p-doping and n-doping in the MoS2 monolayer that led to MoS2 electrochemical devices with different catalytic performances. Specifically, the electron-rich MoS2 surface showed lower overpotential and Tafel slope compared to the MoS2 with surface functional groups that contributed to p-doping. We attributed such enhancement to the increase in the carrier density and the corresponding Fermi level that accelerated HER and charge transfer kinetics. These findings are of high importance in designing electrocatalysts based on two-dimensional TMDCs.
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Голубев, О. Л. "Некоторые особенности конденсации атомов кремния на поверхности монокристалла вольфрама." Журнал технической физики 90, no. 3 (2020): 465. http://dx.doi.org/10.21883/jtf.2020.03.48933.283-19.
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Using the methods of the field emission microscopy, the condensation of Si on the W surface at various temperatures T of the substrate and numbers n of monoatomic layers of the deposited condensate is studied. At low temperatures T ~ 600 K, a low-temperature Si-monolayer with the structure of pure W is formed on the surface, whereas another structure of a high-temperature monolayer, namely surface siliside is formed at T > 1000 K. The low-temperature monolayer and surface siliside are differ in their orienting effect when constructing the Si layers. In the case of condensation on a low-temperature monolayer, crystallites of Si are formed starting already from the third monolayer at n > 3, whereas the Si crystallites grow during the condensation on surface siliside starting from n > 300 monolayers. The energy activation of the volume diffusion Qdif of the Si-atoms into W and desorption Qdes from W surface are determined.
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Hasan, Sayedul, Mohammad Tanvir Ahmed, Abdullah Al Roman, Shariful Islam, and Farid Ahmed. "Investigation of Structural, Electronic, and Optical Properties of Chalcogen-Doped ZrS2: A DFT Analysis." Advances in Materials Science and Engineering 2023 (February 23, 2023): 1–10. http://dx.doi.org/10.1155/2023/6525507.
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The electrical and optical characteristics of a ZrS2 monolayer doped with chalcogen atoms (O, Se, or Te), where dopants are introduced by substituting the S atom, are examined on the basis of the density functional theory. The semiconductors pristine ZrS2 and O, Se, and Te-doped ZrS2 monolayers possessed indirect band gaps of 1.187 eV, 1.227 eV, 1.146 eV, and 0.922 eV, respectively. According to the formation energy, the O-doped ZrS2 monolayer is more stable compared to Se-doped and Te-doped ZrS2 monolayers. The optical properties are very similar for both the undoped and doped ZrS2 monolayers. The absorption coefficient and optical conductivity are the highest in the ultraviolet energy region. The designed materials are potentially suitable for UV photodetection and UV filtering applications.
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Jo, Sunghwan, Jin-Woo Jung, Jaeyoung Baik, Jang-Won Kang, Il-Kyu Park, Tae-Sung Bae, Hee-Suk Chung, and Chang-Hee Cho. "Surface-diffusion-limited growth of atomically thin WS2 crystals from core–shell nuclei." Nanoscale 11, no. 18 (2019): 8706–14. http://dx.doi.org/10.1039/c9nr01594a.
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Sun, Zhiyuan, Jing Xu, Nsajigwa Mwankemwa, Wenxing Yang, Xianwen Wu, Zao Yi, Shanjun Chen, and Weibin Zhang. "Alkali-metal(Li, Na, and K)-adsorbed MoSi2N4 monolayer: an investigation of its outstanding electronic, optical, and photocatalytic properties." Communications in Theoretical Physics 74, no. 1 (January 1, 2022): 015503. http://dx.doi.org/10.1088/1572-9494/ac3ada.
Full textAbstract:
Abstract Single-layer MoSi2N4, a high-quality two-dimensional material, has recently been fabricated by chemical vapor deposition. Motivated by this latest experimental work, herein, we apply first principles calculations to investigate the electronic, optical, and photocatalytic properties of alkali-metal(Li, Na, and K)-adsorbed MoSi2N4 monolayer. The electronic structure analysis shows that pristine MoSi2N4 monolayer exhibits an indirect bandgap (E g = 1.89 eV). By contrast, the bandgaps of one Li-, Na-, and K-adsorbed MoSi2N4 monolayer are 1.73 eV, 1.61 eV, and 1.75 eV, respectively. Moreover, the work function of MoSi2N4 monolayer (4.80 eV) is significantly reduced after the adsorption of alkali metal atoms. The work functions of one Li-, Na-, and K-adsorbed MoSi2N4 monolayer are 1.50 eV, 1.43 eV, and 2.03 eV, respectively. Then, optical investigations indicate that alkali metal adsorption processes substantially increase the visible light absorption range and coefficient of MoSi2N4 monolayer. Furthermore, based on redox potential variations after alkali metals are adsorbed, Li- and Na-adsorbed MoSi2N4 monolayers are more suitable for the water splitting photocatalytic process, and the Li-adsorbed case shows the highest potential application for CO2 reduction. In conclusion, alkali-metal-adsorbed MoSi2N4 monolayer exhibits promising applications as novel optoelectronic devices and photocatalytic materials due to its unique physical and chemical properties.