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1
Baker, MV, e J. Landau. "Self Assembled Alkanethiolate Monolayers as Thin Insulating Films". Australian Journal of Chemistry 48, n. 6 (1995): 1201. http://dx.doi.org/10.1071/ch9951201.
Testo completoAbstract (sommario):
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.
2
Takeshita, Naoki, Masanari Okuno e 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, n. 3 (2017): 2060–66. http://dx.doi.org/10.1039/c6cp07800a.
Testo completoAbstract (sommario):
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).
3
Lv, Ming-Hao, Chang-Ming Li e Wei-Feng Sun. "Spin-Orbit Coupling and Spin-Polarized Electronic Structures of Janus Vanadium-Dichalcogenide Monolayers: First-Principles Calculations". Nanomaterials 12, n. 3 (24 gennaio 2022): 382. http://dx.doi.org/10.3390/nano12030382.
Testo completoAbstract (sommario):
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.
4
Mazzei, Aurora, Patrizia Pagliara, Gianmarco Del Vecchio, Lucia Giampetruzzi, Francesca Croce, Roberta Schiavone, Tiziano Verri e Amilcare Barca. "Cytoskeletal Responses and Aif-1 Expression in Caco-2 Monolayers Exposed to Phorbol-12-Myristate-13-Acetate and Carnosine". Biology 12, n. 1 (25 dicembre 2022): 36. http://dx.doi.org/10.3390/biology12010036.
Testo completoAbstract (sommario):
The dis(re)organization of the cytoskeletal actin in enterocytes mediates epithelial barrier dys(re)function, playing a key role in modulating epithelial monolayer’s integrity and remodeling under transition from physiological to pathological states. Here, by fluorescence-based morphological and morphometric analyses, we detected differential responses of cytoskeletal actin in intestinal epithelial Caco-2 cell monolayers at two different stages of their spontaneous differentiation, i.e., undifferentiated cells at 7 days post-seeding (dps) and differentiated enterocyte-like cells at 21 dps, upon challenge in vitro with the inflammation-mimicking stimulus of phorbol-12-myristate-13-acetate (PMA). In addition, specific responses were found in the presence of the natural dipeptide carnosine detecting its potential counteraction against PMA-induced cytoskeletal alterations and remodeling in differentiated Caco-2 monolayers. In such an experimental context, by both immunocytochemistry and Western blot assays in Caco-2 monolayers, we identified the expression of the allograft inflammatory factor 1 (AIF-1) as protein functionally related to both inflammatory and cytoskeletal pathways. In 21 dps monolayers, particularly, we detected variations of its intracellular localization associated with the inflammatory stimulus and its mRNA/protein increase associated with the differentiated 21 dps enterocyte-like monolayer compared to the undifferentiated cells.
5
Zhang, Bo, Tomas Mikysek, Veronika Cicmancova, Stanislav Slang, Roman Svoboda, Petr Kutalek e Tomas Wagner. "2D GeSe2 amorphous monolayer". Pure and Applied Chemistry 91, n. 11 (26 novembre 2019): 1787–96. http://dx.doi.org/10.1515/pac-2019-0501.
Testo completoAbstract (sommario):
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.
6
HASHIMOTO, YUICHI, KUNIHARU IJIRO, TETSURO SAWADAISHI e MASATSUGU SHIMOMURA. "ELECTRIC CONDUCTIVITY OF NUCLEIC ACID POLYMER MONOLAYER". International Journal of Nanoscience 01, n. 05n06 (ottobre 2002): 707–11. http://dx.doi.org/10.1142/s0219581x02000930.
Testo completoAbstract (sommario):
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.
7
Kajiyama, Tisato. "Novel Concepts of the Aggregation Structure of Organic Monolayers on the Surface of Water". MRS Bulletin 20, n. 6 (giugno 1995): 32–38. http://dx.doi.org/10.1557/s0883769400036952.
Testo completoAbstract (sommario):
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.
8
Dickie, Adam J., Ashok K. Kakkar e Michael A. Whitehead. "Molecular modelling of self-assembled alkynyl monolayer structures Unnatural symmetry units, surface bonding, and topochemical polymerization1". Canadian Journal of Chemistry 81, n. 11 (1 novembre 2003): 1228–40. http://dx.doi.org/10.1139/v03-110.
Testo completoAbstract (sommario):
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.
9
Huang, Zhaoming, Kai Ren, Ruxin Zheng, Liangmo Wang e Li Wang. "Ultrahigh Carrier Mobility in Two-Dimensional IV–VI Semiconductors for Photocatalytic Water Splitting". Molecules 28, n. 10 (16 maggio 2023): 4126. http://dx.doi.org/10.3390/molecules28104126.
Testo completoAbstract (sommario):
Two-dimensional materials have been developed as novel photovoltaic and photocatalytic devices because of their excellent properties. In this work, four δ-IV–VI monolayers, GeS, GeSe, SiS and SiSe, are investigated as semiconductors with desirable bandgaps using the first-principles method. These δ-IV–VI monolayers exhibit exceptional toughness; in particular, the yield strength of the GeSe monolayer has no obvious deterioration at 30% strain. Interestingly, the GeSe monolayer also possesses ultrahigh electron mobility along the x direction of approximately 32,507 cm2·V−1·s−1, which is much higher than that of the other δ-IV–VI monolayers. Moreover, the calculated capacity for hydrogen evolution reaction of these δ-IV–VI monolayers further implies their potential for applications in photovoltaic and nano-devices.
10
Williams, Ian, e Todd M. Squires. "Evolution and mechanics of mixed phospholipid fibrinogen monolayers". Journal of The Royal Society Interface 15, n. 141 (aprile 2018): 20170895. http://dx.doi.org/10.1098/rsif.2017.0895.
Testo completoAbstract (sommario):
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.
11
Lu, L., H. Cui, W. Li, H. Zhang e S. Xi. "Study of the mechanism for controlled crystallization of BaF2 under two kinds of monolayers". Journal of Materials Research 16, n. 8 (agosto 2001): 2415–20. http://dx.doi.org/10.1557/jmr.2001.0331.
Testo completoAbstract (sommario):
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.
12
Białkowska, Katarzyna, Małgorzata Bobrowska-Hägerstrand e Henry Hägerstrand. "Expansion of Phosphatidylcholine and Phosphatidylserine/Phosphatidylcholine Monolayers by Differently Charged Amphiphiles". Zeitschrift für Naturforschung C 56, n. 9-10 (1 ottobre 2001): 826–30. http://dx.doi.org/10.1515/znc-2001-9-1024.
Testo completoAbstract (sommario):
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.
13
Cott, G. R. "Modulation of bioelectric properties across alveolar type II cells by substratum". American Journal of Physiology-Cell Physiology 257, n. 4 (1 ottobre 1989): C678—C688. http://dx.doi.org/10.1152/ajpcell.1989.257.4.c678.
Testo completoAbstract (sommario):
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).
14
Dabkowska, A. P., D. J. Barlow, A. V. Hughes, R. A. Campbell, P. J. Quinn e M. J. Lawrence. "The effect of neutral helper lipids on the structure of cationic lipid monolayers". Journal of The Royal Society Interface 9, n. 68 (10 agosto 2011): 548–61. http://dx.doi.org/10.1098/rsif.2011.0356.
Testo completoAbstract (sommario):
Successful drug delivery via lipid-based systems has often been aided by the incorporation of ‘helper lipids’. While these neutral lipids enhance the effectiveness of cationic lipid-based delivery formulations, many questions remain about the nature of their beneficial effects. The structure of monolayers of the cationic lipid dimethyldioctadecylammonium bromide (DODAB) alone, and mixed with a neutral helper lipid, either diolelyphosphatidylethanolamine or cholesterol at a 1 : 1 molar ratio was investigated at the air–water interface using a combination of surface pressure–area isotherms, Brewster angle microscopy (BAM) and specular neutron reflectivity in combination with contrast variation. BAM studies showed that while pure DODAB and DODAB with cholesterol monolayers showed fairly homogeneous surfaces, except in the regions of phase transition, monolayers of DODAB with diolelyphosphatidylethanolamine were, in contrast, inhomogeneous exhibiting irregular bean-shaped domains throughout. Neutron reflectivity data showed that while the thickness of the DODAB monolayer increased from 17 to 24 Å as it was compressed from a surface pressure of 5–40 mN m −1 , the thickness of the helper lipid-containing monolayers, over the same range of surface pressures, was relatively invariant at between 25 and 27 Å. In addition, the monolayers containing diolelyphosphatidylethanolamine were found to be more heavily hydrated than the monolayers of cationic lipid, alone or in combination with cholesterol, with hydration levels of 18 molecules of water per molecule of lipid being recorded for the diolelyphosphatidylethanolamine-containing monolayers at a surface pressure of 30 mN m −1 compared with only six and eight molecules of water per molecule of lipid for the pure DODAB monolayer and the cholesterol-containing DODAB monolayer, respectively.
15
Vu, Tuan V., Tran P. T. Linh, Huynh V. Phuc, C. A. Duque, A. I. Kartamyshev e Nguyen N. Hieu. "Structural, electronic, and transport properties of Janus GaInX 2 (X = S, Se, Te) monolayers: first-principles study". Journal of Physics: Condensed Matter 34, n. 4 (4 novembre 2021): 045501. http://dx.doi.org/10.1088/1361-648x/ac316e.
Testo completoAbstract (sommario):
Abstract Two-dimensional Janus monolayers have outstanding electronic and transport properties due to their asymmetric atomic structures. In the present work, we systematically study the structural, electronic, and transport properties of the Janus GaInX 2 (X = S, Se, Te) monolayers by using the first-principles calculations. The stability of the investigated monolayers is confirmed via the analysis of vibrational spectrum and molecular dynamics simulations. Our calculations demonstrate that while GaInS2 and GaInSe2 monolayers are direct semiconductors, GaInTe2 monolayer exhibits the characteristics of an indirect semiconductor. The band gap of GaInX 2 decreases when the chalcogen element X varies from S to Te. Obtained results reveal that small spin–orbit splitting energy in the valence band is found around the Γ point of the Brillouin zone when the spin–orbit coupling is included. Interestingly, GaInS2 and GaInSe2 have high and directional isotropic electron mobility meanwhile the directional anisotropy of the electron mobility is found in the Janus GaInTe2 monolayer. Our findings not only present superior physical properties of GaInX 2 monolayers but also show promising potential applications of these materials in nanoelectronic devices.
16
NISHIDA, JIN, JIN MATSUMOTO, MITSUHIKO MORISUE, KUNIHARU IJIRO e MASATSUGU SHIMOMURA. "CIRCULAR ARRANGEMENT OF AZOBENZENE CHROMOPHORES IN THE NUCLEOAMPHIPHILE MONOLAYER BY BASE-PAIRING WITH CYCLIC DNA". International Journal of Nanoscience 01, n. 05n06 (ottobre 2002): 677–81. http://dx.doi.org/10.1142/s0219581x02000887.
Testo completoAbstract (sommario):
In order to construct chromophores arrays that precisely controlled their arrangement, monolayers of an azobenzene bearing nucleoamphiphile were prepared on various oligoDNA solutions. Monolayers of the amphiphilic adenine derivative bearing an azobenzene moiety ( C 12 AzoC 5 Ade ) were prepared on thymidylic acid tetramer (dT4) and octamer (dT8) solutions, and UV-vis reflection absorption spectra of the monolayers were measured to investigate aggregation structures of the azobenzene. The absorption maximum of the monolayer was blue-shifted on the dT4 solution and red-shifted on the dT8 solution. It shows that azobenzene groups in the monolayer have parallel orientation (H aggregate) on the dT4 solution. Though, azobenzene groups have head-to-tail orientation (J aggregates) on the dT8 solution. When monolayers of C 12 AzoC 5 Ade were prepared on the synthesized cyclic oligonucleotides, the absorption spectra were totally different from those of the corresponding linear oligonucleotides.
17
Ueda, Yuki, Yuto Miyake, Akirabha Chanuntranont, Kazuki Otani, Masato Tsugawa, Daiki Saito, Shuntaro Usui et al. "Detecting nuclear spins in an organosilane monolayer using nitrogen-vacancy centers for analysis of precursor self-assembly on diamond surface". Japanese Journal of Applied Physics 62, SG (9 maggio 2023): SG1049. http://dx.doi.org/10.35848/1347-4065/accc91.
Testo completoAbstract (sommario):
Abstract We demonstrated the correlation spectroscopy of organosilane monolayers using an ensemble of shallow nitrogen-vacancy centers as the quantum sensor. Several types of organosilane monolayers were grown directly on the diamond surface by exposing the surface to a silane precursor vapor. The feasibility of detecting 1H and 19F in the monolayer was examined by correlation spectroscopy measurements. The effect of the magnetic dipole–dipole interaction on the peak width was also discussed by comparing the spectrum of the monolayer with that of surface-attached 1H and that of immersion oil. The results highlight the feasibility of nitrogen-vacancy centers as the spin probe for physicochemical analyses of monolayers grown on the diamond surface.
18
Guo, Jia-Xing, Shao-Yi Wu, Si-Ying Zhong, Gao-Jun Zhang, Xing-Yuan Yu e Li-Na Wu. "Exploring promising gas sensing and highly active catalysts for CO oxidation: transition-metal (Fe, Co and Ni) adsorbed Janus MoSSe monolayers". Physical Chemistry Chemical Physics 23, n. 18 (2021): 11004–14. http://dx.doi.org/10.1039/d1cp00994j.
Testo completoAbstract (sommario):
From first-principles calculations, the transition-metal (TM) atom (Fe, Co and Ni) adsorbed Janus MoSSe monolayer, toxic gas molecules (CO, NH3 and H2S) adsorbed on Ni-MoSSe monolayers and CO catalytic oxidation on Fe-MoSSe monolayers are systematically investigated.
19
Hasan, Sayedul, Mohammad Tanvir Ahmed, Abdullah Al Roman, Shariful Islam e Farid Ahmed. "Investigation of Structural, Electronic, and Optical Properties of Chalcogen-Doped ZrS2: A DFT Analysis". Advances in Materials Science and Engineering 2023 (23 febbraio 2023): 1–10. http://dx.doi.org/10.1155/2023/6525507.
Testo completoAbstract (sommario):
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.
20
Lipp, Michael M. "Monolayer Morphology and Collapse Induced by Lung Surfactant Protein: Observation Via Fluorescence and Atomic Force Microscopy". Proceedings, annual meeting, Electron Microscopy Society of America 54 (11 agosto 1996): 322–23. http://dx.doi.org/10.1017/s0424820100164076.
Testo completoAbstract (sommario):
Understanding the role of lung surfactant specific proteins in lipid monolayers is essential for improved treatments for Respiratory Distress Syndrome, which is a leading cause of death in premature infants. Fluorescence (FM) and Atomic Force (AFM) microscopies reveal that the amino-terminal peptide of lung surfactant protein SP-B alters the behavior of palmitic acid (PA) monolayers, enhancing their in vivo performance. The combination of these techniques provides an excellent correlation between the protein-lipid interactions on the molecular level with the macroscopic properties of the monolayer.SP-B protein incorporates into monolayers of PA, an important component of natural and synthetic lung surfactants monolayers. The effect of the protein on the monolayer is evidenced in the isotherm data shown in Fig 1, in which the area per PA molecule, compressibility, and surface pressure at collapse all increase as a function of increasing protein concentration. The protein accomplishes this by inhibiting the formation of ordered phases of PA. This is seen via FM as a transition from a homogeneous, dark ordered phase without protein (Fig 2a) to a network of a disordered, bright phase (the fluorescent lipid probes used in this study prefer to partition into disordered phases, making them appear as bright regions in FM images) that separates ordered phase domains at coexistence (Fig. 2b). The network is stabilized by the low line tension between the bright phase and other lipid phases as confirmed by the formation of extended linear domains of bright phase in a dark background, or “stripe” phases (Fig. 3a) under certain subphase conditions. Similar stripe phases also occur in single component fluorescein-labeled SP-B monolayers (Fig 3b), implying that the protein is responsible for the reduction in line tension. The formation of the fluid phase network is responsible for the increased collapse resistance of these mixed monolayers. The mechanism of collapse shifts from a heterogeneous process of nucleation and growth of large rigid crystalline collapse phases (Fig. 4a) to a more homogeneous process with nucleation and growth of smaller domains distributed uniformly across the film (Fig. 4b). This is due to the protein-induced network breaking up and isolating the domains of ordered phase, effectively lowering the probability of finding a heterogeneous nucleation site within each domain (analagous to the classic experiments of Turnbull on supercooled microemulsions of metallic liquids). The partitioning of the protein into the bright phase network was confirmed through the use of a dual-probe system. Fluorescein-labeled SP-B was added to a PA monolayer incorporating a fluorescent lipid analogue that emits at a higher wavelength. Upon imaging the same region of a monolayer at the different wavelengths (Fig. 5a and 5b), the protein is seen to be located in the bright phase network regions as expected.
21
Pak, Sangyeon, Jungmoon Lim, John Hong e SeungNam Cha. "Enhanced Hydrogen Evolution Reaction in Surface Functionalized MoS2 Monolayers". Catalysts 11, n. 1 (6 gennaio 2021): 70. http://dx.doi.org/10.3390/catal11010070.
Testo completoAbstract (sommario):
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.
22
Galli-Resta, Lucia, Elena Novelli e Alessandro Viegi. "Dynamic microtubule-dependent interactions position homotypic neurones in regular monolayered arrays during retinal development". Development 129, n. 16 (15 agosto 2002): 3803–14. http://dx.doi.org/10.1242/dev.129.16.3803.
Testo completoAbstract (sommario):
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.
23
Vi, Vo T. T., Cuong Q. Nguyen, Bui D. Hoi, Huynh V. Phuc, Chuong V. Nguyen e 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, n. 50 (3 novembre 2022): 505302. http://dx.doi.org/10.1088/1361-6463/ac9e07.
Testo completoAbstract (sommario):
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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Pires, Cristiana L., Catarina Praça, Patrícia A. T. Martins, Ana L. M. Batista de Carvalho, Lino Ferreira, Maria Paula M. Marques e Maria João Moreno. "Re-Use of Caco-2 Monolayers in Permeability Assays—Validation Regarding Cell Monolayer Integrity". Pharmaceutics 13, n. 10 (26 settembre 2021): 1563. http://dx.doi.org/10.3390/pharmaceutics13101563.
Testo completoAbstract (sommario):
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.
25
Palada, C., P. Schouten e C. Lemckert. "Testing the effectiveness of monolayers under wind and wave conditions". Water Science and Technology 65, n. 6 (1 marzo 2012): 1137–41. http://dx.doi.org/10.2166/wst.2012.959.
Testo completoAbstract (sommario):
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.
26
Vu, Tuan V., e Nguyen N. Hieu. "Novel Janus group III chalcogenide monolayers Al2XY2 (X/Y = S, Se, Te): first-principles insight onto the structural, electronic, and transport properties". Journal of Physics: Condensed Matter 34, n. 11 (31 dicembre 2021): 115601. http://dx.doi.org/10.1088/1361-648x/ac4401.
Testo completoAbstract (sommario):
Abstract Motivated by the recent successful synthesis of 2D quintuple-layer atomic materials, for the first time, we design and investigate the electronic and transport properties of Janus Al2XY2 (X/Y = S, Se, Te; X ≠ Y) monolayers by using the density functional theory. Our calculations demonstrate that most of the models of Al2XY2 (except for Al2STe2 monolayer) are dynamically and mechanically stable. By using the hybrid functional, all models of Al2XY2 are semiconductors with an indirect bandgap. Meanwhile, Al2TeS2 monolayer is found to be metal at the Perdew–Burke–Ernzerhof level. Due to the vertical asymmetry structure, an intrinsic built-in electric field exists in the Al2XY2 and leads to a difference in the vacuum levels between the two sides of the monolayers. Carrier mobilities of Al2XY2 monolayers are high directional anisotropic due to the anisotropy of their deformation potential constant. Al2XY2 monolayers exhibit high electron mobility, particularly, the electron mobility of Al2SeS2 exceeds 1 × 104 cm2 V−1 s−1, suggesting that they are suitable for applications in nanometer-sized electronic devices.
27
Su, Peng, Han Ye, Naizhang Sun, Shining Liu e Hu Zhang. "Second Harmonic Generation in Janus Transition Metal Chalcogenide Oxide Monolayers: A First-Principles Investigation". Nanomaterials 13, n. 14 (24 luglio 2023): 2150. http://dx.doi.org/10.3390/nano13142150.
Testo completoAbstract (sommario):
Due to the unique optical responses induced by vertical atomic asymmetry inside a monolayer, two-dimensional Janus structures have been conceived as promising building blocks for nanoscale optical devices. In this paper, second harmonic generation (SHG) in Janus transition metal chalcogenide oxide monolayers is systematically investigated by the first-principles calculations. Second-order nonlinear susceptibilities are theoretically determined for Janus MXO (M = Mo/W, X = S/Se/Te) monolayers. The calculated values are comparable in magnitude with Janus MoSSe monolayer. X-M-O symmetry breaking leads to non-zero components in vertical direction, compared with the non-Janus structure. Focusing on the SHG induced by incident light at 1064 nm, polarization-dependent responses of six Janus MXO monolayers are demonstrated. The symmetry of p-polarization changes from six-fold to three-fold with acute incidence angle. Moreover, the effects of biaxial strain on band structures and SHG are further investigated, taking MoSO as an exemplary case. We expect these results to bring in recipes for designing nonlinear optical devices based on Janus transition metal chalcogenide oxide monolayers.
28
Rao, A. K., e G. R. Cott. "Ontogeny of ion transport across fetal pulmonary epithelial cells in monolayer culture". American Journal of Physiology-Lung Cellular and Molecular Physiology 261, n. 2 (1 agosto 1991): L178—L187. http://dx.doi.org/10.1152/ajplung.1991.261.2.l178.
Testo completoAbstract (sommario):
The transition of the fetal lung from a fluid-secreting to a fluid-absorbing organ is dependent on ion transport across the pulmonary epithelium. This study examined the ion transport characteristics of distal pulmonary epithelial cells isolated from rat fetuses in late gestation and maintained in differentiation-arrested monolayer cultures. The response to inhibitors of active ion transport suggested the presence of apical to basolateral Na+ transport in monolayers derived from each gestational age. However, amiloride inhibition of short-circuit current (Isc) varied with gestational age, decreasing Isc by 30% in monolayers derived from day 18 fetuses and by 55% in monolayers from day 21 fetuses. A portion (10%) of the residual Isc remaining after amiloride addition to monolayers from day 18 fetuses could be inhibited by bumetanide, suggesting the induction of net Cl- transport. Ion-substitution experiments confirmed the presence of Na+ and inducible Cl- transport mechanisms in monolayers from day 18 fetuses and only Na+ transport mechanisms in monolayers from day 21 fetuses. beta-Adrenergic stimulation increased Isc but maintained the age-dependent characteristics of Na(+)- and Cl(-)-dependent ion transport. In summary, monolayer cultures of fetal pulmonary epithelial cells exhibit age-dependent differences in ion transport properties that are consistent with a transition or maturation of the distal pulmonary epithelium from an epithelium capable of Na+ absorption and Cl- secretion preterm to one capable of only Na+ absorption at term.
29
Elkins, Amy L., John G. Eley, Merrill C. Miller III, Iris H. Hall, Anup Sood e Bernard Spielvogel. "Transepithelial Transport and Metabolism of Boronated Dipeptides Across Caco-2 and HCT-8 Cell Monolayers". Metal-Based Drugs 3, n. 6 (1 gennaio 1996): 277–86. http://dx.doi.org/10.1155/mbd.1996.277.
Testo completoAbstract (sommario):
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.
30
Iritani, Kohei. "Fabrication of monolayer with aggregation-induced emission at the air/water interface". Impact 2022, n. 3 (30 giugno 2022): 21–23. http://dx.doi.org/10.21820/23987073.2022.3.21.
Testo completoAbstract (sommario):
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.
31
Martín, Santiago, Luz M. Ballesteros, Alejandro González-Orive, Hugo Oliva, Santiago Marqués-González, Matteo Lorenzoni, Richard J. Nichols, Francesc Pérez-Murano, Paul J. Low e 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, n. 38 (2016): 9036–43. http://dx.doi.org/10.1039/c6tc03319a.
Testo completo
32
Sammak, P. J., L. E. Hinman, P. O. Tran, M. D. Sjaastad e T. E. Machen. "How do injured cells communicate with the surviving cell monolayer?" Journal of Cell Science 110, n. 4 (15 febbraio 1997): 465–75. http://dx.doi.org/10.1242/jcs.110.4.465.
Testo completoAbstract (sommario):
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.
33
Kudernac, Tibor, Natalia Shabelina, Wael Mamdouh, Sigurd Höger e Steven De Feyter. "STM visualisation of counterions and the effect of charges on self-assembled monolayers of macrocycles". Beilstein Journal of Nanotechnology 2 (11 ottobre 2011): 674–80. http://dx.doi.org/10.3762/bjnano.2.72.
Testo completoAbstract (sommario):
Despite their importance in self-assembly processes, the influence of charged counterions on the geometry of self-assembled organic monolayers and their direct localisation within the monolayers has been given little attention. Recently, various examples of self-assembled monolayers composed of charged molecules on surfaces have been reported, but no effort has been made to prove the presence of counterions within the monolayer. Here we show that visualisation and exact localisation of counterions within self-assembled monolayers can be achieved with scanning tunnelling microscopy (STM). The presence of charges on the studied shape-persistent macrocycles is shown to have a profound effect on the self-assembly process at the liquid–solid interface. Furthermore, preferential adsorption was observed for the uncharged analogue of the macrocycle on a surface.
34
PENG, QING, JARED CREAN, ALBERT K. DEARDEN, CHEN HUANG, XIAODONG WEN, STÉPHANE P. A. BORDAS e SUVRANU DE. "DEFECT ENGINEERING OF 2D MONATOMIC-LAYER MATERIALS". Modern Physics Letters B 27, n. 23 (9 settembre 2013): 1330017. http://dx.doi.org/10.1142/s0217984913300172.
Testo completoAbstract (sommario):
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.
35
Stine, Keith J. "Investigations of monolayers by fluorescence microscopy". Proceedings, annual meeting, Electron Microscopy Society of America 50, n. 2 (agosto 1992): 1018–19. http://dx.doi.org/10.1017/s0424820100129723.
Testo completoAbstract (sommario):
Understanding the organization of amphiphilic molecules at interfaces is of fundamental importance in a number of fields of research. Langmuir-Blodgett technology and membrane mimetic chemistry are based on understanding the structural and physical properties of monolayers of amphiphilic compounds. This is a challenging area with numerous unresolved questions. For example, monolayers of amphiphilic compounds as simple as long-chain fatty acids and esters exhibit complex phase behavior which is still under investigation. In order to investigate biomembrane structure and processes, model systems can be constructed. Monolayers of phospholipids at the air/water interface serve as membrane models and have been used to investigate the effects of varying temperature, surface density, and subphase conditions. Study of the interaction of a protein introduced into the subphase with the monolayer can provide insight into a specific membrane process. In this review, fluorescence microscopy studies by a number of research groups of monolayers of fatty acids and esters, phospholipids, and of interactions of proteins with phospholipid monolayers will be discussed.
36
ELMERS, HANS-JOACHIM. "FERROMAGNETIC MONOLAYERS". International Journal of Modern Physics B 09, n. 24 (30 ottobre 1995): 3115–80. http://dx.doi.org/10.1142/s0217979295001191.
Testo completoAbstract (sommario):
The ferromagnetic properties of ultrathin films grown on non-magnetic substrates provide interesting new insights into the physics of magnetism. In this report we review experiments in the very low coverage regime (Θ < 2 atomic layers). The Fe monolayer on W plays an outstanding role, because it forms a ferromagnetic and thermodynamically stable monolayer. Ferromagnetic Fe monolayers on W can be prepared with a high degree of perfection. We therefore focus on ultrathin Fe films on W(110) and W(100) substrates. Experimental results for these in-plane magnetized films, prepared as close as possible to 2-dimensional structures of perfect translational symmetry, are compared with appropriate theoretical models, We also discuss experimental results for the perpendicularly magnetized Co monolayer on Cu(111). The symmetry of the magnetic anisotropy is found to play an important role for the understanding of the magnetic phase transition in 2 dimensions. A new aspect is provided by finite size effects resulting from the morphology of magnetic ultrathin films. Microscopy with atomic resolution allows a systematic approach to the understanding of these finite size effects. Starting from the well-known magnetic properties of the extended Fe monolayer on W(110), we focus on ultrathin Fe films on W(110) deviating from the nearly perfect structure.
37
Rubio, Ramón G., Eduardo Guzmán, Francisco Ortega e 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, n. 2 (20 maggio 2021): 30. http://dx.doi.org/10.3390/colloids5020030.
Testo completoAbstract (sommario):
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.
38
Yu, Yawei, Xiao Xie, Xiaobiao Liu, Jia Li, François M. Peeters e Linyang Li. "Two-dimensional semimetal states in transition metal trichlorides: A first-principles study". Applied Physics Letters 121, n. 11 (12 settembre 2022): 112405. http://dx.doi.org/10.1063/5.0105605.
Testo completoAbstract (sommario):
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.
39
Jadhav, Sushilkumar. "Self-assembled monolayers (SAMs) of carboxylic acids: an overview". Open Chemistry 9, n. 3 (1 giugno 2011): 369–78. http://dx.doi.org/10.2478/s11532-011-0024-8.
Testo completoAbstract (sommario):
AbstractThe field of self-assembled monolayers (SAMs) of organic compounds on different substrates is of importance because it provides a suitable and efficient method of surface modification. The formation of robust, stable monolayers from carboxylic acids on two and three dimensional surfaces of different substrates have been reported. Carboxylic acids are promising class of organic compounds for monolayer formations where traditional alkanethiols or alkoxysilanes show limitations.
40
Cheek, J. M., R. J. McDonald, L. Rapalyea, B. K. Tarkington e D. M. Hyde. "Neutrophils enhance removal of ozone-injured alveolar epithelial cells in vitro". American Journal of Physiology-Lung Cellular and Molecular Physiology 269, n. 4 (1 ottobre 1995): L527—L535. http://dx.doi.org/10.1152/ajplung.1995.269.4.l527.
Testo completoAbstract (sommario):
After acute exposure to oxidant gases in vivo, migration and accumulation of inflammatory cells in pulmonary epithelium coincides with epithelial cell necrosis. The present study was designed to test quantitatively the hypothesis that quiescent neutrophils enhance the removal of oxidant-injured pulmonary epithelial cells after exposure to ozone in vitro. Primary isolated rat alveolar type II cells were cultured as monolayers, using serum-free medium. After exposure to 0.1-0.5 ppm ozone for 0.5 h, apical sides of monolayers were administered either fresh nutrient medium only or medium containing quiescent human neutrophils. Monolayer bioelectric properties and cellular uptake of vital dye were recorded from 5 to 48 h after ozone exposure. Ozone dose-dependent increases in monolayer permeability were associated with proportionally higher numbers of injured epithelial cells. However, the direction and magnitude of neutrophil effects on monolayer permeability after ozone exposure were dependent on ozone concentration. Furthermore, neutrophil-treated monolayers exposed to 0.1 ppm ozone had significantly fewer attached cells positive for uptake of vital dye relative to monolayers exposed to the low level of ozone only; this effect was ablated with increasing ozone concentration. These data suggest that at high levels of ozone neutrophils may exacerbate injury to oxidant-impaired epithelial cells, whereas the presence of neutrophils after exposure to ambient concentrations of ozone may expedite the restoration of epithelial barrier function. We conclude that, by enhancing the removal of injured cells, neutrophils may facilitate the repair of centriacinar epithelium after ozone exposure in vivo.
41
Carterson, A. J., K. Höner zu Bentrup, C. M. Ott, M. S. Clarke, D. L. Pierson, C. R. Vanderburg, K. L. Buchanan, C. A. Nickerson e M. J. Schurr. "A549 Lung Epithelial Cells Grown as Three-Dimensional Aggregates: Alternative Tissue Culture Model for Pseudomonas aeruginosa Pathogenesis". Infection and Immunity 73, n. 2 (febbraio 2005): 1129–40. http://dx.doi.org/10.1128/iai.73.2.1129-1140.2005.
Testo completoAbstract (sommario):
ABSTRACT A three-dimensional (3-D) lung aggregate model was developed from A549 human lung epithelial cells by using a rotating-wall vessel bioreactor to study the interactions between Pseudomonas aeruginosa and lung epithelial cells. The suitability of the 3-D aggregates as an infection model was examined by immunohistochemistry, adherence and invasion assays, scanning electron microscopy, and cytokine and mucoglycoprotein production. Immunohistochemical characterization of the 3-D A549 aggregates showed increased expression of epithelial cell-specific markers and decreased expression of cancer-specific markers compared to their monolayer counterparts. Immunohistochemistry of junctional markers on A549 3-D cells revealed that these cells formed tight junctions and polarity, in contrast to the cells grown as monolayers. Additionally, the 3-D aggregates stained positively for the production of mucoglycoprotein while the monolayers showed no indication of staining. Moreover, mucin-specific antibodies to MUC1 and MUC5A bound with greater affinity to 3-D aggregates than to the monolayers. P. aeruginosa attached to and penetrated A549 monolayers significantly more than the same cells grown as 3-D aggregates. Scanning electron microscopy of A549 cells grown as monolayers and 3-D aggregates infected with P. aeruginosa showed that monolayers detached from the surface of the culture plate postinfection, in contrast to the 3-D aggregates, which remained attached to the microcarrier beads. In response to infection, proinflammatory cytokine levels were elevated for the 3-D A549 aggregates compared to monolayer controls. These findings suggest that A549 lung cells grown as 3-D aggregates may represent a more physiologically relevant model to examine the interactions between P. aeruginosa and the lung epithelium during infection.
42
Tizazu, Getachew. "A Simple Method for Patterning Nanoparticles on Planar Surfaces". Journal of Nanotechnology 2019 (4 giugno 2019): 1–7. http://dx.doi.org/10.1155/2019/8263878.
Testo completoAbstract (sommario):
This paper describes a simple method to pattern nanoparticles on planar surfaces using the antifouling property of poly(ethylene glycol) monolayers deposited from a solution on the native oxide of titanium. Atomic force microcopy was used to pattern the poly(ethylene glycol) monolayers producing protein active sites on the protein-resistant surface. Patterns with different sizes have been generated by shaving the monolayers with different repetitions. Friction force microscopy was used to image the patterns. The smallest patterns are 50 nm and the largest patterns are 500 nm at full width half maximum. The smallest pattern was produced with one shave, whereas the largest pattern was produced by shaving the monolayers 112 times. Protein-coated nanoparticles were immobilised on the shaved (protein active) part of the monolayers by dipping the patterned samples into a solution that contains 2% by volume protein-functionalized nanoparticles with a nominal diameter of 40 nm. Atomic force microscopy was used to take a topographic image of the samples. The topographic image showed that the protein-functionalized nanoparticles were attached onto the shaved part of the substrate but not on the poly(ethylene glycol)-covered part of the substrate. The level of aggregation of the nanoparticles was also investigated from the topographic image. The section analysis of the topographic image of the nanoparticle patterns showed a height of 40 nm which proved that only a monolayer of particles were deposited on the shaved part of the monolayer.
43
Tucker, Torry A., Karoly Varga, Zsuzsa Bebok, Akos Zsembery, Nael A. McCarty, James F. Collawn, Erik M. Schwiebert e Lisa M. Schwiebert. "Transient transfection of polarized epithelial monolayers with CFTR and reporter genes using efficacious lipids". American Journal of Physiology-Cell Physiology 284, n. 3 (1 marzo 2003): C791—C804. http://dx.doi.org/10.1152/ajpcell.00435.2002.
Testo completoAbstract (sommario):
Transient transfection of epithelial cells with lipid reagents has been limited because of toxicity and lack of efficacy. In this study, we show that more recently developed lipids transfect nonpolarized human airway epithelial cells with high efficacy and efficiency and little or no toxicity. Because of this success, we hypothesized that these lipids may also allow transient transfection of polarized epithelial monolayers. A panel of reagents was tested for transfer of the reporter gene luciferase ( LUC) into polarized monolayers of non-cystic fibrosis (non-CF) and CF human bronchial epithelial cells, MDCK epithelial cell monolayers, and, ultimately, primary non-CF and CF airway epithelial cells. Lipid reagents, which were most successful in initial LUC assays, were also tested for transfer of vectors bearing the reporter gene green fluorescent protein (GFP) and for successful transfection and expression of an epithelial-specific protein, the cystic fibrosis transmembrane conductance regulator (CFTR). Electrophysiological, biochemical, and immunological assays were performed to show successful complementation of an epithelial monolayer with transiently expressed CFTR. We also present findings that help facilitate monolayer formation by these airway epithelial cell lines. Together, these data show that polarized monolayers are transfected transiently with more recently developed lipids, specifically LipofectAMINE PLUS and LipofectAMINE 2000. Transient transfection of epithelial monolayers provides a powerful system in which to express the cDNA of any epithelium-specific protein transiently in a native polarized epithelium to study protein function.
44
Jo, Sunghwan, Jin-Woo Jung, Jaeyoung Baik, Jang-Won Kang, Il-Kyu Park, Tae-Sung Bae, Hee-Suk Chung e Chang-Hee Cho. "Surface-diffusion-limited growth of atomically thin WS2 crystals from core–shell nuclei". Nanoscale 11, n. 18 (2019): 8706–14. http://dx.doi.org/10.1039/c9nr01594a.
Testo completo
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Strange, Charlie, Andrew Gottehrer, Karen Birmingham e John E. Heffner. "Platelets attenuate oxidant-induced permeability in endothelial monolayers: glutathione-dependent mechanisms". Journal of Applied Physiology 81, n. 4 (1 ottobre 1996): 1701–6. http://dx.doi.org/10.1152/jappl.1996.81.4.1701.
Testo completoAbstract (sommario):
Strange, Charlie, Andrew Gottehrer, Karen Birmingham, and John E. Heffner. Platelets attenuate oxidant-induced permeability in endothelial monolayers: glutathione-dependent mechanisms. J. Appl. Physiol. 81(4): 1701–1706, 1996.—We studied the effects of adding washed human platelets or platelets with nonintact glutathione redox cycles to endothelial cell monolayers treated with glucose oxidase to initiate oxidant stress and increase permeability. Changes in125I-labeled albumin transmonolayer movement were used as the index of monolayer permeability. Washed human platelets attenuated oxidant-induced increases in albumin flux. Platelets treated with 1,3-bis(2-chloroethyl)-1-nitrosurea, 1-chloro-2,4-dinitrobenzene, or buthionine sulfoximine to inhibit selective enzymatic steps in the glutathione redox cycle decreased permeability to a lesser degree. We conclude that 1) washed human platelets attenuate monolayer permeability defects in aortic endothelial monolayers exposed to glucose oxidase and 2) the protective effects of platelets are partially dependent on an intact platelet glutathione redox cycle.
46
Xu, Xiaotao, Xi He, Anthony T. Bollinger, Myung-Geun Han, Yimei Zhu, Xiaoyan Shi e Ivan Božović. "A Method to Probe the Interfaces in La2−xSrxCuO4-LaSrAlO4-La2−xSrxCuO4 Trilayer Junctions". Condensed Matter 8, n. 1 (10 febbraio 2023): 21. http://dx.doi.org/10.3390/condmat8010021.
Testo completoAbstract (sommario):
C-axis trilayer cuprate Josephson junctions are essential for basic science and digital circuit applications of high-temperature superconductors. We present a method for probing the interface perfection in La2−xSrxCuO4 (LSCO)-LaSrAlO4 (LSAO)-La2−xSrxCuO4 trilayer junctions. A series of LSCO-LSAO superlattices with atomically smooth surfaces and sharp interfaces were grown by the atomic-layer-by-layer molecular beam epitaxy (ALL-MBE) technique. We have systematically varied the thickness of LSCO and LSAO layers with monolayer precision. By studying the mutual inductance and electrical transport in these superlattices, we detect the non-superconducting (“dead”) layers at the interfaces and quantify their thicknesses. Our results indicate that two optimally doped LSCO monolayers just above and below the one monolayer LSAO barrier are no longer superconducting, rendering the actual barrier thickness of five monolayers. Next, we have shown that introducing a protective highly-overdoped LSCO layer reduces the thickness of dead layers by one or two monolayers.
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GUO, YUDI, DONGYAN TANG e SHUO GU. "EFFECTS OF SUBSTRATE AND EXPERIMENTAL CONDITIONS ON THE FABRICATION OF WELL-ORDERED SILICA PARTICULATE LANGMUIR–BLODGETT FILMS". Surface Review and Letters 20, n. 03n04 (agosto 2013): 1350039. http://dx.doi.org/10.1142/s0218625x1350039x.
Testo completoAbstract (sommario):
The dependence of particulate Langmuir–Blodgett (LB) monolayer quality on the surface nature of the substrate was investigated by pretreating the substrates with different methods, and the optimal withdrawal speed was determined by detecting the quality of particulate monolayers deposited at different withdrawal speeds. Furthermore, the effects of stearic acid (SA) concentration on the quality of particulate monolayers were discussed. Results indicated that surface amination would favor the transfer of the floating particulate monolayer from the interface to the substrate, which would be attributed to the formation of chemical bonds between the – NH 2 groups on the substrate surface and the functional groups of – COOH and Si – OH groups on surfaces of particles floating at the interface. And the withdrawal speed of 1 mm ⋅ min-1 was appropriate for the fabrication of high-quality particulate LB monolayer because low withdrawal speed can offer sufficient time to form chemical bonds and expel the subphase from the substrate. Additionally, SEM images illustrated that the SA concentration of 0.40 mg ⋅ mL-1 was suitable for the fabrication of well-ordered particulate LB monolayers composed by the particles of 380 nm.
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Ncube, Keith N., Tamarin Jurgens, Vanessa Steenkamp, Allan D. Cromarty, Iman van den Bout e Werner Cordier. "Comparative Evaluation of the Cytotoxicity of Doxorubicin in BT-20 Triple-Negative Breast Carcinoma Monolayer and Spheroid Cultures". Biomedicines 11, n. 5 (19 maggio 2023): 1484. http://dx.doi.org/10.3390/biomedicines11051484.
Testo completoAbstract (sommario):
Three-dimensional cell culture models are increasingly adopted as preferred pre-clinical drug testing platforms, as they circumvent limitations associated with traditional monolayer cell cultures. However, many of these models are not fully characterized. This study aimed to characterize a BT-20 triple-negative breast carcinoma spheroid model and assess its susceptibility to doxorubicin in comparison to a monolayer model. Spheroids were developed using the liquid overlay method. Phenotypic attributes were analyzed by characterizing changes in size, gross morphology, protein content, metabolic activity, hypoxic status, and cell–cell junctions. The cytotoxic range of doxorubicin in monolayers was determined using the sulforhodamine B assay, and the comparative effect of toxic and sub-toxic concentrations was assessed in both spheroids and monolayers. Similar to the in vivo microenvironment, spheroids had a heterogeneous spatial cytoarchitecture, inherent hypoxia and strong adherens junctions. Doxorubicin induced dose-dependent cytotoxicity in monolayers (IC25: 130 nM, IC50: 320 nM and IC75: 1580 nM); however, these concentrations did not alter the spheroid size or acid phosphatase activity. Only concentrations ≥6 µM had any effect on spheroid integrity. In comparison to monolayers, the BT-20 spheroid model has decreased sensitivity to doxorubicin and could serve as a better model for susceptibility testing in triple-negative breast cancer.
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Wasserman, Stephen R., Hans Biebuyck e George M. Whitesides. "Monolayers of 11-trichlorosilylundecyl thioacetate: A system that promotes adhesion between silicon dioxide and evaporated gold". Journal of Materials Research 4, n. 4 (agosto 1989): 886–92. http://dx.doi.org/10.1557/jmr.1989.0886.
Testo completoAbstract (sommario):
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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Arefi, Hadi H., Michael Nolan e Giorgos Fagas. "Binary functionalization of H:Si(111) surfaces by alkyl monolayers with different linker atoms enhances monolayer stability and packing". Physical Chemistry Chemical Physics 18, n. 18 (2016): 12952–63. http://dx.doi.org/10.1039/c5cp07601c.
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