Langmuir-Schaefer Films Research Articles

Aggregation behavior of unsubstituted magnesium porphyrazine in monolayers at air–water interface and in Langmuir–Schaefer films

The aggregation behavior of unsubstituted magnesium porphyrazine (MgPz) was studied in layers at the water–air interface and in Langmuir–Schaefer films. Regions of existence and characteristics of the structure and properties of stable nanostructured monolayers of MgPz were determined with the method of quantitative analysis of compression isotherms of floating layers in a wide range of initial surface coverage degrees (ISCD). MgPz on the water surface forms monolayers of three types: a face-on type and two edge-on types that differ in the structure. The specific feature of the monolayers of the second type is the independence of the structure of two-dimensional MgPz nanoparticles formed on water on the ISCD. A mathematical model and a state diagram of the monolayer were constructed and a passport of MgPz monolayers was compiled. For the first time, the state diagram contains boundary isotherms based on data obtained from the model. Langmuir–Schaefer films of MgPz formed from layers of various types were prepared and studied by UV-vis absorption spectroscopy.

Supramolecular Arrangement of Iron Phthalocyanine in Langmuir-Schaefer and Electrodeposited Thin Films.

The supramolecular arrangement in thin film technology has been explored through different deposition techniques aiming to control the film properties at the molecular level. We report on the formation of iron phthalocyanine (FePc) films using both Langmuir-Schaefer (LS) and electrodeposition methods. The multilayer formation was monitored with ultraviolet-visible absorption spectroscopy (UV-vis) and electrochemical measurements. According to Raman spectroscopy, atomic force microscopy (AFM), and scanning electron microscopy (SEM), the surface morphology of electrodeposited films is more homogeneous than LS films at micro and nanometer scales. From FTIR spectroscopy, the FePc molecules in the electrodeposited films are oriented preferentially with the macrocycle parallel to the substrate surface (flat-on), while a slight tilt is suggested in LS films, being both films crystalline. Therefore, the use of different deposition techniques allowed the fabrication of thin films from FePc with distinct supramolecular arrangements, leading to distinct electrochemical properties. For instance, the electrodeposited films show higher surface coverage, suggesting a more compact structure, which favors the charge transfer and smaller energy gap. The possibility of tuning some properties according to deposition technique for the same material can help the development of technological applications such as electronic or sensing devices.

Universality of Ethane-Bridged Bis-Porphyrin Structural Motiff for Chirality and Molecular Sensing

Covalently linked porphyrins are of particular interest for the scientific community as efficient artificial systems widely used in various practical applications in the numerous research and technoligical fields such as polymer and nano science, light harvesting and nonlinear optics, different sensors and catalysis, molecular and chiral recognition, various supramolecular and chiroptical devices, chirogenesis and absolute configuration determination. Recently, we have found that a simple ethane-bridged bis-porphyrin structural motif, 1 (M = Zn, Mg, Cu, Co, 2H), can be effectively served for various application purposes owing to the specific molecular and supramolecular functionalities. In particular, the unique functional property of this bis-porphyrin host is based upon the structural semi-flexibility of covalent linkage between two porphyrin units resulting in the environmentally assisted syn-anti conformational switching and tweezer formation depending upon the guest structure, which can be effectively employed in different sensing areas.1-11 For example, in the case of monodentate chiral guests there is the unidirectional screw formation in the anti form of 1 (M = Zn, Mg, 2H) upon the corresponding host-guest interaction. The direction of screw governs by the size difference of ligand’s substituents at the chirogenic center resulting in chirality transfer to the bis-porphyrin host and induction of the noticeable exciton couplet CD signals in the porphyrin absorption region.1-6 This chirogenic phenomenon was efficiently utilized for determining the absolute configuration of various chiral guests, thus making it possible to apply 1 as effective and universal chirality sensors for different types of organic molecules as in solution and in solid state. To expand further the applicability of these supramolecular systems Langmuir–Schaefer (LS) thin-films on the basis of 1 have been prepared and employed as highly selective and sensitive sensors for aromatic amines.7-9 For example, the monometallated Cu complex of 1 is able to detect the presence of aniline in aqueous solution at a concentration as low as 1 nM.9 The sensory mechanism includes the corresponding host-guest interaction resulting in the syn-to-anti conformational switching, which can be easily detected by various spectroscopic methods. Another sensing application of the LS film of monometallated Co complex of 1was found in the field of detection of volatile organic compounds like alcohol vapors and oxidizing gas as NO2 by using magneto-optical surface plazmon resonance spectroscopy.10 The detection mechanism is based upon the molecular recognition correlating with the alcohol molecular structure. More simple sensing system was developed on the basis of spin-coated thin films of the monometallated Zn complex of 1.11 The obtained thin films were successfully employed to detect ammonia and acetone as the relevant analytes in aqueous solutions. This was a result of the supramolecular interaction between each of these two compounds and the bis-porphyrin active layer, inducing the corresponding tweezer conformation easily detectable by UV–vis absorption spectroscopy in the range of concentrations between 1 ppm and 20 ppm for both the analytes. Further developments and prospects toward new sensing systems on the basis of heterometallic bis- and multi-porphyrin structures will be discussed. Borovkov, Symmetry 2014, 6, 256.Borovkov, Symmetry 2010, 2, 184.Borovkov, Y. Inoue, Eur. J. Org. Chem. 2009, 189.A. Hembury, V. V. Borovkov, Y. Inoue, Chem. Rev. 2008, 108, 1.V. Borovkov, Y. Inoue, Top. Curr. Chem. 2006, 265, 89.V. Borovkov, G. A. Hembury, Y. Inoue, Acc. Chem. Res. 2004, 37, 449.Giancane, V. Borovkov, Y. Inoue, L. Valli, J. Colloid Interface Sci. 2012, 385, 282.Giancane, V. Borovkov, Y. Inoue, S. Conoci, L. Valli, Soft Matter 2013, 9, 2302. Bettini, E. Maglie, R. Pagano, V. Borovkov, Y. Inoue, L. Valli, G. Giancane, Beilstein J. Nanotechnol. 2015, 6, 2154.Colombelli, M.G. Manera, V. Borovkov, G. Giancane, L. Valli, R. Rella, Sensor Actuat. B-Chem., 2017, 246, 1039.A. Buccolieri, D. Manno, A. Serra, A. Santino, M. Hasan, V. Borovkov, G. Giancane, Sensor Actuat. B-Chem., 2018, 257, 685.

Mobile liquid-substrate for self-assembly of solution-processable poly (5-aminoindole) by Langmuir technique

Polymers based device performance greatly depends on the π-backbone chain orientation along the charge transportation direction. Therefore, rearrangement of polymer chains at molecular level and thin film fabrication via Langmuir technique is highly desirable for large area electronic device applications. Here, we have utilized air-water interface of Langmuir technique for proper molecular orientation of the interfacially (water-chloroform interface) synthesized, electroactive poly (5-aminoindole) (5-APIn). 5-APIn is assembled over aqueous (mobile) subphase and variation in film compactness with varying surface pressure has been plotted as surface-pressure per area (п-A) isotherm. The films fabricated via Langmuir-Schaefer (LS) technique at surface pressures 35, 45 and 55 mN/m are qualitatively investigated using scanning electron microscopy (SEM). Surface roughness of the 5-APIn LS film is also investigated via atomic force microscopy (AFM). Polymer ordered assembly obtained in LS film is compared to bulk via Raman spectroscopy. Further, we have explored its large area electronic application via Al/5-APIn LS film/ITO diode configuration. Our study illustrates the significant role of mobile liquid substrate in formation of large area, smooth and ordered LS film of 5-APIn that unlocks its way for utilization in low cost and large area display electronic applications.

Temperature-Dependent Phase Behavior of Langmuir Films of 10,12-Pentacosadiynoic Acid at the Air/Water Interface and Its Effects on Chromatic Stability of the Polymerized Langmuir-Schaefer Films

The effect of temperature on the two-dimensional phase of 10,12-pentacosadiynoic acid (PCDA) Langmuir films at the air/water interface was investigated. The temperature of the Langmuir films was precisely controlled from 5 to 50 °C and their surface isotherms and in-situ visible absorption spectra were acquired. Depending on the temperature, the PCDA Langmuir films were found to be classified into a liquid-condensed (low temperatures, 5 and 25 °C) and a liquid-expanded phase (high temperatures, 40 and 50 °C). After polymerizing the PCDA Langmuir films with 254 nm UV light at the specific temperatures, the films were transferred to hydrophobic glass using the Langumir-Schaefer (LS) method. Upon thermal and pH stimuli, their chromatic transition characteristics were analyzed by visible spectroscopy. The liquid-condensed films were found to be more susceptible to thermal stimulus than the liquid-expanded films. The latter also showed remarkable chromatic stability against the pH in the region from 2 to 11, compared to the former. Thus, when sturdy films are required, the multilayered PCDA LS films prepared at the liquid-expanded phase are more suitable than the liquid-condensed films, and vice versa. This result is expected to be very useful for controlling the sensitivity and stability of polydiacetylene-based sensory systems simply by changing the polymerization temperature, even without synthesizing new monomers.

Fabrication of ultrathin MIL-96(Al) films and study of CO2 adsorption/desorption processes using quartz crystal microbalance

This contribution reports the fabrication and characterization of ultrathin films of nanoparticles of the water stable microporous Al tricarboxylate metal organic framework MIL-96(Al). The preparation of MOF dispersions in chloroform has been optimized to obtain dense monolayer films of good quality, without nanoparticle agglomeration, at the air-water interface that can be deposited onto solid substrates of different nature without any previous substrate functionalization. The MOF studied shows great interest for CO2 capture because it presents Al3+ Lewis centers and hydroxyl groups that strongly interact with CO2 molecules. A comparative CO2 adsorption study on drop-cast, Langmuir-Blodgett (LB) and Langmuir-Schaefer (LS) films using a Quartz Crystal Microbalance-based setup (QCM) has revealed that the CO2 uptake depends strongly on the film fabrication procedure and the storage conditions. Noteworthy the CO2 adsorption capacity of LB films is increased by 30% using a simple and green treatment (immersion of the film into water during 12 h just after film preparation). Finally, the stability of LB MOF monolayers upon several CO2 adsorption/desorption cycles has been demonstrated, showing that CO2 can be easily desorbed from the films at 303 K by flowing an inert gas (He). These results show that MOF LB monolayers can be of great interest for the development of MOF-based devices that require the use of very small MOF quantities, especially gas sensors.

Thin-Film Nanocomposite Membrane with the Minimum Amount of MOF by the Langmuir-Schaefer Technique for Nanofiltration.

An innovative procedure for positioning a monolayer of hydrophilic metal organic framework (MOF) MIL-101(Cr) (MIL, Materials of Institute Lavoisier) nanoparticles (NPs) in thin-film nanocomposite (TFN) membranes has been implemented by transferring a Langmuir-Schaefer (LS) film of the MOF in between the polyamide thin layer at the top and the cross-linked asymmetric polyimide (P84) support at the bottom. The presence and layout of the LS-MIL-101(Cr) monolayer in the TFN membrane was confirmed by scanning transmission electron microscopy imaging with a high-angle annular dark-field detector images and X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy, electron energy loss spectroscopy, and atomic force microscopy analyses. This methodology requires the smallest amount of MOF reported to date, 3.8 μg cm-2, and promotes the formation of a defect-free ultrathin MOF film. Although conventional TFN membranes tend to show MOF agglomerates that could contribute to the formation of unselective defects, LS-TFN membranes, characterized by a homogeneous and continuous MOF coating, exhibit an optimal membrane performance, without a significant decrease in selectivity. Outstanding methanol permeances, one of the best results reported to date, of 10.1 ± 0.5 L m-2 h-1 bar-1 when filtering sunset yellow and of 9.5 ± 2.1 L m-2 h-1 bar-1 when filtering rose bengal have been achieved in LS-TFN membranes with a rejection higher than 90% in all cases. Methanol permeates through the polyamide and the LS-MIL-101(Cr) monolayer, greatly enhanced by the MOF pore system, in comparison to thin-film composite and conventional TFN membranes (7.5 ± 0.7 and 7.7 ± 1.1 L m-2 h-1 bar-1 when filtering sunset yellow), respectively, in which polyamide areas free of MOF NPs are present.

Homogenous Dispersion of MoS2 Nanosheets in Polyindole Matrix at Air-Water Interface Assisted by Langmuir Technique.

Two-dimensional (2D) inorganic layered materials when embedded in organic polymer matrix exhibit exotic properties that are grabbing contemporary attention for various applications. Here, nanosheet morphology of molybdenum disufide (MoS2) synthesized via one-pot facile hydrothermal reaction are exfoliated in benign aqueous medium in the presence of indole to obtain a stable dispersion. These exfoliated nanosheets then act as host to template the controlled polymerization of indole. The preassembled MoS2-polyindole (MoS2-PIn) nanostructures are reorganized at the air-water interface using the Langmuir method to facilitate maximum interfacial interaction between nanosheet and polymer. This report emphasizes large area, homogeneous dispersion of uniform-sized MoS2 nanosheets (40-60 nm diameter) in the PIn matrix and the formation of stable and uniform film via the Langmuir-Schaefer (LS) method. These self-assembled, MoS2 decorated PIn LS films are characterized using atomic force microscopy (AFM) and transmission electron microscopy (TEM). The fabricated LS films in sandwiched structure Al/MoS2-PIn/ITO as the Schottky diode portrayed remarkable enhancements in charge transport properties. Our study illustrates the potential of the MoS2-PIn LS film in electronic applications and opens a new dimension for uniform dispersion of 2D materials in other polymers via the Langmuir method for device fabrication and enhancement of electrical properties.

Stable blue phase polymeric Langmuir-Schaefer films based on unsymmetrical hydroxyalkadiynyl N-arylcarbamate derivatives

Unsymmetrical diynes containing N-arylcarbamate groups in the hydrophobic part and hydroxymethylene groups in the hydrophilic part of the molecules were synthesized and studied. The Langmuir monolayer formation process was followed by Brewster angle microscopy (BAM). The Langmuir-Schaefer monolayer films, transferred on solid substrates (quartz or Si), were investigated by absorption spectroscopy and atomic force microscopy (AFM). Four substances had 2 methylene groups in the hydrophilic part of the molecule (n) and 4 or 5 of these groups in the hydrophobic part (m). At the same time the aryl substituent had a hydrogen atom or a MeO group in the p-position of the benzene ring. After 20min of UV irradiation the initially colorless monomeric films of all four compounds turned into stable blue phase polymeric films. The blue phase is unusual for alcoholic diacetylene derivatives. The BAM and AFM measurements demonstrated higher homogeneity of the films with a MeO group in the aryl substituent in comparison to the molecules with a hydrogen atom. The reasons for these different structural organizations as well as potential applications of stable blue phase polydiacetylene thin films are discussed.

Understanding the gas adsorption kinetics of Langmuir-Schaefer porphyrin films using two comparative sensing systems

This study investigated Langmuir-Schaefer (LS) films of a free base porphyrin 5,10,15,20-tetrakis[3,4-bis(2-ethylhexyloxy)phenyl]-21H,23H-porphine (EHO) as sensors to detect acetic acid and methylamine. Such films are known to adsorb VOCs, resulting in a color change and a swelling of the film resulting in a thickness increase for the film. The adsorption kinetics of this process were studied using two different techniques, namely UV–vis absorbance spectroscopy and surface plasmon resonance (SPR), to investigate the color change and film thickness change respectively when exposed to acetic acid and methylamine vapors. These two techniques were used to allow a comparative study to be made of the color change and film swelling in order to enhance understanding of the interaction between the thin films and both acidic and basic vapor molecules.The transfer process of the LS thin films was performed using the constant transfer pressure of 5mNm−1. EHO films with different numbers of layers were fabricated and exposed to 855ppm acetic acid and 900ppm methylamine vapor. Sensor responses were recorded using both UV–vis and surface plasmon resonance techniques. The EHO films exhibited high sensitivity and fast responses using both techniques. Using two different detection systems permitted the investigation of the interaction mechanism with a quantitative, comparative study with the aim of obtaining an enhanced understanding of the nature of the interaction of the organic vapors with the sensor. The interaction between EHO and the analytes can be considered in terms of three processes which are surface adsorption, diffusion and desorption process. Although both the optical techniques have distinct sensing principles, similar vapor interaction characteristics can be distinguished in both sets of experiments. For both techniques the response to the acid was stronger than the response to methylamine. However, apart from this difference in the magnitude of the responses the interaction with the acid and base were remarkably similar. The sensitivity of the sensor is largely independent of the measurement system.

Nanostructured Stable Floating М-Mono- and Bilayers and Langmuir-Schaefer Films of 5,10,15-Triphenylcorrole

5,10,15-Triphenylcorrole is a tetrapyrrolic macrocyclic compound similar to B12 vitamin, with pyrrole-pyrrole direct coupling and a carbon skeleton. Stable floating nanostructured mono-, bi-, and tetralayers of the compound were prepared. The main characteristics of the structure, properties, and formation conditions of the layers were determined. A model of monolayers consisting of nanoaggregates was built. The triphenylcorrole produces nanostructured face-on and edge-on monolayers. Stable bilayers and tetralayers form at high values of the initial surface coverage, featuring a constant degree of surface coverage by 3D nanoaggregates at the initial point of the stable state (75%). The layers with bilayered 3D nanostructures demonstrate very high stability. Their size (8 nm) and the number of molecules in them (109) are independent of the initial degree of surface coverage. For the first time, a model of floating bilayers of a macroheterocyclic compound was constructed. Langmuir-Schaeffer films of the corrole were prepared from nanostructured floating polylayers produced on the water surface and then were studied spectrally.

Trans-cis photoisomerization in nanostructured floating layers and x-ray diffraction study of Langmuir-Schaefer films of nonyloxypheylazocinnamic acid

ABSTRACTAzo-functionalised materials are of special interest due to their photochromic nature, i.e. reversible trans–cis isomerisation upon photoirradiation. The structure and properties of Langmuir monolayers of nonyloxyphenylazocinnamic acid (NOPACA) with and without exposure to UV-irradiation were studied. The NOPACA floating layer structure was determined by using a quantitative method of compression isotherm analysis. The results showed that the structure of two dimensional face-on M-nanoaggregates, the stable structural elements of floating monolayers, changes when exposed to UV-irradiation. Langmuir-Schaefer films of NOPACA were prepared by deposition of floating layers and studied using X-ray diffraction technique.

Synthesis and spectral properties of preorganized BODIPYs in solutions and Langmuir-Schaefer films

Abstract In order to investigate the influence of molecular structure peculiarities of boron-dipyrrine dyes (BODIPYs) on their properties in solutions and supramolecular organization in Langmuir-Schaefer (LS) films, four new BODIPY dyes with various aliphatic, aromatic or mixed nature meso-subtituents were synthesized and investigated. Spectral characteristics (electronic absorption and fluorescence) of the synthesized compounds in organic solvents and LS-films were studied. Floating monolayers of the BODIPYs were formed from chloroform solutions placed onto water subphase in Langmuir-Blodgett through. Thin films were prepared using the Langmuir-Schaefer technique by the transfer of floating monolayers onto standard polished glass, ITO covered glass or pure silicon substrate. The variation of the dye structure we consider as a preorganization aiming to influence the structure of LS-films. The morphology and structure of the LS-films was examined by fluorescent microscopy, scanning electron microscopy, atomic force microscopy and small angle X-ray diffraction analysis. It was found that the introduced substituents have no substantial influence on the position of the absorption and fluorescence bands in dilute solutions. In contrast, the fluorescent characteristics of the LS-films significantly depend on the substituent nature. Therefore, this strategy could be used for the direct tuning of compounds fluorescent properties in LS-films. Concerning the LS-film surface characteristics it was proved that the films are homogeneous, without disruptions and only some widely-spaced microcrystals could be observed. With respect to the LS-film structure, the change of the substituents introduced to the BODIPY molecule did not influence the average given periodicity of layers (d = 0.3–0.4 nm). This value corresponds to a single-layer arrangement of BODIPY molecules located parallel to the substrate surface. Nevertheless, the diffraction peak intensities depended on the molecular structure of BODIPYs and therefore the structurization in thin films. Moreover, the combination of the rigid phenyl moiety with long alkyl chains in one compound completely suppresses the aggregation of molecules maintaining the intense fluorescence in thin films. On the basis of used range of experimental and calculation methods the intralayer and interlayer structures were proposed. Intermolecular hydrogen bond formation and π-π staking of the BODIPY cores were found to be the structure forming forces during the films manufacturing, resulting the differences in crystallinity of the materials. While the alkyl-substituents prevent the type of interactions and suppress the association of the dyes and formation of excimers. Compounds under investigation show a manifestation of the intense solvatochromic properties which allow their application as sensors, including naked eye sensorics for solution polarity. Besides, the obtained results broaden prospective of functional materials usage based on BODIPY thin films as components of optoelectronics.

Study of the Nanostructure Effect on Polyalkylthiophene Derivatives Films Using Impedance Spectroscopy

In this paper, devices fabricated with a diode-like structure (electrode/polymer/electrode) from spin-coated and nanostructured (Langmuir-Schaefer) films of polythiophene derivatives were characterized by impedance spectroscopy and studied by theoretical fitting to reach a better understanding of the physical processes in the devices. The materials used for this research were the polyalkylthiophene (P3AT) derivatives poly(3-butylthiophene) (P3BT), poly(3-hexylthiophene) (P3HT), poly(3-octylthiophene) (P3OT) and poly(3-decylthiophene) (P3DT). Electrical measurements were performed from 1 Hz to 1 MHz (100 mV ac) while increasing the dc bias in the range from 0 to 2.5 V. The fittings of the experimental results were performed using equivalent circuits. By plotting the theoretical and experimental spectra on a single graph, it was possible to obtain information related to the film morphology, interfacial effects, resistance, capacitance and conductivity of the polymer, thereby enhancing the understanding of this particular type of device. Among the P3AT films, those grown by the Langmuir-Schaefer technique showed higher electrical conductivity, with the only exception being that of P3BT.

Langmuir-Schaefer film deposition onto honeycomb porous films for retinal tissue engineering.

Age-related macular degeneration (AMD) is a leading cause of central blindness in developed countries, associated with the degeneration of the retinal pigment epithelium (RPE), a specific cell layer at the back of the eye. Transplantation of RPE cells derived from stem cells is considered the best option to treat these patients. In this work, we developed a cell carrier for human embryonic stem cell-derived RPE that resembled the upper layers of the membrane that naturally supports the RPE cells in the retina. The new combination of technologies employed in this study resulted in very promising materials as confirmed by our studies on cell proliferation, morphology and function.

Influence of the Supramolecular Arrangement in the Electrical Conductivity of Poly(thiophene) Thin Films.

Thin films of regioregular polythiophene derivatives have had their optical, structural and morphological properties characterized, but there is still a lack of comparative studies to determine the effect from deposition techniques, especially on the electrical properties. In this study, we produced Langmuir-Schaefer and spin-coated films of regioregular alkyl-substituted polythiophene derivatives (P3AT) to investigate how distinct supramolecular arrangements can affect their properties. The Langmuir-Schaefer films deposited on indium-tin oxide substrates were observed to grow linearly with the number of layers, according to UV-visible absorption spectroscopy. Atomic force microscopy and Brewster angle microscopy were carried out for morphological characterization. From electrical transport measurements, the DC electrical conductivity of Langmuir-Schaefer films of P3AT was higher than the corresponding spin-coated films, which can be related to the dissimilar roughness and molecular-level organization provided by the Langmuir-Schaefer technique.

Solvent driven polymorphism in Langmuir and Langmuir Schaefer film of poly(vinylidene fluoride)

Ultrathin film of poly(vinylidene fluoride), PVDF is formed by Langmuir technique using different solvents (good and swelling) as spreading agents at the air-water interface. Surface manometry on PVDF film shows that the lift-off area of the polymer depends on the nature of the solvent. Surface potential-area per monomer isotherm of the PVDF film shows a negative (positive) potential for good (swelling) solvents. Brewster angle microscope studies show that the textures of the PVDF film are found to be largely homogeneous for the good solvents in contrast to swelling agents. Further, multilayers of PVDF were transferred onto silicon substrates using Langmuir-Schaefer method and characterized using grazing incidence X-ray diffraction, Fourier transform infrared spectroscopy and field emission scanning electron microscopy techniques. Analysis of the signature peaks from FTIR studies yield evidence for the occurrence of a relatively larger fraction of polar β phase of PVDF film formed using good solvents.

Langmuir–Schaefer films of fibronectin as designed biointerfaces for culturing stem cells

Glycoproteins adsorbing on an implant upon contact with body fluids can affect the biological response in vitro and in vivo, depending on the type and conformation of the adsorbed biomacromolecules. However, this process is poorly characterized and so far not controllable. Here, protein monolayers of high molecular cohesion with defined density are transferred onto polymeric substrates by the Langmuir–Schaefer (LS) technique and were compared with solution deposition (SO) method. It is hypothesized that on polydimethylsiloxane (PDMS), a substrate with poor cell adhesion capacity, the fibronectin (FN) layers generated by the LS and SO methods will differ in their organization, subsequently facilitating differential stem cell adhesion behavior. Indeed, atomic force microscopy visualization and immunofluorescence images indicated that organization of the FN layer immobilized on PDMS was uniform and homogeneous. In contrast, FN deposited by SO method was rather heterogeneous with appearance of structures resembling protein aggregates. Human mesenchymal stem cells showed reduced absolute numbers of adherent cells, and the vinculin expression seemed to be higher and more homogenously distributed after seeding on PDMS equipped with FN by LS in comparison with PDMS equipped with FN by SO. These divergent responses could be attributed to differences in the availability of adhesion molecule ligands such as the Arg‐Gly‐Asp (RGD) peptide sequence presented at the interface. The LS method allows to control the protein layer characteristics, including the thickness and the protein orientation or conformation, which can be harnessed to direct stem cell responses to defined outcomes, including migration and differentiation. Copyright © 2016 John Wiley & Sons, Ltd.

The red, purple and blue modifications of polymeric unsymmetrical hydroxyalkadiynyl-N-arylcarbamate derivatives in Langmuir-Schaefer films

Solid topochemical photopolymerization (STP) of Langmuir-Schaefer films of a new class of unsymmetrical diynes, containing N-arylcarbamate groups in the hydrophobic part and hydroxymethylene groups in the hydrophilic part of the molecules was examined. In addition, the monomeric Langmuir monolayer formation was studied by Brewster angle microscopy and the surface morphology of monomer and polymer films on solid substrates were studied by scanning electron microscopy and atomic force microscopy. Three phases of polydiacetylene (PDA) (red, purple and blue) were observed after UV-light polymerization of above-mentioned films of alcohol diacetylene (DA) derivatives. The substitution of MeO group in the aryl ring substituent by hydrogen atom and the variation of the methylene group number in the hydrophobic part from 5 to 6 changed significantly the result of STP: instead of blue phase PDA observed for diynes with MeO group, the red phase PDA was observed for DA with H-atom from the very beginning of diyne film UV irradiation. For two other diynilic N-arylcarbamates of identical chemical structures except of the substituents in the aryl ring of hydrophobic parts of the molecules, no changes in the efficiency of polymerization or the position and shape of absorption bands were observed. This indicated the formation of the purple phase PDA. For these molecules, the number of methylene groups in hydrophobic and hydrophilic parts of the molecules was 9 and 2, respectively.

Binding properties of a streptavidin layer formed on a biotinylated Langmuir–Schaefer film of unfolded protein

A Langmuir monolayer of carbonic anhydrase (CA) unfolded at an air/water interface was transferred onto the hydrophobic surface of a silicon wafer by means of the Langmuir–Schaefer technique. The transferred CA film was biotinylated and was incubated in a streptavidin (SAv) solution to obtain a densely packed SAv layer by biotin–SAv linkage. Biotinylated proteins including ferritin, catalase, alcohol dehydrogenase, and carbonic anhydrase were incubated with the SAv layer and binding of these proteins was examined by atomic force microscopy. High-density binding of the biotinylated proteins was observed, whereas the amount of adsorbed non-biotinylated proteins was low or negligible. The SAv layer on the Langmuir–Schaefer film of unfolded protein could become a basic architecture for protein immobilization studies.