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The partitioning of doxorubicin, a potent anticancer drug, was examined in relation to the composition and structural properties of the biomimetic molecular films. We have systematically studied the passive permeation of doxorubicin across the two-component monolayers of different organization, following the drug interactions with the hydrophilic part of the monolayer and then, with its hydrophobic moiety, separately. We investigated independently these two types of the interactions, likely competing in a native membrane, respectively for the Langmuir monolayers on an aqueous subphase and for Langmuir–Blodgett monolayers on gold, exposed to the drug in an aqueous solution. This gave us a unique possibility to monitor the drug interactions with different regions of biomimicking film. The overall picture emerging from these results suggests that the hydrophobicity of monolayer interior allows for the penetration and accumulation of the drug, while its organization controls the rate and amount of doxorubicin molecules through such films.

Al2O3 films have been deposited at 85 °C by atomic layer deposition onto single 100 nm thick tris-(8-hydroxyquinoline) aluminium (AlQ3) films made onto silicon wafers. It has been found that a thick ALD-deposited Al2O3 layer (> 11 nm) greatly prevents the photo-oxidation of AlQ3 films when exposed to continuous UV irradiation (350 mW/cm2). Thin Al2O3 thicknesses (< 11 nm) on the contrary yield lower barrier performances. Defects in the Al2O3 layer have been easily observed as non-fluorescent AlQ3 singularities, or black spots, under UV light on the system Si/AlQ3/Al2O3 stored into laboratory conditions (22 °C/50% Relative Humidity (RH)) for long time scale (~ 2000 h). Accelerated aging conditions in a climatic chamber (85 °C/85% RH) also allow faster visualization of the same defects (168 h). The black spot density grows upon time and the black spot density occurrence rates have been calculated to be 0.024 h− 1·cm− 2 and 0.243 h− 1·cm− 2 respectively for the two testing conditions. A detailed investigation of these defects did show that they cannot be ascribed to the presence of a detectable particle. In that sense they are presumably the consequence of the existence of nanometre-scaled defects which cannot be detected onto fresh samples. Interestingly, an additional overcoating of ebeam-deposited SiO2 onto the Si/AlQ3/Al2O3 sample helps to decrease drastically the black spot density occurrence rates down to 0.004 h− 1·cm− 2 and 0.04 h− 1·cm− 2 respectively for 22 °C/50% RH and 85 °C/85% RH testing conditions. These observations highlight the moisture sensitivity of low temperature ALD-deposited Al2O3 films and confirm the general idea that a single Al2O3 ALD film performs as an ultra-high barrier but needs to be overprotected from water condensation by an additional moisture-stable layer.

A surface confined redox group contributes to an interfacial charging (quantifiable by redox capacitance) that can be sensitively probed by impedance derived capacitance spectroscopy. In generating mixed molecular films comprising such redox groups, together with specific recognition elements (here antibodies), this charging signal is able to sensitively transduce the recognition and binding of specific analytes. This novel transduction method, exemplified here with C-reactive protein, an important biomarker of cardiac status and general trauma, is equally applicable to any suitably prepared interfacial combination of redox reporter and receptor. The assays are label free, ultrasensitive, highly specific and accompanied by a good linear range.

The formation of metallic layers on ultrathin molecular films via a well-controlled interface is essential for constructing organic nanodevices composed of metal/molecule/metal sandwich junctions. The scanning tunneling microscopy and spectroscopy studies demonstrate that an ultrasharp metal/molecule interface is realizable by depositing size-selected Ag nanoclusters (Agn) from the gas phase on few-layer films of C60 molecules. It is also demonstrated that Agn nanoclusters can be immobilized on monolayer films of oligothiophene molecules via C60 molecules, although they three-dimensionally aggregate on bare oligothiophene films. It is also shown that electrons and holes are injected into the topmost layer of C60 films via the Agn/C60 interface. Moreover, the barrier height for carrier injection at the Agn/C60 interface can be modified depending on the size of Agn nanoclusters and the kinetic energy during the deposition. The present results demonstrate that the controlled immobilization of metallic nanoclusters on molecular films can be used as a fabrication technology for metal/molecule/metal junctions.

Low-energy electron diffraction (LEED) is a widely employed technique for the structural characterization of crystalline surfaces and epitaxial adsorbates. For technical reasons the accessible reciprocal space is limited at a given primary electron energy E. This limitation may be overcome by sweeping E to observe higher diffraction orders decisively enhancing the quantitative examination. Yet, in many cases, such as molecular films with rather large unit cells, the adsorbate reflexes become less pronounced at energies high enough to observe substrate reflexes. One possibility to overcome this problem is an intentional inclination of the sample surface during the measurement at the expense of the quantitative interpretability of then severely distorted diffraction patterns. Here, we introduce a correction method for the axially symmetric distortion in LEED images of tilted samples. We provide experimental confirmation for micro-channel plate LEED and spot-profile analysis LEED instruments using the (7×7) reconstructed surface of a Si(111) single crystal as a reference sample. Finally, we demonstrate that the correction of this distortion considerably improves the quantitative analysis of diffraction patterns of adsorbates since substrate and adsorbate reflexes can be evaluated simultaneously. As an illustrative example we have chosen an epitaxial monolayer of 3,4,9,10-perylenetetracarboxylic dianhydride on Ag(111) that is known to form a commensurate superstructure.

Organic thin film devices are investigated for many diverse applications, including light emitting diodes, organic photovoltaic and organic field effect transistors. Modeling of their properties on the basis of their detailed molecular structure requires generation of representative morphologies, many of which are amorphous. Because time-scales for the formation of the molecular structure are slow, we have developed a linear-scaling single molecule deposition protocol which generates morphologies by simulation of vapor deposition of molecular films. We have applied this protocol to systems comprising argon, buckminsterfullerene, N,N-Di(naphthalene-1-yl)-N,N'-diphenyl-benzidine, mer-tris(8-hydroxy-quinoline)aluminum(III), and phenyl-C61-butyric acid methyl ester, with and without postdeposition relaxation of the individually deposited molecules. The proposed single molecule deposition protocol leads to formation of highly ordered morphologies in argon and buckminsterfullerene systems when postdeposition relaxation is used to locally anneal the configuration in the vicinity of the newly deposited molecule. The other systems formed disordered amorphous morphologies and the postdeposition local relaxation step has only a small effect on the characteristics of the disordered morphology in comparison to the materials forming crystals.

The growth of a molecular water film on the basic plane of a silver iodide monocrystal is studied through computer simulation. Decomposition into domains with spontaneous polarization is observed in the contact layer of the film at the interface with the substrate. The formation of domains is found to be sharply enhanced on a model substrate with the double polarizability of iodine ions; heteropolarization interactions caused by the formation of domain structures increase the film’s coupling with the substrate. It is demonstrated that the vapor pressure needed for molecular film growth is reduced appreciably via heteropolarization interactions.

In this paper, epoxy resin-based monolayers (ER monolayers) were prepared as water evaporation retardants. The interfacial stability performances of molecular films on resisting disruption of temperature and wind were investigated. The dependence of evaporation resistance on temperature was explicit and supported. Energy barrier theory was performed to explain the retardation mechanism of water evaporation of ER monolayers. The disruption of wind on monolayers was researched through simulation of surface waves over the subphase water. The results showed that ER monolayers presented better stability to resist disturbances of temperature shift and surface waves compared to C16OH monolayer. ER monolayers had a good effect on retardation of water evaporation due to their ability to spread spontaneously and form closely packed films over the water surface.

When dipolar gases are condensed at sufficiently low temperature onto a solid surface, they form films that may spontaneously exhibit electric fields in excess of 108V/m. This effect, called the ‘spontelectric effect’, was recently revealed using an instrument designed to measure scattering and capture of low energy electrons by molecular films. In this review it is described how this discovery was made and the properties of materials that display the spontelectric effect, so-called ‘spontelectrics’, are set out. A discussion is included of properties that differentiate spontelectrics from ferroelectrics and other species in which spontaneous polarisation may be found. Spontelectric films may be composed of a number of quite mundane dipolar molecules that involve such diverse species as propane, nitrous oxide or methyl formate. Experimental results are presented for spontelectrics illustrating that the spontelectric field generally decreases monotonically with increased deposition temperature, with the exception of methyl formate that shows an increase beyond a critical range of deposition temperature. Films of spontelectric material show a Curie temperature above which the spontelectric effect disappears. Heterolayers may also be laid down creating potential wells on the nanoscale. A model is put forward based upon competition between dipole alignment and thermal disorder, which is successful in reproducing the variation of the degree of dipole alignment and the spontelectric field with deposition temperature, including the behaviour of methyl formate. This model and associated data lead to the conclusion that the spontelectric effect is new in solid-state physics and that spontelectrics represent a new class of materials.

Ternary component hybrid films of amphiphilic alkylammonium cations, clay nanosheets, and ruthenium(II) complex cations were prepared by the modified Langmuir–Schaefer method. When a solution of the amphiphilic ammonium salt (octadecylammonium chloride, ODAH+Cl−) was spread at an air–clay dispersion interface, the clay nanosheets in the dispersion were adsorbed on the floating molecular film of ODAH+ by the electrostatic interaction. Then the floating film of ODAH+ and the clay was deposited on a glass plate and immersed in an aqueous solution of [RuL3]Cl2 (L = 2,2′-bipyridine (bpy), 1,10-phenanthroline (phen), 5,6-dimethyl-1,10-phenanthroline (dmphen), and 4,7-diphenyl-1,10-phenanthroline (dpp)) to form a ternary component hybrid monolayer. By repeating these procedures, a hybrid multilayer was fabricated. Characterization of the hybrid multilayers was carried out by electronic and IR spectral measurements and X-ray diffraction (XRD) method. Areas per [RuL3]2 + estimated from the analysis of the electronic spectra suggested that the Ru(II) complex cations interacted with each other through hydrophobic interaction. IR and XRD data indicated disordered alkylchains of ODAH+ which would occupy spaces between the [RuL3]2 + cations in the film. The tilt angles of 3-fold axes of [RuL3]2 + were determined to be 32–35° by analyzing electronic spectra measured with p- and s-polarized beams. An orientation model of the [RuL3]2 + cations in the film was proposed, in which substitution groups at 4- or 5-positions of 1,10-phenanthroline ligand were in contact with the clay nanosheet layers. It was likely that the sizes of the ligands and the interaction between the ligands affected the structure of the hybrid film.

Patterned nanoscale molecular films will be a key componentof advanced devices such as novel chemical and biologicalsensors and nanoelectronic systems. For long-establishedsurface modification strategies such as the use of self-assembledmonolayers ofalkanethiolsat noblemetal surfacesandreactionsofsilanesatoxidesurfaces,patterningstrategieshave reached a high level of sophistication.

The adsorption of a model quaternary ammonium surfactant, octyltrimethylammonium triflate, on Au(111) has been studied using capacity and chronoculometry methods. The surfactant adsorbs on the metal surface as a non-dissociated ion pair at moderate potentials but can be desorbed by either positive or negative polarization. Within the adsorption region, two states are observed which correspond to a horizontal monolayer and a higher coverage vertically oriented film. Measurements of capacity transients upon potential steps reveal a slow organization of the molecular film. Although it is possible to equate the transients to known surfactant film aggregate geometries, the results are in disagreement with thermodynamic results. In comparison with other studies, the results indicate that the states of surfactant adsorption depend on surfactant chain length and electrode crystallography. Copyright © 2013 John Wiley & Sons, Ltd.

This article reviews the surface adsorption of p-benzoquinonemonoimine zwitterions from the class of N-alkyldiaminoresorcinones (or 4,6-bis-dialkylaminobenzene-1,3-diones, i.e. C6H2(···NHR)2(···O)2), where R = H, R = C2H5, n-C4H9), on a variety of conducting surfaces. These small molecules with a large electrical dipole exhibit molecular orientation and packing on surfaces depending on the deposition methodology (from solution or from the vapor) as well as the substrate. What is very clear from the investigations of this class of molecules is that inter-molecular interaction is not simply driven by dipolar interactions alone, but frontier orbital symmetry as well. This is illustrated by the reversible adsorption of di-iodobenzene on molecular films of (6Z)-4-(butylamino)-6-(butyliminio)-3-oxocyclohexa-1,4-dien-1-olate C6H2(···NHR)2(···O)2 where R = n-C4H9, where it is clear that absorption is isomer specific.

Some trigonal Schiff base amphiphiles with symmetric aromatic cores and different substituted headgroups were designed and their interfacial assemblies were investigated. When on the metal ions subphases, an in situ coordination can occur for all compounds. The coordinated films could be transferred onto solid substrates and subsequently characterized by morphological characterization with atomic force microscopy measurement. Depending on the trigonal molecular structures and different substituted headgroups, these amphiphiles showed distinct assembly behaviors in the organized molecular films.

A novel aromatic Schiff base ligand has been designed and its interfacial phase behavior as well as the in situ coordination with Cu(II) ion was investigated. A series of measurement methods, such as surface pressure-area isotherms and atomic force microscopy measurement, have been used to characterize the deposited monolayer and multilayer films. It has been found that both the ligand and the corresponding complex formed stable monolayer or multilayer films at the air/water interface, which could be subsequently transferred onto solid substrates to construct Langmuir-Blodgett films. It was interesting to note that there existed a novel phase transition when the ligand was spread on pure water surface. During this phase transition, the two dimensional flat film changed into a three dimensional fiber-like nano-architectures. However, upon coordinating with Cu(II) ions, only flat films were obtained. Such distinct difference was suggested to be mainly due to the change of molecular conformation and/or the hydrophobicity in the process of supramolecular assembly at the air/water interface.

The evolution of the phase state of the water vapor condensate of the silver iodide crystal surface in an applied electric field up to 10 V/nm is studied by computer simulation. The previously found domain structure of the contact layer is stable against the external field and remains up to the complete break of the molecular film. In a strong electric field, the film condensation mode is changed by the formation of a new phase consisting of molecular nanothreads growing in the direction of the electric field lines. The transition to the new state is sharp. The presence of a phase transition is likely analogous to that accompanying the transformation of water microdrops to the superpolarized state under the action of an external electric field at stratospheric temperatures.

In this work, we studied properties of Langmuir and Langmuir-Blodgett molecular films formed by mixture of arachidic acid with nematic liquid crystal mixture having the negative dielectric anisotropy. The Langmuir films were characterised by surface pressure versus mean molecular area isotherms (π–A isotherms) and subsequently were transferred at a particular surface pressure onto hydrophillic and hydrophobic quartz substrates forming monolayer and multilayer Langmuir-Blodgett films. Miscibility of the compounds in the Langmuir films was determined. Absorption spectra of the Langmuir-Blodgett films were recorded in UV-Vis region in order to reveal organisation of the molecules. Morphology of deposited films was visualised using atomic force microscope (AFM) working in tapping mode. Finally, Langmuir-Blodgett films were deposited onto glass plates covered with indium tin oxide (ITO, transparent and conductive electrodes) and were used as aligning layers in laboratory model of Vertical Alignment-type liquid...

A key question in the epitaxial growth of materials is whether vapor-deposited molecules acquire an ordered structure that depends on the structure and chemical composition of the underlying substrate. In this paper we examine this question for metallic and chemically-tailored self-assembled monolayer (SAM) substrates, and show that proper selection of the templating substrate can lead to the deposition of nearly 100 layer thick molecular films that retain the alignment of the initial interface. In particular, we have examined benzene growth on gold, alkanethiol and phenoxy-terminated SAMs using a combination of in situ infrared spectroscopy and molecular beam techniques. When benzene molecules stick to a clean metal surface, the molecules in the first layer lie flat. However, after the deposition of a few layers, growth occurs as three-dimensional crystallites, resulting in randomly aligned polycrystalline domains. We found that there need not be an orientational transformation from the thin to thick structure for vapor-deposited molecules. Here, we vapor deposited benzene on phenoxy-terminated self-assembled monolayers (SAMs), and grew thick films of aligned benzene molecules. The alignment of the first layer of benzene molecules on the SAM was retained for more than 80 layers. In contrast, when methyl-terminated SAMs were used as a substrate, the thick film structure was indistinguishable from those with Au substrates.

Adsorption of imidazole on clean Fe(1 0 0) was addressed by DFT calculations. It is shown that even though the imidazole in protonated form binds stronger to the surface than the neutral form, it is prone to deprotonation (dehydrogenation) resulting in neutral form, which further dehydrogenates due to the breaking of the C2–H bond. Thermodynamically the stablest identified structures thus consist of strongly bound and densely packed C2 dehydrogenated imidazole molecules, which may act as a thin protective film. On the other hand, the polymerization of imidazole molecules upon adsorption has been found improbable.

Gemini amphiphiles have been widely investigated in many aspects due to the unique structure. In this study, two gemini-type Schiff base amphiphiles containing aromatic spacers were synthesized and characterized in Langmuir-Blodgett films. Both compounds formed stable multilayer films and showed distinct phase behaviours on water surface and ion subphase. When the compounds spread on Cu (II) ions subphase, an in-situ coordination occurred for both ligands. While spectral measurements confirmed the coordination with Cu (II) ions and aggregation mode, the morphological investigations showed the distinct nanostructures and molecular rearrangement depended on the molecular spacers and aggregation modes. For both process, the aromatic spacers in gemini amphiphiles have predominant effect in regulating the aggregation modes and spectral changes in organized molecular films.

The electroluminescence of organic films is the central aspect in organic light emitting diodes (OLEDs) and widely used in current display technology. However, its spatial variation on the molecular scale is essentially unexplored. Here, we address this issue by using scanning tunneling microscopy (STM) and present an in-depth study of the electroluminescence from thin C60 films (

International audience; In this work we present a detailed surface science characterization of L-Aspartic acid adsorption on a Cu(110) surface. We replaced the traditional sublimation method to obtain molecular films by dosing aspartic acid directly from an aqueous solution through an Electrospray Ionization (ESI) device. X-ray Photoelectron Spectroscopy (XPS) and Polarization Modulation Reflection Absorption Infra Red Spectroscopy (PM-RAIRS) evidenced different adsorption states ranging from sub-monolayer regime up to multilayers. Molecules-substrate interactions guide the creation of the pattern observed in the sub-monolayer, but molecule-molecule interactions are prevailing from a certain coverage stage, promoting the overlayer growth while leaving exposed areas of bare copper. This is evidenced by Scanning Tunneling Microscopy (STM) results, showing that single aspartic acid molecules self-organize in a 2D chiral network at low coverage and start originating new molecular layers even before a saturated monolayer has been reached.

We present a self-assembled template that consists of tetraphenylmethane derivatives and adopts a periodic lateral arrangement on a Au(111) surface with acetyl groups sticking out of the molecular film. By using the tip of a scanning tunneling microscope, these acetyl groups can be removed in a spatially controlled way without significantly affecting the remaining molecular assembly. The chemically modified molecules can be readily distinguished from the original ones such that information can be engraved in the molecular film. Both the modified nature of an individual molecule and the order of the molecular film are shown to persist at room temperature. The mesh size of this molecular graph paper can be tuned by varying the length of the molecular spacer so that writing and reading information on the nanoscale with variable letter sizes becomes possible.

Nano-devices with embedded molecular films appear as promising nano communications tools. In general, processing in such hybrid nano-device consists of initial energy of both activated electronic and atomic subsystems of an embedded molecular species, followed by intra- and inter-molecular nanoscale signals generation and reception of the transmitted signal at remote site. Actually, electromagnetic radiation can establish wireless nano communication in Visible, Infrared, and Microwave frequency ranges. In this manuscript, we estimate some properties of a microelectronics receiver in such systems, presented by novel dynamic operation pin photodetector, possesses signal integration, and required for receiving and demodulation of an electromagnetic wave. Revealed both theoretical and experimental characteristics of a photodetector have allowed designing dynamic process scenarios, as well as its possible applications inside a nano network.

The decay of electronically excited molecular films of 2-methylnaphthalene (2-MN), 2-methoxynaphthalene (2-MeON), and 2-ethylnaphthalene (2-EN) on a crystal of α-alumina was monitored as a function of temperature with temperature programmed desorption (TPD) experiments. By assuming an exponential decay, the rate constants of the relaxation to the ground state were observed to have two components ( ± 2 0 % ) by laser induced fluorescence (LIF). For the 2-MeON, 2-MN, and 2-EN excimer, the longer components were 35, 25, and 23 × 106 s−1, respectively. Rate constants for the trap fluorescence for 2-MeON, 2-MN, and 2-EN were 100, 44, and 2 3 × 1 0 6 s−1, respectively. In separate experiments, the effect of a molecule that does not fluoresce and has a lower desorption temperature than the fluorophores was studied by deposition of a bilayer. 1-Chlorohexane (1-CH) was chosen as the second layer to the fluorophore and the results gave clues to the complexity of the surface dynamics that occur as the surface is heated. For these bilayer systems, a second excimer formed during the TPD subsequent to the desorption of 1-CH, and their rates are given in parenthesis: for 2-MeON, 2-MN, and 2-EN, the long components were 30 (36), 25 (45), and 23 (42) × 106 s−1, respectively.

Investigations of Langmuir and Langmuir–Blodgett molecular films of hyperbranched polyester with alkyl-terminated branches over a wide temperature range revealed an unusual phase transitions. The measured surface pressure–surface area isotherms clearly show that the hyperbranched polyester formed stable and well-defined monolayers at the air/water interface. At temperatures below 313 K ice floe-like structures of a condensed phase were formed already from very low surface pressures. On the increase of the surface pressure the floes of the condensed phase merged forming a uniform monolayer. Above 313 K a surface liquid phase was formed at the interface. It was shown that the phase transition from the surface liquid phase to the condensed phase occurred on temperature decrease. At lower temperatures the compression process was not reversible. The increase of temperature up to about 323 K made the compression process reversible. The monolayers were transferred from the air/water interface onto silicon and mica substrates using the Langmuir–Blodgett technique at different temperatures. The structure of the polyester monolayer formed at the substrates' surfaces was investigated.

Glycosaminoglycans (GAGs) in the extracellular matrix (ECM) have multiple functions in tissues including providing support, mediating cell division and differentiation, and taking part in important interactions with proteins, e.g. growth factors. Studying GAG related interactions is inherently difficult and requires suitable interaction platforms. We show two strategies to covalently couple the GAG chondroitin sulfate (CS) to supported lipid bilayers (SLBs), either by (a) activating carboxy-functionalized phospholipids in the lipid bilayer, followed by the addition of hydrazide-functionalized CS, or by (b) activating naturally occurring carboxyl groups on CS prior to addition to an amino-functionalized SLB. Bilayer formation and subsequent immobilization was followed in real-time using the Quartz Crystal Microbalance with Dissipation monitoring, a technique that provides unique information when studying highly hydrated molecular films. The two strategies yielded thin CS films (in the nanometer range) with similar viscoelastic properties. Fluidity of the lipid bilayer was retained when CS was coupled. The application of the CS interaction platform was exemplified for type I collagen and the bone inducing growth factor bone morphogenetic protein-2 (BMP-2). The addition of collagen to immoblized CS resulted in soft layers whereas layers formed by addition of BMP-2 were denser, independent on the immobilization strategy used.

Localized and delocalized plasmons in metallic nanoparticles are associated with a strongly confined electromagnetic field, inducing an enhanced interaction with emitters located in the close environment of the metal. When the plasmon/emitter interaction becomes predominant compared to the damping in the system, the system is in strong coupling regime leading to light matter hybridization. This strong coupling has been observed with a large number of materials, in particular disordered materials. These materials are constituted by a collection of independent emitters (molecules, semiconductor quantum dots...). The hybrid light/matter state can be described by considering a homogeneous absorbing system using coupled oscillator model. But if the microscopic structure of the molecular film close to a metallic film is considered, collective effects between the delocalized plasmon and the set of molecules are present. The spatial and dynamic properties of a set of molecules in strong coupling are dramatically modified compared to the same molecules in weak coupling (the usual configuration of emission). The excitations are not localised in a single particle anymore but delocalised on a large number of particles due to the formation of an extended hybridised state on several microns. We will describe some properties of disordered systems strongly coupled to surface plasmons and experimental demonstrations of the collective phenomena associated with the strong coupling. In particular we will present an experimental study of the coherent character of the emission of different emitters with a Young’s interferences setup. The system studied consists of J-aggregated dye (TDBC) in interaction with a surface plasmon on silver. The extension of the coherent state will also be discussed.

The current method for the prediction of molecular contamination build up in systems such as the James Webb Space Telescope and other large astronomical satellites is based on a monotonic linear model of accumulation. Recent long term observations carried out at Northrop Grumman show that the linear monotonic model over predicts thickness of the molecular film. This paper reviews the long term observations of contaminant film thickness accumulation made at Northrop Grumman facilities. The formulation of a semi-empirical method for the prediction of film thickness evolution consistent with both observation and first principles is discussed in detail. The paper concludes with a validation of the predictions of the semi-empirical model. The increased accuracy of the semi-empirical method holds the promise of improved and more effective means of contamination control, thus reducing mission cost and risk.

The phase behavior of a confined liquid at high pressure and shear rate, such as is found in elastohydrodynamic lubrication, can influence the traction characteristics in machine operation. Generic aspects of this behavior are investigated here using Non-equilibrium Molecular Dynamics (NEMD) simulations of confined Lennard-Jones (LJ) films under load with a recently proposed wall-driven shearing method without wall atom tethering [C. Gattinoni et al., Phys. Rev. E 90, 043302 (2014)]. The focus is on thick films in which the nonequilibrium phases formed in the confined region impact on the traction properties. The nonequilibrium phase and tribological diagrams are mapped out in detail as a function of load, wall sliding speed, and atomic scale surface roughness, which is shown can have a significant effect. The transition between these phases is typically not sharp as the external conditions are varied. The magnitude of the friction coefficient depends strongly on the nonequilibrium phase adopted by the confined region of molecules, and in general does not follow the classical friction relations between macroscopic bodies, e.g., the frictional force can decrease with increasing load in the Plug-Slip (PS) region of the phase diagram owing to structural changes induced in the confined film. The friction coefficient can be extremely low (∼0.01) in the PS region as a result of incommensurate alignment between a (100) face-centered cubic wall plane and reconstructed (111) layers of the confined region near the wall. It is possible to exploit hysteresis to retain low friction PS states well into the central localization high wall speed region of the phase diagram. Stick-slip behavior due to periodic in-plane melting of layers in the confined region and subsequent annealing is observed at low wall speeds and moderate external loads. At intermediate wall speeds and pressure values (at least) the friction coefficient decreases with increasing well depth of the LJ potential between the wall atoms, but increases when the attractive part of the potential between wall atoms and confined molecules is made larger.

Based on microscopic (exciton) theory of optical properties of symmetrically perturbed ultrathin molecular films, the absorption, reflection and transparency indices were formulated and presented in the function of frequencies of external electromagnetic field in near infrared (IR) region. It has been showed that all optical properties depend on the position of the crystal plane with regard on boundary planes of the film. We have determined and analyzed optical properties relations for the whole film structure based on the consideration for multiple reflection, absorption and transparency in those multilayered structure. The three-layered dielectric nanofilms with different boundary conditions on surfaces were analyzed and some discrete resonant absorption lines were obtained. Their number, position and distribution depend on the boundary parameter values, i.e. on the type and the technological process of their preparation/fabrication. Practically monochromatic absorption may occur. Unlike the corresponding bulk-samples which are total absorbers throughout the near IR region, in ultrathin films will appear selective and discrete reflection and transparency too. These results could give a great contribution in optical engineering of nanostructures, especially in technology of designing of new electronic and photonic equipment, and for nanoparticles construction for drug carrier/delivery in nano-medicine.

It has recently been demonstrated that nanoscale molecular films can spontaneously assemble to self-generate intrinsic electric fields that can exceed 108 V/m. These electric fields originate from polarization charges in the material that arise because the films self-assemble to orient molecular dipole moments. This has been called the spontelectric effect. Such growth of spontaneously polarized layers of molecular solids has implications for our understanding of how intermolecular interactions dictate the structure of molecular materials used in a range of applications, for example, molecular semiconductors, sensors, and catalysts. Here we present the first in situ structural characterization of a representative spontelectric solid, nitrous oxide. Infrared spectroscopy, temperature-programmed desorption, and neutron reflectivity measurements demonstrate that polarized films of nitrous oxide undergo a structural phase transformation upon heating above 48 K. A mean-field model can be used to describe quantitatively the magnitude of the spontaneously generated field as a function of film-growth temperature, and this model also recreates the phase change. This reinforces the spontelectric model as a means of describing long-range dipole-dipole interactions and points to a new type of ordering in molecular thin films.

In this chapter, a study on two kinds of examples of functional nanofibers has been introduced. In the first section, the formation of nanofiber morphology at a mesoscopic scale and molecular level stacking of a tetrathiafulvalene (TTF) derivative with a chiral group were investigated by the one-dimensional growth method in interfacial molecu‐ lar films. Monomolecular films of a TTF derivative with a chiral borneol group display a two-dimensional phase transition at the air/water interface. The formation of nanonet‐ work domains is attributed to the organized aggregation of the TTF derivatives, which is a result of strong intermolecular interactions. In the second section, the formation of nanofiber morphology at a mesoscopic scale and molecular level packing of an amphi‐ philic diamide derivative with two hydrocarbons were investigated by the in interfacial molecular films. It has found that the growth of this nanofiber morphology is encour‐ aged by the application of the epitaxial growth in the spin-cast film with 1 wt% layered silicate having long hydrocarbons. As mention above, it is found that mesoscopic morphological formation of super-hierarchical structure of the nanofibers having a crystalline arrangement at A level can be induced conductivity and the thixotropy at macroscopic level.

We report the preparation of [2]rotaxanes containing an electrochemically and optically active osmium(II) bipyridyl macrocyclic component mechanically bonded with cationic pyridinium axles. Such interlocked host systems are demonstrated to recognise and sense anionic guest species as shown by 1HNMR, luminescence and electrochemical studies. The rotaxanes can be surface assembled on to gold electrodes through anion templation under click copper(I)-catalysed Huisgen cycloaddition conditions to form rotaxane molecular films, which, after template removal, respond electrochemically and selectively to chloride. Copyright © 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim.

The Fermi level or electrochemical signature of a molecular film containing accessible orbital states is ultimately governed by two measurable series energetic components, an energy loss term related to the charging of appropriately addressable molecular orbitals (resonant or charge transfer resistance), and an energy storage or electrochemical capacitance component. The latter conservative term is further divisible into two series contributions, one being a classic electrostatic term and the other arising from the involvement and charging of quantized molecular orbital states. These can be tuned in and out of resonance with underlying electrode states with an efficiency that governs electron transfer kinetics and an energetic spread dependent on solution dielectric. These features are experimentally resolved by an impedance derived capacitance analysis, a methodology which ultimately enables a convenient spectroscopic mapping of electron transfer efficacy, and of density of states within molecular films.

The spreading characteristics of a fluid on an attractive solid substrate are studied using standard vertical but especially horizontal Solid On Solid models. In case of the horizontal Solid On Solid model the wetting dynamics is investigated both with the Langevin theory and Monte Carlo simulations. In the partially wet case relaxation to stable wetting angle is observed, whereas in the completely wet system a precursor film is found to behave linearly in time and the layers next to the precursor as (t log t)1/2 in agreement with the theory. The layers above the precursor film of molecular thickness seem to show diffusive profiles as found previously in the continuum theory.

The recruitment of DO3A-derived lanthanide complexes by ligation to isophthalic acid and catechol-modified gold surfaces, and their resulting sensitization, is reported herein. Predictably pH-dependent surface recruitment is associated with the expected fingerprint europium and terbium emission characteristics. The intensity of the lanthanide luminescence scales exponentially with spacer length, indicating a strong quenching interaction between the lanthanide and the gold surface. The switchable catechol oxidation state provides a means of electrochemically triggering the release of prior ligated complexes.

International audience; The growth of C60 films on the pseudo-tenfold (100) surface of the orthorhombic Al13Co4 qua-sicrystalline approximant was studied experimentally by scanning tunneling microscopy, low-energy electron diffraction and photoemission spectroscopy. The (100) surface terminates at bulk-planes presenting local atomic configurations with five-fold symmetry-similar to quasicrystalline surfaces. While the films deposited at room temperature were found disordered, high-temperature growth (up to 693 K) led to quasi-ordered molecular films templated on the substrate rectangular unit mesh. The most probable adsorption sites and geometries were investigated by density functional theory (DFT) calculations. A large range of adsorption energies was determined, influenced by both symmetry and size matching at the molecule-substrate interface. The quasi-ordered structure of the film can be explained by C60 adsorption at the strongest adsorption sites which are too far apart compared to the distance minimizing the intermolecular interactions, resulting in some disorder in the film structure at a local scale. Valence band photoemission indicates a broadening of the molecular orbitals resulting from hybridization between the substrate and overlayer electronic states. Dosing the film at temperature above 693 K led to molecular damage and formation of carbide thin films possessing no azimuthal order with respect to the substrate.

Thin film epitaxy typically invokes a superposition of a pair of rigid two-dimensional lattices with a well-defined orientation governed by some form of commensurism. A report by Meissner et al. in this issue of ACS Nano demonstrates that the organization of organic molecules on substrates may not be that simple, as static distortion waves involving miniscule shifts of atomic positions from substrate lattice points can lead to orientations of a molecular film that cannot be described by often used models. Herein, we provide some highlights of epitaxy, with a focus on configurations that reflect the delicate balance between intermolecular interactions within a molecular film and molecule–substrate interactions. Although geometric models for explaining and predicting epitaxial configurations can be used to guide synthesis of materials, their use must recognize energetic factors and the possibility of more complex, and possibly less predictable, interface structures.

Organic nanoscale science and technology relies on the control of phenomena occurring at the molecular level. This is of particular importance for the self-assembly of molecular monolayers (SAM) that can be used in various applications ranging from organic electronics to bioelectronic applications. However, the understanding of the elementary nanoscopic processes in molecular film growth is still in its infancy. Here, we developed a novel in situ and extremely sensitive detection method for the analysis of the electronic properties of molecular layer during molecular layer deposition. This low-frequency sensor (1 kHz) is employed to analyze the standard vapor deposition process of SAMs of molecules and, subsequently, it is used to optimize the growth process itself. By combining this method with an ex situ determination of the effective thickness of the resulting layers via ellipsometry, we observe a large difference of the permittivity (1 kHz) of the examined aminosilanes in the liquid state (εliquid = 5.5-8.8) and in SAMs (εSAM = 22-52, electric field in the plane of the layer). We ascribe this difference to either the different orientation and order of the molecules, the different density of molecules, or a combination of both effects. Our novel in situ analyses not only allows monitoring and optimizing the deposition of organic layers but also demonstrates the high potential of organic SAMs as organic high-k layers in electronic devices.

Optical properties of composite structures comprised of the island films of silver nanoparticles with a thin molecular layer of a dye rhodamine 6G were obtained and studied in this paper. In the near field of plasmonic nanoparticles enhancement and shifting of the maximums of the absorption and fluorescence spectra were observed. In the absorption and fluorescence spectra of thin molecular films with nanoparticles the new red-shifted band in comparison with spectra of thin films without nanoparticles was found. This band was associated with the formation of aggregates. Thus, the silver nanoparticles can contribute to fluorescence enhancement and formation of the aggregates in the rhodamine thin films.

Nanomaterial interfaces and concomitant thermal resistances are generally considered as atomic-scale planes that scatter the fundamental energy carriers. Given that the nanoscale structural and chemical properties of solid interfaces can strongly influence this thermal boundary conductance, the ballistic and diffusive nature of phonon transport along with the corresponding phonon wavelengths can affect how energy is scattered and transmitted across an interfacial region between two materials. In hybrid composites composed of atomic layer building blocks of inorganic and organic constituents, the varying interaction between the phononic spectrum in the inorganic crystals and vibronic modes in the molecular films can provide a new avenue to manipulate the energy exchange between the fundamental vibrational energy carriers across interfaces. Here, we systematically study the heat transfer mechanisms in hybrid superlattices of atomic- and molecular-layer-grown zinc oxide and hydroquinone with varying thicknesses of the inorganic and organic layers in the superlattices. We demonstrate ballistic energy transfer of phonons in the zinc oxide that is limited by scattering at the zinc oxide/hydroquinone interface for superlattices with a single monolayer of hydroquinone separating the thicker inorganic layers. The concomitant thermal boundary conductance across the zinc oxide interfacial region approaches the maximal thermal boundary conductance of a zinc oxide phonon flux, indicative of the contribution of long wavelength vibrations across the aromatic molecular monolayers in transmitting energy across the interface. This transmission of energy across the molecular interface decreases considerably as the thickness of the organic layers are increased.

International audience; Driven by the huge potential of engineering the molecular band offset with highly dipolar molecules for improving charge injection into organic electrics, the anchoring of various N-alkyl substituted quinonoid zwitterions of formula image file: c5nj03251b-t1.tif (R = iPr, Cy, CH2CH(Et)CH2CH2CH2CH3,…) on gold surfaces is studied. The N–Au interactions result in an orthogonal arrangement of the zwitterions cores with respect to the surface, and stabilize adsorbed compact rows of molecules. IR spectroscopy is used as a straightforward diagnostic tool to validate the presence of ultra-thin molecular films. When combined with computational studies, IR measurements indicate that the presence of a CH2 group in α position to the nitrogen atom is important for a successful anchoring through N–Au interactions. The presence of such a flexible CH2 spacer, or of aryl groups, enables π-interactions with the surface, making possible the anchoring of enantiopure or sterically-hindered zwitterions. X-ray diffraction analyses indicate that the intermolecular spacing within a row of molecules can be modulated by the nature of the alkyl substituent R. This modulation is directly relevant to the electronic properties of the corresponding molecular films since these zwitterions are expected to form rows on gold surfaces similar to those observed in the bulk crystalline state.

Block copolymer nanolithography has attracted enormous interest in chip technologies, such as integrated silicon chips and biochips, due to its large-scale and mass production of uniform patterns. We further modified this technology to grow embossed nanodots, nanorods and nanofingerprints of polymer brushes on silicon from their corresponding wet-etched nanostructures covered with pendent SiHx (X = 1–3) species. Atomic force microscopy (AFM) was used to image the topomorphologies and multiple transmission-reflection infrared spectroscopy (MTR-IR) was used to monitor the surface molecular films in each step for the sequential stepwise reactions. In addition, two layers of polymethacrylic acid (PMAA) brush nanodots were observed, which were attributed to the circumferential convergence growth and the diffusion-limited growth of the polymer brushes. The pH response of PMAA nanodots in the same region was investigated by AFM from pH 3.0 to 9.0.

Hard X-ray photoelectron spectroscopy (HAXPES) has been used to study the effects of adding Li-TFSI to hole conducting molecular thin films of 2,2′,7,7′-tetrakis(N,N′-di-p-methoxyphenylamine)-9,9′-spirobifluorene (spiro-OMeTAD). The work shows that a procedure of mixing a Li-TFSI solution into a spiro-OMeTAD solution, and subsequent spin-coating this mixture into a solid thin film causes the Fermi level of the molecular film to move closer to the HOMO level. Hence, adding the Li-TFSI gives similar effects to spiro-OMeTAD as a p-dopant. Specific effects from doping on the valence levels were also characterized. Absorbance measurements also showed that the spiro-OMeTAD film was partially oxidized when Li-TFSI was added before spin-coating. By varying the photon energy in the photoelectron spectroscopy measurements, the probe depth varies between being surface sensitive (

In order to investigate the supramolecular assembly and coordination interaction of special amphiphile, a trigonal Schiff base compound with long alkyl chains was designed and synthesized, and its supramolecular assembly and interaction properties were investigated by spectral and morphological measurements. It was found that the Schiff base compound can be spread on water surface to form stable monolayer. When on the Zn(II) ions subphase, an in situ coordination can occur for all ligands. As a result, a 1:2 complex was formed for the trigonal chain Schiff base with Zn(II) ions through the coordination interaction. Due to the directionality and strong matching of coordination, two Zn(II) ions can be encapsulated into intramolecular space of the trigonal Schiff base compound.

In order to investigate the chiral interfacial assembly of special amphiphile, a trigonal Schiff base compound with long alkyl chains was designed and synthesized, and its supramolecular assembly and interaction properties were investigated by spectral and morphological measurements. Condensed monolayers were obtained on pure water surface, in which flat and uniform domains were obtained for the monolayers. When an anionic tetrakis(4-sulfonatonphenyl)porphine (TPPS) was added into an acidic subphase, an in situ complex formation between the trigonal amphiphile and TPPS occurred. The complex monolayers were transferred onto solid substrate and TPPS existed as J-aggregate and J-aggregate in the complex films. Due to the multisited positive charges in the spacer on acidic subphase, the complex films of trigonal amphiphile with TPPS appeared as short nanorod structures and formed two-dimensional (2D) conglomerate chiral domains.

Small molecules with different film-forming properties and electron traps were synthesized and characterized in the meantime. An electrical memory device with the indium-tin-oxide (ITO)/Small-Molecule/Al sandwich structure was fabricated and its electrical performance was investigated. WORM storage devices with different threshold voltages were obtained, some of which present “ternary” property. The relationship between turn-on voltage and the energy barrier between active materials and electrodes was revealed by the cyclic voltammetry measurement. The molecular film-forming properties and electron traps are responsible for device performances collectively, which could be elucidated unambiguously from UV–vis absorption spectra and X-ray diffraction patterns.