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Small amounts of nonpolar additives can have a tremendous impact on viscosity and viscoelasticity of giant micelles and completely change macroscopic properties. The effect can be best understood with the establishment of complete salt curves by screening surfactant viscosity as a function of electrolyte concentration. From previous studies in micellar systems of sodium laureth sulfate (SLES) with fragrance molecules, two independent mechanisms could be identified, co-solvent type interactions leading to a decrease of the maximum viscosity, and co-surfactant type interactions that cause the salt curve shift to the left. Our studies here reveal two new mechanisms with different effects on the salt curve. In particular, with long-chain hydrocarbons from n-octane to n-tetradecane a right shift was observed, whereas with short-chain or cyclic hydrocarbons such as n-hexane or cyclohexane the maximum viscosity increases. The two effects are interpreted via an extension of a recently developed thermodynamic model where changes in viscosity can be rationalized by a rebalance of the relative concentration of the three co-existing microphases: endcaps, cylinders and branching points. The right shift is linked to a continuous transformation of giant micelles into microemulsions containing an internal fluid. On the other hand, viscosity at maximum scales with the generalized bending constant of the molecular film forming the three microphases of the surfactant system. The total of four proposed mechanisms of solute-surfactant interactions that can impact amplitude and position of salt curves are independent and of different origin, but they are all intimately linked to the location of the additives within the surfactant film: headgroup, micellar interface, surfactant tail region or micellar core. Further investigation will be necessary to understand the molecular driving forces that position nonpolar additives within micellar aggregates, which would be the key for successful prediction of their impact on macroscopic viscosity.

The azo chalcone derivative 3-(4-(dimethylamino)phenyl)diazenyl)phenyl)-1- (2-nitrophenyl)prop-2-en-1-one (AZOC-2N) was designed and synthesized. The active layer was prepared by solution spin coating and vacuum evaporation methods, respectively. The accumulation of molecular film was studied by AFM and crystalline structure. It was found that the device had a non-volatile binary write once read many (WORM) memory performance and device in which form by vacuum evaporation with a higher threshold voltage -2.1 V. Finally, the electrical memory performance of the device is analysed by theoretical calculation simulation.

The self-assembly is the primary mechanism responsible for organization of the components into ordered and/or functional structures found in nature. The liquid crystals (LCs) and cellulose nanocrystals (CNCs) display strong intermolecular interactions, forming different ordered structures. Using this property, a new nanocomposite based on LC/CNC mixtures have been designed and prepared as molecular films. The Langmuir technique was used to prepare the investigated materials and study their properties. We have used three different LCs – 5CB, 5FCB, and 5PCH, combined with CNC at the air-water interphase. The study aimed to check if obtained nanocomposites benefit from the advantages of both constituents and results in new quality. Such natural derived systems could be used to manufacture materials with specific properties for task-specific applications. This paper focuses on the characterization of the surface and its features (morphology, topography, roughness) and reconstruction of the obtained surfaces in the 3D image. Studied systems have shown different surface characteristics related to the intermolecular interactions between the liquid crystal and cellulose nanocrystals. The computational methods implemented in Gwyddion software has been used to characterize the obtained surfaces. The Brewster Angle Microscopy (BAM) has been used for imaging of the molecular ordering in the composed LC/CNC Langmuir film.

We provide a brief overview of recent measurements and predictions of thermoelectric properties of single-molecules and porous nanoribbons and discuss some principles underpinning strategies for enhancing their thermoelectric performance. The latter include (a) taking advantage of steep slopes in the electron transmission coefficient T(E)T(E), (b) creating structures with delta-function-like transmission coefficients and (c) utilising step-like features in T(E)T(E). To achieve high performance, we suggest that the latter may be the most fruitful, since it is less susceptible to inhomogeneous broadening. For the purpose of extrapolating thermoelectric properties of single or few molecules to monolayer molecular films, we also discuss the relevance of the conductance-weighted average Seebeck coefficient.

Transition metal dichalcogenides (TMDC) are important representatives in the emerging field of two-dimensional materials. At present their combination with molecular films is discussed as it enables the realization of van der Waals bound organic/inorganic hybrids which are of interest in future device architectures. Here, we discuss the potential use of molybdenum disulfide (MoS2) as supporting substrate for the growth of well-defined, crystalline organic adlayers. By this means, hybrid systems between the TMDC surface and organic compounds can be prepared, allowing for the profound investigation of mutual optical and electronic coupling mechanisms. As model system, we choose pentacene and perfluoropentacene as prototypical organic semiconductors and analyze their film formation on MoS2(001) surfaces. In both cases, we observe smooth, crystalline film growth in lying molecular configuration, hence enabling the preparation of well-defined hybrid systems. By contrast, on defective MoS2 surfaces both materials adopt an upright molecular orientation and exhibit distinctly different film morphologies. This emphasizes the importance of highly ordered TMDC surfaces with low defect density for the fabrication of well-defined hybrid systems.

The effect of an external electric field on the C–O stretch frequency, ν(C–O), of carbon monoxide was studied for CO in different environments of condensed molecular films: (I) chemisorbed CO on Pt(111) covered with amorphous solid water (ASW), (II) CO trapped in an ASW matrix, (III) chemisorbed CO on Pt(111) covered with solid Ar, and (IV) CO trapped in a solid Ar matrix. Changes in ν(C–O) of these samples under an electric field were measured to investigate the Stark frequency shift and the effect of metal–adsorbate charge transfer on the frequency change. The electric field was applied up to 4.3 × 108 V·m–1 using the ice film capacitor method. Reflection absorption infrared spectroscopy was used to monitor the spectral changes of the ν(C–O) band. The Stark shift was measured from the ν(C–O) change of isolated CO in the ASW matrix under the field. The effect of metal–adsorbate charge transfer was estimated for chemisorbed CO by measuring the ν(C–O) shift under the field and subtracting the electrostatic...

The adsorption of manganese-phthalocyanine molecules on Au(110) was investigated using a low-temperature scanning tunneling microscope. A rich variety of commensurate superstructures was observed upon increasing the molecule coverage from submonolayers to ultrathin films. All structures were associated with reconstructions of the Au(110) substrate. Molecules adsorbed in the second molecular layer exhibited negative differential conductance occurring symmetrically around zero bias voltage. A double-barrier tunneling model rationalized this observation in terms of a peaked molecular resonance at the Fermi energy together with a voltage drop across the molecular film.

Sequential assembly of layers containing redox-active dinuclear Ru complexes that differ in their redox potential on ITO substrates afforded a series of layered structures with different potential gradients. The Ru complexes Ru-NP and Ru-CP contain tetrapodal phosphonate anchors and bridging 2,3,5,6-tetra(2-pyridyl)pyrazine or 1,2,4,5-tetra(2-pyridyl)benzene ligands, respectively. Oxidation potentials of E 1/2 = +0.83 and +1.04 V vs. Fc + /Fc ( Ru-NP ) and E 1/2 = −0.37 and 0.09 V ( Ru-CP ) were observed for the Ru(II)-Ru(II)/Ru(II)-Ru(III) and Ru(II)-Ru(III)/Ru(III)-Ru(III) couples. As the Ru-NP and Ru-CP units contain several accessible redox-active electronic states, electron transfer (ET) blockage and mediation occurred at the Ru-NP / Ru-CP heterojunction on account of the large potential gradient. An examination of the electrochemical behavior of the multilayer diblock ITO||( Ru-CP ) n |( Ru-NP ) n ( n = 1–5) heterofilms revealed that in ITO||( Ru-CP ) 4 |( Ru-NP ) 4 , the Ru(III)-Ru(III)/Ru(III)-Ru(IV) couple is involved in the electron mediation pathway on the Ru-NP / Ru-CP heterojunction. In the case of the multilayer triblock ITO||( Ru-NP ) n |( Ru-CP ) n |( Ru-NP ) n ( n = 4) heterofilms, two catalytic peaks were observed, indicating that the inner and outer Ru-NP / Ru-CP junctions display two different catalytic ET processes. In the alternating Ru-NP / Ru-CP multilayer heterofilms, the ET mediation processes are governed by the sequence order of the Ru-NP / Ru-CP heterojunction attached to the ITO electrode. In multilayer homo- and heterofilms, the dependence of the ET distance on the layer number is discussed on the basis of potential-step chronoamperometry (PSCA) results. In the multilayer Ru-NP and Ru-CP homofilms, relatively low β values were observed, while in the multilayer heterofilms, the ET rate of the catalytic wave was not affected by the number of layers, as the energy gap between the Ru-NP / Ru-CP units is the rate-determining factor. Therefore, the molecular sequence in such multilayer heterofilms, composed of layers containing Ru-NP or Ru-CP complexes, plays an important role.

Oligomeric o-phenylenes are an emerging class of helical molecules that exhibit complex conformational behaviour, which is determined by their terminal groups and the solvent environment. Using scanning tunnelling microscopy (STM), we investigated the conformational behaviour of octameric o-phenylenes (OP8s) featuring Br or NO2 terminal groups (OP8Br and OP8NO2). These o-phenylene oligomers are known to adopt a well-defined helical conformation in the solid state, but undergo a rapid helical inversion in solution at ambient temperature. We show that STM microscopy allows the direct observation of perfectly and partially folded helical conformers of OP8Br and OP8NO2, both of which are simultaneously present in their respective molecular films on Au(111). Possible electronic interactions between the Au(111) surface and the exposed π-system of the OP8 derivatives might result in a thermodynamic bias able to stabilize the metastable, partially folded conformation. Recent studies have revealed that the helical inversion rate of OP8NO2 in solution decreases substantially upon oxidation to the corresponding radical cation (OP8NO2˙+). The OP8NO2 and OP8NO2˙+ film morphologies on Au(111) observed by STM differed substantially with respect to each other, most likely reflecting differences arising from the conformational states of OP8NO2 and OP8NO2˙+ at the molecular level, as well as improved charge-transport properties of the oxidized state.

2D organic materials with in-plane van der Waals forces among molecules have unique characteristics that ensure a brilliant future for multifunctional applications. Soluble organic semiconductors can be used to achieve low-cost and high-throughput manufacturing of electronic devices. However, achieving solution-processed 2D single-crystalline semiconductors with uniform morphology remains a substantial challenge. Here, the fabrication of 2D molecular single-crystal semiconductors with precise layer definition by using a floating-coffee-ring-driven assembly is presented. In particular, bilayer molecular films exhibit single-crystalline features with atomic smoothness and high film uniformity over a large area; field-effect transistors yield average and maximum carrier mobilities of 4.8 and 13.0 cm2 V−1 s−1, respectively. This work demonstrates the strong potential of 2D molecular crystals for low-cost, large-area, and high-performance electronics.

With its potential for ultrasensitive, label-free detection of molecular interactions, sensing methods based on the surface plasmon resonance (SPR) effect fully meet the requirements for modern analytical techniques. Already established by using propagating SPR in thin gold layers, the last years witnessed the emergence of another related technique utilizing extremely miniaturized noble metal sensor structures, based on a localized SPR.This paper provides a critical comparison of these kinds of SPR sensing, reviews the foundation of both general approaches, presents experimental data on exactly the same molecular model system using both techniques, as well as theoretical considerations in order to allow reasonable comparison. It highlights the specific features and effects, in order to provide guidance in choosing the right technique for given bioanalytical tasks.The study demonstrated the capabilities of LSPR for sensing of molecular layers even in the lower nanometer dimension. For the detection of small (bio)molecules, smaller particle diameters are favored regarding highest sensitivity. It also presents an approach to obtain refractive index and the thickness of a molecular film by analyzing the signal response of plasmonic sensors with metal nanoparticles. Moreover, an additional method for the improvement of the parameters' determination is introduced. Keywords: Plasmon, Sensing, Nanoparticles, Metallic layers, Spectroscopy, thin-layer adsorption

We explored the interaction of a molecular beam of dimethyl methylphosphonate with a multilayer graphene surface to better understand the fate of chemical warfare agents in the environment. The experiments were done at surface temperatures between 120 and 900 K and translational energies between 200 and 1500 meV. At the lowest temperatures, the dimethyl methylphosphonate is adsorbed, with the molecules next to the carbon surface held slightly more strongly than the bulk molecular film that grows with continued dosing. We measured the desorption energy for submonolayer coverage using modulated beam techniques and found a value of 290 meV (28 kJ/mol). At higher surface temperatures, where the residence times are very short, we measured the scattering of the dimethyl methylphosphonate as a function of angle and translational kinetic energy. For a surface temperature of 250 K, with translational kinetic energies between 200 and 1500 meV, much of the incident flux has nearly been accommodated by the surface temperature and has no memory of the incident momentum. The internal energy also seems to be at least partially accommodated. As the surface temperature increases, the scattering transitions to direct-inelastic reflection, where much of the incident translational energy is retained, and the intensity of the scattering peaks superspecularly toward glancing final angles. These results demonstrate the efficacy of using kinetic energy controlled molecular beams to probe the interactions of complex organic molecules with well-defined surfaces, extending our fundamental understanding of how the dynamics for such systems crossover from trapping-desorption to direct inelastic scattering. Moreover, these results indicate that simulations that model the dispersal of chemical warfare agents using common interfaces in the environment need to account for multiple bounce trajectories and survival of the impinging molecules.

A dual-layer film composed of alkylsilane with amino groups and semi-spherical molecules was constructed on silicon substrate by a two-step strategy. 3-[2-(2-aminoethylamino)ethylamino]propyl-trimethoxysilane (TA) was self-assembled on silicon surface to form amino-terminated underlayer, followed by deriving with hexachlorotribenzotriquinacene (HCTQ) through surface coupling reaction to form the second layer. The formation and structure of the as-prepared films were analyzed, and the nano- and micro-tribological properties were estimated, respectively. The results showed that the dual-layer film possesses excellent friction-reducing and anti-wear abilities, which is attributed to the combination of enhanced stability by hydrogen bonding and the high stiffness of rigid outer layer. In other words, the cross-linked underlayer with internal hydrogen bonds enhances the stability of the film against rubbing the counterpart ball, and the rigid backbone in HCTQ molecules improves the load-carrying capacity of the dual-layer film. High wear stability along with superior load-carrying capacity made these molecular films very promising as a new generation of molecular lubricants for MEMS/NEMS.

Well-ordered molecular films play an important role in nanotechnology, from device fabrication to surface patterning. Self-assembled monolayers (SAMs) of 6-mercaptopurine (6MP) on the Au(100)-(1 × 1) and Au(111)-(1 × 1) have been used to understand the interplay of molecule-substrate interactions for heterocyclic thiols capable of binding to the surface by two anchors, which spontaneously form a highly disordered film on Au(111). Our results reveal that for the same surface coverage the simple change of the substrate from Au(111)-(1 × 1) to Au(100)-(1 × 1) eliminates molecular disorder and yields well-ordered SAMs. We discuss these findings in terms of differences in the surface mobility of 6MP species on these surfaces, the energetics of the adsorption sites, and the number of degrees of freedom of these substrates for a molecule with reduced surface mobility resulting from its two surface anchors. These results reveal the presence of subtle molecule-substrate interactions involving the heteroatom that drastically alter SAM properties and therefore strongly impact on our ability to control physical properties and to build devices at the nanoscale. Fil: Lobo Maza, Flavia Emilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina Fil: Grumelli, Doris Elda. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina Fil: Carro, Pilar. Universidad de La Laguna; España Fil: Vericat, Carolina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina Fil: Kern, Klaus. Max Planck Institut für Festkörperforschung; Alemania Fil: Salvarezza, Roberto Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina

Self assembled monolayers (SAM) formed by fluoro-phosphonic and undecenyl-phosphonic acids on carbon steel surfaces as anticorrosive nanocoatings were investigated. The anticorrosive efficacy of these SAM layers was followed by atomic force microscopy, when the change in the surface morphology caused by layer deposition and corrosion processes was monitored. The corrosion process was determined by electrochemical potentiodynamic polarization and cyclic voltammetry. Results showed that both chemicals produced good protection against corrosion as anodic inhibitors specially with increasing the time of layer formation which results in a more compact molecular film. According to the AFM images, the fluoro-phosphonic acid self-assembled molecular layer can control the general as well as the pitting corrosion, but the SAM layers of the undecenyl-phosphonic acid cannot inhibit the pitting corrosion. The AFM measurements confirmed the electrochemical results.

Semiconductor molecular films based on a gallium phthalocyanine chloride (GaPcCl) and a bidentate amine were prepared by using vacuum thermal evaporation and electrochemical techniques in order to investigate the preferred conduction paths within the films. Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) were employed to characterize the morphology of the films. The conductivity measurements were performed with two different methods in order to investigate preferential conduction directions. The film transverse conductivity was obtained by using scanning tunneling spectroscopy (STS) and the in-plane film conductivity was measured with a four-point probe system. From spectroscopy measurements, the tunneling conductance (dI/dV) was also obtained. From these results, it was found that the conductive nature of the films was strongly influenced by the deposition technique which in turn defined the morphological characteristics of the film. The evaporated method showed better conductivity response and provided semiconductor characteristics in the film transverse direction with an in-plane ohmic response. Finally, contact angle measurements were performed and showed hydrophobic characteristics in all cases.

Room temperature ferromagnetism was observed in rare earth dysprosium (Dy)-doped tris(8-hydroxyquinoline) aluminum (Alq3) organic small molecular films. The Dy-doped Alq3 films were prepared by co-evaporating pure Alq3 and Dy powders on Si substrates in a vacuum. The maximum room temperature coercive field and the saturation magnetization are about 70 Oe and 9.5 × 10−6 emu, respectively. The structures were studied by the atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR) and synchrotron radiation X-ray absorption fine structure (XAFS). The magnetic properties were investigated by the MicroMag Alternating Gradient Magnetometer (AGM), Quantum Design superconducting quantum interference device (SQUID) and first-principles calculations. The room temperature ferromagnetism is ascribed to the magnetic moments induced by the Dy atom and the large energy difference between ferromagnetic and antiferromagnetic coupling.

Optical differential reflectance spectroscopy in combination with low-energy electron diffraction and scanning tunneling microscopy is used to investigate (ultra-)thin rubrene films grown on epitaxial graphene. The optical absorption behavior is compared to thin films on graphite(0001), muscovite mica(0001), and amorphous glass. All the optical spectra can be explained by the presence of two different spectral components, namely a high-energy and a low-energy component. We assign these two optical species to two different conformations of the rubrene molecule.

The “topological polymer chemistry” of amphiphilic linear and cyclic block copolymers at an air/water interface was investigated. A cyclic copolymer and two linear copolymers (AB-type diblock and ABA-type triblock copolymers) synthesized from the same monomers were used in this study. Relatively stable monolayers of these three copolymers were observed to form at an air/water interface. Similar condensed-phase temperature-dependent behaviors were observed in surface pressure–area isotherms for these three monolayers. Molecular orientations at the air/water interface for the two linear block copolymers were similar to that of the cyclic block copolymer. Atomic force microscopic observations of transferred films for the three polymer types revealed the formation of monolayers with very similar morphologies at the mesoscopic scale at room temperature and constant compression speed. ABA-type triblock linear copolymers adopted a fiber-like surface morphology via two-dimensional crystallization at low compression speeds. In contrast, the cyclic block copolymer formed a shapeless domain. Temperature-controlled out-of-plane X-ray diffraction (XRD) analysis of Langmuir–Blodgett (LB) films fabricated from both amphiphilic linear and cyclic block copolymers was performed to estimate the layer regularity at higher temperatures. Excellent heat-resistant properties of organized molecular films created from the cyclic copolymer were confirmed. Both copolymer types showed clear diffraction peaks at room temperature, indicating the formation of highly ordered layer structures. However, the layer structures of the linear copolymers gradually disordered when heated. Conversely, the regularity of cyclic copolymer LB multilayers did not change with heating up to 50 °C. Higher-order reflections (d002, d003) in the XRD patterns were also unchanged, indicative of a highly ordered structure. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015

The solubility of water in five liquid perfluoroalkylalkanes was measured as a function of temperature (283 K–313 K) and the thermodynamic functions of solution and solvation were calculated. The studied perfluoroalkylalkanes cover a range of relative lengths of the hydrogenated and perfluorinated segments. This is the first time the solubility of water in these substances has been measured, which is surprising given their pharmaceutical and medical relevance. The new data thus fills an important gap in the literature. The liquid organization of the water-in-PFAAs solutions was further investigated using atomistic molecular dynamics simulations, providing structural and energetic evidence about the solvation shell of water within the different solvents. The results indicate the existence of a specific interaction between the water molecule and the dipole located at the centre of the surfactant molecules, which explains the increased solubility of water in these solvents, relatively to alkanes and perfluoroalkanes. These findings also help to interpret the formation of nano-patterned molecular films of PFAA at the surface of water and of wet silicon wafers.

Monitoring thermal processes occurring in molecular films on surfaces can provide insights into physical events such as morphology changes and phase transitions. Here, we demonstrate that temperature-programmed contact potential difference (TP-∆CPD) measurements employed by a Kelvin probe under ultrahigh vacuum conditions and their temperature derivative can track films' restructure and crystallization occurring in amorphous solid water (ASW) at temperatures well below the onset of film desorption. The effects of growth temperature and films' thickness on the spontaneous polarization that develops within ASW films grown at 33 K-120 K on top of a Ru(0001) substrate are reported. Electric fields of ∼106 V/m are developed within the ASW films despite low average levels of molecular dipole alignment (

N-oxygenated and N-hydrogenated molecules of 8-hydroxyquinoline with a wide range of N values, generated by the deposition of Al, ITO, and MgAg electrodes on 10 nm thick tris(8-hydroxyquinoline) aluminum (Alq3) molecular films are analyzed by liquid extraction surface analysis combined with nanoelectrospray ionization mass spectrometry (LESA nano-ESI-MS) for the first time. Based on the relative ion intensities of oxygenated and hydrogenated molecules, Al deposition causes greater chemical reduction of Alq3 than ITO and MgAg deposition. Additionally, the relative ion intensities of 1-, 2-, and 3-oxygenated molecules decrease stepwise, so that oxidation of the 8-hydroxyquinoline molecules is thought to proceed stochastically.

The liquid-liquid interfacial tension of water with four liquid perfluoroalkanes (perfluoropentane, perfluorohexane, perfluorooctane and perfluorononane) and four liquid perfluoroalkylalkanes (perfluorobutylpentane, perfluorobutylhexane, perfluorohexylhexane and perfluorohexyloctane) was measured as a function of temperature in the 273 K–340 K range. The studied perfluoroalkylalkanes cover a range of relative lengths of the hydrogenated and perfluorinated segments. This is the first time the liquid-liquid interfacial tension with water has been measured for these substances, which is surprising given their pharmaceutical and medical relevance. The new data thus fills an important gap in the literature. The organization and interactions of the liquid-liquid interfaces was further investigated using atomistic molecular dynamics simulations, providing structural and energetic information of the systems. The results demonstrate the contribution of the interaction between the water molecule and the dipole located at the center of the perfluoroalkylalkane molecules, which explains the lower interfacial tension of these solvents with water, relatively to alkanes and perfluoroalkanes. Ultimately, these findings will help to interpret the formation of nano-patterned molecular films of PFAA at the surface of water and of wet silicon wafers.

Owing to the high demand of conducting molecular systems for various electronics and technological applications, development of new polyaniline (PANI)/carbon nanomaterial is a continued research interest in cross-disciplinary area of material chemistry. In the literature, for the preparation of PANI/carbon nanomaterial composite electrode systems ex-situ preparation method, in which, chemical oxidation of aniline in presence of carbon nanomaterial, followed by modification on solid substrate has been widely adopted. In this work, a systematic study has been carried out for in-situ electrochemical polymerization of 4-chloroaniline and other substituted aniline monomers to respective PANI on graphitized mesoporous carbon (GMC), that show porous structure and enormous sp2 sites to aniline and PANI for π-π interaction, unusually in neutral pH condition. The new GMC@PANI modified electrode showed a highly redox active peak at Eo’ = 0.12 V vs Ag/AgCl in pH 7 phosphate buffer solution. No such behaviour was noticed when an unmodified glassy carbon was used as working electrode for the polymerization in the above mentioned condition. The redox peak is found to be stable, surface-confined and Nernstian type of proton-coupled electron-transfer in nature. Based on the physicochemical characterization techniques using Raman, IR, X-Ray photoelectron-spectroscopy, scanning electron-microscope and scanning electrochemical microscope (SECM) instruments and electrochemical studies with several ortho, para and meta substituted aniline monomers, mechanism for the in-situ polymerization has been revealed that 4-chloroaniline monomer has undergone a surface-confined electrochemical oxidation reaction with involvement of aniline(4-Cl)-cation radical species, anti-orientation of the monomer (that exist in solution phase), head-to-tail collision (C-N bonding), ejection of the para-substituents as Cl- and Cl•, partial chlorination and PANI(4-Cl) formation mechanism. Such a PANI(4-Cl) film showed a wave-like 2D molecular film structure with enhanced redox and electrical property over the conventional PANI system.

The paper presents preliminary results of studies of the temporal dependence of refractive index, current-voltage characteristics, the dependence of resistance on voltage, and dynamics of resistance variations in time for biomolecular films during dehydration. The experimental results demonstrated the efficiency of the use of refractometry in the regime of total internal reflection for determining optical and physical properties of self-assembled molecular films in biomolecular electronics.

The functionalities offered by single-molecule electrical junctions are yet to be translated into monolayer or few-layer molecular films, where making effective and reproducible electrical contact is one of the challenging bottlenecks. Here we take a significant step in this direction by demonstrating that excellent electrical contact can be made with a monolayer biphenyl-4,4'-dithiol (BPDT) molecular film, sandwiched between gold and graphene electrodes. This sandwich device structure is advantageous, because the current flows through the molecules to the gold substrate in a 'cross-plane' manner, perpendicular to the plane of graphene, yielding high-conductance devices. We elucidate the nature of the cross-plane graphene/molecule/Au transport using quantum transport calculations and introduce a simple analytical model, which captures generic features of the current-voltage characteristic. Asymmetry in junction properties results from the disparity in electrode electrical properties, the alignment of the BPDT HOMO-LUMO energy levels and the specific characteristics of the graphene electrode. The experimental observation of scalability of junction properties within the junction area, in combination with a theoretical description of the transmission probability of the thiol-graphene contact, demonstrates that between 10% and 100% of the molecules make contact with the electrodes, which is several orders of magnitude greater than that achieved to date in the literature.

Contamination control engineers provide critical plans to monitor, mitigate, and reduce the impact of molecular and particulate contamination on spacecraft systems. Witness monitoring programs are dependable methods that utilize strategically placed witness samples on space flight hardware to monitor particulate and molecular contaminants during the assembly, integration, and test (AI&T) phases. Traditionally, optical characterization of these witness plates is the tool to determine the presence of molecular films on space flight hardware in the AI&T environment. Once a visual inspection or optical measurement identifies the presence of a contaminant, analysts collect tape lifts and wipe samples from the witness plate for analysis in an analytical lab with a potential contaminant identified within 24 hours. To speed up this process and reduce the impact to project schedule and cost the use of a non-invasive and in situ method for optical witness plate program with portable Raman spectroscopy to detect molecular contamination on spacecraft was explored.

Contamination control engineers are constantly challenged by time-consuming processes during the system assembly, integration and test phase for spacecraft. Hardware components, subassemblies, and integrated systems must be visually inspected throughout the process, and any signs of contamination found are usually analyzed by processes that can take days to complete. Portable Raman spectroscopy is a promising technology for spacecraft integration, where it may be possible to probe hardware or witness surfaces and identify contaminants throughout the assembly, integration and test phase. This study explored detection of five common spacecraft contaminants with portable Raman spectroscopy: silicone, hydrocarbon, fluorocarbon, ester, and a glycol polymer. It was found portable Raman spectroscopy can provide a quick-look capability which can be followed by more detailed contaminant quantification analysis techniques. In this way, portable Raman spectroscopy can aid contamination control engineers in providing actionable information to projects earlier in the assembly, integration and test phase of the project lifecycle.

Spontaneous pattern formation is an energetically favorable process and is shown in nature in molecular-scale assembly, biological association, and soft material organizations. The opposite regime, the artificial process, which is widely applied to the fabrication of semiconducting devices, such as lithographic techniques, requires enormous amounts of energy. Here, we propose a concept of tuning the properties of semiconducting MoS2 and WSe2 devices using the spontaneous pattern formation of adjacent molecular films. The film used was a 10 nm thick ultrathin film of a molecular electron dopant, which exhibited spontaneous pattern formation and dynamically transformed the morphology of tiny holes, a network, a maze, and dots on substrates, including SiO2, MoS2, and WSe2. These patterns were exhibited only when the film came in contact with water and was tuned with temperature and time. The specific lengths of the patterns were less than 200 nm, which is sufficiently smaller than the exfoliated ∼10 μm semiconducting MoS2 and WSe2 flakes. The properties of the field-effect devices of MoS2 and WSe2 were found to be modified according to the pattern formation process of the ultrathin molecular film on the device. This concept applies the spontaneous patterning phenomena shown in nature to the fabrication and optimization of electronic devices by using molecular films and their responses to the external environment.

Microcantilever transducers can be valuable tools for the investigation of physicochemical processes in organized molecular films. Gold-coated cantilevers are used here to investigate the electrochemomechanics of redox-active self-assembled monolayers (SAMs) of ferrocenylalkanethiolates (Fc(CH2)nS) of different alkyl chain lengths. A significant odd–even effect is observed in the surface stress and cantilever movement generated by the oxidation of the SAM-confined ferrocenes as the number of methylene units n in the SAM backbone is varied. We demonstrate that stronger alkyl chain–chain interactions are at the origin of the larger surface stresses generated by SAMs with an even versus odd n. The findings highlight the impact of subtle structural effects and weak van der Waals interactions on the mechanical actuation produced by redox reactions in self-assembled systems.

We performed SQUID and FMR magnetometry experiments to clarify the relationship between two reported magnetic exchange effects arising from interfacial spin-polarized charge transfer within ferromagnetic metal (FM)/molecule bilayers: the magnetic hardening effect, and spinterface-stabilized molecular spin chains. To disentangle these effects, both of which can affect the FM magnetization reversal, we tuned the metal phthalocyanine molecule central site's magnetic moment to selectively enhance or suppress the formation of spin chains within the molecular film. We find that both effects are distinct, and additive. In the process, we 1) extended the list of FM/molecule candidate pairs that are known to generate magnetic exchange effects, 2) experimentally confirmed the predicted increase in anisotropy upon molecular adsorption; and 3) showed that spin chains within the molecular film can enhance magnetic exchange. This magnetic ordering within the organic layer implies a structural ordering. Thus, by distengangling the magnetic hardening and exchange bias contributions, our results confirm, as an echo to progress regarding inorganic spintronic tunnelling, that the milestone of spintronic tunnelling across structurally ordered organic barriers has been reached through previous magnetotransport experiments. This paves the way for solid-state devices studies that exploit the quantum physical properties of spin chains, notably through external stimuli., None

Submitted by BEATRIZ LUCAS GARROTE (beatluga@gmail.com) on 2018-04-16T14:09:31Z No. of bitstreams: 1 Dissert_BeatrizLG_Biblioteca.pdf: 3636393 bytes, checksum: 269b9e5a63a28e3ce18a83e1f6b13493 (MD5) Approved for entry into archive by Ana Carolina Gonçalves Bet null (abet@iq.unesp.br) on 2018-04-16T17:30:58Z (GMT) No. of bitstreams: 1 garrote_bl_me_araiq_par.pdf: 593360 bytes, checksum: 45f42576bb82ab649a2bfba6bcc04001 (MD5) Made available in DSpace on 2018-04-16T17:30:58Z (GMT). No. of bitstreams: 1 garrote_bl_me_araiq_par.pdf: 593360 bytes, checksum: 45f42576bb82ab649a2bfba6bcc04001 (MD5) Previous issue date: 2018-03-27 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) A pesquisa em biomedicina está direcionando seus esforços para conseguir desenvolver dispositivos analíticos rápidos, simples e point-of-care para o diagnóstico de doenças. Os biossensores eletroquímicos label-free baseados na espectroscopia de impedância eletroquímica (EIE) são uma ferramenta interessante para este fim. EIE é uma técnica mais sensível do que outras técnicas eletroquímicas, como as amperométricas, potenciometricas ou voltamétricas. Em um sistema EIE com configuração faradaica, as variações na superfície do eletrodo são monitoradas, geralmente, pela resistência de transferência de carga (Rct) e pode-se correlacionar as variações no valor do Rct com a concentração do analito específico. Assim, EIE é uma técnica muito usada para biossensoriamento. Neste trabalho foi proposto um sistema baseado em EIE para a detecção da proteína interleukina-6 (IL-6). O eletrodo de trabalho foi modificado com uma monocamada auto-organizada (SAM) de alcanotióis. Nela é imobilizado covalentemente o receptor biológico (Ab IL-6). Durante o desenvolvimento do trabalho, foram enfrentados alguns problemas experimentais que comprometeram a resposta analítica do sistema. Para encontrar a causa da falta de resposta, foi analisado cada etapa de construção do biossensor. Após esses estudos foi concluído que as razões da ausência de resposta eram os defeitos ou pinholes presentes na SAM, devido ao fato de que EIE é uma técnica baseada na transferência de carga e a presença de defeitos na monocamada pode facilitar a migração iônica e/ou eletrônica. Para resolver isso, foi proposto um segundo sistema para a detecção da proteína IL-6 baseado na ECE (espectroscopia de capacitância eletroquímica), usando uma monocamada auto-organizada formada por um peptídeo redox. De novo, a sensibilidade do sistema não foi suficiente para a detecção da proteína. De acordo com trabalhos publicados previamente pelo nosso grupo de pesquisa, foi possível estabelecer uma correlação entre a sensibilidade do sistema e o peso molecular do antígeno e do receptor biológico. Assim, foi observado que sistemas similares mostram maior sensibilidade quanto maior é o analito. Da mesma forma, foi observado que sistemas com receptores biológicos pequenos e analitos maiores mostram maior sensibilidade. Essas duas afirmações podem ter afetado a sensibilidade do sistema proposto, pois a proteína IL-6 é uma proteína de 26 kDa e é a menor proteína já testada pelo nosso grupo em um sistema ECE e o receptor biológico foi um anticorpo de 150 kDa, 5,8 vezes maior do que o analito. Paralelamente, foi realizado um estudo eletroquímico preliminar de um sistema com duas sondas redox, em solução e confinada na superfície. O objetivo foi estudar o fenômeno de amplificação de sinal observado quando ambas as sondas redox formam parte do sistema e entender o processo eletroquímico. Foi observada uma transformação de um sistema capacitivo, quando só a sonda redox confinada na superfície está presente para um sistema impedimétrico, quando a sonda redox em solução participa no processo. A presença das duas sondas redox diminuiu a capacitância redox da monocamada eletroativa e a resistência de ressonância e aumentou a energia do sistema e a frequência de relaxação, devido a que foi favorecido a difusão dos elétrons com a solução. Biomedicine research is directing its effort to achieve fast, simple, point–of–care analytical devices for disease diagnostic. Label-free electrochemical biosensors based on electrochemical impedance spectroscopy (EIS) are an interesting tool for this purpose. For analytical objective, EIS is more sensitive than other electrochemical techniques, such as amperometric, potentiometric or voltammetry. EIS measures the complex resistance of the system. In faradaic EIS system, variations on the electrode surface are monitored by the charge transfer resistance (Rct), so correlations between the variation in Rct value and the concentration of a specific target could be made. Thus, EIS is a widely used technique for biosensing. Here, an EIS based system for the detection of the protein interleukin-6 (IL-6) was proposed. The working electrode was modified with a self-assembled monolayer (SAM) of alkanethiols, in which the biological receptor (Ab IL-6) was covalently immobilized. During the development of the system experimental problems compromised the analytical response. It was analysed every step of the biosensor construction. It was concluded that defects or pinholes on the SAM were the responsible for the absence of response, since EIS is a technique based on charge transfer and the presence of pinholes on the self-assembled monolayer could allow to free ionic and/or electronic migration. Because of this, it was proposed a second system for IL-6 detection based on electrochemical capacitance spectroscopy (ECS) and using a redox peptide SAM. Again, the sensitive of the system was not high enough to the protein detection. According to previous work published by our group, it was possible to correlate the sensitivity of the system with the molecular weight of the biological receptor and the specific target. It was shown that systems with bigger specific target and similar receptors resulted in more sensitive devices. Moreover, it was observed that system with small receptors and bigger targets showed higher sensitivity. IL-6 is a 26 kDa protein and is the smaller protein tested in an ECS based system by our group, and the biological receptor of the system was an antibody (150 kDa), 5.8 times higher than the biological receptor. Thus, the absence of response of the ECS system was attributed to the small molecular weight of the IL-6 protein and the high difference in weight between the biological receptor and the target. At the same time, it was performed a preliminary electrochemical study of a system with a redox probe confined on the electrode surface and a second one in solution. The objective was study the signal amplifier behaviour observed when two redox probes are involved on the system and understand the electrochemical process. It was observed the variation from a capacitive-based system, with the confined redox probe, to an impedance one, when the redox probe in solution was present. The presence of two redox probes decreased the redox capacitance of the electroactive film and the resonance resistance of the electrons between the electrode surface and the film; moreover, increased the energy of the system and the frequency of relaxation, due to the increase of the electron diffusion with the solution. 2015/17332-1

In the following article, we have considered problems and ways of transition from semiconductor to biomolecular electronics. We have used experimental studies of biomolecular materials to achieve goals for biomolecular electronics and communications. The paper studies a joint use of laser correlation spectroscopy and visual microscopic methods for investigation of self-assembling of proteins at transition from the liquid state to films. Furthermore, we have presented preliminary results of studies of molecular solutions. Finally, it is shown that structure evolution of drying out protein solution is a complex multi-stage process, which depends on external conditions.

Досліджено процеси формування та структуру тонких плівок халькогенідного склоподібного напівпровідника As₂S₃, полімеру поліаніліну (ПАНІ) та білка фібриногену (ФБ) на поверхні плівок благородних металів (Ag, Au) з використанням методики призмового збудження поверхневого плазмонного резонансу (ППР) у поєднанні з атомно-силовою мікроскопією. Оптичні параметри шарів As₂S₃ та ПАНІ визначено при підганянні експериментальних і розрахованих резонансних кривих ППР методом мінімізації цільової функції. Властивості плівок ФБ, що отримані з розчину білка у фосфатному буфері при різних концентраціях (9,3–300 muг/мл), вивчено на основі аналізу кінетичних ППР-кривих адсорбції ФБ і його DD- і E-фрагментів з наступним зондуванням моноклональними антитілами. Исследованы процессы формирования и структура тонких пленок халькогенидного стеклообразного полупроводника As₂S₃, полимера полианилина (ПАНИ) и белка фибриногена (ФБ) на поверхности пленок благородных металлов (Ag, Au) с использованием методики призменного возбуждения поверхностного плазмонного резонанса (ПИР) в сочетании с атомно-силовой микроскопией. Оптические параметры слоев As₂S₃ и ПАНИ определены при подгонке экспериментальных и рассчитанных резонансных кривых ППР методом минимизации целевой функции. Свойства пленок ФБ, полученных из раствора белка в фосфатном буфере при различных концентрациях (9,3-300 цг/мл), изучены на основе анализа кинетических ППР-кривых адсорбции ФБ и его DD- и E-фрагментов с последующим зондированием моноклональными антителами. Photodoping process in the thin film structures metal/chalcogenide vitreous semiconductor (Ag-As₂S₃), electro-polymerization mechanism of the polyaniline (PANI) films and formation mechanism of the fibrinogen (FB) molecular films on gold film surfaces were investigated by means of the surface plasmon resonance (SPR) technique based on prism excitation and mechanical scanning of incidence light angle in aggregate with atomic force microscopy (Nanoscope IIIa Dimension 3000). Features of the FB molecular films formation, at the different concentration (9,3–300 mg/ml) of the protein in phosphate buffer (mm 7,4), were studied based on SPR kinetic curve, when the adsorption of three proteins, FB, its DD- and E-fragments and subsequent their adlayers interactions with monoclonal antibodies against different epitops in native molecules, that were going on the gold film surfaces. Displayed is the formation of the continuous film at the 73 Mg/ml concentration in buffer is visualized, during irreversible adsorption the alteration of the FB molecule structure in the sphere of its D-fragment take place, and the local self-assembling process leads to formation of the special molecular arrangement in biofilm, consist of three overlap FB molecules, where approximately 50 M of total adsorbed molecules which retain their biofunctional properties.

International audience; The formation of long-range ordered aperiodic molecular films on quasicrystalline substrates is a new challenge that provides an opportunity for further surface functionalization. This aim can be realized through the smart selection of molecular building blocks, based on symmetry-matching between the underlying quasicrystal and individual molecules. It was previously found that the geometric registry between the C 60 molecules and the 5-and 10-fold surfaces was key to the growth of quasiperiodic organic layers. However, an attempt to form a quasiperiodic C 60 network on i-Ag-In-Yb substrates was unsuccessful, resulting in disordered molecular films. Here we report the growth of 5-fold symmetric corannulene C 20 H 10 molecules on the 5-fold surfaces of i-Ag-In-Yb quasicrystals. Low-energy electron diffraction (LEED) and scanning tunneling microscopy (STM) revealed long-range quasiperiodic order and 5-fold rotational symmetry in self-assembled corannulene films. Recurrent decagonal molecular rings were seen, resulting from the decoration of specific adsorption sites with local pentagonal symmetry by corannulenes, adsorbed with their bowl-openings pointing away from the surface. They were identified as (Ag, In)-containing rhombic triacontahedral (RTH) cluster centers and pentagonal Yb motifs, which cannot be occupied simultaneously due to steric hindrance. It is proposed that symmetry-matching between the molecule and specific substrate sites drives this organization. Alteration of the molecular rim by the introduction of CH substituents appeared to increase molecule mobility on the potential energy surface and facilitate trapping at these specific sites. This finding suggests that rational selection of molecular moiety enables the templated self-assembly of molecules leading to an ordered aperiodic corannulene layer.

Tribology deals with friction, wear, and lubrication of interacting surfaces. Interfacial molecular films refer to adsorbed, self-assembled, or functionally grafted molecular systems that form, through physical and chemical processes, near or on a surface. Understanding molecular origins of friction and other tribological properties of these molecular systems is essential for fundamental scientific and practical purposes. Such research is part of a relatively recent field of tribology, called molecular tribology. In classical tribology, interfacial molecular films are the last line of defense against wear, through their action in boundary lubrication regime. Interfacial molecular films such as self-assembled monolayers are used as a lubricant and protective coating in micro- and nanoscale machinery, and in applications where bulk fluid lubrication is not possible. Biomechanical systems in nature operate at a low friction, by taking advantage of molecular interactions of the interfacial film made of water molecules and polymer brushes in aqueous solutions. Therefore, understanding of the molecular origin of tribological properties of interfacial films is necessary to control friction and wear at the boundary lubrication regime, to create innovative tribological solutions for emerging nanotechnological applications, and to mimic nature’s high-performance tribological solutions. Here we shall briefly overview some of the core knowledge about the tribological properties of three essential class of interfacial films, discuss some of the most recent developments in the field, and provide a prospect for future directions.

One promising route toward encoding information is to utilize the two stable electronic states of a spin crossover molecule. However, while this property is clearly manifested in transport across single molecule junctions, evidence linking charge transport across a solid-state device to the molecular film's spin state has thus far remained indirect. To establish this link, we deploy materials-centric and device-centric operando experiments involving X-ray absorption spectroscopy. We find a correlation between the temperature dependencies of the junction resistance and the Fe spin state within the device's Fe(bpz)2(phen) molecular film. We also factually observe that the Fe molecular site mediates charge transport. Our dual operando studies reveal that transport involves a subset of molecules within an electronically heterogeneous spin crossover film. Our work confers an insight that substantially improves the state-of-the-art regarding spin crossover-based devices, thanks to a methodology that can benefit device studies of other next-generation molecular compounds., Typo in the first name of one of the authors updated (Jinje -> Jinjie)

The evaluation of thickness, refractive index, and optical properties of biomolecular films and self-assembled monolayers (SAMs) has a prominent relevance in the development of label-free detection techniques (quartz microbalance, surface plasmon resonance, electrochemical devices) for sensing and diagnostics. In this framework Spectroscopic Ellipsometry (SE) is an important player. In our approach to SE measurements on ultrathin soft matter, we exploit the small changes of the ellipsometry response (\(\delta \varDelta \) and \(\delta \varPsi \)) following the addition/removal of a layer in a nanolayered structure. So-called \(\delta \varDelta \) and \(\delta \varPsi \) difference spectra allow to recognize features related to the molecular film (thickness, absorptions) and to the film-substrate interface thus extending SE to a sensitive surface UV-VIS spectroscopy. The potential of ellipsometry as a surface spectroscopy tool can be boosted when flanked by other characterizations methods. The chapter deals with the combined application of broad-band Spectroscopic Ellipsometry and nanolithography methods to study organic SAMs and multilayers. Nanolithography is achieved by the accurate removal of molecules from regularly shaped areas obtained through the action of shear forces exerted by the AFM tip in programmed scans. Differential height measurements between adjacent depleted and covered areas provide a direct measurement of film thickness, which can be compared with SE results or feed the SE analysis. In this chapter we will describe the main concepts behind the SE difference spectra method and AFM nanolithograhy. We will describe how SE and AFM can be combined to strengthen the reliability of the determination of thickness and, as a consequence, of the optical properties of films. Examples will be discussed, taken from recent experiments aimed to integrate SE and AFM nanolithography applied to SAMs and nano layers of biological interest. By analysing in detail the changes of the spectroscopic features of compact versus non-compact layers and correlating such changes with the post-lithography AFM analysis of surface morphology SE unravels the specific versus unspecific adsorption of biomolecules on gold surfaces functionalized with suitable SAMs.

in films as response to femtosecond and picosecond laser pulse heating by timeresolved X-ray diffraction. This method allows a direct absolute determination of the molecular displacements induced by electron−phonon interactions, which are crucial for, for example, charge transport in organic electronic devices. We demonstrate that two different modes of coherent shear motion can be photoexcited in a thin film of organic molecules by careful tuning of the laser penetration depth relative to the thickness of the film. The measured response of the organic film to impulse heating is explained by a thermoelastic model and reveals the spatially resolved displacement in the film. Thereby, information about the profile of the energy deposition in the film as well as about the mechanical interaction with the substrate material is obtained. © 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/

Molecular communication systems became a promising paradigm of modern nanonetworks. Quantum carrier transfer creates communication channels between parts of a molecule and/or connects a few domains inside a molecular metamaterial network. This manuscript presents our studies of such channels activated by means of modulated laser beam irradiation resulting in molecular fluorescence, probably at a shifted frequency. The acquisition system for the electromagnetic field generated by a molecule based on the novel dynamic pin-photo diode is characterized by a high sensitivity and a low noise level due to the signal amplitude-time function integration.

The frontier orbitals of molecules are the prime determinants of their chemical, optical, and electronic properties. Arguably, the most direct method of addressing the (filled) frontier orbitals is ultra-violet photoemission spectroscopy (UPS). Although UPS is a mature technique from the early 1970s on, the angular distribution of the photoemitted electrons was thought to be too complex to be analyzed quantitatively . Recently angle-resolved UPS work on conjugated molecules, both in ordered thick films and chemisorbed monolayers, has shown that the angular (momentum) distribution of the photocurrent from orbital emissions can be simply understood when a plane wave final state is assumed. This approach, becoming known as orbital or photoemission tomography, relates the emission distribution to the Fourier transform of the ground state orbitals. The examples given will introduce photoemission tomography and demonstrate its potential as a technique to determine both electronic and geometric structures not just complementary but also competitive to methods as diverse as scanning tunneling microscopy and near-edge X-ray absorption spectroscopy.

We report on the measurements of electrons trapped in solid molecular films of H $$_{2}$$ , HD, and D $$_{2}$$ . A narrow ESR line associated with the trapped electrons was detected with $$g=2.00233(5)$$ , which turned out to be shifted by $$-$$ 0.3 G from the free electron resonance. Comparison is made with earlier measurements where a similar line has been seen. In addition, for a $$\text {D}_{2}{:}\text {H}_{2}$$ mixture, after raising the temperature above 1 K, we observe a strong line at the location of the electron cyclotron resonance. The line amplitude is dependent on temperature and has an activation energy of 26 K. We believe that at elevated temperatures, electrons diffuse from the bulk of the film to the surface.

Dye molecules like porphyrins alter their optical properties upon condensation to a solid film. Besides intermolecular interactions, specific substrates can influence their optical characteristics, especially if the molecular film is in contact to plasmonic nanostructures. We apply multiphoton photoemission electron microscopy (nP-PEEM) with tunable laser excitation to the laterally resolved spectroscopy of magnesium-tetraphenylporphyrin (MgTPP) films deposited on nanostructured silver substrates. The high molecular specificity of nP-PEEM is demonstrated by the observation of a strong resonance at about 425 nm caused by optical excitation of the S0 → S2 transition (Soret band) of the MgTPP molecules. This molecular excitation gives rise to remarkably strong three-photon photoemission. The spectral position of the Soret resonance in our nP-PEEM laser spectra points to reduced excitonic coupling between the surface molecules of the MgTPP film. By comparison of the photoemission intensities from MgTPP on nan...

We report the systematic characterization of anisotropic, π-conjugated oligophenyleneimine (OPI) films synthesized using stepwise imine condensation, or "click" chemistry. Film synthesis began with a self-assembled monolayer (SAM) of 4-formylthiophenol or 4-aminothiophenol on Au, followed by repetitive, alternate addition of terephthalaldehyde (benzene-1,4-dicarbaldehyde) or 1,4-benzenediamine to form π-conjugated films ranging from 0.6-5.5 nm in thickness. By systematically capping the OPI films with a redox or halogen label, we were able to measure the relative surface coverage after each monomer addition via Rutherford backscattering spectrometry, X-ray photoelectron spectroscopy, spectroscopic ellipsometry, reflection-absorption infrared spectroscopy, and cyclic voltammetry. Nuclear reaction analysis was also employed for the first time on a SAM to calculate the surface coverage of carbon atoms after each stepwise addition. These six different analysis methods indicate that the average extent of reaction is 99% for each addition step. The high yield and molecular surface coverage confirm the efficacy of Schiff base chemistry, at least with the terephthalaldehyde and 1,4-benzenediamine monomers, for preparing high-quality molecular films with π conjugation normal to the substrate.

Titanium oxide–titanium carbide (TiOxCy) hybrid materials have tunable electronic properties ranging from semiconductive to semimetallic. They can therefore be employed in solar energy conversion applications and as potential substitute for carbon based electrocatalyst supports for use in fuel cells. Understanding of the optical properties of semimetallic TiOxCy is of great importance. In this paper we report on the optical properties of compact TiOxCy in the mid-IR spectral region. TiOxCy reflects the IR light similarly to metals and is therefore suitable as a new substrate for molecular adsorption studies with infrared reflection absorption spectroscopy. For the first time polarization modulation infrared reflection absorption spectroscopy (PM IRRAS) is applied to study quantitatively at the submolecular level the structure and orientation of fatty acid molecules in monolayers adsorbed on the TiOxCy surface. The analysis of the IR band intensities provides information on the structure, packing, and orie...

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 molecular films. Monomolecular films of a TTF derivative with a chiral borneol group display a two-dimensional phase transition at the air/water interface. At high surface pressures, nanonetwork domains are formed, where the TTF molecular planes are densely packed with an interlayer distance of 4.1 Å. The formation of this network is attributed to the organized aggregation of the TTF derivatives, which is a result of strong intermolecular interactions. Subsequently, the growth of morphology is encouraged by the application of the one-dimensional growth method at low surface pressure conditions, varying compression speeds, and subphase temperatures. At low surface pressure and a subphase temperature of 15 °C, the TTF derivatives aggregated as nanofibers with close packing of molecules. Upon raising the subphase temperature, the thickness of the nanofibers was found to increase and hence, spontaneous morphogenesis at the air/water interface was achieved.

The role of organo-modifying molecular chains in the formation of molecular films of organo-modified nanodiamond is discussed herein based on interfacial chemical particle integration of organo-modified nanodiamond having a particle size of 5 nm. The surface of nanodiamond is known to be covered with a nanolayer of adsorbed water. This water nanolayer was exploited for organo-modification of nanodiamond with long-chain fatty acids via adsorption, leading to nanodispersion of nanodiamond in general organic solvents as a mimic of solvency. The organo-modified nanodiamond dispersed "solution" was used as a spreading solution for depositing a mono-"particle" layer on the water surface, and a Langmuir particle layer was integrated at the air/water interface. Multi-"particle" layers were then formed via the Langmuir-Blodgett technique and were subjected to fine structural analysis. The effect of organo-modification enabled integration and multilayer formation of inorganic nanoparticles due to enhancement of the van der Waals interactions between the chains. That is to say, the "encounter" between the organo-modifying chain and the inorganic particles led to solubilization of the inorganic particles and enhanced interactions between the particles, which can be regarded as imparting new function to the organic molecules. The morphology of the single-particle layer was maintained after removal of the organic region of the composite via the baking process, whereas the regularity of the layered period was disordered. Thus, the organic chains are essential as modifiers for maintenance of the layered structure.