Self-assembled monolayers of reduced graphene oxide for robust 3D-printed supercapacitors.

Herein, additive manufacturing, which is extremely promising in different sectors, has been adopted in the electrical energy storage field to fabricate efficient materials for supercapacitor applications. In particular, Al2O3-, steel-, and Cu-based microparticles have been used for the realization of 3D self-assembling materials covered with reduced graphene oxide to be processed through additive manufacturing. Functionalization of the particles with amino groups and a subsequent "self-assembly" step with graphene oxide, which was contextually partially reduced to rGO, was carried out. To further improve the electrical conductivity and AM processability, the composites were coated with a polyaniline-dodecylbenzene sulfonic acid complex and further blended with PLA. Afterward, they were extruded in the form of filaments, printed through the fused deposition modeling technique, and assembled into symmetrical solid-state devices. Electrochemical tests showed a maximum mass capacitance of 163 F/g, a maximum energy density of 15 Wh/Kg at 10 A/g, as well as good durability (85% capacitance retention within 5000 cycles) proving the effectiveness of the preparation and the efficiency of the as-manufactured composites.

Experimental and simulation-based characterization of surfactant adsorption layers at fluid interfaces.

Adsorption of surfactants to fluid interfaces occurs in numerous technological and daily-life contexts. The coverage at the interface and other properties of the formed adsorption layers determine the performance of a surfactant with regard to the desired application. Given the importance of these applications, there is a great demand for the comprehensive characterization and understanding of surfactant adsorption layers. In this review, we provide an overview of suitable experimental and simulation-based techniques and review the literature in which they were used for the investigation of surfactant adsorption layers. We come to the conclusion that, while these techniques have been successfully applied to investigate Langmuir monolayers of water-insoluble surfactants, their application to the study of Gibbs adsorption layers of water-soluble surfactants has not been fully exploited. Finally, we emphasize the great potential of these methods in providing a deeper understanding of the behavior of soluble surfactants at interfaces, which is crucial for optimizing their performance in various applications.

In situ via Contact to hBN-Encapsulated Air-Sensitive Atomically Thin Semiconductors.

Establishing reliable electrical contacts to atomically thin materials is a prerequisite for both fundamental studies and applications yet remains a challenge. In particular, the development of contact techniques for air-sensitive monolayers has lagged behind, despite their unique properties and significant potential for applications. Here, we present a robust method to create contacts to device layers encapsulated within hexagonal boron nitride (hBN). This method uses plasma etching and metal deposition to create 'vias' in the hBN with graphene forming an atomically thin etch-stop. The resulting partially fluorinated graphene (PFG) protects the underlying device layer from air-induced degradation and damage during metal deposition. PFG is resistive in-plane but maintains high out-of-plane conductivity. The work function of the PFG/metal contact is tunable through the degree of fluorination, offering opportunities for contact engineering. Using the in situ via technique, we achieve ambipolar contact to air-sensitive monolayer 2H-molybdenum ditelluride (MoTe2) with more than 1 order of magnitude improvement in on-current density compared to previous literature. The complete encapsulation provides high reproducibility and long-term stability. The technique can be extended to other air-sensitive materials as well as air-stable materials, offering highly competitive device performance.

Functionalized Thienopyrazines on NiOx Film as Self-Assembled Monolayer for Efficient Tin-Perovskite Solar Cells Using a Two-Step Method.

Three functionalized thienopyrazines (TPs), TP-MN (1), TP-CA (2), and TPT-MN (3) were designed and synthesized as self-assembled monolayers (SAMs) deposited on the NiOx film for tin-perovskite solar cells (TPSCs). Thermal, optical, electrochemical, morphological, crystallinity, hole mobility, and charge recombination properties, as well as DFT-derived energy levels with electrostatic surface potential mapping of these SAMs, have been thoroughly investigated and discussed. The structure of the TP-MN (1) single crystal was successfully grown and analyzed to support the uniform SAM produced on the ITO/NiOx substrate. When we used NiOx as HTM in TPSC, the device showed poor performance. To improve the efficiency of TPSC, we utilized a combination of new organic SAMs with NiOx HTM, the TPSC device exhibited the highest PCE of 7.7% for TP-MN (1). Hence, the designed NiOx/TP-MN (1) acts as a new model system for the development of efficient SAM-based TPSC. To the best of our knowledge, the combination of organic SAMs with anchoring CN/CN or CN/COOH groups, and NiOx HTM for TPSC has never been reported elsewhere. The TPSC device based on the NiOx/TP-MN bilayer exhibits great enduring stability for performance, retaining ~80% of its original value for shelf storage over 4000 h.

Interfacial Electron Beam Lithography Converts an Insulating Organic Monolayer to a Patterned Single-Layer Conductor with Puzzling Charge Transport Performance.

The direct generation of conducting paths within an insulating surface represents a conceptually unexplored approach to single-layer electrical conduction that opens vistas for exciting research and applications fundamentally different from those based on specific layered materials. Herein we report surface channels with single-layer -COOH functionality patterned on insulating n-octadecyltrichlorosilane monolayers on silicon that exhibit unusual ionic-electronic conduction when equipped with ion-releasing silver electrodes. The strong dependence of charge transport in such channels on their lateral dimensions (nanosize, macro-size), the type (p, n) and resistivity (doping level) of the underlying silicon substrate, the nature of the insulating spacer layer between the conducting channel and the silicon surface, and the postpatterning chemical manipulation of channel's -COOH functionality allows designing channels with variable resistivities, ranging from that of a practical insulator to some unexpectedly low values. The unusually low resistivities displayed by channels with nanometric widths and micrometer-millimeter lengths are attributed primarily to enhanced electronic transport within ultrathin nanowire-like silver metal films formed along their conductive paths. Function-structure correlations derived from a comprehensive analysis of electrical, atomic force microscopy, and Fourier transform infrared spectral data suggest an unconventional mode of conduction in these channels, which has yet to be elucidated, apparently involving coupled ionic-electronic transport mediated and enhanced by interfacial electrical interactions with charge carriers located outside the conducting channel and separated from those carrying the measured current. These intriguing findings hint at effects akin to Coulomb pairing in the proposed mechanisms of excitonic superconductivity in interfacial nanosystems structurally related to the present metalized surface channels.

Review of the Interfacial Structure and Properties of Surfactants in Petroleum Production and Geological Storage Systems from a Molecular Scale Perspective.

Surfactants play a crucial role in tertiary oil recovery by reducing the interfacial tension between immiscible phases, altering surface wettability, and improving foam film stability. Oil reservoirs have high temperatures and high pressures, making it difficult and hazardous to conduct lab experiments. In this context, molecular dynamics (MD) simulation is a valuable tool for complementing experiments. It can effectively study the microscopic behaviors (such as diffusion, adsorption, and aggregation) of the surfactant molecules in the pore fluids and predict the thermodynamics and kinetics of these systems with a high degree of accuracy. MD simulation also overcomes the limitations of traditional experiments, which often lack the necessary temporal-spatial resolution. Comparing simulated results with experimental data can provide a comprehensive explanation from a microscopic standpoint. This article reviews the state-of-the-art MD simulations of surfactant adsorption and resulting interfacial properties at gas/oil-water interfaces. Initially, the article discusses interfacial properties and methods for evaluating surfactant-formed monolayers, considering variations in interfacial concentration, molecular structure of the surfactants, and synergistic effect of surfactant mixtures. Then, it covers methods for characterizing microstructure at various interfaces and the evolution process of the monolayers' packing state as a function of interfacial concentration and the surfactants' molecular structure. Next, it examines the interactions between surfactants and the aqueous phase, focusing on headgroup solvation and counterion condensation. Finally, it analyzes the influence of hydrophobic phase molecular composition on interactions between surfactants and the hydrophobic phase. This review deepened our understanding of the micro-level mechanisms of oil displacement by surfactants and is beneficial for screening and designing surfactants for oil field applications.

Application of the Knife-Edge Technique on Transition Metal Dichalcogenide Monolayers for Resolution Assessment of Nonlinear Microscopy Modalities.

We report application of the knife-edge technique at the sharp edges of WS2 and MoS2 monolayer flakes for lateral and axial resolution assessment in all three modalities of nonlinear laser scanning microscopy: two-photon excited fluorescence (TPEF), second- and third-harmonic generation (SHG, THG) imaging. This technique provides a high signal-to-noise ratio, no photobleaching effect and shows good agreement with standard resolution measurement techniques. Furthermore, we assessed both the lateral resolution in TPEF imaging modality and the axial resolution in SHG and THG imaging modality directly via the full-width at half maximum parameter of the corresponding Gaussian distribution. We comprehensively analyzed the factors influencing the resolution, such as the numerical aperture, the excitation wavelength and the refractive index of the embedding medium for the different imaging modalities. Glycerin was identified as the optimal embedding medium for achieving resolutions closest to the theoretical limit. The proposed use of WS2 and MoS2 monolayer flakes emerged as promising tools for characterization of nonlinear imaging systems.

Correcting Edge Defects in Self-Assembled Monolayers through Thermal Annealing.

Self-assembled monolayers (SAMs) are emerging as platform technology for a myriad of applications, yet they still possess varied spatial stability and predictability issues as their properties are heavily dependent on subtle structural features. Reducing entropy within such a system serves as one of many potential solutions to increase order and therefore coherence/precision in measured properties. Here we explore controlled thermal annealing to improve edge disorders in SAMs and significantly reduce data variance. Using both odd- and even-numbered n-alkanethiol SAMs on Au, we observe statistically significant difference in the contact angles between edge and center. Thermal annealing at 40°C significantly narrows differences between edges and centre of the SAM, albeit with significant reduction in the parity dependent odd-even effect. This study provides a pathway to improve SAMs consistency through minimal external perturbation as reflected by the minimization of odd-even effect as SAMs become increasingly ordered.

Tuning Hole-Injection in Organic-Light Emitting Diodes with Self-Assembled Monolayers.

Improving hole injection through the surface modification of indium tin oxide (ITO) with self-assembled monolayers (SAMs) is a promising method for modulating the carrier injection in organic light-emitting diodes (OLEDs). However, developing SAMs with the required characteristics remains a daunting challenge. Herein, we functionalize ITO with various phosphonic acid SAMs and evaluate the SAM-modified anodes in terms of their work function (WF), molecular distribution, coverage, and electrical conductivity. We fabricate and characterize green phosphorescent SAM-based OLEDs and compared their performance against devices based on the conventional poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) hole-injection layer. We find that the usage of [2-(3,6-diiodo-9H-carbazol-9-yl)ethyl]phosphonic acid (I-2PACz) SAM yields devices with superior performance characteristics, including a maximum luminance of ∼57,300 cd m-2 and external quantum efficiency of up to ∼17%. This improvement is attributed to synergistic factors, including the deep WF of ITO/I-2PACz (5.47 eV), the formation of larger I-2PACz molecular clusters, and the intrinsic I-2PACz dipole, that collectively enhance hole-injection.

Interfacial Water Is Separated from a Hydrophobic Silica Surface by a Gap of 1.2 nm.

The interaction of liquid water with hydrophobic surfaces is ubiquitous in life and technology. Yet, the molecular structure of interfacial liquid water on these surfaces is not known. By using a 3D atomic force microscope, we characterize with angstrom resolution the structure of interfacial liquid water on hydrophobic and hydrophilic silica surfaces. The combination of 3D AFM images and molecular dynamics simulations reveals that next to a hydrophobic silica surface, there is a 1.2 nm region characterized by a very low density of water. In contrast, the 3D AFM images obtained of a hydrophilic silica surface reveal the presence of hydration layers next to the surface. The gap observed on hydrophobic silica surfaces is filled with two-to-three layers of straight-chain alkanes. We developed a 2D Ising model that explains the formation of a continuous hydrocarbon layer on hydrophobic silica surfaces.

Multiphoton-pumped UV-Vis transient absorption spectroscopy of 2D materials: basic concepts and recent applications.

2D materials are considered a key element in the development of next-generation electronics (nanoelectronics) due to their extreme thickness in the nanometer range and unique physical properties. The ultrafast dynamics of photoexcited carriers in such materials are strongly influenced by their interfaces, since the thickness of 2D materials is much smaller than the typical depth of light penetration into their bulk counterparts and the mean free path of photoexcited carriers. The resulting collisions of photoexcited carriers with interfacial potential barriers of 2D materials in the presence of a strong laser field significantly alter the overall dynamics of photoexcitation, allowing laser light to be directly absorbed by carriers in the conduction/valence band through the inverse bremsstrahlung mechanism. The corresponding ultrafast carrier dynamics can be monitored using multiphoton-pumped UV-Vis transient absorption spectroscopy. In this review, we discuss the basic concepts and recent applications of this spectroscopy for a variety of 2D materials, including transition-metal dichalcogenide monolayers, topological insulators, and other 2D semiconductor structures.

Illuminating the nanostructure of diffuse interfaces: Recent advances and future directions in reflectometry techniques.

Diffuse soft matter interfaces take many forms, from end-tethered polymer brushes or adsorbed surfactants to self-assembled layers of lipids. These interfaces play crucial roles across a multitude of fields, including materials science, biophysics, and nanotechnology. Understanding the nanostructure and properties of these interfaces is fundamental for optimising their performance and designing novel functional materials. In recent years, reflectometry techniques, in particular neutron reflectometry, have emerged as powerful tools for elucidating the intricate nanostructure of soft matter interfaces with remarkable precision and depth. This review provides an overview of selected recent developments in reflectometry and their applications for illuminating the nanostructure of diffuse interfaces. We explore various principles and methods of neutron and X-ray reflectometry, as well as ellipsometry, and discuss advances in their experimental setups and data analysis approaches. Improvements to experimental neutron reflectometry methods have enabled greater time resolution in kinetic measurements and elucidation of diffuse structure under shear or confinement, while innovation in analysis protocols has significantly reduced data processing times, facilitated co-refinement of reflectometry data from multiple instruments and provided greater-than-ever confidence in proposed structural models. Furthermore, we highlight some significant research findings enabled by these techniques, revealing the organisation, dynamics, and interfacial phenomena at the nanoscale. We also discuss future directions and potential advancements in reflectometry techniques. By shedding light on the nanostructure of diffuse interfaces, reflectometry techniques enable the rational design and tailoring of interfaces with enhanced properties and functionalities.

Stimuli-Responsive Oligourea Molecular Films.

We have designed and synthesized a helical cysteamine-terminated oligourea foldamer composed of ten urea residues featuring side carboxyl and amine groups. The carboxyl group is located in proximity to the C-terminus of the oligourea and hence at the negative pole of the helix dipole. The amine group is located close to the N-terminus and hence at the positive pole of the helix dipole. Beyond the already remarkable dipole moment inherent in oligourea 2.5 helices, the incorporation of additional charges originating from the carboxylic and amine groups is supposed to impact the overall charge distribution along the molecule. These molecules were self-assembled into monolayers on a gold substrate, allowing us to investigate the influence of an electric field on these polar helices. By applying surface-enhanced infrared reflection-absorption spectroscopy, we proved that molecules within the monolayers tend to reorient themselves more vertically when a negative bias is applied to the surface. It was also found that surface-confined oligourea molecules affected by the external electric field tend to rearrange the electron density at urea groups, leading to the stabilization of the resonance structure with charge transfer character. The presence of the external electric field also affected the nanomechanical properties of the oligourea films, suggesting that molecules also tend to reorient in the ambient environment without an electrolyte solution. Under the same conditions, the helical oligourea displayed a robust piezoresponse, particularly noteworthy given the slender thickness of the monolayer, which measured approximately 1.2 nm. This observation demonstrates that thin molecular films composed of oligoureas may exhibit stimulus-responsive properties. This, in turn, may be used in nanotechnology systems as actuators or functional films, enabling precise control of their thickness in the range of even fractions of nanometers.

Evolution of transition metal dichalcogenide films properties during chemical vapor deposition: from monolayer islands to nanowalls.

Unique properties possessed by transition metal dichalcogenides (TMD) attract much attention to investigation of their formation and dependence of their characteristics on the production process parameters. Here we investigate formation of TMD films during chemical vapor deposition (CVD) in the mixture of the thermally activated gaseous H2S and vaporized transition metals. Our observations of changes in morphology, Raman spectra, and photoluminescent (PL) properties in combination with in-situ measurements of electrical conductivity of the deposits formed at various precursors concentrations and CVD duration are evidencing on existence of particular stages in the TMD materials formation. Gradual transformation of PL spectra from trion to exciton type is detected for different stages of the material formation. Obtained results and proposed methods provide tailoring of TMD film characteristics demanded for the particular applications like photodetectors, photocatalyst, gas sensors.

Formation of sparsely tethered bilayer lipid membrane on a biodegradable self-assembled monolayer of poly(lactic acid).

The utilization of biomimetic membranes supported by advanced self-assembled monolayers is gaining attraction as a promising sensing tool. Biomimetic membranes offer exceptional biocompatibility and adsorption capacity upon degradation, transcending their role as mere research instruments to open new avenues in biosensing. This study focused on anchoring a sparsely tethered bilayer lipid membrane onto a self-assembled monolayer composed of a biodegradable polymer, functionalized with poly(ethylene glycol)-cholesterol moieties, for lipid membrane integration. Real-time monitoring via quartz crystal microbalance, coupled with characterization using surface-enhanced infrared absorption spectroscopy and electrochemical impedance spectroscopy, provided comprehensive insights into each manufacturing phase. The resulting lipid layer, along with transmembrane pores formed by gramicidin A, exhibited robust stability. Electrochemical impedance spectroscopy analysis confirmed membrane integrity, successful pore formation, and consistent channel density. Notably, gramicidin A demonstrated sustained functionality as an ion channel upon reconstitution, with its functionality being effectively blocked and inhibited in the presence of calcium ions. These findings mark significant strides in developing intricate biodegradable nanomaterials with promising applications in biomedicine.

The Secret Ballet Inside Multivesicular Bodies.

Lipid bilayers possess the capacity for self-assembly due to the amphipathic nature of lipid molecules, which have both hydrophobic and hydrophilic regions. When confined, lipid bilayers exhibit astonishing versatility in their forms, adopting diverse shapes that are challenging to observe through experimental means. Exploiting this adaptability, lipid structures motivate the development of bio-inspired mechanomaterials and integrated nanobio-interfaces that could seamlessly merge with biological entities, ultimately bridging the gap between synthetic and biological systems. In this work, we demonstrate how, in numerical simulations of multivesicular bodies, a fascinating evolution unfolds from an initial semblance of order toward states of higher entropy over time. We observe dynamic rearrangements in confined vesicles that reveal unexpected limit shapes of distinct geometric patterns. We identify five structures as the basic building blocks that systematically repeat under various conditions of size and composition. Moreover, we observe more complex and less frequent shapes that emerge in confined spaces. Our results provide insights into the dynamics of multivesicular systems, offering a richer understanding of how confined lipid bodies spontaneously self-organize.

Optimal Control of Collective Electrotaxis in Epithelial Monolayers.

Epithelial monolayers are some of the best-studied models for collective cell migration due to their abundance in multicellular systems and their tractability. Experimentally, the collective migration of epithelial monolayers can be robustly steered e.g. using electric fields, via a process termed electrotaxis. Theoretically, however, the question of how to design an electric field to achieve a desired spatiotemporal movement pattern is underexplored. In this work, we construct and calibrate an ordinary differential equation model to predict the average velocity of the centre of mass of a cellular monolayer in response to stimulation with an electric field. We use this model, in conjunction with optimal control theory, to derive physically realistic optimal electric field designs to achieve a variety of aims, including maximising the total distance travelled by the monolayer, maximising the monolayer velocity, and keeping the monolayer velocity constant during stimulation. Together, this work is the first to present a unified framework for optimal control of collective monolayer electrotaxis and provides a blueprint to optimally steer collective migration using other external cues.

SERS Detection of Trace Carcinogenic Aromatic Amines Based on Amorphous MoO3 Monolayers.

Aromatic amines are important commercial chemicals, but their carcinogenicity poses a threat to humans and other organisms, making their rapid quantitative detection increasingly urgent. Here, amorphous MoO3 (a-MoO3) monolayers with localized surface plasmon resonance (LSPR) effect in the visible region are designed for the trace detection of carcinogenic aromatic amine molecules. The hot-electron fast decay component of a-MoO3 decreases from 301 fs to 150 fs after absorption with methyl orange (MO) molecules, indicating the plasmon-induced hot-electron transfer (PIHET) process from a-MoO3 to MO. Therefore, a-MoO3 monolayers present high SERS performance due to the synergistic effect of electromagnetic enhancement (EM) and PIHET, proposing the EM-PIHET synergistic mechanism in a-MoO3. In addition, a-MoO3 possesses higher electron delocalization and electronic state density than crystal MoO3 (c-MoO3), which is conducive to the PIHET. The limit of detection (LOD) for o-aminoazotoluene (o-AAT) is 10-9 M with good uniformity, acid resistance, and thermal stability. In this work, trace detection and identification of various carcinogenic aromatic amines based on a-MoO3 monolayers is realized, which is of great significance for reducing cancer infection rates.

The influence of Leucidal, a natural cosmetic preservative, on fibroblast and keratinocytes. Studies on cells and on model membrane systems.

The aim of this work was to investigate the influence of Leucidal® Liquid (abbr. Leucidal), which is recommended as a natural cosmetic ingredient of antimicrobial properties, on model membranes of keratinocytes and fibroblasts. The toxicity tests on cell lines were also performed to allow for a more detailed discussion of the results. As model membrane systems the lipid Langmuir monolayers were applied. During the investigations, the surface pressure/area measurements, penetration studies and Brewster Angle Microscopy (BAM) visualization were performed for one component and mixed lipid monolayers. It was evidenced that at the membrane - corresponding conditions, the components of Leucidal do not penetrate either model keratinocyte and fibroblast membranes or one component films composed of the major lipids of skin cell membranes. Leucidal makes these systems slightly more expanded and less stable, however this is not reflected in the changes in the film morphology. Only the ceramide systems were sensitive to the presence of Leucidal, i.e. the incorporation of Leucidal components manifested well in the decrease of the films' condensation and alterations in their morphology. The tests on cells demonstrated that Leucidal is non toxic for these types of cells at the concentrations suggested by the producer. A thorough comparison of these results with those published for bacteria model membranes enabled us to discuss them in the context of the mechanism of action of Leucidal components. It was concluded that Leucidal components are of low affinity to the skin cellular model membranes of low content of Leucidal-sensitive ceramides and are not toxic for fibroblast and keratinocyte cell lines. Moreover, the lipid composition of the membrane and its molecular organization can be important targets for Leucidal components, decisive from the point of view of the activity and selectivity of the studied composition.

Using an amphiphilic diblock copolymer to understand the shear-induced structural transformation of bicontinuous microemulsions.

HYPOTHESIS: Amphiphilic diblock copolymers are known to increase the surfactant's efficiency to stabilize microemulsion, leading to higher structural order and monolayer rigidity. We thus seek to evaluate whether the addition of such polymers alters the shear behavior of bicontinuous microemulsions, in particular, their shear transformation towards lamellar structures. EXPERIMENTS: We examine the initial structure and shear response of bicontinuous /n-octane//PEP5-b-PEO5 microemulsions by coupling microfluidics with small-angle neutron scattering (SANS), attaining wall shear rates in excess of . The azimuthal analysis of the obtained 2D scattering patterns allows us to follow their structural transformation by means of the degree of anisotropy. FINDINGS: The amphiphilic diblock copolymer promotes the shear-induced transformation of bicontinuous microemulsions, resulting in up to ∼ higher degrees of anisotropy than for corresponding polymer-free microemulsions. The increased shear response observed with increasing polymer content is rationalized by combining the influence of domain size and viscosity with the stability limits of the bicontinuous microemulsion in the isothermal phase diagram. As a result, a consistent description of the degree of anisotropy is obtained, enabling the prediction of the shear-induced bicontinuous-to-lamellar transformation.