Interfacial Media Research Articles

Self-Assembly of Functional Organic Chromophores

Aggregate structures of organic chromophores strongly affect their properties and so has become an active area of research. Self-assembly and supramolecular methods present important means to influence aggregation processes, and these have become active areas of research. We have studied the self-assembly of differently structured chromophore molecules with emphasis on porphyrins,1 pyrazinacenes,2 hexabenzocoronenes (HBC) and oligophenylenes (such as sexiphenyl), and the various methods of doing this including molecular design, surface assembly (under ambient or UHV conditions), and using interfacial media such as in the Langmuir and Langmuir-Blodgett techniques. For the latter, we have applied principles of amphiphilicity to generate on-interface structures,3 which can be lifted as multilayered films and exploited for the preparation of electronic devices.4 In this work, we will describe the self-assembly properties based on precipitation/gelation, assembly at solid surfaces, and interactions at an air-water interface. We will emphasize the molecular structure as a key feature including the effects of π-π stacking, conformational flexibility and amphiphilicity. Self-assembly and supramolecular techniques stand out as the most effective methods for obtaining nanomaterials having the molecule-level definition of structure important for any applications of the resulting materials.

Mechanisms of the copper third body as an interfacial media on copper matrix friction materials with different compositions

PurposeThis paper aims to reveal the effects of the copper third body on different copper matrix friction materials with a novel experimental way called “exogenous powder.”Design/methodology/approachAn accurate adding device of exogenous copper powder was designed to control the flow rate. The tribological properties with and without exogenous copper powder were investigated by a pin-on-disc tribometer during dry sliding.FindingsExperimental results indicate that the Cu addition tends to increase the friction coefficient. For pure Cu material, the exogenous copper third body exhibits poor fluidity on the friction surface, causing serious adhesive wear on the friction interface. For the Cu 90% + 10% Gr material, the plasticity of exogenous copper powder may intensify the deformation of the third body of the surface, presenting layered accumulation distribution. For the pure Cu and Cu 95% + 5% SiO2 material, the Cu addition makes the composition and density of the third body uneven in the direction of depth.Originality/valueThe role of the copper component on different materials is revealed from a new perspective, and the relationship between the third body structure and the friction properties is explored.

Water and Ion Dynamics in Confined Media: A Multi-Scale Study of the Clay/Water Interface

This review details a large panel of experimental studies (Inelastic Neutron Scattering, Quasi-Elastic Neutron Scattering, Nuclear Magnetic Resonance relaxometry, Pulsed-Gradient Spin-Echo attenuation, Nuclear Magnetic Resonance Imaging, macroscopic diffusion experiments) used recently to probe, over a large distribution of characteristic times (from pico-second up to days), the dynamical properties of water molecules and neutralizing cations diffusing within clay/water interfacial media. The purpose of this review is not to describe these various experimental methods in detail but, rather, to investigate the specific dynamical information obtained by each of them concerning these clay/water interfacial media. In addition, this review also illustrates the various numerical methods (quantum Density Functional Theory, classical Molecular Dynamics, Brownian Dynamics, macroscopic differential equations) used to interpret these various experimental data by analyzing the corresponding multi-scale dynamical processes. The purpose of this multi-scale study is to perform a bottom-up analysis of the dynamical properties of confined ions and water molecules, by using complementary experimental and numerical studies covering a broad range of diffusion times (between pico-seconds up to days) and corresponding diffusion lengths (between Angstroms and centimeters). In the context of such a bottom-up approach, the numerical modeling of the dynamical properties of the diffusing probes is based on experimental or numerical investigations performed on a smaller scale, thus avoiding the use of empirical or fitted parameters.

Strengthening and Toughening Hierarchical Nanocellulose via Humidity-Mediated Interface.

Undoubtedly humidity is a non-negligible and sensitive problem for cellulose, which is usually regarded as one disadvantage to cellulose-based materials because of the uncontrolled deformation and mechanical decline. But the lack of an in-depth understanding of the interfacial behavior of nanocellulose in particular makes it challenging to maintain anticipated performance for cellulose-based materials under varied relative humidity (RH). Starting from multiscale mechanics, we herein carry out first-principles calculations and large-scale molecular dynamics simulations to demonstrate the humidity-mediated interface in hierarchical cellulose nanocrystals (CNCs) and associated deformation modes. More intriguingly, the simulations and subsequent experiments reveal that water molecules (moisture) as the interfacial media can strengthen and toughen nanocellulose simultaneously within a suitable range of RH. From the perspective of interfacial design in materials, the anomalous mechanical behavior of nanocellulose with humidity-mediated interfaces indicates that flexible hydrogen bonds (HBs) play a pivotal role in the interfacial sliding. The difference between CNC-CNC HBs and CNC-water-CNC HBs triggers the humidity-mediated interfacial slipping in nanocellulose, resulting in the arising of a pronounced strain hardening stage and the suppression of strain localization during uniaxial tension. This inelastic deformation of nanocellulose with humidity-mediated interfaces is similar to the Velcro-like behavior of a wet wood cell wall. Our investigations give evidence that the humidity-mediated interface can promote the mechanical enhancement of nanocellulose, which would provide a promising strategy for the bottom-up design of cellulose-based materials with tailored mechanical properties.

Nanoarchitectonics for Coordination Asymmetry and Related Chemistry

Abstract Nanoarchitectonics is a concept envisioned to produce functional materials from nanoscale units through fusion of nanotechnology with other scientific disciplines. For component selection, coordination complexes with metallic elements have a wider variety of element selection because metallic elements cover ca. 80% of the periodic table of the elements. Application of nanoarchitectonics approaches to coordination chemistry leads to huge expansion of this concept to a much wider range of elements. Especially, coordination asymmetry strategy architects asymmetrical and/or chiral structures and/or electronic states through formation of metal coordination complexes, leading to functional material systems in certain anisotropy and selectivity. This review article presents expansion of the nanoarchitectonics concept to coordination asymmetry through collecting recent examples in the field of coordination asymmetry. Introduced examples are classified into several categories from various viewpoints: (i) basic molecular and material designs; (ii) specific features depending on interfacial media, space and contact with bio-functions; (iii) functions; (iv) supporting techniques such as analyses and theory.

Methods with Nanoarchitectonics for Small Molecules and Nanostructures to Regulate Living Cells

AbstractAmong all kinds of functional systems and mechanisms, living cells may be regarded as the most advanced functional material systems. Creation of cell‐like highly functional systems can be an ultimate goal of nanoarchitectonics research. Although full construction of cell‐like functional objects may not be going to happen anytime soon, controls of living cells by small molecules and their nanoarchitected assemblies can be accomplishable research subjects. Nanoarchitectonics approaches are helpful for small molecules and nanostructures to regulate living cells. In this review article, several examples in cell regulation with bio‐related molecules and cell regulation with the aid of external stimuli such as electronic and photonic stimuli are first exhibited. Following these examples, controls of cell alignments and differentiations at extremely different interfacial media, the surface with hard nanocarbon structures, and completely soft liquid–liquid interface, are discussed. Especially, interaction at contacting external surface can trigger integrated relayed processes within living cells which may finally alter cellular behaviors and eventually guide stem cell differentiation. Surface designing by interfacial nanoarchitectonics can be a crucial key in regulation of living cells. It can lead to technology connection between surface nanofabrication and tissue engineering and cell‐based technology.

Frontispiece: 2D Nanoarchitectonics: Soft Interfacial Media as Playgrounds for Microobjects, Molecular Machines, and Living Cells

Frontispiece: 2D Nanoarchitectonics: Soft Interfacial Media as Playgrounds for Microobjects, Molecular Machines, and Living Cells

Molecular Tuning Nanoarchitectonics for Molecular Recognition and Molecular Manipulation

AbstractAlthough forefront research fields on molecular machineries and nano‐manipulation have been developed, their current achievements stay mostly in basic science and are far from practical usages in daily life. In this short review, interfacial nanoarchitectonics for structural and functional tuning of molecular machines, molecular receptors, and related molecular objects is conceptually overviewed towards possible applications. As their typical functions, regulation methods of molecular recognitions and the other functions in three mode, (i) fixed structure mode, (ii) switching mode, and (iii) tuning mode, are mainly discussed. The exemplified facts reveal great possibilities in molecular tuning at interfaces. The functional molecules immobilized at interfacial media can be manipulated in relation with macroscopic human motions, which would be one of the promising ways to use molecular‐level functions in life‐related activities.

Supramolecular nanoarchitectonics for functional materials

Nanoarchitectonics has been paid much attention as an emerging concept to architect functional materials from molecular and nanounits through the combination of nanotechnology-oriented strategies and supramolecular-chemistry-like methodologies. This perspective article aims to figure out important keys for materials nanoarchitectonics. In the initial part, recent trends in materials nanoarchitectonics upon supramolecular self-assembly are overviewed. The overview processes extract several key words including dynamic natures, dimensional controls, and interfacial processes according to the following sections: (i) preparation of assembled structures and conversion into nanostructured materials, (ii) dynamic structural transformation to hierarchic materials, and (iii) material preparation and functions with dynamic flows at interfacial media. Not limited to the material production, dynamic processes at the interface can be also connected with forefront functions such as tuning of molecular receptors and mechanical controls. This perspective article can conclude that fabrication of functional materials and controls of nanosystems would be well-considered on the basis of these three key terms.

Fabrication and optical properties of nanostructured plasmonic Al2O3/Au–Al2O3/Al2O3 metamaterials

Discontinuous multilayer (DML) thin films, which consist of nano-granular metals (NGMs) embedded in a dielectric matrix, have attracted significant interest as engineered plasmonic metamaterials. In this study, a systematic layer-by-layer deposition of three-dimensional sub-wavelength periodic plasmonic DML structures via the radio frequency sputtering of a composite target has been reported. The overall optical response of the DML films composed of Au–Al2O3 NGM homogenous layers, which are periodically sandwiched between two amorphous Al2O3 layers, are studied using reflection spectroscopic ellipsometry and transmission spectroscopy techniques. By applying the analytical optical approaches based on multiple Gaussian oscillators, ambient DML sub-wavelength structures have been successfully modeled. As a result, the effects of the size and shape of the Au nanoparticles as well as of the surrounding and interfacial media on their localized surface plasmon resonance (LSPR) are elucidated, and the related films thickness and effective optical constants are determined. Interestingly, during the examination of resonance frequencies and dielectric functions, the obtained DML structures exhibit unusual characteristics that are different from those of their NGM constituents due to the electromagnetic interactions of the NGM layers with the LSPR, which represent metamaterial features.

Pin-on-disc tribotests with the addition of Cu particles as an interfacial media: Characterization of disc tribosurfaces using SEM-FIB techniques

The present paper focuses on the effect of Cu addition (400μm, 20μm and 50nm) on the microstructure and topography of discs after pin-on-discs tribotests (steel/steel). These results were compared with the condition without any particulate addition. SEM, FIB, EDS and XEDS techniques were used to characterize the discs’ tribosurfaces. X-ray mapping characterization showed O associated with Fe adhered to the tribosurfaces for all conditions. Additionally, expressive adhesion of Cu particles on the disc tribosurface was detected via FIB combined with XEDS mapping for the 20μm and 50nm conditions. The formation of a compact iron oxide layer on the discs´ tribosurface was only observed for the 400μm Cu condition and without any Cu addition.

Failure analysis as a tool to optimize the design of a ring on disc tribotest investigating the role of surface roughness

The influence of the surface roughness of pearlitic grey cast iron discs on the formation of tribofilms and the evolution of the friction coefficient during a ring on disc tribotest with the addition of magnetite and magnetite–graphite nanopowders as interfacial media was investigated. The roughness parameters of the cast iron discs were varied by electro discharge machining (EDM) and grinding processes, producing four distinct surface roughness conditions. The evolution of the friction coefficient, however, did not reach the steady state for most of the samples and the role of the surface roughness on the friction coefficient could not be identified. Focused ion beam (FIB) microscopy on the cast iron discs was carried out to investigate the microstructure of the discs near the tribosurface. These results showed that the EDM process not only varied the surface roughness, but also changed the microstructure of the cast iron discs, promoting the incipient fusion of the cast iron surface, with the formation of ridges and casting defects (pores). As a result, a layer of rapidly solidified metal with a dendritic microstructure was formed near to the surface of the EDMed discs.

“Chessboard” effect and mass transfer in interfacial media of organic and inorganic nature

The paper reviews our previous research work on the origin of mass transfer through interfaces of solids and biological membranes. Using the thermodynamic approach of physical mesomechanics we conclude that the propagation of transport flows through interfaces and membranes in organic and inorganic nature is based on structural phase transformations in nanostructural states at interfaces of heterogeneous media. Such states arise at interfaces and in membranes under a chessboard-like distribution of stresses, strains and chemical potentials of components of conjugated dissimilar media. The practical applications of the developed approach in biology and modern materials science are considered.

Influence of the State of Interfaces on the Character of Local Displacements in Fault-Block and Interfacial Media

We have studied the possibility of producing a directed action upon the process of local stress relaxation in interfacial media occurring in a complex stressed state by changing the state of boundaries between structural elements. The experiments were performed on the ice sheet of Lake Baikal, which represents a hierarchically organized fault-block structure and belongs to the class of interfacial media. It is shown that, by changing the state of boundaries between structural elements, it is possible to influence the regime of deformation of the interfacial medium as a whole. The general features of the observed effect are confirmed within the framework of a theoretical model.