Single Particle Layer Research Articles

Control of Fine Structure in "Polymer Nanosphere Multilayered Organization" and Enhancement of Its Optical Property.

This paper reports on a new functionality exhibited by "polymer nanosphere multilayered organization", a new type of molecular organization, and the relationship between their structure and function. The polymer nanosphere multilayered organization is a fine structural material formed by the accumulation of single-particle layers of a hydrophobic polymer at the air/water interface; these single-particle layers have uniform height along the c-axis. By employing the "alternate compression-relaxation method", high-density, low-defect particle layers are formed with a clear increase in their crystallite sizes. In the case of a ternary comb copolymer containing a carbazole ring, one particle is formed by the assembly of approximately 60 units of collapsed monolayer-like double layers. This structure is stabilized by the formation of side-chain crystals in the interlayer, with oriented π-π stacking of carbazole rings, resulting in enhanced fluorescence emission intensity.

Creation of giant two-dimensional crystal of zinc oxide nanodisk by method of single-particle layer of organo-modified inorganic fine particles

In this study, the formation and structure of a single-particle layer of organo-zinc oxide are investigated using surface-pressure-area (π-A) isotherms, out-of-plane X-ray diffraction (XRD) analysis, and atomic force microscopy (AFM). Further, techniques for achieving the solubilization of inorganic fine particles in general solvents have been proposed, and a single-particle layer has been formed using such an inorganic solution as a “spreading solution” for an interfacial film. Surface modification of ZnO is performed using a long-chain carboxylic acid. Accordingly, a regular arrangement of ZnO can be easily achieved in order to overcome the relatively weak van der Walls interactions between inorganic materials. A condensed Langmuir monolayer of these particles is also formed. A multiparticle layered structure is constructed by the Langmuir–Blodgett (LB) technique. Out-of-plane XRD measurement results for a single-particle layer of organo-ZnO clearly show a sharp peak at 42Å. This peak is attributed to the distance between ZnO layers. The AFM image of this single-particle layer of organo-ZnO shows a particle assembly with a uniform height of 60nm. These aggregated particles form large two-dimensional crystals. In other words, a regular periodic structure along the c-axis and a condensed single-particle layer had been fabricated using Langmuir and LB techniques.

Fine structural analysis, formation of interfacial particle films, and accurate estimation of orientation in polyguanamine derivatives with a high refractive index

ABSTRACTPrecise analyses of the molecular arrangement of three‐dimensional crystals, two‐dimensional molecular films, and interfacial particle layers of polyguanamine derivatives with a high refractive index have been performed. The high refractive index of the polyguanamine derivatives is not due to the chemical structure of the molecule, but is based on the packing of molecular chains or the refraction of transmitted light due to the difference in electron density between the crystalline and amorphous regions. A highly crystalline polymer has been produced by polycondensation of guanamine derivatives bearing a triazine ring and phenyl rings. The packing models of molecular chains in the three‐dimensional crystal have been determined using wide‐angle X‐ray diffraction measurements and reciprocal lattice analysis. Highly hydrophobic polyguanamine derivatives undergo a transition from monolayer to single particle layer at the air/water interface. The π‐conjugated molecular plane in the two‐dimensional films is densely stacked. Multiparticle layers are formed with a highly ordered layered structure. Polymer nanoparticles are formed by the integration of units of the collapsed polymer monolayer folded along the height direction. Since this folding occurs within the amorphous region, formation of fine particles with a high refractive index and their integrated films with densely packed π‐conjugated planes is feasible. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 999–1009

Creation of high-density and low-defect single-layer film of magnetic nanoparticles by the method of interfacial molecular films.

A technique to solubilize fine magnetic inorganic particles in general organic solvents is proposed via surfaces modification by long-chain carboxylic acids. This organic modification should overcome the relatively weak van der Waals interactions between the nanoparticles, allowing the formation of ordered arrangements of the modified Fe3O4 and CoFe2O4 materials. Using nanodispersions of these organo-modified magnetic nanoparticles as "spreading solutions", Langmuir monolayers of these particles were formed. Multiparticle layered structures were constructed by the Langmuir-Blodgett (LB) technique. The fabrication of single- and multiparticle layers of organo-modified magnetic nanoparticles was investigated using surface pressure-area (π-A) isotherms, out-of-plane X-ray diffraction (XRD), in-plane XRD, and atomic force microscopy (AFM). The out-of-plane XRD profile of a single-particle layer of organo-modified Fe3O4 clearly showed a sharp peak which was attributed to the distance between Fe3O4 layers along the c-axis. The AFM image of single-particle layer of organo-modified CoFe2O4 revealed integrated particle organization with a uniform height; these aggregated particles formed large two-dimensional crystals. For both nanoparticle species, regular periodic structures along the c-axis and high-density single-particle layers were produced via the Langmuir and LB techniques.

The role of modifying molecular chains in the formation of organized molecular films of organo-modified nanodiamond: construction of a highly ordered low defect particle layer and evaluation of desorption behavior of organic chains.

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.

Colloid-probe AFM studies of the interaction forces of proteins adsorbed on colloidal crystals.

In recent years, colloid-probe AFM has been used to measure the direct interaction forces between colloidal particles of different size or surface functionality in aqueous media, as one can study different forces in symmerical systems (i.e., sphere-sphere geometry). The present study investigates the interaction between protein coatings on colloid probes and hydrophilic surfaces decorated with hexagonally close packed single particle layers that are either uncoated or coated with proteins. Controlled solvent evaporation from aqueous suspensions of colloidal particles (coated with or without lysozyme and albumin) produces single layers of close-packed colloidal crystals over large areas on a solid support. The measurements have been carried out in an aqueous medium at different salt concentrations and pH values. The results show changes in the interaction forces as the surface charge of the unmodified or modified particles, and ionic strength or pH of the solution is altered. At high ionic strength or pH, electrostatic interactions are screened, and a strong repulsive force at short separation below 5 nm dominates, suggesting structural changes in the absorbed protein layer on the particles. We also study the force of adhesion, which decreases with an increment in the salt concentration, and the interaction between two different proteins indicating a repulsive interaction on approach and adhesion on retraction.

Formation and structure of fine multi-particle layered organo-modified zirconium dioxides fabricated by Langmuir–Blodgett technique

Formation and structure of multilayered organization of organo-modified zirconium dioxide are investigated by surface pressure–area (π–A) isotherms, out-of-plane and in-plane X-ray diffraction (XRD) analysis, and atomic force microscopy (AFM). In this study, solubilization technology of inorganic fine particles into general solvent has proposed and formation technology of highly ordered single-particle layer has also established by using that inorganic solution as “spreading solution” of the interfacial film. The surface modification of zirconia particles is performed using several long-chain carboxylic acids of different lengths. Accordingly, it is easily achieve a regular arrangement of ZrO2 particles to overcome the relatively weak van der Waals interactions between the inorganic materials. A Langmuir monolayer of these particles is extremely condensed. A multi-particle layered structure is constructed by the Langmuir–Blodgett (LB) technique. The out-of-plane XRD measurement of multilayered organization of stearate-modified ZrO2 particles confirms sharp peaks at 59Å. AFM images on a mesoscopic scale of this single-particle layer of stearate-modified ZrO2 show the aggregate of particles with 50nm diameters. However, fine particles with ∼5nm diameter are confirmed from high-resolution AFM observations in the case of single-particle layers transferred at low surface pressure. That is to say, a regular periodic structure along the c-axis and a hierarchical aggregated particle form are fabricated by Langmuir and LB techniques.

Elucidation of Internal Fine Structure of "Polymer Nanosphere" in the Interfacial Particle Film

Transition behavior from a monolayer on the water surface to a single particle layer of a ternary comb copolymer with highly hydrophobic carbazole units and both hydrogenated and fluorinated side-chains have been investigated by surface pressure−area (π−A) isotherm and atomic force microscopic (AFM) observation. Moreover, we fabricated a polymer nanosphere multilayered organization consisting of such polymer nanoparticles by the Langmuir–Blodgett (LB) technique, and estimated the particle arrangement by performing out-of-plane X-ray diffraction (XRD) analysis. This polymer monolayer is able to form the polymer nanosheet with amorphous layers. The multiparticle layered organization of polymer nanosphere is fabricated from the single particle layer by the LB technique. These layer structures have highly regular arrangement along the c-axis. Further, we investigated molecular arrangement inside of polymer particles by performing in-plane XRD analysis and fluorescence spectroscopy. This copolymer formed side-chain crystals inside the particles. Fluorocarbon chains had a short spacing of 5.0 A for the two-dimensional side-chain lattice whereas hydrocarbon chains formed sub-cell at short spacing of 4.2 A. In addition, aggregated structure of carbazole rings is formed by π-π interaction.

Formation and Structure of Single Particle Layer Induced to Construction of New Type Two-dimensional Organic / Inorganic Nanohybrids

Formation and Structure of Single Particle Layer Induced to Construction of New Type Two-dimensional Organic / Inorganic Nanohybrids

Fabrication and structure of “polymer nanosphere multilayered organization”

We constructed a multiparticle layered organization of aromatic polyamides with rigid main chains and flexible side chains by the Langmuir–Blodgett (LB) technique, which resulted in a highly regular arrangement along the c-axis. The particle arrangement was estimated by performing out-of-plane X-ray diffraction (XRD) analysis and atomic force microscopic (AFM) observation. The results suggest that a double-particle layered structure (Y-type) is formed by the LB technique, forming amphiphilic particles at the air/water interface. Copolymers with highly hydrophobic carbazole contents and both hydrogenated and fluorinated side-chains also formed a single-particle layer at the air/water interface and exhibited multiparticle layers by a LB technique. Therefore, it is possible to control the formation of single- and double-particle layered structure using these techniques. Further, it was found that multiparticle layered organization of polymer nanospheres and polymer nanosheets could be formed simultaneously with the same component material.

Ring deposition of drying suspension droplets

Deposition of colloidal particles in a drying droplet is important in many scientific researches and technological applications. In this work, the ring deposition of drying droplets on a solid substrate is investigated experimentally at a microscopic level. A ring deposition is formed at the contact line as the water solution droplet containing SiO2 particles is drying, just like the formation of coffee ring. Contact line pinning is crucial to the ring deposition formation. There will be a replenish flow in the droplet towards the edge, and the particles are driven to the contact line, deposited on the substrate. As the particle mass fraction is large, the particles which are left inside the spot, when the droplet dries out, may form a single particle layer, packing in order. The contact angle of the droplet on glass substrate is very small, the SiO2 particles will gather at the rim of the droplet, which initially form a chain along the contact line. As more particles come to the rim, they are deposited in a line by line way to form a 2D close packing. Since the contact angle decreases with evaporation when the contact line is pinned, a capillary force between liquid surface and particles arises once the height of droplet surface near the contact line is lower than that of the particle, pushing the particles to move inward. The effect on the larger particles is more pronounced-it even leads to a separation of the particles, with the smaller ones at the outer side.

Fabrication and Structural Estimation of “Polymer Nanosphere Multilayered Organization”

We have newly constructed “multi-particle layered organization” of aromatic polyamide (poly-(N- alkylated benzamide), abbrev . PABAn , n : carbon number of side-chains) derivatives having both a rigid main chain and a flexible side chains by a Langmuir-Blodgett (LB) technique. This organization is composed of the build-up particle layers with highly regular arrangement along the c -axis. The particle arrangement of this organization of polymer nanosphere was estimated by performing out-of plane X-ray diffraction (XRD), and atomic force microscopic (AFM) observation. In addition, it is also proposed that ternary comb copolymers with carbazole units and both hydrogenated and fluorinated side-chains are candidates of newly typed “polymer nanosheet” material. These copolymers with high hydrophobic carbazole contents also formed single particle layer at air/water interface and “multi-particle layered organization” was constructed by a LB technique. Therefore, it was found that “multi-particle layered organization of polymer nanosphere” and “polymer nanosheet” are simultaneously formed by same component copolymer materials with hydrophobic carbazole units.

Morphological Control of Gold Nanoparticle Aggregates via Photoisomerization of Azobenzene Liquid Crystals

Gold nanoparticles having a monolayer of azobenzene liquid crystals (LCs) were synthesized and their aggregation structures on solid surfaces were observed. The gold nanoparticles formed a single-particle layer on bare mica and mica with a polyimide layer. We demonstrated that the morphology of the gold nanoparticle aggregates could be controlled by UV light irradiation at 366 nm; the mass transfer of gold nanoparticles from the exposed area to the nonexposed area was induced by the isomerization of azobenzene LC molecules.

Morphological Transition from Nanosheet to Nanosphere in Ternary Comb Copolymers with Carbazole Rings

Abstract The transition behavior of ternary comb copolymers containing carbazole rings from a monolayer on a water surface to a single particle layer has been investigated by surface pressure–area isotherms and atomic force microscopy. It has been found that these copolymers form a monolayer in the low-surface-pressure region and a single particle layer in the high-surface-pressure region.

Morphological Transition from Nanosheet to Nanosphere of Ternary Comb Copolymers with Carbazole Rings Induced by an Increase in Surface Pressure

Fax: +81-48-858-3503, e-mail: fujimori@fms.saitama-u.ac.jp Transition behavior from a monolayer on the water surface to a single particle layer of a ternary comb copolymer containing carbazole rings have been investigated by surface pressure-area isotherm, atomic force microscopy, X-ray diffraction. This polymer monolayer is able to form the “polymer nanosheet” with amorphous layers and strong interaction between main-chains prepared by the Langmuir-Blodgett (LB) technique. Further, the single particle layer is able to form the multi-particle layered organization of “polymer nanosphere” by the LB technique. This ternary comb copolymers were synthesized by radical copolymerization with hydrogenated and fluorinated long-chain vinyl compounds. Poly(N-vinylcarbazole) homopolymer formed a single particle layer on the water surface immediately after spreading. Spontaneous “particulation” behavior is accelerated by incorporation of carbazole units in ternary copolymer films. Organized molecular film of these copolymers formed a monolayer on the water surface below 10 m Nm

Probing Ag nanoparticle surface oxidation in contact with (in)organics: an X-ray scattering and fluorescence yield approach

Characterizing interfacial reactions is a crucial part of understanding the behavior of nanoparticles in nature and for unlocking their functional potential. Here, an advanced nanostructure characterization approach to study the corrosion processes of silver nanoparticles (Ag-Nps), currently the most highly produced nanoparticle for nanotechnology, is presented. Corrosion of Ag-Nps under aqueous conditions, in particular in the presence of organic matter and halide species common to many natural environments, is of particular importance because the release of toxic Ag(+) from oxidation/dissolution of Ag-Nps may strongly impact ecosystems. In this context, Ag-Nps capped with polyvinolpyrrolidone (PVP) in contact with a simple proxy of organic matter in natural waters [polyacrylic acid (PAA) and Cl(-) in solution] has been investigated. A combination of synchrotron-based X-ray standing-wave fluorescence yield- and X-ray diffraction-based experiments on a sample consisting of an approximately single-particle layer of Ag-Nps deposited on a silicon substrate and coated by a thin film of PAA containing Cl revealed the formation of a stable AgCl corrosion product despite the presence of potential surface stabilizers (PVP and PAA). Diffusion and precipitation processes at the Ag-Nps-PAA interface were characterized with a high spatial resolution using this new approach.

Surface Morphological Changes in Monolayers of Aromatic Polyamides Containing Various N-Alkyl Side Chains

We synthesized new aromatic polyamides (poly-(N-alkylated benzamides), abbrev. PABA(n)) having both a rigid main chain and a flexible side chain with different lengths. We investigated the solid-state structures, that is, the molecular orientation and surface morphology, of organized molecular films of PABA(n) by performing surface pressure-area (pi-A) isotherm, in-plane and out-of plane X-ray diffraction (XRD), polarized infrared spectroscopy, and atomic force microscopy (AFM) measurements. The solid-state structure of poly-(N-methyl benzamide) (PABA(1)) belonged to the monoclinic system, whereas PABA(3), PABA(4), and PABA(5) showed an orthorhombic packing pattern. PABA(7) and PABA(8) formed amorphous polymers. In the case of PABA(17), a two-dimensional hexagonal lattice was formed as a subcell consisting of side chains. These polymer monolayers were highly condensed on a water surface at 15 degrees C. Out-of-plane XRD measurement results showed that the PABA(1), PABA(3), PABA(4), and PABA(5) multilayers showed large periodicities of 50-60 A. From AFM observation results, it was found that these aromatic polyamides formed single particle layers of hydrophilic groups localized at the bottom of the particles. On the other hand, PABA(7) and PABA(8) monolayers showed irregularity and exhibited shapeless morphologies. In addition, an organized molecular film of PABA(17) formed a highly ordered layer structure (periodicity of 30 A) and a giant circular domain (diameter of 20 nm) made of a side chain crystal. The PABA(17) monolayer showed a hexagonal packing pattern formed due to van der Waals interaction between the flexible side chains. From these experimental findings, it was concluded that the polymer synthesis method employed in the present study can be directly used to control the crystal structure (the third order structure of polymers), molecular arrangement, and surface morphologies of polymer monolayers.

Investigation of Surface Properties of Soil Particles and Model Materials with Contrasting Hydrophobicity Using Atomic Force Microscopy

Surface images and force measurements obtained using atomic force microscopy (AFM) were used to assess the hydrophobicity of particles from soils and model soil material (smooth glass and acid-washed sand (AWS) exposed to soil-derived humic acid (HA) or lecithin (LE)). Height and phase images, and phase distributions (from soil particles) show complex morphology and heterogeneously distributed organic matter. Forces at model surfaces indicate that, in air, reduction in adhesion corresponded with increased hydrophobicity, but in water, corresponded with a decrease (and serve to guide interpretation of data from natural particles). Adhesion forces on hydrophobic soil particles in water were larger than those for hydrophilic ones, but surface roughness and complexity may obscure any opposite trend for measurements in air. Combination of force measurements, applied forthe first time to soil particles, together with those on model surfaces, and independent assessments of hydrophobicity of corresponding single particle layers, indicate good, but not consistent qualitative agreement between hydophobicity at bulk and nanoscales. AFM is likely to facilitate detailed evaluation of soil particle surface hydrophobicity, which contributes to bulk wetting behavior of soils and other porous systems, including assessments of the potential for contributons to supehydrophobicity from surfaces at the micro- and nanoscales.

Colloidal Hard-Sphere Crystal Growth Frustrated by Large Spherical Impurities

Impurities affect the nucleation, growth, and structure of crystals. Here we report the effect of large, spherical, polymethylmethacrylate impurities on the crystal growth of monodisperse, hard, polymethylmethacrylate colloids in a density- and optically matching apolar solvent mixture. Crystal growth, initiated at the bottom of the sample, was studied by imaging sequences of two-dimensional xy slices in the plane of the impurity's center with a laser scanning confocal microscope. Impurities form the center of grain boundaries, and a single fluid particle layer around the impurity persists in all cases. The growth rate sensitively depends on the impurity's size. Crystal growth is inhibited to a greater extent near smaller impurities, pointing to local crystal frustration induced by the curvature of the impurity.

Heterogeneous Uptake of Gaseous Nitric Acid on Dolomite (CaMg(CO3)2) and Calcite (CaCO3) Particles: A Knudsen Cell Study Using Multiple, Single, and Fractional Particle Layers

In this study, the heterogeneous uptake of gaseous nitric acid on dolomite, CaMg(CO3)2, and calcite, CaCO3, particles under dry conditions at 296 K was investigated. A Knudsen cell reactor was used to measure heterogeneous uptake coefficients for these reactions. Several different experiments were performed including those on many, single, and fractional layers of particles. For experiments using multiple particle layers, the Knudsen cell data were modeled to take into account gas diffusion into the underlying layers of the sample. From this analysis, initial heterogeneous uptake coefficients, gamma(o,t), were determined to be (5 +/- 2) x 10(-4) and (2 +/- 1) x 10(-3), for dolomite and calcite, respectively, at a nitric acid concentration of 6.5 x 10(10) molecules cm(-3). For experiments that employed single or fractional particle layers, the initial heterogeneous uptake coefficient was analyzed using a recent method described in the literature. Values of the initial heterogeneous uptake coefficient using this analysis were in agreement with the above analysis and determined to be (7 +/- 4) x 10(-4) and (2 +/- 0.4) x 10(-3) for CaMg(CO3)2 and CaCO3, respectively. In addition, these results are compared to previous literature values.