Planar Nanoparticles Research Articles

Two-state nanocomposite based on symmetric diblock copolymer and planar nanoparticles: mesoscopic simulation

A method for controlling the distribution and orientation of 2D fillers in the copolymer matrix is presented.

Polymer Composites Based on Polylactide-Containing Various Kinds of Carbon Nanofillers

Filled nanocomposites of polylactide with graphite nanoplates (GNPs) and reduced grapheneoxide (RGO) are prepared by liquid-phase synthesis. A comparative study of the mechanical, electric, andthermophysical characteristics of the compositions depending on the nature of the nanofillers is carried out.An insignificant difference in the mechanical parameters of the compositions containing GNPs and RGO asfillers is established. At the same time, when studying the electrical properties, it is found that the use of RGOas a filler leads to the production of composites with a lower percolation threshold of the flow than in the caseof GNPs and increased conductivity. The differential scanning calorimetry (DSC) method shows that compositionscontaining GNPs as a filler have a higher degree of crystallinity in comparison with similar compositionscontaining RGO. This is caused by the structure of the filled compositions, which influences thenucleation rate of polylactide (PLA) crystallites on the surface of ordered planar nanoparticles of the GNPsand imperfect RGO particles. Thus, the use of different carbon nanofillers may promote the production ofcompositions that differ in their characteristics.

Nonlinear-optical microscopy of asymmetric-shaped nanoantennas

Arrays of metal nanostructures have attracted much interest due to their unique potential as optical nanoantennas and nanosensors. Here we use the second harmonic generation (SHG) microscopy technique for the studies of the nonlinear optical (NLO) response of cobalt nanoparticles of triangular and trapezoid shapes separated from a Py/Si3N4 film by a 1.5 nm thick MgO spacer. We demonstrate that the nonsymmetric elongated shape of planar nanoparticles along with the strong light localization effects result in the enhancement of the NLO response, including SHG and two-photon fluorescence. We also demonstrate that the efficiency of the SHG in nanoparticles is rather sensitive to the polarization of the incident laser beam, the visibility of the nanostructures in the nonlinear microscopy images being the highest for the linear polarization of the laser beam.

Solution deposition conditions influence the surface properties of 3-mercaptopropyl(trimethoxysilane) (MPTS) films

The deposition of organosilanes onto semiconducting and metal oxide surfaces is a versatile approach to impart corrosion resistance or provide a site for the subsequent immobilization of a range of molecules. Organosilane deposition is however, quite a complex process, with many factors influencing the film properties. Here, we investigated the deposition of 3-mercaptopropyl(trimethoxysilane) (MPTS) in organic solvents on Si substrates with various post-deposition treatments and subsequently characterize film properties using surface analytical techniques including ellipsometry, X-ray photoelectron spectroscopy (XPS), static water contact angles, and attenuated total reflection Fourier transform infra-red (ATR-FTIR) spectroscopy. Condensation of MPTS onto Si surfaces was most efficient in more anhydrous and hydrophobic solvents such as toluene, with monolayer thickness values (≈0.77 nm) being observed at MPTS concentrations of 0.08–1% (v/v), whereas all thickness values were seen to be below monolayer coverage when deposition was carried out in ethanol, regardless of the concentration used. It was found that the shortcomings of ethanol deposition can be overcome by applying a pre-hydrolysis period at low pH to achieve similar film thicknesses and properties compared to toluene at shorter deposition times - which is important when functionalization needs to be carried out in plastic consumables. Moreover, with minimal post-deposition treatments it was found that controllable film thicknesses can also be achieved with a high-retention of thiol functional groups which is evidenced by a clear S 2p XPS peak at a binding energy of 164.0 eV. However, these films will only be loosely bound to the surface and be lost upon further treatments. Overall, the procedures developed are important for many applications such as biomolecule immobilization, and the functionalization of planar substrates and nanoparticles, where the organosilane thickness, degree of order, reactivity and surface concentration of thiols influence film functionality.

Molecular Dynamics Study of Melting Behavior of Planar Stacked Ti–Al Core–Shell Nanoparticles

Selective laser sintering (SLS) is one of the most commonly used methods in additive manufacturing, due to its high prototyping speed and applicability to various materials. In the present work, molecular dynamics (MD) simulations were performed to study the thermodynamic behaviors of the planar stacked nanoparticles (NPs) model and explore the potential capability of the SLS process with nano-sized metal powders in the zero-gravity space environment. A multi-particle model of titanium–aluminum (Ti–Al) core–shell NP with a particle radius of 50 Å was constructed to investigate the characteristics of the melted pattern during sintering. Two patterns with different spatial densities were considered to study the influence of particle stacking on the melting process. Various core volume fractions and heating rates were examined to investigate their effects on the quality of the final sintered product. The stacked-NPs models with core volume fractions (CVFs) of 3%, 12%, and 30% were linearly heated up to 1100 K from room temperature (298 K) with heating rates of 0.04, 0.2, 0.5, and 1.0 K ps−1. The initial fusion temperature and final sintering temperature for each stacking pattern were obtained via the validation from the radial distribution function, mean squared displacement, and the radius of the gyration analysis. The 30% CVF yields the largest neck size before the melting point, while beyond the melting point, a larger core helps delay the formation of the fully-melted products. It is observed that using the close-packed stacked-NPs model under a slow heating rate (long melting duration) would help form a stable, completely sintered product with a relatively low final sintering temperature.

Use of nanofluids based on carbon nanoparticles to displace oil from the porous medium mode

Understanding the interaction mechanisms between graphene nanoparticles (GNs) and oil molecules is crucial for successful oil recovery. Numerous studies have shown that nanofluids, and in particular nanofluids (NF) from the graphene family (GNF), are suitable candidates for enhanced oil recovery in various reservoirs. Increased oil recovery from nanofluid injection is attributed to changes in wettability, decreases in interfacial tension and changes in viscosity. Therefore, knowing the mechanisms that influence the viscosity of the GNF is an urgent task of modern science, both fundamental and applied. A comprehensive study of the molecular interaction between graphene nanoparticles and hydrocarbon oil molecules was carried out in order to understand the mechanisms that affect the viscosity of nanofluids. The paper presents the results of a study of the rheological properties of oil with different content of graphene nanoparticles in it. At low concentrations of graphene nanoparticles, a 10%-17% decrease in the dynamic viscosity of the base fluid was observed. It is also shown that the relative viscosity is affected not only by the concentration, but also by the temperature. Thus, for the mass fraction of graphene nanoparticles wt = 0.5 × 10-3% and temperature T = 50 °C, a maximum viscosity reduction of 17% is observed. By increasing the concentration of graphene nanoparticles from wt = 5 × 10-3% and more, the oil shows the rheological properties of nanofluid. Based on the data obtained by computer simulation and direct observation of self-assembly of graphene nanoparticles and hydrocarbon molecules of oil, a mechanism has been proposed to explain the reason for the decrease of viscosity of nanofluid at low concentrations of nanoparticles. It was also shown that this nanofluid behavior is mainly possible for hydrocarbon liquids as base fluid and planar graphene nanoparticles.

Resolving Chemical Gradients Around Seagrass Roots—A Review of Available Methods

Steep geochemical gradients surround roots and rhizomes of seagrass and protect the plants against the harsh conditions in anoxic sediment, while enabling nutrient uptake. Imbalance of these gradients, due to e.g., low plant performance and/or changing sediment biogeochemical conditions, can lead to plant stress and large-scale seagrass meadow die-off. Therefore, measuring and mapping the dynamic gradients around seagrass roots and rhizomes is needed to better understand plant responses to human impact and environmental changes. Historically, electrochemical microsensors enabled the first measurements of important chemical species like O2, pH or H2S with high sensitivity and spatial resolution giving important insights to the seagrass rhizosphere microenvironment; however, such measurements only provide information in one dimension at a time. In recent years, the use of reversible optical sensors (in the form of planar optodes or nanoparticles) and accumulative gel sampling methods like Diffusive Gradients in Thin films (DGT) have extended the array of analytes and allowed 2-D mapping of chemical gradients in the seagrass rhizosphere. Here, we review and discuss such microscale methods from a practical angle, discuss their application in seagrass research, and point toward novel experimental approaches to study the (bio)geochemistry around seagrass roots and rhizomes using a combination of available techniques, both in the lab andin situ.

The Use of Nanoparticles to Displace Oil from a Porous Medium

The formation of supramolecular structures forming a transition region at the oil-nanofluid interface with a low surface tension is studied as a result of a synergistic effect in the interaction of planar graphene nanoparticles and silicon carbide nanoparticles coated with graphene layers (Core-shell). In model experiments on a Hele-Shaw cell, it was shown that in a porous medium such hybrid nanofluids have a high displacing ability of residual oil. At the same time, the oil – nanofluid interface remains stable, without the formation of sticky fingers. In the process of research using power electron microscopy, a transition region was observed, in the structuring of which nanoparticles were directly involved. The efficiency of displacement by hybrid nanofluid depends on the concentration of nanoparticles and their interaction.

Thermocapillary waves formation at the interface of hydrocarbons and graphene-like nanofluids

The paper presents the study of supramolecular structuring forming a transition region at the hydrocarbon – nanofluid interface resulting from synergistic effect by the interaction of multilayer graphene planar nanoparticles and silicon carbide nanoparticles covered with graphene layers (Core-shell). During the film formation on the interphase, filamentous formations were obtained, which resulted from interaction with thermocapillary waves. It was found that the structure of the filamentous formation was influenced by the composition and concentration of nanofluids.

Influence of a planar metal nanoparticle assembly on the optical response of a quantum emitter

We develop an analytical framework to study the influence of a weakly intercoupled inplane spherical metal nanoparticle (MNP) assembly on a coherently illuminated quantum emitter (QE). We reduce the analytical expressions derived for the aforementioned generic planar setup into simple and concise expressions representing a QE mediated by a symmetric MNP constellation, by exploiting the symmetry. We use the recently introduced generalized nonlocal optical response (GNOR) theory that has successfully explained plasmonic experiments to model the MNPs in our system. Due to the use of GNOR theory, and our analytical approach, the procedure we suggest is extremely computationally efficient. Using the derived model, we analyse the absorption rate, resultant Rabi frequency, effective excitonic energy shift and dephasing rate shift spectra of an exciton bearing QE at the centre of a symmetric MNP setup. We observe that the QE experiences plasmon induced absorption rate spectral linewidth variations that increase in magnitude with decreasing MNP-QE centre separation and increasing number of MNPs. Our results also suggest that, parameter regions where the QE exhibits trends of decreasing linewidth against decreasing MNP-QE centre separation are likely to be associated with plasmon induced excitonic energy redshifts. Similarly, regions where the QE absorption rate linewidth tends to increase against decreasing MNP QE centre separation are likely to be accompanied by plasmon induced excitonic energy blueshifts. In both these cases, the magnitude of the observed red/blueshift was seen to increase with the number of MNPs in the constellation, due to enhancement of the plasmonic influence.

Enhanced coherent interaction between monolayer WS2 and film-coupled nanocube open cavity with suppressed incoherent damping pathway

Future quantum information devices will most likely rely on the realization of coherent light-matter interactions in strong coupling regime and the maintaining of the coherence with minimized incoherent damping pathways. Here, utilizing film-coupled planar nanoparticle supporting unique plasmon-induced magnetic resonance (PIMR), we theoretically study a strong coupling of a single nanocube to a monolayer of two-dimensional atomic crystal. We demonstrate that the nanocube-based planar configuration with magnetic flux passing through the dielectric layer exhibits much higher in-plane field confinement with respect to traditional plasmon electric modes, leading to an efficient coherent coupling to only a few in-plane excitonic dipoles with a record of normal mode splitting over 280 meV. Importantly, a much reduced incoherent coupling strength down to 3 meV is obtained. We reveal that the underlying mechanism lies in two main facts: (i) the small radiative damping rate of the excitonic system giving very limited contribution to the linewidth broadening of the A-exciton resonance, and (ii) the excitation of magnetic resonance provides a net electric dipole moment orientating mainly normal to the film surface, thus greatly suppressing the exchange of photons between the two subsystems via the continuum reservoir. The numerical simulations and theoretical analysis quantitatively evaluate the dependence of both the coherent and incoherent coupling strength on the thickness of the dielectric layer, revealing the fact that coherent/incoherent coupling strength can be simultaneously enhanced/suppressed with the decrease/increase of the film thickness, which can be appropriately designed to achieve the optimal coherent coupling with minimized incoherent coupling strength. Such hybrid nanostructure with simple geometry and ease of fabrication may not only offer as an attractive platform to explore light-matter interaction in the strong coupling regime but also show potential applications in realizing novel quantum and nanophotonic optical devices.

The formation of planar crystalline flocs of γ-FeOOH in Fe(II) coagulation and the influence of humic acid

Although Fe(II) salts have been widely used as coagulants in water treatment for many years, the underlying mechanisms of their performance remain unclear. Here, we present a detailed study of the coagulation behavior of Fe(II) salts and crystallization of flocs, and investigate the effect of humic acid (HA) under different DO concentrations and pH conditions. The behavior of Fe(II) and Fe(III) coagulants was found to be markedly different with the flocs from Fe(II) consisting of planar-like crystalline γ-FeOOH in contrast to the small amorphous spherical-like flocs from Fe(III) dosing. The effect of HA on Fe(II) coagulation was different under different DO concentrations and pH, where by the growth of γ-FeOOH was inhibited by the presence of HA, but independent of DO concentration and pH. It was found that Fe(II) was present within the internal structure of γ-FeOOH, and a plausible formation mechanism is proposed. Firstly, planar nanoparticles of Fe(OH)2 were formed via Fe(II) ion hydrolysis which then servedas the nucleus for subsequent crystal growth. With oxidation, Fe(II) on the surface of nanoparticles transformed to Fe(III). Finally, the formation of γ-FeOOH in Fe(II) coagulation was accompanied by a change in solution colour to yellow.

Optical alignment of achiral nanoparticles via the use of induced chiral force

A chiral force was found to be induced upon rotation of planar nanoparticles under irradiation of linearly polarized light. The chiral force arises due to differing absorptions of left and right circularly polarized light, correlating with the circular dichroism (CD) of rotated nanoparticle. Charge distribution profiles, which arises from the excited localized surface plasmon polaritons induced by the light, can be used to predict the CD. This offers a simple method of using charge distributions to predict the dynamics of nanoparticles for optical alignment and orientation in the fabrication of various optical devices.

Engineering the Cellulose Fiber Interface in a Polymer Composite by Mussel-Inspired Adhesive Nanoparticles with Intrinsic Stress-Sensitive Responsivity

The interface between the fiber and matrix plays a key role in polymer composite performance and is adapted by chemical modification of the fiber surface. In this study, biomimetic adhesive nanoparticles formed by the self-assembly of polymer-peptide amphiphiles with a polydiacetelyene tail and local presentation of 3-hydroxyphenylalanine or DOPA adhesive groups at the outer surface are adsorbed on cellulose fiber surfaces for (i) probing the nanoscale adhesion in combination with a functionalized atomic force microscopy tip and (ii) evaluating the macroscale adhesion by single-fiber pull out tests from a solvent cast cellulose/poly(methyl methacrylate) composite. The interface properties are altered by changing the structure of the nanoparticles into either vesicular or planar shapes depending on the number of incorporated amphiphiles with adhesive groups and the nanoparticle concentration at the cellulose fiber surface. Based on nanoscale adhesive measurements, the adhesion force on modified cellulose fibers increases as a function of the nanoparticle concentration and is higher for the vesicular than for the planar nanoparticle structures. However, the local presentation and number of adhesive groups seems to rule over the surface roughness effects. From macrosale tests, an optimum concentration of adhesive vesicles provides maximum interface strength, while the formation of nanoparticle multilayers at higher concentrations results in lower interface adhesion. In addition, the intrinsic fluorescent properties of the adhesive vesicles under mechanical stress provide a unique tool to evaluate local failure and stress concentrations in the fiber/matrix interface. The incorporation of both adhesive and sensitive properties and versatility of the adhesive functional group may be an attractive strategy for the surface modification of fiber-reinforced composites in general.

Study of the effects of particle shape and base fluid type on density of nanofluids using ternary mixture formula: A molecular dynamics simulation

Ternary mixture formula with consideration of the effect of nanolayer formation is capable of predicting nanofluid density more accurately compared with the traditional mixture rule. The aim of this investigation is to study the effect of particle shape and type of base fluid on density of nanofluid based on the ternary mixture formula using molecular dynamics simulations. In this regard, two types of base fluids, i.e. water and liquid argon, as well as four different particle shapes, i.e. spherical, planar, block and rod-shaped with different aspect ratios are examined. The results showed that different particle shapes show different behaviors in attracting base fluid molecules and forming nanolayer. The thickness of nanolayer is assumed from the surface of nanoparticle to the place that the density fluctuations stay within a tolerance of 2% of the base fluid density. Accordingly, the thicknesses of nanolayers are 0.9 nm and 1.3 nm for silver-water and silver-liquid argon nanofluids, respectively. Moreover, it was found that the density of nanofluids containing planar nanoparticles as well as spherical nanoparticles decreases with increasing nanoparticle diameter and planar nanoparticle has the highest density of nanolayer among planar, spherical and rod-shaped particles. The comparison between the densities of three nanofluids containing equal volume nanoparticles with different shapes reveals that the ternary mixture formula has significant advantages over the traditional binary mixture.

Responses of an Isolated Anisotropic Magnetic Nanoparticle and Nanoparticle Lattice to a Magnetic Field Pulse

We have performed numerical simulations to evaluate responses of the magnetic moments of a single nanoparticle possessing uniaxial anisotropy and a planar nanoparticle lattice to excitation by a magnetic field pulse. The precession dynamics of magnetic moment for a wide range of the pulse parameters and the lattice anisotropy value has been studied. We have explored and analyzed periodic dependences of the response duration and the resulted orientation of the magnetic moments on the pulse duration and its amplitude. The effect of an additional noise signal on the lattice magnetization reversal is studied. The regimes of partial and complete magnetization reversal of dipole systems achievable only in the presence of noise have been revealed. We report on the conditions enabling the pulse magnetizations reversal most and least sensitive to the noise signal.

USE OF NANOFLUIDS BASED ON CARBON NANOPARTICLES TO DISPLACE OIL FROM THE POROUS MEDIUM MODEL

Graphene, due to its two-dimensional structure, has some unique properties. For example, the thermal conductivity and electrical conductivity of graphene are an order of magnitude higher than the thermal conductivity and electrical conductivity of copper. For this reason, graphene-based nanofluids are now used in many industries. Due to the effect of self-organization of graphene nanoparticles with hydrocarbon molecules, the use of graphene has become possible in the oil industry. Graphene-based nanofluids are used as a displacement fluid to increase the oil recovery coefficient. The displacing ability of graphene-based nanofluids is concentration dependent. An increase in the concentration of nanoparticles entails an increase in viscosity, which negatively affects the performance characteristics of the nanofluid. This problem is partially solved due to the synergistic effect, hybrid nanofluids consisting of nanoparticles of graphene and metals or carbides enhance the displacing ability. Using atomic force microscopy, scanning electron microscopy and molecular modelling methods, this work has studied the formation of supramolecular structures that form a transition region at the oil-nanofluid interface with low surface tension as a result of a synergistic effect in the interaction of graphene planar nanoparticles and silicon carbide nanoparticles covered with graphene layers (Core-shell). The model experiments on a Hele-Shaw cell have shown that in a porous medium, such hybrid nanofluids have a high displacement ability of residual oil. At the same time, the oil — nanofluid interface remains stable, without the formation of viscous fingers. During the study by scanning electron microscopy, a transition region was observed, in the structuring of which the nanoparticles were directly involved. The displacement efficiency of a hybrid nonofluid depends on the concentration of nanoparticles and their interaction.

Smart-Responsive Nucleic Acid Nanoparticles (NANPs) with the Potential to Modulate Immune Behavior.

Nucleic acids are programmable and biocompatible polymers that have beneficial uses in nanotechnology with broad applications in biosensing and therapeutics. In some cases, however, the development of the latter has been impeded by the unknown immunostimulatory properties of nucleic acid-based materials, as well as a lack of functional dynamicity due to stagnant structural design. Recent research advancements have explored these obstacles in tandem via the assembly of three-dimensional, planar, and fibrous cognate nucleic acid-based nanoparticles, called NANPs, for the conditional activation of embedded and otherwise quiescent functions. Furthermore, a library of the most representative NANPs was extensively analyzed in human peripheral blood mononuclear cells (PBMCs), and the links between the programmable architectural and physicochemical parameters of NANPs and their immunomodulatory properties have been established. This overview will cover the recent development of design principles that allow for fine-tuning of both the physicochemical and immunostimulatory properties of dynamic NANPs and discuss the potential impacts of these novel strategies.

An impedimetric biosensor for E. coli O157:H7 based on the use ofself-assembled gold nanoparticles and protein G.

Two kinds of electrochemical impedimetric biosensors for the detection of E. coli O157:H7 are described and compared. They were fabricated using self-assembled layers of thiolated protein G (PrG-thiol) on (i) planar gold electrodes and (ii) gold nanoparticles (Au NPs) modified gold electrodes. The fabrications of the biosensors were characterized using cyclic voltammetry, electrochemical impedance spectroscopy, scanning electron microscopy and atomic force microscopy techniques. The modification of the planar gold electrode by Au NPs via self-assembled monolayer of 1,6-hexadithiol as a linker molecule increased the electrochemically active surface area by about 2.2 times. The concentration of PrG-thiol and its incubation time, as well as the concentration of IgG were optimized. The Au NP-based biosensor exhibited a limit of detection of 48 colony forming unit (cfumL-1) which is 3 times lower than that of the planar gold electrode biosensor (140cfumL-1). It also showed a wider dynamic range (up to 107cfumL-1) and sensitivity. The improved analytical performance of the Au NP-modified biosensor is ascribed to the synergistic effect between the Au NPs and the PrG-thiol scaffold. The biosensor exhibited high selectivity for E. coli O157:H7 over other bacteria such as Staphylococcus aureus and Salmonella typhimurium. Graphical abstract Schematic representations of sensor fabrication using Au NP-modified electrode (HKEC = heat- killed E. coli O157:H7).

Oil Filtration in a Porous Medium in the Presence of Graphene Nanoparticles

The filtration of a graphene suspension through a core sample has been studied experimentally. It has been found that at the oil–water interface in the porous medium of the core sample, a transient multilayer microheterophase structure consisting of planar graphene nanoparticles, hydrocarbon oil molecules, and surfactants is formed. It has been found that with an increase in the concentration of graphene nanoparticles, the volume fraction of displaced oil increases and the water volume fraction in oil decreases.