Self-organization Of Nanoparticles Research Articles

Optical diffraction properties of three superimposed self-organized nanostructures induced by a laser process.

Controlling the diffraction properties of materials over a large area holds great promise for a wide range of optical applications. Laser-based techniques have emerged as a viable solution to address this need. Here, we present the diffraction properties of laser-induced self-organized structures, which consist of three interlaced grating-like structures: self-organized nanoparticles, self-organized cracks, and laser marking lines. Under normal incidence external illumination, the sample exhibits an asymmetric diffraction pattern. However, when the incidence angle is tilted, circular diffraction patterns are observed in the plane perpendicular to both the sample and the incidence plane. These phenomena are attributed to the combination effect of the diffraction gratings. To elucidate the underlying physics of multiple diffraction, we use rigorous coupled-wave analysis (RCWA) and grating equations written in direction cosine space, extended to account for the presence of three superimposed gratings. Exploiting the laser-induced diffraction properties of these samples may have great potential for various industrial implementations, including security, display, and design.

On the Mechanical Concept of Self-Assembly of Nanomaterials

The article presents the mechanical concept of self-assembly of nanoparticles. It is assumed that nanoparticles are deformable stamps in a plane dynamic contact problem, lying on the boundary of a multilayer deformable medium. The constant vibration in the microcosm is caused by the oscillatory mode by the energy of phonons and magnons. Earlier, in the works of the authors, the mechanical concept of self-organization of nanoparticles was presented. It is based on high-frequency resonance, which causes the formation of standing waves. They localize the available aggregates of nanoparticles on the crest of standing waves. The self-assembly of nanoparticles is based on resonance, previously predicted by Academician I. I. Vorovich and inherent only in deformable dies in contact problems on a multilayer medium. Deformable nanoparticles are modeled by fractals representing packed block elements described by the Helmholtz equation. The resonance of the deformable dies allows the capture of nanoparticles, dictated by the Coulomb forces of attraction. It is shown that the combination of two fractals generates a new fractal with a combined carrier, and in the case of multiple association, a fragment of a nanomaterial is obtained. To implement the study, for the first time it was possible to construct a high-precision approximate solution of a plane contact problem on the action of a stamp of any finite size on a multilayer base. This result is dictated by the need for an analytical construction of the theory of self-assembly of nanomaterials.

SERS sensing of Metanil yellow in turmeric solution using self-organized nanoparticle arrays grown on Ion beam patterned soda-lime glass

Metanil yellow is a potential carcinogen that is commonly used as a food adulterant in turmeric powder. In this study, we detected Metanil Yellow from turmeric powder solution using a Surface Enhanced Raman Spectroscopy (SERS) substrate based on nano patterned soda-lime glass. Low amplitude ripples with an average wavelength around 65 nm was produced on commercially available soda-lime glass using low energy argon ion beam irradiation. Large area SERS templates were produced by growing self-organized ordered Ag nanoparticles on the rippled soda-lime glass. The optical analysis of the produced substrates shows the anisotropic plasmonic response and better Localized Surface Plasmon Resonance (LSPR) activity than Ag nanoparticles grown on rippled Si substrate. A biaxial layer consisting of Lorentz and Drude oscillators describes the real and imaginary parts of the dielectric function. The SERS analysis using Crystal Violet (CV) molecules demonstrates a five-fold improvement in the efficiency of silver grown on glass ripples than silver grown on Si ripples. We have tested the substrate for detecting Metanil yellow up to 10-6 M concentration in the water. Further, using the substrate, up to 10-4 M concentration of Metanil Yellow is detected from the turmeric solution.

Магнитное взаимодействие нанокластеров в бимодальном ферроколлоиде

The paper discusses the problem of interaction between a pair of superparamagnetic nanoclusters suspended in a nano-dispersed ferrocolloid and subjected to a uniform magnetic field. The main re-search instrument is the Langevin dynamics simulation method. Dipole-dipole and steric interactions between nanoparticles and clusters are directly taken into account. The net force acting on the clus-ters is calculated for various values of the controlling parameters –the intensity of the applied field and the energy of dipole-dipole interparticle interactions. In the wide ranges of these values, there is observed an effective short-range attraction between the clusters. The strength of the interaction in-creases with an increase in the dipolar coupling parameter. It has been established that the self-organizationof nanoparticles in the vicinity of the clusters also enhances their attraction. Other con-ditions being equal, the force of intercluster attraction in a structured ferrocolloid can be 1.5–2 times higher than in a homogeneous one.

Au/Ag SERS active substrate for broader wavelength excitation

Self-organized Ag nanoparticles arrays capped with Au layer are produced by depositing Ag nanoparticles on ion beam produced ripple patterned Si substrate followed by Au deposition. Au/Ag combination of nanoparticles shows intermediate plasmonic properties of Ag and Au nanoparticles by overcoming the associated drawbacks. Such combination redshifts the Localized Surface Plasmon Resonance (LSPR) compared to pure Ag and makes them suitable to excite the surface plasmon by both 532 nm and 785 nm laser for a wider range SERS application. The optimized Au deposition decreases the interparticle gap and elongates the nanoparticles along the ripple direction and makes a larger redshift in the LSPR. FDTD simulation also revealed that the electric field enhancement is higher along the ripple direction for both exciting lasers and shows that the LSPR of the combined Au/Ag system is shifted towards 785 nm. The limit of detection of Crystal Violet using the optimized Au/Ag substrate is found to be 10−10 M for 532 nm laser and 10−8 M for 785 nm laser, respectively. The substrate shows good spatial uniformity with a relative standard deviation of less than 10% with SERS enhancement factors in the order of 104-105 for both lasers. These studies suggest that the as-prepared substrate is a promising candidate for detecting molecules sensitive to different wavelengths of laser excitation.

On One Mechanical Model of Self-Organization of Nanoparticles

On One Mechanical Model of Self-Organization of Nanoparticles

EPR study of self-organized magnetic nanoparticles in biomaterials

An innovative approach based on the effect of bio-mineralization as a response reaction of cells to decrease their damage under stress was applied to Juniperus communis (JC) and JC-based biomaterials (Nefrovil and Immunostan drugs with properties increasing the antioxidant activity and improving the immune system of human organism, respectively). Electron paramagnetic resonance spectroscopy (EPR), also called electron spin resonance (ESR), was used as the main experimental tool for detecting paramagnetic species resulted from the existence of antioxidant activity system, represented by superoxide dismutase with manganese, catalase etc., as well as formation of superparamagnetic iron oxide nanoparticles (SPIONs). The influence of temperature and microwave power on the intensity of EPR signals detected in JC, Nefrovil and Immunostan was examined. Obtained g-factor values of EPR signals from JC shell and seeds as well as from Nefrovil and Immunostan were attributed to the paramagnetic species of Mn (g = 2.0), Fe3O4 SPIONs (g = 2.17…2.60), Fe aggregates (g = 3.22…3.94) and Fe3+ ions (g = 4.3). The EPR signals from SPIONs and Fe3+ ions in Immunostan were found to be fully correlated, showing an additional experimental evidence of the bio-mineralization effect (i.e., transformation of Fe3+ ions to Fe3O4 SPIONs). The results of the EPR study of Fe3O4 SPIONs incorporated into polymer matrix were taken into account in comparative analysis. The results reported in the present work support well self-organization of magnetic nanoparticles in the investigated biomaterials.

Impact of Charge Regulation on Self-Assembly of Zwitterionic Nanoparticles.

Zwitterionic modification of colloids with weak acids and bases represents a promising strategy in creating functional materials with tunable properties and modeling the self-organization of charged proteins. However, accurate incorporation of the dynamic dissociation or association of ionization groups known as charge regulation (CR) is often intractable in theoretical and computational investigations since charge redistribution and configuration need to be evolved self-consistently. Using hybrid MonteCarlo and molecular dynamics simulations, we demonstrate that a dilute suspension of overall charge-neutral zwitterionic Janus nanoparticles shows a conformational transition from an open assembly of string or bundle to compact cluster along with the variation in pH. The behavior under CR is qualitatively different from the commonly employed constant charge condition where the transition is absent. The CR-induced clustering is due to the inhomogeneous and fluctuating charges localized near the equatorial boundary of the Janus particle. These features are enhanced particularly at low salt concentration and high electrostatic coupling strength. Our results indicate the critical role of charge regulation in the spatial self-organization of zwitterionic nanoparticles.

АТОМНО-СИЛОВАЯ МИКРОСКОПИЯ ПОЛИМЕРНЫХ НАНОЧАСТИЦ

The paper presents the results of an experimental study of polymer nanoparticles on different substrates by atomic force microscopy. The main metrological parameters of polymer nanoparticles are determined, the results are compared with the available data on the supramolecular structure of solid films. It is established that the size and shape of the observed structures, other things being equal, significantly depend on the type of substrate. It is shown that aggregation and self-organization of polymer nanoparticles occurs during the preparation of samples on silicon. The work was carried out with the support of the project "Mirror Laboratories" of the National Research University "Higher School of Economics" and Bashkir State Pedagogical University named after M. Akmulla.

Self-Organized Nanoparticles of Random and Block Copolymers of Sodium 2-(Acrylamido)-2-methyl-1-propanesulfonate and Sodium 11-(Acrylamido)undecanoate as Safe and Effective Zika Virus Inhibitors.

A series of anionic homopolymers, poly(sodium 2-(acrylamido)-2-methyl-1-propanesulfonate) (PAMPS) and amphiphilic copolymers of AMPS and sodium 11-(acrylamido)undecanoate (AaU), both block (PAMPS75-b-PAaUn), and random (P(AMPSm-co-AaUn)), were synthesized and their antiviral activity against Zika virus (ZIKV) was evaluated. Interestingly, while the homopolymers showed limited antiviral activity, the copolymers are very efficient antivirals. This observation was explained considering that under the conditions relevant to the biological experiments (pH 7.4 PBS buffer) the macromolecules of these copolymers exist as negatively charged (zeta potential about −25 mV) nanoparticles (4–12 nm) due to their self-organization. They inhibit the ZIKV replication cycle by binding to the cell surface and thereby blocking virus attachment to host cells. Considering good solubility in aqueous media, low toxicity, and high selectivity index (SI) of the PAMPS-b-PAaU copolymers, they can be considered promising agents against ZIKV infections.

Functional and technological properties of food additive "Magnetofood" in production of shaped jelly marmalade on agar and pectin

Jelly and marmalade products are "lyophilic colloids" – lyophilic colloidal-dispersed, ie microheterogeneous (multi- or polyphasic) systems based on high molecular weight compounds (gelatin, pectin, agar, etc.). Therefore, the problem of stabilizing their polyphasic structure is relevant. In addition, the expansion and improvement of the production of jelly and marmalade products requires the search for simplified resource- and energy-saving technology, increasing the stability of the colloidal disperse system, improving the quality and extending the shelf life of finished products. Promising technological applications have food additives in the nanometer range, due to specific and stable physical and chemical parameters, a wide range of functional and technological properties. The paper proposes the solution of the problem of stabilization of the polyphase structure of jelly-marmalade products and the formation of their quality by using the food additive "Magnetofood" (based on double oxide of divalent and trivalent iron: FeO×Fe2O3). "Magnetofood" - highly dispersed powder with a particle size (70–80) nm, which has a fairly diverse functional and technological potential: high ζ-potential and surface activity; clusterophilicity and amphiphilicity; complexing, thickening, structuring, stabilizing, thixotropic properties. This allows us to recommend "Magnetofood" as a food additive of complex action to improve the quality and prolong the shelf life of jelly-marmalade products, in particular jelly-shaped marmalade. The surface-active properties of nanoparticles of the food additive "Magnetofood" are determined: a rather significant value of ζ-potential (34-44) mV, amphiphilicity (marginal wetting angle Q<90o by polar-nonpolar medium) - show signs of stability and stability on polyphasic colloidal-dispersed systems , which increases in acidic environments, in solutions of polysaccharides, proteins on average by (55±)%, which is due to clusterophilicity and self-organization of nanoparticles "Magnetofood" into electrostatic complexes with proteins, polysaccharides and their spatial structuring. It was found that the addition of "Magnetofood" in the mass fraction (0,10–0,20)% to the mass of the structurant increases the viscosity of aqueous solutions of gelling agents in (1,22–1,27) times for agar and in (1,24–1,29) times for pectin and the rate of structuring of gel masses in (1,73±0,01) times for agar and in (1,67±0,01) times for pectin due to the structure-forming action of nanoparticles "Magnetofood". In addition, the ability of the gel structure to thixotropy increases by (1,4–1,5) times and the mechanical strength of the gel well by (1,32–1,80) times for agar and (1,49–1,57) times for pectin due to the stabilizing action of Magnetofood nanoparticles, which allows to reduce the amount of gelling agent by (9.0–11.0)% for agar and by (7.0–9.0)% for pectin.

Self-organization of nanoparticles and molecules in periodic Liesegang-type structures.

Chemical organization in reaction-diffusion systems offers a strategy for the generation of materials with ordered morphologies and structural hierarchy. Periodic structures are formed by either molecules or nanoparticles. On the premise of new directing factors and materials, an emerging frontier is the design of systems in which the precipitation partners are nanoparticles and molecules. We show that solvent evaporation from a suspension of cellulose nanocrystals (CNCs) and l-(+)-tartaric acid [l-(+)-TA] causes phase separation and precipitation, which, being coupled with a reaction/diffusion, results in rhythmic alternation of CNC-rich and l-(+)-TA-rich rings. The CNC-rich regions have a cholesteric structure, while the l-(+)-TA-rich bands are formed by radially aligned elongated bundles. The moving edge of the pattern propagates with a finite constant velocity, which enables control of periodicity by varying film preparation conditions. This work expands knowledge about self-organizing reaction-diffusion systems and offers a strategy for the design of self-organizing materials.

Evolution of plasmonic nanostructures under ultra-low-energy ion bombardment

Metal nanostructures supported on a dielectric substrate possess unique plasmonic properties that are highly dependent on their morphologies. We show that such nanostructures can be modified upon exposure to an ultra-low-energy ion-beam bombardment (< 100 eV) near the sputtering threshold of the metal. This plasma treatment can be easily implemented in a vacuum deposition chamber and allows the achievement of morphologies, and therefore optical properties, that are difficult to achieve otherwise by physical vapor deposition. We present the effects obtained (i) on self-organized Ag nanoparticles with unidirectional orientation and bimodal distribution, and (ii) on Ag layers in the form of percolated, quasi-continuous or island thin films. Our results show that the plasmonic dichroism of self-organized assemblies can be tuned thanks to the preferential sputtering of the smaller particles associated with gradual erosion of the larger ones. Ion-induced modifications of percolated or quasi-continuous films lead to the formation of isolated tiny particles with areal densities smaller than 500 μm−2. In both cases, the duration of the ion bombardment makes it possible to finely control the desired structural and plasmonic modifications.

Rhodamine B Doped ZnO Monodisperse Microcapsules: Droplet-Based Synthesis, Dynamics and Self-Organization of ZnO Nanoparticles and Dye Molecules.

In the present work, droplet-based microfluidics and sol-gel techniques were combined to synthesize highly monodisperse zinc oxide (ZnO) microspheres, which can be doped easily and precisely with dyes, such as rhodamine B (RhB), and whose size can be finely tuned in the 10–30 μm range. The as-synthesized microparticles were analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and confocal microscopy. The results reveal that the microspheres exhibit an excellent size monodispersity, hollow feature, and a porous shell with a thickness of about 0.6 μm, in good agreement with our calculations. We show in particular by means of fluorescence recovery after photobleaching (FRAP) analysis that the electric charges carried by ZnO nanoparticles primary units play a crucial role not just in the formation and structure of the synthesized ZnO microcapsules, but also in the confinement of dye molecules inside the microcapsules despite a demonstrated porosity of their shell in regards to the solvent (oil). Our results enable also the measurement of the diffusion coefficient of RhB molecules inside the microcapsules ( cm/s), which is found two order of magnitude smaller than the literature value. We attribute such feature to a strong interaction between dye molecules and the electrical charges carried by ZnO nanoparticles. These results are important for potential applications in micro-thermometry (as shown recently in our previous study), photovoltaics, or photonics such as whispering gallery mode resonances.

In Situ Liquid Cell Transmission Electron Microscopy Observation of Dynamic Process of Oleic Acid Emulsion with Gold Nanorods

Oleic acid (OA) emulsion is widely used in nanomaterial synthesis and applications. The emulsion droplets can serve as template scaffolds for nanoparticle self-organization, while adding nanopartic...

Colloidal Suprastructures Self-Organized from Oppositely Charged All-Inorganic Nanoparticles

The self-organization of colloidal nanoparticles into programmed suprastructures is an important research area in various disciplines of nano, colloid, and polymer sciences. However, despite the recent advances in their fundamental understanding and practical applications, the self-organization of organic-free inorganic nanoparticles remains unexplored. Herein, we present the controlled organization of oppositely charged all-inorganic nanoparticles through the electrostatic interaction and the colloidal behaviors of organized suprastructures. Depending on the charge states of the assembled suprastructures, three different phases, including patchy, patchy bridged, and fully coated particles, are identified, enabling the construction of the phase diagram with nanoparticle concentrations. Especially, the fully coated particles exhibit unexpected colloidal stability through the action of nanoparticles as surface stabilizers to induce the overcharged surface state; thus, we propose the concept of “nanoligands”. It is demonstrated that this concept can be extended to a wide range of material combinations, including semiconducting, metallic, and oxide nanoparticles. The currently developed approach will enable the chemical designing of self-organized nanostructures.

Automated Searching and Identification of Self-Organized Nanostructures.

Currently, researchers spend significant time manually searching through large volumes of data produced during scanning probe imaging to identify specific patterns and motifs formed via self-assembly and self-organization. Here, we use a combination of Monte Carlo simulations, general statistics, and machine learning to automatically distinguish several spatially correlated patterns in a mixed, highly varied data set of real AFM images of self-organized nanoparticles. We do this regardless of feature-scale and without the need for manually labeled training data. Provided that the structures of interest can be simulated, the strategy and protocols we describe can be easily adapted to other self-organized systems and data sets.

Self-organization of Mo nanoparticles embedded in MoOx matrix for efficient solar energy absorption

Complex multilayer stacks based on metal-dielectric (cermet) or metal nitrides and borides are widely explored for solar energy harvesting. Inevitably, complicated multi-target co-sputtering process and expensive material costs are required. To address this issue, herein, we demonstrate that Mo nanoparticles spontaneously embedded in amorphous MoOx matrix (Mo@MoOx), facilely achieved by one-step limited reactive sputtering approach with a very low oxygen/argon ratio using only a single Mo target, possess excellent optical absorption. The developed Mo@MoOx absorber film exhibits a superior solar absorptivity of 0.91, a low thermal emissivity of 0.06, as well as a remarkable long-term thermal stability of up to 450 °C in vacuum, which is the equivalent photo-thermal performance compared to the multilayer absorbers. These findings deliver a new insight into pathway for designing simple, efficient but feasible absorber in large-scale industrial processing.

Self-Assembly of Ag2S Colloidal Nanoparticles Stabilized by MPS in Water Solution.

Self-assembly of colloidal Ag2S nanoparticles (NPs) was studied in the presence of (3-mercaptopropyl)trimethoxysilane (MPS). Solutions with different molar ratios of Ag2S/MPS were prepared. The appearance of nano- and microtubes was detected. Self-organized NPs were studied with optical microscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and high-resolution transmission electron microscopy (HRTEM). Silicon nuclear magnetic resonance spectroscopy (29Si NMR) was used to study polycondensation of MPS molecules. Geometrical parameters of the nano- and microtubes depended on the molar ratio of Ag2S/MPS. The scheme and mechanism of self-assembly of Ag2S NPs in nanotubes in the presence of MPS were proposed. The effect of MPS on the preservation of the initial stoichiometry of Ag2S NPs was discussed.

Observation of photovoltaic effect within locally doped silicon nanojunctions using conductive probe AFM

Abstract Localized p-doped nanojunctions (200–300 nm in diameter) were formed in n-type crystalline silicon substrates and were characterized using scanning electron microscopy (SEM) and conductive-probe atomic force microscopy (C-AFM). Localized doping was performed by diffusion through sub-micron sized holes in a silicon-oxide mask defined using self-organized polystyrene nanoparticles. After oxide removal, a significant brightness contrast in the SEM top and side view images strongly suggested the successful local doping of these areas. Furthermore, local current-voltage measurements performed by C-AFM revealed an open circuit voltage and a short-circuit current only in the areas defined as nanojunctions. This photovoltaic effect is driven by the laser used to control cantilever deflection in the AFM.