Aggregation Of Nanoparticles Research Articles

Structural Basis for Alternative Self-Assembly Pathways Leading to Different Human Immunodeficiency Virus Capsid-Like Nanoparticles.

The mechanisms that underlie the spontaneous and faithful assembly of virus particles are guiding the design of self-assembling protein-based nanostructures for biomedical or nanotechnological uses. In this study, the human immunodeficiency virus (HIV-1) capsid was used as a model to investigate what molecular feature(s) may determine whether a protein nanoparticle with the intended architecture, instead of an aberrant particle, will be self-assembled in vitro. Attempts of using the HIV-1 capsid protein CA for achieving in vitro the self-assembly of cone-shaped nanoparticles that contain CA hexamers and pentamers, similar to authentic viral capsids, had typically yielded hexamer-only tubular particles. We hypothesized that a reduction in the stability of a transient major assembly intermediate, a trimer of CA dimers (ToD), will increase the propensity of CA to assemble in vitro into cone-shaped particles instead of tubes. Certain amino acid substitutions at CA-CA interfaces strongly favored in vitro the assembly of cone-shaped nanoparticles that resembled authentic HIV-1 capsids. All-atom MD simulations indicated that ToDs formed by CA mutants with increased propensity for assembly into cone-shaped particles are destabilized relative to ToDs formed by wt CA or by another mutant that assembles into tubes. The results also indicated that ToD destabilization is mediated by conformational distortion of different CA-CA interfaces, which removes some interprotein interactions within the ToD. A model is proposed to rationalize the linkage between reduced ToD stability and increased propensity for the formation of CA pentamers during particle growth in vitro, favoring the assembly of cone-shaped HIV-1 capsid-like nanoparticles.

PEFC Electrocatalysts using Highly-Graphitized Mesoporous Carbon Supports

The electrocatalysts used in polymer electrolyte fuel cells (PEFCs) are subject to oxidative corrosion of the carbon catalyst support due to start-stop cycling, as well as aggregation of Pt nanoparticles due to load fluctuations. The use of mesoporous carbon (MC) as a catalyst support has previously been shown to suppress aggregation. In this study, highly graphitized MC is prepared as a catalyst support to suppress both carbon corrosion and aggregation in Pt/MC electrocatalysts. The effect of graphitization temperature on the catalytic performance is evaluated, as well as the effect of pretreatment via either ball milling or pulverization to achieve suitable particle size. The results indicate that the initial activity of the electrocatalysts is improved by graphitization of the MC support after milling, and that the graphitization step improves the start-stop cycle durability.

Heat transfer and entropy production analysis of Casson nanofluid under cylindrical stretching motion in the existence of aggregates nanoparticles

This paper focuses on the heat transfer and entropy production of the Casson nanofluid under cylindrical stretching motion in the case of nanoparticle aggregation. Calculations derived from the BVP4C numerical solution were utilized in the study to verify the accuracy of the calculations in comparison with previous results. The results showed that when the nanoparticle volume fraction was increased from 1% to 3%, the heat transfer efficiency improved by 2.72% in the absence of nanoparticle aggregation, while the heat transfer efficiency improved by 12.42% in the existence of nanoparticle aggregation. It is also found that the existence of aggregation of nanoparticles significantly increased the heat transfer capacity and flow resistance of the Casson nanofluid compared to the absence of aggregation. The results of this study can provide important theoretical support for applications in thermal management of stretched cylinders, biomedical drilling, and other fields.

Single Particle Insights into the Thermal Sensing of Conjugated Polyelectrolyte–Nanoparticle Assemblies

Single Particle Insights into the Thermal Sensing of Conjugated Polyelectrolyte–Nanoparticle Assemblies

Effect of nanofluid cooling on electrical power of solar panel system in existence of TEG implementing magnetic force

This study investigates the efficacy of applying a Lorentz force to improve the efficiency of a photovoltaic-thermal (PVT) system featuring a finned duct, while also addressing challenges associated with dust accumulation. The magnetic field helps to prevent nanoparticle aggregation, enhancing the cooling process. The use of a finned duct combined with a nanofluid as the cooling medium efficiently dissipates excess heat from the silicon layer. Dust accumulation on the glass layer reduces transmissivity, negatively impacting system performance. The magnetic field's interaction with the nanoparticles enhances convective cooling of the upper layer, leading to an overall improvement in performance. Increased pumping power results in higher cooling rates, with improvements of approximately 3.48 % in thermal efficiency (ηth), 75.01 % in thermoelectric generator efficiency (ηTEG), and 39.37 % in photovoltaic efficiency (ηPV). An increase in the Hartmann number (Ha) improves ηth by about 1.87 %, with corresponding enhancements in electrical performance components. A higher concentration of ferrofluid further boosts performance, with the effect being roughly 1.7 times more significant in the absence of MHD compared to when Ha = 97. Dust presence decreases ηth, ηTEG, and ηPV by approximately 9.39 %, 8.55 %, and 25.77 %, respectively. Furthermore, the presence of Ha diminishes the influence of Vin on ηth by around 1.33 %.

Facile microwave synthesis of various-shaped magnetite/ reduced graphene oxide heterostructures and their magnetization properties

Heterostructures of magnetite (Fe3O4) nanoparticles and reduced graphene oxide (RGO) sheets are very common composite materials for different applications such as catalysis, energy storage, and biomedicine. Developing methods for the facile control of the size and shape of both freestanding Fe3O4 nanoparticles and those anchored onto RGO sheets is in demand. Herein, we report on the rapid and facile microwave synthesis (MWS) of Fe3O4 nanoparticles and Fe3O4/RGO with various sizes and shapes using the oleylamine (OAm)/oleic acid (OAc) ligand pair. The solvothermal synthesis using microwave irradiation (MWI) resulted in the concurrent conversion of graphene oxide (GO) into RGO and the in-situ formation of various-shaped Fe3O4 on RGO sheets. Freestanding Fe3O4 nanoparticles of various shapes were prepared using MWS for comparison. The morphological, structural, and surface properties of the samples were studied using different characterization techniques. The magnetization properties of the prepared samples were determined using a vibrating sample magnetometer. Various-shaped standalone and RGO-supported Fe3O4 nanoparticles including nanospheres, nanocubes, and nanotriangles were synthesized via MWI at 1000 W for 20 min by changing the ratios of the iron precursor and the OAm/OAc ligand pair. Interestingly, the MWI using OAm/OAc ligand pair of a molar ratio of 3:4 resulted in the in-situ formation of large hexagonal Fe3O4/RGO. The X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) results confirm the crystallinity and spinel structure of the prepared Fe3O4 samples and prove the concurrent conversion of GO into RGO with assemblies of Fe3O4 nanoparticles. The magnetization measurements further emphasized the role of size and shape in affecting the magnetic properties of Fe3O4 and Fe3O4/RGO heterostructures. The results identify the qualities of the prepared samples and prove the MWS as a facile one-pot method for the preparation of Fe3O4 and Fe3O4/RGO heterostructures.

Microwaves in ferromagnetic composites Fe/Epoxy with aggregates of nanoparticles: Theory and experiment

Microwave transmission through plates of a composite material containing spherical Fe nanoparticles in an epoxyamine matrix and reflection from plates have been studied. Measurements were carried out at the frequencies from 26 to 32 GHz in the magnetic fields up to 12 kOe. The ferromagnetic resonance phenomenon in the composite has been investigated. The theory of electromagnetic waves transmitting through a composite material containing ferromagnetic particles, taking into account aggregating the particles, has been developed. A good agreement of calculation results and experimentally obtained field dependences of the transmission and reflection coefficients, as well as microwaves dissipation, has been achieved.

The nanoparticles aggregation aspects on the chemically reactive unsteady flow of alumina-water based nanofluid: A Keller box approach with applications of wavelet physics inspired neural networks

The present study explores the unsteady flow of a nanoliquid past a stretching cylinder with the consequence of heat source/sink and chemical reaction. Additionally, the effect of nanoparticle aggregation, convective boundary conditions, and magnetic field on the liquid flow is taken into consideration. Utilizing similarity variables, the modeled equations are transformed into dimensionless ordinary differential equations (ODEs). Further, the obtained ODEs are numerically solved by using the Keller box method. Moreover, the physics-informed neural network (PINN) is applied to analyze the flow, heat, and mass transport features. Graphical illustrations are used to display the influence of various parameters on the velocity, concentration, and temperature profiles for aggregation and without aggregation cases. As the value of the magnetic parameter increases, the temperature and concentration profile upsurge, but the reverse trend can be seen in the velocity profile. The concentration and temperature profiles rise as the unsteadiness parameter increases, but the velocity profile declines. The concentration, velocity, and temperature profiles are strengthened by an improvement in the curvature parameter value. The intensification in the values of the chemical reaction parameter declines the concentration.

Supramolecular blends of C-alkylpyrogallol[4]arenes and polytetrahydrofurans

A small series of the amphiphilic macrocycles – C-alkylpyrogallol[4]arenes has been synthesized and examined by single crystal X-ray analysis which showed the formation of two supramolecular arrangements depending on solvent used for crystallization, i.e., multilayered motif and hexameric capsule. Those structural findings provided an insight into blends prepared from aforementioned macrocycles and various polytetrahydrofurans (polyTHFs). Thus, 1:1 wt ratio mixtures were obtained and investigated by combination of Fourier-transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). As it turned out, the viscosity of these blends was increased compared to starting materials, which imply that pyrogallol[4]arenes can be successfully utilized as supramolecular cross-linkers enhancing H-bonding between adjacent macromolecular chains. As the major difference between compounds synthesized is the length and geometry of their respective alkyl side chains attached directly to macrocyclic core, i.e., n-propyl- and cyclohexyl- vs. n-dodecyl-, it seemed likely that even insignificant increase in their hydrophobicity can induce high order aggregation of nanoparticles in the slurries, thus affecting their viscosity. Overall, material viscoelastic properties are tunable at macroscopic level by choosing particular pyrogallol[4]arene/solvent combination and adjusting the temperature, which may be advantageous for the design of hybrid materials.

Polymer-Mediated Crack Suppression in Deposit of Nanoellipsoids.

Uniform distribution of particles and crack suppression in dried particulate deposits are major challenges for applications in coating and printing technologies. To address this, we investigated the impact of the addition of a water-soluble polymer, poly(vinyl alcohol) (PVA), on the evaporative self-assembly and kinetics of crack formation in deposits of anisotropic colloids. The fluid flow inside the drying drop is significantly altered due to polymer-mediated adsorption of ellipsoids to the drop surface. The competition between outward capillary flow and Marangoni flow developed in the drying colloid-polymer dispersion drop dictates the distribution of particles in the final dried patterns. The deposits formed by drying drops of ellipsoids dispersed in PVA solutions show three distinct patterns depending on the PVA concentration. A transition from ring-like deposit to uniform deposition with intermittent cracks was observed for a critical PVA concentration of 0.3 wt %. Radial as well as annular cracks were observed in the case of no PVA, while only annular cracks were formed in the dried patterns as the PVA content increased, thus indicating the change of capillary stresses in the films. Analyses of the particle dynamics and deposition patterns confirmed the effectiveness of gelation-driven crack prevention. This method offers a facile and straightforward solution for obtaining crack-free coatings in drying-mediated colloidal nanoparticle assembly.

Concave Grain Boundaries Stabilized by Boron Segregation for Efficient and Durable Oxygen Reduction.

The oxygen reduction reaction (ORR) is a critical process that limits the efficiency of fuel cells and metal-air batteries due to its slow kinetics, even when catalyzed by platinum (Pt). To reduce Pt usage, enhancing both the specific activity and electrochemically active surface area (ECSA) of Pt catalysts is essential. Here, ultrafine, grain boundary (GB)-rich Pt nanoparticle assemblies are proposed as efficient ORR catalysts. These nanowires offer a large ECSA and a high density of concave GB sites, which improve specific activity. Atoms at these GB sites exhibit increased coordination and lattice distortion, leading to a favorable reduction in oxygen binding energy and enhanced ORR performance. Furthermore, boron segregation stabilizes these GBs, preserving active sites during catalysis. The resulting boron-stabilized Pt nanoassemblies demonstrate ORR specific and mass activities of 9.18 mA cm-2 and 6.40 A mg-1 Pt (at 0.9 V vs. RHE), surpassing commercial Pt/C catalysts by over 35-fold, with minimal degradation after 60000 potential cycles. This approach offers a versatile platform for optimizing the catalytic performance of a wide range of nanoparticle systems.

Monomer Composition as a Mechanism to Control the Self-Assembly of Diblock Oligomeric Peptide-Polymer Amphiphiles.

Diblock oligomeric peptide-polymer amphiphiles (PPAs) are biohybrid materials that offer versatile functionality by integrating the sequence-dependent properties of peptides with the synthetic versatility of polymers. Despite their potential as biocompatible materials, the rational design of PPAs for assembly into multichain nanoparticles remains challenging due to the complex intra- and intermolecular interactions emanating from the polymer and peptide segments. To systematically explore the impact of monomer composition on nanoparticle assembly, PPAs were synthesized with a random coil peptide (XTEN2) and oligomeric alkyl acrylates with different side chains: ethyl, tert-butyl, n-butyl, and cyclohexyl. Experimental characterization using electron and atomic force microscopies demonstrated that the tail hydrophobicity impacted accessible morphologies. Moreover, the characterization of different assembly protocols (i.e., bath sonication and thermal annealing) revealed that certain tail compositions provide access to kinetically trapped assemblies. All-atom molecular dynamics simulations of micelle formation unveiled key interactions and differences in core hydration, dictating the PPA assembly behavior. These findings highlight the complexity of PPA assembly dynamics and serve as valuable benchmarks to guide the design of PPAs for a variety of applications, including catalysis, mineralization, targeted sequestration, antimicrobial activity, and cargo transportation.

Navigating the Landscape of Dry Assembling Ordered Particle Structures: Can Solvents Become Obsolete?

A spur on miniaturized devices led scientists to unravel the fundamental aspects of micro- and nanoparticle assembly to engineer large structures. Primarily, attention is given to wet assembly methods, whereas assembly approaches in which solvents are avoided are scarce. The "dry assembly" strategies can overcome the intrinsic disadvantages that are associated with wet assembly, e.g., the lack of versatility and scalability. This review uniquely summarizes the recent progress made to create highly ordered particle arrays without using a wet environment. Before delving into these methods, the surface interactions (e.g., van der Waals, contact mechanics, capillary, and electrostatics) are elaborated, as a profound understanding and balancing these are a critical aspect of dry assembly. To manipulate these interactions, strategies involving different forces, e.g., mechanical-based, electrical-based, or laser-induced, sometimes in conjunction with pre-templated substrates, are employed to attain ordered colloidal structures. The utilization of the ordered structures obtained without solvents is accompanied by specific examples. Dry assembly methods can aid us in achieving more sustainable assembly processes. Overall, this Review aims to provide an easily accessible resource and inspire researchers, including novices, to broaden dry assembly horizons significantly and close the remaining knowledge gap in the physical phenomena involved in this area.

Investigation of Thermodynamic Properties and Stability of Metal Oxide (CuO and Al2O3)/Deionized Water Nanofluids for Enhanced Heat Transfer Applications

The potential of nanofluids in improving heat transfer efficiency is well recognized, although there is a lack of clarity regarding the methods for assessing their stability and the influence on thermophysical properties. Moreover, the prevention of nanoparticle aggregation, which is essential for stability, requires further investigation. This study aims to address these issues by investigating the thermodynamic properties and stability of Al2O3/deionized water and CuO/deionized water nanofluids, which were prepared using magnetic stirring and ultrasonication. The stability assessment, conducted through standard deviation analysis, revealed that CuO (80 nm)/deionized water nanofluids exhibited greater stability compared to Al2O3 (80 nm)/deionized water nanofluids. The research explored the impact of temperature, volume concentration, and nanoparticle type under both static and dynamic conditions. Static tests focused on measuring thermal conductivity, viscosity, and specific heat, while dynamic tests involved a heat exchanger setup to determine heat transfer rates. The findings indicated that CuO nanofluids displayed the highest thermal conductivity and the most significant reduction in specific heat and heat transfer rate. Viscosity was found to increase with nanoparticle concentration and decrease with temperature. This study provides valuable insights into the thermophysical characteristics and stability of nanofluids, emphasizing the advantages of CuO-based nanofluids for heat transfer applications.

In-situ hydrothermal upgrading and mechanism of heavy oil with nano-Fe2O3 in the porous media

Hydrothermal upgrading is a promising technology for heavy oil, yet the impact of reservoir conditions on the catalytic effect of catalysts and the pathway are not clear. In this study, the effect of the formation environment on the catalytic upgrading process was investigated through simulating the reservoir conditions (2000 mD permeability, 25 % porosity) for catalytic hydrothermal cracking of heavy oil. Under the hydrothermal upgrading conditions（240 ℃, 24 h, 50 wt%, 0.1 wt% nano-Fe2O3）, 9.15 % of the heavy component(5.1 % resin and 4.05 % asphaltene) was converted to light component. The content of hydrocarbons below C17 in the saturated fraction increased from 36.29 % to 59.85 %. The structure of the asphaltene was disrupted resulting in a lower level of asphaltene stacking, and NC/NH ratio increased 13.61 % compared to heavy oil. In addition, the reservoir condition with quartz as the supporting medium improved the catalytic ability of iron oxide nanoparticles. When injected into the reservoir medium, nano-size facilitated dispersion on the surface of the proppant and inhibited the aggregation of nanoparticles, which ensured the continuous operation of the active sites on the surface of the catalyst. Electron transfer of Fe2+/Fe3+ catalyzed the heterolytic cleavage of covalent bonds of H2O/heavy oil molecules was the mechanism for heavy oil upgrading. These findings demonstrated the feasibility of in-situ upgrading of heavy oil through the use of nano-catalysts under reservoir conditions.

Cooperative aggregation of gold nanoparticles on phospholipid vesicles is electrostatically driven.

Gold nanoparticles (AuNP) are known to aggregate on the surface of lipid vesicles, yet the molecular mechanism behind this phenomenom remains unclear. In this work, we have investigated the binding behaviour of AuNPs, synthesized with pulsed laser ablation, to phospholipid vesicles under varying conditions of ionic strength (KCl concentration) and NP to vesicle ratios. Our observations reveal a strong influence of electrolyte concentration on AuNP aggregation mediated by vesicles. Notably, cluster formation is observed even at less than one AuNP per vesicle ratio at low enough ionic strengths. These results evidence a binding mechanism governed by electrostatic attraction with a distinct cooperative behaviour at very low salt concentrations, resulting in a significant increase in nanoparticle clustering. This behaviour is quantitatively analysed through a model that incorporates the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, considering the electrical double layer attraction between dissimilar, non-oppositely charged objects. This study not only provides insight into the fundamental understanding of nanoparticle-vesicle interactions but also suggests potential strategies for controlling nanoparticle assembly in biological and synthetic systems by tuning the ionic strength.

Development of cement slurries with additives of nanoclay particles for the construction of oil wells at elevated temperatures

Relevance. Strength decrease is a phenomenon that becomes more pronounced as the temperature rises above 110°C. It is characterized by significant chemical and microstructural changes that Portland cement undergoes at high temperatures. Adding silica particles (SiO2) to cement can significantly increase cement resistance to strength reduction when the temperature exceeds 110°C. Nanoclays are currently used in the cement industry to increase the strength of the cement matrix due to their ability to fill capillary micropores and due to their relatively small particle size. Aim. To investigate the effect of adding nanoparticles (nanoclay) to Saudi grade G cement on compressive and tensile strength, and cement stone permeability under high temperature conditions (300°С). Objects. Six samples of cement mortars with different concentrations of nanoclay, cement stones from, tested after 7 and 28 days of hardening at 25 and 300°C. Methods. Cement chemical composition was evaluated by the X-ray fluorescence method with the WORKSTN-V Olympus Vanta X-ray fluorescence analyzer. Cement physical composition was evaluated by the method of ray diffraction on the Mastersizer 2000 laser particle size analyzer. The test of the grouting stone samples was carried out in accordance with ISO 10426-2:2003 on a hydraulic press 65-L1132. The tensile strength of the samples by the Brazilian method was tested in accordance with ASTM D 3967-08 standard on a hydraulic press 65-L1132. The permeability of the samples was determined by single-phase stationary filtration at a facility for studying the filtration and capacitance properties of the PIK-OFP-UCH core in accordance with ISO 10426-2:2003. Results. The data obtained showed that cement destruction at extremely high temperatures can be avoided by using nanoclay (up to 3% by weight of cement). The microstructure of the cement matrix was significantly affected due to the aggregation of nanoparticles when more than 3% of nanoclay was added. All rheological characteristics of the cement slurry were improved by the addition of nanoclay particles.

Rational growth of highly luminescent CsPbBr3 nanoparticles via alkali metal doping-enabled modification of glass networks

Embedding halide perovskite nanoparticles (NPs) into glasses can be regarded as a feasible approach to improve their long-term stability when they are exposed to air or moisture. However, it remains elusive to rationally grow highly luminescent halide perovskite NPs owing to poor understanding of the relationship between glass network topology and NP precipitation. Here, by introducing alkali metal ions as “B-phase structural scissors”, the precipitation and aggregation of NPs are optimized based on glass network topology modulation, which boosts their photoluminescence performance. After Li doping, the photoluminescence quantum yield of CsPbBr3 perovskite NPs embedded in glass increases by 39% with respect to that of the undoped counterpart. The alkali metal ions are utilized to reduce thermal activation energy from 130.04 KJ mol-1 to 125.35 KJ mol-1 according to thermodynamics analysis, which corresponds to an increase in the size of the NPs. Benefiting from excellent chemical inertness, the luminescence intensity of as-made CsPbBr3 NP embedded glass retains near unity after soaking them in water for 180 days. The utilization of alkali metals as a facile strategy to modify the glass network enables improved performance of target NPs, thereby providing deeper insights into the design of host-dependent NP-functionalized glass.

Timescale dependent homogeneous assembly of lipid-polymer hybrid nanoparticles in laminar mixing for enhanced lung cancer treatment

The homogeneity of core–shell structure lipid-polymer hybrid nanoparticles (HNPs) is crucial for efficient intracellular cargo delivery. While microfluidic techniques have been recognized for their capabilities in precisely controlling the size and drug encapsulation efficiency, there is little research exploring the impact of mass transfer behavior within microchannels on the homogeneous assembly process of HNPs. Here, we manipulated the laminar flow state within TrM device to achieve controlled assembly of HNPs and explored a timescale dependent assembly technique to ensure the homogeneity of folate modified HNPs (FHNPs). Our founding indicate that this method enabled the control over the growth kinetics of PLGA cores within a timescale (τgrow) of 1–15 ms. The homogeneous ligand assembly on the surface of FHNPs can only be achieved when τgrow exceeds the timescale of functional lipid coating (τcoating). Compared to conventional bulk mixing methods, this strategy significantly reduces the risk of heterogeneous assembly in FHNPs fabrication and ensures consistent reproducibility across batches. The homogeneous FHNPs (HFHNPs) fabricated through this method exhibit precise control over particle size (ranging from 75 nm to 150 nm), low polydispersity index, and consistent core–shell structure. Furthermore, this strategy enhances the density of available folate ligands on the surface of FHNPs. In subsequent in vitro and in vivo anti-tumor assays, the icariside Ⅱ (IS) loaded HFHNPs (IS@HFHNPs) exhibited enhanced cellular uptake and tumor accumulation behavior. the timescale dependent homogeneous assembly method for HNPs developed in this research presents a promising avenue for maintaining quality in the synthesis of self-assembly composite nanomecidine.

Crystallization-dictated assembly of block copolymers and nanoparticles under three-dimensional confinement.

Crystallization-dictated self-assembly of crystalline block copolymers (BCPs) in solution has been utilized to produce many impressive nanostructures. However, when the assembly of crystalline BCPs happens in a three-dimensional (3D) confined space, predicting the self-assembly structure of BCPs becomes challenging due to the competition between crystallization and microphase separation. In this feature article, we summarize the recent progress in the self-assembly of crystalline BCPs under confinement, emphasizing the impact of crystallization behavior on the assembly structure. Furthermore, we highlight the crystallization-directed assembly of inorganic nanoparticles (NPs), either by pre-assembling crystalline polymers as templates or using crystalline polymer chain segments as ligands. By exploring the impact of crystallization behavior on the assembled structure of BCPs and NPs, it is helpful to predict and manipulate the properties of polymer/nanoparticle composites, thereby enabling the precise design of polymer metamaterials.