Formation Of Nanoparticle Clusters Research Articles

One-Pot Facile Synthesis of a Cluster of ZnS Low-Dimensional Nanoparticles for High-Performance Supercapacitor Electrodes.

To maximize the use of ZnS low-dimensional nanoparticles as high-performance supercapacitor electrodes, this work describes a simple one-pot synthesis method for producing a cluster of these particles. The ZnS nanoparticles fabricated in this work exhibit a cluster with unique low-dimensional (0D, 1D, and 2D) characteristics. Structural, morphological, and electrochemical investigations are all part of the thorough characterization of the produced materials. An X-ray diffraction pattern of clustered ZnS nanoparticles reflects the phase formation with highly stable cubic blende sphalerite polymorph. The confirmation of nanoparticle cluster formation featuring multiple low-dimensional nanostructures was achieved through field emission scanning electron microscopy (FE-SEM), while the internal structure was assessed using transmission electron microscopy (TEM). Systematically assessing the ZnS nanoparticles' electrochemical performance reveals their prospective qualities as supercapacitor electrode materials. The electrode assembled with this material on Ni foam demonstrates elevated specific capacitance (areal capacitance) values, reaching 716.8 F.g⁻1 (2150.4 mF.cm-2) at a current density of 3 mA.cm⁻2. Moreover, it reflects 69.1% capacitance retention with a four times increase in current density, i.e., 495.5 F.g-1 (1486.56 mF.cm-2) capacitance was archived at 12 mA.cm-2 with 100% Coulombic efficiency. Furthermore, the electrode exhibits prolonged cycling capability with 77.7% capacitance retention, as evidenced by its charge-discharge measurements sustained over 15,000 cycles at a current density of 25 mA cm⁻2.

Unusual gold nanoparticle-antibody interactions

The formation of an antibody (Ab) protein corona surrounding gold nanoparticles (AuNPs) is a crucial step in the design of immunological assays. The Ab corona stabilizes AuNPs, preventing their aggregation even at high ionic strength, and can be achieved by simply mixing Abs and AuNPs. In this paper, we report the unusual interactions between AuNPs and the antibody against L1 Cell Adhesion Molecule (L1CAM) purified from rabbits. We have observed that at low ionic strength, the addition of a wide range of concentrations of rabbit monoclonal Abs against L1CAM protein immediately causes the coagulation of citrate-capped gold nanoparticles. This finding is surprising since the addition of proteins to colloidal gold usually forms a stable protein corona. The combination of extinction spectra, dynamic light scattering (DLS), and transmission electron microscopy (TEM) measurements reveals the presence of small clusters of AuNPs coated by the antibodies, as well as micron-sized antibody aggregates. Furthermore, static light scattering measurements demonstrate that Ab self-interactions are attractive (with a negative second virial coefficient, B2) and induce very slow Ab self-aggregation over several months. Overall, these results indicate that, at low ionic strength, the presence of AuNPs enhances Ab-Ab interactions, leading to their rapid aggregation. Simultaneously, the self-aggregation of the antibodies coating the AuNPs results in the formation of nanoparticle clusters. The addition of NaCl to increase the ionic strength fully reverses the coagulation of AuNPs (the Ab-coated AuNPs repel each other) and dissolves the Ab aggregates (the Ab interactions become repulsive, with a positive B2). The AuNPs-induced enhancement of the aggregation process can be explained by considering that the highly favorable binding of Abs on the gold surface compensates for the entropic penalty associated with Ab-Ab aggregation. The phenomenon we observed is specific to anti-L1CAM purified from rabbits and aligns with very old reports on AuNP coagulation induced specifically by the immunoglobulins present in the cerebrospinal fluid of patients suffering from neurosyphilis or multiple sclerosis (C. Lange Zeitschr. Chemotherap., 1912, 1, 44). It is reasonable to hypothesize that other antibodies exhibit this unusual behavior, so this work may aid in the interpretation of “anomalous” results that might otherwise be attributed to errors in fine-tuning AuNPs-Abs conjugation protocols.

Exploring Pt-Pd Alloy Nanoparticle Cluster Formation through Conventional Sizing Techniques and Single-Particle Inductively Coupled Plasma-Sector Field Mass Spectrometry.

Accurate characterization of Pt-Pd alloy nanoparticle clusters (NCs) is crucial for understanding their synthesis using Gas-Diffusion Electrocrystallization (GDEx). In this study, we propose a comprehensive approach that integrates conventional sizing techniques-scanning electron microscopy (SEM) and dynamic light scattering (DLS)-with innovative single-particle inductively coupled plasma-sector field mass spectrometry (spICP-SFMS) to investigate Pt-Pd alloy NC formation. SEM and DLS provide insights into morphology and hydrodynamic sizes, while spICP-SFMS elucidates the particle size and distribution of Pt-Pd alloy NCs, offering rapid and orthogonal characterization. The spICP-SFMS approach presented enables detailed characterization of Pt-Pd alloy NCs, which was previously challenging due to the absence of multi-element capabilities in conventional spICP-MS systems. This innovative approach not only enhances our understanding of bimetallic nanoparticle synthesis, but also paves the way for tailoring these materials for specific applications, marking a significant advancement in the field of nanomaterial science.

Magnetic Relaxation Switching Assay Using IFNα-2b-Conjugated Superparamagnetic Nanoparticles for Anti-Interferon Antibody Detection

Type I interferons, particularly IFNα-2b, play essential roles in eliciting adaptive and innate immune responses, being implicated in the pathogenesis of various diseases, including cancer, and autoimmune and infectious diseases. Therefore, the development of a highly sensitive platform for analysis of either IFNα-2b or anti-IFNα-2b antibodies is of high importance to improve the diagnosis of various pathologies associated with the IFNα-2b disbalance. For evaluation of the anti-IFNα-2b antibody level, we have synthesized superparamagnetic iron oxide nanoparticles (SPIONs) coupled with the recombinant human IFNα-2b protein (SPIONs@IFNα-2b). Employing a magnetic relaxation switching assay (MRSw)-based nanosensor, we detected picomolar concentrations (0.36 pg/mL) of anti-INFα-2b antibodies. The high sensitivity of the real-time antibodies’ detection was ensured by the specificity of immune responses and the maintenance of resonance conditions for water spins by choosing a high-frequency filling of short radio-frequency pulses of the generator. The formation of a complex of the SPIONs@IFNα-2b nanoparticles with the anti-INFα-2b antibodies led to a cascade process of the formation of nanoparticle clusters, which was further enhanced by exposure to a strong (7.1 T) homogenous magnetic field. Obtained magnetic conjugates exhibited high negative MR contrast-enhancing properties (as shown by NMR studies) that were also preserved when particles were administered in vivo. Thus, we observed a 1.2-fold decrease of the T2 relaxation time in the liver following administration of magnetic conjugates as compared to the control. In conclusion, the developed MRSw assay based on SPIONs@IFNα-2b nanoparticles represents an alternative immunological probe for the estimation of anti-IFNα-2b antibodies that could be further employed in clinical studies.

Factors affecting nanofluids behaviour: A review

AbstractNanotechnology applications have occupied a wide range in engineering applications and achieved distinctive performance due to their potential as a working fluid instead of conventional liquids due to their outstanding performance. Sustaining stable performance nanofluids for a longer time retaining their properties without clustering and nanoparticles aggregation in the base fluid represents a significant challenge that can influence nanofluid properties and thermal behaviour. This review highlights some important factors that influence the stability of nanofluids, such as the size, concentration ratio of nanoparticles, and the type of base fluid, in addition discussing the methods used to improve the stability of nanofluids, such as the effect of cluster formation of nanoparticles in the base fluid due to Brownian motion and the role of the surfactants in preventing or reducing the agglomeration of nanoparticles, zeta potential and pH in estimating nanofluids stability. The factors mentioned affect the thermophysical properties of nanoparticles in preparing nanofluids and enhance their performance. This review provides information which helps improve the wide range usability of nanofluids for preparing stable nanofluids with good thermophysical properties.

Nanoparticle cluster formation mechanisms elucidated via Markov state modeling: Attraction range effects, aggregation pathways, and counterintuitive transition rates.

Nanoparticle clusters are promising candidates for developing functional materials. However, it is still a challenging task to fabricate them in a predictable and controllable way, which requires investigation of the possible mechanisms underlying cluster formation at the nanoscale. By constructing Markov state models (MSMs) at the microstate level, we find that for highly dispersed particles to form a highly aggregated cluster, there are multiple coexisting pathways, which correspond to direct aggregation, or pathways that need to pass through partially aggregated, intermediate states. Varying the range of attraction between nanoparticles is found to significantly affect pathways. As the attraction range becomes narrower, compared to direct aggregation, some pathways that need to pass through partially aggregated intermediate states become more competitive. In addition, from MSMs constructed at the macrostate level, the aggregation rate is found to be counterintuitively lower with a lower free-energy barrier, which is also discussed.

Fate of Antibody-Targeted Ultrasmall Gold Nanoparticles in Cancer Cells after Receptor-Mediated Uptake.

Nanoparticles with ultrasmall sizes (less than 10 nm) offer many advantages in biomedical applications compared to their bigger counterparts, including better intratumoral distribution, improved pharmacokinetics (PK), and efficient body clearance. When functionalized with a biocompatible coating and a target-specific antibody, ultrasmall nanoparticles represent an attractive clinical translation platform. Although there is a tremendous body of work dedicated to PK and the biological effects of various nanoparticles, little is known about the fate of different components of functionalized nanoparticles in a biological environment such as in live cells. Here, we used luminescence properties of 5 nm gold nanoparticles (AuNPs) to study the intracellular trafficking and fate of the AuNPs functionalized with an organic layer consisting of a polyethylene glycol (PEG) coating and epidermal growth factor receptor (EGFR)-targeting antibody. We showed that intracellular uptake of the targeted 5 nm AuNPs results in a strong two-photon luminescence (TPL) that is characterized by broad emission and very short lifetimes compared to the fluorescence of the nanoparticle-conjugated fluorophore-tagged antibody, thereby allowing selective imaging of these components using TPL and two-photon excited fluorescence lifetime microscopy (2P-FLIM). Our results indicate that the nanoparticle’s coating is detached from the particle’s surface inside cells, leading to formation of nanoparticle clusters with a strong TPL. Furthermore, we observed an optically resolved spatial separation of the gold core and the antibody coating of the particles inside cells. We used data from two-photon microscopy, 2P-FLIM, electron microscopy, and in vitro assays to propose a model of interactions of functionalized 5 nm AuNPs with live cells.

On evaluation of magnetic field effect on the formation of nanoparticles clusters inside aqueous magnetite nanofluid: An experimental study and comprehensive modeling

This experimental study is conducted to explore the rheological behavior of magnetite-water ferrofluid in the attendance of an external magnetic field (MF). Tetramethylammonium hydroxide is used as surfactant to increase the stability of prepared ferrofluids. The impacts of MF strength (0–480 G) and volume concentration of nanoparticles (0.3–1.5%) on the outcomes are examined. It was found that as the shear rate increases, the viscosity decreases sharply and then tends to a fixed number and therefore, the magnetite-water has non-Newtonian pseudoplastic behavior. It was also found that the application of the MF both increases the viscosity and enhances the non-Newtonian behavior of the ferrofluid. Moreover, it was found that the rise of nanoparticle concentration (φ) leads to the increase of ferrofluid viscosity. Then, the artificial neural network is applied to develop a prediction model for the rheological behavior of water- magnetite ferrofluid in both the absence and attendance of an external MF based on the obtained experimental data. The outcomes revealed that the developed models are capable of predicting the outputs in the absence and attendance of an external MF with R2 value of 0.9772 and 0.9692.

Initial interaction of citrate-coated iron oxide nanoparticles with the glycocalyx of THP-1 monocytes assessed by real-time magnetic particle spectroscopy and electron microscopy

Interaction with biological material can alter physicochemical parameters of magnetic nanoparticles and might thereby change their magnetic behavior with potentially important implications for various nanoparticle applications. Little is known about changes of the magnetic behavior that occur during the initial phase of cell binding and uptake. We investigate the magnetic behavior of very small superparamagnetic iron-oxide nanoparticles (VSOP) during initial contact with THP-1 monocytes. We combine real-time magnetic particle spectroscopy (MPS), a fast and sensitive method for specific detection of magnetic nanoparticles in biological specimen with high-pressure-freezing/freeze-substitution transmission electron microscopy (HPF/FS-TEM), enabling us to generate snapshots of the interaction of VSOP with the cellular glycocalyx. MPS reveals significant changes of the dynamic magnetic behavior within seconds after VSOP injection into monocyte suspensions that correlate with the formation of nanoparticle clusters in the glycocalyx. The combination of real-time MPS and HPF/FS-TEM provides an ideal platform to analyze magnetic behaviors of nanoparticles upon interaction with cells and tissues.

The effect of structure on the low-temperature electrical conductivity of carbon nanocomposite temperature sensors

The electrical conductivity of carbon nanocomposite TVO-series resistors used as temperature sensors are studied in a wide temperature range of 300–1.8 K. It is found that hopping conductivity emerges at temperatures below 77 K. The shape of its temperature dependence varies for resistors having different resistance at room temperature. Raman spectra measurements have shown that the resistors differ according to the size of the carbon nanoparticles in the composite material of the conducting region and its dispersion along the direction of the current. The measured dependences of conductivity on temperature and magnitude of the applied electric field, wherein the charge carriers are heated by the field, are used to determine charge carrier localization lengths, which are almost two orders of magnitude greater than the carbon nanoparticles. The observed features of the conductivity can be explained by a nonuniform distribution of carbon in the composite material and the formation of nanoparticle clusters with quasi-metallic conductivity, while the conductivity between the clusters occurs due to carrier hopping.

Green Synthesis of Copper Oxide Nanoparticles Using Ixiro coccinea Plant Leaves and its Characterization

A green method using biological dependable processes has been established for the synthesis of CuO nanoparticles. Synthesis of CuO nanoparticles were done using an environmental friendly method by taking aqueous solution of copper(II) sulfate and leaf extract of Ixoro coccinea. Characterization of the synthesized CuO nanoparticles was done using instruments such as UV-visible spectrophotometer, scanning electron microscopy, transmission electron microscopy, and Fourier-transform infrared spectroscopy. The existence of peaks obtained in FTIR confirms CuO nanoparticles. A visible change was observed in the solution prepared as it changed from light blue to light brown to dark brown once the extract was added to the copper sulfate solution. An average size of 300 nm was obtained during SEM analysis due to the formation of nanoparticle clusters. The TEM images of CuO nanoparticles separated after ultrasonication of the dispersion show that they possess an average size of 80–110 nm. It was found that the ultrasonication increases the distribution of nanoparticles in a fluid by preventing the formation of clusters. It was found that Ixiro coccinea plant leaves are a suitable alternative for the easy and green synthesis of CuO nanoparticles.

Tunable clustering of magnetic nanoparticles in microgels: enhanced magnetic relaxivity by modulation of network architecture.

In the present work we used microgels as colloidal containers for the loading of hydrophobic magnetic nanoparticles using the solvent exchange method. We varied systematically two parameters: (i) the crosslinking degree of microgels (1-4.5 mol% crosslinker) and (ii) loading of hydrophobic magnetite nanoparticles (d = 7 nm) in microgels (2-10 wt%). The experimental data show that the interplay between these two parameters provides efficient control over the clustering of magnetic nanoparticles in the microgel structure. Transverse magnetization relaxation measurements indicate that the formation of nanoparticle clusters in microgels induces non-linear enhancement of the relaxivity with the increase of nanoparticle loading in microgels. The results suggest that the modulation of the microgel network architecture can be efficiently applied to trigger self-assembly processes inside microgels and design hybrid colloids with unusual morphologies and properties.

Synthesis of colloidal silver nanoparticle clusters and their application in ascorbic acid detection by SERS

Ascorbic acid (vitamin C) has an essential role in the human body mainly due to its antioxidant function. In this work, metallic silver nanoparticle (AgNP) colloids were used in SERS experiments to detect ascorbic acid in aqueous solution. The AgNPs were synthesized by a green method using potato starch as reducing and stabilizing agent, and water as the solvent. The optical properties of the yellowish as-synthesized silver colloids were characterized by UV–vis spectroscopy, in which besides a typical band at 410 nm related to the localized surface plasmon resonance of the silver nanoparticles, a shoulder band around 500 nm, due to silver nanoparticle cluster formation, is presented when relatively higher concentrations of starch are used in the synthesis. These starch-capped silver nanoparticles show an intrinsic Raman peak at 1386 cm−1 assigned to deformation modes of the starch structure. The increase of the intensity of the SERS peak at 1386 cm−1 with an increase in the concentration of the ascorbic acid is related to a decrease of the gap between dimers and trimers of the silver nanoparticle clusters produced by the presence of ascorbic acid in the colloid. The limit of detection of this technique for ascorbic acid is 0.02 mM with a measurement concentration range of 0.02–10 mM, which is relevant for the application of this method for detecting ascorbic acid in biological specimen.

Two-Dimensional Nanoparticle Cluster Formation in Supercritical Fluid CO2.

Supercritical fluid carbon dioxide (sc-CO2) is capable of depositing nanoparticles in small structures of silicon substrates because of its gas-like penetration, liquid-like solvation abilities, and near-zero surface tension. In nanometer-sized shallow wells on silicon surface, formation of two-dimensional (2D) monolayer metal nanoparticle (NP) clusters can be achieved using the sc-CO2 deposition method. Nanoparticles tend to fill nanostructured holes first, and then, if sufficient nanoparticles are available, they will continue to cover the flat areas nearby, unless defects or other surface imperfections are available. In addition, SEM images of two-dimensional gold (Au) nanoparticle clusters formed on a flat silicon surface with two to a dozen or more of the nanoparticles are provided to illustrate the patterns of nanoparticle cluster formation in sc-CO2.

Effect of nanostructured composite powders on the structure and strength properties of the high-temperature inconel 718 alloy

The experimental results of the effect of powder nanomodifiers of refractory compounds on the strength properties, the macro- and microstructure of the high-temperature Inconel 718 alloy have been presented. It has been shown that the introduction of powder modifiers into the melt leads to a decrease in the average grain size by a factor of 1.5–2 in the alloy. The long-term tensile strength of the alloy at 650°C increases 1.5–2 times, and the number of cycles at 482°C before fracture grows by more than three times. The effect of nanoparticles on the grain structure and strength properties of the alloy is due to an increase in the number of generated crystallization centers and the formation of nanoparticle clusters of refractory compounds at boundaries and junctions in the formed grain structure, which hinder the development of recrystallization processes in the alloy.

Dehydration-mediated cluster formation of nanoparticles.

Drying procedure is a powerful method to modulate the bottom-up assembly of basic building component. The initially weak attraction between the components screened in a solution strengthens as the solvent evaporates, organizing the components into structures. Drying is process-dependent, irreversible, and nonequilibrated, thus the mechanism and the dynamics are influenced by many factors. Therefore, the interaction of the solvent and the elements during the drying procedure as well as the resulting pattern formations are strongly related. Nonetheless still many things are open in questions in terms of their dynamics. In this study, nanoscale dehydration procedure is experimentally investigated using a nanoparticle (NP) model system. The role of water is verified in a single NP scale and the patterns of collective NP clusters are determined. Stepwise drying procedures are proposed based on the location from which water is removed. Effective water exodus from a unit NP surface enhances the attractive interaction in nanoscale and induces heterogeneous distribution in microscale. This study provides fundamental proof of systematic relation between the dehydration process and the resultant cluster patterns in hierarchical multiscales.

Different interaction modes of biomolecules with citrate-capped gold nanoparticles.

In this study, we investigated the interaction between five biorelevant molecules and citrate-capped gold nanoparticles using dynamic light scattering, ζ-potential analysis, UV-vis absorption spectroscopy, and transmission electron microscopy. The five biomolecules are bovine serum albumin (BSA), two immunoglobulin G (IgG) proteins, immunoglobulin M (IgM), and a polysaccharide molecule, hyaluronan. BSA, IgG, and IgM are high abundance proteins in blood. Hyaluronan is a major component of the extracellular matrix. An abnormal level of hyaluronan in blood is associated with a number of medical conditions including rheumatoid arthritis and malignancy. Five different interaction modes were observed from these molecules. While BSA and IgM interact with the gold nanoparticles by forming electrostatic interactions with the citrate ligands, IgG and hyaluronan adsorb to the nanoparticle metal core by displacing the citrate ligands. BSA, rabbit IgG, and hyaluronan formed a stable monolayer on the nanoparticle surface. Human IgG and IgM caused nanoparticle cluster formation upon interacting with the gold nanoparticles. For the first time, we discovered that hyaluronan, a highly negatively charged polyglycosaminoglycan, exhibits an exceptionally strong affinity toward the citrate-gold nanoparticles. It can effectively compete with IgG to adsorb to the gold nanoparticles. This finding has exciting implications for future research: the molecular composition of a protein corona formed on a nanoparticle surface upon mixing the nanoparticle with blood or other biological fluids may vary according to the pathological conditions of individuals, and the analysis of these compositions could potentially lead to new biomarker discovery with diagnostic applications.

Nozzleless spray cooling using surface acoustic waves

Surface acoustic wave (SAW) atomization is an attractive approach for generating monodispersed microdroplets for a diversity of applications, from drug delivery to mass spectrometry, due to its reliability, miniaturizability, and portability. Here, we demonstrate a nozzleless spray cooling technique based on SAW atomization, with the key advantage of downward scalability: increasing the operating frequency facilitates the fabrication of a chip-sized atomizer to use in compact cooling of electronic devices. Using deionised water, cooling is improved by 15% when the atomization rate is increased by 40%; when the gap separating the SAW device and heat source is halved, the cooling is improved by 20%. By constructing the device such that the atomized droplets are easily deposited upstream of the flow circulation, the performance is improved further. The atomization of CuO nanoparticle suspensions (at 3%) increased the cooling performance by 30%. Merely increasing the nanoparticle mass concentration in the suspension from 1% to 3% leads to an improvement in the cooling by 10% due to the deposition and formation of nanoparticle clusters on the heated surface, thereby increasing the total surface area. Further increases in the nanoparticle concentration to 10% however results in a diminution in the cooling due to the increase in the suspension viscosity μ, that leads to a reduction in the atomization rate ṁ~μ−1/2 for a given input power. Finally, we demonstrate the concept of using tapered finger transducers to selectively enhance local cooling in a desired area by simply changing the excitation frequency, without requiring repositioning of the SAW device.

Influence of semiconducting properties of nanoparticle coating on the electrochemical actuation of liquid metal marble

Semiconducting properties of nanoparticle coating on liquid metal marbles can present opportunities for an additional dimension of control on these soft objects with functional surfaces in aqueous environments. We show the unique differences in the electrochemical actuation mechanisms of liquid metal marbles with n- and p-type semiconducting nanomaterial coating. A systematic study on such liquid metal marbles shows voltage dependent nanoparticle cluster formation and morphological changes of the liquid metal core during electrochemical actuations and these observations are unique to p-type nanomaterial coated liquid metal marbles.

Study of the bioconjugation of ternary alloyed ZnCdTe nanocrystals to Concanavalin A

Abstract This work describes the first spectroscopic study of the covalent binding of Concanavalin A with ZnCdTe semiconductor nanocrystals, together with structural characterization of the bioconjugates. Glutathione-capped ZnCdTe nanocrystals were prepared in an aqueous medium and conjugated to Concanavalin A using glutaraldehyde as the coupling agent. Morphological characterization of the bioconjugates revealed the formation of nanoparticle clusters resulting from the binding of protein molecules and the formation of bridges between two or more ZnCdTe nanocrystals. This caused a progressive decrease in the photoluminescence intensity of the nanocrystals when the amount of protein was increased. Nonetheless, the emission intensity remained at a satisfactory level after bioconjugation. The presence of the protein also greatly reduced the thermal quenching of quantum dot photoluminescence at higher temperatures, indicating that changes in the protein conformation might favor passivation of the nanocrystal surface.