Size Of Nanoparticle Clusters Research Articles

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.

Study of the Effect of ZnO Functionalization on the Performance of a Fully Formulated Engine Oil.

The automotive sector is demanding higher specifications to achieve maximum efficiency; in this sense a new generation of lubricants with higher thermo-oxidative stability and superior tribological properties is being explored. The formulation of nanolubricants based on the nature of different nanomaterials is one of the most recent approaches, with several gaps to cover, such as dispersion stability, related to the compatibility of proposed nanomaterials with conventional additives and baseoils used in lubricant formulation. This study evaluated the effect of ZnO nanomaterial dispersed in a commercial engine oil using two different approaches; the use of surfactant and nanomaterial surface functionalization to promote higher stability and lower cluster size. Experimental evidence shows a synergetic effect between the tribological protection mechanism and the antioxidant properties in the lubricant. The effect of nanoparticle cluster size, functionalization level, and nanomaterial content are presented.

Mechanical behavior and reinforcement mechanism of nanoparticle cluster fillers in dental resin composites: Simulation and experimental study.

In dental resin composites (DRCs), the structure of fillers has a great impact on the mechanical behavior. The purpose of this study is to gain an in-depth understanding of the reinforcement mechanism and mechanical behavior of DRCs with nanoparticle clusters (NCs) fillers, thereby providing a guidance for the optimal design of filler structures for DRCs. This work pioneers the use of discrete element method (DEM) simulations combined with experiments to study the mechanical behavior and reinforcement mechanism of DRCs with NCs fillers. The uniaxial compressive strength (UCS) of NCs-reinforced DRCs have an improvement of 9.58 % and 15.02 % in comparison with nanoparticles (NPs) and microparticles (MPs), respectively, because of the ability of NCs to deflect cracks and absorb stress through gradual fracturing. By using NCs and NPs as co-fillers, the internal defects of DRCs can be reduced, resulting in a further improvement of UCS of DRCs by 6.21 %. Furthermore, the mechanical properties of DRCs can be effectively improved by increasing the strength of NCs or reducing the size of NCs. This study deepens the understanding of relationship between filler structure and mechanical behavior in DRCs at the mesoscale and provides an avenue for the application of DEM simulations in composite materials.

Controlled synthesis of gemini surfactant-capped gold nanoparticles. Gemini structure-nanoparticle properties relationship study

Gold nanoparticles were prepared by the method of chemical reduction utilising sodium borohydride as reducing agent and stabilised with bisammonium gemini surfactants with variable length of polymethylene spacer. Physico-chemical investigations indicated the presence of plasmon resonance peaks in the wavelength range 507–544 nm for all investigated Au nanodispersions. The nanoparticle size analysis shows the relationship between the size of gold nanoparticles and the spacer length of stabilising gemini molecules. The strong aggregation tendency of gemini surfactants with short polymethylene spacer composed of 2–4 methylene units in aqueous solutions may be responsible for the formation of clusters of gold nanoparticles which results in the observed large hydrodynamic size of nanoparticle clusters at the surfactants concentrations below the CMC. At higher surfactant-to-gold molar ratio values, clusters disintegration occurs and the decrease in size of the nanoparticles is observed. The shape of gold nanoparticles was found to be spherical and polyhedral, as evidenced by the SEM images. The size values varied between 30–60 nm and 10–15 nm for AuNPs capped with gemini molecules with short and medium/long spacer, respectively. Gold nanoparticles are strongly positively charged, with positive zeta potential values being in the interval +44 to +90 mV in the whole analysed region of molar ratio values and surfactant spacer length. The biological experiments indicate a dependence of biological activity of gold nanoparticles on the structural parameter (spacer length) of stabilising gemini molecules. Both cytotoxicity and anti-inflammatory activity of gold nanoparticles were found to increase with the increasing gemini spacer length up to 12 methylene groups in the spacer.

Терапевтический эффект наноалмазов взрывного синтеза при кобальтиндуцированном дерматите

The aim of the research. To evaluate the therapeutic eff ect of modifi ed nanodiamonds (MND) of explosive synthesis for treatment of allergic contact dermatitis induced by cobalt ions. Material and methods. Th e study was performed on guinea pigs. Th e animals were divided into 3 groups (6 animals in each group). Allergic contact dermatitis was initiated using 2% aqueous solution of cobalt nitrate applied to the animals’ skin for 14 days according to the common procedure. For allergic contact dermatitis treatment, glycerol and MND suspension with the nanoparticle concentration of 5g · l-1 prepared in glycerol were used. MND with high colloidal stability in water suspensions and the average nanoparticle cluster size of d50 = 50nm was used in the work. Th e animals of group I were controls: aft er allergic contact dermatitis development, their skin was not treated by any means for 7 days. Th e animals in groups II and III were experimental: aft er allergic contact dermatitis initiation, their skin was treated for 7 days using glycerol and MND suspension, respectively. Upon experiment completion, biopsy of skin sample was performed on all animals for histological and spectral examination. The content of cobalt in skin samples was determined through atomic adsorption spectroscopy. Results. The results of histological and morphometric analysis indicate that, in the case with dermatitis modelled in guinea pigs using cobalt ions, treatment of the animals’ skin with MND suspension reduces allergic inflammation intensity. Th e therapeutic effect of MND is caused by adsorption of cobalt ions onto nanoparticles and their subsequent elimination from the skin, which complies with the atomic adsorption spectroscopy data. Conclusion. Th e prospects of MND as a new therapeutic agent for binding and elimination of chemical allergens (particularly, cobalt ions inducing the allergic contact dermatitis development) are discussed.

Deposition of Ureido and Methacrylate Functionalities Onto Silica Nanoparticles and its Effect on the Properties of Polypropylene-Based Nanodielectrics

Surface modification of nanoparticles is often utilized to tailor the interfacial properties in dielectric nanocomposites. Introducing different functional groups to the nanoparticles’ surface may induce localized states (traps) that can enhance the dielectric performance of the material depending on their density and energy levels. Furthermore, surface modification of the filler can affect the dispersion quality and crystallization of the nanocomposites which can ultimately alter the dielectric response of the material. In this study, functionalization of silica nanoparticles is demonstrated using 3-(trimethoxysilyl)propyl methacrylate (TMPM) and 1-[3-(trimethoxysilyl)propyl]urea (TMPU) as modifying agents. The effect of such modifications on the crystallization behavior, dispersion quality of the nanoparticles, as well as charge trapping and transport under a medium DC field is studied in nanocomposites based on polypropylene (PP)/ethylene-octene-copolymer (EOC) blends at 1% and 5% of filler concentrations. The results show that both ureido and methacrylate functional groups introduce localized states, but with different energy levels. Nitrogen containing ureido groups in TMPU tend to introduce deeper traps to the filler-polymer interfaces, compared to the methacrylate silane modification. Comparing the two types of surface functionalization, the ureido-functionalized silica resulted in a suppression of space charge formation at the interfaces under a medium DC electric field, despite the relatively larger mean cluster size of nanoparticles.

Blowup of Accidental Images as a Passageway to Discovery: Insights into the Interaction between Hydroxyapatite Nanoparticles and Human Mesenchymal Stem Cells

Despite decades of research into the interaction between cells and nanoparticles, there is a lack of consensus regarding how specific physicochemical characteristics of the nanoparticles, including chemical composition, crystallinity, size, morphology, charge, and aspect ratio, among others, govern their internalization and intracellular fate. Methodological novelties offer new perspectives on the same old problematics, and often translate into an improved understanding of the given topic. Inspired by an analogy with the theme of the movie, Lisbon Story, a conceptually unconventional method for gaining insight into the interaction between nanoparticles and cells is proposed here. It involves the random, “Take 1” capture of an atomic force micrograph showing the interaction of human mesenchymal stem cells and clusters of spherical hydroxyapatite nanoparticles with a broad distribution of sizes and shapes, the blowup of its segments, and their detailed qualitative inspection. This method led to the derivation of three illustrative hypotheses, some of which were refuted and some corroborated. Specifically, the presupposition that there is an inverse relationship between the cellular uptake efficiency and the size of nanoparticle clusters was confirmed, both empirically and through a literature meta-analysis, but the idea that the geometry of these clusters affects the uptake was refuted. The definite presence of morphological determinants of the cellular uptake at the level of elementary particles, not clusters thereof, however, was confirmed in an alternative experiment. Likewise, immunofluorescent studies demonstrated that relatively large and irregularly shaped nanoparticle clusters do get internalized and localized to the perinuclear area, where they engage in an intimate interaction with the cell nucleus. The proposed enhancement of the binding between cells and biomaterials by increasing the surface ruffling consequential to the nanoparticle uptake - in analogy with the enhanced cell adhesion achieved by introducing topographic irregularities to smooth biomaterial surfaces - was also confirmed by showing that the uptake improves the stem cell adhesion. The uptake also augmented the stem cell viability and the proliferative capacity of cells reseeded with this internal nanoparticle cargo on a fresh surface, albeit with moderate levels of statistical significance and the caveat of its presumed dependence on the cell type, the nanoparticle chemistry and dose, and the overall stage in the transition of the multipotent cells toward an osteoprogenitor lineage.

Optical limiting in suspension of detonation nanodiamonds in engine oil

The optical limiting (OL) of detonation nanodiamond (DND) suspensions in engine oil was studied at a temperature range of 20°C to 100°C. Oil suspensions were prepared on the basis of the DNDs with an average nanoparticle cluster size in hydrosols (Daver) of 50 and 110 nm. Raman spectroscopy was used to characterize the samples. The OL investigation was carried out by the z-scan technique. The fundamental (1064 nm) and second (532 nm) harmonic radiations of YAG:Nd3+ laser with passive Q-switching as an excitation source were used. The OL thresholds for both suspensions at 532 and 1064 nm were determined. It is shown that a decrease in the average nanoparticle cluster size as well as an increase of the wavelength of the incident radiation leads to the OL threshold increase. It is established that the OL performance is not influenced by increasing the temperature from 20°C to 100°C. The results obtained show the possibility of using the DNDs suspensions in engine oil as an optical limiter in a wide temperature range.

Cluster size distribution of spherical nanoparticles in polymer nanocomposites: rheological quantification and evidence of phase separation.

Currently, it is a great challenge to characterize the dispersion quality of nanoparticles in nanocomposites through experimental techniques. In this work, we suggest a new rheological method based on the strain rate amplification effect to determine the cluster size distribution in polymer nanocomposites. The dispersion exponents of nanoparticles from this rheological method are in good agreement with the cluster analysis of transmission electron microscope (TEM) images. We also obtain a critical value of the dispersion exponent from the effective specific surface area of clusters, which separates the well-dispersed state and the phase-separated state. Our results indicate that rheology can be used as a convenient and effective structural analysis method to characterize the nanoparticle cluster size distribution in polymer nanocomposites.

Controlled aggregation and cell uptake of thermoresponsive polyoxazoline-grafted superparamagnetic iron oxide nanoparticles.

Hydrophilic polymer-coated iron oxide nanoparticles are potential materials for a plethora of applications in the biotechnological field. Typical such polymers, e.g. dextran or poly(ethylene glycol), lack the ability to tailor the biological response to an environmental trigger, while common responsive polymers such as poly(N-isopropylacrylamide) or poly(acrylic acid) are not suitable for biomedical applications. We present the synthesis and characterization of superparamagnetic iron oxide nanoparticles with thermoresponsive polyoxazoline brushes grafted at unprecedented density using nitrodopamine anchor chemistry. Reversible aggregation/deaggregation is observed in water and biological medium, confirming control over the colloidal stability. Thermal switching of the solubility could only be achieved by global heating of the sample, while local magnetothermal heating did not produce a sufficiently strong temperature gradient through the brush. Varying the polymer composition allows for tuning of the lower critical solution temperature (LCST) as well as the average nanoparticle cluster size obtained upon heating. The LCST of polyoxazolines and the thermal colloidal stability are shown to be greatly affected by ion concentration, by polymer grafting density and also by the presence of serum protein; this shows that transition temperatures of free polymers in water can be very misleading for the design of polymer-coated nanomaterials for biomedical applications. Finally, the thermoresponsive SPION are shown to be non-cytotoxic and with a low cell uptake scaling with the hydration of the polymer brush, which is tuned by the polymer composition. Thus, we demonstrate that pozylated nanoparticles provide the advantages of PEG- and PNIPAM-grafted nanoparticles, but provide a tunable and more easily functionalizable platform for further development.

Growth of tin oxide thin films composed of nanoparticles on hydrophilic and hydrophobic glass substrates by spray pyrolysis technique

In this paper, we have demonstrated the growth of tin oxide (SnO2) thin films composed of nanoparticles on hydrophobic (siliconized) and hydrophilic (non-siliconized) glass substrates by using the spray pyrolysis technique. X-ray diffraction (XRD) analysis confirmed the formation of SnO2 thin films with tetragonal rutile-phase structure. Average particle size of nanoparticles was determined to be in the range of 3–4nm measured from the front view images obtained by a field emission gun scanning electron microscope (FESEM), while the size of nanoparticle clusters, when present, were in the range of 11–20nm. Surface morphology of SnO2 films grown over hydrophobic substrates revealed larger isolated particles which are less crowded compared to the highly crowded and agglomerated smaller particles in films on hydrophilic substrates. Blue shift in the band gap is observed in samples in which the average particle size is slightly larger than the exciton Bohr radius. Photoluminescence (PL) analysis of samples grown over hydrophobic substrates exhibited an intense defect level emission and a weak near band edge emission. The enhanced visible emission from these SnO2 thin films is attributed to lattice defects formed during the film growth due to the mismatch between the film and the hydrophobic substrate surface.

Modeling of particle agglomeration in nanofluids

Agglomeration strongly influences the stability or shelf life of nanofluid. The present computational and experimental study investigates the rate of agglomeration quantitatively. Agglomeration in nanofluids is attributed to the net effect of various inter-particle interaction forces. For the nanofluid considered here, a net inter-particle force depends on the particle size, volume fraction, pH, and electrolyte concentration. A solution of the discretized and coupled population balance equations can yield particle sizes as a function of time. Nanofluid prepared here consists of alumina nanoparticles with the average particle size of 150 nm dispersed in de-ionized water. As the pH of the colloid was moved towards the isoelectric point of alumina nanofluids, the rate of increase of average particle size increased with time due to lower net positive charge on particles. The rate at which the average particle size is increased is predicted and measured for different electrolyte concentration and volume fraction. The higher rate of agglomeration is attributed to the decrease in the electrostatic double layer repulsion forces. The rate of agglomeration decreases due to increase in the size of nano-particle clusters thus approaching zero rate of agglomeration when all the clusters are nearly uniform in size. Predicted rates of agglomeration agree adequate enough with the measured values; validating the mathematical model and numerical approach is employed.

Stabilization of nano-TiO2 aqueous dispersions with poly(ethylene glycol)-b-poly(4-vinyl pyridine) block copolymer and their incorporation in photocatalytic acrylic varnishes

Abstract In this work, TiO 2 nanoparticles were dispersed and stabilized in water using a novel type of dispersant based on tailor-made amphiphilic block copolymers of poly(ethylene glycol)-block-poly(4-vinyl pyridine) (mPEG- b -P4VP) prepared by atom transfer radical polymerization (ATRP). The performance of this new block copolymer as dispersant was compared to a polyelectrolyte dispersant commonly used for TiO 2 , sodium salt of polyacrylic acid (Na-PAA). The effect of dispersion technique and type and amount of dispersant on deagglomeration and stability of the TiO 2 aqueous suspensions were studied. After incorporation in a standard waterborne acrylic varnish formulation, dry film transparency, photocatalytic activity, and nanoparticle cluster size were also evaluated. The results show that mPEG- b -P4VP copolymer with appropriate block lengths can have a better performance than Na-PAA in terms of aqueous dispersion stabilization and cluster size reduction in the acrylic matrix. This translates into higher film transparency and photocatalytic performance.

Dispersion of nanoparticles: From organic solvents to polymer solutions

This work is devoted to a systematic study of nanoparticle dispersion by ultrasonication in different solutions: from organic solvents to polymer solutions. The cluster size of nanoparticles at different concentrations in both organic solvents and polymer solutions were directly characterized by Dynamic Light Scattering to study the effect of solid concentration, surfactant and polymer on the dispersion. It reveals that in stabilized suspensions, the smallest attainable size or aggregate size of nanoparticles is independent of solvent type and solid content over the tested range. Furthermore, nanoparticles in simple solvent and in polymer solutions had the similar evolution of cluster size and almost the same final size, which could be very helpful to optimize the dispersion of nanofillers in polymer solutions and nanocomposites. It is also shown that, with appropriate sonication amplitudes, the dispersion procedure developed for very dilute suspensions could be transferred to higher concentration suspensions or even to polymer suspensions.

NMR relaxation in systems with magnetic nanoparticles: A temperature study

To measure and model nuclear magnetic resonance (NMR) relaxation enhancement due to the presence of gadolinium (Gd)-substituted Zn-Mn ferrite magnetic nanoparticles (MNP) at different temperatures. Relaxation rates were measured at 1.5 T using fast spin echo (FSE) sequences in samples of agarose gel doped with uncoated and polyethylene glycol (PEG)-coated Mn0.5 Zn0.5 Gd0.02 Fe1.98 O4 nanoparticles over the temperature range 8-58°C. Physical characterization of the MNPs synthesized using chemical coprecipitation included scanning (SEM) and transmission (TEM) electron microscopy, inductively coupled plasma (ICP), dynamic light scattering (DLS), and magnetometry. Relaxivity (in s(-1) mM(-1) Fe) for the uncoated and coated particles, respectively, increased as follows: from 2.5 to 3.2 and 0.4 to 0.7 for T1, while for T2 it increased from 162.3 to 253.7 and 59.7 to 82.2 over the temperature range 8-58°C. T2 data were fitted to the echo limited motional regime using one fitting parameter that reflects the degree of agglomeration of particles into a cluster. This parameter was found to increase linearly with temperature and was larger for the PEG-coated particles than the uncoated ones. The increase of 1/T2 with temperature is modeled successfully using echo limited motional regime where both diffusion of the protons and nanoparticle cluster size increase with temperature. Both transverse and longitudinal relaxation efficiencies are reduced by PEG coating at all temperatures. If prediction of relaxation rates under different particle concentrations and operating temperatures is possible then the use of MNP in temperature monitoring and hyperthermia applications may be achieved.

Influence of cluster size and surface functionalization of ZnO nanoparticles on the morphology, thermomechanical and piezoelectric properties of P(VDF-TrFE) nanocomposite films

Few studies have been reported concerning the nanocomposites of copolymers of vinylidene difluoride and trifluoroethylene (P(VDF-TrFE)) with piezoelectric nanofillers. This study deals with the preparation and characterization of piezoelectric nanocomposite films based on P(VDF-TrFE) filled with several ZnO piezoelectric nanoparticles with different sizes and surface states. The influence of cluster size and surface state of ZnO nanoparticles on the morphology and electromechanical properties of (PVDF-TrFE) nanocomposite films is investigated.The dispersion of nanoparticles and the microstructure of nanocomposite are observed by Environmental Scanning Electron Microscope (ESEM) and Transmission Electron Microscopy (TEM). The crystallinity of the copolymer matrix is characterized by X-ray diffraction and Differential Scanning Calorimetry (DSC). The piezoelectric and mechanical properties are measured to evaluate the influence of cluster size and surface functionalization with respect to the P(VDF-TrFE) matrix. The nanocomposites filled with 10% nanoparticles showed an increase up to 25% of storage modulus while keeping a high piezoelectric activity. Furthermore, storage modulus of nanocomposites slightly linearly increased with decreasing cluster size of nanoparticles.

Thermal conductivity of Fe nanofluids depending on the cluster size of nanoparticles

Nanofluids have been attractive for the last few years with the enormous potential to improve the efficiency of heat transfer fluids. This work focuses on the effect of the clustering of nanoparticles on the thermal conductivity of nanofluids. Large enhancement of the thermal conductivity is observed in Fe nanofluids sonicated with high powered pulses. The average size of the nanoclusters and thermal conductivity of sonicated nanofluids are measured as time passes after the sonication stopped. It is found from the variations of the nanocluster size and thermal conductivity that the reduction of the thermal conductivity of nanofluids is directly related to the agglomeration of nanoparticles. The thermal conductivity of Fe nanofluids increases nonlinearly as the volume fraction of nanoparticles increases. The nonlinearity is attributed to the rapid clustering of nanoparticles in condensed nanofluids. The thermal conductivities of Fe nanofluids with the three lowest concentrations are fitted to a linear function. The Fe nanofluids show a more rapid increase of the thermal conductivity than Cu nanofluids as the volume fraction of the nanoparticles increases.

Photoacoustic microscopy and quantitative measurements : Kojima, S. Ultrasonic Technology 1987. Proceedings of the Toyohashi International Conference on Ultrasonic Technology, Toyohashi (Japan), 20–22 Apr. 1987. pp. 141–150. Edited by K. Toda. MYU (1987)

Few studies have been reported concerning the nanocomposites of copolymers of vinylidene difluoride and trifluoroethylene (P(VDF-TrFE)) with piezoelectric nanofillers. This study deals with the preparation and characterization of piezoelectric nanocomposite films based on P(VDF-TrFE) filled with several ZnO piezoelectric nanoparticles with different sizes and surface states. The influence of cluster size and surface state of ZnO nanoparticles on the morphology and electromechanical properties of (PVDF-TrFE) nanocomposite films is investigated.The dispersion of nanoparticles and the microstructure of nanocomposite are observed by Environmental Scanning Electron Microscope (ESEM) and Transmission Electron Microscopy (TEM). The crystallinity of the copolymer matrix is characterized by X-ray diffraction and Differential Scanning Calorimetry (DSC). The piezoelectric and mechanical properties are measured to evaluate the influence of cluster size and surface functionalization with respect to the P(VDF-TrFE) matrix. The nanocomposites filled with 10% nanoparticles showed an increase up to 25% of storage modulus while keeping a high piezoelectric activity. Furthermore, storage modulus of nanocomposites slightly linearly increased with decreasing cluster size of nanoparticles.