Initial Nanoparticle Concentration Research Articles

Case study of freezing-induced loading of silver nanoparticles into vaterite microcrystals

Hybrid materials composed of porous vaterite CaCO3 microcrystals loaded with functional inorganic nanoparticles are actively studied with respect to various practical applications. Recently, freezing-induced loading method was demonstrated as a versatile and effective approach for preparation of vaterite-based functional hybrid microparticles. However, despite of its high efficiency, the effect of nanoparticle concentration on the freezing-induced loading process and the structural properties of the resulted hybrids were not studied previously. Herein, for the first time, we have evaluated the feasibility of the conventional adsorption models to describe the freezing-induced loading of citrate-capped silver nanoparticles (AgNPs). The fitting of the dependence of the loading capacity of vaterite crystals on the residual concentration of AgNPs to two- or three-parameter models revealed that the best fit was obtained with the Freundlich model (R2 = 0.969), suggesting non-uniform deposition of AgNPs and interparticle agglomeration (Freundlich n > 1). This was confirmed with electron microscopy and elemental analysis demonstrating the formation and growth of AgNP aggregates on the CaCO3 surface with increasing initial nanoparticle concentration. Overall, the reported findings are valuable for a better understanding of the freezing-induced loading process and for further optimization of the preparation of vaterite-based functional hybrid microparticles.

Investigating the Influence of Precursor Concentration on the Photodegradation of Methylene Blue using Biosynthesized ZnO from Pometia pinnata Leaf Extracts

The ZnO nanoparticles were synthesized at various precursor concentrations i.e. 0.05, 0.1, and 0.5 M by biosynthesis method based on Pometia pinnata Leaf Extracts. Initial nanoparticle concentration influenced the optical bandgap, shape, and structure of nanoparticles. The photodegradation process was carried out under UV illumination. The efficiency of MB degradation was determined by measuring the decrease in MB concentration and by analyzing the optical absorption at 663 nm recorded by UV-Vis spectroscopy. Results showed that the biosynthesized ZnO nanoparticles exhibited efficient photodegradation of MB, with a maximum degradation rate of 80% after 90 minutes of exposure to UV-C light. The study highlights the potential of Pometia pinnata leaf extracts as a low-cost and eco-friendly alternative for synthesizing ZnO nanoparticles for use in environmental remediation processes

Lattice Boltzmann modelling of colloidal suspensions drying in porous media accounting for local nanoparticle effects

A two-dimensional (2-D) double-distribution lattice Boltzmann method (LBM) is implemented to study isothermal drying of a colloidal suspension considering local nanoparticle effects. The two LBMs solve isothermal two-phase flow and nanoparticle transport, respectively. The three local nanoparticle effects on the fluid dynamics considered in this paper are viscosity increase, surface tension drop and local drying rate reduction. The proposed model is first validated by the study of the drying of a 2-D suspended colloidal droplet for two different Péclet numbers, where the evolution of the diameter squared agrees well with experimental results. The model is further validated looking at drying of a colloid in a 2-D capillary tube with two open ends. Compared with experimental results, the best agreement in terms of deposition profile and drying time is obtained when considering all three nanoparticle effects. Afterwards, we apply the model to investigate the complicated drying of a colloidal suspension in a 2-D porous asphalt, considering all three local nanoparticle effects. The drying dynamics, resultant nanoparticle transport, accumulation and deposition are first analysed for a base case. Then a parametric study is conducted varying the initial nanoparticle concentration, porous medium contact angle, nanoparticle contact angle and nanoparticle diffusion coefficient. The influence of these parameters on drying dynamics, drying rate, deposition process and final deposition configurations is analysed in detail, together with the mutual influence of local nanoparticle behaviour. Finally, a unified relation between the average drying rate and the studied parameters is proposed and verified, covering the full parameter ranges of simulations.

Effect of segregation and advection governed heterogeneous distribution of nanoparticles on NEPCM discharging behavior

A numerical study is performed to investigate the role of heterogeneous distribution of nanoparticles in discharging behavior of nanoparticle-enhanced phase change materials (NEPCM). The numerical model considers solidification, multiphase convection, nanoparticles segregation, sedimentation, drags on nanoparticles and Brownian and thermophoresis diffusion phenomena. The discharging behavior of NEPCM is analyzed for the solidification of n-octadecane (PCM)-Cu-nanoparticles in a rectangular cavity. The discharging stage of NEPCM is also being investigated experimentally. The experiments were equipped with Particle Image Velocimetry (PIV), high-resolution imaging and thermocouples to measure real-time flow field, solidified layer thickness and local temperature. The numerically predicted results are compared with these experimental results to validate the model. Using the numerical model, the transient evolution of solidification interface morphology, nanoparticles concentration, fluid flow, temperature field, and thermophysical properties during solidification of NEPCM is described. Subsequently, the effect of process parameters such as initial nanoparticles concentration and Stefan number on system's thermal performance is delineated. It is noticed that adding nanoparticles up to a certain limit increases the discharging rate. The discharging time for 0 wt%, 2.5 wt%, 4.5 wt% and 6.5 wt% Cu-nanoparticles concentration are found to be 1115, 895, 980 and 1075 min, respectively. Thus, NEPCM with 2.5 wt% Cu-nanoparticles discharges 19.7 % faster than pure PCM. Furthermore, it is found that the heterogeneous distribution of the rejected nanoparticles significantly affects the solid-liquid interface morphology, solidification rate and alters the thermophysical properties locally as well as globally. The effective density and thermal conductivity increase with an increase in the local concentration of nanoparticles, whereas the effective specific heat capacity decreases with the increase in the local concentration of nanoparticles.

Ozonation/UV irradiation of dispersed Ag/AgI nanoparticles in water resources: stability and aggregation.

Proliferation of nanoparticles (NPs) as aqueous pollutants is a matter of growing concern today. The aggregation kinetics of colloidal bare silver (Ag, 20.5nm) and silver iodide (AgI, 15.3nm) NPs were investigated during ozone/ultraviolet (O3/UV) oxidation. Dynamic light scattering was applied to monitor the aggregation of NPs, and the z-average of treated samples was considered aggregate diameter. The effect of temperature, pH, and initial concentration of NPs was investigated on the aggregation rate constant and stability ratio. At a short oxidation period of approximately 1min, the lower stability ratio was achieved for Ag NPs (< 50) than AgI NPs (> 100). Under acidic conditions, the negative surface charge of both NPs was neutralized that resulted in faster aggregation. In contrast, the impact of temperature and initial concentration of NPs on the aggregation rate was different for both NPs, which was due to the type of O3/UV interaction with the surface of NPs and the thickness of the electrical double layer surrounding the NPs. The aggregation behavior of Ag NPs obeyed diffusion-limited regime, while an intermediate regime between diffusion- and reaction-limited was observed for AgI NP aggregation. The resulting aggregate morphologies showed that the clusters were ramified for Ag and compressed for AgI NPs. Applying the O3/UV oxidation process for water treatment purposes leads to a significant reduction in aggregation time for inherently unstable Ag and stable AgI toxic NPs from several hours or days to several minutes.

Isotherm and thermodynamic studies on the removal of gelatin-stabilized silver nanoparticles from water by activated carbon

Gelatin-stabilized silver nanoparticles (AgNPs) with a particle size of 6.9 (±3.2) nm were synthesized and employed in nanoparticle adsorption onto activated carbon (AC). Subsequently, the synthesized AgNPs and the adsorbed nanoparticles onto the AC (AgNP@AC) were characterized by various techniques including UV–Vis spectrophotometry, transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT–IR) and X–ray diffraction (XRD). AgNPs possessed colloidal stability at a wide pH interval ranging between 4 and 13. Adsorption was studied batch-wise as a function of initial nanoparticle concentration (4–14 mg L-1), temperature (298–323 K), pH (4–13) and adsorbent dosage (0.01–0.05 g). Adsorption isotherms were investigated by fitting the data to different isotherm models including Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich (D–R). Error analysis indicated that the adsorption is well described by the Langmuir model with a monolayer adsorption capacity of 10.36 mg g-1 for 0.05 g AC at pH 7 and 323 K. Thermodynamic parameters such as enthalpy (66.77 kJ mol-1), entropy (232.92 J mol-1 K-1), and Gibbs free energy (–8.31 kJ mol-1) indicated that the process is endothermic, favorable and spontaneous through physical interactions.

Three influential factors on colloidal nanoparticle deposition for heat conduction enhancement in 3D chip stacks

Thermal management is one of the major challenges facing the development of three-dimensional (3D) chip stacks. Recently, experimental studies have shown that neck-based thermal structure (NTS) between chip layers formed by drying of colloidal suspension in cavity filled with micro-size particles can improve the vertical heat conduction threefold. However, a deep understanding of the mechanisms of neck formation and its influence on heat conduction is still lacking. In this paper, we numerically study the effects of three parameters, i.e., initial nanoparticle concentration, drying temperature and chip surface wettability on neck formation between filler particles and on the resulting heat conduction of the NTS. With increasing nanoparticle concentration, the size and number of necks increase, resulting in an increased effective thermal conductivity (ETC) of NTS. The drying temperature is found to have only little influence on the ETC of resultant NTS, while the neck size and spatial distribution become more uniform at higher drying temperature. When reducing the wettability of the top and bottom surfaces of the cavity, the necks shrink in size until completing evacuating at the top and bottom layers, while the size of the necks between filler particles in the middle height of the cavity expands slowly. In consequence, the ETC of NTS drops at an increasing rate. Being able to reveal the underlying multiple mechanisms of two-phase flow, phase change and heat transport, the current numerical study suggests optimal values for the deposition process, with initial nanoparticle concentration over 0.8%, a drying temperature of 60°C and a uniform contact angle of 30° for practical production of NTS.

Limitations of Nanoparticles Size Characterization by Asymmetric Flow Field\u2011Fractionation Coupled with Online Dynamic Light Scattering

The development of reliable protocols suitable for the characterisation of the physical properties of nanoparticles in suspension is becoming crucial to assess the potential biological as well as toxicological impact of nanoparticles. Amongst sizing techniques, asymmetric flow field flow fractionation (AF4) coupled to online size detectors represents one of the most robust and flexible options to quantify the particle size distribution in suspension. However, size measurement uncertainties have been reported for on-line dynamic light scattering (DLS) detectors when coupled to AF4 systems. In this work we investigated the influence of the initial concentration of nanoparticles in suspension on the sizing capability of the asymmetric flow field-flow fractionation technique coupled with an on-line dynamic light scattering detector and a UV–Visible spectrophotometer (UV) detector. Experiments were performed with suspensions of gold nanoparticles with a nominal diameter of 40 nm and 60 nm at a range of particle concentrations. The results obtained demonstrate that at low concentration of nanoparticles, the AF4-DLS combined technique fails to evaluate the real size of nanoparticles in suspension, detecting an apparent and progressive size increase as a function of the elution time and of the concentration of nanoparticles in suspension.

Concentration of Polymer Nanoparticles Through Dialysis: Efficacy and Comparison With Lyophilization for PEGylated and Zwitterionic Systems

Biodegradable polymeric nanoparticles (NPs) are attracting increasing attention as carriers for drug delivery. However, one of the main factors limiting their transition to the market is their premature degradation and release of the payload during the storage. Therefore, for increasing the formulation shelf-life, the removal of water is of paramount importance. In this work, we synthesized both polyethylene glycol (PEG)-stabilized and zwitterionic NPs via Reversible Addition Fragmentation Chain Transfer (RAFT) Polymerization. We demonstrated that lyophilization leads the PEGylated NPs to irreversible aggregation, while the stability of the zwitterionic NPs was preserved only using a cryoprotectant. Therefore, we developed an alternative method for the NP concentration, based on the dialysis against a concentrated PEG solution. This method was optimized in terms of concentration factor (Fc), the ratio between the final and initial NP concentration, by acting on the PEG concentration in the dialysis medium, on its volume and on the initial NP concentration. With this approach, Fc up to 40 can be achieved in less than 10 h, preserving the possibility of redispersing the NPs to their original particle size distribution. Therefore, the dialysis proposed herein is a valuable alternative to lyophilization for the concentration of polymer NPs preserving their stability.

A comparative study for evaluating the performance of five coatings applied on Fe3O4 nanoparticles for inhibition of asphaltene precipitation from crude oil

In this study, potential of Graphene oxide (GO), Silica (SiO2) and Chitosan coatings on Fe3O4 magnetic nanoparticles was investigated for asphaltene adsorption. The comparison between coated and uncoated nanoparticles was made to evaluate the adsorption performance of coatings. The synthesis of nanoparticles was conducted using the co-precipitation method. All nanoparticles were verified using FT-IR, FESEM and XRD analyses. The experiments were performed in two stages. The different parameters effects such as temperature, initial concentration of nanoparticles and initial asphaltene concentration in the synthetic solutions were investigated in the first sets of experiments. Decrease of nanoparticles concentration and temperature and increase in initial asphaltene concentration resulted in increase of asphaltene adsorption capacities. GO-Fe3O4 showed the highest adsorption efficiency followed by chitosan-Fe3O4, Fe3O4 and SiO2-Fe3O4. The average values for adsorption efficiency were 70.47, 66.94, 64.56 and 65.94% for GO-Fe3O4, chitosan-Fe3O4, SiO2-Fe3O4 and Fe3O4 nanoparticles, respectively. In the second stage, the tests with crude oil were performed using the optimum amount of nanoparticles concentration under atmospheric pressure and simulated reservoir conditions. The satisfactory results were obtained for improving adsorption of asphaltenes from crude oil similar to synthetic solution trends. The amount of adsorption increased with increasing pressure. The experimental data for adsorption isotherms models followed the Langmuir model. For adsorption kinetics, the pseudo-second-order Lagergren model showed more precise results. The results showed that we could apply appropriate coatings for inhibition of asphaltene precipitation and enhancement of asphaltene adsorption. However, the asphaltene adsorption amount depends strongly on the kind of coatings applied.

Microwave-assisted catalytic oxidation of methomyl pesticide by Cu/Cu2O/CuO hybrid nanoparticles as a Fenton-like source

Heterogeneous catalytic oxidation, Fenton-like (FL) hybrid nanoparticles (NPs) induced by microwave (MW) irradiation, was applied as a green technology pathway for methomyl pesticide oxidation. Three different hybrid nanostructured particles, C300, C400 and C500 containing various phase structures, i.e., Cu, Cu2O and CuO, were successfully synthesized by the thermal decomposition technique and used as a FL source in microwave-induced (MW/FL) system. The microstructure and morphology of the hybrid nanostructured particles were studied using an X-ray diffraction (XRD) field-emission scanning electron microscope (FE-SEM), respectively. Also, MW/FL system was compared to MW/H2O2 and (MW) alone. The influence of various operating parameters, i.e., microwave irradiation time and power, initial NPs concentration, H2O2 concentration and pH for the three MW/FL systems, was investigated, and the optimal operating conditions were compared. The results indicated that the MW/FL process outperformed the other systems, and around 91% of methomyl was removed after only 8 min of MW irradiation for the C300-based MW/FL system under optimal conditions. Notably, the results verified that the heterogeneous MW/FL oxidation system catalyzed over the synthesized NPs reacted with the wastewater at its initial pH without adjustment, which overcomes the weakness of the homogeneous Fenton catalyst. Hence, this advantage could expand the application of this oxidation technique and thus improves the system efficiency. Finally, the catalyst showed good reusability. The success of this technique explores the possibility of copper as a non-iron FL system in a MW-assisted system for the rapid removal of methomyl from wastewater.

Reactive Gelation Synthesis of Monodisperse Polymeric Capsules Using Droplet‐Based Microfluidics

AbstractA novel methodology, combining reactive gelation and droplet‐based microfluidics, is described for the synthesis of rigid, porous, and hollow polymeric nanoparticles (NPs). The precursors of such capsules are microfluidically generated latex droplets, with diameters tunable between 20 and 100 µm. The conversion of latex droplets to polymeric capsules involves two steps, namely self‐migration and gelation of the NPs toward the oil–water interface to form a solid‐like shell, and then postpolymerization to covalently fix the shell structure. The hollow structure of the capsules results from the interaction between negatively charged NPs inside the droplet and positive charges present on fluorosurfactant at the droplet interface. Significantly, the porosity and average pore size in the capsule shell can be controlled through variation of the initial NP concentration in the droplet. Based on the analysis of diffusion of fluorescent molecules of known size, it is shown that penetration of molecules into the internal volume of the capsules increases as the initial NP concentration in the droplet decreases, thus the porosity of the formed shell increases. This novel synthetic methodology defines a powerful tool in the generation of hollow capsules of controlled size and morphology, and has significant application in material sciences.

Removal of Synthetic Azo Dye Using Bimetallic Nickel-Iron Nanoparticles

Bimetallic nanoparticles comprised of iron (Fe) and nickel (Ni) were investigated for the removal of an azo dye contaminant in water. Morphology (core shell and alloy) and metal molar ratio (Ni2Fe10, Ni5Fe10, and Ni10Fe10) were tested as key nanoparticle properties. The shelf life of the nanoparticles was tested over a 3-week period, and the effect of initial nanoparticle concentration on dye removal was evaluated. The highest initial nanoparticle concentration (1000 mg/L) showed consistent Orange G removal and the greatest extent of dye removal, as compared to the other tested concentrations (i.e., 750 mg/L, 500 mg/L, and 250 mg/L) for the same nanoparticle morphology and metal molar ratio. The metal molar ratio significantly affected the performance of the core shell morphology, where overall dye removal was found to be 66%, 89%, and 98% with an increasing molar ratio (Ni2Fe10 → Ni5Fe10 → Ni10Fe10). In contrast, the overall removal of the dye for all molar ratios of the alloy nanoparticles only resulted in a variability of ±0.005%. When stored in water for 3 weeks, core shell nanoparticles lost reactivity with an average&gt;17% loss in removal with each passing week. However, the alloy nanoparticles were able to continually remove Orange G from solution after 3 weeks of storage to ~97% when used at a starting nanoparticle concentration of 1000 mg/L. Overall, the Ni2Fe10, Ni5Fe10, and Ni10Fe10 alloy nanoparticles with a starting nanoparticle concentration of 1000 mg/L resulted in the greatest dye removal of 97%, 99%, and 98%, respectively. Kinetic rate models were used to analyze dye removal rate constants as a function of nanoparticle properties. Kinetic rate models were seen to differ from core shell (first-order kinetics) to alloy morphology (second-order kinetics). Alloy nanoparticles resulted in as high as X kinetic rate constant, and core shell nanoparticles resulted in as high as XX kinetic rate constant. Metal leaching from the nanoparticles was investigated; alloy nanoparticles resulted in leaching of 3% Fe and 5% Ni which is similar to core shell leaching of 3.2% Fe and 4.3% Ni from the Fe10Ni10 nanoparticles.

Formation of self-assembled gold nanoparticle supercrystals with facet-dependent surface plasmonic coupling

Metallic nanoparticles, such as gold and silver nanoparticles, can self-assemble into highly ordered arrays known as supercrystals for potential applications in areas such as optics, electronics, and sensor platforms. Here we report the formation of self-assembled 3D faceted gold nanoparticle supercrystals with controlled nanoparticle packing and unique facet-dependent optical property by using a binary solvent diffusion method. The nanoparticle packing structures from specific facets of the supercrystals are characterized by small/wide-angle X-ray scattering for detailed reconstruction of nanoparticle translation and shape orientation from mesometric to atomic levels within the supercrystals. We discover that the binary diffusion results in hexagonal close packed supercrystals whose size and quality are determined by initial nanoparticle concentration and diffusion speed. The supercrystal solids display unique facet-dependent surface plasmonic and surface-enhanced Raman characteristics. The ease of the growth of large supercrystal solids facilitates essential correlation between structure and property of nanoparticle solids for practical integrations.

Erratum to: Quantification of the cellular dose and characterization of nanoparticle transport during in vitro testing.

The constant increase of the use of nanomaterials in consumer products is making increasingly urgent that standardized and reliable in vitro test methods for toxicity screening be made available to the scientific community. For this purpose, the determination of the cellular dose, i.e. the amount of nanomaterials effectively in contact with the cells is fundamental for a trustworthy determination of nanomaterial dose responses. This has often been overlooked in the literature making it difficult to undertake a comparison of datasets from different studies. Characterization of the mechanisms involved in nanomaterial transport and the determination of the cellular dose is essential for the development of predictive numerical models and reliable in vitro screening methods. This work aims to relate key physico-chemical properties of gold nanoparticles (NPs) to the kinetics of their deposition on the cellular monolayer. Firstly, an extensive characterization of NPs in complete culture cell medium was performed to determine the diameter and the apparent mass density of the formed NP-serum protein complexes. Subsequently, the kinetics of deposition were studied by UV-vis absorbance measurements in the presence or absence of cells. The fraction of NPs deposited on the cellular layer was found to be highly dependent on NP size and apparent density because these two parameters influence the NP transport. The NP deposition occurred in two phases: phase 1, which consists of cellular uptake driven by the NP-cell affinity, and phase 2 consisting mainly of NP deposition onto the cellular membrane. The fraction of deposited NPs is very different from the initial concentration applied in the in vitro assay, and is highly dependent of the size and density of the NPs, on the associated transport rate and on the exposure duration. This study shows that an accurate characterization is needed and suitable experimental conditions such as initial concentration of NPs and liquid height in the wells has to be considered since they strongly influence the cellular dose and the nature of interactions of NPs with the cells.

Morphological transitions and buckling characteristics in a nanoparticle-laden sessile droplet resting on a heated hydrophobic substrate

In this work, we have established the evaporation-liquid flow coupling mechanism by which sessile nanofluid droplets on a hydrophobic substrate evaporate and agglomerate to form unique morphological features under controlled external heating. It is well understood that evaporation coupled with internal liquid flow controls particle transport in a spatiotemporal sense. Flow characteristics inside the heated droplet are investigated and found to be driven by the buoyancy effects. Velocity magnitudes are observed to increase by an order at higher temperatures with similar looking flow profiles. The recirculating flow induced particle transport coupled with collision of particles and shear interaction between them leads to the formation of dome shaped viscoelastic shells of different dimensions depending on the surface temperature. These shells undergo sol-gel transition and subsequently undergo buckling instability leading to the formation of daughter cavities. With an increase in the surface temperature, droplets exhibit buckling from multiple sites over a larger sector in the top half of the droplet. Irrespective of the initial nanoparticle concentration and substrate temperature, growth of a daughter cavity (subsequent to buckling) inside the droplet is found to be controlled by the solvent evaporation rate from the droplet periphery and is shown to exhibit a universal trend.

Quantification of the cellular dose and characterization of nanoparticle transport during in vitro testing.

BackgroundThe constant increase of the use of nanomaterials in consumer products is making increasingly urgent that standardized and reliable in vitro test methods for toxicity screening be made available to the scientific community. For this purpose, the determination of the cellular dose, i.e. the amount of nanomaterials effectively in contact with the cells is fundamental for a trustworthy determination of nanomaterial dose responses. This has often been overlooked in the literature making it difficult to undertake a comparison of datasets from different studies. Characterization of the mechanisms involved in nanomaterial transport and the determination of the cellular dose is essential for the development of predictive numerical models and reliable in vitro screening methods.ResultsThis work aims to relate key physico-chemical properties of gold nanoparticles (NPs) to the kinetics of their deposition on the cellular monolayer. Firstly, an extensive characterization of NPs in complete culture cell medium was performed to determine the diameter and the apparent mass density of the formed NP-serum protein complexes. Subsequently, the kinetics of deposition were studied by UV-vis absorbance measurements in the presence or absence of cells. The fraction of NPs deposited on the cellular layer was found to be highly dependent on NP size and apparent density because these two parameters influence the NP transport. The NP deposition occurred in two phases: phase 1, which consists of cellular uptake driven by the NP-cell affinity, and phase 2 consisting mainly of NP deposition onto the cellular membrane.ConclusionThe fraction of deposited NPs is very different from the initial concentration applied in the in vitro assay, and is highly dependent of the size and density of the NPs, on the associated transport rate and on the exposure duration. This study shows that an accurate characterization is needed and suitable experimental conditions such as initial concentration of NPs and liquid height in the wells has to be considered since they strongly influence the cellular dose and the nature of interactions of NPs with the cells.Electronic supplementary materialThe online version of this article (doi:10.1186/s12989-016-0157-1) contains supplementary material, which is available to authorized users.

Coupled Mechanisms of Precipitation and Atomization in Burning Nanofluid Fuel Droplets.

Understanding the combustion characteristics of fuel droplets laden with energetic nanoparticles (NP) is pivotal for lowering ignition delay, reducing pollutant emissions and increasing the combustion efficiency in next generation combustors. In this study, first we elucidate the feedback coupling between two key interacting mechanisms, namely, secondary atomization and particle agglomeration; that govern the effective mass fraction of NPs within the droplet. Second, we show how the initial NP concentration modulates their relative dominance leading to a master-slave configuration. Secondary atomization of novel nanofuels is a crucial process since it enables an effective transport of dispersed NPs to the flame (a pre-requisite condition for NPs to burn). Contrarily, NP agglomeration at the droplet surface leads to shell formation thereby retaining NPs inside the droplet. In particular, we show that at dense concentrations shell formation (master process) dominates over secondary atomization (slave) while at dilute particle loading it is the high frequency bubble ejections (master) that disrupt shell formation (slave) through its rupture and continuous outflux of NPs. This results in distinct combustion residues at dilute and dense concentrations, thereby providing a method of manufacturing flame synthesized microstructures with distinct morphologies.

Cooperative sequential-adsorption model in two dimensions with experimental applications for ionic self-assembly of nanoparticles.

Self-assembly of nanoparticles is an important tool in nanotechnology, with numerous applications, including thin films, electronics, and drug delivery. We study the deposition of ionic nanoparticles on a glass substrate both experimentally and theoretically. Our theoretical model consists of a stochastic cooperative adsorption and evaporation process on a two-dimensional lattice. By exploring the relationship between the initial concentration of nanoparticles in the colloidal solution and the density of particles deposited on the substrate, we relate the deposition rate of our theoretical model to the concentration.

Translocation of SiO2-NPs across in vitro human bronchial epithelial monolayer

Safe development and application of nanotechnologies in many fields require better knowledge about their potential adverse effects on human health. Evidence of abilities of nanoparticles (NPs) to cross epithelial barriers and reach secondary organs via the bloodstream led us to investigate the translocation of SiO2 NPs of 50 nm (50 nm-SiO2-NPs) across human bronchial epithelial cells that are primary targets after exposure to inhaled NPs. We quantified the translocation of fluorescently labelled SiO2 NPs at non-cytotoxic concentrations (5 and 10 μg/cm2) across Calu-3 epithelial monolayer. After 14 days in culture Calu-3 cells seeded onto 3 μm-polycarbonate Transwell membranes formed an efficient bronchial barrier assessed by measurement of the transepithelial electric resistance and quantification of the permeability of the monolayer. After 24 hours of exposure, we observed a significant translocation of NPs that was more important when the initial NP concentration decreased. Confocal microscopy observations revealed NP uptake by cells and an important NP retention inside the porous membrane. In conclusion, 50 nm-SiO2-NPs can cross the human bronchial epithelial barrier without affecting the integrity of the epithelial cell monolayer.