Bare Particles Research Articles

Size effects on the magnetic behavior of γ-Fe2O3 core/SiO2 shell nanoparticle assemblies

Theeffect of core size on the magnetic behavior of nanoparticle assemblies of γ-Fe2O3 core/SiO2 shell morphology is investigated. Long-range magnetostatic interactions are probed in two highly monodispersed experimental test systems of spherical nanoparticles with core diameters of 10 nm and 12.5 nm, and a shell thickness varying from 0 nm (bare particles) to ~50 nm. Zero-Field-Cooled magnetization curves are calculated by employing the Monte Carlo simulation technique in a mesoscopic-scale model for the assembly, assuming spin collinearity and coherent spin-reversal mechanisms. Simulation results reproduce the trend in the behavior of the Zero-Field-Cooled magnetization versus T curves in good qualitative agreement with the experimental findings. They also demonstrate that the increase of the magnetic core size results in a shift of the maximum magnetization peak, Tmax, to higher temperatures due to enhanced dipolar coupling. The results shed light on how interparticle distance and magnetic core size influence the value of Tmax through collective behavior and its transition to a single-particle superparamagnetic blocking temperature, TB, as the assembly becomes magnetically diluted with increasing shell thickness.

Carbon Monoxide Activation on Small Iron Magnetic Cluster Surfaces, FenCO, n = 1-20. A Theoretical Approach.

The chemical activation of the carbon monoxide (CO) molecule on the surface of iron clusters Fen (n = 1-20) is studied in this work. By means of density functional theory (DFT) all-electron calculations, we have found that the adsorption of CO over the bare magnetic Fen (n = 1-20) clusters is thermochemically favorable. The Fen-CO interaction increases the C-O bond length, from 1.128 ± 0.014 Å, for isolated CO, up to 1.251 Å, for Fe9CO. Also, the calculated wavenumbers associated with the stretching modes νCO are decreased, or red-shifted, as another indicator of the CO bond weakening, passing from 2099 ± 4 to 1438 cm-1. Markedly, wavenumbers of vibrational modes νCO agree admirably well in comparison with experimental results reported for FenCO (n = 1, 18-20), getting small errors below 2.6%. The C-O bond is enlarged on the FenCO (n = 1-20) composed systems, as the CO molecule increases its bonding, charge transference, and coordination with the iron cluster. Therefore, small bare iron particles Fen (n = 1-20) can be proposed to promote the CO dissociation, especially Fe9CO, which has been proven to obtain the most prominent activation of the strong C-O bond by means of the charge transference from the metal core.

The effects of morphology, mobility size, and secondary organic aerosol (SOA) material coating on the ice nucleation activity of black carbon in the cirrus regime

Abstract. There is evidence that black carbon (BC) particles may affect cirrus formation and, hence, global climate by acting as potential ice nucleating particles (INPs) in the troposphere. Nevertheless, the ice nucleation (IN) ability of bare BC and BC coated with secondary organic aerosol (SOA) material remains uncertain. We have systematically examined the IN ability of 100–400 nm size-selected BC particles with different morphologies and different SOA coatings representative of anthropogenic (toluene and n-dodecane) and biogenic (β-caryophyllene) sources in the cirrus regime (−46 to −38 ∘C). Several BC proxies were selected to represent different particle morphologies and oxidation levels. Atmospheric aging was further replicated with the exposure of SOA-coated BC to OH. The results demonstrate that the 400 nm hydrophobic BC types nucleate ice only at or near the homogeneous freezing threshold. Ice formation at cirrus temperatures below homogeneous freezing thresholds, as opposed to purely homogeneous freezing, was observed to occur for some BC types between 100 and 200 nm within the investigated temperature range. More fractal BC particles did not consistently act as superior INPs over more spherical ones. SOA coating generated by oxidizing β-caryophyllene with O3 did not seem to affect BC IN ability, probably due to an SOA-phase state transition. However, SOA coatings generated from OH oxidation of various organic species did exhibit higher IN-onset supersaturation ratio with respect to ice (SSi), compared with bare BC particles, with the toluene-SOA coating showing an increase in SSi of 0.1–0.15 while still below the homogeneous freezing threshold. Slightly oxidized toluene SOA coating seemed to have a stronger deactivation effect on BC IN ability than highly oxidized toluene SOA, which might be caused by oligomer formation and the phase state transition of toluene SOA under different oxidation levels. n-dodecane and β-caryophyllene-derived SOA-coated BC only froze in the homogeneous regime. We attribute the inhibition of IN ability to the filling of the pores on the BC surface by the SOA material coating. OH exposure levels of n-dodecane and β-caryophyllene SOA coating experiments, from an equivalent atmospheric exposure time from 10 to 90 d, did not render significant differences in the IN potential. Our study of selected BC types and sizes suggests that increases in diameter, compactness, and/or surface oxidation of BC particles lead to more efficient IN via the pore condensation freezing (PCF) pathway, and that coatings of common SOA materials can inhibit the formation of ice.

Preparation and characterization of superabsorbent polymers (SAPs) surface-crosslinked with polycations

For the application of superabsorbent polymer (SAP) particles in personal hygiene products such as disposable diapers, the SAP surface is additionally crosslinked to minimize gel blocking and enhance absorbency under external pressure. Physically surface-crosslinked poly(acrylic acid)(PAA)-based SAP microspheres were prepared using polycations (branched polyethylene imine (bPEI) and polyamidoamine (PAMAM)). Compared with chemical crosslinking, which requires a high temperature and prolonged reaction, physical crosslinking via electrostatic interaction between the polycations and negatively charged PAA chains was achieved within 20 min at room temperature. The polycation-crosslinked SAP particles had a rougher surface and lower water absorption capacity. The thickness of the physically crosslinked surface, visualized using fluorescence labeled polycations, increased with increasing polycation concentration and reaction time, eventually reaching saturation. PAMAM produced mechanically stronger and thicker surface-crosslinking than bPEI, owing to its lower molecular weight. Micro-CT analysis of the collective swelling behavior of a gel bed packed with the SAP particles confirmed that the shapes of the SAP particles crosslinked with polycations were better maintained during swelling and there was a greater void fraction in the packed gel bed than with the use of bare SAP particles, which might minimize gel blocking and improve the permeability of fluid through gel bed.

Turning a yield-stress calcite suspension into a shear-thickening one by tuning inter-particle friction

We show that a suspension of non-Brownian calcite particles in glycerol-water mixtures can be tuned continuously from being a yield-stress suspension to a shear-thickening suspension—without a measurable yield stress—by the addition of various surfactants. We interpret our results within a recent theoretical framework that models the rheological effects of stress-dependent constraints on inter-particle motion. Bare calcite particle suspensions are found to have finite yield stresses. In these suspensions, frictional contacts that constrain inter-particle sliding form at an infinitesimal applied stress and remain thereafter, while adhesive bonds that constrain inter-particle rotation are broken as the applied stress increases. Adding surfactants reduces the yield stress of such suspensions. We show that, contrary to the case of surfactant added to colloidal suspensions, this effect in non-Brownian suspensions is attributable to the emergence of a finite onset stress for the formation of frictional contacts. Our data suggest that the magnitude of this onset stress is set by the strength of surfactant adsorption to the particle surfaces, which therefore constitutes a new design principle for using surfactants to tune the rheology of formulations consisting of suspensions of adhesive non-Brownian particles.Graphical Impact of surfactants on the rheology of concentrated calcite suspensions. Black, schematic flow curve for bare particles. Low stress: adhesive contact, rolling and sliding between particles prevented (red). High stress: frictional contact, rolling allowed (green), constraints broken → shear thinning. Blue, with surfactant. Low stress: repulsion prevents contact, rolling and sliding allowed, removing yield stress entirely. High stress: surfactant displaced (see inset), particles bare and sliding prevented; constraints formed → shear thickening

Toxicological implications of amplifying the antibacterial activity of gallic acid by immobilisation on silica particles: A study on C. elegans

Immobilisation of natural compounds on solid supports to amplify antimicrobial properties has reported successful results, but modifications to physico-chemical properties can also imply modifications from a toxicological viewpoint. This work aimed to study the immobilising process of gallic acid in the antibacterial activity of L. innocua and its toxicological properties in vivo using Caenorhabditis elegans. The experiment was based on obtaining the minimum bactericidal concentration for free and immobilised gallic acid by comparing lethality, locomotion behaviour, chemotaxis and thermal stress resistance on C.elegans at those concentrations. The results showed a lowering minimum bactericidal concentration and modifications to nematode responses. Increased lethality and velocity of movements was observed. Immobilisation increased the repellent effect of gallic acid with a negative chemotaxis index. Thermal stress resistance was also affected, with higher mortality for immobilised gallic acid compared to bare particles and free gallic acid. Thus despite evidencing a generalised increase in the toxicity of gallic acid in vivo, lowering the minimum bactericidal concentration allowed a bacterial reduction of 99 % with less than one third of mortality for the nematodes exposed to free gallic acid.

Directing near-infrared photon transport with core@shell particles

Directing the propagation of near-infrared radiation is a major concern in improving the efficiency of solar cells and thermal insulators. A facile approach to scatter light in the near-infrared region without excessive heating is to embed compact layers with semiconductor particles. The directional scattering by semiconductor@oxide (core@shell) spherical particles (containing Si, InP, TiO2, SiO2, or ZrO2) with a total radius varying from 0.1 μm to 4.0 µm and in an insulating medium at a low volume fraction is investigated using Lorenz–Mie theory and multiscale modeling. The optical response of each layer is calculated under irradiation by the Sun or a blackbody emitter at 1180 K. Reflectance efficiency factors of up to 83.7% and 63.9% are achieved for near-infrared solar and blackbody radiation in 200 µm thick compact layers with only 1% volume fraction of bare Si particles with a radius of 0.23 µm and 0.50 µm, respectively. The maximum solar and blackbody efficiency factors of layers containing InP particles were slightly less (80.2% and 60.7% for bare particles with a radius of 0.25 µm and 0.60 µm, respectively). The addition of an oxide coating modifies the surrounding dielectric environment, which improves the solar reflectance efficiency factor to over 90%, provided it matches the scattering mode energies with the incident spectral density. The layers are spectrally sensitive and can be applied as a back or front reflector for solar devices, high temperature thermal insulators, and optical filters in gradient heat flux sensors for fire safety applications.

Comparative Study of Particle Swarm Optimization Algorithms in Solving Size, Topology, and Shape Optimization

This paper focuses on optimizing truss structures while propose best PSO variants. Truss optimization is one way to make the design efficient. There are three types of optimization, size optimization, shape optimization, and topology optimization. By combining size, shape and topology optimization, we can obtain the most efficient structure. Metaheuristics have the ability to solve this problem. Particle swarm optimization (PSO) is metaheuristic algorithm which is frequently used to solve many optimization problems. PSO mimics the behavior of flocking birds looking for food. But PSO has three parameters that can interfere with its performance, so this algorithm is not adaptive to diverse problems. Many PSO variants have been introduced to solve this problem, including linearly decreasing inertia weight particles swarm optimization (LDWPSO) and bare bones particles swarm optimization (BBPSO). The metaheuristic method is used to find the solution, while DSM s used to analyze the structure. A 10-bar truss structure and a 39-bar truss structure are considered as case studies. The result indicates that BBPSO beat other two algorithms in terms of best result, consistency, and convergence behaviour in both cases. LDWPSO took second place for the three categories, leaving PSO as the worst algorithm that tested.

Is water ice an efficient facilitator for dust coagulation?

ABSTRACT Beyond the snow line of protoplanetary discs and inside the dense core of molecular clouds, the temperature of gas is low enough for water vapour to condense into amorphous ices on the surface of pre-existing refractory dust particles. Recent numerical simulations and laboratory experiments suggest that condensation of the vapour promotes dust coagulation in such a cold region. However, in the numerical simulations, cohesion of refractory materials is often underestimated, while in the laboratory experiments, water vapour collides with surfaces at more frequent intervals compared to the real conditions. Therefore, to re-examine the role of water ice in dust coagulation, we carry out systematic investigation of available data on coagulation of water-ice particles by making full use of appropriate theories in contact mechanics and tribology. We find that the majority of experimental data are reasonably well explained by lubrication theories, owing to the presence of a quasi-liquid layer (QLL). Only exceptions are the results of dynamic collisions between particles at low temperatures, which are, instead, consistent with the JKR theory, because QLLs are too thin to dissipate their kinetic energies. By considering the vacuum conditions in protoplanetary discs and molecular clouds, the formation of amorphous water ice on the surface of refractory particles does not necessarily aid their collisional growth as currently expected. While crystallization of water ice around but outside the snow line eases coagulation of ice-coated particles, sublimation of water ice inside the snow line is deemed to facilitate coagulation of bare refractory particles.

A novel sulfur@void@hydrogel yolk-shell particle with a high sulfur content for volume-accommodable and polysulfide-adsorptive lithium-sulfur battery cathodes

High-energy-density secondary batteries are required for many applications such as electric vehicles. Lithium–sulfur (Li-S) batteries are receiving broad attention because of their high theoretical energy density. However, the large volume change of sulfur during cycling, poor conductivity, and the shuttle effect of sulfides severely restrict the Li-storage performance of Li-S batteries. Herein, we present a novel core–shell nanocomposite consisting of a sulfur core and a hydrogel polypyrrole (PPy) shell, enabling an ultra-high sulfur content of about 98.4% within the composite, which greatly exceeds many other conventional composites obtained by coating sulfur onto some hosts. In addition, the void inside the core–shell structure effectively accommodates the volume change; the conductive PPy shell improves the conductivity of the composite; and PPy is able to adsorb polysulfides, suppressing the shuttle effect. After cycling for 200 cycles, the prepared S@void@PPy composite retains a stable capacity of 650 mAh g−1, which is higher than the bare sulfur particles. The composite also exhibits a fast Li ion diffusion coefficient. Furthermore, the density functional theory calculations show the PPy shell is able to adsorb polysulfides efficiently, with a large adsorption energy and charge density transfer.

Synthesis and Dispersion of Ni-Doped Cu<sub>2</sub>ZnSnS<sub>4</sub>

This paper reports the preliminary study on the synthesis of Ni doped CZTS (Cu2ZnSnS4:Ni) particle 5 at.% of Cu by solution method and dispersion of the obtained particles by beads mill method at various dispersing agents (SDS, CTAB, and Tween80). The phase transformation of the obtained particles was analyzed from the XRD spectra and XRF elemental analysis. The phase transformation and amount of Ni-doped to particles was predicted employing commercially available analytical software tool Match! Version 2.x. Moreover, the dispersion characteristics were investigated includes size, size distribution, and zeta potential of bare particles in comparison to various dispersing agents. This characteristic related to the future application of CZTS as an absorber in a thin-film based PV. The XRD analysis showed that the obtained particle contained crystal structure of copper sulfate pentahydrate (75.9 %), Ni(HN2S2)2 (12.5 %), and Cu2ZnSnS4 (11.6%). The XRF elemental analysis showed that amount of Ni-doped was 6.8 at.%; it was higher than the initial design amount of Ni doping. The dispersion of suspended particles was the majority (90%) with an average size of 3.06 µm and only 10 % with size 255 nm. Beads-milling of particles without dispersing agents did not disintegrate agglomerated particles. It is highlighted dispersion only using magnetic stirred with SDS dispersing agent provides the best suspension with a majority (60%) in 166 nm and only 30 % with average size 3.06 µm with relatively high zeta potential (-17 mV). It was concluded that the presence of a multi-phase crystal needs to be resolved either by proper calcination at a higher temperature than 400°C or further heating at a higher temperature during film preparation. High-energy centrifugation of zirconia beads mill caused desorption of adsorbed steric stabilization of dispersing agent under investigation. Further investigation on the coating process to facilitated laboratory fabrication of thin-film absorber with SDS as a dispersing agent is necessary to carry out concerning the properties of the thin-film.

Silica supported metal organic framework 808 composites as adsorbent for solid-phase extraction of benzodiazepines in urine sample

A novel silica supported metal organic framework 808 core–shell adsorbent (MOF-808@SiO2) was fabricated via the controllable in-situ growth for the solid-phase extraction of benzodiazepines (bromazepam, triazolam and diazepam) in urine samples. The prepared sorbent was characterized by scanning electron microscopy, X-ray powder diffractometry and nitrogen adsorption experiment. Compared with the bare silica particles, the MOF-808@SiO2 sorbent gave enhanced surface area and improved extraction efficiency for benzodiazepines. It was developed as solid-phase extraction sorbent and combined with high-performance liquid chromatography for the determination of three benzodiazepines in urine samples. The parameters influencing the loading and eluting processes were investigated in detail. Under the optimized conditions, the proposed method provided the linear range of 2.0–200 ng/mL for bromazepam, 1.7–170 ng/mL for triazolam and 1.5–150 ng/mL for diazepam (r = 0.999). The method detection limits (S/N = 3) and the limits of quantification (S/N = 10) ranged from 0.4 to 0.6 ng/mL and 1.5 to 2.0 ng/mL, respectively. Besides, the enhancement factors of 16.2–19.2 were achieved and the recoveries for spiked urine samples with three levels were in the range of 81.2–95.9%. The developed method was successfully applied for the determination of benzodiazepines in urine samples.

Cationic polyelectrolyte grafted mesoporous magnetic silica composite particles for targeted drug delivery and thrombolysis

Magnetic iron oxide (Fe3O4) microparticles prepared by solvothermal route are modified with SiO2 layer and then functionalized with vinyl groups. Finally, polyelectrolyte layer composed of isobornyl methacrylate (iBMA) and (3-acrylamidopropyl)trimethylammonium chloride (APTMACl) is grafted onto the surface of magnetic SiO2 particles via free radical polymerization to produce composite particles abbreviated as Fe3O4/SiO2/P(iBMA-APTMACl). The size distribution and structural composition of Fe3O4/SiO2/P(iBMA-APTMACl) composite particles are measured by electron microscopy and different spectroscopy techniques. Fe3O4/SiO2/P(iBMA-APTMACl) composite particles possessed moderate paramagnetic property. The mesoporous surface structure of composite particles is confirmed from average pore diameter (3.8 nm), measured by Barrett–Joyner–Halenda (BJH) method. The composite particles exhibited pH dependent phase transition near 5.8. The pH dependent adsorption and release study of anionic drug (aspirin) through off- and on-capping of polyelectrolyte valve/gate confirmed the ion exchange property of Fe3O4/SiO2/P(iBMA-APTMACl) composite particles. Compared to Fe3O4/SiO2 particles, the loading capacity of biomolecules in polyelectrolyte grafted composite particles (∼ 30 mg g−1) is relatively larger at the respective isoelectric point. In presence of 11.2 kU mg−1 conjugated streptokinase (SK), Fe3O4/SiO2/P(iBMA-APTMACl) composite particles exhibited significant amount of thrombolytic activity (56%). A brief study of hemolysis suggested that composite particles are hemocompatible up to 0.18 mg mL−1. The higher inhibition percentage of protein denaturation also indicated the anti-inflammatory property of bare composite particles. The prepared Fe3O4/SiO2/P(iBMA-APTMACl) composite particles can therefore be applied in targeted thrombolysis, drug/gene carrier, anti-inflammatory agent and hyperthermia.

Shape and orientation of bare silica particles influence their deposition under intermediate ionic strength: A study with QCM–D and DLVO theory

Theory developed by Derjaguin, Landau, Verwey, and Overbeek (DLVO) is commonly used to interpret and predict the deposition of particles, but it was originally simplified for spherical particles. Many types of bacteria and particles in nature are not spherical. Previous literature has experimentally shown that particle shape has an effect on drug delivery, retention in porous media, self-assembly, and flotation, but the quantitative interpretation of these results has been hindered by experimental (e.g., uniform rod shaped particles and flow fields at controlled chemistries) and theoretical (e.g., consideration of rod shape particles with different surface orientations) challenges. For example, the deposition of ellipsoidal polystyrene particles has been investigated in the presence of non-DLVO interactions, due to residual poly(vinyl) alcohol, hindering the effect of shape. In our study, bare spherical and bullet-like silica particles of well-defined surface chemistry were used for deposition tests on bare silica surfaces using a Quartz Crystal Microbalance with Dissipation (QCM–D) over six ionic strengths (IS). At the same time, the DLVO theory was modified to consider particle shape and orientation of deposition. We found that particle shape had an effect on deposition at intermediate IS. A modified DLVO approach was able to interpret the deposition of bullet-like silica particles. Specifically, bullet-like silica particles of certain aspect ratio may find angles that minimize repulsive energies and overcome energy barriers so that deposition on the silica surfaces is energetically favorable. Therefore, there are conditions of water chemistry where particle shape and orientation cannot be ignored and their deposition must be systematically investigated.

Silaffin-3-derived pentalysine cluster as a new fusion tag for one-step immobilization and purification of recombinant Bacillus subtilis catalase on bare silica particles

Bio-catalysis by enzymes on solid surfaces has been implemented in several practical applications. However, the current methods for efficient enzyme immobilization with retained activity need further development. Herein, a simple, rapid, and economical, bio-affinity-based approach was developed for the direct immobilization with high activity recovery of the Bacillus subtilis catalase (CAT), recombinantly expressed in Escherichia coli. Silaffin-3-derived pentalysine cluster (Sil3K) from Thalassiosira pseudonana and its mutant variant (penta-arginine peptide; Sil3R) were used for the first time in the non-covalent immobilization of the recombinant enzyme on silica particles. The fusion proteins CAT-Sil3K and CAT-Sil3R were selectively loaded from the cell lysates onto the silica surface. Unexpectedly, the Lys-based tag (Sil3K) was the superior to Arg-based tag (Sil3R) or tag-less system for the high recovery of CAT activity upon immobilization; an 8.4-fold and 1.5-fold increase in the catalytic activity was observed for CAT-Sil3K compared with the tag-less CAT and CAT-Sil3R, respectively. Furthermore, the CAT-Sil3K immobilized on silica particles exhibited improved thermal, pH and storage stabilities, and retained 72% of the initial activity after five reaction cycles. Moreover, CAT-Sil3K was released with approximately 85% recovery and 91% purity, in a biologically active form when free lysine solution was used as the eluent. Our data proved that Sil3K-tag, 12-mer peptide, can be a highly promising silica-affinity tag for effective enzyme immobilization with preserved activity. Additionally, the novel findings obtained here may open a new route not only for cost-effective enzyme immobilization approaches but also for high recovery of enzyme activity.

Pickering Emulsions of Hydrophilic Silica Particles and Symmetrical Organic Electrolytes.

At high pH, bare silica particles are not an effective Pickering emulsion stabilizer of nonpolar oils with water due to their high surface charge. One way to promote particle adsorption to the oil-water interface is to add salt to the aqueous phase, although particle flocculation normally ensues. In most cases, inorganic salts are added, while little attention has been paid to the use of organic salts. Here, we describe the effects of adding tetraalkylammonium salts (R4NX, X is an anion) to aqueous dispersions of silica nanoparticles at high pH and investigating the possibility of subsequently stabilizing octane-in-water (o/w) emulsions. The chain length of the R group is systematically increased from 1 (methyl) to 4 (butyl). Unlike inorganic electrolytes, the addition of these salts does not lead to particle flocculation in water, although the particle charge is reduced. No stable emulsion forms for the methyl analogue, but very stable o/w emulsions can be prepared with the other three members, with the minimum concentration of salt being required decreasing with R chain length to as low as 5 × 10-5 M. The three-phase oil-water-solid contact angle increases with salt concentration and R chain length, confirming the increase in particle hydrophobicity on addition of salt. We show that the butyl analogue behaves similarly to that of cetyltrimethylammonium bromide surfactant with respect to promoting silica particles to emulsion drop interfaces. Finally, we compare the arrangement of micrometer-sized silica particles at both curved droplet interfaces and at a planar oil-water interface at different concentrations of the most hydrophobic salt.

Preparation and in vivo evaluation of red blood cell membrane coated porous silicon nanoparticles implanted with 155Tb

IntroductionPorous silicon (PSi) nanoparticles are capable of delivering therapeutic payloads providing targeted delivery and sustained release of the payloads. In this work we describe the development and proof-of-concept in vivo evaluation of thermally hydrocarbonized porous silicon (PSi) nanoparticles that are implanted with radioactive 155Tb atoms and coated with red blood cell (RBC) membrane (155Tb-THCPSi). The developed nanocomposites can be utilized as an intravenous delivery platform for theranostic radionuclides. MethodsTHCPSi thin films were implanted with 155Dy ions that decay to 155Tb at the ISOLDE radioactive ion-beam (RIB) facility at CERN. The films were processed to nanoparticles by ball-milling and sonication, and subsequently coated with either a solid lipid and RBC membrane or solely with RBC membrane. The nanocomposites were evaluated in vitro for stability and in vivo for circulation half-life and ex vivo for biodistribution in Balb/c mice. ResultsNanoporous THCPSi films were successfully implanted with 155Tb and processed to coated nanoparticles. The in vitro stability of the particles in plasma and buffer solutions was not significantly different between the particle types, and therefore the RBC membrane coated particles with less laborious processing method were chosen for the biological evaluation. The RBC membrane coating enhanced significantly the blood half-life compared to bare THCPSi particles. In the ex vivo biodistribution study a pronounced accumulation to the spleen was found, with lower uptake in the liver and a minor uptake in the lung, gall bladder and bone marrow. ConclusionsWe have demonstrated, using 155Tb RIB-implanted PSi nanoparticles coated with mouse RBC membranes, the feasibility of using such a theranostic nanosystem for the delivery of RIB based radionuclides with prolonged circulation time. Advances in knowledge and implications for patient careFor the first time, the RIB implantation technique has been utilized to produce PSi nanoparticle with a surface modified for better persistence in circulation. When optimized, these particles could be used in targeted radionuclide therapy with a combination of chemotherapeutic payload within the PSi structure.

Magnetic nanoparticles of Ga‐substituted ε‐Fe2O3 for biomedical applications: Magnetic properties, transverse relaxivity, and effects of silica‐coated particles on cytoskeletal networks

Magnetic nanoparticles of ε-Fe1.76 Ga0.24 O3 with the volume-weighted mean size of 17 nm were prepared by thermal treatment of a mesoporous silica template impregnated with metal nitrates and were coated with silica shell of four different thicknesses in the range 6-24 nm. The bare particles exhibited higher magnetization than the undoped compound, 22.4 Am2 kg-1 at 300 K, and were characterized by blocked state with the coercivity of 1.2 T at 300 K, being thus the very opposite of superparamagnetic iron oxides. The relaxometric study of the silica-coated samples at 0.47 T revealed promising properties for MRI, specifically, transverse relaxivity of 89-168 s-1 mmol(f.u.)-1 L depending on the shell thickness was observed. We investigated the effects of the silica-coated nanoparticles on human A549 and MCF-7 cells. Cell viability, proliferation, cell cycle distribution, and the arrangement of actin cytoskeleton were assessed, as well as formation and maturation of focal adhesions. Our study revealed that high concentrations of silica-coated particles with larger shell thicknesses of 16-24 nm interfere with the actin cytoskeletal networks, inducing thus morphological changes. Consequently, the focal adhesion areas were significantly decreased, resulting in impaired cell adhesion.

Equilibrium clustering of colloidal particles at an oil/water interface due to competing long-range interactions

HypothesisColloids at fluid interfaces organize according to inter-particle interactions. The main contributions to an effective interaction potential are expected to be electrostatic dipole-dipole repulsion and capillary attraction due to fluid interface deformation. When these interactions are weak, a secondary minimum in the particle pair interaction potential is expected. ExperimentsClean bare silica particles were deposited at an oil/water interface and their organization as well as dynamics were observed under a light microscope and analyzed in terms of radial distribution function and mean squared displacement. FindingsWeak long-range competing interactions between colloids at an oil/water interface result in cluster formation. The clusters have a liquid-like structure and grow with increasing particle packing fraction. System ‘ergodicity’ suggests near-equilibrium assembly, which is confirmed by free particle dynamics outside the clusters. The interplay between dipole-dipole repulsion and capillary attraction responsible for the cluster formation is reflected in a secondary minimum of the effective interaction potential predicted theoretically but inaccessible experimentally from collective particle properties prior to this work.

Discovery of an Unexpected Metal Dissolution of Thin‐Coated Cathode Particles and Its Theoretical Explanation

AbstractThe degree of metal dissolution of cathode materials is a critical parameter in determining the performance of lithium‐ion batteries (LIBs). Ultra‐thin coated cathode particles, fabricated via atomic layer deposition (ALD), exhibit superior battery performance over that of bare particles. Therefore, it is generally believed that a coating layer protects the particles from metal dissolution of active materials, which is a critical cathode degradation mechanism. However, it is observed that ultra‐thin CeO2 coating intensified the Mn dissolution of LiMn2O4 (LMO) during cycling of LIBs, whereas ultra‐thin Al2O3 coating tended to inhibit Mn dissolution. A detailed density functional theory (DFT) study is carried out to explain these experimental observations by analyzing interaction of Mn atoms with neighboring electrode atoms in terms of energetic and structural aspect. All atomic and electronic analyses are consistent with the experimental observations. Several common materials are investigated as possible ALD coatings for LIBs to provide general insight, and it is found that Mn dissolution can be suppressed or accelerated depending on the material selection. This is the first report finding that depending on the coating material, metal dissolution can be accelerated, providing new insights into the impact of ALD coating materials on metal dissolution in cathode materials.