Bare Particles Research Articles

Sulfidation of air-stable iron nanoparticles: A novel strategy how to boost their reactivity demonstrated on Cr(VI) reduction

Sulfidated zero-valent iron nanoparticles (S-nZVI) have been extensively studied as environmentally promising alternative material, which enables reduction of variety of extremely dangerous pollutants directly in the environment. However, synthesis and manipulation with these extremely reactive/pyrophoric nZVI particles represents a challenge and requires special precautions. In this study, we report a synthesis of S-nZVI from air-stable core-shell nZVI, which reactivity with contaminants and properties are comparable with the commonly prepared S-nZVI particles (where the precursor was bare/pyrophoric nZVI particles). The undeniable novelty dwells in the simplicity of the synthetic process, which ensures consequential safe and easy handling, manipulation, and application of S-nZVI particles. This material, especially highly effective against halogenated organic compounds and heavy metals, was characterized in detail and its advanced characteristics were evaluated in the process of hexavalent chromium (Cr(VI)) reduction from model aqueous solutions and polluted groundwater. The results offer valuable insights into the preparation of a novel nanomaterial with high application potential in the effective degradation of heavy metals in polluted water. Overall, the novel way prepared S-nZVI particles, designed for the potential large-scale production, eliminates the drawbacks of S-nZVI synthesized from bare nZVI particles and offers the effective material suitable for any on-site application.

In-situ self-catalyzed fabricating carbon nanotubes on [010] preferential LiMn0.5Fe0.5PO4 nanoplates to achieve excellent high rate performance

Nano carbon material composites significantly enhance the performance of lithium manganese iron phosphate (LMFP) cathode materials. This study investigates the self-catalytic growth mechanism of highly conductive carbon nanotubes (CNTs) on bare LMFP particles via chemical vapor deposition (CVD), focusing on the influence of particle size and crystallographic orientation. It is found that the Fe3C particles formed on static solvothermal synthesized LMFP nanoplates with high [010] orientation were effective to catalyze the generation of CNTs. Diverse CVD durations produced CNTs coatings with varying structures to impact electrochemical properties of final products. The MP-L/CNTs-2 sample, with 3.6 wt% carbon, showed the highest reversible capacity of 158 mAh g−1 at 1 C with 99.3 % capacity retention after 400 cycles, after 3000 cycles at 10 C, the retention rate was 74.5 %. In contrast, LMFP synthesized via solid-phase method (MP-S/C) only formed a carbon film on the surface and delivered 143 mAh g−1 at 1 C (97.6 % retention after 400 cycles) with prominent capacity loss at 10 C. This study provides new insights into the self-catalytic growth mechanism of CNTs to promote ion-electron conductivity and structural stability of LMFP materials, thus improving kinetic property and cycling stability for high-performance lithium-ion batteries.

Electroless Deposition of Ni Nanoparticles on Boron Particles: Physicochemical and Oxidation Properties

Elemental boron also has a high volumetric heat of combustion (136 kJ/cm3), the third highest gravimetric heat of combustion (58.5 MJ/kg) and its oxidation is a highly exothermic process. All these features make boron an attractive constituent of propellants, explosives, and high energy density solid fuels for air-breathing propulsion as an energetic material. Given these uses, researchers have worked on the ignition and combustion processes of boron. However, boron has several serious issues that limit its practical use, including large ignition delay, inefficient combustion, and a complex burning process in solid propellants due to the formation of a defensive boron oxide (B2O3) layer on the boron surface. Previous studies have found that the ignition and combustion performance of boron can be improved by coating it with metal particles, metal oxides, or organic materials, as well as by removing the boron oxide layer.In the literature, there are limited studies on metal particle coating of a boron surface using the electroless Ni plating method. The electroless coating has several impressive advantages over conventional electrolytic coating. The prime advantage is that electroless plating does not require any electricity to operate and is a low-cost process. Among other advantages, it provides a uniform coating and can be used with all kinds of substrates with complex shapes. Conductive and non-conductive materials/powders can be coated with constant thickness with good adhesion.The present work investigated Ni nanoparticle coating on irregularly shaped/non-spherical boron particles using the electroless Ni-plating method at room temperature to prevent the oxidation of boron particles. This is preferable since it is very difficult to coat large quantities at relatively high temperatures. The four different simple paths were chosen during the electroless Ni plating to coat Ni on boron particles: no rinsing and no drying (Path A), only drying (Path B), both rinsing and drying (Path C) and only rinsing (Path D). Previous studies have explored the effect of bath concentration, pH, and temperature on the Ni coating. However, the influence of the four different paths mentioned above on Ni coating with boron particles or any other materials has rarely been investigated. Surface morphology confirmed the Ni nanoparticles coating on the surface of boron particles. The size of the Ni nanoparticles varied between 10 and 120 nm concerning the chosen paths used for preparation using TEM. XRD characterization results of the Ni coated boron particles showed the formation of crystalline Ni nanoparticles. EDAX and XPS results showed the presence of the primary B and Ni elements in samples synthesized in the present study. Thermogravimetric analysis conducted in air atmosphere found the boron particles coated with Ni nanoparticles had enhanced oxidation resistance compared to bare boron particles. Also, the Ni coated boron particles showed a shift in exothermic peak to a lower temperature and higher heat evolution than the bare boron particles.Acknowledgements:This work was supported by the National Research Foundation (NRF) of Korea grant funded by the Korea government (MSIT) No. 2019R1A2C1010862, 2022R1A2C2013508

Synthesis of bare and modified zerovalent iron nanoparticles and their use in porous polylactic acid composites for methyl orange removal

The main objective of this study was to assess the efficacy of two types of immobilised zerovalent iron nanoparticles (nZVI) incorporated into a porous biopolymer matrix of polylactic acid (PLA) as a novel multifunctional composite system for potential use in dye wastewater treatment. The study involved the preparation of unmodified and 2,6-pyridinedicarboxylic acid (PDCA) modified nZVI material using liquid phase reduction method. Zeta potential measurement and UV-Vis spectrophotometry revealed that the ligand-modified nZVI particles exhibited better dispersion stability in aqueous media than bare particles. SEM-EDS analysis showed a higher oxidation state of the ligand-modified nZVI particles and good dispersion and adhesion of nZVI particles in the mesoporous structure of PLA matrix. The removal efficiency of methyl orange was determined spectrophotometrically where a high efficiency (above 90 %) for high concentration of bare nZVI was detected. Its composites also showed an efficiency of 75 – 100 %. However, modified nZVI showed much lower efficiency, especially after embedding in the PLA matrix.

Dynamic and phase transition studies of ionic surfactant-stabilized oil/water microemulsion: Effects of volume fraction, polymer grafting, and temperature

In this work, we study the dynamic/phase transition relationship of a system composed of spherical particles of oil/water microemulsion, stabilised by an ionic surfactant based on cetylpyridinium chloride (CpCl) and an octanol-based cosurfactant, and dispersed in salt water. We examine a large range of volume fractions Φ. To do this, we use molecular dynamics simulations with an appropriate interaction potential that accounts for Van der Waals and electrostatic interactions. We also graft different numbers of dodecyl-(polyethylene oxide)227-dodecyltriblock copolymers onto the microemulsion nanodroplets, which we denote (n(D−PEO227−D)), where n varies from 0 to 12. Specifically, we treat the dynamic properties, using the mean square displacement (MSD) and diffusion coefficients, and then use Arrhenius law to determine the activation energy. In our study, we vary three main parameters: the volume fraction, the number of polymer added to the n(D−PEO227−D) microemulsion, and the temperature. The result shows a transition from the sol to the gel state of the bare microemulsion as the volume fraction increases or as the temperature decreases. Also, it proves that when a D-PEO-D polymer is added to the microemulsion, the system rapidly changes its state either as the volume fraction Φ increases or as the temperature T decreases. We also calculate the activation energy of the bare particles in the microemulsion at different volume fractions (ϕ) using the Arrhenius equation.

Thiol Coordination Softens Liquid Metal Particles To Improve On-Demand Conductivity.

Achieving tunable rupturing of eutectic gallium indium (EGaIn) particles holds great significance in flexible electronic applications, particularly pressure sensors. We tune the mechanosensitivity of EGaIn particles by preparing them in toluene with thiol surfactants and demonstrate an improvement over typical preparations in ethanol. We observe, across multiple length scales, that thiol surfactants and the nonpolar solvent synergistically reduce the applied stress requirements for electromechanical actuation. At the nanoscale, dodecanethiol and propanethiol in toluene suppress gallium oxide growth, as characterized by transmission electron microscopy and X-ray photoelectron spectroscopy. Quantitative AFM imaging produces force-indentation curves and height images, while conductive AFM measures current while probing individual EGaIn particles. As the applied force increases, thiolated particles demonstrate intensified softening, rupturing, and stress-induced electrical activation at forces 40% lower than those for bare particles in ethanol. To confirm that thiolation facilitates rupturing at the macroscale, a laser is used to ablate samples of EGaIn particles. Scanning electron microscopy and resistance measurements across macroscopic samples confirm that thiolated EGaIn particles coalesce to exhibit electrical activation at 0.1 W. Particles prepared in ethanol, however, require 3 times higher laser power to demonstrate a similar behavior. This unique collection of advanced techniques demonstrates that our particle synthesis conditions can facilitate on-demand functionality to benefit electronic applications.

Utilizing banana peel in conjunction with TiO2 photocatalyst for the efficient decolorization of malachite green

Porous materials are frequently integrated into TiO2 photocatalysts due to their enhanced surface area and reaction efficiency. This study aimed to enhance the efficiency of wastewater treatment by developing a TiO2 combined with banana peel (BP) through the sol-gel method. The TiO2/BP composite was extensively analyzed using a range of methods, such as X-ray diffraction (XRD), field emission transmission electron microscopy (FESEM), energy dispersive X-ray (EDX) analysis, diffuse reflectance spectroscopy (DRS UV–vis), photoluminescence spectra (PL), and Brunauer–Emmett–Teller (BET) analysis. Subsequent evaluation of the photoactivity of the TiO2/BP composite compared to bare TiO2 particles revealed a noteworthy enhancement in decolorizing malachite green (MG) dye under visible light. Furthermore, recyclability testing further demonstrated consistent performance for up to four cycles, highlighting the potential application of this porous material-based photocatalytic composite in wastewater treatment.

Double Nitrogenation Layer Formed Using Nitric Oxide for Enhancing Li+ Storage Performance, Cycling Stability, and Safety of Si Electrodes.

To enhance Li storage properties, nitrogenation methods are developed for Si anodes. First, melamine, urea, and nitric oxide (NO) precursors are used to nitrogenize carbon-coated Si particles. The properties of the obtained particles are compared. It is found that the NO process can maximize the graphitic nitrogen (N) content and electronic conductivity of a sample. In addition, optimized N functional groups and O─C species on the electrode surface increase electrolyte wettability. However, with a carbon barrier layer, NO hardly nitrogenizes the Si cores. Therefore, bare Si particles are reacted with NO. Core-shell Si@amorphous SiNx particles are produced using a facile and scalable NO treatment route. The effects of the NO reaction time on the physicochemical properties and charge-discharge performance of the obtained materials are systematically examined. Finally, the Si@SiNx particles are coated with N-doped carbon. Superior capacities of 2435 and 1280 mAh g-1 are achieved at 0.2 and 5Ag-1, respectively. After 300 cycles, 90% of the initial capacity is retained. In addition, differential scanning calorimetry data indicate that the multiple nitrogenation layers formed by NO significantly suppress electrode exothermic reactions during thermal runaway.

The role of biocompatible coatings of magnetic nanorods on their thermal response in hyperthermia. Consequences on tumor cell survival

There are so many hopes for nanoscience as a tool in the fight against various diseases, notably cancer, that the problem can be approached from many different points of view. In this paper, we focus on two essential aspects. One is the preparation of non-spherical and superparamagnetic magnetic particles, with the right size to be able to exit the blood vessels and be incorporated by cells. The second is their use as agents of hyperthermia. For the first purpose, a two-step method was followed, in which hematite templates with the desired shape and size were first prepared, and these were subsequently reduced by heat treatment. As a result, nanorods with a length of 40 nm and an axis ratio of 1:8 were obtained. The bare particles were coated with a triple layer of cationic/anionic/cationic polymers. Electrophoretic mobility, thermogravimetric analysis, x-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy evaluations confirmed the presence of the coating and the positive charge of the last polymeric layer, while x-ray diffraction and micro-Raman spectroscopy indicated that the crystal structure of the core particles was magnetite/maghemite. The magnetization cycles of the particles showed that they were superparamagnetic, with a saturation magnetization of 82 emu/g in the case of the bare particles. For concentrations up to 300 μg/mL, they were found to be compatible with MCF7 (Michigan Cancer Foundation-7) breast cancer cell line, for cell uptakes higher than 80 %. Both bare and polymer-coated particles produced heating by magnetic hyperthermia and laser-light irradiation. Finally, cytotoxicity against the cancer cells was evaluated, and it was found that photothermia and, above all, magnetic hyperthermia applied to the coated particles could induce more than 50% cell death.

Seedless and electroless plating of silver on silica particles by using microreactor

Synthesis of silver nanoshells is still a challenge especially in the absence of surface modification of core particles and/or metal seed decoration on core surfaces. In this study, we applied a microrector to seedless and electroless plating of silver on bare silica particles, and investigated the effects of reaction temperatures and silver ion concentrations on the morphology and surface coverage of silver on the core particle surface. Our experiments demonstrated that the use of the microreactor enabled the one-step direct deposition of silver with a morphology close to complete shells and that silver ion concentrations from 0.2 to 0.5 mM at a moderate temperature of 50 °C produced high coverage and yield. Besides, the mixing sequence of NH3 and HCHO in the synthesis procedure was found to be a key factor to achieve the high silver coverage. In addition, we demonstrated that the addition of polyvinylpyrrolidone (PVP) after the silver shell growth reaction increases the stability without decreasing the reaction rate.

In situ Tracking the Constrained Reconstruction of Cu3Pd@SiO2 Nanoparticles Driven by Redox Atmospheres

AbstractEndowed with flexible surface coordination and synergetic electronic status, bimetallic particles serve as promising heterogeneous catalysts as their microstructures evolved sensitively to the treatment atmospheres, whereas knowledge of dynamic manners is less. Herein, utilizing environmental transmission electron microscopy (ETEM), the reconstructions of Cu3Pd particles in oxidization/reduction atmospheres were explored at atomic scale. Specifically, bare Cu3Pd particles went through a phase separation of CuOx and PdOx during in situ oxidation, and subsequent agglomeration after H2 reduction. While protected in a silica shell, the confined Cu3Pd particles were oxidized into Cu1.5Pd0.5O2 phase after air calcination and subsequently restructured into versatile configurations during H2 reduction. Specifically, hollow Cu3Pd alloy architecture with Pd enriched layer near surface as reduced at 200 °C. Further rising 400 to 600 °C, it yielded disordered Cu3Pd alloys with slightly Pd atoms enrichment at outmost surface. The dynamical behaviors of single Cu1.5Pd0.5O2 particle during in situ reduction have been visualized in ETEM, wherein a series of deformation, elongation and rotation is involved during the hollow architecture firstly formation, and then vanished into a Cu3Pd solid solution nanoparticle. The tunable microstructures of Cu3Pd@SiO2 driven by redox atmospheres demonstrate efficient approach for precisely regulating the chemical environments of constrained bimetallic nanocatalysts.

Enhanced Methanol Synthesis from CO2 Hydrogenation Achieved by Tuning the Cu-ZnO Interaction in ZnO/Cu2O Nanocube Catalysts Supported on ZrO2 and SiO2.

The nature of the Cu-Zn interaction and especially the role of Zn in Cu/ZnO catalysts used for methanol synthesis from CO2 hydrogenation are still debated. Migration of Zn onto the Cu surface during reaction results in a Cu-ZnO interface, which is crucial for the catalytic activity. However, whether a Cu-Zn alloy or a Cu-ZnO structure is formed and the transformation of this interface under working conditions demand further investigation. Here, ZnO/Cu2O core-shell cubic nanoparticles with various ZnO shell thicknesses, supported on SiO2 or ZrO2 were prepared to create an intimate contact between Cu and ZnO. The evolution of the catalyst's structure and composition during and after the CO2 hydrogenation reaction were investigated by means of operando spectroscopy, diffraction, and ex situ microscopy methods. The Zn loading has a direct effect on the oxidation state of Zn, which, in turn, affects the catalytic performance. High Zn loadings, resulting in a stable ZnO catalyst shell, lead to increased methanol production when compared to Zn-free particles. Low Zn loadings, in contrast, leading to the presence of metallic Zn species during reaction, showed no significant improvement over the bare Cu particles. Therefore, our work highlights that there is a minimum content of Zn (or optimum ZnO shell thickness) needed to activate the Cu catalyst. Furthermore, in order to minimize catalyst deactivation, the Zn species must be present as ZnOx and not metallic Zn or Cu-Zn alloy, which is undesirably formed during the reaction when the precatalyst ZnO overlayer is too thin.

Dust and Ice in the Interstellar Medium

In this paper, we present an introduction to bare dust particles and grains covered by ice sheets in diffuse and dense interstellar clouds. It follows the life cycle of dust from its formation in stellar environments to its incorporation into the body of the Solar system. Dust particles play an important role in the physics and chemistry of many space environments. Regarding dust composition, two different populations are generally observed: silicate and carbonaceous dust. Energetic processing of ice layers with UV rays, X – rays or cosmic rays, after which the heat leads to the formation of complex organic molecules; some of them have prebiotic properties. Delivery of this organic fraction to the early Earth by meteorites and asteroids may have contributed to the origin of life.

CeO2-based peelable gel for neutralization and skin decontamination toward chemical warfare agents

Accidents with toxic industrial chemicals and threats posed by chemical warfare agents, as organophosphorus nerve agents and blistering agents, has become an increasing concern over the last decades. Intoxication is not only due to inhalation but dermal route can also be important and can quickly lead to death. It is therefore crucial to have suitable means of personal protection and decontamination. Some are already commercially available but often present drawbacks. Efforts have been made to develop new systems and several studies have shown the interest of metallic nanoparticles. The challenge remains to entrap the particles in an adapted matrix to limit their diffusion in the immediate environment, while preserving the bare particles decontamination efficacy. In this study, an easy to handle peelable gel, incorporating CeO2 nanoparticles has been developed for efficient skin decontamination against toxic chemicals. The main objective has been to make it suitable in any context of application (battlefield or civil exposure). Nano-octahedra (NO) CeO2 particles synthetized in this study have been able to increase the degradation of paraoxon, a simulant warfare agent in liquid media. NO have then been incorporated in a peelable gel, the formulation has been optimized through design of experiments and its physico-chemical properties characterized. Even after incorporation to the gel, NO retained their neutralization properties. The formulation efficiency towards neutralization and skin decontamination have been evaluated in vitro on Franz diffusion cells. The interest of the peelable gel have been clearly demonstrated with a decrease by about 5-fold of the quantity of POX absorbed into the skin and a decrease of 3–4-fold in the viable skin, which was much higher than the use of cotton or nanoparticles as powder.

Effect of solution chemistry on the sedimentation, dissolution, and aggregation of the bimetallic Fe/Cu nanoparticles pre- and post-grafted with carboxymethyl cellulose

The suitability of iron-based nanomaterials or composites for in-situ remediation hinges on their physicochemical stability. Introducing surface modifications like metal doping or polymer grafting can regulate interparticle forces, influencing particle stability. Thus, probing how grafting methods (i.e., pre- or post-grafting) tune material properties controlling interparticle forces, comprehend the synergistic effect of metal doping and polymer grafting, and evaluate stability under varying geochemical conditions are the way forward in designing sustainable remediation strategies. To this end, time-dependent sedimentation, dissolution, and aggregation of four synthesized iron-based nanoparticles (bare iron (Fe), copper doped bimetallic iron/copper (Fe/Cu), pre- and post-grafted Fe/Cu with carboxymethyl cellulose (CMC) – CMCpre-Fe/Cu and CMCpost-Fe/Cu, respectively) were carried out as a function of solution chemistry (i.e., pH – 5 to 10, ionic strength, IS – 0 to 100 mM NaCl, initial particle concentration, C0–20 to 200 mg.L−1) mimicking geoenvironmental conditions. CMCpre-Fe/Cu exhibited markedly higher particle availability (> 91 %) against sedimentation than others (bare Fe/Cu (11.28 %) > bare Fe (7.33 %) > CMCpost-Fe/Cu (6.09 %)) – suggesting the pivotal role of grafting method on particle stability. XDLVO energy profiles revealed pre-grafting altered magnetic properties favoring surface charge-driven electrostatic repulsion over magnetic attraction, thereby limiting aggregation-induced particle settling. In contrast, superior magnetic force overrides the electrostatic behavior for bare and post-grafted particles. Unlike bare and post-grafted nanoparticles, CMCpre-Fe/Cu aggregate size correlated positively with [H+] and IS, consistent with their settling behavior. Rise in C0 showed a visible negative effect on particle aggregation and, thereby, sedimentation except for CMCpre-Fe/Cu by facilitating particle collision through Brownian movement. Both acidic pH and copper doping promoted nanoparticle dissolution, whereas pre-grafting can provide a plausible solution against nanoparticle toxicity and loss of reactivity due to ionic release. To recapitulate, these findings are imperative in building a sustainable framework for environmental remediation application.

Higher absorption enhancement of black carbon in summer shown by 2-year measurements at the high-altitude mountain site of Pic du Midi Observatory in the French Pyrenees

Abstract. Black-carbon-containing particles strongly absorb light, causing substantial radiative heating of the atmosphere. The climate-relevant properties of black carbon (BC) are poorly constrained in high-altitude mountain regions, where many complex interactions between BC, radiation, clouds and snow have important climate implications. This study presents 2-year measurements of BC microphysical and optical properties at the Pic du Midi (PDM) research station, a high-altitude observatory located at 2877 m above sea level in the French Pyrenees. Among the long-term monitoring sites in the world, PDM is subject to limited influence from the planetary boundary layer (PBL), making it a suitable site for characterizing the BC in the free troposphere (FT). The classification of the dominant aerosol type using aerosol spectral optical properties indicates that BC is the predominant aerosol absorption component at PDM and controls the variation in single-scattering albedo (SSA) throughout the 2 years. Single-particle soot photometer (SP2) measurements of refractory BC (rBC) show a mean mass concentration (MrBC) of 35 ng m−3 and a relatively constant rBC core mass-equivalent diameter of about 180 nm, which are typical values for remote mountain sites. Combining the MrBC with in situ absorption measurements, a rBC mass absorption cross-section (MACrBC) of 9.2 ± 3.7 m2 g−1 at λ=880 nm has been obtained, which corresponds to an absorption enhancement (Eabs) of ∼2.2 compared to that of bare rBC particles with equal rBC core size distribution. A significant reduction in the ΔMrBC/ΔCO ratio when precipitation occurred along the air mass transport suggests wet removal of rBC. However we found that the wet removal process did not affect the rBC size, resulting in unchanged Eabs. We observed a large seasonal contrast in rBC properties with higher MrBC and Eabs in summer than in winter. In winter a high diurnal variability in MrBC (Eabs) with higher (lower) values in the middle of the day was linked to the injection of rBC originating from the PBL. On the contrary, in summer, MrBC showed no diurnal variation despite more frequent PBL conditions, implying that MrBC fluctuations are rather dominated by regional and long-range transport in the FT. Combining the ΔMrBC/ΔCO ratio with air mass transport analysis, we observed additional sources from biomass burning in summer leading to an increase in MrBC and Eabs. The diurnal pattern of Eabs in summer was opposite to that observed in winter with maximum values of ∼2.9 observed at midday. We suggest that this daily variation may result from a photochemical process driving the rBC mixing state rather than a change in BC emission sources. Such direct 2-year observations of BC properties provide quantitative constraints for both regional and global climate models and have the potential to close the gap between model-predicted and observed effects of BC on the regional radiation budget and climate. The results demonstrate the complex influence of BC emission sources, transport pathways, atmospheric dynamics and chemical reactivity in driving the light absorption of BC.

Separating Geometric and Diffusive Contributions to the Surface Nucleation of Dislocations in Nanoparticles.

While metal nanoparticles are widely used, their small size makes them mechanically unstable. Extensive prior research has demonstrated that nanoparticles with sizes in the range of 10-50 nm fail by the surface nucleation of dislocations, which is a thermally activated process. Two different contributions have been suggested to cause the weakening of smaller particles: first, geometric effects such as increased surface curvature reduce the barrier for dislocation nucleation; second, surface diffusion happens faster on smaller particles, thus accelerating the formation of surface kinks which nucleate dislocations. These two factors are difficult to disentangle. Here we use in situ compression testing inside a transmission electron microscope to measure the strength and deformation behavior of platinum particles in three groups: 12 nm bare particles, 16 nm bare particles, and 12 nm silica-coated particles. Thermodynamics calculations show that, if surface diffusion were the dominant factor, the last two groups would show equal strengthening. Our experimental results refute this, instead demonstrating a 100% increase in mean yield strength with increased particle size and no statistically significant increase in strength due to the addition of a coating. A separate analysis of stable plastic flow corroborates the findings, showing an order-of-magnitude increase in the rate of dislocation nucleation with a change in particle size and no change with coating. Taken together, these results demonstrate that surface diffusion plays a far smaller role in the failure of nanoparticles by dislocations as compared to geometric factors that reduce the energy barrier for dislocation nucleation.

Membrane Binding Strength vs Pore Formation Cost─What Drives the Membrane Permeation of Nanoparticles Coated with Cell-Penetrating Peptides?

Cell-penetrating peptides (CPPs) enable the transport of nanoparticles through cell membranes. Using molecular simulations, we conduct an in-depth investigation into the thermodynamic forces governing the passive translocation of CPP-coated nanoparticles across lipid bilayers, contrasting their behavior with that of bare particles to dissect the contribution of the peptides. Our analysis unveils a distinctive two-stage translocation mechanism, where the adsorption energy of the particles overcomes the cost of forming a hydrophilic transmembrane pore. Proper evaluation of the translocation mechanisms is only possible when using two reaction coordinates, in particular, one that explicitly includes the density of the lipids on the binding site of the particle. An analysis of adsorption and activation free energies in terms of a simple kinetic model provides a clearer understanding of the CPP effect. Experimental validation using nonendocytic cells confirms the superior membrane permeation of CPP-coated particles. Our findings have implications for the rational design of more efficient cell-permeating particles.

The study of optical properties of single soot aggregate using three-dimension soft X-ray tomographic reconstruction

The linear depolarization ratio (LDR) is a key parameter used in remote sensing to distinguish particle types. The LDR of the soot fractal model is uneasy to match the measured values. In this paper we used three-dimensional (3D) synchrotron soft X-ray tomography (SXT) for the 3D reconstruction of the toluene-burning soot particles and used discrete dipole approximation to calculate optical properties. The obtained results showed the 3D reconstructed soot particles can efficiently reproduce the measured LDR. The results of this study will encourage us to develop a new morphology model, completely different from the traditional fractal model, for bare soot based on 3D reconstruction. This study is helpful for the understanding and explanation of LDR of bare soot particles.

Concentration polarization around polyelectrolyte-coated electrodes. Model and observations

An investigation on the phenomenon of concentration polarization (CP) in conducting porous particles is presented in this work, considering both bare and polyelectrolyte-coated particles. The conducting nature of the porous structure brings about the induction of a surface (and hence volume) charge distribution by the applied external field. The polymer charge (with its counterions from solution) is superimposed on this field-induced component. From the solution of Poisson’s equation, the concentration and potential profiles are evaluated, and from them, the concentration polarization can be calculated. The results are presented as concentration perturbation as a function of time after application of the field, both for bare and coated particles. Experiments are also performed aimed at measuring the CP using a solution of fluorescent dye (rhodamine B). From the increase or decrease of fluorescence, the concentration perturbations are observed around the particle. Importantly, depletion of concentration is observed on both sides of the particle when this is bare. In contrast, if the particles are coated, the classical pattern of a pole of increased concentration and an opposite one of decreased concentration is found. Dielectric dispersion experiments in suspensions of bare and brush-coated particles confirm this fact.