Submicron Particles Research Articles

Reduction of Submicron-Sized Aerosols by Aerodynamically Assisted Electrical Attraction with Micron-Sized Aerosols

A vortex generator was installed inside an electric agglomeration device to apply aerodynamic agglomeration in the same space as electric agglomeration. Computational fluid dynamics simulation was utilized to assess the combined effects of electric and aerodynamic agglomeration, and this was subsequently validated through experiments. The discrete phase model was used to track particle trajectories. The results showed that both the aerodynamic agglomeration through the vortex generator and the electric agglomeration through the electric field were effective. When these two agglomerations existed individually in series, the total removal efficiency for submicron particles was 32.5%. However, when they coexisted in the same space, the efficiency increased to 50%. This increase is attributed to the increase in residence time when the vortex generator was added to a space with an electric field. This led to particles being exposed to the electric field for a longer duration, thus generating a synergistic effect.

Determination of ultrafine particle number emission factors from building materials in standardized conditions

Abstract When comparing the particle emissivity for different materials and/or mechanical activities, a serious methodological issue emerges due to the dynamic nature of solid aerosols. Particle size distribution and concentration depend on initial particle emission that constantly evolves due to aerodynamic collisions. In this context, we propose a methodological approach and an experimental setup that enables to assess the release of fine/ultra-fine particles maintaining a steady-state inhalable mass concentration, here chosen at the Swiss occupational exposure level value for biopersistent granular particles (OEL: 10 mg/m3) in a controlled ventilation chamber. As a case study, this methodological protocol was tested in the occupational exposure scenario in which a series of insulating materials based on silica aerogel and conventional mortar and concrete were subjected to handling or sawing. Once the OEL was reached, the particle size distribution and morphology of the aerosols were characterized using direct reading instruments (scanning mobility sizer, aerosol photometer) and electron microscopy (SEM and TEM) analyses. As a main result, the presence of silica aerogel in the mortar did not modify the emission profile for submicronic particles during sawing in comparison to the bulk mortar. Emission factors for ultra-fine particles were found to be 88 × 106 and 81 × 106 particles/µg of inhalable dust for the aerogel mortar and bulk mortar, respectively. For concrete sawing, the number concentration of submicronic particles at the OEL is one order of magnitude greater. The aerogel-glass-wool handling generated similar particle number concentration at the OEL with ultra-fine particle emission factors of 647 × 106 particles/µg of inhalable dust, in comparison to 758 × 106 particles/µg of inhalable dust during dry concrete sawing. In conclusion, the methodology introduced in this work provides standardized particle emission factors for comparing materials and activities, while establishing a link between particle number emissions and occupational exposure limits.

Tuning Thin Film Thickness and Porosity with Layer‐by‐Layer Submicronic Particles Assembly

AbstractPorous NiO films were prepared using Layer‐by‐Layer assembly of submicronic β‐Ni(OH)2 nanoplatelets and size‐controlled poly(methyl methacrylate) (PMMA) particles. β‐Ni(OH)2/PMMA thin films were elaborated using different PMMA particle sizes and concentrations. The elaborated films were then heated at a temperature of 325 °C in air for one hour to form porous NiO films by calcining β‐Ni(OH)2 nanoplatelets. PMMA polymeric particles were also calcined during this process, leading to film porosity. Thermal treatment experiments clearly showed a relationship between PMMA particle size and film properties i. e., porosity and thickness. NiO films exhibited huge pores, around 1 μm, and matter loss after calcination when PMMA particles with a diameter of 190±43 nm were employed. Partial collapsing of the films was also denoted. Experiments were then carried out by decreasing PMMA particle size (100±19 nm) leading to cohesive NiO films. Finally, the specific surface area (SSA) of the NiO films prepared with PMMA particles of 100 nm was determined by adsorption‐desorption of nitrogen gas using the BET (Brunauer–Emmet–Teller) method. This showed an increase in SSA with PMMA particle concentration.

Ultra-Stretchable Microfluidic Devices for Optimizing Particle Manipulation in Viscoelastic Fluids.

Viscoelastic microfluidics leverages the unique properties of non-Newtonian fluids to manipulate and separate micro- or submicron particles. Channel geometry and dimension are crucial for device performance. Traditional rigid microfluidic devices require numerous iterations of fabrication and testing to optimize these parameters, which is time-consuming and costly. In this work, we developed a flexible microfluidic device using ultra-stretchable and biocompatible Flexdym material to overcome this issue. Our device allows for simultaneous modification of channel dimensions by external stretching. We fabricated a stretchable device with an initial square microchannel (30 μm × 30 μm), and the channel aspect ratio can be adjusted from 1 to 5 by external stretching. Next, the effects of aspect ratio, particle size, flow rate, and poly(ethylene oxide) (PEO) concentration that make the fluid viscoelastic on particle migration were investigated. Finally, we demonstrated the feasibility of our approach by testing channels with an aspect ratio of 3 for the separation of both particles and cells.

Enhancing strength and toughness simultaneously: Diblock-grafted cellulose nanofiber one-component nanocomposites

To overcome the drawbacks of homopolymer-grafted CNF one-component nanocomposites, a range of diblock-grafted cellulose nanofiber (CNF), CNF-g-(polybutyl acrylate-b-polymethyl methacrylate)s were synthesized through reversible-deactivation radical polymerization (RDRP) methods. The chemical structures and ratios between the two blocks were confirmed, with surface-grafted CNF observed as submicron particles. Both thermal and thermodynamic analysis revealed two glass transition temperatures (Tg) in the diblock-grafted CNF, and phase-separated morphology was observed in the nanocomposites. The densely grafted CNF displayed island structures, while sparsely grafted samples transitioned into continuous structure. Thermodynamic analysis showed that the diblock-grafted CNF nanocomposites maintained mechanical properties at high temperatures. These nanocomposites demonstrated robust strength and toughnes, with tensile strength reaching as high as 43.7 ± 1.6 MPa and elongation at break of 70.3 ± 16.2 %. Moreover, while densely grafted CNF exhibited higher modulus and strength, whereas sparsely grafted CNF displayed behavior more reminiscent of thermoplastic elastomers, indicated by lower modulus and higher elongation.

Surface-enhanced infrared spectroscopic study of extracellular vesicles using plasmonic gold nanoparticles

Extracellular vesicles (EVs), sub-micrometer lipid-bound particles released by most cells, are considered a novel area in both biology and medicine. Among characterization methods, infrared (IR) spectroscopy, especially attenuated total reflection (ATR), is a rapidly emerging label-free tool for molecular characterization of EVs. The relatively low number of vesicles in biological fluids (~1010 particle/mL), however, and the complex content of the EVs’ milieu (protein aggregates, lipoproteins, buffer molecules) might result in poor signal-to-noise ratio in the IR analysis of EVs. Exploiting the increment of the electromagnetic field at the surface of plasmonic nanomaterials, surface-enhanced infrared spectroscopy (SEIRS) provides an amplification of characteristic IR signals of EV samples. Negatively charged citrate-capped and positively charged cysteamine-capped gold nanoparticles with around 10nm diameter were synthesized and tested with blood-derived EVs. Both types of gold nanoparticles contributed to an enhancement of the EVs’ IR spectroscopic signature. Joint evaluation of UV-Vis and IR spectroscopic results, supported by FF-TEM images, revealed that proper interaction of gold nanoparticles with EVs is crucial, and an aggregation or clustering of gold nanoparticles is necessary to obtain the SEIRS effect. Positively charged gold nanoparticles resulted in higher enhancement, probably due to electrostatic interaction with EVs, commonly negatively charged.

Phase changes in burning precursor-laden single droplets leading to puffing and micro-explosion

When producing metal-oxide nanoparticles via flame spray pyrolysis, precursor-laden droplets are ignited and undergo thermally induced disintegration, called ‘puffing’ and ‘micro-explosion’. In a manner that is not fully understood, these processes are associated with the formation of dispersed phases inside the droplets. This work aims at visualizing the interior of precursor-laden burning single droplets via diffuse back illumination and microscopic high-speed imaging. Solutions containing iron(III) nitrate nonahydrate (INN) and tin(II) 2-ethylhexanoate (Sn-EH) were dispersed into single droplets of sub-100 μm diameter that were ignited by passing through a heated coil. At low precursor concentration, 50% of the INN-laden droplets indicate a gas bubble of about 5 μm diameter in the center of the droplet. The bubble persists for several hundred microseconds at a similar size. In almost all of these cases, the bubble expands at some point and the droplet ends up in a micro-explosion. In some of these instances, the droplet’s surface shows spatial brightness modulations, i.e., surface undulations, indicating the formation of a viscous shell. With increasing INN concentration, the fraction of droplets showing surface undulations, gas bubbles, and micro-explosions drastically decreases. This may be associated with a more rigid viscous shell and reduced mobility of bubbles. Bright incandescent streaks originating from the disrupting INN-laden droplets, may indicate sub-micrometer droplets or particles from within the droplets or formed in the gas phase. In contrast, Sn-EH-laden droplets show very fast disruptions, typically less than 10 μs from first visible deformation to ejection of secondary droplets. Bubbles and surface undulations were not observed.Graphical abstract

Transient Dynamics of a Porous Sphere in a Linear Fluid

This article describes the unsteady translational motion of a porous sphere with slip-surface in a quiescent viscous fluid. Apart from its radius a and density ρs , the particle is characterized by its permeability parameter γ , slip-length l and effective viscosity-ratio ϵ for interior flow. The Reynolds number for the system is assumed to be small leading to negligible convective contribution, though the transient inertia for both the liquid and the solid is comparable to viscous forces. The resulting linearized but unsteady flow-equations for both inside and outside the porous domain are solved in time-invariant frequency domain by satisfying appropriate boundary conditions. The analysis ultimately renders frequency-dependent hydrodynamic friction for the suspended body. The frictional coefficient is computed under both low and high frequency limit for different values of γ, l and ϵ so that the findings can be compared to known results with impermeable surface. Moreover, the parametric exploration shows that the sphere acts like a no-slip body even with non-zero l if aγ ≫ 1/√ϵ . Scaling arguments from a novel boundary layer theory for flow inside porous media near interfaces explain this rather unexpected observation. Also, computed fluid resistance is incorporated in equation of motion for the particle to determine its time-dependent velocity response to a force impulse. This transient response shows wide variability with ρs, γ, l and ϵ insinuating the significance of the presented study. Consequently, the paper concludes that slip and permeability should be viewed as crucial features of submicron particles if unexpected variability is to be explained in nano-scale phenomena like nano-fluidic heat conduction or viral transmission. Thus, the theory and findings in this paper will be immensely useful in modeling of nano-particle dynamics.

Dual Loading of Trans-Cinnamaldehyde and Either Paclitaxel or Curcumin in Chitosan Nanoparticles: Physicochemical Characterization and Biological Evaluation Against MDCK and HeLa Cells

Biopolymer chitosan sub-micron particles (CSMPs) were prepared by the ionic gelation technique crosslinked with sodium tripolyphosphate co-loaded with trans-cinnamaldehyde (TCIN), and either curcumin (CUR) or paclitaxel (PTX). The size of the spherical CSMPs increased from 118 nm to 136 nm and 170 nm after the loading of TCIN and CUR, whereas the loading of PTX led to a slight decrease (114 nm). Polydispersity indexes of all the samples were smaller than 0.4, indicating monodisperse particles. Zeta potential values higher than +40 mV were determined, which is direct proof of the high stability of these nanoparticles. TCIN and PTX release studies in vitro, at pH 6.5 and 7.4, showed a pH dependence on the release rate with a higher value at pH 6.5. However, CUR was not released from CSMPs probably due to strong interactions with CS biopolymer chains. Cytotoxicity studies showed that the systems loaded with TCIN and PTX were more cytotoxic for HeLa cancer cells than for MDCK cells. Moreover, a synergistic effect against HeLa cells was observed for the TCIN-PTX-loaded CSMP samples. The Sensitivity Index indicated that the CSMPs loaded with TCIN have a prospective attraction to carry and release conventional or new chemotherapeutic drugs. This study demonstrates the in vitro efficiency of the obtained drug delivery system, but in vivo studies are necessary to confirm its potential for clinical applications.

Prediction of Transport and Deposition of Porous Particles in the Respiratory System Using Eulerian-Lagrangian Approach.

Deep lung delivery is crucial for respiratory disease treatment. Although nano and submicron particles exhibited a good deposition efficiency in deep regions of the lung, powder nonuniformity and particle agglomeration reduce their efficiency. Inhalation of porous particles (PPs) can overcome the mentioned challenges due to their larger size and low-density. The present study numerically investigates the deposition and penetration efficiency of orally inhaled PPs. A revised drag coefficient was implemented for PP transport. A realistic mouth-throat to the fifth generation of the lung was reconstructed from CT-scan images. A dilute suspension of uniformly distributed particles was considered at three inhalation flow rates (15, 30, and 45 L/min). Governing equations of the flow field and particle transport are solved using an Eulerian-Lagrangian approach. The results demonstrate that inhaling PPs significantly reduces the total and regional deposition of particles. There was also a critical porosity value under moderate and high inhalation flow rates for large PPs. Below this critical value, PP deposition efficiency substantially decreases. Additionally, it was also found that under low inhalation flow rates, the impact of porosity value is negligible. Almost 95% of the PPs penetrate the lower branches. These findings provide particle engineers and pharmaceutics with profound insight into developing novel inhalation techniques and drug delivery methods for deep lung delivery.

Highly Robust, Pressureless Silver Sinter-Bonding Technology Using PMMA Combustion for Power Semiconductor Applications

This study presents the development of a highly robust, pressureless, and void-free silver sinter-bonding technology for power semiconductor packaging. A bimodal silver paste containing silver nanoparticles and sub-micron particles was used, with polymethyl methacrylate (PMMA) as an additive to provide additional thermal energy during sintering. This enabled rapid sintering and the formation of a dense, void-free bonding joint. The effects of sintering temperature and PMMA content on shear strength and microstructure were systematically investigated. The results showed that the shear strength increased with rising sintering temperatures, achieving a maximum of 41 MPa at 300 °C, with minimal void formation due to enhanced particle necking facilitated by PMMA combustion. However, at 350 °C, the shear strength decreased to 35 MPa due to cracks and voids at the copper substrate–copper oxide interface caused by thermal expansion mismatch. The optimal PMMA content was found to be 5 wt.%, balancing sufficient thermal energy and void reduction. This pressureless sintering technology demonstrates significant potential for high-reliability applications in power semiconductor modules operating under high-temperature and high-stress conditions.

Fully Atom-Efficient Solvent-Mediated Biopolymer Manufacturing: A Base Case Illustrated with Macromolecular Surfactants Tailored to Stable Polymer-Water Interfaces.

This work introduces a novel 1-pot, 0-waste, 0-VOC methodology for synthesizing polymeric surfactants using acrylated epoxidized soybean oil and acrylated glycerol as primary monomers. These macromolecular surfactants are synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization, allowing for tunable hydrophilic-lipophilic balance (HLB) and ionic properties. We characterize the copolymers' chemical composition and surface-active properties, and evaluate their effectiveness in forming and stabilizing emulsions of semiepoxidized soybean oil and poly(acrylated epoxidized high oleic soybean oil). Comprehensive analyses, including gel permeation chromatography, nuclear magnetic resonance spectroscopy, dynamic light scattering, particle size distribution, zeta potential, and critical micelle concentration, provide detailed insights into the copolymers and the emulsions they form. The results demonstrate that the RAFT-polymerized surfactants offer long-lasting stability and effectively disperse both common oil-in-water emulsions and highly viscous and hydrophobic polymer latexes. These surfactants outperform traditional small molecule surfactants by reducing particle size and preventing phase separation, even over extended storage periods. Stable polymer-water interfaces are achieved through HLB control, tailored by monomer composition, and the final product requires no additional purification since polymerization occurs in liquid surfactants. While small molecules contribute to rapid micelle formation, the polymeric components enhance long-term stability through steric repulsion and slower dynamics. This method enables even the emulsification of polymers with submicron particle size, which ordinarily requires emulsion polymerization. Integrating biobased polymeric surfactants with advanced polymer processing techniques opens new possibilities for transforming highly hydrophobic polymers into latexes, facilitating downstream applications. This innovation enhances the environmental sustainability of surfactant production and broadens the potential for polymer emulsification technologies. Additionally, the integrated solution-processing approach demonstrated here can be applied to other emerging polymers, where judiciously selected nonvolatile solvents facilitate the polymerization and play a role in the final application.

Chemical synthesis, structural and magnetic properties of Al-doped neodymium orthoferrite

Crystalline and single phase of Al doped orthoferrite with stoichiometry NdFe1-xAlxO3 was synthesized by a hydrothermal method. The effect of Al doping on the structure features was investigated by powder X-ray diffraction (PXRD) technique. In this sense, Rietveld refinement was applied in refining the PXRD data. Scanning electron microscopy (SEM) was used to characterize the morphology. And from image analyses show a sub-micron particle size distributions for all samples. Using hydrothermal synthesis method, a micro-sized particle distribution is reached. Measurement of magnetic hysteresis loops showed that the highest coercivity (Hc) obtained was 5.2 kOe for the sample with x=2. Compared to previous results using sol-gel synthesis, the hydrothermal method used in this study showed improved magnetization properties.

Tuning the Magnetocaloric and Structural Properties of La0.67Sr0.28Pr0.05Mn1-x Co x O3 Refrigeration Materials

Abstract The impact of the structural, magnetic, and magnetocaloric effect of perovskite manganites La0.67Sr0.28Pr0.05Mn1-x Co x O3 (x = 0.05, 0.075, and 0.10) is investigated. LSPMCO crystallizes as a rhombohedral structure with R-3c space groups. As the Co content increases, the cell volume expands, the Mn-O-Mn bond angle reduces, and the length of the Mn-O bond rises. The samples show irregular submicron particles under the Zeiss scanning electron microscopy. The particle size becomes larger with the amount of doping. The chemical composition of the samples is confirmed by X-ray photoelectron spectroscopy (XPS). The ferromagnetic (FM) to paramagnetic (PM) phase transition occurs near the Curie temperature (TC), and all transitions are second order phase transitions (SMOPT) characterized by minimal thermal and magnetic hysteresis. Critical behavior analysis indicates that the critical parameters of LSPMCO closely align with those predicted by the mean field model. The TC declines with Co doping and reaches near room temperature (302 K) at x = 0.075. The maximum magnetic entropy change (-Δ S M max) at x = 0.05 is 4.27(J/kg·K), and the relative cooling power (RCP) peaks at 310.81 J/K. Therefore, the system holds significant potential for development as a magnetic refrigeration material, meriting further professional and objective evaluation.

Significant Improvement in Magnetorheological Performance by Controlling Micron Interspaces with High Permeability Submicron Particles.

The shear yield strength, sedimentation stability and zero-field viscosity of magnetorheological fluids (MRFs) are crucial for practical vibration damping applications, yet achieving a balanced combination of these performances remains challenging. Developing MRFs with excellent comprehensive performance is key to advancing smart vibration damping technologies further. Theoretically, incorporating a multiscale particle system and leveraging synergistic effects between their can somewhat enhance MRFs' performance. However, this approach often faces issues such as insignificant increases in shear yield strength and excessive rise in zero-field viscosity. In response, this study employs a DC arc plasma method to synthesize a high magnetic permeability, low coercivity submicron FeNi particles, and further develops a novel CIPs-FeNi bidisperse MRFs. The introduction of submicron FeNi particles not only significantly enhances the shear2019 yield strength of MRFs under low magnetic fields but also promotes improvements in sedimentation stability and redispersibility without excessively increasing viscosity. Comprehensive performance analysis is conducted to explore the optimal content ratio, and detailed mechanisms for the enhancement of performance are elucidated through analysis of parameters such as chain-like structure, magnetic flux density and friction coefficient. Most importantly, the superior comprehensive performance combined with straightforward fabrication methods significantly enhances the engineering applicability of the CIPs-FeNi bidisperse MRFs.

Extended Monte Carlo modeling for submicron particle size measurement under high light extinction conditions

The light extinction method (LEM) based on Lambert Beer's law (LB) is widely used to characterize particle size distribution (PSD) in multiphase flow. However, as the optical thickness increases with concentration, the phenomenon of multiple scattering is enhanced, potentially leading to reduced accuracy and a limited application range. In this study, an extended Monte Carlo-based light extinction model (EMC) was developed, which was initially employed to calculate and evaluate the impact of multiple scattering. Subsequently, it was used to predict the extinction spectrum that incorporates multiple scattering effects under varying concentrations. To validate the modeling, a compact setup was constructed to perform a series of experiments on polystyrene and silica dioxide (SiO2) suspensions. A differential evolution algorithm was also implemented for the inversion of PSD based on spectral content, with the incorporation of an improved coefficient matrix that considers multiple scattering effects. In comparison to the linear LB model, the EMC exhibits a markedly enhanced capacity in handling higher particle concentrations and improving measurement accuracy. For a 700 nm PS suspension, the particle size inversion error of the EMC can be kept within 4% (93.86% for the LB model) compared with the nominal value, even with an optical thickness of 5.

UV Filter NanoCapsule with Broad‐Spectrum UV Protection

AbstractIn this study, nanocapsules encapsulating avobenzone (AVB) compounded with isooctyl p‐dimethylaminobenzoate (OD‐PABA) were prepared via miniemulsion polymerization using methyl methacrylate (MMA) as the monomer, ethylene glycol dimethacrylate (EGDMA) as the cross‐linker, and poly(styrene‐co‐methacrylic acid) (P(St‐co‐MAA)) as the polymeric emulsifier. When a solid ultraviolet radiation A (UVA) filter, AVB, was encapsulated in nanocapsules (A‐UVNCs), the encapsulation and loading rates were 67.6% and 9.7%, respectively. When a liquid ultraviolet radiation B (UVB) filter, OD‐PABA, was combined with AVB, the encapsulation and loading rates of the nanocapsules (A/O‐UVNCs) of AVB and OD‐PABA increased to 90.0% and 15.6%, respectively, and 71.5% and 14.0%, respectively. The A/O‐UVNCs realized broad‐spectrum ultraviolet (UV) protection with an SPF value of 46.3. The A/O‐UVNCs have raspberry‐like nanostructures. These submicron particles can scatter and reflect a portion of the UV radiation and synergistically enhance UV protection. After exposure to simulated sunlight for four hours, the UVAPF of a sunscreen containing A‐UVNCs or A/O‐UVNCs decreased to a smaller extent than that of the sunscreen containing free AVB. Cell toxicity experiments showed that the cell viability of A‐UVNCs and A/O‐UVNCs was 85.9% and 83.0%, respectively. Therefore, UVNCs not only enhance UV protection but also improve photostability and safety.

Strength-ductility synergy of Mg-7.5 wt.% Sn binary alloys promoted by semisolid isothermal treatment coupled with hot extrusion

In this paper, we propose to adopt a new process for as-extruded Mg-7.5wt.%Sn binary alloy, i.e., semisolid isothermal heat treatment coupled with hot extrusion. Semi-solid isothermal treatment achieved nanosizing of micron-layer lamellar eutectic in the Mg-7.5wt.% Sn binary alloy, while subsequent hot extrusion crushed this nanoeutectic to nanoparticles, resulting in high strength (303 ± 2.8MPa for UTS and 246 ± 0.7MPa for YS,) and high elongation (11.5 ± 0.1% for EL) of the Mg-7.5wt.% Sn binary alloy. Grain refinement, multi-scale particles (broken nanoscale and submicron particles, and dynamically precipitated nanoscale phases), and high-density dislocations are the main contributors to the high strength. Meanwhile, the good ductility of the alloy is promoted by the softening effect due to dynamic recrystallisation as well as the weakening and random distribution of the texture.

Alkyne-rich patchy polymer colloids prepared by surfactant-free emulsion polymerization

While free radical polymerization methods are employed frequently to prepare sub-micron polymer particles, we hypothesized that surfactant-free emulsion polymerization (SFEP)1Surfactant-free emulsion polymerization1 methodology may prove beneficial for obtaining functional polymer particles by solution polymerization methods that preclude the need for conventional surfactants. To test the effectiveness of SFEP for the preparation of functional colloids, solution polymerization of several monomers, including propargyl acrylate (PA),2Propargyl acrylate.2 styrene (Sty)3Styrene.3 and tert-butyl acrylate (t-BA),4Tert-butyl acrylate.4 was performed over a range of monomer ratios and reaction scales. Electron microscopy and infrared spectroscopy were employed to evaluate the outcome of SFEP for particle size, shape, surface anisotropies, and chemical composition. Combining this characterization with optimized SFEP synthesis, we found that spherical polymer particles—homopolymers of PA as well as copolymers—were obtained in the 60–300 nm diameter size range. Successful inclusion of PA enabled the use of the particles in copper-catalyzed azide-alkyne cycloaddition reactions (CuAAc).5Copper-catalyzed azide-alkyne cycloaddition5 Moreover, electron microscopy characterization with backscattering revealed chemical and shape anisotropies on copolymer particles indicative of monomer phase-separation during particle formation. Overall, the SFEP methodology represents a straightforward, one-pot, bottom-up approach to yield a library of functional polymer particles, while avoiding undesirable aspects associated with conventional surfactants.

The Variability of the Size Distributions of Submicron Particles in the Oceans

AbstractThe size distribution of submicron particles is essential for understanding their biogeochemical and optical roles, but it has seldom been measured. This study utilizes ViewSizer 3000, an instrument that tracks Brownian motions of particles, to measure the particle size distributions (PSD) from 250 to 1,050 nm in the North Pacific Ocean (NP) and the North Atlantic Ocean (NA) at depths from 5 to 500 m. The concentration of particles varies over one order of magnitude at any given size bin, with greater variations up to two orders of magnitude at sizes >600 nm. In both locations, concentrations decrease with depth. Bacterioplankton are a dominant component, accounting for 65%–90% of the submicron particles in the surface waters (<100 m) and approximately 30%–40% at depths >150 m at both sites. In the NP, the volume mean diameter increased approximately 5% from the morning to noon at the surface, probably resulting from the diurnal growth of bacterioplankton. In the NA, the concentration and mean size increased by >60% and ∼10% respectively after one storm that introduced a different particle population into the study area.