Real‐time non‐invasive detection of inhalable particulates delivered into live mouse airways

Fine non‐biological particles small enough to be suspended in the air are continually inhaled as we breathe. These particles deposit on airway surfaces where they are either cleared by airway defences or can remain and affect lung health. Pollutant particles from vehicles, building processes and mineral and industrial dusts have the potential to cause both immediate and delayed health problems. Because of their small size, it has not been possible to non‐invasively examine how individual particles deposit on live airways, or to consider how they behave on the airway surface after deposition. In this study, synchrotron phase‐contrast X‐ray imaging (PCXI) has been utilized to detect and monitor individual particle deposition. The in vitro detectability of a range of potentially respirable particulates was first determined. Of the particulates tested, only asbestos, quarry dust, fibreglass and galena (lead sulfate) were visible in vitro. These particulates were then examined after delivery into the nasal airway of live anaesthetized mice; all were detectable in vivo but each exhibited different surface appearances and behaviour along the airway surface. The two fibrous particulates appeared as agglomerations enveloped by fluid, while the non‐fibrous particulates were present as individual particles. Synchrotron PCXI provides the unique ability to non‐invasively detect and track deposition of individual particulates in live mouse airways. With further refinement of particulate sizing and delivery techniques, PCXI should provide a novel approach for live animal monitoring of airway particulates relevant to lung health.     

Dry deposition of pollutant and marker particles onto live mouse airway surfaces enhances monitoring of individual particle mucociliary transit behaviour

Particles suspended in the air are inhaled during normal respiration and unless cleared by airway defences, such as the mucociliary transit (MCT) system, they can remain and affect lung and airway health. Synchrotron phase‐contrast X‐ray imaging (PCXI) methods have been developed to non‐invasively monitor the behaviour of individual particles in live mouse airways and in previous studies the MCT behaviour of particles and fibres in the airways of live mice after deposition in a saline carrier fluid have been examined. In this study a range of common respirable pollutant particles (lead dust, quarry dust and fibreglass fibres) as well as marker particles (hollow glass micro‐spheres) were delivered into the trachea of live mice using a dry powder insufflator to more accurately mimic normal environmental particulate exposure and deposition via inhalation. The behaviour of the particles once delivered onto the airway surface was tracked over a five minute period via PCXI. All particles were visible after deposition. Fibreglass fibres remained stationary throughout while all other particle types transited the tracheal surface throughout the imaging period. In all cases the majority of the particle deposition and any airway surface activity was located close to the dorsal tracheal wall. Both the individual and bulk motions of the glass bead marker particles were visible and their behaviour enabled otherwise hidden MCT patterns to be revealed. This study verified the value of PCXI for examining the post‐deposition particulate MCT behaviour in the mouse trachea and highlighted that MCT is not a uniform process as suggested by radiolabel studies. It also directly revealed the advantages of dry particle delivery for establishing adequate particulate presence for visualizing MCT behaviour. The MCT behaviour and rate seen after dry particle delivery was different from that in previous carrier‐fluid studies. It is proposed that dry particle delivery is essential for producing environmentally realistic particle deposition and studying how living airway surfaces handle different types of inhaled particles by MCT processes.     

Evaluation of DNA damage and cytotoxicity of polyurethane-based nano- and microparticles as promising biomaterials for drug delivery systems

The in vitro cytotoxicity and DNA damage evaluation of biodegradable polyurethane-based micro- and nanoparticles were carried out on animal fibroblasts. For cytotoxicity measurement and primary DNA damage evaluation, MTT and Comet assays were used, respectively. Different formulations were tested to evaluate the influence of chemical composition and physicochemical characteristics of particles on cell toxicity. No inhibition of cells growth surrounding the polyurethane particles was observed. On the other hand, a decrease of cell viability was verified when the anionic surfactant sodium dodecyl sulfate (SDS) was used as droplets stabilizer of monomeric phase. Polyurethane nanoparticles stabilized with Tween 80 and Pluronic F68 caused minor cytotoxic effects. These results indicated that the surface charge plays an important role on cytotoxicity. Particles synthesized from MDI displayed a higher cytotoxicity than those synthesized from IPDI. Size and physicochemical properties of the particles may explain the higher degree of DNA damage produced by two tested formulations. In this way, a rational choice of particles’ constituents based on their cytotoxicity and genotoxicity could be very useful for conceiving biomaterials to be used as drug delivering systems.     

Exposure assessment of nano-sized and respirable particles at different workplaces

In this study, nanoparticle (NP, diameter < 100 nm) and respirable particles measurements were conducted at three different nanopowder workplaces, including the mixing area of a nano-SiO₂-epoxy molding compound plant (primary diameter: 15 nm), bagging areas of a nano-carbon black (nano-CB) (primary diameter: 32 nm) and a nano-CaCO₃ (primary diameter: 94 nm) manufacturing plant. Chemical analysis of respirable particle mass (RPM) and NPs was performed to quantify the content of manufactured nanoparticles in the collected samples. Nanopowder products obtained from the plants were used in the laboratory dustiness testing using a rotating drum tester to obtain particle mass and number distributions. The obtained laboratory data were then used to elucidate the field data. Both field and laboratory data showed that NP number and mass concentrations of manufactured materials were close to the background level. Number concentration was elevated only for particles with the electrical mobility diameter >100 nm during bagging or feeding processes, unless there were combustion-related incidental sources existed. Large fraction of nanomaterials was found in the RPM due to agglomeration of nanomaterials or attachment of nanomaterials to the larger particles. From this study, it is concluded that RPM concentration measurements are necessary for the exposure assessment of nanoparticles in workplaces.     

Reversible surface structural changes in Pt-based bimetallic nanoparticles during oxidation and reduction cycles

The surface states of supported PtNi nanoparticles treated at alternating O₂ and H₂ atmosphere were studied by X-ray photoelectron spectroscopy. Reversible structural changes at the surfaces of the supported PtNi nanoparticles in response to reaction gases were observed, showing NiO-rich surface in oxidizing gases and Pt-rich surface in reducing gases. The dynamic behaviors can be attributed to two opposite gas-driven mass transport processes at bimetallic particle surfaces, including surface segregation of Pt at the bimetallic particles in H₂ and encapsulation of the particles by NiO in O₂. The similar surface structural changes can be observed in other bimetallic catalyst systems, as exemplified in supported PtCu and PtCo nanoparticles.     

Computing Particle Surface Areas and Contact Areas from Three‐Dimensional Tomography Data of Particulate Materials

Microtomography is an emerging technique for particle and particulate‐materials characterization. To use this technology effectively, robust and accurate computational algorithms are needed to compute relevant particle properties, including particle surface area and particle‐particle contact area. However, the most accurate algorithms that have been developed for computing the exposed (void/solid) surface area in a microtomography image cannot be used directly for computing surface areas or particle‐particle contact areas for individual particles in a dense packing. This paper presents an algorithm for extracting particle contact areas from a digitized, segmented image of a packed granular material, which in turn can be used to find individual particle surface areas (even if the complete surfaces are not exposed because of contacts in the packing). Results show that small errors in the binary surface‐area computations are magnified in the course of determining particle contact areas; the total error in the computation depends mainly on the size of the contact area in voxel units.     

Performance Assessment of Probes Dedicated to the Monitoring of Surface Particle Contamination

Surface probes, based on airflow particle detachment coupled with optical particle counter, are actually available to measure the particle cleanliness of surfaces in cleanroom. No reliable data exits dealing with the performance assessment of these probes in unstuck and counting particles deposited on surfaces. This work presents a method for determining the efficiency of instruments dedicated to particle surface cleanliness measurements. The method is based on the realisation of standard particle deposits by sedimentation and analysis of whole of the contaminated surface by microscopy combined with a micrometric displacement bench. The method is used to assess a trial surface probe with 30 μm and 80 μm glass beads deposited on transparent (glass) or opaque (aluminium) surfaces at concentrations ranging from 1 particle·cm^–2 to 50 particles·cm^–2. The results obtained show that the overall efficiency of the instrument tested is less than 5 %. The detailed analysis of results shows that this low value is mainly due to poor efficiency of sampling and detection of particles in the optical counter. When analysed in terms of particle detachment efficiency, the results agree qualitatively with a force balance analysis taking into account the friction by airflow and the distribution of adhesion forces of glass particles to glass substrates or rough aluminium substrates. Such result shows that airflow based surface probes for particle cleanliness measurements should be systematically qualified for representative conditions of operations whereas analytical microscopy measurements could be considered as reference.     

Binding of Resonant Dielectric Particles to Metal Surfaces Using Plasmons

Forces between dielectric particles induced by optical fields can bind them into new systems, varying from optical molecules to large aggregates. Here it is shown that surface plasmons can bind resonant dielectric particles to the waveguiding surfaces resulting in stable levitation of the particles by the optical forces alone. At the same time, the particles can be propelled efficiently along the surface. The predictions follow from solving the 3D electromagnetic problem of plasmon scattering on a dielectric microsphere near the metal surface. To tackle the problem, an accurate and fast hybrid approach is developed: the fields are expanded into 2D angular components which are calculated using finite-difference time-domain simulations. The rigorous numerical results are also explained qualitatively using an analytically solvable model in which a resonant magnetic dipole illuminated by a plasmon interacts with the surface. The particle binding to surfaces is a remarkable outcome of the strong optical interaction at nanoscale and it may offer new configurations for particle manipulations by guided waves, especially in chip-scale structures.     

Heterogeneous Nanoassembling: Microfluidically Prepared Poly(methyl methacrylate) Nanoparticles on Ag Microrods and ZnO Microflowers

The heterogeneous assembly of colloidal polymer particles on the nano‐ and microstructures of a metal is a versatile platform for adjusting the mechanical and electrical properties simultaneously. The assemblies of silver (Ag) microrods and flower‐like zinc oxide (ZnO) microparticles with poly(methyl methacrylate) (PMMA) nanospheres are presented to prepare advanced composite materials. PMMA nanoparticles are prepared via the emulsion polymerization technique using a microfluidic preparation step in the presence of cationic surfactant. The surface charge of PMMA particles determines the binding interaction strength with inorganic constituents. Ag microrods and ZnO microparticles are prepared in a batch and in a continuous flow process, respectively. The assembling process can be explained by a particle–particle binding process due to the electrostatic interaction for both types of nanoassemblies. The observed binding pattern reveals certain lateral mobility of the small polymer particles at the surface of larger metal particle. The particle ratios in the nanoassemblies can be tuned over a wide range by changing the reaction parameters.     

Fractal Analysis of Surface Roughness of Particles in Porous Media

A fractal dimension for roughness height （RH） is introduced to characterize the degree of roughness or disorder of particle surface characters which significantly influence physical-chimerical processes in porous media. An analytical expression for the fractal dimension of RH on statistically self-similar fractal surfaces is derived and is expressed as a function of roughness parameters. The specific surface area （SSA） of porous materials with spherical particles is also derived, and the proposed fractal model for the SSA of particles with rough surfaces is expressed as a function of fractal dimension for RH and fractal dimension for particle size distribution, relative roughness of particle surface, and ratio of the minimum to the maximum particle diameters of spherical particles.     

纳米Ag颗粒复合薄膜的制备及其吸收特性

利用磁控溅射分层制备Ag和SiO₂薄膜,通过快速热处理,使Ag颗粒富集在复合薄膜的表面.研究了Ag膜层厚度、退火时间、退火温度和退火方式对Ag颗粒形貌的影响,以及Ag颗粒致密度对其共振吸收的影响.结果表明:通过控制每层Ag膜的厚度,可有效控制Ag颗粒形貌.当每层金属为2 nm、退火温度为500 ℃时,形成的颗粒粒径大小均匀且致密度较高.通过间断退火可有效降低Ag颗粒的粒径.发现Ag颗粒表面等离子共振吸收并没有随颗粒粒径的减小而明显降低,甚至提高.这和以往的报道不同.通过深入研究金属颗粒表面等离子体产生机理,发现其表面等离子共振吸收增强的原因是致密度较高的颗粒表面能级与费米能级差值较大,Ag颗粒内部的电子向颗粒表面迁移越多,形成新的费米能级E'_F的电子数就越多,表面等离子共振吸收就越强.最终得出了金属颗粒共振吸收不单纯依赖于金属粒径、和颗粒的致密度也有很大关系的结论.     

Monitor for detecting and assessing exposure to airborne nanoparticles

An important safety aspect of the workplace environment concerns the severity of its air pollution with nanoparticles (NP; <100 nm) and ultrafine particles (UFP; <300 nm). Depending on their size and chemical nature, exposure to these particles through inhalation can be hazardous because of their intrinsic ability to deposit in the deep lung regions and the possibility to subsequently pass into the blood stream. Recommended safety measures in the nanomaterials industry are pragmatic, aiming at exposure minimization in general, and advocating continuous control by monitoring both the workplace air pollution level and the personal exposure to airborne NPs. This article describes the design and operation of the Aerasense NP monitor that enables intelligence gathering in particular with respect to airborne particles in the 10–300 nm size range. The NP monitor provides real time information about their number concentration, average size, and surface areas per unit volume of inhaled air that deposit in the various compartments of the respiratory tract. The monitor’s functionality relies on electrical charging of airborne particles and subsequent measurements of the total particle charge concentration under various conditions. Information obtained with the NP monitor in a typical workplace environment has been compared with simultaneously recorded data from a Scanning Mobility Particle Sizer (SMPS) capable of measuring the particle size distribution in the 11–1086 nm size range. When the toxicological properties of the engineered and/or released particles in the workplace are known, personal exposure monitoring allows a risk assessment to be made for a worker during each workday, when the workplace-produced particles can be distinguished from other (ambient) particles.     

Optical levitation and manipulation of stuck particles with pulsed optical tweezers

We report on optical levitation and manipulation of microscopic particles that are stuck on a glass surface with pulsed optical tweezers. An infrared pulse laser at 1.06 microm was used to generate a large gradient force (up to 10(-9) N) within a short duration (approximately 45 micros) that overcomes the adhesive interaction between the particles and the glass surface. Then a low-power continuous-wave diode laser at 785 nm was used to capture and manipulate the levitated particle. We have demonstrated that both stuck dielectric and biological micrometer-sized particles, including polystyrene beads, yeast cells, and Bacillus cereus bacteria, can be levitated and manipulated with this technique. We measured the single-pulse levitation efficiency for 2.0 microm polystyrene beads as a function of the pulse energy and of the axial displacement from the stuck particle to the pulsed laser focus, which was as high as 88%.     

CdS半导体超微粒子的光学性质

本文研究了水溶胶中的CdS半导体超微粒子和有机溶胶中的粒子表面被有机分子化学修饰的CdS超微粒子的光学性质.我们观察到,当粒子尺寸小于5nm时,CdS超微粒子表现出明显的尺寸量子化效应,并指出CdS超微粒子的表面修饰,增强了它们的发光强度,显著地影响了它们的光学性质。     

Image enhancement in near-field scanning optical microscopy with laser-trapped metallic particles

A trapped-particle near-field scanning optical microscope is constructed by use of submicrometer- or micrometer-sized metallic particles (gold and silver) to increase scattering efficiency. The image contrast of the evanescent-wave interference pattern on the surface of a prism upon total internal reflection, obtained with trapped gold particles of diameter 0.1 and 2microm , is improved by a factor of approximately 2 and 1.5, respectively, compared with that obtained with trapped polystyrene particles of similar size. The use of a 2-microm gold particle leads to image contrast that is approximately three times as great as that obtained with a 0.1-microm gold particle, and interference patterns of a subwavelength period are obtained in both cases.     

Irreversible adsorption of colloid particles on heterogeneous surfaces

Irreversible adsorption of polystyrene latex particles of micrometer size range at heterogeneous surfaces was studied experimentally. Model substrate surfaces of controlled site coverage (heterogeneity degree) used in these studies were produced by preadsorption of positively charged latex particles on mica sheets. Deposition kinetics of latex was studied as a function of the site coverage, particle to site size ratio λ and ionic strength of the colloid suspension. Particle distributions over surfaces and coverage were quantitatively evaluated by the direct microscope observation techniques using the diffusion cell. In this way, pair correlation function for various coverage degree and particle size ratio was evaluated. It also was determined the dependence of the jamming coverage of colloid particles on site coverage and ionic strength of the suspension. It was demonstrated that the decrease in the ionic strength of the suspension resulted in a significant decrease in the jamming coverage. This was attributed to the effect of the electrostatic field generated by the interface whose range was increased for low ionic strength. These experimental data revealed, in accordance with theoretical predictions derived from numerical simulations, that the multiple site coordination exerted a pronounced effect on the jamming coverage and the structure of adsorbed layers. It also was shown that this effect can be regulated by changes in the ionic strength of particle suspensions. This could allow one to produce particle clusters at the surface of targeted composition.     

Electrochemical performance of surfactant-processed LiFePO4 as a cathode material for lithium-ion rechargeable batteries

This study focuses on the effect of addition of surfactant as a dispersing agent during vibratory ball milling of LiFePO₄ (LFP) precursor materials on the electrochemical performance of solid-state reaction synthesized LFP for lithium-ion battery cathode material. LFP particles formed after calcinations of ball milled LFP precursors (Li₂CO₃, FeC₂O₄, and NH₄H₂PO₄) showed better size uniformity, morphology control, and reduced particle size when anionic surfactant (Avanel S-150) was used. The specific surface area of LFP particles increased by approximately twofold on addition of surfactant during milling. These particles showed significantly enhanced cyclic performance during charge/discharge due to a reduced polarization of electrode material. Electrodes fabricated from LFP particles by conventional milling process showed a 22 % decrease in capacity after 50 cycles, whereas the performance of electrode prepared by surfactant processed LFP showed only 3 % loss in capacity. The LFP particles were characterized using XRD, FE-SEM, particle size distribution, density measurement, and BET-specific surface area measurement. Electrochemical impedance spectra and galvanostatic charge/discharge test were performed for the electrochemical performance using coin-type cell.     

界面活性剂对Fe3O4磁性与穆斯堡尔谱的影响

测量了不同颗粒尺寸Fe₃O₄覆盖界面活性剂前后磁性、红外谱以及穆斯堡尔谱。实验结果表明界面活性剂与Fe₃O₄微粒表面为化学吸附,覆盖界面活性剂后在相同磁场下磁化强度有所下降,穆斯堡尔谱变得弥散,随着颗粒尺寸变小,穆斯堡尔谱内场减小,谱线变得更为弥散,实验结果可以用表面各向异性的理论进行解释。 关键词：     

Studies on synthetic conditions of spray pyrolysis by acids addition for development of highly active Ni-SDC cermet anode

NiO-Ce_0.8Sm_0.2O_1.9 (SDC) composite particles were synthesized by spray pyrolysis method using the starting solutions containing the components for NiO-SDC and various amounts of nitric acid or acetic acid. It was found that the particles had the smooth surface due to the presence of the dissociated acetic acid in the starting solution and the large specific surface area due to the presence of the nitrate ion in the starting solution. SOFC single cell performance using the composite particles for an anode was examined at the operating temperature of 750 °C to clarify the relationship between particle morphology and cell performance. The NiO-SDC composite particles which had smooth surfaces with large specific surface areas gave reproducibly high SOFC performances. It was considered that the morphologies and the specific surface areas of NiO-SDC composite particles played an important role of realizing a high performance anode.