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We report the magnetic field and temperature dependences of magnetoconductance (MC) and magnetoelectroluminescence (MEL) in organic light emitting diodes (OLED) made of homopolymer organic layers. We show that in these OLEDs a spin mixing mechanism due to the anisotropy of the organic layer $g$ factor has a significant effect in the measured MC($B$) and MEL($B$) at fields of order of $\ensuremath{\sim}1\phantom{\rule{0.16em}{0ex}}\mathrm{T}$. We discuss the model of spin mixing among polaron pairs due to the anisotropy of the $g$ factor and show that it can be described as an angle dependent $\mathrm{\ensuremath{\Delta}}g$ mechanism that is known to have significant magnetoresponse effects. We show that the internal structure of the polaron pair is material dependent rationalizing thus the differences in their electrical mobility.

The Aerodynamic Aerosol Classifier (AAC) and Differential Mobility Analyzer (DMA) are aerosol classifiers commonly used to generate a monodispersed aerosol by selecting particles within a narrow range of relaxation times or electrical mobilities, respectively. However, generating an aerosol of homogeneous particles, which has narrow ranges of particle mass, mobility and relaxation time simultaneously, with either of these methods is challenging. Particles classified by the DMA are often not homogeneous (or monodispersed) due to multiply-charged particles. While the AAC overcomes this challenge for spherical particles, homogeneity is not achieved with non-spherical particles due to their effective density varying with particle size. This study demonstrates using an AAC and DMA in tandem to generate an aerosol of homogeneous, non-spherical particles. This approach is validated using scanning electron microscope (SEM) images and electrical mobility measurements of the tandem-classified particles to highlight their homogeneity. To limit the effects of multiple charging during DMA classification, only a subset of DMA and AAC setpoints are permitted. While this subset is not representative of “average” non-spherical particles from the same aerosol source, this subset of low-density particles deviates the most from spherical morphology, and thus, provides insights into the upper bound of other particle properties, such as charging. Using this approach to select homogeneous particles, the bipolar charge distribution of low-density soot aggregates is then measured using another DMA. This AAC-DMA-DMA approach is demonstrated to measure up to 17 individual charge states (i.e. −8 to +8) after neutralization (with 85Kr) of size-resolved, soot aggregates with mobility diameters between 80 and 433 nm. The low-density soot aggregates obtain higher charges than predicted by theory, which overestimates the uncharged fraction (by 0.042–0.069) and, to a lesser extent, the single charge fractions (by up to 0.037) of the low-density soot aggregates, while underestimating their proportion of multiple charging (by up to 0.135 cumulatively at one particle size or up to 0.039 at one multiple charge state and size). These charging discrepancies represent an upper bound of the bipolar charging of average aggregates from the same source of flame soot.

We have investigated the optoelectrical properties of the In2O3 thin films deposited with hydrogen and oxygen gas concentration variation during the sputtering process. As-deposited films have shown amorphous nature and post-annealing treatment has led to polycrystalline films with better optoelectrical properties. The hydrogen and oxygen gas concentration optimization has led to the In2O3:H films' with electrical mobility of ~80 cm2/V.s at the carrier concentration of ~1 × 1020 cm−3, and the resistivity of ~5 × 10−4 Ω cm. The better carrier mobility of the In2O3:H films in comparison to the pure In2O3 films is due to minimization of carrier scattering, after replacing some of the doubly ionized oxygen vacancies (in In2O3) with the singly charged hydrogen (in In2O3:H). The spectroscopic ellipsometry (SE) analysis of the In2O3:H films' have revealed the role of oxygen in the free carrier absorption in near-infrared wavelength region; apart from quantification of optical mobility, and plasma energy of the In2O3:H films. The post-annealed In2O3:H films’ carrier mobility obtained from the Hall and SE measurements have pointed out the influential role of carrier impurity scattering rather than the grain boundary scattering.

Electrical Mobility is arguably the property upon which some of the most successful classification criteria are based for aerosol particles and ions in the gas phase. Once the value of mobility is empirically obtained, it can be related to a geometrical descriptor of the charged entity through a size-mobility relationship. Given the multiscale range of sizes in the aerosol field, approaches that can provide accurate transformations from mobility to size are not straightforward, and many times rely on experimentally derived parameters. The most well-known size-mobility analytical expression covering the whole Knudsen range for spherical particles is the semi-empirical Stokes-Millikan correlation. This expression matches Stokes' drag friction coefficient in the continuum regime and the friction factor for a predominantly diffuse reemission of the gas molecule in the free molecular regime, as theorized by Epstein, with empirical slip coefficients chosen to agree with Millikan's oil drop experiments. Despite its success, the Stokes-Millikan correlation has its shortcomings. For example, it needs to be modified to predict the mobility of non-spherical entities and needs correction terms when potential interactions or reduced mass effects are non-negligible. The Stokes-Millikan asymptotic behavior also fails to predict the gradual transition from diffuse to specular reemission behavior that is observed for increasingly smaller ions within the free molecular regime. Here we make an attempt at providing a comprehensive account of the existing mass-mobility relations in the continuum, transition and free molecular regimes for both spherical and non-spherical particles. Epstein's diffuse interaction is critically explored experimentally and numerically for different gases in the free molecular regime with the observation that, as the size of the particle increases, a progression from specular to diffuse reemission occurs for all gases studied. The rate at which this variation happens seems to differ from gas to gas and to be related to the conditions for which diffuse reemission effects stem from a combination of scattering and potential interactions.

To solve the challenge of extracting nano- to micrometer-sized atmospheric particles from a mixed sample, we developed an electrostatic sieve system, the Fine Sieving of Collected Atmospheric Particles using Oil Electrophoresis (iSCAPE), based on the application of an electrostatic field to a non-conductive mineral oil. Using atmospheric samples, which were collected from different cities, in addition to soil and road dust samples, we tested this system under different conditions and found that the “iSCAPE’d” particles moved rapidly at varying velocities and in two opposite directions. The diverse origins of the sample—ambient air, soil, or road dust—exhibited specific charged properties, and clearly affected the electrical mobility, as demonstrated by the graphs, of the particles following the “iSCAPEing,” which lasted from seconds to minutes. We also observed an increased abundance of particles in specific mobility ranges. Furthermore, according to our adenosine triphosphate (ATP) monitoring results, the iSCAPE is capable of separating bacterial particles by size and electrical mobility. The experimental data suggests that the iSCAPE relies heavily on the electrostatic field strength, mineral oil viscosity, and run time. In theory, this method can extract any targets from a complex sample, thus creating many research opportunities in environmental, biomedical, and life sciences.

To compare ambient air quality standards for the mass concentration of aerosol particles smaller than approximately 2.5 μm (PMWe did a review of government documents and literature on air quality standards. We extracted and summarized the PMWe obtained data on standards from 62 jurisdictions worldwide, including 58 countries. Of the world's 136.06 million kmThe metrics used in PMComparer les normes de qualité de l'air ambiant en termes de concentration massique des particules en suspension dont le diamètre est inférieur à 2,5 μm environ (MPNous avons examiné les publications et documents officiels consacrés aux normes de qualité de l'air. Nous en avons extrait les limites de concentration en MPNous avons obtenu des informations sur les normes en vigueur au sein de 62 juridictions à travers le monde, réparties dans 58 pays. Sur les 136,06 millions de kmLes chiffres employés pour déterminer les normes MPComparar las normas de calidad del aire ambiente en lo que respecta a la concentración en masa de partículas de aerosol inferiores a 2,5 μm (PMRealizamos una revisión de los documentos del gobierno y la literatura sobre las normas de calidad del aire. Extrajimos y resumimos los límites de concentración de PMObtuvimos datos sobre las normas de 62 jurisdicciones de todo el mundo, incluidos 58 países. De los 136,06 millones de kmLas mediciones utilizadas en las normas de calidad del aire ambiente de PMالغرض مقارنة معايير جودة الهواء المحيط لتركيز كتلة جزيئات الهواء الأقل من 2.5 ميكرومتر تقريبًا (PM2.5)، والتعرض لهذه الجسيمات في السلطات القضائية الوطنية والإقليمية في جميع أنحاء العالم. الطريقة قمنا بمراجعة الوثائق والمؤلفات الحكومية عن معايير جودة الهواء. قمنا باستخراج وتلخيص حدود تركيز جزيئات الهواء 2.5 ميكرومتر التي كانت سارية قبل يوليو/تموز 2020، مع ملاحظة ما إذا كانت المعايير إجبارية أو طوعية أو مستهدفة. قمنا بمقارنة طرق حساب المتوسط والفترات الزمنية المسموح بها والتي قد يتم تجاوز المعايير فيها. لقد أجرينا تحليلًا وصفيًا لمعايير 2.5 ميكرومتر حسب السكان، ومساحة الأرض، والكثافة السكانية للسلطات القضائية. قمنا أيضًا بمقارنة البيانات الخاصة بجودة الهواء بتركيز 2.5 ميكرومتر في مقابل المعايير. النتائج حصلنا على بيانات بخصوص المعايير من 62 سلطة قضائية في حول العالم، بما يشمل 58 دولة. من بين 136.06 مليون كيلومتر مربع من الأراضي الخاضعة للسلطات القضائية الوطنية، تفتقر مساحة 71.70 مليون كيلومتر مربع (52.7%) إلى معيار رسمي لجودة الهواء بتركيز 2.5 ميكرومتر، ويعيش 3.17 مليار نسمة في مناطق دون معيار. تراوحت المعايير الحالية من 8 إلى 75 ميكروجرام/متر مكعب، وهي في الغالب أعلى من الحد السنوي لتوجيه منظمة الصحة العالمية، والبالغ أقل من 10 ميكروجرام/متر مكعب. تم غالبًا تجاوز أضعف معايير تركيز 2.5 ميكرومتر، بينما تم في الأغلب الوفاء بالمعايير الأكثر صرامة. أظهرت العديد من السلطات القضائية ذات الكثافة السكانية الأعلى امتثالها لمعايير صارمة نسبياً. الاستنتاج يجب تنسيق المقاييس المستخدمة في معايير جودة الهواء المحيط بتركيز 2.5 ميكرومتر في جميع أنحاء العالم، وذلك لتسهيل التقييم الدقيق للمخاطر المرتبطة بالتعرض لتركيز 2.5 ميكرومتر. لا تعيق الكثافة السكانية وحدها المعايير الصارمة لتركيز 2.5 ميكرومتر. يمكن كذلك أن يشمل تحديث المعايير معايير قصيرة الأجل لكشف تقلبات التركيز 2.5 ميكرومتر في المناطق عالية التلوث.旨在比较世界各国和各地区有关气溶胶颗粒【直径大约小于 2.5 微米 (PM我们已查阅有关空气质量标准的政府文件和文献。我们提取并汇总了 2020 年 7 月前生效的 PM我们采纳了全球 62 个司法管辖区(包括 58 个国家)与标准有关的数据。在全球 13,606 万平方公里受国家管辖的土地中,7,170 万平方公里(占 52.7%)缺乏正规的 PMPMСравнить стандарты качества окружающего воздуха для массовой концентрации аэрозольных частиц размером менее прибл. 2,5 мкм (PMАвторы выполнили критическую оценку официальных государственных документов и литературы по стандартам качества воздуха. Авторы извлекли и обобщили данные по предельной концентрации PMАвторы получили данные по стандартам из 62 юрисдикций в мировом масштабе, включая 58 стран. Из 136,06 млн кмПоказатели, используемые в стандартах качества окружающего воздуха PM

We present a theoretical study on the electrophoresis of a soft particle with a dielectric charged rigid core grafted with a charge-regulated polyelectrolyte layer. The polyelectrolyte layer possesses either an acidic or a basic functional group and the charge dissociation depends on the local pH and ionic concentration of the electrolyte. The dielectric rigid core is considered to possess a uniform volumetric charge density. The electric potential distribution is determined by computing the Poisson-Boltzmann equation outside the core coupled with a Poisson equation inside the impermeable core along with suitable matching conditions at the core-shell interface. The computed electric field is used to determine the mobility of the particle through an existing analytic expression based on the Debye-Huckel approximation. Our results are found to be in good agreement with the existing solutions for the limiting cases. The influence of the core charge density, ionic concentration, and pH of the electrolyte on the particle mobility is studied for different choice of hydrodynamic penetration length of the polyelectrolyte and dissociation constant of the functional group. The critical value of the pH required to achieve zero mobility is estimated. We find that in a monovalent electrolyte solution, the soft particle with a net negative (positive) charge can have positive (negative) mobility.

The necessity of odor sensing has been increasing from environmental and health standpoints. Here, we propose the novel concept of a small device which can select odor molecules based on electrostatic spraying. For high selectivity of the target gas or odor, we conducted computational fluid dynamics coupled with an electrostatic field, as well as measurements by particle image velocimetry and anemometry. The computational model successfully reproduced characteristic features of ionic wind. Different trajectories of charged particles were computationally obtained owing to their electrical mobility. The results imply that different materials might be separated by the arrangement of the collecting electrode.

Therapeutic proteins (TPs) are critical in modern medicine, yet shortage of TPs in disaster situations and remote areas remains a worldwide challenge. Manufacturing and real-time release of TPs on demand at the point-of-care is considered the key to this issue, which requires reliable and rapid analytics techniques for quality assurance. Herein we report a microfluidic platform that could be implemented in-line and at the point-of-care for real-time decision-making about the quality of a TP. The in vivo efficacy and duration of efficacy of TPs were assessed by the equilibrium and kinetics of TP and TP receptor (TPR) binding, using electrokinetic concentration (EC) and molecular charge modulation (MCM). EC can simultaneously concentrate and separate bound and unbound species in an assay based on electrical mobility, allowing for the quantification of binding. MCM enables the application of EC to arbitrary TPs by enhancing the mobility differences between TPs, TPRs, and TP-TPR complexes. This technology is homogeneous and overcomes many practical challenges of conventional heterogeneous assays. We developed various formats of assays for equilibrium and kinetic analysis and rapid determination of degradation of TPs, obtaining results comparable to state-of-the-art technologies with significantly less time (1 h) and simpler setup. Finally, we demonstrated that the results of MCM-EC based assays correlated well with those from mass spectrometry and cell-based assay, which are the industrial standards for quality testing of TPs.

Phosphorene, a single atomic layer of black phosphorus, has recently emerged as a new twodimensional (2D) material that holds promise for electronic and photonic technology. Here we experimentally demonstrate that the electronic structure of few-layer phosphorene varies significantly with the number of layers, in good agreement with theoretical predictions. The interband optical transitions cover a wide, technologically important spectrum range from visible to mid-infrared. In addition, we observe strong photoluminescence in few-layer phosphorene at energies that match well with the absorption edge, indicating they are direct bandgap semiconductors. The strongly layer-dependent electronic structure of phosphorene, in combination with its high electrical mobility, gives it distinct advantages over other twodimensional materials in electronic and opto-electronic applications., 17 pages, 4 figures, Likai Li, Jonghwan Kim, Chenhao Jin contributed equally to this work

We describe development of a Portable Aerosol Mobility Spectrometer (PAMS) for size distribution measurement of submicrometer aerosol. The spectrometer is designed for use in personal or mobile aerosol characterization studies and measures approximately 22.5 × 22.5 × 15 cm and weighs about 4.5 kg including the battery. PAMS uses electrical mobility technique to measure number-weighted particle size distribution of aerosol in the 10-855 nm range. Aerosol particles are electrically charged using a dual-corona bipolar corona charger, followed by classification in a cylindrical miniature differential mobility analyzer. A condensation particle counter is used to detect and count particles. The mobility classifier was operated at an aerosol flow rate of 0.05 L/min, and at two different user-selectable sheath flows of 0.2 L/min (for wider size range 15-855 nm) and 0.4 L/min (for higher size resolution over the size range of 10.6-436 nm). The instrument was operated in voltage stepping mode to retrieve the size distribution, which took approximately 1-2 minutes, depending on the configuration. Sizing accuracy and resolution were probed and found to be within the 25% limit of NIOSH criterion for direct-reading instruments (NIOSH 2012). Comparison of size distribution measurements from PAMS and other commercial mobility spectrometers showed good agreement. The instrument offers unique measurement capability for on-person or mobile size distribution measurements of ultrafine and nanoparticle aerosol.

Ion mobility is a powerful tool for separating and characterizing the structures of ions. Here, a radio-frequency (rf) confining drift cell is used to evaluate the drift times of ions over a broad range of drift field strengths (E/P, V cm–1 Torr–1). The presence of rf potentials radially confines ions and results in excellent ion transmission at low E/P (less than 1 V cm–1 Torr–1), thereby reducing the dependence of ion transmission on the applied drift voltage. Non-linear responses between drift time and reciprocal drift voltages are observed for extremely low E/P and high rf amplitudes. Under these conditions, pseudopotential wells generated by the rf potentials dampen the mobility of ions. The effective potential approximation is used to characterize this mobility dampening behavior, which can be mitigated by adjusting rf amplitudes and electrode dimensions. Using SIMION trajectories and statistical arguments, the effective temperatures of ions in an rf-confining drift cell are evaluated. Results for the doubly charged peptide GRGDS suggest that applied rf potentials can result in a subtle increase (2 K) in effective temperature compared to an electrostatic drift tube. Additionally, simulations of native-like ions of the protein complex avidin suggest that rf potentials have a negligible effect on the effective temperature of these ions. In general, the results of this study suggest that applied rf potentials enable the measurement of drift times at extremely low E/P and that these potentials have negligible effects on ion effective temperature.

An electrostatic size classification technique was used to segregate particles of known composition prior to being injected into an inductively coupled plasma mass spectrometer (ICP-MS). Size-segregated particles were counted with a condensation nuclei counter as well as sampled with an ICP-MS. By injecting particles of known size, composition, and aerosol concentration into the ICP-MS, efficiencies of the order of magnitude aerosol detection were calculated, and the particle size dependencies for volatile and refractory species were quantified. Similar to laser ablation ICP-MS, aerosol detection efficiency was defined as the rate at which atoms were detected in the ICP-MS normalized by the rate at which atoms were injected in the form of particles. This method adds valuable insight into the development of technologies like laser ablation ICP-MS where aerosol particles (of relatively unknown size and gas concentration) are generated during ablation and then transported into the plasma of an ICP-MS. In this study, we characterized aerosol detection efficiencies of volatile species gold and silver along with refractory species aluminum oxide, cerium oxide, and yttrium oxide. Aerosols were generated with electrical mobility diameters ranging from 100 to 1000 nm. In general, it was observed that refractory species had lower aerosol detection efficiencies than volatile species, and there were strong dependencies on particle size and plasma torch residence time. Volatile species showed a distinct transition point at which aerosol detection efficiency began decreasing with increasing particle size. This critical diameter indicated the largest particle size for which complete particle detection should be expected and agreed with theories published in other works. Aerosol detection efficiencies also displayed power law dependencies on particle size. Aerosol detection efficiencies ranged from 10− 5 to 10− 11. Free molecular heat and mass transfer theory was applied, but evaporative phenomena were not sufficient to explain the dependence of aerosol detection on particle diameter. Additional work is needed to correlate experimental data with theory for metal-oxides where thermodynamic property data are sparse relative to pure elements. Lastly, when matrix effects and the diffusion of ions inside the plasma were considered, mass loading was concluded to have had an effect on the dependence of detection efficiency on particle diameter.

Here, an anodic electrophoretic deposition was adopted to facilitate the large-scale uniform coating of nano-fillers onto carbon fibers to enhance the interfacial properties between carbon fibers and epoxy matrix. As interface–reinforcing materials, aramid nanofibers were introduced because of their superior mechanical properties and epoxy matrix-friendly functional groups. Furthermore, aramid nanofibers can be readily coated on carbon fibers via electrophoretic deposition because they are negatively-charged in solution with high electrical mobility. Finally, aramid nanofiber-coated carbon fibers showed significantly improved interfacial properties such as higher surface free energy and interfacial shear strengths (39.7% and 34.9% increases, respectively) than those of a pristine carbon fiber despite a very small amount of embedding (0.025 wt% of aramid nanofibers in a carbon fiber), and the short beam strength of the laminated composite prepared with the aramid nanofiber-coated carbon fibers was also improved by 17.0% compared to a non-modified composite.

The feasibility of determining ion mobilities from measurements conducted in non-stationary buffer gases and in the presence of dynamic and non-uniform electric fields is examined theoretically and experimentally. First, an equation of motion of an ion ensemble is derived on the basis of a solution to the Boltzmann transport equation. Subsequently, this equation of motion is applied to derive the relationship between ion mobility and arrival time for the conditions present in an ion mobility drift tube and a trapped ion mobility spectrometry (TIMS) apparatus. Finally, the theoretical analysis is tested by determining the ion mobility of compounds present in an ESI tune mix directly from experimental TIMS data. Comparison to ion mobilities measured on a drift tube shows that relative ion mobilities are currently directly amenable from TIMS experiments. The analysis further suggests that absolute ion mobilities are, in principle, directly amenable from ion mobility measurements performed with non-stationary buffer gases and non-uniform and dynamic electric fields.

Aerosol measurement is used in a variety of fields such as nanotechnology, materials science, pollution monitoring, air quality measurements, combustion and engine exhaust analysis, inhalation toxicology, and medical studies. One of the most prevalent methods for aerosol measurement is to use electrical mobility. An electrical mobility spectrometer (EMS) is used to measure aerosol particles size distribution ranging from 10 – 1000 nanometers, under the influence of an electric field. The accuracy of this distribution is influenced by flow conditions, the geometry of the EMS, the electric field, and the number of electrode rings. In this work, a multi-channel EMS is studied using computational fluid dynamics to numerically simulate the flow pattern, electric field and particle trajectories in the device. We found that neglecting the effect of the electric field on particles outside the sizing region generates an oversimplified model leading to high particle loss to the flow guide. In order to reduce the number of particle losses and obtaining a more realistic particle distribution we proposed a modification to the electrode electric potential which effectively reduces the particle loss. The applied modification has quintupled the number of particles which are classified by the EMS.

A methodology for the quantification of the ratio of multiple- to single-charged fractions acquired in aerosol neutralizers is presented. These quantities are necessary for an accurate monodisperse calibration of aerosol instrumentation. A tandem Differential Mobility Analyzer (DMA) setup is required, with the second DMA scanning the electrical mobility spectra classified in the first DMA. In contrast to previous studies on the quantification of bipolar charge distribution utilizing tandem DMA schemes, the methodology targets at the direct determination of the multiple- to single-charge fractions and does so through the analysis of the raw signal instead of the inverted size distributions, thus circumventing errors associated with the assumptions in the DMA data inversion. The proposed methodology is employed for the characterization of different types of aerosols commonly employed for instrument calibration. Spherical liquid particles (emery oil and dioctyl sebacate) were found to acquire lower m...

Particle size distributions measured by the Engine Exhaust Particle Sizer Spectrometer (EEPS) have been reported to disagree with those by scanning mobility particle sizers (SMPS). The discrepancies are larger for the accumulation mode engine exhaust particles than for compact-shape particles. Engine exhaust particles, specifically carbonaceous aggregates, have different charging characteristics compared to nearly spherical particles because aggregates acquire more charges at a given mobility diameter in a unipolar charging environment. Therefore, different instrument matrices, that represent the relationship between particle size and EEPS electrometer current distributions, are needed for compact-shape particles and aggregates. This paper reports on a study to improve the EEPS performance for engine exhaust measurements. The EEPS was calibrated with monodisperse particles from the exhaust of a diesel engine. The geometric mean diameters measured by the EEPS using the original instrument matrix agreed with SMPS within 15% for particles

Solution-processed zinc oxide (ZnO) thin-film transistors (TFTs) obtained via hydrolysis/pyrolysis of an organic precursor present an excellent technique to obtain high performance electronic devices with low manufacturing cost. In the current work, we propose the use of an alternative deposition method, based on a polymeric precursor route (known as Pechini), to obtain solution-processed ZnO compact films as the active layer of TFTs. The elimination of the organic phase and the formation of inorganic thin-films was carried out by thermal treatment at different temperatures (ranging from 200oC to 500oC) and at different times (from 5 min to 2 hours), being monitored by UV-vis and infrared (IR) optical absorption spectroscopy. It was observed that, for temperatures above 400oC and treatment times superior to 30 min, the organic phase was completely eliminated, remaining only the inorganic (metal oxide) phase. The optical bandgap of the resulting ZnO films, determined from UV-vis absorption, is about 3.4 eV. The electrical characteristics (output and transfer curves) of the obtained devices demonstrate the feasibility of Pecchini method to build solution-processed metal oxide TFTs. The results for the electrical mobility of the majority charge-carriers (electrons) and for the threshold voltage were 0.39 cm2.V-1.s-1 and 0.45 V, respectively.

Comparisons between the Engine Exhaust Particle Sizer Spectrometer (EEPS) and scanning mobility particle sizers (SMPS) have shown that the EEPS underestimates size and concentration of particles >~75 nm and that the discrepancies vary by particle type. This paper describes the development of a new EEPS instrument matrix to improve size distribution measurements for compact-shape particles. Both the operating principle and the mathematical model of the EEPS data inversion are described. Monodisperse and polydisperse sucrose, poly-α-olefin oil (PAO), and sodium chloride (NaCl) particles were used for calibration. A new instrument matrix was developed and implemented for data inversion. This study confirms the literature findings that the geometric mean diameter, geometric standard deviation, and total number concentration by EEPS with the default instrument matrix (referred to as IM-2004) agrees with SMPS within ±20% for compact-shape particles

The electrophoresis of a charged soft particle with charged rigid core is considered under a weak imposed field condition. The rigid core of the soft particle is considered to have a finite dielectric permittivity and a fixed volume charge density. The electric potential distribution is determined by solving the Poisson-Boltzman equation out side the rigid core and a Poisson equation within the core along with continuity conditions on the core-shell interface. We have extended the analytic expression of Ohshima (Electrophoresis 27:526–533, 2006) for the electrophoretic mobility of a soft particle with a charged shell to include the effect of the volume charge density of the rigid core. Mobility based on the present expression matches exactly with the existing analytical solutions for a soft particle with an uncharged core. We have also made a comparison of our solution for mobility with an uncharged rigid core with the existing experimental results. The impact of the core charge density on the soft particle mobility is analyzed.

This study aims to simulate depositions of size-segregated particles in human airway in Beijing, China during seasons when fine particulate matter concentrations are high (December 2011 and April 2012). Particle size distributions (5.6–560 nm, electrical mobility diameter) near a major road in Beijing were measured by the TSI Fast Mobility Particle Sizer (FMPS). The information of size distributions provided by FMPS was applied in the Multiple-Path Particle Dosimetry model (MPPD) to quantify number and mass depositions of particles in human airway including extrathoracic (ET), tracheobronchial (TB), and pulmonary (PUL) regions of exposed Chinese in Beijing. Our results show that under ambient conditions, particle number concentration (NC) deposition in PUL is the highest in the three major regions of human airway. The total particle NC deposition in human airway in winter is higher than that in spring, especially for ultrafine particles (1.8 times higher) while particle mass concentration (MC) deposition is higher in spring. Although particle MC in clean days are much lower than that in heavily polluted days, total particle NC deposition in human airway in clean days is comparable to that in heavily polluted days. NC deposition for nucleation mode particles (10–20 nm, aerodynamic diameter) in clean days is higher than that in heavily polluted days. MC deposition for accumulation mode particles (100–641 nm, aerodynamic diameter) in heavily polluted days is much higher than that in clean days, while that of nucleation mode is negligible. The temporal variation shows that the arithmetic mean and the median values of particle NC and MC depositions in the evening are both the highest, followed by morning and noon, and it is most likely due to increased contribution from traffic emissions.

Through advanced electro-thermal simulations we demonstrate that self-heating effects play a significant role in ultrascaled nanowire field-effect transistors, that some crystal orientations are less favorable than others (⟨111⟩ for n-type applications, ⟨100⟩ for p-type ones), and that Ge might outperform Si at this scale. We further establish a relationship between the dissipated power and the electrical mobility and another one between the current reduction induced by self-heating and the phonon thermal conductivity.

Atmospheric aerosol particles were collected in Budapest, Hungary in April–June onto lacey Formvar substrates by using an electrostatic precipitator during the beginning phase of the particle growth process in ten nucleation and growth events. Median contribution of the nucleated particles - expressed as the concentration of particles with a diameter between 6 and 25 nm to the total particle number concentration – was 55%, and the median electrical mobility diameter of the particles was approximately 20 nm. The sample was investigated using high-resolution transmission electron microscopy (TEM) and electron energy-loss spectroscopy. Major types of individual particles such as soot, sulphate/organic and tar ball particles were identified in the sample. In addition, particles with an optical diameter range of 10–30 nm were also observed. They clearly differed from the other particle types, showed homogeneous contrast in the bright-field TEM images, and evaporated within tens of seconds when exposed to the electron beam. They were interpreted as representatives of freshly nucleated particles.

The conditioning of the aerosol particle population into a bipolar charge equilibrium is an essential prerequisite to calculate the particle number size distribution using mobility particle size spectrometers. This is commonly realized by diffusion charging of bipolar air ions generated by e.g. a 85Kr source. Because of strict legal regulations on radioactive sources in several countries, soft-X-ray (SXR) appears as a suitable alternative. However, multiple measurements showed a systematical and significant difference between the particle charge distribution delivered by a radioactive source and an SXR charger, respectively. In this investigation, a calibrated particle charge distribution, suitable for the SXR chargers, was calculated based on the Fuchs model. An approximation analogous to the commonly used Wiedensohler approximation formula ( Wiedensohler, 1988 ) was computed. The use of the new SXR approximation of the bipolar charge equilibrium for the inversion of an electrical mobility distribution to a particle number size distribution improves the comparability of these results, compared to measurements involving a 85Kr charger or to bipolar chargers using radioactive material in general. A systematic error in case of using the SXR charger could be eliminated and hence the root mean square deviation could be reduced from 13% using the common parameters for both charger types to 7% using the new SXR approximation for the SXR bipolar charger.

Interest in understanding gas-to-particle phase transformation in several disciplines such as atmospheric sciences, material synthesis, and combustion has led to the development of several distinct instruments that can measure the particle size distributions down to the sizes of large molecules and molecular clusters, at which the initial particle formation and growth takes place. These instruments, which include the condensation particle counter battery, a variety of electrical mobility spectrometers and the particle size magnifier, have been usually characterized in laboratory experiments using carefully prepared calibration aerosols. They are then applied, alone or in combination, to study the gas-to-particle transition in experiments that produce particles with a wide range of compositions and other properties. Only a few instrument intercomparisons in either laboratory or field conditions have been reported, raising the question: how accurately can the sub-10 nm particle number size distributions be measured with the currently available instrumentation? Here, we review previous studies in which sub-10 nm particle size distributions have been measured with at least two independent instruments. We present recent data from three sites that deploy the current state-of-the-art instrumentation: Hyytiala, Beijing, and the CLOUD chamber. After discussing the status of the sub-10 nm size distribution measurements, we present a comprehensive uncertainty analysis for these methods that suggests that our present understanding on the sources of uncertainties quite well captures the observed deviations between different instruments in the size distribution measurements. Finally, based on present understanding of the characteristics of a number of systems in which gas-to-particle conversion takes place, and of the instrumental limitations, we suggest guidelines for selecting suitable instruments for various applications.

Electrical Mobility is a transport property that describes a particle behavior in the gas phase. When dealing with the free molecular regime, ascertaining the shape of a nanoparticle or an ion directly from measurements of mobility becomes quite difficult as the particle no longer can be assumed to have spherical shape. Here we propose an efficient parallelized tool, IMoS, that makes use of all-atom models to calculate the mobility of nanoparticles in a variety of gases. The program allows for different types of calculations that range from the efficient Projection Approximation (PA) algorithm to the 4-6-12 Lennard-Jones potential Trajectory Method. It also includes a diffuse inelastic simulation that achieves Millikan's predicted 1.36 value over PA. When compared to experimental results, the error of the most efficient calculations is shown to be approximately 2–4% on average.

Electrostatic separation of particles from air onto a liquid surface has attracted increasing attention for various applications such as wet electrostatic precipitators and bioaerosol samplers. In this study, the electrostatic separation of particles onto the liquid surface is numerically modeled in a simplified manner. The simulated separation efficiency is validated by experimental values reported in literature. The effects of ionic wind and Coulombic force on particle separation for various electrical mobilities, applied voltages, and air flow rates are studied by decomposing the total separation efficiency into two components: Coulombic and ionic-wind separation efficiencies. Both Coulombic and ionic-wind separation efficiencies show the same behaviors as the total separation efficiency with changes in the operating conditions: they increase with increasing applied voltage and particle electrical mobility, and with decreasing air flow rate. Overall, the ionic-wind separation efficiency is higher than the Coulombic separation efficiency, mainly because of the short residence time. However, when the applied voltage and particle electrical mobility are high, and the air flow rate is low, the Coulombic force outperforms the ionic wind. Time-scale analysis well explains the relations between the relative importance of each separation mechanism and the operating parameters.

Atmospheric environment has a significant influence on ion current, space charge and ground-level electric field profiles of HVDC transmission lines, which attracts a huge amount of interest already. This work presents that the upwind finite element method is applied to calculate the ion flow model in the presence of aerosol particulates. The ion-aerosol attachment coefficient, electrical mobility and diffusion coefficient of charged aerosol are calculated by Fuchs theory and Stokes–Einstein relation. Application of the proposed approach to calculate monopolar and bipolar DC line provides an insight into the physical mechanism of effect of aerosol. Making some appropriate assumptions, computational results present a reasonable agreement with the long-term measured data within a certain aerosol density. It is found that aerosol has a significant influence on the spatial distributions of charge density. In the downwind direction, the ground-level electric field increases significantly because of the dominant of charged aerosol particles.

Fractal aggregate model has shown significant superiority in simulating integral optical properties (like optical cross sections etc.) of soot aerosol. In this study, angular distributions of scattering matrices for soot samples were measured at 532 nm wavelength. Experiments were conducted over scattering angles from 5° to 175° using an improved and validated apparatus. Soot particles emitted from burning of toluene and n-heptane were collected and re-aerosolized for matrix measurements. Electrical mobility diameter distributions of soot aggregates were measured and converted to volume equivalent diameter distributions according to various conversion factors. Size distributions of soot monomers and fractal parameters were obtained through statistical analyses of transmission electron microscope (TEM) images. Fractal aggregate models were generated by a tunable particle-cluster algorithm, using measured size distributions of aggregates and statistically obtained morphological parameters. Multiple sphere T-matrix (MSTM) method was employed for the calculation of individual particles, and bulk scattering matrices were integrated from particles with same morphology parameters. Results indicated that measured scattering matrices for these two soot samples show similar angular behaviors. Compared with fresh soot particles, the collection and re-aerosolization treatments lead to larger mobility diameters and more compact particle structures. Fractal parameter, conversion factor, refractive index and polydisperse monomer all have various effects on different matrix elements. Inter-comparisons between simulations and measurements focus more on the performance of ideal fractal model consisting of point-contact monomers in simulating measured scattering matrices, and there is no doubt that ideal fractal aggregates cannot simultaneously reproduce measured angular distributions of all matrix elements.

The simultaneous realization of low thermal conductivity and high thermoelectric power factor in materials has long been the goal for the social use of high-performance thermoelectric modules. Nanostructuring approaches have drawn considerable attention because of the success in reducing thermal conductivity. On the contrary, enhancement of the thermoelectric power factor, namely, the simultaneous increase of the Seebeck coefficient and electrical conductivity, has been difficult. We propose a method for the power factor enhancement by introducing coherent homoepitaxial interfaces with controlled dopant concentration, which enables the quasiballistic transmission of high-energy carriers. The wavenumber of the high-energy carriers is nearly conserved through the interfaces, resulting in simultaneous realization of a high Seebeck coefficient and relatively high electrical mobility. Here, we experimentally demonstrate the dopant-controlled epitaxial interface effect for the thermoelectric power factor enhancement using our "embedded-ZnO nanowire structure" having high-quality nanowire interfaces. This presents the methodology for substantial power factor enhancement by interface carrier scattering.

Analysis of large electrosprayed biopolymers by electrical mobility alone is greatly facilitated by reducing their charge to unity. Here, we combine within a single chamber positive aqueous electrospray (ES), producing multiply charged protein cations, with negative methanolic ES, yielding small singly charged anions. Use of a 100 mM triethylammonium formate buffer in both solutions yields very small drops. The two sprays are decoupled electrostatically by an interposed 50% transparent, grounded metallic grid. This screen is readily crossed by the ions, resulting in substantial charge reduction. In spite of the grid, the aqueous spray is easily destabilized by the presence of anions in the positive ES region. Nonetheless, practical ES stabilization is achieved by using relatively small capillary tips (∼15 μm) in the positive emitter. Protein peaks obtained are as narrow as those previously reported via charge reduction with a radioactive Ni-63 source. Controlling the position of the negative ES permits spanning the full range of charge states, from high natural values to predominantly singly charged ions, even for large proteins such as immunoglobulin G (∼150 kDa).

Differences between static and dynamic behavior of microwave transistors have been studied through different models. Behavioral models are very accurate for prediction of this phenomena without the necessity of electrical equivalent circuits. From other side, device level models based on semi-empirical equations can also model this phenomena by using non linear equivalent circuits but without the necessity of the knowledge of the physical parameters of the transistor. In this paper we will show the impact of the electrical mobility parameter in the prediction of the difference between static and dynamic behavior of microwave devices, establishing a link between this parameter and electrical equivalent circuits. Modeling and characterization of mobility for different transistors will be presented.

We report a single-step growth process of graphene nanostripes (GNSPs) by adding certain substituted aromatics (e.g., 1,2-dichlorobenzene) as precursors during the plasma enhanced chemical vapor deposition (PECVD). Without any active heating and by using low plasma power (≤60 W), we are able to grow GNSPs vertically with high yields up to (13 ± 4) g/m^2 in 20 min. These GNSPs exhibit high aspect ratios (from 10:1 to >∼130:1) and typical widths from tens to hundreds of nanometers on various transition-metal substrates. The morphology, electronic properties and yields of the GNSPs can be controlled by the growth parameters (e.g., the species of seeding molecules, compositions and flow rates of the gases introduced into the plasma, plasma power, and the growth time). Studies of the Raman spectra, scanning electron microscopy images, ultraviolet photoelectron spectroscopy, transmission electron microscopy images, energy-dispersive x-ray spectroscopy and electrical conductivity of these GNSPs as functions of the growth parameters confirm high-quality GNSPs with electrical mobility ∼10^4 cm^2/V-s. These results together with residual gas analyzer spectra and optical emission spectroscopy taken during PECVD growth suggest the important roles of both substituted aromatics and hydrogen plasma in the rapid vertical growth of GNSPs with large aspect ratios.

Because nanomaterials have been increasingly developed and used in many technology and industry sectors over the last 20 years, an increasing number of workers is likely to be exposed to airborne nanoparticles. In addition, the question of the nanomaterial characteristics that should be assessed in epidemiological studies remains open. Thus, assessing occupational exposure to airborne nanoparticles will not only rely on mass concentration and chemical composition. Rather, key parameters, such as particle size, have to be included in measurement strategies. We previously proposed a methodology to estimate the Count Median Diameter (CMD) of an aerosol based on the simultaneous size-integrated measurement of two particle concentrations, lung-deposited surface area, and number, thanks to field-portable, commercially available aerosol instruments (Nanoparticle Surface Area Monitor/Condensation Particle Counter combination). In addition to previous work, this study investigates the case of various polydisperse metal oxides, organic oil, and salt particles with CMDs ranging from 16-410 nm. Once corrected, the CMDs derived from the NSAM/CPC agree within ±20% with regard to the reference electrical mobility equivalent diameter, regardless of aerosol composition, morphology, or geometric standard deviation (GSD). Furthermore, the field-applicability of the method was tested through 6 sets of experimental data stemming from workplace measurement campaigns where different materials were produced and handled (TiO2, SiO2, Ag, Multi-Walled Carbon Nanotubes-MWCNT), covering a range of CMDs between 40 and 190 nm. All situations considered, the approach based on the combination of a NSAM and a CPC leads to a satisfying estimation of particle CMD, within ±20% compared to reference CMD.

Measuring particle size distribution accurately down to approximately 1 nm is needed for studying atmospheric new particle formation. The scanning particle size magnifier (PSM) using diethylene glycol as the working fluid has been used for measuring sub-3 nm atmospheric aerosol. A proper inversion method is required to recover the particle size distribution from PSM raw data. Similar to other aerosol spectrometers and classifiers, PSM inversion can be deduced to a problem described by the Fredholm integral equation of the first kind. We tested the performance of the step-wising method, the kernel function method (Lehtipalo et al., 2014), the H&A linear inversion method (Hagen and Alofs, 1983), and the expectation-maximization (EM) algorithm. The step-wising method and the kernel function method were used in previous studies on PSM. The H&A method and the expectation-maximization algorithm were used in data inversion for the electrical mobility spectrometers and the diffusion batteries (Maher and Laird., 1985), respectively. In addition, Monte Carlo simulation and laboratory experiments were used to test the accuracy and precision of the particle size distributions recovered using four inversion methods. When all of the detected particles are larger than 3 nm, the step-wising method may report false sub-3 nm particle concentrations because of assuming an infinite resolution, while the kernel function method and the H&A method occasionally reports false sub-3 nm particles because of using the unstable least square method. The accuracy and precision of the recovered particle size distribution using the EM algorithm are the best among the tested four inversion methods. Compared to the kernel function method, the H&A method reduces the uncertainty while keeping a similar computational expense. The measuring uncertainties in the present scanning mode may contribute to the uncertainties of the recovered particle size distributions. We suggest using the EM algorithm to retrieve the particle size distributions using the particle number concentrations recorded by the PSM. Considering the relatively high computation expenses of the EM algorithm, the H&A method is recommended to be used for preliminary data analysis. We also gave practical suggestions on PSM operation based on the inversion analysis.

A recent CLOUD (Cosmics Leaving OUtdoor Droplets) chamber study showed that sulfuric acid and dimethylamine produce new aerosols very efficiently, and yield particle formation rates that are compatible with boundary layer observations. These previously published new particle formation (NPF) rates are re-analyzed in the present study with an advanced method. The results show that the NPF rates at 1.7 nm are more than a factor of 10 faster than previously published due to earlier approximations in correcting particle measurements made at larger detection threshold. The revised NPF rates agree almost perfectly with calculated rates from a kinetic aerosol model at different sizes (1.7 nm and 4.3 nm mobility diameter). In addition, modeled and measured size distributions show good agreement over a wide range (up to ca. 30 nm). Furthermore, the aerosol model is modified such that evaporation rates for some clusters can be taken into account; these evaporation rates were previously published from a flow tube study. Using this model, the findings from the present study and the flow tube experiment can be brought into good agreement. This confirms that nucleation proceeds at rates that are compatible with collision-controlled (a.k.a. kinetically-controlled) new particle formation for the conditions during the CLOUD7 experiment (278 K, 38% RH, sulfuric acid concentration between 1×106 and 3×107 cm-3 and dimethylamine mixing ratio of ~40 pptv). Finally, the simulation of atmospheric new particle formation reveals that even tiny mixing ratios of dimethylamine (0.1 pptv) yield NPF rates that could explain significant boundary layer particle formation. This highlights the need for improved speciation and quantification techniques for atmospheric gas-phase amine measurements.

We study the effects of electric field strength on the mobility of soot-like fractal aggregates (fractal dimension of 1.78). The probability distribution for the particle orientation is governed by the ratio of the interaction energy between the electric field and the induced dipole in the particle to the energy associated with Brownian forces in the surrounding medium. We use our extended Kirkwood–Riseman method to calculate the friction tensor for aggregates of up to 2000 spheres, with primary sphere sizes in the transition and near-free molecule regimes. Our results for electrical mobility versus field strength are in good agreement with published experimental data for soot, which show an increase in mobility on the order of 8% from random to aligned orientations. Our calculations show that particles become aligned at decreasing field strength as particle size increases because particle polarizability increases with volume. Large aggregates are at least partially aligned at field strengths below 1000 V/cm, though a small change in mobility means that alignment is not an issue in many practical applications. However, improved differential mobility analyzers would be required to take advantage of small changes in mobility to provide shape characterization. Copyright © 2018 American Association for Aerosol Research

A magnetic field effects on carrier charge mobility in spin coated Fe(III)–Mesoporphyrin thin layer is presented. Sample is fabricated by spin coating methods on Cu PCB substrates at atmospheric condition. The procedure for a Fe(III)–Mesoporphyrin films deposition following the previous Electrical characteristic experiment. Then, the electrical property is evaluated by using the I–V measurement under external magnetic field. The I–V characteristic measure without magnetic field is considered as reference. Experimental result show that the I–V characteristic change when the measurement under a magnetic field. The gradient of the I–V curve also change with the increase of the magnetic field. That result indicate that the electric mobility decrease with the increase of the magnetic field. This is can be attribute with the carrier charge of the sample due to recombination process during under magnetic field.

Analysis of scanning electrical mobility spectrometer (SEMS) or SMPS data requires coupling the scanning differential mobility analyzer (DMA) transfer function with the response functions for the instrument plumbing and the detector. In the limit of plug flow (uniform velocity) within the DMA, the scanning DMA transfer function has the same form as that for constant voltage. Most SEMS/SMPS data analysis uses this model, though previous studies have shown that boundary layers distort the transfer function during scanning DMA measurements. Part I determined the instantaneous transfer function during scanning of the TSI Model 3081 A long column DMA by modeling the flows, fields, and particle trajectories within the actual DMA geometry. This study (Part II) combines that transfer function with empirical data on the efficiencies and delay time distributions of the plumbing and detector of the SEMS/SMPS to determine the instantaneous rate at which particles are counted, and integrates the count rate over the finite counting time interval to obtain the integrated SEMS/SMPS response function. Simulations using this geometrical model are compared with those obtained using traditional, idealized DMA models for scan rates ranging from slow (240 s) to very fast (10 s), and with measurements of monodisperse calibration aerosols. Data inversion studies show that both increasing and decreasing voltage scans can be used to determine the particle size distribution, even with fast scans. Copyright © 2018 American Association for Aerosol Research

Electrical mobility size spectrometers are widely used to measure particle number size distributions (PNSD) in the range of 1–1000 nm (Wang and Flagan 1990; Jiang et al. 2011). These instruments co...

The accuracy of instruments measuring the alveolar lung deposited surface area (LDSA) concentration based on unipolar diffusion charging has been assessed. Monodisperse particles with sizes between 10 nm and 700 nm were used. The results indicate that the LDSA concentration can be measured with at least ±30% accuracy for particle sizes between 20 nm and 400 nm. The LDSA concentrations of particles 400 nm increasingly underestimated by the instruments. The LDSA concentration of 685 nm particles was on average underreported by a factor of approximately 2. LDSA concentrations measured with agglomerated particles were consistently higher than those measured with spherical particles of the same electrical mobility diameter. The accuracy was, however, still mostly within ±30% for a size range from 20 nm to 400 nm. Due to the strong and increasing deviation for large particles, the use of an appropriate preseprator is recommended when measuring LDSA concentrations.

Theoretical and experimental analyses of the steady state, bipolar diffusion charge distribution on nanoparticles are reviewed. This charge distribution plays a critical role in electrical mobility measurements of nanoparticle size distribution functions, where it is approximated via empirical regression equations. While the regression approach has been broadly successful, there remain several unresolved issues related to charge distribution calculations. Specifically, research to date has not revealed a method to reliably calculate nanoparticle-ion collision rates in the presence of strong attractive potentials, charge distribution predictions do not routinely consider the mass and (electrical) mobility distributions of the charging ions, and calculation approaches applicable to both spherical and nonspherical particles have not been compared to experimental data. In light of these issues, we examine the steady-state bipolar charge distribution on gold nanospheres and gold nanorods via tandem differentia...

The mass and electrical mobility size of nascent soot generated by aircraft turbine engines were measured using a Differential Mobility Analyzer, a Centrifugal Particle Mass Analyzer and a Condensation Particle Counter in series. The measurements were conducted with a commonly used engine at a maintenance facility at airport Zurich, Switzerland. The aircraft engine under investigation was a CFM56-7B26/3. The used standardized sampling system conforms to the emission certification regulations captured by the “Society of Automotive Engineers, Aerospace Information Report 6241”. Effective densities of the aircraft soot were derived using measured power-law relationships between mass and electrical mobility size. The values ranged from 530 kg/m 3 to 1865 kg/m 3 depending on the particle mobility size and applied engine thrust. Trends in these effective densities suggest that the size of primary particles in the soot aggregates increase with increasing thrust. The mass-mobility exponents associated with these engine thrusts ranged from 2.54 to 2.79 and 1.86 to 2.32 for thrust levels above 30% and below 30%, respectively. Comparison with a second engine, a CFM56-5B4/2P, revealed higher effective densities for particles smaller than 40 nm.

The measurement of ion mobility is important for calculating the corona loss of the transmission lines, and for establishing corona loss and ion current models that take humidity and air pressure into consideration. This paper describes a needle-ring corona discharge experiment setup based on a prior study, which simulates different humidity and air pressure conditions; it is observed that the execution of the ion gate is improved in this experiment from off-on-off to off-on to achieve higher ion current amplitude. Additionally, positive and negative ion mobility under different humidity and air pressure is obtained, with the positive ion mobility measurements in the range of 1.1126 to 1.9167 cm 2 /V·s, and the negative ion mobility measurements in the range of 1.3574 to 2.5643 cm 2 /V·s. The experimental results indicate that ion mobility decreases nonlinearly with increase in humidity, but trends towards saturation in the 30%-70% relative humidity range. Finally, a parameter correction method for calibrating the relationship among the ion mobility, humidity, and air pressure is proposed.

The properties of gas-borne aggregates are important in nano-technology and for potential health effects. Gold aggregates from three generators (one commercial and one custom built spark discharge generator and one high-temperature furnace) have been characterized. The aggregate surface areas were determined using five approaches - based on aggregation theory and/or measured aggregate properties. The characterization included mass-mobility relationships, effective densities (assessed by an Aerosol Particles Mass analyzer), primary particle analysis (based on Transmission Electron Microscopy), as well as total mass and number concentration outputs. The relationships between mass and mobility are well described by power-law functions with exponents of 2.18-2.35. For all generators, the primary particles of the aggregates were fused together by a bridge with a diameter typically similar to 60-70% of the primary particle diameter (5-10 nm). The total mass outputs were 6.1-48.1 mg/m3 and the predicted surface area outputs in the range 0.9 x 10(-3)-17 x 10(-3) cm(2)/cm(3). The aggregate effective densities differed considerably between generators. The difference could partly be explained by the differences in primary particle diameter, but not fully. This in turn may be explained either by a varying primary particle size with aggregate size, or by that there are slight differences in the morphology of the aggregates from the generators. (C) 2015 The Authors. Published by Elsevier Ltd. (Less)

A new method for generating metal clusters in the gas phase is described and characterized in this work. The method is based on material evaporation by spark ablation at atmospheric pressure. The characterization of atomic clusters was done by measuring their electrical mobility. The measured mobilities were compared with values found in literature in order to identify the cluster species. We show that silver clusters consisting from one up to 25 atoms can be produced in helium at atmospheric pressure. In addition, the effect of oxygen concentration on the resulting cluster mobility distribution was investigated. Results show that at higher oxygen level, the mobility distribution is dominated by the abundance of stable clusters (i.e., magic number clusters). This can be attributed to an oxidation etching effect.Copyright 2015 American Association for Aerosol Research

Liquid entrainment from coalescence filter media—i.e. flow induced “blow-off” of previously deposited oil—in the form of droplets is poorly understood, for one because the generated spectrum is very wide and difficult to characterize with temporal and size resolution, especially for very large drops which carry most of the mass. Such filters operate at much lower flow rates than classical demisters, often in vertical orientation, with much finer geometries, and gravity plays no direct role for entrainment. We present a novel combination of four measurement techniques used to capture the entrained oil drop spectrum from filters during operation in the size range of 0.01–2400 µm. The diameter range below 10 μm combines two established real-time methods including an electrical mobility particle spectrometer (EMPS; This measuring system was applied to two representative types of glass microfiber media operated with oil mist generated from compressor oil, in order to characterize time resolved drop formation rates and spectra in the range of nanometers to millimeters. Wettable and non-wettable filter media were found to show similar entrainment characteristics, each with multi-modal drop spectra having two pronounced peaks in the ranges of 1–2 μm and 200–300 μm, respectively. During steady-state operation both modes were generated quasi-continually, the large drops at the rate of a few drops per hour and cm 2 of filter surface, the micron size drops 10 3 –10 4 times more frequently. Available indirect evidence suggests the same underlying entrainment mechanism for both types of fibrous media, namely the break-up of air bubbles formed periodically on the oil that drains on the downstream filter face. Direct detachment (blow-off) of large drops is unlikely at the prevailing operating conditions.