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Micrographs of ultrafine particles: (a) silver particles, (b) cadmium oxide particles, (c) iron oxide particles, (d) iridium particles, and (e) carbon particles. (Continued)
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Ultrafine carbon, metal, and metal oxide particles were generated with a commercially available spark generator designed for the production of carbon particles. Aerosols with number concentrations up to 10 cm were produced at flow rates up to 150 lpm. Lognormal size distributions with modal diameters in the range of 18–150 nm and geometric standard...
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... Whereas several examples of the formation of, e.g., hydrides and oxides by spark discharge generation [33][34][35][36][37] are known, the possibility of nitride formation as a result of carrier gas ionization during spark discharge generation was under discussion but not validated hitherto. In contrast, the methodologically related laser ablation synthesis was employed, e.g., to obtain aluminum nitride nanoparticles [38]. ...
Spark ablation is an advantageous method for the generation of metallic nanoparticles with defined particle sizes and compositions. The reaction of the metal particles with the carrier gas during the synthesis and, therefore, the incorporation of those light elements into structural voids or even compound formation was confirmed for hydrides and oxides but has only been suspected to occur for nitrides. In this study, dispersed nanoparticles of Mo3Ni2N and Mo with Janus morphology, and defined particle sizes were obtained by spark discharge generation as a result of carrier gas ionization and characterized using transmission electron microscopy and powder X-ray diffraction. Metal nitrides possess beneficial catalytic and thermoelectric properties, as well as high hardness and wear resistance. Therefore, this method offers the possibility of controlled synthesis of materials which are interesting for numerous applications.
... Moreover, organics evaporating from the walls and tubing of the generator can also play a major role in defining the purity of the generated carbonaceous particles. It was shown that the weight percent of organic volatile materials in SDG-generated carbon particles can be reduced from ca. 25% to 6% by employing ceramic and stainless-steel components, instead of polymers [29]. By varying the operational parameters, such as flow rate, spark energy, and spark repetition rate, different microphysical properties of the soot aerosol can be mimicked both on the primary particle and on the agglomerate level [27]. ...
The mimicking of atmospheric soot with versatile chemophysical properties is a critical issue in many applications, starting from instrument calibration, through producing aerosol standards for academic research, and ending with the reduction of uncertainties associated to carbonaceous particulate matter in the atmosphere, just to name a few. The present study deals with laser ablation as a novel and interesting technique for the generation of soot with high elementary carbon (EC) content with microphysical features similar to diesel or atmospheric soot and for modelling biomass emission under well-controlled laboratory conditions. The operation of the laser-excitation-based soot generator and the characteristics of the produced particles are compared to the most widely used techniques like flame, spark discharge generators, and real combustion soot originating from diesel- and aircraft engines or from field measurement. The comparison shows that significant differences in the physicochemical features exist between the real combustion soot and the soot originating from different excitation mechanisms. Moreover, the soot produced by different techniques shown also significant differences. However, due to some inherent and favorable attributes of the laser ablation technique—such as the possibility of the independent variation of physical characteristics of the generated soot particles—the potential for modelling biomass burning or to produce soot particles even in the accumulation mode makes it a useful tool in many cases.
... A spark discharge (SD) method of synthesis is of particular interest [28][29][30][31]. The primary NPs obtained by this method are characterized by a log-normal size distribution with an average size of about 10 nm and a low standard deviation value [32,33], which are comparable to the distributions parameters of NPs obtained by laser ablation [34] and are significantly better than the distribution parameters obtained by other gas-phase synthesis methods. ...
This study investigates the processes of interaction of nanosecond pulsed-periodic laser radiation with the flow of aerosol agglomerates of gold nanoparticles synthesized in a spark discharge. Nanoparticles in a gas flow are spatially separated nano-objects whose interaction with each other and with the walls of an experimental cell was insignificant. Therefore, the energy absorbed by nanoparticles was used only for their own heating with further shape and size modification and on heat transfer to the surrounding gas. In the research, we used laser radiation with wavelengths of 527 and 1053 nm at pulse energies up to 900 µJ and pulse repetition rates up to 500 Hz. The dynamics of changes in the nanoparticles size during their sintering process depending on the laser pulses energy is characterized by an S-shaped shrinkage curve. Complete sintering of the initial agglomerates with their transformation into spherical nanoparticles is achieved by a series of impacting laser pulses. The result of nanoparticles’ laser modification is largely determined by the pulse energy and the efficiency of the nanoparticles’ radiation absorption.
... In our study, elementary carbon and organic carbon were measured using a thermo-optical analyzer and total carbon was considered in the results. Though pure graphite electrodes were used, the fraction of organic carbon was higher than 50% in all the samples what might be due to the degradation of the polyamide chamber of the generator [41]. ...
To avoid multiple instruments to be deployed in field measurement campaigns based on airborne nanoparticles characterization, this study aims at investigating the capability of a Scanning Mobility Particle Sizer (SMPS) to provide accurate data relative to the mass
concentration. Two series of test nanoaerosols were produced using a spark-discharge generator equipped with carbon or titanium electrodes (modal number diameters between ~ 50 and ~ 170 nm). The mass concentration was monitored by means of a personal AM520 photometer operated in parallel with the SMPS and closed-face cassette sampling for further off-line analysis: gravimetric analysis, and chemical analysis (thermo-optical analysis for carbon, ICPOES for titanium). For each operating condition, the average number size distribution stemming from the SMPS was converted into mass size distribution accounting for particle effective density and integrated over the whole range of particle diameters to determine the corresponding mass concentration. Results highlight correlations (R2 ~ 0.9) between SMPS-based and chemical analysis or gravimetric mass concentrations below 1 mg/m3, with relative discrepancies lower than ~ 15% and ~ 25%, respectively. The AM520 photometric response remains dependent on particle physical and light scattering properties, which differ with the test dust used for factory calibration.
... Particles size distributions with slightly lower modes (6-9 nm) have been measured by Wallace et al. [85]. Particles with greater sizes (e.g., 15-30 nm) probably derives from particle coagulation and/or contribution from the graphite brushes [86]. Spike PN concentrations and ADSA as high as 10 6 particles cm -3 and 200 m 2 cm -3 and as high as 1.1 × 10 5 particles cm -3 and 110 m 2 cm -3 , were measured (1 s time resolution) on switching on, respectively, an electric drill and a vacuum cleaner [77]. ...
This paper presents an overview of the literature studies on the sources of ultrafine particles (UFPs), nanomaterials (NMs), and nanoparticles (NPs) occurring in indoor (occupational and residential) and outdoor environments. Information on the relevant emission factors, particle concentrations, size, and compositions is provided, and health relevance of UFPs and NPs is discussed. Particular attention is focused on the fraction of particles that upon inhalation deposit on the olfactory bulb, because these particles can possibly translocate to brain and their possible role in neurodegenerative diseases is an important issue emerging in the recent literature.
... Soot particle formation within a spark discharge generator occurs through homogenous nucleation of carbon vapor at high temperatures. The nuclei grow in size through condensation of single molecules, followed by coagulation with other particles (Roth et al., 2004). The coagulation process can either be characterized by complete fusion leading to spherule like particles or by incomplete fusion leading to agglomerates. ...
Spark discharge generators enable a fast, reliable, continuous, and highly reproducible production of nanoparticle aerosols along with a widely tunable size distribution. Graphite spark discharge generators have been particularly applied for studies of instrument calibration, filter testing, soot reactivity studies, and in toxicological risk evaluation of soot. Until now, it has been consensus that soot produced in spark discharge generators is highly reactive because of its high surface area and its amorphous nanostructure. In this paper, we will demonstrate that the properties of soot produced in spark discharge generators strongly depend on the used carrier gas (i.e. argon, nitrogen). Soot produced in argon (spark discharge argon soot, SDS-Ar) as carrier gas is composed of a major fraction with high reactivity exhibiting a temperature at maximum oxidation rate Tmax between 796 K and 803 K. Soot produced in nitrogen (spark discharge nitrogen soot, SDS-N2) has a similar size distribution as SDS-Ar, whereas the main fraction is less reactive (963 K < Tmax < 983 K). This can be derived from temperature programmed oxidation (TPO) and thermogravimetric analysis (TGA) and also correlates well with a considerable higher BET surface area of SDS-Ar (679 m² g⁻¹) compared with SDS-N2 (426 m² g⁻¹). C/H/N Elemental Analysis, High-Resolution Transmission Electron Microscopy (HRTEM), Raman- and FTIR-spectroscopy complement the measurements, all leading to the observation that SDS-N2 has a more graphitic nanostructure than the highly amorphous nanostructure of SDS-Ar (Raman spectra SDS-Ar: I(D, disordered bands)/I(G, graphite band) = 0.76, SDS-N2: I(D)/I(G) = 1.0 or elemental analysis SDS-Ar: H/C = 0.25, SDS-N2: H/C = 0.10). These findings imply that studies applying spark discharge soot have to be critically viewed with respect to the used carrier gas. Spark-over field strength, Paschen's law, the energy release within the arc, decaying plasma or cooling rates, as well as dissociation/ionization processes are discussed to explain the observations above. Finally, we want to emphasize that it is possible to vary the reactivity towards oxidation and nanostructure of spark discharge soot simply by applying different mixtures of the carrier gas.
... Particles size distributions with slightly lower modes (6-9 nm) have been measured by Wallace et al. [85]. Particles with greater sizes (e.g., 15-30 nm) probably derives from particle coagulation and/or contribution from the graphite brushes [86]. Spike PN concentrations and ADSA as high as 10 6 particles cm -3 and 200 m 2 cm -3 and as high as 1.1 × 10 5 particles cm -3 and 110 m 2 cm -3 , were measured (1 s time resolution) on switching on, respectively, an electric drill and a vacuum cleaner [77]. ...
This paper presents an overview of the literature studies on the sources of ultrafine particles (UFPs), nanomaterials (NMs), and nanoparticles (NPs) occurring in indoor (occupational and residential) and outdoor environments. Information on the relevant emission factors, particle concentrations, size, and compositions is provided, and health relevance of UFPs and NPs is discussed. Particular attention is focused on the fraction of particles that upon inhalation deposit on the olfactory bulb, because these particles can possibly translocate to brain and their possible role in neurodegenerative diseases is an important issue emerging in the recent literature.
... The layout of the experimental setup employed for the characterization of the two technical solutions is shown in Figure 1. Following the regulatory requirements, soot-like particles, produced by a spark graphite generator (DNP 3000 from Palas, Karlsruhe, Germany) were employed [28]. Thermal treatment was performed by passing through an AVL catalytic stripper (CS) operating at 350 • C [29]. ...
Onboard measurement of non-volatile particle number (PN) emissions with portable emissions measurement systems (PEMS) was introduced for the type-approval of passenger cars in Europe since 2017 and is foreseen for heavy-duty (HD) vehicles in 2021. First studies on the performance of PN-PEMS with HD engine exhaust revealed larger differences between established PN-PEMS techniques than what was observed for passenger cars. Particles forming in selective catalytic reduction (SCR) systems for NOx of late technology HD engines have recently been identified as a potential reason for the observed differences. The formed particles have a size distribution peaking below the regulatory limit of 23 nm and most importantly acquire high (more than one) positive charges at the elevated exhaust temperatures. Precise measurement of such highly charged nanosized particles with PN-PEMS instrumentation utilizing diffusion charger (DC) based counters requires proper conditioning of these charges. Two approaches were investigated in this study: (a) an electrofilter (EF) to completely remove charged particles below the regulated size and (b) a tandem negative-positive corona (TC) charger to directly condition pre-charged particles. The two technical solutions were tested alongside the unmodified DC-based PN-PEMS, a PN-PEMS utilizing a condensation particle counter (CPC) and a reference stationary PN system using exhaust of two SCR-equipped HD engines. The results confirmed that the particles forming in such SCR systems are responsible for the observed inconsistencies and that both technical solutions efficiently address the interferences of these pre-charged nanoparticles.
... For these appliances, a major mode was present at about 10 nm, due to the Cu NPs emitted by the electric arc discharge between the Cu windings and the graphite electrodes of the brush electric motor (Manigrasso et al., 2015Szymczak et al., 2007). A minor mode at about 16 nm and, for the hairdryer and the vacuum cleaner, a shoulder at about 29 nm were probably due to particle coagulation and/or to the contribution from the graphite brushes (Roth et al., 2004). Following a single respiratory act, due to aerosol spike emissions, up to 7.6 × 10 4 , 1.7 × 10 5 and 3.3 × 10 5 particles were respectively deposited on the olfactory bulb, with a major contribution, respectively of 1.3 × 10 4 , 2.7 × 10 4 and 6.2 × 10 4 particles, from 9 to 10 nm particles. ...
A variety of appliances operated by brush electric motors, widely used in indoor environments, emit nanoparticles (NPs). Due to electric arc discharge during the operation of such motors, some NPs contain copper (Cu). Their dimensions are the same of those found in brain tissue samples by other authors who speculated their possible translocation to brain through olfactory bulb. Cu has been reported to play an important role in the etiopathogenesis of Alzheimer's disease. Thus, the present study was performed to 1. estimate by means of Multiple-Path Particle Dosimetry model the doses of NPs released by electric appliances that can potentially deposit on the olfactory bulb; 2. investigate the morphology and the composition of particles emitted by some electric appliances daily used in indoor environments; 3. monitor for a long time period the Cu contamination of indoor environments due to this kind of appliances. About 10⁶–10⁷ NPs deposit on the olfactory bulb during the operation (1.5–6 min) of such appliances, with a major contribution due to 10–20 nm NPs. HR-FESEM characterization confirmed the presence of such NPs, that were observed both as individual particles (20–40 nm) and aggregated to form particles in the μm sizes range. XEDS microanalysis revealed the presence of Cu together with other elements. Relevant daily contamination of indoor environments due to these appliances has been confirmed by monitoring throughout a year the Cu content of PM10 samples collected both indoor and outdoor private dwellings. Cu was present in great part as an insoluble form. This means that, following protracted exposure, Cu NPs of such origin may undergo tissue accumulation. This is cause of concern because general population is chronically exposed to such Cu nanoparticles in indoor environments and in view of the role assigned to Cu in the development of neurological disorders.
... The copper-containing particles are generated by brush sparks and by mechanical abrasion of the brush. Roth et al. (2004) describe generation of ultrafine particles by spark discharging. Szymczak et al. (2007), and Knibbs et al. (2012) reported about copper particle emission of universal motors. ...
Adverse health effects of airborne particulate matter depend on parameters like particle size, particle surface and chemical composition. Major emission of indoor particles is caused by combustion processes like tobacco smoking and cooking. Nevertheless, the use of household electrical appliances, such as vacuum cleaners, flat irons or hair dryers, can produce particles as well.
In this study the emissions of different hair dryers and flat irons were investigated using a test chamber. The particle number concentrations, particle volume concentrations, as well as the size distributions were measured. Particles were sampled and analyzed by electron microscopy, inductively coupled plasma mass spectrometry and gas chromatography mass spectrometry. Moreover different volatile organic compounds (VOCs) were measured.
Each tested appliance, especially flat irons produced small particles with diameters far below 100 nm and might be a nonnegligible source for indoor particles. Copper was the main identified element in most of the particles emitted from hair dryers, but in the emission of two hair dryers silver-containing nanoparticles were found as well. Various VOCs were observed in the emission of both flat irons and hair dryers, while cyclic siloxanes were detected only in the emission of flat irons. The use of flat irons or hair dryers may significantly contribute to the personal particle exposure.
