| 1. |
- Cha, Yingying, et al.
(författare)
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Airborne Wear Particles Generated from Conductor Rail and Collector Shoe Contact : Influence of Sliding Velocity and Particle Size
- 2016
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Ingår i: Tribology letters. - : Springer-Verlag New York. - 1023-8883 .- 1573-2711. ; 64:3
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Tidskriftsartikel (refereegranskat)abstract
- The mechanical wear of train components is one of the main sources of airborne particles in subway air. A certain contribution is suspected to derive from third-rail systems due to the sliding of two metallic surfaces between conductor rail and collector shoe during operation. In this study, a pin-on-disc apparatus was used to simulate the friction between such two sliding partners (shoe-to-rail). Airborne particles generated from the sliding contact were measured by particle counters (a fast mobility particle sizer spectrometer and an optical particle sizer) and were collected by an electrical low-pressure impactor for physical and chemical analysis. Interface temperature for each test was measured by a thermocouple. The influence of sliding velocity and temperature on particulate number concentration, size distribution, and chemical composition was investigated. Atomic absorption spectroscopy, cyclic voltammetry, and energy-dispersive spectroscopy measurements were carried out to determine the chemical compositions. Results show that increasing sliding velocity results in a higher temperature at the frictional interface and a higher concentration of ultrafine particles. The ratio of manganese to iron surface oxides increased strongly with smaller particle size. A copper compound was observed in some particle samples, probably gerhardite (Cu2NO3(OH)(3)) formed due to high temperature.
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| 2. |
- Cheng, Jie, et al.
(författare)
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Interactions in Composite Film Formation of Mefp-1/graphene on Carbon Steel
- 2021
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Ingår i: Coatings. - : MDPI AG. - 2079-6412. ; 11:10
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Tidskriftsartikel (refereegranskat)abstract
- Mefp-1 adhesive protein derived from marine blue mussels, together with the 2D material graphene, was used to build the green composite film with enhanced anti-corrosion property and mechanical strength. The corrosion inhibition of the composite film, formed by different methods, was evaluated by using electrochemical impedance spectroscopy. The non-degraded adhesion of the composite film to the carbon steel substrate was proved by nano-scratch tests. Infrared spectroscopy was utilized to investigate the film formation process and "three-body interactions " between Mefp-1, graphene and carbon steel surface. The results show that the Mefp-1 adsorbs on the carbon steel surface mainly through the covalent bond between catechols and Fe(III). Meanwhile, Mefp-1 can bond to non-adhesive graphene by forming hydrogen bonds and pi-pi interaction non-covalent bonds, which facilitate the formation of a robust Mefp-1/graphene composite film on the carbon steel surface.
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| 3. |
- Hedberg, Yolanda, 1985-, et al.
(författare)
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Nanoparticles of WC-Co, WC, Co and Cu of relevance for traffic wear particles – Particle stability and reactivity in synthetic surface water and influence of humic matter
- 2017
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Ingår i: Environmental Pollution. - : Elsevier. - 0269-7491 .- 1873-6424. ; 224, s. 275-288
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Tidskriftsartikel (refereegranskat)abstract
- Studded tyres made of tungsten carbide cobalt (WC-Co) are in the Northern countries commonly used during the winter time. Tungsten (W)-containing nano- and micron-sized particles have been detected close to busy roads in several European countries. Other typical traffic wear particles consist of copper (Cu). The aims of this study were to investigate particle stability and transformation/dissolution properties of nanoparticles (NPs) of WC-Co compared with NPs of tungsten carbide (WC), cobalt (Co), and Cu. Their physicochemical characteristics (primarily surface oxide and charge) are compared with their extent of sedimentation and metal release in synthetic surface water (SW) with and without two different model organic molecules, 2,3- and 3,4-dihydroxybenzoic acid (DHBA) mimicking certain sorption sites of humic substances, for time periods up to 22 days. The WC-Co NPs possessed a higher electrochemical and chemical reactivity in SW with and without DHBA molecules as compared with NPs of WC, Co, and Cu. Co was completely released from the WC-Co NPs within a few hours of exposure, although it remained adsorbed/bonded to the particle surface and enabled the adsorption of negatively charged DHBA molecules, in contrast with the WC NPs (no adsorption of DHBA). The DHBA molecules were found to rapidly adsorb on the Co and Cu NPs. The sedimentation of the WC and WC-Co NPs was not influenced by the presence of the 2,3- or 3,4-DHBA molecules. A slight influence (slower sedimentation) was observed for the Co NPs, and a strong influence (slower sedimentation) was observed for the Cu NPs in SW with 2,3-DHBA compared with SW alone. The extent of metal release increased in the order: WC < Cu < Co < WC-Co NPs. All NPs released more than 1 wt-% of their metal total mass. The release from the Cu NPs was most influenced by the presence of DHBA molecules.
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| 4. |
- Khort, Alexander, et al.
(författare)
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Corrosion and transformation of solution combustion synthesized Co, Ni and CoNi nanoparticles in synthetic freshwater with and without natural organic matter
- 2021
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Ingår i: Scientific Reports. - : Nature Research. - 2045-2322. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- Pure metallic Co, Ni, and their bimetallic compositions of Co3Ni, CoNi, and CoNi3 nanomaterials were prepared by solution combustion synthesis. Microstructure, phase composition, and crystalline structure of these nanoparticles (NPs) were characterized along with studies of their corrosion and dissolution properties in synthetic freshwater with and without natural organic matter (NOM). The nanomaterials consisted of aggregates of fine NPs (3–30 nm) of almost pure metallic and bimetallic crystal phases with a thin surface oxide covered by a thin carbon shell. The nanomaterials were characterized by BET surface areas ranging from ~ 1 to 8 m2/g for the Ni and Co NPs, to 22.93 m2/g, 14.86 m2/g, and 10.53 m2/g for the Co3Ni, CoNi, CoNi3 NPs, respectively. More Co and Ni were released from the bimetallic NPs compared with the pure metals although their corrosion current densities were lower. In contrast to findings for the pure metal NPs, the presence of NOM increased the release of Co and Ni from the bimetallic NPs in freshwater compared to freshwater only even though its presence reduced the corrosion rate (current density). It was shown that the properties of the bimetallic nanomaterials were influenced by multiple factors such as their composition, including carbon shell, type of surface oxides, and the entropy of mixing. © 2021, The Author(s).
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| 5. |
- Khort, Aliaksandr, Dr, 1987-, et al.
(författare)
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Influence of natural organic matter on the transformation of metal and metal oxide nanoparticles and their ecotoxic potency in vitro
- 2022
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Ingår i: Nanoimpact. - : Elsevier BV. - 2452-0748. ; 25
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Tidskriftsartikel (refereegranskat)abstract
- Increased use and production of engineered nanoparticles (NPs) lead to an elevated risk of their diffuse dispersion into the aquatic environment and increased concern on unknown effects induced by their release into the aquatic ecosystem. An improved understanding of the environmental transformation processes of NPs of various surface characteristics is hence imperative for risk assessment and management. This study presents results on effects of natural organic matter (NOM) on the environmental transformation and dissolution of metal and metal oxide NPs of different surface and solubility properties in synthetic freshwater (FW) with and without NOM. Adsorption of NOM was evident on most of the studied NPs, except Sb and Sb2O3, which resulted in the formation of negatively charged colloids of higher stability and smaller size distribution compared with the same NPs in FW only. The dissolution rate of the NPs in the presence of NOM correlated with the strength of interactions between the carboxylate group of NOM and the particle surface, and resulted in either no (Mn, Sb, ZnO NPs), increased (Co, Sn NPs) and decreased (Ni, NiO, Sb2O3, Y2O3 NPs) levels of dissolution. One type of metal NP from each group (Mn, Ni, Sn) were investigated to assess whether observed differences in adsorption of NOM and dissolution would influence their ecotoxic potency. The results showed Mn, Ni, and Sn NPs to generate intracellular reactive oxygen species (ROS) in a time and dose-dependent manner. The extent of ROS generation in FW was similar for both Mn and Ni NPs but higher for Sn NPs. These findings are possibly related to interactions and infiltration of the NPs with the cells, which lead to redox imbalances which could induce oxidative stress and cell damage. At the same time, the presence of NOM generally reduced the intracellular ROS generation by 20-40% for the investigated NPs and also reduced cytotoxicity of Sn NPs, which can be attributed to the stronger interaction of carboxylate groups of NOM with the surface of the NPs.
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| 6. |
- Mei, Nanxuan, et al.
(författare)
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Food web transfer of cobalt nanoparticles in algae, zooplankton, and fish
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Cobalt (Co) nanoparticles (NPs) may be diffusely dispersed to natural ecosystems from various sources such as traffic settings, and hence eventually end up in aquatic systems, such as lakes and oceans. This has motivated our studies on the transfer of Co NPs through an aquatic food web including algae (Scendesmus sp), zooplankton (Daphnia magna) and fish (Crucian carp, Carassius carassius). The influence of excreted biomolecules from D. magna, potentially adsorbing and forming an eco-corona at the surfaces of the Co NPs, was also investigated from an environmental fate perspective. ATR-FTIR measurements show adsorption of algae constituents and excreted biomolecules onto the Co NPs. The initially adsorbed smaller molecules of the excreted biomolecules were eventually replaced with larger molecules of higher surface affinity, originating from the algae. In tap water (TW) containing algae, less than 1.5% of the Co NPs mass was dissolved within 24 h, mainly as a result of the near neutral pH. Less than 5% of the Co NPs formed heteroagglomerates with algae, which was partly an effect of agglomeration and settling of the Co NPs. The presence of excreted biomolecules in solution did not affect the extent of heteroagglomeration between the Co NPs and the algae. Some Co NPs were transferred to the next trophic level (D. magna) despite the low extent of heteroagglomeration of Co NPs to algae. The Co uptake in D. magna was 300 times larger compared to the control samples (without Co NP), results that were not influenced by the addition of excreted biomolecules to the solution. A significant uptake of Co by the fish was observed in the intestine, without any evident effect of the presence of excreted biomolecules in the solution. No bioaccumulation of Co was observed in the fish feeding on D. magna containing Co NPs, and 10-20% of the Co NP mass was dissolved after 24 h in its simulated gut solution (pH 7.4). In all, extensive agglomeration and sedimentation of the Co NPs and small extent of heteroagglomeration between the Co NPs and the algae resulted in only a small fraction of Co transferred between the algae and D. magna. No significant bioaccumulation of Co NPs was observed in any of the fish organs, even though a small difference was observed in the fish stomachs and intestines. The dissolution findings in the simulated fish stomach solution (pH 7.4) imply that 60% of the Co NPs will dissolve within 24 h if reached this trophic level.
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| 7. |
- Mei, Nanxuan, et al.
(författare)
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Influence of Biocorona Formation on the Transformation and Dissolution of Cobalt Nanoparticles under Physiological Conditions
- 2019
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Ingår i: ACS Omega. - : American Chemical Society (ACS). - 2470-1343. ; 4:26, s. 21778-21791
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Tidskriftsartikel (refereegranskat)abstract
- Cobalt (Co) nanoparticles (NPs) are produced in different applications and unintentionally generated at several occupational and traffic settings. Their diffuse dispersion may lead to interactions with humans and aquatic organisms via different exposure routes that include their transformation/dissolution in biological media. This paper has investigated the particle stability and reactivity of Co NPs (dispersed by sonication prior to exposure) interacting with selected individual biomolecules (amino acids, polypeptides, and proteins) in phosphate-buffered saline (PBS). No or minor adsorption of amino acids (glutamine, glutamic acid, lysine, and cysteine) was observed on the Co NPs, independent of the functional group and charge. Instead, phosphate adsorption resulted in the formation of a surface layer (a corona) of Co phosphate. The adsorption of larger biomolecules (polyglutamic acid, polylysine, lysozyme, and mucin) was evident in parallel with the formation of Co phosphate. The dissolution of the Co NPs was rapid as 35-55% of the particle mass was dissolved within the first hour of exposure. The larger biomolecules suppressed the dissolution initially compared to exposure in PBS only, whereas the dissolution was essentially unaffected by the presence of amino acids, with cysteine as an exception. The formation of Co phosphate on the NP surface reduced the protective properties of the surface oxide of the Co NPs, as seen from the increased levels of the released Co when compared with the nonphosphate-containing saline. The results underline the diversity of possible outcomes with respect to surface characteristics and dissolution of Co NPs in biological media and emphasize the importance of surface interactions with phosphate on the NP characteristics and reactivity.
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| 8. |
- Mei, Nanxuan, et al.
(författare)
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Size-separated particle fractions of stainless steel welding fume particles – A multi-analytical characterization focusing on surface oxide speciation and release of hexavalent chromium
- 2018
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Ingår i: Journal of Hazardous Materials. - : Elsevier BV. - 0304-3894 .- 1873-3336. ; 342, s. 527-535
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Tidskriftsartikel (refereegranskat)abstract
- Welding fume of stainless steels is potentially health hazardous. The aim of this study was to investigate the manganese (Mn) and chromium (Cr) speciation of welding fume particles and their extent of metal release relevant for an inhalation scenario, as a function of particle size, welding method (manual metal arc welding, metal arc welding using an active shielding gas), different electrodes (solid wires and flux-cored wires) and shielding gases, and base alloy (austenitic AISI 304L and duplex stainless steel LDX2101). Metal release investigations were performed in phosphate buffered saline (PBS), pH 7.3, 37°, 24 h. The particles were characterized by means of microscopic, spectroscopic, and electroanalytical methods. Cr was predominantly released from particles of the welding fume when exposed in PBS [3–96% of the total amount of Cr, of which up to 70% as Cr(VI)], followed by Mn, nickel, and iron. Duplex stainless steel welded with a flux-cored wire generated a welding fume that released most Cr(VI). Nano-sized particles released a significantly higher amount of nickel compared with micron-sized particle fractions. The welding fume did not contain any solitary known chromate compounds, but multi-elemental highly oxidized oxide(s) (iron, Cr, and Mn, possibly bismuth and silicon).
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| 9. |
- Mei, Nanxuan, et al.
(författare)
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Transfer of Cobalt Nanoparticles in a Simplified Food Web : From Algae to Zooplankton to Fish
- 2021
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Ingår i: Applied Nano. - : MDPI AG. - 2673-3501. ; 2:3, s. 184-205
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Tidskriftsartikel (refereegranskat)abstract
- Cobalt (Co) nanoparticles (NPs) may be diffusely dispersed into natural ecosystems from various anthropogenic sources such as traffic settings and eventually end up in aquatic systems. As environmentally dispersed Co NPs may be transferred through an aquatic food web, this study investigated this transfer from algae (Scendesmus sp.) to zooplankton (Daphnia magna) to fish (Crucian carp, Carassius carassius). Effects of interactions between naturally excreted biomolecules from D. magna and Co NPs were investigated from an environmental fate perspective. ATR-FTIR measurements showed the adsorption of both algae constituents and excreted biomolecules onto the Co NPs. Less than 5% of the Co NPs formed heteroagglomerates with algae, partly an effect of both agglomeration and settling of the Co NPs. The presence of excreted biomolecules in the solution did not affect the extent of heteroagglomeration. Despite the low extent of heteroagglomeration between Co NPs and algae, the Co NPs were transferred to the next trophic level (D. magna). The Co uptake in D. magna was 300 times larger than the control samples (without Co NP), which were not influenced by the addition of excreted biomolecules to the solution. Significant uptake of Co was observed in the intestine of the fish feeding on D. magna containing Co NPs. No bioaccumulation of Co was observed in the fish. Moreover, 10–20% of the transferred Co NP mass was dissolved after 24 h in the simulated gut solution of the zooplankton (pH 7), and 50–60% was dissolved in the simulated gut solution of the fish (pH 4). The results elucidate that Co NPs gain different properties upon trophic transfer in the food web. Risk assessments should hence be conducted on transformed and weathered NPs rather than on pristine particles.
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| 10. |
- Mei, Nanxuan
(författare)
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Transformation/dissolution characteristics of cobalt and welding fume nanoparticles in physiological and environmental media: surface interactions and trophic transfer
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Nanoparticles (NPs) and nanomaterials (NMs) are present everywhere in the environment. They can form both as an act of nature and during human activities. Various kinds of NPs and NMs are engineered for different applications in the ongoing development of nanoscience and technology. Nowadays, concerns have emerged related to potential adverse effects of NPs on human health and the environment. Knowledge related to effects induced by more reactive metal NPs is scarce or even missing in some cases. Such information is crucial for risk assessments. The focus of this doctoral thesis has therefore mainly been placed on reactive metal NPs: stainless steel welding fume particles, cobalt (Co) NPs, and solution combustion synthesized (SCS) Co NPs, to investigate their transformation/dissolution characteristics in environmental and biological media.Environmental interaction studies were performed in terms of adsorption of biomolecules and natural organic matter (NOM) onto the surfaces of the NPs and their influence on dissolution, agglomeration, and size of the NPs in solution. Trophic transfer of Co NPs was investigated in an aquatic food web.The Co NPs rapidly agglomerated and sedimented in solution. Co ions were released from the NPs in both phosphate buffer solution and in freshwater, dissolution processes that were influenced by the adsorption of biomolecules and NOM. The trophic transfer of Co in the aquatic food web was shown to be affected by the extent of both agglomeration and sedimentation. No biomagnification was observed during the trophic transfer, and the addition of excreted biomolecules had no effect on the transfer.The dissolution of stainless steel welding fume particles was studied in PBS. The metal release data could help estimate the risk assessment of stainless steel welding fume particles.
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