| 1. |
- Brobbey, Kofi, et al.
(author)
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Effect of plasma coating on antibacterial activity of silver nanoparticles
- 2019
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In: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 672, s. 75-82
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Journal article (peer-reviewed)abstract
- Silver nanoparticles (NPs) are known to provide antimicrobial properties for surfaces. However, there are environmental concerns due to reports of toxicity after exposure to the environment during or after end-use. Immobilizing silver NPs to the surface of substrates could ensure that particles are readily available for antibacterial activity with limited environmental exposure. A plasma coating on top of silver NPs could improve the adhesion of NPs to a substrate, but it could also impede the release of silver NPs completely. Furthermore, silver has been shown to require direct contact to demonstrate antibacterial activity. This study demonstrates immobilization of silver NPs with plasma coating onto a surface while maintaining its antibacterial properties. Silver NPs are simultaneously synthesized and deposited onto a surface with liquid flame spray aerosol technique followed by hexamethyldisiloxane plasma coating to immobilize the NPs. Atomic force microscope scratch testing is used to demonstrate improved nanoparticle adhesion. Antibacterial activity against gram-negative Escherichia coli is maintained even for plasma coating thicknesses of 195 nm. NP adhesion to the surface is significantly improved. Gram-positive Staphylococcus aureus was found be resistant to all the plasma-coated samples. The results show promise of using plasma coating technology for limiting NP exposure to environment.
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| 2. |
- Brobbey, Kofi, et al.
(author)
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High-speed production of antibacterial fabrics using liquid flame spray
- 2019
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In: Textile research journal. - : SAGE Publications Ltd. - 0040-5175 .- 1746-7748. ; 90:5-6, s. 503-511
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Journal article (peer-reviewed)abstract
- Healthcare associated infections (HAIs) are known as one of the major problems of the modern healthcare system, which result in additional cost and mortality. It has also been shown that pathogenic bacteria are mostly transferred via surfaces in healthcare settings. Therefore, antibacterial surfaces, which include fabrics and textiles, can be used in a healthcare environment to reduce the transfer of pathogenic bacteria, hence reducing HAIs. Silver nanoparticles have been shown to have broad spectrum antibacterial properties, and therefore they have been incorporated into fabrics to provide antibacterial functionality. Liquid flame spray (LFS) nanoparticle synthesis allows nanoparticles to be produced and deposited on surfaces at speeds up to and beyond 300 m/min. Herein, LFS is used to deposit silver nanoparticles onto two fabrics that are commonly used in the hospital environment with the aim of producing antibacterial fabrics. A thin plasma coating on top of the fabrics after silver deposition is used to improve nanoparticle adhesion. Fabrics coated with silver nanoparticles demonstrated antibacterial properties against Escherichia coli. Nanoparticle imaging and surface chemical characterization are performed using scanning electron microscopy and X-ray photoelectron spectroscopy. The highlights of this research are as follows: • high-speed synthesis and deposition of silver nanoparticles on fabrics; • plasma coating onto fabrics with silver nanoparticles; • antibacterial fabrics for potential use in healthcare environments.
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| 3. |
- Ejenstam, Lina, 1985-, et al.
(author)
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Long-term corrosion protection by a thin nano-composite coating
- 2015
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In: Applied Surface Science. - : Elsevier. - 0169-4332 .- 1873-5584. ; 357:Part B, s. 2333-2342
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Journal article (peer-reviewed)abstract
- We report and discuss the corrosion protective properties of a thin nano-composite coating system consisting of an 11μm thick polyester acrylate (PEA) basecoat, covered by an approximately 1-2μm thick layer of TiO2 nanoparticles carrying a 0.05μm thick hexamethyl disiloxane (HMDSO) top coat. The corrosion protective properties were evaluated on carbon steel substrates immersed in 3wt% NaCl solution by open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS) measurements. The protective properties of each layer, and of each pair of layers, were also evaluated to gain further understanding of the long-term protective properties offered by the nano-composite coating. The full coating system showed excellent corrosion protective properties in the corrosive environment of 3wt% NaCl-solution for an extended period of 100 days, during which the coating impedance, at the lower frequency limit (0.01Hz), remained above 108 Ωcm2. We suggest that the excellent corrosion protective properties of the complete coating system is due to a combination of (i) good adhesion and stability of the PEA basecoat, (ii) the surface roughness and the elongated diffusion path provided by the addition of TiO2 nanoparticles, and (iii) the low surface energy provided by the HMDSO top coat.
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| 4. |
- Eriksson, Mimmi, et al.
(author)
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Effects of liquid surface tension on gas capillaries and capillary forces at superamphiphobic surfaces
- 2023
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In: Scientific Reports. - : Springer Nature. - 2045-2322. ; 13:1
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Journal article (peer-reviewed)abstract
- The formation of a bridging gas capillary between superhydrophobic surfaces in water gives rise to strongly attractive interactions ranging up to several micrometers on separation. However, most liquids used in materials research are oil-based or contain surfactants. Superamphiphobic surfaces repel both water and low-surface-tension liquids. To control the interactions between a superamphiphobic surface and a particle, it needs to be resolved whether and how gas capillaries form in non-polar and low-surface-tension liquids. Such insight will aid advanced functional materials development. Here, we combine laser scanning confocal imaging and colloidal probe atomic force microscopy to elucidate the interaction between a superamphiphobic surface and a hydrophobic microparticle in three liquids with different surface tensions: water (73 mN m−1), ethylene glycol (48 mN m−1) and hexadecane (27 mN m−1). We show that bridging gas capillaries are formed in all three liquids. Force-distance curves between the superamphiphobic surface and the particle reveal strong attractive interactions, where the range and magnitude decrease with liquid surface tension. Comparison of free energy calculations based on the capillary menisci shapes and the force measurements suggest that under our dynamic measurements the gas pressure in the capillary is slightly below ambient.
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| 5. |
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| 6. |
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| 7. |
- Ferreira, Ana R. V., et al.
(author)
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Comparison of different coating techniques on the properties of FucoPol films
- 2017
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In: International Journal of Biological Macromolecules. - : Elsevier BV. - 0141-8130 .- 1879-0003. ; 103, s. 268-274
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Journal article (peer-reviewed)abstract
- Plasma deposition, liquid flame spray (LFS) and atomic layer deposition (ALD) were used to form inorganic coatings in new exopolysaccharide (FucoPol) biodegradable films. Coated films were characterised in terms of surface, optical and barrier properties in order to evaluate their potential use in food packaging. FucoPol films presented dense and homogeneous surface with instant water contact angle of 95̊. Plasma deposition of perfluorohexane (PFH) on FucoPol surface has not shown significant improvement in the hydrophobic behaviour over the time. The FucoPol coating of SiO2 nanoparticles deposited by LFS and plasma deposition of PFH have shown higher instant water contact angle (135°) caused by coating surface roughness, but this hydrophobic behaviour was not stable over time. FucoPol films coated only with TiO2 deposited by ALD and combination of that with plasma deposition of PFH have shown stable water contact angle during time (90̊ and 115̊, respectively), transparency in the same order of magnitude and significantly lower permeability to water vapour (3.45 × 10−11 mol/m s Pa and 3.45 × 10−11 mol/m s Pa when compared to uncoated films with 5.32 × 10−11 mol/m s Pa). Moreover, films coated with TiO2-PFH have also shown a permeability to oxygen of 1.70 × 10−16 molm/m2s Pa which is 67% lower than uncoated films.
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| 8. |
- Flynn, Michael J., et al.
(author)
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Modelling cloud processing of aerosol during the ACE-2 HILLCLOUD experiment
- 2000
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In: Tellus. Series B: Chemical and Physical Meteorology. - : Stockholm University Press. - 0280-6509. ; 52:2, s. 779-800
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Journal article (peer-reviewed)abstract
- A numerical model has been used to simulate the conditions observed during the ACE-2 Hillcloud experiment and to study the processes which may be taking place. The model incorporates gas phase chemistry of sulphur and nitrogen compounds upstream of the cloud, and the interaction of aerosol, precursor trace gases and oxidants within the cloud. Gas phase and aerosol inputs to the model have been provided from measurements made in the field. Dynamics of the air flow over the hill consisted of simple prescribed dynamics based on wind speed measurements, and also for some cases modelled dynamics. In this modelling study, it was found that during clean case studies particles down to 40-55 nm diameter were activated to form cloud droplets, the total number of droplets formed ranging from 200 to 400 drops/cm3. Significant modification of the aerosol spectra due to cloud processing was observed. In polluted cases particles down to 65-80 nm diameter were activated to form cloud droplets, the total number of droplets ranging from 800 to 2800 drops/cm3. Modification of the aerosol spectra due to cloud processing was slight. In all cases, changes in the aerosol spectra were due to both the uptake of HNO3, HCl, NH3 and SO2 from the gas phase, (the SO2 being oxidised to sulphate) and the repartitioning of species such as HNO3, HCl, and NH3 from larger particles onto smaller ones. Modelling results have been compared with observations made. Modelled droplet numbers are typically within 20% of the best measured values. The mode of the droplet distribution typically around 10-20 μm for clean cases and 4-8 μm for polluted cases was found to be in good agreement with the measured values of 10-25 μm for clean cases, but not in such good agreement for polluted cases. Measurements of upwind and interstitial aerosol distributions showed that the smallest particles activated were 30 and 50 nm for clean and polluted cases respectively, slightly smaller than the model values quoted above. Measured upwind and downwind aerosol spectra showed similar modification to that predicted by the model in eight out of the eleven model runs carried out. Chemistry measurements also give general evidence for both the uptake of species from the gas phase, and repartitioning of species from large particles onto smaller ones, though comparisons for individual cases are more difficult. From this modelling study, it can be concluded that in general, in the remote environment the exchange of hydrochloric acid, nitric acid and ammonia between aerosol particles and take up from the gas phase in the vicinity of cloud may be a very important mechanism in regulating the evolution of the aerosol spectrum. Further, the much more linear relationship between cloud droplet and accumulation mode aerosol number, which was observed in the measurements made during the ACE-2 HILLCLOUD project is supported by these modelling results. The implications of this for the indirect effect will be explored in future work.
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| 9. |
- Haapanen, Janne, et al.
(author)
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Binary TiO2/SiO2 nanoparticle coating for controlling the wetting properties of paperboard
- 2015
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In: Materials Chemistry and Physics. - : Elsevier BV. - 0254-0584 .- 1879-3312. ; 149, s. 230-237
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Journal article (peer-reviewed)abstract
- We introduce a flame based aerosol method to fabricate thin films consisting of binary TiO2/SiO2 nanoparticles deposited directly from the flame onto the paperboard. Nanocoatings were prepared with Liquid Flame Spray (LFS) in a roll-to-roll process with the line speed of 50 m/min. Surface wetting behavior of nanocoated paperboard was studied for different Ti/Si ratios in the precursor, affecting TiO2/SiO2 ratio in the coating. Wettability could be adjusted to practically any water contact angle between 10 and 160° by setting the Ti/Si ratio in the liquid precursor. Structure of the two component nanocoating was analysed with FE-SEM, TEM, EDS, XPS and XRD. The porous thin film coating was concluded to consist of ca. 10 nm sized mixed oxide nanoparticles with segregated TiO2 and SiO2 phases. Accumulation of carbonaceous compounds on the surface was seen to be almost linearly dependent on the Ti/Si ratio, indicating of each species being exposed in corresponding amount. However, wetting of the surface was observed to follow merely an S-shaped curve, caused by the roughness of the nanocoated surface. Reasons for the observed superhydrophobicity and superhydrophilicity of these binary nanocoatings on paperboard are discussed.
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| 10. |
- Harra, Juha, et al.
(author)
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Characteristics of nFOG, an aerosol-based wet thin film coating technique
- 2018
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In: JCT Research. - : Springer Science and Business Media LLC. - 1547-0091 .- 2168-8028 .- 1935-3804. ; 15:3, s. 623-632
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Journal article (peer-reviewed)abstract
- An atmospheric pressure aerosol-based wet thin film coating technique called the nFOG is characterized and applied in polymer film coatings. In the nFOG, a fog of droplets is formed by two air-assist atomizers oriented toward each other inside a deposition chamber. The droplets settle gravitationally and deposit on a substrate, forming a wet film. In this study, the continuous deposition mode of the nFOG is explored. We determined the size distribution of water droplets inside the chamber in a wide side range of 0.1–100 µm and on the substrate using aerosol measurement instruments and optical microscopy, respectively. The droplet size distribution was found to be bimodal with droplets of approximately 30–50 µm contributing the most to the mass of the formed wet film. The complementary measurement methods allow us to estimate the role of different droplet deposition mechanisms. The obtained results suggest that the deposition velocity of the droplets is lower than the calculated terminal settling velocity, likely due to the flow fields inside the chamber. Furthermore, the mass flux of the droplets onto the substrate is determined to be in the order of 1 g/m3s, corresponding to a wet film growth rate of 1 µm/s. Finally, the nFOG technique is demonstrated by preparing polymer films with thicknesses in the range of approximately 0.1–20 µm.
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