| 1. |
- Andersson Trojer, Markus, 1981, et al.
(författare)
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Directed self-assembly of silica nanoparticles in ionic liquid-spun cellulose fibers
- 2019
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 1095-7103 .- 0021-9797. ; 553, s. 167-176
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Tidskriftsartikel (refereegranskat)abstract
- The application range of man-made cellulosic fibers is limited by the absence of cost- and manufacturing-efficient strategies for anisotropic hierarchical functionalization. Overcoming these bottlenecks is therefore pivotal in the pursuit of a future bio-based economy. Here, we demonstrate that colloidal silica nanoparticles (NPs), which are cheap, biocompatible and easy to chemically modify, enable the control of the cross-sectional morphology and surface topography of ionic liquid-spun cellulose fibers. These properties are tailored by the silica NPs’ surface chemistry and their entry point during the wet-spinning process (dope solution DSiO2 or coagulation bath CSiO2). For CSiO2-modified fibers, the coagulation mitigator dimethylsulphoxide allows for controlling the surface topography and the amalgamation of the silica NPs into the fiber matrix. For dope-modified fibers, we hypothesize that cellulose chains act as seeds for directed silica NP self-assembly. This results for DSiO2 in discrete micron-sized rods, homogeneously distributed throughout the fiber and for glycidoxy-surface modified DSiO2@GLYEO in nano-sized surface aggregates and a cross-sectional core-shell fiber morphology. Furthermore, the dope-modified fibers display outstanding strength and toughness, which are both characteristic features of biological biocomposites.
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| 2. |
- Gårdebjer, Sofie, 1985, et al.
(författare)
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The impact of interfaces in laminated packaging on transport of carboxylic acids
- 2016
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Ingår i: Journal of Membrane Science. - : Elsevier BV. - 0376-7388 .- 1873-3123. ; 518, s. 305-312
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Tidskriftsartikel (refereegranskat)abstract
- The permeability of oleic and acetic acid through low density polyethylene (LDPE) and ethylene acrylic acid (EAA) have been measured using diffusion cells. In addition, the permeability through combinations of LDPE and EAA in the form of laminates with different numbers of layers has been determined. Oleic acid shows an almost 30 times higher permeability compared to acetic acid, which was partly explained by the adsorption of oleic acid to the film surface during the permeability experiment. In addition, the permeability is lower for both oleic and acetic acid in the laminates compared to the pure films. The decreased permeability can be explained by the presence of crystalline domains close to the interface. This is supported by SAXS data which suggests an ordering of polymer chains in the EAA film close to the interface. In summary, the results show that it is possible to create barrier materials with decreased permeability, which is interesting for example in the packaging industry.
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| 3. |
- Pihl, Maria, 1978, et al.
(författare)
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Silica-based diffusion probes for use in FRAP and NMR-diffusometry
- 2019
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Ingår i: Journal of Dispersion Science and Technology. - : Informa UK Limited. - 0193-2691 .- 1532-2351. ; 40:4, s. 555-562
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Tidskriftsartikel (refereegranskat)abstract
- Development of multi-purpose probes for mass transport measurements is of importance to gain knowledge in diffusional behaviour in heterogeneous structures such as food, hygiene or pharamceuticals. By combining different techniques, such as Fluorescence Recovery After Photobleaching (FRAP) and Nuclear Magnetic Resonance Diffusometry (NMR-d), information of both local and global diffusion can be collected and used to gain insights on for example material heterogeneities and probe-material interactions. To obtain a FRAP-responsive probe, fluorescent silica particles were produced using fluorescent preconjugates added in a modified Stöber process. A NMR-d responsive moiety was introduced by derivatizing the fluorescent silica particles with polyethylene glycol. The particle size distributions were determined by dynamic light scattering and transmission electron microscopy and these measurements were compared to value extrapolated from diffusion measurements using FRAP and NMR-d. The good agreement between the FRAP and NMR-d measurements demonstrates the potential of multi-purpose probes for future applications concerning mass transport at local and global scale simultaneously. © 2018, © 2018 The Author(s).
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| 4. |
- Argyri, Smaragda Maria, 1994, et al.
(författare)
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Contact-free measurement of surface tension on single droplet using machine learning and acoustic levitation
- 2023
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 1095-7103 .- 0021-9797. ; 640, s. 637-646
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Tidskriftsartikel (refereegranskat)abstract
- Hypothesis Acoustic levitation provides the possibility to deform levitated droplets in a controllable, and quantifiable manner, thus offering a means to measure the surface tension of a liquid droplet based on its deviation from sphericity. However, for new generation of multi-source and highly stable acoustic levitators, no model relates the acoustic pressure field to the deformation and surface tension. Utilizing a machine learning algorithm is expected to identify correlations between the experimental data without any set preconditions. Experiments A series of aqueous surfactant solutions with a large range of surface tensions were prepared, and evaporated under levitation, while the acoustic pressure was varied. A dataset of over 50,000 images was used for the training and evaluation of the machine learning algorithm. Prior to that, the machine learning approach was validated on in silico data that also included artificial noise. Findings We achieved high accuracy in predicting the surface tension of single standing droplets (±0.88 mN/m), and we surpassed certain physical conditions related to the size, and shape of the suspended samples that simpler theoretical models are subject to.
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| 5. |
- Argyri, Smaragda Maria, 1994, et al.
(författare)
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Customized and high-performing acoustic levitators for contact-free experiments
- 2024
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Ingår i: Journal of Science: Advanced Materials and Devices. - 2468-2284 .- 2468-2179. ; 9:3
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Tidskriftsartikel (refereegranskat)abstract
- Acoustic levitators are becoming an increasingly common research instrumentation for contact-free, lab-in-a-droplet studies. Recently, levitators that employ multiple, small, ultrasonic transducers have gained popularity, given their low price, temperature and spatial stability, low voltage, and accessibility. Yet, the current state-of-the-art device, TinyLev, presents limitations for certain applications in terms of stability, strength, and compactness. Herein, we developed three new levitators and evaluated the effect of the construction parameters (e.g., distance of opposing arrays, number and arrangement of transducers, etc.) on their performance. Compared to TinyLev, the best performing levitator from this work had half the number of transducers while presenting 1.7 and 3.5 times higher levitation capacity along the horizontal and vertical configurations, respectively, while the horizontal and vertical stability of a levitated object was improved 4.7 and 2.0 times, respectively. Additionally, we present a direct means to evaluate the acoustic radiation net force acting on a deformable object for uniaxial levitators, without the use of a microphone or a schlieren deflectometer for this type of levitators. The theoretical and experimental observations provide insights for adapting the acoustic levitator design for specific applications. Finally, we developed an open-source software which allows the evaluation of the acoustic pressure field generated by customized designs and provides the necessary files for 3D printing the scaffold of the levitator. This study aims to increase accessibility and promote further developments in contact-free experiments.
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| 6. |
- Baglioni, M., et al.
(författare)
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Nanostructured fluids from degradable nonionic surfactants for the cleaning of works of art from polymer contaminants
- 2014
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Ingår i: Soft Matter. - : Royal Society of Chemistry (RSC). - 1744-6848 .- 1744-683X. ; 10:35, s. 6798-6809
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Tidskriftsartikel (refereegranskat)abstract
- Nanostructured fluids containing anionic surfactants are among the best performing systems for the cleaning of works of art. Though efficient, their application may result in the formation of a precipitate, due to the combination with divalent cations that might leach out from the artifact. We propose here two new aqueous formulations based on nonionic surfactants, which are non-toxic, readily biodegradable and insensitive to the presence of divalent ions. The cleaning properties of water-nonionic surfactant-2-butanone (MEK) were assessed both on model surfaces and on a XIII century fresco that could not be cleaned using conventional methods. Structural information on nanofluids has been gathered by means of small-angle neutron scattering, dynamic light scattering and nuclear magnetic resonance with diffusion monitoring. Beside the above-mentioned advantages, these formulations turned out to be considerably more efficient in the removal of polymer coatings than those based on anionic surfactants. Our results indicate that the cleaning process most likely consists of two steps: initially, the polymer film is swollen by the MEK dissolved in the continuous domain of the nanofluid; in the second stage, surfactant aggregates come into play by promoting the removal of the polymer film with a detergency-like mechanism. The efficiency can be tuned by the composition and nature of amphiphiles and is promoted by working as close as possible to the cloud point of the formulation, where the second step proceeds at maximum rate.
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| 7. |
- Barai, Manas, et al.
(författare)
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Interfacial and Aggregation Behavior of Dicarboxylic Amino Acid-Based Surfactants in Combination with a Cationic Surfactant
- 2019
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 35:47, s. 15306-15314
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Tidskriftsartikel (refereegranskat)abstract
- The interfacial and micellization behavior of three dicarboxylic amino acid-based anionic surfactants, abbreviated as AAS (N-dodecyl derivative of -aminomalonate, -aspartate, and -glutamate) in combination with hexadecyltrimethylammonium bromide (HTAB) were investigated by surface tension, conductance, UV–vis absorption/emission spectroscopy, dynamic light scattering (DLS), and viscosity studies. Critical micelle concentration (CMC) values of the surfactant mixtures are significantly lower than the predicted values, indicating associative interaction between the components. Surface excess, limiting molecular area, surface pressure at the CMC, and Gibbs free energy indicate spontaneity of the micellization processes compared to the pure components. CMC values were also determined from the sigmoidal variation in the plot of micellar polarity and pyrene UV–vis absorption/emission intensities with surfactant concentration. The aggregation number, determined by static fluorescence quenching method, increases with decreasing mole fraction of the AAS (αAAS), where the micelles are mainly dominated by the HTAB molecules. The size of the micelle increases with decreasing αAAS, leading to the formation of larger and complex aggregates, as also supported by the viscosity studies. Micelles comprising 20–40 mol % AAS are highly viscous, in consonance with their sizes. Some of the mixed surfactant systems show unusual viscosity (shear thickening and increased viscosity with increasing temperature). Such mixed surfactant systems are considered to have potential in gel-based drug delivery and nanoparticle synthesis.
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| 8. |
- Baresel, Christian, et al.
(författare)
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Functionalized magnetic particles for water treatment
- 2019
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Ingår i: Heliyon. - : Elsevier BV. - 2405-8440. ; 5:8
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we have taken the concept of water treatment by functionalized magnetic particles one step forward by integrating the technology into a complete proof of concept, which included the preparation of surface modified beads, their use as highly selective absorbents for heavy metals ions (Zinc, Nickel), and their performance in terms of magnetic separation. The separation characteristics were studied both through experiments and by simulations. The data gathered from these experimental works enabled the elaboration of various scenarios for Life Cycle Analysis (LCA). The LCA showed that the environmental impact of the system is highly dependent on the recovery rate of the magnetic particles. The absolute impact on climate change varied significantly among the scenarios studied and the recovery rates. The results support the hypothesis that chelation specificity, magnetic separation and bead recovery should be optimized to specific targets and applications.
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| 9. |
- Bonini, M., et al.
(författare)
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Adsorption of Amino Acids and Glutamic Acid-Based Surfactants on Imogolite Clays
- 2017
-
Ingår i: Langmuir. - : American Chemical Society (ACS). - 1520-5827 .- 0743-7463. ; 33:9, s. 2411-2419
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Tidskriftsartikel (refereegranskat)abstract
- Aluminum oxide surfaces are of utmost interest in different biotech applications, in particular for their use as adjuvants (i.e., booster of the immune response against infectious agents in vaccines production). In this framework, imogolite clays combine the chemical flexibility of an exposed alumina surface with 1D nanostructure. This work reports on the interaction between amino acids and imogolite, using turbidimetry, zeta-potential measurements, and Fourier transform infrared spectroscopy as main characterization tools. Amino acids with different side chain functional groups were investigated, showing that glutamic acid (Glu) has the strongest affinity for the imogolite surface. This was exploited to prepare a composite material made of a synthetic surfactant bearing a Glu polar head and a hydrophobic C-12 alkyl tail, adsorbed onto the surface of imogolite. The adsorption of a model drug (rhodamine B isothiocyanate) by the hybrid was evaluated both in water and in physiological saline conditions. The findings of this paper suggest that the combination between the glutamate headgroup and imogolite represents a promising platform for the fabrication of hybrid nanostructures with tailored functionalities.
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| 10. |
- Bordes, Romain, 1981, et al.
(författare)
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Adsorption of Dianionic Surfactants Based on Amino Acids at Different Surfaces Studied by QCM-D and SPR
- 2010
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 1520-5827 .- 0743-7463. ; 26:13, s. 10935-10942
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Tidskriftsartikel (refereegranskat)abstract
- The adsorption of three dicarboxylic amino acid-based surfactants, disodium N-lauroylaminomalonate, disodium N-lauroylaspartate, and disodium N-lauroylglutamate, has been studied by surface plasmon resonance (SPR) and the quartz crystal microbalance with dissipation monitoring (QCM-D). These surfactants have high cmc values, which means that the unimer concentration is high at the plateau value of adsorption. This gives rise to a considerable "bulk effect", which must be deducted from the observed value in order to obtain the true value of the adsorbed amount. In this article, we show how this can be done for the QCM-D technique. Adsorption is studied on silica, gold, gold hydrophobized by a self-assembled layer of an alkane thiol, and hydroxyapatite. Adsorption on hydroxyapatite differs very much among the three surfactants, with the aspartate derivative giving the strongest and the glutamate giving the weakest adsorption. This difference is explained as the difference in ability of the dicarboxylic amphiphiles to chelate calcium in the crystal lattice.
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| 11. |
- Bordes, Romain, 1981, et al.
(författare)
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Amino acid-based surfactants
- 2009
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Ingår i: Encyclopedia of Surface and Colloid Science. ; , s. 1-17
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 12. |
- Bordes, Romain, 1981, et al.
(författare)
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Amino acid-based surfactants - Do they deserve more attention?
- 2015
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Ingår i: Advances in Colloid and Interface Science. - : Elsevier BV. - 0001-8686. ; 222, s. 79-91
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Forskningsöversikt (refereegranskat)abstract
- The 20 standard amino acids (together with a few more that are not used in the biosynthesis of proteins) constitute a versatile tool box for synthesis of surfactants. Anionic, cationic and zwitterionic amphiphiles can be prepared and surfactants with several functional groups can be obtained by the proper choice of starting amino acid. This review gives examples of procedures used for preparation and discusses important physicochemical properties of the amphiphiles and how these can be taken advantage of for various applications. Micelles with a chiral surface can be obtained by self-assembly of enantiomerically pure surfactants and such supramolecular chirality can be utilized for asymmetric organic synthesis and for preparation of mesoporous materials with chiral pores. Surfactants based on amino acids with two carboxyl groups are effective chelating agents and can be used as collectors in mineral ore flotation. A surfactant based on cysteine readily oxidizes into the corresponding cystine compound, which can be regarded as a gemini surfactant. The facile and reversible cysteine-cystine transformation has been taken advantage of in the design of a switchable surfactant. A very attractive aspect of surfactants based on amino acids is that the polar head-group is entirely natural and that the linkage to the hydrophobic tail, which is often an ester or an amide bond, is easily cleaved. The rate of degradation can be tailored by the structure of the amphiphile. The ester linkage in betaine ester surfactants is particularly susceptible to alkaline hydrolysis and this surfactant type can be used as a biocide with short-lived action. This paper is not intended as a full review on the topic. Instead it highlights concepts that are unique to amino acid-based surfactants and that we believe can have practical implications.
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| 13. |
- Bordes, Romain, 1981, et al.
(författare)
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Counterion Specificity of Surfactants Based on Dicarboxylic Amino Scids
- 2009
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 1095-7103 .- 0021-9797. ; 338:2, s. 529-536
-
Tidskriftsartikel (refereegranskat)abstract
- The behavior in solution of a series of amino acid-based surfactants having two carboxyl groups separated by a spacer of one, two, or three carbon atoms has been investigated. All three surfactants precipitated on addition of acid, but the aspartate surfactant (with a two-carbon spacer) was considerably more resistant to precipitation than the aminomalonate surfactant (one-carbon spacer) and the glutamate surfactant (three-carbon spacer). The interactions with the monovalent counterions lithium, sodium, and potassium were investigated by conductivity. It was found that lithium ions bound the strongest and potassium ions the weakest to the surfactant micelles. These results were interpreted using the hard and soft acid-base theory. Comparing the three surfactants with respect to binding of one specific counterion, sodium, showed that the aminomalonate surfactant, which has the shortest spacer, bound sodium ions the strongest and the glutamate surfactant, which has the longest spacer, had the lowest affinity for the counterion. Also that could be explained by the hard and soft acid-base concept. The glutamate surfactant was found to be considerably more resistant to calcium ions than the two other surfactants. This was attributed to this surfactant forming an intermolecular complex with the calcium ion at the air-water interface while the aminomalonate and the aspartate surfactants, with shorter distance between the carboxylate groups could form six- and seven-membered intramolecular calcium complexes.
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| 14. |
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| 15. |
- Bordes, Romain, 1981, et al.
(författare)
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Nanocellulose: What used to be cellulose micelles
- 2017
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Ingår i: Current Opinion in Colloid and Interface Science. - : Elsevier BV. - 1359-0294 .- 1879-0399. ; 29, s. A1-A2
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 16. |
- Bordes, Romain, 1981, et al.
(författare)
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Physical chemical characteristics of dicarboxylic amino acid-based surfactants
- 2011
-
Ingår i: Colloids and Surfaces A: Physicochemical and Engineering Aspects. - : Elsevier BV. - 1873-4359 .- 0927-7757. ; 391:1-3, s. 32-41
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Tidskriftsartikel (refereegranskat)abstract
- Three dicarboxylic amino acid-based surfactants, the disodium salts of dodecylaminomalonic acid, dodecylaspartic acid and dodecylglutamic acid, having one, two and three carbon atoms, respectively between the carboxyl groups, have been studied with respect to solution behavior and adsorption at the air-water interface, as well as on a number of solid surfaces. The dicarboxylic surfactants had 4-5 times higher CMC than the dodecylglycinate, which only has one carboxyl group. The role of the amide bond for the self-assembly process was assessed by comparing sodium dodecylglycinate with sodium dodecylsarcosinate. The former can build hydrogen bonds between adjacent molecules via the amide groups but the latter which has an N-methyl group, cannot, It was found that the ability to form intermolecular hydrogen bonds lead to tighter packing both at the air-water interface and in micelles. The CMC was not affected, however. Dodecylglutamate was found to be very calcium tolerant compared to the two other dicarboxylic surfactants. This was attributed to differences in chelating calcium. Whereas dodecylaminomalonate and dodecylaspartate can form intramolecular chelates with calcium ions, dodecylglutamate prefers to form an intermolecular complex. Formation of an intermolecular complex leads to tight packing at the air-water interface and to very low surface tension values. The ability to form intramolecular chelates is advantageous for adsorption at calcium-containing surfaces, however. Whereas dodecylaminomalonate and, in particular, dodecylaspartate adsorb strongly on hydroxyapatite, dodecylglutamate shows very weak adsorption. On other surfaces, where there exist no specific interactions involving the surfactant headgroup, the three surfactants gave similar adsorption behavior.
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| 17. |
- Bordes, Romain, 1981, et al.
(författare)
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Role of an amide bond for self-assembly of surfactants
- 2010
-
Ingår i: Langmuir. - : American Chemical Society (ACS). - 1520-5827 .- 0743-7463. ; 26:5, s. 3077-3083
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Tidskriftsartikel (refereegranskat)abstract
- Self-assembly in Solution and adsorption at the air-water interface and at Solid Surfaces were investigated for two amino-acid-based surfactants with conductimetry, NMR, tensiometry, quartz crystal microbalance with monitoring or the dissipation (QCM-D), and surface plasmon resonance (SPR). The surfactants studied were sodium N-lauroylglycinate and sodium N-lauroylsarcosinate, differing only in a methyl group on the amide nitrogen for the sarcosinate. Thus, the glycinate but not the surfactant is capable of forming intermolecular hydrogen bonds via the amide group. It was found that the amide bond, N-methylated or not, gave a substantial contribution to the hydrophilicity of the amphiphile. The ability to form intermolecular hydrogen bonds led to tighter packing at the air-water interface and ill a hydrophobic surface. It also increased the tendency for precipitation as all acid-soap pair oil addition of acid. Adsorption of the surfactants at a gold surface Was also investigated and gave unexpected results. The sarcosine-based surfactant seemed to give bilayer adsorption, while the glycine derivative adsorbed as a monolayer.
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| 18. |
- Bordes, Romain, 1981, et al.
(författare)
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Separation of Bulk Effects and Bound Mass during Adsorption of Surfactants Probed by Quartz Crystal Microbalance with Dissipation: Insight into Data Interpretation
- 2010
-
Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 82:21, s. 9116-9121
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Tidskriftsartikel (refereegranskat)abstract
- The assessment of adsorbed surfactant mass by quartz crystal microbalance with dissipation (QCM-D) monitoring is often complicated due to large bulk responses, particularly for surfactants with high critical micelle concentration (CMC). We present in this work means to interpret QCM-D data that enables the response from the bulk contribution to be separated from the response originating from adsorbed mass. Adsorption of two surfactants, Triton X100 and C12AspNa(2) with low and high CMCs, respectively, at the gold-liquid interface surface has been evaluated. Two different approaches to quantify the bulk response are compared. The first approach involves the use of a nonadsorbing surface (silica), yielding a calibration curve for the concentration dependent bulk response. The second method is based on the fact that the overtone-dependent QCM-D response that originates from changes in the bulk differs from that induced by the adsorbed layer of the surfactants. Under the reasonable assumption that the bulk solution and the adsorbed surfactants can be treated as a Newtonian liquid and an acoustically rigid film, it is demonstrated that the bulk contribution can be quantified without control measurements involving inert surfaces. An excellent agreement between the two methods is reported.
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| 19. |
- Bridarolli, Alexandra, et al.
(författare)
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Evaluation of the Adhesion and Performance of Natural Consolidants for Cotton Canvas Conservation
- 2018
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society. - 1944-8244 .- 1944-8252. ; 10:39, s. 33652-33661
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Tidskriftsartikel (refereegranskat)abstract
- Recent developments in paper and canvas conservation have seen the introduction of nanocellulose (NC) as a compatible treatment for the consolidation of historical cellulosic artifacts and manuscripts. However, as part of the assessment of these new materials for canvas consolidation, the adhesion of the consolidation treatment (which takes place between the applied material and the substrate) has not yet been evaluated, and as a result, it is poorly understood by both the scientific and conservation communities. After evaluating the potential of NC treatments for the consolidation of cotton painting canvas, we investigate a route to promote the interaction between the existing canvas and the nanocellulose treatment, which is in our case made of cellulose nanofibrils (CNF). This was carried out by introducing a cationic polymer, polyamidoamine-epichlorohydrin (PAAE), as an intermediate layer between the canvas and the CNF. The morphological, chemical, and mechanical evaluation of the canvas samples at different relative humidity (RH) levels demonstrated how the adhesion of the added PAAE layer is a dominant factor in the consolidation process. Improvement in the coating of canvas single fibers by the CNF, higher adhesion energy between the canvas fibers and the CNF treatment, and finally overall stronger canvas reinforcement were observed following the introduction of PAAE. However, an increase in mechanical response to moisture sorption and desorption was also observed for the PAAE-treated canvases. Overall, this study shows the complexity of such systems and, as such, the relevance of using a multiscale approach for their assessment.
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| 20. |
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| 21. |
- Capron, Isabelle, et al.
(författare)
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Behavior of nanocelluloses at interfaces
- 2017
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Ingår i: Current Opinion in Colloid and Interface Science. - : Elsevier BV. - 1359-0294 .- 1879-0399. ; 29, s. 83-95
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Forskningsöversikt (refereegranskat)abstract
- Despite being non-surface active, nanocelluloses position efficiently at interfaces, already at very low concentration. This behavior has lately triggered a strong interest in the cellulose and colloids communities. This review reports the recent developments on the use of nanocelluloses at interfaces and highlights the fundamental principles governing the high efficiency observed in reinforcing the boundary between two phases. The use of nanocelluloses as emulsifier and emulsion stabilizer is first discussed, and the structural properties of nanocelluloses such as aspect ratio and surface properties are correlated with the high efficiency in forming colloidally-stable multiphase systems. Then, the behavior at the air/water interface is presented and the most recent advances are reviewed with focus on the surface free energy of nanocelluloses and their role in the interfacial self-assembly process.
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| 22. |
- Chauhan, Vinay, 1985, et al.
(författare)
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A reverse degradation vs. temperature relationship for a carbonate-containing gemini surfactant
- 2018
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 1095-7103 .- 0021-9797. ; 531, s. 189-193
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Tidskriftsartikel (refereegranskat)abstract
- The rate of hydrolysis of cleavable surfactant is known to have a strong temperature dependence. A nonionic gemini surfactant with a readily hydrolysable carbonate bond as spacer unit has been synthesized and evaluated. A carbonate linkage is special as spacer unit in a gemini surfactant because the hydrolysis results in two identical molecules, in this case a hydroxy-substituted nonionic surfactant, along with carbon dioxide. The critical micelle concentration for the gemini surfactant was an order of magnitude lower than that of the degradation product. The degradation of the new surfactant and specifically the effect of temperature on the rate of hydrolysis was investigated in detail. It was found that alkaline hydrolysis was rapid at 15 °C but very slow at 30 °C, i.e. there was a reverse relationship between rate of hydrolysis and temperature. The same behavior was found for monomeric nonionic carbonate-containing surfactants that were synthesized and used as references. This unusual behavior, which can be of practical use, is explained by the reverse solubility vs. temperature profile for amphiphiles carrying a polyoxyethylene chain.
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| 23. |
- Chelazzi, D., et al.
(författare)
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The use of surfactants in the cleaning of works of art
- 2020
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Ingår i: Current Opinion in Colloid and Interface Science. - : Elsevier BV. - 1359-0294 .- 1879-0399. ; 45, s. 108-123
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Forskningsöversikt (refereegranskat)abstract
- Surfactants have been historically used for cleaning artifacts, but it was only in the last decades that serendipitous approaches were replaced by research in the field of soft matter and colloid science. Surfactants are components of nanostructured fluids, which were assessed for the removal of soil and aged coatings from paintings and are fundamental in processes that range from the inclusion of grime in micelles to the swelling and dewetting of polymer layers. Intriguing aspects involve the synthesis and use of biodegradable and self-cleavable surfactants, and the confinement of nanostructured fluids in gels, which boost the selectiveness of cleaning interventions. The performances of these advanced systems surpass those of traditional cleaning materials such as solvent blends and thickeners. The most important results are here reviewed and future perspectives given. Besides granting the transfer of cultural heritage to future generations, advanced cleaning materials are relevant to transversal fields, such as detergency, cosmetics, and drug delivery.
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| 24. |
- Cheng, J., et al.
(författare)
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One-pot synthesis of porous gold nanoparticles by preparation of Ag/Au nanoparticles followed by dealloying
- 2013
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Ingår i: Colloids and Surfaces A: Physicochemical and Engineering Aspects. - : Elsevier BV. - 1873-4359 .- 0927-7757. ; 436, s. 823-829
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Tidskriftsartikel (refereegranskat)abstract
- Porous gold nanoparticles were obtained from nanoparticle alloys of gold and silver. The alloy nanoparticles were prepared by reducing the gold and silver precursors, HAuCl4 and AgNO3, respectively with NaBH4. The reduction was made in a microemulsion of water-in-oil type and the precursors were contained in the water droplets. The droplet size of the microemulsion was 25-30 nm and the size of the mixed nanoparticles was 5-7 nm. The position of the plasmon band in the absorption spectrum, as well as analysis by energy-dispersive X-ray spectroscopy linked to high resolution scanning transmission electron microscopy showed that the nanoparticles were true alloys, not of core-shell type. The mixed nanoparticles were subsequently dealloyed by treatment with nitric acid, which dissolved silver much more readily than gold.
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| 25. |
- Craig, Marina, 1978, et al.
(författare)
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Polypeptide multilayer self-assembly and enzymatic degradation on tailored gold surfaces studied by QCM-D
- 2012
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Ingår i: Soft Matter. - : Royal Society of Chemistry (RSC). - 1744-6848 .- 1744-683X. ; 8:17, s. 4788-4794
-
Tidskriftsartikel (refereegranskat)abstract
- This study deals with the build up and enzymatic degradation of a nanofilm made by the layer-by-layer (LbL) self-assembly technique on a surface that mimics nonwoven, which is commonly used in wound dressings. The nanofilm is composed of alternating layers of the cationic polyelectrolyte poly-L-lysine (PLL) and the anionic polyelectrolyte poly-L-glutamic acid (PLGA) and is intended as a lid for bactericides inserted into a dressing for chronic wounds. Chronic wounds are often infected by bacteria such as Staphylococcus aureus and a mechanism to trigger release of bactericides into such wounds when they become infected is of interest. QCM-D (quartz crystal microbalance with dissipation monitoring) was used to monitor both build-up and degradation of the nanofilm on a surface tailored by the self-assembly monolayer technique to resemble the nonwoven surface. It was found that whereas a normal protease present in the body and wound, as well as a bovine protease that was used as reference, did not catalyze degradation of the polyelectrolyte multilayer, a protease from Staphylococcus aureus, V8 glutamyl endopeptidase, caused rapid break-down of the film. However, a prerequisite of the degradation was that the LbL assembly had been terminated by the anionic PLGA. The results open for products where the wound infection is the trigger for release of bioactive substances from a wound dressing.
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| 26. |
- Fameau, Anne Laure, et al.
(författare)
-
Liquid foams as sensors for the detection of biomarkers
- 2023
-
Ingår i: Journal of Colloid and Interface Science. - 1095-7103 .- 0021-9797. ; 651, s. 987-991
-
Tidskriftsartikel (refereegranskat)abstract
- Bioassays are widely used in healthcare to detect and quantify biomarkers, such as molecules or enzymes, which are crucial in monitoring diseases and health conditions. In developed countries, healthcare professionals use specialized reagents and equipment's to perform these bioassays. However, in less-industrialized countries, the creation of low cost, fast, and technically simple bioassays is required. Herein, we propose a simple approach for detecting biochemical markers using host–guest complexes containing a surfactant. When the biochemical marker is present, the host–guest complex is disrupted, releasing the surfactant and producing foam. The read-out mechanism relies on the change of foam volume as function of biomarker concentration. This change is quantifiable by the naked eye and can be measured with a simple ruler. We claim that the use of foams as sensing tool is an attractive, inexpensive, fast, and easy to handle on-site detection method.
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| 27. |
- Forghani Targhi, Bita, 1973, et al.
(författare)
-
Recovery of a protein-rich biomass from shrimp (Pandalus borealis) boiling water: A colloidal study
- 2020
-
Ingår i: Food Chemistry. - : Elsevier BV. - 0308-8146 .- 1873-7072. ; 302, s. 125299-
-
Tidskriftsartikel (refereegranskat)abstract
- Flocculation and sedimentation of a protein-rich biomass from shrimp boiling water (SBW) using food grade polysaccharides (carrageenan, alginate and carboxymethyl cellulose (CMC)) as flocculants was investigated at different pH-values. The effect of flocculant concentration on particle size and viscosity of SBW was also evaluated. Flocculation with carrageenan (0.45 g/L) at pH = 4 exhibited the most efficient protein sedimentation; protein concentration of the upper phase was here reduced by 77%, allowing 86% protein to be sedimented from SBW. Flocculation by alginate and CMC at pH = 4 showed 67% and 60% protein reduction of the upper phase at concentrations of 0.5 and 0.2 g/L, respectively. Contrary to alginate and CMC, carrageenan concentration affected the size distribution of flocs. Finally, carrageenan at 0.45 g/L and pH = 4 was successfully tested in a scaled up trial (5L) providing 78.5% protein recovery and a biomass with 75% protein on dry weight basis.
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| 28. |
- Glaria, A., et al.
(författare)
-
Understanding the Role of omega-End Groups and Molecular Weight in the Interaction of PNIPAM with Gold Surfaces
- 2013
-
Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 1520-5002 .- 0897-4756. ; 25:9, s. 1868-1876
-
Tidskriftsartikel (refereegranskat)abstract
- Modification of nanoparticle surfaces by adsorption or grafting of polymers allows fine control of hybrid materials propertieds for diverse applications. To obtain such a control, it is of paramount importance to understand the impact of the polymer structure on the nature and strength of its interaction with teh nanoparticle. We investigated here a simple model of hybrid materials made of poly(N-isopropylacrylamide) of different molar masses and end groups interacting with gold surfaces. A series of poly(N-isopropylacrylamide) with number-average molar masses ranging from 3700 to 10000 g.mol(-1) were synthesized by reversible addition-fragmentation chain transfer/macromolecular design by interchange of xanthates (RAFT/MADIX): The terminal xanthate group was then reduced into either a thiol or a hydrogen group. Quartz crystal microbalance adsorption/desorption experiments demonstrated that the polymer termini have a strong impact on the mechanism of polymer adsorption on flat gold surface's. These differences in polymer structure have, in return, a Strong influence on the colloidal stability and growth mechanism of nanoparticles directly synthesized in polymer solution. For those properties, the effect of xanthate group compared very favorably to the conventional thiol moiety. Interestingly, the properties of nanohybrids were, poorly affected by the molar mass of the polymer.
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| 29. |
- Gmoser, Rebecca, et al.
(författare)
-
Effect of dispersed particles on instant coffee foam stability and rheological properties
- 2017
-
Ingår i: European Food Research and Technology. - : Springer Science and Business Media LLC. - 1438-2377 .- 1438-2385. ; 243:1, s. 115-121
-
Tidskriftsartikel (refereegranskat)abstract
- Properties of instant coffee foam constitute the focus of this study. The coffee, obtained from commercial sources, was dispersed in water at a concentration in the range of standard use. The resulting solution contained a substantial amount of micron and submicron size particles that were filtered with membranes having difference size cut-offs in order to investigate the relationship foam properties—particles size. The foams produced from these solutions have been imaged by confocal laser scanning microscopy, and their moduli and stability have been measured by oscillatory rheology, using an in-house developed rheometric set-up. The results show that particles larger than 0.8 µm have little effect on the reduction of drainage while a clear strengthening effect on the foam was evident. This was a result of their diffusion to the lamellae borders, which increases the viscosity of the liquid–air interface. Particles smaller than 0.2 µm affect bubble coarsening and likely hinder the migration of soluble surface active species to the bubble surface. Particles also participate in the stabilization of the air–water interface, and this affects both the foam stability and mechanical properties. Established models developed for ideal foam systems containing particles are difficult to apply due to the complexity of the system studied. Despite this limitation, these results provide increased understanding of the effect of particles on instant coffee foams.
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| 30. |
- Grenda, Kinga, 1989, et al.
(författare)
-
An analytical approach to elucidate the architecture of polyethyleneimines
- 2022
-
Ingår i: Journal of Applied Polymer Science. - : Wiley. - 1097-4628 .- 0021-8995. ; 139:7
-
Tidskriftsartikel (refereegranskat)abstract
- Polyethyleneimine (PEI) is a common polymer used in many industrial applications and in research, especially in surface chemistry. It is available in a wide range of molecular weights and different degrees of branching. It is classified as linear or branched and sometimes the term hyperbranched is also used. This description, however, is quite rough, which limits the possibility to correlate the structure of the PEI to its properties. The aim of this study is to provide analytical tools to characterize the polymer at a level of detail not normally provided by the supplier of PEI. To this end, five commercially available polyethyleneimines were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, and nuclear magnetic resonance spectroscopy to gain insight into the structure and the functional groups present in the polymers. Quantitative 13C NMR analysis turned out to be particularly useful, revealing the degree of branching of the polymer based on the ratio of primary, secondary, and tertiary amino groups.
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| 31. |
- Gugole, Marika, 1993, et al.
(författare)
-
Comparison of Electrodeposited and Sputtered Tungsten Trioxide Films for Inorganic Electrochromic Nanostructures
- 2023
-
Ingår i: ACS Applied Optical Materials. - : American Chemical Society (ACS). - 2771-9855 .- 2574-0962. ; 1:2, s. 558-568
-
Tidskriftsartikel (refereegranskat)abstract
- Electrochromic materials and their implementation with structural colors are currently being intensely researched because of their promising applications as non-emissive display devices utilizing ambient light. In particular, several fully inorganic devices that rely on electrochromic tungsten trioxide (WO3) have been presented. For preparing nanoscale films of this material, sputtering is the most established technique, but electrodeposition has recently been shown to be capable of achieving exceptionally high electro-optical modulation contrast without the need for expensive equipment. In this work, we investigate the possibilities of electrodeposited WO3 and present a systematic comparison with sputtered WO3 with respect to performance in electrochromic devices. Importantly, we show that “ultralarge” electro-optical modulation (∼95% change in transmission) is possible for both types of films. However, it is only the sputtered films that enable such high contrast in a stable electrolyte such as LiClO4 in propylene carbonate. The electrodeposited films are less uniform and difficult to make thicker than ∼500 nm. We find no evidence that the electrochromic properties of the electrodeposited WO3 are intrinsically better than those of sputtered WO3. However, the electrodeposited films are much rougher and/or porous on the nanoscale, which increases the switching speed considerably. We conclude that electrodeposited WO3 is mainly useful in applications in which high contrast is not essential while switching speed is. As an example, we present the first electrodeposited WO3 integrated with structural colors by sandwiching the material between two metal films. By electrical control, the reflective colors can then be tuned at least one order of magnitude faster (a few seconds) than previously reported while having fair color quality and without any loss of brightness.
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| 32. |
- Gupta, Govind, et al.
(författare)
-
Development of Microfluidic, Serum-Free Bronchial Epithelial Cells-on-a-Chip to Facilitate a More Realistic In vitro Testing of Nanoplastics
- 2021
-
Ingår i: Frontiers in Toxicology. - : Frontiers Media SA. - 2673-3080. ; 3
-
Tidskriftsartikel (refereegranskat)abstract
- Most cell culture models are static, but the cellular microenvironment in the body is dynamic. Here, we established a microfluidic-based in vitro model of human bronchial epithelial cells in which cells are stationary, but nutrient supply is dynamic, and we used this system to evaluate cellular uptake of nanoparticles. The cells were maintained in fetal calf serum-free and bovine pituitary extract-free cell culture medium. BEAS-2B, an immortalized, non-tumorigenic human cell line, was used as a model and the cells were grown in a chip within a microfluidic device and were briefly infused with amorphous silica (SiO2) nanoparticles or polystyrene (PS) nanoparticles of similar primary sizes but with different densities. For comparison, tests were also performed using static, multi-well cultures. Cellular uptake of the fluorescently labeled particles was investigated by flow cytometry and confocal microscopy. Exposure under dynamic culture conditions resulted in higher cellular uptake of the PS nanoparticles when compared to static conditions, while uptake of SiO2 nanoparticles was similar in both settings. The present study has shown that it is feasible to grow human lung cells under completely animal-free conditions using a microfluidic-based device, and we have also found that cellular uptake of PS nanoparticles aka nanoplastics is highly dependent on culture conditions. Hence, traditional cell cultures may not accurately reflect the uptake of low-density particles, potentially leading to an underestimation of their cellular impact.
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| 33. |
- Gupta, G., et al.
(författare)
-
Exploiting Mass Spectrometry to Unlock the Mechanism of Nanoparticle-Induced Inflammasome Activation
- 2023
-
Ingår i: Acs Nano. - : AMER CHEMICAL SOC. - 1936-0851 .- 1936-086X. ; 17:17, s. 17451-17467
-
Tidskriftsartikel (refereegranskat)abstract
- Nanoparticles (NPs) elicit sterile inflammation, but the underlying signaling pathways are poorly understood. Here, we report that human monocytes are particularly vulnerable to amorphous silica NPs, as evidenced by single-cell-based analysis of peripheral blood mononuclear cells using cytometry by time-of-flight (CyToF), while silane modification of the NPs mitigated their toxicity. Using human THP-1 cells as a model, we observed cellular internalization of silica NPs by nanoscale secondary ion mass spectrometry (nanoSIMS) and this was confirmed by transmission electron microscopy. Lipid droplet accumulation was also noted in the exposed cells. Furthermore, time-of-flight secondary ion mass spectrometry (ToF-SIMS) revealed specific changes in plasma membrane lipids, including phosphatidylcholine (PC) in silica NP-exposed cells, and subsequent studies suggested that lysophosphatidylcholine (LPC) acts as a cell autonomous signal for inflammasome activation in the absence of priming with a microbial ligand. Moreover, we found that silica NPs elicited NLRP3 inflammasome activation in monocytes, whereas cell death transpired through a non-apoptotic, lipid peroxidation-dependent mechanism. Together, these data further our understanding of the mechanism of sterile inflammation.
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| 34. |
- Hellström, Anna-Karin, 1974, et al.
(författare)
-
Carbamate Chemistry at Interfaces: Practical Considerations and Challenges of Studying Amine Surfactants
- 2019
-
Ingår i: Journal of Surfactants and Detergents. - : Wiley. - 1558-9293 .- 1097-3958. ; 22:5, s. 1109-1117
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- It is well known that CO2 reacts with primary and secondary amines in aqueous solutions and forms carbamates. This reaction can have consequences when studying the self-assembly of amines. In this article, we discuss the practical challenges when working with an alkyl Y-shaped amine (Y12-amine) and demonstrate how the formation of carbamate species influences the physicochemistry of the amine-based surfactant. A drift in dynamic surface tension was observed for Y12-amine at pH above pKa due to the reaction with the naturally occurring CO2 from the atmosphere. The drift in dynamic surface tension was more pronounced at pH above pKa, than at and below pKa. Furthermore, the drift in dynamic surface tension of Y12-amine at pH 12 also affected the surfactant's critical micelle concentration (CMC). CMC of Y12-amine determined by the pendant drop at the air/water interface was almost five times higher than at the N-2/water interface. The latter result was in agreement with the one determined by monitoring the change in chemical shift of H-1 NMR in a N-2 atmosphere. Moreover, it was also shown that the adsorption of the amine at different interfaces influences carbamate formation.
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| 35. |
- Hellström, Anna-Karin, 1974, et al.
(författare)
-
Formation, physicochemical and interfacial study of carbamate surfactants
- 2018
-
Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 1095-7103 .- 0021-9797. ; 511, s. 84-91
-
Tidskriftsartikel (refereegranskat)abstract
- Carbon dioxide is commonly used as pH regulator in switchable surfactant systems and in the formation of alkyl ammonium-alkyl carbamate ion-pair. Its use to form a meta-stable anionic surfactant has been less explored and can impart a cleavable character to the amphiphile. The reaction between CO2 and an alkylamine, N,N-di(propylamino)dodecylamine (Y12-amine), under alkaline pH conditions, produced a stable anionic carbamate-based surfactant (Y12-carbamate). By heating and exposure to N-2, anionic Y12-carbamate could slowly be reverted into Y12-amine. The surface activity of Y12-amine and Y12-carbamate was investigated by surface tension measurements. To study the behavior of Y12-amine at the gas-water interface during CO2 exposure, we used the pendant drop technique with a sealed chamber where the gas composition could be controlled. The Y12-carbamate had a higher CMC than Y12-amine at pH 12, and was also less surface active. The ion pair Y12-ammonium- Y12-carbamate, obtained at neutral pH, exhibited the lowest CMC and the highest surface activity. The interfacial formation of anionic Y12-carbamate induced an increase in surface tension. When CO2 was exchanged to N-2, the migration from the bulk to the interface of Y12-amine induced a decrease in surface tension. The rate was dependent on the concentration of Y12-amine.
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| 36. |
- Hellström, Anna-Karin, 1974, et al.
(författare)
-
Reversible flocculation of nanoparticles by a carbamate surfactant
- 2019
-
Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 1095-7103 .- 0021-9797. ; 536, s. 722-727
-
Tidskriftsartikel (refereegranskat)abstract
- Fatty alkyldiamine readily reacts with CO2 in aqueous solution at pH 12 to reversibly form surface active carbamate species. The carbamate can be reverted to the amine by exposure to N2 and heat. In this work, a carbamate-based surfactant (Y12-carbamate) has been used to disperse and stabilize hydrophobic nanoparticles. This state could be regarded as the “on” state of a series of cycle. The nanoparticles were then flocculated when the carbamate groups were cleaved by exposure to N2 and heating, corresponding to the “off” state. In a subsequent cycle, the nanoparticles were re-dispersed by exposure to CO2, while the pH remained at 12. This cycle of re-dispersion and flocculation could be repeated two times without impairing the particle size. However, further cycles increased the particle size, indicating that all particles could not be completely re-dispersed. In addition, we also investigated the effect of pH on the colloidal stability with sodium Y12-carbamate, by measuring particle size and electrophoretic mobility. The results showed that pH strongly influenced the stability of the nanoparticles. Sodium Y12-carbamate stabilized the particles with a negative electrophoretic mobility at pH well above pKa whereas at pH close to pKa of Y12-amine (pKa = 9.0), the particles quickly flocculated, as a result of an ion-pair formation between Y12-ammonium and Y12-carbamate.
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| 37. |
- Iselau, Frida, 1979, et al.
(författare)
-
Competitive adsorption of amylopectin and amylose on cationic nanoparticles: a study on the aggregation mechanism
- 2016
-
Ingår i: Soft Matter. - : Royal Society of Chemistry (RSC). - 1744-6848 .- 1744-683X. ; 12:14, s. 3388-3397
-
Tidskriftsartikel (refereegranskat)abstract
- In this study we investigate the interactions between cationic nanoparticles and anionic starch, where the starch was composed of 20 wt% of amylose, a linear polymer, and 80 wt% of amylopectin, a branched polymer. The mechanism of aggregation was investigated by scattering techniques. It was found that the cationic particles formed large aggregates with the starch as a result of selective adsorption of the amylopectin. Amylose did not participate significantly in the aggregate formation even when the charge ratio of starch to particles was <1. For starch to particle ratio 41 stabilization was recovered mostly due to the large hindrance brought about by the highly branched amylopectin. This results in a shift of the stabilization mechanism from electrostatic to electrosteric. The internal structure of the aggregates was composed of primary particles with starch coils adsorbed on the surface. This information supports the proposed aggregation mechanism, which is based on adsorption of the negatively charged starch in patches on the positively charged nanoparticles causing attractive interaction between the particles.
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| 38. |
- Iselau, Frida, 1979, et al.
(författare)
-
Formation and relaxation kinetics of starch-particle complexes
- 2016
-
Ingår i: Soft Matter. - 1744-6848 .- 1744-683X. ; 12:47, s. 9509-9519
-
Tidskriftsartikel (refereegranskat)abstract
- The formation and relaxation kinetics of starch-particle complexes were investigated in this study. The combination of cationic nanoparticles in suspension and anionic starch in solution gave rise to aggregate formation which was studied by dynamic light scattering, revealing the initial adsorption of the starch molecules on the particle surface. By examining the stability ratio, W, it was found that even in the most destabilized state, i.e. at charge neutralization, the starch chains had induced steric stabilization to the system. At higher particle and starch concentrations relaxation of the aggregates could be seen, as monitored by a decrease in turbidity with time. This relaxation was evaluated by fitting the data to the Kohlrausch-Williams-Watts function. It was found that irrespective of the starch to particle charge ratio the relaxation time was similar. Moreover, a molecular weight dependence on the relaxation time was found, as well as a more pronounced initial aggregated state for the higher molecular weight starch. This initial aggregate state could be due to bridging flocculation. With time, as the starch chains have relaxed into a final conformation on the particle surface, bridging will be less important and is gradually replaced by patches that will cause patchwise flocculation. After an equilibration time no molecular weight dependence on aggregation could be seen, which confirms the patchwise flocculation mechanism.
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| 39. |
- Iselau, Frida, 1979, et al.
(författare)
-
Parameters influencing hydrophobization of paper by surface sizing
- 2018
-
Ingår i: Nordic Pulp and Paper Research Journal. - : Walter de Gruyter GmbH. - 2000-0669 .- 0283-2631. ; 33:1, s. 95-104
-
Tidskriftsartikel (refereegranskat)abstract
- Paper surface hydrophobization, also referred to as "surface sizing", is often necessary for printing and packaging purposes. Typically, hydrophobic polymeric nanoparticles, in combination with starch are applied on the paper surface at the dry-end of the paper machine. In the surface sizing process, the nature of the nanoparticles, starch type, starch concentration and ratio between starch and nanoparticles, paper quality, ionic strength, and application as well as drying temperature are parameters that influence the result. The aim of this work was to systematically evaluate these parameters in order to create knowledge to be used for optimization of the process. Laboratory scale surface sizing trials were performed and the results from the trials showed that cationic particles gave superior performance compared to anionic particles. Both the starch type and the concentration of the oxidized starch had an impact on the performance. The effect of the ionic strength was found to depend on the particle charge: for cationic particles, the addition of salt was detrimental while for the anionic particles it was beneficial. An increase of the application or the drying temperature was found to enhance the performance up to a temperature around the glass transition temperature of the polymer.
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| 40. |
- Iselau, Frida, 1979, et al.
(författare)
-
Role of the aggregation behavior of hydrophobic particles in paper surface hydrophobation
- 2015
-
Ingår i: Colloids and Surfaces A: Physicochemical and Engineering Aspects. - : Elsevier BV. - 1873-4359 .- 0927-7757. ; 483, s. 264-270
-
Tidskriftsartikel (refereegranskat)abstract
- Three types of hydrophobic particles with different charge, i.e. cationic (SP+), anionic (SP-) and amphoteric (SPA) have been synthesized by emulsion polymerizations and evaluated in paper surface hydrophobation performance (frequently referred to as surface sizing). The surface sizing evaluation was done according to a well-established process, i.e. mixing of the particles with negatively charged starch followed by application in a conventional puddle size press using a fine paper grade containing calcium carbonate filler as model system. Prior to the application, the particles were characterized by light scattering and the surface charge was determined by particle charge density titrations and ζ-potential measurements. The SP+ particles were determined to be 30. nm in diameter while SP- and SPA particles were around 65. nm. Their colloidal behavior in the presence of anionic starch differed. The SP+ particles formed aggregates via bridging flocculation up to a charge ratio of 1:1 of starch:particles. At higher starch content the aggregates were partly redispersed. The SP- and SPA particles showed no sign of aggregation in the presence of anionic starch. In addition, the sizing performance of the different particles was evaluated by assessing the decrease of water uptake in a surface treated paper as well as water contact angle measurements on the paper surface. All three types of particles decreased the water penetration. However, the SP+/starch mixtures showed superior performance, which was attributed to a stronger sensitivity to the high electrolyte concentration usually found in the vicinity of the paper surface when the semi-soluble minerals composing the filler are exposed to water.
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| 41. |
- Iselau, Frida, 1979, et al.
(författare)
-
Surface Treatment by Hydrophobic Particles: Influence of Starch and Ionic Strength
- 2017
-
Ingår i: ACS Sustainable Chemistry & Engineering. - : American Chemical Society (ACS). - 2168-0485. ; 5:7, s. 6107-6115
-
Tidskriftsartikel (refereegranskat)abstract
- This paper deals with the colloidal behavior of mixtures of cationic polymer particles and anionic starch. Such mixtures are commonly used for the hydrophobization of paper. The effect of the concentration of anionic starch and of the presence of different electrolytes was assessed. In a previous study, oxidized starch had been found to induce aggregation of cationic hydrophobic nanoparticles, and in the study reported here it is demonstrated that this aggregated state is beneficial for the performance, enabling a substantial reduction of the amount of polymer nanoparticles needed to reduce the water uptake. It was found that when the particles were in a highly aggregated state, the water uptake by the paper surface was very small. The effect of mono- and divalent ions on the colloidal stability was also investigated. In general, it was found that an increased ionic strength gave a less hydrophobic paper surface. Na2SO4 was more detrimental than NaCl and CaCl2, which is explained by the valence of the anion. This implies that the hydrophobization can be tuned by controlling the aggregation of the polymer particles.
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| 42. |
- Iselau, Frida, 1979, et al.
(författare)
-
Towards a mechanism for surface hydrophobization of paper
- 2017
-
Ingår i: Paper Conference and Trade Show, PaperCon 2017: Renew, Rethink, Redefine the Future. - 9781510847286 ; 1, s. 131-139
-
Konferensbidrag (refereegranskat)abstract
- Surface hydrophobization of paper, also referred to as surface sizing, is often needed for printing and packaging purposes. Typically, hydrophobic nanoparticles in combination with starch are applied on the paper surface. In this study two types of hydrophobic nanoparticle suspensions, one cationic and one anionic, were investigated in order to gain deeper knowledge about the mechanism behind surface sizing. A study was performed where the interactions between the particles and anionic starch were investigated and this study revealed that on addition of starch the cationic particles formed aggregates while the anionic particles were unaffected. This aggregation behaviour was found to be beneficial for the surface sizing performance. The impact of salt was also investigated and it was found that by increasing the ionic strength with NaCl or with Na 2 SO 4 larger agglomerates were formed. The surface hydrophobization efficiency of such aggregates was found to be lower, however.
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| 43. |
- Karlkvist, Tommy, et al.
(författare)
-
Flotation selectivity of novel alkyl dicarboxylate reagents for apatite-calcite separation
- 2015
-
Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 1095-7103 .- 0021-9797. ; 445, s. 40-47
-
Tidskriftsartikel (refereegranskat)abstract
- The investigation aims to demonstrate the conceptual thoughts behind developing mineral specific reagents for use in flotation of calcium containing ores. For this purpose, a series of dicarboxylate-based surfactants with varying distance between the carboxylate groups (one, two or three methylene groups) was synthesized. A surfactant with the same alkyl chain length but with only one carboxylate group was also synthesized and evaluated. The adsorption behavior of these new reagents on pure apatite and pure calcite surfaces was studied using Hallimond tube flotation, FTIR and zeta potential measurements. The relation between the adsorption behavior of a given surfactant at a specific mineral surface and its molecular structure over a range of concentrations and pH values, as well as the region of maximum recovery, was established. It was found that one of the reagents, with a specific distance between the carboxylate groups, was much more selective for a particular mineral surface than the other homologues. For example, out of the four compounds synthesized, only the one where the carboxylate groups were separated by a single methylene group floated apatite but not calcite, whereas calcite was efficiently floated with the monocarboxylic reagent, but not with the other reagents synthesized. This selective adsorption of a given surfactant to a particular mineral surface relative to other mineral surfaces as evidenced in the flotation studies was substantiated by zeta potential and infra-red spectroscopy data.
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| 44. |
- Karlkvist, Tommy, et al.
(författare)
-
Flotation selectivity of novel alkyl dicarboxylate reagents for calcite-fluorite separation
- 2016
-
Ingår i: Tenside, Surfactants, Detergents. - : Walter de Gruyter GmbH. - 0932-3414 .- 2195-8564. ; 53:6, s. 516-523
-
Tidskriftsartikel (refereegranskat)abstract
- A series of amino acid-based surfactants with a fixed alkyl chain length and with two carboxyl groups separated by a spacer of one, two or three carbon atoms have been synthesized and evaluated as potential collectors for flotation of calcite and fluorite. A monocarboxylate amino acid-based surfactant having the same length of the hydrocarbon tail was also included for comparison in the study. Experiments using a Hallimond flotation tube showed that although the flotation reagents solely differ in terms of spacer, their efficacy in terms of flotation recovery varied very much. Whereas on calcite at pH 10.5 only the monocarboxylate collector gave a high yield, on fluorite at the same pH both the monocarboxylate and the dicarboxylate collectors with one carbon between the carboxyl groups gave good results. On calcite at the natural pH the monocarboxylate collector was most efficient but the dicarboxylate collectors with a two and a three-carbon spacer also gave a reasonable recovery. On fluorite at the natural pH the dicarboxylate collectors with a two- and a three-carbon spacer were most efficient. The zeta-potential and the flotation recovery of the mineral particles as a function of added collector were assessed and the adsorption was also monitored by diffuse reflectance infra-red spectroscopy. Taken together, the results showed that small changes in the head group region of the collector can radically affect flotation recovery. This type of knowledge is important to understand flotation selectivity in a mixture of similar minerals.
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| 45. |
- Karlkvist, Tommy, et al.
(författare)
-
Molecular recognition in mineral flotation : Selectivity in apatite-calcite system
- 2014
-
Ingår i: 27th International Mineral Processing Congress, IMPC 2014, Santiago, Chile, 20-24 October 2014.
-
Konferensbidrag (refereegranskat)abstract
- The present investigation aims to develop and distinguish mineral specific reagents with two functional groups for use in flotation of calcium containing minerals. For this purpose, a series of dicarboxylate-based surfactants with varying length between the carboxylate groups (one, two or three methylene groups) were synthesized. As reference, a surfactant with the same alkyl chain length but with only one carboxylate group in the polar part was synthesized. The adsorption behavior of these new reagents on pure apatite and calcite mineral surfaces was studied using Hallimond tube flotation, FTIR and ζ potential measurements. The relation between the adsorption behavior of a given surfactant on a specific mineral surface and its molecular structure over a range of concentration and pH values, as well as the region of maximum recovery were established. It was found that one of the reagents, with a specific distance between the carboxylate groups, was much more selective for a particular mineral surface than the other homologues synthesized. This selective adsorption of a given surfactant to a particular mineral surface relative to other mineral surfaces as evidenced in flotation studies is substantiated by ζ potential and infra-red spectroscopy data.
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| 46. |
- Karlsson, Mikael, 1978, et al.
(författare)
-
Characterisation of silicon, zirconium and aluminium coated titanium dioxide pigments recovered from paint waste
- 2019
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Ingår i: Dyes and Pigments. - : Elsevier BV. - 0143-7208 .- 1873-3743. ; 162, s. 145-152
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Tidskriftsartikel (refereegranskat)abstract
- © 2018 Elsevier Ltd Titanium dioxide (TiO2) is the major white pigment used by the paint industry. However, the production of TiO2is associated with a high carbon footprint. An alternative source of pigment could be created by developing a method to recover it from waste paint. In this paper two rutile pigments with different surface treatments were recovered from paint by a thermal recycling process. The pigments were analysed using powder x-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), surface area measurements (BET), laser diffraction for particle size analysis and zeta potential measurements before and after the recycling process. It was concluded that the rutile cores of both pigments were intact and there were no major changes in particle size distribution or surface charge for either pigment induced by the recycling process. However, XPS and zeta potential measurements showed that the surface coating of the pigments can be more or less degraded depending on the chemical nature, which might imply the need for further re-coating after-treatment. Another option would be to find another application for the pigment where the quality and function of the coating is of less importance.
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| 47. |
- Karlsson, Mikael, 1978, et al.
(författare)
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Characterization of paint formulated using secondary TiO2 pigments recovered from waste paint
- 2019
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Ingår i: JCT Research. - : Springer Science and Business Media LLC. - 1547-0091 .- 2168-8028 .- 1935-3804. ; 16:2, s. 607-614
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Tidskriftsartikel (refereegranskat)abstract
- The paint industry is continuously striving to reduce its environmental impact, especially when it comes to the major virgin white pigment, titanium dioxide (TiO2). In this work, recycled TiO2 pigment was used in a paint formulation as a replacement for pigment made from virgin raw materials. The paint was evaluated based on pH, Stormer and ICI viscosities, gloss, hiding power, and color characteristics. The paint films were also characterized by LVSEM–EDS, AFM, and profilometry. The most significant difference between a paint based on recycled pigments and a paint based on virgin pigments was the agglomeration of pigment particles which gave a reduction in gloss and a rougher surface of the dried paint film based on recycled pigment, and it could be concluded that the recycled pigment could not be used without accepting a small decrease in paint quality. This points toward two main directions: (1) the use of recycled pigment in applications with less demand on surface finish and gloss, such as ceiling paints, and (2) that further work on formulation should be carried out with the recycled pigment as for any other new pigment introduced in a paint formulation to optimize its performance. © 2018, The Author(s).
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| 48. |
- Karlsson, Mikael, 1978, et al.
(författare)
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Surface properties of recycled titanium oxide recovered from paint waste
- 2018
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Ingår i: Progress in organic coatings. - : Elsevier BV. - 0300-9440 .- 1873-331X. ; 125, s. 279-286
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Tidskriftsartikel (refereegranskat)abstract
- Aluminium oxide coated rutile pigment was extracted from a paint matrix by means of a thermal recycling process. The objective was to investigate the effect of the recycling process on the surface properties of the pigment. The pigment was analysed using powder x-ray diffraction (XRD), surface area measurements (BET), laser diffraction for particle size analysis and X-ray photoelectron spectroscopy (XPS) before and after the recycling process. Investigations on the zeta potential and the surface charge were performed as well. It was concluded that the rutile crystalline core and the aluminium oxide coating of the pigment were still intact after the recycling process. The particle size distribution of the recycled pigment was slightly broader compared to the virgin pigment. The measured magnitude in zeta potential of the recycled pigment was lower than for the virgin pigment. This difference is thought to be caused by alteration in the surface hydroxyl concentration. Surface charge titrations showed differences between the virgin and the recycled pigment at alkaline pH and at low salt concentrations.
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| 49. |
- Kolman, Krzysztof, 1986, et al.
(författare)
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Combined Nanocellulose/Nanosilica Approach for Multiscale Consolidation of Painting Canvases
- 2018
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Ingår i: ACS Applied Nano Materials. - : American Chemical Society (ACS). - 2574-0970. ; 1:5, s. 2036-2044
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Tidskriftsartikel (refereegranskat)abstract
- The restoration of painting canvases is a complex problem that, because of the hierarchical nature of the canvas, requires intervention at several length scales. We propose an approach combining polyelectrolyte-treated silica nanoparticles (SNP) and cellulose nanofibrils (CNF) for canvas consolidation. The formulations, applied on model degraded canvases, gave a total weight increase of
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| 50. |
- Kolman, Krzysztof, 1986, et al.
(författare)
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pH-Controlled assembly of polyelectrolyte layers on silica nanoparticles in concentrated suspension
- 2022
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 1095-7103 .- 0021-9797. ; 615, s. 265-272
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Tidskriftsartikel (refereegranskat)abstract
- Hypothesis: Preparation of suspensions of nanoparticles (>1 wt%) coated with a polyelectrolyte multilayers is a challenging task because of the risk of flocculation when a polyelectrolyte is added to a suspension of oppositely charged nanoparticles. This situation can be avoided if the charge density of the polymers and particles is controlled during mixing so as to separate mixing and adsorption events. Experiments: The cationic polyethylenimine (PEI) and the anionic carboxymethylcellulose (CMC) were used as weak polyelectrolytes. Polyelectrolyte multilayers build-up was conducted by reducing the charge of one of the components during the addition of the next component. Charge density was controlled by tuning pH. Analysis of the suspension of coated nanoparticles was done by means of dynamic light scattering, electrophoresis and small angle x-ray scattering measurements, while quartz crystal microbalance was used to study the build-up process on flat silica surfaces. Findings: Charge density, controlled through pH, can be used as a tool to avoid flocculation during layer-by-layer deposition of polyelectrolytes on 20 nm silica particles at high concentration (∼40 wt%). When added to silica at pH 3, PEI did not induce flocculation. Adsorption was triggered by raising the pH to 11, pH at which CMC could be added. The pH was then lowered to 3. The process was repeated, and up to five polyelectrolyte layers were deposited on concentrated silica nanoparticles while inducing minimal aggregation.
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