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Abreu, B., Rocha, J., Ferreira Fernandes, R. M., Regev, O., Furo, I. & Marques, E. F. (2019). Gemini surfactants as efficient dispersants of multiwalled carbon nanotubes: Interplay of molecular parameters on nanotube dispersibility and debundling. Journal of Colloid and Interface Science, 547, 69-77
Open this publication in new window or tab >>Gemini surfactants as efficient dispersants of multiwalled carbon nanotubes: Interplay of molecular parameters on nanotube dispersibility and debundling
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2019 (English)In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 547, p. 69-77Article in journal (Refereed) Published
Abstract [en]

Surfactants have been widely employed to debundle, disperse and stabilize carbon nanotubes in aqueous solvents. Yet, a thorough understanding of the dispersing mechanisms at molecular level is still warranted. Herein, we investigated the influence of the molecular structure of gemini surfactants on the dispersibility of multiwalled carbon nanotubes (MWNTs). We used dicationic n-s-n gemini surfactants, varying n and s, the number of alkyl tail and alkyl spacer carbons, respectively; for comparisons, single-tailed surfactant homologues were also studied. Detailed curves of dispersed MWNT concentration vs. surfactant concentration were obtained through a stringently controlled experimental procedure, allowing for molecular insight. The gemini are found to be much more efficient dispersants than their single-tailed homologues, i.e. lower surfactant concentration is needed to attain the maximum dispersed MWNT concentration. In general, the spacer length has a comparatively higher influence on the dispersing efficiency than the tail length. Further, scanning electron microscopy imaging shows a sizeable degree of MWNT debundling by the gemini surfactants in the obtained dispersions. Our observations also point to an adsorption process that does not entail the formation of micelle-like aggregates on the nanotube surface, but rather coverage by individual molecules, among which the ones that seem to be able to adapt best to the nanotube surface provide the highest efficiency. These studies are relevant for the rational design and choice of optimal dispersants for carbon nanomaterials and other similarly water-insoluble materials.

Place, publisher, year, edition, pages
ACADEMIC PRESS INC ELSEVIER SCIENCE, 2019
Keywords
Gemini surfactant, Carbon nanotube, Exfoliation, Dispersion efficiency, Molecular structure, Spacer length, Tail length, Adsorption, Hydrophobicity
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-252363 (URN)10.1016/j.jcis.2019.03.082 (DOI)000466826600007 ()30939346 (PubMedID)2-s2.0-85063650726 (Scopus ID)
Note

QC 20190718

Available from: 2019-07-18 Created: 2019-07-18 Last updated: 2019-07-18Bibliographically approved
Chen, P., Terenzi, C., Furo, I., Berglund, L. & Wohlert, J. (2019). Heterogeneous dynamics in cellulose from molecular dynamics simulations. Paper presented at National Meeting of the American-Chemical-Society (ACS), MAR 31-APR 04, 2019, Orlando, FL. Abstracts of Papers of the American Chemical Society, 257
Open this publication in new window or tab >>Heterogeneous dynamics in cellulose from molecular dynamics simulations
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2019 (English)In: Abstracts of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 257Article in journal, Meeting abstract (Other academic) Published
Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2019
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-257590 (URN)000478860502701 ()
Conference
National Meeting of the American-Chemical-Society (ACS), MAR 31-APR 04, 2019, Orlando, FL
Note

QC 20190919

Available from: 2019-09-19 Created: 2019-09-19 Last updated: 2019-10-15Bibliographically approved
Chaudhary, H., Ferreira Fernandes, R. M., Gowda, V., Claessens, M. M. A., Furo, I. & Lendel, C. (2019). Intrinsically disordered protein as carbon nanotube dispersant: How dynamic interactions lead to excellent colloidal stability. Journal of Colloid and Interface Science, 556, 172-179
Open this publication in new window or tab >>Intrinsically disordered protein as carbon nanotube dispersant: How dynamic interactions lead to excellent colloidal stability
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2019 (English)In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 556, p. 172-179Article in journal (Refereed) Published
Abstract [en]

The rich pool of protein conformations combined with the dimensions and properties of carbon nanotubes create new possibilities in functional materials and nanomedicine. Here, the intrinsically disordered protein α-synuclein is explored as a dispersant of single-walled carbon nanotubes (SWNTs) in water. We use a range of spectroscopic methods to quantify the amount of dispersed SWNT and to elucidate the binding mode of α-synuclein to SWNT. The dispersion ability of α-synuclein is good even with mild sonication and the obtained dispersion is very stable over time. The whole polypeptide chain is involved in the interaction accompanied by a fraction of the chain changing into a helical structure upon binding. Similar to other dispersants, we observe that only a small fraction (15–20%) of α-synuclein is adsorbed on the SWNT surface with an average residence time below 10 ms

Place, publisher, year, edition, pages
Academic Press, 2019
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-258234 (URN)10.1016/j.jcis.2019.08.050 (DOI)2-s2.0-85070901886 (Scopus ID)
Note

QC 20191014

Available from: 2019-09-10 Created: 2019-09-10 Last updated: 2019-10-15Bibliographically approved
Gao, J., Yang, W., El-Zohry, A. M., Prajapati, G. K., Fang, Y., Dai, J., . . . Kloo, L. (2019). Light-induced electrolyte improvement in cobalt tris(bipyridine)-mediated dye-sensitized solar cells. Journal of Materials Chemistry A, 7(33), 19495-19505
Open this publication in new window or tab >>Light-induced electrolyte improvement in cobalt tris(bipyridine)-mediated dye-sensitized solar cells
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2019 (English)In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 7, no 33, p. 19495-19505Article in journal (Refereed) Published
Abstract [en]

Lithium-ion-free tris(2,2 '-bipyridine) Co(ii/iii)-mediated electrolytes have previously been proposed for long-term stable dye-sensitized solar cells (DSSCs). Such redox systems also offer an impressive DSSC performance improvement under light soaking exposure, manifested by an increase in photocurrent and fill factor without the expense of decreasing photovoltage. Kinetic studies show that charge transfer and ion diffusion at the electrode/electrolyte interface are improved due to the light exposure. Control experiments reveal that the light effect is unambiguously associated with electrolyte components, [Co(bpy)(3)](3+) and the Lewis-base additive tert-butylpyridine (TBP). Electrochemical and spectroscopic investigation of the [Co(bpy)(3)](3+)/TBP mixtures points out that the presence of TBP, which retards the electrolyte diffusion, however causes an irreversible redox reaction of [Co(bpy)(3)](3+) upon light exposure that improves the overall conductivity. This discovery not only provides a new strategy to mitigate the typical J(sc)-V-oc trade-off in Co(ii/iii)-mediated DSSCs but also highlights the importance of investigating the photochemistry of a photoelectrochemical system.

Place, publisher, year, edition, pages
ROYAL SOC CHEMISTRY, 2019
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-259417 (URN)10.1039/c9ta07198a (DOI)000482139000027 ()2-s2.0-85071187004 (Scopus ID)
Note

QC 20190924

Available from: 2019-09-24 Created: 2019-09-24 Last updated: 2019-09-24Bibliographically approved
Rohlmann, P., Munavirov, B., Furo, I., Antzutkin, O., Rutland, M. W. & Glavatskih, S. (2019). Non-halogenated Ionic Liquid Dramatically Enhances Tribological Performance of Biodegradable Oils. Frontiers in Chemistry, 7, Article ID 98.
Open this publication in new window or tab >>Non-halogenated Ionic Liquid Dramatically Enhances Tribological Performance of Biodegradable Oils
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2019 (English)In: Frontiers in Chemistry, E-ISSN 2296-2646, Vol. 7, article id 98Article in journal (Refereed) Published
Abstract [en]

It is demonstrated that a phosphonium orthoborate ionic liquid may serve as a wear reducing additive in biodegradable oils at steel-steel surfaces in the boundary lubrication regime. Tribological tests were performed in a bail-on-three plate configuration. A set of surface characterization techniques-SEM/EDS, FIB and white light interferometry were used to characterize surfaces following the tribotests and to observe the formation of any tribofilms. B-11 NMR was used to follow changes in the composition of the ionic-liquid-oil blends and to identify boron-containing decomposition products after the tribotests. The ionic liquid reduces the wear of steel surfaces by up to 92% compared to the neat oil at 90 degrees C; it is shown that the reduction in wear can be correlated with the formation of boron enriched patches in the boundary films.

Place, publisher, year, edition, pages
FRONTIERS MEDIA SA, 2019
Keywords
biodegradable oil, ionic liquid, wear, friction, boundary lubrication, NMR
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Identifiers
urn:nbn:se:kth:diva-246253 (URN)10.3389/fchem.2019.00098 (DOI)000459858200001 ()2-s2.0-85068538860 (Scopus ID)
Note

QC 20190401

Available from: 2019-04-01 Created: 2019-04-01 Last updated: 2019-10-04Bibliographically approved
Niga, P., Hansson-Mille, P. M., Swerin, A., Claesson, P. M., Schoelkopf, J., Gane, P. A. C., . . . Johnson, C. M. (2019). Propofol adsorption at the air/water interface: a combined vibrational sum frequency spectroscopy, nuclear magnetic resonance and neutron reflectometry study. Soft Matter, 15(1), 38-46
Open this publication in new window or tab >>Propofol adsorption at the air/water interface: a combined vibrational sum frequency spectroscopy, nuclear magnetic resonance and neutron reflectometry study
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2019 (English)In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 15, no 1, p. 38-46Article in journal (Refereed) Published
Abstract [en]

Propofol is an amphiphilic small molecule that strongly influences the function of cell membranes, yet data regarding interfacial properties of propofol remain scarce. Here we consider propofol adsorption at the air/water interface as elucidated by means of vibrational sum frequency spectroscopy (VSFS), neutron reflectometry (NR), and surface tensiometry. VSFS data show that propofol adsorbed at the air/ water interface interacts with water strongly in terms of hydrogen bonding and weakly in the proximity of the hydrocarbon parts of the molecule. In the concentration range studied there is almost no change in the orientation adopted at the interface. Data from NR show that propofol forms a dense monolayer with a thickness of 8.4 angstrom and a limiting area per molecule of 40 angstrom(2), close to the value extracted from surface tensiometry. The possibility that islands or multilayers of propofol form at the air/water interface is therefore excluded as long as the solubility limit is not exceeded. Additionally, measurements of the 1H NMR chemical shifts demonstrate that propofol does not form dimers or multimers in bulk water up to the solubility limit.

Place, publisher, year, edition, pages
ROYAL SOC CHEMISTRY, 2019
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-241311 (URN)10.1039/c8sm01677a (DOI)000454838800015 ()30516226 (PubMedID)2-s2.0-85058894693 (Scopus ID)
Note

QC 20190125

Available from: 2019-01-25 Created: 2019-01-25 Last updated: 2019-04-09Bibliographically approved
Ferreira Fernandes, R. M., Dai, J., Regev, O., Marques, E. F. & Furo, I. (2018). Block Copolymers as Dispersants for Single-Walled Carbon Nanotubes: Modes of Surface Attachment and Role of Block Polydispersity. Langmuir, 34(45), 13672-13679
Open this publication in new window or tab >>Block Copolymers as Dispersants for Single-Walled Carbon Nanotubes: Modes of Surface Attachment and Role of Block Polydispersity
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2018 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 34, no 45, p. 13672-13679Article in journal (Refereed) Published
Abstract [en]

When using amphiphilic polymers to exfoliate and disperse carbon nanotubes in water, the balance between the hydrophobic and hydrophilic moieties is critical and nontrivial. Here, we investigate the mode of surface attachment of a triblock copolymer, Pluronics F127, composed of a central hydrophobic polypropylene oxide block flanked by hydrophilic polyethylene oxide blocks, onto single-walled carbon nanotubes (SWNTs). Crucially, we analyze the composition in dispersant of both the as-obtained dispersion (the supernatant) and the precipitate-containing undispersed materials. For this, we combine the carefully obtained data from H-1 NMR peak intensities and self-diffusion and thermogravimetric analysis. The molecular motions behind the observed NMR features are clarified. We find that the hydrophobic blocks attach to the dispersed SWNT surface and remain significantly immobilized leading to H-1 NMR signal loss. On the other hand, the hydrophilic blocks remain highly mobile and thus readily detectable by NMR. The dispersant is shown to possess significant block polydispersity that has a large effect on dispersibility. Polymers with large hydrophobic blocks adsorb on the surface of the carbonaceous particles that precipitate, indicating that although a larger hydrophobic block is good for enhancing adsorption, it may be less effective in dispersing the tubes. A model is also proposed that consistently explains our observations in SWNT dispersions and some contradicting findings obtained previously in carbon nanohorn dispersions. Overall, our findings help elucidating the molecular picture of the dispersion process for SWNTs and are of interest when looking for more effective (i.e., well-balanced) polymeric dispersants.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2018
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-239775 (URN)10.1021/acs.langmuir.8b02658 (DOI)000450695000023 ()30335395 (PubMedID)2-s2.0-85056155151 (Scopus ID)
Note

QC 20190108

Available from: 2019-01-08 Created: 2019-01-08 Last updated: 2019-01-09Bibliographically approved
Dai, J., Ferreira Fernandes, R. M., Regev, O., Marques, E. F. & Furo, I. (2018). Dispersing Carbon Nanotubes in Water with Amphiphiles: Dispersant Adsorption, Kinetics, and Bundle Size Distribution as Defining Factors. The Journal of Physical Chemistry C, 122(42), 24386-24393
Open this publication in new window or tab >>Dispersing Carbon Nanotubes in Water with Amphiphiles: Dispersant Adsorption, Kinetics, and Bundle Size Distribution as Defining Factors
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2018 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 122, no 42, p. 24386-24393Article in journal (Refereed) Published
Abstract [en]

Debundling and dispersing single-walled carbon nanotubes (SWNTs) is essential for applications, but the process is not well understood. In this work, aqueous SWNT dispersions were produced by sonicating pristine SWNT powder in the presence of an amphiphilic triblock copolymer (Pluronic F127) as dispersant. Upon centrifugation, one obtains a supernatant with suspended individual tubes and thin bundles and a precipitate with large bundles (and impurities). In the supernatant, that constitutes the final dispersion, we determined the dispersed SWNT concentration by thermogravi-metric analysis (TGA) and UV-vis spectroscopy, and the dispersant concentration by NMR The fraction of dispersant adsorbed at the SWNT surface was obtained by H-1 diffusion NMR Sigmoidal dispersion curves recording the concentration of dispersed SWNTs as a function of supernatant dispersant concentration were obtained at different SWNT loadings and sonication times. As SWNT bundles are debundled into smaller and smaller ones, the essential role of the dispersant is to sufficiently quickly cover the freshly exposed surfaces created by shear forces induced during sonication. Primarily kinetic reasons are behind the need for dispersant concentrations required to reach a substantial SWNT concentration. Centrifugation sets the size threshold below which SWNT particles are retained in the dispersion and consequently determines the SWNT concentration as a function of sonication time.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2018
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-239095 (URN)10.1021/acs.jpcc.8b06542 (DOI)000448754300065 ()2-s2.0-85054962387 (Scopus ID)
Funder
Swedish Research Council
Note

QC 20181121

Available from: 2018-11-21 Created: 2018-11-21 Last updated: 2019-08-20Bibliographically approved
Chen, P., Terenzi, C., Furo, I., Berglund, L. & Wohlert, J. (2018). Hydration-Dependent Dynamical Modes in Xyloglucan from Molecular Dynamics Simulation of C-13 NMR Relaxation Times and Their Distributions. Biomacromolecules, 19(7), 2567-2579
Open this publication in new window or tab >>Hydration-Dependent Dynamical Modes in Xyloglucan from Molecular Dynamics Simulation of C-13 NMR Relaxation Times and Their Distributions
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2018 (English)In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 19, no 7, p. 2567-2579Article in journal (Refereed) Published
Abstract [en]

Macromolecular dynamics in biological systems, which play a crucial role for biomolecular function and activity at ambient temperature, depend strongly on moisture content. Yet, a generally accepted quantitative model of hydration-dependent phenomena based on local relaxation and diffusive dynamics of both polymer and its adsorbed water is still missing. In this work, atomistic-scale spatial distributions of motional modes are calculated using molecular dynamics simulations of hydrated xyloglucan (XG). These are shown to reproduce experimental hydration-dependent C-13 NMR longitudinal relaxation times (T-1) at room temperature, and relevant features of their broad distributions, which are indicative of locally heterogeneous polymer reorientational dynamics. At low hydration, the self-diffusion behavior of water shows that water molecules are confined to particular locations in the randomly aggregated XG network while the average polymer segmental mobility remains low. Upon increasing water content, the hydration network becomes mobile and fully accessible for individual water molecules, and the motion of hydrated XG segments becomes faster. Yet, the polymer network retains a heterogeneous gel-like structure even at the highest level of hydration. We show that the observed distribution of relaxations times arises from the spatial heterogeneity of chain mobility that in turn is a result of heterogeneous distribution of water-chain and chain chain interactions. Our findings contribute to the picture of hydration-dependent dynamics in other macromolecules such as proteins, DNA, and synthetic polymers, and hold important implications for the mechanical properties of polysaccharide matrixes in plants and plant-based materials.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2018
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-232788 (URN)10.1021/acs.biomac.8b00191 (DOI)000438470800020 ()29688710 (PubMedID)2-s2.0-85046395682 (Scopus ID)
Funder
Swedish Research CouncilKnut and Alice Wallenberg Foundation
Note

QC 20180803

Available from: 2018-08-03 Created: 2018-08-03 Last updated: 2018-08-03Bibliographically approved
Nadiv, R., Fernandes, R. M. F., Ochbaum, G., Dai, J., Buzaglo, M., Varenik, M., . . . Regev, O. (2018). Polymer nanocomposites: Insights on rheology, percolation and molecular mobility. Polymer, 153, 52-60
Open this publication in new window or tab >>Polymer nanocomposites: Insights on rheology, percolation and molecular mobility
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2018 (English)In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 153, p. 52-60Article in journal (Refereed) Published
Abstract [en]

The integration of carbon nanotubes (CNTs) into a polymer matrix strongly affects the rheological behavior that in turn may hamper the overall performance of the resulting composite. Research in this topic has focused on bulk rheological properties, while here we employ NMR diffusion experiments to explore the mobility (diffusivity) of epoxy molecules when loaded with CNTs. Rheology and light microscopy indicate percolation of CNT aggregates. Those aggregates cage a substantial amount of epoxy molecules while small angle X-ray scattering indicates some rearrangement of epoxy molecules in the vicinity of the nanotubes. NMR diffusion experiments distinguish between the slow diffusion of the caged molecules and that of the free ones, and relate the fraction of the former to the macroscopic system viscosity. The demonstrated surface-induced slowing-down of diffusion is attributed to strong intermolecular π-π interactions among the epoxy molecules, and between them and the CNT surface. These findings demonstrate the utility of NMR diffusion experiments as an additional method applied to nanocomposites. 

Place, publisher, year, edition, pages
Elsevier Ltd, 2018
Keywords
Nanocomposites, NMR diffusion, Rheology, Aggregates, Carbon nanotubes, Diffusion, Elasticity, Molecules, Solvents, X ray scattering, Yarn, Macroscopic systems, Molecular mobility, Pi interactions, Polymer nanocomposite, Rheological behaviors, Rheological property, Slow diffusion, Polymer matrix composites
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-236679 (URN)10.1016/j.polymer.2018.07.079 (DOI)000445783300007 ()2-s2.0-85053160650 (Scopus ID)
Funder
Swedish Research Council, CA15107
Note

Export Date: 22 October 2018; Article; CODEN: POLMA; Correspondence Address: Nadiv, R.; Department of Chemical Engineering, Ben-Gurion University of the NegevIsrael; email: roeynadiv@gmail.com; Funding details: NORTE-01-0145-FEDER-000028; Funding details: UID/QUI/00081/2013; Funding details: POCI-01-0145-FEDER-006980; Funding details: CA15107; Funding details: Aichi Science and Technology Foundation; Funding details: COST, European Cooperation in Science and Technology; Funding details: FCT, Fuel Cell Technologies Program; Funding text: The authors are grateful for excellent technical support by Dr. Jürgen Jopp (Light microscopy). The authors are grateful for excellent technical support by Carmen Tamburu and Prof. Uri Raviv (SAXS). The authors acknowledge useful discussions with Dr. Gleb Vasilyev. This article is based upon work from COST action CA15107 (MultiComp), supported by COST (European Cooperation in Science and Technology) and the Swedish Research Council VR. RF also acknowledges the CIQUP and the Science and Technology Foundation (FCT), Portugal , and FEDER/COMPETE for financial support through grants UID/QUI/00081/2013 , POCI-01-0145-FEDER-006980 and NORTE-01-0145-FEDER-000028 . Appendix A

Available from: 2018-11-13 Created: 2018-11-13 Last updated: 2018-11-13Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0002-0231-3970

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