| 1. |
- Kehoe, Laura, et al.
(författare)
-
Make EU trade with Brazil sustainable
- 2019
-
Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 364:6438, s. 341-
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
|
|
| 2. |
- Neville, George M., et al.
(författare)
-
Interactions of Choline and Geranate (CAGE) and Choline Octanoate (CAOT) Deep Eutectic Solvents with Lipid Bilayers
- 2023
-
Ingår i: Advanced Functional Materials. - 1616-301X.
-
Tidskriftsartikel (refereegranskat)abstract
- Mixtures between choline and geranic acid (CAGE) have previously been shown to insert into lipid bilayers. This may be useful for the transdermal delivery of larger pharmaceuticals, however, little is known about the mechanism of activity. By comparing the interactions between CAGE and lipid bilayers with those of a less-active, yet closely-related analogue, choline octanoic acid (CAOT), a chemical basis can be investigated. Overall, six systems are studied here by neutron reflectivity, where d54-1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) solid-supported phospholipid bilayers are first formed on SiO2 substrates before exposure to the deep eutectic solvent (DES). Components of the DES could be identified within the bilayer by exploiting contrast variation and selective deuteration. CAGE is shown to be a mild disruptive agent, free to insert and diffuse across the bilayer, preserving much of the bilayer integrity. Experiments identify co-mingling of geranate ions inhibits the efficient packing of lipid tails, increasing hydration across the bilayer. Conversely, CAOT is found to both exchange and remove lipid molecules to achieve incorporation, inducing swelling and the formation of solvent patches. It appears these behaviors derive from the structures of the anions and thus amphiphilicity of the DES, laying the foundations for the rational design and optimization of these candidates toward transdermal delivery.
|
|
| 3. |
- Sanchez-Fernandez, Adrian, et al.
(författare)
-
Long-Range Electrostatic Colloidal Interactions and Specific Ion Effects in Deep Eutectic Solvents
- 2021
-
Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 143:35, s. 14158-14168
-
Tidskriftsartikel (refereegranskat)abstract
- While the traditional consensus dictates that high ion concentrations lead to negligible long-range electrostatic interactions, we demonstrate that electrostatic correlations prevail in deep eutectic solvents where intrinsic ion concentrations often surpass 2.5 M. Here we present an investigation of intermicellar interactions in 1:2 choline chloride:glycerol and 1:2 choline bromide:glycerol using small-angle neutron scattering. Our results show that long-range electrostatic repulsions between charged colloidal particles occur in these solvents. Interestingly, micelle morphology and electrostatic interactions are modulated by specific counterion condensation at the micelle interface despite the exceedingly high concentration of the native halide from the solvent. This modulation follows the trends described by the Hofmeister series for specific ion effects. The results are rationalized in terms of predominant ion-ion correlations, which explain the reduction in the effective ionic strength of the continuum and the observed specific ion effects.
|
|
| 4. |
- Hall, Stephen C.L., et al.
(författare)
-
The interaction of styrene maleic acid copolymers with phospholipids in Langmuir monolayers, vesicles and nanodiscs; a structural study
- 2022
-
Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797. ; 625, s. 220-236
-
Tidskriftsartikel (refereegranskat)abstract
- Hypothesis: Self-assembly of amphipathic styrene maleic acid copolymers with phospholipids in aqueous solution results in the formation of ‘nanodiscs’ containing a planar segment of phospholipid bilayer encapsulated by a polymer belt. Recently, studies have reported that lipids rapidly exchange between both nanodiscs in solution and external sources of lipids. Outstanding questions remain regarding details of polymer-lipid interactions, factors influencing lipid exchange and structural effects of such exchange processes. Here, the dynamic behaviour of nanodiscs is investigated, specifically the role of membrane charge and polymer chemistry. Experiments: Two model systems are investigated: fluorescently labelled phospholipid vesicles, and Langmuir monolayers of phospholipids. Using fluorescence spectroscopy and time-resolved neutron reflectometry, the membrane potential, monolayer structure and composition are monitored with respect to time upon polymer and nanodisc interactions. Findings: In the presence of external lipids, polymer chains embed throughout lipid membranes, the extent of which is governed by the net membrane charge. Nanodiscs stabilised by three different polymers will all exchange lipids and polymer with monolayers to differing extents, related to the properties of the stabilising polymer belt. These results demonstrate the dynamic nature of nanodiscs which interact with the local environment and are likely to deposit both lipids and polymer at all stages of use.
|
|
| 5. |
- Hammond, Oliver S., et al.
(författare)
-
Resilience of Malic Acid Natural Deep Eutectic Solvent Nanostructure to Solidification and Hydration
- 2017
-
Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 121:31, s. 7473-7483
-
Tidskriftsartikel (refereegranskat)abstract
- Little is presently known about the unique nanostructure of deep eutectic solvents (DES). The order of the liquid-solid phase transition is contended and whether DES-water mixtures are merely aqueous solutions, or have properties dominated by the eutectic pair, is unclear. Here, we unambiguously show the structure of choline chloride-malic acid (malicine) as a liquid, and also in solid and hydrated forms, using neutron total scattering on D/H isotope-substituted samples, and quasi-elastic neutron scattering (QENS). Data were refined using empirical potential structure refinement. We show evidence for a stoichiometric complex ion cluster in the disordered liquid, with strong choline-chloride bonding and a hydrogen bond donor (HBD) contribution. The 1:1 eutectic stoichiometry makes these ionic domains more well-defined, with less HBD clustering than seen previously for reline. There is minimal structural difference for the solidified material, demonstrating that this DES solidification is a glass transition rather than a first order phase change. QENS data support this by showing a gradual change in solvent dynamics rather than a step change. The DES structure is mostly retained upon hydration, with water acting both as a secondary smaller HBD at closer range to choline than malic acid, and forming transient wormlike aggregates. This new understanding of DES structure will aid understanding of the properties of these novel green solvents on the molecular length scale in chemical processes, as well as giving an insight into the apparent role of natural DESs in plant physiology.
|
|
| 6. |
- Lee, Sarah C., et al.
(författare)
-
Nano-encapsulated Escherichia coli Divisome Anchor ZipA, and in Complex with FtsZ
- 2019
-
Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 9:1
-
Tidskriftsartikel (refereegranskat)abstract
- The E. coli membrane protein ZipA, binds to the tubulin homologue FtsZ, in the early stage of cell division. We isolated ZipA in a Styrene Maleic Acid lipid particle (SMALP) preserving its position and integrity with native E. coli membrane lipids. Direct binding of ZipA to FtsZ is demonstrated, including FtsZ fibre bundles decorated with ZipA. Using Cryo-Electron Microscopy, small-angle X-ray and neutron scattering, we determine the encapsulated-ZipA structure in isolation, and in complex with FtsZ to a resolution of 1.6 nm. Three regions can be identified from the structure which correspond to, SMALP encapsulated membrane and ZipA transmembrane helix, a separate short compact tether, and ZipA globular head which binds FtsZ. The complex extends 12 nm from the membrane in a compact structure, supported by mesoscale modelling techniques, measuring the movement and stiffness of the regions within ZipA provides molecular scale analysis and visualisation of the early divisome.
|
|
| 7. |
- McCluskey, Andrew R., et al.
(författare)
-
Bayesian determination of the effect of a deep eutectic solvent on the structure of lipid monolayers
- 2019
-
Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 21:11, s. 6133-6141
-
Tidskriftsartikel (refereegranskat)abstract
- In this work, we present the first example of the self-assembly of phospholipid monolayers at the interface between air and an ionic solvent. Deep eutectic solvents are a novel class of environmentally friendly, non-aqueous, room temperature liquids with tunable properties, that have wide-ranging potential applications and are capable of promoting the self-assembly of surfactant molecules. We use a chemically-consistent Bayesian modelling of X-ray and neutron reflectometry measurements to show that these monolayers broadly behave as they do on water. This method allows for the monolayer structure to be determined, alongside the molecular volumes of the individual monolayer components, without the need for water-specific constraints to be introduced. Furthermore, using this method we are able to better understand the correlations present between parameters in the analytical model. This example of a non-aqueous phospholipid monolayer has important implications for the potential uses of these solvents and for our understanding of how biomolecules behave in the absence of water.
|
|
| 8. |
- Nilsson, Emelie J., et al.
(författare)
-
A neutron scattering and modelling study of aqueous solutions of tetramethylammonium and tetrapropylammonium bromide
- 2016
-
Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 18:16, s. 11193-11201
-
Tidskriftsartikel (refereegranskat)abstract
- We have investigated the properties in water of two tetraalkylammonium bromides (tetramethylammonium, TMA+, and tetrapropylammonium, TPA+), at 0.4 M, using neutron scattering coupled with empirical potential structure refinement to arrive at an atomistic description. Having both a polar and an apolar moiety, it is of interest to determine the strength of each moiety as a function of the alkyl chain length. TMA+ and TPA+, having different impact as structure directors in zeolite synthesis, were chosen for this study. Water arranges tetrahedrally around TMA+ and in an almost featureless manner around TPA+. TMA+ and TPA+ show an apolar hydration with TPA+ being slightly more apolar. TPA+ has a tendency to form small clusters of 2-4 molecules and to fold into a compact configuration. Both molecules correlate similarly with the bromide ion but do not dissociate completely at this concentration.
|
|
| 9. |
- Nilsson, Emelie J., et al.
(författare)
-
Stability and behaviour in aqueous solutions of the anionic cubic silsesquioxane substituted with tetramethylammonium
- 2019
-
Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 21:12, s. 6732-6742
-
Tidskriftsartikel (refereegranskat)abstract
- The aqueous behaviour of the anionic octa-tetramethylammonium substituted cubic silsesquioxane, [N(CH 3 ) 4 ] 8 [Si 8 O 20 ], was studied with quantitative 29 Si-NMR. This molecule partially fragments in aqueous solutions, forming several smaller entities. The most abundant silica species are the monomer, dimer, cyclic trimer, cyclic tetramer and double three-ring. Higher concentrations are required in order to prevent complete fragmentation of the cubic structure. Additives such as alcohols and tetraalkylammonium salts have a stabilising effect on the cubic silsesquioxane, unlike sodium salts that destabilise it. A high concentration solution, containing the non-fragmented molecule as well as entities resulting from fragmentations, was investigated with neutron scattering coupled with modelling, using empirical potential structure refinement (EPSR). The modelling reveals that TMA + ions coordinates to all different silica species, with approximately three TMA + per cube. These are located at the faces of the cube.
|
|
| 10. |
- Sanchez-fernandez, Adrian, et al.
(författare)
-
Micellization of alkyltrimethylammonium bromide surfactants in choline chloride:glycerol deep eutectic solvent
- 2016
-
Ingår i: Physical Chemistry Chemical Physics. - 1463-9076. ; 18:48, s. 33240-33249
-
Tidskriftsartikel (refereegranskat)abstract
- Deep eutectic solvents have shown the ability to promote the self-assembly of surfactants in solution. However, some differences have been found compared with self-assembly in pure water and other polar organic solvents. The behaviour of alkyltrimethylammonium bromides in choline chloride:glycerol deep eutectic solvent has been studied by means of surface tension, X-ray and neutron reflectivity and small-angle neutron scattering. The surfactants were found to remain surface active and showed comparable critical micelle concentrations to the same surfactants in water. Our scattering studies demonstrate that these surfactants form globular micelles with ellipsoidal shape in solution. The size, shape and aggregation number of the aggregates were found to vary with the chain length of the surfactant. Specific solvent-headgroup interactions were not found in this system, unlike those we have previously postulated for anionic surfactants in choline chloride deep eutectic solvents.
|
|
| 11. |
- Sanchez-Fernandez, Adrian, et al.
(författare)
-
Surfactant-Solvent Interaction Effects on the Micellization of Cationic Surfactants in a Carboxylic Acid-Based Deep Eutectic Solvent
- 2017
-
Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 33:50, s. 14304-14314
-
Tidskriftsartikel (refereegranskat)abstract
- Deep eutectic solvents have been demonstrated to support amphiphile self-assembly, providing potential alternatives as structure-directing agents in the synthesis of nanostructures, and drug delivery. Here we have expanded on this recent research to investigate the self-assembly of alkyltrimethylammonium bromide surfactants in choline chloride:malonic acid deep eutectic solvent and mixtures of the solvent with water. Surface tension and small-angle neutron scattering were used to determine the behavior of the amphiphiles. Surfactants were found to remain active in the solvent, and surface tension measurements revealed changes in the behavior of the surfactants with different levels of hydration. Small-angle neutron scattering shows that in this solvent the micelle shape depends on the surfactant chain length, varying from globular micelles (aspect ratio ∼2) for short chain surfactants to elongated micelles (aspect ratio ∼14) for long chain surfactants even at low surfactant concentration. We suggest that the formation of elongated micelles can be explained through the interaction of the solvent with the surfactant headgroup, since ion-ion interactions between surfactant headgroups and solvent may modify the morphology of the micelles. The presence of water in the deep eutectic solvents promotes an increase in the charge density at the micelle interface and therefore the formation of less elongated, globular micelles.
|
|
| 12. |
- Atri, Ria S., et al.
(författare)
-
Morphology Modulation of Ionic Surfactant Micelles in Ternary Deep Eutectic Solvents
- 2020
-
Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 124:28, s. 6004-6014
-
Tidskriftsartikel (refereegranskat)abstract
- Deep eutectic solvents (DES) are potentially greener solvents obtained through the complexation of simple precursors which, among other applications, have been investigated in recent years for their ability to support the self-assembly of amphiphilic molecules. It is crucial to understand the factors which influence surfactant solubility and self-assembly with respect to the interaction of the surfactant molecule with the DES components. In this work, small-angle neutron scattering (SANS) has been used to investigate the micellization of cationic (CnTAB) and anionic (SDS) surfactants in a ternary DES comprising choline chloride, urea, and glycerol, where the hydrogen bond donors are mixed in varying molar ratios. The results show that in each case either globular or rodlike micelles are formed with the degree of elongation being directly dependent on the composition of the DES. It is hypothesized that this composition dependence arises largely from the poor solubility of the counterions in the DES, especially at low glycerol content, leading to a tighter binding of the counterion to the micelle surface and giving rise to micelles with a high aspect ratio. This potential for accurate control over micelle morphology presents unique opportunities for rheology control or to develop templated syntheses of porous materials in DES, utilizing the solvent composition to tailor micelle shape and size, and hence the pore structure of the resulting material.
|
|
| 13. |
- Bathke, Elly K., et al.
(författare)
-
The influence of chirality on the structure of a tartaric acid-choline chloride deep eutectic solvent
- 2024
-
Ingår i: Journal of Molecular Liquids. - 0167-7322. ; 402
-
Tidskriftsartikel (refereegranskat)abstract
- The wide range of properties, relative ease and low cost of using Deep Eutectic Solvents garners them interest in an ever expanding range of applications. Among common DES components many are naturally occurring chiral molecules. Here we present the liquid structure of either single enantiomeric or racemic tartaric acid with choline chloride at a molar ratio of 2 choline chloride to 1 tartaric acid, as well as the influence of low amounts of added water (2:1:2) from neutron scattering data with H/D isotropic substitution, refined using empirical potential structure refinement. We show that the overall structure remains the same between the different enatiomeric compositions, with small differences in interactions only occurring between the tartaric acid molecules. The overall structure is also robust towards hydration, similar to what has been found in other DES. We also compare our structures to the structures of DES comprising of similar carboxylic acids (1:1 choline chloride - malic acid, 1:1 choline chloride - oxalic acid), finding overall similar dominant interactions, with differences that may be attributable to the number of available hydrogen bonding sites and steric effects.
|
|
| 14. |
- Callaghan, Ciarán, et al.
(författare)
-
Cellulose Acetate Microbeads for Controlled Delivery of Essential Micronutrients
- 2023
-
Ingår i: ACS Sustainable Chemistry and Engineering. - : American Chemical Society (ACS). - 2168-0485. ; 11:12, s. 4749-4758
-
Tidskriftsartikel (refereegranskat)abstract
- The controlled delivery of micronutrients to soil and plants is essential to increase agricultural yields. However, this is today achieved using fossil fuel-derived plastic carriers, posing environmental risks and contributing to global carbon emissions. In this work, a novel and efficient way to prepare biodegradable zinc-impregnated cellulose acetate beads for use as controlled release fertilizers is presented. Cellulose acetate solutions in DMSO were dropped into aqueous antisolvent solutions of different zinc salts. The droplets underwent phase inversion, forming solid cellulose acetate beads containing zinc, as a function of zinc salt type and concentration. Even higher values of zinc uptake (up to 15.5%) were obtained when zinc acetate was added to the cellulose acetate-DMSO solution, prior to dropping in aqueous zinc salt antisolvent solutions. The release profile in water of the beads prepared using the different solvents was linked to the properties of the counter-ions via the Hofmeister series. Studies in soil showed the potential for longer release times, up to 130 days for zinc sulfate beads. These results, together with the efficient bead production method, demonstrate the potential of zinc-impregnated cellulose acetate beads to replace the plastic-based controlled delivery products used today, contributing to the reduction of carbon emissions and potential environmental impacts due to the uptake of plastic in plants and animals.
|
|
| 15. |
- Engel, Emile, et al.
(författare)
-
Composite Hydrogel Spheroids Based on Cellulose Nanofibrils and Nanofibrous Chiral Coordination Polymer by Green Synthesis
- 2020
-
Ingår i: Advanced Sustainable Systems. - : Wiley-VCH Verlag. - 2366-7486.
-
Tidskriftsartikel (refereegranskat)abstract
- Cellulose-based hydrogels are promising sustainable materials for a variety of applications, including tissue engineering, water treatment, and drug delivery. However, the tailoring of diverse properties by efficient green chemistry methods is an ongoing challenge. Here, composite hydrogels of consistent spheroidal structure, incorporating TEMPO-oxidized cellulose nanofibrils and nanofibrous chiral Cu(II) aspartate coordination polymer, are presented. The hydrogels are prepared by a single-step procedure in aqueous media at ambient temperature and pressure, adhering to the principles of green chemistry. With a view to adapting this method for a variety of alternative coordination polymers (to tailor functional properties), the following critical factors for formation of robust composite hydrogel spheroids are identified: rheological properties of the primary matrix used for spheroidal hydrogel formation and coordination polymer self-assembly rate.
|
|
| 16. |
- Gustavsson, Charlotte, et al.
(författare)
-
Water-Responsive Internally Structured Polymer Surfactant Films on Solid Surfaces
- 2014
-
Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 30:42, s. 12525-12531
-
Tidskriftsartikel (refereegranskat)abstract
- Water-insoluble films of oppositely charged polyionsurfactant ion complex salts (CS) are readily cast on solid surfaces from ethanolic solutions. The methodology introduces new possibilities to study and utilize more or less hydrated CS. Direct SAXS measurements show that the surface films are water-responsive and change their liquid crystalline structure in response to changes in the water activity of the environment. In addition to the classical micellar cubic and hexagonal phases, a rectangular ribbon phase and a hexagonal close-packed structure have now been detected for CS composed of cationic alkyltrimethylammonium surfactants with polyacrylate counterions. Added cosurfactants, decanol or the nonionic surfactant C12E5, yield additional lamellar and bicontinuous cubic structures. Images of the surfaces by optical and atomic force microscopy show that the films cover the surfaces well but have a more or less irregular surface topology, including craters of sizes ranging from a few to hundreds of micrometers. The results indicate possibilities to create a wealth of water-responsive structured CS films on solid surfaces.
|
|
| 17. |
- Hammond, Oliver S., et al.
(författare)
-
Evidence for an L3 phase in ternary deep eutectics : composition-induced L3-to-Lα transition of AOT
- 2023
-
Ingår i: Nanoscale. - 2040-3364. ; 15:47, s. 19314-19321
-
Tidskriftsartikel (refereegranskat)abstract
- Pure and hydrated deep eutectic solvents (DES) are proposed to form self-assembled nanostructures within the fluid bulk, similar to the bicontinuous L3 phase common for ionic liquids (ILs). Labelled choline chloride : urea : water DES were measured using small-angle neutron scattering (SANS), showing no long-range nanostructure. However, solutions of the surfactant AOT in this DES yielded scattering consistent with the L3 “sponge” phase, which was fitted using the Teubner-Strey model. A disclike model gave local structural information, namely, a linear increase in radius versus solvent water content (w = molar ratio of DES : water), eventually forming large, turbid lamellar phases at 10w; an L3-to-Lα transition was observed. Simultaneous multi-contrast SANS fits show the surfactant headgroup region is dominated by interactions with poorly-soluble Na+ at low water contents, and numerically-superior [cholinium]+ as water content increases. The modified interfacial Gaussian curvature from cation : anion volume matching stabilizes the lamellar morphology, allowing the bilayer aggregation number to increase.
|
|
| 18. |
- Hammond, Oliver S., et al.
(författare)
-
Neutron Diffraction Study of Indole Solvation in Deep Eutectic Systems of Choline Chloride, Malic Acid, and Water
- 2022
-
Ingår i: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 28:41
-
Tidskriftsartikel (refereegranskat)abstract
- Deep eutectic systems are currently under intense investigation to replace traditional organic solvents in a range of syntheses. Here, indole in choline chloride-malic acid deep eutectic solvent (DES) was studied as a function of water content, to identify solute interactions with the DES which affect heterocycle reactivity and selectivity, and as a proxy for biomolecule solvation. Empirical Potential Structure Refinement models of neutron diffraction data showed [Cholinium]+ cations associate strongly with the indole π-system due to electrostatics, whereas malic acid is only weakly associated. Trace water is sequestered into the DES and does not interact strongly with indole. When water is added to the DES, it does not interact with the indole π-system but is exclusively in-plane with the heterocyclic rings, forming strong H-bonds with the -NH group, and also weak H-bonds and thus prominent hydrophobic hydration of the indole aromatic region, which could direct selectivity in reactions.
|
|
| 19. |
- Lin, Ruiyu, et al.
(författare)
-
Kinetic Influence of Siliceous Reactions on Structure Formation of Mesoporous Silica Formed via the Co-Structure Directing Agent Route
- 2016
-
Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 120:7, s. 3814-3821
-
Tidskriftsartikel (refereegranskat)abstract
- We investigate the mechanism responsible for the formation of mesoporous silica formed with the so-called costructure directing agent (CSDA) route. The synthesis relies on the interaction between silica source (tetraethylorthosilicate), cationic surfactant (C18H37N+(CH3)2(CH2)3N+(CH3)3Br2), and CSDA (carboxyethylsilanetriol), which results in a material functionalized with carboxylic groups. Depending on the concentration of HCl in the synthesis, the structure is defined by Fm3¯m (at high pH) and by Fd3¯m (at low pH), with a gradual transition in the intermediate pH range. Here, we aim at finding the origin for the structural change triggered by pH and investigate the effects of the hydrolysis of the silica source on the overall kinetics of the synthesis. A fast process results in Fm3¯m, regardless of pH, and a slow process results in Fd3¯m. The hydrolysis step is the important structural control parameter. We studied the cross-linking of silica and CSDA using 29Si NMR. The cross-linking is similar for the two structures, and possibly the Fd3¯m structure contains slightly more CSDA. 13C PT ssNMR was used to investigate the surfactant mobility/rigidity during the synthesis. The rigidity of the Fm3¯m is established much faster than that of the Fd3¯m.
|
|
| 20. |
- López-alled, Carlos M., et al.
(författare)
-
Azulene–boronate esters: colorimetric indicators for fluoride in drinking water
- 2017
-
Ingår i: Chemical Communications. - 1359-7345. ; 53:93, s. 12580-12583
-
Tidskriftsartikel (refereegranskat)abstract
- Low cost andin situfluoride detection by non-experts is importantfor the determination of drinking water safety in developing countries.Colour reagents can provide results quickly without expensiveequipment, but colorimetric fluoride indicators are often non-specific, complex to use or do not work in water. Here we showthat azulene–boronate indicators respond selectively to fluoride atconcentrations relevant to the WHO limit of 1.5 mg L1.
|
|
| 21. |
- Manasi, Iva, et al.
(författare)
-
Cationic Micelles in Deep Eutectic Solvents: Effects of Solvent Composition
- 2024
-
Ingår i: Faraday Discussions. - 1359-6640.
-
Tidskriftsartikel (refereegranskat)abstract
- Deep eutectic solvents (DES) are mixtures of hydrogen bond donors and acceptors that form strongly hydrogen-bonded room temperature liquids. Changing the H-bonding components and their ratios can alter the physicochemical properties of deep eutectic solvents (DES). Recent studies have shown p-toluene sulfonic acid (pTSA) forms room temperature liquids with choline chloride (ChCl) at different molar ratios: 1:1, 1:2 and 2:1 [Rodriguez Rodriguez et al., ACS Sustainable Chemistry and Engineering, 2019, 7(4), 3940]. They also showed that the composition affects the physical properties of these liquids and their ability to dissolve metal oxides. In this work we evaluate the solubility and self-assembly of cationic surfactants alkyltrimethyl ammonium bromides (CnTAB) in these pTSA/ChCl based liquids. CnTABs are insoluble in 1pTSA:2ChCl, whereas in 1pTSA:1ChCl and 2pTSA;1ChCl they form micelles. We characterise CnTAB (n=12, 14, 16) micelles using Small Angle Neutron Scattering and also look at interaction of water with the micelles. These studies help determine the interaction of DES components with the surfactant and the influence of varying pTSA and water ratios on these interactions. This provides potential for controlled surfactant templating and for tuning rheology modification in such systems.
|
|
| 22. |
- Manasi, Iva, et al.
(författare)
-
Nanostructure in Amphiphile-Based Deep Eutectic Solvents
- 2023
-
Ingår i: Langmuir. - 0743-7463. ; 39:47, s. 16776-16784
-
Tidskriftsartikel (refereegranskat)abstract
- Deep eutectic solvents (DESs) are an emerging class of modern, often “green” solvents with unique properties. Recently, a deep eutectic system based on amphiphilic surfactant N-alkyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (C12 & C14 sulfobetaine) and (1S)-(+)-10-camphor-sulfonic acid in the molar ratio 1:1.5 has been reported. Nanostructuring can be expected in this DES due to the nature of the components. In this work, we have investigated the native nanostructure in the DES comprising C12-C18 alkyl chain sulfobetaines with camphor sulfonic acid and how it interacts with polar and nonpolar species, water and dodecane, respectively, using small angle neutron scattering. By using contrast variation to highlight the relative position of the solvent components and additives, we can resolve the structure of the solvent and how it changes upon interaction with water and dodecane. Scattering from the neat DES shows structures corresponding to the self-assembly of sulfobetaines; the size of the structure increases as the alkyl chain length of the sulfobetaines increases. Water and dodecane interact, respectively, with the hydrophilic and hydrophobic moieties in the DES structure, primarily the sulfobetaine, thereby swelling and solvating the entire structure. The extent of the shift of the peak position, and the swelling, depend on concentration of the additive. The solution phase organization and the interaction of polar and nonpolar species as observed here, have the potential to affect the ordering of inorganic or polymeric materials grown in such solvents, paving new avenues for templating applications.
|
|
| 23. |
- Mokhtari, Tahereh, et al.
(författare)
-
Controlling interfacial film formation in mixed polymer-surfactant systems by changing the vapor phase.
- 2014
-
Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 30:33, s. 9991-10001
-
Tidskriftsartikel (refereegranskat)abstract
- Here we show that transport-generated phase separation at the air-liquid interface in systems containing self-assembling amphiphilic molecules and polymers can be controlled by the relative humidity (RH) of the air. We also show that our observations can be described quantitatively with a theoretical model describing interfacial phase separation in a water gradient that we published previously. These phenomena arises from the fact that the water chemical potential corresponding to the ambient RH will, in general, not match the water chemical potential in the open aqueous solution. This implies nonequilibrium conditions at the air-water interface, which in turn can have consequences on the molecular organization in this layer. The experimental setup is such that we can control the boundary conditions in RH and thereby verify the predictions from the theoretical model. The polymer-surfactant systems studied here are composed of polyethylenimine (PEI) and hexadecyltrimethylammonium bromide (CTAB) or didecyldimethylammonium bromide (DDAB). Grazing-incidence small-angle X-ray scattering results show that interfacial phases with hexagonal or lamellar structure form at the interface of dilute polymer-surfactant micellar solutions. From spectroscopic ellipsometry data we conclude that variations in RH can be used to control the growth of micrometer-thick interfacial films and that reducing RH leads to thicker films. For the CTAB-PEI system, we compare the phase behavior of the interfacial phase to the equilibrium bulk phase behavior. The interfacial film resembles the bulk phases formed at high surfactant to polymer ratio and reduced water contents, and this can be used to predict the composition of interfacial phase. We also show that convection in the vapor phase strongly reduces film formation, likely due to reduction of the unstirred layer, where diffusive transport is dominating.
|
|
| 24. |
- Schmitt, Julien, et al.
(författare)
-
Outset of the Morphology of Nanostructured Silica Particles during Nucleation Followed by Ultrasmall-Angle X-ray Scattering
- 2016
-
Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 32:20, s. 5162-5172
-
Tidskriftsartikel (refereegranskat)abstract
- Nucleation and growth of SBA-15 silica nanostructured particles with well-defined morphologies has been followed with time by small-angle X-ray scattering (SAXS) and ultrasmall-angle X-ray scattering (USAXS), using synchrotron radiation. Three different morphologies have been compared: platelets, toroids, and rods. SEM observations of the particles confirm that two key physical parameters control the morphology: the temperature and the stirring of the solution. USAXS curves demonstrate that primary particles with a defined shape are present very early in the reaction mixture, immediately after a very fast nucleation step. This nucleation step is detected at 10 min (56 degrees C) or 15 min (50 degrees C) after the addition of the silica precursor. The main finding is that the USAXS signal is different for each type of morphology, and we demonstrate that the difference is related to the shape of the particles, showing characteristic form factors for the different morphologies (platelet, toroid, and rod). Moreover, the size of the mesocrystal domains is correlated directly with the particle dimensions and shape. When stirred, aggregation between primary particles is detected even after 12 min (56 degrees C). The platelet morphology is promoted by constant stirring of the solution, through an oriented aggregation step between primary particles. In contrast, toroids and rods are only stabilized under static conditions. However, for toroids, aggregation is detected almost immediately after nucleation.
|
|
| 25. |
- Schmitt, Julien, et al.
(författare)
-
TEMPO-oxidised cellulose nanofibrils; Probing the mechanisms of gelation : Via small angle X-ray scattering
- 2018
-
Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 20:23, s. 16012-16020
-
Tidskriftsartikel (refereegranskat)abstract
- The structure of dispersions of TEMPO-oxidised cellulose nanofibrils (OCNF), at various concentrations, in water and in NaCl aqueous solutions, was probed using small angle X-ray scattering (SAXS). OCNF are modelled as rod-like particles with an elliptical cross-section of 10 nm and a length greater than 100 nm. As OCNF concentration increases above 1.5 wt%, repulsive interactions between fibrils are evidenced, modelled by the interaction parameter νRPA > 0. This corresponds to gel-like behaviour, where G′ > G′′ and the storage modulus, G′, shows weak frequency dependence. Hydrogels can also be formed at OCNF concentration of 1 wt% in 0.1 M NaCl(aq). SAXS patterns shows an increase of the intensity at low angle that is modelled by attractive interactions (νRPA < 0) between OCNF, arising from the screening of the surface charge of the fibrils. Results are supported by ζ potential and cryo-TEM measurements.
|
|
| 26. |
- Vidal, Lorena, et al.
(författare)
-
Chemically surface-modified carbon nanoparticle carrier for phenolic pollutants : Extraction and electrochemical determination of benzophenone-3 and triclosan
- 2008
-
Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670. ; 616:1, s. 28-35
-
Tidskriftsartikel (refereegranskat)abstract
- Chemically surface-modified (tosyl-functionalized) carbon nanoparticles (Emperor 2000 from Cabot Corp.) are employed for the extraction and electrochemical determination of phenolic impurities such as benzophenone-3 (2-hydroxy-4-methoxybenzophenone) or triclosan (5-chloro-2-(2,4-dichlorophenoxy)phenol). The hydrophilic carbon nanoparticles are readily suspended and separated by centrifugation prior to deposition onto suitable electrode surfaces and voltammetric analysis. Voltammetric peaks provide concentration information over a 10-100 μM range and an estimated limit of detection of ca. 10 μM (or 2.3 ppm) for benzophenone-3 and ca. 20 μM (or 5.8 ppm) for triclosan. Alternatively, analyte-free carbon nanoparticles immobilized at a graphite or glassy carbon electrode surface and directly immersed in analyte solution bind benzophenone-3 and triclosan (both with an estimated Langmuirian binding constants of K ≈ 6000 mol-1 dm3 at pH 9.5) and they also give characteristic voltammetric responses (anodic for triclosan and cathodic for benzophenone-3) with a linear range of ca. 1-120 μM. The estimated limit of detection is improved to ca.5 μM (or 1.2 ppm) for benzophenone-3 and ca. 10 μM (or 2.3 ppm) for triclosan. Surface functionalization is discussed as the key to further improvements in extraction and detection efficiency.
|
|
| 27. |
- Yang, Philip B., et al.
(författare)
-
Comparison of Cyclic and Linear Poly(lactide)s Using Small-Angle Neutron Scattering
- 2022
-
Ingår i: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 55:24, s. 11051-11058
-
Tidskriftsartikel (refereegranskat)abstract
- Small-angle neutron scattering (SANS) experiments were conducted on cyclic and linear polymers of racemic and l-lactides (PLA) with the goal of comparing chain configurations, scaling, and effective polymer–solvent interactions of the two topologies in acetone-d6 and THF-d8. There are limited reports of SANS results on cyclic polymers due to the lack of substantial development in the field until recently. Now that pure, well-defined cyclic polymers are accessible, unanswered questions about their rheology and physical conformations can be better investigated. Previously reported SANS experiments have used cyclic and linear polystyrene samples; therefore, our work allowed for direct comparison using a contrasting (structurally and sterically) polymer. We compared SANS results of cyclic and linear PLA samples with various microstructures and molecular weights at two different temperatures, allowing for comparison with a wide range of variables. The results followed the trends of previous experiments, but much greater differences in the effective polymer–solvent interaction parameters between cyclic and linear forms of PLA were observed, implying that the small form factor and hydrogen bonding in PLA allowed for much more compact conformations in the cyclic form only. Also, the polymer microstructure was found to influence polymer–solvent interaction parameters substantially. These results illustrate how the difference in polymer–solvent interactions between cyclic and linear polymers can vary greatly depending on the polymer in question and the potential of neutron scattering as a tool for identification and characterization of the cyclic topology.
|
|
| 28. |
- Åberg, Christoffer, et al.
(författare)
-
Nonequilibrium Phase Transformations at the Air-Liquid Interface.
- 2009
-
Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 25:20, s. 12177-12184
-
Tidskriftsartikel (refereegranskat)abstract
- A theoretical model is presented for the formation of an ordered phase close to the air-liquid interface of an open binary aqueous solution. The chemical potential of water in the liquid phase is, in general, not equal to the chemical potential of water in the ambient atmosphere. There are therefore nonequilibrium conditions close to the air-liquid interface. There is also a gradient in the chemical potential of water, which could lead to the formation of a new interfacial phase. The formation of an interfacial phase is analyzed in terms of the equilibrium phase behavior corresponding to the local water chemical potential. The possibility of forming an interfacial phase is strongly dependent on the ambient conditions, bulk composition, and diffusive transport properties of the phases in question. Explicit calculations are presented for the formation of a lamellar liquid-crystalline phase close to the air-liquid interface of an isotropic surfactant solution with parameters chosen from the sodium bis(2-ethylhexyl)sulfosuccinate (AOT)/water system. We consider the relevance of the model to neutron reflectivity studies of the interface between air and surfactant/water systems, as well as to surfactant/polymer/water systems.
|
|
