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Instruments / Technical Area	Publication Details	Published
I07-Surface & interface diffraction	Monovalent - divalent cation competition at the muscovite mica surface: experiment and theory Sander J. T. Brugman , Ben L. Werkhoven , Eleanor R. Townsend , Paolo Accordini , René Van Roij , Elias Vlieg Journal Of Colloid And Interface Science DOI: 10.1016/j.jcis.2019.10.009 Diamond Proposal Number(s): [20228] Open Access Show Abstract ▼ Abstract: Hypothesis: Ion adsorption on mineral surfaces depends on several factors, such as the mineral surface structure and the valency, size and hydration of the ion. In order to understand competitive adsorption at mineral surfaces, experimental techniques are required that can probe multiple ionic species at the same time. By comparing adsorption of two different cations, it should be possible to derive the factors governing ion adsorption. Divalent cations are expected to bind stronger to the negatively-charged muscovite surface than monovalent cations. Experiments: Here, the competition between the monovalent Cs+ and the divalent Ca2+ cation for adsorption at the muscovite mica basal plane was investigated using surface X-ray diffraction. Using an extended surface complexation model, we simultaneously fit the measured cation coverages and net surface charges reported in literature. Findings: In order to reproduce those complementary data sets, both cation adsorption and anion coadsorption were included in the surface complexation model. Moreover, the intrinsic muscovite surface charge and the maximum of available adsorption sites had to be reduced compared to existing literature values. Competition experiments revealed that the affinity of Cs+ for the muscovite surface is larger than the affinity of Ca2+, showing that hydration forces are more important than electrostatics.	Oct 2019
I22-Small angle scattering & Diffraction	Nuclear magnetic resonance and small-angle X-ray scattering studies of mixed sodium dodecyl sulfate and N,N-dimethyldodecylamine N-oxide aqueous systems performed at low temperatures Emily Summerton , Martin J. Hollamby , Cécile S. Le Duff , Emma S. Thompson , Tim Snow , Andrew Smith , Christopher Jones , Jeanluc Bettiol , Serafim Bakalis , Melanie M. Britton Journal Of Colloid And Interface Science DOI: 10.1016/j.jcis.2018.09.053 Diamond Proposal Number(s): [16560] Show Abstract ▼ Abstract: Surfactant crystallisation is important in many applications in the food, consumer product and medical sectors. However, these processes are not well understood. In particular, surfactant crystallisation can be detrimental to the stability of detergent formulations, such as dish liquid products, resulting in a turbid solution that fails appearance criteria. With the rising global demand for detergent products, understanding the factors that influence formulation stability is of increasing importance. To enable industry to build more robust formulations, it is important to understand the underlying chemistry of the crystallisation process. Here, a model system containing anionic (sodium dodecyl sulfate, SDS) and amphoteric (N,N-dimethyldodecylamine N-oxide, DDAO) surfactants, at concentrations typical of dish liquid products, is studied. Variable temperature 1H nuclear magnetic resonance (NMR) spectroscopy and small-angle X-ray scattering (SAXS) is used to probe the compositional and structural properties of this system, as a function of pH. On cooling, at pH 9, a mixture of hydrated crystals, predominately composed of SDS, and micelles containing both surfactants, have been observed prior to complete freezing. At pH 2, both surfactants appear to undergo a simultaneous phase transition, resulting in the removal of micelles and the formation of hydrated crystals of mixed composition.	Sep 2018
I22-Small angle scattering & Diffraction	Understanding heat driven gelation of anionic cellulose nanofibrils: Combining Saturation Transfer Difference (STD) NMR, Small Angle X-ray Scattering (SAXS) and rheology Vincenzo Calabrese , Juan C. Muñoz-garcía , Julien Schmitt , Marcelo A. Da Silva , Janet L. Scott , Jesús Angulo , Yaroslav Z. Khimyak , Karen Edler Journal Of Colloid And Interface Science DOI: 10.1016/j.jcis.2018.09.085 Diamond Proposal Number(s): [163641] Show Abstract ▼ Abstract: A novel mechanism of heat-triggered gelation for oxidised cellulose nanofibrils (OCNF) is reported. We demonstrate that a synergistic approach combining rheology, small-angle X-ray scattering (SAXS) and saturation transfer difference NMR (STD NMR) experiments enables a detailed characterisation of gelation at different length scales. OCNF dispersions experience an increase in solid-like behaviour upon heating as evidenced by rheological studies, associated with enhanced interfibrillar interactions measured using SAXS. Interactions result in an increased fibrillar overlap and increased population of confined water molecules monitored by STD NMR. By comparison, cationic cellulose nanofibrils (produced by reaction of cellulose with trimethylglycidylammonium chloride) were found to be heat-unresponsive.	Sep 2018
I22-Small angle scattering & Diffraction	The impact of N,N-dimethyldodecylamine N-oxide (DDAO) concentration on the crystallisation of sodium dodecyl sulfate (SDS) systems and the resulting changes to viscosity, crystal structure, shape and the kinetics of crystal growth Emily Summerton , Martin J. Hollamby , Georgina Zimbitas , Tim Snow , Andrew J. Smith , Jens Sommertune , Jeanluc Bettiol , Christopher Jones , Melanie Britton , Serafim Bakalis Journal Of Colloid And Interface Science DOI: 10.1016/j.jcis.2018.05.058 Diamond Proposal Number(s): [16560] Show Abstract ▼ Abstract: Hypothesis: At low temperatures stability issues arise in commercial detergent products when surfactant crystallisation occurs, a process which is not currently well-understood. An understanding of the phase transition can be obtained using a simple binary SDS (sodium dodecyl sulfate) + DDAO (N,N-dimethyldodecylamine N-oxide) aqueous system. It expected that the crystallisation temperature of an SDS system can be lowered with addition of DDAO, thus providing a route to improve detergent stability. Experiments: Detergent systems are typically comprised of anionic surfactants, non-ionic surfactants and water. This study explores the crystallisation of a three component system consisting of sodium dodecyl sulfate (SDS), N,N–dimethyldodecylamine N-oxide (DDAO), and water using wide-angle X-ray scattering (WAXS), differential scanning calorimetry (DSC) and confocal Raman microscopy. Findings: The presence of DDAO lowered the crystallisation temperature of a 20 wt. % SDS system. For all aqueous mixtures of SDS + DDAO at low temperatures, SDS hydrated crystals, SDS.1/2H2O or SDS.H2O, formed. SDS hydrates comprising of layers of SDS separated by water layers. DDAO tended to reside in the vicinity of these SDS crystals. In the absence of DDAO an additional intermediary hydrate structure, SDS.1/8H2O, formed whereas for mixed SDS + DDAO systems no such structure was detected during crystallisation.	May 2018
B21-High Throughput SAXS	Water-based fractionation of a commercial humic acid. Solid-state and colloidal characterization of the solubility fractions Weronika M. Swiech , Ian Hamerton , Huang Zeng , David J. Watson , Eleonore Mason , Spencer E. Taylor Journal Of Colloid And Interface Science DOI: 10.1016/j.jcis.2017.08.031 Diamond Proposal Number(s): [15403] Show Abstract ▼ Abstract: Background and hypothesis: Humic acid (HA) is of considerable environmental significance, being a major component of soil, as well as being considered for application in other technological areas. However, its structure and colloidal properties continue to be the subject of debate, largely owing to its molecular complexity and association with other humic substances and mineral matter. As a class, HA is considered to comprise supramolecular assemblies of heterogeneous species, and herein we consider a simple route for the separation of some HA sub-fractions. Experiments: A commercial HA sample from Sigma-Aldrich has been fractionated into two soluble (S1, S2) and two insoluble (I1, I2) fractions by successive dissolution in deionized water at near-neutral pH. These sub-fractions have been characterized by solution and solid-state approaches. Findings: Using this simple approach, the HA has been shown to contain non-covalently bonded species with different polarity and water solubility. The soluble and insoluble fractions have very different chemical structures, as revealed particularly by their solid-state properties (13C NMR and IR spectroscopy, and TGA); in particular, S1 and S2 are characterized by higher carbonyl and aromatic contents, compared with I1 and I2. As shown by solution SAXS measurements and AFM, the soluble fractions behave as hydrophilic colloidal aggregates of at least 50 nm diameter.	Aug 2017
I22-Small angle scattering & Diffraction	The internal structure of poly(methyl methacrylate) latexes in nonpolar solvents Gregory N. Smith , Samuel D. Finlayson , David Gillespie , Jocelyn Peach , Jonathan Pegg , Sarah Rogers , Olga Shebanova , Ann Terry , Steven P. Armes , Paul Bartlett , Julian Eastoe Journal Of Colloid And Interface Science 479, 234 - 243 DOI: 10.1016/j.jcis.2016.06.027 Show Abstract ▼ Abstract: Hypothesis Poly(methyl methacrylate) (PMMA) latexes in nonpolar solvents are an excellent model system to understand phenomena in low dielectric media, and understanding their internal structure is critical to characterizing their performance in both fundamental studies of colloidal interactions and in potential industrial applications. Both the PMMA cores and the poly(12-hydroxystearic acid) (PHSA) shells of the latexes are known to be penetrable by solvent and small molecules, but the relevance of this for the properties of these particles is unknown. Experiments These particles can be prepared in a broad range of sizes, and two PMMA latexes dispersed in n-dodecane (76 and 685 nm in diameter) were studied using techniques appropriate to their size. Small-angle scattering (using both neutrons and X-rays) was used to study the small latexes, and analytical centrifugation was used to study the large latexes. These studies enabled the calculation of the core densities and the amount of solvent in the stabilizer shells for both latexes. Both have consequences on interpreting measurements using these latexes. Findings The PHSA shells are highly solvated (∼85% solvent by volume), as expected for effective steric stabilizers. However, the PHSA chains do contribute to the intensity of neutron scattering measurements on concentrated dispersions and cannot be ignored. The PMMA cores have a slightly lower density than PMMA homopolymer, which shows that only a small free volume is required to allow small molecules to penetrate into the cores. Interestingly, the observations are essentially the same, regardless of the size of the particle; these are general features of these polymer latexes. Despite the latexes being used as a model physical system, the internal chemical structure is complex and must be fully considered when characterizing them.	Oct 2016
I07-Surface & interface diffraction	Langmuir monolayers composed of single and double tail sulfobetaine lipids Gavin Hazell , Anthony P. Gee , Tom Arnold , Karen J. Edler , Simon E. Lewis Journal Of Colloid And Interface Science 474, 190 - 198 DOI: 10.1016/j.jcis.2016.04.020 Diamond Proposal Number(s): [9909] Open Access Show Abstract ▼ Abstract: Owing to structural similarities between sulfobetaine lipids and phospholipids it should be possible to form stable Langmuir monolayers from long tail sulfobetaines. By modification of the density of lipid tail group (number of carbon chains) it should also be possible to modulate the two-dimensional phase behaviour of these lipids and thereby compare with that of equivalent phospholipids. Potentially this could enable the use of such lipids for the wide array of applications that currently use phospholipids. The benefit of using sulfobetaine lipids is that they can be synthesised by a one-step reaction from cheap and readily available starting materials and will degrade via different pathways than natural lipids. The molecular architecture of the lipid can be easily modified allowing the design of lipids for specific purposes. In addition the reversal of the charge within the sulfobetaine head group relative to the charge orientation in phospholipids may modify behaviour and thereby allow for novel uses of these surfactants.	Jul 2016
B18-Core EXAFS	Phosphate effects on cadmium(II) sorption to ferrihydrite Charlotta Tiberg , Jon Petter Gustafsson Journal Of Colloid And Interface Science 471, 103 - 111 DOI: 10.1016/j.jcis.2016.03.016 Diamond Proposal Number(s): [8188] Show Abstract ▼ Abstract: Hypothesis Phosphate influences the sorption of metals to iron (hydr)oxides. An enhanced formation of inner-sphere complexes on the (hydr)oxide surface can be attributed to electrostatic interactions and/or to changes in metal coordination on the iron (hydr)oxide surface. Phosphate was expected to increase cadmium(II) sorption on ferrihydrite. It should be possible to identify changes in cadmium(II) coordination upon phosphate addition by Extended X-ray absorption fine structure (EXAFS) spectroscopy and implement the identified complexes in a surface complexation model (SCM). Experiments The effect of phosphate addition on cadmium(II) sorption to ferrihydrite was studied by a series of batch experiments covering the pH range from 4 to 8. EXAFS spectroscopy was performed on ferrihydrite from the batch experiments at the cadmium K edge. The identified surface complexes were incorporated in the Charge distribution multisite complexation (CD-MUSIC) model, and new surface complexation constants were optimized. Findings Without phosphate addition cadmium(II) formed inner-sphere bidentate complexes on the ferrihydrite surface. With phosphate there was an increased cadmium(II) sorption that could not be explained by electrostatic interactions alone. The enhancement was best explained by the formation of a ternary complex including cadmium(II), phosphate and ferrihydrite surface groups.	Jun 2016
I07-Surface & interface diffraction	Adsorption of Aerosol-OT at the Calcite/Water Interface - Comparison of the sodium and calcium salts Isabella N. Stocker , Kathryn Miller , Rebecca Welbourn , Stuart Clarke , Ian R. Collins , Christy Kinane , Philipp Gutfreund Journal Of Colloid And Interface Science DOI: 10.1016/j.jcis.2013.11.046 Show Abstract ▼ Abstract: The adsorption of the surfactant Aerosol-OT (AOT) at the calcite–water interface has been investigated using batch adsorption isotherms and neutron reflection. The adsorption isotherms showed that NaAOT adsorption followed S-type adsorption behaviour with a maximum surface excess of 2.5 mg m−2 but the method could not be used for the investigation of Ca(AOT)2 adsorption owing to the changes in the bulk phase behaviour of the solution. The surface excess, determined by neutron reflection at the critical micelle concentration (CMC), was 2.5 mg m−2 for Ca(AOT)2 and 1.8 mg m−2 for NaAOT. The time dependence of the NaAOT adsorption suggests a slow conversion from the sodium to the calcium salt of AOT at the calcite–water interface by binding calcium ions released from the slightly soluble calcite. The layer thickness in both cases was 35 Å which indicates adsorption as bilayers or distorted micelles. At higher concentrations of NaAOT (∼10× CMC) adsorption of an AOT lamellar phase was evident from Bragg peaks in the specular reflection. To our knowledge, this is the first time that adsorption of a surfactant at the calcite–water interface has been investigated by neutron reflection. The technique provided significant new insight into the adsorption behaviour of AOT which would not have been accessible using traditional techniques.	Dec 2013
I22-Small angle scattering & Diffraction	Structural and thermal study of mesomorphic dodecylammonium carrageenates M. Vincekovic , A. Pustak , Lj. Tusek-Bozic , Feng Liu , Goran Ungar , M. Bujan , I. Smit , N. Filipovic-Vincekovic Journal of Colloid and Interface Science 341 (1), 117-123 DOI: 10.1016/j.jcis.2009.09.021 Show Abstract ▼ Abstract: Structural characteristics and thermal stability of a series of dodecylammonium carrageenates formed by stoichiometric complexation of dodecylammonium chloride and differently charged carrageenans (kappa-, iota- and lambda-carrageenan, respectively) were investigated. IR spectral analysis confirmed the electrostatic and hydrogen bond interactions between the dodecylammonium and carrageenan species. X-ray diffraction experiments show increased ordering in the complexes compared to that in the parent carrageenans. Dodecylammonium carrageenates have a layer structure, in which a polar sublayer contains layers of carrageenan chains and a nonpolar sublayer consists of conformationally disordered dodecylammonium chains electrostatically attached to the carrageenan backbone. The major factor that determines the dodecylammonium carrageenate structure is cationic surfactant, while the carrageenans moiety plays a major role in determining thermal properties. (C) 2009 Elsevier Inc. All rights reserved.	Jan 2010

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