ORCID Profile
0000-0002-4548-3558
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ANSTO
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Colloid and Surface Chemistry | Physical Chemistry (Incl. Structural)
Industrial Chemicals and Related Products not elsewhere classified |
Publisher: International Union of Crystallography (IUCr)
Date: 10-2022
DOI: 10.1107/S1600576722008056
Abstract: An approach is presented for analysis of real-time X-ray reflectivity (XRR) process data not just as a function of the magnitude of the reciprocal-space vector q , as is commonly done, but as a function of both q and time. The real-space structures extracted from the XRR curves are restricted to be solutions of a physics-informed growth model and use state-of-the-art convolutional neural networks (CNNs) and differential evolution fitting to co-refine multiple time-dependent XRR curves R ( q , t ) of a thin film growth experiment. Thereby it becomes possible to correctly analyze XRR data with a fidelity corresponding to standard fits of in idual XRR curves, even if they are sparsely s led, with a sevenfold reduction of XRR data points, or if the data are noisy due to a 200-fold reduction in counting times. The approach of using a CNN analysis and of including prior information through a kinetic model is not limited to growth studies but can be easily extended to other kinetic X-ray or neutron reflectivity data to enable faster measurements with less beam damage.
Publisher: Wiley
Date: 04-09-2023
Abstract: Slippery covalently‐attached liquid surfaces (SCALS) with low contact angle hysteresis (CAH, ◦) and nanoscale thickness display impressive anti‐adhesive properties, similar to lubricant‐infused surfaces. Their efficacy is generally attributed to the liquid‐like mobility of the constituent tethered chains. However, the precise physico‐chemical properties that facilitate this mobility are unknown, hindering rational design. This work quantifies the chain length, grafting density, and microviscosity of a range of polydimethylsiloxane (PDMS) SCALS, elucidating the nanostructure responsible for their properties. Three prominent methods are used to produce SCALS, with characterization carried out via single‐molecule force measurements, neutron reflectometry, and fluorescence correlation spectroscopy. CO2 snow‐jet cleaning was also shown to reduce the CAH of SCALS via a modification of their grafting density. SCALS behavior can be predicted by reduced grafting density, Σ, with the lowest water CAH achieved at Σ ≈ 2. This study provides the first direct examination of SCALS grafting density, chain length, and microviscosity and supports the hypothesis that SCALS properties stem from a balance of layer uniformity and mobility.
Publisher: American Chemical Society (ACS)
Date: 30-08-2005
DOI: 10.1021/LA050680P
Abstract: The adsorption of selected poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) tri-block copolymers on synthetic clay particles (laponite) has been investigated. The adsorbed amount and distribution of polymer was determined as a function of relative block composition and size, using the technique of contrast variation small-angle neutron scattering. The pluronic molecules appear to adsorb via a preferential segregation of hydrophobic PPO segments at the surface, with hydrophilic PEO segments dangling into solution. The effect of the PPO segments is substantial with large increases in adsorbed amount and layer thickness as the anchor fraction decreases/PEO chain length increases. This is in direct contrast to the behavior observed for PEO homopolymer adsorption (of much higher molecular weights) where the adsorbed amount and layer thickness are smaller and change little with molecular weight.
Publisher: Elsevier BV
Date: 02-2021
Publisher: Wiley
Date: 08-10-2023
Publisher: American Chemical Society (ACS)
Date: 18-11-2020
Publisher: American Chemical Society (ACS)
Date: 25-06-2021
Publisher: Wiley
Date: 15-06-2023
Abstract: The effect of electron‐beam patterning on the water uptake and ionic conductivity of Nafion films using a combination of X‐ray photoelectron spectroscopy, quartz crystal microbalance studies, neutron reflectometry, and impedance spectroscopy is reported. The aim is to further characterize the nanoscale patterned Nafion structures recently used as a key element in novel ion‐to‐electron transducers by Gluschke et al. To enable this, the electron beam patterning process is developed for large areas, achieving patterning speeds approaching 1 cm 2 h −1 , and patterned areas as large as 7 cm 2 for the neutron reflectometry studies. It is ultimately shown that electron‐beam patterning affects both the water uptake and the ionic conductivity, depending on film thickness. Type‐II adsorption isotherm behavior is seen for all films. For thick films (≈230 nm), a strong reduction in water uptake with electron‐beam patterning is found. In contrast, for thin films (≈30 nm), electron‐beam patterning enhances water uptake. Notably, for either thickness, the reduction in ionic conductivity arising from electron‐beam patterning is kept to less than an order of magnitude. Mechanisms are proposed for the observed behavior based on the known complex morphology of Nafion films to motivate future studies of electron‐beam processed Nafion.
Publisher: Wiley
Date: 20-11-2006
Publisher: American Chemical Society (ACS)
Date: 14-10-2020
Publisher: MDPI AG
Date: 06-12-2020
DOI: 10.3390/NANO10122439
Abstract: We have characterized and compared the structures of ergosterol- and cholesterol-containing 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) membranes before and after interaction with the hiphilic antifungal drug hotericin B (AmB) using neutron reflection. AmB inserts into both pure POPC and sterol-containing membranes in the lipid chain region and does not significantly perturb the structure of pure POPC membranes. By selective per-deuteration of the lipids/sterols, we show that AmB extracts ergosterol but not cholesterol from the bilayers and inserts to a much higher degree in the cholesterol-containing membranes. Ergosterol extraction by AmB is accompanied by membrane thinning. Our results provide new insights into the mechanism and antifungal effect of AmB in these simple models of fungal and mammalian membranes and help understand the molecular origin of its selectivity and toxic side effects.
Publisher: Crossref
Date: 06-2006
Publisher: Wiley
Date: 13-03-2023
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C6SM02420C
Abstract: The melanins are a class of pigmentary bio-macromolecules ubiquitous in the biosphere. They possess an intriguing set of physico-chemical properties and have been shown to exhibit hybrid protonic-electronic electrical conductivity, a feature derived from a process termed chemical self-doping driven by the sorption of water. Although the mechanism underlying the electrical conduction has been established, how the sorbed water interacts with the melanin structure at the physical level has not. Herein we use neutron reflectometry to study changes in the structure of synthetic melanin thin films as a function of H
Publisher: IOP Publishing
Date: 08-02-2012
Publisher: Royal Society of Chemistry (RSC)
Date: 2009
DOI: 10.1039/B916046A
Abstract: The effect of water on the surface structure of 1-butyl-1-methylpyrrolidinium trifluoromethylsulfonylimide [C(4)mpyr][NTf(2)] ionic liquid was investigated using X-ray reflectometry. The measured reflectivity data suggests a significant amount of water is adsorbed at the surface, with the first layer from the gas (nitrogen)-liquid phase boundary mainly occupied by a mixture of cations and water. Beyond the cation + water layer, the scattering length density increases towards the bulk value, indicating a decreasing amount of water and cations, and/or an increasing amount of anions. The orientation of the butyl chain of cation at the phase boundary and the population of water at the surface were described based on results from an independent molecular dynamics (MD) simulation. We show that the presence of water in the ionic liquid has a non-monotonic effect on the overall thickness of the surface. At low water content, the addition of water does not change the surface thickness since water is mainly present in the bulk. As the water content increases, the surface swells before eventually shrinking down close to the solubility limit of water. The non-monotonic surface thickness is used to explain the anomalous trend of surface tension in ionic liquid-water mixtures reported in the literature.
Publisher: American Chemical Society (ACS)
Date: 27-01-2014
DOI: 10.1021/LA403951J
Abstract: Fullerene derivatives are commonly used as electron acceptors in combination with (macro)molecular electron donors in bulk heterojunction (BHJ) organic photovoltaic (OPV) devices. Understanding the BHJ structure at different electron donor/acceptor ratios is critical to the continued improvement and development of OPVs. The high neutron scattering length densities (SLDs) of the fullerenes provide effective contrast for probing the distribution of the fullerene within the blend in a nondestructive way. However, recent neutron scattering studies on BHJ films have reported a wide range of SLDs ((3.6-4.4) × 10(-6) Å(-2)) for the fullerenes 60-PCBM and 70-PCBM, leading to differing interpretations of their distribution in thin films. In this article, we describe an approach for determining more precisely the scattering length densities of the fullerenes within a polymer matrix in order to accurately quantify their distribution within the active layers of OPV devices by neutron scattering techniques.
Publisher: Elsevier BV
Date: 11-2014
Publisher: American Chemical Society (ACS)
Date: 13-11-2015
DOI: 10.1021/ACS.LANGMUIR.5B02458
Abstract: Damage to cellular membranes from oxidative stress has been implicated in aging related diseases. We report the effects of oxidative damage on the structure and properties of biomimetic phospholipid membrane systems. Two oxidation methods were used, in situ oxidation initiated using Fe(II) and ascorbate, and the incorporation of a synthetic "oxidized" phospholipid, PoxnoPC, into biomimetic membranes. The biomimetic systems employed included multibilayer stacks, tethered bilayers, and phospholipid monolayers studied using a combination of reflectometry, attenuated total reflection infrared spectroscopy, electrochemical impedance spectroscopy, and neutron diffraction. We show that oxidation with Fe(II) and ascorbate caused an increase in the order of the membrane, attributed to cross-linking of the phospholipids, and a change in the electrical permeability of the membrane, but no significant impact on the thickness or completeness of the membrane. Incorporation of PoxnoPC, on the other hand, had a larger impact on the structure of the membrane. Inversion of the aldehyde-terminated truncated sn-2 chain of PoxnoPC into the head group region was observed, along with a slight decrease in the thickness and order of the membrane.
Publisher: Elsevier BV
Date: 12-2018
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C8SM01824C
Abstract: The internal structure of PNIPAM brush modified silica particles has been probed as a function of temperature and molecular weight.
Publisher: American Chemical Society (ACS)
Date: 05-06-2007
DOI: 10.1021/LA700642D
Abstract: We have measured the viscosity of suspensions of colloidal silica particles (d = 300 nm) and the properties of silica surfaces in solutions of a polymer consisting of zwitterionic monomer groups, poly(sulfobetaine methacrylate), polySBMA. This polymer has potential use in modifying surface properties because the polymer is net uncharged and therefore does not generate double-layer forces. The solubility of the polymer can be controlled and varies from poor to good by the addition of sodium chloride salt. Ellipsometry was used to demonstrate that polySBMA adsorbs to silica and exhibits an increase in surface excess at lower salt concentration, which is consistent with a smaller area per molecule at low salt concentration. Neutron reflectivity measurements show that the adsorbed polymer has a thickness of about 3.7 nm and is highly hydrated. The polymer can be used to exercise considerable control over suspension rheology. When silica particles are not completely covered in polymer, the suspension produces a highly viscous gel. Atomic force microscopy was used to show this is caused by bridging of polymer between the particles. At higher surface coverage, the polymer can produce either a high or very low viscosity slurry depending on the sodium chloride concentration. At high salt concentration, the suspension is stable, and the viscosity is lower. This is probably because the entrainment of many small ions renders the polymer film highly hydrophilic, producing repulsive surface forces and lubricating the flow of particles. At low salt concentrations, the polymer is barely soluble and more densely adsorbed. This produces less stable and more viscous solutions, which we attribute to attractive interactions between the adsorbed polymer layers.
Publisher: Elsevier BV
Date: 03-2017
DOI: 10.1016/J.JCIS.2016.11.044
Abstract: The thermoresponse of poly(di(ethyleneglycol) methyl ether methacrylate) (PMEO
Publisher: AIP Publishing
Date: 07-2010
DOI: 10.1063/1.3455178
Abstract: We describe the design and use of a closed three-electrode electrochemical cell for neutron reflectometry studies of the structure of the electrical double-layer in ionic liquids. A transparent glass counter electrode was incorporated to allow easy monitoring of any gas bubbles trapped in the cell. A 100 mm diameter silicon wafer polished to 0.1 nm rms roughness coated with gold over a chromium adhesion layer was used as the working electrode. The utility of the cell was demonstrated during neutron reflectometry measurements of the ultrahigh purity ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([C4mpyr][NTf2]) at two different applied potentials.
Publisher: American Chemical Society (ACS)
Date: 21-02-2002
DOI: 10.1021/LA0156863
Publisher: Wiley
Date: 22-05-2007
Publisher: Elsevier BV
Date: 10-2015
Publisher: International Union of Crystallography (IUCr)
Date: 02-2023
DOI: 10.1107/S160057672201086X
Abstract: The Spatz neutron beam instrument is the second time-of-flight neutron reflectometer to be installed at the OPAL research reactor. The instrument was formerly the V18 BioRef reflectometer at the BER-II reactor in Berlin and was transferred to Australia in 2016. Subsequently the instrument was re-installed in the neutron guide hall of the OPAL reactor at the end position of the CG2B cold-neutron guide and recommissioned. The instrument performance has not been compromised by the move, with reflectivity achieved down to 10 −7 and good counting statistics within a reasonable time frame using a wavelength range of 2–20 Å. Several different s les at the solid–air interface and the solid–liquid interface have been measured to demonstrate the instrument's capabilities.
Publisher: IOP Publishing
Date: 11-2010
Publisher: Elsevier BV
Date: 11-2006
Publisher: American Chemical Society (ACS)
Date: 07-2018
DOI: 10.1021/ACS.LANGMUIR.8B00434
Abstract: This work systematically explores the biomineralization of calcium phosphate (CaP) and carbonate (CaCO
Publisher: American Chemical Society (ACS)
Date: 19-03-2010
DOI: 10.1021/LA904697G
Abstract: X-ray reflectivity and vibrational sum frequency spectroscopy are used to probe the structure of the ethylammonium nitrate (EAN)-air interface. X-ray reflectivity reveals that the EAN-air interface is structured and consists of alternating nonpolar and charged layers that extend 31 A into the bulk. Vibrational sum frequency spectroscopy reveals interfacial cations have their ethyl moieties oriented toward air, with the CH(3) C(3) axis positioned approximately 36.5 degrees from interface normal. This structure is invariant between 15 and 51 degrees C. On account of its molecular symmetry, the orientation of the nitrate anion cannot be determined with certainty.
Publisher: American Chemical Society (ACS)
Date: 17-07-2009
DOI: 10.1021/LA9017689
Abstract: Determining how analytes are sequestered into thin films is important for solid-state sensors that detect the presence of the analyte by oxidative luminescence quenching. We show that thin (230 +/- 30 A) and thick (750 +/- 50 A) films of a first-generation dendrimer comprised of 2-ethylhexyloxy surface groups, biphenyl-based dendrons, and a 9,9,9',9'-tetra-n-propyl-2,2'-bifluorene core, can rapidly and reversibly detect p-nitrotoluene by oxidative luminescence quenching. For both the thin and thick films the photoluminescence (PL) is quenched by p-nitrotoluene by approximately 90% in 4 s, which is much faster than that reported for luminescent polymer films. Combined PL and neutron reflectometry measurements on pristine and analyte-saturated films gave important insight into the analyte adsorption process. It was found that during the adsorption process the films swelled, being on average 4% thicker for both the thin and thick dendrimer films. At the same time the PL was completely quenched. On removal of the analyte the films returned to their original thickness and scattering length density, and the PL was restored, showing that the sensing process was fully reversible.
Publisher: American Chemical Society (ACS)
Date: 22-05-2013
DOI: 10.1021/LA401074Y
Abstract: The development of novel nano-engineered materials poses important questions regarding the impact of these new materials on living systems. Possible adverse effects must be assessed in order to prevent risks for health and the environment. On the other hand, a thorough understanding of their interaction with biological systems might also result in the creation of novel biomedical applications. We present a study on the interaction of model lipid membranes with gold nanoparticles (AuNP) of different surface modifications. Neutron reflectometry experiments on zwitterionic lipid double bilayers were performed in the presence of AuNP functionalized with cationic and anionic head groups. Structural information was obtained that provided insight into the fate of the AuNPs with regard to the integrity of the model cell membranes. The AuNPs functionalized with cationic head groups penetrate into the hydrophobic moiety of the lipid bilayers and cause membrane disruption at an increased concentration. In contrast, the AuNPs functionalized with anionic head groups do not enter but seem to impede the destruction of the lipid bilayer at an alkaline pH. The information obtained might influence the strategy for a better nanoparticle risk assessment based on a surface charge evaluation and contribute to nano-safety considerations during their design.
Publisher: International Union of Crystallography (IUCr)
Date: 23-08-2008
Publisher: Elsevier BV
Date: 02-2021
Publisher: Elsevier BV
Date: 08-2018
Publisher: Elsevier BV
Date: 03-2023
Publisher: American Vacuum Society
Date: 06-2017
DOI: 10.1116/1.4984010
Abstract: The authors present surface engineering modifications through chemistry of poly(methylmethacrylate) (PMMA) that have dramatic effects on the result of surface-bound fluorescence immunoassays, both for specific and nonspecific signals. The authors deduce the most important effect to be clustering of antibodies on the surface leading to significant self-quenching. Secondary effects are attributable to the formation of sparse multilayers of antibody. The authors compare PMMA as an antibody support surface with ultraviolet-ozone oxidized PMMA and also to substrates that were, after the oxidation, surface modified by a four-unit poly(ethyleneglycol) carboxylic acid (PEG4), a branched tricarboxylic acid, and a series of carboxylic acid-terminated dendrimers, from generation 1.5 to 5.5. Fluorescence immunoassay and neutron reflectometry were used to compare the apparent antibody surface loading, antigen binding and nonspecific binding on these various surfaces using anti-human IgG as a model antibody, chemically coupled to the surface by amide formation. Simple physical adsorption of the antibody on PMMA resulted in a thick antibody multilayer with small antigen binding capacity. On the carboxylated surfaces, with chemical coupling, a simple monolayer was formed. The authors deduce that antibody clustering was driven by conformational inflexibility and high carboxylate density. The PEG4-modified surface was the most conformationally flexible. The dendrimer-modified interfaces showed a collapse and densification. In fluorescence immunoassay, the optimal combination of high specific and low nonspecific fluorescence signal was found for the G3.5 dendrimer.
Publisher: Elsevier BV
Date: 09-2022
Publisher: American Chemical Society (ACS)
Date: 18-09-2018
Publisher: Springer Science and Business Media LLC
Date: 24-02-2020
DOI: 10.1038/S41592-020-0772-5
Abstract: An amendment to this paper has been published and can be accessed via a link at the top of the paper.
Publisher: American Chemical Society (ACS)
Date: 22-01-2018
Abstract: Organic light-emitting devices containing solution-processed emissive dendrimers can be highly efficient. The most efficient devices contain a blend of the light-emitting dendrimer in a host and one or more charge-transporting layers. Using neutron reflectometry measurements with in situ photoluminescence, we have investigated the structure of the as-formed film as well as the changes in film structure and dendrimer emission under thermal stress. It was found that the as-formed film stacks comprising poly(3,4-ethylenedioxythiophene):polystyrene sulfonate/host:dendrimer/1,3,5-tris(N-phenylbenzimidazol-2-yl)benzene (where the host was deuterated 4,4'-N,N'-di(carbazolyl)biphenyl or tris(4-carbazol-9-ylphenyl)amine, the host:dendrimer layer was solution-processed, and the 1,3,5-tris(N-phenylbenzimidazol-2-yl)benzene evaporated) had well-defined interfaces, indicating good wetting of each of the layers by the subsequently deposited layer. Upon thermal annealing, there was no change in the poly(3,4-ethylenedioxythiophene):polystyrene sulfonate/host:dendrimer interface, but once the temperature reached above the T
Publisher: The Chemical Society of Japan
Date: 05-10-2012
DOI: 10.1246/CL.2012.1247
Publisher: The Royal Society
Date: 28-09-2011
Abstract: Plasma-enhanced chemical vapour-deposited films of di(ethylene glycol) dimethyl ether were analysed by a combination of X-ray photoelectron spectroscopy, atomic force microscopy, quartz crystal microbalance with dissipation monitoring (QCM-D), X-ray and neutron reflectometry (NR). The combination of these techniques enabled a systematic study of the impact of plasma deposition conditions upon resulting film chemistry (empirical formula), mass densities, structure and water solvation, which has been correlated with the films' efficacy against protein fouling. All films were shown to contain substantially less hydrogen than the original monomer and absorb a vast amount of water, which correlated with their mass density profiles. A proportion of the plasma polymer hydrogen atoms were shown to be exchangeable, while QCM-D measurements were inaccurate in detecting associated water in lower power films that contained loosely bound material. The higher protein resistance of the films deposited at a low load power was attributed to its greater chemical and structural similarity to that of poly(ethylene glycol) graft surfaces. These studies demonstrate the utility of using X-ray and NR analysis techniques in furthering the understanding of the chemistry of these films and their interaction with water and proteins.
Publisher: Informa UK Limited
Date: 07-2005
Publisher: American Chemical Society (ACS)
Date: 04-11-2011
DOI: 10.1021/MA201717E
Publisher: Royal Society of Chemistry (RSC)
Date: 2023
DOI: 10.1039/D2PY01487D
Abstract: Structural characterisation of thermoresponsive polymer brushes in binary DMSO–water mixtures reveals both LCST and UCST behaviour.
Publisher: American Chemical Society (ACS)
Date: 22-10-2004
DOI: 10.1021/LA049323P
Abstract: Dynamic light scattering has been used to determine the hydrodynamic thickness of poly(ethylene oxide) (PEO) adsorbed on synthetic anisotropic clay particles (Laponite) as a function of molecular weight. The layer thicknesses, and their increase with molecular weight, indicate that the conformation of the adsorbed layer is very compact and is much smaller than those normally observed for polymer adsorption on flat interfaces. The aggregation kinetics of the polymer coated particles in 5 mM NaCl was analyzed in a quantitative manner, revealing that the potential barrier to aggregation is strongly enhanced when polymer is present.
Publisher: American Chemical Society (ACS)
Date: 09-08-2010
DOI: 10.1021/JP105317E
Abstract: The electrical double-layer structure and capacitance in room temperature ionic liquids at electrified interfaces were systematically studied with use of the self-consistent mean-field theory. The capacitance curve departs from symmetry with respect to the point of zero charge when unequal ion-size is implemented or when specific adsorption of ions is introduced. For the case of unequal ion-size, the shape of the capacitance curve is strongly determined by the size of the counterion and only weakly influenced by the co-ion size. When present, specifically adsorbed ions would change the capacitance within a limited range of applied potential from the point of zero charge, which itself varies with the strength of specific adsorption.
Publisher: International Union of Crystallography (IUCr)
Date: 10-05-2014
DOI: 10.1107/S1600576714009595
Abstract: In the paper by Nelson [ J. Appl. Cryst. (2013), 46 , 1338–1346], Charles Dewhurst is missing from the list of authors. The complete list of authors should be A. R. J. Nelson and C. D. Dewhurst.
Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C2RA22643J
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C8NR08195F
Abstract: Self-assembled monolayers of iodo-perfluoro alkanes are shown to form on silica surfaces, guided by halogen bonding.
Publisher: International Union of Crystallography (IUCr)
Date: 16-04-2021
DOI: 10.1107/S160057672100251X
Abstract: Neutron reflectometry is the foremost technique for in situ determination of the volume fraction profiles of polymer brushes at planar interfaces. However, the subtle features in the reflectometry data produced by these diffuse interfaces challenge data interpretation. Historically, data analyses have used least-squares approaches that do not adequately quantify the uncertainty of the modeled profile and ignore the possibility of other structures that also match the collected data (multimodality). Here, a Bayesian statistical approach is used that permits the structural uncertainty and multimodality to be quantified for polymer brush systems. A free-form model is used to describe the volume fraction profile, minimizing assumptions regarding brush structure, while only allowing physically reasonable profiles to be produced. The model allows the total volume of polymer and the profile monotonicity to be constrained. The rigor of the approach is demonstrated via a round-trip analysis of a simulated system, before it is applied to real data examining the well characterized collapse of a thermoresponsive brush. It is shown that, while failure to constrain the interfacial volume and consider multimodality may result in erroneous structures being derived, carefully constraining the model allows for robust determination of polymer brush compositional profiles. This work highlights that an appropriate combination of flexibility and constraint must be used with polymer brush systems to ensure the veracity of the analysis. The code used in this analysis is provided, enabling the reproduction of the results and the application of the method to similar problems.
Publisher: American Chemical Society (ACS)
Date: 05-2012
DOI: 10.1021/LA3005757
Abstract: The structure of 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([C(4)mpyr][NTf(2)]) room-temperature ionic liquid at an electrified gold interface was studied using neutron reflectometry, cyclic voltammetry, and differential capacitance measurements. Subtle differences were observed between the reflectivity data collected on a gold electrode at three different applied potentials. Detailed analysis of the fitted reflectivity data reveals an excess of [C(4)mpyr](+) at the interface, with the amount decreasing at increasingly positive potentials. A cation rich interface was found even at a positively charged electrode, which indicates a nonelectrostatic (specific) adsorption of [C(4)mpyr](+) onto the gold electrode.
Publisher: AIP Publishing
Date: 06-06-2023
DOI: 10.1063/5.0146847
Abstract: The capture of moisture from the atmosphere through condensation has the potential to provide a sustainable source of water. Here, we investigate the condensation of humid air at low subcooling condition (11 °C), similar to conditions for natural dew capture, and explore how water contact angle and contact angle hysteresis affect the rates of water capture. We compare water collection on three families of surfaces: (i) hydrophilic (polyethylene oxide, MPEO) and hydrophobic (polydimethylsiloxane, PDMS) molecularly thin coatings grafted on smooth silicon wafers, which produce slippery covalently attached liquid surfaces (SCALSs), with low contact angle hysteresis (CAH = 6°) (ii) the same coatings grafted on rougher glass, with high CAH (20°–25°) (iii) hydrophilic polymer surfaces [poly(N-vinylpyrrolidone), PNVP] with high CAH (30°). Upon exposure to water, the MPEO SCALS swell, which likely further increases their droplet shedding ability. MPEO and PDMS coatings collect similar volume of water (around 5 l m−2 day−1), both when they are SCALS and non-slippery. Both MPEO and PDMS layers collect about 20% more water than PNVP surfaces. We present a basic model showing that, under low heat flux conditions, on all MPEO and PDMS layers, the droplets are so small (600–2000 µm) that there is no/low heat conduction resistance across the droplets, irrespective of the exact value of contact angle and CAH. As the time to first droplet departure is much faster on MPEO SCALS (28 min) than on PDMS SCALS (90 min), slippery hydrophilic surfaces are preferable in dew collection applications where the collection time frame is limited.
Publisher: Inderscience Publishers
Date: 2017
Publisher: American Chemical Society (ACS)
Date: 22-09-2023
Publisher: Springer US
Date: 02-12-2021
Publisher: American Chemical Society (ACS)
Date: 06-01-2012
DOI: 10.1021/BM201404X
Abstract: Tropoelastin is the precursor of the extracellular protein elastin and is utilized in tissue engineering and implant technology by adapting the interface presented by surface-bound tropoelastin. The preferred orientation of the surface bound protein is relevant to biointerface interactions, as the C-terminus of tropoelastin is known to be a binding target for cells. Using recombinant human tropoelastin we monitored the binding of tropoelastin on hydrophilic silica and on silica made hydrophobic by depositing a self-assembled monolayer of octadecyl trichlorosilane. The layered organization of deposited tropoelastin was probed using neutron and X-ray reflectometry under aqueous and dried conditions. In a wet environment, tropoelastin retained a solution-like structure when adsorbed on silica but adopted a brush-like structure when on hydrophobized silica. The orientation of the surface-bound tropoelastin was investigated using cell binding assays and it was found that the C-terminus of tropoelastin faced the bulk solvent when bound to the hydrophobic surface, but a mixture of orientations was adopted when tropoelastin was bound to the hydrophilic surface. Drying the tropoelastin-coated surfaces irreversibly altered these protein structures for both hydrophilic and hydrophobic surfaces.
Publisher: Elsevier BV
Date: 02-2018
Publisher: Elsevier BV
Date: 03-2021
Publisher: Wiley
Date: 29-12-2012
Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C3SM50350J
Publisher: AIP Publishing
Date: 08-2012
DOI: 10.1063/1.4738579
Abstract: This review presents the implementation and full characterization of the polarization equipment of the time-of-flight neutron reflectometer PLATYPUS at the Australian Nuclear Science and Technology Organisation (ANSTO). The functionality and efficiency of in idual components are evaluated and found to maintain a high neutron beam polarization with a maximum of 99.3% through polarizing Fe/Si supermirrors. Neutron spin-flippers with efficiencies of 99.7% give full control over the incident and scattered neutron spin direction over the whole wavelength spectrum available in the instrument. The first scientific experiments illustrate data correction mechanisms for finite polarizations and reveal an extraordinarily high reproducibility for measuring magnetic thin film s les. The setup is now fully commissioned and available for users through the neutron beam proposal system of the Bragg Institute at ANSTO.
Publisher: Royal Society of Chemistry (RSC)
Date: 2011
DOI: 10.1039/C0SM01284J
Publisher: American Chemical Society (ACS)
Date: 05-08-2016
Publisher: American Chemical Society (ACS)
Date: 24-11-2006
DOI: 10.1021/LA052196S
Abstract: Radio-frequency glow-discharge plasma polymer thin films of allylamine (AA) and hexamethyldisiloxane (HMDSO) were prepared on silicon wafers and analyzed by a combination of X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), X-ray reflectometry (XRR), and neutron reflectometry (NR). AFM and XRR measurements revealed uniform, smooth, defect-free films of 20-30 nm thickness. XPS measurements gave compositional data on all elements in the films with the exception of hydrogen. In combination with XRR and NR, the film composition and mass densities (1.46 and 1.09 g cm(-)(3) for AA and HMDSO, respectively) were estimated. Further NR measurements were conducted with the AA and HMDSO films in contact with water at neutral pH. Three different H(2)O/D(2)O mixtures were used to vary the contrast between the aqueous phase and the polymer. The amount of water penetrating the film, as well as the number of labile protons present, was determined. The AA film in contact with water was found to swell by approximately 5%, contain approximately 3% water, and have approximately 24% labile protons. The HDMSO polymer was found to have approximately 6% labile protons, no thickness increase when in contact with water, and essentially no solvent penetration into the film. The difference in the degree of proton exchange within the films was attributed to the substantially different surface and bulk chemistries of the two films.
Publisher: Wiley
Date: 05-2017
DOI: 10.1002/SDTP.11839
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C5TB00702J
Abstract: A zein protein layer was used to mineralize thin films of calcium phosphate at the air–solution interface producing an iridescent mineral film with novel nano-morphology.
Publisher: Elsevier BV
Date: 07-2012
Publisher: Royal Society of Chemistry (RSC)
Date: 2011
DOI: 10.1039/C1SM05287J
Publisher: Elsevier BV
Date: 12-2022
Publisher: Elsevier BV
Date: 03-2023
Publisher: Elsevier BV
Date: 10-2023
Publisher: International Union of Crystallography (IUCr)
Date: 12-03-2006
DOI: 10.1107/S0021889806005073
Abstract: The contrast-variation technique is employed in multiple-contrast neutron/X-ray reflectometry experiments to highlight scattering from different structural components that are present at a surface or interface. The advantage of this technique is that the structural model used to describe the interfacial scattering length density profile must apply to all the contrasts measured. A new reflectivity analysis package, MOTOFIT , which runs in the IGOR Pro environment (www.wavemetrics.com), has been created to aid the simultaneous fitting (with the same structural model) of these multiple-contrast data, using an intuitive graphical user interface, which most co-refinement packages do not possess. MOTOFIT uses a slab-model approach with the Abeles matrix method, and extensions for surface roughness to perform non-linear least-squares regression on the experimental reflectivity curves. Other features, such as the ability to create complicated interparameter constraints or analyse reflectivity from multilayers, simulated annealing, etc. , make MOTOFIT a powerful reflectometry analysis package
Publisher: American Chemical Society (ACS)
Date: 02-10-2019
DOI: 10.1021/ACS.LANGMUIR.9B02054
Abstract: Ultraviolet irradiation (UVI) of varied duration caused cross-linking and neutralization of polystyrene (PS) homopolymers of molar mass (
Publisher: Royal Society of Chemistry (RSC)
Date: 2011
DOI: 10.1039/C1CP22351H
Abstract: The structure of the free liquid surface of three protic ionic liquids, ethylammonium nitrate (EAN), propylammonium nitrate (PAN), and ethylammonium formate (EAF), has been elucidated using X-ray reflectivity. The results show all three liquids have an extended interfacial region, spanning at least five ion pairs, which can be ided into two parts. Adjacent to the gas phase are aggregates consisting of multiple cations and anions. Below this are layers oriented parallel to the macroscopic surface that are alternately enriched and depleted in cation alkyl chains and polar domains of cation ammonium groups and their anions, gradually decaying to the isotropic sponge-like bulk structure. The most pronounced layering is observed for PAN, driven by strong solvophobic interactions, while reduced hydrogen bonding in EAF results in the least structured and least extensive interfacial region.
Publisher: American Chemical Society (ACS)
Date: 09-03-2022
Publisher: Royal Society of Chemistry (RSC)
Date: 2023
DOI: 10.1039/D3CP02206D
Abstract: Hypersaline environments are ubiquitous in nature and are found in myriad technological processes. Recent empirical studies have revealed a significant discrepancy between the predicted and observed screening lengths at high...
Publisher: Royal Society of Chemistry (RSC)
Date: 2012
DOI: 10.1039/C2SM25082A
Publisher: American Chemical Society (ACS)
Date: 08-02-2016
Publisher: American Chemical Society (ACS)
Date: 13-02-2004
DOI: 10.1021/LA035268T
Abstract: The adsorption of poly(ethylene oxide) (PEO) on synthetic anisotropic clay particles (Laponite) has been investigated as a function of the molecular weight. Contrast variation small-angle neutron scattering (SANS) measurements were used to characterize the distribution and adsorbed amount of polymer on the particles. These experiments show not only that polymer is present on the face of the clay particle but that it also extends or "wraps" over the edges. The edge layer was thicker than the face layer for all the molecular weights studied. The polymer layers are unusually thin, with a thickness and adsorbed amount that show little variation with molecular weight.
Publisher: Elsevier BV
Date: 03-2011
Publisher: Wiley
Date: 22-06-2016
Publisher: Royal Society of Chemistry (RSC)
Date: 2008
DOI: 10.1039/B714248J
Publisher: Springer Science and Business Media LLC
Date: 03-02-2020
DOI: 10.1038/S41592-019-0686-2
Abstract: SciPy is an open-source scientific computing library for the Python programming language. Since its initial release in 2001, SciPy has become a de facto standard for leveraging scientific algorithms in Python, with over 600 unique code contributors, thousands of dependent packages, over 100,000 dependent repositories and millions of downloads per year. In this work, we provide an overview of the capabilities and development practices of SciPy 1.0 and highlight some recent technical developments.
Publisher: American Chemical Society (ACS)
Date: 07-06-2017
Abstract: Understanding the interaction of adsorbed or covalently immobilized proteins with solid substrates at the molecular level guides the successful design of functionalized surfaces used in biomedical applications. In this report, neutron reflectometry (NR) was used to characterize the structure of surface-attached antimicrobial protein films, with antimicrobial activity assessed using an adaption of the Japanese Industrial Standard Test JIS Z 2801. NR allowed parameters influencing bioactivity to be measured at nanometer resolution and for conclusions about structural characteristics relating to bioactivity to be drawn. Hydramacin-1 (HM-1) and lysozyme were covalently attached to poly(methyl methacrylate) (PMMA) and 3-aminopropyltriethoxysilane (APTES) films in the presence and absence of a four-unit poly(ethylene glycol) PEG-based spacer and measured using NR, followed by antimicrobial assays. APTES-PEG-protein films were structurally unique, with a layer of 80% water directly beneath the protein layer, and were the only films that displayed antimicrobial activity against Escherichia coli and Bacillus subtilis. The hydration content of these films combined with the subtle difference in the PEG layer thickness of APTES versus PMMA films played a role in defining antimicrobial activity of the prepared surface coatings.
Publisher: American Chemical Society (ACS)
Date: 12-07-2018
DOI: 10.1021/ACS.LANGMUIR.8B01686
Abstract: The interfacial structures of a range of hiphilic molecules are studied with both "soft" and "hard" hydrophobic substrates. Neutron reflection and quartz crystal microbalance with dissipation measurements highlight the differences between the adsorbed structures adopted by sodium dodecyl sulfate (SDS), cetyltrimethylammonium bromide (C
Publisher: Wiley
Date: 25-10-2018
Publisher: Elsevier BV
Date: 11-2018
Publisher: Elsevier BV
Date: 02-2023
DOI: 10.1016/J.JCIS.2022.10.071
Abstract: Anionic surfactants have been reported to interact with poly(N-isopropyl acrylamide) (PNIPAM), suppressing its thermoresponse. Scattering and NMR studies of the anionic sodium dodecylsulfate (SDS) system propose that the PNIPAM-surfactant interaction is purely hydrophobic. However, prior phenomenological investigations of a range of surfactant identities (anionic, cationic, nonionic) show that only anionic surfactants affect the thermoresponse and conformation of PNIPAM, implying that the hydrophilic head-group also contributes. Crucially, the phenomenological experiments do not measure the affinity of the tested surfactants to the polymer, only their effect on its behaviour. We study the adsorption of six surfactants within a planar PNIPAM brush system, elucidating the polymer conformation, thermoresponse, and surfactant adsorption kinetics using ellipsometry, neutron reflectometry (NR), optical reflectometry and the quartz crystal microbalance technique. NR is used to measure the distribution of surfactants within the brush. We find that only anionic surfactants modify the structure and thermoresponse of PNIPAM, with the greater affinity of anionic surfactants for PNIPAM (relative to cationic and nonionic surfactants) being the primary reason for this behaviour. These results show that the surfactant head-group has a more critical role in mediating PNIPAM-surfactant interaction than previously reported. Taking inspiration from prior molecular dynamics work on the PEO-surfactant system, we propose an interaction mechanism for PNIPAM and SDS that reconciles evidence for hydrophobic interaction with the observed head-group-dependent affinity.
Publisher: International Union of Crystallography (IUCr)
Date: 02-2019
DOI: 10.1107/S1600576718017296
Abstract: refnx is a model-based neutron and X-ray reflectometry data analysis package written in Python. It is cross platform and has been tested on Linux, macOS and Windows. Its graphical user interface is browser based, through a Jupyter notebook. Model construction is modular, being composed from a series of components that each describe a subset of the interface, parameterized in terms of physically relevant parameters (volume fraction of a polymer, lipid area per molecule etc. ). The model and data are used to create an objective, which is used to calculate the residuals, log-likelihood and log-prior probabilities of the system. Objectives are combined to perform co-refinement of multiple data sets and mixed-area models. Prior knowledge of parameter values is encoded as probability distribution functions or bounds on all parameters in the system. Additional prior probability terms can be defined for sets of components, over and above those available from the parameters alone. Algebraic parameter constraints are available. The software offers a choice of fitting approaches, including least-squares (global and gradient-based optimizers) and a Bayesian approach using a Markov-chain Monte Carlo algorithm to investigate the posterior distribution of the model parameters. The Bayesian approach is useful for examining parameter covariances, model selection and variability in the resulting scattering length density profiles. The package is designed to facilitate reproducible research its use in Jupyter notebooks, and subsequent distribution of those notebooks as supporting information, permits straightforward reproduction of analyses.
Publisher: Wiley
Date: 03-03-2023
Abstract: Coatings of anisotropic nanoparticles such as cellulose nanocrystals (CNCs) can provide tuneable physicochemical surface properties to a substrate such as modifying wettability. These coatings are often formed using dip coating, with CNCs enriched at the air–water interface transferred to a substrate as a monolayer. This process is commonly facilitated by surfactants, which can remain present in the final product, affecting coating properties. In this work, an “additive free” method for creating CNC coatings by exploiting electrostatic interactions within the pH window between pH 2–4 is demonstrated. Within this pH window, the air–water interface is positively charged and CNCs are negatively charged, with surface pressure tensiometry, X‐ray reflectivity, and Brewster angle microscopy indicating that CNCs are driven to the air–water interface. The optimal condition for monolayer coverage was pH 3 at pH 2 charge screening causes localized flocculation at the air–water interface, and at pH 4 interparticle repulsion leads to incomplete, patchy coverage. These findings successfully translate to dip coated CNC monolayers as characterized by atomic force microscopy, showing that the manipulation of pH can facilitate the surfactant‐free dip coating of CNCs, with advantages over the surfactants that are more typically used.
Publisher: American Chemical Society (ACS)
Date: 23-02-2021
Publisher: Wiley
Date: 14-09-2022
Abstract: Coating a substrate with anisotropic nanoparticles such as cellulose nanocrystals (CNCs) confers some of their desirable physicochemical properties, such as strength, wettability, and barrier properties. The formation of monolayer coatings of CNCs via dip coating is affected by the enrichment of CNCs at both air–liquid and substrate–liquid interfaces. In this work, a surfactant‐free method for dip coating CNCs is presented through use of the hydrotrope tetraethylammonium chloride. Hydrotropes demonstrate a different mechanism for facilitating interfacial enrichment, adsorbing to CNCs and rendering them weakly hydrophobic, causing them to adsorb to both solid–liquid and air–liquid interfaces without affecting the surface tension of the system. This new coating mechanism may be more robust as adsorption onto the substrate from the bulk dispersion is less sensitive to the air–liquid interface. Adsorption at the solid–liquid interface showed two distinct CNC layers, with a tightly bound, close‐packed CNC layer at the interface, and a loosely associated outer layer. Adsorption of both layers is shown to be fully reversible after washing with ultra pure water, highlighting the potential of hydrotropes for facilitating new coating mechanisms.
Publisher: Elsevier BV
Date: 12-2020
Publisher: Elsevier BV
Date: 03-2019
Publisher: Elsevier BV
Date: 06-2012
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C8CP06644B
Abstract: The temperature induced swelling/collapse transition of poly(oligoethylene glycol methacrylate) (POEGMA) brushes has been investigated in electrolyte solutions comprised of multiple anions.
Publisher: The Open Journal
Date: 17-11-2019
DOI: 10.21105/JOSS.01864
Publisher: Wiley
Date: 04-09-2023
Abstract: Slippery covalently‐attached liquid surfaces (SCALS) with low contact angle hysteresis (CAH, ◦) and nanoscale thickness display impressive anti‐adhesive properties, similar to lubricant‐infused surfaces. Their efficacy is generally attributed to the liquid‐like mobility of the constituent tethered chains. However, the precise physico‐chemical properties that facilitate this mobility are unknown, hindering rational design. This work quantifies the chain length, grafting density, and microviscosity of a range of polydimethylsiloxane (PDMS) SCALS, elucidating the nanostructure responsible for their properties. Three prominent methods are used to produce SCALS, with characterization carried out via single‐molecule force measurements, neutron reflectometry, and fluorescence correlation spectroscopy. CO2 snow‐jet cleaning was also shown to reduce the CAH of SCALS via a modification of their grafting density. SCALS behavior can be predicted by reduced grafting density, Σ, with the lowest water CAH achieved at Σ ≈ 2. This study provides the first direct examination of SCALS grafting density, chain length, and microviscosity and supports the hypothesis that SCALS properties stem from a balance of layer uniformity and mobility.
Publisher: Elsevier BV
Date: 2005
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C7CE01303E
Abstract: An 11 Å mineral film above a dense prenucleation cluster subphase is shown to be the structure of the early stage of calcium phosphate nucleation from a simulated body fluid.
Publisher: International Union of Crystallography (IUCr)
Date: 18-09-2013
DOI: 10.1107/S0021889813021936
Abstract: In this article a `detailed' form of the resolution kernel used to analyse data from reactor-based time-of-flight (TOF) neutron reflectometers is derived. In contrast to monochromatic neutron reflectometers, where the resolution kernel is close to Gaussian, TOF neutron reflectometers can have trapezoidal resolution kernels. This is a consequence of the disc chopper systems used to pulse the beam having a wavelength uncertainty that is rectangular in shape. The effect of using the detailed and approximate kernels is compared, with the main effects occurring where the width of the kernel is approximately the same as the width of the features in the reflectivity curve, i.e. around the critical edge and at high Q z . The difference between the two kernels is greatest when the wavelength and angular components are of different sizes.
Publisher: American Chemical Society (ACS)
Date: 08-2008
DOI: 10.1021/AC800823F
Publisher: American Chemical Society (ACS)
Date: 13-04-2017
Abstract: Organic light-emitting diodes (OLEDs) are subject to thermal stress from Joule heating and the external environment. In this work, neutron reflectometry (NR) was used to probe the effect of heat on the morphology of thin three-layer organic films comprising materials typically found in OLEDs. It was found that layers within the films began to mix when heated to approximately 20 °C above the glass-transition temperature (T
Publisher: Wiley
Date: 15-10-2016
Publisher: The Royal Society
Date: 06-03-2013
Abstract: Mixtures of a large, structured protein with a smaller, unstructured component are inherently complex and hard to characterize at interfaces, leading to difficulties in understanding their interfacial behaviours and, therefore, formulation optimization. Here, we investigated interfacial properties of such a mixed system. Simplicity was achieved using designed sequences in which chemical differences had been eliminated to isolate the effect of molecular size and structure, namely a short unstructured peptide (DAMP1) and its longer structured protein concatamer (DAMP4). Interfacial tension measurements suggested that the size and bulk structuring of the larger molecule led to much slower adsorption kinetics. Neutron reflectometry at equilibrium revealed that both molecules adsorbed as a monolayer to the air–water interface (indicating unfolding of DAMP4 to give a chain of four connected DAMP1 molecules), with a concentration ratio equal to that in the bulk. This suggests the overall free energy of adsorption is equal despite differences in size and bulk structure. At small interfacial extensional strains, only molecule packing influenced the stress response. At larger strains, the effect of size became apparent, with DAMP4 registering a higher stress response and interfacial elasticity. When both components were present at the interface, most stress-dissipating movement was achieved by DAMP1. This work thus provides insights into the role of proteins' molecular size and structure on their interfacial properties, and the designed sequences introduced here can serve as effective tools for interfacial studies of proteins and polymers.
Publisher: American Chemical Society (ACS)
Date: 04-10-2022
DOI: 10.1021/ACS.LANGMUIR.2C02003
Abstract: Protein-polysaccharide composite materials have generated much interest due to their potential use in medical science and biotechnology. A comprehensive understanding of the assembly mechanism and the mesoscale architecture is needed for fabricating protein-polysaccharide composite materials with desired properties. In this study, complex assemblies were built on silica surfaces through a layer-by-layer (LbL) approach using bovine beta-lactoglobulin variant A (βLgA) and pectin as model protein and polysaccharide, respectively. We demonstrated the combined use of quartz crystal microbalance with dissipation monitoring (QCM-D) and neutron reflectometry (NR) for elucidating the assembly mechanism as well as the internal architecture of the protein-polysaccharide complexes formed at the solid-liquid interface. Our results show that βLgA and pectin interacted with each other and formed a cohesive matrix structure at the interface consisting of intertwined pectin chains that were cross-linked by βLgA-rich domains. Although the complexes were fabricated in an LbL fashion, the complexes appeared to be relatively homogeneous with βLgA and pectin molecules spatially distributed within the matrix structure. Our results also demonstrate that the density of βLgA-pectin complex assemblies increased with both the overall and local charge density of pectin molecules. Therefore, the physical properties of the protein-polysaccharide matrix structure, including density and level of hydration, can be tuned by using polysaccharides with varying charge patterns, thus promoting the development of composite materials with desired properties.
Publisher: American Chemical Society (ACS)
Date: 13-12-2016
Publisher: American Chemical Society (ACS)
Date: 25-10-2021
Publisher: Elsevier BV
Date: 2013
Publisher: American Chemical Society (ACS)
Date: 27-03-2012
DOI: 10.1021/JP300533M
Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C3TC00063J
Publisher: Elsevier BV
Date: 2011
Publisher: Wiley
Date: 10-07-2022
Abstract: Herein, a strategy to control conformational changes in grafted polymer brushes via photoinduced crosslinking of photoreactive groups embedded into the lateral architecture of a polymer brush is reported. Poly(methylmethacrylate)‐based polymer brushes containing UV‐light (λ = 325 nm) photoreactive o ‐methyl benzaldehyde moieties are synthesized using surface‐initiated reversible deactivation polymerization. The conformational changes in polymer brushes upon UV‐light triggered crosslinking are comprehensively analyzed through a full suite of surface sensitive characterization methods including time of flight secondary ion mass spectrometry, quartz crystal microbalance with dissipation monitoring, UV/vis spectroscopy, atomic force microscopy, nanoplasmonic sensing, and neutron reflectometry. The spatiotemporal control of the induced conformational changes is demonstrated via photolithography experiments. To enable an additional level of control, a second gate, the visible light (λ = 445 nm) active styrylpyrene moiety, is incorporated into the polymer brush architecture. Critically, wavelength‐selective crosslinking behavior is observed in the diblock copolymer structures allowing to crosslink specific sections of the lateral brush architecture as a function of irradiation wavelength.
Publisher: International Union of Crystallography (IUCr)
Date: 02-2023
DOI: 10.1107/S1600576722011426
Abstract: As a result of the availability of modern software and hardware, Bayesian analysis is becoming more popular in neutron and X-ray reflectometry analysis. The understandability and replicability of these analyses may be harmed by inconsistencies in how the probability distributions central to Bayesian methods are represented in the literature. Herein advice is provided on how to report the results of Bayesian analysis as applied to neutron and X-ray reflectometry. This includes the clear reporting of initial starting conditions, the prior probabilities, the results of any analysis and the posterior probabilities that are the Bayesian equivalent of the error bar, to enable replicability and improve understanding. It is believed that this advice, grounded in the authors' experience working in the field, will enable greater analytical reproducibility in the work of the reflectometry community, and improve the quality and usability of results.
Publisher: Royal Society of Chemistry (RSC)
Date: 2012
DOI: 10.1039/C2CP23694J
Abstract: The nanostructure of the ethanolammonium nitrate (EtAN)-air surface has been investigated using X-ray reflectometry (XRR), vibrational sum frequency spectroscopy (VSFS) and neutral impact collision ion scattering spectroscopy (NICISS). The XRR data decays more rapidly than expected for a perfectly sharp interface, indicating a diffuse electron (scattering length) density profile. Modelling of the XRR data using three different fitting routines produced consistent interfacial profiles that suggest the formation of interfacial EtAN clusters. Consistent with this, VSFS reveals that the EtAN surface is predominantly covered by -CH(2)- moieties, with the -NH(3)(+) and -OH groups of the cation buried slightly deeper in the interface. The elemental profiles determined using NICISS also show enrichment of carbon relative to nitrogen and oxygen in the outermost surface layer, which is consistent with the surface cation orientation deduced from VSFS, and with the presence of EtAN aggregates at the liquid surface.
Publisher: American Chemical Society (ACS)
Date: 13-10-2017
Publisher: MDPI AG
Date: 07-03-2019
Abstract: Neutron scattering experiments are a unique tool in material science due to their sensitivity to light elements and magnetic induction. However, for kinetic studies the low brilliance at existing sources poses challenges. In the case of periodic excitations these challenges can be overcome by binning the scattering signal according to the excitation state of the s le. To advance into this direction we have performed polarised and time resolved grazing incidence neutron scattering measurements on an aqueous solution of the polymer F127 mixed with magnetic nano-particles. Magnetic nano-composites like this provide magnetically tuneable properties of the polymer crystal as well as magnetic meta-crystals. Even though the grazing incidence small angle scattering and polarised signals are too weak to be evaluated at this stage we demonstrate that such experiments are feasible. Moreover, we show that the intensity of the 111 Bragg peak of the fcc micellar crystal depends on the actual shear rate, with the signal being maximised when the shear rate is lowest (and vice-versa).
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C8SM00777B
Abstract: We investigate the effect of side chain length on the chain shape and thin film behaviour of conjugated graft copolymers.
Publisher: American Chemical Society (ACS)
Date: 21-07-2021
Publisher: Elsevier BV
Date: 11-2007
Start Date: 02-2021
End Date: 02-2022
Amount: $320,000.00
Funder: Australian Research Council
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