I22-Small angle scattering & Diffraction
|
Diamond Proposal Number(s):
[16566]
Abstract: Lactose is the major carbohydrate in milk and, similarly to other sugars, it can exist as two anomers in solution, the α and β forms, with a ratio depending on factors including temperature and pH (mutarotation equilibrium). Lactose is extracted from whey mostly to prevent environmental pollution. In fact, the presence of this sugar can contribute to a dramatic increase in the biological oxygen demand (BOD) of whey, making its direct disposal potentially dangerous for the environment. However, preserving our ecosystem is not the only reason why lactose is recovered. Purified lactose is, in fact, a high value product, commonly used as an excipient in pharmaceutical formulations and as a carrier in dry powder inhalers. Despite the increasing interest that lactose crystallization has recently received, a full understanding of this process is still missing, particularly the link between the process parameters of the crystallization step and the properties of the final product in terms of crystalline structure, purity and particle size and shape distribution. This work is the first comprehensive study of lactose crystallization, exploring cooling and anti-solvent operations, for the determination of the effect of several operative conditions on: (i) the kinetics of nucleation, growth and agglomeration; (ii) the yield of lactose recovery from solution; (iii) the final crystal size and shape distributions; and (iv) the purity of the obtained crystals.
|
Jan 2019
|
|
I22-Small angle scattering & Diffraction
|
Diamond Proposal Number(s):
[9121]
Open Access
Abstract: The self-assembly and crystal packing of a unique series of nanocrystalline fluoride ion-encapsulated polyhedral oligomeric silsesquioxane (F-POSS) compounds, with substituted electron-withdrawing group (EWG) perfluorinated alkyl chain arms of varying lengths, were investigated. The fluorine-encapsulated T8[(CH2)n-EWG]8F−-18-crown-6-ether-M+ and T8[(CH2)n-EWG]8F−-tetrabutyl ammonium TBA+ compounds with fluorinated alkyl chain arms were synthesized and subsequently analyzed using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and simultaneous small- and wide-angle X-ray scattering (SAXS/WAXS) techniques. DSC and TGA of the compounds showed that the melting temperatures occurred below 100 °C and the compounds were thermally stable above their melting temperatures. SAXS/WAXS data probed the crystalline structure and self-assembly of the nanocrystalline compounds. At ambient temperatures, the crystalline structures of the compounds were seen to be complex with triclinic unit cells. On cooling from the melt, the self-assembly of the compounds with shorter fluorinated alkyl chain arms is dominated by the ionic attraction between the cages such that the arms form a disordered state that only reorder on standing. In contrast, the self-assembly of the compounds with longer fluorinated alkyl chain arms is dominated by the alignment of the arms into rod-like morphologies such that a fully ordered solid is formed from the melt. Electrical characterization has revealed that the POSS cages exhibited an insulating behavior. The POSS cages with or without fluoride ion encapsulation had similar AC conductivities but cages without fluoride ion encapsulation have the highest relative permittivity. The results show that due to the inorganic–organic-ionic nature of the F-POSS ion encapsulated compounds and nanocrystalline self-assembly, they have great potential as interfacial compatibilizers enhancing the miscibility of polymer composites and aiding interactions between polar and non-polar solvents as ionic liquids.
|
Jan 2019
|
|
I16-Materials and Magnetism
I22-Small angle scattering & Diffraction
|
Abstract: We have designed a compound that forms square liquid crystal honeycomb patterns with a cell size of only 3 nm and with zero in-plane thermal expansion. The compound is a bolaamphiphile with a π-conjugated rod-like core and two mutually poorly compatible side-chains attached on each side of the rod at its centre. The system exhibits a unique phase transition between a “single colour” tiling pattern at high temperatures, where the perfluoroalkyl and the carbosilane chains are mixed in the square cells, to a “two-colour” or “chessboard” tiling where the two chain types segregate in their respective cells. Small-angle transmission and grazing incidence X-ray studies (SAXS and GISAXS) indicate critical behaviour both below and above the transition. Both phase types are of considerable interest for sub-5 nm nanopatterning. The temperature dependence of ordering of the side chains has been investigated using Monte Carlo (MC) simulation with Kawasaki dynamics. For a 3-dimensional system with 2 degrees of freedom, universality predicts that the transition falls into the 3d Ising class; MC was therefore used to calculate observables and determine the critical exponents accessible in experiment. Theoretical values of ν, γ and, perhaps most importantly, of the order parameter β have been calculated and then compared with those determined experimentally. β found experimentally is close to the theoretical value, but ν and γ values are significantly smaller than predicted. To explain the latter, the measured susceptibility above Tc is compared with those from simulations of different lattice sizes. The results suggest that the discrepancies result from a reduced effective domain size, possibly due to kinetic suppression of large scale fluctuations.
|
Jan 2019
|
|
I22-Small angle scattering & Diffraction
|
Diamond Proposal Number(s):
[17191]
Abstract: Stimuli-responsive nanocarriers based on lipid self-assemblies have the potential to provide targeted delivery of antimicrobial peptides, limiting their side effects while protecting them from degradation in the biological environments. In the present study, we design and characterize a simple pH-responsive antimicrobial nanomaterial, formed through the self-assembly of oleic acid (OA) with the human cathelicidin LL-37 as model for an amphiphilic antimicrobial peptide. Colloidal transformations from core-shell cylindrical micelles with a cross-section diameter of ~ 5.5 nm and a length of ~ 23 nm at pH 7.0, to aggregates of branched thread-like micelles at pH 5.0 were detected using synchrotron small angle X-ray scattering, cryogenic transmission electron microscopy, and dynamic light scattering. Biological in vitro assays using an Escherichia coli bacteria strain showed high antimicrobial activity of the positively charged LL-37/OA aggregates at pH 5.0, which was not caused by the pH conditions themselves. Contrary to that, negligible antimicrobial activity was observed at pH 7.0 for the negatively charged cylindrical micelles. The nanocarrier’s ability to switch its biological activity ‘on’ and ‘off’ in response to changes in pH could be used to focus the antimicrobial peptides’ action to areas of specific pH in the body. The presented findings contribute to the fundamental understanding of lipid-peptide self-assembly, and may open up a promising strategy for designing simple pH-responsive delivery systems for antimicrobial peptides.
|
Dec 2018
|
|
I22-Small angle scattering & Diffraction
|
Diamond Proposal Number(s):
[18388]
Abstract: The inefficiency of the chromium (III)-collagen cross-linking reaction during conventional leather processing results in severe environmental pollution from the waste chromium in the effluent. A mechanistic study using synchrotron-based small-angle X-ray scattering (SAXS) and differential scanning calorimetry (DSC) on ThruBlu tanned leather, revealed the effect of chromium sulphate and its pre-treatments on collagen structure and stability. By pre-treating with complexing agents such as sodium formate and disodium phthalate, as well as nanoclay (sodium montmorillonite), the uniformity through bovine hide collagen matrix were improved significantly. These pre-treatments effectively reduce the reactivity of chromium during its cross-linking reaction with collagen while retaining its bound water. However, collagen pre-treated with a covalent cross-linker (glutaraldehyde) results in a decrease in both chromium-collagen cross-linking and bound water while improving uniformity. These molecular-level insights can be developed into metrics to guide us towards a more sustainable future for the leather industry.
|
Dec 2018
|
|
I22-Small angle scattering & Diffraction
|
Abstract: By electrospinning poly(ethylene oxide) (PEO)-blended sodium dodecyl sulfate (SDS) functionalized carbon nanotube (CNT) solutions, we engineered single- and double-walled nanotubes into highly aligned arrays. CNT alignment was measured using electron microscopy and polarised Raman spectroscopy. Mechanical tensile testing demonstrates that a CNT loading of 3.9 wt% increases the ultimate tensile strength and ductility of our composites by over a factor of 3, and the Young's modulus by over a factor of 4, to ∼260 MPa. Transmission electron microscopy (TEM) reveals how the aligned nanotubes provide a solid structure, preventing polymer chains from slipping, as well as polymer crystallisation structures such as ‘shish-kebabs’ forming, which are responsible for the improved mechanical properties of the composite. Differential scanning calorimetry (DSC) and small angle X-ray scattering (SAXS) reveals micellar and hexagonal columnar structures along the axis of the fibers, some of which are associated with the presence of the CNT, where these hexagonal structures are associated with the SDS functionalization on the CNT surfaces. This work demonstrates the benefits of CNT alignment within composites, revealing the effectiveness of the electrospinning technique, which enables significantly improved functionality, increasing the utility of the composites for use in many different technological areas.
|
Nov 2018
|
|
I22-Small angle scattering & Diffraction
|
Diamond Proposal Number(s):
[16024]
Abstract: Microfluidics has become recognized as a powerful platform technology associated with a constantly increasing array of applications across the life sciences. This surge of interest over recent years has led to an increased demand for microfluidic chips, resulting in more time being spent in the cleanroom fabricating devices using soft lithography - a slow and expensive process that requires extensive materials, training and significant engineering resources. This bottleneck limits platform complexity as a by-product of lengthy delays between device iterations and impacts on the time spent developing the final application. To address this problem we report a new, rapid and economical approach to microfluidic device fabrication using dry resist films to laminate laser cut sheets of acrylic. We term our method laser lithography and show that our technique can be used to engineer 200 μm wide channels for assembling droplet generators capable of generating monodisperse water droplets in oil and micromixers designed to sustain chemical reactions. Our devices offer high transparency, negligible device-to-device variation, and low X-ray background scattering, demonstrating their suitability for real-time X-ray-based characterization applications. Our approach also requires minimal materials and apparatus, is cleanroom-free and at a cost of around $1.00 per chip, could significantly democratize device fabrication, thereby increasing the interdisciplinary accessibility of microfluidics.
|
Nov 2018
|
|
I22-Small angle scattering & Diffraction
|
Abstract: Silicon oxide‐containing diamond‐like carbon (a‐C:H:Si:O) films are a promising class of protective coatings for environmentally‐demanding applications owing to their lower residual stresses and superior thermal stability and oxidation resistance relative to undoped diamond‐like carbon. However, existing versions of a‐C:H:Si:O deposited by traditional methods such as plasma‐enhanced chemical vapor deposition (PECVD) undergo substantial degradation and oxidation at temperatures above 250 °C. This, together with the difficulty of PECVD in depositing conformal coatings on complex geometries such as high‐aspect‐ratio features, has limited the applicability of a‐C:H:Si:O. Here, the unique capabilities of plasma immersion ion implantation and deposition (PIIID) to grow silicon oxide‐rich diamond‐like carbon materials that are ultrasmooth, continuous, and conformal on high‐aspect‐ratio topographies are explored. The high concentration of silicon and oxygen in PIIID‐grown films (23 ± 5 at.% and 11 ± 4 at.%, respectively) is unrivalled for this class of materials, and drastically increases the resistance to oxidation at high temperatures, compared with PECVD‐grown films. The results open the path for using a‐C:H:Si:O in applications involving exposure of materials to extreme environments.
|
Nov 2018
|
|
I15-1-X-ray Pair Distribution Function (XPDF)
I22-Small angle scattering & Diffraction
|
Chao
Zhou
,
Louis
Longley
,
Andraž
Krajnc
,
Glen J.
Smales
,
Ang
Qiao
,
Ilknur
Erucar
,
Cara M.
Doherty
,
Aaron W.
Thornton
,
Anita J.
Hill
,
Christopher W.
Ashling
,
Omid T.
Qazvini
,
Seok J.
Lee
,
Philip A.
Chater
,
Nicholas J.
Terrill
,
Andrew J.
Smith
,
Yuanzheng
Yue
,
Gregor
Mali
,
David A.
Keen
,
Shane G.
Telfer
,
Thomas D.
Bennett
Diamond Proposal Number(s):
[18236]
Open Access
Abstract: To date, only several microporous, and even fewer nanoporous, glasses have been produced, always via post synthesis acid treatment of phase separated dense materials, e.g. Vycor glass. In contrast, high internal surface areas are readily achieved in crystalline materials, such as metal-organic frameworks (MOFs). It has recently been discovered that a new family of melt quenched glasses can be produced from MOFs, though they have thus far lacked the accessible and intrinsic porosity of their crystalline precursors. Here, we report the first glasses that are permanently and reversibly porous toward incoming gases, without post-synthetic treatment. We characterize the structure of these glasses using a range of experimental techniques, and demonstrate pores in the range of 4 – 8 Å. The discovery of MOF glasses with permanent accessible porosity reveals a new category of porous glass materials that are elevated beyond conventional inorganic and organic porous glasses by their diversity and tunability.
|
Nov 2018
|
|
I22-Small angle scattering & Diffraction
|
Diamond Proposal Number(s):
[13815]
Open Access
Abstract: Stress oscillation has been observed in a number of linear thermoplastic polymers during the cold-drawing process, where the polymers exhibit periodic self-excited oscillatory neck propagation. However, the origin of the mechanical stress oscillation process and its relationship with the crystalline morphology of the polymer are still under debate. In this work, we revisit the stress oscillation behavior by studying a semi-crystalline polyester, poly(butylene succinate) (PBS), a biodegradable polymer suitable for biomedical and packaging applications. Stress oscillation of PBS is observed when deformed at a range of elongation rates from 10 to 200 mm min−1, and the fluctuation magnitude decays as the deformation temperature increases from 23 to 100 °C. Periodic transparent/opaque bands form during necking of PBS, which consists of alternating regions of highly oriented crystalline zones and microcavities due to crazing and voiding, although the degree of crystallinity did not change significantly in the bands. Simultaneous small- and wide-angle X-ray scattering confirms that the alternating stress increases, as shown in the stress–strain curves, correspond to the appearance of the transparent bands in the sample, and the abrupt drop of the stress is the result of voiding during the neck propagation. The voiding and cavitation are ultimately responsible for the stress oscillation process in PBS. The in-depth analysis of this work is important in understanding and controlling the occurrence of instabilities/cavitation during polymer processing such as film blowing, biaxial stretching and injection moulding of biodegradable polymer materials.
|
Nov 2018
|
|