I13-2-Diamond Manchester Imaging
|
Diamond Proposal Number(s):
[19533]
Abstract: Capillary driven ink infiltration through a porous powder bed in 3D binderjet printing (inkjet printing onto a powder bed) controls the printing resolution and as-printed ‘green’ strength of the resulting object. However, a full understanding of the factors controlling the kinetics of the infiltration remains incomplete. Here, high resolution in situ synchrotron radiography provides time resolved imaging of the penetration of an aqueous solution of eythylene glycol through a porous alumina powder bed, used as a model system. A static drop-on-demand inkjet printer was used to dispense liquid droplets onto a powder surface. The subsequent migration of the liquid front and its interactions with powder particles was tracked using fast synchrotron X-radiography in the Diamond Synchrotron, with phase contrast imaging at a frame rate of 500 Hz. Image processing and analysis reveal both the time dependent increment in the wetting area and the propagation of the ‘interface leading edge’ exhibit heterogeneous behavior in both the temporal and spatial domain. However, mean infiltration kinetics are shown to be consistent with existing infiltration models based on the Washburn equation modified to account for the spreading of the liquid drop on the powder surface and using a modified term for the bed porosity.
|
Jun 2020
|
|
B21-High Throughput SAXS
|
Diamond Proposal Number(s):
[18523]
Abstract: A molecular design approach to fabricate nanofibrous membranes by self-assembly of aromatic cationic peptides with hyaluronic acid (HA) and nanofiber alignment under a magnetic field is reported. Peptides are designed to contain a block composed of four phenylalanine residues at the C-terminus, to drive their self-assembly by hydrophobic association and aromatic stacking, and a positively charged domain of lysine residues for electrostatic interaction with HA. These two blocks are connected by a linker with a variable number of amino acids and ability to adopt distinct conformations. Zeta potential measurements and circular dichroism confirm their positive charge and variable conformation (random coil, beta-sheet or alpha-helix), which depend on the pH and sequence. Their self-assembly, examined by fluorescence spectroscopy, small-angle X-ray scattering and transmission electron microscopy, show the formation of fiber-like nanostructures in the micromolar range. When the peptides are combined with HA, hydrogels or flat membranes are formed. The molecular structure tunes the mechanical behavior of the membranes and the nanofibers align in the direction of magnetic field due to the high diamagnetic anisotropy of phenylalanine residues. Mesenchymal stem cells cultured on magnetically-aligned membranes elongate in direction of the nanofibers supporting their application for soft tissue engineering.
|
Apr 2020
|
|
B21-High Throughput SAXS
|
Diamond Proposal Number(s):
[21470, 22925]
Abstract: The self-assembly of the amphiphilic lipopeptide PAEPKI-C16 (P = proline, A = alanine, E = glutamic acid, K = lysine, I = isoleucine, and C16 = hexadecyl) was investigated using a combination of microscopy, spectroscopy, and scattering methods and compared to that of C16-IKPEAP with the same (reversed) peptide sequence and the alkyl chain positioned at the N-terminus and lacking a free N-terminal proline residue. The catalytic activity of these peptides was then compared using a model aldol reaction system. For PAEPKI-C16, the cryo-TEM images showed the formation of micrometer-length fibers, which by small-angle X-ray scattering (SAXS) were found to have radii of 2.5–2.6 nm. Spectroscopic analysis shows that these fibers are built from β-sheets. This behavior is in complete contrast to that of C16-IKPEAP, which forms spherical micelles with peptides in a disordered conformation [Hutchinson J. Phys. Chem. B 2019, 123, 613]. In PAEPKI-C16, spontaneous alignment of fibers was observed upon increasing pH, which was accompanied by observed birefringence and anisotropy of SAXS patterns. This shows the ability to form a nematic phase, and unprecedented nematic hydrogel formation was also observed for these lipopeptides at sufficiently high concentrations. SAXS shows retention of an ultrafine (1.7 nm core radius) fibrillar network within the hydrogel. PAEPKI-C16 with free N-terminal proline shows enhanced anti:syn diastereoselectivity and better conversion compared to C16-IKPEAP. The cytotoxicity of PAEPKI-C16 was also lower than that of C16-IKPEAP for both fibroblast and cancer cell lines. These results highlight the sensitivity of lipopeptide properties to the presence of a free proline residue. The spontaneous nematic phase formation by PAEPKI-C16 points to the high anisotropy of its ultrafine fibrillar structure, and the formation of such a phase at low concentrations in aqueous solution may be valuable for future applications.
|
Mar 2020
|
|
I09-Surface and Interface Structural Analysis
|
Diamond Proposal Number(s):
[19033]
Abstract: Heteromolecular bilayers of π-conjugated organic molecules (COM) on metals, considered as model systems for more complex thin film heterostructures, are investigated with respect to their structural and electronic properties. By exploring the influence of the organic-metal interaction strength in bilayer systems, we determine the molecular arrangement in the physisorptive regime for copper-hexadecafluorophthalocyanine (F16CuPc) on Au(111) with intermediate layers of 5,7,12,14-pentacenetetrone (P4O) and perylene-3,4,9,10-tetracarboxylic diimide (PTCDI). Using the X-ray standing wave (XSW) technique to distinguish the different molecular layers, we show that these two bilayers are ordered following their deposition sequence. Surprisingly, F16CuPc as the second layer within the heterostructures exhibits an inverted intramolecular distortion compared to its monolayer structure.
|
Feb 2020
|
|
|
|
Abdullah M
Alotaibi
,
Benjamin A. D.
Williamson
,
Sanjay
Sathasivam
,
Andreas
Kafizas
,
Mahdi
Alqahtani
,
Carlos
Sotelo-vazquez
,
John
Buckeridge
,
Jiang
Wu
,
Sean P.
Nair
,
David O.
Scanlon
,
Ivan P.
Parkin
Abstract: Multifunctional thin films which can display both photocatalytic and antibacterial activity are of great interest industrially. Here, for the first time, we have used aerosol assisted chemical vapour deposition (AACVD) to deposit highly photoactive thin films of Cu-doped anatase TiO2 on glass substrates. The films displayed much enhanced photocatalytic activity relative to pure anatase, and showed excellent antibacterial (vs S.Aureus and E.Coli) ability. Using a combination of transient absorption spectroscopy (TAS), photoluminescence (PL) measurements and hybrid density functional theory calculations, we have gained nanoscopic insights into the improved properties of the Cu-doped TiO2 films. Our analysis has highlighted that the interactions between substitutional and interstitial Cu in the anatase lattice can explain the extended exciton lifetimes observed in the doped samples, and the enhanced UV/visible light photoactivities observed.
|
Feb 2020
|
|
I11-High Resolution Powder Diffraction
|
Diamond Proposal Number(s):
[19093]
Abstract: With the potential of delivering reversible capacities of up to 300 mAh/g, Li-rich transition metal oxides hold great promise as cathode materials for future Li-ion batteries. However, a cohesive synthesis-structure-electrochemistry relationship is still lacking for these materials, which impedes progress in the field. This work investigates how and why different synthesis routes, specifically solid-state and modified Pechini sol-gel methods, affect the properties of Li2MnO3, a compositionally simple member of this material system. Through a comprehensive investigation of the syn-thesis mechanism along with crystallographic, morphological and electrochemical characterization, the effects of different synthesis routes were found to predominantly influence the degree of stacking faults and particle morphology. That is, the modified Pechini method produced isotropic spherical particles with approx. 57% faulting and the solid state samples possessed heterogeneous morphology with approx. 43% faulting probability. Inevitably, these differences lead to variations in electrochemical performance. This study accentuates the importance of understanding how syn-thesis affects the electrochemistry of these materials, which is critical considering the crystallographic and electrochemical complexities of the class of materials more generally. The methodology employed here is extendable to studying synthesis-property relationships of other compositionally complex Li-rich layered oxide systems.
|
Jan 2020
|
|
B22-Multimode InfraRed imaging And Microspectroscopy
|
Barbara E.
Souza
,
Lorenzo
Donà
,
Kirill
Titov
,
Paolo
Bruzzese
,
Zhixin
Zeng
,
Yang
Zhang
,
Arun S.
Babal
,
Annika F.
Moeslein
,
Mark D.
Frogley
,
Magda
Wolna
,
Gianfelice
Cinque
,
Bartolomeo
Civalleri
,
Jin-chong
Tan
Diamond Proposal Number(s):
[14902, 20281]
Abstract: Nanocomposites comprising metal organic frameworks (MOFs) embedded in a polymeric matrix are promising carriers for drug delivery applications. While understanding the chemical and physical transformations of MOFs during the re-lease of confined drug molecules is challenging, this is central to devising better ways for controlled release of therapeutic agents. Herein we demonstrate the efficacy of synchrotron microspectroscopy to track the in situ release of 5-fluorouracil (5-FU) anticancer drug molecules from a drug@MOF/polymer composite (5-FU@HKUST-1/polyurethane). Using experimental time-resolved infrared spectra jointly with newly developed density functional theory calculations, we reveal the detailed dynamics of vibrational motions underpinning the dissociation of 5-FU bound to the framework of HKUST-1 upon water exposure. We discover that HKUST-1 creates hydrophilic channels within the hydrophobic polyurethane matrix hence helping to tune drug release rate. The synergy between a hydrophilic MOF with a hydrophobic polymer can be harnessed to engineer a tunable nanocomposite that alleviates the unwanted burst effect commonly encountered in drug delivery.
|
Jan 2020
|
|
I09-Surface and Interface Structural Analysis
|
Diamond Proposal Number(s):
[18974]
Abstract: Potassium-ion (K-ion) batteries potentially offer numerous advantages over conventional lithium-ion batteries as a result of the high natural abundance of potassium and its lower positive charge density, compared with lithium. This introduces the possibility of using K-ion in fast charging applications, in which cost effectiveness is also a major factor. Unlike for sodium-ion batteries, graphite can be used as an anode in K-ion cells, for which an extensive supply chain, electrode manufacturing infrastructure, and knowledge already exists. However, the performance of graphite anodes in K-ion cells does not meet expectations, with rapid capacity fading and poor first cycle irreversible capacities often reported. Here we investigate the formation and composition of the solid electrolyte interphase (SEI) as well as K+ insertion in graphite anodes in K-ion batteries. Through the use of energy-tuned synchrotron-based X-ray photoelectron spectroscopy, we make a detailed analysis at three probing depths up to ~50 nm of graphite anodes cycled to various potentials on the first discharge-charge cycle. Extensive SEI formation from a KPF6/DEC:EC electrolyte system is found to occur at low potentials during the insertion of potassium into graphite. During the subsequent removal of potassium from the structure, the thick SEI is partially stripped from the electrode, demonstrating that the SEI layer is unstable and contributes to a significant proportion of the capacity on both discharge and charge. With this in mind, further work is required to develop an electrolyte system with stable SEI layer formation on graphite in order to advance K-ion battery technology.
|
Nov 2019
|
|
B21-High Throughput SAXS
|
Diamond Proposal Number(s):
[18523]
Abstract: A novel lipopeptide C16KTTβAH was designed that incorporates the KTT tripeptide sequence from “Matrixyl” lipopeptides along with the bioactive βAH (β-alanine-histidine) carnosine dipeptide motif, attached to a C16 hexadecyl lipid chain. We show that this peptide amphiphile self-assembles above a critical aggregation concentration into β-sheet nanotape structures in water, PBS and cell culture media. Nanotape bundle structures were imaged in PBS, the bundling resulting from nanotape associations due to charge screening in the buffer. In addition, hydrogelation was observed and the gel modulus was measured in different aqueous media conditions, revealing tunable hydrogel modulus depending on concentration and nature of the aqueous phase. Stiff hydrogels were observed by direct dissolution in PBS and it was also possible to prepare hydrogels with unprecedented high modulus from low concentration solutions by injection of dilute aqueous solutions into PBS. These hydrogels have exceptional stiffness compared to previously reported β-sheet peptide-based materials. In addition, macroscopic soft threads can be drawn from concentrated aqueous solutions of the lipopeptides which contain aligned nematic structures. The anti-cancer activity of the lipopeptide was assessed using two model breast cancer cell lines, compared to two fibroblast cell line controls. These studies revealed selective concentration-dependent cytotoxicity against MCF-7 cancer cells in a mM concentration range. It was shown that this occurs below the onset of lipopeptide aggregation (i.e. below the critical aggregation concentration), indicating that the cytotoxicity is not related to self-assembly but is an intrinsic property of C16KTTβAH. Finally, hydrogels of this lipopeptide demonstrated slow uptake and release of the dye Congo red, a model diagnostic compound.
|
Aug 2019
|
|
|
|
Thomas J.
Whittles
,
Tim D.
Veal
,
Christopher N.
Savory
,
Peter J.
Yates
,
Philip A. E.
Murgatroyd
,
James T.
Gibbon
,
Max
Birkett
,
Richard J.
Potter
,
Jonathan D.
Major
,
Ken
Durose
,
David O.
Scanlon
,
Vinod R.
Dhanak
Abstract: The earth-abundant semiconductor Cu3BiS3 (CBS) exhibits promising photovoltaic properties and is often considered analogous to the solar absorbers copper indium gallium diselenide (CIGS) and copper zinc tin sulfide (CZTS) despite few device reports. The extent to which this is justifiable is explored via a thorough X-ray photoemission spectroscopy (XPS) analysis: spanning core levels, ionization potential, work function, surface contamination, cleaning, band alignment, and valence-band density of states. The XPS analysis overcomes and addresses the shortcomings of prior XPS studies of this material. Temperature-dependent absorption spectra determine a 1.2 eV direct band gap at room temperature; the widely reported 1.4–1.5 eV band gap is attributed to weak transitions from the low density of states of the topmost valence band previously being undetected. Density functional theory HSE06 + SOC calculations determine the band structure, optical transitions, and well-fitted absorption and Raman spectra. Valence band XPS spectra and model calculations find the CBS bonding to be superficially similar to CIGS and CZTS, but the Bi3+ cations (and formally occupied Bi 6s orbital) have fundamental impacts: giving a low ionization potential (4.98 eV), suggesting that the CdS window layer favored for CIGS and CZTS gives detrimental band alignment and should be rejected in favor of a better aligned material in order for CBS devices to progress.
|
Jul 2019
|
|
