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33 items found (0 items not approved), displaying 1 to 10.[First/Prev] 1, 2, 3, 4 [Next/Last]

Instruments / Technical Area	Publication Details	Published
I04-1-Macromolecular Crystallography (fixed wavelength)	Biomacromolecular charge chirality detected using chiral plasmonic nanostructures Marion Rodier , Chantal Keijzer , Joel Milner , Affar S. Karimullah , Aleksander W. Roszak , Laurence D. Barron , Nikolaj Gadegaard , Adrian J. Lapthorn , Malcolm Kadodwala Nanoscale Horizons 45 DOI: 10.1039/C9NH00525K Diamond Proposal Number(s): [16258, 16258] Open Access Show Abstract ▼ Abstract: The charge distributions of solvent exposed surfaces of complex biomolecules such has proteins are unique fingerprints. The chirality of these charge distributions result in stereo-specific electrostatic interactions which help define how proteins interact with each other, contributing to specificity in protein–protein interactions. Thus it is a key concept in understanding chemical processes in biology. There is currently no known spectroscopic phenomenon that allows rapid characterisation of chiral surface charge distributions. We show that this essential property that is currently “invisible” to optical spectroscopy, can be detected by monitoring asymmetries in the chiroptical response of protein–plasmonic nanostructure complexes. The unique capabilities of the phenomenon are utilised to discriminate between a structurally homologous series of proteins, type II dehydroquinase (DHQase) derived from different organisms. The proteins are indistinguishable with conventional structurally sensitive spectroscopy (i.e. circular dichroism). We show that discrimination between proteins can be achieved by detecting differences in chiral surface charge distributions. The phenomenon is explained with a simple model whereby the chiroptical properties of the plasmonic structures are perturbed by the induction of an enantiomeric mirror image charge distribution of the protein in the metal. This new phenomenon has broad impact, it is a powerful tool for discriminating between structurally homologous biomaterials, but will also provide information relevant to macromolecular interactions.	Oct 2019
I15-1-X-ray Pair Distribution Function (XPDF)	X-ray total scattering study of magic-size clusters and quantum dots of cadmium sulphide Lei Tan , Alston J. Misquitta , Andrei Sapelkin , Le Fang , Rory M. Wilson , Dean S. Keeble , Baowei Zhang , Tingting Zhu , Frank S. Riehle , Shuo Han , Kui Yu , Martin T. Dove Nanoscale 437 DOI: 10.1039/C9NR06355B Diamond Proposal Number(s): [22866, 23168] Show Abstract ▼ Abstract: Four types of magic-size CdS clusters and three different CdS quantum dots have been studied using the technique of X-ray total scattering and pair distribution function analysis. We found that the CdS quantum dots could be modelled as a mixed phase of atomic structures based on the two bulk crystalline phases, which is interpreted as representing the effects of random stacking of layers. However, the results for the magic-size clusters are significantly different. On one hand, the short-range features in the pair distribution function reflect the bulk, indicating that these structures are based on the same tetrahedral coordination found in the bulk phases (and therefore excluding new types of structures such as cage-like arrangements of atoms). But on the other hand, the longer-range atomic structure clearly does not reflect the layer structures found in the bulk and the quantum dots. We compare the effect of two ligands, phenylacetic acid and oleic acid, showing that in one case the ligand has little effect on the atomic structure of the magic-size nanocluster, and in another it has a significant effect.	Oct 2019
B18-Core EXAFS	Shape-persistent porous organic cage supported palladium nanoparticles as heterogeneous catalytic materials Shan Jiang , Harrison J. Cox , Evangelos I. Papaioannou , Chenyang Tang , Huiyu Liu , Billy J. Murdoch , Emma K. Gibson , Ian S. Metcalfe , John S. O. Evans , Simon K. Beaumont Nanoscale 11, 14929 - 14936 DOI: 10.1039/C9NR04553H Diamond Proposal Number(s): [15151] Show Abstract ▼ Abstract: Porous Organic Cages (POCs) are an emerging class of self-assembling, porous materials with novel properties. They offer a key advantage over other porous materials in permitting facile solution processing and re-assembly. The combination of POCs with metal nanoparticles (NPs) unlocks applications in the area of catalysis. In this context, POCs can function as both the template of ultra-small NPs and a porous, but reprocessable, heterogeneous catalyst support. Here, we demonstrate the synthesis of ultra-small Pd NPs with an imine linked POC known as ‘CC3’, and show that hydrogen gas can be used to form metallic NPs at ∼200 °C without the reduction of the organic cage (and the accompanying, unwanted loss of crystallinity). The resulting materials are characterized using a range of techniques (including powder diffraction, scanning transmission electron microscopy and synchrotron X-ray absorption spectroscopy) and shown to be recrystallizable following dissolution in organic solvent. Their catalytic efficacy is demonstrated using the widely studied carbon monoxide oxidation reaction. This demonstration paves the way for using ultra-small NPs synthesized with POCs as solution-processable, self-assembling porous catalytic materials.	Aug 2019
I20-Scanning-X-ray spectroscopy (XAS/XES)	Extracting structural information of Au colloids at ultra-dilute concentrations: identification of growth during nanoparticle immobilization George F. Tierney , Donato Decarolis , Norli Abdullah , Scott M. Rogers , Shusaku Hayama , Martha Briceno De Gutierrez , Alberto Villa , C. Richard A. Catlow , Paul Collier , Nikolaos Dimitratos , Peter Wells Nanoscale Advances 4 DOI: 10.1039/C9NA00159J Diamond Proposal Number(s): [17283] Open Access Show Abstract ▼ Abstract: Sol-immobilization is increasingly used to achieve supported metal nanoparticles (NPs) with controllable size and shape; it affords a high degree of control of the metal particle size and yields a narrow particle size distribution. Using state-of-the-art beamlines, we demonstrate how X-ray absorption fine structure (XAFS) techniques are now able to provide accurate structural information on nano-sized colloidal Au solutions at μM concentrations. This study demonstrates: (i) the size of Au colloids can be accurately tuned by adjusting the temperature of reduction, (ii) Au concentration, from 50 μM to 1000 μM, has little influence on the average size of colloidal Au NPs in solution and (iii) the immobilization step is responsible for significant growth in Au particle size, which is further exacerbated at increased Au concentrations. The work presented demonstrates that an increased understanding of the primary steps in sol-immobilization allows improved optimization of materials for catalytic applications.	May 2019
E02-JEM ARM 300CF	Atomic structural catalogue of defects and vertical stacking in 2H/3R mixed polytype multilayer WS 2 pyramids Gyeong Hee Ryu , Jun Chen , Yi Wen , Si Zhou , Ren-jie Chang , Jamie H. Warner Nanoscale 10 DOI: 10.1039/C9NR01783F Diamond Proposal Number(s): [16854] Show Abstract ▼ Abstract: We examine the atomic structure of chemical vapour deposition grown multilayer WS2 pyramids using aberration corrected annular dark field scanning transmission electron microscopy coupled with an in situ heating holder. The stacking orders and specific types of defects after partial degradation by S and W atomic loss at high temperature are resolved layer-by-layer. Our study of an individual WS2 pyramid with at least six layers, reveals a mixed 2H and 3R polytype stacking. Etching occurred both top and bottom of the WS2 pyramid, which aids in determining the exact vertical layer stacking configurations in the thicker regions. We provide an extensive catalogue of the contrast profiles associated with defects in WS2 as a function of layer number and stacking type, as imaged using ADF-STEM. These results provide extensive details about the identification of a wide range of defects in S2 layers, and the unique ADF-STEM contrast patterns that arise from complex multilayer stacking.	May 2019
I22-Small angle scattering & Diffraction	A template-free and low temperature method for the synthesis of mesoporous magnesium phosphate with uniform pore structure and high surface area Jorn Hovelmann , Tomasz M. Stawski , Rogier Besselink , Helen M. Freeman , Karen M. Dietmann , Sathish Mayanna , Brian R. Pauw , Liane G. Benning Nanoscale 11, 6939 - 6951 DOI: 10.1039/C8NR09205B Diamond Proposal Number(s): [16256] Open Access Show Abstract ▼ Abstract: Mesoporous phosphates are a group of nanostructured materials with promising applications, particularly in biomedicine and catalysis. However, their controlled synthesis via conventional template-based routes presents a number of challenges and limitations. Here, we show how to synthesize a mesoporous magnesium phosphate with a high surface area and a well-defined pore structure through thermal decomposition of a crystalline struvite (MgNH4PO4·6H2O) precursor. In a first step, struvite crystals with various morphologies and sizes, ranging from a few micrometers to several millimeters, had been synthesized from supersaturated aqueous solutions (saturation index (SI) between 0.5 and 4) at ambient pressure and temperature conditions. Afterwards, the crystals were thermally treated at 70–250 °C leading to the release of structurally bound water (H2O) and ammonia (NH3). By combining thermogravimetric analyses (TGA), scanning and transmission electron microscopy (SEM, TEM), N2 sorption analyses and small- and wide-angle X-ray scattering (SAXS/WAXS) we show that this decomposition process results in a pseudomorphic transformation of the original struvite into an amorphous Mg-phosphate. Of particular importance is the fact that the final material is characterized by a very uniform mesoporous structure with 2–5 nm wide pore channels, a large specific surface area of up to 300 m2 g−1 and a total pore volume of up to 0.28 cm3 g−1. Our struvite decomposition method is well controllable and reproducible and can be easily extended to the synthesis of other mesoporous phosphates. In addition, the so produced mesoporous material is a prime candidate for use in biomedical applications considering that magnesium phosphate is a widely used, non-toxic substance that has already shown excellent biocompatibility and biodegradability.	Apr 2019
I09-Surface and Interface Structural Analysis	Two-dimensional growth of dendritic islands of NTCDA on Cu(001) studied in real time Janina Felter , Markus Franke , Jana Wolters , Caroline Henneke , Christian Kumpf Nanoscale 11, 1798 DOI: 10.1039/C8NR08943D Diamond Proposal Number(s): [13837] Show Abstract ▼ Abstract: The success of future organic electronic devices distinctively depends on the electronic and geometric properties of thin organic films. Although obviously these properties are strongly influenced by the growth mechanisms, real time growth studies are relatively rare since not many experimental techniques exist that allow in situ studies in ultra high vacuum. In this context, we investigated the prototypical system 1,4,5,8-naphtalene-tetracarboxylic-dianhydride (NTCDA) on Cu(001). We used low-energy electron microscopy (LEEM) for the real-time growth study, and a variety of other techniques for investigating the geometric and electronic structure. While for similar model systems well known and well characterized growth modi occur (e.g., compact, well ordered islands or disordered, gas-like layers), for NTCDA/Cu(001) we observe the growth of dendrite-like, fractal structures. The dendritic structures arise from a strongly preferred one-dimensional growth mode forming a long-range ordered network of thin molecular chains spanning over the entire surface already at small coverages. Later in the growth process, the voids in the network structure are incrementally filled. These results are very unexpected for such a simple adsorbate system consisting of well investigated components, the properties of which were believed to be already well understood. We explain this unexpected behavior by a dendritic growth model that is supported by energetic arguments based on pair-potential calculations. These calculations give reason for the experimentally observed growth of one-dimensional structures, and therefore represent the key to a semi-quantitative understanding of this dendritic growth mode.	Jan 2019
E02-JEM ARM 300CF	In situ high temperature atomic level dynamics of large inversion domain formations in monolayer MoS 2 Jun Chen , Si Zhou , Yi Wen , Gyeong Hee Ryu , Christopher Allen , Yang Lu , Angus I. Kirkland , Jamie H. Warner Nanoscale 27 DOI: 10.1039/C8NR08821G Show Abstract ▼ Abstract: Here we study the high-temperature formation and dynamics of large inversion domains (IDs) that form in monolayer MoS2 using atomic-resolution annular dark-field scanning transmission electron microscopy (ADF-STEM) with an in situ heating stage. We use temperatures above 700 °C to thermally activate rapid S vacancy migration and this leads to a formation mechanism of IDs that differs from the one at room temperature, where S vacancy migration is limited. We show that at high temperatures the formation of IDs occurs from intersected networks of long S vacancy line defects, whose strain fields are non-orthogonal and trigger large scale atomic reconstructions. Once formed, the IDs are influenced by the dynamic behaviour of nearby line defects and voids. With Mo and S atoms undergoing movement, the two types of ID grain boundaries can shift to allow further expansion of the ID area along the adjoining line defects. We reveal that IDs serve as metastable configurations between line defect rearrangements and eventual void formation under electron beam irradiation during heating. The formation of voids near to the IDs causes them to revert back to pristine lattice, which has the effect of restricting the ID domain size to a certain range (e.g. 3–5 nm in our observation) instead of continuously enlarging. This study provides insights into how the MoS2 IDs form and evolve at high temperature and can benefit the tailoring of electronic properties of two dimensional materials by structural manipulation.	Jan 2019
I09-Surface and Interface Structural Analysis	Quantitative determination of a model organic/insulator/metal interface structure Martin Schwarz , David A. Duncan , Manuela Garnica , Jacob Ducke , Peter S. Deimel , Pardeep K. Thakur , Tien-lin Lee , Francesco Allegretti , Willi Auwärter Nanoscale 28 DOI: 10.1039/C8NR06387G Diamond Proposal Number(s): [14624] Open Access Show Abstract ▼ Abstract: By combining X-ray photoelectron spectroscopy, X-ray standing waves and scanning tunneling microscopy, we investigate the geometric and electronic structure of a prototypical organic/insulator/metal interface, namely cobalt porphine on monolayer hexagonal boron nitride (h-BN) on Cu(111). Specifically, we determine the adsorption height of the organic molecule and show that the original planar molecular conformation is preserved in contrast to the adsorption on Cu(111). In addition, we highlight the electronic decoupling provided by the h-BN spacer layer and find that the h-BN–metal separation is not significantly modified by the molecular adsorption. Finally, we find indication of a temperature dependence of the adsorption height, which might be a signature of strongly-anisotropic thermal vibrations of the weakly bonded molecules.	Nov 2018
E02-JEM ARM 300CF	Atomically sharp interlayer stacking shifts at anti-phase grain boundaries in overlapping MoS 2 secondary layers Si Zhou , Shanshan Wang , Zhe Shi , Hidetaka Sawada , Angus I. Kirkland , Ju Li , Jamie H. Warner Nanoscale 13 DOI: 10.1039/C8NR04486D Show Abstract ▼ Abstract: When secondary domains nucleate and grow on the surface of monolayer MoS2, they can extend across grain boundaries in the underlying monolayer MoS2 and form overlapping sections. We present an atomic level study of overlapping antiphase grain boundaries (GBs) in MoS2 monolayer-bilayers using aberration-corrected annular dark field scanning transmission electron microscopy. In particular we focus on the antiphase GB within a monolayer and track its propagation through an overlapping bilayer domain. We show that this leads to an atomically sharp interface between 2H and 3R interlayer stacking in the bilayer region. We have studied the micro-nanoscale “meandering” of the antiphase GB in MoS2, which shows a directional dependence on the density of 4 and 8 member ring defects, as well as sharp turning angles 90°–100° that are mediated by a special 8-member ring defect. Density functional theory has been used to explore the overlapping interlayer stacking around the antiphase GBs, confirming our experimental findings. These results show that overlapping secondary bilayer MoS2 domains cause atomic structure modification to underlying anti-phase GB sites to accommodate the van der Waals interactions.	Aug 2018

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