Multicomponent signal unmixing from nanoheterostructures: overcoming the traditional challenges of nanoscale X-ray analysis via machine learning.

The chemical composition of core-shell nanoparticle clusters have been determined through principal component analysis (PCA) and independent component analysis (ICA) of an energy-dispersive X-ray (EDX) spectrum image (SI) acquired in a scanning transmission electron microscope (STEM). The method blindly decomposes the SI into three components, which are found to accurately represent the isolated and unmixed X-ray signals originating from the supporting carbon film, the shell, and the bimetallic core. The composition of the latter is verified by and is in excellent agreement with the separate quantification of bare bimetallic seed nanoparticles.D.R. acknowledges support from the Royal Society’s Newton International Fellowship scheme. B.R.K. thanks the U.K. EPSRC for financial support (EP/J500380/1). F.d.l.P. and C.D. acknowledge funding from the ERC under grant no. 259619 PHOTO EM. P.A.M and P.B. acknowledges financial support from the European Research Council under the European Union’s Seventh Framework Programme (FP7/ 2007-2013)/ERC grant agreement 291522-3DIMAGE. P.A.M. also acknowledges financial support from the European Union’s Seventh Framework Programme of the European Commission: ESTEEM2, contract number 312483.This is the final published version. It first appeared at http://pubs.acs.org/doi/abs/10.1021/acs.nanolett.5b00449

Characterisation of Co@Fe3O4 core@shell nanoparticles using advanced electron microscopy

Cobalt nanoparticles were synthesised via the thermal decomposition of Co2(CO)8 and were coated in iron oxide using Fe(CO)5. While previous work focused on the subsequent thermal alloying of these nanoparticles, this study fully elucidates their composition and core@shell structure. State-of-the-art electron microscopy and statistical data processing enabled chemical mapping of individual particles through the acquisition of energy-filtered transmission electron microscopy (EFTEM) images and detailed electron energy loss spectroscopy (EELS) analysis. Multivariate statistical analysis (MSA) has been used to greatly improve the quality of elemental mapping data from core@shell nanoparticles. Results from a combination of spatially resolved microanalysis reveal the shell as Fe3O4 and show that the core is composed of oxidatively stable metallic Co. For the first time, a region of lower atom density between the particle core and shell has been observed and identified as a trapped carbon residue attributable to the organic capping agents present in the initial Co nanoparticle synthesis.Junta de Andalucía Feder PE2009-FQM-4554 TEP-217EU FP7 AL-NANOFUNC CT-REGPOT2011-1-28589

Megacity pumping and preferential flow threaten groundwater quality

Many of the world’s megacities depend on groundwater from geologically complex aquifers that are over-exploited and threatened by contamination. Here, using the example of Dhaka, Bangladesh, we illustrate how interactions between aquifer heterogeneity and groundwater exploitation jeopardize groundwater resources regionally. Groundwater pumping in Dhaka has caused large-scale drawdown that extends into outlying areas where arsenic-contaminated shallow groundwater is pervasive and has potential to migrate downward. We evaluate the vulnerability of deep, low-arsenic groundwater with groundwater models that incorporate geostatistical simulations of aquifer heterogeneity. Simulations show that preferential flow through stratigraphy typical of fluvio-deltaic aquifers could contaminate deep (>150 m) groundwater within a decade, nearly a century faster than predicted through homogeneous models calibrated to the same data. The most critical fast flowpaths cannot be predicted by simplified models or identified by standard measurements. Such complex vulnerability beyond city limits could become a limiting factor for megacity groundwater supplies in aquifers worldwide.National Institute of Environmental Health Sciences. Superfund Research Program (Grant P42 ES010349)National Science Foundation (U.S.) (Grant EAR-115173

Impregnation of carbon black for the examination of colloids using TEM

Nanoparticles are frequently synthesised as colloids, dispersed in solvents such as water, hexane or ethanol. For their characterisation by transmission electron microscopy (TEM), a drop of colloid is typically deposited on a carbon support and the solvent allowed to evaporate. However, this method of supporting the nanoparticles reduces the visibility of fine atomic details, particularly for carbonaceous species, due to interference from the 2-dimensional carbon support at most viewing angles. We propose here the impregnation of a 3 dimensional carbon black matrix that has been previously deposited on a carbon film as an alternative means of supporting colloidal nanoparticles, and show examples of the application of this method to advanced TEM techniques in the analysis of monometallic, core@shell and hybrid nanoparticles with carbon-based shellsPeer reviewe

Research Data Supporting "A New Method for Determining the Composition of Core-Shell Nanoparticles via Dual-EDX+EELS Spectrum Imaging"

Supporting data for the publication "A New Method for Determining the Composition of Core-Shell Nanoparticles via Dual-EDX+EELS Spectrum Imaging". TEM and EELS/EDX data plus post analytical statistical data manipulation (ICA) for nanoparticles made at Cambridge in 2014.Royal Society Newton International Fellowship schemeEU Seventh Framework Programme (FP7/ 2007-2013)ERC grant agreement 291522-3DIMAGEEU Seventh Framework Programme ESTEEM2 (312483)UK EPSRC (EP/J500380/1

Multicomponent signal unmixing from nanoheterostructures ::overcoming the traditional challenges of nanoscale X-ray analysis via machine learning

The chemical composition of core–shell nanoparticle clusters have been determined through principal component analysis (PCA) and independent component analysis (ICA) of an energy-dispersive X-ray (EDX) spectrum image (SI) acquired in a scanning transmission electron microscope (STEM). The method blindly decomposes the SI into three components, which are found to accurately represent the isolated and unmixed X-ray signals originating from the supporting carbon film, the shell, and the bimetallic core. The composition of the latter is verified by and is in excellent agreement with the separate quantification of bare bimetallic seed nanoparticles

Research Data Supporting "Selective hydrogenation of arenes to cyclohexanes in water catalyzed by chitin-supported ruthenium nanoparticles"

Supporting data for the publication "Selective hydrogenation of arenes to cyclohexanes in water catalyzed by chitin-supported ruthenium nanoparticles" by Morioka et al. Synthesis and analytical data for ruthenium-based nanoparticulate catalysts immobilized on chitin. These were prepared in Cambridge in 2015-16. Results of catalytic tests (selective hydrogenation of arenes to cyclohexanes) using these materials conducted in Cambridge and in Nagoya in 2015-16.EPSRC (EP/J500380/1)Royal Society (International Exchange Scheme)Ichihara International Scholarship FoundationInstitute for Quantum Chemical ExplorationMEX

Facile synthesis of SnO2-PbS nanocomposites with controlled structure for applications in photocatalysis.

Recent studies have shown that SnO2-based nanocomposites offer excellent electrical, optical, and electrochemical properties. In this article, we present the facile and cost-effective fabrication, characterization and testing of a new SnO2-PbS nanocomposite photocatalyst designed to overcome low photocatalytic efficiency brought about by electron-hole recombination and narrow photoresponse range. The structure is fully elucidated by X-ray diffraction (XRD)/Reitveld refinement, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET) surface area analysis, and transmission electron microscopy (TEM). Energy-dispersive X-ray spectroscopy (EDX) spectrum imaging analysis demonstrates the intermixing of SnO2 and PbS to form nanocomposites. A charge separation mechanism is presented that explains how the two semiconductors in junction function synergistically. The efficacy of this new nanocomposite material in the photocatalytic degradation of the toxic dye Rhodamine B under simulated solar irradiation is demonstrated. An apparent quantum yield of 0.217 mol min(-1) W(-1) is calculated with data revealing good catalyst recyclability and that charge separation in SnO2-PbS leads to significantly enhanced photocatalytic activity in comparison to either SnO2 or PbS.A. K. and D. R. acknowledge support from the Royal Society’s Newton International Fellowship scheme. D.R would also like to thank Prof. Paul Midgley for access to the TEM at the University of Cambridge and Prof. Gianluigi Botton for access to the CCEM, a national facility supported by NSERC, the Canada Foundation for Innovation and McMaster University. B. R. K. thanks the UK EPSRC for financial support (EP/J500380/1). Thanks go also to Drs. Tim Jones and Jill Geddes of Schlumberger Gould Research for help with the acquisition of Raman and X-ray photoelectron spectra and to Dr. Zlatko Saracevic of the Department of Chemical Engineering and Biotechnology (University of Cambridge) for help with BET surface area analysis. The authors would also like to thanks Miss Georgina Hutton (University of Cambridge) for valuable discussions and input. Unprocessed data for this paper are available at the University of Cambridge data repository (see https://www.repository.cam.ac.uk/handle/1810/252973). These include some data in the file format .dm3 (HRTEM data), which can be opened using the software program Gatan Digital Micrograph 3.6.5 or similar.This is the final version of the article. It first appeared from the Royal Society of Chemistry via http://dx.doi.org/10.1039/C5NR07036

Research data supporting 'Facile synthesis of SnO2-PbS nanocomposites with controlled structure for applications in photocatalysis'.

This research data supports the publication "Facile Synthesis of SnO2-PbS Nanocomposites with Controlled Structure for Visible Light Photocatalysis", which is published in 'Nanoscale'. Synthetic and analytical data for SnO2 nanoparticles, PbS nanocubes and SnO2-PbS nanocomposites prepared in Cambridge in 2014-2015. Analysis includes X-ray diffraction data and Rietveld refinement, transmission electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, Brunauer-Emmett-Teller (BET) surface area analysis. Photocatalytic data is presented for each material for the degradation of Rhodamine B in aqueous solution.This work was supported by the Royal Society [grant number NF130808 (RS)], the EPSRC grant number [EP/J500380/1 (EPSRC)] and the Canada Foundation for Innovation

Shape-defined nanodimers by tailored heterometallic epitaxy

© the Partner Organisations 2014. The systematic construction of heterogeneous nanoparticles composed of two distinct metal domains (Au and Pt) and exhibiting a broad range of morphologically defined shapes is reported. It is demonstrated that careful Au overgrowth on Pt nanocrystal seeds with shapes mainly corresponding to cubeoctahedra, octahedra and octapods can lead to heterometallic systems whose intrinsic structures result from specific epitaxial relationships such as {111} + {111}, {200} + {200} and {220} + {220}. Comprehensive analysis shows also that nanoparticles grown from octahedral seeds can be seen as comprising of four Au tetrahedral subunits and one Pt octahedral unit in a cyclic arrangement that is similar to the corresponding one in decahedral gold nanoparticles. However, in the present case, the multi-component system is characterized by a broken five-fold rotational symmetry about the [011] axis. This set of bimetallic dimers could provide new platforms for fuel cell catalysts and plasmonic devices. This journal isCSIC - Unidad de Recursos de Información Científica para la Investigación (URICI)Peer Reviewe