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.

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.

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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.

The synthesis of gold nanoparticles (Au NPs) capped by poly(1‐vinylpyrrolidin‐2‐one (PVP, average M¯w = 10 000 kDa) yields moderately dispersed (6–8.5 nm) product with limited morphological control while larger NPs (15–20 nm) are reliably prepared using trisodium citrate (Na3Cit) as a reductant/capping agent. Excellent size control in the intermediate 10 nm regime is achieved by hybridizing these methodologies, with highly monodisperse, polycrystalline Au NPs forming. For a Na3Cit:PVP:Au ratio of 3.5:3.5:1, anisotropic NPs with an aspect ratio of 1.8:1 suggest the systematic agglomeration of NP pairs. Enhanced control of NP morphology is allowed by the 1,2‐tetradecanediol reduction of AuIII in the presence of straight chain, molecular anti‐agglomerants. Last, ligand substitution is used to controllably grow preformed Au seeds. In spite of the extended growth phase used, the replacement of phosphine by 1‐pentadecylamine affords highly monodisperse, cuboidal NPs containing a single clearly visible twinning plane. The allowance of particle growth parallel to this close‐packed plane explains the remarkable particle morphology.