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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.

We have studied the effect of unsupported Pd nanoparticle (NP) size in the selective CC semi-hydrogenation of alkynols with different alkyl chains, i.e., C16 in dehydroisophytol (DIP) (to isophytol (IP)) vs C1 in 2-methyl-3-butyn-2-ol (MBY) (to 2-methyl-3-buten-2-ol (MBE)). The Pd NPs were synthesized via colloidal technique with poly­(N-vinyl-2-pyrrolidone) (PVP) as stabilizing agent where a range of crystal sizes (2.1–9.8 nm; confirmed by HRTEM) was generated. Both reactions show antipathetic structure sensitivity consistent with higher specific activity (TOF) over larger Pd NPs where the structure sensitivity effect is more pronounced for NPs ≤ 3.0 nm. All the Pd NPs exhibit high (≥88%) selectivity to the target alkenol product at almost complete (98%) conversion. Increased IP selectivity (S IP; XDIP=98% ca. 95%) was observed over smaller (2.1–3.0 nm) Pd NPs while ca. 98% selectivity to MBE (S MBE; XDIP=98%) is obtained irrespective of particle size. The kinetic results were consistent with a Langmuir–Hinshelwood model. The observed Pd NPs size effect on catalytic response is ascribed to a contribution of Pd electronic surface modifications, fraction of Pdplane active sites and the steric effects which impact akynol/alkenol adsorption constants. The results obtained in this work provide a powerful tool for catalyst design for industrial applications.

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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.