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Abstract Magnetic Fe 3 O 4 (magnetite) nanoparticles are synthesized via a chemical precipitation route in different alkaline environments (NH 3 or NaOH) and subsequently functionalized with a (propynylcarbamate)triethoxysilane moiety, with the aim of promoting the nucleation and subsequent stabilization of gold nanoparticles. The propynylcarbamate group is able to capture the gold precursor (HAuCl 4), spontaneously reduce it, and stabilize the resulting Au nanoaggregates. The obtained results show that though the dimensions of the starting magnetite substrate depend on the base used in the preparation, they remain unaltered upon the subsequent modification. Conversely, the average Au nanoparticle dimensions can be conveniently tailored as a function of the base used in Fe 3 O 4 preparation and the presence/absence of the organic functionalization. The smallest dimensions (15 nm) are obtained for AuNP supported on propynylcarbamate-functionalized Fe 3 O 4 prepared in the presence of ammonia. Magnetization measurements highlight that all the Au/Fe 3 O 4 nanocomposites display a superparamagnetic behavior and those obtained using ammonia showed consistently smaller Hc and Mr values (av. values of 7.4 Oe and 0.8 emu/g) than those prepared with sodium hydroxide (av. values of 28 Oe and 2.8 emu/g). [ABSTRACT FROM AUTHOR]

Abstract: In this work the novel, robust, air- and moisture-stable gold(III)-aminoethyl imidazolium aurate salt [Cl3AuNH2(CH2)2ImMe][AuCl4] (1) has been employed as precursor for the electrosynthesis of gold nanoparticles (AuNPs) onto ITO electrodes in 0.5moldm−3 H2SO4 aqueous solution without the use of additional additives and/or stabilizers. The electrode termed ILNH2-AuNPs200 prepared at a fixed electrodeposition time (t d) of 200s was characterized with AFM, SEM, XRD diffraction as well as cyclic voltammetry (CVs) and compared with an electrode in which the AuNPs have been electrodeposited from KAuCl4 in the presence of KI as additive at the same t d (AuNPs200). The effect of the t d (i.e. 50s or 500s; electrodes ILNH2-AuNPs50 and ILNH2-AuNPs500, respectively) was also investigated together with the electrocatalytic activity towards methanol oxidation in alkaline medium of all the prepared electrodes. The comparison with AuNPs obtained with KI as additive shows that the presence of the amino-functionalized imidazolium moiety although not relevant in relation to the particle size, favours the metal electrodeposition process and plays an important role in the enhancement of the following parameters: (i) surface coverage (S.C.), (ii) electroactive particle coverage Φ p %, (iii) electroactive surface area σ red(exp)/σ red(theor) and (iv) catalytic efficiency. [ABSTRACT FROM AUTHOR]

Abstract: Bimetallic Au–Pt nanoparticles (Au–PtNPs) have been synthesized using an electrochemical reduction approach. The effects of the addition of different additives in the electrodeposition bath namely KI, 1-nonanesulfonic acid sodium salt and Triton X-100 have been investigated. The structural characterization of the bimetallic nanoparticles has been carried out using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), UV–vis spectroscopy, X-ray diffraction (XRD) and cyclic voltammetry (CV). The Au–PtNPs prepared in the presence of KI and Triton X-100 characterized by a relatively narrow size distribution as well as a higher particle density and surface coverage whereas no changes in the morphology were observed. These results suggest a dependence of the size and distribution of the bimetallic nanoparticles from the type and concentration of the additives employed. [ABSTRACT FROM AUTHOR]