Herein, we report a new approach of an FePt nanoparticle formation mechanism studying the evolution of particle size and composition during the synthesis using the modified polyol process. One of the factors limiting their application in ultra-high-density magnetic storage media is the particle-to-particle composition, which affects the A1-to-L10 transformation as well as their magnetic properties. There are many controversies in the literature concerning the mechanism of the FePt formation, which seems to be the key to understanding the compositional chemical distribution. Our results convincingly show that, initially, Pt nuclei are formed due to reduction of Pt(acac)2 by the diol, followed by heterocoagulation of Fe cluster species formed from Fe(acac)3 thermal decomposition onto the Pt nuclei. Complete reduction of heterocoagulated iron species seems to involve a CO-spillover process, in which the Pt nuclei surface acts as a heterogeneous catalyst, leading to the improvement of the single-particle composition control and allowing a much narrower compositional distribution. Our results show significant decreases in the particle-to-particle composition range, improving the A1-to-L10 phase transformation and, consequently, the magnetic properties when compared with other reported methods.

Size and shape-controlled nanomaterials based on modified polyol and thermal decomposition approaches. A brief review.. An Acad Bras Cienc 91: e20181180.

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In the last few years, transition metal carbides have emerged as novel materials with promising catalytic properties toward important practical reactions. In this work, cubic and hexagonal molybdenum carbides are synthesized and evaluated as carbon‐supported catalysts and as support materials for Pt nanoparticles for the electrochemical oxygen reduction reaction (ORR). The catalysts are characterized by XRD, energy‐dispersive X‐ray spectroscopy, TEM, XPS, and cyclic voltammetry on stationary and rotating ring‐disk electrodes. The results suggest different reactivity of the molybdenum carbide phases as both catalysts and supports for the ORR. Enhanced mass and specific ORR activities at 0.9 V are calculated for Pt–molybdenum carbide‐derived composites compared to commercial Pt and Pt/C catalysts prepared by depositing Pt by the same method. The origin of the improved ORR activity is discussed in terms of the synergistic effect between Pt and the carbide‐derived support and a decrease in the adsorption strength of oxygen‐containing species on the Pt surface, similar to that proposed for Pt–metal alloys. Additionally, the possible formation of a Pt–Mo alloy on the catalyst surface is proposed.

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A new approach for the one-pot synthesis of alkynyl chalcogenides, exemplified mainly by selenides, was developed in which dual activation of diorgano dichalcogenides and terminal acetylenes is achieved by using an indium(III) catalyst.

In this work, we report the preparation of a copper-silica material (Cu/SiO 2) by a sol-gel methodology and its characterization concerning composition and textural properties. The Cu/SiO 2 material was successfully applied as a Lewis acid heterogeneous catalyst for the A 3-coupling from 2-aminopyridine, aldehydes and alkynes to imidazo[1,2-a]pyridines (45-82%), which are relevant pharmacological scaffolds. The synthesis shows a number of advantages, such as easy separation from the reaction media and the minimal formation of metal aqueous wastes. Investigation of the mechanism supports the involvement of the formation of reaction intermediates inside the pores of the mesoporous material prior to 5-exo-dig cyclization.

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