One-step chemical synthesis of Ag–Au alloy nanoparticles for modulating the catalytic hydrogenation reaction

Surface Deposition of Magnesium Ferrite-Based Supports with Bimetallic Gold/Silver Nanoparticles for the Catalytic Reduction of Nitroaromatics

Surface deposition of magnesium ferrite nanoparticles (MgFe2O4 NPs) with bimetallic gold/silver (Au/Ag) nanoparticles was conducted using the seed-mediated growth method to obtain magnetic-metallic composite catalysts for use in the catalytic reduction of nitroaromatics. Two types of amine-functionalized MgFe2O4 and MgFe2O4@SiO2 NPs were used as magnetic supports for the surface deposition process. The combination of several characterization analyses (i.e., XRD, XPS, TEM, SEM, EDS, and VSM) confirmed the successful syntheses of the MgFe2O4/Au/Ag and MgFe2O4@SiO2/Au/Ag NPs. The catalytic reduction of 4-nitrophenol using sodium borohydride as a reducing agent revealed that the reaction was completed within 2 min by using MgFe2O4/Au/Ag and MgFe2O4@SiO2/Au/Ag NPs as catalysts. The appearance rate constant of the MgFe2O4/Au/Ag NPs was slightly higher than that of the MgFe2O4@SiO2/Au/Ag NPs. In terms of reusability, high conversion (>80%) of the reduction of 4-nitrophenol was still obtained after 7 and 10 consecutive cycles for the MgFe2O4/Au/Ag and MgFe2O4@SiO2/Au/Ag catalysts, respectively. Interestingly, these two catalysts exhibited the highly catalytic conversion of the chosen nitroaromatic derivatives (i.e., 4-nitrobenzaldehyde and 4-nitroaniline). On the whole, the MgFe2O4/Au/Ag and MgFe2O4@SiO2/Au/Ag NPs could be utilized as suitable and sustainable catalysts for the catalytic reduction of nitroaromatics due to several desirable features (i.e., high activity, facile and rapid separation by a magnet, and good reusability).

Ag@Au bimetallic nanoparticles: an easy and highly reproducible synthetic approach for photocatalysis

An Ag@Au bimetallic nanoparticle (BNP) formulation was developed in this work. The proposed formulation was developed using photochemical and chemical methods and non-toxic reagents, showing high reproducibility and homogeneity. The synthesized BNPs have an average size of 7 nm, a core-shell-like structure (silver core and gold shell), high colloidal and long-term stability, and superior catalytic activity under darkness and white light irradiation conditions when evaluating the reduction of 4-nitrophenol to 4-aminophenolate, with respect to the monometallic Ag and Au counterparts. Furthermore, BNP concentrations as low as 2 nM were required to reach 100% conversions in less than 30 minutes. Therefore, considering future applications, the high surface-to-volume ratio of the prepared BNPs coupled with their well-defined optical properties makes them a great candidate for developing heterogeneous catalyzer materials to be applicable under sunlight as an environmentally friendly catalytic system.

Preparation of In/Sn Nanoparticles (In3Sn and InSn4) by Wet Chemical One-Step Reduction and Performance Study

The preparation of binary alloys by surfactant-assisted chemical reduction in aqueous solution at room temperature has become a hot topic. In this article low melting point tin/indium (Sn/In) nanoparticles are synthesized. The formation process of the alloy was studied. Scanning electron microscopy, energy spectrometry, and X-ray diffraction are used to determine the morphology, composition, and crystal structure of the nanoparticles. Study found that fully alloyed indium-tin nanoparticles can be obtained by wet chemical method and the main phases of indium-tin alloy are β-phase (In3Sn) and γ-phase (InSn4). However, the Sn phase appears at a low content of indium (40 wt%). When the content of indium increases to 45 (wt%), the tin phase disappears. In addition, the most important finding is that the composition of the indium-tin alloy can be changed by ratio control, and the content of In3Sn increases with the increase of indium content. The relative content of In3Sn attains a maximum when the content of indium increases to 60 (wt%). In contrast, the content of InSn4 decreases. Finally, differential scanning calorimetry measurements is performed to understand the melting behavior of the nanoparticles and low melting temperatures are achieved for a wide range of indium compositions (from 40% to 60%). The melting temperature is found to be in the range of 125–132 °C and it increased with increasing In3Sn (also the increase of indium content). This gives us a new understanding into the binary alloy nano-system and gives important information for the application of low temperature alloy solders. The choice of composition can be based on the corresponding melting point.