Vacuum-assisted synthesis of tiny Au nanoparticles entrapped into mesoporous carbon matrix with superior catalytic activity for 4-nitrophenol reduction

Properties of Micro-Arc Oxidation Coatings on 5052 Al Alloy Sealed by SiO2 Nanoparticles

Micro-arc oxidation (MAO) treatment can effectively improve the wear resistance, corrosion resistance, and mechanical strength of aluminum alloy substrates. Improving the porous structure of MAO film and effectively sealing the pores is a significant research issue. In this study, the MAO treatment of 5052 aluminum alloy was carried out in silicate electrolytes. The MAO films were sealed with different concentrations of SiO2 nanoparticles. The effects of SiO2 nanoparticle content on the MAO films’ microstructure, mechanical properties, and corrosion performance were systematically investigated. When adding SiO2 nanoparticles to electrolytes, the particles were deposited at the micropores of the film, which could effectively seal the porous MAO film and significantly improve its corrosion and wear resistance. The corrosion resistance and wear resistance properties were optimal with 5.0 g/L SiO2 addition. Compared to the unsealed film, the corrosion current density and corrosion rate decreased from 1.24 × 10−9 A/cm2 and 1.47 × 10−5 mm/a to 7.78 × 10−10 A/cm2 and 9.15 × 10−6 mm/a, respectively. Moreover, the average friction coefficient of the sealed film was 0.606, which was ~19.3% lower than that of the substrate and 3.3% lower than for the unsealed film.

Facile synthesis of silver nanocatalyst decorated Fe3O4@PDA core–shell nanoparticles with enhanced catalytic properties and selectivity

In this work, we have successfully prepared core–shell nanoparticles (Fe₃O₄@PDA) wrapped with Ag using a simple and green synthesis method. Without an external reducing agent, silver nanoparticles (Ag NPs) with good dispersibility were directly reduced and deposited on a polydopamine (PDA) layer. Fe₃O₄@PDA@Ag showed excellent catalytic activity and recyclability for 4-nitrophenol, and also exhibited good catalytic selectivity for organic dyes (MO and MB). This simple and green synthesis method will provide a platform for other catalytic applications.

In this work, we have successfully prepared core–shell nanoparticles (Fe₃O₄@PDA) wrapped with Ag using a simple and green synthesis method.

Electrospun metal-organic frameworks with polyacrylonitrile as precursors to hierarchical porous carbon and composite nanofibers for adsorption and catalysis

A facile and effective method has been developed to prepare hierarchical porous carbon nanofibers (PCNFs), carbon nanofibers supported nickel nanoparticles (PCNFs-Ni) and carbon nanofibers encapsulating gold nanoparticles (PCNFs-Au). PCNFs or PCNFs-Au were obtained by embedding metal-organic frameworks (e.g. ZIF-8 or ZIF-8-Au) into polyacrylonitrile via electrospinning and subsequent carbonization. In addition, PCNFs-Ni were obtained by impregnating PAN/ZIF-8 nanofibers in Ni(NO₃)₂·6H₂O followed by carbonization. Both PCNF and PCNF-Ni exhibited excellent adsorption activities for methylene blue (MB) and congo red (CR). Especially, PCNF-Ni could be removed and separated via a magnet. PCNFs-Au showed excellent catalytic properties in the reduction reaction of 4-nitrophenol (4-NP).