Abstract This study performs natural sand-based synthesis using the sonochemical route for preparing Zn-doped magnetite nanoparticles. The nanoparticles were dispersed in water as a carrier liquid to form Zn-doped magnetite aqueous ferrofluids. Structural data analysis indicated that the Zn-doped magnetite nanoparticles formed a nanosized spinel structure. With an increase in the Zn content, the lattice parameters of the Zn-doped magnetite nanoparticles tended to increase because Zn2+ has a larger ionic radius than those of Fe3+ and Fe2+. The existence of Zn–O and Fe–O functional groups in tetrahedral and octahedral sites were observed in the wavenumber range of 400–700 cm–1. The primary particles of the Zn-doped magnetite ferrofluids tended to construct chain-like structures with fractal dimensions of 1.2–1.9. The gas-like compression (GMC) plays as a better model than the Langevin theory to fit the saturation magnetization of the ferrofluids. The ferrofluids exhibited a superparamagnetic character, with their magnetization was contributed by aggregation. The Zn-doped magnetite ferrofluids exhibited excellent antibacterial activity against gram-positive and negative bacteria. It is suggested that the presence of the negatively charged surface and the nanoparticle size may contribute to the high antibacterial activity of Zn-doped magnetite ferrofluids and making them potentially suitable for advanced biomedical.

O potencial catalítico para reações de interface de fases em reações catalisadas por ácidos foi demonstrado pelo zeólito NaY enriquecido com ácido nióbico recoberto por alquilsilano na reação de hidratação do 1,2-epoxioctano com água em fase líquida. O catalisador foi preparado através da impregnação do ácido nióbico na superfície externa de NaY, seguida da modificação parcial da superfície externa de NaY com grupos alquilsilanos. As partículas adicionadas a uma mistura contendo água e 1,2-epoxioctano foram facilmente localizadas na interface das fases líquido-líquido, e catalisaram eficientemente a hidratação do epóxido, mesmo sem agitação. Com o objetivo de investigar o efeito da localização dos sítios ativos, foram preparados HZSM-5 alquilsililado e NaY funcionalizado com ácido sulfônico, em que os sítios ativos estão localizados predominantemente na superfície interna dos zeólitos. Neste caso, foi necessária agitação mecânica para aumentar a velocidade de reação. Sugere-se que a alquisilação da superfície externa do zeólito, quando o sítio ativo se encontra principalmente dentro do poro, não pode modificar o modo de ação do catalisador; ainda é necessário agitar a mistura reacional para promover a transferência de massas de substratos e reagentes.

The catalytic potential of phase-boundary catalyst for acid-catalyzed reactions has been demonstrated by NaY zeolite loaded with alkylsilane-covered niobic acid in the liquid phase hydration of 1,2-epoxyoctane with water. The catalyst was prepared by impregnation of niobic acid on the external surface of NaY and followed by a partial modification of the external surface of NaY with alkylsilyl groups. When the particles were added to a mixture of water and 1,2-epoxyoctane, they were feasibly located just at the liquid-liquid phase boundary and efficiently catalyzed hydration of the epoxide even without stirring. In order to investigate the effect of the location of the active sites, alkylsilylated HZSM-5 and sulfonic acid functionalized NaY in which the active sites are located dominantly on the internal surface of zeolites were prepared. In that case, mechanical stirring was needed to increase the reaction rate. It was suggested that alkylsilylation on the external surface of zeolite, when the active site is mainly inside the pore, could not change the mode of the catalytic action; it is still necessary to stir the reaction mixture to drive the mass transfer of substrates and reagents.