Multiple Silver Nanoparticles Anchored Hollow Mesoporous Silica Nanospheres by Polyacrylic Acid Aggregate Templating Approach for Catalytic Reduction of p-Nitrophenol.

Anchoring metal cores inside porous shells can endow metal catalyst with high selectivity and stability. Herein, multiple silver nanoparticles were successfully anchored in hollow mesoporous silica nanospheres (Ag@HMSNs) through a facile one-pot method. Polyacrylic acid aggregates self-assembled in water/ethanol solvent were used as core templates and Ag nanoparticles captors, and hexadecyl trimethoxysilane (C16TMS) was used as the pore-making agent. The hollow cavity, encapsulated multiple Ag nanoparticles, and mesoporous silica shell of the Ag@HMSNs were confirmed by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and nitrogen sorption analysis. Just as expected, Ag nanoparticles (2-5 nm) were encapsulated in the cavity of hollow mesoporous silica nanospheres with the size of about 200 nm. The fabricated Ag@HMSNs showed excellent performance for catalytic reduction of p-nitrophenol (4-NP). Also, catalytic activity of the Ag@HMSNs for 4-NP reduction was increased with the addition amount of the pore-making agents and surface areas. The superior catalytic performance was attributed to the unique structural features of Ag@HMSNs architecture, in which the mesoporous shell provided readily accessible pathway for fast transport of reactants to the encapsulated Ag nanoparticles.

Facile fabrication of silver nanoparticles deposited cellulose microfiber nanocomposites for catalytic application.

In this study, we have prepared silver nanoparticles deposited cellulose microfibers (Ag-CMFs) with excellent catalytic property. The cellulose microfibers with a mean diameter of approximately 270 nm are regenerated by deacetylation of cellulose acetate microfibers. Silver nanoparticles are deposited onto the surface of the cellulose microfibers by a simple wet reduction of silver precursor using glucose as reducing agent. The morphology, thermal stability and catalytic activities of the samples have been investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TG), and UV-vis spectrophotometer. The average size of Ag nanoparticles deposited on the fibers is approximately 10 ±â€¯5 nm, and the deposition of the Ag nanoparticles does not change the morphology of the cellulose microfibers. The obtained Ag-CMFs exhibit excellent catalytic activity and reusable character for the reduction of p-nitrophenol by sodium borohydride. Therefore, the Ag-CMFs prepared by the facile method is expected to be an effective and promising catalytic material.

Magnetic separable chitosan microcapsules decorated with silver nanoparticles for catalytic reduction of 4-nitrophenol.

In the work, we have synthesized silver (Ag) nanoparticles deposited chitosan (CS) microcapsules with magnetic multiple Fe3O4 cores (denoted as Fe3O4/CS-Ag) as efficient catalysts for the reduction of 4-nitrophenol. The Fe3O4/CS-Ag catalysts are prepared by coating hydrophobic Fe3O4 nanoparticles with chitosan via a multiple emulsion-chemical crosslinking method and following in situ deposition of Ag nanoparticles onto the surfaces. The morphology and composition of the Fe3O4/CS-Ag microcapsules are characterized by Fourier transform infrared (FT-IR) spectra, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy. Moreover, the catalytic activity of the Fe3O4/CS-Ag catalyst was investigated, which shows a conversion efficiency as high as 98% within 15min for the reduction of p-nitrophenol to p-aminophenol. At the same time, the recovered Fe3O4/CS-Ag catalyst with an external magnet can retain good activity after 10 cycles. These results indicate that the multiple emulsion-chemical crosslinking method is an efficient and simple way for the preparation of magnetic separable chitosan microcapsules, and the fabricated Fe3O4/CS-Ag is a promising catalytic material with excellent catalytic activity and convenient recovery ability.

Facile synthesis of monodisperse of hollow mesoporous SiO2 nanoparticles and in-situ growth of Ag nanoparticles for antibacterial.

Monodispersed hollow mesoporous silica nanoparticles (HMSNs) are successfully synthesized via a facile dual template method, in which poly(styrene-co-methyl methacrylate-co-methacrylic acid) (PS-PMMA-PMAA) particles are used as hard template for producing the hollow structure and cetyltrimethylammonium bromide (CTAB) used for introducing the mesopores in the silica shells. The obtained HMSNs possess uniform diameter and morphology, and the shell of which could be adjusted by changing the addition of silicon precursor. The synthesized HMSNs have been characterized by transmission electron microscopy (TEM) and nitrogen physisorption. Furthermore, the HMSNs are used as support for in-situ deposition of silver nanoparticles (Ag NPs) using n-butylamine as reducing agent for AgNO3 in ethanol. Significantly, Ag NPs were successfully supported in the HMSNs without any aggregation. The Ag-deposited HMSNs showed excellent dispersibility in ethanol and water, and their antibacterial activity against Escherichia coli (E. coli) ATCC 25922 and Staphylococcus aureus (S. aureus) ATCC 6538 have been demonstrated. Therefore, the unique nanostructure based on the HMSNs provided a useful platform for the fabrication of antibacterial agent with superior activity and accessibility. And also, it is expected to be a significant template for the synthesis of other novel nanostructures.