Green assembly of stable and uniform silver nanoparticles on 2D silica nanosheets for catalytic reduction of 4-nitrophenol

A facile, environment-friendly route is illustrated for the efficient assembly of stable and uniform silver nano particles (AgNPs) on the surface of two-dimensional (2D) silica nanosheets (SiNSs, derived from natural kaolinite mineral) via in-situ reduction using Sn(II) as reductant. Compared to the common reduction method using NaBH4 reductant, the loaded AgNPs on AgNPs/SiNSs nanocomposite showed higher purity, uniformity and stability (antioxygenation). The catalytic reduction of 4-nitrophenol (4-NP) over AgNPs/SiNSs nanocatalyst was almost complete within 40 s without stirring and the apparent kinetic rate constant k(app) (80.19 x 10(-3) s(-1)) is much higher than those of other substrate-supported Ag/Au nanocatalysts. The effects of support material and assembly approach of AgNPs on the catalytic performance were discussed in detail. The high turnover frequency (TOF) for AgNPs/SiNSs nanocatalyst (3.52 min(-1)) indicates that the high-density dispersion of uniform small sized AgNPs on 2D SiNSs surface is responsible for the excellent catalytic property, which offer many active sites for effective contact with the reactants and fast interfacial electron transfer from the AgNPs surface to 4-NP. It exhibits the great potential of 2D silica nanosheets as support materials for the efficient assembly of uniform noble-metal nanoparticles. Moreover, the 2D AgNPs/SiNSs nanocomposite holds a stable catalytic efficiency (around 100%) over five reaction cycles. The high efficiency and convenience have been demonstrated by purifying the 4-NP polluted water in the "filtering and catalyzing" device, in which the polluted water could become colorless within 10 s.