Enhanced catalytic nitrophenol reduction via highly porous hollow silica nanospheres stabilized Au nanoclusters

In this work, we report the synthesis of Au nanoparticles encaged in hollow porous silica nanospheres (Au@HPSNs), which features extremely small Au nanoclusters (-1.3 nm) encapsulated in high specific surface area (-800 m2/g) HPSNs. We used the electrostatic attraction between the anions of poly(acrylic acid) (PAA) and protonated poly(ethylenimine) (PEI) to build the micelles system in an ethanol-water system, which was employed as the templates for deposition of silica to give the core-shell structured PEI-PAA@SiO2. The final materials Au@HPSNs were obtained by soaking PEI-PAA@SiO2 in HAuCl4 solution and subsequent calcination. The Au@HPSNs show extremely high catalytic efficiency for 4-nitrophenol (4-NP) reduction with NaBH4, and exhibit the highest heterogeneous Au-based catalytic efficiency up to date for 4-NP reduction. The greatly enhanced performance of Au@HPSNs could be ascribed to ultra-fine Au nanoclusters and the small mass transfer hindrance with high specific surface area hollow porous silica.