Continuous synthesis of hedgehog-like Ag–ZnO nanoparticles in a two-stage microfluidic system

Abstract

Hedgehog-like Ag–ZnO nanoparticles (NPs) were successfully prepared in a continuous two-stage microfluidic system. The first stage was the synthesis of monodispersed triangular Ag nanoprisms by the reduction of AgNO₃ with NaBH₄ in the presence of trisodium citrate, H₂O₂ and sodium dodecyl sulfate. The second stage was the growth of Zn(OH)₂ nanorods on triangular Ag nanoprisms to form a hedgehog-like shape. Hedgehog-like Ag–ZnO NPs were finally obtained by the thermal decomposition of as-prepared hedgehog-like Ag–Zn(OH)₂ NPs. The structure, morphology and chemical state of the obtained samples were characterized by X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy. It was found that H₂O₂, the molar ratio of NaOH to Zn(NO₃)₂ and the flow rate ratio of AgNO₃ to Zn(NO₃)₂ played a crucial role in the preparation of hedgehog-like Ag–ZnO NPs. In addition, the photocatalytic activity of hedgehog-like Ag–ZnO NPs was evaluated in the degradation of methyl orange. The results showed that the photocatalytic activity was greatly enhanced by hedgehog-like Ag–ZnO NPs in comparison to pure ZnO and spherical-like Ag–ZnO NPs. The reaction rate constant of the hedgehog-like Ag–ZnO NPs was twelve times the value of pure ZnO and twice the value of spherical-like Ag–ZnO NPs.