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M/Cu 2 O (M ¼ Ag, Au) heterogeneous nanocrystals are successfully prepared by depositing noble metal nanoparticles onto the surfaces of Cu 2 O octahedral nanocrystals through a simple photocatalytic process. The samples are characterized by means of X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and energy dispersive X-ray analysis (EDX). The influence of the light source and solution temperature on the deposition of noble metal (taking Ag as an example) nanoparticles has been studied. The experimental results show that visible light is more favorable for the deposition of Ag nanoparticles onto Cu 2 O nanocrystals, and a solution temperature of more than 30 C can prevent the erosion of Cu 2 O. The photocatalytic properties of the prepared M/Cu 2 O heterogeneous nanocrystals are studied, showing enhanced photocatalytic activities.

Ag nanoparticles with average sizes of 20 nm were well-dispersed on the surfaces of Fe3O4@SiO2 composite microspheres through a simple wet-chemical method employing the Ag-mirror reaction. The as-synthesized Ag-coated Fe3O4@SiO2 three-ply composite microspheres are monodisperse and bifunctional, with ferromagnetic and surface-enhanced Raman scattering (SERS) properties. The products were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray analysis (EDX). SERS signals of typical analytes such as rhodamine 6G (Rh 6G) were observed on Ag nanoparticles from the Ag-coated Fe3O4@SiO2 microspheres, even though the concentration of the analyte was as low as 1 × 10−15 M (Rh 6G). The Ag-coated Fe3O4@SiO2 microspheres were applied to detecting melamine, and strong SERS signals were obtained with melamine concentration of 1 × 10−6 M. This work may provide a potential and unique technique to detect melamine.

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