Polystyrene@silica hybrid microspheres (PS@SiO2) and hollow spheres of SiO2(HSSi) were prepared using positively charged polystyrene (PS) microspheres as the template.Then

gold nanoparticles (Au-NPs) and silver nanoparticles (Ag-NPs) were modified onto the surface of PS@SiO2and HSSi

respectively

through the bridging coupling by mercapto silane coupling agents

which leads to the following four kinds of composite microspheres with uniform structures and narrow size distributions:(1) HSSi with the surface being modified with Au-NPs (HSSi-AuNPs); (2) PS@SiO2 with the surface being modified with AuNPs (PS@SiO2-AuNPs); (3) HSSi with the surface being modified with Ag-NPs (HSSi-AgNPs) and (4) PS@SiO2 with the surface being modified with AgNPs (PS@SiO2-AgNPs).These composite microspheres were used as SERS substrates

whose sensitivity

reproducibility and stability were evaluated by using crystal violet (CV) as the probe.The detection limits of CV by HSSi-AuNPs

PS@SiO2-AuNPs

HSSi-AgNPs and PS@SiO2-AgNPs are 10-10 mol/L

10-9 mol/L

10-11 mol/L and 10-11 mol/L

respectively.All these substrates exhibit relatively high sensitivities; the hollow structures make positive contributions to the sensitivities.Results of repeated Raman measurements of CV on the different spots randomly selected from the substrates confirm that all the substrates have good reproducibility.Moreover

all the substrates have a good stability

because they still have good sensitivities after having been stored in ambient environment for 3 months.