With the seeding method

α-Fe2O3/Ag core-shell composite powders were prepared by the reduction of Ag［(NH3)2］+ with formaldehyde as reductant

and 3-aminopropyl triethoxysilane as additive.3-Aminopropyl triethoxysilane (APS) acted as a “bridge” to connect α-Fe2O3 and Ag particles.The obtained nanocomposites were characterized by X-ray diffraction (XRD)

transmission electron microscope (TEM) and energy-dispersive X-ray spectrometry (EDX).The influences of concentration of APS

volume ratio of alcohol to water on the coating effect and performance of nanocomposites were investigated.With pyridine (Py) as a molecule probe

Raman spectroscopy (SERS) properties and stability of the α-Fe2O3/Ag core/shell composite particles were studied.The results showed that the obtained α-Fe2O3/Ag composites were coated completely

well-dispersed and the average sizes were approximately 65 nm

when the dosage of APS was 0.75%(mass) and the volume ratio of alcohol to water was 5∶1.By coating Ag layer，the intensities of SERS were enhanced at 1010 cm-1 and 1038 cm-1.Especially

the signals of Py absorbed on α-Fe2O3/Ag substrate were greatly increased at 1038 cm-1.And this substrate was fairly stable after being placed in air for one month.