An in situ reduction method for preparing silver/poly(vinyl alcohol) nanocomposite as surface-enhanced Raman scattering (SERS)-active substrates

Novel silver/poly(vinyl alcohol) (PVA) nanocomposite films were obtained by an in situ reduction method, in which the silver nitrate, sodium poly(γ-glutamic acid) (PGA) and PVA acted as precursor, stabilizer and polyol reducant, respectively. The surface-enhanced Raman scattering (SERS)-activity of as-prepared nanocomposite films was investigated using benzoic acid (BA) as probed molecule. The results showed that the surface plasmon resonance (SPR) absorption band on silver films was more symmetric with stronger intensity than silver colloidal solution, indicating that the Ag nanoparticle distribution on the film substrate was uniform. The fact was further confirmed by X-ray diffraction (XRD), transmission electron microscopy (TEM) and field-emission scanning electron microscope (FE-SEM) measurements. It was found that PGA-stabilized silver/PVA nanocomposite film revealed the presence of well-dispersed and spherical silver nanoparticles with average diameter of 90 nm, while the particle sizes were enlarged as the PGA concentration increased. The new substrate presented high SERS enhancement and the enhanced factor was estimated to be 106 for the detection of benzoic acid.