Preparation And Sers Study Of Polypyrrole/Silver Nanocomposites

Surface-enhanced Raman scattering （SERS）, which is used to detect chemical orbiological molecules attaching to the surface of metal nanostructures and greatlyadvance the part of standard Raman spectroscopy, is an ultrasensitive vibrationalspectroscopic method. SERS has been put into use to many analyses since itsdiscovery in the1970s, especially in biochemistry and life sciences. The four-starapplication is the direct sensing of multifarious analytes absorbing on a metallicSERS active substrate, producing both qualitative and quantitative information basedon the enhancing Raman spectra of analytes.Up to now, polypyrrole is one of the most widely researched conductingpolymers since its discovery. The reasons for this stong concern on polypyrroleproperly owing to the fact that the pyrrole monomer is easy to oxidation, soluble towater and available to commerce. Therefore, polypyrrole appears some superiorityincluding reversible redox properties, better environmental stability and the ability togive high electroconductibility. Polypyrrole has proven great application prospect insupercapacitors, electrochemical/biosensors, conductive fabrics and textiles,electromagnetic interference shielding, mechanical actuators, antistatig coatings anddrug delivery systems due to its good inherent nature. Despite the availability ofmany synthesis methods, electropolymerization remains the most popular andefficient technique for preparing PPy films. What’s more, there is no need to useoxidants and the electrodeposited PPy are spontaneously integrated into a continuousuniform film on the electrode.The PPy/Ag nanocomposites which could be used as SERS active substrateswere synthesized through adjusting the experimental conditions, basing onpolypyrrole as the reductant and supporter. The morphology and crystal form of thecomposites were investigated by SEM, XRD and so on. And the SERS properties ofthe PPy/Ag nanocomposites were studied using various kinds of molecules as thetarget analytes. The different morphology of doped PPy films electrodepositing ondiverse electrodes could be obtained by regulating the electropolymerization time inthe pyrrole solution containing a variety of organic acid. The homogeneous Agnanorods fully covering PPy surface which had a detection limit of10^-7mol/L4-MBA could be achieved when the PPy film doped with malic acid andelectrodepositing on ITO was immersed in1.0mol/L AgNO₃solution. Themorphology of the Ag nanostructures is Ag microspheres, which were produced onPPy films doped with sulfosalicylic acid and obtained on stainless steel sheets in1.0 mol/L AgNO₃solution, with a detection limit of10^-9mol/L4-MBA. The Agnanostructures completely covering the PPy surface doped with sulfosalicylic acid in0.1mol/L AgNO₃solution with the presence of mandelic acid not only showextremely high sensitivity in SERS detection of the target analyte, MB, with adetection limit up to0.2ppm, but also are promising as recyclable SERS substrates.