Vertically aligned Ag nanoplate-assembled film as a sensitive and reproducible SERS substrate for the detection of PCB-77.

Vertically aligned Ag nanoplate-assembled film has been achieved by spin-coating Ag seeds on an ITO substrate and subsequent electrodeposition in a mixed aqueous solution of AgNO(3) and citric acid. As sufficient hot spots are located in the deep gaps between the neighboring nanoplates across the whole substrate, the Ag nanoplate-assembled film shows strong Surface enhanced Raman scattering (SERS) effect, together with good signal reproducibility. Therefore, the Ag nanoplate-assembled films were tried as robust, highly sensitive and reproducible SERS substrates for the rapid detection of 3,3',4,4'-tetrachlorobiphenyl (PCB-77) and a detection limit of about 10(-6)M was reached. For further reducing the detection limit, a layer of decanethiol was modified on the Ag nanoplate surface to capture the PCB-77 molecules efficiently, and a lower detection limit of 10(-7)M was achieved. A linear dependence was found between the logarithmic concentrations of PCB-77 and the intensities of the fingerprint peaks. Furthermore, the Ag nanoplate-assembled film can also be used as a SERS substrate to distinguish characteristic peaks of different polychlorinated biphenyls (PCBs) in their mixed solutions. Therefore the vertically aligned Ag nanoplate-assembled film has potentials as effective SERS substrates in rapid and direct detection of trace PCBs.