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In Situ Fabricated Cu–Ag Nanoparticle-Embedded Polymer Thin Film as an Efficient Broad Spectrum SERS Substrate

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journal contribution
posted on 05.01.2017, 14:52 by V. Kesava Rao, Pankaj Ghildiyal, T. P. Radhakrishnan
Thin films of polymer–metal nanocomposites can serve as efficient surface-enhanced Raman scattering (SERS) substrates; it would be highly advantageous if it can be fabricated by a cost-effective and facile protocol, and high enhancement factors (EF) can be realized for a range of excitation wavelengths, enabling sensitive detection of different analytes. Poly­(vinyl alcohol) (PVA) thin films with embedded Cu–Ag nanoparticles are fabricated through a simple in situ procedure via stepwise formation of CuO–PVA and Cu–PVA; the fabrication is monitored through the different stages, by spectroscopy, microscopy, electron diffraction, and elemental analysis. Choice of the Cu–Ag combination is dictated by its broad plasmonic extinction, favorable cost factor, and chemical stability of the nanocomposite; the hydrogel character of PVA facilitates analyte absorption and contact with the nanoparticles, leading to efficient SERS. Cu–Ag–PVA thin film with an optimal composition is shown to display plasmonic extinction over an appreciable part of the visible range and to provide EF of the order of 107–108 for the analytes, rhodamine 6G and methylene blue, at three different excitation wavelengths; the EF values are significantly higher than those reported earlier, with most of the Cu–Ag based SERS substrates. The novel polymer–bimetal nanocomposite thin film is an efficient SERS substrate providing subpicomolar limits of detection.