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The polypyrrole (PPy) films were electrochemically deposited on roughened gold substrates with different predominant crystalline orientations of (111) and (220), respectively. Gold was roughened via a cyclic voltammetry procedure. The result indicates that the (220) crystalline orientation of gold was partially changed into (111) one after gold was roughened with oxidation−reduction cycles (ORC) treatment. The surface-enhanced Raman scattering (SERS) spectroscopy of PPy deposited on gold with predominant (111) orientation exhibits higher intensity and more excellent resolution. Meanwhile, the redox behavior of gold and the resulting complex in ORC were strongly sensitive to the crystalline orientation. A mechanism of the roughening procedure on gold was also proposed to illustrate the resulting complex and its effect on the SERS enhancement.

In this work, polypyrrole (PPy) films were electrodeposited on electrochemically roughened gold substrates modified by argon plasma treatment. First, a gold substrate was roughened by a triangular-wave oxidation-reduction cycle (ORC) in an aqueous solution containing 0.1 N HCl. Then the roughened gold substrate was further treated by argon plasma. Encouragingly, the surface-enhanced Raman scattering (SERS) spectroscopy of polypyrrole electrodeposited on this roughened gold substrate modified by argon plasma treatment exhibits a higher intensity by 8-fold, as compared with the SERS of PPy electrodeposited on an unmodified roughened gold substrate. Meanwhile, the electropolymerization for pyrrole monomers occurring on the modified roughened gold substrate is easier. Also, the nucleation and growth of electropolymerization of pyrrole monomers on the modified and unmodified gold substrates are different.

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