Studies of the interaction of two organophosphonates with nanostructured silver surfaces.

Electrochemical cycling of silver surfaces in the presence of the organophosphonates paraoxon and malathion leads to changes in the electrochemical response of silver and the formation of silver nanostructures. Adsorption of the organophosphonates onto the silver surfaces causes a significant reduction in the observed current response due to an increase in the charge transfer resistance. Surface enhanced Raman spectroscopy (SERS) measurements indicate that paraoxon adsorbs with no structural changes, while malathion decomposes and a thiophosphonate interacts with the surface. The SERS study of these adsorbates was carried out by changing the electrochemical conditions and the concentration of the organophosphonates. The size of the nanostructures greatly influences the SERS signal and it is observed that the strongest enhancement is observed for mid-sized nanostructures with a uniform thickness on the surface. The limit of detection was shown to be in the range of 10 nM to 10 pM for paraoxon and malathion, respectively.