SMART POLYMER MODIFIED ELECTRODE SWITCHED BY IONIC STRENGTH AND pH

Abstract

-Poly(N,N-dimethylaminoethyl methacrylate) modified ITO (indium tin oxide) covered with gold nanoparticles electrode was synthesized by grafting to method and stimuli responses to pH and ionic strength (IS) was evaluated in PBS solution. At pH<5 PDMAEMA chains were found to be stretched generating a great electrochemical signal and at pH<5 collapsed with a signal decreasing. In IS≤0.001 molL -1 NaCl polymer chains were stretched and IS≥0.001mol L -1 collapsed. An interesting fact was observed when adding 0.001 molL -1 NaCl in a pH 7.40 solution, the signal response was increased comparing to pH 7.40 and 0 molL -1 NaCl, but when adding 0.001 molL -1 NaCl to a pH 3.00 solution, the signal response was decreased. This behavior can be explained in terms of protonation/deprotonation process and polymer brush regime. PDMAEMA brushes response was investigated by localized surface plasmonic resonance measurements (L-SPR), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS).