Self-Aligned Electrochemical Fabrication of Gold Nanoparticle Decorated Polypyrrole Electrode for Alkaline Phosphatase Enzyme Biosensing

Figure (above): ESEM images of electroplated Au NPs on Ppy for different current density at 10 minutes a) 4 mA/cm^2,b) 20 mA/cm², c) 40 mA/cm², d) 60 mA/cm², e) 80 mA/cm², f) 100 mA/cm², g) 120 mA/cm².

Richa Pandey^a, Rakefet Ofek Almog^b, Yelena Sverdlov^a and Yosi Shacham-Diamand^a

^aDepartment of Physical Electronics, School of Electrical Engineering, Faculty of Engineering, Tel Aviv University, Tel-Aviv 69978, Israel

^bDepartment of Advanced Material Engineering, Azrieli College of Engineering,Jerusalem 9103501, Israel

Journal of The Electrochemical Society, 164 (4) B168-B175 (2017)

Here we report a novel self-aligned process for gold nanoparticle (AuNP) decorated polypyrrole (Ppy) biosensing microelectrodes, where the AuNP selectively electro-grows out of the Ppy. The self-aligned process allows "on chip" AuNP preparation and deposition in one step, saving time and cost. The Au nanoparticles were galvanostatically deposited, yielding a random array of nanoparticles under specific conditions. A study of the AuNP size and coverage as function of deposition time and current density was accomplished using environmental scanning electron microscope (ESEM). AuNP array with less than one nano-particle monolayer thickness could be reproducibly maintained keeping the device mechanical flexible. This yields electrochemical behavior that was similar to that of bare gold electrode as was determined by cyclic voltammetry in biological solution with the Fe³⁺/Fe²⁺ redox couple. The electrochemical impedance spectroscopy (EIS) study of such AuNP electrodes was performed and modeled taking into consideration the composite nature of the electrode. The fabricated electrode with 10mA/cm²AuNP deposited Ppy electrode demonstrated good sensing ability of alkaline phosphatase enzyme by cyclic voltammetry and chronoamperometry at 0.22 V (vs. Ag/AgCl quasi reference electrode in 0.1M PBS pH 7.2). The average current response of the AuNP/Ppy was found to be 30% higher than the standard Au electrode.