Gold Nanoparticle Metallization of Flexible Conducting Polymer Electrode

Novel gold/ polypyrrole/ gold electrodes for biochip applications are presented.  The electrodes demonstrated better conductivity than polypyrrole electrodes and better sensitivity than conventional gold electrodes. We describe the device fabrication and the electrical properties of the electrodes.  Polypyrrole was deposited by electrochemical polymerization, and a thin top gold layer was electro-deposited on the Polypyrrole.

A study of the nucleation and growth of the top gold using high resolution scanning electron microscope is presented. Under stagnant conditions a significant electro-crystallization was observed. Electrochemical characterization essential for future bio-sensing application was demonstrated.  The electrochemical behavior of the metal/Ppy/metal electrodes was tested by CV and impedance spectroscopy. The novel electrode system was tested for their application as whole cell biosensors using substrate - enzyme interaction by product electrochemical activity. We studied the response of the new electrode in biological solutions (PBS).

We found that depositing Ppy on thin metal seed layer dramatically increases the measured current of the electrodes, as compared to Au electrode. This effect was also demonstrated by CV measurements as well as in amperometric detection of alkaline-phosphatase enzymatic activity using biological chips. This high current produces noise that interferes with the proper operation.  However, when sufficient metal is electrodeposited on the Ppy, the behavior of the electrode becomes similar to that of a metal electrode, as demonstrated by CV and by amperometric detection of enzymatic activity. The CV curve has the same characteristics as that of the planar gold electrode, with a considerably higher current peak (Ip).

The modified Au/Ppy/Au electrode yielded an improved signal, compared with that from a flat gold electrode. The electrodeposition of Ppy followed by Au, on the surface of the biochip’s Au seed layer, affected the electrocrystallization of the Au particles on the Ppy (Fig 1) resulting in a high surface area. This electrode can serve as a highly sensitive, high surface area and flexible sensor for biological species.