Polypyrrole-Tannin (PPy/TA) nanocomposite was prepared in the presence of cationic
surfactant, cetyltrimethylammonium bromide (CTAB) using the chemical
polymerization method. The resulting PPy/TA/CTAB nanocomposite was used to
modify screen printed carbon electrode (SPCE) for developing a dopamine (DA)
biosensor. The presence of TA was able to repel the interference molecules (AA and
UA) in DA detection, while CTAB act as a soft-template in tailoring the nanostructure
of PPy. The electrochemical properties of the modified electrode were studied via
cyclic voltammetry (CV) and SPCE/PPy/TA/CTAB-modified electrode revealed a
higher current response compared to modified electrode of SPCE/PPy and
SPCE/PPy/TA. The results obtained from Electrochemical Impedance Spectroscopy
(EIS) exhibited a lower value of charge transfer resistance (Rct) for the
SPCE/PPy/TA/CTAB-modified electrode indicating an enhancement in the electron
transfer rate.
The Fourier-Transform Infrared (FTIR) spectra of nanocomposite displayed the typical
characteristic peaks of TA and CTAB which are evidences of the incorporation of these
components into PPy. Electron Microscopy (TEM) revealed a rod-like structure with a
lumpy surface for PPy/TA/CTAB nanocomposite, justifying the highest current
response for the modified electrode. Brunauer-Emmet-Teller (BET) measurement
displayed a surface area of 23.5 m2/g for PPy/TA/CTAB nanocomposite.
Response Surface Methodology (RSM) has been applied to optimize the selected
parameters and conditions in order to maximize the biosensor’s performance and its
sensitivity. Amperometry and Differential Pulse Voltammetry (DPV) analysis were
employed for all electrochemical measurements and dopamine detection in two
different ranges of 0.1–2 μM and 2–50 μM. The good adhesion of nanocomposite on
the electrode surface, as well as the high surface area and porosity of the modified electrode, enhanced the diffusion of DA molecules inside the matrix. Amperometry
analysis of the SPCE/PPy/TA/CTAB modified electrode displayed a good sensitivity of
0.039 μA (μM)−1 towards dopamine with the limit of detection (LOD) of 2.9×10−7 M.
The modified biosensor also excludes the interfering species of ascorbic acid (AA) and
uric acid (UA) which makes the sensor suitable for DA determination. This biosensor
showed an acceptable reproducibility and repeatability with low relative standard
deviations (RSD) of 4.8% and 4.4%, respectively. The current response remained about
81.5% of the original value after 21 days indicating an accepted stability over time
