Apparent electrocatalytic activities of composites of self-doped polyaniline, chitosan, and carbon nanotubes

• Electrocatalytic activity of SPAN, CS, CNT composite depends on casting procedures.
• SPAN exhibits synergistic effects with CNT on the electrocatalytic activity.
• SPAN in the outer layer of the composite exhibits higher electrocatalytic activity.

Composites of self-doped polyaniline (SPAN), chitosan (CS), and carbon nanotubes (CNT) (or COOH-functionalized CNT, denoted by fCNT) were cast on glassy carbon electrodes (GCE) via different casting procedures for investigations on their apparent electrocatalytic activities in buffer solutions of pH 2, 7, and 11 using the Fe(CN)63-/4- redox couple as a probe by cyclic voltammetry (CV). CV curves revealed that the cast CS–CNT and CS–fCNT composites both exhibited apparent electrocatalytic activities to the reactions of the probe at pH 2 and 7. The SPAN was found to exhibit synergistic effects with (f)CNT on the apparent electrocatalytic activity, with CNT exhibiting higher synergism than fCNT. SPAN in the outer layer of the SPAN/CS–(f)CNT/GCE exhibited more enhanced apparent electrocatalytic activity than that in the inner layer of the CS–(f)CNT/SPAN/GCE or that being mixed in the CS–(f)CNT–SPAN/GCE. At pH 7, the layered SPAN/CS–CNT/GCE and CS–CNT/SPAN/GCE that exhibited fairly high apparent electrocatalytic activities to the redox reactions of the probe exhibited also high apparent electrocatalytic activities to the oxidation reactions of dopamine (DA) and uric acid (UA) and were suitable for their detections. The layered SPAN/CS–fCNT/GCE and CS–fCNT/SPAN/GCE, and the non-layered CS–(f)CNT–SPAN/GCE exhibited low anodic peak current densities and were not suitable for the detections of both analytes.