The electrochemical experiments were performed using a CHI 410a potentiostat (CH Instruments, USA). The GCE with a diameter 0.3 cm from Bioanalytical Systems, Inc., USA was used for electrode modifications. A conventional three-electrode system which consisting of Ag/AgCl (saturated KCl) as a reference electrode, f-MWCNT/AuNPs-AT modified GCE as a working electrode and platinum wire as a counter electrode was employed for the electrochemical studies. Electrochemical impedance studies (EIS) were performed using a ZAHNER impedance analyzer (Germany). The atomic force microscope (AFM) images were recorded using a multimode scanning probe microscope (Being Nano-Instruments CSPM-4000, China). Scanning electron microscope (SEM) images were recorded using a HITACHI S-4700 (Japan).