Direct electrochemistry of catalase at multiwalled carbon nanotubes-nafion in presence of needle shaped DDAB for H2O2 sensor

The direct electrochemistry of catalase (CAT) at didodecyldimethylammonium bromide (DDAB) present on nafion dispersed multiwalled carbon nanotubes (MWCNTs-NF) modified glassy carbon electrode (GCE) has been reported. The presence of DDAB in MWCNTs-NF-CAT film enhances the surface coverage concentration of CAT (Fe-III/II) to 48%. Similarly, in presence of DDAB, there is a 57% enhancement in electron transfer rate (k(s)) with 66% increase in CAT stability. (Fe-III/II) redox couple exhibits linear dependence with the pH variation (-51 mV pH(-1)). The UV-vis absorption spectroscopy study reveals the entrapped CAT in DDAB film retains its native structure at MWCNTs-NF modified electrodes. Similarly, electrochemical impedance spectroscopy results confirm the co-existence of CAT and DDAB in the modified film. Further, scanning electron microscopy results reveal the structural morphological difference between various components in MWCNTs-NF-(DDAB/CAT) film. The cyclic voltammetry (CV) and amperometry (i-t curve) have been used for the measurement of electroanalytical properties of H2O2 by means of various film modified GCEs. The sensitivity values of MWCNTs-NF-(DDAB/CAT) film for H2O2 using CV (35.62 mu A mM(-1) cm(2)) are higher than the values which are obtained for MWCNTs-NF-CAT film (2.74 mu A mM(-1) cm(2)). Similarly, the sensitivity values using i-t curve are 101.74 mu A mM(-1) cm(2) for MWCNTs-NF-(DDAB/CAT) and 74.69 mu A mM(-1) cm(2) for MWCNTs-NF-CAT film. Finally, the diffusion coefficient of H2O2 at MWCNTs-NF-(DDAB/CAT) film (3.4 x 10(-10) cm(2) s(-1)) has been calculated using rotating disc electrode studies. (C) 2009 Elsevier B.V. All rights reserved.