Multiwalled carbon nanotubes dispersed in carminic acid for the development of catalase based biosensor for selective amperometric determination of H2O2 and iodate

We report the preparation of stable dispersion of multiwalled carbon nanotubes (MWCNTs) using carminic acid (CA) as a dispersing agent. The transmission electron microscopy (TEM), scanning electron microscopy (SEM), and atomic force microscopy (AFM) results confirmed that MWCNT is well dispersed in CA aqueous solution and CA has been well adsorbed at MWCNT walls. Fourier transform infrared (FTIR) and UV-vis absorption spectra results also confirmed the adsorption of CA at MWCNT. To develop a highly selective amperometric biosensor for H2O2 and iodate, the model enzyme catalase (CAT) was immobilized at CACNT modified glassy carbon electrode surface. The immobilized CAT exhibits well defined quasi reversible redox peaks at a formal potential (E°′) of −0.559 V in 0.05 M pH 7 phosphate buffer solution (PBS). The proposed CAT/CACNT biosensor exhibits excellent amperometric response towards H2O2 and iodate in the linear concentration range between 10 μM to 3.2 mM and 0.01-2.16 mM. The sensitivity values are 287.98 μA mM−1 cm−2 and 0.253 mA mM−1 cm−2, respectively. Moreover, the developed CAT biosensor exhibits high affinity for H2O2 and iodate with good selectivity.