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 M to 3.2 mM and 0.01–2.16 mM. The sensitivity
values are 287.98 A 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.