Preparation and characterization of bismuth oxide nanoparticles-multiwalled carbon nanotube composite for the development of horseradish peroxidase based H2O2 biosensor

In this work, preparation and characterization of a novel nanocomposite containing bismuth oxide (Bi2O3) nanoparticles and multiwalled carbon nanotubes (MWCNTs) was presented. Powder X-ray diffraction (XRD) studies revealed that as-synthesized Bi2O3 nanoparticles are crystalline and belong to α-phase with monoclinic symmetry. Field emission scanning electron microscopy (FESEM) study results showed that the size of Bi2O3 nanoparticles is 50 nm. Energy-dispersive X-ray (EDX) spectra of as-prepared Bi2O3–MWCNT nanocomposite displayed characteristic Bi and C peaks which confirmed the incorporation of Bi2O3 with MWCNT. The prepared Bi2O3–MWCNT was also characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM) studies. The direct electron transfer of horseradish peroxidase (HRP) has been revealed at Bi2O3–MWCNT modified glassy carbon electrode (GCE). In order to firmly anchor the HRP molecules onto Bi2O3–MWCNT matrix, a thin layer of 1% nafion (NF) solution was coated as a binder. The fabricated NF/HRP/Bi2O3–MWCNT/GCE exhibits well defined quasi-reversible redox peaks at a formal potential (E0′) of −0.326 V vs. Ag/AgCl reference electrode in 0.05 M phosphate buffer solution (PBS), pH 7. NF/HRP/Bi2O3–MWCNT film remarkably lowers the over potential for H2O2 reduction than MWCNT, Bi2O3–MWCNT and unmodified GCEs. The proposed composite film exhibits quick amperometric i–t response (5 s) towards H2O2 in the linear range of 8.34–28.88 mM with a sensitivity of 26.54 μA μM−1 cm−2. The developed NF/HRP/Bi2O3–MWCNT biosensor has a good operational stability and high selectivity towards H2O2.