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 alpha-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 (E-0') 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 mu A mu M-1 cm(-2). The developed NF/HRP/Bi2O3-MWCNT biosensor has a good operational stability and high selectivity towards H2O2. (C) 2011 Elsevier B.V. All rights reserved.