Fig. 4

CVs of GCE (curve a) in PBS (0.1 M, pH 4.0), GCE (curve b), B₂O₃/GCE (curve c), MWCNT/GCE (curve d), and Bi₂O₃/ MWCNT/GCE (curve e), in 0.1 mM paracetamol (0.1 M PBS, pH 4.0). Scan rate: 100 mV s⁻¹