Enhanced electrochemiluminescence from luminol at multi-walled carbon nanotubes decorated with palladium nanoparticles: A novel route for the fabrication of an oxygen sensor and a glucose biosensor

Incorporation of palladium nanoparticles on the surface of multi-walled carbon nanotubes and modification of glassy carbon electrode with the prepared nano-hybrid material led to the fabrication of a novel electrode. The modified electrode showed attractive electrocatalytic activity and sensitizing effect on luminol-O₂ and luminol-H₂O₂ electrochemiluminescence (ECL) reactions at neutral media. The sensitized luminol-O₂ and luminol-H₂O₂ reactions were successfully applied for the ECL determination of dissolved O₂ and glucose, respectively. Under the optimal conditions for luminol-O₂ system, the ECL signal intensity of luminol was linear with the concentration of dissolved oxygen in the range between 0.08 and 0.94mM (r=0.9996) and for luminol-H₂O₂ system, the ECL signal intensity of luminol was linear with the concentration of glucose in the range between 0.1 and 1000μM (r=0.9998). The limits of detection (S/N=3) for dissolved oxygen and glucose were 0.02mM and 54nM, respectively. The relative standard deviations (RSD) for repetitive measurements of 0.50mM oxygen (n=10) and 10μM glucose (n=30) were 3.5% and 0.3%, respectively. Also, under the optimal conditions for luminol-H₂O₂ system, the ECL signal intensity of luminol was linear with the concentration of H₂O₂ in the range between 1nM and 0.45mM (r=0.9997). The limit of detection (S/N=3) for H₂O₂ detection was 0.5nM and the relative standard deviation for repetitive measurements of 10μM H₂O₂ (n=10) was 0.8%.