Influence of Al 2 O 3 nanoparticles structure immobilized upon glassy-carbon electrode on the electrocatalytic oxidation of phenolic compounds

Abstract Electrocatalytic oxidation of catechol (CT), dopamine (DP) and tert-butylhydroquinone (TBHQ) is demonstrated on glassy-carbon electrode (GCE) surfaces modified with alumina nanoparticles of different structures and morphologies. Higher electrochemical activity for the oxidation of CT, DP and TBHQ (peak-to-peak separation reduced from 500 to 50 mV in average) was verified on a GCE polished with α-Al 2 O 3 suspension in comparison with the surfaces modified with θ and γ-Al 2 O 3 . This result seems to be correlated with the alumina structure instead of the surface area, as the α-Al 2 O 3 presented 10-fold lower surface area than θ and γ-Al 2 O 3 , or particle size. Gold and platinum surfaces were similarly modified with α-Al 2 O 3 suspension and the distinguished electrochemistry of the phenolic compounds was not observed on the platinum-modified surfaces, which may indicate effect of the substrate on the immobilization of alumina. High stability of the GCE surface modified with α-Al 2 O 3 was attested by continuous amperometric detection of the phenolic compounds under hydrodynamic conditions, and superior analytical sensitivity of the α-Al 2 O 3 -modified electrode was observed with comparable results to those obtained on GCE modified with multi-walled carbon nanotubes. These results demonstrate that α-Al 2 O 3 particles commercially available for electrode polishing can be used to develop highly sensitive, reproducible and stable electrochemical sensors, but also indicate that electrode polishing may generate improved electrochemical responses attributed to “cleaned surfaces”.