A ZnO film was electrodeposited onto a gold substrate obtained from a recordable compact disc and tested as photocatalyst in degradation of dye in aqueous solution. X-ray diffractometry and atomic force microscopic analysis showed a pure ZnO phase with particle sizes in the nanometric scale. The results showed that the photocatalytic activity of the film is significant, with more than 90 % degradation of the dye in under 6 h sunlight irradiation. The photocatalytic process in sunlight follows first-order kinetics.

The construction of gold electrodes using 3 kinds of gold recordable compact discs (CDtrodes) and characterization by electrochemical and spectroscopic techniques are herein reported. Following a surface pretreatment in 0.5 mol L-1 sulfuric acid (H2SO4), the electrochemical experiments were performed in the presence of redox couple ferro/ferricyanide [Fe(CN)6]3-/4-. The immobilization of an oligopeptide bio-inspired by acetylcholinesterase onto the CDtrode was also evaluated. Surface characterization was done by cyclic voltammetry, electrochemical impedance spectroscopy, diffuse reflectance infrared Fourier transform spectroscopy and atomic force microscopy. CDtrodes are known to be of low cost, fast and simple construction. They are suitable for immobilizing biological molecules and could be used as disposable transducer for the construction of biosensors.