Cu₂O/TiO₂ heterostructures on a DVD as easy&cheap photoelectrochemical sensors

Cu₂O nanoparticles have been grown by pulse-electrochemical deposition on a Digital Versatile Disk (DVD) which acts as a nanostructured electrode. Prior to Cu₂O deposition, the silver-coated rectangular-shaped grooves of the disassembled DVD were coated with a TiO₂ thin film by a modified sol–gel method, where oxalic acid is used in place of the usual mineral acids to peptize the precipitated hydrous titania formed from the hydrolysis of titanium iso-propoxide. This procedure leaves no inorganic residues after UV-curing, resulting in a high quality film, mainly composed of TiO₂-anatase. As demonstrated by Atomic Force Microscopy (AFM) measurements, the DVD grooves are filled by a 120–130 nm thick TiO₂ film, while the thickness of the TiO₂ deposit on the crests is only ca. 50 nm. This inhomogeneous thickness leads to an inhomogeneous electric field when the DVD is used as an electrode for depositing Cu₂O nanoparticles, which eventually leads to the growth of Cu₂O nanoparticles only on the DVD crests. A highly regular and reproducible Cu₂O/TiO₂ stripe-like heterostructure is obtained where both semiconducting oxides are aside. This system has been characterized by Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), X-ray photoemission spectroscopy (XPS), Diffuse Reflectance Infrared Fourier Transform (DRIFT) spectroscopy, Raman spectroscopy and photocurrent measurements. A possible use of this easy&cheap electrode as a visible light responsive sensor to water soluble organics in basic solution is suggested. - Highlights: • A commercial DVD is recycled to prepare cheap photo-electrochemical sensors. • The sensing elements are Cu₂O nanostripes grown on a nanostructured TiO₂ thin film obtained at room temperature. • Water soluble organics can be detected by dissolved O₂ activation with visible light.