Heavy Metal Ion Detection Using TiO2 Nanotubes and Self-Reduced TiO2 Nanotube Electrodes

TiO2 nanotubes and self-reduced TiO2 nanotube semiconductor electrodes were used for electrochemical metal ion detection in an open circuit under photo-accumulation conditions. Due to their surface properties, the electrodes showed different responses towards metal ions at different wavelengths of light radiation. Using TiO2 nanotube-based electrodes, Pb(II) and Cu(II) ions were detected at irradiation wavelengths of 389 nm and 426 nm. Detection limits of 8 × 10−9 M and 5 × 10−9 M for Pb(II) and 3 × 10−8 and 7 × 10−9 M for Cu(II) were obtained at the two wavelengths, respectively. The self-reducing electrode showed a response to Pb(II) and Cu(II) ions when irradiated with light at 389 nm, while at 426 nm, Hg(II) ions along with Pb(II) and Cu(II) ions were detected. The obtained detection limits with self-reduced TiO2 nanotube electrodes for Pb(II) and Cu(II) at 389 nm were 2 × 10−7 M and 8 × 10−9 M, respectively. At a wavelength of 426 nm, the detection limits were 1 × 10−7 M, 3 × 10−9, and 4 × 10−9 M for Pb(II), Cu(II), and Hg(II), respectively.