One-step anodization versus chronoamperometric electrodeposition for the fabrication of gold nanoparticle–TiO₂ nanotube nanocomposites for biosensing applications

Abstract Titanium dioxide nanotubes (TNTs) modified with gold nanoparticles (AuNPs) are attractive materials for electrochemical sensing owing to their high surface area and enhanced electron-transfer properties. In this study, AuNP/TNT nanocomposites were fabricated using two different approaches: one-step anodization and chronoamperometric electrodeposition. In the first approach, AuNPs were generated directly during TNTs anodization by introducing HAuCl₄ into the electrolyte at final concentrations of 1, 5, and 10 mM. To the best of our knowledge, this is the first report describing the fabrication of AuNPs/TNTs through the direct incorporation of HAuCl₄ into the anodization electrolyte. In the second, AuNPs were deposited onto annealed TNTs (TNTs-A) by chronoamperometry at − 0.3, − 0.9, and − 1.2 V. The obtained materials were characterized using scanning electron microscopy, X-ray diffraction, contact angle measurements, open-circuit potential measurements, and electrochemical impedance spectroscopy. Among the investigated samples, the nanocomposite fabricated by one-step anodization in the presence of 1 mM HAuCl₄ and subsequently annealed in argon atmosphere at 450 °C for 2 h exhibited a well-dispersed AuNPs distribution (25.97 ± 2.84 nm) and 30% and 34% reductions in impedance modulus and real impedance, respectively, compared with TNTs-A. Furthermore, this platform showed an enhanced electrochemical response toward hydrogen peroxide (0.1–0.5 mM) in the presence of thionine and horseradish peroxidase, exhibiting higher sensitivity and a lower detection limit (0.001 mM) than TNTs-A (0.003 mM).