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

Abstract

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).