Highly Dense TiO₂ Nanorods as Potential Electrode Material for Electrochemical Detection of Multiple Heavy Metal Ions in Aqueous Medium

This study describes the direct deposition of extremely dense TiO₂ nanorods (NRs) on an ITO substrate for the improved detection of heavy metal ions (HMIs). A facile hydrothermal method was employed to synthesize TiO₂ NRs on the ITO substrate at ~130 °C. Synthesized TiO₂ NRs were analyzed for morphological, structural, and electrochemical properties. As an electrode material, TiO₂ NRs were used for the simultaneous detection of three HMIs (i.e., Cr³⁺, Cu²⁺, and Hg²⁺), which showed a remarkably high sensitivity of ~92.2 µA.mM⁻¹.cm⁻² for the Cu²⁺ ion. Relatively low sensitivities of ~15.6 µA.mM⁻¹.cm⁻² and ~19.67 µA.mM⁻¹.cm⁻² were recorded for the Cr³⁺ and Hg²⁺ ions, respectively. The fabricated TiO₂ NR-based HMI sensor showed an effective dynamic linear detection range with low LOD values of ~21.7 mM, 37 mM, and ~ 28.5 mM for Cr³⁺, Cu²⁺, and Hg²⁺, respectively. The TiO₂ NR-based HMI sensor exhibited efficient charge transfer over the electrode toward the trace detection of Cr³⁺, Cu²⁺, and Hg²⁺. Moreover, the reliability of the TiO₂ NR-based HMI sensor was assessed, which exhibited a promising stability of 30 days. The obtained results indicate that TiO₂ NRs grown on an ITO substrate are a promising electrode material for detecting hazardous Cr³⁺, Cu²⁺, and Hg²⁺ and might eventually be commercialized in the near future.