Narrowing of bandgap with silver doping on TiO2 nanotubes arrays for electrochemical sensing application

Although one-dimensional anodic TiO2 nanotube arrays (TNTs) have attracted considerable attention in various fields due to their remarkable functionalities, their poor electrical conductivity limits their practical applications. Here, we present a simple approach of electrochemical silver doping of TNTs electrodes that significantly improves electronic conductivity and electrocatalytic performance towards electrochemical sensing. Glucose was chosen as an analyte to investigate the electrocatalytic sensing properties of Ag doped TNTs, and various analysis such as cyclic voltammetry, sensitivity, chronoamperometry, and electrochemical impedance spectroscopy (EIS) were performed using a three-electrode system. The Ag doped TNTs showed nearly 50 times higher sensitivity (from 0.4 µA mM-1 cm-2 to 21 µA mM-1 cm-2), lesser detection limit (from 0.52 mM to 0.07 mM), less charge transfer resistance (from 3.63 Ω to 2.35 Ω), and reduced bandgap (from 3.2 eV to 3 eV) as compared to plain TNTs. The enhanced response of Ag doped sensors was attributed to the reduced bandgap that induced defect states and increased electron transfer rate required for oxidation of glucose. Perspective wise, the synthesis of Ag doped TNTs through a single electrochemical anodization step can be a faster and a promising technique that is highly desirable for enhancing the performances of nanomaterial-based electrochemical sensors.