Controlling the geometric design of anodic 1D TiO2 nanotubes for the electrochemical reduction of 2,4,6-trinitrotoluene in ambient conditions

[Display omitted] •Anodization of TiO2 nanotube arrays with various geometries was demonstrated.•The inner diameter and length of TiO2 nanotubes can be altered by adjusting anodization parameters.•Long nanotube arrays exhibited high performance for 2,4,6-TNT detection in ambient conditions.•LOD and LOQ were 6.49 and 21.6 ppm, respectively, using optimized nanotube arrays. In this study, we investigated how the geometric design of anodic one-dimensional (1D) TiO2 nanotube arrays affected their performance in the electrochemical reduction of 2,4,6-trinitrotoluene (2,4,6-TNT) in aqueous solutions and ambient conditions. Two main geometric parameters were considered: the inner diameter and length of TiO2 nanotubes. The various TiO2 nanotubes were fabricated using an anodization technique performed in four types of fluoride-containing organic solvents by adjusting various anodization parameters. All as-prepared samples successfully detected 2,4,6-TNT in an aqueous solution using cyclic voltammetry and linear sweep voltammetry. Three peaks corresponding to the reduction of each nitro group in 2,4,6-TNT were observed between − 0.5 and − 1.0 V (versus Ag/AgCl, 3 M KCl). Further, we discovered that nanotube length affected 2,4,6-TNT reduction performance. We also performed experiments at various concentrations of 2,4,6-TNT and determined the sensitivity to be 1.78 × 10-3 mA cm−2 ppm−1, the limit of detection to be 6.49 ppm, and the limit of quantitation to be 21.6 ppm 2,4,6-TNT over a linear range of 20 – 100 ppm using an electrode with nanotube inner diameter of 75 nm and length of 6 µm. A simple and fast fabricated composite-free 1D TiO2 nanotube arrays electrode can form the basis for future studies in enhancing the detection sensitivity. Electrochemical detection of other nitro-based compounds, such as nitroglycerin, nitrocellulose, picric acid, and their mixtures, require further investigation.