ZnO Nanorods Aligned in a Vertical Configuration for\nTargeted Electrochemical Detection of Aniline

This study demonstrates the synthesis\nof 1D surface vertically\naligned nanorods of ZnO on the fluorine-doped tin oxide-coated glass\nsubstrate (ZnO-VANRs/FTOs) synthesized via a chemical route for the\ntargeted electrochemical sensing of aniline. The ZnO-VANRs/FTOs were\n1.57 ± 0.03 μm in length with excellent crystallinity and\nhigh density (1.52 × 10<sup>13</sup> rod no./m<sup>2</sup>).\nZnO-VANRs formation increased surface roughness by 2.4- and 4.7-fold\ncompared to the bare FTOs and seeded FTOs (ZnO-seed/FTOs), respectively.\nThe ZnO-VANRs/FTOs electrodes could increase the effective surface\narea from 0.154 to 0.384 cm<sup>2</sup> with about 86.85% reduction\nin charge transfer resistance compared to the bare FTOs. The peak\ncurrent response (at 0.281 V vs Ag/AgCl) of aniline deposition was\nboosted by 81.52% with the rise in temperature from 15 to 45 °C.\nThe reduction of aniline at ZnO-VANRs/FTOs involved a reversible two-electron\ndiffusion control process with a heterogeneous reaction rate constant\n(<i>k</i><sup>0</sup>) of 1.82 s<sup>–1</sup> and\na formal potential (<i>E</i><sup>0</sup>) of 0.289 V vs\nAg/AgCl. The ZnO-VANRs/FTOs electrode showed limits of detection of\n0.193 μM (sensitivity 0.198 μA·μM<sup>–1</sup>·cm<sup>–2</sup>) and 0.588 μM (sensitivity of\n0.065 μA·μM<sup>–1</sup>·cm<sup>–2</sup>) between the working ranges of 0–20 and 20–160 μM,\nrespectively. The fabricated sensor was unprecedently selective toward\naniline sensing, and <i>p</i>-nitroaniline, chlorobenzene,\nchlorpyrifos, Cu<sup>2+</sup>, Pb<sup>2+</sup>, Ni<sup>2+</sup>, Cd<sup>2+</sup>, albumin bovine, Escherichia coli, and ciprofloxacin could not interfere with aniline sensing and\nits sensitivity. However, the peak current was marginally decayed\nby 2.63% up to the 6th cycle. Moreover, ZnO-VANRs/FTOs catalyzed the\nsensing of aniline spiked in the environmental matrices, conforming\nwell to liquid chromatography.