Improving Trace Detection of Methylene Blue by Designing Nanowire Array on Boron-Doped Diamond as Electrochemical Electrode

In this study, a boron-doped diamond nanowire array (BDD-NWA)-based electrode is prepared by using a microwave plasma chemical vapor deposition system and treated with inductively coupled plasma reactive ion etching. The BDD-NWA electrode is used for trace detection of methylene blue, which has a wide linear range of 0.04–10 μM and a low detection limit of 0.72 nM. Both the superhydrophilicity (contact angle ~0°) and the dense nanowire array’s structure after the etching process improve the sensitivity of the electrochemical detection compared to the pristine BDD. In addition, the electrode shows great repeatability (peak current fluctuation range of −3.3% to 2.9% for five detection/cleaning cycles) and stability (peak current fluctuation range of −5.3% to 6.3% after boiling) due to the unique properties of diamonds (mechanical and chemical stability). Moreover, the BDD-NWA electrode achieves satisfactory recoveries (93.8%–107.5%) and real-time monitoring in tap water.