High-Performance Oxidation and Nanomolar Detection of Phenylhydrazine Using a 6-Hydroxyflavone-Based Molecular...

The development of simple and rapid methods for preparing redox-active molecular catalyst-functionalized carbon electrodes for electrocatalytic applications is a significant research area. 6-Hydroxyflavone (HFLA), a naturally occurring flavonoid with known anxiolytic properties, also acts as a noncompetitive inhibitor of cytochrome. This study focuses on the in situ functionalization of multiwalled carbon nanotubes (MWCNTs) with redox-active HFLA, resulting in a modified electrode denoted as GCE/MWCNT@HFLA-Redox, where HFLA-Redox represents the redox-active product of HFLA. The constructed-modified electrode exhibits a well-defined and stable surface-confined redox response at E° of 0.55 V versus Ag/AgCl, with a surface excess of 6.26 × 10^-9 mol cm^-2 in a pH 2 KCl-HCl solution. The modified electrode is characterized by Fourier transform infrared, Raman, UV-vis, field-emission scanning electron microscopy, high-resolution mass spectrometry (organic extract), and control electrochemical studies. This GCE/MWCNT@HFLA-Redox electrode selectively oxidizes phenylhydrazine (PhHyd) in a pH 2 KCl-HCl solution. A screen-printed-modified electrode facilitates highly selective electrocatalytic oxidation of PhHyd via amperometric i-t measurements and batch injection analysis, without interference from hydrazine or other common electroactive species. This method exhibits an excellent linear calibration curve (200 nM to 2 μM), demonstrating a high-current sensitivity of 0.413 μA μM^-1 cm^-2 and a detection limit of 7 nM (signal-to-noise ratio of 3).