Mono-6-thio-β-cyclodextrin-functionalized AuNP/two-dimensional TiO₂ nanosheet nanocomposite for the electrochemical determination of trace methyl parathion in water

In this study, two-dimensional (2D) TiO₂ nanosheets (TiO₂NSs) composited with Au nanoparticles and mono-6-thio-β-cyclodextrin (SH-β-CD) monolayers were prepared for constructing an electrochemical sensing interface on a glassy carbon electrode (SH-β-CD/AuNP/TiO₂NS/GCE) surface. Because of the outstanding advantages of a large active surface area, excellent electron-transfer speed and electrocatalytic activity of AuNPs/TiO₂NSs and the selective recognition properties of SH-β-CD, the as-prepared sensor could remarkably improve the electrochemical response signals of trace methyl parathion (MP) pesticide. The square-wave voltammetry (SWV) signal of MP at the as-prepared sensor was ca. 4.2 and 5.7 times larger than that at the AuNP/TiO₂NS/GCE and TiO₂NS/GCE without SH-β-CD, respectively, while a weak SWV signal was detected at the AuNP/GCE. Therefore, both AuNP/TiO₂NS hybrids and SH-β-CD played important roles in the sensing of MP. A wide linear relationship was obtained between the SWV signals and MP concentrations from 1.5-60.0 nM with a low MP detection limit of 0.05 nM (0.012 ppb) being experimentally achieved under the optimum conditions. The as-prepared sensor also showed a higher response selectivity to MP than to other aromatic pesticide molecules and was further applied in the determination of MP in real river samples.