Phenothiazine-Capped Gold Nanoparticles: Photochemically Assisted Synthesis and Application in Electrosensing of Phosphate Ions

We describe a green photochemical route for the synthesis of gold nanoparticles (AuNPs) using phenothiazine (PTZH) as a reductant as well as a stabilizer without any extra control (i.e. surfactant, pH, etc.). The synthesized AuNPs are characterized by using UV/Vis spectroscopy, cyclic voltammetry, and transmission electron microscopy. Furthermore, a possible mechanism for the formation of the AuNPs is proposed. This hybrid electrode material, derived from nanoscale gold particles capped with PTZH and its oxidation product, is explored for the development of a highly sensitive amperometric sensor for phosphate ions. The electrochemistry behind the electrocatalytic sensing of phosphate is attributed to the nano-sized gold particles that are capped with PTZH and its oxidation product, which exhibit high electron-transfer kinetics through the interaction of the hybrid PTZH-AuNPs with oxygen atoms of PO43-. The modified electrode efficiently gives an electrochemical signature of phosphate ions at a potential of -0.336 V versus AgCl/Ag and shows a linear response toward phosphate sensing, with a sensitivity of 0.794 mu A mu m(-1) and a limit of detection of 0.022 mu m, at a signal-to-noise ratio of 3.