Electrochemical serotonin monitoring of poly(ethylenedioxythiophene): Poly(sodium 4-styrenesulfonate)-modified fluorine-doped tin oxide by predeposition of self-assembled 4-pyridylporphyrin

A 5,10,15,20-tetrakis(4-pyridyl)-21. H,23. H-porphyrin (TPyP)-modified self-assembled functional layer was prepared on a fluorine-doped tin oxide (FTO) substrate. We employed a bifunctional molecule, 3-iodopropionate (3IP), to covalently bind TPyP to the FTO substrate. The 3IP-monolayered FTO and the TPyP-3IP-bilayered FTO electrodes were characterized by cyclic voltammetry, electrochemical impedance spectroscopy, and Fourier transform-infrared spectroscopy. Compared to conventional electropolymerized poly(ethylenedioxythiophene):poly(sodium 4-styrenesulfonate) (PEDOT:PSS) film on bare FTO, the PEDOT:PSS film on the TPyP-3IP-bilayered FTO showed better sensitivity and selectivity in monitoring serotonin in the presence of high concentrations of interfering agents such as ascorbic acid, urea, d-(+)-glucose, epinephrine, and l-3,4-dihydroxyphenylalanine. Both PEDOT:PSS films on the bare FTO and the TPyP-3IP-bilayered FTO showed electrocatalytic effects in serotonin detection, and only the TPyP-3IP-based PEDOT:PSS film acted as a pH resistant buffer layer in the selective detection of serotonin.