Visible light photoelectrochemical sensor based on Au nanoparticles and molecularly imprinted poly(o-phenylenediamine)-modified TiO2 nanotubes for specific and sensitive detection chlorpyrifos.

A molecular imprinted polymer thin film for photoelectrochemical (PEC) sensing of chlorpyrifos molecules was first constructed by electropolymerizing the o-phenylenediamine (o-PD) monomer and chlorpyrifos template molecule on gold nanoparticles-modified titanium dioxide nanotubes. The resulting PEC sensors were characterized by scanning electron microscopy, ultraviolet (UV)-vis spectra and electrochemical impedance spectra. Clearly, the imprinted film showed high selectivity to chlorpyrifos in our case. Under visible light irradiation, poly(o-phenylenediamine) (PoPD) can generate the photoelectric transition from the highest occupied molecular orbital (HOMO) to the lowest unoccupied molecular orbital (LUMO), delivering the excited electrons to the AuNPs, and then to the conduction band (CB) of the titanium dioxide nanotubes (TiO(2) NTs). Simultaneously, it is believed that a positively charged hole (h(+)) of PoPD that took part in the oxidation process was consumed to promote the amplification of photocurrent response. Under the optimal experimental conditions, the photocurrents were proportional to the concentrations of chlorpyrifos ranging from 0.05 to 10 μmol L(-1) with the detection limit of 0.96 nmol L(-1). The PEC sensor had an excellent specificity and could be successfully applied to the detection of reduced chlorpyrifos in green vegetables, indicating a promising application in PEC sensing.