Rational design of semiconducting polymer poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(6-{4-ethyl-piperazin-1-yl}-2-phenyl-benzo{de}isoquinoline-1,3-dione)] for highly selective photoelectrochemical assay of p-phenylenediamine

Abstract

Herein, this paper reports a simple and label-free photoelectrochemical (PEC) sensor based on the organic semiconducting conjugated polymer-polyfluorene derivative, poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(6-{4-ethyl-piperazin-1-yl}-2-phenyl-benzo{de}isoquinoline-1,3-dione)] (PFNA). The PFNA was designed and obtained the lowest unoccupied molecular orbital (LUMO)/highest occupied molecular orbital (HOMO) values via spectral characterizations. The PFNA modified electrode produced a stable and enhanced photocurrent signal under white light irradiation at a bias of −0.1 V in phosphate buffer solution. A sensitive increment of the photocurrent was observed with the addition of p-phenylenediamine (p-PD). A possible mechanism for this photoelectrochemical process including the photoexcitation of the polymer, electron injection from polymer toward the electrode, and the hole-scavenging process by the reductants were studied. The π bond in the polymer might facilitate the photoelectrochemical process owing to the enhanced electronic coupling between the polymer and the reductants. A PEC analysis on p-PD has been carried out to evaluate the photoelectrochemical performances of the modified electrode, which presents the wide linear ranges of 0.2–400 μM, with a lower detection limit of 0.13 μM. This work reports the PEC performance of organic semiconducting conjugated polymer-polyfluorene derivative, which would promote more efficient photoelectrochemical design of sensors and devices.