Overoxidized polypyrrole/overoxidized poly(3,4-ethylenedioxythiophene)/graphene quantum dots-chitosan as enhanced electrochemical sensing platform for luteolin determination in peanut shells

Abstract

A novel electrochemical sensor was constructed based on an overoxidized polypyrrole/overoxidized poly(3,4-ethylenedioxythiophene)/graphene quantum dots-chitosan composite film modified glass carbon electrode (oPPy/oPEDOT/GQDs-CS/GCE), for the accurate determination of luteolin in peanut shells. The oPPy/oPEDOT/GQDs-CS/GCE was prepared using layer-by-layer assembly methods. After incubation in NaOH–EtOH solution, the current of luteolin on the composite electrode increased from 0 to ∼30 μA, the R_ct value decreased by ∼80 fold, and the specific surface area (A) increased by ∼7 fold. Based on a three-level four-factor Box–Behnken design (BBD), the optimal preparation conditions for the composite electrode were as follows: a mass ratio of CS to GQDs of 5, a polymerization cycle number for EDOT of 4, a polymerization cycle number for Py of 4, with the peak current increased to 43.21 μA (RSD = 3.51%, n = 3). A morphology with multi-channels and grooves was observed on the surface of the incubated composite film via SEM analysis. The additional –CN– and –SO/–SO₂ groups formed were observed by XPS and FTIR analysis. The electrochemical sensor constructed exhibited good anti-interference ability, repeatability, and stability. The linear detection range recorded by the current responses of the composite electrode to luteolin was 0.01 to 10.0 μM (R² = 0.991) and the limit of detection was 7.5 nM (S/N = 3). The observed content of luteolin in peanut shells was 0.769%, which was close to the results obtained from High Performance Liquid Chromatography (HPLC) analysis (0.808%). This agreement indicated that the constructed electrochemical sensor based on oPPy/oPEDOT/GQDS-CS/GCE was capable of accurate detection of luteolin in peanut shells.