▎ 摘　　要

This work describes the development of a novel nanocomposite- graphene/poly (3,4-ethylenedioxythiophene): poly (styrenesulfonate) modified screen-printed carbon electrode (G/PEDOT:PSS/SPCE) for the evaluation of total antioxidant capacity (TAC) based on 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. Droplet-like nanostructures of G/PEDOT: PSS were fabricated on the SPCE surface via electrospraying. The electrochemical behaviors of both unmodified SPCE and G/PEDOT: PSS modified SPCE were investigated by cyclic voltammetry (CV) using a standard ferri/ferrocyanide [Fe(CN)(6)](3/4-). Interestingly, electrosprayed G/PEDOT: PSS can enhance the current response due to simple increase of the SPCE surface area. Compared to an unmodified SPCE, the peak potential difference (Delta E-p) between anodic and cathodic peak potential of G/PEDOT: PSS modified SPCE substantially decreased, indicating the faster electron transfer kinetics. Moreover, our system can be used for quantitation of TAC by chronoamperometric detection of residual non-reacted DPPH level at the interference free cathodic region. With addition of standard Trolox antioxidant, the cathodic DPPH current decreased. The calibration curve of Trolox antioxidant was found in a range of 5-30 mu M with a limit of detection (S/N = 3) of 0.59 mu M and a limit of quantification (S/N = 10) of 1.97 mu M. Finally, this novel electrochemical sensor was successfully applied for TAC evaluation in Thai herb and herbal beverage. The results showed a good agreement with the conventional UV-visible spectrophotometric results. (C) 2015 Published by Elsevier B.V.