An electrochemical/colorimetric dual-mode sensor for the detection of AFB1 in agricultural products based on CoFe2O4@Au nanoparticles and smartphone imaging

An electrochemical/colorimetric dual-model sensor was developed for the specific detection of aflatoxin B1, utilizing the high catalytic activity and magnetic separation properties of CoFe 2 O 4 @Au along with the conformational alterations in the hairpin DNA structure. The CoFe 2 O 4 @Au nanocomposite demonstrated excellent peroxidase-like activity, characterized by the relatively low Michaelis constant ( K m  = 0.14 mM and 0.94 mM) and the relatively high reaction rate ( V max  = 4.43 × 10 −8  M·s −1 and 9.01 × 10 −8  M·s −1 ). Besides, the visualization results could be obtained using a smartphone in colorimetric mode. The detection linear ranges of the electrochemical workstation, ultraviolet-visible spectrophotometer, and smartphone were 0.001–100 ng mL −1 , 0.05–100 ng mL −1 , and 0.1–100 ng mL −1 , respectively, with corresponding limits of detection were 0.34 pg mL −1 , 0.016 ng mL −1 , and 0.043 ng mL −1 . Furthermore, the matrix effect values of these methods were 91.03 %–112.96 % in peanut, corn, and wheat. This work provided a new direction to explore dual-mode sensor to improve the detection accuracy in real samples.