▎ 摘　　要

A unique ON/OFF switch electrochemical aptasensor was constructed based on the poly (4-vinyl pyridine) (P4VP), titanium carbide (Ti3C2Tx), and carboxylated graphene oxide (GO-COOH) composite. The "ON"/"OFF" response of the aptasensor against the pH was caused by the protonation/deprotonation of the pH-sensitive P4VP material depending on the solution pH value above or below 4.9 (pKa of P4VP is 4.9). Thus, it was designed specifically to detect Aflatoxin B1 (AFB1) in acidic environmental. Here, because of its greater specific surface region, Ti3C2Tx with high conductivity enhanced the current signal significantly. The electrochemical performance of the aptasensor was optimized when the electrochemical aptasensor was turned to an "ON" state. Results showed that the strongest current signal of the fabricated aptasensor appeared at pH = 4. GO-COOH with a plenty of carboxyl groups was applied as the fixing platform for AFB1 aptamers with amide groups by forming the firm amido-bonds, which was beneficial for the stability of the fixed aptamers. The fabricated aptasensor exhibited a wider linear range of 0.01 to 50 ng mL(-1) with a limit of detection of 3 pg mL(-1). The wide linear range and low-detection limit of the fabricated aptasensor was due to the exceptional electrochemical efficiency and the ideal synergetic effect of the modifying materials.