Method for preparing ratiometric electrochemical aptasensor for Vaniline based on nanocomposite modified electrode

A method for preparing a ratiometric electrochemical aptasensor for vanillin based on an aptamer-gold nanoparticle-ferrocene-Ketjenblack-ZIF-8 nanocomposite modified electrode, comprising the following steps:

• (1) dissolving 2-methylimidazole (Hmim) in ethanol, adding ferrocene and Ketjenblack, stirring to obtain a homogenous mixture, adding zinc nitrate to the homogenous mixture and stirring evenly to obtain a first solution, and then transferring the first solution to a high-pressure reactor;
• wherein a reaction in the first solution is continuously carried out for a period of time at a set temperature to obtain a product, and the product is centrifuged, washed with ethanol, and dried in a vacuum to obtain a ferrocene-Ketjenblack-ZIF-8 nanocomposite;
• (2) dripping a cross-linking agent Nafion on a surface of a polished bare glassy carbon electrode, and then dripping and coating the ferrocene-Ketjenblack-ZIF-8 nanocomposite on a surface of the cross-linking agent Nafion to form a ferrocene-Ketjenblack-ZIF-8 nanocomposite modified glassy carbon electrode;
• immersing the ferrocene-Ketjenblack-ZIF-8 nanocomposite modified glassy carbon electrode in a buffer electrolyte solution, adding chloroauric acid to the buffer electrolyte solution to obtain a second solution;
• and then in a set potential range, employing cyclic voltammetry to scan the second solution and generate gold nanoparticles in situ by one-step electrodeposition, thereby obtaining a gold nanoparticle-deposited ZIF-8 nanocomposite;
• (3) adding aptamer DNA of the vanillin with a sulfydryl terminal on a surface of the gold nanoparticle-deposited ZIF-8 nanocomposite, and incubating for a period of time at 4° C. to obtain an aptamer modified gold nanoparticle-ferrocene-Ketjenblack-ZIF-8 nanocomposite modified electrode;
• (4) using the aptamer modified gold nanoparticle-ferrocene-Ketjenblack-ZIF-8 nanocomposite modified electrode obtained from the step (3) as a working electrode, and measuring electrochemical square-wave voltammetry curves in the presence of different vanillin concentrations;
• taking current peak intensities of the ferrocene and the vanillin as a reference signal and a response signal, respectively, fitting a linear relationship between ratios Iresponse signal/Ireference signal of the current peak intensities of the ferrocene and the vanillin and molar concentrations of the vanillin, and constructing the ratiometric electrochemical aptasensor for the vanillin.