Preparation method and application of flexible transparent SERS substrate

The invention discloses a preparation method and an application of a flexible transparent SERS substrate. The method comprises the following steps of heating an HAuCl4 water solution to be boiling under vigorous stirring, rapidly adding a citrate aqueous solution, and condensing and refluxing for 13-17 minutes after the color change of the solution is stable, stopping heating, and cooling to roomtemperature under stirring to obtain Au nano-sol; and adding the Au nano-sol into a beaker, and slowly injecting a mixed solution of n-hexane and ethanol into the Au nano-sol by using a needle cylinder syringe at room temperature, slowly forming two phases of water oil, wherein a layer of nanometer Au film is gradually formed at the water-oil interface, and after the oil phase naturally volatilizes, directly covering by using an adhesive tape for uncovering the single-layer nano Au on the water phase surface, removing residual gold sol on the surface of the adhesive tape by using deionized water to prepare the flexibl