Electrochemical detection of fipronil in vegetable and fruit based on Ti3C2TX-Chinese tower-like nanogold, DNA tetrahedron and catalytic hairpin assembly with outstanding sensitivity, selectivity and reproducibility

[Display omitted] •We report one way for synthesis of Chinese tower-like nanogold using glutathione as chiral inducer.•The formed nanogold offers excellent catalytic activity due to full exposure of high-index faces.•The introduction of graphene quantum dot induce production of viscous Ti3C2TX-nanogold hydrogel.•Proposed electrochemical method for fipronil shows superhigh sensitivity and selectivity. The current electrochemical methods cannot meet the requirements of sensitivity, specificity and stability for detection of pesticides in vegetable and fruit. The paper reports an electrochemical method for detection of fipronil integrating Ti3C2TX-Chinese tower-like nanogold (CT-Au) with DNA tetrahedron (T-DNA) and catalytic hairpin assembly. Firstly, CT-Au was synthesized by formation, growth of trioctahedron gold nanocrystal and subsequent structural evolution in L-glutathione. Then, it was combined with Ti3C2TX to form Ti3C2TX-CT-Au hydrogel via self-assembly of Ti3C2TX nanosheets induced by arginine-functionalized graphene quantum dot. The resulting Ti3C2TX-CT-Au film offers good catalytic activity owing to more exposure of high-index faces, conductivity and mechanical property owing to the existence of three-dimensional Ti3C2TX network. The modified electrode with Ti3C2TX-CT-Au was developed for electrochemical detection of fipronil, coupling with T-DNA and DNA cycle. In the presence of fipronil, fipronil triggers the DNA cycle and results in the immobilization of ferrocene molecules on the electrode surface, producing a significant signal amplification. Differential pulse voltammetry current linearly increases with increasing fipronil between 1 × 10−18 and 1 × 10−13 M with detection limit of 4.3 × 10−19 M (S/N = 3). The proposed analytical method exhibits outstanding sensitivity, selectivity and reproducibility. It has been satisfactorily applied in electrochemical detection of fipronil in vegetable and fruit.