Self-template synthesis of flower-like hierarchical graphene/copper oxide@copper(II) metal-organic framework composite for the voltammetric determination of caffeic acid.

Flower-like graphene/CuO@Cu-BTC (GR/CuO@Cu-BTC) composite was employed as electrode material for the voltammetric determination of caffeic acid (CA) in the wine. The composite material was prepared via the self-template method. In this synthetic process, budlike CuO not only acts as the template, but also provides Cu2+ ions for in situ growth of the Cu-BTC shell. The utilization of GR as petal greatly boosts the stability and electronic conductivity of CuO@Cu-BTC. The GR/CuO@Cu-BTC composite possesses unique structural features with high specific surface area and good conductivity, exhibiting excellent electrocatalytic activity towards the oxidation of CA. Under optimized conditions, the sensor shows a good linear response to CA concentration over the range 0.020-10.0 μM, together with a low limit of detection (LOD) of 7.0 nM. Selectivity, reproducibility, and stability were investigated, and the method has been applied for the determination of CA in wine samples. Graphical abstract Schematic representation of electrochemical sensor for the detection of caffeic acid was designed based on flower-like graphene/copper oxide@copper(II) metal-organic framework (GR/CuO@Cu-BTC) composite electrode material.