Fabrication and electrochemical sensing performance of a composite film containing a phosphovanadomolybdate and cobalt(II) tetrasulfonate phthalocyanine

A novel composite film consisting of the phosphovanadomolybdate H4[PMo11VO40] (PMo11V) and cobalt(II) tetrasulfonate phthalocyanine (CoTsPc) was fabricated on quartz, silicon and ITO by the layer-by-layer self-assembly method. The composite film was characterized by UV–vis spectroscopy, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and cyclic voltammetry (CV). The electrochemical behavior of the composite film was investigated by cyclic voltammetry, amperometry and electrochemical impedance spectra. The results show that the composite film exhibits enhanced electrocatalytic performance for the oxidation of dopamine, which is related to the VV/VIV and CoII/CoIII couples. The proposed electrochemical sensor shows rather high sensitivity of 0.82 μA/μM, low detection limit of 1.3 × 10−8 M (S/N = 3) and a linear response range from 8.3 × 10−8 to 5.0 × 10−4 M for detecting dopamine. Furthermore, compared to the single component polyoxometalate or cobalt(II) tetrasulfonate phthalocyanine film, the composite film shows superior catalytic efficiency, repeatability and long-term stability due to coexist of PMo11V and CoTsPc in the composite film. Therefore, this work demonstrates a successful paradigm for the fabrication of electroactive species in an organic/inorganic composite film, which can be potentially used for practical applications in electrochemical sensors.