Layer-by-layer assembly of layered double hydroxide/cobalt phthalocyanine ultrathin film and its application for sensors†

This paper reports the preparation of cobalt phthalocyanine/layered double hydroxide ultrathin films (UTFs) through an electrostatic layer-by-layer (LBL) technique as well as its application in electrocatalysis for dopamine oxidation. UV-vis absorption and electrochemical impedance spectra indicate the uniform deposition of the LBL films. XRD measurements demonstrate the long-range ordered structure of organic/inorganic UTFs, with an average repeating distance of 1.89 nm. SEM images show that the film surface displays a continuous and uniform morphology, with the root-meansquare (rms) roughness of 6.4 nm revealed by AFM. The UTF modified ITO electrode exhibits significant electrocatalytic performance for the oxidation of dopamine which is related to the Co(II)/ Co(III) couple in the (LDH/CoPcTs)n UTF. The dopamine biosensor shows rather high sensitivity, low detection limit and excellent anti-interference properties in the presence of ascorbic acid. Furthermore, compared with pristine organic multilayer (PDDA/CoPcTs)n modified electrodes, the (LDH/CoPcTs)n electrodes show superior repeatability and long-term stability, due to the immobilization and dispersion of electroactive CoPcTs molecules by LDH nanosheets. Therefore, this work demonstrates a successful paradigm for the fabrication of electroactive species in an inorganic 2D matrix, which can be potentially used for practical applications in bioanalysis and biodetection.