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-mean-square (rms) roughness of similar to 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.