Layer-By-Layer Assembly And Property Studies On Ultrathin Films Of LDH/Protein And LDH/Europium(Ⅲ)-Containing Polyoxometalate

In this thesis, the fabrication of LDH/protein and LDH/europium(III)-containing polyoxometalate ultrathin film via layer by layer self-assembly (LBL) technique has been carried out. The direct electrochemistry and electrocatalysis behavior of the LDH/protein ultrathin film modified ITO electrode were investigated. Photoluminescence properties of the LDH/europium(Ⅲ)-containing polyoxometalate ultrathin film were also studied.A new enzyme electrode system was fabricated by alternate assembly of inorganic LDH nanosheets and horseradish peroxidase (HRP) molecules on ITO substrates. The structural and morphological studies show that the ultrathin film is continuous and uniform with long range stacking order in the normal direction of the substrate, and the immobilized HRP maintains its pristine structure. In addition, the facile direct electrochemistry behavior of HRP was obtained for the ultrathin film modified electrode, indicating that this assembly method achieves a suitable microenvironment for HRP to maintain its electroactivity. A bi-proteinic electrode based on (LDH/hemoglobin(HB)/LDH/HRP)n ultrathin film modified ITO substrate was prepared through the LBL technique, and its electrocatalytic performances for oxidation of catechol has been demonstrated. The results of XRD indicate that the HB-HRP/LDH ultrathin film possesses a long range stacking order in the normal direction of the substrate, with the two proteins accommodated in the LDH gallery respectively as a monolayer arrangement. A stable direct electrochemical redox behavior of the proteins was successfully obtained for the HB-HRP/LDH film modified electrode. In addition, it exhibits remarkable electrocatalytic activity towards oxidation of catechol based on the synergic effect of the two proteins. The catechol biosensor in this work displays a wide linear response range 6-170μM (r= 0.999), low detection limit (5μM), high sensitivity and acceptable reproducibility.The ultrathin film (LDH/EuW10)n was fabricated based on alternate depositon of Mg-Al-LDH nanosheets and europium(Ⅲ)-containing polyoxometalate Na9EuW10O36 (EuW10). The structural characterization shows that the ultrathin film exihibts long range stacking order in the normal direction of the substrate. Typical photoluminescence of the 5D0→7F2 and 5D0→7F1 transition of EuW10 was observed for the ultrathin films. The relative intensity ratio of the 5D0→7F2 transition vs.5D0→7F1 transition increases gradually upon increasing the bilayer number.