Preparation And Characterization Of The Different Methods Of Multi-core Metal Hexacyanoferrates

This thesis investigated systematically chemical preparation, electrochemical preparation and characteristics of a new rare earth hexacyanoferrates, gadolinium hexacyanoferrate (GdHCF). Porous anodic aluminum oxide (AAO) template can be formed on aluminum surface by electrochemical method. Key factors affecting on thickness and pore diameter of anodized aluminum films were investigated. The cobalt hexacyanoferrate (CoHCF) nanotubes with high-aspect-ratio were fabricated in AAO template via a simple method. These nanotubes were characterized by some physical and chemical technologies, and compared with that of bulk CoHCF sample. The main research works are described as follows:1. A new electroactive polynuclear inorganic compound of rare earth metal, gadolinium hexacyanoferrate (GdHCF), was chemically prepared and characterized by using the techniques of FTIR spectroscopy, thermogravimetric analysis (TG), UV-Vis spectrometry and X-ray photoelectron spectroscopy (XPS) etc. The results of ICP atomic emission spectroscopy, EDX and TGA indicated the prepared GdHCF sample had a stoichiometry of NaGdFe(CN)₆·12H₂O (when GdHCF was prepared in NaCl solution). FTIR spectrum of GdHCF showed that there were two types of water molecules in the structure of GdHCF, one was the interstitial water (5 H₂O), which resulted from the association of water due to H-bonding, the other was the water coordinated with Gd (7 H₂O). The results of XPS verified the oxidation state of Fe and Gd in GdHCF sample was +2 and +3, respectively. GdHCF was immobilized on the surface of spectroscopically pure graphite (SG) electrode forming the GdHCF/SG electrode and the solid-state electrochemistry of the resulted electrode was studied by cyclic voltammetry. The cyclic voltammetric results indicated that GdHCF/SG electrode exhibited a pair of well-defined and stable redox peaks with the formal potential of E⁰' = (197±3) mV. The effects of the concentration of supporting electrolyte on the electrochemical characteristics of GdHCF was studied and the results showed the value of E⁰' increased linearly with the activity of cationic ion of supporting electrolyte (lgαNa+) with a slope of 54.1 mV, which may become a new method fordetermination the activity of some cationic ions in solution, for example Na⁺ ion in NaCl solution. Further experimental results indicated that GdHCF had electrocatalytic activities toward the oxidation of dopamine (DA) and ascorbic acid (AA) and the electrocatalytic current increased linearly with the concentration of DA (or AA) in the range of 1.0～10.0 mmol/L (for DA) or 0.5～20.0 mmol/L (for AA).2. A new electroactive polynuclear inorganic compound of rare earth metal hexacyanoferrate, GdCHF, was prepared by electrochemically deposition on the surface of a glassy carbon electrode with a potential cycling procedure. The result of SEM indicated that GdHCF was in the form of particles adhered on the surface of electrode. There were two different shapes and sizes of GdHCF forming on the surface of electrode. FTIR spectrum of GdHCF showed a very strong and sharp peak, which located at 2062.5 cm^-1 and corresponded to the stretching vibration of the C(?)N group in the GdHCF. The cyclic voltammetric results indicated that GdHCF/GC electrode exhibited two pairs of redox peaks with the formal potential of E⁰' (I) = 192.5 mV and E⁰' (II) = 338.5 mV, respectively. The effect of the different supporting electrolyte on the electrochemical characteristics of GdHCF was studied and the results showed that GdHCF had an ability of prior to select Na⁺ ion.3. Porous anodic aluminum oxide (AA0) template can be formed on aluminum surface in acidic electrolyte solution by electrochemical method. Key factors affecting on thickness and pore diameter of anodized aluminum films, including oxidizing voltage, temperature and time, were investigated. Moreover, micromorphology of the formed oxide films were analysed through scanning electron microscopy. The experimental results show that the structure characteristics of porous aluminum anodizing films is dependant on the adopted oxidizing conditions and on the choice of voltage and time for anodizing. Two-step anodization method in acid electrolytes at constant voltage was used to form porous anodic aluminum oxide template. The pore radius was in nanometer with highly uniformity.4. Molecule-based CoHCF nanotubes were fabricated using the porous anodic alumina as template, which was prepared by two-step anodization method. The nanotubes were characterized by scanning electron miscroscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR), and ultraviolet/visible (UV-Vis) spectroscopy. The results of X-rays energy dispersive analysis and XRD indicated that the nanotunbes had a cubic structure with a = 10.24 A and atomic ratio of Co to Fe of 3:2. The formation mechanism of CoHCF nanotubes in the inner wall of AAO template was discussed and verified by the cross-sectional SEM images. The electrochemical characteristics of CoHCF nanotubes were investigated by cyclic voltammetry and its cyclic voltammogram was characterized with two couples of redox preaks with the formal potential of 652 and 467 mV, respectively, in 0.2 mol/L KCl solution at a scan rate of 20 mV/s. These characteristics were compared with that of bulk CoHCF sample.