Electrochemical Sensors Based On Metal-Organic Frameworks Nanocomposites

Owing to excellent properties such as flexible structure, porosity, large specific surface area and ects, metal-organic frameworks materials?MOFs? have been widely used in the selective catalysis, gas adsorption and separation, biological chemical sensing, drug delivery, immobilized small active molecules, photoelectric material, etc. The feature of MOFs-based derivative nanocomposites have been greatly improved which depending on the further studies. In this paper, the main work was prepared three kinds of nonenzyme sensor and one enzyme glucose sensor, which were all based on MOFs and MOFs derivaties nanomaterials. The final nanomaterials were characterized by scanning electron microscope?SEM?, Fourier infrared spectrum analysis?FT-IR?, X-ray powder diffraction?XRD?, N₂ adsorption-desorption isotherm, electrochemical techniques, and etc. The main research overview concluded as the following four parts:1. We taken a moderate and simple MOFs-derivated method to construct hierarchical flake nanostructures Co?OH?₂ on the glassy carbon electrode?GCE?. In order to making the material and GCE substrate bonding more stable and orderly, the GCE was treated with functional groups and then immersed in cobalt salt solution to form crystallization point. The Co?BTC? MOFs were growth into uniform layer-by-layer rod-like structure along the crystallization point in order. After that, the integrated Co?BTC? MOFs/GCE was dipping in the sodium hydroxide solution and then erosion to integrated Co?OH?₂/GCE combination electode with hierarchical flake nanostructures. The SEM was taken to obseve the morphology of materials, and we used FT-IR and XRD characterization to further proved the successful synthesis of the materials. The as-prepared electrode could use as novel integrated electrode for nonenzyme glucose sensor with with a wide linear range?0.005 6.7 m M? and low detection limit?1.73 ?M?. The preparation in this experiment, which was obtained in situ growth multi-level structure nanometer materials with integrated electrode, provides a new way for prepared nonenzyme sensors.2. The biomimetic catalytic enzyme activity molecule chlorhematin?iron porphyrin, hemin? was used as organic ligands to formate a novel 3D flower-like copper-iron porphyrin MOFs?Cu-hemin MOFs?. The nanomaterials were prepared on one step in room temperature and this synthesis process was consuming less time and easy to operate. The structure was characterized by SEM. The specific surface of MOFs was enhanced by the fold on the surface. Meanwhile, the inner cavity of the MOFs offered a perfect opportunity for loding small biological molecules?GOD? and other small biological molecules. Due to the specificity structure of MOF, the as-prepared GOD/Cu-hemin MOFs/GCE electrode retained the catalytic activity of hemin and the biological activity GOD in glucose detection. Hence, the detection result of linear range?9.10 ?M- 36.0 m M? and detection limit?2.73 ?M? were better than other GOD-based glucose sensors, which was also hopeful to be applied in the actual sample testing. The good electrochemical performance of nanocomposites was enriched the idea for immobilizing enzyme or protein on the MOFs nanomaterials, and provided a new way to enjoy the good properties both of nanomaterials and enzyme.3. Based on the second section, the Cu-hemin MOFs were still poor in electrical conductivity. In order to improve electrochemical activityof MOFs, the third section introduced graphene oxide as active conductive material and synergy with MOFs by ultrasonic. The graphene oxide was reducted by chitosan, which was increased the yield and enhanced the composite ability with nanomaterials. We successfully synthesized flower-liked Cu-hemin MOFs/CS-r GO nanocomposits. The characterization results were proved that graphene not only promoted the mass transfer and electrochemical catalytic activity of MOFs, also could smaller particle size of MOFs nanoparticles, and which was increased the effective surface area of catalyst for annocomposites. Compared with other materials such as horseradish peroxidase?HRP? and Fe3O4, Cu-hemin MOFs/CS-r GO nanocomposits exhibited a good linear range?0.065 ?M 0.410 m M?, low detection limit?0.019 ?M? and better selection as a material for hydrogen peroxide sensor. We widen the preparation method for sythesing composites with MOFs and graphene materials.4. At last section, we manufactured a novel Fc?COOH?₂/ZIF-8/KCS nanocomposites at room temperature by on step, which was via ZIF-8 immobilizing ferrocenemonocarboxylic acid and using natural biological porous carbon materials--kenaf stem carbon?KSC? as supporting material. With the advantages of porosity and thin wall, the Fc?COOH?₂/ZIF-8 was easily growth in the porous and wall of KSC with a rod-like morphology from the SEM figures, which was different with the structure of ZIF-8. And the FT-IR/XRD/N₂ isothermal adsorption stripping test results also further shown that the differences of the two nanomaterials. Meanwhile, the KSC could directly make into an integrated electrode results from the conductivity of biologic carbon materials. The result was that the electrode preparation process was simplified and the efficiency of the experiment was improved. The as-prepared Fc?COOH?₂/ZIF-8/KCS electrode shown good electrochemical performance in ascorbic acid detection, including a wide dectetion range of 0.06 ?M 5.01 m M and a low dectetion limit of 0.017 ?M. This experiment also provide a new thought for developing Fc?COOH?₂ derivaties nanocomposite with stablility in aqueous solution.