| This article focuses on the application of MOFs in sensing applications. Combination of the advantages of MOFs and electrochemical sensor is used to fabricate novel MOFs-based electrochemical sensor. This article takes advantage of ZIF-8, MOF-5, and NH2-MIL-125(Ti) to prepare novel MOFs-based electrochemical sensor and study their applications in the detection of glucose, H2O2, inorganic salts, and ascorbic acid. The final goal of our research is developing MOFs-based chemical sensor.This thesis was divided into seven parts. The details are given as follows:Part1. PrefaceIn this chapter, we detailedly review the synthesis, characterization, and the typical applications of MOFs materials, and emphatically describe the current state of MOFs research and the application prospect. And then, we review the research progress of electrochemical and photoelectrochemical sensor, and MOFs-based chemical sensors. Finally, we expound the aim and the significance, pointed out the research content in this paper.Part2. Fabricate ZIF-8thin films on ITO and its fluorescence sensing of solvent moleculesZeolitic imidazolate frameworks (ZIF)-8thin films with controllable thickness are successfully deposited on indium tin oxide (ITO) electrodes at room temperature. The method applied uses3-aminopropyltriethoxysilane (APTES) in the form of self-assembled monolayers (SAMs), followed by a subsequent adoption of the layer-by-layer (LBL) method. A possible mechanism for the growth of the (110)-oriented ZIF-8thin films on3-aminopropyltriethoxysilane modified ITO is proposed. The observed cross-sectional scanning electron microscopy (SEM) images and photoluminescent (PL) spectra of the ZIF-8thin films indicate that the thickness of the ZIF-8layers is proportional to the number of growth cycles. However, acetone can significantly enhance the luminescent density of the ZIF-8films while other solvents quench the luminescence such as methanol, ethanol, DMF, and H2O2. This result reveals that the ZIFs films might be a good luminescent sensor for acetone molecules. Part3. Metal-organic framework templated synthesis of Co3O4nanoparticles for direct glucose and H2O2detectionCO3O4nanoparticles (NPs) with an average diameter of about20nm were synthesized by using MOFs as template. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were employed to characterize the as-prepared CO3O4NPs. Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) were used to confirm the structure of the CO3O4NPs. Then the CO3O4NPs were modified on glassy carbon electrode (GCE) to obtain a non-enzymatic glucose and H2O2sensor. The NPs show electrocatalytic activity toward oxidation of glucose and H2O2in alkaline medium. For glucose detection, the developed sensor shows a short response time (less than6s), a high sensitivity of520.7μAmM-1cm-2, a detection limit of0.13μM (S/N=3), and good selectivity. The high concentration of NaCl does not poison the electrode. Its application for the detection of glucose in human blood serum sample shows good agreement with the results obtained from the hospital. Furthermore, the proposed sensor was used for the detection of H2O2. The results indicate that the detection limit and sensitivity for H2O2are0.81μM and107.4μAmM-1cm-2, respectively. The high sensitivity and low detection limit can be attributed to the excellent electrocatalytic performance of the as-prepared Co3O4NPs. These results demonstrate that the as-prepared Co3O4NPs have great potential applications in the development of sensors for enzyme-free detection of glucose and H2O2.Part4. Preparation of ZIF-Mo and its use in electrochemical sensingIn this section, ZIF-Mo with large surface areas and catalytic group was synthesized by hydrothermal method. FT-IR and XRD were used to confirm its structure. Then the ZIF-Mo was modified on carbon paste electrode (CPE) to obtain an electrochemical sensor. Cyclic voltammetric curves of the ZIF-Mo modified CPE in0.1M LiCl/HCl show that the redox peak currents increase linearly with the scan rate in the range from25mVs-1to200mVs-1, suggesting a surface-controlled electrochemical process. The obtained CPE shows electrocatalytic activity toward reduction of BrO3-and NO2-. CV was used to detection of BrO3-and NO2-. For BrO3-detection, the linear range of0.05to3.5mM (R=0.9996) and the detection limit of0.02mM (S/N=3) were obtained. Furthermore, the proposed sensor was used for the detection of NO2. The cathode current increases linearly with the increase of concentration of NO2-from0.3to3.6mM (R=0.9985). Part5. Fabrication of MOF-5thin films on a glassy carbon electrode (GCE) for photoelectrochemical sensorsThis section describes the method to deposit continues MOF-5thin films on glassy carbon electrode (GCE), by firstly reducing of4-carboxyphenyl diazonium salt on GCE surface to form an organic monolayer, and then immersing it in the pre-prepared MOF-5mother liquid. The obtained films were characterized by SEM, EDX, and XRD. Moreover, to expand the applicability of MOFs, the MOF-5thin films modified GCE was firstly used as a photoelectrochemical sensor for the detection of ascorbic acid (AA), and a considerable linear range from0.05to1.4mM was obtained (R=0.999).Part6. Adjustment of the topography of NH2-MIL-125(Ti) and synthesis of Pt@NH2-MIL-125(Ti) compositesThis experiment adjusted the topography of NH2-MIL-125(Ti) by controlling the quantity of polyvinylpyrrolidone (PVP) in the synthesis process. The results show that, by adjusting the quantity of PVP, three nanostructures were obtained:nanoparticles, tablet-like nanosheets, and hollow spheres. XRD patterns of the as-synthesized nanostructures show that the nanoparticles and tablet-like nanosheets are NH2-MIL-125(Ti) while the hollow spheres are amorphous solids. The diffuse reflective spectra (DRS) of NH2-MIL-125(Ti) nanoparticles indicate that NH2-MIL-125(Ti) is a semiconducting MOF with a band gap of2.2eV. And then, we synthesized Pt@NH2-MIL-125(Ti) composites by photocatalytic reduction of K2PtCl4@NH2-MIL-125(Ti). Finally, SEM, TEM, HR-TEM, EDX, and PXRD were used to characterize the as-synthesized composites. |
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