| With good biocompatibility, abundant PO43-, and3D skeleton structure, FePO4has been widely applicated in catalysis, which also has potential application in biosenseor and new energy. Research of FePO4and its composite is beneficial to the protection of the ecological environment. This work develops the facile synthesis of FePO4and its composite. Their application in sensors and lithium ion battery is investigated, which expand the platform of application. The main conclusions are summarized as following:(1) Iron phosphate nanostructures synthesized by microwave method and their applications in biosensingA fast, simple microwave heating method has been developed for synthesizing iron phosphate (FePO4) nanostructures. The nanostructures were characterized and confirmed by transmission electronic microscope (TEM), scanning electronic microscope (SEM), energy dispersive x-ray spectroscopy (EDS), x-ray photoelectron spectroscopy (XPS), x-ray powder diffraction (XRD), Fourier transform infrared (FT-IR), and UV-vis spectroscopy. The morphology and the size of the nanomaterials are significantly influenced by the concentration of the precursors and the kinds of surfactants. CTAB plays a crucial role in controlling the spherical morphology of the product, as well as preventing the nanomaterials from aggregation. The nanoparticles are easily aggregated in the course of their growth in the case of SDS, PEG and PVP. The nanospheres with the average diameters of (50±10) nm are obtained at the molar ratio of1:2. The average size of the nanomaterials increases to (80±20) and (150±20) nm, respectively, at the molar ratio of1:1and2:1. The nanostructures have been employed as electrode substrate to immobilize myoglobin (Mb) and to facilitate the direct electron transfer (DET) reaction of the protein. After immobilized on the nanomaterials, Mb can keep its natural structure and undergo effective DET reaction with a pair of well-defined redox peak, the anodic (Epa) and cathodic (Epc) peak potentials of at ca.-284and-373mV, respectively, at a scan rate of100mV s-1. The formal potential, E0’ is found to be-(330±3.0) mV (pH6.8) and the apparent electron transfer rate constant of5.54s-1. The Mb-FePO4/GC electrode displays good features in electrocatalytic reduction of H2O2, and thus can be used as a biosensor for detecting the substrate. The response displays a good linear range from0.01to2.5mM, the sensitivity is evaluated to be ca.(85±3) μA mM-1cm-2. The detection limit is estimated to be ca.(5±1) μM with good stability and reproducibility. Therefore, FePO4 nanomaterials can be become a simple and effective biosensing platform for the integration of proteins/enzymes and electrodes, which can provide analytical access to a large group of enzymes for a wide range of bioelectrochemical applications.(2) Indirect electrocatalytic determination of choline by monitoring hydrogen peroxide at the choline oxidase-prussian blue modified iron phosphate nanostructuresCholine, as a marker of cholinergic activity in brain tissue, is very important in biological and clinical analysis, especially in the clinic detection of the neurodegenerative disorders disease. This work presents an electrochemical approach for the detection of choline based on Prussian blue (PB) modified iron phosphate (FePO4) nanostructures (PB-FePO4). The nanostructures were characterized and confirmed by transmission electronic microscope (TEM), x-ray powder diffraction (XRD), Fourier transform infrared (FT-IR), and UV-vis spectroscopy. The nanostructures have been employed as electrode substrate to immobilize ChOx. After immobilized on the nanomaterials, ChOx can keep its electrocatalytic reduction of Choline. The response current of the biosensor usually depends on the solution pH, performance temperature, and detection potential. The pH8.0、temperature37℃and the detection potential of-0.05V are chosen as the optimal condition for the ChOx-PDDA-PB-FePO4/GC electrode sensing choline chloride. The response current displays a good linear range2μM-3.2mM. The sensitivity is evaluated to be-75.2μA mM-1cm-2. The detection limit is estimated to be ca.0.4±0.05μM. The electrode displays good stability and repeatability. In addition, the common interfering species, such as ascorbic acid, uric acid and4-acetamidophenol did not cause obvious interference due to the low detection potential (-0.05V vs. saturated calomel electrode). This nanostructure could be used as a platform for the construction of other oxidase-based biosensors.(3) Enhanced cathode performances of amorphous FePO4hollow nanospheres with tunable shell thickness in lithium ion batteriesWe report the facile synthesis of an amorphous FePO4hollow nanosphere with tunable shell thickness for use as a cathode material in lithium ion batteries (LIBs). The nanostructures were characterized and confirmed by transmission electronic microscope (TEM, HRTEM), scanning electronic microscope (SEM), energy dispersive x-ray spectroscopy (EDS), x-ray photoelectron spectroscopy (XPS) and x-ray powder diffraction (XRD). The morphology and the size of the nanomaterials are significantly influenced by the amount of surfactant SDS and reaction time. The0.05g SDS and12h are chosen as the optimal condition. The thickness of the shell of the prepared sample can be easily controlled by adjusting the molar ratio of the precursors. When the samples were prepared at the Fe2+/PO43-ratio of1:1, FePO4solid nanospheres with the average diameters of (250±20) nm were obtained. While the samples were prepared at the Fe2+/PO43-ratio higher than1:1, FePO4hollow nanospheres were obtained. Moreover, the shell thickness of the nanospheres significantly depends on the ratio of the precursors. It decreases from approximately40nm at the ratio of1:2to about10nm at the ratio of1:4. At a current rate of20mA g-1The first discharge-charge cycle delivered specific capacities of170.5,166.2and159.4mAh g-1, respectively, for the hollow nanosphere with shell thickness of10nm,22and40nm, respectively. The discharge capacity maintains a reversible capacity after50cycles of approximately167.1,163.8and156.6mAh g-1, respectively. The discharge capacities were approximately166,150,133,114, and90mAh g-1at current rates of100,200,500,1000, and2000mA g-1, respectively, for the nanospheres with shell thickness of10nm. Moreover, with increase of the shell thickness, the rate capacities have only slight decrease. These results indicate good cycling stability and a good rate performance of the hollow nanosphere. The electrochemical performance of these hollow nanospheres was much better than that of the solid nanospheres.The high rate capacity is due to the unique hollow structure of the FePO4nanospheres, which shortens the diffusion path for both electrons and Li+ions, ensures a high electrode-electrolyte contact area, and offers more active sites for electrochemical reactions. The approach offers an effective route to improve the performance of highly insulating electrode materials for batteries.(4) Graphene-Amorphous Hollow FePO4Nanosphere Hybrids as Cathode Materials for Lithium Ion BatteriesA facile one-step synthesis approach to prepare the graphene-amorphous hollow FePO4nanosphere hybrids (amorphous hollow FePO4nanospheres were directly grew on graphene) for use as cathode materials in lithium ion batteries (LIBs) is developed. The nanostructures were characterized and confirmed by transmission electronic microscope (TEM, HRTEM), scanning electronic microscope (SEM), energy dispersive x-ray spectroscopy (EDS), x-ray photoelectron spectroscopy (XPS), x-ray powder diffraction (XRD) and Fourier transform infrared (FT-IR). The0.1g SDS is chosen as the optimal condition.This hybrid exhibits good electrochemical performance with high specific capacity up to174.1mAh g-1(at a current rate of20mA g-1), the discharge capacity maintains a reversible capacity after50cycles of approximately173.3mAh g-1. The discharge capacities were approximately157.2,149.1,121.4, and99.2mAh g-1based on the weight of amorphous FePO4hollow nanospheres at current rates of100,200,500, and1000mA g-1, respectively, indicating good capacity retention and high rate capability upon cycling due to facile Li+ions diffusion through the thin wall of the hollow FePO4nanospheres and fast electron transport through the graphene. The hybrid could be a promising candidate material for a high-capacity, low-cost, and environmentally friendly cathode for LIBs. The growth-on-graphene approach offers an effective and convenient technique to improve the specific capacities and rate capabilities of highly insulating electrode material in battery area, and is also beneficial to the industrial-scale synthesis of various graphene-based hybrid nanomaterials. |
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