| Based on previous studies, this master’s thesis is mainly involved using electrochemical approaches to prepare dendritic silver, graphene (Gr)/Ni1-xCox and Gr/AuPt nanomaterials, using dendritic nano-silver to achieve trace analysis and detection of biological macromolecules, studying the absorbing properties of Gr/Ni1-xCox and the electrocatalytic performance of Gr/AuPt nanomaterials. Details are as follows:1. Analysis and detection of biological macromolecules using dendritic nano-silver prepared by electrochemical deposition on aluminum foilIn this work, symmetrical dendritic silver nanostructures are prepared via electroless deposition using [Ag (NH3)2]Cl solutions, which is a green process that not only without using any template, surfactants, antioxidants, but also avoiding to the introduction of fluoride ions that can cause hypocalcaemia. It has been characterized by scanning electron microscope (SEM), transmission electron microscope (TEM) and X-ray powder diffraction (XRD). By using SEM to study morphology evolution in different times, as well as Tafel curves and open circuit potential-time (OCP-t) method, it has been proved that chloride ions are the key to the formation of dendritic structures. Dendritic structures of silver has good surface enhancement Raman effect for deoxyribonucleic acid (DNA), ribonucleic acid (RNA), folic acid, thus the detecting limit can be expanded to10-12mol/L. Therefore, these dendritic structures have potential applications in making ultrasensitive surface enhanced Raman scattering (SERS) sensor, and to detect bio-macromolecules without labeling.2. Synthesis and electro-catalytic properties analysis of graphene/AuPt compositeThis work reports a new method for the synthesis of Gr/AuPt battery active materials via electro-reduction, which has superior electrical catalytic properties toward methanol. Wherein the conductive and the specific surface area of the substrate has been dramatically improved using Gr, which can provide more binding sites for the AuPt nanoparticles. The as-prepared Gr/AuPt nanocomposite membrane electrode has an big electrochemical active surface area, and shows better resistance to COad poisoning. Therefore, Gr/AuPt nanocomposite membrane electrode can be used as a direct methanol fuel cell electrode material. In addition, we also analyzed how the concentration of metal precursor can affect the electro-catalytic properties, and its electro-catalytic properties toward other alcohol (ethanol, isopropanol). The results show that:Gr/AuPt nanocomposite membrane electrode has the best electro-catalytic properties when the concentration of graphene oxide is1mg/mL, HAuCl4is0.4mmol/L, and H2PtCl6is1.6mmol/L; that electrode has the same character to ethanol and isopropyl alcohol, but compared with methanol, catalytic activity and ability to resist poisoning were slightly inferior.3. Preparation and performance analysis of graphene/Ni1-xCox composite absorbing materialsThis work using Gr as supporting layer, metals nickel (Ni) and cobalt (Co) sulfate salt as precursor, through electrochemical deposition to fabricate NiCo nanoparticles on Gr surface to form Gr/Ni1-xCox composite materials in-suit. XRD shows that NiCo nanoparticles have crystal structures after annealing, irregularly dispersing on Gr surface. With the increasement of Ni content, the coercivity and magnetization strength of the composite material are decreased from magnetic measurement. Using a vector network analyzer electromagnetic wave reflection loss, the results show that in the frequency range of2-18GHz, the permittivity values of Gr/Ni1-xCox-paraffin mixtures exhibit decreasing tendency as Ni content increases; but complex permeability has a slight increase. When Ni-Co atomic ratio is3:1in the starting solution, the maximum value of the reflection loss is-17.84dB, the matching thickness is1.5mm, a frequency of9.32GHz at this time. |
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