Fabrication Of SiO₂/Ag Fiber Composites By Dopamine Surface Functionazation

The techniques to modify substrate surfaces are significant for manyindustrial and research applications. In this work，dopamine was used tomodification of glass fiber (GF) and fibrillar silicate nanofiber (FS) viadopamine self-polymerization to polydopamine (PDA) on the materialsurfaces. What’s more, silver-plating glass fiber and Ag/fibrillar silicatenanofiber were synthesized by PDA-assisting electroless plating or PDAoxidation reduction directly. The details of the work are as follows:(1) Highly conductive silver-coated GF was fabricated in an efficientand environment-friendly way. When the GF powder was immersed indopamine solution, an adherent self-polymerized PDA layer was formedon the GF surface. PDA acts as both a linker between GF and silvernanoparticles and a reducing agent for reducing silver ions to metallicsilver. The silver nanoparticles can be chemically bound to the catecholand amine functional groups in PDA by electroless plating using glucoseas reducing agent. Chemical and physical characterizations of thesilver-coated GF were carried out by using X-ray photoelectronspectroscopy (XPS), X-ray diffraction (XRD), and scanning electron microscopy (SEM). Four-point probe was used to study the electricalresistivity of the silver-coated glass fibers. The results indicated that thesilver coated on the GF surface was compact, uniform, continuous, and ina metallic crystal state. The silver content could be well controlled from9.5to24wt.%by adjusting the reduction conditions. The electricalresistivity of the silver-coated glass fibers could be as low as1.0mΩ cm.(2) The transition from micron to nanometer, in this work, a novelmethod was developed for the preparation of silver/FS nanocomposite, inwhich dopamine acts as both modification agent and reducing agent. Onthe one hand, the effects of dopamine concentration and polymerizationtime on the modified FS nanofiber were studied. On the other hand, theeffects of extra-reducing agent, pH, temperature and complexing agenton the Ag/FS nanocomposites were also studied. The surface elementalcomposition and functional groups of FS before and after dopaminemodification were characterized by using X-ray photoelectronspectroscopy (XPS) and fourier transform infrared spectrometer (FTIR),surface morphology of samples were characterized by scanning electronmicroscopy (SEM), microscopic morphology and structure of Ag/FS wasdetected by transmission electron microscope (TEM) or high resolutiontransmission electron microscope (HRTEM), phase composition ofsample was characterized by X-ray diffraction (XRD). The resultindicated that metal silver nanoparticles with mean diameter of2.15nm and narrow particle size distribution deposited on the FS, when the pH is8.5, temperature is60℃.In conclusion, this paper shows that dopamine is a versatile methodto functionalize the surface of inorganic materials, and the combination ofthe following electroless plating technique and redox method couldprepare surface metalized composites good adhesion between the metalwith the substrate.