"Green" Control Synthesis Of Silver Nanostructures And Studies On Their Growth Mechanism

The intrinsic properties of silver nanostructures, such as optical and catalystproperties, are mainly detennined by their shapes and sizes. Shape-controlled synthesisof silver nanostructures has been and continues to be an area of challenging andactive research. As these issues to be addressed, we create a stable environment for thegrowth of single crystalline silver based on the principle that reductive groups inbiomass-derived monolithic activated carbon (MAC) could be electrochemicallyconversed to sustain the growth of silver and other noble metals. Then we show thatdifferent morphologies single crystalline silver including silver nanoflowers, nanoplates,belts or dendritic grow abundantly on the surface of MAC in a high-quality, low-costand eco-friendly way, and their growth mechanism are studied. A simple and effectivesynthesis method making silver coat or coated composite structure is presenting, andcatalytic and inhibitory properties of composite structure are tested. The followingresearches have been carried out.1.Tunable growth of different morphologies single crystalline silver by galvaniccell mechanism on MACHere we show that a large scale strip or flake single crystal silver grow throughbiomass-derived monolithic activated carbon (MAC) with [Ag(NH3)2]OH solution only.Based on the principle that reductive groups in MAC could be electrochemicallyconversed to sustain the growth of silver and other noble metals, through introducingcubic AgCl crystal seed, selecting silver ammonia solution as precursor, and OH-setfree from precursor facilitating the regeneration of the consumed reductive groups, ourwork achieves a green low-cost “planting” of single crystal silver and follows newmechanism of silver growth. It further suggests that functional groups on porousmaterials can be electrochemically conversed for more applications.2.Dendritic silver were prepared on monolithic activated carbon (MAC)pre-absorbed with PO43-anions Dendritic silver were prepared on monolithic activated carbon (MAC)pre-absorbed with PO43-anions. It is virtal that moderate Cl-, OH-and PO43-pre-absorbed in MAC to form the corresponding morphsynthesis of silver. A galvaniccell reaction mechanism by reductive functional groups on MAC is established.3.Nanobelts silver were prepaired through a galvanic cell reaction mechanism andlower Ag+concentrationBased on the principle that reductive groups in MAC could be electrochemicallyconversed to sustain the growth of silver, through introducing Ag2O precursor, selectinglower Ag+concentration，a continually grow mechanism of single crystal belts silver isestablished. Nanobelts silver with different colours and sizes were obtained by changingtemperature and distance.4.The synthesis of core-shell silver composite structure(1) Blending plant extracts and silver nanoparticles with ultrasonic, a carbonencapulsated silver composite structure was produced. The amount of extract andreaction temperature are important to the composite structure.(2) The silver nanoparticles with different sizes was prepaired by hydrogenreduction. Blending silver nanoparticles and chitosan, a chitosan-encapulsated silvercomposite structure was formed. Chitosan-encapulsated silver composite structure havesynergistic antibacterial effect on Escherichia coli.(3) The synthesis of silver-encapulsated silica microspheres composite structure.Silver-encapulsated silica microspheres were prepared by sensitization and chemicaldeposition. And that, these composite structure have catalytic reduction ofp-nitrophenol.