Controllable Synthesis And Properties Of Ag-based Nanomaterials

For the synthesis and application of Ag-based nanomaterials,we should first master the growth mechanism of Ag nanocrystalline,then different kinds of Ag can be designed and synthesized as what we desired.Furthermore,designing various Ag-based structures with different properties is meaningful for application.Among the noble mental,Ag shows high surface plasma characteristics,high electrical conductivity and good sterilization ability,so it is more suitable for industrial production.Herein,we designed and achieved the large-scale synthesis of Ag nanoplates and Ag/MnO₂ hollow structures according to the formation mechanism of Ag nanocrystalline.In addition,Ag-based plasmon catalysts and composite catalysts were synthesized to explore the relationship between structures and properties.Those all extend our cognition to the Ag-based nanomaterials.1.Large-scale synthesis of size-controllable silver nanoplates and their application in detecting strong oxidants in aqueous solutionsIn recent decades,silver nanocrystals with different morphologies have been prepared,but the large-scale synthesis of them is not achieved.and realizing the industrial production of silver nanomaterials is still a challenge for us.For Ag nanoplates,whose growth is kinetically controlled,the reduction and deposition rate of Ag atoms in solution should be kept in a low level,so the Ag atoms can be hexagonally close packed and formed Ag nanoplates.Weak reducing agents or etching agents were used to reduce the reduction rate of Ag’.but the yield of Ag nanoplates was low.To achieve the large-scale synthesis of Ag nanoplates,wc added some insoluble silver salt,such as AgSCN,AgCl,AgBr,Agl,AgCO₃,Ag2SO₃,and Ag2C2O₄ to the solution,so the added Ag+ can combine with insoluble silver salt anions and avoid the presence of partial concentrated Ag+.Through this method.we achieved the large-scale synthesis of Ag nanoplates and the productivity is high.the yield is 6g/L.This method is facile and can be completed in one step.so it is proper to the industry application.The Ag nanoplates can be used to detect aqucous strong oxidizing substances and showed low detection limit and wide linear range.2.Novel Hollow Ag/MnO₂ Nanostructures with Controllable Shell:Designed Synthesis and Significantly Enhanced ORR Catalytic PerformanceHollow structures arouse high interests because of their high surface area and well-defined interior voids,and they show many excellent properties compared with the bulk materials.But the shell structures are not easy to control and those limit their application.In recent years,double-shell or multi-shell structures were synthesized,but the comprised materials is homogeneous.To combine the synergistic effect of composite materials and hollow characteristics,hollow structures with complex and controllable shell should be designed.Herein,we synthesized hollow Ag/MnO₂ nanostructures with controllable shell by utilizing KMnO₄ oxidate Ag nanocrystals:the first one is constituted by Ag and MnO₂ uniformly distributed in the shell;the second one is composed of interior MnO₂ and outer Ag as double shell.This two kinds of hollow structures showed superior ORR activity than the Ag/MnO₂ composites.In addition,the Ag/MnO₂ hollow structures with Ag and MnO₂ uniformly distributed in the shell exhibited higher onset potential and smaller charge transfer resistance because of the synergistic effect of Ag and MnO₂.3.Facile synthesis of sphere-like Ag@AgSCN plasmonic photocatalyst with enhanced photocatalytic activity for degradation of oxytetracyclineLoading some amount of silver nanoparticles on semiconductors or metal oxides is an effective method to improve the catalytic activity because the superior surface plasmon resonance of Ag.For example,plasmonic photocatalysts of Ag/AgX（X＝CI、Br、I）are one kind of effective and environmental kindly catalysts for the degradation of dyes and antibiotics.As we all know.AgX（X=Cl、Br、I）arc unstable under light and that is not proper for the application.But AgSCN is very stable and is not easy decomposed under light.So we synthesized a kind of’ sphere-like plasmonic photocatalysts Ag@AgSCN,the growth mechanism of Ag@AgSCN was discussed and the sphere-like structure showed big surface area and high catalytic activity.In addition,the amount of loaded Ag was discussed and when the atomic ratio of Ag:AgSCN=0.0463,Ag@AgSCN nanostructures exhibited a higher photocatalytic property for the degradation of oxytetracycline under visible light,and the value of reaction rate constants is 4.8-fold faster than the bare AgSCN.Furthermore,Ag@AgSCN nanostructures exhibited superior photocatalytic stability which kept nearly the same catalytic activity after five cyclic experiments.4.Accelerating electron-transfer of Ni（OH）₂-Ag-rGO for efficient electrocatalytic oxygen evolutionAg nanostructures can combine with some oxide,hydroxide to improve the conductivity of some composites.The superior conductivity of Ag also can be used in the electrochemical catalysis.In this work,we designed a kind of Ni（OH）₂-Ag-rGO ternary nonocatalysts.In this structure,the electrons of Ni（OH）₂ will transfer to Ag nanoparticles,through the synergistic effect of Ag and rGO,the electrons on the surface of Ag will transfer to rGO nanosheets because of its excellent ability to store and transfer electrons.This leads to the Ni（Ⅱ）of Ni（OH）₂ translated into Ni（III/IV）.The increase of valence state of Ni will accelerate the production of O₂ from OH-.Though Ni（OH）₂ is rich,inexpensive and environmental friendly,the OER catalytic activity is not high enough.The Ni（OH）₂-Ag-rGO nonocatalysts can improve its OER performance.The results of experiments showed that the current density and overpotential at 20 mA cm-2 of Ni（OH）₂-Ag-rGO is superior than that of IrAO₂.The catalytic activity of Ni（OH）₂-Ag-rGO is also higher compared with Ni（OH）₂-Ag,Ni（OH）₂-rGO and Ni（OH）₂.DFT calculations were used to verify the feasibility of the electron transfer path of Ni（OH）₂-Ag-rGO in the process of OER.The universality of this system will be tried in the next step by designing Co/Fe-based nonocatalysts.