Photochemical Preparation,Formation Mechanism And Properties Of Silver Single Atoms

Silver nanoparticles have a wide range of applications in the fields of antibacterial materials,biosensing,chemical catalysis,electronics,and surface enhanced Raman spectroscopy,but the release of silver nanoparticles caused by human factors may bring specific environmental impacts.Previous studies proved that silver exists in nature in the form of silver salt and silver nanoparticles,and the two are dynamically transformed.However,the structure of environmental organic matter is complex and can mediate and promote various reduction reactions.As a photosensitive substance,silver is easily affected by environmental organic matter in the photochemical conversion path.The intermediates involved in the process not only determine the cycle characteristics of silver itself,but also determine its environmental impact.Metal single atom means that the metal is dispersed on the carrier in the form of a single atom,thereby maximizing the utilization efficiency of the metal.The metal single atom has both high stability and heterogeneous properties of nanoparticles and high activity similar to that of homogeneous particles Many studies have reported that Ag(0)single atoms have extremely high activity and can catalyze a variety of chemical reactions.However,most of these Ag(0)single atoms materials are obtained by high-temperature calcination,and there are very few reports on the preparation of Ag(0)single atoms in an aqueous solution at room temperature and pressure.Based on the above background,this thesis used electronic paramagnetic resonance spectroscopy and high-resolution spherical aberration correction electron microscopy to reveal that the photochemical process of phenolic compounds and silver ions in aqueous solutions at room temperature and pressure could produce and accumulate Ag(0)single atoms.The key role of phenolic compounds was demonstrated through kinetic analysis,and the accumulation mechanism of Ag(0)single atoms during the reduction of silver ions by phenol was proposed.By changing the type and concentration of phenolic compounds,a high-load material was prepared,and its excellent antibacterial activity was demonstrated through bacterial experiments.This paper provides a new theoretical support and experimental basis for studying the environmental effects of silver.The contents of this thesis are divided into three chapters as follows:In Chapter I,the dynamic transformation and environmental risks of silver nanoparticles in the environment are reviewed,the nucleation and crystallization process of silver nanoparticles are introduced,the research progress of single-atom catalysts is discussed,and the significance and research content of this thesis are described.In Chapter II,The photoreduction process of silver nitrate in the phenolic compound solution was studied.used high-resolution spherical aberration correction electron microscope to determine the formation of Ag(0)single atoms in this process.The formation mechanism of Ag(0)single atoms was studied by electron paramagnetic resonance spectrometer.The effect of phenolic compounds on the stabilization of Ag(0)single atoms was analyzed,which proved that Ag(0)single atoms were dynamically stable under mild conditions.In Chapter Ⅲ,the effects of solvents,phenolic compounds and concentrations on the selectivity of Ag(0)single atoms generation were studied,and the material with higher load was prepared.The bactericidal properties of Ag(0)single atoms were tested.