Preparation And Investigation Of Catalytic Properties Of Silver Nanocrystals

In this thesis,silver sulfate and silver nitrate were used as silver source,throughmicrowave-assisted liquid phase synthesis method and gas-solid phase reduction methodseperately to prepare silver nanocrystals.Silver nanocrystals were characterized by X-raydiffraction (XRD),transmission electron microscopy (TEM),scanning electron microscope(SEM).The results showed that silver nanocrystals prepared with microwave-assisted liquidphase synthesis were all cubic in crystal phase,and silver nanoparticles with small size andnarrow size distribution.Black silver nanocrystals were prepared by gas-solid phasereduction method.Gas-solid phase reduction method provided a simple way to preparesilver nanocrystals,and the reaction conditions were easy to be controlled.The influence ofsilver nitrate concentration,dosage ratios of silver nitrate to polyvinylpyrrolidone(PVP) onthe size and morphology of silver nanocrystals were studied and the formation mechanismof silver nanocrystals were investigated.The catalytic tests results showed that silver nanocrystals prepared withmicrowave-assisted liquid phase synthesis method as catalysts,which proved to be anexcellent oxidation in the oxidation system of silver nanocrystals and hydrogen peroxide.Silver nanocrystals proved to be an excellent deoxidation in the deoxidation system ofsilver nanocrystals and potassium borohydride.The results showed that the silvernanocrystals both exhibited catalytic activities of the special performance in the catalyticoxidation and catalytic reduction reactions.The influence of catalysts silver nanocrystalsdosage, reaction temperature,reaction time on the oxidation and deoxidation effect ofmethylene blue were studied.Catalysts still had high catalytic activities after that wererepeatedly used.Then the kinetic of the catalytic oxidation process was studied,resultsshowed that the process followed pseudo first-order kinetic,and possible catalytic reactionmechanism was studied.Silver nanocrystals prepared with gas-solid phase reduction methodhad no obvious catalytic properties in the oxidation and deoxidization reactions ofmethylene blue.The as-prepared silver nanocrystals with large size and part of the reunion,which affected their surface catalytic properties.