| Ag-AgCl nanocomposites are a type of surface plasmonic photocatalysts,which not only combine the surface plasma resonance（SPR）characteristics of Ag nanoparticles and the excellent photocatalytic properties of semiconductor AgCl,but also exhibit stable structure,low cost and photo-responsive characteristics for visible light.However,Ag-AgCl nanocomposites without supporting materials are easy aggregating which lead to enormous decrease of their specific surface area and catalytic activity in the practical application.In addition,it is difficult to separate and recycle nano-sized Ag-AgCl nanocatalyst.In order to effectively avoid these deficiencies,researchers have designed and synthesized Ag-AgCl nanoparticles loaded on different components of the carrier surface,such as inorganic oxide（TiO2、SiO2、Al2O3、ZnO and WO3,etc.）、graphene and carbon nanotubes and polymers etc.The interaction between the carrier and Ag-AgCl nanoparticles can not only improve the dispersion stability of the catalyst,but also greatly increase the specific surface of the nano-catalyst.Meanwhile,the supporting materials can play a role in enriching the reaction substrate,which could significantly improve the photocatalytic activity of Ag-AgCl composite nanocatalyst.Based upon the above research background and our group’s previous work,inthis thesis,we proposed a novel method to prepare AgNPs using pH sensitive hybrid microspheres with core-shell structure as support.In situ controlled reduction of silver ammonia solution,the PDA/PAA-Ag composites loaded with nano silver were obtained.Ag-AgCl nanocomposite plasma photocatalysts were prepared by the conversion of nano-silver with different chlorine sources（FeCl3 and CCl4）.As both the carrier and reducing agent,PDA with the core component,can effectively regulate the nanocomposite particles size and dispersion stability,because of the strong interaction between the carboxyl group（-COOH）of shell layer and AgNPs,as well as the spatial confinement effects from the three-dimensional chain structure of the shell.The composite structure and relative amount of Ag and AgCl in composite materials can be effectively adjusted by varying dosage.Besides,the optical properties and catalytic performance of Ag-AgCI composite nanoparticles can be effectively controlled by external changeable pH condition.The synthetic PDA/PAA-Ag-AgCl nanocomposites with pH sensitive would be of great importance in the fields of catalysis,sensors and biological detection and so on.The thesis involves two parts:（1）The core-shell polydopamine/poly（acrylic acid）（PDA/PAA）composite microspheres with uniform particle size were synthesized through two-step polymerization method.By changing the amount of shell AA monomer and the concentration of silver ammonia solution,the PDA/PAA-Ag composites with different nano-silver particle size and dispersity can be obtained by controlled reduction.The results demonstrated that the thickness of the shell of PDA/PAA increased apparently with the increasing of the amount of monomer AA.The size of nano-silver particles in composite microspheres turned out to be more uniform when the thickness of the shell PAA increased at the same concentration of silver ammonia solution.Controlling the thickness of the shell,it is easier to obtain nano-silver particles with good monodispersity because of the small amount of nano-silver particles produced through the reaction at lower reaction rate.Consequently,when increasing the concentration of silver ammonia solution,the more number of silver nanoparticles on the surface of PDA/PAA would cause more obvious aggregation of nanoparticles,which eventually leads to the deterioration of the dispersion of nano silver on the surface of the carrier.The surface plasmon absorption of PDA/PAA-Ag composites at different pH conditions results showed that the maximum absorption peak of PDA/PAA-Ag composite materials was 482 nm under the neutral conditions;under the strong pH condition（pH=2）,the maximum absorption peak of the nano-silver loaded in its network structure shifted to 497 nm because the shell PAA was fully swollen state.Compared with neutral conditions,PAA shells showed complete swelling state under strong alkaline condition（pH=10）.At this time,the maximum absorption peak of PDA/PAA-Ag composites shifted to 479 nm.（2）The Ag-AgCl nanocomposite plasmonic photocatalyst with different relative contents of Ag and AgCl were prepared by changing the amount of different chlorine sources（FeCl3 and CCl4）and controlled conversion with the good monodisperse of PDA/PAA-Ag composites.The results show that Ag-AgCl composite nanoparticles with different structure can be obtained by using different chlorine sources and solvents.To systematically evaluate the regulating effect of the relative content,structure and pH of PDA/PAA-Ag-AgCl composite photocatalyst,the photocatalytic degradation of methylene blue（MB）were carried out as the model reaction.It was found that the photocatalytic activities of the composites were enhanced by increasing the relative content of AgCl nanoparticles in PDA/PAA-Ag-AgCI composite materials.The polymer chains of carrier shell are fully swollen state in the basic condition,which is beneficial to the hydrophilic reaction substrate MB diffuses into the network structure.In addition,the PDA surface can adsorb more reaction substrate,which significantly enhanced the catalytic activity of Ag-AgCl composite photocatalyst for the degradation of MB. |
