| Nanomaterials have unique properties due to their small size,which make them widely used in many fields such as new energy,medical,environmental monitoring,sensing,and optoelectronics.Compared to general metals,metal nanoparticles have a higher catalytic activity owing to a larger specific surface area and a richer active site.The hydrogel possesses the large specific surface area and stable structure,and its porous structure in the solution is very favorable for the diffusion of the substance.Hybrid gels prerpared by the combination of metal nanoparticles and polymer hydrogels have obvious advantages in the field of catalysis.Metals can be complexed with the groups in the gel network,and due to the limited network space inside the gel,the metal particles synthesized by the gel as a template generally have small particle size,good dispersion,good stability,and are difficult to agglomerate.These characteristics are used in catalytic reactions to exhibit high catalytic activity.The hydrogel with three-dimensional porous structure is beneficial to the diffusion of the reactants and enhances the catalytic efficiency.In addition,the hydrogel can be prepared into a multifunctional intelligent material to meet the requirements of hybrid gel catalysts under different requirements.With reference to the definition of nanomaterials,the description of size in the article is based on 100 nm.In our studies,a P?PVP-co-MBAAm?hydrogel was synthesized on the outer layer of the magnetic center to form a gel sphere with a magnetically responsive core-shell structure,and Ag nanoparticles were loaded in the gel network by in situ reduction.The research contents of this paper are as follows:?1?The Fe3O4 magnetic center was synthesized by the co-precipitation method.Through the coating of silicon oxide,the precipitation polymerization of PVP-MBAAm,and the in-situ reduction deposition of Ag nanoparticles,prepared the small-size S-Fe3O4@SiO2/PVP-MBAAm/Ag?1.0?hybrid gel catalyst;the structural composition and morphology of the hybrid microgel catalyst were characterized by TEM,FT-IR,wide-angle XRD,VSM,TGA and others,which proved that the preparation was successful,and it had certain stability and obvious magnetic properties.The reaction of p-nitrophenol with sodium borohydride as a probe was used toinvestigatethecatalyticpropertiesofsmall-size S-Fe3O4@SiO2/PVP-MBAAm/Ag?1.0?hybrid gel catalyst.Under the best reaction conditions:the conversion of p-nitrophenol is 95.7%,Kapp=35 s-1·10-4,the yield of p-aminophenol is 95.6%,and the catalyst can be recycled 5 times.?2?The Fe3O4 magnetic center was synthesized by the Solvothermal Method.Through the coating of silicon oxide,the precipitation polymerization of PVP-MBAAm,and the in-situ reduction deposition of Ag nanoparticles,prepared the large-size L-Fe3O4@SiO2/PVP-MBAAm/Ag?1.0?hybrid gel catalyst;the structural composition and morphology of the hybrid microgel catalyst were characterized by TEM,FT-IR,wide-angle XRD,VSM,TGA and others,which proved that the preparation was successful,and it had certain stability and obvious magnetic properties.Under the same experimental conditions,the activity of reducing L-Fe3O4@SiO2/PVP-MBAAm/Ag?0.12?hybrid gel catalyst for p-nitrophenol reaction was investigated.Under the best reaction conditions:the conversion rate of p-nitrophenol is 99.3%,the yield of p-aminophenol is 99.2%,Kapp=71 s-1·10-4,and the reaction activity does not reduce after the catalyst is used 5 times. |
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