Preparation Of "Core-Satellite" Bimetallic Nanoparticle-Polymer Composite And Its Catalytic Degradation Of Organic Pollutants

Noble metal nanoparticles have been widely studied for their excellent catalytic properties.However,due to the interaction between van der Waals force and high surface energy,these nanoparticles have a strong tendency of aggregation in the solutionwhich reduce the catalytic performance and stability of the catalyst.Immobilization of metal nanoparticles on substrate materials is one of the most effective ways to solve these problems.Due to its special adhesion and particular structure,polydopamine?PDA?is often used as the immobilized material for precious metal nanoparticles.The catalytic activity of noble metal nanoparticles can be maintained after immobilization,and it is significantly higher than that of carrier free noble metal catalysts.In the field of environment,heterogeneous catalysis using this nanocatalyst is one of the most effective methods to degrade aromatic nitro compounds and organic dyes in aqueous solution.In this paper,the properties of polydopamine,the recent research progress and the construction methods of nanomaterials loaded Pt were reviewed.At the same time,based on the adhesive properties of polydopamine and the reduction properties of catechol structure,"core-satellite"Ag@PDA/Pt bimetallic nanocomposite were prepared through a simple and eco-friendly method.By TEM,FTIR,XRD,XPS characterization,the morphology,composition and formation mechanism of the material were analyzed,and the influence of reaction conditions on the material preparation was studied.Finally,the potential application in the field of environment was explored.The details are as follow:1.Preparation of"core-satellite"Ag@PDA/Pt bimetallic nanomaterialsDopamine could be oxidized and self-polymerized in alkaline solution to form polydopamine,then the PDA could be coated on the surface of prepared Ag nanoparticles by its adhesion property.The thickness of the polydopamine shell and the satisfactory morphology after coating,was related to the initial concentration of dopamine solution and the reaction time of self-polymerization.The polydopamine shell with good appearance and appropriate thickness could be prepared at the initial concentration of 0.25 mg/mL and the reaction time of 2 h.In the absence of common metal reductants?such as NaBH₄?,Pt nanoparticles were formed by reducing Pt ions with polydopamine assisted by ultraviolet light,and the catechol structure in polydopamine was transformed into quinone structure.Pt ions also reacted with Ag nucleus to form elemental Pt,which was deposited on the surface of Ag and forms partial bimetallic alloy by diffusion.By exploring the reaction conditions,it was found that the formation of"core-satellite"Pt based bimetallic nanomaterials relate to the reaction time and the amount of chloroplatinic acid added.When 1 mL chloroplatinic acid was added and let them reacted for 1 h,well-prepared nanomaterials could be obtained.2."Core-satellite"Ag@PDA/Pt bimetallic nanomaterials removing organic pollutantsThe resultant Ag@PDA/Pt nanomaterials contain a large number of precious metal nanoparticles?metal element mass ratio of 36%?,as well as a polydopamine shell layer that could effectively adsorb organic dyes through hydrogen bonding,electrostatic action and?-?deposition.Based on the two characteristics of the material,p-nitrophenol,an aromatic nitrocompound,was used as the catalytic reduction target.It has been proved that Ag@PDA/Pt nanomaterials have good catalytic activity for aromatic nitro compounds,and the apparent rate constant k_app is 0.213 min^-1.After repeated using for five times,the catalytic performance remained 91%.The organic dye-methylene blue was used as the adsorption and degradation object.It was found that the adsorption efficiency of the material reached 80%,and a small amount of catalyst could rapidly degrade MB within 2 min.When the pH value increased,the electrostatic interaction between the material and MB could be enhanced,thus improving the adsorption performance of the material.After five using cycles of Ag@PDA/Pt,the degradation and catalytic efficiency were maintained at 85%and 87%,respectively,illustrating its good reuse performance.In the study on the extension of application scope,the material has a good degradation effect on rhodamine B and methyl orange,showing the prospect of practical application in simulating the actual polluted water sample.