Study On The Preparation Of Polydopamine Micro/Nanaospheres And Their Surface Modification Of Metal Nanoparticales

Poly-dopamine(PDA) is the major components of adhesive proteins that marine mussels screrted. As polydopamine have excellent water dispersion, stability and biocompatibility, it can be widely used in biology, medicine, chemistry, and other fields.Dopamine monomer can be oxidized and self-polymerized under alkaline aerobic conditions to generate polydopamine. Changing the polymerization conditions such as DA concentration, polymerization medium, reaction time can controllably prepare monodisperse polydopamine micro/nanospheres(PDS). Moreover, there are many fuctional groups like amino and phenolic hydroxyl in polydopamine, which exhibit an extraordinary chelation and weak reduction. Thus,polydopamine can be used as a in-situ reductant for the synthesis of various polydopamine/metal nanoparticle composites. In this dissertation, we established a one-step method to prepare polydopamine micro/nanospheres. In addition, two different metal nanoparticles were loaded on PDS surface to prepare polydopamine microspheres/metal nanoparticle composite materials. We also explore the application of polydopamine microspheres /silver nanoparticles(AgNPs/PDS) in catalysis field. The detailed results were summarized as follows:(1) A one-step method to prepare polydopamine micro/nanospheres was established. As dopamine can be oxidized and self-polymerize under alkaline aerobic conditions to generate polydopamine, we use ethanol and water as solvent, and the size of polydopamine nanospheres can be regulated by concentration of ammonia in the polymerization process. The thermal field emission scanning electron microscope showed that the size of PDS is uniform and ranged from 180 nm to 1.2 μm with the increasing of concentration of ammonia. The X-ray photoelectron spectroscopy analyzer(XPS), ultraviolet spectrophotometer(UV-Vis) and fourier infrared spectroscopy(FTIR) were used to characterize polydopamine micro/nanospheres. Results proved the successful preparation of PDS. The stability of PDS with a diameter of 200 nm under different pH was investigated and resistance of acid and alkila as well as water-disperse were revealed.(2) A simple method to prepare AgNPs/PDS was established. Firstly, we use dopamine to obtain polydopamine in alcohol/water system. Owing to the weak reduction ability of polydopamine, AgNPs were loaded on the suface of PDS without the addition of any stable and reduction agents. AgNPs/PDS composites were prepared. The results of SEM showed that AgNPs uniformly distribute on the surface of polydopamine nanospheres. The X-ray photoelectron spectroscopy, ultraviolet spectrophotometer, X-ray energy spectrum, electrochemical stripping voltammetry method and inductively coupled plasma mass spectrometry were used to characterize AgNPs/PDS composites, which proved the successful loading of AgNPs on PDS. Finally, the catalysis of AgNPs/PDS to the reduction of sodium brohydide with organic pollutant 4-nitrophenol in water was investigated, the results showed that AgNPs/PDS possess excellent catalytic performance.(3) A simple method to prepare polydopamine/gold nanoparticles(Au NPs/PDS) was established. Firstly, we use dopamine to obtain polydopamine in alcohol/water system. Owing to the weak reduction ability of polydopamine, AuNPs were loaded on the suface of PDS without the addition of any stable and reduction agents. AuNPs/PDS composites were prepared. The results of scanning electron microscopy(SEM) showed that AuNPs were uniformly distributed on the surface of polydopamine nanospheres. The X-ray photoelectron spectroscopy, ultraviolet spectrophotometer, X-ray energy spectrum, and elementary mapping method were used to characterize AuNPs/PDS composites, which proved the successful loading of AuNPs on PDS.