Research On The Preparation And Application Of Polydopamine-assisted Composite Microspheres

Recently the composite microspheres have been pursued and further studied by researchers because of the uniqueness of their chemical compositions and structures.Compared with single component microspheres,composite microspheres are the spheres comprised of two or more components.As a consequence,composite microspheres not only own the function of the single phase,but also possess the properties of each component.In addition,they have the advantages of functionality diversification,enhanced performances,wide applications,etc.In this thesis,based on the adhesion characteristics and chemical reactivity of polydopamine(PDA),we had fabricated a series of different tectonic composite microspheres.At first,the raspberry-like PDA/Ag composite microspheres were synthesized with the aid of PDA.Two kinds of hydrophilic-hydrophobic silane coupling agents were simultaneously used to modify SiO2 microspheres to obtain wettability tunable silica particles,which were the foundation of Pickering emulsions.The functional platform was constructed by PDA assisted preparation of Janus particles.By varying the wettability types of loaded particles,different kinds of Janus particles can be obtained,such as SiO2/PDA Janus particles,SiO2/Ag Janus particles,SiO2/Fe304 Janus particles.We also explored the applications of antimicrobial activity,emulsifying capacity,oil-water separation and interfacial catalysis capacity of the composite microspheres.The details were listed as follows:(1)The uniform PDA particles were obtained by self-polymerization of dopamine monomer in a water-ethanol solution mixed with alkaline.Then the as-prepared PDA particles were added into a solution of[Ag(NH3)2]+,after which the precursors were in-situ reduced into Ag nanoparticles combined onto the surface by the functional catechol and amine groups of PDA.Therefore the raspberry-like PDA/Ag composite microspheres were synthesized.Furthermore,we also assessed the antibacterial properties of PDA/Ag microspheres on Escherichia coli and staphylococcus aureus.The biocompatibility against human embryonic kidney cells was also investigated.(2)The monodisperse SiO2 microspheres were prepared by Stober method.By adjusting the dosages of two different kinds of silane coupling agents,namely 3-aminopropyltriethoxysilane and dimethyldichlorosilane,continuous wettability tunable silica particles were obtained,which were used to form Pickering emulsions next.The system consisted of paraffin wax(mt=52?54 C),water,modified SiO2 particles were executed to emulsification experiment by IKA T18 homogenizer.The types of the emulsions could be tuned by means of the wettability of SiO2 particles.In order to validate the scheme for the universality of the silica modification method,880 nm and 1.25 ?m SiO2 microspheres had been tested with the similar scheme.What's more,mesoporous SiO2 nanorods(143.82 um in diameter,474.11 nm in length,4.43 nm in channel)were also involved in the modification tests to explore the universality in dimensions of the scheme.(3)Different types of Pickering emulsions were fabricated using the wettability tunable SiO2 particles.The surfaces of them were asymmetrically modified by the adhesion characteristics of PDA.The well-defined asymmetric SiO2/PDA particles were obtained after the remove of paraffin wax.The series of particles were selected as templates to fabricate SiO2/Ag Janus particles by the reduction of[Ag(NH3)2]+.Furthermore,we explored the applications of oil-water separation and interfacial catalysis capacity of the SiO2/Ag Janus particles.Besides,880 nm and SiO2 microspheres could be utilized to obtain akin Janus particles.(4)The monodisperse Fe304 nanoparticles were synthesized through the co-precipitation of Fe2+and Fe3+ in aqueous phase.SiO2/PDA Janus particles were selected as substrates to fabricate SiO2/Fe3O4 Janus particles with the aid of the robust adhesion and surface affluent catechol and amine groups of PDA.PDA functional coatings acted as a bridge between the magnetic particles and Janus particles.FETEM was used to verify the asymmetric structure.