Controllable Coating Of Inorganic Nanoparticles With Boronate Polymer And Its Etching Process By Metal Ions

Composition diversity and refined structure of materials are important to achieve high performance.Therefore,the exploitation and construction of new nanomaterials with multi-component and unique structure have become the direction of the research on materials.Yolk-shell structured nanomaterials consisting of the inner core,cavity and outer shell have broad application prospects in the field of catalysis,biomedicine,energy,stealth,absorption and so on.By using organic polymers with adjustable composition,structure and properties used as shells,and inorganic nanoparticles as inner cores,to form yolk-shell structure,synergistic effect can be generated,thus improving the intrinsic properties of materials and even deriving new characteristics.Based on the interaction between catechol group and inorganic surface,the cooperative polymerization of catechol monomers and boromic monomers,as well as the Kirkendall effect associated with the coordination of metal ions with boronate polymer,a method for fabricating yolk-shell structured nanomaterials with high adaptability and good controllability was developed.The nanomaterials consisted of inorganic nanoparticles as the inner cores,metal coordination polymers as the outer shells and a controllable cavity located between the inner core and the outer shell.Focusing on the selection of inorganic nanoparticles,the synthesis of building blocks of polymer shells and the control of metal ions species,this method realized the effective regulation of the composition,cavity layer,structure and morphology of the yolk-shell particles.Furthermore,yolk-shell structured nanomaterials with double-shell were successfully prepared by two-step coating/two-step etching method,which provided a new route for the synthesis of complex multi-chamber nanocontainers.The detail contents of this research are shown as follows:(1)The monomers containing two catechol groups(DAC)and two boronic acid groups(DAB)were synthesized by a Schiff base formation reaction of amino groups and aldehyde groups.The condensation polymerization of DAC and DAB monomer was limited to the surface of Fe2O3 nanospindles by the strong binding force between DAC monomer and Fe2O3.At the same time,the B-N coordination formed among the polymer segments can drive the controllable coating of boronate polymer on the Fe2O3 surface.Fe2O3@boronate polymer core-shell nanoparticles can be easily prepared from monomers by this method.Using Fe3+ as etching agent,the boronate bonds were cleaved by the coordination of Fe3+ with catechol group.This process is accompanied by a Kirkendall effect similar to that of an inorganic system,and the core-shell structure can be in situ etched into Fe2O3@metallosupramolecular polymer yolk-shell structure with a cavity inside.(2)By using spherical SiO2,rod-liked ZnO and irregular TiO2 and ZnO nanoparticles as the cores,the adaptability of the above method was systematically studied,and the yolk-shell structured nanoparticles with different morphologies were successfully constructed.(3)Monomers with three catechol groups(TBC)and three boromic groups(TBB)were synthesized.The effects of boronate polymers with different crosslinking degrees synthesized by the cooperative polymerization of TBC and TBB(or DAB)on the formation of yolk-shell structured were studied.The types of etching agent are discussed extensively,the results showed that Cu2+,Al3+ and Sn4+ could be used to fabricate yolk-shell structured nanomaterialss composed of different metal coordination polymers.In addition,by adjusting the thickness of the boronate polymer shell and the amount of metal ions,the cavity volume of the yolk-shell structured nanoparticles can be controlled.(4)Yolk-shell structured nanoparticles with double-shell were prepared successfully by two-step coating/two-step etching method,which provided a new strategy for the preparation of nanomaterials with more complex structure and diversified components.