Preparation Of Micromotor Materials Derived From Polyoxoanions And Polynuclear Silver Clusters And Study Of Bubble-driven Motion

Micro/nanomotors have attracted considerable attention due to their broad applications in the fields of sensing,tracking,biomedicine,environmental monitoring and cleaning.The widespread research interest in bubble-driven micro/nanomotors is because of their high velocity and power arising from the effect of bubble detachment.Platinum is a commonly used material for bubble-driven micro/nanomotors,but its practical application is limited as it is highly expensive and influenced by inorganic and organic contaminants significantly.In addition,the motion control means of bubble-driven micro/nanomotors are very limited,which hinders their further research and application.Due to the advantages of low cost,easy preparation,controllable structure and excellent catalytic performance,polyoxometalates（POMs）are favored by catalytic micro/nanomotors.In addition,supramolecular crystalline materials based on polyoxometalates and silver clusters are potential micro/nanomotors materials with polyoxoanions and silver active sites.Based on the influence of different types of polyoxometalates properties on the motion behavior of micromotors,this paper explores the bubble motion behaviors of polyoxometalate/silver cluster micromotors and the applications as photocatalytic degradation"agitator"and micropower device pusher.The specific contents are as follows:1.Two kinds of Keggin-type polyoxometalate/silver-alkynyl cluster supramolecular materials are synthesized by Keggin-type polyoxometalates and silver-alkynyl clusters.After calcination,the acetylene ligand and tetrabutylammonium cation in the Keggin-type polyoxometalate/alkynyl-silver cluster supramolecular material are dissolved and derived into nitrogen-doped carbon-coated Keggin-type polyoxometalate/silver nanoparticle micromotor material.The two kinds of micromotor materials maintain the shapes of the supramolecular material,thus showing two morphologic shapes of powder and cuboid crystal.Compared with powder micromotors,the growth of microbubbles on the surface of the high-density cuboid micromotor provides sufficient buoyancy.After the upward buoyancy generated by attached bubbles and the downward gravity of the micromotor reached equilibrium,the vertical reciprocating motion of the micromotor in H₂O₂solution was achieved.The highest speed of the cuboid micromotor can reach 1.4 cm/s.Compared with the circular or irregular motion of ordinary micromotors,the motion path of the cuboid micromotor is more predictable.In addition,the synergistic effect of the peroxide-like activity of polyoxoanions and silver nanoparticles in the cuboid micromotor and the agitation induced by the high speed movement of the micromotor significantly accelerated the degradation of the organic dye methyl orange.The research results indicate that the cuboid micromotor exhibits better bubble motion behavior,which provides a new strategy for controlling the motion direction of bubble-driven micro/nanomotors.2.Based on the research in the previous chapter,two Dawson-type polyoxometalate/silver-alkynyl clusters supramolecular crystalline materials are synthesized by the reaction of Dawson-type polyoxometalates with silver-alkynyl clusters.After calcination,two kinds of nitrogen-doped carbon coated Dawson-type polyoxometalate/silver nanoparticle micromotor materials are synthesized.Both of the two micromotor materials maintain the shape of supramolecular materials,namely cuboid crystal state,and both realize vertical reciprocating motion,which accelerates the photocatalytic degradation of methyl orange.Compared with Keggin-type polyoxometalates,Dawson-type polyoxometalates carry a higher negative charge and introduce more silver active components in the synthesis of crystalline material precursors.The resulting micromotor materials exhibit higher motion velocities,up to 2 cm/s.The experimental results are of great significance for the control of motion velocity of bubbles-driven micro/nanomotors.3.The micromotors adhered to the surface of a magneton can achieve good floating and diving motion.Through the relative motion of magneton and electromagnetic coil,the mechanical energy is converted into electric energy.But in the process of magneton movement,the micromotor may fall off in the solution,causing pollution to the environment.Therefore,the MIL-88A（Fe）composite material supported by polyoxometalate/silver-alkynyl cluster was obtained by in-situ loading polyoxometalate/silver-alkynyl cluster on the surface of MIL-88A（Fe）by means of electrostatic interaction.After calcination,MIL-88A（Fe）was transformed into Fe₃O₄,and the composite was derived into a capsule micromotor material with polyoxoanions,silver nanoparticles and Fe₃O₄components.Similarly,the prepared micromotors adhered to the surface of a magnet can achieve stable floating and diving motion and realize the conversion of mechanical energy to electric energy.In addition,the existence of magnetic Fe₃O₄particles in the micromotor solves the problem that the micromotors falling off in the solution is not suitable for recovery.The research result lays a solid foundation for the design of environmental protection small generators.