Design And Motion Behavior Of Micro/nanomotors Driven By Crystal Growth And/or Photocatalytic Reaction

elf-propelled micro/nanomotors which are capable of converting other energy into autonomous motion in the micro/nano scale are the micro/nano deceives.They have important potential applications in picking up and transporting cargos,environmental remediation,biological medicine,bionic simulation system and micro/nano-engineering,etc.Now,micro/nanomotors have received extensive attention by researchers throughout the world and become one of the hotspots in the nano research.Now,the reported micro/nanomotors are mainly liquid motors and/or solid motors.For liquid motors,most of them are driven by interface tension gradients via changing solution composition and show a simple motion mode.And for solid motors,their motion is usually driven by chemical reactions,light,electric and magnetic field as well as ultrasound,etc.Recently,our group reported an intelligently isotropic micromotor with positive and negtive phototaxis by taking an advantage of the limited penetration depth of light to induce the asymmetrical surface photocatalytic reaction.This effectively solve the problems of most light-driven micro/nanomotors such as complex structures and hard to control.In view of the result,it has been found that the motion of the micromotor is closely related to the distribution of photocatalytic products.Therefore,the research on how the motor properties?crystal phase?and light condition influence the motion mode is helpful for the explanation of its motion mechanism.In this thesis,we firstly design a novel self-driven isotropic oil droplet powered by the growth of the adjacent crystal,which can break the asymmetry of the oil droplet and change the interface tension.The motion trajectory can be clearly indicated by the grown crystals.The research shows that the AIBN crystal seed in the aqueous phase and the AIBN dissolved in the oil phase are the necessary factors for the motion of the oil droplet;and the solubitily and diffusion velocity of solvent in the oil phase into the aqueous phase have an important effect on motion of the oil droplet;the stability of oil droplets that is closely related to the system composition is essential for its sustained motion.By the study on the motion behavior of the oil droplet,we analyze the motion mechanism that the approach of the grown AIBN crystal to the oil droplet change the interface tension of the oil droplet to break the asymmetry of the oil droplet,which induces the motion of the oil droplet along the grown direction of the crystal.Because of the obviously indicated motion trajectory,themotorshowsapotentialapplicationinbionicsimulationand micro/nanoengineering.econd,on the basis of our early research,the photocatalytic activity of TiO₂which is closely realted to the crystal phase influences its motion behavior.Therefore,we have studied the motion of anatase TiO₂?A-TiO₂?and rutile TiO₂?R-TiO₂?under365 and 420 nm light irradiation in 0.5%H₂O₂ or in pure H₂O after loading by Pt.The results show that A-TiO₂ micromotors have a negative phototaxis and R-TiO₂micromotors show a positive phototaxis under 365 nm light irradiation.The intelligent control of the motors can be achieved involving in the start-stop,the motion speed and direction,etc.When using 420 nm light and in 2.5%H₂O₂,A-TiO₂micromotors hardly move due to the low activity and R-TiO₂ micromotors show a negative phototaxis.By comparing the difference of A-TiO₂ and R-TiO₂,we reasonably explain the distinct pototaxis of TiO₂ micromotors with different crystal phases.Finally,the development of photocatalytic materials has a significant effect on the micro/nanomotors based on phototcatalytic reactions.In view of this,we also carried out some works on the preparation of low valance Ta self-doping TaO₂F compounds by a solvothermal method using TaF₅ as the starting materials and isopropanol as the solvent.The influence of the solvothermal time on the structure and composition of products has been explored;the formation mechanism of low valance Ta has been studied;the light absorption property and photocatalytic activity have been tested.However,the prepared material does not show the motion under light irradiation due to its relatively low activity.The study shows that the activity of photocatalytic materials significantly influences their movement behavior as micro/nanomotors.