Reserch On The Motion And Raman Enhancement Effect Of SiO₂@Ag Nanomotors

Micro/nano-motors(MNM)have attracted wide attentions from researchers due to their self-driving ability and controllable motion.In recent years,there have been various types of MNM,such as chemicaly driven MNM,external field driven MNM,and micro/organism driven MNM.Among them,the light driven MNM is considered to be the most promising type of MNM because of its good controllability.On the other hand,nano-probes used in surface-enhanced Raman spectroscopy(SERS)do not have selfdriving ability,and they mainly contact analytes through the diffusion of the nano-probes and detecte molecules.In this paper,MNM and SERS nano-probes are combined together to make use of the self-driving ability of MNM,which helps SERS nano-probes fully in contact with the analytes to be detected.Such strategy can make full use of the advantages of self-propelled MNM for Raman signal enhancement.This dissertation designs and prepares a photocatalytic one-dimensional nano-motor with silica coated silver nanowire as the main component and silver chloride particles as the tail.Using silver nanowires as a template,an ultra-thin silica shell is grown on the surface to form a silica-coated core-shell structure.The coated silver nanowires are broken by an ultrasonic treatment,and the silver regrowth is performed in the crosssection using a hydrothermal reaction to form a spherical tail.Through the redox reaction with Fe Cl3,the tail of silver particles are converted into silver chloride.The main body of the core-shell structure is used as a SERS nano-probe,and the silver chloride tail is providing self-propulsion force from a photocatalytic reaction.We observe and analyze the influencing factors on the speed of photocatalytic one-dimensional nano-motor and obtained the relationship between the ultraviolet light intensity and the moving speed,as well as the relationship between the length of the nano-motor and the moving speed.By switching on and off the ultraviolet light,we can realize the “ON”/ “OFF” motion control on the nano-motors.Furthermore,an attempt is made to explain the phototaxis behavior and the mechanism of nano-motor’s motion.We explore the ability of photocatalytic one-dimensional nano-motor to detect SERS signal in crystal violet and breast cancer cells.Utilizing the phototaxis of the photocatalytic nanomotor,the nano-probes of SERS are pre-aggregated before the SERS detection,and the SERS detection capability is improved by up to 7 times.Therefore,the photocatalytic nano-motor prepared in this paper not only provides an important reference for the preparation of photocatalytic nano-motors with large aspect ratio,but also holds potential to become the next generation of active and intelligent SERS nano-probes.