Precise Construction And Performance Study Of Bioinspired Hierarchical Tubular Micromotors

Micro/nano-motor is a new kind of artificially synthesized micro/nano materials or devices that convert chemical energy or other forms of energy into its own kinetic energy on the micro/nano scale.Because of the function of autonomous movement,Micro/nano-motor can perform various tasks of drug delivery,disease diagnosis/treatment,and environmental remediation after specific functionalization,so it has attracted the attention of the majority of scientists in recent years.Aiming at the increasingly serious water pollution in the current environmental problems,we innovatively combined nanozymes,detection and removal,as well as the autonomous movement of micro/nanomotors and successfully constructed several multi-functional micro/nanomotors with hierarchical structure.Using the natural plant fibers in nature as the biological templates to carry out the orderly assembly of multi-dimensional structural units on the mesoscopic scale and precisey construct multi-functional tubular micromotors.The micromotors with hierarchical structure and diverse functions that use hydrogen peroxide as the driving fuel and utilize inexpensive and easily available manganese oxide as the driving catalyst can realize rapid determiantion,effective adsorption and catalytic degradation of various pollutants in environmental water bodies.The detailed research contents are as follows:1.Pt-free three-dimensional EDTA-functionalized Eu-MOF-based fluorescent micromotor acted as an active self-propelled micromachine for the detection,capturing,and removal of Fe³⁺from water were successfully fabricated using naturally-hollow kapok as biotemplate for the first time.This micromotor was composed of EDTA-NiAl-CLDH(calcined layered double hydroxides)/MnO₂and Eu-MOF,which function of each component was different.The outer fluorescent Eu-MOF layer acted as fluorescence sensor for Fe³⁺,while the inner EDTA-functionalized NiAl-CLDH/MnO₂ layer functioned as the function unit for Fe³⁺adsorption,as well as the buffer layers for the nucleation and growth of Eu-MOF,MnO₂ served as catalyst decomposing H₂O₂ for self-propulsion of micromotors.The obtained micromotors exhibited circle motion form with an average speed of 56.9?m·s^-1 in 5 wt.%H₂O₂.This EDTA-functionalized Eu-MOF-based fluorescent micromotor possessed excellent selectivity,high sensitivity(Stern-Volmer constant K_sv=1.3×10⁴ L/mol,limit of detection LOD=0.15?M)and high adsorption capacity(the maximum equilibrium adsorption capacity q_max=112 mg·g^-1)for Fe³⁺.Therefore,the novel 3D bifunctional fluorescent micromotor combining the MOF,EDTA-functionalized CLDH and autonomous motion are promising for the simultaneous detection/adsorption and removal of pollutants,expanding the potential resources for micromotors and providing an efficient option for water quality monitoring and wastewater treatment.2.Bioinspired bovine serum albumin-functionalized NiCo₂O₄@MnO₂/C(BSA-NiCo₂O₄@MnO₂/C)micromotors with dual enzyme-like activities for simultaneous colorimetric determination and removal of environmental contaminants was firstly developed.Thanks to the tubular morphology inherited from kapok fibers,the multifunctional micromotors with inherent oxidase/peroxidase-like activity can move forward quickly in aqueous solutions via a bubble recoil mechanism,which can not only enhance the colorimetric sensing performance,but also improve the removal efficiency toward Cu²⁺ion by enhancing the mass transfer both in the detection and catalytic degradation systems.Moreover,the unique 3D hierarchical architecture assembled by core-shell NiCo₂O₄@MnO₂ nanosheets and C microtubes can provide more accessible reactive sites and thus dramatically facilitate such detection process.In combination with the autonomous motility,intrinsic oxidase/peroxidase-like activities and precisely tuned hierarchical architecture,these automatic micromachines not only are able to detect Cu²⁺selectively and sensitively with the limit of detection of 2.0 n M,but also quickly remove Cu²⁺from wastewater with maximal adsorption capacity of 161.8 mg·g^-1.Furthermore,these micromotors exhibit excellent catalytic activity for the degradation of tetracycline hydrochloride.This multifunctional mobile platform will provide a new and promising strategy for the simultaneous detection and decontamination of poisonous metal ions and other pollutants in aqueous samples.3.Using cynanchum hollow fibers as biotemplate,ZrO₂/MnFe₂O₄/FeZr-MOF magnetic micromotor was firstly prepared by impregnation-calcination and two-step solvothermal method.Among them,the MnFe₂O₄ component provides magnetism for the micromotor,which is used for the control of the movement direction and subsequent magnetic recovery,and acts as a catalyst to catalyze the decomposition of H₂O₂ to provide driving force for the micromotor's movement.FeZr-MOF endows the micromotor to possess intrinsic nanozymes activity and provide the active sites for the specific capture of glyphosate.The micromotor retained the hollow tubular structure of cynanchum fibers,and its 3D hierarchical structure provides larger specific surface area and more reactive sites,further improving detection and adsorption capabilities.The ZrO₂/MnFe₂O₄/FeZr-MOF magnetic micromotor can perform a circular motion in 5 wt.%H₂O₂ with average speed of 101.6?m·s^-1.The effective motion of the micromotors was beneficial for the subsequent dynamic detection and removal of glyphosate.A colorimetric detection method of glyphosate under neutral conditions was established based on the inhibitory effect of glyphosate on peroxidase-like activity of micromotors,and the detection limit for glyphosate was0.05 mg·m L^-1.The colorimetric assay of glyphosate exhibited good selectivity and specificity,which was not affected by other common organophosphorus and non-organophosphorus pesticides,and can be further used for the detection of glyphosate in real water samples.Moreover,the micromotors can also realize the dynamic adsorption of glyphosate in wastewater.The adsorption kinetics experiment suggested that its adsorption mechanism conformed to the pseudo-second order model.The isothermal adsorption experiment indicated that the adsorption fitted to the Langmuir model,and the maxium adsorption capacity can reach 313.5 mg·g^-1.The synergistic effect between each component of ZrO₂/MnFe₂O₄/FeZr-MOF micromotor,the enhanced molecular collisions chance and mass transfer efficiency caused by the movement of the micromotor,as well as the unique 3D hieraichical structure were mainly responsible for the satisfactory detection and removal performance.