Quantitative Characterization And Spatiotemporal Control Of Complex Micro-/Nano-Environment Based On Single Particle Tracking

Compared with the traditional analysis methods that merely provide the ensemble average information of the complex micro-/nano-environment at the macro level,single particle tracking(SPT)techniques allow in situ,real-time monitor the dynamic diffusion behaviors of the probes with nanometer spatial localization accuracy and millisecond temporal resolution.By extracting the dynamic parameters of the tracers,the structural information and dynamic evolution of micro-/nano-environment can be obtained,which lays the powerful experimental basis for analyzing and understanding the complex environment.However,to get more details of micro-/nano-environment,the SPT technique with higher spatiotemporal resolution and higher efficiency remains to be exploited.Based on in-depth understanding of the spatiotemporal characteristics of the micro-/nano-environment,we may find a more precise control method of environment.In this dissertation,we optimized the SPT techniques by developing the high temporal-resolution imaging setups and efficient data processing methods.The improved SPT techniques have been applied to the fields of chemical catalysis,materials,life sciences and nanoparticle assemblies.The main research content are as follows:1.The high-speed laser darkfield microscopy(HSLDFM)has been developed to monitor the rapid rotation and the variation of angle distribution of single gold nanorods(Au NRs).The reliability of HSLDFM has been verified by adjusting the volume ratio of glycerol/water to obtain the solutions with different viscosities.This method could accurately detect the environmental viscosity as low as 20 c P,which greatly broadens the measurable solution viscosity range(Chapter 2).Subsequently,the method was applied to exploring H₂O₂ decomposition reactions that were catalyzed by Au NRs coated with Pt nanodots(Au NRs@Pt NDs)and observed two different rotational states.The two states and their transitions are related to the production and the amalgamation of O₂nanobubbles on the nanorod surface depending on H₂O₂ concentration.This technique could be applied to study other chemical and biochemical reactions in solution(Chapter 3).2.The darkfield imaging based single Au NR translational tracking method has been established to characterize the UV-induced gelation process of the glycyrrhizic acid(GL)-acrylamide(AAm)double network(DN)hydrogel.Three gelation stages and the hop diffusion behavior of Au NRs in the gel network have been obtained,providing a space-and time-resolved microstructure of DN hydrogels(Chapter 4).The SPT method in Chapter 4 was further developed.Using the SPT method,we not only obtained the structural and material properties of liquid-liquid phase separation-mediated p62condensates,such as viscoelasticity,compartmentalization and the recruitment of the nanocomplex,but also observed that the droplet underwent further phase transition or aging to form a multivacuole-containing gel structure with the size effect(Chapter 5).3.Based on darkfield imaging and SPT analysis,a controllable microvortex-pair array composed of hundreds or thousands of Au NRs emerged when a dc electric field was applied to the monodisperse Au NRs via a pair of sawtooth electrodes.We monitored the entire emergence processes and revealed the underlying mechanism(Chapter 6).We further explored the controllability of the vortex-pair array,and obtained many complex dynamic vortex patterns,as well as the distinct growth and emergence paths of vortex pairs(Chapter 7).