Construction And Regulation Of Stimuli-Responsive Pickering Emulsion And Study On Electrochemical Behavior Of The Emulsion

In recent years,based on the rapid development of nanotechnology,the use of solid nanoparticles as emulsifiers instead of traditional surfactant-stabilized Pickering emulsions has attracted widespread attention.The solid nanoparticle emulsifier is adsorbed on the interface of two immiscible solutions to form a solid particle film,which effectively prevents coalescence between droplets,so Pickering emulsion has strong stability.The key to the development of Pickering emulsions is to select solid particle emulsifiers with suitable surface wettability.In addition to artificially synthesized functional polymer nanoparticles,natural inorganic nanoparticles do not possess such properties.However,the chemical synthesis steps of high molecular polymer nanoparticles are usually complicated.If solid particle emulsifiers can be prepared by hydrophobically modifying inorganic nanoparticles with non-covalent bonds,the problem of difficult synthesis can be avoided.In the application of Pickering emulsions,such as in petroleum transportation and emulsion polymerization,the demulsification of ultra-stable Pickering emulsions can be a huge challenge.Therefore,switching the stability of the emulsion through proper environmental triggering,the stimulating responsive Pickering emulsion has attracted considerable attention.Based on the above discussion,the feasibility of non-covalent surface-modified inorganic nanoparticles and the stabilization mechanism of Pickering emulsions as solid particle emulsifiers,the triggering mechanism of emulsion stimuli are studied.The specific research results are as follows:1. Fe₃O₄@SiO₂ nanoparticles with core-shell structure were prepared.The amphiphilic dye molecule rhodamine B was used for hydrophobic modification,and the modified nanoparticles were used as stabilizer to prepare Pickering emulsion.As the mass concentration of the emulsifier particles increases,the particle size of the prepared emulsion droplets decreases.In addition,the obtained Pickering emulsion has good magnetic field response,and the stability of the emulsion can be controlled reversibly by applying a magnetic field,and this process can be repeated more than 3 times.2. A novel redox-responsive oil-in-water Pickering emulsion was constructed by non-covalently combining the synthesized acetylferrocene-9-anthaldehyde azine fluorescent molecule?Fc A?with SiO₂ nanoparticles as a solid particle emulsifier.It is found that the volume ratio of oil-water phase,the concentration of emulsifier particles,and the speed can affect the performance of the emulsion.When the oil-water ratio is 6:4 and the emulsifier mass fraction is 0.3 wt%,a homogeneous mixer can be emulsified for 5 min?10000 r/min?to obtain Pickering emulsion with uniform particle size and best stability.Pickering emulsion alternately adds oxidant and reducing agent at normal temperature.On the one hand,the hydrophobicity of SiO₂ nanoparticles changes due to the adsorption of oxidation state Fc A and the desorption of Fc A on the surface of SiO₂.The stability of the emulsion can be converted between stable and unstable by redox triggering at room temperature,and the regulation process can be repeated at least three times.On the other hand,the fluorescence intensity and amphiphilicity of Fc A molecules can be adjusted by redox stimulation,so changes in the fluorescence behavior of the emulsion droplets can be observed in the redox cycle.This work will help to better understand the regulation mechanism of redox-stimulated Pickering emulsions,and at the same time open up new ways for fluorescent labeling of Pickering emulsions without introducing additional fluorescent molecules.3. The stability of the oil-in-water Pickering emulsion prepared by non-covalent surface-modified inorganic nano-SiO₂particles was studied by electrical impedance spectroscopy?EIS?.Observe that the emulsion is characterized by a semicircle in the Nyquist diagram,and the average particle size of the emulsion droplets decreases with the increase of the emulsification rate,indicating that the stability of the emulsion is higher.Through simulation analysis of the frequency response data of the emulsion obtained by EIS,it was found that the fitted impedance R_O/Wvalue of the emulsion prepared at different emulsification speeds decreased with decreasing particle size.In addition,with the increase of the storage time of the emulsion,the average particle size of the emulsion increases and the stability is poor.The fitted impedance R_O/W value of the emulsion is consistent with the particle size trend.It shows that EIS is a suitable technique for characterizing the stability of O/W Pickering emulsions prepared by modified SiO₂ particles,and it is of great significance for the storage and use of emulsions.