The Study Of The Charging Behavior And The Activation Of Nano/Submicron Particles In Solution Phase Containing Surfactant

Over the years, the study and applications of nano-and sub-micron particles (hereinafter referred to as "micro-nano particles") in physics, chemistry, biology, materials, electronics and medicine and other disciplines have been developed rapidly. The charging behavior of micro-nano particles in the solution phase, as a traditional research topic, presents a series of new features due to added of surfactant. It has become a research hotspot in recent years. Numerous domestic and abroad papers gave in-depth discussions and achieved fruitful results on this issue. However, a lot of problems are still unsolved yet. It is also well-known that surfactant can foam in the solution phase, and the participation of micro-nano particles will lead to a synergistic or antagonistic effect on the foamability and the foam stability of surfactant in the solution phase. This speciality has been used to synthesize new materials and explained some new phenomena. Therefore, they have attracted worldwide attention in the scientific society.This research work was divided into two parts:the first part was involved the changing behavior and mechanism of the micro-nano particles in polar/non-polar solution on addition of surfactant. We not only investigated systemically the charging mechanism of particles in polar/nonpolar solution by a series of experiments, but also gave a preliminary theoretical consideration, including the influences of the surfactant concentration, particles concentration and sizes on the charging of the particle. In the second part, based on different surfactants and micro-nano particles, the influence of the synergistic or antagonistic interactions between surfactants and micro-nano particles on the foamability was analyzed preliminarily in the liquid phase. These results may be are beneficial to understand the charging behavior, transport properties, surface electro-catalytic characteristics of micro-nano particles in different liquid phases. Furthermore, they could also be worthful for the synthesis of new nano-materials, the application of their physical/ chemical properties, and the development of nanoparticles in different fields, especially in the biomedical area.The main results and conclusions of this paper are listed as follow:Firstly, on the study for the charging mechanism of particles in the solution phrase containing the surfactants.1) The influence of AOT (sodium di-2-ethylhexylsulfosuccinate) concentration, particle concentration and the particle sizes on the charging behaviors of PS (polystyrene) particle in nonpolar solvent containing surfactant was researched by phase angle light scattering (PALS). The results showed the relation of PS particles and the above parameters at a wide measurement range. A simple quantitative analysis based on preferential adsorption explained the experimental data. The study showed, the charging mechanism of PS particles in nonpolar solution met the "preferential adsorption mechanism."2) According to the nonlinear Poisson-Boltzmann equation and the "micelles preferential adsorption mechanism", a model was introduced under the conditions of the nonpolar system. We simulated the charging of the particles in nonpolar solution containing the charged reverse micelles. The simulation showed two different micelle concentration-dependent regions for the surface potential. And then, we studied the charging behavior of TiO2 in the AOT-dodecane solutions by PALS. The experimental results were in agreement with the simulation on the whole region. One the hand, these findings revealed our theoretical model for the particle/surfactant/nonpolar system was suitable and predictable; On the other hand, the model proved the charging mechanism of TiO2/dodecane system also satisfied the "preferential adsorption mechanism."3) The influence of nonionic surfactant Span80 (sodium di-2-ethylhexylsulfosuccinate) concentration, particle concentration and particle size on the charging behavior of SiO2 particles in Span80-dodecane solution was researched systemically by PALS. The results showed that the Zeta potential of SiO2 particle is nearly independent on the three above-mentioned parameters.4) In polar solution (deionized water), we measured the conductivities of AOT solution and PS-AOT solution. Based on this case, the effects were also studied systematically for the AOT concentration, particle concentration and the particle size on the charging of PS particle by PALS. Then using the mean-field Poisson-Boltzmann equation and preferential adsorption mechanism, under the conditions of the polar system, we established a model to simulate the relations between the micelle concentration, particle concentration and particle size with particle surface potential at a wide range. Numerical simulation not only validated the experimental results but also performed some predictions and judgments for the further experimental work.5) On the basis of the same charging mechanism- preferential adsorption mechanism, comparing to the impacts of the AOT concentration, particle concentration and the particle size on the PS/AOT/dodecane and PS/AOT/water solvent systems, we found that the former relation about the Zeta potential and three parameters was relative complex, for instance, Zeta potential decreased with the increase of the particle concentration and the particle size at the more high concentration situation. However, it was independent of the change of these parameters at relatively low concentration. For the latter system, Zeta potential all increased with the increase of these three parameters. Meantime, we also realized that the adjustment of surfactant concentration on the Zeta potential for the former was much higher than the latter. Secondly, the systematic study of the influences for the different particles dispersed in aqueous solution adding with anionic, nonionic and cationic surfactant has been inveasticated, especially on their foamability and foam stability. We analyzed the activation excitated by the interaction between the surfactant and the surface of these particles preliminarily.The highlights of my research works:1) The systematic study of the charging behavior of PS particle in nonpolar solution with surfactant, found out the optimal experimental conditions for PS particle charging, providing a reference for further applications.2) The charging mechanism of metal oxide nanoparticles in surfactant/nonpolar solutions was study systemically which is helpful to understand well the charging mechanism of the micro-nano particles in nonpolar systems.3) Theoretical models were introduced based on micro-sodium particle/surfactant/non-polar solvent and micro-nano particle/surfactant /water solvent systems. The models provided the possibility for further explaining, verifying the experimental results (although they seems to be rather rough as a preliminary theoretical analysis).4) Numerical simulation integrated the experimental results so that the experimental phenomena were explained by simulation; Vice versa, the results may validate the rationality of simulation. Therefore, a good foundation has been established for the related study in future.5) By means of the numerical simulation, it can be further extrapolated to the corresponding results which can't be achieved under the present experimental conditions including more high or much lower concentrations of the system. It might be to provide a basis to predict some interesting results for the next experiments.