Synthesis Of Nanostructured SiO₂ Particles By St(?)ber Method

SiO₂ nanoparticles, as one typical nanomaterial, exhibit characteristics such as chemical and colloidal stability, biocompatiblity and ease to modification, and it has become one hotspot of the nanoscience researches. Sto|¨ber method has its top priority in the preparing of SiO₂ nanoparticles because it has advantages in mild condition, easy and facile to control. So in this paper, we choose the system using Sto|¨ber method in the synthesis of SiO₂ nanoparticles as our research subject, starting with the study of their growth theory, design and prepare the SiO₂ nanoparticles with specific structure. The contents are as follows.(1) We start with comparing the influences with different reaction conditions on the radius of the particles, summarizing the relationship among the hydrolysis rate, the concentration of forming cores and the size of particles. On this basis, we have synthesized mono dispersed SiO₂ nanoparticles, with sizes ranging from ten to one hundred nanometers, by control the hydrolysis rate and the concentration of forming cores through base-catalyzed concentration. The shape of the SiO₂ nanoparticles and the stability of the colloids can be effectively controlled through changing the base-catalyzed types. These findings further widen our knowledge on the growth mechanism of synthesis of nanostructured SiO₂ particles by Sto|¨ber method, and provide the fundamentals for the design of more complexity and delicate nanostructures.(2) Without the existence of template agents, by adopting different electrolyte to induce the aggregation of the primary SiO₂ particles in the Sto|¨ber process, we have prepared SiO₂ particles with mesoporous structures. The experiment results show that the presence of strong electrolyte (NaCl) can induce the aggregation of the primary SiO₂ particles in the Sto|¨ber process, thus allowing the formation of SiO₂ particles with mesoporous structure, on the other hand, weak electrolyte (ammonia) can induce the aggregation of smaller SiO₂ particles (20 nm), compared with materials formerly mentioned, they have higher surface area and larger pore volume. We use surface activities as simulate molecule in order to study the sorption ability of the two mesoporous materials separately. It is found that the absorption ability of SiO₂ particles with mesoporous structure, versus the ones prepared by regular Sto|¨ber method, is improved obviously. Especially the SiO₂ particles, preparing by the latter method, exhibit desirable absorption ability even to the molecules having weak forces with silanol, thus allowing their potential application in bio-medical and environmental fields in the future.(3) In the process of synthesizing SiO₂ particles through Sto|¨ber method, using cetyltrimethylammoniumbromide (CTAB) as template agent, only by simply changing the ratio of ethanol and water into an appropriate one, hollow SiO₂ particles will be produced. Furthermore, we discuss the growth mechanism of the hollow structure formation. Through the BET analysis we find that the shell is still with high surface and narrow pore-size distributed mesostructure. And by adopting the TMAOH catalyst synthesized silica sol gel as silica precursor, the shell of hollow microspheres will be thicken appropriately, and thermal stability and hydrothermal stability of the hollow materials may be improved effectively. Because of its low density, large surface area, stability in mechanics and thermal, high ability of surface penetration, it has a promising application in fields of catalysis, drug synthesis etc..