Surface Modification Of Nano-silica And Its Application

Recently, silica nanoparticles (SNPs, S1O2) have been explored in interdisciplinary research focus and widely applied in various field of biology/pharmacy, nano-electrode, sensors, catalyst, green chemistry/environment, which had attracted considerable attention due to the lots of silanol group on the surface of SiO2. The elaborate modified particles have both original nature and the special propertiest, such as stimuli-responsive cleavage, fast efficient adsorb for heavy metal ions, ect. Especially they have a growing trend for fast examine the trace element in the aqueous solution.In this thesis, stober method was used to prepare the spherical silica particles (≈300nm) from tetraethoxysilane (TEOS) using NH3as catalyst. According to the tailoring design of molecular, the different structure and properties of organic functional molecules were grafted to the nano-silica surface, so we successfully synthesized special properties as follow.1) Combined with the advantages of extreme selectivity of "click chemistry" and molecular controlled of atom transfer radical polymerization (ATRP), the monopolymer can be grafted onto the surface of silica by the both technique simultaneously. In the modified process, the Poly-(ethylene glycol) methacrylate was introduced on the surface by the copper (I)-catalyzed azide-alkyne1,3-dipolar Huisgen cycloaddition to realized the reaction of click chemistry and ATRP simultaneously. And the grafted polymer can significantly increase the active adsorption point of the surface which can lead the nanoparticles adsorb the metal ions in the aqueous solution as quickly as they can. Particularly, the results showed that PEGMA modified silica adsorbed the Pb2+faster than that of the prinstin particles within1h.2) The disulfide molecular can be cleaved in the presence of thiol-containing materials under the mild condition, and formed a new disulfide bond and by-product. In this experiment, the thiol-modified silica has been prepared to attack the4,4'-Dithiodipyridine to obtained the disulfide bond modified silica particles. Then we used2-mercaptobenzimidazole to attack the disulfide bond modified silica, the disulfide bond cleaved again that the benzimidazole modified particles were prepared. These functionalized particles were easy to dissociate in response to the milimolar concentration of glutathione. Therefore, the particles were utilized to absorb the trace metal ions in aqueous solutions and then attacked by the milimolar concentration of glutathione to release the molecular which were containing plenty of metal ions. From the experiments, the particles have a good enrichment capacity of Cd2+that the concentrate rate is approximately10times, and for the Pb2+is merely not. However, they can't absorb the Ca2+, Cu2+and Zn2+in the aqueous solutions.3)4-Bromo-1,8-naphthalic anhydride were reacted with3-aminopropyltriethoxysilane firstly, then introduced to the surface of silica and coupled with N,N-Dimethylethylenediamine. The modified particles performed a good capacity adsorption of Pb2+in the aqueous. The Langmuir and Freunlich linear fitting showed that the absorb process is good fitted with the two isothermal model, the maximum linear correlation coefficients are0.9964and0.9479respectively, and the maximum adsorption capacity is293.26mg/g.Fourier transform infrared (FT-IR) spectra, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Thermogravimetric analysis (TGA) etc. were applied to characterize the surface of SNPs, which will powerful prove the processes of modification.