Preparation And Application Of Low-condensation Silica Particles And Mesoporous Silica Particles

Silica（SiO₂）nanomaterials have always occupied a very important position in the field of scientific research.Among them,mesoporous silica nanoparticles（MSNs）have their own structural advantages such as huge specific surface area,easy adjustable pore size and pore structure,good biocompatibility and chemical stability,so they have great research value and potential applications in biomedicine,catalysis field and environmental protection,etc.,and have attracted extensive attention from scientists.Through the unremitting research of scientific researchers,there are many options for the preparation of monodisperse SiO₂ particles and MSNs,but a simpler and gentler method for preparing low-condensation SiO₂ particles and MSNs need to be further studied.This paper analyzes the current research status of monodisperse SiO₂ particles and MSNs on the basis of extensive reading of the literature,and specifically explores the following aspects for the simple preparation and application of low-condensation SiO₂ particles and MSNs:（1）According to the theory of the"pre-Ouzo"effect in the non-surfactant microemulsion,the mixing method of the typical St?ber method is innovatively changed.Ultrapure water,tetraethyl silicate（TEOS）and absolute ethanol are formulated into a TEOS-H₂O-EtOH ternary mixed solution with a molar ratio of 124H₂O:1 TEOS:45.8 EtOH,the reaction system was detected using dynamic light scattering（DLS）,and the results showed that there are stable microemulsion droplets around 160 nm in TEOS-H2O-EtOH.Subsequently,different volumes of ammonia were added to catalyze the reaction.Transmission electron microscopy（TEM）and²⁹Si NMR showed that as the volume of ammonia increased,SiO₂ particles with the size of 140-320 nm were synthesized,the particle size and degree of condensation showed an increasing trend.When the volume of ammonia water is small,the SiO₂particles obtained have a low degree of condensation.Preparation of low-condensation SiO₂ particles is the key to mild and simple preparation of MSNs.（2）Innovative use of water dilution-ammonia etching combined method（referred to as dilution etching method）to process parent SiO₂ colloid to prepare MSNs with a particle size of 100-230 nm.Adjust the initial volume of ammonia water and the multiple of water used for dilution to explore the changes in the morphology of the parent SiO₂ particles.The research shows that the parent SiO₂ particles obtained when the initial volume of ammonia water is 0.3-1 mL can be etched into MSNs after being diluted to 5 times with water.And the SiO₂ particles obtained when the ammonia concentration is low,that is,the parent SiO₂ particles with low degree of condensation are more easily etched into MSNs.The SiO₂ particles obtained by the St?ber method will not be etched into MSNs,which also verifies from the side that the TEOS-H₂O-EtOH ternary system method has a lower degree of condensation than the St?ber method.（3）Innovatively changing the reaction environment and preparing SiO₂ particles using dialysis conditions for the first time.Utilizing the presence of osmotic pressure under dialysis conditions,the formation of SiO₂ particles can be accompanied by material dilution and ammonia etching at the same time,so MSNs can be obtained in one step.Explore the effect of changing the initial ammonia volume and the ammonia concentration in the dialysate on the obtained MSNs.The results show that the concentration of dialysate is the key to the formation of MSNs.The MSNs obtained at a dialysate concentration of 10%（v/v）of ammonia solution have a good morphology.（4）After the MSNs obtained by the two methods are subjected to amination treatment,the gold nanoparticles are loaded.A UV spectrophotometer was used to detect the change of characteristic peaks in the reaction of NaBH₄ to reduce4-nitrophenol（4-NP）to 4-aminophenol（4-AP）to verify the catalytic performance of Au@MSNs.The results show that both MSNs can be uniformly loaded with gold nanoparticles of 1-3 nm,and Au@MSNs exerts excellent catalytic performance in the experiment of reducing 4-NP to 4-AP by NaBH₄.