Designed Synthesis And Properties Of Mesoporous Organosilica Hybrid Nanomaterials

Since the class of M41S materials was synthesized in 1992,mesoporous silica materials have received particular attention.Due to nano-scaled size,unique pore structure and hydrothermal stability,mesoporous silica nanomaterials have been widely employed in different fields.Mesoporous organosilica hybrid nanomaterials combine the characteristics of both organic materials and inorganic mesoporous materials?such as high surface area,large pore volume,uniform and tunable pore structure,easily modified inner/outer surfaces and the organic/inorganic components homogeneously distributed over the whole framework?,and have potential application in many fields including biomedicine,dyes loading and release,catalysis and so on.In this work,we have concentrated on fabricating novel mesoporous organosilica hybrid nanomaterials via two kinds of different pathways: 1)synthesize novel mesoporous organosilica nanomaterials with different morphologies and pore structures by the use of simple ethyl bridging bissilylated organosilica precursors,2)synthesize novel organo-functionational mesoporous silica nanomaterials by the co-condensation of corresponding silica and organosilica precursors.The major achievements are described as following.A facile and controllable asymmetrical/symmetrical coating strategy is developed for the preparation of various novel periodic mesoporous organosilica?PMO?nanostructures,including Au&PMO Janus,Au@PMO yolk-shell and Au@PMO/m SiO₂ yolk-double shell nanoparticles,by using Au@SiO₂ nanoparticles as seeds.During this process,firstly,ammonia functionalizes as a basic catalyst facilitating the hydrolyzation and condensation of the organosilica precursor,additionally as an etching agent,it selectively in-situ dissolves the SiO₂ shells of Au@SiO₂ nanoparticles to form these unique nanostructures.All these three types of nanoparticles have high surface areas,large pore volumes and tailorable cavity structures.Both the Au&PMO and Au@PMO nanoparticles exhibit excellent catalytic activity for the decomposition of H₂O₂ and the reduction of 4-nitrophenol.Because of these unique structural merits and organic-inorganic hybrid components,the fabricated Janus and hollow PMO nanoparticles show much improved hemocompatibility,which could be further applied in nano-biomedicines without the need of surface modification.Transformation from single-mesoporous to dual-mesoporous structured organosilica nanoparticles can be achieved by varying the volume fraction of ethanol in the synthesis system,using lauryl sulfonate betaine and sodium dodecyl sulfonate as dual-templates.Core-shell structured dual-mesoporous organosilica nanoparticles possess smaller mesopores?4.0 nm?in the shell and larger flower-like mesopores?46 nm?in the core.Owing to the unique mesostructure,dual-mesoporous organosilica nanoparticles show high loading capacity and slow release rate for cargo molecules.The inside large mesopores can provide large storage space for the cargo molecules and small mesopores in the outer shell act as nature valve,slowing the cargo release.In addition,both single-mesoporous and dual-mesoporous organosilica nanoparticles exhibit low cell toxicity and excel ent cell permeability.A simple and generalizable sprout-like growth method is established for the facile synthesis of Janus mesoporous silica nanostructures with organic-inorganic hybrid components.The process uses periodic mesoporous organosilica?PMO?nanoparticles as seeds,while mesoporous SiO₂ branches grow on the PMO surface.The morphology of Janus nanostructures with different lengths and numbers of SiO₂ branches can be easily controlled by varying the tetraethoxysilane concentration in the synthesis system.The Janus nanostructures are also easily modified with different SO₃ H and NH₂ groups on the SiO₂ branches and PMO cores,respectively,and the bifunctional Janus nanoparticles exhibit excellent catalytic performance in the deacetalization-Henry cascade reaction.Using simple yolk-shell nanoparticles as substrates,we successfully synthesized multifunctional megranate-like nanoparticles,consisting of multiple metal cores and thiol modified mesoporous SiO₂ shells.Different metal nanoparticles?Pd,Pt,Au?can be incorporated into the structure as cores in our synthesis process,and the thiol groups in the shells can be oxidized to acidic-SO₃ H groups.Different from simple yolk-shell nanoparticles,megranate-like nanoparticles possess a unique structure,megranate-like nanoparticles can combine the properties of each component and be used as nanoreactors.The megranate-like nanoparticles exhibit good bifunctional catalytic properties and recyclability in a cascade catalytic reaction for the desired benzimidazole derivative.Moreover,the individual components of the megranate-like nanoparticles also show good catalytic activities in the hydrogenation reduction of nitro-aromatics and the deprotection reaction of benzaldehyde dimethyl acetal.