Preparation And Catalytic Properties Of Dendritic Silicon-titanium Hybrid Nanospheres(DMSTNs)

Dendritic mesoporous silica nanospheres（DMSNs）possess unique three-dimensional center-radial channels and hierarchical pore structure,resulting in excellent surface area and pore volume.The structural advantage makes DMSNs widely used to load nano-sized guest species as novel carrier/delivery/reaction platforms.Previous studies have shown that DMSNs can load more nanoparticles than traditional MCM-41（Mobil Composition of Matters）and SBA-15（Santa Barbara）.As the research on DMSNs becomes more and more mature,dendritic mesoporous silica-titanium hybrid nanospheres have become the research object.Due to its large surface area,high mesoporosity,and excellent mechanical properties,it is very promising in the fields of catalytic luminescence,photohydrolysis for hydrogen production,and reduction of p-nitrophenol.In view of this,this study was based on DMSNs composed of pure silica and introduced titania particles to form dendritic mesoporous silica-titanium hybrid nanospheres（DMSTNs）.The specific research contents are:1.Black dendritic silicon-titanium hybrid nanospheres（b-DMSTNs）were prepared by a two-step post-grafting method.DMSNs have three-dimensional center-radiating channels with large specific surface area and pore volume,which can load or transport guest substances into the channels of DMSNs.Therefore,DMSNs have great application prospects as a carrier platform in the fields of catalysis,tumor therapy,and drug delivery.In this study,we adopted a facile method to introduce black Ti O_2-xnanoparticles into the central radial channel of DMSNs.Dendritic silicon-titanium hybrid nanospheres（DMSTNs）were prepared by coating with tetrabutyl titanate precursor and calcined in air.After reduction with Na BH4 under Ar atmosphere,the DMSTNs turned into black dendritic silicon-titanium hybrid nanospheres（b-DMSTNs）with Ti O_2-xparticles in the b-DMSTNs pores.The ether-catalyzed luminescence sensor based on b-DMSTNs was constructed and characterized by SEM,TEM,XRD,etc.The results showed that the nanomaterial has excellent morphology and uniform dispersion.Catalytic luminescence experiments showed that:based on b-DMSTNs,the response speed to diethyl ether was fast and the response signal was stable,and the relative CTL intensity was almost unchanged after seven repeated experiments.Under optimal conditions,the diethyl ether concentration was linearly related to the relative intensity of CTL,and its linear expression was y=2574x-114 and R²=0.9933.The sensor based on b-DMSTNs has good reproducibility for the detection of ether,and has great application prospects in the field of environmental monitoring.2.Magnetic dendritic silicon-titanium hybrid nanospheres（Fe₃O₄@DMSTNs）were prepared by hydrothermal synthesis,and the catalytic luminescence,such as sensitivity and selectivity,of ether based on Fe₃O₄@DMSTNs catalyst was studied.According to the experimental results,the mechanism of CTL was discussed.The results show that the nanomaterials have good selectivity to ether.At 440 nm filter,the optimal reaction temperature is 280℃,the optimal carrier gas flow rate is 270m L/min,and the relative CTL intensity has a good linear relationship with the ether concentration（y=8321x-28433,R²=0.9904）,the detection The limit was 1.5 m M（S/N=3）,and the relative standard deviation（RSD）was 2.6%（n=7）.Fe₃O₄@DMSTNs catalyzed the luminescence reaction.3.Dendritic nanospheres with unique three dimension（3D）center-radial channels possess excellent specific surface area and pore volume.Objects can be loaded into the nanochannels of dendritic nanospheres,developing novel carrier,delivery vehicle,or reaction platform.In the work,a novel kind of highly stable multifunctional composite material has been explored for the first time,i.e.,dendritic mesoporous silica（5）titania nanospheres（DMSTNs）supported gold（Au）nanoparticles.Even though DMSTNs have suffered series of chemical reactions and modifications,3D center-radial textures are still unchanged.Anatase Ti O₂and Au nanoparticles have been successfully decorated onto the channels.The as-prepared catalysts exhibit more outstanding multipurpose catalytic performances than those of a contrast sample,i.e.,dendritic mesoporous silica nanospheres（DMSNs）supported gold（Au）nanoparticles.Under simulated sunlight for splitting water,the amount of produced H₂and the corresponding rate are 210.01?mol·g^-1,ca.ten-folds of the contrast sample.Without light irradiation,the apparent kinetic constant of p-nitrophenol reduction by our catalyst is 2.150?10^-3s^-1,being about nineteen times than that of the reference(0.111?10^-3s^-1).4.With the purpose of energy development like photocatalytic water splitting for hydrogen production and environmental protection like organics degradation,supported noble metal catalysts have made considerable progress in terms of design,fabrication,and theory.Herein,dendritic mesoporous silica nanospheres（DMSNs）were first utilized as the supports due to their specific morphology and structure.Ti O₂nanoparticles（NPs）were introduced into their channels via sol-gel method,developing dendritic mesoporous silica&titania nanospheres（DMSTNs）.Amino group（-NH₂）was then grafted onto DMSTNs surfaces by organic modification technology.Finally,ultrasmall gold（Au）NPs were anchored onto the as-prepared DMSTNs-NH₂through impregnation method and sodium borohydride（Na BH₄）reduction.DMSTNs supported Au NPs catalysts could be successfully constructed,as verified by scanning electron microscope,transmission electron microscopy,X-ray photoelectron spectroscopy,and Fourier transform infrared reflectance spectroscopy.Under simulated sunlight for splitting water,the amount of produced H₂by the brand-new catalysts and the corresponding rate are 69.08μmol·g^-1and 13.82μmol·g^-1·h^-1,ca.seven times of the contrast sample（DMSNs supported Au NPs）.Without light irradiation,the apparent kinetic constant of p-nitrophenol reduction by our catalysts is 6.540?10^-3s^-1,being about seventeen times than that of the reference(0.372?10^-3s^-1).All in all,DMSTNs supported Au NPs exhibit more superior multifunctional catalytic activity.