Preparation Of Functionalized Mesoporous Silicon-based Materials And Their Drug-Loading And Catalytic Performances

Mesoporous silicon-based materials can be employed to prepare drug carriers,catalysis materials,and other functional materials due to its high surface area,various pore structures,facile surface functionalization and good adsorption abilities for many molecules in pores and surface.Thus,the mesoporous silicon-based materials have great potential applications in sensor,adsorption and desorption,drug delivery and industrial catalysis.As a kind of biocompatible materials,mesoporous silica nanoparticles(MSN)has been widely applied for the synthesis of various stimuli-response drug carriers.Acid-response system was considered as the most widely studied endogenous stimuli-response system.However,the current methods for linking small molecular acid-response group and MSN have the issues of harsh synthesis condition and low efficiency.Therefore,in this thesis,acid-response drug delivery carriers were synthesized by organic grafting on MSN surface using click reaction as a mild linking method.The relationships between the structure and its release profiles were studied,and an efficient drug delivery system was constructed.The main work is summarized as follows:1.Doxorubicin(Dox)was used as a model drug,the azide-alkyne cycloaddition Click reaction was utilized as the linking method,and 2,3-dimethylmaleic anhydride was employed as the acid-response group to synthesize Dox-MSN drug carrier.N2 adsorption and desorption(N2-BET),X-ray diffraction(XRD),fourier transform infrared radiation(FT-IR)spectroscopy,and transmission electron microscope(TEM)were used to characterize the structure and properties of Dox-MSN.The release kinetic profiles,cell viability analysis and cell uptake behaviour were also studied.The results indicate the successful conjugation between acid-response Dox prodrugs and the surface of MSN by azide-alkyne cycloaddition Click reaction.Under the acidic pH conditions(pH=4.0 and 5.0),this drug carrier could release the active pharmaceutical ingredient.The cumulative release fraction increased with the increase of acidity.Under normal plasma pH conditions(pH=7.4),doxorubicin was barely released.The Dox-MSN showed the almost equivalent ability to inhibit the cell growing with Dox and could be engulfed by tumor cells and release doxorubicin.2.Campothecin(CPT)was used as a model drug,the thiol-ene Click reaction was utilized as the linking method,and the silyl ether was employed as the acid-response group to synthesize the CPT-MSN drug carriers.The release rate was regulated by altering the steric bulk of the substituent on the silicon atom.The structures of as-synthesized two different drug carriers(MSN-Me-CPT and MSN-Et-CPT),were characterized by 13C nuclear magnetic resonance(13C-NMR),X-ray photoelectron spectroscopy(XPS),thermal gravimetric analyzer(TGA)and FT-IR.The release kinetic profiles,cell viability analysis and cell uptake behaviour of these two drug carriers were also studied.The results exhibited that two acid-response groups and camptothecin were successfully tethered to the surface of MSNs by thiol-ene Click reaction.Under pH=4.0 condition,camptothecin was released from both MSN-Me-CPT and MSN-Et-CPT.Moreover,camptothecin was completely released from MSN-Me-CPT within 1 h,but the release of camptothecin from MSN-Et-CPT started after 2 h and completed after 6 h.However,under pH=7.4 condition,both types of camptothecin-loaded carriers did not release the model drug.Both types of the CPT-MSN showed the almost equivalent abilities to inhibit the cell growing with CPT and could be engulfed by tumor cells and release camptothecin.Finally,the control on the drug release rate of mesoporous silicon nanoparticles based on acid-response was achieved.On the other side,metal doped mesoporous silicon-based materials were utilized for various catalytic reactions.However,the studies on synthesis of mesoporous Silicalite-1 and metal doping functionalization by steam-assisted method were lack of the cognizance on the influence of different synthesis conditions and different metal doping functionalization.Therefore,in this thesis,Co and Cu doped mesoporous Silicalite-1 was synthesized by steam-assisted preparation;the regularity of metal doping under different synthesis conditions was explored;the catalytic activity of the catalysts for biomass conversion was evaluated;the relationship between structure and catalytic activity was studied,and a preparation method for efficient catalyst with controllable active sites was established.The main work is summarized as follows:1.Co-doped Silicalite-1 catalyst was synthesized by steam-assisted preparation and applied for the conversion of fructose to methyl lactate under near-critical methanol conditions.The properties of the catalysts with different Co loadings were characterized by Raman spectrum,extended X-ray absorption near edge structure(EXANES),XRD,TEM.The catalytic activities of these different Co loading catalysts were evaluated.The optimization of reaction conditions and the stability of the best catalyst were also investigated.The results revealed that the Co@Silicalite-1 with 1.21 wt%Co loading showed the highest catalytic activity,in which the Co was well dispersed and doped into the Silicalite-1 framework with strong covalent interaction.The MlA yield was52.0%at 180 ? for 18 h over Co1.21,and the catalyst exhibited good reusability after.calcination treatment.The Silicalite-1 framework of the catalyst with a Co loading of 6.50 wt%was incomplete,due to the formation of Co3O4 from the dehydration of precursor during preparation.Therefore,its catalytic activity was low.2.Highly dispersed CuO-doped Silicalite-1 was synthesized using ammonia hydroxide to precipitate the Cu precursor based on the synthesis method of Co@Silicalite-1 and applied for the in-situ hydrogenation of furfural(FAL)to furfural alcohol(FOL)under near-critical ethanol conditions.The properties of different Cu-based catalysts were characterized by XRD,TEM,TGA.The catalytic activity,reusability and the optimization of reaction conditions were also studied.The results exhibited that the copper in the as-synthesized catalyst was CuO with a loading of 1.48 wt%,and highly dispersed inside the pores of Silicalite-1 after introducing the ammonium hydroxide.Its catalytic activity was much higher than that of Cu@Silicalite-1,whose copper was well dispersed and doped into the Silicalite-1 framework with covalent interaction.The yield of FOL reached 88%with the conversion of FAL reached 91%at 240 ? after 1.5 h with CuO@Silicalite-1,and the catalyst exhibited good reusability after calcination treatment.