Microwave-assisted Synthesis Of Nano-zeolite And Its Biological Applications

Compared with the traditional zeolites,nanosized zeolites(nanozeolites) exhibit shorter intracrystal nanochannels and much larger external surface area,which not only results in the shorter diffusion pathlength to decrease the probability of coking, but also supplies more exposed active sites to extend their catalytic performance. Furthermore,the physicochemical properties of nanozeolite surface,including the size, morphology,surface potential,modified organic group,also influence the application of nanozeolite on the area of biology.All of these emphasize the importance and necessarily to synthesize nanozeolites with controllable size,morphology and other surface properties.To achieve the goal,in this thesis,we study the parameters influencing the properties of nanozeolite in the synthesis process and summary the rules.We also choose proper model proteins to study their adsorption on nanozeolites with different sizes,plans and modified organic groups,which help us to understand the interaction of nanozeolite with proteins.Firstly,a microwave-assisted two-step hydrothermal procedure was proposed successfully to prepare various zeolite nanocrystals(e.g.,silicalite-1,ZSM-5,LTL, BEA and LTA) with controllable size,morphology and SiO₂/Al₂O₃ ratio.The effects of the starting gel composition(such as water content,alkalinity and ratio of SiO₂/Al₂O₃) as well as the hydrothermal synthesis condition(temperature and time) on the size of the zeolite nanocrystals have been studied in detail.It is found that high synthesis temperature and long reaction time benefit the growth of all the referred zeolite nanocrystals.However,the effects of the gel composition are very complex to different kinds of nanozeolites.These results would provide a solid foundation to fully exploit the traditional and untraditional applications of various nanozeolites.Secondly,the nanozeolites LTL with different exposed crystal planes and sizes were synthesized as an excellent model material to study the effects of crystal plane and size of nanozeolite on the protein adsorption behaviors.A larger protein adsorption amount is observed on the smaller nanocrystals due to their larger surface area and surface charge density.More importantly,it is found that the(001) crystal plane with 12-membered ring channel array has a larger contribution for protein adsorption on zeolite LTL nanocrystals than other two dimensions with very small pore-opening(1.5 (?)).It is proposed that the protein adsorption difference of the different crystal planes could be attributed to abundant exposed pore-opennings on the top(bottom) surface and curved surface of the side surface in columned nanozeolites LTL.This fact exhibits that topography at the nanoscale is also an important factor determining protein adsorption on the surface of nanozeolites,and new efforts in the future should be focused on synthesis of nanozeolites LTL with abundant exposed(001) planes. This observation will provide a new view for the bioapplication and design of crystalline nanomaterials.At the end of this thesis,a microwave assisted synthesis method is applied to in-situ prepare ZSM-5 nanozeolites with different organic groups including NH₂,SH, CN and CH=CH₂.It is found that,the in situ synthesized nanozeolites were comprised of aggregates of primary units with size even below 20 nm,which results in the supermicropore and the increase of surface,porous volume of nanozeolites.We also study the adsorption of model proteins(BSA,Myoglobin and Lysozyme) on all the modified nanozeoltes to find the influence of the organic groups on the nanozeolite surface.And the interaction between the organosilyl groups and the silanol species is mainly through RSi(OSi_zeolite)₃.The huge amount of protein adsorption on the surface of ZSM-5-SH,indicate the strong interaction forming disulfide bonds between SH groups of nanozeolite surface and BSA proteins.