Bioinspired Cu2O Nanowire Mesocrystals Hybrid Materials and Its Biocatalytic Properties

Author:Li Ga Long

Supervisor:fan hai ming luo yan e


Degree Year:2019





Mesocrystals are ordered mesoscale superstructures,composed of inorganic nanoparticle building blocks and organic stabilizing agent,formed by bottom-up approaches through a nonclassical crystallization process.Mesocrystals exhibit large specific surface area,ordered porous structure and high crystallinity.Cu2O nanowire mesocrystals(NWMCs),which possess well-defined octahedral morphology and high-porosity architecture with anisotropic interpenetrating nanowires,have attracted considerable attention owing to their superior physical and chemical properties.However,the current synthetic approach for NWMCs using graphene oxide(GO)as a modifier leads to uncontrollable products and low productivity(30%),which largely hinder their further applications.In this work,we report a novel synthetic approach for controllable and large-scale synthesis of NWMCs.And the mesocrystal has further been studied as nanozyme and enzyme immobilizing carrier.1.Large-scale synthesis of NWMCs and their superior peroxidase-like activity:We report a modified synthetic approach for controllable and large-scale preparation of NWMCs using perylene-3,4,9,10-tetracarboxylic dianhydride(PTCDA)molecule as a modifier.The effects of growth time and initial solution pH on the morphology of final products have been systemically investigated.Under the optimal reaction condition with initial pH of 5.3,reaction temperature of 180 oC and reaction time of 15 hours,the well-defined octahedral NWMCs can be obtained with a productivity as high as75%,2.5times than that of early reported method using GO modifier.In addition,this method can be scaled up from 50 mL to 500 mL autoclave without significant changes in morphology of the products.The ability of high productivity and reproducibility in synthesis of NWMCs enables us to further study their peroxidase-like activity by catalyzing the oxidation of o-phenylenediamine(OPD)in the presence of H2O2.The NWMCs exhibit a superior catalytic activity with the Kcat of 1.14×10-2,10 times higher than that of native horseradish peroxidase(HRP).Moreover,the NWMCs can also retain 69.5%of their initial activities after 10-batch redox reactions.Our results provide a facile approach to controllable and large-scale synthesis of NWMCs using homogeneous PTCDA molecule modifier and open up opportunities to use NWMCs as nanozyme for future industrial application.2.Bioinspired laccase-NWMCs hybrid materials(LAC-NWMCs)and its biocatalytic activity:Laccase was immobilized on NWMCs via EDC/NHS reaction.The effects including enzyme loading amount,temperature and pH were studied.When pH of solution is 3 and the temperature is 50?C,the LAC-NWMCs obtained the highest enzyme activity.The enzyme and nanobiocatalyst activities of the obtained hybrid material exhibited the approximate 10-fold(specific enzyme activity)and 2.2-fold(specific bionanocatalyts activity)increase than the free enzyme,surpassing the currently available nanobiocatalysts.Compared with the free enzyme,the LAC-NWMCs have shown the improved stability and reusability,which can retain 70%of their initial activities after 10-batch reactions.3.The mechanism of enhanced enzymatic activity of LAC-NWMCs:The LAC-NWMCs hybrid materials were developed with a superior catalytic activity inspired by natural biocatalysis processes in living cells that highly resemble the metal ions activation and the well-organized spatial structure of the natural rough endoplasmic reticulum.The ultrahigh catalytic activity is ascribed to the unique features of NWMCs,which vividly imitate the characteristics of the rER biomachinery,such as by a well-organized spatial structure and environment-responsive Cu+/Cu2+ion-regulated enzyme activity.4.Biodegradation of 2,4-dichlorophenol(2,4-DCP)by LAC-NWMCs:Encouraged by the promising catalytic activity of LAC-NWMCs,we exploited their potential in the catalytic biodegradation of 2,4-DCP,phenol,m-cresol,and epinephrine,all of which are representative hazardous contaminants of industrial wastewater.The final biodegradation ratio of 2,4-DCP,phenol,m-cresol and epinephrine at 10 h are up to85.94%,92.16%,81.53%,and 85.09%respectively,which is 4.34,2.09,2.50 and 2.16times than that of free LAC.The comprehensive catalytic performance of the hybrid materials has been further demonstrated using a prototype continuous-flow reactor for the bioremediation of 2,4-DCP-contaminated water,which showed a high degradation efficiency and remarkable reusability.The reactor in this condition could remove 99.17%of the residual 2,4-DCP in one cycle,the efficiency went down to~74.82%after 10 cycles.The reactor regained its efficiency,up to 96.32%by automated LAC refilling and reconjugation to NWMCs.The wastewater bioremediation experiment using a continuous-flow reactor further demonstrates the outstanding performance of LAC-NWMCs including a superior catalytic efficiency,high stability,and feasibility to be recycled and scaled up,all of which are desirable for sustainable industrial chemical process.These new highly efficient nanobiocatalysts are expected to be used for diverse applications in biotechnology,biosensing,and environmental remediation.