Calculation Of The Interface Interaction Between Biomass Cellulose And Zinc Oxide Nanocluster Particles

Biomass is a kind of abundant renewable resource,whose rational utilization and development is of significant importance to solve issues of energy shortage and environment pollution.In-depth understanding of interfacial behavior between biopolymer and semiconductor metal oxides is crucial to developing potential applications of their composites.In this thesis,structural and interfacial properties of binary and ternary composites containing cellulose,ZnO and g-C₃N₄ were systematically studied by relativisitc density functional theory?DFT?and experiment.Firstly,a structure-ordered cellulose/ZnO binary composite was prepared by a simple hydrothermal method,together with various properties calculated by DFT.The experimental characterization shows that the newly-synthesized material exhibits overall multi-level composite structure,where the primary structural unit is composed of ZnO nanoparticles with an average particle diameter of about 30 nm uniformly grown on cellulose.The all-electron relativistic calculation based on the molecular model reveals that the electrostatic attraction between cellulose and ZnO is the main driving force for the formation of the primary structure,while the electron transfer from cellulose to ZnO in the formed complex enhances the interface interaction and stabilizes the system.The interfacial interaction between cellulose and ZnO is mainly contributed by the chemical bond of Zn-O_c?O_c is the oxygen atom in cellulose?;Zn-O_c is a dative bond per sur;and the calculated interfacial interaction strength falls within-1.39^-1.83eV,which is dominated by orbital attraction.Secondly,we explored effects of hydrogen position originally binding to cellulose on structures and interfacial behavior of the newly formed cellulose and zinc oxide complex.DFT optimizations find energetically stable isomers,which are classified as three types according to hydrogen atom location:hydrogen atom?s?are retained on the cellulose?labeled HR?,transfered to the ZnO part?HT?,and dissolved into water?HD?.It is found that different hydrogen location directly changed electron structures of the complex,for instance,narrowing HOMO-LUMO band gap along HR?HT?HD.In addition,in the series the interfacical interaction was gradually enhanced,which was reflected in shortened Zn-O_c distances,increased QTAIM topological parameters?absolute value?,raised electron transfer amount from cellulose to ZnO,and increased interfacial interaction energies?absolute value?.Finally,structures and interfacial properties of the cellulose/ZnO/g-C₃N₄ ternary composite were theoretically calculated.We find that N?Zn dative bond mainly contributes to interfacical interaction,while O-N and O-C couplings are very small.The time-dependent density functional theory was used to calculate spin-allowed excited states of the complex.The chemical coupling between ZnO and g-C₃N₄ extended electronic absorption of the complex to the visible region.It provides theoretical support for the complex that may be applied as a photocatalyst.