The Theory Studies Of The Interactions Between Glucose Oxidase Active Center And Carbon Nanomaterial Electrodes

Biofuel cells are the power generation devices of using enzymes ormicroorganisms group as a catalyst to convert chemical energy of fuel into electricity.Enzyme biofuel cells are attracting wide attention in recent years, of which usingglucose oxidase as anode catalyst and glucose as "fuel". Therefore, the theory study ofthe interaction between glucose oxidase activity center (flavin) and carbon nanomaterialelectrodes is very important to the development of biofuel cell.This work includes three parts：The first part is the theory study of the interaction between glucose oxidase activitycenter (flavin) and the surface of carbon nanotubes (sCNT). By using density functionaltheory, the reduction state, the half reduction state, and the oxidation state of flavininteracted with sCNT in different coupling modes, and the system is optimized in thetheory level of M062X/6-31+g(d). We analyzed the binding energy, electron clouddistribution, band gap, density of state and other properties concretely. Studies haveshown that the combination of flavin and sCNT is physical adsorption, van der Waalsforce plays the main role, and the electron cloud distribution is different when sCNTinteract with the different states of flavin. The adsorption of the reduction state of flavinis most conducive to the electron transfer between flavin and sCNT, second is the halfreduction state, the last is the oxidation state. The adsorption of flavin can make theelectrical conductivity of sCNT enhanced. The parallel coupling mode is better thanvertical coupling mode based on binding energy and band gap properties.The second part is the in-depth study on the basis of the first part. It is the theorystudy of the interaction between glucose oxidase activity center (flavin) and carbonnanotubes (CNT). The problem of the interaction between CNT and flavin in differentconformations were analyzed using ONIOM layered calculation method of which thehigh-level with the M062X/6-31+g(d) theoretical level and the low-level with theM062X/sto-3g theoretical level. We also calculated the properties of the binding energy,electron cloud distribution, band gaps, density of state, and compared them with the firstpart. Results show that it is same to the first part, the interaction between flavin andCNT is physical adsorption whether it is the parallel conformation, surroundingconformation or vertical conformation. The structure of flavin in the surroundingconformation changed and it is a butterfly shaped structure benting with CNT. Thedifference of conformations, the different redox states and the structure shape of flavin can make the distribution of the electron cloud change. In addition, combined with theresearch of the first part, we can know that the existence of carbon chain of flavin has alight effect on the interaction between flavin and carbon nanomaterial electrodes.The third part mainly studies the issue of the transition state. I try to find thetransition states of the interaction between flavin and glucose. And then consideredsCNT or CNT to participate in reactions, I explore the influence of them on theinteraction as well as the mechanism of proton/electron transfer reactions. Myinvestigations reveal that N-H distance decreases and C-H distance increases graduallyfrom the reactant, the transition state, to the product, a proton is transferred from the C1of glucose to the N5of flavin; The reactions between flavin and glucose is aproton-coupled double-electron transfer mechanism. It is a proton-coupled one-electrontransfer mechanism with the presence of sCNT or CNT. The presence of sCNT or CNTcan regulate the electron cloud distribution and promote the electron transfer, whichresult in the decrease of activation energy. Furthermore, When sCNT or CNT isparticipated in the interaction, the forward reaction activation energy is far less than thebackward reaction activation energy. Therefore, the forward reaction is more easily thanthe backward reaction. All these suggest that enzymes biofuel cell which using glucoseoxidase as catalyst, glucose as fuel and carbon nanomaterials as electrodes is feasible intheory.