The Fabrication,Ananlysis And Application Of Nano-Cu₂O And Plant Tissue Based Enzyme Electrodes

In this thesis, it includes the fabrication of Cu2O and its modified electrodes, photoelectrocatalytic degradation intermediates electroanalytic application, and the plant tissue based biofuel cells and nanomotors. Nano-CU2O were fabricated from new system Cu (Ⅱ)-citrate using pulsed electrodeposition and solution reduction method, respectively. The structures, compositions, sizes and morphologies were characterized by using some techniques such as X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The photoelectrochemical properties of CU2O were characterized by light switch open circuit potential (OPC-t) experiments. The photoelectrocatalytic performance of Cu2O nanoparticles for p-nitrophenol (pNP) was studied using rotating ring-disk electrode (RRDE). In addition, the plant tissue based biofuel cells made with banana pulp and potato tissue micromotors were developed. The main contents are as follows:1. Preparation of flower-like Cu2O nanoparticles and their electrocatalytic applicationPulsed electrodeposition technique was employed for preparation of highly dispersed flower-like CU2O nanoparticles from Cu (Ⅱ)-citrate solution. The morphology analysis of the particles using SEM reveals that the flower-like particles were from sequential growth of Cu2O along the (111) direction on the cubic Cu2O (100). The structure and the chemical composition of the deposits were characterized by XRD and XPS. Optical property and band gap of the Cu2O was investigated using UV/vis diffuse reflection spectra (DRS). The dark and light open circuit potential-time characterization study showed that the flower-like Cu2O nanoparticles exhibited good photoelectric response. Cyclic voltammetry carried out in the presence of p-nitrophenol (pNP) shows that the electrocatalytic performance of the CU2O particles for the reduction of pNP. The influence of the incidence of light on the electrocatalysis is also discussed.2. Investigation of photoelectrocatalytic degration behavior of Cu2O nanoparticles for pNP using Cu2O modified RRDE Cu2O nanoparticles were obtained by reducing the copper-citrate complex with hydrazine hydrate (NaH4·H2O) in a template-free process. A Cu2O nanoparticles modified Pt RRDE was successfully fabricated, the hydrodynamic differential pulse voltammetry (HDPV) technique was applied for in situ monitor the photoelectrochemical behavior of pNP under visible light. pNP undergoes photoelectrocatalytic degradation on nano-Cu2O modified disk to give electroactive p-hydroxylamino phenol species which is compulsive transported and can only be detected at ring electrode at around0.05V with oxidation signal. This signal can be used for the electrocatalytic determination of pNP. The effects of illumination time, applied bias potential, rotation rates and pH of the reaction medium have been discussed. Under optimized conditions for electrocatalytic determination, the anodic current is linear with pNP concentration in the range of1.0×10-5to1.0×10-3M, with a detection limit of1.0×10-7M and good precision (RSD=2.8%, n=10).3. Template-free Fabrication of Nano-sized Cu2O Hollow Spheres, Sheets and Octahedrons and their Morphology-dependent Semiconductor TypeNano-sized cuprous oxide (Nano-Cu2O) materials with different morphologies such as hollow spheres, two-dimensional (2D) sheets and octahedrons were synthesized using a simple hydrothermal method in a Cu-citrate complex solution by making small adjustments to the solution’s pH value under alkaline conditions. The morphology and crystalline features of the Cu2O was observed using XRD, SEM and HRTEM. The formation mechanism is associated with localized Ostwald ripening. The photoelectrochemical experiments showed that the hollow Cu2O structure synthesized under a pH range of8-11exhibited n-type semiconductor characteristics. Alternatively, solid octahedral Cu2O formed in the presence of strong alkaline conditions (i.e. pH greater than or equal to12) and exhibited p-type behavior.4. High-Power Low-Cost Plant Tissue-Based Biofuel CellThe banana tissue rich with polyphenol oxidase (PPO), an enzyme able to reduce oxygen to water, which can be used as catalyst for the biocathode. We demonstrate the first example of using plant tissues for the operation of biofuel cells (BFC), the banana modified carbon paste electrode as biocathode and glucose dehydrogenase (GDH) as bioanode. Meldola’s blue (MDB) were used as anode mediator, while the phenolic constituents of the banana serve as mediator for PPO. The maximum power output and open circuit voltage (OCV) of the banana-based tissue biofuel cell were57μW/cm2and0.46V, respectively. Cost analysis of this tissue biofuel cell system indicates dramatic improvements in terms of the power-output/dollar compared to the use of pure enzyme tryosinase (166502μW/＄vs.17.8μW/＄, i.e.,9354times improvement). The banana-based biofuel cell displayed an extended lifetime of over2weeks. We also demonstrate a fuel-free full plant-tissue based BFC concept, combining the banana biocathode with a bioanode based on germinated tomato-seeds that contain alcohol dehydrogenase (ADH), NAD+and ethanol.5. Self-propelled chemically-powered plant-tissue biomotorsSelf-propelled biocatalytic motors based on plant tissues are described. The potato, carrots and millet motors were developed. The tissue motors rely on their rich catalase activity towards biocatalytic decomposition of the H2O2fuel and generation of the bubble thrust. Compared with the pure enzyme (catalase) biomotors, these biomotors obviate the need for pure enzymes, and offer a remarkably low cost, good lifetime, good biocompatibility and thermostability.