Electrochemical Characteristics Of Gold Microarray Electrode And Its Application In Microbial Fuel Cells

As a kind of new fuel cell technology,microbial fuel cells(MFCs)can convert chemical energy directly into electrical energy used microorganism as catalyst,which showed wide application prospect in organic wastewater treatment,environmental bioremediation,biosensor and et al,and gradually has caused wide attention of research workers in the past ten years.Particularly as a biosensor,MFCs has emerged in the field of biochemical analysis such as the determination of biochemical oxygen demand,toxic substances,microbial quantity and metabolic activity.Electrode is the important component section of MFCs,and its property could directly influence on the performance of MFCs.In order to improve the adhesion and electron transfer between electrochemically active bacteria(EAB)and electrode surface,scientific research workers have made extensive and profound studies on the material and structure of electrodes in MFCs.Gold microarray electrode is composed by many gold microelectrodes in parallel prepared by ultra-violet lithography technology.And it could not only keep the excellent electrochemical characteristics of single microelectrode,which including advanced steady state current density,very short response time,high rate of mass transfer and et al,but also amplify the detection signals by parallel gold microelectrode.What is more,gold microarray electrode also could achieve the manipulation of microorganism by designing special electrode structure,controlling the liquid flow velocity,adding the external electric field and et al,which makes it become a very effective research tool in the field of electrochemistry and biology.In this study,it was the first attempt to apply gold microarray electrode into the study of MFCs,and the main contributions of this thesis are described as follows:1.The extended Derjaguin-Landau-Verwey-Overbeek(DLVO)theory was introduced to analyze the adsorption behavior of electrochemical active bacteria on the microarray electrode.So far,classical DLVO theory is a kind of relatively perfect theory to explain colloid stability.And extended-DLVO theory has developed to explain the adsorption phenomena between bacteria and solid surface by introducing Lewis acid-base forces based on classical DLVO theory,which is the most comprehensive analysis of the free energy of short term interactions between bacteria and substrate.In this study,it had been done to make an analysis and prediction of the adhesion between EAB and the surface of gold microarray electrode,and it had successfully explained why EAB formed diverse biofilm on different substrate which was as a support layer of gold microarray electrode,which also could provide theory support in the application of MFCs using gold microarray electrode.As a result,gold microarray electrode on substrate of polymethyl methacrylate(PMMA)made EAB form loose and instability biofilm on it because of its high repulsion barrier,on the contrary,EAB form dense and stability biofilm on gold microarray electrode on substrate of glass because EAB could overcome the low repulsion barrier.2.The electrochemical characteristics of gold microarray electrodes were studied to understand the influence of different substrates on the electrochemical behavior of gold microarray electrodes.Gold microarray electrode usually needs substrate as support layer during micromachining process,and different substrate could impact electrochemical response of gold microarray electrode.In this study,potassium ferricyanide solution was used to investigate electrochemical catalytic activity of gold microarray electrode,it was discovered that gold microarray electrode on PMMA and glass showed similar electrochemical catalytic activity,better than gold plate electrode with the same surface area.Then riboflavin,a kind of redox mediator secreted by EAB during the process of the electrons transfer,was treated as studied object.The electrochemical response of riboflavin on the surface of gold microarray electrode was investigated by cyclic voltammetry,and the influence of different substrate during the process of electrochemical response was discussed.It was found that gold microarray electrode on substrate of PMMA and glass were controlled by the process of adsorption and diffusion respectively.It means that different substrate materials could influence the electrochemical response of riboflavin on the surface of gold microarray electrode.3.The current output and stability of MFCs constructed with a microarray electrode anode were observed to study the influence of the microarray electrode on the electric performance of MFCs.Compared with other conventional meso-MFCs,the MFCs constructed with a microarray electrode anode in this study had the advantages of short start-up time and quick recovery,especially using gold microarray electrode on substrate of PMMA.Combined with the aforementioned theoretical and experimental analysis,this result was related with the adsorption of riboflavin on PMMA and the loose and instability EAB biofilm.The gold microarray electrode prepared by micro-machining technology was suitable for MFCs research due to its excellent electrochemical properties and controllable and changeable electrode structure.It was helpful to improve the performance of MFCs by deeply understand of EAB adhesion on the surface and its electron transfer mechanism.In this study,the influence of gold microarray electrode on improving the electric performance of MFCs was investigated,which was helpful to further understand the adhesion behavior of EAB on the electrode surface and its electric generation mechanism,and provide research basis for future application of gold microarray electrode in MFCs at macro and micro scales.