Redox Rectification And Electrochemiluminescence Imaging Of Micro/Nanoporous Electrode Ensembles

The micro-/nanoelectrode has the advantages of high mass transfer rate,fast steady-state response,short response time,small size,and etc.It has become an indispensable tool in the study of electrode reaction kinetics,microsystem process,life analysis and so on.In addition to retaining the unique properties of the micro-/nanoelectrode,the micro-/nanoelectrode ensembles can provide a larger current signal and even larger-scale spatial resolution information due to its larger electrode area.Micro-/nanoporous electrode arrays are a type of micro-/nano electrode ensembles,which can be prepared either by directly physically/chemically partitioning large electrode surface or by embedding electrodes in micro-/nanochannels or micro-/nanoporous templates.Because of their microporous structure,micro-/nanoporous electrode arrays are widely used for antifouling electrochemical analysis,molecular selective electrochemical analysis,redox cycling signal amplification,cascade reaction and many other fields.The selectivity of traditional electrochemical analysis mainly depends on the functional modification of electrode surface or the electrochemical characteristics of molecules themselves.It is the same for the electrochemical analysis using micro-/nanoelectrodes.On the other hand,traditional electrochemical analysis focuses on the measurement of electrical signals（such as current,potential and impedance）.These signals reflect the collective response of whole electrode surface,lacking of spatially resolved information and failing to reveal contribution and difference of local electrode surface or individual electrode of ensembles.How to improve the selectivity and spatial resolution of electrode response signal remains to be one of the scientific and technical concerns in the field of micro-/nanoelectrode electrochemistry.This thesis focuses on this issue.The thesis is divided into four chapters.The first chapter briefly introduces the basic theory of micro-/nanoelectrodes,mainly including the theory of electrical double layer（EDL）and diffusion.Subsequently,the preparation methods of micro-/nanoelectrode ensembles are summarized.Finally,the analytical application of micro-nano array electrodes is overviewed.In the second chapter,silica nanochannel membrane（SNM）consisting of uniform and vertically ordered channels was prepared on the indium tin oxide（ITO）electrode surface using the st（?）ber-solution growth approach.The modified electrode is equivalent to a nanopore electrode ensembles.Subsequently,the ferrocene molecule was modified at the bottom of the nanochannel（namely,the surface of the ITO electrode）to obtain functionalized electrode.Given the size of silica nanochannels is extremely small（2-3 nm in diameter）and the channel wall is negatively charged（due to deprotonation of surface silanol groups）,the functionalized electrode has strong selective permselectivity for charged ions.The entry of anions(such as Fe（CN）₆^4-and Ir Cl₆^2-)into the nanochannel depends on the ionic strength of electrolyte solution.Anions enter into the nanochannels and interact with ferrocene to produce rectification effect at a high buffer concentration（>10 m M）.In addition,based on the difference in the relative redox potentials of Fe（CN）₆^4-（+0.25 V）,Ir Cl₆^2-（+0.73 V）and ferrocene molecules（+0.30 V）,an electrochemical rectifier with potential selectivity was constructed.In the third chapter,polycarbonate（PC）films with micropore and nanopore was employed as templates to prepare microtube electrode ensembles and nanotube electrode ensembles via the electroless deposition（also called chemical deposition）.Subsequently,electrochemiluminescence（ECL）imaging was performed to visualize and resolve spatially the electrochemical signal of individual pore electrodes.Meanwhile,the mechanism of ECL generation by tris（2,2’-bipyridyl）ruthenium（II）([Ru（bpy）₃]²⁺)/tri-n-propylamine（TPr A）can be rationalized.The results show that we have successfully realized the signal resolution of ensembles electrode.In addition,compared with the"the direct oxidation route"electrochemiluminescence,the electrochemiluminescence layer thickness in"the catalytic route"is larger.In the fourth chapter,above two works were summarized and future work in the field was proposed.