Investigation On Amperometry Enzyme Biosensors For Phenolic Compound Based On Signal Amplification

Phenolic compounds have been widely found in industrial wastewater generated by modern industrial fields such as textiles,pesticides,dyes,petrochemicals and pharmaceutical industries,causing pollution of rivers and groundwater.Various kinds of analytical techniques have been available for the detection of phenol,such as chromatography-mass spectrometry,high performance liquid chromatography,and colorimetry,etc.However,these methods usually required expensive apparatus,time-costing and tedious pretreatment procedures.Electrochemical enzyme biosensors,especially amperometric enzyme biosensors,were widely used in the detection of phenolic compounds in view of its selectivity,sensitivity,and response speed.However,single amplification with enzyme reaction alone was often not sufficient for detection of a trace target.Therefore,it was necessary to introduce one or two chemicals to form redox cycle through coupling with the enzymatic reaction resulted in signal amplification of electrochemical detection.The mechanism was as follows:after the electroactive molecule donated electrons on the electrode,it was regenerated by accepting electron from the introduced redox cycle system,so that each molecule generated a large amount of electronic signals through several recycling.Therefore,the redox cycle system as a signal amplification strategy could improve the analytical performance of the electrochemical enzyme biosensor.In this work,multi-signal amplification strategy was introduced in design of two kinds of tyrosinase biosensors,which achieved the highly sensitive electrochemical detection of phenol,and provided a new idea for the detection of phenol in actual water samples.The first chapter mainly presented a summary of the electrochemical biosensor and amperometric enzyme biosensors,and focused on the research progress of signal amplification strategy in amperometric enzyme biosensors based on nanomaterial catalytic and redox cycle system.In the second chapter,the sulfonated polyaniline-chitosan（SPAN-CS）composite as a redox capacitor was introduced in a design of amperometric tyrosinase biosensors for signal amplification in electrochemical detection of phenol.The electrode reaction,and electron transfer between enzyme product（catechol/o-benzoquinone）,redox capacitor（SPAN-CS composite）,and hexaammineruthenium（II）chloride（Ru（NH₃）₆Cl₂）generated a novel electrochemical-chemical-chemical（ECC）redox cycling resulted in signal amplification of the detection.Additionally,the proposed method led to a high signal-to-background ratio for this determination.The linear range of detection of phenol was 3.5 to 200.0 nmol L^-11 and200.0 to 2000.0 nmol L^-1,with a detection limit of 0.8 nmol L^-1（S/N=3）.Furthermore,the proposed approach exhibited good repeatability,stability and specificity,and could offer practicality in the detection of phenol in tap water.In the third chapter,a novel amperometry tyrosinase biosensor was deaigned through combining redox cycle system with electrocatalysis of nonmaterial to achieve multiple signal amplification in detection phenol.The electron transfer between enzyme product（catechol）,Ferrocenecarboxylic acid（FcCOOH）and Tris（2-carboxyethyl）phosphine hydrochloride（TCEP）in solution form an ECC redox cycle system,which achieved the amplification of oxidation current of FcCOOH.Next,the oxidation current of FcCOOH was improved furtherly on molybdenum disulfide（MoS₂）and gold nanoparticles（AuNPs）modified electrode.The linear range of phenol detection was 0.12¹268.72 nmol L^-1,and with the detection limit of 0.035 nmol L^-1（S/N=3）.The proposed method showed good repeatability and stability,and could be used for the detection of phenol in actual water samples.