| In recent years,electrochemical sensors,with high sensitivity,selectivity,rapid detection,low cost,and ease of miniaturization,have been widely used in biomedical,Biomedical,Environmental Monitoring,Agriculture and Food Safety and Clinical Analysis environmental,agricultural and clinical analysis.Sensitivity is an important indicator of electrochemical detection.Over the several years,researchers have devoted themselves to developing various electrochemical signal amplification technologies to realize high sensitive detection.Redox capacitor can form a redox cycle system by repeating the charging process(receiving electrons from the redox medium)and the discharging process(donating electrons to the redox medium),amplifying the electrochemical signal of redox medium,and improving the sensitivity of electrochemical detection.Therefore,this paper was based on the redox activity of sulfonated polyaniline derivatives combined with non-conductive chitosan,constructed two types of redox capacitor electrochemical sensors,which could realize the quantitative detection of chloramphenicol and sialic acid respectively.The first chapter mainly summarized the signal amplification strategy of electrochemical sensors,and focused on the principle and applications of redox capacitors for electrochemical signal amplification.In addition,a brief introduction to the properties of sulfonated polyaniline derivatives and their applications in electrochemical sensor was provided.In the second chapter,a novel redox capacitor was designed for signal amplification in electrochemical detection.It was fabricated by co-electrodeposition of a conducting polymer,sulfonated polyaniline(SPAN)and chitosan on a glass carbon electrode,and its function was evaluated for being a localized source to transfer electron between FcCOOH and Ru(NH3)6Cl3 in solution via redox cycling.Furthermore,the electrochemical detection of chloramphenicol was performed using the redox capacitor in the presence of FcCOOH.A significant amplification in cathodic current response of chloramphenicol was obtained through a continuous redox-cycling reaction.The performance of the amplifying signal responded linearly to chloramphenicol in a concentration range of 0.05-50.0 μmol L-1 with a low detection limit of 0.01 μmol L-1.The proposed approach exhibited good reproducibility and stability,and could be used for detection of chloramphenicol in eye drops by standard addition method with the recoveries from 96.5%to 103.0%.In the third chapter,a novel redox capacitor was constructed using redox-active sulfonated polyaniline/polyaminophenyl boronic acid copolymer(SPAN/PABA)combined with non-conductive chitosan membrane(CS)for sensitive detection of sialic acid.Firstly,chitosan was electrodeposited on a glassy carbon electrode and then SPAN/PABA was dropped on the electrode,forming a SPAN/PABA-CS modified electrode with redox capacitor properties.The modified electrode could exchange electrons with redox medium(FcCOOH and Ru(NH3)6Cl3)to form a redox cycle system,resulting in amplification of the electrochemical signal of the redox medium.The combination of SPAN/PABA and sialic acid caused the positive shift of SPAN/PABA redox potential,which restrained the process of electron exchange between SPAN/PABA and FcCOOH,leading to the attenuation of amplified electrochemical signals of redox mediators.Highly sensitive quantitative detection of sialic acid was achieved through the attenuation degree of FcCOOH oxidation current.The results showed that two linear relationships between the change of FcCOOH oxidation current and the concentration of sialic acid in the ranges of 40.0-400.0 μmol L-1 and 400.0 μmol L-1-3.0 mmol L-1 with a detection limit was 18μmol L-1.In addition,the sensor could selectively detect sialic acid compared with other monosaccharides.This method provided a new idea for the detection of sialic acid. |
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