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Investigation Of Functional Electrochemical Sensors And Their Application In Fishery Ecological Environmental Monitoring

Posted on:2014-01-21Degree:MasterType:Thesis
Country:ChinaCandidate:M LiFull Text:PDF
GTID:2248330392962866Subject:Aquaculture
Abstract/Summary:PDF Full Text Request
Electrochemical sensors are centered great expectations for their obviousadvantages, such as portability, low-cost, sensitivity and stability. The goals of thepresent work are the achievement of sensitive and practical electrochemical sensorsand their applications in determining a few target substances in fishery environment.Working electrode is one of the key factors which affect the performance ofelectrochemical sensor. Two functional working electrodes, conductive carbon pasteelectrode (CCBPE) and graphene-ionic liquid electrode (G-ILPE), were fabricatedand characterized here. The results show they both have good voltammetricperformances. Diethylstilbestrol (DES) and Lead were rapidly determined on thesensors successfully. In addition, the electrochemical behaviors of calcein (CA), aswell as the mechanism of the interaction between calcein and DNA, were studied onthe sensors, too.The paper consists of six chapters in all.The first chapter is the introduction, in which the background of the research isreviewed and the direction of my work is stated.The second chapter is the fabrication, characterization and application of theCCBPE. The CCBPE, prepared by CCB and paroline with a desired ratio, has lots ofgood voltammetric performances, like the low background current, high chargetransfer rate, good adsorbability, etc. The electrochemical behavior of DES wasstudied by cyclic voltammetry (CV) and linear sweep voltammetry (LSV). Themechanism of electrode reaction was investigated preliminarily. Based on the results,some of important factors, including species of the supporting electrolyte, pH,accumulation potential and accumulation time, which had effect on the voltammetricresponse signal, were studied and optimized. Under the optimized conditions, therewas a linear relationship between the oxidative peak value and the concentration ofDES in the range of3.1×10-9-1.55×10-7M with a detection limit of1.55×10-9M(signal/noise=3). Then a rapid and highly sensitive detection method for DES wasestablished. Satisfactory results were obtained when the new method was used tomeasure DES in the real fishery water samples.The third chapter is the development of a new rapid method for determiningLead in fishery seawater using high sensitive CCBPE as working electrode. Some ofimportant relevant factors, including species of the supporting electrolyte, pH,accumulation potential, accumulation time, bismuth plating, interference substances, etc., were studied. Under the optimized conditions, a detection limit of0.1μg/L wasobtained. Based on the results, a new method for determining Lead in seawater wasdeveloped. The new method was used to determine the Lead concentration in realseawater samples collected from nearshore site in Qingdao. It was found that thesense data were in good agreement with that obtained by atomic absorptionspectrometry, indicating that the simple, fast, mercury-free and cost-effective methodhad a great potential value of application.The fourth chapter is the study of the electrochemical behaviors of CA and theinteraction between CA and DNA. CA exhibits a single well-defined redox peak at theCCBPE, which attributes to the irreversible oxidation with2electrons and2protonsparticipation. Under the optimized analytical conditions, the proposed linear sweepvoltammetry (LSV) method allows the determination of CA in linear concentration inthe range of0.64-9.60μM, and the limit detection is0.32μM. Further, theinteraction between CA and DNA were studied by voltammetric and spectrometricmethods. Both studies have shown that CA can bind to DNA by the intercalationbinding mode. Under the present experimental condition, the binding constant β ofCA and dsDNA is1.10×107. Meanwhile, in the loop-mediated isothermalamplification (LAMP) reaction mixture there is obvious interaction between CA andDNA, resulting in a non-ignorable decrease of the indicating sensitivity.The fifth chapter is the fabrication and characterization of G-ILPE. The G-ILPE,fabricated by n-octylpyridinium hexafluorophosphate (OPFP) and graphite powderwith a desired ratio, was characterized by electrochemical techniques. Furthermore,spectrometric methods were used to explore the mechanism of the electrode for itsexcellent electrochemical performances. And a new hypothesis was proposed toexplain the formation of the attractive electrochemical performances.The mechanicalforce produces mono-or multilayer graphene during the grinding process. The OPFPmolecules are prone to combine with the graphene, which causes the avoidance of theagglomeration of the exfoliated flakes. The presence of graphene, which is edge planecharacteristic, provides high density of electrochemical reactive sites on the surface ofthe electrode.The sixth chapter is the conclusion and prospect of the subject. The results of the research are summarized and some interesting aspects, which may be worth of furtherinvestigating, were listed, respectively.
Keywords/Search Tags:electrochemical sensor, conductive carbon black paste electrode, graphene-ionic liquid paste electrode, diethylstilbestrol, lead, calcein
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