Preparation And Property Study Of Novel Imprinted Electrochemical Sensors Based On Dye Probes

Due to the easy preparation,low cost,good selectivity and resistance of harsh environment,molecularly imprinted polymer(MIP)has been extensively applied in the fields of separation and purification,immunoassay,mimic enzymes catalysis,and biosensing.The combination of MIP and electrochemical sensor will realize the selective detection toward target substances.However,commonly used MIP is poorly conductive,which brings difficulty to the sensitive detection of the sensor.Dye molecules,such as Prussian blue and thionine,have been employed as excellent mediators of transferred electron in the preparation and application of electrochemical sensors because of their good redox acitvity,electrocatalysis and stability.The sensor will possess two current signals if the redox potentials of dye molecules modified on electrode surface and target substances bound to electrode surface are non-interfering.The combination of these two current signals will certainly improve the sensitivity of the sensors.For this,this thesis employs dye molecules(Prussian blue and thionine)as electrochemical probe to fabricate three kinds of novel MIP based electrochemical sensors for template molecules specific recognition and sensitive detection.1.The authors report on a ratiometric electrochemical sensor for paracetamol(PR)which was fabricated by successively electropolymerizing a layer of Prussian blue(PB)and a layer of molecularly imprinted polypyrrole(MIP)on the surface of a glassy carbon electrode(GCE).The binding of PR molecules to the MIP has two effects: The first is an increase of the oxidation current for PR at 0.42 V(vs.SCE),and the second is a decrease in the current for PB(at 0.18 V)due to partial blocking of the channels which results in reduced electron transmissivity.Both currents,and in particular their ratio,can serve as analytical information.Under optimized conditions,the sensor displays enhanced sensitivity for PR in the 1.0 × 10-9 mol·L-1-1.0 × 10-4 mol·L-1 concentration range and a 5.3 × 10-10 mol·L-1 lower limit of detection.The sensor was applied to the determination of PR in tablets and urines where it gave recoveries in the range between 94.6 and 104.9%.This dual-signal(ratiometric)detection scheme(using electropolymerized Prussian Blue and analyte-specific MIPs)in our perception has a wide scope in that it may be applied to numerous other electroactive species for which specific MIP can be made available.2.A new strategy based on sign-on and sign-off was proposed for propyl gallate(PG)determination by an electrochemical sensor.The successively modified poly(thinone)(PTH)and molecular imprinted polymer(MIP)showed an obvious electrocatalysis and a good recognition toward PG,respectively.Furthermore,the rebound PG molecules in imprinted cavities not only were oxidated but also blocked the electron transmission channels for PTH redox.Thus,a sign-on from PG current and a sign-off from PTH current were combined as a dual-sign for PG detection.Meanwhile,the modified MIP endowed the sensor with recognition capacity.The electrochemical experiments results demonstrated that the prepared sensor possessed good selectivity and high sensitivity.A linear ranging from 5.0 × 10-8 to 1.0 × 10-4 mol·L-1 for PG detection was obtained with a limit of detection of 2.4 × 10-8 mol·L-1.And the sensor has been applied to analyze PG in real samples with satisfactory results.The simple,low cost,and effective strategy reported here can be further used to prepare electrochemical sensors for other compounds selective recognition and sensitive detection.3.Pesticide residues becomes one a hotspot of social attention currently.A novel double-template imprinted polymer based electrochemical sensor was developed for the successive analysis of bensulfuron-methyl(BSM)and imidacloprid(IMI)by using PTH as an electrochemical probe.BSA,a non-electroactive template,was first added into electrolyte,which was bound into the imprinted cavities in MIP to block the the electron transmission channels for PTH redox.Thus,the peak current of PTH decreased with the addition of BSM,which was used to sensitively detect BSM with a wide linear range of 1.0 × 10-8 mol L-1-1.0 × 10-5 mol L-1.IMI,an electroactive template,was then added into electrolyte,which was also bound into imprinted cavities to block the the electron transmission channels for PTH redox.A typical reductive peak of IMI at about-0.94 V was observed,which increased with the increase of IMI concentration.Meanwhile,the current of PTH further decreased with the increase of IMI concentration.These two current signals were combined for IMI sensitive detection with a linear range of 1.0 × 10-7-1.0 × 10-4 mol L-1.Also,the sensor showed good recognition capacity for template molecules from their analogues.And the sensor has been applied to analyze BSM and IMI in real samples with satisfactory results.The dual-template and dual-signals strategy proposed here will provide new way for both of electroactive and non-electroactive molecules sensitive and selective detection.