Design And Application Of Spectral Resolution Photoelectrochemical And Ratiometric Electrochemical Sensors

Molecularly imprinted polymers（MIPs）,as artificial antibodies,have imprinted cavities matching template molecules in shape,size and functional groups,simulating the antigen-antibody recognition interaction to enrich selectively template molecules.Compared with natural biological antibodies,MIPs have the advantages of low preparation cost and good stability.To improve the sensitivity and selectivity of target analytes,many detection methods have been used in combination with MIPs.The imprinted cavities within MIPs are helpful to enrich specifically the template molecules.But other interfering substances can also be adsorbed on the surface of MIPs via non-specific adsorption mechanism,which reduces the selectivity of MIPs based sensors.In this thesis,a difference strategy is used to correct the non-specific adsorption from interfernts and improve the anti-interference ability of the MIPs-based analysis method.The main research contents are outlined as follows.1.Determination of acetaminophen and rutin by photoelectrochemical sensor at two excitation wavelengthsPhotoelectrochemical（PEC）sensor is an electrochemical sensing technique based on photoelectric effect with photocurrent as analysis signal,offering the advantages of high sensitivity,simple instrument and good selectivity.In the applications of PEC sensors,the full-spectrum or visible region of the light source are usually used to excite the photocurrent.The influence of the spectrum of the excited light source on the response of PEC sensors is not well studed.In this thesis,copper indium sulfur/zinc sulfide（CIS/Zn S）was used as modification material of Ti O₂ nanotube（NTs）photosensitive electrode.MIPs films were obtained by electropolymerization on the surface of CIS/Zn S/Ti O₂ NTs photosensitive electrode with acetaminophen（AP）or rutin（RT）was used as template molecule and pyrrole as functional monomer.By using a simple UV light source with two wavelengths of 254 nm and 365 nm,the photocurrent responses of AP and RT were significant different at the two wavelengths.Excited at 254 nm,the photocurrent is decreased with increasing AP or RT concentration.At the excitation of 365 nm,the photocurrent is increased with increasing AP concentration while is decreased with increasing RT concentration.The influence of excitation light source spectrum on the response performance of PEC sensor is further studied.It was shown that if a substance can absorbs the energy of excitation light source at the excitation wavelength,the photocurrent signal will be decreased.The decrease in photocurrent is 5～15 times higher than the light absorption of the same amount of substance in solution.Hence,two MIPs-PEC sensors for AP and RT detection are fabracted.In order to improve the analytical sensitivity of the sensors,the ratio of photocurrents at 365 nm and 254nm is used as the analysis signal in the determination of AP in the ratiometric PEC sensor.In the determination of RT,the sum of the photocurrents at 365 nm and 254 nm was used as the analysis signal.In order to further improve the anti-interference ability of MIPs-PEC sensor,the response of NIPs-PEC photosensitive electrode without imprinted cavities is used as reference to correct the interference caused by non-selective adsorption of interferents on MIPs.Under optimized conditions,the proposed MIPs@CIS/Zn S/Ti O₂ NTs are used to determine AP and RT in linear range were 0.05～6mM and 0.05～12.5mM,with the limits of detection of 9.0 and 8.3 n M respectively.The recoveries of AP and RT in human serum samples were 96.2%～103.6%.2.Determination of sulfamerazine by differential and ratiometric MIPs electrochemical sensorGlassy carbon electrode（GCE）was modified by copper indium sulfur/zinc and was used to determine sulfamemethazine（SMZ）.MIPs for SMZ and propyl gallate（PG）were prepared on the surface of CIS/Zn S/GCE by electropolymerization polypyrrole menbrane with SMZ and PG as templates.During the determination,PG and SMZ were enriched on the surface of the modified electrode by MIPs.In differential pulse voltammetry,the peak potential of PG and SMZ is 0.2 V and 0.9 V respectively,which can be used for the simultaneous determination of PG and SMZ.In the samples without PG,a cview of the low possibility of coexistence of PG and SMZ in samples,a constant PG concentration of 10μM was added into the sample solution and used as the internal standard.The ratio of the current peaks from SMZ and PG(ΔI_SMZ/ΔI_PG),was used as the analytical signal,which can reduce the influence of the variations in electrode modification,MIPs film preparation and sample enrichent conditions on the detection of SMZ,improving the stability of the sensor.In order to further improve the selectivity of the sensor,a differential strategy is used to correct the response signals from non-specific adsorption of interferents on the surface of MIPs film.Under optimized conditions,the MIPs-based ratio differential electrochemical sensor has a linear response range of 0.05～20μM to SMZ,and the detection limit is 4.0 nM.