Study On Nano-composite Imprinted Electrochemical Sensor

Due to the high stability, simple preparation process, high temperature and highpressure resistant, and offering the specific recognition sites for target molecules, themolecularly imprinted polymers can be modified onto the surface of electrodes toimprove their selectivities. At the same time, the nano-materials have the uniqueproperties of large specific surface area, high surface reactivity and incongruent surfaceatomic coordination. After modifying onto the electrochemical sensor, it can be used asa tool to amplify the signals. Thus, in this paper, highly selective and sensitiveelectrochemical sensors for determination of target compounds were synthesized bycombining the molecularly imprinted technology with nano-technology, based onmodifying the nanocomposites and molecularly imprinted polymers onto the surface ofcarbon electrodes. And the applications for determination of amino acid, naturalproducts and pollutants were investigated. The main contents are as follows:1. An imprinted electrochemical sensor with specific recognition ability forL-phenylalaine was synthesized by multi-layer modifying zinc oxide nanofilms（ZnO-NFs）, multi-walled carbon nanotubes （MWNTs）, copper nanoparticles （Cu-NPs）and sol-gel molecularly imprinted polymer （MIP） on the surface of carbon electrode insuccession. The morphologies of the modified sensors were investigated by scanningelectron microscope （SEM）. The electrochemical performance and the optimalconditions for detection of L-phenylalaine were investigated by cyclic voltammetry（CV）, differential pulse voltammetry （DPV）, amperometric i-t curve and linear sweepvoltammetry （LSV）. When the scanning rate was100mV/s, operating voltage was0.15V and pH was5.5, the linear range of response toward L-phenylalaine on the imprintedsensor is over the concentration ranging from5.0×10^-8mol/L to2.0×10^-5mol/L, andthe limit of detection is3.9×10^-9mol/L. This sensor was successfully employed todetect L-phenylalaine in human serum sample with recoveries of98%-101%.2. A sensitive molecularly imprinted electrochemical sensor with specific recognitionability for oleanolic acid was synthesized by modification of multiwalled carbonnanotubes （MWNTs） decorated with tin oxide nanoparticles （nano-SnO₂/MWNTs） andpolypyrrole-imprinted polymer on a carbon electrode. The morphology andelectrochemical performance of the imprinted sensor were investigated by usingscanning electron microscope （SEM）, X-ray diffraction （XRD）, cyclic voltammetry（CV）, linear sweep voltammetry （LSV） and amperometric i–t curve. The results showedthat the imprinted sensor displayed excellent selectivity toward oleanolic acid. A linearrelationship be-tween the response currents and oleanolic acid concentrations rangingfrom5.0×10^-8g/L to2.0×10^-5g/L was obtained for the imprinted sensor. The limit ofdetection （LOD） of the imprinted sensor toward oleanolic acid was calculated as8.6× 10^-9g/L at a signal to noise ratio （S/N） of3. This imprinted sensor was successfullyapplied to the determination of oleanolic acid in Acitinidia deliciosa root samples.3. A novel magnetic molecularly imprinted polymer sensing determination systemcombined with magnetic molecularly imprinted solid-phase extraction was developed todetect critical levels of emodin in complex matrix. In this work, magnetic molecularlyimprinted polymer （MIP/Fe₃O₄-PEG） bead was used as sorbent for molecularlyimprinted solid-phase extraction （MISPE） and sensing element for MIP/Fe₃O₄-PEGmodified carbon electrode to improve the sensitivity and selectivity. The morphologiesof MIP/Fe₃O₄-PEG and MIP-sensor were characterized by using scanning electronmicroscope （SEM）. The electrochemical performance of MIP-sensor was investigatedby cyclic voltammetry （CV） and differential pulse voltammetry （DPV）. The resultsshowed that trace emodin can be determined by the combination of MISPE followed bydetection with an MIP-sensor. The detection limit was as low as6.8×10^-9g/L bydetecting with DPV technique （S/N=3）. The proposed method was successfully appliedfor the determination of trace emodin in complex matrix samples.4. A sensitive and selective magnetic molecularly imprinted （MMIP） sensor combinedwith magnetic molecularly imprinted solid phase extraction （MMISPE） was developedfor determination of dibutyl phthalate （DBP） in complex matrixes. In this work,magnetic molecularly imprinted polymer （MMIP） was synthesized as solid phaseextraction （SPE） sorbent to extract DBP from complex matrixes and as sensing elementto improve the sensor sensitivity and selectivity. The morphologies of MMIP andMMIP-sensor were characterized by using scanning electron microscope （SEM）. Theelectrochemical performances of MMIP-sensor were tested by cyclic voltammetry （CV）and differential pulse voltammetry （DPV）. The results showed that trace DBP can bedetermined by the MMIP sensor combined with MMISPE. The detection limit wasfound to be as low as5.2×10^-11g/L by detecting with DPV technique （S/N=3）. Thismethod was successfully applied to detect DBP in complex samples.