| Due to big specific surface area,good conductivity and excellent electrocatalytic property,2-D covalent organic frameworks（COFs）have attracted more and more attention in electrochemical sensing field and related investigations are entering a stage of rapid development.However,it is a pity that the action mechanism of COF is still unclear.In this thesis,a-NH-linked 2-D COF was prepared by selecting melamine and tripolychlorazine as the building units.And then by its composition with some commonly-used nanomaterials such metal nanoparticles and nanocarbon materials,a series of novelty electrochemical sensors for detecting some medical and biological small molecueles were fabricated and their morphologies and properties were characterized in detail with SEM,EDS,CV and EIS technologies.It was found that this imine bonded triazine based COF not only improved effectively conductivity of the composition materials,but also showed excellent electrocatalytic performances for the electrode reactions of the analytes,and as a result,the response singals of the modified electrodes were remarkably enhanced and the resulted detection sensitivities wereconsiderably increased.This thesis consists of five parts as follows:1.Using simple drop-coating and electrodeposition methods,a new electrochemical sensor COFs/Au NPs/COOH-MWCNT@NRs/GCE was prepared based on the synthesized COF,Au NPs and carboxylated carbon nanotubebelts.The obtained modified electrode showed strong electrocatalytic property for for the redox reactions of acetaminophen（AMP）and dopamine（DA）on the electrode and could be applied to rapidly and sensitively detect AMP and DA simultaneously with detection limits of 1.18 nmol·L-1 and 32 nmol·L-1（S/N=3）,repectively.The developed analytical method possessed a high sensitivity,good selectivity,high stability and wide linear range and could redectly be used to determine AMP and DA in real samples including human urine and commercially available tablet samples with a satisfactory result.2.A new electrochemical sensor for AMP and p-aminophenol（AP）,Ni Co NPs-COF/GCE,based on the synthesized COF,Ni Co bimetallic nanoparticles was prepared with an electrodeposition procedure.The electrochemical study proved that the obtained nanocomposite film possessed good conductivity and excellent electrocatalytic performances toward the redox reactions of AMP and AP.This fabricated sensor could be used to measure the contents of AMP and AP in Yellow water and medical samples with low detection limits down to 83.5 nmol·L-1 and0.15μmol·L-1（S/N=3）,respectively.3.Using the COF,Ni NPs and ferrocenecarboxylic acid（Fc）as modified materials,a new electrochemical sensor Ni NPs/COF-Fc/GCE was prepared by a simple electrodeposition method.And this modified electrode also exhibited good electrocatalytic ability for the electrode reactions of AMP and AP.Enough big peak-peak separation（（35）Ep=300 m V）ensured their simultaneous determination without interference with each other.As a result,a sensitive,rapid,exact and selective analytical method for simultaneous determination of AMP and AP was proposed with detection limits down to 68.3 nmol·L-1and 25.0 nmol·L-1（S/N=3）and employed to determine AMP and AP in Yellow water and medical samples simultaneously.The excellent electrochemical performance resulted from a synergistic effect of good conductivity and high electrocatalytic activities of Ni NPs,COF and Fc.4.A new electrochemical biosensor DNA/COF/GCE was obtained using DNA and the COF as modified materials with an electropolymerization procedure for uric acid（UA）.It displayed a high electrocatalytic activity toward oxidation reaction of UA and could be exploited to determine UA sensitively and selectively.The hydrogen bond and（?）-（?）interactions between DNA and UA ensured the modified electrode a high selectivity,while the COF enhanced the current response and the detection sensitivity of the sensor owing to its high condectivity and good electrocatalytica activity.The developed method was successfully used in determination of UA in human urine sample with a detection limit of 0.13μmol·L-1（S/N=3）.4.This experiment uses electropolymerization and electrodeposition methods to prepare dual nanoparticle bioelectrochemical sensors（COFs/DNA/GCE）based on covalent organic compounds and DNA,using different detection methods:scanning electron microscopy（SEM）,the electrochemical behavior of uric acid（UA）was analyzed by CV and DPV.Under a series of optimized conditions,uric acid（UA）showed a good linear range with oxidation peak current in the range of 4-1000μmol·L-1,and the detection limit of uric acid（UA）was 1.259×10-7mol·L-1（S/N=3）.The modified electrode has high sensitivity and selectivity and a wide detection range.At the same time,the uric acid content in the urine is determined by the spiked recovery rate,and the experimental results are satisfactory.5.Using sequential electrodeposition and electropolymerization method,Au NPs and poly（L-cysteine-β-cyclodextrin）were introduced onto the surface of GCE to produce a new electrochemical sensor for AMP and rutin（RT）,P（L-Cys-β-CD）/Au NPs/GCE.The prepared composition membrane showed excellent electrocatalytic properties for the redox reactions of AMP and RT on the electrode and the obtained sensor was successfully used in simultaneous determination of AMP and RT in commercially available medical tablet samples,with detection limits of 91.0 nmol·L-1 and 0.14μmol·L-1（S/N=3）,respectively.Because of hydrogen bond interaction between the target molecules and the modified materials and sieve effect ofβ-cyclodextrin,the prepared sensor possessed a high selectivity.At the same time,because of strong Au-S covalent interaction of Au NPs with the polymer film and hydrogen interaction betweenβ-cyclodextrin and L-Cys,the modified electrode had a high stability. |
PDF Full Text Request