Applications Of Thiophene-based Conjugated Polymers For Electrochemical Sensors

Electrochemical sensor is one of the most popular detection devices in the field of analytical chemistry,owing to its high sensitivity,fast response,simple operation,low cost and easy miniaturization.The analytical performance of an electrochemical sensor is closely related to the modified materials.Conjugated polymers have been demonstrated to be excellent electrochemical sensing materials due to their intrinsic conductivity,high electron affinity and sensitive response to small perturbations.Among them,Thiophene-based conjugated polymers also possess high stability and tunable molecular chain structure.Unfortunately,their applications in electrochemical sensors are relatively limited.Only poly?3,4-ethylenedioxythiophene?and its derivatives are often used as electrode modified materials to take advantage of their good conductivity or immobilize other materials by polymerization,and the application for electrochemical sensing using their intrinsic physicochemical properties and the influence of these properties on sensing performance are relatively rare.In this research,the application of thiophene-based conjugated polymers for chemically modified electrodes was expanded,and the main work and results are as follows:?1?A thiophene-based conjugated microporous polymer film modified glassy carbon electrode was simply fabricated via electrochemical polymerization with the monomer 1,3,5-tri-?thiophen-2-yl?benzene?PTTB/GCE?.The PTTB/GCE was successfully used for the simultaneous detection of nitrophenol isomers?o-NP,m-NP and p-NP?.A uniform nanoball-like morphology with the diameter about 200 nm of PTTB polymer was observed from SEM,and the microporous structure was observed by TEM.The microporous surface of PTTB polymer significantly increased the contact areas for analytes,and the strong interactions between electron-poor nitro-analytes and electron-rich thiophene-based microporous polymers further helped to improve the adsorption capability and facilitate the electron-transfer process.Accordingly,the electrochemical responses of nitrophenol isomers were drastically enhanced.The proposed sensor has displayed satisfactory linear ranges(0.3–10?mol L^-1 for o-NP,0.3–12.5?mol L^-1 for m-NP and 0.3–15?mol L^-1 for p-NP)and low detection limits(0.04?mol L^-1 for o-NP,0.05?mol L^-1 for m-NP and p-NP)with favorable selectivity,stability and reproducibility.?2?Two kinds of thiophene-based conjugated polymer film modified electrodes were prepared and applied for the detection of paracetamol.The reaction mechanism was studied and the oxidation of paracetamol on the modified electrodes was demonstrated to be adsorption-controlled process.The strong intermolecular interactions between electron-rich,broad-surface-area thiophene-based conjugated polymer film and electron-poor acyl group on paracetamol significantly improved the adsorption capability,thus enhancing the electrochemical sensing ability.More than 13 times increase in the oxidation peak current of paracetamol,compared to that of bare electrode,were obtained,when using both modified electrodes.The modified electrode with better performance was chose to construct the paracetamol electrochemical sensor.The analytical performance was investigated,and the linear range was 0.10–25?mol L^-1 with a detection limit of 0.04?mol L^-1.The sensor was also used for determination of paracetamol in real samples,and a satisfactory recovery of 93.3%–98.7%was obtained.?3?The applicability of thiophene-based conjugated polymer film modified electrode was preliminarily investigated.With the study of the detection performance towards various analytes,we found that the thiophene-based polymer film modified electrode tended to show better detection ability for the small molecules with electron-poor group and simple molecular structure.The polymer film thickness has a great effect on the conductivity and detection performance of the prepared electrode,so it's necessary to optimize the film thickness to achieve the best performance.Furthermore,the conductivity was improved when combining the proposed modified electrode with metal nanoparticles like Pt nanoparticles,thus the analytical performance was obviously enhanced.