Synthesis And Electrochemical Applications Of Functionalized Graphene Based Nanocomposites

Since the oxygen sensor was fabricated in the 1950s,electrochemical sensors have got wide interest because of their advantage,such as low cost,simple operation and fast analysis speed.With the development of science,electrochemical sensors have been applied more and more extensive.Because of this background,it has become the key point of people's research to improve the sensitivity and stability of the sensor.Meanwhile,nanocomposites show good conductivity and high electrocatalytic activity,which can effectively increase the sensitivity of sensors.The high specific surface area of graphene provides a supporting platform for the modification of the nanocomposite on the electrode,and also plays a unique role in improving the catalytic performance of the sensors.Focusing on the graphene/nanocomposites,we carried out the following research works:1.The ionic liquid functionalized graphene oxide?IL-GO?and MnO₂ nanosheets were prepared separately,and combined to modify the electrode?MnO₂/IL-GO/GCE?to construct a novel theophylline?TP?sensor.The cyclic voltammetry?CV?was employed to evaluate the electrochemical behavior of the modified electrode,and the surface concentration of the electroactive species was calculated to be approximately 2.316×10^-10 mol cm^-2.Differential pulse voltammetry?DPV?results indicate that MnO₂/IL-GO/GCE has a high ability to catalyze the oxidation of TP.DPV determination of TP gave linear responses over the concentration range from 1 to 220?M,and the detection limit was 0.1?M.Finally,MnO₂/IL-GO/GCE was successfully applied in the analysis of real samples.2.An electrochemical sensor was constructed by compounding gold nanoparticles?AuNP?,CoS₂ and IL-GO for detecting dopamine?DA?.The electrode was first modified by IL-GO and CoS₂,and then AuNP was electrodeposited to obtain a well-defined three-dimensional and porous structure.The nanohybrid material displays high catalytic activity and an ultrasensitive CV response to DA.The peak current?best measured at a working voltage of 0.17 V?increases linearly in the 0.1?M to0.4 mM DA concentration range,with a 40 nM detection limit?at S/N=3?.In addition,the sensor we constructed was also successfully applied to the determination of DA in spiked serum samples.3.A novel sensor based on Pt nanoparticle-carbon quantum dot/ionic liquid functionalized graphene oxide?PtNPs-CDs/IL-GO?nanocomposite was constructed for detection of H₂O₂.The morphology and electrochemical performance of the modified electrode were characterized by scanning electron microscopy?SEM?,transmission electron microscopy?TEM?,Raman spectroscopy?Raman?and CV method,respectively.The unique chemical structure of PtNPs-CDs/IL-GO greatly accelerates the catalytic action of H₂O₂ and provides plenty of active sites for electrochemical redox reactions.Electrochemical experiments have demonstrated that high selectivity,a wide linear range from 1 to 900?M,and a low detection limit of 0.1?M with respect to the reduction of H₂O₂.This simple and effective method has potential applications in chemical sensors and electrochemical catalysis.4.Guanine and adenine were determinated respectively and simultaneously by the preared MnO₂/IL-GO/GCE sensor.The results of CV and DPV showed some superior electrochemical performances,such as wide linear range,low detection limit,and good stability,whether at single detection of guanine or adenine,or simultaneous determination of both.