Investigation Of Electrochemical Sensing For Three Kinds Of Small Molecules Based On Nanocomposites

Natural or man-made nanomaterials have been widely used in the construction of sensing interface due to their unique structure,morphology and properties.In this paper,eight kinds of nanocomposites were prepared via chemical reduction method,one-step polymerization method,sol-gel method and template method,and eight enzyme-free electrochemical sensors with brilliant performance based on the nanomaterials have been set up.Not only the microstructure and electrochemical performance of nanocomposites have been studied,but also the actual samples containing H₂O₂,DA and NO₂^-have been detected.This study provided a valuable reference for preparing high catalytic activity nanomaterials with special shape and high dispersion,and also gave a reliable reference for the development of high-performance electrochemical sensors.The thesis was divided into three chapters,the main research by the author are as follows:1.Three kinds of nanocomposites including Ag-HNTs-MnO₂,Ag/Co₃O₄/rGO and PB/PANI/MWCMTs were prepared by chemical reduction method,one-step polymerization method and sol-gel method,and the H₂O₂ electrochemical sensors based on these materials were fabricated.The morphologies and electrocatalytic behaviors towards the three nanocomposites were studied,and new analytical methods for the determination of H₂O₂ were also established.The experimental research showed that the detection limit of H₂O₂ based on Ag-HNTs-MnO₂ electrochemical sensor was 0.7μmol L^-11 with a linear range of 2.0μmol L^-1-4.71 mmol L^-11 and a sensitivity of 11.9μA(mmol L^-1)^-11 cm^-2,the detection limit of H₂O₂based on Ag/Co₃O₄/rGO electrochemical sensor was 0.17μmol L^-11 with a linear range of 0.5μmol L^-1-6.48 mmol L^-11 and a sensitivity of 413.72μA(mmol L^-1)^-11 cm^-2,and the the detection limit of H₂O₂ based on PB/PANI/MWCMTs electrochemical sensor was 1.6μmol L^-11 with a linear range of 5.0μmol L^-1-1.03 mmol L^-11 and a sensitivity of 4018.57μA(mmol L^-1)^-11 cm^-2.Compared with other chemical methods,the prepared silver nanoparticles via chemical reduction and one-step polymerization have good dispersion.Besides,the sensitivity of H₂O₂ electrochemical sensors based on PB/PANI/MWCMTs nanocomposites has increased by two orders of magnitude.2.Three kinds of nanocomposites including Au/a-Fe₂O₃@SnO₂,Ni（OH）₂/NiCo-LDHs and Au@Pt/GO nanocomposites were prepared by the template method,hydrothermal method and one-step synthesis method,and the DA electrochemical sensors based on these materials were fabricated.The relationship between the electrocatalytic properties of modified electrode sensing interface nanomaterials and the sensor properties were studied,and novel approaches of enzyme-free DA determination were also established.The results of electrochemical experiments showed that the detection limit of Au/a-Fe₂O₃@SnO₂ DA electrochemical sensor was 0.17μmol L^-11 with a linear range of 0.5μmol L^-1-1.37 mmol L^-1,the detection limit of Ni（OH）₂/NiCo-LDHs DA electrochemical sensor was 0.017μmol L^-11 with a linear range of0.05μmol L^-1-1.08 mmol L^-1,and the detection limit of Au@Pt/GO DA electrochemical sensor was 0.11μmol L^-11 with a linear range of 0.5μmol L^-1-1.18 mmol L^-1.Compared with other two electrochemical sensors,the detection limit and linear range of the second sensor were lower and wider by one order of magnitude,respectively.3.Au NPs were regarded as the catalytic material of the electrode and they were dispersed onto some different substrate materials,and two kinds of nanocomposites including Au NPs/MoS₂ and Au-HNTs-GO nanocomposites were prepared successfully.Then the NO₂^-electrochemical sensors based on the two materials were fabricated.The structure,elemental composition and electrochemical behavior of these two materials towards the sensor performance were discussed.Besides,two novel methods for the detection and analysis of NO₂^-were established.The experiment investigation showed that the detection limit of Au NPs/MoS₂ NO₂^-electrochemical sensor was 1.7μmol L^-11 with a linear range of 5.0μmol L^-1-27.78 mmol L^-1,the detection limit of Au-HNTs-GO NO₂^-electrochemical sensor was0.03mM and the linear range were 0.1μmol L^-1-6.33 mmol L^-1,6.33 mmol L^-1-61.9 mmol L^-1,respectively.Compared with other nitrite sensors,the Au-HNTs-GO electrochemical sensor towards NO₂^-detection showed a wider linear range,ten times lower detection limit and a simpler synthesis method,and it provided a new platform for the simple preparation of high-performance nanomaterials in sensor construction.