Preparation Of Several Carbon-based Composite Materials And Their Electrochemical Detection Of Nitrogenous Compounds

Electrochemical sensors are widely used in environmental monitoring,food safety and poison detection due to their advantages,such as simple preparation,low cost and high sensitivity.The material of the modified electrode plays a decisive role in the performance of electrochemical sensor.In recent years,carbon-based materials,including graphene,carbon quantum dots,and conductive polymers,have attracted widespread attention on account of their excellent electrical conductivity,good stability and large specific surface area.This thesis starts with improving the conductivity and catalytic performance of carbon-based composite materials,and combining common carbon-based materials with metal,metal oxides,and inorganic nonmetallic compound,etc.The aim is to build an electrochemical sensor platform which can detect the nitrogenous compounds.The main work is as follows:（1）Zirconia/N-doped carbon quantum dots（ZrO₂/NCQDs）were successfully prepared by in-situ growth method and modified on the surface of glassy carbon electrode（GCE）for the detection of nitrite.The experiments showed that the prepared composites have good electrocatalytic activity towards nitrite.Under the optimal experimental conditions,the square wave voltammetry（SWV）method was applied to quantitatively detect nitrite.The detection range was 0.5～30000μM,and the LOD was 0.25μM（S/N?=?3）.The ZrO₂/NCQDs/GCE electrode had the advantages of high selectivity,good reproducibility and stability,which could be successfully applied to the detection of real samples.（2）Amorphous hydroxyapatite（a-HA）was prepared by ion spraying and successfully combined with MWCNTs.The obtained MWCNTs/a-HA was modified on the surface of glassy carbon electrode for electrochemical detection of metronidazole.The experiments showed a synergistic effect between a-HA and MWCNTs that made the modified electrode had high specific surface area and excellent electrocatalytic performance.Under the optimal experimental conditions,metronidazole was quantitatively determined,with a linear range of0.2～500μM and a LOD of 0.088μM（S/N?=?3）.In addition,This sensor had excellent selectivity,reproducibility and stability.（3）An electroreduction process was used to prepare electrochemically reduced graphene oxide/multi-wall carbon nanotubes（Er GO/MWCNTs）for detecting 2,4-dinitroanisole（DNAN）by linear sweep stripping voltammetry（LSSV）.The composite materials showed the feature of high specific surface area,high conductivity and good electrocatalytic activity which enhanced the electrocatalysis for DNAN.Under the optimized conditions,the reduction peak current of Er GO/MWNTs/GCE had a good linear relationship with the corresponding concentration of DNAN in the range of 0.1～5?μM and 5～30?μM.The limit of detection（LOD）was 0.084?μM（S/N?=?3）.（4）Polypyrrole nanotubes（PPy NTs）were prepared by soft template method using pyrrole as raw materials.Manganese dioxide（MnO₂）and silver nanoparticles（Ag）were grown on the polypyrrole nanotubes via in-situ growth method.PPy NTs/MnO₂/Ag composite was obtained and successfully modified on the surface of glassy carbon electrodes.Electrochemical experiments showed that PPy NTs/MnO₂/Ag has a significant electrocatalytic effect on the energetic material 2,4,6-trinitrophenol（TNP）.The SWV was used for quantitative detection of TNP,and its linear range was 0.5～200μM,and the detection limit was 0.092μM（S/N?=?3）.