Synthesis Of Functionalized Iminazole-based Ionic Liquid And Its Application In Oxygen Sensor

Oxygen is not only an essential substance for human life activities but also a substance that needs to be controlled and measured in most of fields such as industry,agriculture,energy,transportation,medical care and ecological environment.There are many types of sensors for oxygen detection nowadays and electrochemical gas sensors are regarded as the most promising sensors because of their superior sensitivity and selectivity.However,electrochemical gas sensors are normally made up of conventional solvents,which have some problems such as solvent evaporation and short lifecycle.These problems can be avoided by using room temperature ionic liquids（RTILs）which have varieties of attractive physical and chemical properties including non-toxic,low vapor pressure,high conductivity,wide electrochemical windows,high chemistry and physical stability and high solubility for a range of gases.In particularly,negligible vapor pressure eliminates the problem of solvent evaporation,making it very successful to be an oxygen sensor electrolyte.In this dissertation,imidazole-based ionic liquids were synthesized as the electrolyte of oxygen sensor,and the ionic liquids（ILs）were modified to further improve the electrochemical performance and oxygen sensitivity of the electrolyte.In this thesis,we successfully prepared 1-ethyl-3-methylimidazolium hexafluorophosphate（EMIMPF₆）,1-propyl-3-methylimidazoliumhexafluorophosphate（PMIMPF₆）and1-butyl-3-methylimidazolium hexafluorophosphate（BMIMPF₆）which is liquid state at room temperature.The electrochemical tests of the three ILs showed that BMIMPF₆ had the best performance.Then the ordered mesoporous carbon modified platinum（Pt/CMK-3-COOH）,which prepared by the chemical reduction method,was uniformly mixed with BMIMPF₆.The oxygen concentration showed a good linear relationship with the response current,and the hybrid system was proved to be an electrolyte for oxygen sensor with better sensitivity.In order to improve the drawbacks of high viscosity for single ILs,this thesis considered the idea of mixing two kinds of ILs.Based on the simple operation,BMIMPF₆,which is liquid at room temperature,was selected from the three ILs,and 1-vinylimidazole（VIM）was mixed with it.Adjusting the mass percentages of the two ILs,we get the best performance.Next,we mixed the solid state EMIMPF₆ and PMIMPF₆ with the VIM according to the ratio.By analyzing the cyclic voltammetry,the alternating current impedance and chronoamperometry results,the solvent of 40%EMIMPF6+60%VIM possesses best performance for detection of oxygen.Based on these results,a series of tests were carried out to confirm that 38%EMIMPF6+57%VIM+5%Co/C composites had outstanding electrochemical properties and oxygen sensitivity.In this thesis,three kinds of 1-alkyl-3-vinylimidazolium bromide（AVIMBr）were synthesized by controlling the reaction temperature and the reaction time and mixing VIM with C2H5Br,C3H7Br and C4H9Br,respectively.Subsequently,intermediates were exchanged anions to prepare three 1-alkyl-3-vinylimidazolium bistrifluoromethylsulfonimide salts（AVIMTFSI）.The 1-butyl-3-vinylimidazolium bistrifluoromethylsulfonylimide（BVIMTFSI）had optimal performance,which was determined by electrochemical tests.VIM was added to this ILs to prepare a mixture.The mixed system was tested and the oxygen sensitivity of the ILs was also studied.The viscosity of the ILs was reduced by adding cosolvent,which increased the conductivity of the ILs.The results showed that the performance of the ILs was significantly improved.