All-solid-state Ion Selective Electrodes Based On Ordered Mesoporous Carbons

As an important branch of electrochemical sensors,ion-selective electrodes?ISE?has been widely used in medical and health,environmental monitoring and process control in recent years due to the low detection cost,high sensitivity and wide applicability.Compared with the traditional internal liquid-filled ISE,the all-solid-state ISE with the ion-selected membrane?ISM?directly coated on the solid electronic conductors is more appealing for the miniaturization.Additionally,the structure of the all-solid-state ISEs allow them to avoid the cumbersome daily maintenance of the internal liquid-filled ones and therefore have much enhanced durability.However,many factors including charge transfer resistance,redox capacitance or electric double layer capacitance,and water layer could affect the interface potential between the solid conductive substrate and the ion-selective membrane,which is regarded as the key for the performances of the all-solid-state ISEs.With the rapid development of nanotechnology,a large number of nanomaterials have been used as solid contact layers for ISEs to improve their electrode potential stability.As one of the most important carbon nanomaterials,ordered mesoporous carbon?OMC?have attracted much attention due to their high surface area,excellent electrical conductivity,good thermal stability and chemical stability.In this work,we developed the methods to construct OMC modified all-solid state ISEs,which can realizes rapid,sensitive and accurate ion detection.Specific research contents in the thesis are as follows:?1?A novel approach towards potassium ion selective electrode was established with ordered mesoporous carbon as the ion-electron transducer.Firstly,the ordered mesoporous polymer nanospheres were synthesized by hydrothermal method with block copolymer Pluronic F127 as soft template and phenolic resin as carbon source.Through calcination carbonization,OMC spheres with high specific surface area were prepared,and different pyrolysis temperatures were adjusted to investigate the capacitance properties of OMC spheres.At the same time,these OMC spheres were used to be solid contact and covered with potassium ion selective membrane to prepare ion selective electrode based on glassy carbon electrode.The resulting electrode exhibits a good Nernstian response in the range from 10^-4.19 to 10^0.01 mol L^-1 with the 95%of steady-current within 10 s.The response slope of the electrode is 62 mV/decade?±0.6 mV/decade?and the detection limit is as low as 5.5?M.In addition,the sensor device also exhibits high potential stability by keeping the voltage monitoring for 70 h with the potential offset value of about 28±1.9 uV/h.The all-solid-state ISE also shows high selectivity,consistency and stability.The excellent performances of the ISE should be due to the interconnected mesopore structure of the electrode,which can make the ISE membrane perfectly contact the OMC spheres,thus providing good ion-to-electron transduction.In the end,the feasibility of the reliable ISM/OMC-750/Au is demonstrated by constructing a handheld ion-sensitive field-effect transistors?ISFET?potassium measurement system.?2?A simple and effective solution processing method for chloride ISE is also developed in this work.Based on the method in previous chapter,the ordered mesoporous carbon with high capacitance was directly mixed with ion carrier to in a co-solvent of Nafion and cyclohexanone,and drop-casting onto the surface of the glassy carbon electrode to reduce the phase interface of the detection system,which could improve the ion transport efficiency.Compared with the working electrode corresponding to commercial carbon black,the sensor based ordered mesoporous carbon shows better analytical performance with a detection limit of 257?M and the stable Nernstian response from 10^-3.29 to 10^0.01 mol L^-1,and the response slope of 60mV/decade?±0.6 mV/decade?.In addition,after storage for one month at room temperature,the sensitivity of the electrode can still maintain 90%of the initial value,showing good long-term stability.Finally,this kind of electrode was successfully prepared into a miniature structure and used as a working electrode in a handheld ISFET sensing system which showed good sensing performance.