The Construction And Analytic Application Of Electrochemical Sensors Based On Layered Double Hydroxides

In recent years,the electrochemical analysis and detection technology has been used in many fields such as biological, medicine and so on because of it has the advantage of fast speed,simple operation and low cost. However, in order to achieve the better effect,the most important part of the electrochemical biosensor is that the modified electrode should possess high sensitivity, wide linear range, high selectivity and reduce the redox potential of the materials effectively, so we need to find out the better modified electrode materials. The layered double metal hydroxides can be used to modify electrodes and construct electrochemical sensors due to its advantages of the unique structure, large specific surface area, good mechanical strength and excellent anion exchange ability.In this paper, we use the layered double metal hydroxide to prepare three different modified electrodes which have good catalytic performance.Then the modified electrodes were characterized by SEM and electrochemical technology. At last,the modified electrodes were applied to detect biological substances and organic pollutants.The main research is as follows:1.With the Ni Al-LDHs, chitosan and carbon nanotubes mixed solution as the electrolyte, we use one-step electrodeposition to deposit the materials on the surface of bare QCM gold electrode.At the same time, we use the RQCM to monitor the deposition process of the composite film and adjust the thickness of composite film, then we optimize the concentration of the carbon nanotubes to achieve the better sensing performance of the detection of glucose. By this way, we construct a new type of non-enzyme glucose sensor(Ni-Al-LDHs/CS/CNTs modified electrodes).The modified electrode was characterized by SEM,CV and so on. The results show that the modified electrode has good catalytic performance to the oxidation of glucose.It has a wide linear range of 10μM-5.85 mM,high sensitivity of 1.056 mA·mM-1cm-2,and low limit of detection of 1μM(S/N=3).In addition, this sensor show good reproducibility, stability and high selectivity.2.With the hemoglobin、carbon nanotubes、chitosan and Ni(NO3)2、Al(NO3)3、KNO3 as the electrolyte,we prepare a Hb/Ni Al-LDHs/CNTs/CS composite electrode under the constant potential by depositing the materials on the surface of QCM gold electrode.We also ues the RQCM to monitor the deposition process of the composite film. Then the composite electrode was characterized by SEM,CV and so on.The results show that the Ni Al- LDHs/CNTs/CS film can promote the electron transfer between the hemoglobin and the surface of modified electrode effectively. In addition,the test for the electriccatalytic reduction of hydrogen peroxide dispalys that hemoglobin does not denature after the immobilization on the surface of modified electrode.Itcan retain the catalytic activity very well.3.As we know, the layered double metal hydroxides have the inorganic layered structure and the carbon nanotubes have excellent electrical conductivity,so we can ues them to prepare a Zn Al-LDHs/CNTs composite electrode through a convenient electrochemical deposition method without any additional immobilization. On this basis,we construct a new kind of electrochemical sensor which can effectively detect the catechol and hydroquinone at the same time.The results show that the CNTs/Zn Al-LDHs modified electrode displays two couples of independent and well-de?ned redox peaks under the optimal experimental conditions, and the separation of the△Ep is 130 mV which is large enough to distinguish the catechol and hydroquinone from each other. Compared with the bare QCM gold electrode,we can find that the peak current of the modified electrode increases markedly.This shows that the join of carbon nanotubes and Zn Al-LDHs can effectively promote the electric catalytic proces of catechol and hydroquinone.Further tests show that the modified electrode has good reproducibility and stability.