Construction And Application Of A Ratiometric Electrochemical Sensor Based On Carbon Nanotubes,Gold Nanoparticles And Electroactive Dye Composites

In recent years,a variety of advanced analytical methods have been developed and used in chemical analysis detection.Compared with other high-cost and time-consuming analytical methods,electrochemical sensors are easy to operate,time-saving and efficient,and are used in environmental monitoring,food security and biomedical and other fields.Ratiometric electrochemical sensors are widely praised for their higher detection accuracy than traditional single-signal sensors due to their built-in calibration function.The key to the high performance of ratiometric sensors lies in the selection and use of nanomaterials and internal reference probes.The former can not only improve the detection sensitivity of the sensor based on the electron transfer ability,but also facilitate the immobilization of the probe and the adsorption of the analyte based on the large specific surface area.The latter can monitor the progress of electrochemical reactions based on self-stabilization and prominent redox signals.In this paper,based on the synergistic effect of metal nanomaterials,carbon nanomaterials and electroactive organic compounds,ratiometric electrochemical sensors with different functions have been developed for accurate and sensitive analysis of hormone analogs in environmental water and food.The main research contents of this paper is the following two aspects:（1）The bare electrode（GCE）was directly electrochemically reduced in chloroauric acid solution to obtain gold nanoparticles（Au NP）,and then the PTB/Au NP/GCE modified electrode was obtained by electropolymerization of toluidine blue（TB）,and a ratiometric electrochemical sensor for bisphenol A（BPA）detection was constructed.The gold nanoparticles（Au NP）have large surface area,good electrical conductivity and electrocatalytic ability,and poly（toluidine blue）（PTB）can serve as a good internal reference electroactive probe,and the poly（toluidine blue）/gold nanocomposites can effectively improve the sensitivity of the detection of bisphenol A.The oxidation peak current of bisphenol A increases gradually with the increase of bisphenol A concentration,while the oxidation peak current of poly（toluidine blue）almost remains stable.The ratiometric signal I_BPA/I_PTB,the ratio of the oxidation peak currents of bisphenol A to poly（toluidine blue）,increases linearly with the bisphenol A concentration in the range of 0.2-5.0μM.The sensor has a detection limit of 0.15μM and can be successfully applied to the detection of BPA in water samples.（2）Multi-walled carbon nanotubes（MWCNT）were firstly treated with acid,and then modified on the bare GCE to obtain MWCNT/GCE.After that,neutral red（NR）was electropolymerized on the modified electrode to construct a PNR/MWCNT/GCE–based ratiometric electrochemical sensor for estriol detection.Among them,poly（neutral red）/multi-walled carbon nanotube composites can be used as internal reference electroactive probes.The results show that the glassy carbon electrode modified with poly（neutral red）and acidified multi-walled carbon nanotubes has good chemical stability,high specific surface area,high conductivity and good electrocatalytic property,which enhance the electrochemical signal of estriol,thereby improving the detection sensitivity of estriol.The ratiometric signal I_Estriol/I_PNR（the oxidation peak current ratio of estriol to poly（neutral red））is obtained in the range of 0.1-2.0μM and increases linearly with the estriol concentration with a detection limit of 0.08μM.The sensor can be used for the detection of estriol in milk with satisfactory results.