| Electroluminescence?ECL?method has the advantages of simple equipment,high sensitivity,no need for light source and low background signal,and has been widely used in analysis and detection.But the selectivity is not good enough for organic small molecules,especially for structurally similar substances.Molecularly imprinted polymer film?MIP?technology is a polymer film technology which uses the molecule to be measured as the template molecule to synthesize the polymer film with molecular recognition site by polymerization reaction.MIP technology is introduced into the ECL sensor,a layer of MIP film is modified on the surface of the sensor,and the high sensitivity and high selectivity detection of the target molecule can be achieved by using the specific recognition ability of the MIP film.The graphite phase carbon nitride nanosheets?g-C3N4 NSs?were used as luminescent materials to fix them on glassy carbon electrodes using their good ECL properties and film-forming properties.Then,the MIP film was introduced on the modified electrode surface by electropolymerization to construct a MIP-ECL sensor to achieve highly sensitive and selective detection of organic small molecule hydroquinone?HQE?and organic drug dopamine?DA?.The contents of the study are as follows:1.The construction of MIP-ECL sensor based on g-C3N4 NSs and the high sensitivity and selectivity detection of hydroquinone:The study found that g-C3N4 NSs had a strong cathode ECL signal under the condition of K2S2O8 as co-reacting agent,while HQE had a strong inhibitory effect on this ECL signal.Using this feature,combined with mip technology,the high sensitivity and high selectivity detection of HQE were realized.The g-C3N4 NSs was synthesized firstly and successfully immobilized on glassy carbon electrode to obtain C3N4/GCE modified electrode.Then using HQE as template molecule and o-phenylenediamine as functionalized monomer,cyclic voltammetry was performed in 0.1 mol·L-1 phosphate buffer solution?PBS??pH=7.4?,and the MIP film was introduced on the surface of the C3N4/GCE by electrochemical polymerization.The MIP-ECL sensor was obtained after remove the template molecular HQE.The sensor was used to achieve HQE highly sensitive and highly selective detection by using the specific recognition ability of the sensor and the inhibition of the sensor ecl signal.Under the optimized conditions,HQE have a good linear response to the MIP-ECL sensor in the range of 5.0×10-91.0×10-5 mol·L-1,and the detection limit is 0.2 nmol·L-1.The sensor was used for the detection of HQE in river water samples,and the results were satisfactory.The sensor prepared in this paper not only has good sensitivity and selectivity,but also has good stability,continuous multiple scans,and the signal is basically stable.To further demonstrate the specific recognition ability of the sensor,we prepared the non-molecule imprinted membrane?NIP?sensor by the same method NIP-ECL,the results show that only MIP-ECL have good recognition ability for HQE,while NIP-ECL sensor have no specific recognition ability.And the inhibition mechanism of HQE on g-C3N4 NSs was discussed.2.Construction of MIP-ECL sensor for sensitive and selective detection of dopamine based on g-C3N4 NSs-Et3N system:Further studies have found that g-C3N4 NSs not only cathode ECL signal can be produced,but also strong ECL signal can be produced at the anode when triethylamine?Et3N?is used as a co-reaction agent.Interestingly,DA has a strong inhibitory effect on the anode signal.Using this inhibitory effect on anode signal,combined with MIP technology,high sensitivity and high selectivity detection of DA can be achieved.The fabrication method of the sensor is similar to that of the upper side.To further improve the sensitivity and stability,we doped a certain amount of multi-walled carbon nanotubes?MWCNTs?in the g-C3N4 NSs.The mixture of MWCNTs and g-C3N4 NSs were introduced on the glassy carbon electrode followed by the same method.Then DA was used as the template molecule and o-phenylenediamine as the functionalized monomer.The MIP film was introduced on the electrode surface by electrochemical polymerization.After elution of the template molecule,the MIP-ECL sensor with specific recognition ability for the DA was obtained.Using Et3N as a co-reaction agent,the high sensitivity and high selectivity detection of the MIP-ECL sensor anode ECL signal were realized by using the inhibition effect of the anode.Under the optimized conditions,DA has a good linear response to the MIP-ECL sensor in the range of 4.0×10-103.0×10-7 mol·L-1,and the detection limit is 0.19 n mol·L-1.This method was applied to detect DA in human blood samples and obtained satisfactory results.3.Establishment of double-potential ratiometric MIP-ECL sensor for accurate detection of dopamine based on g-C3N4 NSs-Et3N system:Dual-potential ratiometric electrochemiluminescence is a method to make quantitative analysis by using the relationship between the ratio of luminous signal to the content of the substance to be tested at different potentials.Compared with the traditional single signal detection technology,the ratio detection technology can correct the influence caused by electrode,instrument and environment change,so as to improve the accuracy of the detection results.g-C3N4 NSs produced ECL signals in both the anode?+1.48 V?and cathode?-1.2V?in the presence of Et3N.But the anode signal was quenched by DA and did not have much effect on the cathode signal.Using this feature,we established a dual-potential ratio ECL method to detect DA by measuring the ratio of the signal at two different potentials,which further improved the reproducibility and improved the accuracy of the detection results. |
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