| In recent years,carbon-based nanomaterials have received wide attention due to their unique photoelectrochemical properties and good environmental compatibility.Graphitic carbon nitride?g-C3N4?is one of graphite-like layered materials with semiconducting poperties and capable of absorbing visible light.It has been widely used as a non-mertallic catalyst in the field of photocatalysis.In addition,it also exhibits excellent fluorescent and electrochemiluminescent properties;with the advantages of high mechanical strength,non-toxicity and good biocompatibility.It is suitable for constructing of biosensor.However,the bulk g-C3N4 shows poor dispersion stability and the small specific surface area,which limit its application.In this paper,graphite phase carbon nitride nanosheets?g-C3N4 NSs?was obtained by a simple and environmentally friendly liquid exfoliation method.Compared to the bulk g-C3N4,the electrochemical luminescence?ECL?efficiency of g-C3N4 NSs was improved obviously.The morphology and chemical composition of the obtained g-C3N4 NSs were characterized by various means.The ECL performance was systematically studied,and the ECL sensor was constructed with simple method.The sensor was applied in high sensitivity detection the organic drug epinephrine.And then we combined ECL with molecular imprinting technology to improve the selectivity of detection.In addition,g-C3N4 NSs combined with graphene quantum dots?GQDs?to construct a two-potential ratio method for the detection metal ions Cu2+.This method can improve the reproducibility of the detection significantly and make the results more accurate and reliable.The research of the full paper as follows:?1?The synthesis and characteristic of g-C3N4 NSsThe bulk g-C3N4 was synthesized with melamine as a precursor by thermal polymerization,and then the weak vander Waals force between g-C3N4 layer and layer was destroyed by hydrochloric acid?HCl?intercalation,meanwhile combined with ultrasonic assisted liquid phase exfoliation.The morphologies and optical properties of obtained g-C3N4 NSs were characterized by Transmission electron microscope?TEM?,X-rayphotoelectronspectroscopy?XPS?,UV-vis spectrophotometer and fluorospectrometer?FL?,It was proved that the obtained ultra-thin g-C3N4 NSs were uniform in size,and exhibited excellent optical properties.?2?Investigation on ECL performance of g-C3N4 NSsThe ECL signals of g-C3N4 NSs was investigated with the three-electrode system in the phosphate buffer medium and it was found g-C3N4 NSs could produce an obvious strong and stable ECL signal at-1.19 V?vs Ag/AgCl?.Compared with the bulk g-C3N4,the ECL signal of g-C3N4 NSs was significantly improved.Furthermore,we founded that multi-walled carbon nanotubes?MWCNT?could enhance the ECL emission of g-C3N4 NSs effectively,which can accelerate the electron transfer between the luminescent material and the electrode surface.?3?Establishment of g-C3N4 NSs/MWCNT ECL sensor and its application for EP detectionThe g-C3N4 NSs and acidified MWCNT were modified on the surface of the glassy carbon electrode by the combination ofp-pand electrostatic action,which not only could save reagents,improve sensitivity,but also it could be used to on-line analysis.The performance of the sensor was characterized by electrochemical impedance and ECL.Subsequently,the effects of the pH of the buffer solution and the concentration of K2S2O8 on the ECL signal of g-C3N4 NSs were investigated,and the optimal detection environment was selected.We found that EP can produce a quenching effect on the ECL intensity of g-C3N4 NSs.Based on the quenching effect,we established a method for sensitive determination of EP in human serum samples.The linear response range is 1.0×10-91.5×10-6mol·L-1,and the detection limit is0.21 nmol·L-1.Compared with other methods of EP determination,this method shows a wider linear range and a lower detection limit.?4?Construction of g-C3N4 NSs surface molecularly imprinted sensor and high selectivity detection of epinephrineA highly sensitive and highly selective ECL-MIP sensor was prepared for the detection of adrenaline by combining ECL with MIP.Firstly,the luminescent substance g-C3N4 NSs was modified on the surface of the GCE to obtain an ECL solid-phase electrode,and then a molecularly imprinted membrane with specific recognition function for epinephrine was prepared.The performance of the sensor was characterized by electrochemical impedance and ECL.The sensor exhibits high sensitivity and selectivity to the target molecule,and the linear range of is 0.5nmol·L-1-5?mol·L-1,the detection range of can reach to 0.19 nmol·L-1.?5?Establishment of double-potential ECL ratiometric sensor based on g-C3N4 NSs/GQDs and its application for Cu2+determinationThe double-potential ratio ECL detection is a detection method that utilizes the ratio or difference between ECL signals of two luminescent materials at different potentials.Based on this,substance can be tested for quantitative analysis.This method can effectively prevent interference from the environment and instrument and improve the accuracy of the analysis results.In this study,it was found that g-C3N4NSs and GQDs can emit light in the same system,but the luminescence potentials of them are different.The g-C3N4 NSs/GQDs ratio ECL system is established for determination of Cu2+,and the linear range is 5.5×10-104.5×10-66 mol·L-1,and the detection limit is 0.37 nmol·L-1.By comparing the ratiometric sensor with a non-ratio type sensor,the reproducibility of theatiometric sensor method can be improved satisfactorily. |
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