Research On The Fabrication Of And Application Electrochemiluminescence Sensor

Electrochemiluminescence(ECL)was a process that the measurable luminescent signals were emitted by excited states generated at electrodes via an applied voltage undergo high-energy electron-transfer reactions,which combines the electrochemical and luminescent techniques.It was a way to convert electrical energy into radiative energy.Besause of attractive superiorities such as high sensitivity,simple instrumentation,low cost,miniaturization and the controlled time and position of the light-emitting reaction,ECL had become a very powerful analytical technique and been quickly developed in many fields,such as bioassay,food and water monitoring,and environmental pollutant testing.Various strategies were proposed to improve the ECL intesity of the ECL sensor,for example,dopped technology,capped methods or employing nanoscaled materials.Thus,this thesis was committed to development some novel ECL sensors with high sensitivity and selectivity based on the signal amplification strategy.These sensors were constructed with the composites of semiconductor nanoparticles and graphene-based nanomaterials and applied to 2,4,6-trinitrotoluene(TNT)detection.1.A novel sensor based on graphene quantum dots enhanced electrochemiluminescence of cadmium selenium quantum dots for the detection of 2,4,6-trinitrotoluene in soilA highly sensitive and selective ECL sensor was developed for the detection of TNT through an assembly strategy of cadmium selenium quantum dots(CdSe QDs)and graphene quantum dots(GQDs).In this sensing strategy,the poly(diallyldimethylammonium chloride)(PDDA)-protected graphene(P-GR)was employed to firmly immobilize CdSe QDs.Then,the P-GR was assembled with CdSe QDs to form P-GR/CdSe by electrostatic interaction.The carboxyl functionalized CdSe QDs were coupled with amino-functionalized graphene quantum dots(afGQDs)through amide covalent bond by using N-(3-dimethylaminoproyl)-N'-ethylcarbodiimide hydrochlorede/N-hydroxysuccinimide(EDC/NHS).Owing to the presence of GQDs,the resulting CdSe-GQDs film exhibited about 8-fold enhanced ECL intensity than pure CdSe QDs with the ECL reaction onset potential positively shifted.In presence of TNT,the ECL quenching phenomenon was generated by forming the TNT-amine complex,which promoted electrons to transfer from excited CdSe QDs to TNT-amine complex.The decreased ECL intensity was related to the logarithm of TNT concentration in the range from 0.01 to 100 ppb with a detection limit of 3 ppt.The results of real soil samples detection for spiked TNT showed good recoveries(99.20-105.00%)and RSD(3.02-8.19%).This sensing strategy may offer a new perspective for developing ECL sensors with semiconductor nanoparticles and graphene-based nanomaterials for explosives analysis.2.Electrochemiluminescence aptasensor based on the composite of CdSe QDs and amino-functionalized GQDs for the ultrasensitive determination of 2,4,6-trinitrotoluene in soilA novel aptasensor based on the CdSe@afGQDs nanocrystals(CdSe@afGQDs NCs)was developed to detect TNT in soil.The aptamer was conjugated onto the CdSe@afGQDs NCs modified electrode by using EDC/NHS coupling reactions between-COOH of CdSe@afGQDs NCs and-NH2 of the aptamer.The modified electrode displayed an about 9.2-fold enhanced ECL intensity compared to an glassy carbon electrode(GCE)with CdSe QDs only,and the onset potential of the ECL reaction was positively shifted by 10 mV.Under the optimal conditions,the concentrations of TNT were measured through the decrease in ECL intensity resulting from the biorecognition between the aptamer and TNT inhibited the electrons transfer in the ECL reaction.The decrease in ECL intensity was related to the logarithm of the TNT concentration in the range from 0.1 to 100 ng L-1,with a detection limit as low as 0.1 pg L'1.The sensor obtained highly sensitivity and showed high selectivity towards TNT against 2,4-dinitrotoluene(DNT),p-nitrotoluene(NT)and nitrobenzene(NB).This strategy may open a new perspective for developing ECL sensors with the composite of semiconductor QDs and GQDs to analyse...