Study On Electrochemiluminescence Sensors Constructed By Dual Molecular Recognition Strategy For DA Sensing

Electrolenerated chemiluminescence（ECL）is a special chemiluminescence phenomenon which is caused by electrochemical redox reaction.Due to the attractive advantages of ECL,such as simple operation,low background signal,high sensitivity,rapid detection,ECL technique has been of great interest in clinical research,food industry and environmental analysis.Dopamine（DA）is a catecholamine neurotransmitter.Abnormal DA levels in the body will cause a variety of diseases,such as parkinson’s disease and severe mental disorders and schizophrenia.Therefore,it is significant to develop a rapid,sensitive and accurate quantitative method to detect DA for the diagnosis and treatment of certain diseases.ECL sensor,which use ECL nanomaterials as a sensing element,has been applied in fast and high sensitivity detection of DA.But most of these sensors are poor selectivity and the need for large quantities of drugs.In order to solve this problem,combined bimolecular recognition strategy with the nanomaterials,this paper has constructed the signal enhancement sensor,the signal quenching sensor and the dual signal ratio ECL sensor for the detection of small molecular DA.Part 1 Electrochemiluminescence sensor for dopamine with a dual molecular recognition strategy based on graphite-like carbon nitride nanosheets/ 3,4,9,10-perylenetetracarboxylic acid hybridsGraphite-like carbon nitride nanosheets/3,4,9,10-perylenetetracarboxylic acid hybrids（g-C₃N₄ NSs-PTCA）were synthesized via π-π conjugate action.Based on a novel dual molecular specific recognition of oxyethyl group to diol and carboxyl to amine group,a signal-on ECL sensor for DA was constructed utilizing g-C₃N₄ NSs-PTCA as signal probe and K2S2O8 as coreactant.Under the optimal conditions,the prepared ECL sensor presented a response to DA with a linear range from 6.0 pmol·L-1 to 30.0 nmol·L-1.The detection limit（LOD）of the sensor was 2.4 pmol·L-1.The g-C₃N₄ NSs-PTCA as signal probe coupling with the novel dual molecular recognition strategy would provide a promising ECL sensing platform for detecting DA sensitively and selectively.Part 2 The electrochemiluminescence resonance energy transfer between Fe-MIL-88 metal–organic framework and 3,4,9,10-perylenetetracar-boxylic acid for dopamine sensingHere,the cathodic electrochemiluminescence（ECL）behavior of 3,4,9,10-perylenetetracar-boxylic acid（PTCA）coreacted with hydrogen peroxide was firstly reported.The quenching effect of Fe-MIL-88 MOFs（iron based metal-organic framework）on the ECL of PTCA was found,and the ECL quenching mechanism was investigated,which was speculated to be via the resonance energy transfer from PTCA to Fe-MIL-88 MOFs and steric hindrance effect from Fe-MIL-88 MOFs.Combining with dual molecular recognition strategy and the quenching effect of Fe-MIL-88 MOFs on the ECL of PTCA-H₂O₂ system,an “on-off” ECL sensor was designed to detect dopamine（DA）with a broad linear range（five orders of magnitude）.The detection limit was low to 2.9×10-13 mol·L-1.The PTCA-H₂O₂ system would provide a new ECL platform,especially for constructing enzyme based ECL sensor with H₂O₂ as product in enzymatic reaction.Furthermore,the electrochemiluminescence resonance energy transfer between Fe-MIL-88 metal–organic framework and PTCA would expand a new application of Fe-MIL-88 MOFs in ECL field.The dual molecular recognition strategy ensured the selectivity of the sensor for DA detection.Part 3 A dual-potential electrochemiluminescence ratiometric sensor for detecting dopamine based on graphene-Cd Te quantum dots and self-enhanced Ru（II）complexA novel dual-potential ratiometric ECL sensor was designed for detecting DA based on graphene-Cd Te quantum dots（G-Cd Te QDs）as the cathodic emitter and self-enhanced Ru（II）composite（TAEA-Ru）as the anodic emitter.TAEA-Ru was prepared by linking ruthenium（II）tris（2,2′-bipyridyl-4,4′-dicarboxylato）with tris（2-aminoethyl）amine.Firstly,3-aminopropyltriethoxysilane（APTES） founctionalized G-Cd Te QDs was used as the substrate for capturing target DA via the specific recognition of the diol of DA to the oxyethyl group of APTES.Then,Cu₂ O nanocrystals supported TAEA-Ru was further bound by the strong interaction between amino groups of DA and carboxyl groups of the Cu₂O-TAEA-Ru.With the increase in DA concentration,the loading of Cu₂O-TAEA-Ru at the electrode increased.As a result,the anodic ECL signal from TAEA-Ru increased,and the cathodic ECL signal from G-Cd Te QDs/O2 system decreased correspondingly.Such a decrease was resulted from the ECL resonance energy transfer（RET）from G-Cd Te QDs to TAEA-Ru as well as the dual quenching effects of Cu₂ O to G-Cd Te QDs,namely the ECL-RET from G-Cd Te QDs to Cu₂ O and the consumption of coreactant O2 by Cu₂ O.Based on the ratio of two ECL signals,the determination of DA was achieved with a linear range from 10.0 fmol·L-1 to 1.0 nmol·L-1 and a detection limit low to 2.9 fmol·L-1（S/N = 3）.The combination of G-Cd Te QDs/O2 and TAEA-Ru would break the limitation of the same coreatant shared in previous ECL ratiometric systems and provide a potential application of ECL ratiometric sensor in the detection of biological small molecules with the assistance of the dual molecular recognition strategy.