Study On Electrochemiluminescence Of Pyronine-based Organic Small Molecule

Electrochemiluminescence（ECL）is a luminescence phenomenon resulting from oxidation or reduction reactions of a luminophore on the electrode surface,generating an excited state that emits light upon returning to the ground state.ECL is extensively utilized in sensing,imaging,and single-cell analysis due to its low background signal,high sensitivity,wide detection range,and facile operation.The performance of the ECL system is heavily dependent on the luminophore employed.Small organic molecule ECL luminophores,in particular,offer excellent biocompatibility,well-defined molecular structures,facile tuning of luminescent properties,and adjustable luminescence potential,making them an attractive option among various organic luminophores.In recent years,remarkable advancements have been achieved in the investigation of small organic molecule ECL luminophores.On one hand,through the introduction of various functional groups or structural modifications,the properties of ECL luminophores can be adjusted,leading to improved luminescence efficiency and stability.On the other hand,researchers are continuously exploring novel types of small organic molecule ECL luminophores to fulfill practical application requirements.Despite the wide-ranging potential of small organic molecule ECL luminophores in diverse fields,further endeavors are necessary to enhance their luminescence efficiency,improve water solubility,introduce functional groups,develop new luminophores,and broaden practical applications.Pyronin,an organic xanthene-based fluorescent dye,exhibits excellent photochemical properties,high water solubility,wide applicability,and facile modification.Despite being commonly employed in the design and development of fluorescent probes,the electrochemiluminescence properties of pyronin and its derivatives have not been reported.Biothiols,such as cysteine,homocysteine,and glutathione,play critical roles in maintaining redox homeostasis and protein conformation in biological systems,and are implicated in numerous diseases.By leveraging the substitution reaction between thio-pyronin and biothiols,the individual detection of these biothiols can be achieved.Two experimental systems were devised based on these principles:1.Electrochemiluminescence properties of pyronin and its derivativesBenzylthiol-substituted pyronin（BTP）and phenylamine-substituted pyronin（PAP）were synthesized from pyronin（PYR）.These three organics serve as novel small organic molecule ECL luminophores that can generate strong ECL emissions.When tri-propylamine（TPr A）is used as the coreactant,they exhibit anodic ECL emission,and when K₂S₂O₈ is used as the coreactant,they exhibit cathodic ECL emission.Taking BTP as an example,annihilation,reductive-oxidative,and oxidative-reductive ECL mechanisms are investigated,respectively.Substituents can affect the luminescence potential and wavelength of the organic compounds,particularly the cathodic ECL emission of BTP,which has the advantages of a lower luminescence potential at-0.54 V and a higher luminescence wavelength at 728 nm.Therefore,we focused on the ECL performance of the BTP/K₂S₂O₈ system in the range of-0.70 V to 0.00 V.The luminescence potential is lower than that of the previous K₂S₂O₈ cathodic ECL system,and it can operate under physiological p H conditions,which has great potential for applications in ECL biosensors and cell imaging.2.Bioanalytical application of electrochemiluminescence of thio-pyroninPyronin derivatives have excellent electrochemiluminescence properties.Therefore,sensitive detection of cysteine（Cys）,homocysteine（Hcy）,and glutathione（GSH）has been achieved under physiological p H conditions based on their substitution-rearrangement cascade reaction induced by Cys/Hcy and substitution reaction induced by GSH with thio-pyronin.By controlling the reaction conditions,we obtain three new thio-pyronins,namely C-BTP,H-BTP,and G-BTP,and their ECL signals increase significantly with K₂S₂O₈ as coreactant.We use the differences in the interaction between BTP and Cys,Hcy,and GSH to design and implement their respective detection,and systematically study the mechanism of action by electrochemical characterization,theoretical calculation,and optical characterization.We have achieved selective detection of Hcy and Cys in the low potential range of-0.70 V to 0.00 V and GSH in the potential range of-1.50 V to 0.00 V under physiological p H conditions.Additionally,considering the advantages of the C-BTP/K₂S₂O₈ system,such as low potential,high stability,and good solubility in water,we have also achieved I^-detection based on the oxidation-reduction reaction between S₂O₈^2-and I^-.