Exploration On The Mechanism Of Ion-π Interaction Enhancing Electrochemiluminescence

Electroluminescence（ECL）is a chemiluminescence phenomenon generated by electrochemical reactions near the electrode.Obtaining an efficient and stable ECL signal plays a crucial role in the sensitivity and accuracy of ECL analysis.Currently,ECL bioanalysis and imaging applications are performed in an aqueous environment,and the corresponding ECL luminescent and co-reactive reagents are usually in the form of anions and cations.However,it is not clear what role the ionic forms of these luminescent or co-reactive reagents play in the ECL luminescence process.Therefore,understanding and utilizing the mechanism of the role of luminescent reagents or co-reactive reagent ions in ECL reactions is of great importance for the development of efficient ECL systems.Based on this,this thesis aims to construct molecular films with aπsystem on the electrode surface,introduce cation-πinteraction into the Ru（bpy）₃²⁺/TEA system,and anion-πinteraction into the luminol/O₂ system,achieve efficient enrichment of TEA protonated cations and luminol anions near the electrode,thus obtaining significantly enhanced electrochemical reaction rate and ECL signal,and providing a new strategy for constructing highly sensitive ECL analysis platforms.1.The hydrophobic andπ-system microenvironments were constructed usingcetyltrimethylammoniumbromide(C₁₆TAB),octadecyltrimethylammoniumbromide(C₁₈TAB)and dodecyltrimethylammonium bromide(TPE-C₁₂TAB)with hydrophobic termini modified with tetraphenylene to self-assemble on the gold electrode surface to form monolayer hydrophobic membranes,respectively.The ECL performance of C₁₆TAB modified gold electrode,C₁₈TAB modified gold electrode and TPE-C₁₂TAB modified electrode was investigated in phosphate buffer solution at p H=7 using Ru（bpy）₃²⁺/TEA system as the ECL model.The results showed that the enhancement of ECL signal by TPE-C₁₂TAB modified electrode was much greater than that by C₁₆TAB modified gold electrode and C₁₈TAB modified gold electrode.Characterization by ECL spectroscopy,cyclic voltammetry（CV）curves,nuclear magnetic resonance（¹H NMR）and nuclear overhauser effect spectroscopy（NOESY）showed a strong cation-πinteraction between the TEA protonated cation and TPE at p H=7,leading to an efficient oxidation of TEA near the TPE-C₁₂TAB modified electrode,which greatly enhanced the ECL signal.This work successfully introduces the cation-πinteraction to the field of ECL and provides a new strategy to improve the sensitivity of ECL detection.2.The ECL performance of TPE-C₁₂TAB,C₁₆TAB and C₁₈TAB modified gold electrodes was investigated by using TPE-C₁₂TAB to construct a monolayer hydrophobic membrane on the surface of gold electrode and C₁₆TAB and C₁₈TAB to construct a bilayer hydrophilic membrane on the surface of electrode,using the lumino/O₂ system as the ECL model,in sodium hydroxide solution at p H=12.The results showed that C₁₆TAB,C₁₈TAB and TPE-C₁₂TAB all improved the ECL signal of luminol,with TPE-C₁₂TAB improving the multiplicity much more than the other two.Characterization by ECL spectroscopy,CV curves,electrochemical impedance spectroscopy（EIS）,¹H NMR and NOESY showed that the TPE-C₁₂TAB-modified gold electrode was able to attract luminol anions by anion-πinteraction,which led to an efficient ECL reaction.The present work successfully extends the cation-πinteraction to enhance ECL to anion-πinteraction,indicating that ion-πinteraction is a general strategy to improve the sensitivity of ECL detection.