A method for enhancing electrochemiluminescence signal by ion-pi interaction

Abstract

The application relates to a method for enhancing electrochemiluminescence signals by ion-pi interaction, belonging to the fields of electrochemiluminescence and analytical chemistry. 2+ By modifying the working electrode with a conjugated pi system, cation-pi interaction is introduced into the Ru(bpy)3 / triethylamine (TEA) system, efficient enrichment of TEA protonated cations near the electrode is realized, thereby greatly enhancing the electrochemical reaction rate and ECL signal. Further, anion-pi interaction is utilized to realize ECL signal enhancement of the luminol ECL system. In addition, the conjugated pi system is exposed to the outermost boundary of the electrode, so as to provide effective ion-pi interaction for ECL; when the pi system is covered by an alkyl chain, the modified electrode can only exhibit hydrophobic interaction. The method disclosed by the application provides a new strategy for extending ion-pi interaction to all types of ECL systems and constructing a high-sensitivity ECL analysis platform.

Description

Technical Field

[0001] This invention relates to a method for enhancing electrochemiluminescence signals using ion-π interactions, belonging to the fields of electrochemiluminescence and analytical chemistry. Background Technology

[0002] Electrochemiluminescence (ECL) is an analytical method based on the generation of luminescent substances through electrochemical reactions. It boasts advantages such as high sensitivity, good selectivity, and minimal interference. Enhancing the ECL signal is crucial for improving the sensitivity and accuracy of ECL analysis. ECL was initially developed based on the annihilation mechanism in organic solutions, but it is not generated or is generated with low efficiency in aqueous solutions. By introducing various co-reactants, ECL can be generated efficiently in aqueous environments, greatly expanding the application scope and practical value of ECL analysis. Ion-π interactions are considered the primary force in molecular recognition and are increasingly widely used in organic synthesis, supramolecular assembly, catalysis, and biology. π-molecule systems generate a negative electrostatic potential region on their surface and a positive electrostatic potential region around them, effectively attracting positively charged cations and negatively charged anions.

[0003] We boldly hypothesize that by modifying the surface of the ECL working electrode with different π-molecule systems, we can explore whether the anions and cations of the ECL luminescent reagent / co-reactant can form efficient ion-π interactions with the π-molecule systems. Unlike the current main application of ion-π interactions in molecular recognition, we aim to explore the enhancement effect of ion-π interactions on ECL signals. To realize this hypothesis, Ru(bpy)3... 2+ Taking the triethylamine (TEA) ECL system as an example, using TPE-C 12 Three cationic surfactants, TAB, C4-TPE-C8TAB, and C8-TPE-C4TAB, with the same hydrophilic head group and different hydrophobic tail groups, were used to modify the surface of a gold electrode. The three surfactant molecules formed a self-assembled monolayer on the gold electrode surface, with the hydrophilic head group pointing towards the electrode and the hydrophobic tail group pointing towards the solution. In a phosphate buffer solution at pH 7.4, compared with a bare gold electrode, the C8-TPE-C4TAB-modified gold electrode and the C4-TPE-C8TAB-modified gold electrode showed enhanced Ru(bpy)3... 2+ The ECL signal of the / TEA system is approximately 4 times that of TPE-C. 12 TAB-modified gold electrodes enhanced the ECL signal by up to 14 times. (One-dimensional nuclear magnetic resonance) 1 ¹H NMR and two-dimensional NMR (NOESY) spectra confirmed the existence of cation-π interactions between TPE and TEA cations, indicating that cation-π interactions can significantly enhance the ECL signal. Furthermore, TPE-C 12The TAB-modified gold electrode exhibits a higher signal enhancement capability than the C8-TPE-C4TAB and C4-TPE-C8TAB-modified gold electrodes, indicating that ion-π interactions can only function in ECL when the π system is exposed at the outermost boundary of the electrode. Summary of the Invention

[0004] The purpose of this invention is to achieve TPE-C 12 Using TAB-modified gold electrodes to construct π systems, and utilizing the protonated cations of TEA and the cation-π interaction of tetraphenylethylene (TPE), a new approach is provided to enhance ECL signals.

[0005] The present invention discloses a method for enhancing electrochemiluminescence signals using ion-π interactions. The method is characterized by adding a surfactant containing a π system to an ionic electrochemiluminescence system solution, which allows the surfactant to self-assemble on the electrode surface to form a monolayer hydrophobic film, thereby constructing a π system microenvironment. The π system microenvironment on the electrode surface interacts with the corresponding ionic electrochemiluminescent material, thereby further enhancing the electrochemiluminescence signal.

[0006] The surfactant in the π-containing system is selected from cationic surfactants, specifically dodecyltrimethylammonium bromide (C646). 12 Derivatives of TAB, with molecular formulas C8-TPE-C4TAB, C4-TPE-C8TAB, and TPE-C 12 TAB. The difference between the three derivatives lies in the fact that the TPE group is modified at a distance of C. 12 The TAB quaternary ammonium head group is located at the 4th, 8th, and 12th methyl groups. The surfactant of the π-containing system of the present invention is further preferably TPE-C. 12 TAB.

[0007] The concentration of the surfactant containing π in the electrochemiluminescence system solution is greater than or equal to the critical micelle concentration (e.g., the critical micelle concentration is 45 μM), preferably 65 μM.

[0008] The ions mentioned are either anions or cations, and the cationic electrochemiluminescence system further includes Ru(bpy)3. 2+ / TEA system, anionic electrochemiluminescence system includes luminol / O2 system.

[0009] The electrode is a gold electrode.

[0010] In the self-assembly of a monolayer hydrophobic film, the gold electrode surface is arranged in a single layer with the hydrophilic head group facing the electrode surface and the hydrophobic tail chain facing the solution.

[0011] The specific method includes the following: adding the surfactant containing the π system to the ionic electrochemiluminescence system solution and mixing it evenly, then inserting it into the corresponding electrode for 3-5 minutes, and then conducting the electrochemiluminescence experiment by applying electricity.

[0012] Advantages of this invention:

[0013] By modifying the working electrode with a conjugated π system, cation-π interactions are introduced into Ru(bpy)3. 2+ The triethylamine (TEA) system achieves efficient enrichment of protonated TEA cations near the electrode, resulting in a significantly enhanced electrochemical reaction rate and ECL signal. Under the same conditions, the ECL signal enhanced by cation-π interactions can be increased from 4-fold to 14-fold compared to traditional hydrophobic interactions. Further enhancement of the ECL signal in the luminol ECL system was achieved using anion-π interactions. Moreover, the conjugated π system must be exposed at the outermost boundary of the electrode to provide effective ion-π interactions for ECL; when the π system is covered by alkyl chains, the modified electrode only exhibits hydrophobic interactions. The method disclosed in this invention provides a new strategy for constructing highly sensitive ECL analysis platforms by extending ion-π interactions to all types of ECL systems.

[0014] By inserting gold electrodes into TPE-C 12 Contact angle tests were performed on the gold electrode surface after immersion in a TAB solution for 3-5 minutes, indicating that the electrode surface is hydrophobic. In Ru(bpy)3... 2+ In the / TEA system, TPE-C 12 TAB enhances Ru(bpy)3 2+ ECL signals, detected by one-dimensional nuclear magnetic resonance (NMR) 1 ¹H NMR and two-dimensional nuclear magnetic resonance (NOESY) methods revealed a cation-π interaction between the protonated TEA cation and TPE, and that this cation-π interaction was enhanced in Ru(bpy)₃. 2+ Electrochemiluminescence signal. Similarly, through... 1 ¹H NMR and NOESY methods revealed anion-π interaction between luminol anions and TPE, and that the anion-π interaction enhanced the electrochemiluminescence signal of luminol. Attached Figure Description

[0015] Figure 1 For TPE-C 12 Molecular structure diagrams of TAB, C4-TPE-C8TAB, and C8-TPE-C4TAB. Figure 2 For TPE-C 12 Contact angle data for gold electrodes modified with TAB, C4-TPE-C8TAB, and C8-TPE-C4TAB.

[0016] Figure 3 For TPE-C 12 TAB, C4-TPE-C8TAB, and C8-TPE-C4TAB enhance Ru(bpy)3 2+ Electrochemiluminescence signal diagram (A) and its cyclic voltammetry curve (B).

[0017] Figure 4 For TEA protonated cations and TPE 1 H NMR spectrum.

[0018] Figure 5 The NOESY spectrum is of TEA protonated cations and TPE.

[0019] Figure 6 In the middle (A), luminol anion reacts with TPE. 1 H NMR spectrum, (B) is TPE-C 12 TAB-enhanced electrochemiluminescence signal diagram of luminol. Detailed Implementation

[0020] To illustrate the present invention more clearly, the following embodiments are provided, but the scope of protection of the present invention is not limited to the following embodiments.

[0021] Unless otherwise specified, the methods described in this invention are conventional methods, and the raw materials are all available from publicly available commercial sources.

[0022] Example 1

[0023] Final concentrations of each substance in a homogeneous mixed solution: Ru(bpy)3 2+ In the / TEA system, Ru(bpy)3 2+ The concentration of the active ingredient was 5 μM, the concentration of TEA was 15 mM, the solvent was a phosphate buffer solution with pH = 7.4, and the surfactant was TPE-C. 12 The concentrations of TAB, C4-TPE-C8TAB, and C8-TPE-C4TAB were all 65 μM. In the luminol / O2 system, the final concentration of luminol was 20 μM, and the solvent was a sodium hydroxide solution with pH = 12.

[0024] Ru(bpy)3 with added surfactant 2+ Preparation of homogeneous mixed solutions in the TEA system: Different surfactants TPE-C 12 TAB, C4-TPE-C8TAB, and C8-TPE-C4TAB were respectively supplemented with Ru(bpy)3. 2+ In the / TEA system, after thorough mixing, electrochemical tests were performed, and the final concentrations of each substance were: Ru(bpy)3 2+The concentration of the active ingredient was 5 μM, the concentration of TEA was 15 mM, the solvent was a phosphate buffer solution with pH = 7.4, and the surfactant was TPE-C. 12 The concentrations of TAB, C4-TPE-C8TAB, and C8-TPE-C4TAB were all 65 μM.

[0025] The preparation of a luminol / O2 system with added surfactant, including TPE-C 12 TAB was added to the luminol solution, with the following final concentrations: luminol final concentration 20 μM, solvent is sodium hydroxide solution with pH = 12, TPE-C 12 The TAB concentration was 65 μM.

[0026] Example 2

[0027] Verification of the formation of a hydrophobic thin film on the surface of a gold electrode to construct a π system.

[0028] Using contact angle experiments to investigate different surfactants ( Figure 1 The modification status of the electrode surface. The gold electrodes were immersed in 65 μM TPE-C... 12 After soaking in TAB, C4-TPE-C8TAB, and C8-TPE-C4TAB solutions for 3-5 minutes, blow dry and immediately measure the contact angle of the electrode surface. The results are as follows: Figure 2 As shown. The contact angle reading of the exposed gold electrode is 72.6°, TPE-C. 12 When the concentration of TAB, C4-TPE-C8TAB, and C8-TPE-C4TAB is 65 μM, their contact angles are 95.8°, 95.4°, and 94.7°, respectively, indicating that TPE-C 12 TAB, C4-TPE-C8TAB, and C8-TPE-C4TAB are arranged in a monolayer on the gold electrode surface, with the hydrophilic head group facing the electrode surface and the hydrophobic tail chain facing the solution. Among them, TPE-C... 12 The TPE groups of the TAB surfactant face the solution.

[0029] Example 3

[0030] Study on the enhancement of electrochemiluminescence by cation-π interaction: using Ru(bpy)3 2+ / TEA is a representative example of Ru(bpy)3 with added surfactant in Example 1. 2+ Study on electrochemiluminescence signal and cyclic voltammetry of the / TEA system.

[0031] TPE-C with similar critical micelle concentration (CMC) and hydrophobicity was investigated using an electrochemical workstation and a weak luminescence meter. 12TAB, C4-TPE-C8TAB, and C8-TPE-C4TAB enhance Ru(bpy)3 2+ The electrochemiluminescence of the system yielded the following results: Figure 3 (A) Electrochemiluminescence signal diagram and Figure 3 The cyclic voltammetry curves (B) are shown in Figure 1. The results indicate that... Figure 3 TPE-C can be found in (A). 12 TAB-modified gold electrodes enhanced the ECL signal by up to 14 times, while C8-TPE-C4TAB and C4-TPE-C8TAB enhanced Ru(bpy)3. 2+ The ECL signal is approximately four times stronger. Additionally, through... Figure 3 Cyclic voltammetry experiments in (B) show that TPE-C can be observed in the potential range of 0.7–1.2 V. 12 The current oxidized by TAB to TEA was much greater than that of the other two molecules, indicating that TPE-C 12 TAB-modified gold electrodes can accumulate more TEA molecules on the electrode surface, thereby increasing the direct oxidation rate of TEA on the electrode. Furthermore, the π system must be exposed at the outermost boundary of the electrode to enhance the ECL signal by approximately 14 times; when the π system is covered by alkyl chains, the modified electrode only exhibits hydrophobic interactions. The cyclic voltammetry experiment was conducted at a scan rate of 100 mV / s.

[0032] Example 4

[0033] In this invention, the cation-π interaction enhances electrochemiluminescence utilization. 1 Verification by H NMR characterization.

[0034] use 1 Further research using H NMR characterization methods was conducted on Ru(bpy)3 2+ TPE-C in the TEA luminescent system 12 TAB for Ru(bpy)3 2+ The effect of electrochemiluminescence. To avoid interference from the carbon chain, TPE molecules were used instead of TPE-C. 12 TAB is used to acidify TEA with sodium acetate to provide protonated TEA cations. TPE is mixed with an equal molar amount of the protonated TEA cation solution, and then... 1 ¹H NMR characterization further confirmed the cation-π interaction between TPE and the protonated cation of TEA. Results are as follows: Figure 4 As shown, when cation -π is present, compared with the proton peaks of TPE and TEA protonated cations respectively, when TPE is mixed with the same molar amount of TEA protonated cation solution, all the proton peaks of TEA shift to the higher field and the chemical shift becomes smaller.

[0035] Example 5

[0036] The enhancement of electrochemiluminescence by cation-π interaction in this invention was verified using NOESY characterization.

[0037] Further investigation was conducted using the NOESY characterization method in Ru(bpy)3. 2+ TPE-C in the TEA luminescent system 12 TAB for Ru(bpy)3 2+ The effect of electrochemiluminescence. To avoid interference from the carbon chain, TPE molecules were used instead of TPE-C. 12 TAB was used to acidify TEA with sodium acetate to provide protonated TEA cations. TPE was mixed with an equal molar amount of the protonated TEA cation solution, and the cation-π interaction between TPE and the protonated TEA cations was further confirmed by NOESY characterization. Results are as follows: Figure 5 As shown, the selected region reveals some weak but clearly visible cross-peaks between the proton peaks of TPE and the protonated cations of TEA, indicating a strong NOE correlation. These further demonstrate the existence of cation-π interactions between TPE and the protonated cations of TEA, which attract more TEA molecules to the electrode surface to participate in the reaction, ultimately generating a strong ECL signal.

[0038] Example 6

[0039] This invention investigates the enhancement of electrochemiluminescence by anion-π interaction: using a luminol / O2 system with added surfactant as a representative example, the enhancement of luminol electrochemiluminescence by anion-π interaction is studied.

[0040] use 1 The interaction between luminol anion and TPE was investigated using 1H NMR characterization. To avoid interference from the carbon chain, the TPE molecule was used instead of the TPE-C chain. 12 TAB, luminol exists in an anionic state under alkaline conditions with sodium hydroxide. TPE is mixed with an equal molar amount of anionic luminol solution, and then... 1 1H NMR characterization further confirmed the anion-π interaction between TPE and luminol anions. Results are as follows: Figure 6 As shown in (A), when the anion -π is present, compared with the individual proton peaks of TPE and luminol anions, the proton peak of luminol shifts to a lower field and the chemical shift increases when TPE is mixed with the same molar amount of luminol anion solution. The interaction between TPE and luminol anions due to the anion -π was investigated using an electrochemical workstation and a weak luminescence meter. 12 TAB enhances the electrochemiluminescence of the luminol system, and the results are as follows: Figure 6 (B) Electrochemiluminescence signal diagram shows TPE-C 12Due to the anion-π interaction between TAB and luminol anions, TAB attracts luminol anions to the electrode surface to participate in the reaction, thereby enhancing the electrochemiluminescence of luminol.

Claims

1. A method for enhancing electrochemiluminescence signals using ion-π interactions, characterized in that, Adding a π-system-containing surfactant to the ionic electrochemiluminescence system solution allows the π-system-containing surfactant to self-assemble on the electrode surface to form a monolayer hydrophobic film, thus constructing a π-system microenvironment. The π-system microenvironment on the electrode surface interacts with the corresponding ionic electrochemiluminescent material, thereby further enhancing the electrochemiluminescence signal. The surfactant in the π-containing system is selected from cationic surfactants, specifically dodecyltrimethylammonium bromide C. 12 TAB derivatives C8-TPE-C4TAB, C4-TPE-C8TAB, and TPE-C 12 One or more of the TABs.

2. The method according to claim 1, characterized in that, The surfactants containing π-systems exhibit the best performance in electrochemiluminescence systems when their concentration is between 0 and 80 μM and greater than the critical micelle concentration of 45 μM.

3. The method according to claim 2, characterized in that, The concentration of the surfactant containing π in the electrochemiluminescence system solution was 65 μM.

4. The method according to claim 1, characterized in that, The ions mentioned are either anions or cations.

5. The method according to claim 4, characterized in that, Cationic electrochemiluminescence systems include Ru(bpy)3 2+ / TEA system, anionic electrochemiluminescence system includes luminol / O2 system.

6. The method according to claim 1, characterized in that, The electrode is a gold electrode.

7. The method according to claim 1, characterized in that, In the self-assembly of a monolayer hydrophobic film, the gold electrode surface is arranged in a single layer with the hydrophilic head group facing the electrode surface and the hydrophobic tail chain facing the solution.

8. The method according to claim 1, characterized in that, The specific method includes the following: adding the surfactant containing the π system to the ionic electrochemiluminescence system solution and mixing it evenly, then inserting it into the corresponding electrode for 3-5 minutes, and then conducting the electrochemiluminescence experiment by applying electricity.

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