A method for morphology control of Ir(piq)3 molecular crystals and its application in electrochemiluminescence waveguides

Abstract

The application discloses a morphology regulation method of Ir(piq)3 molecular crystals and application of the Ir(piq)3 molecular crystals in electrochemiluminescence waveguides, and belongs to the field of micro-nano material processing and photoelectric application. The Ir(piq)3 molecular crystals capable of morphology regulation are prepared by reprecipitation. Tetrahydrofuran (THF) is used as a good solvent, and ethanol (EtOH) is used as a poor solvent. Water (H2O) is introduced into the EtOH poor solvent, so that the morphology and size of the molecular crystals are regulated from micro-rods to micro-tubes containing symmetrical cavities to nanorods. The micro-hemitube structure with symmetrical cavities can efficiently confine electrochemiluminescence generated by itself in the molecular crystals, and finally emit strong light at both ends, has high electrochemiluminescence waveguide efficiency, and can overcome the high loss defect of the micro-rod structure in the remote electrochemiluminescence waveguide. The waveguide based on the one-dimensional organic symmetrical micro-hemitube can efficiently convert the electrochemically generated ECL into remote luminescence of a non-conductive area, and is expected to be used for non-contact electrochemical analysis and research of (bio)chemical systems, and has good application prospect.

Description

Technical Field

[0001] This invention belongs to the field of morphology control of electrochemiluminescent aggregates, specifically relating to a method for morphology control of Ir(piq)3 molecular crystals and its application in electrochemiluminescent waveguides. Background Technology

[0002] Electrochemiluminescence (ECL) is a controllable luminescence phenomenon triggered by electrochemical reactions occurring on the electrode surface. ECL possesses characteristics such as low background, high sensitivity, and superior spatiotemporal controllability, making it one of the most advanced signal transduction technologies currently available. It has a very strong application prospect in commercial biochemical analysis and clinical diagnosis. In addition to the above advantages, ECL imaging analysis also features high analytical throughput and visualization, making it a powerful surface analysis technique widely used in ECL-based sensor array microscopy, latent fingerprinting, imaging of single micro / nanoparticles, single cells, and subcellular structures. In recent years, new concepts and technologies in electrochemiluminescence, such as self-enhanced ECL, potential-resolved multicolor ECL, aggregation-induced ECL (AIECL), surface plasmon resonance-modulated ECL, photoinduced ECL, and circularly polarized ECL, have attracted considerable attention. Recently, ECL waveguides (ECLW) were first applied to tri-(1-phenylisoquinoline-C 2 Electrochemically luminescent waveguides (ECLs) have been observed in single-crystal molecular lines of iridium(III) (Ir(piq)3), where they can function not only as ECL emitters but also as active waveguides for long-range ECL propagation. Based on this, ECLs are proposed as a novel concept and technology.

[0003] ECLWs based on molecular wires have broad application prospects in non-contact electrochemical analysis and (bio)chemical system research. Compared with traditional optical waveguides, ECLWs have the advantages of near-zero background and specific molecular functions. Optical loss during the optical waveguide process is the main parameter for evaluating the performance of ECL waveguides. Optical loss depends on the quality of the crystal structure, such as surface roughness and defect density, which affect scattering loss. On the other hand, the low refractive index of (Ir(piq)3) molecular crystal (n=1.79) inevitably leads to a relatively high substrate effect, which is a major drawback in the development of crystalline organic waveguides. To overcome this difficulty, many methods have been tried to reduce the refractive index of the environment surrounding the waveguide. For example, Zhao et al. prepared hollow 9,10-bis-(phenylethyl)anthracene (BPEA) microtubes, using the air inside the tube to minimize the substrate effect and reduce optical loss. Huang and his colleagues demonstrated that vertically grown nanowires can effectively reduce optical loss by minimizing the substrate effect due to the low refractive index of the air surrounding the waveguide. To further improve the photon guiding efficiency of molecular crystals, new synthesis strategies need to be explored to improve waveguide performance. To date, research on waveguide synthesis strategies has mainly focused on solid and hollow structures, including micro / nanowires, microrods, microtubes, and fibers, while less attention has been paid to special structures such as symmetrical hollow microsemitubes.

[0004] One-dimensional organic crystals are well known for their excellent optoelectronic properties and are crucial components of photonic devices such as multichannel signal converters, organic field-effect waveguides, chemical sensors, and optical logic gates. Specifically, organic crystals are generally suitable for the transport of photons, electrons, and excitons. Furthermore, one-dimensional crystals containing π-conjugated organic molecules can enhance charge transport efficiency. These materials possess fundamental advantages such as sizing ability, good processability, few defects, uniform morphology, good thermal stability, solution processing, and high photoluminescence (PL) efficiency. However, controlling the synthesis of microcrystals with regular morphologies remains a significant challenge. Organic micro / nanostructures composed of organic molecules are based on weak intermolecular interactions, such as van der Waals forces, which differ from the strong bond interactions, such as ionic bonds, within inorganic crystals. Therefore, external experimental conditions such as solvent type, temperature, solution concentration, and surfactants can easily affect the nucleation of organic micro / nanostructures. These influencing factors are so numerous and complex that achieving the goal of controllable-shape micro / nanostructures is not easy. Although several groups have reported synthesis processes for organic micro / nanostructures with controllable shapes, morphology engineering of organic micro / nanostructures remains highly desirable. Summary of the Invention

[0005] To address the aforementioned problems, this invention discloses a method for morphology control of Ir(piq)3 molecular crystals, which not only effectively reduces light loss during electrochemiluminescence but also achieves light gain benefits for the electrochemiluminescence signal.

[0006] A method for controlling the morphology of Ir(piq)3 molecular crystals is disclosed. This method involves introducing water as a poor solvent during the crystal growth process via reprecipitation. Different morphologies of Ir(piq)3 molecular crystals are obtained by changing the volume ratio of ethanol to water in the poor solvent. The specific steps are as follows: Step 1: Dissolve the commercial Ir(piq)3 powder completely in a good solvent to prepare an Ir(piq)3 solution of a certain concentration; Step 2: Based on the target morphology of the Ir(piq)3 molecular crystal, prepare a mixed solvent of a certain volume of undesirable solvent by mixing ethanol and water in a certain volume ratio. Step 3: Under ultrasonic conditions, add a certain concentration of Ir(piq)3 solution to a mixed solvent of ethanol and water; Step 4: Let the above mixed dispersion stand; Step 5: Separate and wash to obtain Ir(piq)3 molecular crystals.

[0007] Furthermore, in step 2, the tunable morphology of the Ir(piq)3 crystal includes microrod, symmetrical micro-semiconductor, and nanorod structures; the volume ratio of ethanol to water is 1, 7:3, 5:5, 3:7, or 0.

[0008] Furthermore, when the volume ratio of ethanol to water is 1, the Ir(piq)3 molecular crystal has a microrod structure; when the volume ratio of ethanol to water is 7:3, the Ir(piq)3 molecular crystal has a micro-semi-tubular structure containing symmetrical cavities; and when the volume ratio of ethanol to water is 0, the Ir(piq)3 molecular crystal has a nanorod structure.

[0009] Furthermore, in step 1, the good solvent used to dissolve the Ir(piq)3 powder is a tetrahydrofuran solution, and the concentration of the prepared Ir(piq)3 solution is 1 mM.

[0010] Furthermore, in step 4, the ultrasonic dispersion conditions include: the volume of the Ir(piq)3 solution is 500 μL, the total volume of the mixed solvent of ethanol and water is 2 mL; the ultrasonic temperature is 35 ℃, and the ultrasonic time is 30 s.

[0011] Furthermore, the resting conditions in step 4 are room temperature and protection from light.

[0012] Furthermore, the separation in step 5 is performed using a centrifuge at a speed of 8000 rpm for 3 minutes at a temperature of 25 ℃.

[0013] The electrochemiluminescence waveguide application of Ir(piq)3 molecular crystals obtained by morphology control method is characterized by the fact that both the Ir(piq)3 microrods and symmetrical microsemiconductors have electrochemiluminescence waveguide characteristics of being dark in the middle and bright at both ends. The Ir(piq)3 microrods, due to their high substrate effect, experience partial light leakage during electrochemiluminescence propagation. In contrast, the Ir(piq)3 symmetrical microsemiconductors, due to the presence of air inside the tube, reduce the substrate effect, thereby significantly improving the propagation efficiency of the electrochemiluminescence waveguide. This allows for the efficient conversion of electrochemically generated ECL into long-range luminescence in non-conductive regions, and holds promise for non-contact electrochemical analysis and research in (bio)chemical systems, demonstrating excellent application prospects.

[0014] The technical principle of this invention is as follows: Since molecular crystals are synthesized through weak intermolecular forces, such as π-π stacking, hydrogen bonding, and electrostatic interactions, their morphology can be controlled by adjusting the solvent, ultrasonic time, and concentration. After molecule nucleation, due to the high surface free energy of the (100) facet of the Ir(piq)3 molecular crystal, the molecules preferentially grow along the edge of the hexagonal prism crystal, forming a hollow crystal structure. Ir(piq)3 molecules have high solubility in pure ethanol, and the molecular diffusion rate is greater than the growth rate, ultimately allowing the molecules to fill the cavity and form a microrod structure. By introducing water, the solubility decreases, resulting in a diffusion rate less than the growth rate, preventing the molecules from filling the cavity and ultimately forming a symmetrical hollow micro-semi-tube structure. In pure water solvent, the diffusion length is comparable to the nanorod radius, achieving the synthesis from nanotubes to solid nanorods. Both Ir(piq)3 microrods and microtubes are one-dimensional single-crystal structures, which can be used not only as electrochemiluminescence emitters but also as active electrochemiluminescence waveguides. The Ir(piq)3 symmetrical micro-semiconductor structure contains air in the cavities at both ends, which can effectively reduce the substrate effect, thereby effectively reducing the light loss of electrochemiluminescence and greatly improving the long-range electrochemiluminescence efficiency.

[0015] Beneficial effects of this invention:

[0016] 1. This invention provides a synthesis strategy that modifies the proportion of undesirable solvents to achieve morphological control of Ir(piq)3 molecular crystals, and effectively synthesizes Ir(piq)3 microrods, symmetrical microsemitubes and nanorod structures.

[0017] 2. The Ir(piq)3 microrods and symmetrical microsemitubes synthesized by the morphology control strategy provided by this invention both have the characteristics of optical waveguides with a dark middle and bright ends, and can be applied to electrochemiluminescence waveguides.

[0018] 3. The symmetrical micro-semi-tube structure synthesized by the morphology control strategy provided by this invention can effectively reduce the substrate effect of traditional optical waveguides due to the effect of air inside the tube, thereby greatly reducing the light loss coefficient of electrochemiluminescence and having a more efficient electrochemiluminescence effect. Attached Figure Description

[0019] Figure 1 SEM images of the Ir(piq)3 molecular crystals prepared in Examples 1-3.

[0020] Figure 2 HRTEM images of the Ir(piq)3 molecular crystals prepared in Examples 1-3.

[0021] Figure 3 Electrochemiluminescence imaging images of the Ir(piq)3 molecular crystals prepared in Examples 1-3. Detailed Implementation

[0022] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. It should be noted that the terms "front," "rear," "left," "right," "up," and "down" used in the following description refer to directions in the accompanying drawings, and the terms "inner" and "outer" refer to directions toward or away from the geometric center of a specific component, respectively. Example 1

[0023] Preparation of Ir(piq)3 molecular crystals in pure ethanol The commercial Ir(piq)3 powder was completely dissolved in tetrahydrofuran (THF) solvent to a concentration of 1 mM. Then, 500 μL of the above red stock solution was rapidly injected into 2 mL of ethanol solvent at 35 °C. After sonication for 30 s, the solution was allowed to stand at room temperature in the dark for 2 h. The solution was then centrifuged at 8000 rpm for 3 min, and the crystals were collected and dispersed in 2 mL of ethanol solvent. The morphology of molecular crystal 1 is shown below. Figure 1 and Figure 2 (a) shows that the molecular crystals synthesized in pure ethanol have a microrod structure. Example 2

[0024] Preparation of Ir(piq)3 molecular crystals in an ethanol / water (v / v, 7 / 3) mixed solvent The commercial Ir(piq)3 powder was completely dissolved in tetrahydrofuran (THF) solvent to a concentration of 1 mM. Then, 500 μL of the above red stock solution was rapidly injected into 2 mL of a mixed solvent of ethanol / water (v / v, 7 / 3) at 35 °C. After sonication for 30 s, the solution was allowed to stand at room temperature in the dark for 2 h. Then, it was centrifuged at 8000 rpm for 3 min, and the crystals were collected and dispersed in 2 mL of ethanol solvent. The morphology of molecular crystal 1 is shown below. Figure 1 and Figure 2 (b) shows that the molecular crystal synthesized in the ethanol / water (v / v, 7 / 3) mixed solvent is a symmetrical micro-semi-tubular structure containing symmetrical cavities. Example 3

[0025] Preparation of Ir(piq)3 molecular crystals in pure aqueous solvent The commercial Ir(piq)3 powder was completely dissolved in tetrahydrofuran (THF) solvent to a concentration of 1 mM. Then, 500 μL of the above red stock solution was rapidly injected into 2 mL of a mixed solvent of ethanol / water (v / v, 7 / 3) at 35 °C. After sonication for 30 s, the solution was allowed to stand at room temperature in the dark for 2 h. Then, it was centrifuged at 8000 rpm for 3 min, and the crystals were collected and dispersed in 2 mL of ethanol solvent. The morphology of molecular crystal 1 is shown below. Figure 1 and Figure 2 (c) shows that the molecular crystal synthesized in pure water has a nanorod structure. Example 4

[0026] Pretreatment of ITO electrodes Indium tin oxide (ITO) coated glass (surface resistivity: <7 ohms / square, thickness 220±30 nm) was purchased from Zhuhai Kaiwo (China). The patterned ITO consists of an electroactive surface (ITO) and a non-electroactive surface (glass). It is the result of etching with a high-energy laser beam. Before use, the ITO glass was immersed in a 1 M NaOH / ethanol solution for one hour, followed by ultrasonic cleaning sequentially in acetone, ethanol, and ultrapure water for 15 min. Finally, the ITO glass was rinsed with pure water and dried under a nitrogen stream before use. Example 5

[0027] Electrochemiluminescence imaging of Ir(piq)3 molecular crystals The Ir(piq)3 microrods and symmetrical microsemiconductors prepared in Example 1 were dissolved in 2 mL of ethanol solution. 10 mL of the dispersion was dropped onto an ITO electrode and dried in air before being used for optical imaging. Optical imaging measurements were performed on a vertical microscope equipped with a water immersion objective and an EMCCD camera, using a halogen lamp as the light source, acquiring bright-field and fluorescence images. ECL imaging was performed using a self-made PDMS electrochemical cell, with the ITO electrode as the working electrode, Ag / AgCl wire as the reference electrode, and platinum wire as the counter electrode. Before ECL imaging, BF images of the Ir(piq)3 microrods and symmetrical microsemiconductors were first captured in light reflection mode, followed by PL imaging. Then, the external light source was turned off, and a constant potential of 1.5 V was applied using a CHI 660D electrochemical workstation. Electrochemiluminescence imaging was performed in a PBS solution (0.1 M, pH 7.4) containing 500 mL of 100 mM TPrA at an exposure time of 60 s and a gain of 300.

[0028] The results show that, Figure 3 As shown, nanorods are easily aggregated and exhibit weak electrochemiluminescence (ECL). Ir(piq)3 microrods and symmetrical microsemiconductors, however, exhibit strong ECL and can serve as ECL emitters. Furthermore, both Ir(piq)3 microrods and symmetrical microsemiconductors possess the characteristic of being bright at both ends and dark in the middle, characteristic of optical waveguides. The microrod structure, due to the high substrate effect, suffers from light leakage during ECL propagation, resulting in significantly reduced light intensity at both ends and high ECL loss. In contrast, the symmetrical microsemiconductor structure, due to the presence of air within the tube, effectively reduces ECL loss and efficiently confines the generated light within the structure, ultimately emitting strong light at both ends. The symmetrical microsemiconductor structure significantly improves the propagation efficiency of the ECL waveguide, efficiently converting the electrochemically generated ECL into long-range luminescence in the non-conductive region. It holds promise for non-contact electrochemical analysis and research in (bio)chemical systems, demonstrating promising application prospects.

[0029] The technical means disclosed in this invention are not limited to those disclosed in the above embodiments, but also include technical solutions composed of any combination of the above technical features.

Claims

1. A method for preparing Ir(piq)3 molecular crystal, characterized in that: The specific steps are as follows: Step 1: Dissolve the commercial Ir(piq)3 powder completely in a good solvent to prepare an Ir(piq)3 solution; the good solvent used to dissolve the Ir(piq)3 powder is tetrahydrofuran solution, and the concentration of the prepared Ir(piq)3 solution is 1mM. Step 2: Mix ethanol and water at a volume ratio of 7:3 to obtain a mixed solvent of ethanol and water; Step 3: Under ultrasonic conditions, the Ir(piq)3 solution is added to a mixed solvent of ethanol and water to obtain a mixed dispersion; wherein, the volume of the Ir(piq)3 solution is 500 μL and the volume of the mixed solvent of ethanol and water is 2 mL; Step 4: Let the above mixed dispersion stand; Step 5: Separate and wash to obtain Ir(piq)3 molecular crystals. Ir(piq)3 molecular crystals are micro-semi-tubular structures containing symmetrical cavities.

2. The method for preparing an Ir(piq)3 molecular crystal as described in claim 1, characterized in that, In step 3, the ultrasonic conditions include: ultrasonic temperature of 35°C and ultrasonic time of 30 seconds.

3. The method for preparing an Ir(piq)3 molecular crystal as described in claim 1, characterized in that, The resting conditions for step 4 are room temperature and protection from light.

4. The method for preparing an Ir(piq)3 molecular crystal as described in claim 1, characterized in that, The separation in step 5 is performed using a centrifuge at a speed of 8000 rpm for 3 minutes at a temperature of 25°C.

5. The electrochemiluminescence waveguide application of the Ir(piq)3 molecular crystal obtained by the preparation method according to any one of claims 1-4.

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