A supramolecular light-harvesting system based on pillar[5]arene, its preparation method, and its application in latent fingerprint imaging

Abstract

The present invention discloses a supramolecular light-harvesting system based on pillar[5]arene, a preparation method thereof, and an application thereof in latent fingerprint imaging. Nanoparticles formed by self-assembly of a fluorescent molecule G with aggregation-induced emission (AIE) characteristics and a water-soluble pillar[5]arene (H) serve as a loading platform and energy donor, and a hydrophobic dye (A) serves as an energy acceptor. Due to the excellent FRET effect, the #imgabs0# nanoparticles, which originally emitted yellow fluorescence, became #imgabs1# nanoparticles emitting red fluorescence after being loaded with 1% of A. The aqueous solution of the #imgabs2# fluorescent nanoparticles was concentrated and the red-emitting fluorescent powder was extracted. The fluorescent fingerprint powder was prepared using the #imgabs3# fluorescent powder and montmorillonite (MMT). The fluorescent fingerprint powder was applied to the red fluorescence imaging of LFPs. The imaging effect had high resolution and could clearly generate the primary, secondary, and tertiary information of the fingerprint. The system has high potential application value in the fields of fingerprint imaging and information security.

Description

Technical Field

[0001] The present invention belongs to the field of supramolecular fluorescent materials and information security, and specifically relates to a supramolecular light capture system based on pillar[5]arene, a preparation method thereof, and an application thereof in latent fingerprint imaging. Background Art

[0002] Fingerprints are information patterns consisting of ridges and grooves on the skin of human fingers. Fingerprints are unique and lifelong, and play a vital role in identifying individuals, especially in confirming the identity of criminal suspects in forensic investigations. The fingerprints left at the scene are generally latent fingerprints (LFPs), which are difficult to see with the naked eye. Therefore, the imaging and identification of LFPs are of great significance to forensic medicine. Since LFPs are invisible, various methods have been developed to collect and visualize them. Among these methods, fluorescence imaging technology has received widespread attention in recent years. However, traditional organic fluorescent dyes usually have short emission wavelengths, small Stokes shifts, and aggregation fluorescence quenching (ACQ) behaviors, resulting in poor clarity and low contrast of LFPs images.

[0003] Furthermore, red-emitting materials offer high background contrast and resolution, making them important for LFP imaging. However, AIE fluorophores such as tetraphenylethylene (TPE) typically exhibit short-wavelength, blue fluorescence, making them difficult to use for red fluorescence imaging of biological processes such as fingerprints and cells. Therefore, there is an urgent need to develop phosphor materials with strong fluorescence emission, large Stokes shift, and strong resistance to background interference. Summary of the Invention

[0004] In response to the above technical problems, the present invention provides a light capture system based on red emission of pillar[5]arene and its application method in high-resolution latent fingerprint imaging.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] A supramolecular light harvesting system based on pillar[5]arene, wherein the supramolecular light harvesting system uses compound G with AIE properties as a guest and pillar[5]arene modified with ammonium carboxylate as a host. The assembly formed in water through the host-guest interaction serves as a platform for light harvesting load receptors and an energy donor; a hydrophobic fluorescent dye is used as an energy acceptor.

[0007] The structural formula of compound G is as shown in formula (I):

[0008]

[0009] The structure of the fully carboxylated ammonium modified pillar[5]arene is shown in formula (II):

[0010]

[0011] Preferably, the hydrophobic fluorescent dye is selected from any one of Nile Red, Nile Blue, SR101, and naphthalene diimide derivatives. When the absorption wavelength of the hydrophobic fluorescent dye overlaps with the emission wavelength of compound G, fluorescence resonance energy transfer (FRET) can occur.

[0012] Preferably, the concentration of compound G is 10 -6 ~10 -4 M, within this concentration range, compound G has no self-assembly in water, no Tyndall effect, and no fluorescence emission phenomenon; the concentration of the fully carboxylic acid ammonium modified pillar [5] aromatic hydrocarbon is 2×10 -6 ~2×10 - 5 M, the concentration of hydrophobic fluorescent dye is 10 -8 ~10 -7 M.

[0013] Preferably, the molar concentration ratio of compound G to the fully carboxylated ammonium modified pillar[5]arene is 1 to 20:1, preferably 1:0.3.

[0014] Preferably, the molar concentration ratio of compound G to the hydrophobic fluorescent dye is 50 to 1000:1, for example, 50:1, 75:1, 100:1, 200:1, 300:1, 400:1, 600:1, 1000:1 or any ratio therebetween.

[0015] Preferably, adding a fully carboxylated ammonium modified pillar[5]arene to an aqueous solution of compound G can induce yellow fluorescence emission of compound G; and adding a hydrophobic fluorescent dye can cause fluorescence resonance energy transfer.

[0016] Preferably, the hydrophobic fluorescent dye is Nile red. Adding Nile red to a mixed aqueous solution of compound G and percarboxylic acid ammonium-modified pillar[5]arene can induce red fluorescence emission.

[0017] The present invention also provides a method for preparing the supramolecular light harvesting system based on pillar[5]arene, comprising the following steps:

[0018] Step 1: Compound G and percarboxylic acid ammonium modified pillar[5]arene are dissolved in an aqueous solution at a molar concentration ratio of 1 to 20:1 and self-assembled to form yellow fluorescent emitting nanoassemblies;

[0019] Step 2: adding a dimethyl sulfoxide solution of a hydrophobic fluorescent dye at a molar concentration ratio of 50 to 1000:1 to compound G, and sonicating to obtain a supramolecular light harvesting system that undergoes fluorescence resonance energy transfer.

[0020] Preferably, the preparation method of compound G is as follows:

[0021] Compound 1 represented by formula (III) and trimethylamine were mixed at a molar ratio of 1:10 and dissolved in anhydrous tetrahydrofuran, heated under reflux with stirring for 3 days, during which trimethylamine was added every day. After the reaction was completed, the residue was washed with petroleum ether, ethyl acetate and acetone to obtain a yellow solid, which was compound G;

[0022]

[0023] The present invention also provides an application of the supramolecular light harvesting system based on pillar[5]arene in the preparation of a luminescent material, wherein the luminescent material is a tunable photoluminescent material with an excitation wavelength of 320 to 400 nm.

[0024] The present invention also provides an application of the supramolecular light capture system based on pillar[5]arene in the field of latent fingerprint imaging, comprising the following steps:

[0025] Step 1: Adding a hydrophobic fluorescent dye to a mixed aqueous solution of compound G and percarboxylic acid ammonium-modified pillar[5]arene to perform light harvesting to prepare a supramolecular light harvesting system;

[0026] Step 2: Concentrate the solution of the supramolecular light harvesting system and dry it to form a powder;

[0027] Step 3: Sprinkle the powder on the latent fingerprint;

[0028] Step 4: Record and analyze the fingerprint image.

[0029] Preferably, in step 2, the solid powder is prepared by mixing light-harvesting fluorescent nanoparticles and montmorillonite.

[0030] The above technical solution has the following beneficial effects:

[0031] (1) The light capture system provided by the present invention can well simulate the energy transfer pathway of photosynthesis in nature;

[0032] (2) The light harvesting system provided by the present invention can still transfer energy well under very high donor-acceptor ratios (50-1000:1). Each acceptor can undertake energy transferred by hundreds or even thousands of times the amount of donor. It also has the advantages of high energy transfer capability and ultra-high antenna effect. The highest energy transfer efficiency of the system reaches 60.9%, and the best antenna effect reaches 21.

[0033] (3) The luminescent color of the light capture system provided by the present invention is adjustable. When the hydrophobic fluorescent dye is Nile red, its fluorescence changes from yellow fluorescence to red fluorescence, and solid nanoparticles emitting red fluorescence can be prepared; the solid nanoparticles emitting red fluorescence can be used for latent fingerprint imaging.

[0034] (4) The light harvesting system provided by the present invention is composed of compound G and columnar [5] aromatic hydrocarbon modified with ammonium percarboxylate, which are self-assembled into nanoparticles through host-guest interaction and uniformly dispersed in aqueous solution as energy donors. It has low cost and is green and environmentally friendly; and its structure is stable and can be stored for a long time. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present invention and, together with the description, serve to explain the principles of the invention, in which:

[0036] Figure 1 1 and 2 are fluorescence spectra of guest compound G and host compound H in different ratios in the examples.

[0037] Figure 2 1 and 2 are fluorescence spectra of different ratios of guest compound G and energy acceptor A in aqueous solution in the examples.

[0038] Figure 3 FIG. 4 is a diagram illustrating fingerprint imaging in an embodiment.

[0039] Figure 4 is the H NMR spectrum of compound G.

[0040] Figure 5 is the carbon NMR spectrum of compound G.

[0041] Figure 6 This is the high-resolution mass spectrum of compound G.

[0042] Figure 7 It is a schematic diagram of the process of the present invention.

[0043] Figure 8 Nanoparticles provided by the present invention Schematic diagram of . DETAILED DESCRIPTION

[0044] The following disclosure provides many different embodiments or examples for implementing different structures of the present invention. To simplify the disclosure of the present invention, the components and configurations of specific examples are described below. Of course, these are merely examples and are not intended to limit the present invention. In addition, the present invention may repeat reference numbers and / or reference letters in different examples. Such repetition is for the purpose of simplicity and clarity and does not in itself indicate the relationship between the various embodiments and / or configurations discussed.

[0045] In the present invention, unless otherwise specified, all equipment and raw materials can be purchased from the market or are commonly used in the industry. The methods in the following embodiments, unless otherwise specified, are all conventional methods in the art.

[0046] Example

[0047] 1. Preparation of Compound G:

[0048] Compound G is synthesized using compound 1 as a raw material. The structural formula of compound 1 is shown below:

[0049]

[0050] It was prepared according to the method in the document Chin.Chem.Lett.2021,32,1377-1380.

[0051] Compound G was prepared as follows: In a 100 mL flask, a mixture of compound 1 (0.40 g, 0.67 mmol) and trimethylamine (1.6 mL, 6.7 mmol) was dissolved in 40 mL of anhydrous tetrahydrofuran. The mixture was heated under reflux with stirring for 3 days. During this time, 1.6 mL of trimethylamine was added daily. After the reaction was complete, the tetrahydrofuran and excess triethylamine were evaporated. The residue was washed with petroleum ether, ethyl acetate, and acetone to yield G (0.44 g, 91%) as a yellow solid.

[0052] The H NMR spectrum of compound G is as follows Figure 4 As shown: 1 H NMR (300MHz, DMSO-d6, 298K): δ (ppm) = 7.86 (d, J = 7.5Hz, 2H, Ar-H), 7.30-7.24 (m, 6H, Ar-H), 7.07-6.95 (m, 6H, Ar-H), 6.63 (d, J=8.1Hz,2H,Ar-H),4.14(t,J=5.7Hz,4H,NCH2-),3.54(t,J=8.1Hz,4H,-OCH2-),3.31(s,18H,-N(CH3)3),2.23(m,4H,-CH2-).

[0053] The NMR carbon spectrum of compound G is as follows Figure 5 As shown: 13 C NMR (75MHz, DMSO-d6, 298K): δ (ppm) = 159.0, 146.0, 140.1, 138.7, 135.6, 132.9, 131.6, 128.0, 126.9, 124.4, 120.2. 115.3, 65.3, 63.4, 52.8, 23.1.

[0054] The high-resolution mass spectrometry of compound G is as follows Figure 6 Shown: HR-ESI-MS: m / z [M–2Br] 2+ calcd for[C 38 H 46 N2O2] 2+=281.1774, found 281.1773.

[0055] Based on the above experimental characterization, the structure of compound G was determined to be:

[0056]

[0057] 2. Preparation of supramolecular nanoparticles:

[0058] Compound H (percarboxylic acid ammonium modified pillar [5] aromatic hydrocarbon) was synthesized according to the literature J. Mater. Chem. B, 2016, 4, 2819-2827, and its structure is as follows:

[0059]

[0060] Preparation of supramolecular nanoparticles:

[0061] Step 1: Weigh 2.9 mg of compound G into a 10 mL volumetric flask and add deionized water to make up to 10 mL to prepare a 0.4 mM stock solution;

[0062] Step 2: Weigh 8.7 mg of compound H into a 25 mL volumetric flask and add deionized water to make up to 25 mL to prepare a 0.4 mM stock solution;

[0063] Step 3: Use a pipette to transfer appropriate amounts of the mother solution of compound G and the mother solution of compound H to a 5 mL volumetric flask, mix well, then add deionized water to the volume, and sonicate for 3 minutes to form aqueous dispersed nanoparticles. Structure such as Figure 8 .

[0064] Fluorescence titration experiments with different host-guest ratios:

[0065] At 25°C, an aqueous solution of guest compound G was fixed at a concentration of 20 μM. Different equivalents of host compound H (1 to 20 μM) were added dropwise to the solution, and the fluorescence spectrum was measured. According to the change in fluorescence intensity at 560 nm, the highest point corresponds to a concentration of 6 μM compound H, that is, the optimal ratio of compound G to compound H is 1:0.3, where the concentration of compound G is 2×10 -5 M, the concentration of compound H was 5×10 -6 M

[0066] In this embodiment, the excitation was measured at 370 nm. The fluorescence spectrum of Figure 1 shown.

[0067] In this embodiment, the ultrasonic instrument used is an ultrasonic cleaning machine commonly used in laboratories, and the frequency is 40 kHz.

[0068] 3. Preparation of light harvesting system:

[0069] In this example, compound G is used as the energy donor and fluorescent dye A (Nile Red) is used as the energy acceptor. The preparation method is as follows:

[0070] Step 1: Weigh 8.0 mg of fluorescent dye A into a 5 mL volumetric flask and add dimethyl sulfoxide to the volume to prepare a 5 mM stock solution;

[0071] Step 2: Take 100 μL of the 5 mM stock solution from step 1 to a 5 mL volumetric flask and add dimethyl sulfoxide to make a 0.1 mM stock solution.

[0072] Step 3: Use a pipette to transfer the mother solution of compound G, the mother solution of compound H and the mother solution of fluorescent dye A to a 5 mL volumetric flask, mix them, then add deionized water to the volume, and sonicate for 3 minutes to form nanoparticles. @A aqueous solution; wherein, nanoparticles The concentrations of compound G, compound H, and compound A in the aqueous solution are shown in Table 1.

[0073]

[0074]

[0075] In this embodiment, the above-mentioned prepared @A nanoparticles, Figure 2 This embodiment is shown @A Fluorescence spectra of nanoparticles with different ratios of donor compound G and energy acceptor A in aqueous solution. This example characterizes the energy transfer efficiency and antenna effect of the nanoparticles through the fluorescence spectra obtained through the above test, as follows:

[0076] According to the measured Nanoparticles and @A The fluorescence spectrum of the nanoparticles is used to calculate the energy transfer efficiency (Φ ET ):

[0077] Φ ET =1-I DA / I D (eq.S1)

[0078] Among them, I DA and I D They are @A (donor and acceptor) and The fluorescence intensity of the donor at 560 nm when excited at 370 nm. Substituting the measured data into formula S1, the maximum energy transfer efficiency of energy transfer (compound G to compound A) is 60.9%. At this time, [H] = 6 × 10 -6 M, [G] = 2 × 10 -5 M, [A] = 4 × 10 -7 M.

[0079] According to the measured Nanoparticles and The fluorescence spectrum of @A nanoparticles is used to calculate the antenna effect (AE) of the first step of energy transfer using Equation S2:

[0080] AE=I' DA,370 / I DA,560 =(I DA,370 -I D,370 ) / I DA,560 (eq.S2)

[0081] Among them I DA,370 and I DA,560 They are @A Fluorescence intensity at 640 nm under excitation at 370 nm and 560 nm. D,370 for The emission spectrum was normalized at 560 nm and the fluorescence intensity at 640 nm under 370 nm excitation. According to Equation S2, the antenna effect of energy transfer (compound G to compound A) is up to 21. At this time, [H] = 6 × 10 -6 M, [G] = 2 × 10 -5 M, [A] = 4 × 10 -7 M.

[0082] 4. Light capture system for latent fingerprint imaging:

[0083] In this embodiment, the light capture system nanoparticle solution obtained by the above method is concentrated and dried to obtain red fluorescent solid nanoparticles, which are ground and mixed with montmorillonite and then sprinkled on latent fingerprints, which can be recorded by a camera under a 365nm ultraviolet lamp.

[0084] Here are the steps:

[0085] 20 mL of @Solution A is concentrated to 5 mL, where [G] = 5 × 10 -5 M, [H] = 1.5 × 10 -5 M, [A] = 5 × 10 -7M. Then, add 1g of thoroughly ground montmorillonite to 5mL of the concentrate and remove the water in a vacuum vortex. The resulting solid powder is vacuum dried for 4 hours and stored in a desiccator. All materials used for fingerprint deposition are also vacuum dried for 8 hours and then placed in a desiccator.

[0086] After the volunteer touched his forehead with his finger, he gently touched it on the glass matrix, leaving a latent fingerprint that was difficult to see with the naked eye. The prepared fluorescent fingerprint powder was evenly sprinkled on the latent fingerprint, and the excess fluorescent fingerprint powder on the matrix was gently blown away with an ear bulb. The fingerprint was placed under 365nm ultraviolet light, and a very clear fingerprint image was obtained. The fingerprint photo was recorded using Xiaomi 11. @A-MMT fluorescent fingerprint powder has high resolution imaging effect and can clearly generate primary, secondary and tertiary information of fingerprints, such as Figure 3 shown.

[0087] Other embodiments of the present invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention herein. The present invention is intended to cover any variations, uses, or adaptations of the present invention that follow the general principles of the invention and include common knowledge or customary techniques in the art. The description and examples are to be considered as exemplary only, with the true scope and spirit of the invention being indicated by the claims.

[0088] It should be understood that the present invention is not limited to the exact construction described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present invention is limited only by the appended claims.

Claims

1. A supramolecular light harvesting system based on pillar[5]arene, characterized in that: The supramolecular light harvesting system uses compound G with AIE properties as the guest and pillar[5]arene modified with ammonium carboxylate as the host. The assembly formed in water through the host-guest interaction serves as a platform and energy donor for the light harvesting load receptor; the hydrophobic fluorescent dye Nile red is used as the energy receptor; the structural formula of compound G is as shown in formula (I): The structure of the fully carboxylated ammonium modified pillar[5]arene is as shown in formula (II): The concentration of compound G is 10 -6 ~110 -4 M, within this concentration range, the compound G has no self-assembly in water, no Tyndall effect, and no fluorescence emission phenomenon; the concentration of the fully carboxylic acid ammonium modified pillar [5] aromatic hydrocarbon is 2×10 -6 ~2×10 - 5 M, the concentration of the hydrophobic fluorescent dye is 10 -8 ~10 -7 M; The molar concentration ratio of the compound G and the percarboxylic acid ammonium modified pillar [5] aromatic hydrocarbon is 1 to 20:1; The molar concentration ratio of the compound G to the hydrophobic fluorescent dye is 50 to 1000:

1.

2. The supramolecular light harvesting system based on pillar[5]arene according to claim 1, characterized in that The molar concentration ratio of the compound G to the percarboxylic acid ammonium modified pillar[5]arene is 1:0.

3.

3. The supramolecular light harvesting system based on pillar[5]arene according to claim 1, characterized in that Adding the fully carboxylated ammonium modified pillar[5]arene to the aqueous solution of the compound G can induce yellow fluorescence emission of the compound G; and adding the hydrophobic fluorescent dye can cause fluorescence resonance energy transfer.

4. The method for preparing the supramolecular light harvesting system based on pillar[5]arene according to claim 1, characterized in that: The steps include: Step 1: dissolving the compound G and the percarboxylate ammonium-modified pillar[5]arene in an aqueous solution at a molar concentration ratio of 1 to 20:1 and self-assembling to form a yellow fluorescent emitting nanoassembly; Step 2: adding a dimethyl sulfoxide solution of the hydrophobic fluorescent dye at a molar concentration ratio of 50 to 1000:1 to the compound G, and sonicating to obtain the supramolecular light harvesting system that undergoes fluorescence resonance energy transfer.

5. The method for preparing a supramolecular light harvesting system based on pillar[5]arene according to claim 4, characterized in that: The preparation method of compound G is as follows: Compound 1 represented by formula (III) and trimethylamine were mixed at a molar ratio of 1:10 and dissolved in anhydrous tetrahydrofuran, heated under reflux with stirring for 3 days, during which trimethylamine was added every day. After the reaction was completed, the residue was washed with petroleum ether, ethyl acetate and acetone to obtain a yellow solid, which was the compound G; 6. Application of the supramolecular light harvesting system based on pillar[5]arene according to any one of claims 1 to 3 in the field of latent fingerprint imaging, characterized in that: The following steps are involved: Step 1: adding the hydrophobic fluorescent dye to a mixed aqueous solution of the compound G and the percarboxylic acid ammonium-modified pillar[5]arene to perform light harvesting to prepare the supramolecular light harvesting system; Step 2: concentrating the solution of the supramolecular light harvesting system and drying it to form a powder; Step 3: Sprinkle the powder on the latent fingerprint; Step 4: Record and analyze the fingerprint image.

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