Two-photon luminescent micro / nano materials, their preparation method, and their applications

Abstract

This application discloses a two-photon luminescent micro / nanomaterial, its preparation method, and its application. The two-photon luminescent micro / nanomaterial has the chemical formula shown in Formula I: [(Hdma)K(H2L)] n Formula I; wherein Hdma is a dimethylamine countercation, and H2L is a semi-deprotonated tetraphenylvinylcarboxylic acid ligand. The micro / nano luminescent material has a particle size distribution of 200 nm to 200 μm, exhibiting strong blue fluorescence and a strong two-photon emission effect. Compared with currently commercialized fingerprint recognition technologies, the two-photon luminescent micro / nano material described in this application has advantages such as faster response speed, higher resolution, stronger three-dimensional tomography capability, and greater imaging depth, making it of significant commercial application value in fields such as national defense security, financial security, and criminal investigation.

Description

Technical Field

[0001] This application relates to a two-photon luminescent micro / nano material, its preparation method, and its application, belonging to the field of luminescent materials. Background Technology

[0002] Fingerprint recognition technology is a biometric technology. A fingerprint recognition system is a comprehensive system that includes modules for fingerprint image acquisition, processing, feature extraction, and comparison. It is commonly used in locations requiring personal identification, such as access control systems, attendance systems, laptops, internal bank processing, financial payments, and crime scene investigation. Current fingerprint recognition technologies are complex and diverse, including optical recognition, capacitive sensing, and radio frequency biometrics. Capacitive sensing requires a high degree of finger cleanliness, and the silicon material used in the sensor surface is relatively easily damaged. Radio frequency biometrics emits minute radio frequency signals or ultrasound waves through a sensor transmitter, requiring less cleanliness of the finger; however, this method is expensive and currently only used in high-end financial fields. Optical recognition is currently the most common method; however, it can only reach the epidermis, not the dermis, and is significantly affected by the cleanliness and presence of scars on the finger surface. The accuracy of optical fingerprint recognition depends on how well it utilizes information from the dermis to obtain high-resolution fingerprint information.

[0003] Near-infrared radiation, also known as high-frequency short-wave infrared radiation, has a wavelength of 760nm to 1500nm and can penetrate deep into human tissue, approximately 5 to 10 millimeters. Therefore, infrared imaging technology can improve the optical resolution, strong three-dimensional tomography capabilities, and large imaging depth in fingerprint recognition. Meanwhile, with technological advancements, two-photon imaging technology is a nonlinear optical imaging technique based on two-photon absorption and fluorescence excitation. Two-photon imaging typically uses near-infrared light with a longer wavelength for excitation. Compared to visible light, near-infrared light has stronger penetrating power in biological tissues, enabling the observation of deeper information within biological tissues with lower invasiveness. Summary of the Invention

[0004] This application designs and synthesizes a two-photon luminescent micro / nano material, which, with the aid of computer analysis software such as Matlab and ImageJ, significantly improves the resolution and accuracy of fingerprint optical recognition. It can be applied to high-end fingerprint recognition fields, such as large-amount financial payments, accurate identification of criminal activity, and the establishment of fingerprint databases for abducted children.

[0005] The two-photon luminescent micro / nanomaterial provided in this application has a single-photon photoluminescence emission peak of 475 nm and a two-photon photoluminescence emission peak of 475 nm, a fluorescence lifetime of 0.80 ns, and an extremely fast imaging time resolution.

[0006] According to a first aspect of this application, a two-photon luminescent micro / nanomaterial is provided, the two-photon luminescent micro / nanomaterial having the chemical formula shown in Formula I:

[0007] [(Hdma)K(H2L)] n Formula I;

[0008] In this context, Hdma is a dimethylamine countercation, H2L is a semi-deprotonated tetraphenylvinylcarboxylic acid ligand, and n is a positive integer representing the three-dimensional periodic ordered arrangement of the molecular crystal.

[0009] Optionally, the two-photon luminescent micro / nano material does not contain noble metals such as Ag, Au, Ir, Pd, and Pt.

[0010] Optionally, the particle size of the two-photon luminescent micro / nano material is 200 nm to 200 μm.

[0011] Optionally, the particle size of the two-photon luminescent micro / nano material is selected from any value among 200 nm, 1 μm, 10 μm, 20 μm, 50 μm, 100 μm, 120 μm, 150 μm, 180 μm, and 200 μm, or a range between any two of the above.

[0012] Optionally, the two-photon luminescent micro / nanomaterial has a crystalline structure.

[0013] Optionally, the asymmetric structural unit in the crystalline structure of the two-photon luminescent micro / nanomaterial comprises: one dimethylamine cation and one K+ cation. + An ion and a semi-deprotonated tetraphenylvinylcarboxylic acid ligand.

[0014] Optionally, the microscale of the two-photon luminescent micro / nanomaterial is a three-dimensional molecular structure.

[0015] Optionally, in the two-photon luminescent micro / nano material, K is a +1 valent metal ion that is non-toxic, harmless, non-radioactive, and does not possess inherent fluorescence.

[0016] Optionally, the crystal structure of the two-photon luminescent micro / nano material belongs to the orthorhombic crystal system and has a P212121 chiral space group structure.

[0017] Optionally, in the unit cell parameters of the two-photon luminescent micro / nanomaterial,

[0018] Optionally, in the unit cell parameters of the two-photon luminescent micro / nanomaterial,

[0019] Optionally, in the unit cell parameters of the two-photon luminescent micro / nano material, α = β = γ = 90° and Z = 4.

[0020] Optionally, under ultraviolet excitation, the emission peak of the two-photon luminescent micro / nanomaterial is 475±2nm in the range of 250–425nm.

[0021] Optionally, the fluorescence lifetime of the two-photon luminescent micro / nanomaterial is 0.5 ns to 2.0 ns.

[0022] Optionally, under excitation in the 500–1000 nm femtosecond band, the two-photon luminescent micro / nano material emits two-photon blue light.

[0023] Optionally, under 790nm near-infrared I region femtosecond band excitation, the emission peak of the two-photon luminescent micro / nano material is 475nm.

[0024] Optionally, under ultraviolet light excitation, i.e., single-photon excitation, in the wavelength range of 250–425 nm, the emission peak of the two-photon luminescent micro / nano material is 475 nm.

[0025] Preferably, the photoluminescence quantum yield of the two-photon luminescent micro / nanomaterial can reach 40%, indicating that it is a crystallization-induced fluorescence enhancement material.

[0026] Preferably, the two-photon luminescent micro / nanomaterial exhibits fluorescence emission of 475nm under near-infrared I region, i.e., 790nm femtosecond excitation, with a higher half-maximum emission peak value (WHM) than that under single-photon excitation.

[0027] According to a second aspect of this application, a method for preparing the above-described two-photon luminescent micro / nano material is provided, the method comprising:

[0028] (1) Dissolve the tetraphenylvinylcarboxylic acid ligand in N,N-dimethylformamide and denote it as solution A;

[0029] (2) In a closed reactor, a mixture containing solution A, potassium metal salt, surfactant and low boiling point solvent is reacted and stirred to obtain the two-photon luminescent micro-nano material.

[0030] Optionally, the potassium metal salt is selected from at least one of KI, KBr, KCl, K2CO3, K2SO4, and KNO3.

[0031] Optionally, the surfactant is selected from at least one of tetrabutylammonium chloride, tetrabutylammonium bromide, hexadecyltrimethylammonium chloride, hexadecyltrimethylammonium bromide, benzyltriethylammonium chloride, and benzyltriethylammonium bromide.

[0032] Optionally, the low-boiling-point solvent is selected from at least one of methanol, ethanol, ethylene glycol, and glycerol.

[0033] According to another aspect of this application, a method for producing two-photon luminescent micro / nano materials is provided. This method has simple steps, yields high-purity products with high yields, and is suitable for large-scale industrial production.

[0034] Optionally, the method includes the following steps:

[0035] (1) Dissolve the tetraphenylvinylcarboxylic acid ligand in N,N-dimethylformamide to obtain solution A;

[0036] (2) Dissolve the potassium salt in deionized water to obtain solution B;

[0037] (3) Mix solution A and solution B and stir. Add surfactant and low-boiling-point solvent during stirring and wait for it to become clear.

[0038] (4) After the system has clarified, further heat it while keeping it stirred;

[0039] (5) When the Tyndall effect occurs in the reaction system, stop heating and continue stirring for a period of time.

[0040] (6) Filter and vacuum dry to obtain the crystalline product.

[0041] The organic solvent for dissolving the tetraphenylvinylcarboxylic acid ligand must be N,N-dimethylformamide; the low-boiling solvent is selected from at least one of volatile alcohols such as methanol, ethanol, ethylene glycol, and glycerol.

[0042] Optionally, the potassium metal salt is dissolved in water.

[0043] Optionally, the ratio of the tetraphenylvinylcarboxylic acid ligand, potassium metal salt, surfactant, N,N-dimethylformamide, water, and low-boiling-point solvent is: 1-3 mmol: 1-3 mmol: 1-3 mmol: 50-100 mL: 10-20 mL: 20-40 mL.

[0044] Optionally, the reaction temperature is 100–150°C, and the reaction time is 4–12 h.

[0045] Optionally, the temperature of the reaction is selected from any value of 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, or a range between any two of the above.

[0046] Optionally, the reaction time is selected from any value of 4h, 6h, 8h, 10h, 12h or a range between any two of the above.

[0047] Optionally, the stirring time is 24 to 72 hours.

[0048] Optionally, the stirring time is selected from any value of 24h, 36h, 48h, 72h or a range between any two of the above.

[0049] According to a third aspect of this application, an application of the aforementioned two-photon luminescent micro / nano material in fingerprint recognition is provided.

[0050] Optionally, the fingerprint recognition is optical recognition.

[0051] Optionally, the two-photon luminescent micro / nano material can be used for single-photon / two-photon imaging in fingerprint recognition.

[0052] Optionally, the two-photon luminescent micro / nano material used in fingerprint recognition can be two-photon near-infrared imaging, with a selectable wavelength range of 500–1000 nm.

[0053] Preferably, photonic luminescent micro / nano materials are used for imaging in the near-infrared I region of fingerprint recognition.

[0054] According to the fourth aspect of this application, a method is provided for using computational software such as Matlab and ImageJ to apply the two-photon luminescent micro / nano materials to fingerprint recognition, especially for the extraction of characteristic fingerprints.

[0055] The beneficial effects that this application can produce include:

[0056] 1) This application provides a two-photon luminescent micro / nanomaterial. The two-photon luminescent micro / nanomaterial exhibits excellent single- and two-photon emission performance, and its synthesis process is environmentally friendly. Experimental measurements show that this type of two-photon luminescent micro / nanomaterial has a fluorescence emission of 475 nm, a fluorescence quantum yield as high as 40%, and a fluorescence lifetime of 0.80 ns, exhibiting an extremely fast fluorescence response time. Furthermore, it does not contain noble metals, making it of significant commercial application value in the field of two-photon luminescent micro / nanomaterials.

[0057] 2) This application provides a method for preparing the aforementioned two-photon luminescent micro / nanomaterial. The method is simple, and the resulting two-photon luminescent micro / nanomaterial has high purity, good crystallinity, and high yield, making it suitable for large-scale industrial production.

[0058] 3) This application provides an application of two-photon luminescent micro / nanomaterials in fingerprint recognition. Under two-photon 790nm femtosecond excitation, the two-photon luminescent micro / nanomaterial exhibits an emission spectrum with an increased full width at half maximum (FWHM) of 475nm blue light emission. This high-performance two-photon effect can be applied to near-infrared I-region imaging, which is crucial for improving the image resolution of near-infrared I-region two-photon imaging. It has significant commercial application value in high-end fingerprint recognition fields, such as large-value financial payments, accurate crime detection, and the establishment of fingerprint databases for abducted children. Attached Figure Description

[0059] Figure 1 Sample 1 obtained in Example 1 of this application # A schematic diagram of the crystal structure;

[0060] Figure 1 In the diagram, (a) represents the tetraphenylvinylcarboxylic acid ligand and the metal K. + A schematic diagram of the coordination mode of ions; (b) shows that the crystal exhibits a one-dimensional rod-shaped secondary building block in the b direction; (c) shows the three-dimensional stacking structure of the crystal.

[0061] Figure 2 Sample 1 obtained in Example 1 of this application # Micro-nano morphology at 200 nm under a scanning electron microscope.

[0062] Figure 3 Sample 1 obtained in Example 1 of this application # The theoretical XRD diffraction pattern obtained by fitting single-crystal data is compared with the experimentally measured XRD diffraction pattern.

[0063] Figure 4 Sample 1 obtained in Example 1 of this application # Photoluminescence experimental spectrum.

[0064] Figure 5 Sample 1 obtained in Example 1 of this application # Photoluminescence color coordinates.

[0065] Figure 6 Sample 1 obtained in Example 1 of this application # Photoluminescence quantum yield results.

[0066] Figure 7 Sample 1 obtained in Example 1 of this application # Experimental results on the luminescence stability at temperature.

[0067] Figure 8 This is Sample 1 of Embodiment 1 of this application. # The single- and two-photon emission morphologies and their emission spectra;

[0068] Figure 8 In the image, (a) shows the emission morphology under 405 nm single-photon excitation; (b) shows the emission morphology under 790 nm two-photon near-infrared I-region excitation; and (c) shows the fluorescence emission spectra of single and two-photon excitations. FWHM is its full width at half maximum (FWHM), and the larger the value, the higher the imaging resolution.

[0069] Figure 9 This is Sample 1 of Embodiment 1 of this application. # Applications of fingerprint recognition;

[0070] Figure 9In the image, (a) shows fingerprint images on glass, plastic, coins, CDs, and agate, respectively; (b) shows fingerprint images on aluminum foil; (c) shows the imaging resolution and pixel distribution; and (d) shows fingerprint feature recognition and reconstruction based on the computational software Matlab2017b. Detailed Implementation

[0071] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0072] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0073] The potassium salt was purchased from Shanghai Myriel Chemical Technology Co., Ltd.; the protic solvents such as ethanol and methanol were purchased from Sinopharm Group.

[0074] The following instruments and equipment are used in this application:

[0075] The SEM equipment used was a Supra40 field emission scanning electron microscope manufactured by Zeiss GmbH, Germany.

[0076] The photoluminescence performance test was conducted using the Edinburgh FLS1000, with an Xe lamp as the excitation source, a spherical integrating sphere as the sample chamber, and polytetrafluoroethylene (PTFE) as the reference material provided by the Edinburgh FLS1000 instrument manufacturer.

[0077] Example 1 # Sample preparation

[0078] Compound [(Hdma)K(H2L)] n Synthesized via a solvothermal reaction. The synthesis is as follows: 150 mg mmol tetraphenylvinylcarboxylic acid ligand was weighed and dissolved in 30 mL DMF, and sonicated until the solid was completely dissolved; this is labeled solution A. Then, 332 mg KI was weighed and dissolved in 10 mL deionized water, and sonicated until the metal salt was completely dissolved; this is labeled solution B. Solutions A and B were transferred separately to 250 mL round-bottom flasks and stirred at 1200 rpm. During stirring, 20 mL anhydrous ethanol and 100 mg of surfactant tetrabutylammonium bromide were added until the system turned a clear yellow color. The temperature was rapidly increased to 120 °C and maintained for 8 hours, then cooled to room temperature and stirred for another 24 hours. After the reaction was complete, the supernatant was filtered off, the sample was collected and washed several times with DMF or ethanol, and finally air-dried to obtain a light blue powder, namely compound [(Hdma)K(H2L)]. n The yield was 78% (based on tetraphenylvinylcarboxylic acid ligand), and the average particle size of the sample was 10 μm.

[0079] Comparative Examples 1 and 2 # Sample preparation

[0080] Compound [(Hdma)K(H2L)] n Synthesized via a solvothermal reaction. The synthesis is as follows: 150 mg mmol tetraphenylvinylcarboxylic acid ligand was weighed and dissolved in 30 mL DMF, and sonicated until the solid was completely dissolved; this is labeled solution A. Then, 332 mg KI was weighed and dissolved in 10 mL deionized water, and sonicated until the metal salt was completely dissolved; this is labeled solution B. Solutions A and B were transferred separately to 250 mL round-bottom flasks. Then, 20 mL of anhydrous ethanol was added until the system turned a clear yellow color. The temperature was rapidly increased to 120 °C and maintained for 8 hours, then cooled to room temperature. After the reaction was complete, the supernatant was filtered off, the sample was collected and washed several times with DMF or ethanol, and finally air-dried to obtain pale yellow small crystals, namely the compound [(Hdma)K(H2L)]. n The yield was 65% (based on tetraphenylvinylcarboxylic acid ligand) and the average particle size was 0.15 mm.

[0081] Structural characterization of sample in Test Example 1

[0082] Sample 1 # The single crystals can be obtained by slow evaporation. Compound 1 can be obtained by standing the filtrate for 3-4 days. # The sheet-like single crystal. Its single crystal structure can be obtained on a Rigaku FR-X Microfocus single crystal instrument, with a Mo target and a Kα radiation source ( The test temperature was 100K. And it passed the Olex test. 2 1.2 Structural analysis was performed. Test results are as follows: Figure 1 As shown, the asymmetric unit contains one dimethylamine cation and one K cation. + It consists of an ion and a semi-deprotonated tetraphenylvinylcarboxylic acid ligand; K is a +1 valence metal ion with a distorted octahedral spatial coordination configuration of six coordinations.

[0083] X-ray powder diffraction and X-ray single crystal diffraction results show that:

[0084] Sample l # (Chemical formula [(Hdma)K(H2L)]) n It belongs to the chiral space group P212121 of the orthorhombic crystal system.

[0085] For sample 1 # The unit cell parameters are α=β=γ=90°, Z=4.

[0086] Morphological and phase characterization of sample in Test Example 2

[0087] Sample 1 #The micro- and nano-structures can be obtained using scanning electron microscopy (SEM). The SEM equipment used in this experiment was a Supra 40 field emission scanning electron microscope (SEM) manufactured by Zeiss GmbH, Germany. Secondary electron and backscattered electron signals were primarily used to observe the microstructure of the powder. Its operating voltage was 5 kV and its operating current was 10 μA. Sample 1 # micro and nano structures such as Figure 2 As shown.

[0088] Sample 1 # X-ray powder diffraction (XRD) phase analysis was performed on a Rigaku MiniFlex 600 X-ray diffractometer with a Cu target and a Kα radiation source. The test results are as follows: Figure 3 A comparison of the theoretical XRD diffraction pattern obtained by fitting X-ray single-crystal diffraction data with the XRD diffraction pattern obtained by X-ray powder diffraction phase analysis shows that the XRD diffraction pattern obtained by fitting single-crystal data is highly consistent with the experimentally measured XRD diffraction pattern, proving that the obtained sample is a high-purity and high-crystallinity sample.

[0089] Test Example 3: Photoluminescence Performance Test Experiment

[0090] For sample 1 # The specific steps for conducting the photoluminescence performance test are as follows:

[0091] The selected instrument is the Edinburgh FLS1000 for photoluminescence performance testing. The excitation source is an Xe lamp, and the ultraviolet light of a specific excitation band can be selected through the filtering system. The excitation slit is 0.5 mm and the receiving slit is 0.2 mm.

[0092] Experimental spectra of photoluminescence are as follows Figure 4 As shown. Under excitation at 250–425 nm, sample 1 # The photoluminescence peak remained stable at 475 nm, emitting blue light; its color coordinates were... Figure 5 As shown.

[0093] Test Example 4: Photoluminescence Quantum Yield Performance Test Experiment

[0094] The selected instrument is the Edinburgh FLS1000 for photoluminescence performance testing. The excitation source is an Xe lamp, the sample chamber is a spherical integrating sphere, and the reference material is a polytetrafluoroethylene total reflection sheet provided by the Edinburgh FLS1000 instrument manufacturer. After filtering, a specific excitation band of ultraviolet light can be selected. The excitation slit is 0.5 mm, and the receiving slit is 0.2 mm.

[0095] Experimental spectrum of photoluminescence quantum is shown below Figure 6 As shown. Under the optimal wavelength excitation of 375nm, sample 1# The fluorescence quantum yield is 40%.

[0096] Test Example 5: Luminescence and Thermal Stability Test Experiment

[0097] Sample 1 # The thermal stability of luminescence can be obtained through photoluminescence spectra at different temperatures. For example... Figure 7 As shown, Sample 1 # It exhibits good luminescence thermal stability, maintaining high luminescence characteristics at around 250℃, with a feature size of 475nm.

[0098] Test Example 6: In-situ Single and Two-Photon Fluorescence Testing Experiment

[0099] The selected instrument is Nikon-ARsiMP-LSM-Kit-Legend Elite-USX. The instrument integrates multiple modes such as laser confocal scanning, single-photon and two-photon spectral analysis, and fluorescence lifetime spatial distribution imaging. Among them, in terms of confocal imaging and two-photon imaging: (1) ordinary fluorescence microscope (DAPI, GFP, YFP, RFP, CY3 excitation filter, ≥6-position fluorescent filter electric conversion), with automatic focusing function; (2) ordinary single-photon confocal imaging and spectral mode (laser wavelength 405nm, 457nm, 488nm, 514nm, 561nm, 640nm); (3) two-photon confocal imaging and spectral mode (femtosecond laser wavelength range 680-1080nm, 80MHz and pulse width less than or equal to 140fs); The software system has powerful image processing functions. During the test, sample 1 was recorded. # Real-time emission morphology and output spectrum of in-situ single and two-photon fluorescence test, such as Figure 8 As shown.

[0100] Test Example 7: Fingerprint Recognition Experiment and Analysis Using Matlab and ImageJ Software

[0101] like Figure 9 As shown, after washing their hands, the experimenter pressed their right thumb against their forehead and rubbed repeatedly to obtain more oil. Then, they gently pressed their fingerprint onto various substrates, including glass, plastic, CD, agate, and aluminum foil, before applying a sample coating. To avoid damaging the original fingerprint image, excess powder was blown away with a bulb syringe. The latent fingerprint fluorescence image was then captured using an iPhone 12 camera mode under illumination with a handheld UV light (365nm excitation).

[0102] In latent fingerprint imaging experiments, the contrast and sharpness of fingerprint images are difficult to judge directly with the human eye. Grayscale analysis is mainly used to evaluate the image contrast of fingerprint imaging. Its principle is to convert the original fingerprint image into a grayscale image to remove the color influence of the developing material. Then, the change in grayscale value along any straight line in the fingerprint image reflects the brightness changes between the ridges and grooves in the actual latent fingerprint image. The waveform of the resulting relative grayscale value reflects the imaging contrast and sharpness of the latent fingerprint image. In this experiment, ImageJ version 1.8.0 was used, and Matlab 2017b was employed to perform grayscale analysis on the latent fingerprint images and reconstruct the characteristic fingerprints.

[0103] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for preparing a two-photon luminescent micro-nano material, characterized in that, The preparation method comprises: (1) dissolving tetrakis[4-(4'-carboxylphenyl)phenyl]ethylene in N,N-dimethylformamide, denoted as solution A; (2) in a closed reactor, a mixture containing solution A, a metal potassium salt, a surfactant, and a low-boiling-point solvent is reacted and stirred to obtain the two-photon luminescent micro-nano material; The low-boiling-point solvent is at least one selected from methanol, ethanol, ethylene glycol, and glycerol; The surfactant is at least one selected from tetrabutylammonium chloride, tetrabutylammonium bromide, cetyltrimethylammonium chloride, cetyltrimethylammonium bromide, benzyltriethylammonium chloride, and benzyltriethylammonium bromide; The use amount ratio of tetrakis[4-(4'-carboxylphenyl)phenyl]ethylene, the metal potassium salt, the surfactant, N,N-dimethylformamide, water, and the low-boiling-point solvent is 1-3 mmol: 1-3 mmol: 1-3 mmol: 50-100 mL: 10-20 mL: 20-40 mL.

2. The production method according to claim 1, characterized by, The metal potassium salt is at least one selected from KI, KBr, KCl, K2CO3, K2SO4, and KNO3.

3. The preparation method according to claim 1, characterized in that, The metal potassium salt is dissolved in water.

4. The method of claim 1, wherein, The reaction temperature is 100-150 DEG C, the reaction time is 4-12 h, and the stirring time is 24-72 h.

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