Fluorescent probes for visualizing high-resolution identification of latent fingerprints and methods of making the same

Abstract

The application discloses a fluorescent probe for visualizing high-resolution identification of potential fingerprints and a preparation method thereof, relates to the technical field of biological imaging, and the fluorescent probe is abbreviated as Zn-TC, and a structural formula is shown as follows: The LFPs image after being treated by the complex Zn-TC has wide applicability, high definition and high contrast, and can be applied to the field of LFPs identification; and the complex can obtain LFPs imaging on various substrates in a short time; in addition, under the multi-photon excitation wavelength 800 nm, high-resolution and high-contrast imaging of the complex for recognizing tertiary LFPs can be obtained through a confocal developing technology.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of bio-imaging, in particular to a fluorescent probe for visualizing high-resolution identification of latent fingerprints and a preparation method thereof. BACKGROUND

[0002] Latent fingerprints (LFPs) are the traces left by fingers touching the surface of an object, which are mainly composed of water and lipids. LFPs are the most common fingerprint form at crime scenes, which are difficult to identify directly by naked eyes. In the field of forensic medicine, LFPs are regarded as a key biological identification feature, and the probe for detecting LFPs has important value for the investigation and evidence collection of crime scenes.

[0003] Although traditional LFPs materials have been well applied in primary and secondary detail features, these materials inevitably impair the imaging quality, resulting in long response time and low sensitivity and contrast. In recent years, multi-photon aggregation-induced emission (AIE) materials have great application potential in the field of LFPs imaging due to their deep penetration, high contrast and high sensitivity. The present application synthesizes a carbazole tripyridine zinc complex with multi-photon AIE characteristics, aiming to provide a visualized optical probe material for rapid identification of personal information in criminal investigation activities. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a fluorescent probe and a preparation method and application thereof. The synthesized carbazole tripyridine zinc complex can specifically identify oleic acid (OA) in LFPs, realize high-resolution LFPs imaging with fast response; and utilize the multi-photon excitation fluorescence characteristics of the complex to accurately capture the tertiary details of LFPs, realize high-resolution and high-contrast imaging of the tertiary details of fingerprints.

[0005] The technical problem to be solved by the present application is solved by the following technical solution:

[0006] The first object of the present application is to provide a fluorescent probe, referred to as Zn-TC, whose structural formula is as follows:

[0007]

[0008] The second object of the present application is to provide a preparation method of the fluorescent probe, comprising the following steps:

[0009] (1) substitution reaction of carbazole and bromohexane to obtain compound A;

[0010] (2) Vilsmeier-Haack reaction of compound A with N,N-dimethylformamide (DMF) and phosphorus oxychloride (POCl3) to obtain compound B;

[0011] (3) Compound B undergoes an alkylation reaction with 2-acetylpyridine to obtain compound C;

[0012] (4) Compound C undergoes a ring-closing reaction with 1-[2-oxo-2-(2-pyridyl)ethyl]pyridinium iodide to obtain compound TC;

[0013] (5) Compound TC undergoes coordination reaction with zinc nitrate to obtain the complex Zn-TC.

[0014] The synthetic route is as follows:

[0015]

[0016] Furthermore, the molar ratio of the carbazole to bromohexane is 1:(1-1.5). By adding an excess of bromohexane, the carbazole is reacted as completely as possible.

[0017] Furthermore, the substitution reaction uses sodium hydride (NaH) as a catalyst. NaH acts as a strong base to remove the hydrogen on the nitrogen of carbazole, thereby promoting the substitution reaction between carbazole and bromohexane.

[0018] Furthermore, the molar ratio of compound A to DMF and POCl3 is 1:(2-4):(3-6). Using DMF as a formylating agent, a formyl group is introduced into the aromatic ring of compound A under the catalysis of POCl3.

[0019] Furthermore, the molar ratio of the compound B to 2-acetylpyridine is 1:(1.1-1.2). By adding an excess of 2-acetylpyridine, the compound B is reacted as completely as possible.

[0020] Furthermore, the alkylation reaction is carried out under alkaline conditions, which can be provided by sodium hydroxide. Alkaline conditions can make the hydrogen atom on the α-carbon of the 2-acetylpyridine carbonyl group more easily substituted, thereby promoting the alkylation reaction.

[0021] Furthermore, the molar ratio of compound C to 1-[2-oxo-2-(2-pyridyl)ethyl]pyridinium iodide is 1:(1 to 1.1). A slight excess of 1-[2-oxo-2-(2-pyridyl)ethyl]pyridinium iodide can be used to increase the conversion rate of compound C.

[0022] Furthermore, the molar ratio of the zinc nitrate to the compound TC is 1:(2-3).

[0023] The third object of the present invention is to provide an application of the fluorescent probe in visually identifying LFP.

[0024] The beneficial effects of the present invention are:

[0025] 1. The complex Zn-TC has strong coordination ability to transition metal ion Zn(II) in the structure of 2,2:6',2"-triphenylpyridine, and the hexylcarbazole group has strong electron-donating ability, which is conducive to intramolecular charge transfer and adjustment of complex luminescence; the introduction of Zn(II) center helps to enhance the charge transfer from the center ion to the ligand, improve the multi-photon excitation fluorescence performance of the complex; and the Zn(II) complex has the advantages of low biological toxicity and good compatibility.

[0026] 2. The complex Zn-TC has multi-photon AIE properties, overcomes the fluorescence quenching caused by self-aggregation of most complexes at high concentrations; the AIE phenomenon of Zn-TC is observed in a mixed solution of ethyl acetate, and the fluorescence intensity increases with the increase of the volume fraction of ethyl acetate; when the volume fraction of ethyl acetate is 80%, the three-photon cross section of Zn-TC reaches a maximum value of 19.1*10 -81 cm 6 ·s 2 ·photon -2 .

[0027] 3. The complex Zn-TC can specifically recognize OA in the range of 0-150 μM, and the detection limit is 6.23 μM; at an excitation wavelength of 1300 nm, the multi-photon fluorescence recognition effect of OA is best, and the three-photon fluorescence cross section reaches 5.37*10 - 81 cm 6 ·s 2 ·photon -2 , which is about 1.9 times that before recognition.

[0028] 4. The LFPs image treated by the complex Zn-TC has wide applicability, high definition and high contrast, and can be applied to the field of LFPs recognition; the complex can obtain LFPs imaging on a variety of substrates (tin paper, glass, plastic and optical disc, etc.) in a short time; under the multi-photon excitation wavelength of 800 nm, high-resolution and high-contrast imaging of the complex recognizing three-level LFPs can be obtained by confocal development technology.

[0029] 5. The complex Zn-TC has good stability and anti-photobleaching property, and the fluorescence intensity remains stable within 30 min of white light irradiation without obvious photobleaching phenomenon. DETAILED DESCRIPTION

[0030] Figure 1 is the crystal structure formula of the complex Zn-TC;

[0031] Figure 2 (a) is a three-photon fluorescence spectrum of Zn-TC under an excitation wavelength of 1150-1550 nm (c=10-3 mol / L); Figure 2 (b) is the three-photon absorption cross section of Zn-TC at the excitation wavelength of 1150-1450 nm (c = 10 -3 mol / L); Figure 2 (c) is the three-photon fluorescence spectrum of Zn-TC in mixed solutions with different volume fractions of ethyl acetate at the excitation wavelength of 1300 nm, and the insert is the three-photon fluorescence spectrum of Zn-TC in ethyl acetate at the excitation wavelength of 1300 nm; Figure 2 (d) is the three-photon absorption cross section of Zn-TC in mixed solutions with different volume fractions of ethyl acetate at the excitation wavelength of 1300 nm (c = 10 -3 mol / L);

[0032] Figure 3 (a) is the fluorescence response of Zn-TC to different substances (c = 10 -5 mol / L); Figure 3 (b) is the three-photon fluorescence spectrum of Zn-TC after adding OA at the excitation wavelength of 1150-1550 nm (c = 10 -3 mol / L); Figure 3 (c) is the three-photon fluorescence spectrum of Zn-TC after adding OA (c = 10 -3 mol / L); Figure 3 (d) is the time-dependent fluorescence response of Zn-TC after adding OA at the excitation wavelength of 1300 nm (c = 10 -3 mol / L), error <10%;

[0033] Figure 4 is the fluorescence image of LFPs on different substrates (tin paper, glass, plastic and optical disc) soaked in Zn-TC solution (80 μM, λex=365 nm);

[0034] Figure 5 (a) is the confocal imaging of LFPs on glass soaked in Zn-TC solution (the leftmost image is the camera shot of LFPs on glass soaked in Zn-TC solution; the right (1) (2) (3) (4) are confocal imaging images randomly taken from the fingerprint part of the left image, where the first row is the single-photon light source λex=800 nm, the second row is the two-photon light source λex=405 nm, and the scale bar = 100 μM); Figure 5 (b) is the quantitative fluorescence intensity map of confocal imaging of LFPs on glass soaked in Zn-TC solution; Figure 5 (c) is the time-dependent fluorescence response of Zn-TC under single-photon and two-photon; Figure 5 (d) is the quantitative fluorescence intensity map of the time-dependent fluorescence response of Zn-TC under single-photon and two-photon. DETAILED DESCRIPTION

[0035] In order to make the technical means, creative features, purposes and effects of the present application easy to understand, the present application is further described below in combination with specific examples and drawings.

[0036] Example 1: Preparation of complex Zn-TC

[0037] Preparation of compound A

[0038] Into a 250 mL round bottom flask, sodium hydride (2.6 g, 0.11 mol) and 100 mL DMF were added, stirred at room temperature for 20 min, then carbazole (9.1 g, 0.054 mol) was added, stirred at room temperature for 20 min, then bromoethane (8.4 mL, 0.055 mol) was added, and the mixture was heated to 65°C for 3 h. After the reaction was completed, the reaction solution was poured into ice water, and filtered to obtain a light yellow solid, which was recrystallized from ethanol to obtain white needle-like crystals, i.e. compound A, with a yield of 90%.

[0039] Preparation of compound B

[0040] Into a 250 mL round bottom flask, DMF (9.2 g, 0.13 mol) was added, and POCl3(32 g, 0.21 mol) was slowly added dropwise under an ice-salt bath, then compound A (10 g, 0.042 mol) dissolved in 53 mL chloroform was added, and the mixture was heated to 65°C for 8 h. After the reaction was completed, the reaction solution was poured into ice water, and the pH was adjusted to weak alkalinity with sodium hydroxide, and dichloromethane was used for extraction, and the organic layer was obtained, and after normal pressure distillation, it was purified by column chromatography with petroleum ether and ethyl acetate (10:1, v / v), and then frozen to obtain white solid, i.e. compound B, with a yield of 90%.

[0041] Preparation of compound C

[0042] Compound B (8.4 g, 0.030 mol) was dissolved in 200 mL ethanol and added to a 500 mL flask, stirred at room temperature, then 2-acetylpyridine (4 mL, 0.033 mol) was added, and a 2% sodium hydroxide solution was added dropwise until orange-red solid was formed, and the reaction was carried out for 15 h, and then filtered, and washed with water to obtain yellow solid, i.e. compound C, with a yield of 45%.

[0043] Preparation of compound TC

[0044] Compound C (1.9 g, 5.0 mmol) and 1-[2-oxo-2-(2-pyridyl)ethyl]pyridinium iodide (1.6 g, 5.0 mmol) were dissolved in 50 mL of methanol, and ammonium acetate (2.3 g, 30 mmol) was added, and the reaction was refluxed for 24 h. After the reaction was completed, the reaction solution was allowed to cool, and a solid was precipitated, which was washed with water and dried, and purified by column chromatography using methylene chloride and methanol (10:1, v / v) to obtain a brown solid, which was compound TC, in a yield of 31%.

[0045] Preparation of complex Zn-TC

[0046] Compound TC (2.3 g, 5 mmol) was dissolved in 40 mL of methanol to obtain solution I, and zinc nitrate hexahydrate (0.45 g, 2 mmol) was dissolved in 15 mL of methanol to obtain solution II, and solution I was mixed with solution II, and the reaction was performed at 65°C for 3 h. After the reaction was completed, the reaction solution was cooled to room temperature, and filtered to obtain a yellow solid, which was complex Zn-TC, in a yield of 85%.

[0047] Example 2: Preparation of complex Zn-TC

[0048] Preparation of compound A

[0049] Sodium hydride (2.6 g, 0.11 mol) and 100 mL of DMF were added to a 250 mL round bottom flask, and stirred at room temperature for 20 min, and then carbazole (9.1 g, 0.054 mol) was added, and stirred at room temperature for 20 min, and then bromoethane (9.7 mL, 0.059 mol) was added, and the mixture was heated to 65°C for 3 h. After the reaction was completed, the reaction solution was poured into ice water, and filtered to obtain a light yellow solid, which was recrystallized with ethanol to obtain white needle-shaped crystals, which was compound A, in a yield of 92%.

[0050] Preparation of compound B

[0051] DMF (11.0 g, 0.15 mol) was added to a 250 mL round bottom flask, and POCl3(32 g, 0.21 mol) was slowly added dropwise under an ice-salt bath, and then compound A (10 g, 0.042 mol) dissolved in 53 mL of chloroform was added, and heated to 65°C for 8 h. After the reaction was completed, the reaction solution was poured into ice water, and the pH was adjusted to weak alkalinity using sodium hydroxide, and extracted with dichloromethane, and the organic layer was obtained, and purified by column chromatography using petroleum ether and ethyl acetate (10:1, v / v) after normal pressure distillation, and frozen to obtain a white solid, which was compound B, in a yield of 91%.

[0052] Preparation of compound C

[0053] Compound B (8.4 g, 0.030 mol) was dissolved in 200 mL of ethanol and added to a 500 mL flask, stirred at room temperature, then 2-acetylpyridine (4.4 mL, 0.036 mol) was added and a 2% by mass sodium hydroxide solution was added dropwise until an orange solid was formed, the reaction was carried out for 15 h, filtered, washed with water to obtain a yellow solid, compound C, in a yield of 47%.

[0054] Preparation of compound TC

[0055] Compound C (1.9 g, 5.0 mmol) and 1-[2-oxo-2-(2-pyridyl)ethyl]pyridine iodide (1.7 g, 5.3 mmol) were dissolved in 50 mL of methanol and ammonium acetate (2.3 g, 30 mmol) was added, the reaction was carried out at reflux for 24 h. After the reaction was completed, the reaction solution was allowed to cool and a solid was precipitated, washed with water and dried, and then purified by column chromatography using dichloromethane and methanol (10:1, v / v) to obtain a brown solid, compound TC, in a yield of 35%.

[0056] Preparation of complex Zn-TC

[0057] Compound TC (2.3 g, 5 mmol) was dissolved in 40 mL of methanol to obtain solution I; zinc nitrate hexahydrate (0.45 g, 2 mmol) was dissolved in 15 mL of methanol to obtain solution II; solution I and solution II were mixed and the reaction was carried out at 65°C for 5 h. After the reaction was completed, the reaction solution was cooled to room temperature and filtered to obtain a yellow solid, complex Zn-TC, in a yield of 88%.

[0058] Example 3: Preparation of complex Zn-TC

[0059] Preparation of compound A

[0060] Sodium hydride (2.6 g, 0.11 mol) and 100 mL of DMF were added to a 250 mL round-bottom flask, stirred at room temperature for 20 min, then carbazole (9.1 g, 0.054 mol) was added, stirred at room temperature for 20 min, then bromoethane (8.9 mL, 0.054 mol) was added, and the mixture was heated to 65°C and the reaction was carried out for 3 h. After the reaction was completed, the reaction solution was poured into ice water and filtered to obtain a light yellow solid, which was recrystallized from ethanol to obtain white needle-shaped crystals, compound A, in a yield of 90%.

[0061] Preparation of compound B

[0062] Compound B was prepared by adding DMF (9.2 g, 0.13 mol) into a 250 mL round bottom flask, slowly dropping POCl3(27.6 g, 0.18 mol) under ice-salt bath, then adding compound A (10 g, 0.042 mol) dissolved in 53 mL of chloroform, heating to 65 °C for 8 h. After the reaction was completed, the reaction solution was poured into ice water, and the pH was adjusted to weak alkaline with sodium hydroxide. The reaction solution was extracted with dichloromethane, and the organic layer was obtained. After normal pressure distillation, the product was purified by column chromatography with petroleum ether and ethyl acetate (10:1, v / v) as the eluent, and then frozen to obtain white solid, i.e. compound B, with a yield of 89%.

[0063] Preparation of compound C

[0064] Compound B (8.4 g, 0.030 mol) was dissolved in 200 mL of ethanol and added into a 500 mL flask. After stirring at room temperature, 2-acetylpyridine (4 mL, 0.033 mol) was added, and a 2% sodium hydroxide solution was added dropwise until orange solid was formed. The reaction was carried out for 12 h, and then the product was obtained by filtration and water washing to obtain yellow solid, i.e. compound C, with a yield of 43%.

[0065] Preparation of compound TC

[0066] Compound C (1.9 g, 5.0 mmol) and 1-[2-oxo-2-(2-pyridyl)ethyl]pyridine iodide (1.7 g, 5.3 mmol) were dissolved in 50 mL of methanol, and ammonium acetate (2.3 g, 30 mmol) was added. The reaction was carried out under reflux for 24 h. After the reaction was completed, the reaction solution was cooled to precipitate solid, which was washed with water and dried. After normal pressure distillation, the product was purified by column chromatography with dichloromethane and methanol (10:1, v / v) as the eluent to obtain brown solid, i.e. compound TC, with a yield of 30%.

[0067] Preparation of complex Zn-TC

[0068] Compound TC (2.3 g, 5 mmol) was dissolved in 50 mL of methanol to obtain solution I; zinc nitrate hexahydrate (0.45 g, 2 mmol) was dissolved in 15 mL of methanol to obtain solution II; and solution I and solution II were mixed and reacted at 65 °C for 5 h. After the reaction was completed, the reaction solution was cooled to room temperature, and then filtered to obtain yellow solid, i.e. complex Zn-TC, with a yield of 89%.

[0069] Example 4: Structural characterization of complex Zn-TC

[0070] The complex Zn-TC prepared in Example 1 was characterized by nuclear magnetic hydrogen spectrum, nuclear magnetic carbon spectrum, infrared spectrum, and mass spectrum, and the characterization results are as follows: 1H NMR (400 MHz, DMSO-d6) δ 9.47 (s, 2H), 9.29 (s, 2H), 9.20 (m, 4H), 9.11 (m, 2H), 8.87 (d, J = 4.9 Hz, 1H), 8.56 (d, J = 8.8 Hz, 1H), 8.44 (m, 2H), 8.36 (d, J = 7.8 Hz, 2H), 8.29 (t, J = 7.9 Hz, 4H), 7.93 (m, 6H), 7.70 (dd, J = 14.7, 8.3 Hz, 2H), 7.50 (q, J = 6.6, 6.0 Hz, 4H), 7.33 (dt, J = 14.6, 7.3 Hz, 2H), 4.51 (m, 4H), 1.84 (m, 4H), 1.24 (dd, J = 13.5, 6.6 Hz, 12H), 0.80 (t, J = 7.0 Hz, 6H). 13 C NMR (101 MHz, DMSO-d6) δ 156.10, 155.83, 151.04, 149.87, 141.26, 141.16, 137.97, 128.71, 126.77, 125.23, 124.98, 123.49, 122.78, 121.53, 119.74, 119.57, 118.48, 110.63, 110.10, 42.97, 31.51, 29.05, 26.68, 22.55, 14.37. IR (KBr, cm -1 ): 3431 (m), 3046 (w), 2933 (m), 2856 (w), 1587 (m), 1480 (s), 1411 (m), 1272 (m), 883 (m), 790 (m). ESI-MS: [m-2NO3 - ] / z: calcd for C 66 H 60 N8Zn: 514.21, found: 514.42.

[0071] The above characterization results prove that the complex Zn-TC is successfully prepared in Example 1.

[0072] Example 5: Crystal structure analysis of the complex Zn-TC

[0073] The single crystal of the complex Zn-TC is obtained by solvent evaporation method, and the specific process is as follows: a proper amount of the complex Zn-TC prepared in Example 1 is dissolved in 10 mL of dichloromethane, then filtered into a 25 mL conical flask, 5 mL of ethanol is overlaid on the upper layer, and placed in a dark environment without vibration, yellow prismatic crystals are obtained after two weeks. The obtained crystal is subjected to X-ray diffraction (XRD) analysis.

[0074] The size of the single crystal is 0.30 mm x 0.20 mm x 0.10 mm, belongs to monoclinic system, C2 / c space group. Figure 1 The crystal structure of the complex Zn-TC is shown in Figure 1, which proves the exact structure of the molecule. In order to clearly show the crystal structure, the nitrate anion is deleted. In the crystal structure of Zn-TC, carbazole terpyridine acts as a main ligand to coordinate with the central Zn, forming a conjugated system, which is beneficial to charge exchange and enhances the charge transfer from the central ion to the ligand. The low charge density and the NO3 - The solubility of the complex is increased.

[0075] Example 6: Test of AIE property of the complex Zn-TC

[0076] Acetonitrile (CH3CN) and ethyl acetate (EA) are selected as good and poor solvents respectively, and mixed solvents with ethyl acetate volume fraction between 0 and 98% are prepared by mixing them in different volume ratios, to test the three-photon property of Zn-TC (c = 10 -5 mol / L) in the mixed solvents.

[0077] From Figure 2 (a), it can be seen that the fluorescence intensity signal is the strongest at 1300 nm under continuous excitation wavelength of 1150-1550 nm.

[0078] From Figure 2 (b), it can be seen that the maximum three-photon absorption cross section of Zn-TC reaches 28.1 x 10 -81 cm 6 ·s 2 ·photon -2 at 1400 nm excitation wavelength.

[0079] From Figure 2 (c), it can be seen that the fluorescence intensity signal of Zn-TC is the strongest when the volume fraction of ethyl acetate is 80%.

[0080] From Figure 2 (d), it can be seen that the maximum three-photon cross section of Zn-TC reaches 19.1 x 10 -81 cm 6 ·s 2 ·photon -2 when the volume fraction of ethyl acetate is 80%.

[0081] Example 7: Test of specific recognition ability of the complex Zn-TC to OA

[0082] The concentration of Zn-TC is 10 -3mol / L Zn-TC in dimethyl sulfoxide (DMSO) solution was diluted to 10 -5 mol / L with PBS buffer (pH = 7.4), and then 200 μL of oleic acid (OA), urea, sodium chloride (NaCl), lactic acid (HL), glucose (GLu) and cholesterol (CHOL) with a concentration of 10 -2 mol / L were added respectively for fluorescence test. In addition, the stability of Zn-TC was tested by irradiating the solution with white light.

[0083] From Figure 3 (a), it can be seen that only in the solution reacting with OA, obvious fluorescence enhancement can be observed, while other components do not cause obvious fluorescence emission.

[0084] From Figure 3 (b) and Figure 3 (c), it can be seen that in DMSO and PBS buffer, Zn-TC has a good fluorescence response to OA, and the recognition effect of OA at the excitation wavelength of 1300 nm is the strongest. After calculation and processing, the three-photon cross section σ 3s of the recognition is 5.37 x 10 -81 cm 6 · s 2 · photon -2 , which is about 1.9 times of 2.43 x 10 -81 cm 6 · s 2 · photon -2 before recognition. The calculation formula is as follows:

[0085]

[0086] Wherein, R represents the standard fluorescence reference rhodamine 6G (1.0 x 10 -3 mo / L), S represents the sample to be tested, Q, n and c are the fluorescence quantum yield, the refractive index of the solvent and the concentration of the solution respectively, f is the overall fluorescence collection efficiency intensity of the fluorescence signal collected by the fiber spectrometer, σ 3R is the effective three-photon cross section of rhodamine 6G, and the effective three-photon absorption cross section of rhodamine 6G is 6 x 10 -81 cm 6 · s 2 · photon -2 .

[0087] From Figure 3 (d), it can be seen that Zn-TC has good light stability and strong anti-photobleaching ability, and no obvious light decay appears after 30 min of white light irradiation.

[0088] Example 8: LFPs fluorescence imaging of complex Zn-TC on different substrates

[0089] The forehead was lightly touched with fingers to leave latent fingerprints on the surfaces of tin paper, glass, plastic and optical disc, and then the tin paper, glass, plastic and optical disc were immersed in the aqueous solution of Zn-TC (c = 10 -3 mol / L) respectively, and fluorescence imaging was performed after 2 min.

[0090] It can be seen from Figure 4 that the tin paper, glass, plastic and optical disc treated by Zn-TC all showed high-definition and high-contrast LFP images. The fluctuation amplitude of the gray value curve was large, and the difference was obvious. Zn-TC showed high contrast under the substrates of tin paper, glass, plastic and optical disc.

[0091] Example 9: LFPs confocal imaging of complex Zn-TC on glass

[0092] The forehead was lightly touched with fingers to leave latent fingerprints on the surface of glass, and then the glass was immersed in the aqueous solution of Zn-TC (c = 10 -3 mol / L), and the fine features of the three-level fingerprints were captured and recorded by the two-photon channel of the confocal microscope after 2 min.

[0093] It can be seen from Figure 5 (a) that there are different sizes of lipid deposits, which are the micro-units that constitute LFPs.

[0094] It can be seen from Figure 5 (b) that the fluorescence intensity of LFPs excited by two-photon light source is higher than that of single-photon.

[0095] It can be seen from Figure 5 (c) that the boundary of LFPs excited by single-photon light source is blurred, while LFPs excited by two-photon light source has lower background interference and higher imaging contrast, and the widths of different ridges can be distinguished under the microscope.

[0096] It can be seen from Figure 5 (d) that the fluorescence intensity of LFPs excited by single-photon and two-photon has no obvious change within 15 min, and Zn-TC has good fluorescence response ability.

[0097] The above shows and describes the basic principles and main features of the present application and the advantages of the present application. It should be understood by those skilled in the art that the present application is not limited by the above examples, and the above examples and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A fluorescent probe, referred to as Zn-TC, characterized in that: The structural formula of the Zn-TC is shown below:

2. The method for preparing the fluorescent probe according to claim 1, wherein The preparation method comprises the following steps: (1) Carbazole and bromohexane undergo a substitution reaction to obtain compound A; (2) Compound A undergoes Vilsmeier-Haack reaction with DMF and POCl3 to obtain compound B; (3) Compound B undergoes an alkylation reaction with 2-acetylpyridine to obtain compound C; (4) Compound C undergoes a ring-closing reaction with 1-[2-oxo-2-(2-pyridyl)ethyl]pyridinium iodide to obtain compound TC; (5) Compound TC reacts with zinc nitrate to obtain a complex Zn-TC; The synthetic route is as follows:

3. The preparation method according to claim 2, wherein: The molar ratio of carbazole to bromhexane is 1:(1-1.5).

4. The preparation method according to claim 2, wherein: The substitution reaction uses NaH as a catalyst.

5. The preparation method according to claim 2, wherein: The molar ratio of the compound A to DMF and POCl3 is 1:(2-4):(3-6).

6. The preparation method according to claim 2, wherein: The molar ratio of the compound B to 2-acetylpyridine is 1:(1.1-1.2).

7. The preparation method according to claim 2, characterized in that: The alkylation reaction is carried out under alkaline conditions.

8. The preparation method according to claim 2, wherein: The molar ratio of the compound C to 1-[2-oxo-2-(2-pyridyl)ethyl]pyridinium iodide is 1:(1-1.1).

9. The preparation method according to claim 2, wherein: The molar ratio of the zinc nitrate to the compound TC is 1:(2-3).

10. Use of the fluorescent probe according to claim 1 or the fluorescent probe prepared by the preparation method according to any one of claims 2 to 9 in visual recognition of latent fingerprints.

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