A coumarin dye and fingerprint powder preparation method for latent fingerprint development

Abstract

The invention provides a novel color-changing fluorescent dye that can respond to oils and fats. The dye is synthesized by using 2,4-dihydroxybenzaldehyde, 4-hydroxy-6-methyl-2-pyrone and 3-bromopropyne as raw materials. The dye has a structure different from that of existing fluorescent dyes and is a novel oil-responsive fluorescent dye. The invention adopts a simple preparation method to obtain a product with high stability and low toxicity in high yield. The obtained compound is applied to fingerprint development, and can respond to latent fingerprints to cause color change. The fluorescent fingerprint powder changes from the original orange fluorescent color to the yellow fluorescent color after response. Therefore, the novel oil-responsive fluorescent dye has high anti-interference and high biocompatibility, can develop images with high resolution and high contrast in real time, and can be applied to various materials and complex criminal investigation environments.

Description

Technical Field

[0001] The invention belongs to the technical field of color-changing fluorescent dyes, and in particular relates to a responsive color-changing fluorescent dye and a preparation method and application thereof. Background Art

[0002] Current fingerprint development technology can be divided into physical development method and chemical development method. The physical development method is mainly metal deposition or powder spraying, which is achieved through electrostatic adsorption between fluorescent powder or magnetic powder and biological residues in fingerprints such as amino acids, biological oils or other chemicals. This method is easy to use and has no development delay, but the magnetic powder traditionally used for fingerprint development is mostly micron-level, so the dispersion is poor and it is easy to form large agglomerates. Chemical development methods include ninhydrin method, cyanoacrylate fuming method, silver nitrate method and other methods, which mainly rely on the reaction of the chemical substances used with the organic matter remaining in the fingerprint. This type of method has stable development, but there are defects such as development delay, high toxicity and low contrast. Therefore, both the above-mentioned physical development method and chemical development have problems that need to be solved.

[0003] Fluorescent fingerprint powder development stands out among many methods and has become a very popular latent fingerprint development method in criminal investigation. However, the fluorescent fingerprint powder currently available on the market cannot change color, and all places where the fingerprint powder adheres will show fluorescence. Therefore, it is difficult to achieve high-resolution development of fingerprints left on static electricity or uneven substrates, which cannot meet the requirements of criminal investigation for fingerprint extraction. Summary of the invention

[0004] The present application example provides a new color-changing fluorescent dye that can respond to oil and fat, and its preparation method and application. Its structure is different from that of existing fluorescent dyes. It is a new type of oil-responsive fluorescent dye. The present invention uses a simple preparation method to obtain a product with high stability and low toxicity in high yield. The obtained compound is applied to fingerprint development, which can respond to latent fingerprints and cause color change. The fluorescent fingerprint powder changes from the original orange fluorescent color to the yellow fluorescent color after response. Therefore, the new oil-responsive fluorescent dye has high anti-interference and high biocompatibility, can develop images with high resolution, high contrast, strong anti-drying, and real-time development, and can be applied to a variety of materials and complex criminal investigation environments.

[0005] The technical solution of the present invention is:

[0006] In a first aspect, the present invention provides a lipid-responsive color-changing fluorescent dye having a structure of Formula I:

[0007]

[0008] In a second aspect, the present invention also provides a method for preparing the novel responsive color-changing fluorescent dye, which specifically comprises the following steps:

[0009] Step 1: 2,4-dihydroxybenzaldehyde and 4-hydroxy-6-methyl-2-pyrone are added to a flask in a certain molar ratio, and then ultrapure water is added and magnetic stirring is turned on to fully dissolve the raw materials. L-proline is added as a catalyst at a constant temperature, and refluxed and stirred for 2 hours. As the reaction proceeds, yellow granular substances can be observed to precipitate from the reaction solution, and yellow intermediate powder of the reaction is obtained by suction filtration;

[0010] Step 2: Add acetone to dissolve the intermediate prepared in step 1, then add anhydrous potassium carbonate and 3-bromopropyne and stir at room temperature for 4 hours, add water, extract with dichloromethane in small amounts several times, evaporate to dryness, and finally obtain the target compound (yellow-green solid).

[0011] The reaction process is shown in Formula II:

[0012]

[0013]

[0014] Specifically, the molar ratio of aldehyde, ketone and proline is 10:15:1; the molar ratio of intermediate, anhydrous potassium carbonate and 3-bromopropyne is 1:2:1.

[0015] In a second aspect, the present invention also provides an application of a novel oil-responsive color-changing fluorescent dye, which is prepared into fluorescent fingerprint powder and applied to latent fingerprint recognition.

[0016] Specifically, the preparation of fluorescent fingerprint powder includes the following steps:

[0017] A certain amount of responsive color-changing fluorescent dye is weighed and dissolved in an organic solvent, montmorillonite is added as a carrier, the fluorescent dye and the carrier are evenly mixed in the organic solvent using ultrasonic technology, the solvent is evaporated by a rotary evaporator, and the desired fluorescent fingerprint powder is obtained after grinding and drying.

[0018] Specifically, in the preparation of the fluorescent fingerprint powder, the mass ratio of the responsive color-changing fluorescent dye to the montmorillonite is 20 mg:3 g.

[0019] Specifically, the carrier is montmorillonite.

[0020] Specifically, the application in latent fingerprint recognition includes the following steps:

[0021] Step 1: Dip the prepared new fluorescent fingerprint powder with a clean fluff stick and sprinkle it on the substrate where the latent fingerprint is located, so that the fingerprint powder falls evenly on the surface of the substrate. The fingerprint powder will adhere to the fingerprint and appear orange, and then use a dust blower to blow off the fingerprint outside the fingerprint area.

[0022] Step 2: Irradiate under ultraviolet light, and the new fluorescent fingerprint powder that clearly presents the fingerprint lines responds to yellow fluorescence, thereby obtaining a responsive color-changing fluorescent imaging of the latent fingerprint. Specifically, the ultraviolet light source irradiation is performed under the condition of a wavelength of 350 to 430 nm.

[0023] Specifically, the substrate is at least one of tin foil, glass, marble, and CD.

[0024] Since hydroxysalicylic acid is used as the initial raw material, it first reacts with 4-hydroxy-6-methyl-2-pyrone to obtain a hydroxy-substituted coumarin-β-diketone structure, and then the electron-donating group on the carbon 7 of coumarin is converted from a hydroxyl group to an alkynyloxy group by using a substitution reaction between a halogen alkyne and a phenolic hydroxyl group, thereby obtaining a new dye. After it is prepared as a fluorescent fingerprint powder, it has a photofluorescent color change property. The color change response principle is that the prepared fluorescent dye interacts with biological oils such as oleic acid and cholesterol in fingerprints, causing color change, that is, the orange color of the fluorescent dye changes to yellow. The chemical molecular crystal structure of the fluorescent dye is simple, with good photostability, strong photosensitivity, high fluorescence efficiency, good biocompatibility and low toxicity. Due to its good fat solubility, it can combine with trace amounts of oils and fats remaining in fingerprints, and cause fluorescence color change by changing the dissolving environment, thereby realizing fingerprint development and improving the efficiency of fingerprint identification and the effectiveness of the results.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) The responsive color-changing fluorescent dye prepared by the present invention has a structure different from that of existing fluorescent dyes and is a new type of responsive fluorescent dye. The raw material cost required for preparation is low, the preparation process is simple, and the target product can be obtained in only two steps with high yield. The produced dye has good stability and low biological toxicity. At the same time, the fluorescent dye has color-changing properties and can be applied to latent fingerprint recognition.

[0027] (2) The fluorescent fingerprint powder prepared by the present invention is used in latent fingerprint display. After responding to the fingerprint, the fluorescent color changes. It combines the advantages of the existing physical development method and the chemical development method, has strong anti-interference, high resolution and contrast, high fingerprint display accuracy, and can be developed in real time without damaging the DNA information in the fingerprint;

[0028] (3) The fluorescent fingerprint powder prepared by the present invention is not limited by the substrate material in latent fingerprint recognition. It has excellent latent fingerprint development effect in areas where fingerprints remain on various common substrates in daily life, such as tin foil, glass, marble, and CDs, thereby reducing the applicability limitations of fingerprint powder and reducing the interference caused by the signal of the fluorescent fingerprint powder itself. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly introduce the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be briefly described below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0030] Figure 1 This is the hydrogen nuclear magnetic resonance spectrum of the fluorescent fingerprint powder prepared in Example 1;

[0031] Figure 2 The carbon NMR spectrum of the fluorescent fingerprint powder prepared in Example 1;

[0032] Figure 3 This is a high-resolution mass spectrum of the fluorescent fingerprint powder prepared in Example 1;

[0033] Figure 4a and Figure 4b The fluorescent fingerprint powder prepared in Example 1 interacts with the latent fingerprint on the optical disc and then develops the fingerprint under sunlight and ultraviolet light;

[0034] Figure 5a and Figure 5b The fluorescent fingerprint powder prepared in Example 1 and the latent fingerprint on the optical disc are imaged and compared with the details after being exposed to ultraviolet light;

[0035] Figure 6a and Figure 6b The fluorescent fingerprint powder prepared in Example 1 reacts with the latent fingerprint on the glass and then the fingerprint is developed and imaged under sunlight and ultraviolet light;

[0036] Figure 7a and Figure 7b The fluorescent fingerprint powder prepared in Example 1 reacts with the latent fingerprint on the tin foil and then the fingerprint is developed and imaged under sunlight and ultraviolet light;

[0037] Figure 8a and Figure 8b The fluorescent fingerprint powder prepared in Example 1 interacts with latent fingerprints on marble and then develops fingerprints under sunlight and ultraviolet light; DETAILED DESCRIPTION

[0038] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present invention.

[0039] Example 1

[0040] Preparation of lipid-responsive color-changing fluorescent dye:

[0041] Take a dry 100mL round-bottom flask, add 10mmol 2,4-dihydroxybenzaldehyde and 15mmo 4-hydroxy-6-methyl-2-pyrone, then add 30mL ultrapure water and turn on magnetic stirring to fully dissolve the raw materials, add 1mmol L-proline as a catalyst at a constant temperature of 85℃, and reflux and stir for 2h. As the reaction proceeds, yellow granular material can be observed to precipitate from the reaction solution. The reaction endpoint is determined by TLC detection. After the reaction is completed, the flask is naturally cooled to room temperature, and then filtered to obtain 2.13g of yellow intermediate powder.

[0042] Take another 50mL single-mouth round-bottom flask, add 4.1mmol of the intermediate and 10mL of acetone to dissolve it, then add 8mmol of anhydrous carbonic acid and 4.5mmol of 3-bromopropyne and stir at room temperature for 4h. It is observed that yellow-green insoluble matter appears in the solution. After the reaction is completed by TLC detection, 10mL of water is added, and it is extracted with dichloromethane in small amounts and evaporated to dryness, and finally 1.06g of yellow-green solid is obtained as the target compound, with a yield of 90.6%.

[0043] The structure of the lipid-responsive color-changing fluorescent dye is shown in Formula Ia:

[0044]

[0045] MRI test results:

[0046] Figure 1 This is the hydrogen nuclear magnetic resonance spectrum of the oil-responsive color-changing fluorescent dye prepared in Example 1.

[0047] The NMR information is: 1 H NMR (500MHz, CDCl3) δ = 15.89 (s, 1H), 8.54 (s, 1H), 7.50 (d, J = 8.8Hz, 1H), 6.92 (s, 1H), 6.90 (s, 2H), 4.73 (s, 2H), 2.53 (s, 1H), 2.18 (s, 3H).13C NMR(125MHz, CDCl3)δ=193.56,167.94,157.27,153.04,151.15,140.22,125.5 6,112.23,108.87,107.72,96.26,95.81,51.14,24.44,22.00.HRMS:m / z[M+Na] + Calculate C 16 H 12 NaO5 +, theoretical value: 307.0577, actual value: 307.0587.

[0048] Figure 2 This is the carbon nuclear magnetic resonance spectrum of the oil-responsive color-changing fluorescent dye prepared in Example 1.

[0049] Figure 3 This is a high-resolution mass spectrum of the oil-responsive color-changing fluorescent dye prepared in Example 1.

[0050] The results show that the compound prepared in this example has the structure shown in Formula Ia.

[0051] Example 2

[0052] The fluorescent fingerprint powder prepared in Example 1 was applied to the latent fingerprint on the surface of the optical disc to reveal it.

[0053] Take a clean fluff stick and dip it in fingerprint powder. Gently shake the fluff stick above the surface of the material with fingerprints printed on it to make the fingerprint powder fall evenly on the surface of the material. Then use a dust blower to blow away the fingerprint powder outside the fingerprint area. Take a photo under sunlight. Figure 4a As shown, the image was taken under UV 365nm. Figure 4b shown.

[0054] After the fluorescent fingerprint is developed on the surface of the optical disc, it is photographed with a camera to obtain a clear fingerprint image. The fingerprint image can be used to obtain a variety of characteristic information contained in the fingerprint, such as Figure 5a and Figure 5b , including level 2 and level 3 features. Figure 5b The red marks are the recognizable secondary nodes such as the bifurcation point (position 1), the end point (position 2), the isolated point (position 3), and the short lines (positions 6 and 9), as well as the tertiary node sweat gland pores (positions 4, 5, 7, and 8). Considering that the highest recognition level of the current fingerprint recognition application scenario is the recognition of the third-level node, the fingerprint powder that can achieve the third-level recognition can already meet the conditions for realizing latent fingerprint applications in specific scenarios, that is, the fingerprint powder based on the montmorillonite carrier tested in this section can meet the use requirements in government, law enforcement and other fields.

[0055] Example 3

[0056] The fluorescent fingerprint powder prepared in Example 1 was applied to the latent fingerprint on the glass surface. A clean fluff stick was dipped in the fingerprint powder, and the fluff stick was gently shaken above the surface of the material with the fingerprint printed in advance to make the fingerprint powder fall evenly on the surface of the material, and then the fingerprint powder outside the fingerprint area was blown off with a dust blower. A photo was taken under sunlight. Figure 6a As shown, the image was taken under UV 365nm. Figure 6b shown.

[0057] After the fluorescent fingerprint is developed on the glass surface, it is photographed with a camera to obtain a clear fingerprint image.

[0058] Example 4

[0059] The fluorescent fingerprint powder prepared in Example 1 was applied to the latent fingerprint on the tin foil surface. A clean fluff stick was dipped in the fingerprint powder, and the fluff stick was gently shaken above the surface of the material with the fingerprint printed in advance to make the fingerprint powder fall evenly on the surface of the material, and then the fingerprint powder outside the fingerprint area was blown off with a dust blower. A photo was taken under sunlight. Figure 7a As shown, the image was taken under UV 365nm. Figure 7b shown.

[0060] After the fluorescent fingerprint is developed on the tin foil surface, it is photographed with a camera to obtain a clear fingerprint image.

[0061] Example 5

[0062] The fluorescent fingerprint powder prepared in Example 1 was applied to the latent fingerprint on the marble surface. A clean fluff stick was dipped in the fingerprint powder, and the fluff stick was gently shaken above the surface of the material with the fingerprint printed in advance to make the fingerprint powder fall evenly on the surface of the material, and then the fingerprint powder outside the fingerprint area was blown off with a dust blower. A photo was taken under sunlight. Figure 8a As shown, the image was taken under UV 365nm. Figure 8b shown.

[0063] After the fluorescent fingerprint is developed on the marble surface, it is photographed with a camera to obtain a clear fingerprint image.

[0064] The embodiments described above are only preferred embodiments of the present invention, which are illustrative but not restrictive of the present invention. It is understood by those skilled in the art that many changes and even equivalent modifications may be made to the present invention within the scope defined by the patent requirements of the present invention, but all of them will fall within the protection scope of the present invention.

Claims

1. A fat-responsive color-changing fluorescent dye, characterized in that: Having the structure of Formula I: 。 2. A method for preparing the oil-responsive color-changing fluorescent dye according to claim 1, characterized in that: The specific steps include: Step 1, 4-hydroxy-6-methyl-2-pyrone and 2,4-dihydroxybenzaldehyde are added to a flask in a certain molar ratio, and then ultrapure water is added and magnetic stirring is turned on to fully dissolve the raw materials, L-proline is added as a catalyst at a constant temperature, refluxed and stirred for 2 hours, yellow granular material is precipitated, and the intermediate is filtered to obtain a yellow powder; Step 2: Add acetone to dissolve the yellow powder obtained in step 1, then add anhydrous potassium carbonate and 3-bromopropyne and stir at room temperature for 4 hours, add water, extract with dichloromethane in small amounts several times, evaporate to dryness, and finally obtain the target compound as a yellow-green solid.

3. The method for preparing the oil-responsive color-changing fluorescent dye according to claim 2, characterized in that: The molar ratio of 2,4-dihydroxybenzaldehyde, 4-hydroxy-6-methyl-2-pyrone and L-proline is 10:15:

1.

4. The method for preparing the oil-responsive color-changing fluorescent dye according to claim 2, characterized in that: The molar ratio of the intermediate, anhydrous potassium carbonate and 3-bromopropyne is 1:2:

1.

5. An application of the oil-responsive color-changing fluorescent dye according to claim 1, further preparing it into a responsive fluorescent fingerprint powder, and applying it to fingerprint development technology.

6. The use of the oil-responsive color-changing fluorescent dye according to claim 5, characterized in that: The preparation of fluorescent fingerprint powder specifically includes the following steps: A certain amount of responsive color-changing fluorescent dye is weighed and dissolved in an organic solvent, and montmorillonite is added as a carrier. The mass ratio of montmorillonite to fluorescent dye is 20:

3. Ultrasonic technology is used to evenly mix the fluorescent dye and the carrier in the organic solvent, and the solvent is evaporated by a rotary evaporator. The desired fluorescent fingerprint powder is then obtained by grinding and drying.

7. The use of the responsive color-changing fluorescent dye according to claim 6, characterized in that: Applied to latent fingerprint development, specifically including the following steps: Step 1: Sprinkle the prepared new fluorescent fingerprint powder on the substrate where the latent fingerprint is located, so that the fingerprint powder falls evenly on the surface of the substrate. The fingerprint powder will adhere to the fingerprint area and appear orange, and then blow off the fingerprint powder outside the fingerprint area; Step 2: Irradiate under ultraviolet light, and the new fluorescent fingerprint powder that clearly presents the fingerprint lines responds with yellow fluorescence, thereby obtaining a responsive color-changing fluorescent imaging of the latent fingerprint.

8. The use of the responsive color-changing fluorescent dye according to claim 7, characterized in that: The ultraviolet light source irradiation was carried out under the condition of light with a wavelength of 365 nm.

9. The use of the responsive color-changing fluorescent dye according to claim 8, characterized in that: The substrate is at least one of tin foil, marble and glass.

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