A fluorescent fingerprint developer based on a conjugated polymer containing catechol side groups and its application

Abstract

The invention discloses a fluorescent fingerprint developer and application based on a conjugated polymer containing a catechol side group. A diacetylene monomer, a dibromoarene monomer containing a catechol group and a phenyl group are synthesized by a Sonogashira coupling reaction to synthesize a conjugated polymer precursor with a protected catechol side group, and then the protecting group is removed by tetrabutylammonium fluoride to obtain a fluorescent conjugated polymer containing a catechol side group, which is dissolved in N,N-dimethylformamide to prepare a latent blood fingerprint developer. The fluorescent fingerprint developer provided by the present invention can be a non-woven fabric as a substrate, soaked in a fingerprint developer, and a latent blood fingerprint developer cotton sheet is obtained, and the cotton sheet is covered on an object loaded with a latent blood fingerprint, and after being peeled off, a bright fingerprint pattern can be observed under ultraviolet light of 365 nm. The latent blood fingerprint developer provided by the present invention has bright fluorescence, can clearly show the three-level features of fingerprints, and the cotton sheet can be reused.

Description

Technical Field

[0001] The invention relates to a fingerprint visualization technology, in particular to a fluorescent fingerprint developer based on a conjugated polymer containing catechol side groups, and is applied to fingerprint visualization of latent blood fingerprints, belonging to the technical field of polymer fluorescent material application. Background Art

[0002] Fingerprints are used as a method of identity recognition and identification in various scenarios in life, such as major examinations, entry and exit management, and signing important documents.

[0003] Some reagents have been developed for latent blood fingerprint visualization and have been commercialized, such as amino-reactive compounds ninhydrin (NH), 1,8-diazafluoren-9-one (DFO), protein dyes amino black 10B, Coomassie blue and heme-reactive compounds tetramethylbenzidine (TMB). However, most of these reagents are non-fluorescent, have poor adhesion, require complex operations and are toxic. For example, from the perspective of the working principle, they do not fluoresce by themselves. NH and DFO react with proteins in fingerprints to develop color, which will be washed away if exposed to water or moisture for a long time, and additional luminescent dyes need to be sprayed to obtain better visualization. TMB is no longer used as a fingerprint visualization reagent internationally due to its high toxicity and serious environmental pollution (see the literature: Fingerprint development techniques: theory and application. 2018). Therefore, it is of great significance to develop a simple, low-toxic, fluorescent and good adhesion latent fingerprint visualization reagent.

[0004] Fluorescent reagents can enhance the contrast between the friction ridges of fingerprints and the object, and have advantages in revealing latent blood fingerprints. Among them, conjugated polymers have the advantages of simple synthesis, low toxicity, relatively low cost, adjustable molecular structure and fluorescence emission, strong resistance to photobleaching, and high fluorescence quantum yield, making them ideal materials for fingerprint visualization applications. Catechol groups have multiple interactions with fingerprint components and are widely used in adhesives and biomaterials. Unlike ordinary adhesives, molecules containing catechol groups can overcome hydration films and produce excellent underwater adhesion in humid environments. Therefore, they can be used in industrial scenarios and biological scenarios in the presence of water and human body fluids (see literature: Progress in polymer science, 2001, 26, 535; Progress in polymer science, 2021, 116,101388), but there are no reports on their application in the field of trace inspection. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a fluorescent fingerprint developer containing a conjugated polymer containing catechol side groups, which has stable side group chemical properties, can selectively adhere to and visualize latent blood fingerprints, and obtains a clear and bright fingerprint pattern image, and its application.

[0006] The technical solution to realize the present invention is to provide a fluorescent fingerprint developer based on a conjugated polymer containing a catechol side group, and the preparation method of the fluorescent fingerprint developer comprises the following steps:

[0007] (1) Calculated by molar mass, 1 part of a carboxylic acid compound, denoted as compound C1, 1.5-2.8 parts of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, 0.5-0.8 parts of 4-dimethylaminopyridine and 880-900 parts of dichloromethane are mixed, stirred in an ice-water bath for 0.5-1 h, 1.5-1.8 parts of phenylethylamine are added, stirring is continued for 1.5-2 h, and then heated to reflux for 12-24 h. After the reaction is completed, the mixture is placed at room temperature, extracted, rotary evaporated, separated and purified by column chromatography and dried to obtain a phenyl-containing dibromoaromatic monomer, denoted as M3;

[0008] The structural formula of the compound C1 is:

[0009] ;

[0010] The structural formula of the monomer M3 is:

[0011] ;

[0012] (2) According to the amount of substance, 1 part of diacetylene monomer M1, 0.2 parts of dibromoarene monomer M2 containing catechol group, 0.8 parts of monomer M3 prepared in step (1), 0.15 parts of (PPh3)4Pd, 0.03 parts of CuI and 640 parts of toluene are mixed, and stirred at a temperature of 45 to 50°C until all the monomers are dissolved, and then 1600 parts of diisopropylamine are added, and the mixture is reacted at a temperature of 75 to 80°C; after the reaction is completed, a conjugated polymer precursor is obtained by filtering, recrystallizing, centrifuging and drying, and recorded as pre-P-cat 0.2 ;

[0013] The structural formula of the monomer M1 is:

[0014] ;

[0015] The structural formula of the monomer M2 is:

[0016] ;

[0017] The precursor pre-P-cat 0.2 The structural formula is:

[0018]

[0019] Where n is the degree of polymerization, n=8~21;

[0020] (3) According to the amount of the substance, 1 part of the conjugated polymer precursor pre-P-cat prepared in step (2) 0.2 and 3500-3600 parts of tetrahydrofuran, and slowly dropwise add a mixed solution of 1.25-1.5 parts of tetrabutylammonium fluoride and 1100-1300 parts of tetrahydrofuran in an ice water bath, and react at room temperature; after the reaction, filter, recrystallize, centrifuge, and dry to obtain a fluorescent conjugated polymer containing a catechol side group, recorded as PPETE-cat 0.2 ;

[0021] The fluorescent conjugated polymer PPETE-cat containing catechol side groups 0.2 The structural formula is:

[0022] ,

[0023] Where n is the degree of polymerization, n=8~21;

[0024] (4) Using N,N-dimethylformamide as solvent, the PPETE-cat prepared in step (3) 0.2 The latent blood fingerprint developer of the fluorescent conjugated polymer solution containing catechol side groups is obtained by dissolving the latent blood fingerprint developer in a solvent at a molar ratio of 1:12500 to 1:25000.

[0025] The invention discloses an application of a fluorescent fingerprint developer based on a conjugated polymer containing a catechol side group, and prepares the fluorescent fingerprint developer into a latent fingerprint developer cotton sheet, which is applied to the development of latent blood fingerprints.

[0026] The process for developing latent blood fingerprints includes the following steps:

[0027] (1) Fixation of fresh latent blood fingerprints: Place the object loaded with fresh latent blood fingerprints in a cool and dry place for more than 12 hours;

[0028] (2) Flatly cover the latent fingerprint display cotton sheet loaded with fluorescent fingerprint developer on the object loaded with latent blood fingerprint, press lightly to make the cotton sheet fully contact with the object, and let it stand for 2 to 5 minutes; the object loaded with latent blood fingerprint is a fresh latent blood fingerprint or an old latent blood fingerprint processed in step (1);

[0029] (3) Peel the cotton sheet off the object smoothly, dry it, and then photograph the latent blood fingerprint revealed by the developing cotton sheet under light conditions of 350-400 nm.

[0030] The fluorescent conjugated polymer solution containing catechol side groups provided by the present invention is used as a developer. Since there are multiple non-covalent interactions between the catechol side groups and fingerprint components, the polymer and the latent blood fingerprint components produce adhesion. Therefore, it can be used to visualize latent blood fingerprints, and the visualization effect is bright and the details are clear.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. The catechol side groups of the fluorescent conjugated polymer containing catechol side groups prepared by the present invention have multiple non-covalent interactions with latent blood fingerprint components, such as hydrogen bonds, π-π electronic effects, cation-π interactions, and coordination with metal cations. Therefore, the catechol side groups can provide adhesion between the polymer and the latent blood fingerprint components, and show bright fingerprint lines. The fluorescent high molecular polymer interacts with proteins, amino acids and sodium chloride in latent blood fingerprints, and has an obvious selective display effect on the above latent blood fingerprint components.

[0033] 2. The phenyl side groups of the fluorescent conjugated polymer containing catechol side groups prepared by the present invention are chemically stable and are not prone to chemical reactions in acidic or alkaline environments.

[0034] 3. The catechol side group content of the fluorescent conjugated polymer containing catechol side groups provided by the present invention is 0.2, and the phenyl side group content is 0.8. The polymer under this ratio can weaken the adhesion between the polymer and the object, selectively adhere to the friction ridge, and achieve the purpose of showing fingerprint lines and enhancing contrast.

[0035] 4. Compared with the existing latent blood fingerprint development technology, the concentration of the fluorescent conjugated polymer solution containing catechol side groups provided by the present invention is very low, which can reduce the amount of polymer used, so the cost is relatively lower, and waste and environmental pollution can be reduced.

[0036] 5. The fluorescent conjugated polymer containing catechol side groups provided by the present invention has low toxicity, and the DMF solvent used has no irritating odor and is not easy to volatilize, thereby reducing the harm to the health of users caused by the volatilization of toxic solvents and irritating odors, and greatly reducing environmental pollution.

[0037] 6. The cotton sheet method provided by the present invention is convenient and simple to operate, does not require any pre-treatment or post-treatment, and can be used repeatedly. For example, a cotton sheet (2cm×3cm) loaded with 200 μL of fluorescent conjugated polymer containing catechol side groups can effectively visualize at least 8 latent blood fingerprints.

[0038] 7. Compared with the existing latent blood fingerprint display technology, the fluorescent conjugated polymer solution containing catechol side groups and the cotton piece display method provided by the present invention can effectively display the three-level features of fingerprints, especially the sweat pore details of fingerprints are clear and the contours of friction ridges are clear. The polymer solution has good selectivity for latent blood fingerprint components and can greatly enhance the contrast between friction ridges and objects. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is recorded as pre-P-cat in Example 1 of the present invention 0.2 The precursor polymer is denoted as PPETE-cat 0.2 NMR spectrum of fluorescent conjugated polymers containing catechol side groups;

[0040] Figure 2 It is recorded as pre-P-cat in Example 1 of the present invention 0.2 The precursor polymer is denoted as PPETE-cat 0.2 Infrared spectrum of fluorescent conjugated polymers containing catechol side groups;

[0041] Figure 3 It is the fluorescent conjugated polymer PPETE-cat containing catechol side groups in Example 1 of the present invention 0.2 Photophysical properties characterization diagram;

[0042] Figure 4 These are effect diagrams of the latent blood fingerprint on an aluminum foil object before (a) and after (b) the latent blood fingerprint on the aluminum foil object is revealed by the revealing cotton sheet provided in Example 3 of the present invention;

[0043] Figure 5 These are photographs of latent blood fingerprints on an aluminum foil object deposited under the same conditions that are continuously developed by the same developing cotton sheet for the seventh time (Figure a) and the eighth time (Figure b) provided in Example 3 of the present invention.

[0044] Figure 6 These are enlarged digital photos of the same developing cotton sheet provided in Example 3 of the present invention after developing the latent blood fingerprint on the aluminum foil object for the first time (Figure a) and the seventh time (Figure b);

[0045] Figure 7 This is a diagram showing the effect of the revealing cotton sheet provided in Example 3 of the present invention on revealing different components in latent blood fingerprints. Implementation

[0046] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments. Example 1

[0047] This embodiment provides a conjugated polymer based on catechol side groups (denoted as PPETE-cat0.2 ) of fluorescent fingerprint developer.

[0048] The preparation method comprises the following steps:

[0049] 1. Preparation of a carboxylic acid compound designated as compound C1

[0050] In this example, the synthesis of the carboxylic acid compound referred to as compound C1 can be found in the literature (Journal of colloid and interface science, 2018, 528, 200-207). The specific method is: under an argon atmosphere, adipic acid (15 g, 0.1 mol), potassium carbonate (10 g, 72.35 mmol) and N,N-dimethylformamide (120 mL) are added to a 250 mL round-bottom flask, 1,4-dibromo-3-bromomethylthiophene (5.54 g, 16.5 mmol) is dissolved in an appropriate amount of N,N-dimethylformamide and added to the system, and heated to reflux at 45°C for 12 h. After the reaction is completed, the filtrate is filtered and collected, and an appropriate amount of deionized water and dichloromethane are added to extract the liquid to remove N,N-dimethylformamide. The organic phase is collected, dried over anhydrous sodium sulfate, and then rotary evaporated to obtain a crude product. The crude product is separated and purified by silica gel column chromatography, and the developing solvent is petroleum ether / ethyl acetate (V 石油醚 : V 乙酸乙酯 =3:1), to obtain a yellow viscous compound C1 (3.84 g, yield: 58.1%).

[0051] The structural formula of compound C1 is

[0052] .

[0053] 2. Preparation of a phenyl-containing dibromoarene monomer designated as monomer M3

[0054] Under argon atmosphere, compound C1 (0.7 g, 1.75 mmol) and dichloromethane (100 mL) were added to a 250 mL round-bottom flask. Then 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (0.5 g, 2.60 mmol) and 4-dimethylaminopyridine (0.1 g, 0.82 mmol) were added and stirred in an ice-water bath for 0.5 h. Phenylethylamine (0.33 g, 2.70 mmol) was added and continued to stir in an ice bath for 2 h, and then heated to reflux for 24 h. After the reaction was completed, the mixture was washed three times with deionized water and saturated sodium chloride solution, dried over anhydrous sodium sulfate, and then rotary evaporated to remove the solvent to obtain a crude product. The crude product was separated and purified by silica gel column chromatography with petroleum ether / ethyl acetate (V 石油醚 : V 乙酸乙酯= 5:1), to give a white powder M3 (0.67 g, yield: 76%). 1 H NMR (400 MHz, CDCl3): δ 7.32-7.18 (m, 5H), 6.96 (s, 1H), 5.47 (s, 1H), 4.98 (s, 2H), 3.52 (m, 2H), 2.82 (t, 2H), 2.35 (m, 2H), 2.14(m,2H), 1.64 (m, 4H). Elemental Anal. Calcd for C 19 H 21 N1O3S1Br2(%): C, 45.35; H,4.21; N, 2.78; Found: C, 45.40; H, 4.32; N, 2.92. Elemental Anal. Calcd forC 19 H 21 N1O3S1Br2(%): C, 45.35; H, 4.21; N, 2.78; Found: C, 45.40; H, 4.32; N, 2.92. .

[0055] The structural formula of monomer M3 is:

[0056] .

[0057] 3. Preparation of a diacetylene monomer designated as monomer M1

[0058] The synthesis method of monomer M1 can be found in the literature (ACS Applied Materials & Interfaces, 2014, 6, 5041-5049). The specific method in this embodiment is: using hydroquinone as a raw material, reacting with liquid bromine in an ice-water bath to generate 2,5-dibromohydroquinone; introducing a long alkane side group through a nucleophilic substitution reaction and an esterification reaction; and then generating a diacetylene monomer M1 through a coupling reaction.

[0059] The structural formula of monomer M1 is:

[0060] .

[0061] 4. Preparation of raw materials recorded as monomer M2

[0062] In this example, the synthesis of the raw material recorded as monomer M2 can be found in the literature (ACS Applied Polymer Materials, 2021, 3, 4543-4553). The specific method is: under an argon atmosphere, add compound C1 (0.7 g, 1.75 mmol) and dichloromethane (100 mL) provided in Example 1 to a 250 mL round-bottom flask. Then add 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (0.5 g, 2.60 mmol) and 4-dimethylaminopyridine (0.1 g, 0.82 mmol) and stir in an ice-water bath for 0.5 h. Add dopamine hydrochloride (1.03 g, 2.7 mmol) with protected phenolic hydroxyl groups, continue stirring under ice bath conditions for 2 h, and then heat to reflux for 24 h. After the reaction is completed, wash with deionized water and saturated sodium chloride solution three times, respectively, dry over anhydrous sodium sulfate, and then rotary evaporate to remove the solvent to obtain a crude product. The crude product was separated and purified by silica gel column chromatography with petroleum ether / ethyl acetate (v:v = 2:1) as the developing solvent to obtain monomer M2: yellow viscous liquid (1.06 g, yield: 82.6%).

[0063] The structural formula of monomer M2 is:

[0064] .

[0065] 5. Preparation of pre-P-cat 0.2 Precursor polymer

[0066] In the precursor polymer prepared in this embodiment, the content of the M2 monomer unit is 0.2. The specific method is: under an argon atmosphere, monomer M1 (0.15 g, 0.25 mmol), monomer M2 (0.039 g, 0.05 mmol), monomer M3 (0.10 g, 0.20mmol), tetrakis(triphenylphosphine)palladium (0.005 g, 0.0043 mmol), cuprous iodide (0.0015 g, 0.0079 mmol) and redistilled toluene (17 mL) are added to a 50 mL round-bottom flask and stirred at 50°C until all the monomers are dissolved. Redistilled diisopropylamine (6 mL) is added, and the temperature is raised to 75°C and refluxed for 48 h. After the reaction is completed, the mixed solution is filtered with a syringe filter with a pore size of 0.22 μm, and the organic solvent is removed by rotary evaporation. Dissolve it with a small amount of dichloromethane, and then drop it into cold methanol (pre-placed in a refrigerator) to reprecipitate the polymer. Centrifuge and discard the supernatant, collect the solid precipitate and put it into a vacuum drying oven to fully dry to obtain a red solid pre-P-cat 0.2 (0.213 g, yield: 84.8%). 1H NMR (400 MHz, CDCl3): δ 7.18-7.16(m, 2H), 6.93 (m, 1.5H), 6.73-6.64 (m, 1.5H), 5.62 (1H), 5.23-5.02 (m, 2H), 4.70 (m, 4H), 4.22 (m, 4H), 3.50 (m, 2H), 2.77 (m, 2H), 2.37 (m, 2H), 2.12(m, 2H), 1.64 (m, 8H), 1.24 (m, 36H), 0.98 (s, 9H), 0.87 (t, 6H), 0.18 (s,6H). Elemental Anal. Calcd for C 59.4 H 82.6 N1O 9.4 S1Si 0.4 (%): C, 71.01; H, 8.22; N,1.39; Found: C, 67.41; H, 8.67; N, 1.25. GPC: n = 7,88 kDa; w = 12.78 Da; PDI = 1.66, n=16. .

[0067] pre-P-cat 0.2 The structural formula of the precursor polymer is:

[0068]

[0069] Among them, the content of M2 monomer unit is 0.2, and the content of M3 monomer unit is 0.8; n is the degree of polymerization, n=8~21;

[0070] 6. Preparation of PPETE-cat 0.2 Polymer

[0071] Under argon atmosphere, the precursor polymer pre-P-cat 0.2(0.052 g, 0.052 mmol) and redistilled tetrahydrofuran (15 mL) were added to a 50 mL round-bottom flask. A 1 M tetrabutylammonium fluoride solution in tetrahydrofuran (0.065 mL) and redistilled tetrahydrofuran (5 mL) were added to a constant pressure dropping funnel, slowly added dropwise under an ice-water bath, and reacted at room temperature for 0.5 h. After the reaction, dilute hydrochloric acid was added until the system turned yellow, deionized water and dichloromethane were added to extract the liquid, and after drying over anhydrous sodium sulfate, the solvent was removed by rotary evaporation. Dissolve it with a small amount of dichloromethane, and then drop it into cold methanol (pre-placed in the refrigerator) to reprecipitate the polymer. Centrifuge and pour off the supernatant, collect the solid precipitate and put it into a vacuum drying oven to dry it thoroughly, and the red solid was recorded as PPETE-cat. 0.2 (0.044 g, yield: 88.6%). 1 H NMR (400 MHz, CDCl3): δ 7.18-7.16 (m, 2H), 6.92-6.66 (m, 3H), 5.62 (1H), 5.23-5.02 (m, 2H), 4.70 (m, 4H), 4.21 (m, 4H), 3.48 (m, Elemental Anal.Calcd for C 57 H 77 N1O 9.4 S1(%): C, 71.41; H, 8.03; N, 1.46; Found: C, 65.39; H,7.88; N, 1.27. Φ f =38% in THF.

[0072] The fluorescent conjugated polymer PPETE-cat provided in this embodiment contains catechol side groups. 0.2 The structural formula is:

[0073] ,

[0074] Wherein, n is the degree of polymerization, n=8~21.

[0075] See attached Figure 1 , is the precursor polymer pre-P-cat provided in this embodiment 0.2 and polymer PPETE-ca t0.2 The NMR spectrum of Figure 1 It can be seen that the polymer PPETE-cat0.2 The maximum absorption wavelength is 435 nm, and the maximum emission wavelength is 485 nm.

[0076] See attached Figure 2 , is the precursor polymer pre-P-cat provided in this embodiment 0.2 and polymer PPETE-ca t0.2 Infrared spectrum of .

[0077] See attached Figure 3 , which is the polymer PPETE-cat provided in this embodiment 0.2 Characterization diagram of the photophysical properties.

[0078] 7. Preparation of latent blood fingerprint developer

[0079] Using N,N-dimethylformamide as solvent, PPETE-cat 0.2 (0.01 g, 0.01 mmol) was dissolved in DMF (10 mL) to obtain 10 mL of a fluorescent latent blood fingerprint developer containing a catechol side-group conjugated polymer, denoted as PPETE-cat. 0.2 . Example 2

[0080] This embodiment provides a loaded polymer PPETE-cat 0.2 The preparation method of the cotton sheet is as follows:

[0081] 1. Cut the cotton nonwoven fabric into pieces of 2 cm × 3 cm.

[0082] 2. Take 400 μL of the developer prepared in Example 1 in a weighing bottle, immerse 2 cut cotton pieces in the developer, soak for 1 min and take them out. The cotton pieces are wet, and the loaded PPETE-cat 0.2 Fingerprint developer cotton pads.

[0083] 3. Seal the cotton pads in a plastic bag and store them in a cool and dry place. Example 3

[0084] This embodiment provides a fresh latent blood fingerprint on the surface of an aluminum foil object, using the loaded PPETE-cat prepared in Example 2 0.2 The fingerprint developer's fingerprint cotton pad is used to develop latent blood fingerprints to obtain a fingerprint image under ultraviolet light. The specific steps are as follows:

[0085] 1. Place the aluminum foil object loaded with fresh latent blood fingerprints in a cool and dry place for 24 hours;

[0086] 2. Take a piece of loaded PPETE-cat prepared in Example 2 0.2 The fingerprint developer's fingerprint cotton sheet is evenly covered on the aluminum foil object carrying the latent blood fingerprint, and lightly pressed to ensure that the cotton sheet is in full contact with the object, and then left to stand for 2 minutes;

[0087] 3. Peel the cotton piece off the aluminum foil steadily, dry it, and then photograph the latent blood fingerprint revealed by the revealing cotton piece under 365 nm light.

[0088] See attached Figure 4 , which is the PPETE-cat provided in this embodiment 0.2 Photos of the fingerprint developer's fingerprint cotton pad before and after being used to develop the latent blood fingerprint on the aluminum foil object; Figure a is a photo of the latent blood fingerprint under natural light before being developed with the fingerprint developer's fingerprint cotton pad, and Figure b is a photo of the latent blood fingerprint under 365 nm light after being developed with the fingerprint developer's fingerprint cotton pad; Figure 4 It can be seen that the fingerprint lines on the fingerprint sample before development are not clear, but the fingerprint lines can be clearly seen under 365 nm ultraviolet light after development. The polymer on the fingerprint sample after development is evenly spread and there is no polymer adhesion on the object, achieving the purpose of selectively displaying the fingerprint friction ridges, and the three-level features of the fingerprint are clearly visible, which can be used for fingerprint identification.

[0089] See attached Figure 5 , which is a photograph provided in this embodiment of the latent blood fingerprint deposited under the same conditions on the aluminum foil object continuously displayed by the same display cotton sheet for the seventh and eighth times. Figure a is a photograph of the latent blood fingerprint continuously displayed by the same cotton sheet under 365 nm light for the seventh time, and Figure b is a photograph of the latent blood fingerprint continuously displayed under 365 nm light for the eighth time; it can be seen from the figure that the fingerprints continuously displayed by the same cotton sheet for the seventh and eighth times can still show clear fingerprint lines, the polymer is evenly spread, the selectivity for friction ridges is good, and the contrast between grooves and ridges is high. Therefore, the display method provided in this embodiment can continuously display fingerprints at least eight times while ensuring the display effect.

[0090] See attached Figure 6 , which are enlarged digital photos of the same cotton sheet for the first and seventh consecutive development of the latent blood fingerprint on the aluminum foil object provided in this embodiment; Figure a is an enlarged digital photo of the same cotton sheet for the first development of the latent blood fingerprint under 365 nm light, and Figure b is an enlarged digital photo of the latent blood fingerprint continuously developed for the seventh time under 365 nm light; it also includes three levels of fingerprint details, namely: 1 account pattern, 2 short pattern, 3 bifurcation, 4 termination and 5 sweat pore; Figure 6 In the test, the three-level features of the fingerprint are clearly visible and the contrast with the object is obvious, which can meet the current needs of fingerprint display, identification and recognition in criminal investigation.

[0091] Participate in the Figure 7 , which is a picture showing the effect of the different components of the latent blood fingerprint being revealed by the revealing cotton sheet provided in this embodiment according to the revealing operation in this embodiment. The part where the latent blood fingerprint component is applied has a large amount of fluorescent conjugated polymer adhered, so it fluoresces brightly under ultraviolet light, while the aluminum foil object has only a trace amount of polymer adhered, and it is still black under ultraviolet light. Figure 7 It can be seen that the fluorescent conjugated polymer provided by the present invention interacts with proteins, amino acids and sodium chloride in latent blood fingerprints, and has an obvious selective display effect on the above latent blood fingerprint components.

Claims

1. A fluorescent fingerprint developer based on a conjugated polymer containing catechol side groups, characterized in that The preparation method of the fluorescent fingerprint developer comprises the following steps: (1) Calculated by molar mass, 1 part of a carboxylic acid compound, denoted as compound C1, 1.5-2.8 parts of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, 0.5-0.8 parts of 4-dimethylaminopyridine and 880-900 parts of dichloromethane are mixed, stirred in an ice-water bath for 0.5-1 h, 1.5-1.8 parts of phenylethylamine are added, stirring is continued for 1.5-2 h, and then heated to reflux for 12-24 h. After the reaction is completed, the mixture is placed at room temperature, extracted, rotary evaporated, separated and purified by column chromatography and dried to obtain a phenyl-containing dibromoaromatic monomer, denoted as M3; The structural formula of the compound C1 is: ； The structural formula of the monomer M3 is: ； (2) According to the amount of substance, 1 part of diacetylene monomer M1, 0.2 parts of dibromoarene monomer M2 containing catechol group, 0.8 parts of monomer M3 prepared in step (1), 0.15 parts of (PPh3)4Pd, 0.03 parts of CuI and 640 parts of toluene are mixed, and stirred at a temperature of 45 to 50°C until all the monomers are dissolved, and then 1600 parts of diisopropylamine are added, and the mixture is reacted at a temperature of 75 to 80°C; after the reaction is completed, a conjugated polymer precursor is obtained by filtering, recrystallizing, centrifuging and drying, and recorded as pre-P-cat 0.2 ; The structural formula of the monomer M1 is: ； The structural formula of the monomer M2 is: ； The precursor pre-P-cat 0.2 The structural formula is: ； Where n is the degree of polymerization, n=8~21; (3) According to the amount of the substance, 1 part of the conjugated polymer precursor pre-P-cat prepared in step (2) 0.2 and 3500-3600 parts of tetrahydrofuran, and slowly dropwise add a mixed solution of 1.25-1.5 parts of tetrabutylammonium fluoride and 1100-1300 parts of tetrahydrofuran in an ice water bath, and react at room temperature; after the reaction, filter, recrystallize, centrifuge, and dry to obtain a fluorescent conjugated polymer containing a catechol side group, recorded as PPETE-cat 0.2 ; The fluorescent conjugated polymer PPETE-cat containing catechol side groups 0.2 The structural formula is: ， Where n is the degree of polymerization, n=8~21; (4) Using N,N-dimethylformamide as solvent, the PPETE-cat prepared in step (3) 0.2 The latent blood fingerprint developer of the fluorescent conjugated polymer solution containing catechol side groups is obtained by dissolving the latent blood fingerprint developer in a solvent at a molar ratio of 1:12500 to 1:25000.

2. The use of a fluorescent fingerprint developer based on a conjugated polymer containing catechol side groups as claimed in claim 1, characterized in that: The latent fingerprint revealing cotton sheet is prepared and applied to revealing latent blood fingerprints.

3. The use of the fluorescent fingerprint developer based on the conjugated polymer containing catechol side groups according to claim 2, characterized in that: The method for developing latent blood fingerprints comprises the following steps: (1) Fixation of fresh latent blood fingerprints: Place the object loaded with fresh latent blood fingerprints in a cool and dry place for more than 12 hours; (2) Flatly cover the latent fingerprint display cotton sheet loaded with fluorescent fingerprint developer on the object loaded with latent blood fingerprint, press lightly to make the cotton sheet fully contact with the object, and let it stand for 2 to 5 minutes; the object loaded with latent blood fingerprint is a fresh latent blood fingerprint or an old latent blood fingerprint processed in step (1); (3) Peel the cotton sheet off the object smoothly, dry it, and then photograph the latent blood fingerprint revealed by the developing cotton sheet under light conditions of 350-400 nm.

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