Method for obtaining a reagent and a reagent obtained by the method

Abstract

The present invention relates to a method (100) for obtaining a reagent which enables the synthesis of nitrogen-doped carbon dots with fluorescent properties and the simultaneous detection of both latent fingerprints and fingerprints and TNT (trinitrotoluene) in fingerprints contaminated with TNT using the solution thereof obtained by dissolving in alcohol, and to a reagent obtained by the method (100).

Description

[0001] METHOD FOR OBTAINING A REAGENT AND A REAGENT OBTAINED BY THE METHOD

[0002] Technical Field

[0003] The present invention relates to a method for obtaining a reagent which enables the synthesis of nitrogen-doped carbon dots with fluorescent properties and the simultaneous detection of both latent fingerprints and fingerprints and TNT (trinitrotoluene) in fingerprints contaminated with TNT using the solution thereof obtained by dissolving in alcohol, and to a reagent obtained by the method.

[0004] Background of the Invention

[0005] One of the most important pieces of evidence in forensic incidents is fingerprints. Fingerprints are the first choice of identification method due to their practical application and ability to provide precise results in identification and detection. Besides providing precise results, the fact that they are unchangeable-unalterable, dissimilar-inimitable and classifiable increases the importance of fingerprints.

[0006] In the field of forensic science applications, fingerprint examinations are carried out by physical and chemical methods. Fingerprint examinations are one of the most important fields of examination for positive identification as they are considered as personal data. For this reason, in forensic incidents, latent fingerprints should be made visible.

[0007] Fingerprints, which have an important place in the solving of terrorist incidents as well as forensic incidents, are one of the types of evidence frequently obtained in improvised explosive devices (lEDs). Fingerprint examinations are carried out in order to identify the perpetrators by benefiting from the evidence of lEDs found at the scene. Due to its easy availability, TNT is most commonly used in lEDs, which are one of the most important elements of terrorist incidents.

[0008] Making fingerprints visible and detecting TNT, which is frequently encountered in explosive devices, together with fingerprints is an initiative that will contribute to the rapid solving of forensic terrorism incidents.

[0009] One of the optical, physical or chemical methods must be applied in order to make latent fingerprints visible. The method to be applied is chosen depending on the environment where the fingerprint is found and the characteristics of the surface. The chemicals used in known classical chemical methods are silver nitrate, iodine vapor, super glue (cyanoacrylate), ninhydrin, 1,8-diazafluorene-one (DFO). Silver nitrate is effective on dry, porous surfaces such as paper and cardboard. The fingerprint appears as a result of photochemical degradation with the effect of light in the area where it is applied. However, it has two drawbacks such as the darkening of the background colour due to the interaction of silver with the background substrate and the inability to control the rate of the photochemical reaction. The iodine vapor produces a yellowish-brown appearance by being absorbed by the secretions in the fingerprint. However, the formed colour is short-lived. Therefore, photographing process should be performed without wasting time. Super glue (cyanoacrylate) is applied to smooth surfaces such as plastic, electrical tape, garbage bags, styrofoam and aluminium foil. Since the formed image has a white colour, it is a suitable method for dark coloured surfaces. Ninhydrin is a chemical method especially preferred for porous surfaces such as paper and cardboard. Depending on the ambient temperature and donor, it forms a dark yellow to purple coloured mark. Although fingerprints become visible in a short time, it may take a couple of weeks for full development. DFO is an effective trace determinant for paper, cardboard and derivatives. It creates a slightly pink coloured image that is not easily visible to the naked eye and the fingerprint becomes visible by fluorescing under light. As briefly summarized above, the suitable method is selected after fingerprint experts evaluate the characteristics of the traditional methods that make fingerprints visible and the surface components on which the fingerprint is located. In some cases, multiple reagents can be used in a row in order to make the fingerprint visible. In this case, problems such as deterioration of the fingerprint and failure to obtain a proper image may occur. Such situations reduce the efficiency and accuracy of the investigation, leading to loss of time and prolonging the investigation.

[0010] In recent years, fingerprint imaging methods with fluorescent materials have become the most researched materials since they reduce the interference of background colour. For this reason, researches are being carried out on developing methods that are simple, efficient, and effective against background interference and make fingerprints visible.

[0011] There are materials with fluorescence properties for making fingerprints visible in the literature. Many of these are toxic metal-nano particles or materials used in powder form, such as composite nano silica.

[0012] In recent years, carbon dots which are a new type of carbon nanomaterial with fluorescence properties have great potential in the field of fluorescence sensing and imaging due to their excellent optical properties, low toxicity, good biocompatibility and simple preparation methods. Among these, the carbon dots used for fingerprinting are mostly applied in powder form or after being prepared in the form of a powder nanocomposite material with a material such as silica. Applications in the form of solutions or sprays are less common. Carbon dots for the determination of TNT and similar explosives in water have also been reported in the literature. In the literature and in traditional fingerprinting applications, materials with fluorescence properties have a single function and these materials are used in either making the fingerprint visible or in the detection of TNT. No material has been reported to be used in the field of making fingerprints and TNT hidden in fingerprints visible together. For this reason, in order to overcome the above-mentioned deficiencies, there is a need for a method for obtaining a reagent which enables the simultaneous detection of both latent fingerprints and fingerprints and TNT in fingerprints contaminated with TNT and for a reagent obtained by the method.

[0013] The Chinese patent document no. CN105662425, an application included in the state of the art, discloses a latent fingerprint imaging method based on Cu2-xS selfdoped semiconductor photothermal material. In the method, organic phase dispersed Cu2-xS nanoparticles, x=0-l, wherein the Cu2-xS nanoparticles content is 8-12 mg are taken and mixed with 2-6 mg allyl mercaptan and dispersed in 1-2 mL of chloroform; after being stirred for 10-60 minutes, a 40-100 pL of AIBN solution with a concentration of 0.5-1.0 mg / mL is added; then a 8-12 mL of SDS aqueous solution with a concentration of 1.5-2.0 mg / mL is added; sonicated for 1- 5 minutes in ice bath, and 365 nm is used for light irradiation for 5-20 minutes and stirring at room temperature overnight is performed, centrifugally purified and dispersed in l-2mL ultrapure water to obtain a Cu2-xS self-doped semiconductor photothermal material dispersion. After aging the fingerprint sample at 28-35°C for 42-50 hours, the prepared 100-300pL Cu2-xS self-doped semiconductor photothermal material dispersion is added to the fingerprint area and incubated at room temperature for 1-60 minutes. Finally, the sample is irradiated with nearinfrared light and the latent fingerprints are imaged with the help of a near-infrared imager. The Cu2-xS self-doped semiconductor photothermal material dispersion can be substituted by Cu2-xS self-doped semiconductor photothermal material dispersion and CdSeZnS quantum dot dispersion with a volume ratio of 1:2-2: 1. Therefore, the mass ratio of Cu2-xS self-doped semiconductor photothermal material to CdSeZnS quantum dots is 1:2-2: 1 and this enables the detection of explosive residues containing 2,4,6-trinitrotoluene in fingerprint detection and imaging.

[0014] Summary of the Invention An object of the present invention is to realize a method for obtaining a reagent which is applied in criminal laboratories, and which enables to perform a preliminary test for making latent fingerprints visible and for the identification of TNT; and a reagent obtained by the method.

[0015] Another object of the present invention is to realize a method for obtaining a reagent which enables the simultaneous identification of both fingerprints and TNT if there is TNT contaminated on the fingerprint; and a reagent obtained by the method.

[0016] A further object of the present invention is to realize a method for obtaining a reagent with nano-fluorescence properties for making latent fingerprints and TNT- contaminated latent fingerprints visible on different objects with an alcoholic solution of nitrogen-doped carbon dots; and a reagent obtained by the method.

[0017] A further object of the present invention is to realize a method for obtaining a reagent which is non-toxic and therefore does not harm the practitioner in case of exposure, and which can be produced by inexpensive and simple synthesis methods; and a reagent obtained by the method.

[0018] A further object of the present invention is to realize a method for obtaining a reagent which gives results in a shorter time compared to many known methods, also gives results in aged fingerprints, can maintain the same image after being stored for a long time after the fingerprint identification process, and gives results on non-porous and semi-porous surfaces; and a reagent obtained by the method.

[0019] Detailed Description of the Invention

[0020] “Method for Obtaining a Reagent and a Reagent Obtained by the Method” realized to fulfil the objectives of the present invention is shown in the figures attached, in which: Figure 1 is a flowchart of the inventive method.

[0021] Figure 2 shows FT-IR spectrum of (A) acid, (B) triamine, (C) nitrogen-doped carbon dots.

[0022] Figure 3 is a high-contrast transmission electron microscope (CTEM) image of nitrogen-doped carbon dots.

[0023] Figure 4 is a UV-GB absorption spectrum of nitrogen-doped carbon dots.

[0024] Figure 5 is a fluorescence emission spectrum of nitrogen-doped carbon dots (excitation wavelength 330 nm, 365 nm and 420 nm).

[0025] Figure 6 is the spectrum that gives the fluorescence decay upon addition of TNT to the solution (reagent) of nitrogen-doped carbon dots in alcohol (excitation wavelength 365nm, fluorescence wavelength 445 nm, reagent concentration 0.05mg / mL, TNT 1x10-5 M).

[0026] Figure 7 is the instantaneous and 30-day images taken after applying the reagent to the fingerprints created on the battery surface.

[0027] Figure 8 is the instantaneous and 30-day images taken after applying the reagent to the fingerprints created on the transparent tape surface.

[0028] Figure 9 is the instantaneous and 30-day images taken after applying the reagent to the fingerprints created on the glass surface.

[0029] Figure 10 is the instantaneous and 30-day images taken after applying the reagent to the fingerprints created on the black plastic bag surface.

[0030] Figure 11 is the instantaneous and 30-day images taken after applying the reagent to the fingerprints created on a piece of the radio surface.

[0031] Figure 12 is the images of TNT-containing fingerprints on different surfaces.

[0032] Figure 13 shows the TNT-contaminated fingerprint match on the battery surface.

[0033] Figure 14 shows the TNT-contaminated fingerprint match on the transparent tape surface.

[0034] Figure 15 shows the TNT-contaminated fingerprint match on the glass surface.

[0035] 100. Method The inventive method (100) for obtaining a reagent which enables the simultaneous detection of both latent fingerprints and fingerprints and TNT in fingerprints contaminated with TNT comprises the steps of obtaining nitrogen-doped carbon dots (101); and obtaining the reagent by dissolving nitrogen-doped carbon dots in alcohol (102).

[0036] In the step of obtaining nitrogen-doped carbon dots (101) of the inventive method (100), a 0.7-3.5 g of malic acid or hydroxy succinic acid or hydroxybutanedioic acid as carbon source and a 1.0-5.2 g of bis-2-aminoethylamine or 2,2'- iminodiethylamine or diethylenetriamine as nitrogen source are taken into a vial and mixed at room temperature. In one embodiment of the invention, a 1.0- 1.5 g malic acid as carbon source and a 62% diethylenetriamine by weight as nitrogen source are taken into a vial and mixed at room temperature. After the mixing process, the vial is closed and kept in the oven for 2-6 hours by applying a gradual heating program at 140-250°C. Then, the nitrogen-doped carbon dots are obtained by cooling the mixture to room temperature and carrying out the purification process by dispersing it in water or alcohol.

[0037] In the step of obtaining the reagent by dissolving nitrogen-doped carbon dots in alcohol (102) of the inventive method (100), the reagent is obtained by dissolving nitrogen-doped carbon dots in alcohol at a ratio of 0.05-0.5% w / v. In one embodiment of the invention, the alcohol is methanol.

[0038] The said invention relates to a reagent used in the simultaneous detection of both latent fingerprints and fingerprints and TNT in fingerprints contaminated with TNT, obtained by following the steps of the method (100) described above.

[0039] It is enabled to identify fingerprints by using the reagent obtained by the inventive method (100). Battery, transparent duct tape, glass, plastic bag and a piece of radio were selected as surfaces for fingerprinting. These are the surfaces where improvised explosive devices used by terrorist organizations can be found. Images of the fingerprints created on the selected surfaces were taken and the fingerprints were not visible under daylight. The images shown in Figures 7 to 11 are the images taken after the reagent was applied to the fingerprints created on these surfaces, and the images obtained as a result of photographing the same application again after thirty days. As can be seen from the images, there is no significant difference between the instantaneous and thirty-day waiting period. This shows that the reagent has not lost its effectiveness for at least 30 days.

[0040] It is enabled to identify TNT-contaminated fingerprints by using the reagent obtained by the inventive method (100). The images taken in daylight and under 450 nm light source after reagent application after TNT-contaminated fingerprints were formed on the surfaces of batteries, transparent duct tape, glass, black plastic bags and pieces of radio are shown in Figure 12. As a result of TNT interaction with the amine groups on the surface of nitrogen-doped carbon dots used as reagent, a colour change in pink to brick red tones occurs. Nitro groups in the TNT molecule have the ability to withdraw electrons. Electrons are withdrawn by nitro groups and a charge transfer complex is formed as a result of molecular interaction between the electron-deficient aromatic ring of TNT and the amine group at the nitrogen-doped carbon dots and a pink to brick red colour occurs (Meisenheimer complex). If the images of the TNT-containing fingerprints in Figure 12 are examined, a pink-tile red colour change is observed, especially on light-coloured surfaces. This is the result of the interaction of TNT with -NH2 groups on the surface of nitrogen-doped carbon dots. The TNT-amine complex formed on the surface of nitrogen-doped carbon dots also suppresses fluorescence emission (Figure 6). The second column of Figure 12 shows fluorescence decay in the regions where TNT is present. Both colour change and fluorescence decay after application of the reagent indicate the presence of TNT in the fingerprint. The Automated Fingerprint Identification System (AFIS) is used by fingerprint experts for matching purposes. After the reagent is applied, identification is performed by comparing the distinguishing features as a result of the AFIS query.

[0041] As a result of AFIS query on TNT-contaminated fingerprints, the information belonging to the donor was found on the battery, transparent duct tape and glass surfaces, but could not be found on the plastic bag and piece of the radio. The AFIS results which contain TNT-contaminated fingerprints made visible after applying reagent to the battery, transparent duct tape and glass surface are shown in Figures 13, 14 and 15.

[0042] The AFIS query results are given in Table 1.

[0043] Table 1. The AFIS query results

[0044] Within these basic concepts; it is possible to develop various embodiments of the inventive “Method (100) for Obtaining a Reagent and a Reagent Obtained by the Method (100)”; the invention cannot be limited to examples disclosed herein and it is essentially according to claims.

Claims

CLAIMS1. A method (100) for obtaining a reagent which enables the simultaneous detection of both latent fingerprints and fingerprints and TNT in fingerprints contaminated with TNT; characterized by comprising the steps of obtaining nitrogen-doped carbon dots (101); and obtaining the reagent by dissolving nitrogen-doped carbon dots in alcohol (102).

2. A method (100) according to Claim 1; characterized in that at step of obtaining nitrogen-doped carbon dots (101), a 0.7-3.5 g of malic acid or hydroxy succinic acid or hydroxybutanedioic acid as carbon source and a 1.0-5.2 g of bis-2- aminoethylamine or 2,2'-iminodiethylamine or diethylenetriamine as nitrogen source are taken into a vial and mixed at room temperature.

3. A method (100) according to Claim 2; characterized in that at step of obtaining nitrogen-doped carbon dots (101), a 1.0-1.5 g malic acid as carbon source and a 62% diethylenetriamine by weight as nitrogen source are taken into a vial and mixed at room temperature.

4. A method (100) according to Claim 2 or 3; characterized in that at step of obtaining nitrogen-doped carbon dots (101), after the mixing process, the vial is closed and kept in the oven for 2-6 hours by applying a gradual heating program at 140-250°C.

5. A method (100) according to any one of Claims 2 to 4; characterized in that at step of obtaining nitrogen-doped carbon dots (101), the nitrogen-doped carbon dots are obtained by cooling the mixture to room temperature and carrying out the purification process by dispersing it in water or alcohol.

6. A method (100) according to Claim 1; characterized in that at step of obtaining the reagent by dissolving nitrogen-doped carbon dots in alcohol (102), the reagent is obtained by dissolving nitrogen-doped carbon dots in alcohol at a ratio of 0.05-0.5% w / v.

7. A method (100) according to Claim 6; characterized in that at step of obtaining the reagent by dissolving nitrogen-doped carbon dots in alcohol (102), the alcohol is methanol.

8. A reagent used in the simultaneous detection of both latent fingerprints and fingerprints and TNT in fingerprints contaminated with TNT, obtained by following the steps of the method (100) described above.

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