CN113925500B - Fingerprint developing powder and preparation method and application thereof - Google Patents
Fingerprint developing powder and preparation method and application thereof Download PDFInfo
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Abstract
The invention discloses fingerprint showing powder, a preparation method and application thereof, wherein the fingerprint showing powder comprises the following components in percentage by weight: 92-95% of magnetic powder, 3-8% of binder and 0.5-1% of colorant. Compared with the prior art, the invention has clear color development on the impermeable carrier, does not block sweat pores and wheels Guo Xian, has strong adsorption force, and can still show fingerprints after simple wiping; the invention has wide material sources, is green and nontoxic, and is not easy to raise dust when in use; the preparation method is simple in preparation process, suitable for engineering production and has great practical application value.
Description
Technical Field
The invention relates to the technical field of fingerprint display materials, in particular to fingerprint display powder and a preparation method and application thereof.
Background
The fingerprint is a protruding ridge on the epidermis of a human finger, is a genetic character characteristic of a human, and has the characteristic of 'being different from each other and basically unchanged throughout the life'. Because of its uniqueness, lifelong invariance and convenience, fingerprint has become an important tool for biometric identification. When the finger contacts with the object, sweat, grease and other components in the finger can remain on the surface of the object to form fingerprints invisible to naked eyes, namely latent fingerprints. Researches show that the main component of the latent fingerprints is water with the content of 99% and can be quickly evaporated; of the remaining materials, about 50% are inorganic components (such as sodium chloride, potassium chloride, etc.), which have little value for fingerprint development (except silver nitrate development); while additional organic components (e.g., oils, amino acids, vitamins, etc.) can be visualized by many methods, because of the too small number, the visualization method often needs to have a particularly high sensitivity, which is particularly important when background interference is severe.
The fingerprint developing powder has the following characteristics: (1) Foreign magnetic and fluorescent developing powders, formulations and processes are not disclosed, such as BVDA in the Netherlands and SCENESAFE in the United kingdom; (2) The magnetic developing powder reported in China mainly takes physical mixing as main component, and the research on interface action among different components is perfect. For the commonly used black and white magnetic powder study, patent CN102018516a indicates that the iron powder/silicon powder/sodium chloride/activated carbon powder is uniformly mixed to react chemically with fatty acid and uric acid in sweat, and the fingerprint appears naturally, but does not indicate the chemical mechanism of action. ThatsaneeThongson (J. Forensic. Sci,2010,55, (5): 1343-1346) indicates that 5 μm nickel powder is good for fingerprint development, (Zhang Shujie, yu Mingyang, zhongzheng, study of developing high quality magnetic powder by using nickel powder to formulate fingerprint, national academy of criminal police, 2015,3,46-50.) indicates that nickel powder and carbon powder (100:6) are the best, but the specification of carbon powder is not reported. Research on magnetic powder of ferroferric oxide to show fingerprint, (Ai Kangyun, liu Huan, often Bai Nian, etc.. Research on latent fingerprint developed by suspension method (III). Criminal technique. 1994,4,1-2. Zhang Longji, zhang Weimin, sun Zhongxi, sodium dodecyl benzene sulfonate in nanometer Fe 3 O 4 The adsorption behavior of the surface, university of henna report, 2010, 24,1, 40-43. Zhou Xiaofeng, application study of nanomaterials in the development of latent fingerprints, university of southwest political university's treatise, 2013. He Zhong, zhang Jie, wet object sweat latent fingerprint development method study, department of police officer, henna, university of occupational, 2016,14,3, 99-102.) focused on nanocrystallization and surface modification of ferroferric oxide, unclear contour and detail characteristics from reported fingerprint pictures, and poor dispersibility when developed by completely using solid nanomaterials. (Zhang Zhongliang, mu Andong, zhang Limei, beyond, box-Behnken method based targeted fingerprint MoS2 microparticle suspensions, national academy of criminal police, 2018,1, 80-83.) reported a MoS2 (3000 mesh) suspension, although dispersion was resolvedSex, but MoS 2 The liquid has no magnetism, and is not convenient to carry and use as powder. Patent CN107049331a proposes a fingerprint showing powder of a sandwich structure, which uses iron powder as a core, polyethylene glycol (4000-10000) as an inner shell, ninhydrin as an outer shell developer, only gives a fingerprint picture, and no representation of a shell-core structure is provided, and the sandwich structure has no supporting basis. Patent CN108648891a proposes a preparation method of a latent fingerprint developing powder with a core-shell structure, wherein magnetic powder is used as a core, polyvinyl alcohol is used as a shell, a developer is used as the shell, and the fingerprint developing powder is obtained through a grinding process, but the core-shell structure may be damaged in the grinding process, and no support basis for the core-shell structure is given. The patent CN106175785A adopts black magnetic fingerprint display powder of graphene modified stearic acid, and adds lubricating powder graphene into magnetic powder and stearic acid powder, but stearic acid has weak acidity and reacts with magnetic powder, so that oxide generation can cause detail interference, and the graphene has poor dispersibility and can cause interference. The patent CN105326509a proposes a magnetic powder with fingerprint appearance and a preparation method thereof, wherein iron cobalt nickel magnetic powder and boron nitride are mechanically ground, the iron cobalt nickel powder is gray black, the boron nitride is white, and the density and the interface are different due to no acting force between the magnetic powder and the boron nitride, so that the magnetic powder and the boron nitride cannot be fully and uniformly mixed only by means of physical action.
In the white development powder research, mainly the mixture of magnetic powder and titanium oxide, patent (a kind of TiO 2 The magnetic powder for strengthening fingerprint and its preparation method and application, CN105411598A,2016, a white magnetic fingerprint and its preparation method, CN106175784A,2016, a fingerprint and its preparation method and application, CN105326509A,2016,2.) uses titanium dioxide as white developing powder, the reinforcing agent of colorant, the particle size is 6.5 μm, the dyeing powder is titanium dioxide powder, 3000-5000 mesh, (average particle size 3-5 μm). No acting force exists between the titanium oxide and the magnetic powder, the mechanical mixing can not be uniformly mixed, and the display effect is poor. For modification studies of titanium oxide, (Yang Ruiqin TiO) 2 Development of latent fingerprints by nanopowder research, criminal techniques, 2008,4,3-5.) proposed the addition of small amounts of soybean extract (lecithin), dodecylamine or hexadecylamine modificationTitanium oxide increases the force acting with fingerprints, but has poor dispersibility and affects the effect of the phenomenon. CN101792147a proposes a silica particle surface modification method and a method for latent fingerprint display thereof, (Ai Kangyun, liu Huan, often Bai Nian, etc.,. Research (II) suspension method for latent fingerprint display, (criminal technique: 1994,4,1-2) proposes addition of zinc oxide (or zinc carbonate) to display white color, (Zhang Limei, zhang Dongdong, zhang Zhongliang, wang Shuai, sun Nianfeng), surface modified alumina nanoparticle suspension for sweat latent fingerprint research, criminal technique, 2016, 41 (3): 200-202. Zhang Limei Zhang Dongdong Zhang Zhongliang, technical research for two-step latent fingerprint display of surface modified alumina nanoparticle suspension, police technique, 2016,2, 44-46.) propose that modified alumina realizes effective suspension of nanoparticles and dual effects of physical adsorption and chemical reaction of lipids and amino acids in fingerprints, thereby making binding capacity stronger. Alumina, titania and silica also have a problem of uniformity of dispersion.
In other development studies (except for fluorescent development), colorants are added mainly on the basis of white magnetic powder to present different colors, such as amino black showing bluish black, (Zhang Jiangang, wei Yanli, zhang Li, dong Chuan, spectroscopic studies of the action of amino black 10B with bovine serum albumin, molecular science journal, 2011,27,3, 170-174, cheyne-heart, yan, studies of the binding reaction of amino black 10B with proteins, inner river university journal, 2011,26,6, 29-31.). The latent fingerprint is visualized by a method in which dye molecules (rhodamine or methyl blue) are deposited on amino acid residues in the latent fingerprint. (Chen Q, kerk W, south A, et al application of Dye Intercalated Bentonite for Developing Latent, finger class Sci,2009, 44 (1/2): 156-160.) indigo color, CN1067571A proposes a method for preparing a magnetic powder which is not carcinogenic and develops latent fingerprints, the coloring powder component is indigo, polyvinyl formal, acetanilide and carrier iron powder (80-300 mesh) are thoroughly mixed. The colorants of the red powder are mainly 1,4,5, 8-tetrahydroxy anthraquinone, anthracene deep red (3 rd stage of criminal technique 2014), anthracene deep red (, an initial experiment of the anthraquinone dye showing sweat latent fingerprints, criminal technique 2014,3, 50-51.), rhodamine 6G (alias rose red 6G), alizarin red CN1080511A, and the greatest deficiency of using biological colorants has great toxicity to human bodies and other organisms. Yellow development powder, inorganic powder using nano Gold or copper, (Enhancement of Image Contrast, stability, and SALDI-MS Detection Sensitivity for Latent Fingerprint Analysis by Tuning the Composition of Silver-Gold Nanoalloys, ACS appl. Mater. Interfaces 2016,8,29668-29675), has good development effect, but is expensive, but using lead chromate of various colors, heavy metal pollution exists. Organic yellow coloring agents, such as lemon yellow pigment and leucinbazole, have better appearance effects, but small particles of organic matters raise dust and have organic matters cancerogenic action.
In conclusion, the black developing powder mainly has uneven mixing, poor nanoparticle dispersibility and influence on developing effect, titanium oxide and aluminum oxide in the white developing powder also have problems, and the color developing powder except the fluorescent powder mainly comprises a white powder added with a coloring agent and also has interface problems
Disclosure of Invention
The invention aims to solve the defects in the prior art and provide fingerprint showing powder for sweat and latent fingerprints, which has the advantages of strong adsorption force, no sweat pores blockage, good flowability, no background interference and multiple colors, and a preparation method and application thereof.
In order to achieve the above purpose, the invention is implemented according to the following technical scheme:
the first object of the invention is to provide fingerprint developing powder which comprises the following components in percentage by weight: 92-95% of magnetic powder, 3-8% of binder and 0.5-1% of colorant.
As a further preferable technical scheme of the invention, the magnetic powder is one or more of Fe powder, co powder, ni powder, ferroferric oxide powder, ferrosilicon powder and NdFeB.
As a further preferable technical scheme of the invention, the binder is one or more of pentaerythritol, erythritol, polyvinyl alcohol, polyethylene glycol, polymethyl methacrylate and polyvinylpyrrolidone.
As a further preferable technical scheme of the invention, the colorant is one or more of nano silicon oxide, barium sulfate, aluminum oxide, boron nitride, aluminum powder, colloidal graphite, carbon nano tubes, sudan red, nano ferric oxide, prussian blue, chromium oxide, indigo, glucose and ferrous oxalate.
As a further preferable embodiment of the present invention, the average particle diameter of the magnetic powder is D, and 80 μm < D.ltoreq.250 μm.
As a further preferable technical scheme of the invention, the average molecular weight of the binder is M, and M is more than or equal to 2000 and less than or equal to 8000.
A second object of the present invention is to provide a method for preparing fingerprint developing powder, comprising the steps of:
s1, weighing magnetic powder, a binder and a colorant according to weight percentage for standby;
s2, modifying the surface of the magnetic powder;
s3, completely dissolving the binder with dichloromethane and/or methanol at room temperature, adding the modified magnetic powder for coating, and volatilizing the solvent in a rotary steaming bottle while stirring until the magnetic powder and the binder form pasty slurry;
s4, taking out the pasty slurry, pouring the pasty slurry into a stainless steel ball grinding tank after drying, grinding for 10 minutes at the rotating speed of 300-400rpm, adding a colorant, replacing the colorant with a plastic grinding ball, continuously grinding for 30 minutes at the rotating speed of 300-400rpm, and then using a 40-mesh copper mesh screen, and drying the screened material in vacuum at room temperature for 30 minutes to obtain the fingerprint showing powder.
As a further preferable technical scheme of the present invention, in the step S2, the specific steps of modifying the surface of the magnetic powder are as follows: pouring the magnetic powder into a stirring device, adding citric acid solution with the concentration of 2% to the surface of the magnetic powder, starting stirring at 100-220rpm, stirring for 10-15min, stopping stirring and filtering, leaching the filter cake with absolute ethyl alcohol or methanol for more than three times, taking out the filter cake, and drying in nitrogen atmosphere.
As a further preferable technical scheme of the invention, the stainless steel balls comprise large stainless steel balls and small stainless steel balls, the diameter of the large stainless steel balls is 12mm, the diameter of the small stainless steel balls is 2mm, and the mass of the large balls is 2.5-4 times that of the small balls.
A third object of the present invention is to provide the use of a fingerprint development powder for fingerprint development.
Compared with the prior art, the invention has the following beneficial effects:
(1) The color development on the impermeable carrier is clear, sweat pores and wheels Guo Xian are not blocked, the adsorption force is strong, and fingerprints can still be developed after simple wiping;
(2) The invention has wide material sources, is green and nontoxic, and is not easy to raise dust when in use;
(3) The preparation method is simple in preparation process, suitable for engineering production and has great practical application value.
Drawings
FIG. 1 is a photograph and an electron microscope scanning picture of the black fingerprint development powder prepared in example 1.
Fig. 2 is an EDX spectrum and material composition of the black fingerprint development powder prepared in example 1.
FIG. 3 is a graph showing the effect of the black fingerprint development powder paper prepared in example 1.
Fig. 4 is a drawing showing the fingerprint contour and minutiae on paper of the black fingerprint development powder prepared in example 1.
FIG. 5 shows the brushing effect of the black fingerprint development powder prepared in example 1 on different planar carriers.
FIG. 6 shows the effect of the black fingerprint development powder prepared in example 1 on paper at various times.
Fig. 7 is a graph showing the comparison of the effects of the black fingerprint development powder prepared in example 1 before and after fingerprint wiping on an iron plate of a painted surface.
FIG. 8 is a graph showing the comparison of the effects of the black fingerprint development powder prepared in example 1 before and after wiping the fingerprint on a wood board with a painted surface.
FIG. 9 is a scanning electron microscope and components of the black gray fingerprint development powder prepared in example 2.
Fig. 10 is a photograph and an electron microscope scanning picture of the white fingerprint development powder prepared in example 3.
FIG. 11 is an EDX spectrum and material composition of the white fingerprint development powder prepared in example 3.
FIG. 12 shows the effect of white fingerprint development on a slip sheet prepared in example 3.
FIG. 13 is a fingerprint outline and detail of white fingerprint development slip prepared in example 3.
Fig. 14 is a photograph and an electron microscope scanning picture of the yellow fingerprint development powder prepared in example 4.
FIG. 15 is an EDX spectrum and material composition of the yellow fingerprint development powder prepared in example 4.
FIG. 16 shows the effect of the yellow fingerprint development powder prepared in example 4 on a white tile.
Fig. 17 is a diagram showing the fingerprint contour and detail of the yellow fingerprint development powder prepared in example 4 on a white tile.
Fig. 18 is an electron microscope scanning picture of the silver gray black fingerprint development powder prepared in example 5.
Fig. 19 shows the effect of the silver gray black fingerprint development powder prepared in example 5 on a white tile.
FIG. 20 is a graph showing the effect of the silvery white fingerprint produced in example 6 on a pink tile.
FIG. 21 is a graph showing the effect of the pale red fingerprint obtained in example 7 on a pink tile.
FIG. 22 shows the effect of the green fingerprint obtained in example 8 on a pink tile.
FIG. 23 shows the effect of the blue fingerprint obtained in example 9 on a pink tile.
FIG. 24 is a graph showing the effects of the ferrosilicon powder/polyethylene glycol/ferroferric oxide/aluminum oxide/titanium oxide obtained in example 10.
FIG. 25 is a scanning electron microscope of ferrosilicon powder/polyethylene glycol/ferroferric oxide/aluminum oxide/titanium oxide prepared in example 10.
FIG. 26 shows XPS of the ferrosilicon powder/polyethylene glycol/ferroferric oxide/aluminum oxide/titanium oxide obtained in example 10.
FIG. 27 is a graph showing the effect of neodymium iron boron powder/polyethylene glycol/ferroferric oxide/titanium oxide obtained in example 11.
FIG. 28 is a Scanning Electron Microscope (SEM) of neodymium iron boron powder/polyethylene glycol/ferroferric oxide/titanium oxide obtained in example 11.
Detailed Description
The present invention will be described in further detail with reference to the following examples in order to make the objects, technical solutions and advantages of the present invention more apparent. The specific embodiments described herein are for purposes of illustration only and are not intended to limit the invention.
Example 1
The black fingerprint developing powder is prepared by the following specific preparation process:
4.5 g of iron powder with an average particle diameter of 200 mu m, 0.45 g of ferroferric oxide with a particle diameter of 3.5 mu m and 0.01 g of graphite with a particle diameter of 5 mu m are weighed; weighing 0.18 g of pentaerythritol, and dissolving the pentaerythritol with 15 ml of methanol at room temperature for later use; pouring iron powder into a stirring device, adding citric acid solution with the concentration of 2% to the surface of the magnetic powder, starting stirring at 100-220rpm, stirring for 10-15min, stopping stirring and filtering, leaching the filter cake with absolute ethyl alcohol or methanol for more than three times, taking out the filter cake, and drying in nitrogen atmosphere to finish iron powder modification. Pouring the modified iron powder into a pentaerythritol-dissolved solution, performing ultrasonic treatment for 10min, and volatilizing the solvent in a rotary steaming bottle while stirring until the magnetic powder and the binder form pasty slurry; taking out the pasty slurry, pouring the pasty slurry into a stainless steel ball grinding tank after drying and grinding for 10 minutes at the rotating speed of 300-400rpm, adding ferroferric oxide and graphite, replacing the ferroferric oxide and the graphite with plastic grinding balls, continuously grinding for 30 minutes at the rotating speed of 300-400rpm, and then using a 40-mesh copper mesh screen, and vacuum drying and pumping the screened material for 30 minutes at room temperature to obtain black fingerprint showing powder.
The photograph and the electron microscope scanning picture of the black fingerprint developing powder prepared in the embodiment are shown in fig. 1, and the EDX spectrogram and the material composition are shown in fig. 2.
The black fingerprint of this embodiment is absorbed by the magnetic fingerprint brush tip and is brushed and displayed in one direction along the fingerprint lines on the paper, and the fingerprint contour is photographed by the camera under the condition of sufficient light. The on-paper display effect is shown in fig. 3, and the fingerprint contour and minutiae map are shown in fig. 4. Fingerprint contours and minutiae can be seen cleanly from the figure.
Further, in order to compare the brushing effects on different planar carriers, brushing effects on paper, glass, wood (paint), metal plate, tile, and polymer (plastic) are shown in FIG. 5, respectively. As can be seen from fig. 5, on a smooth planar carrier, the fingerprint is more clearly visible, and for a rough surface carrier, the fingerprint is less visible with less residue.
The display effect of the fingerprint changes with time, and as shown in fig. 6, the display effect of the fingerprint is displayed on the metal plate surface for 1 hour, 6 hours, 12 hours, 24 hours and 48 hours with time, and the display effect of the fingerprint is not clear with time.
When the fingerprint is wiped or washed with water, the display effect after brushing is poor, a comparison graph of the display effect before and after wiping the fingerprint on an iron plate of a painted surface is shown in fig. 7, and a comparison graph of the display effect before and after wiping the fingerprint on a wood plate of the painted surface is shown in fig. 8. As can be seen from fig. 7 and 8, the rough outline can be seen after wiping, but the rough outline cannot be seen after washing.
Example 2
The embodiment prepares the black gray fingerprint developing powder, which comprises the following specific preparation processes:
weighing 4.5 g of nickel powder with the average particle size of 200 mu m and 0.4 g of graphite with the average particle size of 5 mu m; 0.18 g of pentaerythritol, and dissolving the pentaerythritol with 15 ml of methanol at room temperature for later use; pouring nickel powder into a stirring device, adding citric acid solution with the concentration of 2% to the surface of the magnetic powder, starting stirring at 100-220rpm, stirring for 10-15min, stopping stirring and filtering, leaching the filter cake with absolute ethyl alcohol or methanol for more than three times, taking out the filter cake, and drying in nitrogen atmosphere to finish iron powder modification. Pouring the modified iron powder into a pentaerythritol-dissolved solution, performing ultrasonic treatment for 10min, and volatilizing the solvent in a rotary steaming bottle while stirring until the magnetic powder and the binder form pasty slurry; taking out the pasty slurry, pouring the pasty slurry into a stainless steel ball grinding tank for grinding for 10 minutes at the rotating speed of 300-400rpm, adding graphite, replacing the graphite with a plastic grinding ball, continuously grinding for 30 minutes at the rotating speed of 300-400rpm, then using a 40-mesh copper mesh screen, and vacuum drying and pumping the screened material for 30 minutes at room temperature to obtain the black gray fingerprint developing powder.
The scanning electron microscope and the components of the black gray fingerprint developing powder prepared in the embodiment are shown in figure 9.
The black gray fingerprint of this embodiment is picked up by the magnetic fingerprint brush tip and developed in a single direction along the fingerprint lines on the paper, and the fingerprint profile is photographed with the camera under sufficient light. The on-paper display effect is shown in fig. 9. Fingerprint contours and minutiae can be seen cleanly from the figure.
Example 3
The white fingerprint developing powder is prepared by the embodiment, and the specific preparation process is as follows:
4.5 g of iron powder with an average particle size of 200 mu m and 0.45 g of titanium oxide with a particle size of 80nm are weighed; 0.18 g erythritol, and dissolving with 15 ml methanol at room temperature for later use; pouring iron powder into a stirring device, adding citric acid solution with the concentration of 2% to the surface of the magnetic powder, starting stirring at 100-220rpm, stirring for 10-15min, stopping stirring and filtering, leaching the filter cake with absolute ethyl alcohol or methanol for more than three times, taking out the filter cake, and drying in nitrogen atmosphere to finish iron powder modification. Pouring the modified iron powder into a solution dissolved with erythritol, performing ultrasonic treatment for 10min, and volatilizing the solvent in a rotary steaming bottle while stirring until the magnetic powder and the binder form pasty slurry; taking out the pasty slurry, pouring the pasty slurry into a stainless steel ball grinding tank for grinding for 10 minutes at the rotating speed of 300-400rpm, adding titanium oxide, replacing the titanium oxide with a plastic grinding ball, continuously grinding for 30 minutes at the rotating speed of 300-400rpm, then using a 40-mesh copper mesh screen, and vacuum drying and pumping the screened material for 30 minutes at room temperature to obtain black fingerprint showing powder.
The photographs and electron microscope scanning pictures of the white fingerprint appearance powder prepared in the embodiment are shown in fig. 10, and the EDX spectrogram and the material composition are shown in fig. 11.
The white fingerprint of this embodiment is picked up by the magnetic fingerprint brush tip and is brushed and displayed in one direction along the fingerprint lines on the black table top, and the fingerprint contour is photographed by the camera under the condition of sufficient light. The on-paper display effect is shown in fig. 12, and the fingerprint contour and minutiae map are shown in fig. 13. Fingerprint contours and minutiae can be seen cleanly from the figure.
Example 4
The yellow fingerprint developing powder is prepared by the following specific preparation process:
4.5 g of iron powder with an average particle size of 200 mu m, 0.1 g of titanium oxide with a particle size of 5 mu m, 0.1 g of glucose and 0.25 g of ferrous oxalate are weighed; 0.18 g erythritol, and dissolving with 15 ml methanol at room temperature for later use; pouring iron powder into a stirring device, adding citric acid solution with the concentration of 2% to the surface of the magnetic powder, starting stirring at 100-220rpm, stirring for 10-15min, stopping stirring and filtering, leaching the filter cake with absolute ethyl alcohol or methanol for more than three times, taking out the filter cake, and drying in nitrogen atmosphere to finish iron powder modification. Pouring the modified iron powder into a solution dissolved with erythritol, performing ultrasonic treatment for 10min, and volatilizing the solvent in a rotary steaming bottle while stirring until the magnetic powder and the binder form pasty slurry; taking out the pasty slurry, pouring the pasty slurry into a stainless steel ball grinding tank after drying and grinding for 10 minutes at the rotating speed of 300-400rpm, adding titanium oxide, glucose and ferrous oxalate, replacing the materials with plastic grinding balls, continuously grinding for 30 minutes at the rotating speed of 300-400rpm, then using a 40-mesh copper mesh screen, and vacuum drying and pumping the screened material for 30 minutes at room temperature to obtain black fingerprint developing powder.
The photograph of the yellow fingerprint appearance powder prepared in the embodiment and the electron microscope scanning photograph are shown in fig. 14, and the EDX energy spectrum and the material composition are shown in fig. 15.
The yellow fingerprint developing powder of the embodiment is sucked by a magnetic fingerprint brush tip, the fingerprint lines are brushed and displayed in one direction on a white ceramic tile, and the fingerprint outline is shot by a camera under the condition of sufficient light. The display is shown in fig. 16, and the fingerprint profile and minutiae map are shown in fig. 17. Fingerprint contours and minutiae can be seen cleanly from the figure.
Example 5
The difference from example 4 is that silver powder with a particle size of 200 mesh is used as the colorant; iron powder: pentaerythritol: silver powder mass ratio = 100:4:3; a silver gray black fingerprint development powder was prepared in the same manner as in example 4.
An electron microscope scanning picture of the silver gray black fingerprint developing powder prepared in the embodiment is shown in fig. 18.
The silver gray black fingerprint of this embodiment is absorbed by the magnetic fingerprint brush tip and is brushed and displayed in one direction along the fingerprint lines on the white ceramic tile, and the fingerprint contour is photographed by the camera under the condition of sufficient light. The display effect is shown in fig. 19. The fingerprint profile can be cleanly seen from the figure.
Example 6
The difference from example 4 is that aluminum powder is used as the colorant, and the particle size of the aluminum powder is 20 microns; iron powder: pentaerythritol: aluminum powder mass ratio = 100:4:3; a silvery off-white fingerprint developing powder was prepared as in example 4.
The silvery off-white fingerprint of this embodiment is extracted with the magnetic fingerprint brush tip and is brushed and displayed in one direction along the latent fingerprint lines on a white tile, and the fingerprint profile is photographed with a camera under the condition of sufficient light. The display effect is shown in fig. 20. The fingerprint profile cannot be seen too well from the figure.
Example 7
The difference from example 4 is that copper powder is used as the colorant, and the particle size of the copper powder is 600 meshes; iron powder: pentaerythritol: copper powder mass ratio = 100:4:3; a pale red fingerprint-developing powder was obtained in the same manner as in example 4.
The light red fingerprint of this embodiment is absorbed by the magnetic fingerprint brush tip and the fingerprint outline is photographed by the camera under the condition of sufficient light along the pressed and wiped fingerprint lines on the white tile. The display effect is shown in fig. 21. The fingerprint profile can also be seen approximately from the figure.
Example 8
The difference from example 4 is that the colorant used is chromium oxide with a particle size of 400 mesh; aluminum powder: pentaerythritol: chromium oxide mass ratio = 100:4:3; otherwise, as in example 4, a green fingerprint developing powder was prepared.
The magnetic fingerprint brush tip is used for sucking the green fingerprint developing powder of the embodiment, the fingerprint contour is shot by a camera under the condition of sufficient light along the fingerprint lines on the white ceramic tile in a single direction. The display effect is shown in fig. 22. The fingerprint profile can be cleanly seen from the figure.
Example 9
The difference from example 4 is that Prussian blue is used as the colorant; aluminum powder: pentaerythritol: prussian blue mass ratio = 100:4:3; a blue fingerprint development powder was obtained in the same manner as in example 4.
The blue fingerprint developing powder of the embodiment is sucked by a magnetic fingerprint brush tip, the color of the blue fingerprint developing powder is brushed and developed on a white ceramic tile along the latent fingerprint lines in a single direction, and the fingerprint contour is shot by a camera under the condition of sufficient light. The display effect is shown in fig. 23. The fingerprint profile can be cleanly seen from the figure.
Example 10
The difference from example 4 is that ferrosilicon powder is used instead of iron powder, and ferroferric oxide, titanium oxide and aluminum oxide are used as the coloring agent; ferrosilicon powder: polyvinyl alcohol: ferroferric oxide: alumina: titanium oxide mass ratio = 100:3:1:1:1; a gray-black fingerprint developing powder was prepared in the same manner as in example 4.
The gray-black fingerprint developing powder of the embodiment is sucked by a magnetic fingerprint brush tip, the fingerprint is brushed and developed on a white ceramic tile along the latent fingerprint lines in a single direction, and the fingerprint contour is shot by a camera under the condition of sufficient light. The fingerprint display effect is shown in fig. 24. The fingerprint profile can be seen cleanly from the figure, and the scanning electron microscope and XPS images of the fingerprint powder are seen at 25 and 26.
Example 11
The difference from example 4 is that 150 μm neodymium iron boron powder is used instead of iron powder, and the coloring agent is ferroferric oxide and titanium oxide; neodymium iron boron powder: polyethylene glycol: ferroferric oxide: titanium oxide mass ratio = 100:3:2:1; a gray-black fingerprint developing powder was prepared in the same manner as in example 4.
The gray-black fingerprint developing powder of the embodiment is sucked by a magnetic fingerprint brush tip, the fingerprint is brushed and developed on a white ceramic tile along the latent fingerprint lines in a single direction, and the fingerprint contour is shot by a camera under the condition of sufficient light. The fingerprint display effect is shown in fig. 27. The fingerprint profile can be seen cleanly from the figure, and the scanning electron microscope image of the fingerprint powder is shown at 28.
For review, the fingerprint development powder of the invention has clear development on an impermeable carrier, does not block sweat pores and wheels Guo Xian, has strong adsorption force, and can still develop fingerprints after simple wiping.
The technical scheme of the invention is not limited to the specific embodiment, and all technical modifications made according to the technical scheme of the invention fall within the protection scope of the invention.
Claims (8)
1. The fingerprint developing powder is characterized by comprising the following components in percentage by weight: 92-95% of magnetic powder, 3-8% of binder and 0.5-1% of colorant; the preparation method of the fingerprint developing powder comprises the following steps:
s1, weighing magnetic powder, a binder and a colorant according to weight percentage for standby;
s2, modifying the surface of the magnetic powder: pouring the magnetic powder into a stirring device, adding citric acid solution with the concentration of 2% to the surface of the magnetic powder, starting stirring at 100-220rpm, stirring for 10-15min, stopping stirring and filtering, leaching the filter cake with absolute ethyl alcohol or methanol for more than three times, taking out the filter cake, and drying in nitrogen atmosphere;
s3, completely dissolving the binder with dichloromethane and/or methanol at room temperature, adding the modified magnetic powder for coating, and volatilizing the solvent in a rotary steaming bottle while stirring until the magnetic powder and the binder form pasty slurry;
s4, taking out the pasty slurry, pouring the pasty slurry into a stainless steel ball grinding tank after drying, grinding for 10 minutes at the rotating speed of 300-400rpm, adding a colorant, replacing the colorant with a plastic grinding ball, continuously grinding for 30 minutes at the rotating speed of 300-400rpm, and then using a 40-mesh copper mesh screen, and drying the screened material in vacuum at room temperature for 30 minutes to obtain the fingerprint showing powder.
2. The fingerprint development powder according to claim 1, characterized in that: the magnetic powder is one or more of Fe powder, co powder, ni powder, ferroferric oxide powder, ferrosilicon powder and NdFeB.
3. The fingerprint development powder according to claim 1, characterized in that: the binder is one or more of pentaerythritol, erythritol, polyvinyl alcohol, polyethylene glycol, polymethyl methacrylate and polyvinylpyrrolidone.
4. The fingerprint development powder according to claim 1, characterized in that: the colorant is one or more of nano silicon oxide, barium sulfate, aluminum oxide, boron nitride, aluminum powder, colloidal graphite, carbon nano tube, sudan red, nano ferric oxide, prussian blue, chromium oxide, indigo, glucose and ferrous oxalate.
5. The fingerprint development powder according to claim 1, characterized in that: the average particle diameter of the magnetic powder is D, and D is 80 μm and less than or equal to 250 μm.
6. The fingerprint development powder according to claim 1, characterized in that: the average molecular weight of the binder is M, and M is more than or equal to 2000 and less than or equal to 8000.
7. The fingerprint development powder according to claim 1, characterized in that: the stainless steel balls comprise large stainless steel balls and small stainless steel balls, the diameters of the large stainless steel balls are 12mm, the diameters of the small stainless steel balls are 2mm, and the mass of the large balls is 2.5-4 times that of the small balls.
8. Use of a fingerprint development powder according to claim 1, wherein the fingerprint development powder is used for fingerprint development.
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