CN106859659B - Preparation of cobalt/aluminum composite blue nano powder and fingerprint display method thereof - Google Patents
Preparation of cobalt/aluminum composite blue nano powder and fingerprint display method thereof Download PDFInfo
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- CN106859659B CN106859659B CN201710079088.4A CN201710079088A CN106859659B CN 106859659 B CN106859659 B CN 106859659B CN 201710079088 A CN201710079088 A CN 201710079088A CN 106859659 B CN106859659 B CN 106859659B
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- 229910052782 aluminium Inorganic materials 0.000 title claims abstract description 49
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 title claims abstract description 49
- 229910017052 cobalt Inorganic materials 0.000 title claims abstract description 49
- 239000010941 cobalt Substances 0.000 title claims abstract description 49
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 title claims abstract description 49
- 238000000034 method Methods 0.000 title claims abstract description 45
- 239000002131 composite material Substances 0.000 title claims abstract description 40
- 239000011858 nanopowder Substances 0.000 title claims abstract description 40
- 238000002360 preparation method Methods 0.000 title claims abstract description 13
- 239000000843 powder Substances 0.000 claims abstract description 53
- 230000000694 effects Effects 0.000 claims abstract description 29
- 239000011259 mixed solution Substances 0.000 claims abstract description 13
- 238000005507 spraying Methods 0.000 claims abstract description 13
- 239000000725 suspension Substances 0.000 claims abstract description 13
- 238000005406 washing Methods 0.000 claims abstract description 13
- 239000007788 liquid Substances 0.000 claims abstract description 8
- 238000000967 suction filtration Methods 0.000 claims abstract description 7
- 238000001354 calcination Methods 0.000 claims abstract description 4
- 238000006243 chemical reaction Methods 0.000 claims abstract description 4
- 238000001035 drying Methods 0.000 claims abstract description 4
- 238000001556 precipitation Methods 0.000 claims abstract description 4
- 238000010017 direct printing Methods 0.000 claims abstract 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 18
- 239000008367 deionised water Substances 0.000 claims description 12
- 229910021641 deionized water Inorganic materials 0.000 claims description 12
- DBMJMQXJHONAFJ-UHFFFAOYSA-M Sodium laurylsulphate Chemical compound [Na+].CCCCCCCCCCCCOS([O-])(=O)=O DBMJMQXJHONAFJ-UHFFFAOYSA-M 0.000 claims description 9
- 239000002245 particle Substances 0.000 claims description 8
- 239000000243 solution Substances 0.000 claims description 7
- 238000003756 stirring Methods 0.000 claims description 7
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 6
- 239000008280 blood Substances 0.000 claims description 6
- 210000004369 blood Anatomy 0.000 claims description 6
- 238000007598 dipping method Methods 0.000 claims description 6
- 239000000203 mixture Substances 0.000 claims description 6
- 239000002244 precipitate Substances 0.000 claims description 6
- 239000004094 surface-active agent Substances 0.000 claims description 6
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 claims description 5
- 239000004202 carbamide Substances 0.000 claims description 5
- 229910021645 metal ion Inorganic materials 0.000 claims description 5
- XNDZQQSKSQTQQD-UHFFFAOYSA-N 3-methylcyclohex-2-en-1-ol Chemical compound CC1=CC(O)CCC1 XNDZQQSKSQTQQD-UHFFFAOYSA-N 0.000 claims description 3
- 238000007664 blowing Methods 0.000 claims description 3
- 230000003139 buffering effect Effects 0.000 claims description 3
- QGUAJWGNOXCYJF-UHFFFAOYSA-N cobalt dinitrate hexahydrate Chemical compound O.O.O.O.O.O.[Co+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O QGUAJWGNOXCYJF-UHFFFAOYSA-N 0.000 claims description 3
- 238000001816 cooling Methods 0.000 claims description 3
- 238000007667 floating Methods 0.000 claims description 3
- 238000010438 heat treatment Methods 0.000 claims description 3
- 229940113116 polyethylene glycol 1000 Drugs 0.000 claims description 3
- 239000012716 precipitator Substances 0.000 claims description 3
- 239000007921 spray Substances 0.000 claims description 3
- 239000006228 supernatant Substances 0.000 claims description 3
- 238000010408 sweeping Methods 0.000 claims description 3
- 238000001291 vacuum drying Methods 0.000 claims description 3
- 238000005303 weighing Methods 0.000 claims description 3
- 238000004448 titration Methods 0.000 claims description 2
- 238000006748 scratching Methods 0.000 claims 1
- 230000002393 scratching effect Effects 0.000 claims 1
- 230000009286 beneficial effect Effects 0.000 abstract description 2
- 238000010586 diagram Methods 0.000 description 10
- 230000001680 brushing effect Effects 0.000 description 4
- 239000003153 chemical reaction reagent Substances 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 239000006104 solid solution Substances 0.000 description 4
- 210000004243 sweat Anatomy 0.000 description 4
- 150000001875 compounds Chemical class 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 230000007613 environmental effect Effects 0.000 description 3
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 3
- 229910052761 rare earth metal Inorganic materials 0.000 description 3
- 150000002910 rare earth metals Chemical class 0.000 description 3
- 239000004054 semiconductor nanocrystal Substances 0.000 description 3
- 102000001554 Hemoglobins Human genes 0.000 description 2
- 108010054147 Hemoglobins Proteins 0.000 description 2
- 238000002441 X-ray diffraction Methods 0.000 description 2
- 238000000921 elemental analysis Methods 0.000 description 2
- 239000011521 glass Substances 0.000 description 2
- 229910052737 gold Inorganic materials 0.000 description 2
- 239000010931 gold Substances 0.000 description 2
- 239000004519 grease Substances 0.000 description 2
- 238000011835 investigation Methods 0.000 description 2
- 239000002649 leather substitute Substances 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 238000001000 micrograph Methods 0.000 description 2
- 239000002086 nanomaterial Substances 0.000 description 2
- 239000002985 plastic film Substances 0.000 description 2
- 239000002096 quantum dot Substances 0.000 description 2
- 230000035945 sensitivity Effects 0.000 description 2
- 229910052709 silver Inorganic materials 0.000 description 2
- 239000004332 silver Substances 0.000 description 2
- 238000005245 sintering Methods 0.000 description 2
- 231100000331 toxic Toxicity 0.000 description 2
- 230000002588 toxic effect Effects 0.000 description 2
- 239000002023 wood Substances 0.000 description 2
- 229910019114 CoAl2O4 Inorganic materials 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 239000006247 magnetic powder Substances 0.000 description 1
- 210000001595 mastoid Anatomy 0.000 description 1
- 229910000510 noble metal Inorganic materials 0.000 description 1
- 239000012074 organic phase Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 239000010970 precious metal Substances 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
- 229910052596 spinel Inorganic materials 0.000 description 1
- 239000011029 spinel Substances 0.000 description 1
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/117—Identification of persons
- A61B5/1171—Identification of persons based on the shapes or appearances of their bodies or parts thereof
- A61B5/1172—Identification of persons based on the shapes or appearances of their bodies or parts thereof using fingerprinting
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- Life Sciences & Earth Sciences (AREA)
- Health & Medical Sciences (AREA)
- Medical Informatics (AREA)
- Biophysics (AREA)
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- Biomedical Technology (AREA)
- Heart & Thoracic Surgery (AREA)
- Physics & Mathematics (AREA)
- Molecular Biology (AREA)
- Surgery (AREA)
- Animal Behavior & Ethology (AREA)
- General Health & Medical Sciences (AREA)
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- Measurement Of The Respiration, Hearing Ability, Form, And Blood Characteristics Of Living Organisms (AREA)
Abstract
The invention provides a preparation method of cobalt/aluminum composite blue nano powder and a fingerprint display method thereof. The preparation method comprises the following steps: s1, preparing a cobalt and aluminum mixed solution; s2, carrying out precipitation reaction; s3, suction filtration and washing; s4, drying in an oven; s5, and calcining in a muffle furnace. The fingerprint display method comprises a direct printing display method, a powder spraying shaking display method and a suspension liquid spraying display method. The invention has the following beneficial technical effects: the effect of showing the old handprints and the handprints on the permeable objects is good; the product has the characteristics of green and environment protection, and has no damage to operators; the preparation method is simple and easy to implement and is easy to popularize and apply.
Description
Technical Field
The invention relates to the technical field of public security criminal technology fingerprint identification, in particular to a preparation method of cobalt/aluminum composite blue nano powder and a fingerprint display method thereof.
Background
The fingerprint is a reflection image of the surface structure of a contact surface left on the surface of an object when a human hand contacts the object; the human finger print has the characteristics that people are different and basically unchanged throughout the life. Therefore, the person can be identified directly from the handprint. The handprints can play an important role in providing investigation clues and providing case solving and judging evidences in investigation and case solving and judging. Therefore, the latent fingerprint showing technology is the premise and guarantee that crimes are revealed and confirmed by using fingerprints. At present, the powder method and the small particle suspension method become the most effective method for displaying fingerprints on site due to simple operation and simple preparation. Then, the currently used powders, such as gold powder and magnetic powder, cannot be sufficiently combined with the fingerprint material due to their large particle size, and thus have poor effects on old fingerprints and fingerprints on permeable objects. In order to improve the sensitivity of fingerprint detection, researchers utilize some semiconductor nanocrystals (quantum dots), rare earth materials and the like as fluorescent reagents to display latent fingerprints, and although good effects are obtained, the reagents are toxic, complex equipment is needed, the operation procedure is complex, and the reagents are not convenient for popularization in basic technical departments. Some reports also report that the precious metal nano materials such as gold and silver can improve the sensitivity of the biological imprinting, but the method has high cost and is limited to the laboratory stage at present.
Therefore, the prior fingerprint showing technology has the following problems:
1. the traditional powder method has poor effect on old fingerprints and fingerprints on permeable objects.
2. Semiconductor nanocrystals (quantum dots) or rare earth materials are toxic, and require complex equipment, so the operation procedure is complicated, and the popularization of the semiconductor nanocrystals or rare earth materials in basic technical departments is inconvenient.
3. The cost of noble metal nano materials such as gold, silver and the like is high, and the method is limited to a laboratory stage at present.
Disclosure of Invention
The invention provides a preparation method of cobalt/aluminum composite blue nano powder and a fingerprint display method thereof, aiming at solving the problem of poor fingerprint display effect on old fingerprints and permeable objects in the conventional powder method.
The preparation method of the cobalt/aluminum composite blue nano powder comprises the following steps:
s1, preparing a cobalt and aluminum mixed solution: respectively weighing 2.91g of cobalt nitrate hexahydrate and 7.5g of aluminum nitrate nonahydrate, adding into 100mL of deionized water, and preparing into 0.3mol/L mixed solution;
s2, precipitation reaction: putting the mixed solution obtained in the step S1 into a constant-temperature water bath kettle, violently stirring at 95 ℃, and simultaneously, slowly dropwise adding precipitator urea into the reactor through a constant-pressure funnel; continuously titrating until the pH value of supernatant reaches 9, completely reacting metal ions in the solution, and stopping stirring;
s3, suction filtration and washing: carrying out suction filtration on the mixture obtained in the step S2, washing the blue precipitate by using deionized water, repeatedly washing for 10-20 times, and then washing by using ethanol;
s4, drying in an oven: putting the washed precipitate into a vacuum drying oven, and keeping the temperature at 100 ℃ for 2 h;
s5, muffle furnace calcination: and (4) putting the powder obtained in the step (S4) into a muffle furnace, heating the powder to 1000 ℃ from room temperature, preserving the heat for 1h, and then cooling the powder to room temperature to obtain the cobalt/aluminum composite blue nano powder.
Further, in the step S2, before dropping the precipitant urea, 0.177g of the surfactant polyethylene glycol 1000 is added to the mixed solution obtained in the step S1.
Further, in the step S2, the time for dropping the precipitant urea is 1 h.
The invention also comprises a fingerprint display method adopting the cobalt/aluminum composite blue nano powder, which comprises a direct brushing display method, a powder scattering shaking display method and a suspension liquid spraying display method.
Further, the direct brush display method comprises the steps of dipping a proper amount of cobalt/aluminum composite blue nano powder into a fingerprint brush, sweeping the fingerprint brush from bottom to top along the vertical surface of an object to enable the powder to be adhered to the surface of the object, bouncing off the powder on the fingerprint brush after lines are seen, and brushing the powder along one direction along the flowing direction of the lines by the fingerprint brush until the lines are clear.
Further, the powder scattering and shaking display method comprises dipping a proper amount of powder by a fingerprint brush, and flicking a brush handle to cover the powder on an object surface; then two opposite sides of the object are held by two hands to shake the object up and down, the powder scratches the object surface suspected of having the handprint, the handprint can be displayed, the redundant powder is taken back into the container, the back of the object is flicked lightly, and the powder floating in the small furrow is shaken off, so that the method is suitable for permeable or semi-permeable objects such as paper, natural color wood and the like.
Further, the suspension liquid spraying method comprises the following steps: the method comprises the following steps:
s1, preparing a suspension: firstly, 0.5g of surfactant Sodium Dodecyl Sulfate (SDS) is dissolved in 50 mL of deionized water, after the SDS is completely dissolved, 5g of cobalt/aluminum composite nano powder and 50 mL of deionized water are added, and the mixture is stirred until the powder is uniformly dispersed and does not delaminate;
s2, spray display: and (3) spraying and displaying at a position 20cm away from the blood latent fingerprint by using a spraying bottle filled with the suspension liquid to enable the solution to be fully contacted with the sample, after 30s, buffering by using clear water, and then observing the displayed effect, and repeating the operation if the effect is not good until the ideal effect is displayed, and then blowing the sample by using an electric blower to dry.
The cobalt/aluminum composite nano powder prepared by the method has certain dispersibility in an organic phase and stronger bonding capability with fingerprint residues; the particle size is small, the particle size is in a nanometer level, and the adhesion with the fingerprint residues is good; and the compound has high selectivity, and only has adhesion with grease or hemoglobin on the fingerprint lines, so that the effect of background interference of fingerprint images can be reduced, and the contrast is enhanced. Although the powder consists of metal elements such as cobalt, aluminum and the like, the metal ions solid solution is formed by sintering the cobalt and the aluminum at high temperature, and the solid solution cannot be precipitated at normal temperature and normal pressure, so that the powder has the characteristics of environmental protection and no damage to operators. Therefore, the invention has the following beneficial technical effects:
1. has good effect on old fingerprints and fingerprints on permeable objects.
2. The product has the characteristics of green and environmental protection and has no damage to operators.
3. The preparation method is simple and easy to implement and is easy to popularize and apply.
Drawings
FIG. 1 is an X-ray diffraction pattern of the cobalt/aluminum composite nanopowder prepared in the present invention.
FIG. 2 is a scanning electron microscope image of the cobalt/aluminum composite nanopowder prepared in the present invention.
FIG. 3 is an elemental analysis diagram of the cobalt/aluminum composite nanopowder prepared by the present invention.
FIG. 4 is a diagram showing the effect of the cobalt/aluminum composite nanopowder prepared by the present invention on sweat latent fingerprints on glass.
FIG. 5 is a diagram showing the effect of the cobalt/aluminum composite nanopowder prepared by the invention on sweat latent fingerprints on paper.
FIG. 6 is a diagram showing the effect of the cobalt/aluminum composite nanopowder prepared by the present invention on the blood latent fingerprint on the plastic sheet.
FIG. 7 is a diagram showing the effect of the cobalt/aluminum composite nanopowder prepared by the present invention on the appearance of latent fingerprint on artificial leather.
Detailed Description
FIG. 1 is the X-ray diffraction spectrum of the cobalt/aluminum composite nanopowder prepared in the present invention, which shows the main crystal face characteristic diffraction peak and CoAl2O4The standard peaks of (a) are substantially identical, indicating that the powder produced is of a typical spinel structure.
FIG. 2 is a scanning electron microscope image of the cobalt/aluminum composite nanopowder prepared in the present invention. The particle size of the prepared powder is mainly about 20-30 nanometers, and the dispersibility is good.
FIG. 3 is an elemental analysis diagram of the cobalt/aluminum composite nanopowder prepared by the present invention. The powder is composed of three elements of cobalt, aluminum and oxygen, and has high component purity and no impurities.
Fig. 4 is a diagram showing the effect of cobalt/aluminum composite nano powder prepared by the present invention on sweat latent fingerprints on glass, fig. 5 is a diagram showing the effect of cobalt/aluminum composite nano powder prepared by the present invention on sweat latent fingerprints on paper, fig. 6 is a diagram showing the effect of cobalt/aluminum composite nano powder prepared by the present invention on blood latent fingerprints on plastic sheets, and fig. 7 is a diagram showing the effect of cobalt/aluminum composite nano powder prepared by the present invention on blood latent fingerprints on artificial leather. As can be seen from fig. 4-7: the cobalt/aluminum composite nano powder prepared by the invention has good effect of displaying old fingerprints, has smooth fingerprint mastoid lines, has prominent detail characteristics such as small bars and small dots, and is superior to the traditional powder display reagent.
Example 1:
the preparation method of the cobalt/aluminum composite blue nano powder comprises the following steps:
s1, preparing a cobalt and aluminum mixed solution: respectively weighing 2.91g of cobalt nitrate hexahydrate and 7.5g of aluminum nitrate nonahydrate, adding into 100mL of deionized water, and preparing into 0.3mol/L mixed solution;
s2, precipitation reaction: putting the mixed solution obtained in the step S1 into a constant-temperature water bath kettle, adding 0.177g of surfactant polyethylene glycol 1000 into the mixed solution, violently stirring at 95 ℃, meanwhile, slowly dripping precipitator urea into the reactor through a constant-pressure funnel, wherein the titration time is 1h, the pH value of supernatant reaches 9, the metal ions in the solution completely react, and stopping stirring;
s3, suction filtration and washing: and (5) carrying out suction filtration on the mixture obtained in the step S2, washing the blue precipitate by using deionized water, repeatedly washing for 10-20 times, and then washing by using ethanol.
S4, drying in an oven: putting the washed precipitate into a vacuum drying oven, and keeping the temperature at 100 ℃ for 2 h;
s5, muffle furnace calcination: and (4) putting the powder obtained in the step (S4) into a muffle furnace, heating the powder to 1000 ℃ from room temperature, preserving the heat for 1h, and then cooling the powder to room temperature to obtain the cobalt/aluminum composite blue nano powder.
Example 2:
the cobalt/aluminum composite blue nano powder prepared by the invention is used for displaying potential fingerprints on smooth impermeable objects:
direct brushing method: dipping a proper amount of powder by using a fingerprint brush, sweeping from bottom to top along the vertical roof to ensure that the powder is adhered to the object surface, bouncing off the powder on the fingerprint brush after the lines are seen, and brushing along one direction along the flowing direction of the lines until the lines are clear.
Example 3:
the cobalt/aluminum composite blue nano powder prepared by the invention is used for showing potential fingerprints on permeable or semi-permeable objects such as paper, natural color wood and the like:
powder scattering and shaking display method: dipping a proper amount of powder by using a fingerprint brush, and flicking a brush handle to cover the powder on the surface of an object; then two hands hold two opposite sides of the object to shake the object up and down, and the powder scratches the object surface suspected of having the handprint, so that the handprint can be displayed. And taking the redundant powder back to the container, lightly flicking the back of the object, and shaking off the powder floating in the small furrows.
Example 4:
the cobalt/aluminum composite blue nano powder prepared by the invention is used for a suspension liquid spraying method: the method comprises the following steps:
s1, preparing a suspension: firstly, 0.5g of surfactant Sodium Dodecyl Sulfate (SDS) is dissolved in 50 mL of deionized water, after the SDS is completely dissolved by stirring, 5g of cobalt/aluminum composite nano powder and 50 mL of deionized water are added, and the mixture is stirred until the powder is uniformly dispersed and does not delaminate.
S2, spray display: and (3) spraying and displaying at a position 20cm away from the blood latent fingerprint by using a spraying bottle filled with the suspension liquid to enable the solution to be fully contacted with the sample, after 30s, buffering by using clear water, and then observing the displayed effect, and repeating the operation if the effect is not good until the ideal effect is displayed, and then blowing the sample by using an electric blower to dry.
The cobalt/aluminum composite nano powder prepared by the method can quickly and efficiently show old fingerprints. The preparation method has simple and easy process; the particle size is small, the particle size is in a nanometer level, and the adhesion with the fingerprint residues is good; and the compound has high selectivity, only has adhesion with grease or hemoglobin on the fingerprint lines, can reduce the background interference effect of fingerprint images and enhance the contrast, so the compound has good effect on the appearance of old fingerprints. Although the powder consists of metal elements such as cobalt, aluminum and the like, the metal ions solid solution is formed by sintering the cobalt and the aluminum at high temperature, and the solid solution cannot be precipitated at normal temperature and normal pressure, so that the powder has the characteristics of environmental protection and no damage to operators.
Finally, it is also noted that the above-mentioned lists merely illustrate a few specific embodiments of the invention. It should be understood that the present invention is not limited to the above embodiments, and all technical solutions that can be derived or suggested directly from the disclosure of the present invention by those skilled in the art should be considered as falling within the scope of the present invention.
Claims (4)
1. A fingerprint display method is characterized in that cobalt/aluminum composite blue nano powder is adopted for fingerprint display, and the fingerprint display method comprises a direct printing display method, a powder scattering shaking display method and a suspension spraying display method, and the preparation method of the cobalt/aluminum composite blue nano powder comprises the following steps:
s1, preparing a cobalt and aluminum mixed solution: respectively weighing 2.91g of cobalt nitrate hexahydrate and 7.5g of aluminum nitrate nonahydrate, adding into 100mL of deionized water, and preparing into 0.3mol/L mixed solution;
s2, precipitation reaction: putting the mixed solution obtained in the step S1 into a constant-temperature water bath kettle, adding 0.177g of surfactant polyethylene glycol 1000 into the mixed solution, violently stirring at 95 ℃, and simultaneously, slowly dropwise adding precipitator urea into a reactor through a constant-pressure funnel, wherein the titration time is 1 h; continuously titrating until the pH value of supernatant reaches 9, completely reacting metal ions in the solution, and stopping stirring;
s3, suction filtration and washing: carrying out suction filtration on the mixture obtained in the step S2, washing the blue precipitate by using deionized water, repeatedly washing for 10-20 times, and then washing by using ethanol;
s4, drying in an oven: putting the washed precipitate into a vacuum drying oven, and keeping the temperature at 100 ℃ for 2 h;
s5, muffle furnace calcination: and (4) putting the powder obtained in the step (S4) into a muffle furnace, heating the powder to 1000 ℃ from room temperature, preserving the heat for 1h, and then cooling the powder to room temperature to obtain the cobalt/aluminum composite blue nano powder with the particle size of 20-30 nanometers.
2. The fingerprint developing method according to claim 1, wherein said direct brush developing method comprises dipping an appropriate amount of cobalt/aluminum composite blue nano powder with a fingerprint brush, sweeping the cobalt/aluminum composite blue nano powder along a vertical surface of an object from bottom to top to adhere the cobalt/aluminum composite blue nano powder to the surface of the object, flicking the powder on the brush after the streak lines are seen, and developing the powder in one direction along the flow direction of the streak lines with the brush until the streak lines are clear, and the method is suitable for developing latent fingerprints on smooth non-permeable objects.
3. A fingerprint developing method according to claim 1, wherein: the powder scattering and shaking display method comprises dipping appropriate amount of powder with a fingerprint brush, and flicking a brush handle to cover the powder on the object surface; then holding two opposite sides of the object with two hands to shake the object up and down, scratching the powder on the object surface suspected with the handprint to show the handprint, withdrawing the redundant powder into a container, lightly flicking the back of the object to shake off the powder floating in the small furrow, and the method is suitable for permeable or semi-permeable objects.
4. A fingerprint developing method according to claim 1, wherein: the suspension liquid spraying method comprises the following steps: the method comprises the following steps:
s1, preparing a suspension: firstly, 0.5g of surfactant Sodium Dodecyl Sulfate (SDS) is dissolved in 50 mL of deionized water, after the SDS is completely dissolved, 5g of cobalt/aluminum composite nano powder and 50 mL of deionized water are added, and the mixture is stirred until the powder is uniformly dispersed and does not delaminate;
s2, spray display: and (3) spraying and displaying at a position 20cm away from the blood latent fingerprint by using a spraying bottle filled with the suspension liquid to enable the solution to be fully contacted with the sample, after 30s, buffering by using clear water, and then observing the displayed effect, and repeating the operation if the effect is not good until the ideal effect is displayed, and then blowing the sample by using an electric blower to dry.
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