Method for latent fingerprint manifestation by magnetic fluorescent silicon dioxide

A technology of silica and latent fingerprints, applied in the field of detection, to achieve the effect of safe use, low cost, and no side effects

Inactive Publication Date: 2010-04-07
NORTHEAST NORMAL UNIVERSITY
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, fingerprints that appear at crime scenes are often late

Method used

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  • Method for latent fingerprint manifestation by magnetic fluorescent silicon dioxide
  • Method for latent fingerprint manifestation by magnetic fluorescent silicon dioxide
  • Method for latent fingerprint manifestation by magnetic fluorescent silicon dioxide

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0028] Magnetic ferroferric oxide (Fe 3 o 4 ) Synthesis of nanopowder:

[0029] FeCl 2 4H 2 O, FeCl 3 ·6H 2 O is made into a mixed solution, in which FeCl 2 4H 2 O is 0.12mol / L, FeCl 3 ·6H 2 O is 0.2mol / L, make 160ml mixed solution, stir evenly, then heat to 80°C, and keep constant temperature, dilute 1ml concentrated HCl three times and add it dropwise quickly to the mixed solution to make the solution pH=6.5, then slowly Add dropwise NaOH with a mass fraction of 20%, adjust the pH to 11, react for 3 hours, cool to room temperature, use a strong magnet to settle and separate to remove impurities, wash with distilled water and repeat 4 times until pH = 7, then vacuum dry, The obtained magnetic Fe3O4 nanometer powder can be directly used for the visualization of latent fingerprints.

[0030] When in use, use a magnetic brush to pick up the magnetic powder, and the powder will form a "magnetic powder ear" under the action of the magnetic force. Use the tip of the powde...

Embodiment 2

[0032] Preparation of magnetic silica microsphere powder: first Fe 3 o 4 The nano powder is ultrasonically dispersed into a mixed solution of water and ethanol with a volume ratio of 4:1 according to the mass volume ratio of 0.3%, and 6ml of tetraethoxysilane TEOS is added to 25ml of ethanol solution to prepare Solution 1, 10ml of ammonia water, 20ml of ethanol, 5ml of Fe 3 o 4A mixture of water and ethanol is prepared as solution 2. At room temperature, the two solutions are mixed rapidly under fast electric stirring. After 20 hours of reaction, the obtained product is separated by sedimentation with a strong magnet to remove impurities, washed with secondary water, and dried , the magnetic silica microsphere powder with dark gray core-shell structure is obtained.

[0033] When in use, use a magnetic brush to pick up the magnetic powder, and the powder will form a "magnetic powder ear" under the action of the magnetic force. Use the tip of the powder ear to lightly brush t...

Embodiment 3

[0035] Preparation of magnetic fluorescent silica nanopowder:

[0036] First, a certain amount of Fe 3 o 4 The nanometer powder is ultrasonically dispersed into a mixed solution of water and ethanol with a volume ratio of 4:1 at a mass volume ratio of 0.5%, to obtain a mixture for use.

[0037] The microemulsion is composed of the following reagents: at room temperature, under magnetic stirring, 7.5ml of cyclohexane, 1.8ml of n-hexanol, and 1.8ml of Triton X-100 are mixed, and then 0.5ml of 20mM 1,10-phenanthrole is added Aqueous solution of ruthenium phosphate, 0.1 ml of ethyl orthosilicate, mixed and stirred for 20 minutes, then added 70 μl of ammonia water with a mass fraction of 25%, and the mixed solution was stirred rapidly, and after reacting for 24 hours, an equal volume of acetone was added to break the emulsion, and the obtained The product is separated by precipitation with a strong magnet to remove impurities, washed with secondary water, and dried to obtain a ma...

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Abstract

The invention belongs to the technical field of detection, and particularly relates to a method for manifesting latent fingerprints. The invention provides the method for manifesting the latent fingerprints. A magnetic brush is used to attract magnetic powder; the powder forms a 'magnetic powder ear' under the action of magnetic force; and the latent fingerprints on the surfaces of A4 paper, sheet glass, plastic bottles, pop-top cans, sheet copper, aluminum foils, tables or experiment tables can be manifested by using the tip of the powder ear to slightly brush various object surfaces printed with the latent fingerprints. The method is based on magnetic ferroferric oxide nano-powder and utilizes an phase reversal microemulsion polymerization method to prepare fluorescent magnetic silica gel spheres; and the method jointly coats magnetic granular ferroferric oxide and dye molecules in silicon dioxide microspheres by utilizing the hydrolysis of TEOS under alkaline conditions to perform one-step synthesis of magnetic silica monodisperse gel spheres and dye-doped magnetic fluorescent silica gel spheres to obtain magnetic fluorescent multi-functional powder, can be applied to more conditions and ranges, and has simple operation and no toxic or side effect.

Description

technical field [0001] The invention belongs to the technical field of detection, and in particular relates to a method for displaying latent fingerprints. Background technique [0002] Fingerprints that remain unchanged for life refer to the type, specific shape, shape, quantity, and position of the papillae of the finger from the time when the fingerprint is formed at 6 months of the fetus to the time when the papillary dermis rots after death. The sum of features constituted by the and interrelationships is always constant. The lifelong invariance of fingerprints has the basis of molecular genetics, histology and physiology. Based on this, fingerprints were once recognized as "the first evidence" by the judicial circle. Although the emergence of DNA technology in the later stage has challenged the status of fingerprint identification, due to the high cost of DNA testing, long time-consuming, easy contamination of test materials and the incomplete establishment of an aut...

Claims

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Application Information

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IPC IPC(8): A61B5/117G06K9/00C01G49/08C01B33/12A61B5/1172
Inventor 柴芳苏忠民王春刚马占芳王婷婷
Owner NORTHEAST NORMAL UNIVERSITY
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