Latent fingerprint visualization technology based on luminol electrochemiluminescence imaging

Fingerprints play an important role in forensic identification and personal identification. At the same time, they are widely used in security inspection, access control, personal authentication and other fields in daily life. Although there are many ways to show fingerprints, a simple, fast and easy-to-operate method is still needed to show fingerprints. In this paper, based on the selective spatial control of the electrochemiluminescence behavior of luminol on the electrode surface, a potential fingerprint inverse imaging technology is constructed. The effects of the type of co-reactant, applied potential and luminophore concentration on the effect of fingerprint display were investigated. The imaging method has the advantages of simplicity, speed, and no need to process the substrate or sample, and provides a new method and new idea for fingerprint visualization and electrochemical imaging technology.

In the past ten years, chemists have continuously applied various new chemical analysis techniques to fingerprint display technology. Using mass spectrometry to form chemical imaging of latent fingerprints, although the imaging technology of image separation, infrared/Raman imaging, local current imaging and immunolabel imaging, etc., the fingerprint detection has been extended from a single morphological analysis to a lower finger resolution, but Its ability to recognize foreign substances is strong, and it can detect trace amounts of drugs of abuse contaminated on fingerprints, which has very important detection value and safety significance.

At present, although there are many kinds of fingerprint visualization methods, there is still a need for a simple, fast, and easy-to-operate method for fingerprint visualization. Luminol, also known as "luminol", can react with the iron ions in the heme and hematoporphyrin ring under alkaline and oxidizing conditions to emit a light blue light. Although luminol has a specific luminescence reaction with blood, the current formula of luminol can not overcome the technical problems of foaming, line blur, weak luminous intensity and short duration, so it is still used in practice for handprint visualization. There are certain limitations.

In addition to chemiluminescence, luminol is also an important electrochemiluminescence reagent. Electrochemiluminescence is the product of the combination of electrochemical reaction and chemiluminescence. It is realized by converting electrical energy into radiant energy. It has the advantages of high sensitivity, controllable reaction, controllable time and space, and no background interference. In this study, the presence of potential fingerprints will cause the ECL activity of luminol on the electrode surface to be different. Using luminol as the ECL reaction system, by selectively controlling the generation of ECL on the electrode surface, the fingerprints carried on the electrode can be detected. Perform manifestation. It can clearly show the overall morphology and secondary structure of fingerprints, and can be used to show fingerprints on stainless steel objects.

It should be noted that the concentration of luminol has a very large impact on the image imaging of ECL, and the intensity of ECL directly depends on the concentration of the luminophore. The research surface shows that when the concentration of luminol is lower than 5mmol/L, the ECL is too weak to effectively show fingerprint lines. When the concentration of luminol reaches 5mmol/L, the fingerprint morphology begins to appear, but when the concentration is higher, the ECL is too strong and it is not conducive to the appearance of fingerprints. Therefore, the most suitable luminol concentration is 5mmol/L.