When examining blood stains, luminol reacts with hemoglobin (a protein in hemoglobin that transports oxygen), which is a yellow crystal or beige powder at room temperature, and is a relatively stable chemical reagent. Pen × fun × Pavilion www. ｂｉｑｕｇｅ。 In forensic science, the luminol reaction, also known as the aminophenyl-calloyl reaction, can identify blood stains that have been scrubbed and have been used for a long time. Biologically, luminol is used to detect the presence of copper, iron, and cyanide in cells.

Luminol was synthesized in 1853. In 1928, chemists first discovered that this compound had a wonderful property of emitting blue light when it was oxidized. A few years later, someone came up with the idea of using this property to detect blood stains. This test is extremely sensitive, detecting only one part per million of blood, and even a small drop of blood can be detected in a large tank of water, which shows how difficult it is for criminals to clean the scene.

The luminol reaction is actually divided into two steps:

1. Hydrogen peroxide decomposes into oxygen and water;

2. Oxygen and luminol undergo redox reactions to form excited compounds. Due to the instability of the compound in the excited state, in the process of electron transition back to the ground state, photons are released, the wavelength of which is in the wavelength range of blue light. Simply put, luminol is oxidized and emits blue light.

The following are the various speculations I collected according to the principle, without any experimental verification, so if friends are caught after committing the crime, I am not responsible, since the reaction is based on the redox reaction, as a knowledgeable and educated promising youth, you will think of using oxidants (such as 84 disinfectant, bleach, hydrogen peroxide) to treat the site, the oxidant will greatly enhance the background fluorescence, thus covering up the real bloodstains, However, if a trained inspector encounters such a large fluorescence reaction, there are two ways to do so:

1. Let the site dry for a few days, and the interfering effect of bleach will disappear, and the blood stains will allow luminol to shine even after many years.

2. According to the difference between the two fluorescences, perform background removal analysis. Because blood luminescence is a continuous catalytic and continuous oxidation process, it is continuous luminescence; Other oxidants react with luminol almost instantaneously, so they emit strong fluorescence instantaneously, and the background effect can be removed by analyzing photos at different exposure times

So as a literate intellectual youth, so it may be so easy to be defeated, in order to produce sustainable interference, we just need to simulate the principle of blood testing, get iron ions everywhere and the like, theoretically to the chemical market is easy to get hydrochloric acid Shenma, and then throw a piece of iron into it, there will be ferrous ion solution, spray to the scene, perfect interference reaction, of course, excrement can actually occur luminol reaction, and there are a lot of materials in the toilet can be used, hahaha, If you don't think the environment is harsh! It should be noted that the above two methods are to interfere with the results of the investigation by enhancing the background fluorescence, in other words, the police will find that there is light everywhere, if the crime is committed in your living room or something, you will have to explain it to the millet family.

And it was found that after the bloodstain was treated by luminol, the genetic material DNA contained in it was not destroyed, and it could be extracted from it for identification.

Therefore, it is best not to think about the crime of murder, because according to the current investigation technology, there is basically no mystery that cannot be solved.