Remember the luminol reaction that emitted blue light? In fact, it can still oscillate.
remember the luminol reaction that emitted blue light? Today, I just learned that this reaction can actually make an oscillatory reaction. Let's take a look (the phenomenon positive starts at about 1:44 in the video):
Luminol reaction is a classical chemiluminescence reaction, unlike fluorescence, the source of luminescence is an excited state intermediate produced in a chemical reaction, which emits blue light when it returns to the ground state. Luminol reacts with oxidants such as hydrogen peroxide in an alkaline environment to produce luminescent intermediates, which usually require the catalysis of transition metal salts, such as iron, copper or cobalt. When it is used to detect blood, iron in the blood is used to catalyze the reaction. Reaction phenomenon of
Classical version: structural change of Luminol molecule in
in this oscillating reaction solution, a total of five components were added: Luminol, copper sulfate, hydrogen peroxide, potassium thiocyanate and sodium hydroxide. In this system, the solution only emits relatively weak light at first, but after a while, the brightness of the blue light suddenly increases and shows the phenomenon of light-dark oscillation.
the specific mechanism of this oscillatory reaction is quite complicated. I read the paper and don't seem to see the final conclusion, so I won't talk about OTZ here. The concentration of potassium thiocyanate and copper salt has the greatest influence on the period of oscillatory reaction. In the video, the solution is heated to 50 ℃, which speeds up the reaction, shortens the period, and increases the brightness of chemiluminescence. However, the experiment can be carried out at room temperature. The oscillation process can last about 20 minutes at 40 ℃.
if you are interested in understanding the specific operation of the experiment, you can refer to the amount of reagent shown in the video, or you can read this paper: https://pubs.acs.org/doi/abs/10.1021/ed082p53 Note: this kind of experiment should be carried out in a professional laboratory.
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