Fireflies and glow sticks are common things in life that can emit light, so are their luminous principles the same?
Let's first look at the principle of fireflies' luminescence. Fireflies are small beetles belonging to the family Coleoptera. There are specialized light-emitting cells in the tail of fireflies, and there are two types of chemicals in the glowing cells: fluorescein and luciferase. Under the action of luciferase, ATP, oxygen and other substances, fluorescein undergoes a chemical reaction to generate oxidized fluorescein in the excited state, and when the electrons in oxidized fluorescein transition from a high-energy excited state to a low-energy ground state, energy is released, and the energy is converted into light energy, which produces fluorescence.
The detailed mechanism of the formation of oxidized fluorescein is as follows: in the first step, under the catalysis of luciferase, luciferin and ATP form purine adenosine nucleic acid fluorescein, and in the second step, due to the electron-absorbing action of carbonyl, the α-H of purine adenosine nucleic acid fluorescein has a certain acidity, loses protons under the action of alkaline substances in the system, and forms carbon negative ions at the α position. In the third step, carbon anions form peroxyaniedions through a single-electron transfer mechanism. In the fourth step, the peroxy ions undergo a nucleophilic reaction with the carbonyl group, and the adenine nucleotide (AMP) leaves to form dioxetylone. In the fifth step, the unstable dioxanebutanone decomposes, releasing carbon dioxide and forming fluorescein oxide.
Notice the dioxanebutone (red tetracyclic ring)!
In simple terms, the fluorescein in the firefly's body converts the energy into light energy through chemical reactions, resulting in fluorescence. There is no unprovoked love in the world, no unprovoked hate, and no energy generated out of thin air for no reason. From the perspective of energy utilization, fireflies produce fluorescence by consuming their own energy, so it is required that the luminescence has a high efficiency and cannot produce a lot of heat (this type of light is called cold light), otherwise the fireflies will quickly become "roasted whole insects".
Let's take a look at the luminescence principle of glow sticks. Glow sticks, commonly in the shape of long strips, the outer layer is packaged in polyethylene (plastic), built-in a glass tube sandwich, the inner and outer liquids of the sandwich are loaded with different chemicals.
The chemicals in glow sticks are mainly composed of three substances: peroxides, ester compounds, and fluorescent dyes. The glass tube sandwich is filled with peroxides such as hydrogen peroxide, and the liquid outside the sandwich is ester compounds (mostly oxalates and phthalates) and fluorescent dyes.
When the glow stick is bent, beaten, kneaded and other operations, the inner glass tube interlayer is broken, and the hydrogen peroxide inside is in contact with the outside oxalate to undergo a chemical reaction, and the energy generated by the reaction is transmitted to the fluorescent dye, and the fluorescent dye can emit colorful fluorescence.
The detailed mechanism of the fluorescence reaction is as follows: taking diphenol oxalate and hydrogen peroxide as an example, diphenol oxalate is hydroxide to form phenol and dioxacyclobutadione (peroxide ester), dioxetyl butanone is unstable, decomposes to form carbon dioxide, and the energy generated by the reaction is transmitted to the fluorescent dye, and the dye absorbs the energy and emits fluorescence.
Therefore, glow sticks are fluorescent dyes that use the energy generated by chemical reactions of other substances to produce fluorescence, while fireflies are fluorescein that produces oxidized glowin in an excited state through chemical reactions, converting the energy in the fireflies (that is, the energy contained in ATP) into light energy to produce fluorescence.
Let's compare the reaction equations of the two reactions:
We can see that the intermediates of both reactions contain a dioxa tetracyclic ring! This quaternary ring is unstable, easily decomposes to form carbon dioxide, and converts chemical energy to light energy by oxidation of luciferin or dyes. From this point of view, fireflies and glow sticks are more or less related, and the chemistry in the bones is highly similar, maybe five hundred years ago it was one! Their relationship is probably similar to that of bats and radar.