Reactions in which electrons are lost or gained are called redox reactions. They are very important in our daily lives, they are present in several technological inventions, and it is based on them that we can explain the chemistry involved in the photosynthetic lenses of eyeglasses. Sun.
It all starts with the composition of photochromic glass: when tetrahedral oxygen atoms bond with silicon, a crystalline structure of silver chloride emerges. This structure is disordered, so that there are gaps between the atoms, thus, visible light passes through this structure.
The advantages of lenses made with photochromic glass is that they do not let ultraviolet light through, they absorb this light, and an oxidation-reduction reaction between silver and chlorine ions arises. See the equation:
Ag+ + Cl- → Ass2+ + Cl-
Through this reaction, silver chloride crystals are formed, but so that the reaction does not become reversible, Cu+ ions are added. Follow the reaction:
Ass+ + Cl0 → Cu2+ + Cl-
Note that the Cu ions
But why when we go back to the dark environment the lenses clear again? Because the chloride ions present in the crystal of the photochromic glass rejoin silver ions through molecular rearrangements.
Now you know why photosensitive lenses are best for good eye health: blocking ultraviolet rays.
Do not stop now... There's more after the advertising ;)
By Líria Alves
Graduated in Chemistry
Would you like to reference this text in a school or academic work? Look:
SOUZA, Líria Alves de. "Photosensitive lenses: redox reactions"; Brazil School. Available in: https://brasilescola.uol.com.br/quimica/lentes-fotossensiveis-reacoes-oxirreducao.htm. Accessed on June 28, 2021.
