Copper oxide: The mystery behind the changing color

Copper oxide is an important inorganic compound, and there are rich chemical principles behind its color change. Pure copper oxide usually appears black due to the strong absorption of visible light by its crystal structure. However, when the particle size of copper oxide is reduced to the nanometer level, the surface plasmon resonance effect will cause a significant change in color, showing different colors such as red and yellow.
This color change is due to the quantum size effect. When the size of copper oxide particles is reduced to the nanometer level, the movement of electrons is limited, the energy level is split, and the optical properties are changed. At the same time, nano copper oxide has a larger specific surface area, the proportion of surface atoms increases significantly, and the electronic states of these surface atoms are different from those of the internal atoms, which further affects its optical properties.
The color change of copper oxide not only has theoretical significance, but also has important value in practical application. In the field of catalysis, different colors of copper oxide nanomaterials show unique catalytic activity, which can be used in organic synthesis, environmental treatment and other processes. In the field of optoelectronics, the special optical properties of nano copper oxide make it an ideal material for solar cells, photodetectors and other devices. In the biomedical field, specific colored copper oxide nanoparticles can be used for biomarkers, drug delivery and other applications.
With the development of nanotechnology, researchers have been able to precisely regulate the size and morphology of copper oxide to obtain the desired color and properties. This controllability opens up broad prospects for the application of copper oxide in new materials, new energy, biomedicine and other fields.