Explanation

It refers to the phenomenon that when the particle size drops to a certain value, the electronic energy level near the Fermi level changes from quasi continuous to discrete energy level or the energy gap widens. There are discontinuous highest occupied molecular orbital and lowest unoccupied molecular orbital energy level in semiconductor nanoparticles, and the energy gap broadening phenomenon is called quantum size effect. When the change of energy level is greater than that of thermal energy, light energy and electromagnetic energy, the magnetic, optical, acoustic, thermal, electrical and superconducting properties of nanoparticles are significantly different from those of conventional materials. The fluctuation of electrons in discrete quantized energy level brings a series of special properties to nanoparticles, such as high optical nonlinearity, specific catalysis and photocatalysis, strong oxidation and reduction, etc. For example, when the size of a semiconductor materials or metal is reduced to a nanometer size, especially when it is less than or equal to the exciton Bohr radius of the materials, the nearly continuous energy band composed of energy level in the bulk metal is converted into discrete energy level at this time. Therefore, for semiconductor materials, the size of the band gap can be adjusted by changing the size of the particles, thus changing the dependence on some high cost semiconductor materials.

Classification