The compositional properties of organic pigments that you don't know.
We all know that objects can increase brightness and visibility after using organic pigments, but why? In fact, this is inseparable from the composition characteristics of organic pigments. In order to let everyone better understand this knowledge, Xiaobian here will introduce the composition characteristics of organic pigments in detail.
After the organic pigment absorbs energy, almost all of the molecules are excited in the low energy state (ground state). Due to the absorption of the quantum emitted in the ultraviolet region and the visible region, the time is very short (about 10 seconds to 5 seconds), resulting in electrons. Transition to a higher energy orbit. When this transformation occurs, it can be said that the molecule is in an excited state. A molecule can have many excited states, and each excited state has a certain vibrational form. The absorption of the emission energy by a molecule is a quantum effect. The process of light quantum (photon) energy can be defined as E = hv, E is energy, h is Planck constant, v is the frequency of absorbed light, and the absorbed energy corresponds to the change of state of a molecule, organic The pigment must be strictly equal to the energy of the photon. For a given molecule, it can only absorb quantum of a certain frequency, and the molecular structure of the substance determines these frequencies. For many molecules, including fluorescent fluorescent pigments, Their absorption bands are very wide.
In the excited state, the vibration relaxation is faster than the light emission, so the vibration energy disappears immediately due to the collision of adjacent molecules until the molecules enter the low vibration level of the first excited state. Most molecules lose their residual electron and vibrational energy after reaching the lower vibrational level of the first excited (single) state (due to internal conversion and other deactivation processes). When this happens, the molecules fall into the molecule. The base state does not emit, so the organic pigment forms a color when the molecule selectively absorbs a part of the incident light and reflects a part of the remaining light in the process. For example, when a white light falls on a non-fluorescent (general) orange pigment, only the orange wavelength is reflected, and the remaining light is absorbed and converted into heat.
Organic pigments may also be that some excited molecules lose their vibrational energy and then encounter emission transitions to the ground state, which can form fluorescence or phosphorescence, depending on whether the molecule is in excited singlet or triplet state (TripletState) . The term triplet is used to describe an electronic state. It means that the rotation of all electrons in a molecule is paired. Since most molecules are singlet at the ground state energy level, if in the absorption process. The rotation of the electron does not change, and the excited state is still a singlet state, and when a molecule directly enters the ground state from the excited singlet state with the emission of the photon, a fluorescence phenomenon occurs.
The compositional characteristics of organic pigments introduced in the above small series involve some professional terms. If you are too familiar, you can call us.