What material is self-luminous?

1. When a substance is excited (radiation, high-energy particles, electron beam, external electric field, etc. ), the substance will be in an excited state, and the energy of the excited state will be released in the form of light or heat. If this part of energy is visible, ultraviolet or near-infrared electromagnetic radiation, this process is called luminescence. 2. Luminescence means that besides thermal radiation, substances also emit excess energy in the form of light. This launch process has a certain duration. What is luminescent material? The material that can realize the above process is called luminescent material. The process of absorbing energy in a certain way and transforming it into optical radiation (unbalanced radiation) is called luminescence. In practical application, the solid that emits light by external excitation is called luminescent material. They can be used in powder, single crystal, thin film or amorphous form. The main components are rare earth metal compounds and semiconductor materials, which are closely related to non-ferrous metals. Various phosphors made of high-purity rare earth oxides Y2O3, Eu2O3, Gd2O3, La2O3, Tb4O7, etc. Widely used in color TV sets, color and black-and-white large-screen projection TVs, aviation displays, X-ray intensifying screens, and phosphors for making ultra-short afterglow materials and various lamps. Semiconductor luminescent materials include ZnS, CdS, ZnSe and GaP, GaAs 1-xPx, GaAlAs, GaN, etc. It is mainly used to make large and medium-sized digital symbols, graphic displays, digital display clocks, X-ray image enhancement screens, long-life light-emitting diodes, digital tubes and so on. Visible light emitting diodes (LEDs) are widely used in instruments and computers because of their fast display response, and their annual output has doubled, constantly replacing other display devices to edit the main categories of luminescent materials in this section. There are many kinds of luminescent materials. The main types are: photoluminescence, cathode ray luminescence, electroluminescence, thermoluminescence, luminescence, radiation luminescence and so on. Background knowledge of luminescence Theoretical model of optical transition of luminescent materials; Basic theory of solid energy band; Optical transition in solid; Characterization of basic knowledge of solid luminescent materials; Edit the application of this section of photoluminescent materials 1. Reflective material This material can quickly reflect the light shining on its surface. Different materials have different wavelength ranges of reflected light. The color of reflected light depends on the wavelength absorbed and reflected by the material, so the surface of the material can only reflect light when there is light, such as various license plates and traffic signs. Photoluminescent materials emit light outward instead of reflecting light. 2. Fluorescent materials immediately emit different wavelengths of light after absorbing a certain wavelength of light, which is called fluorescence. When the incident light disappears, the fluorescent material will stop emitting light immediately. More precisely, fluorescence refers to some fairly bright colors of light, such as green, orange and yellow, which people usually call neon lights. Fluorescent materials are divided into inorganic fluorescent materials and organic fluorescent materials. Inorganic fluorescent materials, represented by rare earth ion luminescence and rare earth fluorescent materials, have the advantages of strong absorption capacity and high conversion rate. The narrow-band emission of the central ions of rare earth complexes is beneficial to full-color display, and its physical and chemical properties are stable. Rare earth ions, because of their rich energy levels and 4f electron transition characteristics, have become a treasure house of luminescence, providing excellent luminescent materials for high-tech fields, especially information and communication fields. At present, common inorganic fluorescent materials use alkaline earth metal sulfides (such as ZnS and CaS) aluminate (SrAl2O4, CaAl2O4, BaAl2O4) as luminescent matrix, and rare earth lanthanides [Eu (Eu), Sm (Sm), Er (Er), Nd (Nd), etc. ] used as activator and auxiliary activator. The traditional preparation method of inorganic phosphor is high-temperature solid-state method, but with the rapid update of new technology, the improvement of performance index of luminescent materials needs to overcome the inherent defects of classical synthesis methods and some new ones. Such as combustion method, sol-gel method, hydrothermal precipitation method, microwave method, etc. Organic luminescent materials In the field of luminescence, people pay more and more attention to the study of organic materials. Due to the variety of organic compounds, good adjustability, rich colors and high color purity, molecular design is relatively flexible. According to the different molecular structures, organic luminescent materials can be divided into: (1) organic small molecule luminescent materials; (2) organic polymer luminescent materials; (3) Organic complex luminescent materials. These luminescent materials have their own characteristics in luminescent mechanism, physical and chemical properties and applications. There are many kinds of organic small molecule luminescent materials, most of which contain heterocyclic rings and various chromophores, and their structures are easy to adjust. By introducing unsaturated groups such as vinyl bond and benzene ring and various chromophores, the length of its yoke is changed, thus changing the photoelectric properties of compounds, such as oxadiazole. Triazole and its derivatives, rhodamine and its derivatives, coumarin derivatives, 1, 8- naphthalimide derivatives, pyrazoline derivatives, triphenylamine derivatives, porphyrin compounds, carbazole, pyrazine and thiazole derivatives, perylene derivatives, etc. They are widely used in photoelectric devices, DNA diagnosis, photochemical sensors, dyes, fluorescent whitening agents, fluorescent coatings, laser dyes [7], organic electroluminescent devices (ELD) and so on. However, small molecular luminescent materials are prone to fluorescence quenching in solid state, and devices made by general doping methods are prone to aggregation and crystallization, which reduces the service life of devices. Therefore, many researchers devote themselves to the study of small molecules on the one hand. On the other hand, looking for better luminescent materials, polymer luminescent materials came into being. Organic polymer optical materials are usually divided into three types: (1) side chain type: small molecular luminescent groups are attached to polymer side chains; (2) Full-yoke skeleton type: the whole molecule is a large-yoke polymer system; And (3) partial yoke main chain type. However, the luminous centers are separated from each other, and no yoke system is formed. At present, the polymer luminescent materials studied are mainly * * yoke polymers, such as polyphenylene, polythiophene, polyfluorene, triphenylamine and their derivatives, triphenylamine, polycarbocarbazole, polypyrrole, polyporus [8] and its derivatives, and * * * polymers. At present, a lot of research has been done on this. Luminescent groups can also be introduced into the polymer end. Kenneth P. Ghiggino et al. introduced the fluorescent chromophore into the RAFT reagent, and connected the fluorescent chromophore to the polymer through RAFT polymerization. It can be seen from the above various light-emitting polymers that most of them are polymerization of the main chain yoke, and the main chain polymerization is easy to form a larger yoke area, but the solubility and melting are reduced, making it difficult to process; When the luminescent group is introduced into the end of the polymer or the middle of the polymer chain, only the end group emits light, and the molecular weight will not be very large. If the molecular weight is large, the content of luminescent groups in the polymer is low and the fluorescence is weak. Side-chain polymer luminescent materials are a powerful supplement to main-chain polymers. 3. Self-luminescent materials are generally considered as photoluminescent objects. Self-luminous objects can glow in the dark. However, there is no need to be exposed to the sun in advance. These materials are usually used as luminous marks on dials and to produce long-term luminous objects, and they contain radioactive elements. 4. Phosphorus-containing objects glow because they contain phosphorus. This material is usually considered as a photoluminescent material. Application of photoluminescent materials: Photoluminescent powder is an ideal material for making luminescent ink, luminescent coating, luminescent plastic and luminescent printing paste. Luminous ink is not only suitable for screen printing various patterns and characters with luminous effect, such as signs, toys, calligraphy and painting, glass paintings, stickers and so on. , but also because it has the characteristics of high transparency, good film forming and thin coating. It can be sprayed or screen printed on various relief, round sculpture (Buddha statue, porcelain statue, plaster statue, tri-colored Tang Dynasty), polymer painting, lighting and other handicrafts, and its added value is greatly improved without affecting its original decorative colors or lines. The colors of luminous ink are transparent, red, blue, green, yellow and so on. The application of photoluminescence materials in safety is the most common. In terms of safety, photoluminescent materials can be used as exit signs, evacuation signs, etc. When used as these signs, they must undergo rigorous testing to ensure that they meet safety standards. Photoluminescent materials are different from decorations or other small items in safety, which requires luminescent materials to maintain the brightest illumination and lasting illumination.