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Exploring Luminous Matter: Why Do Certain Materials Shine in the Dark?
In our daily lives, objects containing luminescent materials can be found everywhere. From luminous toys and indicator lights to various modern display technologies, luminous materials attract people's attention with their unique optical properties. These materials are called "phosphorescent materials" and they can emit light after being excited by some kind of radiant energy. What makes these materials so amazing? What is the principle of their light emission?
There are two types of phosphorescent materials: fluorescent materials emit light immediately, while phosphorescent materials release light with a delayed release after excitation, continuing to emit light for hours or even days.
Phosphorescent materials can be divided into fluorescent materials and phosphorescent materials. Fluorescent materials glow instantly when exposed to ultraviolet or visible light, but they go out as soon as the radiation stops. Phosphorescent materials, on the other hand, have the property of delayed luminescence, continuing to emit light after radiation stops, gradually reducing in brightness over a period of time that can last from milliseconds to days, making them particularly useful in many applications that require a continuous light source. For example, luminous watch dials and aircraft instruments.
In optoelectronic display technology, phosphorescent materials improve the visibility of a variety of devices, from computer monitors to motorcycle indicator lights.
The luminescence process of phosphorescent materials involves the electronic band structure. In inorganic materials, when particles are exposed to radiation, electrons are excited to move from the valence band to the conduction band, or exciton band. This process leaves behind "holes," which are pairs of electrons and holes that travel through the lattice and are eventually captured by impurity centers, which then emit light. The properties of phosphorescent materials strongly depend on their crystal structure and the added activators.
The activator of the phosphorescent material plays a key role and is usually a transition metal or a rare earth metal. These compounds have different emission colors and intensities and are designed to meet different application requirements.
Traditional phosphorescent materials such as copper-activated zinc sulfide (ZnS:Cu) and silver-activated zinc sulfide (ZnS:Ag) are the most well-known examples, which are characterized by long luminescence time and high brightness. In addition, the newly developed barium aluminate luminescent materials, such as barium aluminate (SrAl2O4), show higher brightness and significant long-lasting luminescence, which makes it popular in luminous toys and safety equipment. .
Degradation of phosphorescent materials is also a concern, as these materials can lose efficiency over time due to oxidation, diffusion of impurities, or chemical reactions with the environment. Materials such as BaMgAl10O17:Eu2+ are easily oxidized during heating, resulting in a decrease in their luminous efficiency. Devices that are used for a long time, such as television monitors and light-emitting diodes, may also experience brightness degradation due to repeated electron bombardment.
The luminescence lifetime of many phosphorescent materials can be significantly affected by moisture or other environmental factors, which is a challenge in many products that believe in advanced technology.
Calcium carbonate and other phosphorescent materials are also commonly used in motorcycles and high-tech equipment. For example, the light-emitting elements on aircraft instrument panels, used to enhance visibility and inspection, contain specially formulated phosphors. In the future, it is expected that as technology advances, these materials will be increasingly used in various emerging applications, such as lighting technology for smart homes and wearable devices.
In addition to lighting, phosphorescent materials also show great potential in temperature measurement, oxygen monitoring and other high-tech fields.
In short, phosphorescent materials are an indispensable part of modern technology, whether in auxiliary lighting or as core components of high-end display technology. Their specialness lies not only in their ability to shine in the dark, but also in the innovation and improvement they represent. As research deepens, will more efficient and multifunctional luminescent materials appear in the future?
