I am a fluorescent whitening agent. Here is my resume

In daily life, there are many products that use fluorescent whitening agents, such as clothes, paper, plastic products, and so on. However, few people know what kind of "magical" existence it is. So, this article will reveal its true face from the following aspects.
Introduction to fluorescent whitening agents
2. Classification of fluorescent whitening agents
3. Factors affecting fluorescent whitening agents
1、 What is a fluorescent whitening agent?
1. Fluorescent whitening agent: It is a fluorescent dye, also known as a white dye, and a complex organic compound. Its characteristic is that it can excite incident light to produce fluorescence, causing the dyed material to achieve a sparkling effect similar to fluorspar, making the material visible to the naked eye very white, achieving the effect of whitening.
2. Whitening principle: Under sunlight irradiation, it can absorb ultraviolet rays (wavelengths of 300-400nm) that cannot be seen by the naked eye, excite molecules, and when they return to the ground state, a portion of the ultraviolet energy disappears, which is then converted into a lower amount of blue purple light (wavelengths of 420-480nm) and emitted. In this way, the reflection of blue and purple light on the target object is increased, thereby offsetting the yellow sensation caused by the excessive reflection of yellow light on the original object, creating a visually clean and dazzling effect.
Note: The whitening effect of fluorescent whitening agents is only an optical brightening and coloring effect, and cannot replace chemical bleaching to give the fabric true "whiteness".
2、 Classification of fluorescent whitening agents
According to the parent classification of fluorescent whitening agents, they can be roughly divided into nine categories: carbocyclic, triazine aminostilbene, stilbene triazole, benzoxazole, furan, benzofuran and benzimidazole, 1,3-diphenyl pyrazoline, coumarin, naphthalimide, and impurities. Below, we will introduce six major categories to you.
1. Carbon ring class
Carbon ring fluorescent whitening agents refer to a type of fluorescent whitening agent in which the parent molecule of the molecule does not contain heterocycles, and the substituents on the parent molecule also do not contain heterocycles. There are mainly three types of parent molecules that make up carbon ring fluorescent whitening agents, namely:
1,4-Distyrelbenzene
2.4,4 '- Styrylbiphenyl
3,4 '- divinylstilbene
Cyanide substituted styrene has a relatively high fluorescence quantum yield and good whitening effect on substrates, especially suitable for use in plastics and synthetic fiber resins. Typical varieties include: Palanil Brilliant White R
2. Triazine aminostilbenes
Triazine aminostilbene is a condensation product of 4,4 '- diamino-stilbene-2,2' - disulfonic acid (DSD acid) and trimeric chlorocyanide
Fluorescent whitening agents with this structural type have the most varieties among the existing commercialized fluorescent whitening agents, with over 80% of them belonging to this structural type.
3. Styrene triazoles
Diphenylene triazole is a condensed compound of stilbene compounds and triazole compounds, and this type of fluorescent whitening agent was introduced earlier. Its disadvantage is that the fluorescent color tone is slightly green, and the whiteness of the fibers is not high enough. It has now been withdrawn from the market.
4. Benzoxazoles
Benzoxazole fluorescent whitening agents are second only to triazine aminostilbene fluorescent whitening agents in terms of production, and most of them are high-performance fluorescent whitening agents. Typical varieties include: Eastabrite OB-1
5. Furans, benzofurans, and benzimidazoles
Furan, benzofuran, and benzimidazole are not the precursors of fluorescent whitening agents themselves, but they are all structural units that make up fluorescent whitening agents. They can form high-performance fluorescent whitening agents together with other structural units (such as biphenyls). The combination of furan and biphenyl is structurally similar to the combination of styrene and biphenyl. Such combinations containing sulfonic acid groups have good water solubility and are particularly suitable for whitening nylon fibers and cellulose fibers
6. Coumarins
The chemical structure of coumarin
Coumarin itself has a very strong fluorescence, and introducing various substituent groups at positions 4 and 7 can make it a practical fluorescent whitening agent.
3、 Some factors affecting the performance of fluorescent whitening agents
1. Pre treatment: The higher the whiteness of the raw material, the better the whitening effect
2. Dosage of fluorescent whitening agents: Each type of fluorescent whitening agent has a specific limit to its saturation concentration. If it exceeds a fixed limit value, not only will the whitening effect not increase, but it will also cause a "yellowing" phenomenon, turning the whitening into "yellowing". The relationship between the concentration of fluorescent whitening agent and the whitening effect is shown in the following figure:
Note: From the curve in the graph, it can be seen that the whitening effect of the fluorescent whitening agent is directly proportional to its concentration below the saturation value. If it exceeds the saturation value, its whitening effect actually decreases.
3. The influence of acidity and alkalinity (pH value)
Dyeing baths with different pH values will directly affect the chemical stability and solubility of fluorescent whitening agents. The pH value has a significant impact on the absorbance of ionic fluorescent whitening agents. Cationic fluorescent whitening agents exhibit a significant decrease in absorbance at pH>9, while anionic fluorescent whitening agents exhibit a sharp decrease in absorbance under acidic conditions.
4. Effects of surfactants
Adding surfactants to an ionic fluorescent whitening agent solution has an impact on the whitening effect of the fluorescent whitening agent. When adding surfactants with opposite charges, it can reduce the absorbance of the solution and sometimes even lead to fluorescence quenching. Adding surfactants with the same charge has no effect or minimal impact
5. Effects of inorganic additives
Some whitening agents can increase (or control) their adsorption rate on fibers by adding table salt (or sodium sulfate) during use. The distribution of whitening agents between dyeing baths and fabrics varies with the concentration of inorganic salts in the solution. Increasing the concentration of inorganic salts can improve the dyeing rate of whitening agents.
6. Color light adjustment
When fluorescent whitening agents are used together with different printing and dyeing auxiliaries, their color tone will be slightly affected by the different auxiliaries. To achieve the same color tone, it is necessary to add trace dyes for adjustment.
4、 Products using fluorescent whitening agents
In daily life, many products are added with fluorescent whitening agents to enhance their photosensitivity.