In a study published in ACS Sustainable Chemistry & Engineering, researchers describe a simple method for removing yellow stains with a high-intensity blue LED light. They demonstrate the method's ability to remove stains from orange juice, tomato juice, and sweat-like substances from various materials, including silk.
Exposing a sweat-like stain on cotton (left image) to a blue LED light for 10 minutes significantly removed the yellow color (right image). Image Credit: Tomohiro Sugahara
Sweat and food stains could ruin a person's favorite clothes. However, bleaching treatments like hydrogen peroxide and dry-cleaning solvents that remove stains are unsuitable for all textiles, particularly fragile ones.
The study team shows that the procedure removes stains from orange juice, tomato juice, and sweat-like substances on a variety of materials, including silk.
Our method utilizes visible blue light in combination with ambient oxygen, which acts as the oxidizing agent to drive the photobleaching process. This approach avoids the use of harsh chemical oxidants typically required in conventional bleaching methods, making it inherently more sustainable.
Tomohiro Sugahara, Study Corresponding Author, Kyoto University
Yellow clothes stains are generated by squalene and oleic acid from skin oils and sweat, as well as natural pigments such as beta carotene and lycopene found in oranges, tomatoes, and other foods. UV radiation has the ability to remove stains more effectively than chemical oxidizers such as bleach and hydrogen peroxide, but it can harm sensitive materials.
Sugahara and Hisanari Yoneda had previously shown that a high-intensity blue LED light could remove yellow color from old resin polymers; therefore, they wanted to explore if blue light could also break down yellow stains on cloth without causing damage.
Initially, they subjected vials containing beta-carotene, lycopene, and squalene to three hours of high-intensity blue LED light. All the samples lost color, and spectroscopic tests revealed that oxygen in the air aided the photobleaching process by breaking bonds, resulting in colorless molecules.
Next, the team added squalene to cotton fabric samples. After heating the swatches to imitate aging, the samples were treated for 10 minutes with a hydrogen peroxide solution or exposed to a blue LED or ultraviolet light.
Blue light removed the yellow stain far more than hydrogen peroxide or UV exposure. UV radiation produced new yellow-colored molecules. Additional experiments revealed that the blue LED treatment removed squalene stains from silk and polyester without harming the textiles. The approach significantly decreased the color of various stains on cotton swatches, such as old oleic acid, orange juice, and tomato juice.
High-intensity blue LED light is a potential method for removing clothing stains, but the researchers want to carry out more colorfastness and safety testing before commercializing a light system for home and industrial usage.
The researchers did not receive external funding for this study; the researchers are employed by Asahi Kasei Corporation, a company that develops fiber products, chemicals, and electronic materials.
Journal Reference:
Sugahara, T. and Yoneda, H., (2025) Environmentally Friendly Photobleaching Method Using Visible Light for Removing Natural Stains from Clothing. ACS Sustainable Chemistry & Engineering. doi.org/10.1021/acssuschemeng.5c03907