A high-intensity blue LED can erase yellow stains from sweat and food on fabrics like cotton, silk, and polyester – without resorting to harsh bleaching agents. The new photobleaching approach relies on ambient oxygen and visible light to degrade pigments such as beta-carotene and lycopene into colorless compounds.
“Our method utilizes visible blue light in combination with ambient oxygen, which acts as the oxidizing agent to drive the photobleaching process,” said Tomohiro Sugahara, corresponding author and researcher at Asahi Kasei Corporation, in a press release. “This approach avoids the use of harsh chemical oxidants typically required in conventional bleaching methods, making it inherently more sustainable.”
To investigate how the method works at a molecular level, the researchers employed ultraviolet-visible (UV-Vis) spectroscopy and nuclear magnetic resonance (NMR) to confirm the degradation of stain molecules and identify the resulting byproducts. These techniques revealed that oxidative cleavage of conjugated double bonds was responsible for the color loss in compounds like squalene, lycopene, and beta-carotene.
In fabric tests, squalene was applied to cotton swatches and heated to simulate aged sweat stains. After 10 minutes of treatment, blue LED light reduced yellowing more effectively than either hydrogen peroxide or UV exposure. The UV-treated samples also generated unwanted yellow byproducts. Further experiments showed the method’s effectiveness on tomato juice, orange juice, and oleic acid stains, across cotton, silk, and polyester.
Unlike UV light, blue LEDs caused no observable damage to the fabric, making the method promising for use on delicate textiles.
The team is now conducting further assessments of colorfastness and material safety before developing a commercial product. “We believe this technique could contribute to more sustainable clothing care practices in both home and industrial settings,” Sugahara added.
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