Natural indigo dye

In news- Scientists have found that the natural indigo dye extracted from leaves of a plant of the bean family is capable of protecting human eyes from harmful laser radiation.

About the dye-

The blue dye is extracted from Indigofera Tinctoria or the famed Indigo plants that has been used over the years to colour clothes and clothing materials.
Researchers from the Raman Research Institute (RRI), Bengaluru, and Kensri School and College, Bengaluru, studied the optical properties of the natural Indigo dye and found that it can act as a device to protect human eyes from harmful laser radiation.
The study is funded by the Department of Science and Technology, Government of India and was published in the journal ‘Optical Materials’.

The researchers extracted the dye and stored it in a refrigerator below 4º Celsius to preserve its natural properties.
Their study on how much it absorbed light at different wavelengths of the electromagnetic spectrum showed that the absorption is maximum in the ultraviolet region of the spectrum.
The absorption is comparatively high for the green light as well.
The absorption’s variation with wavelength indicated that chlorophyll, an organic compound that takes part in photosynthesis, is present in the dye.
The team found that when the intensity of the laser pulse is increased, the dye absorbs more light.
Thus it is more opaque to higher intensity light and is referred to as an ‘optical limiter’.
Optical limiters are useful in weakening the potentially harmful radiation emitted by powerful lasers and protecting both eyes and sensitive optical instruments.

Indigofera tinctoria-

It is also called true indigo, is a species of plant from the bean family that was one of the original sources of indigo dye.
It is a shrub one to two meters high and may be an annual, biennial, or perennial, depending on the climate in which it is grown.
It has been naturalized to tropical and temperate Asia, as well as parts of Africa, but its native habitat is unknown.
The natural dye from I. tinctoria is known as tarum in Indonesia and nila in Malaysia.
In Iran and areas of the former Soviet Union it is known as basma.
It has light green pinnate leaves and sheafs of pink or violet flowers.
The plant is a legume, so it is rotated into fields to improve the soil.
The plant’s leaves are soaked in water and fermented in order to convert the glycoside indican naturally present in the plant to the blue dye indigotin.
The precipitate from the fermented leaf solution is mixed with a strong base such as lye.
Marco Polo (13th century) was the first European to report on the preparation of indigo in India.
Indigo was quite often used in European easel painting, beginning in the Middle Ages.