What could be more unnatural and yet indispensable in the modern world than a light bulb? Made from metal, glass, and a variety of petrochemicals, who would even consider looking for a "green" alternative? And if so, what would that be?

Now, a groundbreaking new study published in Scientific Reports seems to have found exactly such a green solution. Amazingly, Indian researchers discovered that a mixture of two commonly consumed edible plants, red pomegranate and turmeric, when exposed to light wavelengths just below the visible threshold (380 nm), produced almost pure white light emission (WLE).

This finding represents a simple, cheap and environmentally safe alternative to current LED technology, which presently rely on toxic materials, including heavy metals such as arsenic, copper, nickel, and lead, in their production.

In the new study titled "White Light Emission from Vegetable Extracts," Indian researchers described how they were able to conveniently tune the color temperature of the WLE by adjusting the concentrations of the "the primary emitting pigments," namely, anthocyanins from red pomegranate seed juice and curcumin extract from turmeric.

One of the crucial mechanisms behind their ability to produce an almost pure white light emission was identified as "Foster resonance energy transfer" (FREF). FREF is a mechanism that describes energy transfer between two light-sensitive molecules (known as chromophores). The researchers identified A FRET-like, light-induced energy transfer cascade: polyphenolics > curcumin > anthocyanins, resulting in WLE.

The researchers were also able to create an entirely edible gelatin-based mixture of the plant extracts that was capable of emitting almost pure white light when exposed to UV light, depicted below.

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In summary, we have generated white light emission from natural dyes extracted in our laboratory using a green and simple procedure. The optimized mixture of two suitably chosen plant extracts using acidic  ethanol, aided by a FRET cascade from polyphenolics to curcumin to anthocyanins, generates almost  pure white light, with CIE values of (0.35, 0.33) in solution, (0.26, 0.33) in gelatin gel and (0.33, 0.25) in PVA film. White light emission from such cheap and nature friendly resources could be important in the context of lighting and sensing application. It would be interesting to see if such system can be used as dyes for tunable dye laser applications. To the best of our knowledge this is the first time low cost, biocompatible (edible) natural dyes have been a part of white light emitting system. Given the vast  number of excellent natural fluorescent dyes obtainable from renewable biosources, approaches similar to the present could lead to a more extensive range of low-cost and efficient WLE biomaterials with ease of adjusting colour temperature, which will obviate more expensive alternatives currently being pursued."