Indian bioscientists discover novel uses for sugarcane waste

Indian researchers have found a new use for sugarcane pulp as a source of highly fluorescent carbon quantum dots, which could reduce agricultural waste and offer a new revenue stream for farmers.

These dots are tiny carbon nanoparticles, which are about four nanometers across, meaning that more of them would fit on the head of a pin than there are stars in the Milky Way.

Because they emit light and are non-toxic, carbon quantum dots can serve as biosensors, in light-emitting diodes, and even deliver drugs around the human body.

For example, researchers have injected liquids containing carbon quantum dots into a living body to image it from the inside.

"In our study, we developed a simple, low-cost and efficient method for green synthesis of fluorescent carbon quantum dots from sugarcane bagasse," says Ravi Shankaran Dhesingh, co-author of the paper and associate professor at the National Centre for Nanoscience and Nanotechnology at the University of Madras, Chennai, India.

The research demonstrates a new method of producing these versatile nanoparticles.

To begin with, the Indian team cut the sugarcane bagasse into small pieces and sun-dried it for six days, and after burning the dry bagasse, they chemically oxidised and exfoliated it.

While this approach produces a useful substance, it also removes agricultural waste from the environment. More than 90 countries produce sugarcane, and by extension, sugarcane waste.

"Huge quantities of agricultural residues – rice husks, sugarcane bagasse and coconut husks – are produced annually around the world, and these are vastly underutilised," Shankaran said.

To make sugar, machines crush the sugarcane stalks to free the sugary juice inside them.

This juice, when dried and crystallized, will become the sugar you put in your coffee.

But every three tonnes of sugarcane crushed to produce sugar in a factory will yield about one tonne of bagasse.

There have been many attempts to use sugarcane bagasse, but it is a difficult material to work with.

It is unsuitable for paper production because it is very stringy, and so it is often used for bioenergy, but about half of the bagasse is unusable for this because it is too wet.

Given the dwindling margins of sugarcane producers, nanomaterials could provide an answer for both the environment and industry.

"The conversion of solid waste to functional nanomaterials provides a new avenue in solid-waste management, as well as in the production of novel materials," Shankaran added.

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