Waste to wealth

Pomegranate peel can be used to make gold and silver nanoparticles

By Biplab Das
Published: Friday 30 November 2012

imageFRUIT PEEL is not such a waste after all; it can be used to make gold and silver nanoparticles.

A study has shown that discarded pomegranate peel can be used to synthesise nanoparticles of the precious metals. These are ultra-small particles ranging from 1-100 nanometres (a nanometre is a billionth of a metre) and find extensive use in biomedical and electronic devices.

Most processes for the synthesis of nanoparticles are complex and involve harmful chemicals. A joint research team from Patna University and Magadh University in Bihar and Aveiro University in Portugal has developed this eco-friendly method which does not even require heating.

Certain plant-based processes have been developed for synthesising gold and silver nanoparticles in the past but no previous study has ever explored the potential of food waste such as discarded pomegranate peel for the purpose. The findings of the study have been published in the November 2012 issue of Advanced Materials Letters.

Fruit peel extracts are rich in chemical compounds like alkaloids and poly-phenols. The researchers have found that ellagic acid, a phenol found in fruits, can stabilise silver and gold nanoparticles in water. For the experiment, the researchers prepared pomegranate peel extract. They added washed, fresh pomegranate peel to ultrapure water and boiled it for 15 minutes. The solution was filtered to obtain pure extract.

The researchers observed that when this extract was added to silver nitrate, the solution turned yellowish-brown in an hour, indicating the formation of silver nanoparticles. When the extract was added to chloroauric acid, the solution formed gold nanoparticles and turned pink-red in colour after an hour. Both types of nanoparticles were spherical in shape. Silver ones were five nanometres in size and gold ones were 10 nanometres.

“Stable nanoparticles were formed within an hour of the reaction. This is one of the fastest ecological methods to produce silver and gold nanostructures using food waste,” says lead researcher Seema Sharma of the Anugarh Narayan College of Magadh University in Bodh Gaya.

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