Green nanoparticles, clean groundwater

Subhra Priyadarshini

doi:10.1038/nindia.2011.25 Published online 25 February 2011

The nanoparticles in various shapes.

Eco-friendly gold nanoparticles in various shapes — spherical, triangular, pentagonal, hexagonal, urchin-like, wires and rods — could be the next green answer to clean, contamination-free groundwater.

A team of scientists from the biological chemistry department of the Indian Association of the Cultivation of Science in Kolkata has created an array of gold nanoparticles through an eco-friendly approach — using a protein extracted from the fungus Rhizopus oryzae. In making the gold nanoparticles, they did not use any chemical compound, as is the norm in such processes.

Globally, the effort now is towards minimizing the hazardous waste generated while obtaining metal nanoparticles. "Our method of making gold nanoparticles is a simple, green chemical approach that reduces waste, hazard, risk, energy and cost," lead researcher Sujoy Das told Nature India.

Due to their unique properties, gold nanoparticles are finding use in a wide range of applications from material to biological sciences. Metal nanoparticles of various shapes have earlier been synthesized by chemical agents. "But this often raises environmental questions because of the toxicity of chemical compounds used. So development of eco-friendly methodologies for the synthesis of nanoparticles of well-defined size and shape has been a challenge and constitutes an important area of research in nanotechnology," Sujoy says.

Because of high specificity and mild reaction conditions, making nanoparticles through biological means helps curtail its environmental impact. It also facilitates the formation of highly monodisperse nanoparticles with defined size and shape.

In a separate experiment, the scientists had earlier produced nanogold-bioconjugates by spreading out gold nanoparticles of 10 nm average diameter on the surface of the fungus.

The author trio (L to R): Sujoy Das, Akhil Das & Arun Guha.

These nanogold-bioconjugates adsorped different organophosphorous pesticides very well and also exhibited antimicrobial activity. Experiments on water contaminated with pesticides and bacteria showed that they were removed to sub ppb (parts per billion) levels in a single step using the nanogold-bioconjugates. "This suggests a significant advancement in the development of a nanotechnology-based green chemical approach for water purification," Sujoy says.

The removal of pesticides from water using conventional techniques to ppb level is difficult. The finding will help scientists develop a microbe-based biosynthetic method of producing nanoparticles. In addition, it will help them in devising a nanotechnology-based water purification system to combat pesticide contamination in ground water.

The technique will reduce the cost of nanoparticle production as also the environmental burden, Sujoy added.


  1. Das, S. K. et al. Microbial Synthesis of Multishaped Gold Nanostructures. Small. 6, 1012-21 (2010)
  2. Das, S. K. et al. Gold Nanoparticles: Microbial Synthesis and Application in Water Hygiene Management. Langmuir. 25, 8192-8199 (2009)