New Methods for the Synthesis of Nanomaterials

Dr Murali Sastry
Nanoscience Group, Materials Chemistry Division, National Chemical Laboratory, Pune 411008, India.

Abstract

Wet-chemical methods for the synthesis of nanomaterials are extremely popular for a variety of reasons. Nanoparticles over a range of chemical compositions, sizes and shapes can be routinely synthesized in both aqueous and non-polar organic solutions with a variety of surface modifiers that include standard surfactants and biomacromolecules. However, many processes for nanoparticle synthesis often involve the use of toxic chemicals, which are increasingly becoming taboo. Realizing that some of the most exquisite inorganic nanostructures are synthesized by biological systems such as diatoms and bacteria, nanoscience researchers are turning towards biology for inspiration. In the first part of the talk, I will cover the work carried out in my laboratory on the use of fungi, actinomycetes and extracts from various plant parts in the synthesis of nanoparticles of different compositions. We have been successful in synthesizing nanoscale metals, sulphides and oxides by appropriate choice of microorganisms and examples will be given to illustrate this new approach [1]. While achieving tolerable nanoparticle monodispersity continues to be an important issue with biological nanoparticle synthesis methods, shape modulation may be one aspect where select biological methods appear to be superior to chemical synthesis methods.

Bubbles have fascinated man for a very long time. In the second part of my talk, I will show that liquid foams (a dense assembly of bubbles) may be used for the synthesis of nanoparticles over a range of chemical compositions. This is accomplished by ion entrapment in the foam followed by chemical reaction resulting in the formation of nanoparticles in the foam [2]. Liquid foams possess a very complex structure and present nanoscale reactors of variable geometry that may be used creatively in the synthesis of nanoparticles of different shapes. An important advantage of the foam-based method is the in-built scale-up facility that could be of value for commercial scale production of nanomaterials.

< back