CHEM01200604004 Shri Sanyasinaidu Boddu - Homi Bhabha ...

CHAPTER 1: Introduction
1.1 Historical Background of Nanomaterials: Nanomaterials are the materials with
structural features in between those of atoms/ molecules and bulk materials, with at least one
dimension in the range of 1 to 100 nm (1 nm =10 -9 m) and are known to mankind for a long
time starting from the Roman period. In earlier days, nanomaterials of metals (also known as
the colloidal metal particles) were used to dye glass articles and fabrics. For example the age
old popular dye, “The Purple of Cassius”, is formed on reacting stannic acid with chloroauric
acid, and made up of tin oxide and Au nanocrystals [1]. The Romans were adept at
impregnating glass with metal particles to achieve dramatic colour effects. The Lycurgus cup,
a glass cup of 4 th century AD, appears green in reflected light and red in transmitted light
(Fig.1). This effect is due to the presence of Au and Ag nanocrystals in the walls of the cup.
Maya blue, a blue dye used by the Mayas around 7 th century AD is found to consist of silica,
metal and oxide nanocrystals [2]. Systematic studies on nanoparticles began to appear as
early as seventeenth century. In 1612, Antonio Neri, a Florentine glassmaker and priest of
Italy, described the synthesis of colloidal gold in his treatise L’Arte Vetraria.
(a) (b) (c)
Fig.1.The Lycurgus cup appears (a) green in reflected light, (b) red in transmitted light and
this cup is preserved in the British museum in London, (c) Colloidal dispersion of gold
preserved in the Royal Institution, London [3, 4].
John Knuckel of Germany discovered that addition of small gold particles in glass
leads to appearance of red colour. Michael Faraday in 1857 [5] carried out groundbreaking
work on colloidal metals. He called them as divided metals and observed that colloidal metal
1