A material in which one of its dimensions is of the order of one thousand millionth of a meter is said to be a nano material. A nano meter (nm) is one thousand millionth of a meter (10-9 m).   For example in nature RBC ( red blood cell) is approximately 7, 000 nm wide, size of the   water molecule is nearly 0.3nm, 5 hydrogen atoms in a line are about 0.5 nm, a sand grain is about 1 millimetre, the thickness of a  sheet of paper is about  100, 000  nm,  a  human  hair  is  around 80, 000  -  100, 000  nm.  The  relative  size variation of natural and manmade materials is shown in Fig 1.1. The study of objects and phenomena at a very small scale, roughly 1 to 100 nanometer (nm) is termed as nanoscience.  Thus  nanoscience  is  the  study  of  phenomena  and  manipulation  of various  properties  of  materials  from  atomic  level  to  their  macromolecular  level  by using various synthetic methods and by varying various physical conditions [1]. Thus nanoscience  mainly deal  with  the  design,  production,  characterisation  and  various applications of materials at the nanoscale level by controlling the size and shape of the particles.