Do you know that the properties of a substance are also measured by taking large or bulk sample (for example of size 1023 atoms/ molecules) volume? But when these properties were checked for same material at nanoscale level then large differences were observed in many physical properties. This means at nanoscale level, physical properties become size dependent. Today we will discuss the optical properties of nanomaterials:
1) The properties like colour and transparency are considered as optical properties. These properties are observed to change at nanoscale level. For example bulk gold appear yellow in colour while in nanosize gold appear red in colour.
2.) Bulk silicon appears grey in colour while nanosized silicon appears red in colour. 3.) Zinc oxide, which at bulk scale blocks ultraviolet light and scatters visible light and gives white appearance. While nanoscale zinc oxide is very small in particle size compared with wavelength of visible light and it does not scatters it. Thus it appears transparent.
Reason for change in optical properties in nanoscale
1.) The main reason for change in optical properties at nanoscale level is that nanoparticles are so small that electrons in them are not as much free to move as in case of bulk material. Due to this restricted movement of electrons, nanoparticles react differently with light as compared to bulk material.
If you know more properties of nanomaterials, then please share with us.