Experiences

Why nanotechnology?

Milena Gosheva

Bulgaria

High Secondary School

Physics

Extracurricular activity

Direct

Properties of nanoparticles
Theoretical concept:
Nanotechnology process occurs when the molecules of a substance are arranged in a certain way to form a structure. Nanoparticles are the link between the volume of the thick substance and the individual atomic and molecular structures. Bulk materials have the same chemical properties, regardless of their volume. When the amount of the material is changed along with change of the surface, its physical properties change, but the chemical ones remain the same. For example: sugar cube - it has a definite volume. If you chop it into crystals, the properties do not change, only the physical properties change. If the crystals are ground to give a powder of sugar, again the surface increases and the physical properties change. But throughout its chemical properties are retained. According molecule kinetic theory which is introduced to students of grade 8, between molecules act different forces. Substances change properties by increasing their size. Thus more forces act on larger area, there are more strokes of the particles which results in a change in the internal energy of the substances. Why we use nanoparticles and not substances in actual size - the answer lies in their properties. Why are there different colors of gold and why we admire the beautiful stained glass in the cathedral?
Model explaining the theoretical knowledge:

An important characteristic of nanoparticles is their high surface area attached to extremely low volume. Students use sugar lumps as cube and calculate cubic volume and surface area of the so formed cube.








Then they remove the upper two rows and put them next to the base of the cube. Again they calculate the volume and surface area.






Finally all lumps are lined in a row and again the volume and the surface area are calculated.


It turns out that we can change the properties by changing their surface without changing their volume. High surface area increases the solubility of substances. This property is used in the manufacture of dyes, pigments, pharmacy and cosmetics. When the particle size is reduced the physical and chemical properties alter. And when the size decreases to nano, it is possible to occur even new characteristics. Increasing the surface area leads to increasing the reactivity. Particle size also affects the color of the material. On the picture: Gold and silver nanoparticles have different colors depending on the shape and size. © North-western University