Properties at the NanoscaleProperties at the Nanoscale

Factors Influencing Properties

Macroscale Nanoscale

Surface area to volume ratio Small Very large

Gravity Very important Less important

Electromagnetic forces Less important Very important

Random MotionInsignificant compared with size

Large influence

Surface Area

Gravity and Electromagnetic Forces

• Gravitational force– Depends on mass– Larger influence on heavier

particles– Insignificant for very small

particles

• Electromagnetic forces– Do not depend on mass

Force due to gravity

Changing Properties

• Types of properties that often change– Optical (e.g. colour, transparency)– Electrical (e.g. conductivity)– Physical (e.g. hardness, boiling point)– Chemical (e.g. reactivity, reaction rates)

Electrical Conductivity

Bulk Metal Nanomaterials

• Negatively charged particles particles (electrons) move around a fixed arrangement of positively charged particles.

• Electrons can move so they can conduct electricity

• Less electrons to “share” • Electrons tend to stick close

to one positive charge and not move around.

• Not as good at conducting electricity.

Optical Properties

• Particles are so small that electrons are not free to move about.

• Because this movement is restricted, the particles react differently with light.

• Some particles are so small that visible light does not interact with them at all.

Melting

Related to percentage of atoms on the surface (i.e. surface area to volume ratio)

Reactivity