• Physical properties

The melting point generally decreases as a result of its large specific surface area and the greater number of atoms on the surface. This affects the thermodynamic behavior of the volume of the nanoparticle. The atoms of the surface need less energy to move because there are fewer atoms inside the nanoparticle and they need less energy to overcome the intermolecular forces of attraction. Changes in melting point occur because nanoscale materials have a much larger surface to volume ratio than bulk materials, drastically altering their thermodynamic and thermal properties. Changing the metal melting temperature, depends on the particle size. With decreasing the size the melting temperature may be lowered by several hundreds of degrees, as for gold, for example, a compact metal melts at a temperature of 1340 K, and the nanoparticles of 2 nm melt at 340 K.

Other physical properties of nanoparticles caused by quantum effects are: high electrical and thermal conductivity of some nanoparticles, such as silver; Low electrical and thermal conductivity of other nanoparticles such as gold.

Conversion of some metals into semiconductors (ZnO, Si ...); Some semiconductors become insulators.

Absorption of solar radiation is much higher in materials composed of nanoparticles than it is in thin films of continuous sheets of material.

The changes in physical properties are not always desirable. Ferromagnetic materials smaller than 10 nm can switch their magnetization direction using room temperature thermal energy, thus making them unsuitable for memory storage.

• Chemical properties

One of the important factors for the chemical applications of nanomaterials is the increment of their surface area which increases the chemical activity of the material. Due to their enhanced chemical activity, nanostructured materials can be used as catalysts to react with such noxious and toxic gases as carbon monoxide and nitrogen oxide in automobile catalytic converters and power generation equipment to prevent environmental pollution arising from burning gasoline and coal.

Nano metallic or ionic particles exhibit very important chemical properties: self-assembly and the exceptional properties as catalysts.

Its high chemical reactivity is due to its high specific surface area and the important number of atoms at the surface that give rise to a high surface energy of the nanoparticles.

• Mechanical properties

The mechanical properties of nanoparticles and nanostructured materials change with size; At Nano-metric scale, the atomic structure of the nanocrystals is modified, becoming more resistant and acquiring mechanical properties superior to those of macro materials.

For a given nanomaterial, its hardness and strength are increased, generally following a growth inversely proportional to its diameter.

An important property of some nanoparticles is their greater capacity of tensile deformation, before breaking, without reducing their resistance, being able to reach the maximum theoretical resistance of the material. This behavior is due to the fact that the nanocrystal structure is practically devoid of defects.

The elongation or tensile deformation of some nanoparticles may be in the range of 100% - 1000%, prior to rupture, without fracture.