Question

A major thermodynamic reason for nanoparticle agglomeration is:

• A. Low density
• B. High melting point
• C. High surface energy
• D. Low band gap

Hint:

To prevent nanoparticle agglomeration in practical applications, surfactant coatings are used to reduce surface energy and provide steric or electrostatic repulsion.

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
The question asks for the thermodynamic driving force behind the agglomeration (clustering) of nanoparticles.

Step 2: Key Formula or Approach:
The thermodynamic relationship governing surface energy and surface area is:
\[ G_{\text{surface}} = \gamma A \] where:
$G_{\text{surface}}$ is the surface Gibbs free energy.
$\gamma$ is the surface tension or surface energy per unit area.
$A$ is the total surface area.

Step 3: Detailed Explanation:

• Nanoparticles have an extremely high surface-to-volume ratio due to their incredibly small size.

• Atoms at the surface of a particle are under-coordinated, meaning they have fewer neighboring atoms to bond with compared to atoms in the bulk.

• These unsatisfied bonds result in a highly unstable thermodynamic state characterized by high surface energy.

• According to thermodynamic principles, physical systems spontaneously tend to minimize their Gibbs free energy ($\Delta G < 0$).

• To reduce this excess free energy, the nanoparticles tend to merge or stick together (agglomerate).

• Agglomeration reduces the total exposed surface area ($A$) of the particles, thereby lowering the total surface energy of the system and making it more stable.

Step 4: Final Answer:
The major thermodynamic reason for nanoparticle agglomeration is high surface energy.