Thermodynamically Stable Colloidal Solids: Interfacial Thermodynamics from the Particle Size Distribution

Area of Science:

• Colloid and Surface Science
• Materials Chemistry
• Thermodynamics

Background:

• True thermodynamic stability in solid colloidal dispersions is rare and under-investigated.
• Understanding long-term stability and preparation pathway insensitivity is of significant interest.
• Existing models often assume absolute thermodynamic stability, which may not hold true.

Purpose of the Study:

• To apply classical nucleation theory (CNT) to colloidal systems to link particle size distribution with size-dependent interfacial free energy.
• To fit experimental data of nanoparticle size distributions using CNT.
• To investigate the thermodynamic stability of gold-thiol and magnetite nanoparticle systems.

Main Methods:

• Applied classical nucleation theory (CNT) to model colloidal systems.
• Related interfacial free energy density to particle size distribution.
• Fitted experimental size distribution data for gold-thiol and magnetite nanoparticles using CNT.

Main Results:

• Gold-thiol system data fit well with interfacial free energy (γ) following a power law of r⁻³.
• Magnetite nanoparticle data fit well with CNT, with γ following a power law of r⁻².
• Extrapolated flat surface free energy density was small and positive; systems appear metastable.

Conclusions:

• Classical nucleation theory effectively describes size-dependent interfacial free energy in colloidal systems.
• The studied gold-thiol and magnetite systems are likely metastable, challenging assumptions of absolute stability.
• Derived expressions for interfacial energy parameters relevant for future research on surfactant concentration, temperature, and particle distribution.