Concentration and size effects on the size-selective particle purification method using the critical Casimir force

Area of Science:

• Colloid and Interface Science
• Nanotechnology
• Materials Science

Background:

• Critical Casimir force (CCF) arises from solvent fluctuations in binary mixtures.
• CCF induces tunable, size-sensitive particle aggregation.
• This phenomenon is leveraged for nanoparticle purification by size.

Purpose of the Study:

• Investigate the impact of particle size and concentration on CCF-induced purification.
• Determine the optimal conditions for efficient nanoparticle size separation.
• Explore alternative methods for identifying optimal purification temperatures.

Main Methods:

• Combined use of small-angle neutron scattering (SANS) and dynamic light scattering (DLS).
• Systematic variation of particle size, concentration, and solvent composition.
• Evaluation of purification efficiency across a range of nanoparticle sizes and polydispersities.

Main Results:

• Particle concentration has minimal impact on purification efficiency.
• Optimized solvent composition is crucial for efficient size separation.
• The method effectively purifies nanoparticles from 15 nm to 50 nm, even with high polydispersity.
• Aggregation remains size-sensitive regardless of attraction range.

Conclusions:

• CCF-based purification is robust across various conditions and particle sizes.
• Size polydispersity significantly influences colloidal system aggregation.
• Light scattering can replace neutron scattering for identifying optimal purification temperature ranges.