Reversible aggregation/deaggregation of gold nanoparticles induced by a cleavable dithiol linker

Area of Science:

• Colloid and Surface Chemistry
• Nanoparticle Science
• Materials Chemistry

Background:

• Aqueous solutions of gold (Au) colloids exhibit surface plasmon (SP) resonance.
• Controlling nanoparticle aggregation is crucial for developing advanced materials and applications.

Purpose of the Study:

• To investigate the controlled aggregation and deaggregation of gold nanoparticles using dithiol molecules.
• To demonstrate a visual method for monitoring nanoparticle cluster formation and dissociation.

Main Methods:

• Treatment of gold colloids with a blend of mono- and dithiols.
• Utilizing dithiol cleavage with hydrazine to induce deaggregation.
• Monitoring changes in surface plasmon (SP) band position and visual color changes.

Main Results:

• Gold nanoparticles aggregated into stable clusters upon addition of dithiol, indicated by an SP band shift from 512 nm to approximately 600 nm.
• Cleavage of dithiol's carboxylate ester function with hydrazine led to cluster breakdown and SP band shift back to lower wavelengths.
• Reversible aggregation and deaggregation were observed, accompanied by distinct color changes (pink-red to purple and vice versa).

Conclusions:

• Dithiol molecules enable controlled, reversible aggregation of gold nanoparticles in aqueous solutions.
• The aggregation/deaggregation process can be visually monitored through color changes, facilitating real-time observation.
• This system provides a foundation for developing responsive nanomaterials and controlled nanoparticle assembly techniques.