Hydrotrope-Driven Self-Assembly in CTAB/ n-Hexanol/Water/Heptane Reverse Micellar System

Area of Science:

• Materials Science
• Nanotechnology
• Physical Chemistry

Background:

• Self-organization of nanoparticles into one-dimensional (1D) nanochains yields unique physiochemical properties.
• Fabricating 1D nanochains requires nanotemplates for nanoparticle self-assembly.
• Existing methods face challenges in controlled nanochain formation.

Purpose of the Study:

• To design a hydrotrope-based reverse micellar system for controlled fabrication of 1D nanochains.
• To investigate the effect of hydrotrope concentration and water-to-surfactant ratio on self-assembly.
• To explore the potential of these nanochains in photonic and electronic devices.

Main Methods:

• Utilized a sodium salicylate-based CTAB/n-hexanol/water/heptane reverse micellar system.
• Employed small-angle X-ray scattering (SAXS) to study self-assembled structures.
• Varied hydrotrope concentrations and water-to-surfactant ratios (W_x) in CTAB/heptane systems (W₆, W₁₂, W₁₆).
• Modeled SAXS profiles using spherical form factor and Baxter sticky hard sphere structure factor.

Main Results:

• The W₆ system showed decreased electrostatic repulsion, leading to 1D chain-like assembly of nanodroplets.
• The W₁₂ system exhibited dual hydrotrope effects, increasing system size and reducing repulsion, hindering accurate chain formation analysis.
• The W₁₆ system demonstrated decreased micellar size with increased hydrotrope concentration.

Conclusions:

• The developed reverse micellar system offers a versatile method for fabricating high aspect ratio 1D nanochains.
• These nanochains can be utilized for harnessing collective properties in magnetic, catalytic, and opto-electronic applications.
• The hydrotrope effectively modulates interactions within the reverse micellar system to control self-assembly.