Surfactant (bi)layers on gold nanorods.

Area of Science:

• Materials Science
• Nanotechnology
• Physical Chemistry

Background:

• Gold nanorods require surfactants for stability and controlled growth.
• The structure of surfactant layers, like cetyltrimethylammonium bromide (CTAB), influences nanorod properties.
• Direct measurement of surfactant layer thickness and compactness is needed.

Purpose of the Study:

• To directly measure the thickness of surfactant layers on gold nanorods.
• To compare surfactant layers formed by CTAB and a gemini surfactant (16-EO(1)-16).
• To understand how surfactant structure affects gold nanorod self-assembly.

Main Methods:

• Coupled transmission electron microscopy (TEM), small-angle X-ray scattering (SAXS), and small-angle neutron scattering (SANS).
• Synthesis of gold nanorods using the seeded growth method.
• Analysis of samples with CTAB and 16-EO(1)-16 gemini surfactant.

Main Results:

• Determined the precise thickness of the surfactant layer on gold nanorods.
• Observed a bilayer structure for both CTAB and the gemini surfactant.
• Found that surfactant chain length dictates layer thickness, indicating partial interdigitation.

Conclusions:

• The surfactant layer thickness on gold nanorods is primarily determined by the surfactant's chain length.
• A bilayer structure with partial interdigitation is formed, regardless of surfactant type (CTAB or gemini).
• This finding is crucial for understanding and controlling gold nanorod self-assembly and applications.