Extinction coefficient of gold nanoparticles with different sizes and different capping ligands

Area of Science:

• Nanotechnology
• Materials Science
• Spectroscopy

Background:

• Gold nanoparticles (AuNPs) are widely used in various applications due to their unique optical properties.
• Accurate characterization of AuNP size and concentration is crucial for their effective application.
• Existing methods for determining AuNP properties can be complex and time-consuming.

Purpose of the Study:

• To determine the extinction coefficients of gold nanoparticles across a range of core sizes.
• To investigate the influence of capping ligands and solvents on the relationship between extinction coefficients and nanoparticle size.
• To establish a reliable calibration method for quantifying gold nanoparticle characteristics.

Main Methods:

• High-resolution transmission electron microscopy (HRTEM) for precise core size determination.
• UV-vis absorption spectroscopy for measuring extinction coefficients.
• Preparation and analysis of citrate-stabilized, oleylamide-protected, and decanethiol-protected gold nanoparticles.

Main Results:

• A consistent linear relationship was observed between the logarithms of extinction coefficients and the core diameters of gold nanoparticles (4-40 nm).
• This linear correlation was found to be independent of the type of capping ligand (citrate, oleylamide, decanethiol) used.
• The relationship also held true irrespective of the solvent used for nanoparticle dispersion.

Conclusions:

• The established linear relationship provides a simple and effective calibration curve for gold nanoparticles.
• This method can be utilized to determine the concentration or average size of unknown gold nanoparticle samples.
• The findings are applicable to nanoparticle-biomolecule conjugates, aiding in their characterization.