Determination of the Size Distribution of Metallic Colloids from Extinction Spectroscopy

Area of Science:

• Nanotechnology
• Materials Science
• Spectroscopy

Background:

• Colloidal suspensions of gold nanoparticles (Au NPs) are crucial in various applications.
• Accurate characterization of Au NP size distribution is essential for controlling their properties.
• Current methods may require prior knowledge or are less versatile.

Purpose of the Study:

• To explore extinction spectroscopy for characterizing Au NP size distribution.
• To develop a method for deducing size distribution from extinction spectra without prior information.
• To assess the compatibility of the method with in situ measurements.

Main Methods:

• Utilizing extinction spectroscopy to measure optical properties of Au NP suspensions.
• Applying Mie theory to model the interaction of light with Au NPs.
• Employing a non-negative least square algorithm for data analysis.
• Leveraging the plasmon band's sensitivity to Au NP size.

Main Results:

• Successfully deduced Au NP size distribution from extinction spectra.
• Demonstrated the method's effectiveness for monomodal and bimodal suspensions.
• Validated the procedure's independence from a priori size distribution information.
• Confirmed the compatibility with in situ measurements and tracking radius changes during laser exposure.

Conclusions:

• Extinction spectroscopy, analyzed with Mie theory and a non-negative least square algorithm, is a powerful tool for characterizing Au NP size distribution.
• The developed procedure offers a versatile and information-efficient approach for nanoparticle analysis.
• This technique enables real-time monitoring of nanoparticle size, crucial for dynamic processes.