Determination of the Size Distribution of Metallic Colloids from Extinction Spectroscopy.

Yehia Mansour,Yann Battie,Nouari Chaoui,Aotmane En Naciri

doi:10.3390/nano11112872

Abstract

In this paper, we explore the ability of extinction spectroscopy to characterize colloidal suspensions of gold nanoparticles (Au NPs). We demonstrate that the Au NPs’ size distribution can be deduced by analyzing their extinction spectra using Mie theory. Our procedure, based on the non-negative least square algorithm, takes advantage of the high sensitivity of the plasmon band to the Au NP size. In addition, this procedure does not require any a priori information on the Au NP size distribution. The Au NPs’ size distribution of monomodal or bimodal suspensions can be satisfactorily determined from their extinction spectra. Finally, we show that this characterization tool is compatible with in situ measurement and allows following the change in NPs’ radii during laser exposure.

Highlights

Colloidal suspensions of noble metal nanoparticles (NPs) exhibit strong optical absorption due to surface plasmon resonance (SPR) of NPs
By solving the inverse problem using Mie theory, we unambiguously demonstrate that the size distribution of spherical Au NPs can be estimated from their extinction spectra
These simulations were through some simulations based on Mie theory (Equation (6))

Summary

Introduction

Colloidal suspensions of noble metal nanoparticles (NPs) exhibit strong optical absorption due to surface plasmon resonance (SPR) of NPs. Conventional synthesis routes unavoidably produce NPs with sizes distributions that induce drastic changes in the optical properties of colloids. These distributions are commonly determined by transmission electron microscopy (TEM). The development of nonlocal characterization techniques is crucial to evaluate NPs’ size distribution after their synthesis Nonlocal techniques such as small-angle X-ray scattering (SAXS) [7,8,9], wide-angle. The optical properties of isolated spherical nanoparticles are well-described by Mie theory [30] Several authors used this theory to determine NPs’ mean radius and concentration from their extinction spectra [26]. We show that the determination of the size distribution is fast enough to be suitable for in situ measurements

Materials and Methods

Simulations

Comparison

The from spectra of the