New Insight Into the Size Tuning of Monodispersed Colloidal Gold Obtained by Citrate Method

TL;DR

This study clarifies how citrate-to-gold molar ratio influences the size of gold nanoparticles, confirming a monoexponential decay in size with increasing X and validating a theoretical model through multiple experimental techniques.

Contribution

It provides the first experimental validation of the theoretical size decay model for gold nanoparticles across a broad citrate-to-gold ratio range.

Findings

Gold nanoparticle size decreases monoexponentially with citrate-to-gold ratio.

Experimental results agree with Kumar et al.'s theoretical prediction.

Multiple techniques confirm the size decay trend across different synthesis methods.

Abstract

We study the effect of citrate to gold molar ratio (X) on the size of citrated gold nanoparticles (AuNPs). This dependence is still a matter of debate for X $\ge$ 3 where the polydispersity is yet minimized. Indeed, there is no consensus between experiments proposed so far for comparable experimental conditions. Nonetheless, the sole available theoretical prediction has never been validated experimentally in this range of X. We show unambiguously using 3 techniques (UV-Vis spectroscopy, dynamic light scattering and transmission electronic microscopy), 2 different synthetic approaches (Direct, Inverse) and 10 X values for each approach that AuNPs' size decay as a monoexponential with X. This result is, for the first time, in agreement with the sole available theoretical prediction by Kumar et al. on the whole studied range of X.