A mathematical investigation of the Turkevich organizer theory in the citrate method for the synthesis of gold nanoparticles

Abstract

Abstract-Gold nanoparticles are commonly synthesized by reducing chloroauric acid with sodium citrate. This method, referred to as the citrate method, can produce spherical gold nanoparticles (NPs) in the size range 10-150 nm. Gold NPs of this size are useful in many applications. However, the NPs are usually polydisperse and irreproducible. A better understanding of the synthesis mechanisms is thus required. This work thoroughly investigated the only model that describes the synthesis. This model combines mass and population balance equations, describing the NPs synthesis through a sequence of chemical reactions. Chloroauric acid reacts with sodium citrate to form aurous chloride and dicarboxy acetone. The latter organizes aurous chloride in a nucleation step and concurrently degrades into acetone. The unconsumed precursor then grows the formed nuclei. However, depending on the pH, both the precursor and the reducing agent react differently thus affecting the synthesis. In this work, we investigated the model for different conditions of pH, temperature and initial reactant concentrations. To solve the model, we used Parsival, a commercial numerical code, whilst to test it, we considered various conditions studied experimentally by different researchers, for which results are available in the literature. The model poorly predicted the experimental data. We believe that this is because the model does not account for the acid-base properties of both chloroauric acid and sodium citrate.

Continuous flow synthesis of ultrasmall gold nanoparticles in a microreactor using trisodium citrate and their SERS performance

“…A study by Kumar et al concluded that the dicarboxy acetone (DCA) formed from citrate reduction plays a predominant role which aids nucleation and its side product, acetone, could continue reducing the gold nanoparticles precursor and speed up growth (Kumar et al, 2006). Even though the model agreed with several literature results, it does not yield satisfactory predictions in other cases, because it does not take account of the acid-base properties of the reactants (Agunloye et al, 2017). Wuithschick et al (2015) demonstrated experimentally that the Au(III) species are the critical element to control particle size.…”

Physicochemical Aspects of Metal Nanoparticle Preparation

“…However, aside from the three discussed parameters, there are several other parameters with key influence. One is molar ratio among the reactants, which was already effectively used by Turkevich for a tailored preparation of gold nanoparticles [154,160,212,221,222]. The whole reduction process can be also influenced by other substances present in the reaction system-e.g., molecules of surfactants, polymers, and other low-molecular organic substances with O, N, and S heteroatoms, which significantly influence the process of nucleation and growth of the nanoparticles [223][224][225][226] and also the aggregation stability of the final system [227][228][229].…”

Functionalized gold nanoparticles for sample preparation: A review

“…The classical synthesis approach for GNPs was first reported by Turkevich et al. in 1951 . It is based on the chemical reduction of Au(III) in aqueous solution (also named wet‐chemical synthesis) and involves essentially two processes: the nucleation and particle growth .…”