Issue 10, 2014

Direct observation of liquid pre-crystallization intermediates during the reduction of aqueous tetrachloroaurate by sulfide ions

Abstract

Phenomena preceding precipitation of gold(I) sulfide in the reaction of aqueous tetrachloroauric acid with sodium sulfide have been studied applying several time-resolved in situ techniques. As can be deduced from UV-vis absorption spectroscopy, soluble species (“pre-nucleation clusters”) emerge within several seconds and slightly change with time; the spectra, along with the previous data for the immobilized products, are indicative of disordered matter with Au(I)–S bonding and the gap of about 1.5 eV. In situ tapping-mode atomic force microscopy (AFM) directly imaged “soft” droplet-like species from 20–50 nm to about 200 nm in the lateral size and the continuous film condensed on the highly oriented pyrolytic graphite (HOPG) support. Small-angle X-ray scattering (SAXS) revealed quasi-particles (“liquid clusters”) growing to about 12 nm for 30 min, and slowly afterwards. Dynamic light scattering (DLS) was preferentially due to the larger species, although the liquid clusters within 20 nm comprise more than 80% of the total volume of the fluid products. The entities, which exist in solution for many hours before sudden gold sulfide sedimentation, are considered as “dense liquid” intermediates involved in a non-classical nucleation pathway.

Graphical abstract: Direct observation of liquid pre-crystallization intermediates during the reduction of aqueous tetrachloroaurate by sulfide ions

Supplementary files

Article information

Article type
Paper
Submitted
30 Oct 2013
Accepted
27 Dec 2013
First published
07 Jan 2014

Phys. Chem. Chem. Phys., 2014,16, 4538-4543

Direct observation of liquid pre-crystallization intermediates during the reduction of aqueous tetrachloroaurate by sulfide ions

Y. Mikhlin, A. Karacharov, M. Likhatski, T. Podlipskaya and I. Zizak, Phys. Chem. Chem. Phys., 2014, 16, 4538 DOI: 10.1039/C3CP54583K

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