Sonication-Assisted Synthesis of Large, High-Quality Mercury Thiolate Single Crystals Directly from Liquid Mercury

Original entry by Sagar Bhandari, APPHY 225 Fall 2010

Reference

Sonication-Assisted Synthesis of Large, High-Quality Mercury Thiolate Single Crystals Directly from Liquid Mercury, Pokroy B, Aichmayer B, Schenk AS, Haimov B, Kang SH, Fratzl P, Aizenberg J., J Am Chem Soc. 2010 Oct 20;132(41):14355-7.

Keywords

mercury thiolates, sonication, self-assembly

Summary

The conventional approach to make mercury thiolate crystals is by a slow reaction of mercury salts with thiolates or disulfides to produce micrometer sized plate-like crystals of mercury thiolate. In this paper, the author discusses a new technique to produce such crystals - via sonication with neat thiols. The authors report that when a mixture of liquid mercury and an excess of neat 1-dodecanethiol was subjected to a medium-intensity ultrasound, rapid phase transition was observed, resulting in the formation of large crystals.As shown in Fig. 1, structures with a length of up to several hundred micrometers, a width of several tens of micrometers, and a thickness of about 100 nm were observed.

Figure 1:

Powder X-ray diffraction (PXRD) was performed on the structures. The results indicate that the crystalline structures are identical for the two methods of synthesis where the crystals from sonication technique are larger and better in quality than the crystals that can be formed by a conventional Hg salt-based synthesis.

Figure 2:

The authors mention that the exact mechanism of the sonication-induced reaction is still unclear. However, they propose the mechanism as shown in Figure 2 for such crystal formation as a possibility. The first stage involves the self-assembly of alkanethiol molecules on the surface of liquid mercury (Fig 2(a)). Next, the mercury molecules break up due to sonication and form smaller droplets(Fig. 2(b)). The next step is the self-assembly of the mercury thiol layers in stacks, which serves as a basis for the ribbon-like crystals.