Structures and Conformations of Alkanedithiols on
Gold and Silver Nanoparticles in Water
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Abstract
Organodithiols with two distal thiols
have been used extensively
in gold and silver nanoparticle (AuNP and AgNP) applications. However,
understanding the structures and conformations of organodithiols on
these nanoparticles is challenging. Reported in this work is a combined
surface enhanced Raman spectroscopy (SERS), transmission electron
microscope (TEM), inductively coupled plasma mass-spectrometry (ICP-MS),
and localized surface plasmonic resonance (LSPR) study of alkyldithiol
(ADT, (HS-(CH<sub>2</sub>)<sub><i>n</i></sub>-SH, <i>n</i> = 2, 4, and 6) interactions with AuNPs and AgNPs in water.
These complementary techniques revealed a series of new insights that
would not be possible using individual methods. A large-fraction of
ADTs lies flat on AuNP surfaces. The upright ADTs are dimerized horizontally
through disulfide-bond, or remain as monothiolates on the AuNP surfaces.
The possibility of a significant amount of vertically disulfide-linked
organodithiol on the surface is excluded on the basis of ICP-MS and
AuNP LSPR experiments. ADTs induced significant AgNP disintegrations
in which ADTs are predominantly in dithiolate forms. This work highlights
the extraordinary complexity of organodithiol interactions with plasmonic
nanoparticles. The insights provided in this work will be important
for enhancing fundamental understanding of the structure and properties
of organothiol-functionalized AgNPs and AuNPs