posted on 2018-11-25, 00:00authored bySeyyedamirhossein Hosseini, Nouf Alsiraey, Andrew J. Riley, Tykhon Zubkov, Trent Closson, Jesse Tye, Nataraju Bodappa, Zhihai Li
Controlling the size
of nanoscale entities is important because
many properties of nanomaterials are directly related to the size
of the particles. Gold nanoparticles represent classic materials and
are of particular interest due to their potential application in a
variety of fields. In this study, hexanethiol-capped gold nanoparticles
are synthesized via the Brust–Schiffrin method. Synthesized
nanoparticles were characterized by various analytical techniques
such as transmission electron microscopy, scanning tunneling microscopy
(STM), UV–visible absorption spectroscopy and electrochemical
techniques. We have varied the molar ratio of gold to the protecting
agent (hexanethiol) to discover the effect of gold-to-hexanethiol
ligand ratio on the size of gold particles. The clear correlation
between particle size and molar ratio is found that the averaged particle
size decreases from 4.28 ± 0.83 to 1.54 ± 0.67 nm as the
gold-to-ligand molar ratio changes from 1:1 to 1:9. In contrast to
a recent report that thiolated gold nanoparticles are under spontaneous
disintegration when they are assembled on a gold substrate, our STM
experiments proved that these gold nanoparticles can form a stable
monolayer or multiple layers on the platinum electrode without observing
disintegration within 72 h. Therefore, our STM experiments demonstrate
that the disintegration behavior of gold nanoparticles is related
to the type of ligands and the nature of substrate materials. In electrochemical
experiments, these gold nanoparticles displayed an electrochemical
quantized charging effect, making these nanoparticles useful in the
device applications such as electrochemical or biological sensors.