Synthesis of gold nanorods and their dimers
Source
Indian Institute of Technology, Gandhinagar
Date Issued
2016-01-01
Author(s)
Sharma, Deepika
Abstract
Gold Nanorods (NR’s) have received substantial attention due to their unique optical and
electronic properties (which are mainly dependent on their shape, size and aspect ratio) and
have promising applications in the domain of sensing and enhancing electromagnetic fields in
the vicinity of the ends of the nanorods. The enhancement of electromagnetic fields can be
increased to a larger extent by aligning two nanorods in end-to-end manner with small
nanogaps. Molecules adsorbed to the surface of gold nanorod dimers demonstrate large surfaceenhanced
Raman or fluorescence spectroscopy as compared to single nanorods. We performed
several modified versions of the experiment to understand the role of silver nitrate and the
effect of concentration of seed solution in the formation of gold nanorods. We increased the
concentration of silver nitrate and seed solution which resulted in red shift in the LSPR.
The gold nanorods were synthesized via seed mediated method by using two different types of
surfactants namely, CTAB (Cetyl trimethyl ammonium bromide) and Sodium Salicylate. The
former was found to produce lesser number of spherical gold nano particles as compared to the
latter. This was followed by synthesis of gold nanorods dimers via dithiol coupling with
controlling nanogaps. The gap between two rods should preferably be between 5 to 10 nm for
larger field enhancement. Allipahtic dithiol was used for assembly. Experiments were
conducted to study the dependence of the dimer formation on pH of the solution. We could
conclude that pH did not induce any major change in the experiment. The synthesis of dimers
required critical control of several factors like chemical concentration, temperature, and
stability of gold nanorods.
We could thereby successfully synthesize gold nanorods and their dimers (end-to-end
assembly) however; the count of dimers was less than expected. Three type of dimers were
formed which differed in terms of orientation of the two rods.
electronic properties (which are mainly dependent on their shape, size and aspect ratio) and
have promising applications in the domain of sensing and enhancing electromagnetic fields in
the vicinity of the ends of the nanorods. The enhancement of electromagnetic fields can be
increased to a larger extent by aligning two nanorods in end-to-end manner with small
nanogaps. Molecules adsorbed to the surface of gold nanorod dimers demonstrate large surfaceenhanced
Raman or fluorescence spectroscopy as compared to single nanorods. We performed
several modified versions of the experiment to understand the role of silver nitrate and the
effect of concentration of seed solution in the formation of gold nanorods. We increased the
concentration of silver nitrate and seed solution which resulted in red shift in the LSPR.
The gold nanorods were synthesized via seed mediated method by using two different types of
surfactants namely, CTAB (Cetyl trimethyl ammonium bromide) and Sodium Salicylate. The
former was found to produce lesser number of spherical gold nano particles as compared to the
latter. This was followed by synthesis of gold nanorods dimers via dithiol coupling with
controlling nanogaps. The gap between two rods should preferably be between 5 to 10 nm for
larger field enhancement. Allipahtic dithiol was used for assembly. Experiments were
conducted to study the dependence of the dimer formation on pH of the solution. We could
conclude that pH did not induce any major change in the experiment. The synthesis of dimers
required critical control of several factors like chemical concentration, temperature, and
stability of gold nanorods.
We could thereby successfully synthesize gold nanorods and their dimers (end-to-end
assembly) however; the count of dimers was less than expected. Three type of dimers were
formed which differed in terms of orientation of the two rods.
Subjects
14510003