Controlled post synthesis growth and etching of gold nanorods
Source
Indian Institute of Technology, Gandhinagar
Date Issued
2016-01-01
Author(s)
Kumar, Pavneesh
Abstract
It is important to control the aspect ratio of individual gold nanorod as tiny change in aspect ratio
and shape of gold nanorod can lead to different optical properties of gold nanorods. In this work,
we report the synthesis of gold nanorods having the various aspect ratios. Increase in the pH
causes the blue shift of the LSPR of gold nanorods indicating the decrease in the aspect ratio of
gold nanorods whereas the trasverse SPR of gold nanorods remains unaffected to the pH of the
solution. Seed mediated approach for the synthesis of gold nanorods inhibits to look upon the
properties of individual gold nanorod as distribution of the nanorod sizes takes place in this
method. Till now post synthesis growth and/or etching of the gold nanorods has been done in
bulk solution. Herein, we report the post synthesis growth and/or etching of individual gold
nanorod by isolating them over the glass surface and adding the growth solution containing the
HAuCl4, AgNO3, Ascorbic acid in CTAB and sodium oleate in order to do the post synthesis
growth and adding the ferric chloride solution in order to etch them. It will not only be novel
approach to control the aspect ratio of gold inanorods but can also be used to control the
nanosize’s gap between the dimer of gold nanorods which can be used to detect the molecules
with weak emission yield without labeling them with a bright fluorophore just by placing it in the
nanosize’s gap of the dimer of gold nanorods. We also report the effect of CTAB and ferric
chloride concentration on the etching rate of gold nanorods respectively in the bulk solution
keeping all other things constant/same. Ferric chloride oxidises the gold nanorods from the tips
selectively. We found that on decreasing the CTAB and ferric chloride concentration in the
solution, etching rate decreases and etching rate also decreases as the time passes by. Etching
leads to the significant decrease in the length but little change in the diameter of the gold
nanorods.
and shape of gold nanorod can lead to different optical properties of gold nanorods. In this work,
we report the synthesis of gold nanorods having the various aspect ratios. Increase in the pH
causes the blue shift of the LSPR of gold nanorods indicating the decrease in the aspect ratio of
gold nanorods whereas the trasverse SPR of gold nanorods remains unaffected to the pH of the
solution. Seed mediated approach for the synthesis of gold nanorods inhibits to look upon the
properties of individual gold nanorod as distribution of the nanorod sizes takes place in this
method. Till now post synthesis growth and/or etching of the gold nanorods has been done in
bulk solution. Herein, we report the post synthesis growth and/or etching of individual gold
nanorod by isolating them over the glass surface and adding the growth solution containing the
HAuCl4, AgNO3, Ascorbic acid in CTAB and sodium oleate in order to do the post synthesis
growth and adding the ferric chloride solution in order to etch them. It will not only be novel
approach to control the aspect ratio of gold inanorods but can also be used to control the
nanosize’s gap between the dimer of gold nanorods which can be used to detect the molecules
with weak emission yield without labeling them with a bright fluorophore just by placing it in the
nanosize’s gap of the dimer of gold nanorods. We also report the effect of CTAB and ferric
chloride concentration on the etching rate of gold nanorods respectively in the bulk solution
keeping all other things constant/same. Ferric chloride oxidises the gold nanorods from the tips
selectively. We found that on decreasing the CTAB and ferric chloride concentration in the
solution, etching rate decreases and etching rate also decreases as the time passes by. Etching
leads to the significant decrease in the length but little change in the diameter of the gold
nanorods.