Probing the Structure, Composition, and Spatial Distribution of Ligands on Gold Nanorods.
The structure and size of ligands attached to the surfaces of gold nanorods, such as adsorbed surfactants or grafted polymers, are important considerations that facilitate the use of such nanoparticles in the human body, in advanced materials for energy harvesting, or in devices for single molecule detection. Here, we report small-angle neutron scattering (SANS) measurements from surfactant or poly(ethylene glycol) (PEG) coated gold nanorods in solution, which quantitatively determine the location, structure, and composition of these surface layers. In addition, by synthesizing gold nanorods using seed crystals which are coated with deuterated cetyltrimethylammonium bromide (dCTAB), we are able to exploit the isotopic sensitivity of SANS to study, for the first time, the retention of surfactant from the seed crystals to the final gold nanorod product, finding that very little exchange of the deuterated with hydrogenated surfactant occurs. Finally, we demonstrate that, when Au NRs are PEGylated using standard techniques, the surfactant bilayer remains intact, and while mass spectrometry detects the presence of both surfactant and PEG, the composition as measured from SANS is predominantly that of the surfactant. These measurements not only provide new insight into the synthesis and functionalization of gold nanorods but provide a quantitative picture of the structure of grafted polymer and surfactant layers on gold nanorod surfaces which has implications for the fabrication of plasmonic and biomedical materials.
National Institute of Standards and Technology , Center for Neutron Research, 100 Bureau Drive, Gaithersburg, Maryland 20899, United States.|Department of Macromolecular Science & Engineering, Case Western Reserve University , 10900 Euclid Avenue, Cleveland, Ohio 44106, United States.
Michael J A
MJ
Hore
Xingchen
X
Ye
Jamie
J
Ford
Yuzhi
Y
Gao
Jiayang
J
Fei
Department of Macromolecular Science & Engineering, Case Western Reserve University , 10900 Euclid Avenue, Cleveland, Ohio 44106, United States.
Qiong
Q
Wu
Department of Macromolecular Science & Engineering, Case Western Reserve University , 10900 Euclid Avenue, Cleveland, Ohio 44106, United States.
Stuart J
SJ
Rowan
Russell J
RJ
Composto
Christopher B
CB
Murray
National Institute of Standards and Technology , Center for Neutron Research, 100 Bureau Drive, Gaithersburg, Maryland 20899, United States.
Boualem
B
Hammouda
CTAB; CTAC; Small-angle neutron scattering; gold nanorods; polymer brush