1. Andrew van Bommel February 28th, 2006
Gold Nanocages: Engineering Their Structure for Biomedical Appications Xia et al., University of Washington
Andrew van Bommel
February 28th, 2006

2. Introduction
For biomedical applications, the body is highly transparent to near-IR light, nm
Sperical Au particles show extinction at nm
Au particles can be shifted to the near-IR region:
Aggregation of spherical Au nanoparticles
Elongation of Au nanoparticles into nanorods
Emptying the interiors of spherical nanoparticles to form hollow nanostructures
Note: extinction = scattering + absorption

3. Blue-Shift
Surface Plasmon Resonance (SPR)- free electrons in the Au nanoparticles collectively oscillate and scatter/absorb the incident electromagnetic wave
A composite spherical particle consisting of a metallic shell and a dielectric core could give rise to SPR modes with their wavelengths variable over a broad range

4. Synthesis of Ag nanocubes
AgNO3 is reduced by ethylene glycol- nanocrystal seeds
More Ag atoms are added to the seeds as AgNO3 is constantly reduced
Cubes:
Preferential addition to {111}
Sharp corners produces

5. Conversion into Au nanocages
HAuCl4 reduced by Ag nanostructures:
3Ag + AuCl-  Au + 3Ag+ + 4Cl-
Au atoms evolve a thin shell around each Ag nanocube template
By controlling the concentration of reagents, hollow Au nanocages can be obtained with controlled dimensions

6. Mechanism
i) Initiation of replacement by selective pitting of the Ag nanocubes
ii) Formation of nanobox made of a Au/Ag alloy
iii)Generation of pores through a dealloying process (Ag selectively oxidized)
iv) Ag nanotube template is dissolved

7. Optical Characterization
UV-vis-NIR spectra: increasing the amount of HAuCl4:
Peak broadening due to variations in wall thickness

8. Applications
Photothermal effect- selective attachment to cancer cells with localized heating
Can add functionalities to target cancer cells for photothermal therapy or diagnosis