Shih et al.
Fig. 4. Effect of the area of silver plate immersion on the max(SPl) for Au nanorods. Note that the nanorod aspect ratio is linearly related to the max(SPl) value (see Fig. 2).
A. Preparation Scheme A gold nanorod solution (ca. 1 mL) is prepared by redispersing the centrifuged product as described above. The concentration is adjusted to the desired level by monitoring the absorbance at the SPl band maximum. For example, an absorbance of ca. 2 (using a 1-cm-path-length cuvette) at 900 nm was used for a sample of nanorods whose mean aspect ratio was 5. This solution was transferred to a polytetrafluoroethylene (PTFE) bottle for the silica-coating step. The silane reagent was prepared by mixing (3-mercaptopropyl)trimethoxysilane (MPTMS, 97%; Fluka) with ethanol in a 1:1000 volume ratio (VMPTMS: VEtOH). Next, 40 L of this reagent is added to 1 mL of the Au nanorod solution,
Chemistry of metal nanoparticles