Paper SE-TuM2
Gold Nanorod Arrays for Surface Enhanced Raman Scattering Imaging of Micro-objects

Tuesday, October 16, 2007, 8:20 am, Room 617

Recently, we have demonstrated the direct formation of Au nanorods with a quasi-parallel major axis on a template layer of SiO₂ having a strongly anisotropic surface morphology. Those Au nanorods show excellent surface enhanced Raman scattering (SERS) properties.¹ Since the number density of nanorods is considerably high, we tried to apply our nanorod arrays to SERS imaging of micro-objects. Template layers of SiO₂ were prepared by the serial bideposition technique (SBD) on a glass substrate. During the SBD, the deposition angle measured from the surface normal was fixed at an angle of 79°, while the azimuthal angle was changed rapidly by 180° with each deposition of a 10-nm-thick layer. After repeating 30 cycles of the serial bideposition, Au was evaporated at a deposition angle of 73° onto the fabricated template layer. Owing to the self-shadowing, Au nanorods aligned in such a way where their major axes are parallel with each other. On the Au nanorod arrays, surface-modified polystyrene (PS) beads (5 µm in diameter), which have pyridyldithio group on their surface, were distributed. Raman spectra were measured by scanning the laser (λ=785 nm) with 1 µm step in a 40x40 µm² region. Raman peaks those originate from pyridyldithio group were detected only at the points where the PS beads and Au nanorods coexist. By assigning the Raman intensity levels to colors, SERS images were obtained. The PS beads were successfully resolved. Therefore, Au nanorod arrays are useful for the imaging of micro-objects such as cells and dusts without any labeling by other chemicals.

¹ M. Suzuki, K. Nakajima, K. Kimura, T. Fukuoka, and Y. Mori, Analytical Sciences (2007) in press.