[23p-C205-1~11] 4.3 Lasers and laser materials processing

▲ [23p-C205-3] Laser Near-Field Reduction of Metallic Ions for the Fabrication of Plasmonic Superstructure Arra

〇(P)Shi Bai¹, Kotaro Obata¹, Koji Sugioka¹ (1.RAP, RIKEN)

Keywords:laser reduction, near-field, SERS

Laser near-field processing, which allows the surface texturing with a fabrication resolution one or two orders smaller than the diffraction limit, has been developed in around 2000 in which the pulsed laser (mostly femtosecond laser) irradiated through nanoscale objects. Specifically, nano/microspheres can tightly confine the intense laser beam in the nanoscale space below the spheres when their diameter is close to the laser wavelength. The highly enhanced electric field enables nanoscale ablation for surface patterning. In this presentation, we take advantage of nanofabrication capability of the laser near-field fabrication to synthesize 3-dimensional (3D) periodic metal nanostructures by laser-induced reduction. Owing to the enhanced electric field below the glass nano/microsheres, the metal ions in a liquid precursor are reduced to create metal nanoparticles with a diameter of ~ 100 nm (one-fifth of laser wavelength). The nanparticles are further synthesized along the surface of spheres to completely wrap them, resulting in formation of metal nano/microclusters. Utilizing the self-assembled monolayer of glass nano/microshperes as a template, the periodic 2D array of nanoclusters are produced to form the superstructure array. The silver, gold and hybrid silver/gold superstructure array can be generated using different types of precursors. Since the nano/microspheres are used as the template, the period of the superstructure is determined by the diameter of spheres. The absorption in visible and near-infrared regions of superstructures can be tuned by adjusting the period due to localized surface plasmon resonance (LSPR). Ultimately, the plasmonic super structure arrays are applied for the resonant surface-enhanced Raman scattering (SERS) for trace detection of fluorescent materials, which provides the potential applications to environmental protection.