Wide controllable range for the local surface plasmon resonance of Cu NWs

This work demonstrated the wide controllable range of local surface plasmon resonance (LSPR) for Cu nanowires (Cu NWs). The LSPR of Cu nanospheres (Cu NSs) and Cu NWs were calculated by the finite-difference time-domain (FDTD). As the diameter was increased from 75 to 300 nm, the extinction peak of Cu NSs could be mediated from 582 to 599 nm, whereas the extinction peaks for the Cu NWs could be shifted from 568 to 627 nm. This contrast is derived from the anisotropy and enhanced phase delay effect of Cu NWs. In attempts to verify this viewpoint, pure Cu NSs and Cu NWs with controllable diameter were prepared by hydrothermal method. And their LSPR spectrum results are well consistent with the simulation. Moreover, it is simulated that the spacing for NS would alter on LSPR peak for Cu NS. However, the arrangement of Cu NWs shows a negligible influence on their LSPR spectrum. As another anisotropic nanostructure, the LSPR spectrum of Cu nanoplates was investigated. And the experimental results could not be inconsistent well with the simulation, which is derived from the stacking effect of the nanoplates. Considering it is difficult to achieve the arrangement for nanostructures orderly, Cu NWs with negligible stacking effect would be a promising optical material that could apply in real application.