Direct Visualization of Wavelength-Dependent Single Dipoles Generated on Single Gold Nanourchins with Sharp Branches

ABSTRACT: We present the optical properties of singe gold nanourchins (AuNUs) with sharp branches on their surfaces under dark-field (DF) microscopy and spectroscopy. The DF intensities of the single AuNUs were changed periodically as a function of the rotation angle at three localized surface plasmon resonance (LSPR) wavelengths. Furthermore, we demonstrate the generation of single dipoles with different LSPR wavelengths in multiple directions on the same AuNU surface. The multiple LSPR dipoles generated on the AuNU surface were further visualized under defocused DF microscopy and verified by characteristic doughnut-shaped defocused scattering field distributions. GRAPHICAL ABSTRACT: ᅟ [Image: see text] ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s11671-018-2675-2) contains supplementary material, which is available to authorized users.