Single-Molecule Spontaneous Emission in the Vicinity of an Individual Gold Nanorod

An individual gold nanorod as an optical antenna to modulate single-molecule fluorescence spontaneous emission behaviors is investigated theoretically. 2D and 3D numerical finite-difference time-domain methods are implemented to investigate changes in the excitation rate, spontaneous emission rate, quantum efficiency, and emission spectral shape as functions of the separation between the emitter and nanorod. Our simulations reveal that the 3D relative configuration between the gold. nanorod and the single dipole definitely affects the quantum efficiency and emission spectral shape. The orientation of the dipole and the polarization of the excitation light are also investigated to clarify the polarization dependence of the plasmonic-enhanced fluorescence. Furthermore, we calculate the modified quantum efficiency and emission spectral shape of a single Cy5 dye molecule in the vicinity of a single gold nanorod taking experimental requirements into account.