Photoluminescence Quantum Yield from Gold Nanorods: Dependence on Excitation Polarization

We demonstrated that the luminescence quantum yield of single gold nanorods illuminated by a continuous-wave laser at a wavelength of 532 nm depends on the angle of excitation polarization, while that excited by a 633 nm laser does not. The electrons in the sp band dominate the luminescence process under the 633 nm laser, resulting in a constant quantum yield irrespective of whether the excitation polarization is perpendicular or parallel. Under the 532 nm laser, the electrons in both the d band (interband transition) and sp band (surface plasmon) are involved in the luminescence process. The variation of quantum yield under the 532 nm laser results from the different conversion efficiencies of the d-band interband transition and the sp-band plasmons into luminescence. Furthermore, we found that the plasmon mode coupling effect strongly modulated the plasmon emission efficiency by comparing the luminescence of two sets of nanorods with different sizes. Generally, smaller-sized gold nanorods result in high...