Photoluminescence (PL) describes the process of light emission from any kind of matter after interacting with an electromagnetic field, which is an important property of Au nanostructures. With no photobleaching and photoblinking and even brighter emission intensity compared to molecular fluorophores, Au nanostructures have gained popularity in a variety of applications in bio-sensing and bio-imaging. However, a central question on the detailed mechanism of PL from Au nanostructures, which have a bulk-like density of states, remains controversial: whether PL is direct plasmon emission or plasmon enhanced emission. To date, several one-photon PL mechanisms have been proposed based on investigations on isolated gold nanoparticles, including interband transition, intraband transition, and radiative decay of surface plasmon. In order to address this question, it is valuable to investigate capacitively coupled plasmonic Au Nanosheres (AuNS), where we can probe the influence of local electric field enhancement on PL emission. AuNS dimers are the simplest and most fundamental model structures of plasmon coupling and are therefore ideal for PL study. Here, we report PL quantum yield study of strongly coupled AuNS dimers. By using a facile one-pot synthesis method and gel electrophoresis purification method, AuNS dimers with approximate 1-2 nm interparticle spacing were obtained with 23% yield. Single particle technique enabled selective measurement of PL quantum yields from individual AuNS monomers and dimers. We found the quantum yields of monomers and dimers are nearly identical even with 2-3 orders of magnitude difference in their local electric field enhancement. As such, we propose direct plasmon emission as the major PL emission pathway.<br/>

Photoluminescence quantum yield of strongly coupled gold plasmonic molecule

249th National Meeting (2015)

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