In a recent surface plasmonic study published in the journal Nanotechnology, researchers have demonstrated for the first time that the photoluminescence (PL) enhancement factor for a dipole emitter in an emitter/metal/dielectric structure depends on the thickness of the metal film. The team from City University of Hong Kong and Nankai University, China, found that in the Sm3+-doped-polymer/Ag/SiO2 trilayer structure, the PL enhancement factors for samples with different silver film thickness (30–70 nm) were different when the thickness of the Sm3+-doped-polymer film was kept constant.

The researchers believe that other than the coupling of SPP modes, the existence of the zero-conductivity region and the conducting region in the nanometal film leads to a different PL enhancement factor. They further verified this proposition by constructing a Sm3+-doped-polymer/Ag/Au/SiO2 multilayer structure and comparing the assembly with the Sm3+-doped-polymer/Ag/SiO2 trilayer structure.

Overall, the study revealed that the electron density in the metal layer plays an important role in determining the spectral profile and PL enhancement factor, and the idea of modulating the photophysical properties of SPP assisted light emitters by manipulating the electron density of the metal/alloy layer may open up new opportunities for luminescent devices.