Optical tuning of plasmon-enhanced photoluminescence.

Photoluminescence (PL) can be enhanced and tuned with the assistance of surface plasmons. Traditional methods of generating tunable fluorophores are either of low efficiency or complicated with poor controllability. Here, we propose the optical tuning and enhancement of PL by modifying the plasmon modes, which shows unique advantages of generality, simplicity, and on-demand controllability. We adopted gold nanoparticles on a mirror as the plasmonic resonator, and responsive polymers as the spacers as well as the emitters in the nanogaps. By controlling the coating thickness of polymers, we can achieve tunable plasmon resonances as well as PL peaks with an enhancement factor up to ∼7000. Furthermore, we show the optical tuning of the plasmon resonances via laser irradiation which modifies the nanogaps. Thus, the PL peaks of the polymers shift accordingly with plasmon resonances. This tuning mechanism is based on plasmon-enhanced PL, which selectively enhances PL signals at different wavelengths. Such a plasmon-assisted PL selection by the optical tuning method provides new opportunities for photonic devices with applications of multiplex sensing and full colour displays.