Fluorescence or photoluminescence can be enhanced by the strong electric field close to metal nanostructures. This is known as metal enhanced luminescence. However, the effect is strongly dependent of the distance between the metal structure and the luminescent particle. If the distance is too small, nonradiative processes begin to dominate, leading to pronounced quenching of the emission of the emission instead. At larger separations, the enhancement gradually diminishes, reflecting the reduction in effective coupling between the emitter and the metallic nanostructure. There is a sweet spot at about 10-15 nm separation between the particles and the metal structure.
In this paper1, led by Dawid Piątkowski from Toruń, silver nanowires (NWs), characterized by a broadband plasmonic response, were used as a source of localized electromagnetic fields to investigate their effect of the emission from up-converting rare-earth doped nano-crystals (NC). The nanowires were separated from the NCs by a think polymer film with controlled thickness. Depending on the thickness of the film the researcher from Toruń could observe either quenching or enhancement of the emission, or basically no effect at all.
Martin had a small role in this paper, characterising the nanowires using SEM to measure the thickness of PVP coating after synthesis and cleaning, and also using an optical profilometer to measure the thickness of thin polymer films of PVA deposited under different conditions. The first profilometer measurements were made already back in 2019, so it has taken some time for this work to be completed.
- M. Ćwierzona, M. Żebrowski, P. Dziarhai; J. Niedziółka-Jönsson, M. Jönsson-Niedziółka, M. Nyk, S. Maćkowski, D. Piątkowski
Quench, glow, or stay silent: distance-controlled up-conversion emission near metallic nanowires, Phys. Chem. Chem. Phys. (accepted). (link)(Preprint on arXiv)
