Plasmonic Effect on the Liminescence Properties of Rare Earth Doped Nanoparticles

Abstract

Photovoltaic conversion efficiency of solar cells can be enhanced using up conversion (UC)down conversion (DC) emission. With a lot of scientific data available on metal enhanced up-conversion emission, only few studies are found focusing on metal enhanced down-conversion emission. Here we studied the mechanisms of Quenching of the upconversion luminescence for NayF4: Yb3+, Er3+ co-doped nanoparticles spin-coated on the substrate with prefabricated gold thin film of 200nm along with the SAMs of 1-Octane thiol (OT), 1,8-Octane dithiol (ODT), Benzyl Mercaptan (BMT), 1-Do decanethiol (DDT) with an aim of having enhanced down-conversion emission. Based on the PL spectra, we have observed the quenching of the upconversion photoluminescence (PL) of the prepared geometry as compared to the bare upconverting nanophosphors (UCNPs) of NaYF4: Er3+, Yb3+. This includes the emission from energy states of dopants in NaYF4:Yb3+, Er3+ UCNPs by measuring the PL intensity between 525 and 585 and 650 nm upon 514-nm excitation source. The luminescence intensities and decays were measured from both bare and the nanoparticles treated with prepared gold substrates, the quenching of the upconversion photoluminescence intensity of all the coated samples is observed. The main mechanism of quenching was found to be the effect of separation distance between gold and UCNPs. The separation distance of ≈ 2nm lead to the fluorescence quenching. Raman and FTIR was also done for a better understanding of the pathways that are responsible for the non-radiative decay which led to fluorescence quenching in prepared samples.