Duel‐Responsive Hybrid Nanoparticle with Energy Transfer Modulated Near Infrared Emission

Abstract

Lanthanide (Ln) activated systems are characterized by the rich line-shaped emission spectra stemming from the parity-forbidden inner shell f-f transitions. This inherent nature of Ln ions efficiently stabilizes their emissions against environment perturbations, but always necessitates the use of strong and broadband sensitizer to achieve efficient emission. Here, based on a model near-infrared (NIR) emitting system -NaYF 4 : Nd 3 + NPs, we demonstrate sensitized NIR emission by grafting the nanoparticle (NP) surfaces with a visible-light active organic conjugated oligomer, 4,7-(9,9'-bis (4-carboxybutyl)-fluorenyl)-2,1,3-benzothiadiazole (OFBT). Photoluminescence (PL) emission, excitation and time-resolved spectra confirm energy transfer from the OFBT molecules to nanoparticles across the organic/inorganic interfaces, and the efficiency of ET is quantitatively determined by the surface coverage of OFBT molecules and concentration of Ln ions in the NPs. By taking advantage of the environment-sensitive binding strength of OFBT to NP surface, we further demonstrate high sensitivity of the NIR emission from the hybrid NPs to variations in pH and temperature, which is explained by the change in energy transfer efficiency from OFBT to NPs. Therefore, the developed nano-hybrid systems are believed to have potential applications in sensing and detection in physiological environment.[a] Dr.

Coordination mechanism of cyanine dyes on the surface of core@active shell β-NaGdF4:Yb3+,Er3+ nanocrystals and its role in enhancing upconversion luminescence

“…Its absorption cross-section (∼6×10 −16 cm 2 ) is around 30000-times higher than that of Nd 3+ ions (∼2×10 −20 cm 2 ) at 808 nm, thus efficient photosensitization of UCNCs is expected 21 . Moreover, the dye molecules with absorption bands in visible wavelengths can be utilized for sensitizing other luminescent Ln 3+ ions such as Tb 3+ and Eu 3+ , as well as designing upconversion luminescence resonance energy transfer (LRET) sensors [22][23][24][25] , and down-conversion NCs [26][27][28] . Although coating the UCNCs with a protective un-doped shell has been recognized as a robust strategy for minimizing the surface quenching of the lanthanide ions and enhancing BUC and , the inert shell has an adverse effect on the dye-sensitized UC emission since it blocks the energy transfer from the dye to UCNCs 23,29 .…”