A Synergy Approach to Enhance Upconversion Luminescence Emission of Rare Earth Nanophosphors with Million-Fold Enhancement Factor

Crystals

Shiao-Wei Kuo¹  Hung-Chih Kan²  Jiunn-Yuan Lin²  Chia-Chen Hsu²  Yi-Chang Tsai²  Duc Tu Vu²  Quoc Minh Le³  Henri Benisty⁴  Ngoc Diep Lai⁵ 

[1] Department of Materials and Optoelectronic Science, National Sun Yat-sen University,Kaohsiung 804, Taiwan;Department of Physics, National Chung Cheng University, Ming Hsiung, Chiayi 621, Taiwan;Institute of Materials Science, Graduate University of Science and Technology, Vietnamese Academy ofScience and Technology (VAST), 18 Hoang Quoc Viet, Cau Giay, Hanoi 100.000, Vietnam;Laboratoire Charles Fabry, CNRS, Institut d’Optique Graduate School, Université Paris-Saclay,91127 Palaiseau, France;Laboratoire Lumière, Matière et Interfaces (LuMin), Institut D’Alembert, CNRS, Ecole Normale SupérieureParis-Saclay, Université Paris-Saclay, CentraleSupélec, 4 Avenue des Sciences, 91190 Gif-sur-Yvette, France;

关键词: upconversion nanoparticles;    upconversion luminescence;    Nd³⁺ sensitizer;    surface passivation;    guided mode resonance;    resonant waveguide grating;   

DOI  :  10.3390/cryst11101187

来源: DOAJ

【 摘 要 】

Lanthanide (Ln³⁺)–doped upconversion nanoparticles (UCNPs) offer an ennormous future for a broad range of biological applications over the conventional downconversion fluorescent probes such as organic dyes or quantum dots. Unfortunately, the efficiency of the anti−Stokes upconversion luminescence (UCL) process is typically much weaker than that of the Stokes downconversion emission. Albeit recent development in the synthesis of UCNPs, it is still a major challenge to produce a high−efficiency UCL, meeting the urgent need for practical applications of enhanced markers in biology. The poor quantum yield efficiency of UCL of UCNPs is mainly due to the fol-lowing reasons: (i) the low absorption coefficient of Ln³⁺ dopants, the specific Ln³⁺ used here being ytterbium (Yb³⁺), (ii) UCL quenching by high−energy oscillators due to surface defects, impurities, ligands, and solvent molecules, and (iii) the insufficient local excitation intensity in broad-field il-lumination to generate a highly efficient UCL. In order to tackle the problem of low absorption cross-section of Ln3+ ions, we first incorporate a new type of neodymium (Nd³⁺) sensitizer into UCNPs to promote their absorption cross-section at 793 nm. To minimize the UCL quenching induced by surface defects and surface ligands, the Nd³⁺-sensitized UCNPs are then coated with an inactive shell of NaYF₄. Finally, the excitation light intensity in the vicinity of UCNPs can be greatly enhanced using a waveguide grating structure thanks to the guided mode resonance. Through the synergy of these three approaches, we show that the UCL intensity of UCNPs can be boosted by a million−fold compared with conventional Yb³⁺–doped UCNPs.

【 授权许可】

Unknown