Low power density 980 nm-driven ultrabright red-emitting upconversion nanoparticles via synergetic Yb3+/Tm3+ cascade-sensitization. Issue 43 (30th September 2019)

• Record Type: Journal Article
• Authors: Liu, Jiao; Wu, Shihong; Chu, Huiyuan; Wang, Chaozhan; Shen, Ji-Wei; Wei, Yinmao; Wu, Peng
• Is Part Of: Journal of materials chemistry. Volume 7:Issue 43(2019)
• Page Start: 13415
• Page End: 13424
• Publication Date: 2019-09-30
• Subjects: Materials -- Periodicals; Chemistry, Analytic -- Periodicals; Optical materials -- Research -- Periodicals; Electronics -- Materials -- Research -- Periodicals; 543.0284
• DOI: 10.1039/c9tc04174e
• Languages: English
• ISSNs: 2050-7526

Abstract

Abstract : Herein, we report the first example of synergetic Yb 3+ → Tm 3+ → Er 3+ cascade-sensitized ultrabright red-emitting upconversion nanoparticles with high quantum yield under low power density excitation at 980 nm. Abstract : Achieving a bright red upconverting emission under a low excitation power density is the sole approach to address the issues of tissue overheating and limited penetration depth for the classic 980 nm-driven green-emitting UCNPs. Herein, for the first time, synergetic Yb 3+ /Tm 3+ cascade-sensitized NaErF4 with a high quantum yield under a low excitation power density was developed for the to address the above issues. In detail, high levels ( e.g., 69%) of Yb 3+ were used as the sensitizer to realize the efficient population of the 3 H5 state of co-doped ( e.g., 1%) energy-bridging Tm 3+ ions. Moderate Er 3+ content ( e.g., 30%) provided suitable Er 3+ –Er 3+ cross-relaxation, sufficient bridging of energy utilizing centers (Tm 3+ ( 3 H5 ) → Er 3+ ( 4 I13/2 )), and restrained coupled surface and concentration quenching effects for synergistic red emission and red-to-green ratio enhancement. Incredibly, an optimized nanostructure provides a single chromatic red emission with a red-to-green ratio as high as ∼25.0, and a 53.5-fold intensity enhancement for the red emission as compared with that of the well-known, highly efficient β-NaYF4 :Yb/Er. The first example of Yb 3+ → Tm 3+ → Er 3+ cascade-sensitized ultrabright UCNPs exhibits an intense red emission even under an extremely low excitation power density of 0.2 W cm −2, showing great attractiveness for biological applications.