Issue 45, 2021

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

Abstract

The sensitization of lanthanide-doped upconversion nanocrystals (UCNCs) using organic dyes with a broad and intense optical absorption is an interesting approach for efficient excitation-energy harvesting and enhancing the upconversion luminescence of such UCNCs. In this work, an ultrasmall (∼6.5 nm in diameter) β-NaGdF4:Yb3+,Er3+ core and related core@shell UCNCs were sensitized using six NIR-excitable cyanine dyes with a wide range of functional groups and optical properties. The greatest UC enhancement of 680-times was observed for the conjugate between the Cy 754 dye and NaGdF4:Yb3+,Er3+@NaGdF4:10%Yb3+,30%Nd3+ core@shell UCNCs excited using a 754 nm laser. The enhancement was estimated relative to NaGdF4:Yb3+,Er3+@NaGdF4:10%Yb3+,30%Nd3+ core@shell UCNCs capped with oleic acid and excited using a similar intensity (75 W cm−2) of a 980 nm laser. UC intensity measurements for identical dye-sensitized UCNCs carried out in methanol and in deuterated methanol under argon, as well as in air, allowed us to reveal the connection of the dye triplet states with UCNC sensitization as well as of the hydroxyl groups with quenching of the excited states of lanthanide ions. For UCNCs dispersed in methanol, the strong quenching UC luminescence was always observed, including core@shell UCNCs (with a shell of ∼2 nm). A strong influence of the triplet states of the dyes was observed for the two dyes Cy 754 and Cy 792 that bind firmly to UCNCs and allow the distances between the dye and the UCNC to be reduced, whereas the contribution of this sensitization pathway is very insignificant for Cy 740 and Cy 784 dyes that bind weakly to UCNCs.

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

Supplementary files

Article information

Article type
Paper
Submitted
16 Jūl. 2021
Accepted
17 Sept. 2021
First published
21 Sept. 2021
This article is Open Access
Creative Commons BY-NC license

J. Mater. Chem. C, 2021,9, 16313-16323

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

H. Beygi Nasrabadi, E. Madirov, R. Popescu, L. Štacková, P. Štacko, P. Klán, B. S. Richards, D. Hudry and A. Turshatov, J. Mater. Chem. C, 2021, 9, 16313 DOI: 10.1039/D1TC03333F

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