Enhancing multiphoton upconversion emissions through confined energy migration in lanthanide-doped Cs 2 NaYF 6 nanoplatelets

• Published in: Nanoscale 2021-06, Vol.13 (21), p.9766-9772
• Main Authors: Zhou, Chang, Tu, Datao, Han, Siyuan, Zhang, Peng, Wang, Luping, Yu, Shaohua, Xu, Jin, Li, Renfu, Chen, Xueyuan
• Format: Article
• Language: English
• ISSN: 2040-3364; 2040-3372
• DOI: 10.1039/D1NR01745D

Lanthanide (Ln 3+ )-doped upconversion (UC) nanocrystals have drawn tremendous attention because of their intriguing optical properties. Currently, it is highly desired but remains challenging to achieve efficient multiphoton UC emissions. Herein, we report the controlled synthesis of a new class of UC nanocrystals based on Cs 2 NaYF 6 :Yb/Tm nanoplatelets (NPs), which can effectively convert the 980 nm light to five-photon and four-photon UC emissions of Tm 3+ without the fabrication of a complicated core/multishell structure required in traditional nanocrystals. Particularly, the as-prepared Cs 2 NaYF 6 :Yb/Tm NPs exhibit a maximal UV-to-NIR emission intensity ratio of 1.2, which is the highest among Tm 3+ -doped core-only UC nanocrystals. We reveal that the enhanced multiphoton UC emissions may benefit from the confined energy migration of Ln 3+ dopants in the unique two-dimensional-like structure of Cs 2 NaYF 6 NPs. As such, intense red and green UC emissions of Eu 3+ and Tb 3+ can further be generated via the cascade sensitization of Tm 3+ and Gd 3+ in Cs 2 NaYF 6 :Yb/Tm/Gd/Eu and Cs 2 NaYF 6 :Yb/Tm/Gd/Tb NPs, respectively. These results validate the superiority of Cs 2 NaYF 6 for the future design of efficient UC nanocrystals towards versatile applications.