Controlled synthesis of lanthanide-doped Gd 2 O 2 S nanocrystals with novel excitation-dependent multicolor emissions.

Developing multicolor-emitting materials has significant value in many research fields such as displays, bioimaging, and information storage. The widely adopted strategies to realize multicolor emission are tuning the material composition, phase, and size. Herein, the emission color was continuously controlled from yellow to pink by simply changing the excitation wavelength from 254 nm to 365 nm for Tb3+ /Eu3+ co-doped Gd2 O2 S NCs. The Gd2 O2 S NCs with different morphologies, including nanoplate with various sizes and flower-like, were successfully prepared by seed-mediated, Na+ /Y3+ co-doped, and S concentration-tuned methods. The results indicated that Na+ ions greatly promote the growth of Gd2 O2 S NCs and Y3+ ions have an impact on their shape. Moreover, the PL intensity of the 2%Eu-doped flower-like Na/Y:Gd2 O2 S (F-NYG) NCs decreased by about 24.7%, 6.8%, and 5.1% under 254 nm, 316 nm, and 348 nm excitation, respectively; this is due to less non-radiative relaxation paths above the excited state of Eu3+ :5 D0 at longer excitation wavelength, which result in a decreased degree of the PL intensity reduction.