Preparation, characterization and photoluminescence of Sm3+ doped NaGdF4 nanoparticles

•A series of NaGdF4:Sm3+ nanoparticles have been prepared by hydrothermal method.•The particle size gradually increases, indicating fluxing effect of Sm3+ doping.•The highest intensity and longest lifetime are obtained with 5 mol% Sm3+ doping.•The decay lifetime data follow the bi-exponential nature.

A series of NaGdF4:Sm3+ nanoparticles have been prepared with a facile hydrothermal method and characterized by X-ray diffraction (XRD), scanning electron microscopic (SEM), and the photoluminescence (PL) spectra method. XRD results indicate that all the diffraction peaks of the samples can be well indexed to the hexagonal β-phase of NaGdF4. SEM images demonstrate the gradual increase in particle size of the samples with increasing Sm3+ concentration, which suggests the fluxing effect of Sm3+ doping. The luminescent properties in the excitation, emission and time-resolved spectra were studied and analyzed. The strongest emission peaks located around 594 nm is originated from 4G5/2 → 6H7/2 transition of Sm3+, while the peaks centered at about 560, 640, and 704 nm are from 4G5/2 → 6H5/2, 6H9/2, 6H11/2 transitions, respectively. The photoluminescence intensity firstly increases with increasing Sm3+ concentration, maximizes at 5.0 mol%, and then decreases due to the competition between concentration quenching and the enhancement in crystallinity of the samples. This is supported by the lifetime decay studies. The decay lifetime data follow the bi-exponential nature. The as-prepared NaGdF4:Sm3+ nanoparticles may be useful in the display devices.