Eu3+-Activated NaGdF4 Nanorods for Near-Ultraviolet Light-Triggered Indoor Illumination

The Eu3+-activated NaGdF4 nanorods were achieved through a simple precipitation procedure at ambient temperature. With the irradiation at 396 nm, the designed nanorods exhibited visible red light with admirable color purity of 90.5% and the optimal doping concentration was 50 mol %. The concentration quenching mechanism was revealed to be decided by dipole–quadrupole interaction and the critical distance was 11.14 Å. The optical transition parameters, which were estimated from Judd-Ofelt theory, of the Eu3+ ions were obtained to confirm its local symmetry behaviors. Moreover, the emission spectra of the designed nanorods at diverse temperatures were used to identify its thermal quenching performance. In comparison with that of the Y2O3:Eu3+ compound, the emission intensity of the Eu3+-activated NaGdF4 nanorods with optimum doping content was 2.47 times higher and its internal quantum efficiency was around 62.3%. Furthermore, the developed white light-emitting diode device, which was constructed by resultant nanorods, green-emitting phosphor (i.e., (Ba,Sr)2SiO4:Eu2+), blue-emitting phosphor (i.e., BaMgAl10O17:Eu2+), and a near-ultraviolet chip, exhibited admirable colorific properties (i.e., good color coordinates, low correlated color temperature, high color rendering index). These achieved features implied that the NaGdF4 nanorods doped with Eu3+ ions were sutiable red-emitting platforms for indoor illumination.