Hydrothermal synthesis and upconversion luminescence properties of β-NaGdF4:Yb3+/Tm3+ and β-NaGdF4:Yb3+/Ho3+ submicron crystals with regular morphologies

• Published in: Journal of colloid and interface science 2013-02, Vol.392, p.206-212
• Main Authors: Li, Jing, Hao, Zhendong, Zhang, Xia, Luo, Yongshi, Zhao, Jihong, Lü, Shaozhe, Cao, Jian, Zhang, Jiahua
• Format: Article
• Language: English
• Subjects: chelating agents; Chemistry; Citric acid; Colloidal state and disperse state; crystal structure; Crystallinity; Crystallization; Crystals; EDTA; EDTA (chelating agent); energy transfer; Exact sciences and technology; Fluorides - chemistry; Gadolinium - chemistry; General and physical chemistry; Hexagonal prisms; Holmium - chemistry; Hot Temperature; Hydrothermal synthesis; Luminescence; Morphology; Physical and chemical studies. Granulometry. Electrokinetic phenomena; Prisms; Pumps; Sodium - chemistry; Spindles; Thulium - chemistry; UCL properties; Yb3+/Ho3; Yb3+/Tm3; Ytterbium - chemistry; β-NaGdF4
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1016/j.jcis.2012.09.076

[Display omitted] ► β-NaGdF4 of hexagonal prisms, spindles, and spheres was synthesized. ► Regular hexagonal prisms have intense UCL. ► Gd3+:6PJ→8S7/2 transition was found. ► Different spectral distributions for different morphologies were reported. Single phase β-NaGdF4:Yb3+/Tm3+ and β-NaGdF4:Yb3+/Ho3+ submicron crystals with various morphologies including hexagonal prisms, spindles, and spheres were synthesized via the one-step hydrothermal method by controlling the pH values and sort of chelators (EDTA and citric acid). The prepared products showed intense up-converted luminescence (UCL) pumped by infrared laser at 980nm. The hexagonal prisms that meaning high degree crystallinity demonstrated strong UCL in comparison with other morphologies such as spindles and spheres. In β-NaGdF4:Yb3+/Tm3+, UCL not only appeared transitions from 1G4, 1D2, and 1I6 states to the lower lying states of Tm3+, but also 6PJ→8S7/2 transition (310nm) of Gd3+. These UCL were responsible for three, five, and six photons processes determined by pump power dependence of UCL intensities. The observation of UCL of Gd3+ implied occurrence of energy transfer from Tm3+:1I6 to Gd3+:6PJ.