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New phosphors Ca2Mg(BO3)2: Ce3+ were synthesized by the solid-state reaction method at a high temperature. The phase purity was characterized by powder X-ray diffraction (XRD). The ultraviolet-visible (UV-Vis) optical properties of Ce3+ have been investigated, and the lowest 5d levels, the emission, and the Stokes shifts of Ce3+ in the host lattice were identified. In addition, its concentration quenching process was also studied. The results show that Ce3+ ions enter Ca2+ sites with only one emission in a UV-Vis range and that the optimum doping concentration is x = 0.05. The excitation and emission spectra were evaluated to clearly reveal luminescence features. [ABSTRACT FROM AUTHOR]

Phosphors that can emit broadband light from visible to near infrared (NIR) may have applications in the fields like white-light illumination and NIR vessel visualization, the investigation on single phase extra-broadband visible-NIR emitting phosphor is of great significance. Herein, an extra-broadband phosphor with tunable visible-NIR emission from 500 nm to longer than 900 nm (bandwidth >400 nm) was successfully prepared, which originates from the emission of Ce3+ (peaking at 573 nm), Cr3+ (peaking at 750 nm) and energy transfer from Ce3+ to Cr3+ in Y 3 MgAl 3 SiO 12 garnet. The influences of Ce3+/Cr3+ doping concentration and working temperature were discussed systematically by luminescence spectra and decay curves. A visible-NIR full-spectrum phosphor-converted light emitting diode (pc-LED) fabricated with a 460 nm LED chip and Y 3 MgAl 3 SiO 12 :0.03Ce3+, 0.01Cr3+ can generate bright white light and broadband NIR light simultaneously. The co-doping of Ce3+ can perfectly compensate for the missing spectrum of Cr3+ in the visible region, thanks to the extra-broadband emission of Ce3+ in visible region and Cr3+ in NIR region, multifunctional advanced applications may be realized for the prepared phosphors. [ABSTRACT FROM AUTHOR]

The fabrication of rare earth luminescent materials with monodispersed and hierarchical morphology is of great importance due to their various applications. In this report, monodispersed hierarchical Yb(OH) x F 3−x microcrystals assembled by nanorod arrays were synthesized by a mild hydrothermal route. Calcination of Yb(OH) x F 3−x resulted in the formation of Yb 6 O 5 F 8 with the retention of morphology. The crystallographic structure relationship between Yb(OH) x F 3−x and Yb 6 O 5 F 8 and the transformation mechanism from Yb(OH) x F 3−x to Yb 6 O 5 F 8 were disclosed. The upconversion emission properties of the Er 3+ doped samples were investigated. It can be found that Yb 6 O 5 F 8 : 5%Er 3+ exhibited an intense red light upconversion emission with the strongest peaks around 658 nm while Yb(OH) x F 3−x : 5%Er 3+ shows no upconversion emission. [ABSTRACT FROM AUTHOR]

A series of novel near-infrared (NIR) long persistent phosphors of Zn 1.2 Al 1.6 Ge 0.2 O 4 : Cr 3+ , Yb 3+ was synthesized by a solid state method. The crystal structure of Zn 1.2 Al 1.6 Ge 0.2 O 4 was identified. Yb 3+ ions were effective codopants for improving the NIR persistent luminescence intensity even after 100 h of decay. The persistent luminescence decay curves and the thermo-luminescence spectra were analyzed. Results indicated that the increase in efficient electron trap concentration induced by doping Yb 3+ ions was a major factor in the improvement of the NIR persistent luminescence. Moreover, short-wave infrared (SWIR = 900–1700 nm) emission of Yb 3+ was be excited by UV and visible light through charge transfer transition of O 2- –Yb 3+ and energy transfer from Cr 3+ to Yb 3+ , respectively. [ABSTRACT FROM AUTHOR]