Effects of Postannealing on the Photoluminescence Properties of Coprecipitated Nanocrystalline BaFCl:Sm3+

Ultra-high-resolution greyscale fluorescence images via UV-exposure of thin flexible phosphor films

Thin films of BaFCl:Sm nanocrystals prepared using a polymer binder were used to create fluorescence images. The phosphor films were exposed to a UV-C mercury lamp light source via chromium-coated quartz greyscale masks to create 4 μm resolution greyscale fluorescence images. The mechanism relies on the highly efficient conversion of Sm³⁺ to Sm²⁺ ions upon exposure to UV-C light which displays a large linear dynamic range. The red fluorescence around 688 nm of the Sm²⁺ is then read-out using blue-violet illumination under a laser scanning confocal microscope. The greyscale images with 16 greyscale levels had a resolution equivalent to ∼125 line pairs per mm or ∼6400 dpi. Improvements in the resolution would be possible using collimated UV-C laser exposure of the film or the use of higher resolution photomasks. Ultra-high resolution binary fluorescence images were also created with resolutions down to 2 μm (∼250 line pairs per mm, ∼12 700 dpi). Downstream applications of the technology could include tailored covert or overt anti-counterfeiting labelling.

Local atomic environment of Yb3+ in alkaline-earth fluorohalide nanocrystals

The local atomic environment of Yb3+ ions doped into alkaline-earth fluorohalide nanocrystals was probed using Yb L2 edge EXAFS spectroscopy. Two structural models are proposed for the first coordination shell of Yb3+.

Structure and Photoluminescence Properties of Sm3+ Ion-Doped YInGe₂O₇ Phosphor

A new phosphor, Sm³⁺ ion-doped YInGe₂O₇, was synthesized using a planetary ball mill solid state reaction. The XRD patterns show that all of the peaks can be attributed to the monoclinic YInGe₂O₇ crystal structure when the Sm³⁺ ion concentration is increased up to 20 mol %. Under an excitation wavelength of 404 nm, the Sm³⁺ intra-4f transition appears in the emission spectrum including two stronger emission peaks located at 560–570 nm and 598 nm correspond to the ⁴G_5/2 → ⁶H_5/2 and ⁴G_5/2 → ⁶H_7/2 transitions, respectively, and another weak emission peak located at 645 nm is due to the ⁴G_5/2 → ⁶H_9/2 transition. The decay time decreases from 4.5 to 0.8 ms as Sm³⁺ ion concentrations increase from 1 to 20 mol %, and the decay mechanism of the ⁴G_5/2 → ⁶H_7/2 transition is a single decay component between Sm³⁺ ions only. The concentration quenching effect occurs when the Sm³⁺ ion concentration is higher than 3 mol %. The CIE color coordinate of Y_0.97Sm_0.03InGe₂O₇ phosphor is at x = 0.457 and y = 0.407, which is located in the orange-yellow light region.