CHEM01200604004 Shri Sanyasinaidu Boddu - Homi Bhabha ...

Purity of the observed colour from a sample is decided by the CIE coordinates, which
can be calculated from the emission spectrum. The abbreviation CIE stands for the French
word Commission Internationale de l'éclairage and is an international governing body on
light, illumination, color and color spaces. The CIE coordinates have been calculated for the
undoped, Eu 3+ , Tb 3+ , Dy 3+ and Sm 3+ doped CaWO 4 nanoparticle from corresponding
emission spectra obtained by exciting samples at 253 nm. These values are plotted in the
standard CIE diagram (Fig.115) and they are showing blue, red, green, greenish yellow and
orange for undoped, Eu 3+ , Tb 3+ , Dy 3+ and Sm 3+ doped samples, respectively.
* D
A = CaWO 4
: Eu 3+
B = CaWO 4
: Sm 3+
C = CaWO 4
: Dy 3+
D = CaWO 4
: Tb 3+
* C
* B
* A
E = CaWO 4
E
*
Fig.115. CIE diagram. A, B, C, D and E in the diagram represent the color coordinates
corresponding to different CaWO 4 :Ln nanoparticles.
6.11. Luminescence studies on Er 3+ doped CaWO 4 nanoparticles: Emission spectra from
Er 3+ doped CaWO 4 nanoparticles excited at 255, 380 and 522 nm are shown in the Fig.116
(a). Strong NIR emission centered at 1535 nm is observed from these nanoparticles. Highest
emission intensity is observed after exciting at 380 nm light. This emission can be assigned to
4 I 13/2 → 4 I 15/2 transition of Er 3+ ion in the CaWO 4 nanoparticles. The splitting in the emission
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