CHEM01200604004 Shri Sanyasinaidu Boddu - Homi Bhabha ...

heated for 2 hrs at 70°C under argon atmosphere. White solid was obtained and this solid was
dissolved in CHCl 3 and re-precipitated with methanol. The precipitate was separated by
centrifugation and dried under ambient conditions. For preparing thin polymer films
containing the nanoparticles, the white solid obtained was dissolved in CHCl 3 and spin coated
on a quartz substrate at a spinning rate of 2500 rpm.
2.6. Synthesis of un-doped and lanthanide doped MWO 4 (M = Ca, Sr, Ba)
nanomaterials: Starting materials used for the synthesis of undoped and lanthanide doped
metal tungstates were Ca(NO 3 ) 2 .H 2 O, SrCl 2 .6H 2 O, Ba(NO 3 ) 2 , Eu(NO 3 ) 3 .5H 2 O,
Tb(NO 3 ) 3 .xH 2 O, Dy(NO 3 ) 3 .xH 2 O, Sm(NO 3 ) 3 .xH 2 O and Er(OOCCH 3 ) 3 .xH 2 O. For the
synthesis of undoped metal tungstates, 2.12 mmol of metal salt was dissolved in 20 ml of
ethylene glycol while stirring. Around 2.12 mmol of Na 2 WO 4 .2H 2 O was added to this
solution and stirring was continued for two hours. The precipitate formed was separated by
centrifugation and washed with methanol and acetone to remove unreacted species. For the
synthesis of lanthanide doped metal tungstates, same procedure was followed except that the
addition of 2 atom % lanthanide salts to metal salt solution was done prior to the addition of
Na 2 WO 4 .2H 2 O.
2.7. Characterization Techniques: During the present investigation, various
characterization techniques were employed and they are briefly discussed below.
2.7.1. X-Ray Diffraction: X-rays are invisible, electrically neutral, electromagnetic
radiations. Their frequencies are intermediate between the ultra-violet (UV) and gamma
radiations with wavelength (λ) ranging from approximately 0.04 Å to 1000 Å. When the X-
rays are incident on a solid material (grating), they are either elastically/in-elastically
scattered or absorbed. The elastic scattering of X-rays is known as Bragg scattering and
follows the Bragg equation (equation 7)
nλ
= 2dsinθ
…………………………. (7)
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