Keywords : nanophosphors

Ce3+ and Eu3+ activtated Na2Sr2Al2PO4F9 nanophosphor

S.J. Dhoble; K.N. Shinde

Advanced Materials Letters, 2011, Volume 2, Issue 5, Pages 349-353
DOI: 10.5185/amlett.2011.3072am2011

A halophosphate based nanophosphor has been synthesized by wet chemical method. XRD confirms the preparation of nanophosphor and this article presents the luminescence properties of Ce 3+ and Eu 3+ activated Na2Sr2Al2PO4F9 under UV/NUV excitation. The photoluminescence spectrum comprises of a main peak in the range 270–350 nm with a shoulder in the range 350–370 nm, which may be ascribed to transitions from 5d–4f levels of cerium in the mixed host lattice (Na2Sr2Al2PO4F9). In Na2Sr2Al2PO4F9: Eu 3+ nanophosphor, orange/red luminescence under the near ultraviolet excitation of 393 nm, attributed to the transitions from 5D0 excited states to 7FJ (J=0–4) ground states of Eu 3+ ions.

Photoluminescence and ultraviolet photoresponse in ZnO nanophorsphors prepared by thermal decomposition of zinc acetate

Sheo K. Mishra; Smriti Srivastava; Rajneesh K. Srivastava; A.C. Panday; S.G. Prakash

Advanced Materials Letters, 2011, Volume 2, Issue 4, Pages 298-302
DOI: 10.5185/amlett.indias.210

In the present work, simple, low-cost, and direct route is used for the UV- photodetection and photoluminescent zinc-oxide nanoparticles (NPs) by decomposing zinc acetate in air at 400 0 C for 12 hrs. The X-ray diffraction (XRD) result indicates that the synthesized ZnO NPs is pure and single crystalline structure with wurtzite type. The crystallite size of the ZnO nanoparticles is in the range of 20–50 nm and average crystallite size of synthesized nanoparticles is found to be ~33 nm. The synthesized ZnO NPs exhibits several photoluminescence peaks centered at 396 nm, 418 nm, 441 nm, 481 nm and 522 nm. The time-resolved rise and decay of photocurrent spectrum shows initial significant increase in photocurrent and, subsequently falls gradually under UV-illumination. The photocurrent abruptly falls when illumination is turned off. The variation of photo and dark-current with applied field is found to follow power-law i.e I α V. At low voltage the behavior is sub-linear which becomes super-linear at high voltages. The ZnO NPs is found to have double traps of 0.59 eV and 0.67 eV.

Optical properties of MAl12O19:Eu (M = Ca, Ba, Sr) nanophosphors

Abhay D. Deshmukh; S. J. Dhoble; N.S. Dhoble

Advanced Materials Letters, 2011, Volume 2, Issue 1, Pages 38-42
DOI: 10.5185/amlett.2010.10171

The MAl12O19:Eu (M = Ca, Ba, Sr) phosphor were synthesized by combustion method and systematically characterized by photoluminescence excitation and emission spectra, concentration quenching, morphology and X-ray mapping with scanning electron microscopy. In SrAl12O19:Eu phosphor two PL emission peaks are observed at about 389 nm and another around 420 nm as well as BaAl12O19:Eu phosphor shows blue emission around 460 nm is observed in the blue region of the spectrum and CaAl12O19:Eu shows only red emission at 592 as well as 615 nm. Both phosphors can be efficiently excited in the wavelength range of 250-425 nm, where the near UV (~320 nm) solid state excitation is matched. By combining MAl12O19:Eu (M = Ca, Ba, Sr) phosphor with near UV chops emitting intense blue green (Ba), yellow-red (Ca) and blue purple (Sr) LEDs white LEDs can be produced.