This document discusses the luminescence properties of lanthanide compounds. It explains that lanthanide luminescence is sensitized through an energy transfer process involving a pi system. This limits the choice of near-infrared emissive lanthanide ions due to absorption in the visible range. The document also notes that photoluminescent materials generally require a host crystal structure doped with an activator, and sometimes a second dopant is added to act as a sensitizer. Examples of applications include using europium-doped yttrium oxide as a red phosphor in TV tubes or cerium-doped calcium sulfide as a green phosphor.

1. Photoluminescence properties of
lanthanide compounds
Dr. S. H. Burungale
Associate Professor
Head
Department of Chemistry
Yashwantrao Chavan College of Science Karad

4. 4
LUMINESCENCE
Due to the weak absorption coefficient for the f-f transitions, the
luminescence of the lanthanides is sensitized via a  system
E
1CT*
1CT
relaxation
energy
transfer
Absorption
Fluorescence
2F5/2
2F7/2
Luminescence
Emission
Coord. Chem. Rev. 2012, 256, 1604
Limited choice to the Near IR
emissive lanthanide ions due to
absorption in the visible energy range
Ln Acceptor
S
S
S
S
ILCT
ET
Use of the TTF core as organic antenna
hn ~ 20000 cm-1

8. Photoluminescent materials generally require
a host [H] crystal structure, doped with
an activator [A] {sometimes a second dopant is added to act
as a sensitizer [S]}

9. Applications for Fluorescence/Phosphorescence
•e.g. red phosphor in TV tubes from Eu3+ doped into Y2O3
•other luminescence colours:-
•green: Ce3+ in CaS Eu3+ in SrGa2S4
•blue: Eu2+ in (Sr,Mg)2P2O7
•mixed red/green/blue Æ effectively white luminescence
used in fluorescent lamp coatings to convert blue/UV discharge to
white light

10. Anti-Stokes Phosphors have the remarkable property
of emitting photons of higher energy thanthe
incident exciting radiation!e.g. YF3 host doped
with Yb3+ as a sensitizer and Er3+ as
an activator can convert incident IRradiation
into green luminescence