Optical properties of Eu 3+ and Tb 3+ - doped tin dioxide nanoparticles prepared by coprecipitation method

Abstract

Rare earth (RE) ion doped phosphors have attracted great interest during the past several decades due to their unique physical and chemical properties. RE ions can display many meaningful properties in optics, electronics, and magnetics, originating from f-f electronic transitions within the 4f shell. Doping of wide band gap of metaloxide semiconductors with RE proved to be a successful tool for tailoring their electrical, optical and microstructural properties. Tin dioxide combines high electrical conductivity with optical transparency. The luminescence of pure SnO2, observed in the UV and/ or visible region (350-550 nm) is generally correlated with the presence of crystalline defects, mainly oxygen vacancies, the most likely candidates for recombination centers in emission processes for SnO2 samples. In this work, the incorporation of the Tb3+ and Eu3+ - doped SnO2 nanoparticles were prepared by coprecipitation method. In semicontuctor nanocrystals, lattice distortions near the surface may produce distinct RE3+ environments, which may be enough to affect their band structure and to relax the dipole-forbidden rule. SnO2:Eu3+ presents the appropriate energetic configuration, which takes effect the luminescence in visible range. The ground state (7F0) and some of the metastable excited levels of Eu3+ ion (5D0, 5D1) are situated in the band gap of SnO2. It allows to observe a typical orange/red emissiom from the excited 5D0 to 7FJ (J=0-4) levels. SnO2: Tb3+ presents the transition 5D4→ 7F6 more intense than 5D4→7F5 and exhibit bluish emission in chromaticity diagram. The CIE parameters and CCT values were also varied and the emission color can be tuned from warm to cool light. In addition, this work opens the possibility to produce new functionalized nanoparticles with control of luminescent properties for photonic and biomedical applications.