Quenching effect of C-H bond in long lived NIR luminescent erbium complexes
- PDF / 721,457 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 56 Downloads / 126 Views
Quenching effect of C-H bond in long lived NIR luminescent erbium complexes Laurent Divay, Christophe Galindo, Françoise Soyer, Evelyne Chastaing, Renato Bisaro and Pierre Le Barny THALES R&T, 1 avenue Augustin Fresnel, 91767 Palaiseau Cedex, France ABSTRACT Erbium excited state deactivation is studied for two fluorinated complexes based on N-(P,Pditetrafluorophosphinoyl-P,P-ditetrafluorophenyl phosphinimidates and N-(P,P-dipentafluoro phosphinoyl)-P,P-dipentafluorophenyl phosphinimidates ligands. We show that the substitution of a fluorine atom in para-position by an hydrogen atom on each phenyl ring of the perfluorinated organic ligand results in a decrease in near infrared luminescence lifetimes from 800 µs to 70 µs when measured under vacuum on sublimated powder samples. These experiments show that the introduction of C-H bonds, although outside the first coordination sphere of the erbium ion, can still induce a one order of magnitude decrease in its excited state lifetime. The found lifetime however is still longer than most reported partially fluorinated complexes, which opens the way for new functionalized complexes. INTRODUCTION Inorganic erbium-doped glasses are widely used in telecommunications due to the sharp intra-atomic 4I13/2 → 4I15/2 transition in the 4f orbital of erbium resulting in an emission at ~ 1.5 µm, which is the low loss window of silica optical fibres. In these systems, the erbium ion possesses a very long excited state lifetime – several milliseconds – which allows population inversion under moderate intensity pumping light, thus allowing optical amplification. Organic equivalent systems hold the potential to decrease the cost of such devices, and would allow the tuning of the physico-chemical properties of the materials through the ligand formulation. However, organic materials behave as efficient NIR luminescence quenchers due to the coupling between the electronic transition of the erbium ion and the vibrational overtones of O-H, N-H and C-H bonds in the vicinity of the ion [1]. Such coupling is very efficient and luminescence lifetimes as short as a few microseconds are commonly observed. The consequence is a decrease in the emission quantum yield in accordance with the lifetime reduction, up to three orders of magnitude compared to the inorganic counterparts. The substitution of hydrogen atoms by fluorine on the organic ligand is usually proposed [2]. The perfluorinated imidodiphosphinate ligand based complex [Er(F-tpip)3)] shows excited states lifetimes up to 316 μs in powder [2, 3], whereas the perhydrogenated ligand complex [Er(tpip)3] exhibits a luminescence lifetime of few microseconds [4]. This is attributed to the “shell” nature of the ligand and the total absence of hydrogen atoms in close proximity of the lanthanide. The fluorine substitution increases the volatility of the complexes which can then be used as optical quality evaporated thin films with high erbium ion concentration and relatively long luminescence lifetime [5-6]. Another consequence of the fluorine substituti
Data Loading...
