Effects of chromophore dissociation on the optical properties of rare-earth-doped polymers

Abstract

The observed dissociation of tetrakis rare-earth chromophores in rare-earth-doped organic polymers is reported, and a time-resolved spectroscopic technique is presented to determine quantitatively the fractional concentrations of different chromophore species in various solvents. Based on this technique, the equilibrium constants of tetrakis rare-earth chromophores in rare-earth-doped polymers are determined. Thus, the equilibrium constants for tetrakis rare-earth compounds of benzoyltrifluoroacetonate (BTF), for example, Sm(BTF)(4)P and Eu(BTF)(4)P in methyl methacrylate monomer, are K = 4.7 ? 0.5 x 10(-4) M and K = 1.2 ? 0.5 x 10(-4) M, respectively. In contrast, the tetrakis rare-earth compounds of hexafluoroacetylacetonate (HFA), for example, Sm(HFA)(4)Net(4) and Eu(HFA)(4)Net(4), are quite stable and show no evidence of dissociation. We further characterize the dissociation of several chromophore systems and discuss the influence such dissociation has on overall optical performance. The results enable determination of optimal doping concentrations as well as preferred rare-earth chromophore preparation and doped polymer fabrication procedures.

A transparent, flexible, ion conductive, and luminescent PMMA ionogel based on a Pt/Eu bimetallic complex and the ionic liquid [Bmim][N(Tf)2]

“…For example, the Eu(III) complex may partially dissociate in the PMMA matrix, similar to earlier suggestions. 43,57 In summary, and consistent with literature, the current data show that the combination of IL, chromophore, and polymer directly affects the properties of the final material.…”

“…In the later time domain (218 ms # t # 3.6 ms) small spectral changes with time can be found, which are indicative of the existence of two emitting europium species. 57 To evaluate the contribution of these two species, a global fit for the decays of both excitation wavelengths was performed, with the decay times set as global parameters. The global fit yields the decay times s 1 z 1.5 ms, s 2 z 20 ms, s 3 z 450 ms and s 4 z 1100 ms, which are in good agreement with the decay times obtained from the discrete fitting analysis (Table 1).…”

Ionic liquid as plasticizer for europium(iii)-doped luminescent poly(methyl methacrylate) films

“…Gao et al also reported on bi-exponential decay curves found for the luminescent lifetimes of similar samarium(III) and europium(III) tetrakis b-diketonate complexes in lanthanide-doped PMMA polymers. 36 The b-diketonate ligands that they investigated were benzoyltrifluoroacetonate (btfac) and hexafluoroacetylacetonate (hfac). In the case of [Ln(btfac) 4 ] À they associated these bi-exponential decay curves with a partial dissociation of the lanthanide complex resulting in the presence of [Ln(btfac) 3 ] as well as [Ln(btfac) 4 ] À species in the doped polymers.…”

Rare-earth beta-diketonates

“…In a host-guest system, the rare-earth complex is dissolved into the polymer matrix. To make host-guest systems, two techniques can be used (Gao et al, 1998). The first technique involves dissolution of the rare-earth complexes directly into the monomer.…”

“…One has to be aware of the fact that during the processing of the polymer, the complexes can dissociate in coordinating solvents. Gao et al (1998) The first experiments on optical materials based on polymers doped with β-diketonate complexes go back to the 1960's when rare-earth β-diketonates have been tested as active components in chelate lasers (see section 8.1). For instance, Wolff and Pressley (1963) doped [Eu(tta) 3 ] into a polymethylmethacrylate (PMMA) matrix and observed laser action in this material.…”