Intensely Luminescent Materials Obtained by Combining Lanthanide Ions, 2,2‘-Bipyridine, and Poly(ethylene glycol) in Various Fluid or Solid Environments

Abstract

Steady-state luminescence spectroscopy and luminescence decay analysis have been employed to study the association of two rare earth ions (i.e., Eu 3+ and Tb 3+ ) with poly-(ethylene glycol) in the absence and in the presence of 2,2′-bipyridine, which acted as an antenna of near-UV radiation. Three different systems have been studied at various polymer concentrations, i.e., aqueous solutions, transparent composite organic/inorganic sol-gel matrixes made by hydrolysis of tetramethoxysilane, and polymer matrixes. The photophysical behavior of the luminescent species has been studied in conjunction with the poly(ethylene glycol) content. In both aqueous solutions and silica matrixes, luminescence intensity and decay time were found to increase by increasing polymer concentration. Addition of 2,2′bipyridine resulted in complex formation between the ligand and the lanthanide ions. This complex was stabilized by association with the polymer chains. Excitation at the ligand absorption wavelength (337 nm) resulted in ligand-to-metal energy transfer and strong luminescence emission, characterized by the narrow-band emission of the metal. The complex between lanthanide ions and 2,2′-bipyridine possessed its own particular photophysical characteristics and emitted a bright broad blue luminescence with an excitation maximum around 380 nm. Freeze-drying of aqueous solutions of medium size poly(ethylene glycol) containing lanthanide ions and 2,2′-bipyridine produced an intensely luminescent solid material emitting the characteristic luminescence of the metal when excited at the ligand absorption band (337 nm) or the characteristic luminescence of the complex when excited at 380 nm.

Thin Films of Highly Luminescent Lanthanide Complexes Covalently Linked to an Organic−Inorganic Hybrid Material via 2-Substituted Imidazo[4,5-f]-1,10-phenanthroline Groups

“…10,11 To explore the potential of the complexes for photonic applications (light-converting devices), [12][13][14][15][16][17] it is useful to incorporate the complexes in an inert host matrix. [18][19][20][21][22][23][24][25][26][27] A problem often encountered upon embedding of the luminescent complexes in the host matrix is the nonhomogeneous distribution of the compounds, 28,29 which leads to clustering of lanthanide ions and hence a decrease of the luminescence intensity. 30,31 A more homogeneous distribution of the lanthanide complex in the host matrix can be achieved by covalent coupling of the complexes to this host matrix.…”

Optical characterization of Eu3+-doped sol-gel hybrid thin film prepared with various conditions

“…The lines denoted by 1,2,3,4 and 5 are assigned to the Eu 3+ intra-4f 6 transitions between the 5 D 0 and 7 F 0−4 levels. The intensities of these emission spectra depend on the selected excitation wavelength [4,7,8].…”

“…The large broad band clearly presents two components: a main band in the blue spectral region, peaking between 410-425 nm and a shoulder in the green spectral region, peaking around 446 nm. Only the energy of the former component depends on the selected excitation wavelength [4,[7][8][9]. The energy-transfer mechanisms between the host matrixes and the europium ions arise from two different and independent processes: a charge-transfer band, resulting from the interaction between the Eu 3+ and the first ligands, and energy transfer from the hybrid's backbone emitting center.…”

Organic/inorganic nanocomposite gels employed as electrolyte supports in Dye‐sensitized Photoelectrochemical cells

“…PEG oligomers, as the PEG-200 presently used, are liquids and they are known to be ionic conductors [25,26]. When a salt is disolved in PEG, the cations are bound by the ether oxygens by coordinating several PEG chains [27]. Conductivity is mainly carried on by anions [26] and this fact is especially in favour of the presently used redox couple I 3 − /I − .…”