A study of the Eu3+ charge-transfer state in lanthanide-borate glasses

Abstract

The luminescence properties of the Eu 3+ ion in lanthanide-borate glasses were investigated and compared with those of Eu ~+ in crystalline GdB306. In these materials the emission observed is from the SD 0 to the 7Fj levels. The rate of nonradiative relaxation from the charge-transfer state to the 7Fj levels depends strongly on the host material. In the glasses it is high, whereas it is low in the crystalline lattice. Improving the glass quality by increasing the amount of lattice modifiers increases the rate even further. This difference is discussed and explained in terms of a configurational coordinate diagram.

Europium(III) Luminescence and Intramolecular Energy Transfer Studies of Polyoxometalloeuropates

“…However, the observation of a simple exponential decay of the 5 D 0 emission of 2 , 3 , and 5 (with Eu···Eu distances of <6.15 Å) with moderate quantum yield (Tables and ) 2 implies that there is no energy migration between the two Eu 3+ sites at all. The magnetic-dipole character of the 5 D 0 → 7 F 1 transition lets us consider the radiative rate of this transition to be almost independent of the geometry of the Eu 3+ surroundings, as long as the mixing of the electric-dipole character into the 5 D 0 → 7 F 1 transition is small . Therefore, it may be meaningful to use the 5 D 0 → 7 F 1 magnetic-dipole transition as a standard inorder to estimate the radiative rate for 1 − 6 .…”

Enhanced Photostability Luminescent Properties of Er3+-Doped Near-White-Emitting DyxEr(1–x)-POM Derivatives

“…14,15 Although some magnetic-dipole f−f transitions of Ln 3+ are allowed, their intensity is too weak to implement their use in practical applications. 16 The alternative route to overcome such discrepancies like small absorption coefficients is to sensitize Ln 3+ emissions through appropriate sensitizers, which can eventually involve light harvesting and subsequent energy transfer to the Ln 3+ via antenna effect. 17,18 Fortunately, Ln 3+ ions can be utilized as a good electron acceptors due to unfilled 5d or 6s orbitals which can accept lone pair of electrons from various ligands to form covalent bonds.…”

“…It is well-known that lanthanide ion (Ln 3+ )-based complexes are excellent inorganic optical materials and have drawn considerable interest of researchers because of their sharp characteristic emissions, long luminescent lifetime, potentially high quantum efficiency, good reliability, and safety. On account of these excellent features, Ln 3+ -based materials have been employed in various optical applications such as lighting diodes, detection and sensing, lasers, bioimaging, biomedical analysis, etc. − Until now, Ce 3+ -, Dy 3+ -, Er 3+ -, Sm 3+ -, Tm 3+ -, Yb 3+ -, Pr 3+ -, and Eu 3+ -based materials have been scientifically explored and partially commercialized in lighting and display purposes in various disciplines of technology. − Interestingly, the luminescence of Ln 3+ is restricted due to the electric-dipole-forbidden nature of f–f transitions within the unfilled 4f shells, which may lead to small molar absorption coefficients (ε < 10 L mol –1 cm –1 ) and long luminescence lifetime. , Although some magnetic-dipole f–f transitions of Ln 3+ are allowed, their intensity is too weak to implement their use in practical applications . The alternative route to overcome such discrepancies like small absorption coefficients is to sensitize Ln 3+ emissions through appropriate sensitizers, which can eventually involve light harvesting and subsequent energy transfer to the Ln 3+ via antenna effect. , Fortunately, Ln 3+ ions can be utilized as a good electron acceptors due to unfilled 5d or 6s orbitals which can accept lone pair of electrons from various ligands to form covalent bonds. , Moreover, the luminescence of Ln 3+ -based materials are influenced by the following: (1) high concentration of Ln 3+ in complexes which may lead to quenching in luminescence intensity; (2) the ligands such as aqua or similar solvent when coordinated to Ln 3+ would quench the luminescence due to the high frequency of O–H or N–H stretching vibrations; (3) some emitting Ln 3+ ions are sensitive to field effects such as highly symmetrical coordination and molecular symmetry around Ln 3+ centers. − …”

Blue-excited luminescence of Eu-doped strontium boroaluminate glasses

“…Although the type of glasses is a suitable host material for optically active rare-earth ions, it is usually difficult to obtain a high emission efficiency due to a high-frequency borate vibration, which induces nonradiation losses by a multi-phonon relaxation process. However, recent study reveals that the high-frequency vibration could promote the energy transfer in a phononassisted way and consequently improve emission efficiency [3,4]. This holds promise of borate use in host optical materials when further considering glass potentiality to homogeneous doping and flexible geometry being easily fabricated into various forms, from the viewpoint of practical application.…”