Optical studies of s2-ion dimer centers in alkali halide crystals

Tsuboi, Taijū; Jacobs, P. W. M.

doi:10.1016/0022-3697(91)90060-d

Cited by 31 publications

(22 citation statements)

References 57 publications

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“…It was previously reported that Tl + dimers in alkali-halide crystals which form at high concentrations of Tl + ions characterize by absorption bands at the low-energy tail of the absorption A and B bands due to Tl + monomer center. 35,36 In In + -doped alkali halides 37 with high concentration of In + ions a band due to (In + ) 2 dimers was reported at the low-energy tail of the absorption band C. The appearance of these additional bands was explained by splitting of the excited levels C, B, and A due to change of the crystal field symmetry from cubic to D 2h or D 4h . In In-ZSM-5 In + compensating In + ions are exposed in the zeolite channels, and at high indium loading the formation of (In + ) 2 pairs which can interact directly with each other is quite possible.…”

Section: ■ Results and Discussionmentioning

confidence: 96%

Photoluminescence Properties of Indium-Exchanged ZSM-5 Zeolite

Serykh

Rozhdestvenskaya

2015

J. Phys. Chem. C

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Optical properties (optical absorption and photoluminescence) of indium-exchanged ZSM-5 zeolite have been characterized. It has been found for the first time that reduced In-ZSM-5, containing low-valence In + exchanged cations, exhibits efficient ultraviolet and visible-light photoluminescence. The photoluminescence can be induced by the electronic excitation transitions A, B, and C similar to those either in indium halides or in indium-doped alkali halides. The ultraviolet photoluminescence is associated with isolated In + cations, while the visible-light photoluminescence is most probably due to radiative relaxation of In + oligomers or low-dimensional clusters. ■ INTRODUCTIONZeolites are often considered as host materials for different occluded guests, such as small nanoparticles, dyes, complexes, and ions. Zeolites are nanoporous crystalline aluminosilicates with cavity and channel structures. Their framework, which is constructed of SiO 4 and AlO 4 tetrahedra linked through oxygen atoms, can be considered as a large crystalline polyanion which contains either protons or metal cations for charge compensation. Due to unique highly ordered porous and channel structure of zeolites it can be possible to manage a spatial pattern of the guest species to tune their electronic and optical properties. Furthermore, the aluminum content in a zeolite framework defines concentration of charge-compensating cations and can strongly affect their valence state so that zeolites are capable of stabilizing exchanged metal cations in a certain valence state. For instance, optical properties of zeolites, containing exchanged cations of different metals, have been extensively studied over the last decades. In part, photoluminescence (PL) properties of different zeolites, doped with metal cations such as Cu + , 1,2 Ag + , 3−5 Eu 2+ /Eu 3+ , 6,7 Tb 3+ , 8 Yb 3+ , 9 Er 3+ , 10 Bi 3+ , 11,12 and Ga +13 were reported. The band gap of about 7 eV of the aluminosilicate zeolite framework is similar to that of α-quartz. 14−16 The exchanged cations cause new electronic states that can lie within the zeolite band gap region. These cations can interact with each other to form cation pairs or clusters depending on their nature and distance between them.Indium-exchanged ZSM-5 zeolite has attracted much attention from researchers in the last few years since it is considered as a most promising catalyst for NOx reduction by hydrocarbons. 17,18 Indium is usually introduced into zeolites by the reductive solid state ion exchange. For this the hydrogen form of a zeolite is either mixed with In 2 O 3 powder or impregnated with an aqueous solution of indium nitrate with subsequent drying and calcination. After that, the samples are subjected to high-temperature reduction in hydrogen. As a result, the reduced indium species migrate from the external surface into zeolite channels and interact with acidic protons to form exchanged In + cations. 19 Until now optical properties of indium-exchanged zeolites have not been reported in the literature. However, ...

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Section: ■ Results and Discussionmentioning

confidence: 96%

Photoluminescence Properties of Indium-Exchanged ZSM-5 Zeolite

Serykh

Rozhdestvenskaya

2015

J. Phys. Chem. C

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“…The studies of ns 2 -ions-doped alkali halides (see, e.g., [16,17]) and aluminum perovskites and garnets [18] showed that the spectral bands of dimer impurity centers are usually noticeably shifted to lower-energies with respect to the bands of the corresponding single centers. (Fig.…”

Section: The Search For Dimer Bi 3+ -Bi 3+ Centers In Luag:bi and Yag:bimentioning

confidence: 99%

Origin of Bi³⁺‐related luminescence centres in Lu₃Al₅O₁₂:Bi and Y₃Al₅O₁₂:Bi single crystalline films and the structure of their relaxed excited states

Babin

Gorbenko

Krasnikov

et al. 2012

Physica Status Solidi (b)

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Single crystalline films (SCFs) of Y 3 Al 5 O 12 :Bi and Lu 3 Al 5 O 12 :Bi with different Bi 3+ contents are studied at 1.7-300 K by the time-resolved luminescence spectroscopy methods under excitation in the 2.4-20 eV energy range. Two ultraviolet emission bands of these SCFs, located at 3.99-4.08 eV at T<80 K and at 4.11-4.19 eV at 150 K, arise from the radiative decay of the metastable and radiative minima, respectively, of the triplet relaxed excited state (RES) of a single Bi 3+ center, which are related to the 3 P 0 and 3 P 1 levels of a free Bi 3+ ion. Their excitation bands located around 4.6 eV, 5.2 eV, and 5.95 eV are assigned to the 1 S 0 → 3 P 1 , 1 S 0 → 3 P 2 , and 1 S 0 → 1 P 1 transitions, respectively, in free Bi 3+ ions. The luminescence of dimer Bi 3+ -Bi 3+ centers is not detected in the SCFs studied. The lower-energy (2.6 eV) visible emission of these SCFs is due to an exciton, localized near a single Bi 3+ ion, while the higherenergy (2.75 eV) visible emission, an exciton, localized near a dimer Bi 3+ -Bi 3+ center. Temperature dependences of the luminescence decay times are measured for the ultraviolet and visible emissions in the 1.7-300 K temperature range and simulated by phenomenological models of the dynamics of corresponding excited states. The quantitative parameters of RESs (the energy separations between the energy levels and the rates of the radiative and nonradiative transitions from these levels) are calculated.

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“…4. Another reason may consist in the Bi ion pair creation [16]. This effect cannot be excluded as well, at the concentration about 800 ppm of Bi ions in the crystal studied.…”

Section: Article In Pressmentioning

confidence: 93%