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Photoluminescence of monovalent indium centres in phosphate glass

View Article: PubMed Central

ABSTRACT

Valence control of polyvalent cations is important for functionalization of various kinds of materials. Indium oxides have been used in various applications, such as indium tin oxide in transparent electrical conduction films. However, although metastable In+ (5 s2 configuration) species exhibit photoluminescence (PL), they have attracted little attention. Valence control of In+ cations in these materials will be important for further functionalization. Here, we describe In+ species using PL and X-ray absorption fine structure (XAFS) analysis. Three absorption bands in the UV region are attributed to the In+ centre: two weak forbidden bands (1S0 → 3P1,1S0 → 3P2) and a strong allowed band (1S0 → 1P1). The strongest PL excitation band cannot be attributed to the conventional allowed transition to the singlet excited state. Emission decay of the order of microseconds suggests that radiative relaxation occurs from the triplet excitation state. The XAFS analysis suggests that these In+ species have shorter In–O distances with lower coordination numbers than in In2O3. These results clearly demonstrate that In+ exists in a metastable amorphous network, which is the origin of the observed luminescent properties.

No MeSH data available.


Related in: MedlinePlus

PLE spectrum of 1In2Oα–60ZnO–40P2O5 glass along with the absorption spectrum.Dashed lines indicate three Gaussian functions after spectrum deconvolution. Each absorption band is attributable to a PLE band.
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f1: PLE spectrum of 1In2Oα–60ZnO–40P2O5 glass along with the absorption spectrum.Dashed lines indicate three Gaussian functions after spectrum deconvolution. Each absorption band is attributable to a PLE band.

Mentions: The transparent colourless In-doped 60ZnO–40P2O5 glasses have glass transition temperatures (Tgs) of about 420 °C. Because the actual oxidation state of In has not been determined, the chemical composition is denoted as xIn2Oα–60ZnO–40P2O5. Figure 1 shows the PLE spectrum of 1In2Oα–60ZnO–40P2O5 glass along with its absorption spectrum. Because Sn-free glass has an absorption edge at much higher photon energy (>6 eV) than the In-doped glasses, the observed absorption edge is attributed to the In species. Comparing the absorption spectrum with the PLE spectrum, both spectra had at least three excitation bands. After peak deconvolution, the absorption spectrum could be constructed using three Gaussian peaks with peak energies corresponding to those of the PLE bands. In a KI:In+ crystal, there are three excitation bands: A (~4.5 eV), B (~5.0 eV), and C (~5.6 eV)17. Because emissions are difficult to observe in 60ZnO–40P2O5 glass3940, it is likely that the emissions in the In–doped 60ZnO–40P2O5 glasses originated from In+ cations. Although the starting material for the In species was trivalent In2O3, it has been reported that cations in a melt of phosphate glass prepared with ammonium phosphate tend to be reduced43.


Photoluminescence of monovalent indium centres in phosphate glass
PLE spectrum of 1In2Oα–60ZnO–40P2O5 glass along with the absorption spectrum.Dashed lines indicate three Gaussian functions after spectrum deconvolution. Each absorption band is attributable to a PLE band.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4555169&req=5

f1: PLE spectrum of 1In2Oα–60ZnO–40P2O5 glass along with the absorption spectrum.Dashed lines indicate three Gaussian functions after spectrum deconvolution. Each absorption band is attributable to a PLE band.
Mentions: The transparent colourless In-doped 60ZnO–40P2O5 glasses have glass transition temperatures (Tgs) of about 420 °C. Because the actual oxidation state of In has not been determined, the chemical composition is denoted as xIn2Oα–60ZnO–40P2O5. Figure 1 shows the PLE spectrum of 1In2Oα–60ZnO–40P2O5 glass along with its absorption spectrum. Because Sn-free glass has an absorption edge at much higher photon energy (>6 eV) than the In-doped glasses, the observed absorption edge is attributed to the In species. Comparing the absorption spectrum with the PLE spectrum, both spectra had at least three excitation bands. After peak deconvolution, the absorption spectrum could be constructed using three Gaussian peaks with peak energies corresponding to those of the PLE bands. In a KI:In+ crystal, there are three excitation bands: A (~4.5 eV), B (~5.0 eV), and C (~5.6 eV)17. Because emissions are difficult to observe in 60ZnO–40P2O5 glass3940, it is likely that the emissions in the In–doped 60ZnO–40P2O5 glasses originated from In+ cations. Although the starting material for the In species was trivalent In2O3, it has been reported that cations in a melt of phosphate glass prepared with ammonium phosphate tend to be reduced43.

View Article: PubMed Central

ABSTRACT

Valence control of polyvalent cations is important for functionalization of various kinds of materials. Indium oxides have been used in various applications, such as indium tin oxide in transparent electrical conduction films. However, although metastable In+ (5 s2 configuration) species exhibit photoluminescence (PL), they have attracted little attention. Valence control of In+ cations in these materials will be important for further functionalization. Here, we describe In+ species using PL and X-ray absorption fine structure (XAFS) analysis. Three absorption bands in the UV region are attributed to the In+ centre: two weak forbidden bands (1S0 → 3P1,1S0 → 3P2) and a strong allowed band (1S0 → 1P1). The strongest PL excitation band cannot be attributed to the conventional allowed transition to the singlet excited state. Emission decay of the order of microseconds suggests that radiative relaxation occurs from the triplet excitation state. The XAFS analysis suggests that these In+ species have shorter In–O distances with lower coordination numbers than in In2O3. These results clearly demonstrate that In+ exists in a metastable amorphous network, which is the origin of the observed luminescent properties.

No MeSH data available.


Related in: MedlinePlus