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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.

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Related in: MedlinePlus

Correlation between the absorption and PLE spectra of In-doped zinc phosphate glasses prepared under different conditions.(a) PLE and optical absorption spectra of 1In2Oα–60ZnO–40P2O5 glass with and without addition of 10 mol% C. (b) PLE and optical absorption spectra of 1In2Oα–60ZnO–40P2O5 glass melted in air for 20 min and 180 min. The PLE spectra (solid lines) are normalised. The absorption spectra (dashed lines) indicate that absorption bands originating from In+ are correlated with emissions.
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f2: Correlation between the absorption and PLE spectra of In-doped zinc phosphate glasses prepared under different conditions.(a) PLE and optical absorption spectra of 1In2Oα–60ZnO–40P2O5 glass with and without addition of 10 mol% C. (b) PLE and optical absorption spectra of 1In2Oα–60ZnO–40P2O5 glass melted in air for 20 min and 180 min. The PLE spectra (solid lines) are normalised. The absorption spectra (dashed lines) indicate that absorption bands originating from In+ are correlated with emissions.

Mentions: The redox state of the melt condition likely affects the In+ species generated from In2O3. The emissions intensity of 1In2Oα–60ZnO–40P2O5 glass with addition of a reducing agent (10 mol% carbon) was 1.2 times that of non-doped 1In2Oα–60ZnO–40P2O5 glass (Fig. 2a). Since the obtained carbon-added glass was transparent without residual carbon, we can conclude that the carbon, which worked as a reducing agent of In species, was burned off during the melting in the air. On the other hand, both the optical absorption edge and the PLE bands attributed to In+ species disappeared after melting in air for 3 h (Fig. 2b). Because an oxidation reaction of a metastable cation species during air-melting has been reported for another ns2-type cation44, metastable In+ may also be a transient species affected by melting conditions. Based on these redox reactions, we conclude that the three PLE bands in Fig. 1 are associated with different excitation processes of the In+ centre.


Photoluminescence of monovalent indium centres in phosphate glass
Correlation between the absorption and PLE spectra of In-doped zinc phosphate glasses prepared under different conditions.(a) PLE and optical absorption spectra of 1In2Oα–60ZnO–40P2O5 glass with and without addition of 10 mol% C. (b) PLE and optical absorption spectra of 1In2Oα–60ZnO–40P2O5 glass melted in air for 20 min and 180 min. The PLE spectra (solid lines) are normalised. The absorption spectra (dashed lines) indicate that absorption bands originating from In+ are correlated with emissions.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f2: Correlation between the absorption and PLE spectra of In-doped zinc phosphate glasses prepared under different conditions.(a) PLE and optical absorption spectra of 1In2Oα–60ZnO–40P2O5 glass with and without addition of 10 mol% C. (b) PLE and optical absorption spectra of 1In2Oα–60ZnO–40P2O5 glass melted in air for 20 min and 180 min. The PLE spectra (solid lines) are normalised. The absorption spectra (dashed lines) indicate that absorption bands originating from In+ are correlated with emissions.
Mentions: The redox state of the melt condition likely affects the In+ species generated from In2O3. The emissions intensity of 1In2Oα–60ZnO–40P2O5 glass with addition of a reducing agent (10 mol% carbon) was 1.2 times that of non-doped 1In2Oα–60ZnO–40P2O5 glass (Fig. 2a). Since the obtained carbon-added glass was transparent without residual carbon, we can conclude that the carbon, which worked as a reducing agent of In species, was burned off during the melting in the air. On the other hand, both the optical absorption edge and the PLE bands attributed to In+ species disappeared after melting in air for 3 h (Fig. 2b). Because an oxidation reaction of a metastable cation species during air-melting has been reported for another ns2-type cation44, metastable In+ may also be a transient species affected by melting conditions. Based on these redox reactions, we conclude that the three PLE bands in Fig. 1 are associated with different excitation processes of the In+ centre.

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