Ascendancy of Cr3+ on Cr6+ valence state and its effect on borate glass environment through CdO doping

Morshidy, H.Y.; Mohamed, Ahmed; Abul-Magd, Ashraf A.; Hassan, Moukhtar A.

doi:10.1016/j.matchemphys.2022.126128

Cited by 61 publications

(16 citation statements)

References 45 publications

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“…38) For several oxide materials, including Cr 6+ , the absorption bands due to a charge transfer phenomenon between Cr 6+ and O 2− appear in 300-400 nm. 39) In Fig. 4(b), MNO:0Cr exhibits no absorption bands in the 400-1100 nm wavelength range.…”

Section: Evaluation Of the Oxidation State For Chromium Ionsmentioning

confidence: 92%

Broadband NIR luminescence of Cr³⁺-doped Mg₄Nb₂O₉ phosphors toward LED light source applications for NIR spectrometry

Nanai,

Satake,

Kitazawa

2024

Jpn. J. Appl. Phys.

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Herein, we report the photoluminescence (PL) properties of Cr3+-doped Mg4Nb2O9 phosphors for applications in NIR phosphor-converted LEDs. Trigonal Mg4Nb2O9 crystals with Cr3+ substitution at three sites were synthesized as the main phase using a solid-state reaction. X-ray photoelectron spectrometry and diffuse reflectance spectroscopy indicated that only trivalent chromium ions were present in the samples. Broadband NIR emission of Cr3+ suitable for combination with Si photodetectors was confirmed at approximately 850 nm. The maximum PL quantum yield (PLQY) was 0.62, and concentration quenching explained the Cr concentration dependence of the PLQY and PL decay time. Low-temperature PL measurements suggested that the PL spectrum comprised three distinct emission bands. The results of the phonon line simulation, low-temperature photoluminescence excitation measurements, and crystal-field parameter estimation clarified the correlation between these emission bands and the Cr3+ substitution sites.

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Section: Evaluation Of the Oxidation State For Chromium Ionsmentioning

confidence: 92%

Broadband NIR luminescence of Cr³⁺-doped Mg₄Nb₂O₉ phosphors toward LED light source applications for NIR spectrometry

Nanai,

Satake,

Kitazawa

2024

Jpn. J. Appl. Phys.

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“…The peak around 3.45 eV in all spectra is derived from the charge transfer transition of Cr 6+ . 34) The following will discuss the optical absorption of Cr 3+ and Cr 4+ . The five optical absorption bands corresponding to Cr 3+ and Cr 4+ were termed "P1," "P2," "P3," "P4," and "P5" bands, and Table I summarizes their peak positions and related electronic transitions.…”

Section: Optical and Pl Propertiesmentioning

confidence: 99%

Synthesis and luminescence properties of Cr₂O₃-CaO-GeO₂ glass and glass ceramics for broadband NIR-LEDs

Nanai

Satake

Kitazawa

2023

Jpn. J. Appl. Phys.

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We report the fabrication of novel 0.1Cr2O3-25CaO-75GeO2 glass and glass ceramics with wideband NIR luminescence and the annealing temperature dependence of the photoluminescence (PL) properties for applications as NIR phosphors. The anisotropic growth of Ca2Ge7O16 nanocrystals in the annealing samples was confirmed. Annealing-induced variations in the body colors and diffuse reflectance spectra suggest that change in the valence of Cr ions and their coordination environments. Broadband luminescence of 700-1300 nm attributed to the 4T2 → 4A2 transition of Cr3+ was observed for the as-made glass. The peak wavelength is shifted from 860 to 780 nm, and line-shaped 2E → 4A2 emission appears due to the crystallization of Ca2Ge7O16 by heat treatment. The PL quantum efficiency reaches the maximum at 0.19 when the sample is annealed at 775ºC, and the dependence on annealing temperature can be understood by the change in the PL lifetimes and diffuse reflectance spectra.

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“…With the addition of more ZnO, the bands between 400 cm −1 and 600 cm −1 , particularly those observed around 450 cm −1 attributed to the stretching vibrations of the ZnO 4 tetrahedral units, are observed [38]. Also, this band can be attributed to the existence of Cr cations in a hexavalent state (Cr 6+ ) which acts as a network former with (CrO 4 ) −2 structural units [39]. Furthermore, this band can be produced from the overlap between the mentioned bands.…”

Section: Infrared Spectroscopymentioning

confidence: 99%

“…In fact, the existence of Cr 3+ within a glassy system showed a green-yellow color to these glasses [40,41]. The Cr 3+ ions can occupy the octahedral positions in the form of CrO 6 units and work as glass modifiers producing structural modifications such as dangling bonds and NBOs [39]. Certainly, two essential absorption bands within the visible range are the prime causes of all glasses color, and these are positioned at about 425-431 nm (the origin of the yellow color) and 605-640 nm (the origin of the green color), respectively, and are attributed to 4 A 2g → 4 T 1g ( 4 F) and 4 A 2g → 4 T 2g ( 4 F) electronic transitions [39][40][41].…”

Section: Optical Absorption Glass Color and Ligand Field Studiesmentioning

confidence: 99%

“…The Cr 3+ ions can occupy the octahedral positions in the form of CrO 6 units and work as glass modifiers producing structural modifications such as dangling bonds and NBOs [39]. Certainly, two essential absorption bands within the visible range are the prime causes of all glasses color, and these are positioned at about 425-431 nm (the origin of the yellow color) and 605-640 nm (the origin of the green color), respectively, and are attributed to 4 A 2g → 4 T 1g ( 4 F) and 4 A 2g → 4 T 2g ( 4 F) electronic transitions [39][40][41]. The reduction in absorbance values of the bands at 423-432 nm and 605-641 nm, as shown in Figure 5, indicates the decrement in the octahedral Cr 3+ content in the studied glasses.…”

Section: Optical Absorption Glass Color and Ligand Field Studiesmentioning

confidence: 99%

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Influence of ZnO on the structural, optical, ligand field and antibacterial characteristics of sodium borosilicate glasses containing minor Cr₂O₃ additions

et al. 2023

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In this work, the structural, optical, ligand field and antibacterial properties of Cr2O3, ZnO and Na2O borosilicate glasses were studied. A glass system of the compositions 70B2O3-14.8 SiO2-(15-x)Na2O-0.2Cr2O3-xZnO, where x = 0, 3, 5 and 7 mol% were prepared via melt-quenching technique. In this study, X-ray diffraction (XRD) spectra were used to check the amorphous state of the prepared glass specimens. Infrared (IR) spectra were used to study the internal structure of the formed units and groups within the glass matrix. Moreover, the optical absorbance spectra were used to study the optical parameters such as optical band gap (Eg), Urbach energies (EU) and ligand field parameters (10Dq, B, Dq/B and β). Furthermore, the antibacterial activities of the glass samples were investigated against different antibiofilm activities for example, Staphylococcus aureus and Escherichia coli. However, the fixed Cr2O3 concentrations, IR results showed the gradual conversion of Cr3+ cations’ coordination from octahedral (CrO6; glass modifier) to tetrahedral (CrO4; glass former) with more replacement of Na2O by ZnO. This result confirms the significant influence of the environment on Cr cations’ coordination. While the optical studies showed that, Eg values increased from 3.06 to 3.62 with further ZnO doping. Furthermore, 10Dq values increased and B values decreased with the increase in ZnO content. These 10Dq increased values reflect the increased interactions between the Cr3+ cations and their environments, such as oxygen anions. Further, the decreased values of B refer to the tendency of the bonds of Cr3+ cations and their environments toward the covalent nature. On the other hand, the results showed that the investigated glasses are promising materials owing to high antibacterial activity on a large scale (food covering, wound curing, and surface coatings), especially the glass sample that contains the highest concentrations of ZnO. 

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Ascendancy of Cr3+ on Cr6+ valence state and its effect on borate glass environment through CdO doping

Cited by 61 publications

References 45 publications

Broadband NIR luminescence of Cr³⁺-doped Mg₄Nb₂O₉ phosphors toward LED light source applications for NIR spectrometry

Broadband NIR luminescence of Cr³⁺-doped Mg₄Nb₂O₉ phosphors toward LED light source applications for NIR spectrometry

Synthesis and luminescence properties of Cr₂O₃-CaO-GeO₂ glass and glass ceramics for broadband NIR-LEDs

Influence of ZnO on the structural, optical, ligand field and antibacterial characteristics of sodium borosilicate glasses containing minor Cr₂O₃ additions

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Ascendancy of Cr3+ on Cr6+ valence state and its effect on borate glass environment through CdO doping

Cited by 61 publications

References 45 publications

Broadband NIR luminescence of Cr3+-doped Mg4Nb2O9 phosphors toward LED light source applications for NIR spectrometry

Broadband NIR luminescence of Cr3+-doped Mg4Nb2O9 phosphors toward LED light source applications for NIR spectrometry

Synthesis and luminescence properties of Cr2O3-CaO-GeO2 glass and glass ceramics for broadband NIR-LEDs

Influence of ZnO on the structural, optical, ligand field and antibacterial characteristics of sodium borosilicate glasses containing minor Cr2O3 additions

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Broadband NIR luminescence of Cr³⁺-doped Mg₄Nb₂O₉ phosphors toward LED light source applications for NIR spectrometry

Broadband NIR luminescence of Cr³⁺-doped Mg₄Nb₂O₉ phosphors toward LED light source applications for NIR spectrometry

Synthesis and luminescence properties of Cr₂O₃-CaO-GeO₂ glass and glass ceramics for broadband NIR-LEDs

Influence of ZnO on the structural, optical, ligand field and antibacterial characteristics of sodium borosilicate glasses containing minor Cr₂O₃ additions