Absorption Spectroscopy Analysis of Calcium–Phosphate Glasses Highly Doped with Monovalent Copper

Darley

2020

ChemPhysChem

Self Cite

Bismuth borate glasses containing phosphors and luminescent rare‐earths are of interest for applications in light‐emitting devices. Herein, the influence of CuO impurities on red‐emitting Eu3+‐doped bismuth borate glasses of the 25Bi2O3‐15BaO‐10Li2O‐50B2O3 type was investigated by various spectroscopic methods. The glasses were prepared by the melt‐quench technique and characterized by X‐ray diffraction (XRD), Fourier transform‐infrared (FT‐IR) spectroscopy, UV/Vis optical absorption (OA), and photoluminescence (PL) spectroscopy including decay kinetics assessment. The XRD data confirmed the amorphous nature of the glasses whereas FT‐IR spectra indicated the basic structural features of trigonal BO3 units and BO4 tetrahedra. The OA analysis showed that addition of CuO up to 0.5 mol% results in significant growth of the visible Cu2+ absorption band around 715 nm, with slight decrease in the optical band gap energies assessed through Tauc plots. A drastic PL quenching of Eu3+ ions emission was evidenced concurring with the detrimental effect of Cu2+. The assessment of the Eu3+ emission decay curves revealed significant lifetime decrease of the 5D0 emitting state with increasing CuO concentration. An analysis of quenching constants was finally performed comparing results from integrated PL data with the emission decay rates. It is argued that the bismuth borate glass system supports an effective Eu3+→Cu2+ energy transfer (more so than phosphates) in connection with a strong spectral overlap between Eu3+ emission and Cu2+ absorption.

Section: Optical Absorption (Oa) Evaluationmentioning

confidence: 93%

Optical Spectroscopy and Excited‐State Dynamics of Eu³⁺‐Doped Bismuth Borate Glasses Containing CuO

Darley

2020

ChemPhysChem

Self Cite

“…Similarly, the strong near-UV absorption of Cu + ions has been recently reported to have a dependence with concentration correlating ultimately with the Cu + -Cu + inter-ionic distance [25]. Nevertheless, for the silver-containing glasses in the present work, a pronounced non-linear relationship between the band gap energies and the silver oxide contents is recognized from the inset in Fig.…”

Section: Optical Absorption Evaluationmentioning

confidence: 56%

“…For glasses as amorphous materials, the value n = 2 connected to allowed-indirect transitions is usually employed in itting the experimental results [25,26]. This implies the interactions of photons with lattice vibrations in the light absorption process.…”

Section: Optical Absorption Evaluationmentioning

confidence: 99%

Optical Properties of Eu3+-Doped Aluminophosphate Glass with a High Concentration of Silver and Tin

J Inorg Organomet Polym

2016

Self Cite

last decades in search of improvements in the luminescent properties of europium given its relevance for optical device applications [1][2][3][4][5][6][7][8][9][10][11][12][13]. Malta et al. [1] irst reported that an improved photoluminescence (PL) of Eu 3+ ions in glass containing Ag nanoparticles (NPs) occurred due to the surface plasmon resonance (SPR) of the silver particles.Other groups subsequently concluded similarly on the role of local-ield efects of plasmonic Ag particles amplifying Eu 3+ PL in glasses [2,3,5,10,11,13]. On the other hand, several other studies have added to the discussion with respect to the conditions and mechanisms by which Eu 3+ emission is enhanced by the presence of silver [4,[6][7][8][9]12]. Namely, ionic metal species have been argued to be at the origin of energy transfer processes leading to a sensitized Eu 3+ PL rather than the Ag NPs themselves. Moreover, the NPs have been reported to instead lead to an eicient PL quenching of the rare-earth ions [4, 6] through an energy transfer/deactivating efect recently referred to as the plasmonic diluent efect [14]. Hence, achieving the desired enhanced optical properties is not straightforward. Moreover, it requires signiicant research eforts towards understanding the fundamental interactions between europium ions and the diferent oxidation and aggregation states of silver.Silicate [1-3, 7, 9, 12], borate [8], tellurite [10,11], and germanate [5] glasses were often the object of investigation regarding the interaction between europium and silver species. However, phosphate-based glass hosts notable for their high metal solubility, low-melting character, relatively low glass transition temperature, and high thermal stability are promising materials in the ield of photonics [13,15]. In these, the addition of aluminium oxide as a less acid network former results in a strengthened glass network with improved chemical durability and thermo-mechanical stability [16][17][18]. In addition, co-doping with SnO is believed Abstract The optical properties of Eu 3+ -doped aluminophosphate glass containing a high concentration of Ag 2 O and SnO co-dopants (8 mol% of each) are reported. Glass preparation is carried out by melt-quenching, and a subsequent in situ monitored heat treatment (HT) is carried out for the reduction of ionic silver to Ag nanoparticles (NPs) via reducing agent tin(II). An enhanced ultraviolet broadband excitation range for Eu 3+ ions is realized for the meltquenched glass, likely due to the creation of molecule-like silver species such as Ag + -Ag + dimers. The real-time optical monitoring of the glass during isothermal HT shows the steady development of the surface plasmon resonance peak of Ag NPs near 420 nm. Concurrently exciting Eu 3+ ions in situ at 420 nm unveils the plasmonic diluent efect manifested through the quenching of Eu 3+ luminescence. The decay times of the 5 D 0 emitting state in Eu 3+ ions in the melt-quenched and NP-doped glasses are measured and discussed.

“…The analysis of UV absorption in solids is typically performed in the context of a Tauc's plot according to the power law expression for the absorption coefficient α(ν) as a function of photon energy ( E = h ν) which is given by

α false(normalν false) = k \frac{{false(h normalν - E_{opt} false)}^{n}}{h ν}

where the exponent n is related to the nature of the transitions, k is a constant, and E opt is the optical band gap energy . For amorphous materials, the value n = 2 connected to allowed‐indirect transitions is usually employed in fitting experimental results . This implies the interactions of photons with lattice vibrations in the light absorption process.…”

Section: Resultsmentioning

confidence: 99%

“… although NP precipitation was obtained with silicon and copper in place of silver, the UV transparency in the as‐melted CuSi glasses therein was not as much enhanced as with silver in the present work. The reason for this seems to be the strong near‐UV absorption of Cu + ions, phenomenon that has been recently reported to have a particular dependence on Cu + –Cu + interionic distance . And if the copper ions are further reduced to the neutral state and precipitated as Cu NPs, the interband transitions in the metal present significant interference from the visible to the UV …”

Section: Resultsmentioning

confidence: 99%

Ag and Si Codoped Phosphate Glasses: Plasmonic Nanocomposites with Enhanced UV Transparency

2016

J. Am. Ceram. Soc.

Self Cite

The use of silicon powder to produce plasmonic Ag nanocomposite phosphate glasses which also exhibit improved transparency in the ultraviolet (UV) is proposed. Ag2O/Si codoped glasses were prepared in a barium‐phosphate matrix by a simple melt‐quench method in ambient atmosphere. The as‐prepared glasses exhibit enhanced UV transparency, whereby the surface plasmon resonance of Ag nanoparticles (NPs) is manifested for the glasses with higher Ag2O contents. 31P nuclear magnetic resonance spectroscopy is consistent with the formation of P–O–Si bonds, thus suggesting their possible role on the improved UV light transmission. Consequently, a model was presented accounting for the influence of silicon on the polymerization of the phosphate network concomitant with the creation of highly reactive oxygen species. Further exploiting the proposed reactive species, a real‐time spectroscopic study of the plasmonic response of Ag NPs in Ag/Si codoped glass samples was carried out during an in situ thermal processing. The temperature dependence of the Ag particle precipitation was studied in the 400°C–430°C range, from which an Arrhenius‐type plot allowed for estimating the activation energy of the process at 3.42 (±0.38) eV. Ultimately, the vanishing of the luminescence ascribed to Ag+ ions was observed in a heat‐treated sample, consistent with the high reactivity acquired by the glass matrix. Silicon thus appears promising for producing UV transparent glasses for high‐performance optics and for the reduction of Ag+ ions to produce Ag nanocomposites valuable for photonic (nanoplasmonic) applications.