Structural Origin of the Optical Properties of Ag-Doped Fluorophosphate and Sulfophosphate Glasses

Abstract

Given the ubiquity of glass formulations that are functionalized with silver compounds, the electronic interaction between isolated silver cations and the glass network deserves more attention. Here, we report the structural origin of the optical properties that result from silver doping in fluorophosphate (PF) and sulfophosphate (PS) glasses. To achieve this, solid-state nuclear magnetic resonance (NMR) spectroscopy and density functional theory (DFT) are combined with optical spectroscopic analysis and physical property measurements. Comparing the 31 P NMR, 27 Al 1d NMR, and 27 Al multi-quantum magic-angle spinning NMR of doped glasses and glasses with large amounts of Ag + added, we deduce silver's bonding preference in these mixed-anion aluminophosphate glasses. We show that such understanding provides an explanation for the large Stokes shift observed for Ag + in PF and PS glasses, which is related to absorption by the ionic Ag + ••• − O−P species and transfer of the excitation energy within more covalently bonded Ag 2 O-like clusters. This is corroborated by DFT calculations, which show that the Ag + ••• − O−P and Ag + ••• − O−S bonds in corresponding crystals are mostly ionic. The introduction of more silver ions into the crystal structure results in more covalent bonding between Ag + and the phosphate matrix.

Ionic Conductivity of Na3Al2P3O12 Glass Electrolytes—Role of Charge Compensators

“…For all glasses, the observed chemical shift values of the four lines were approximately −22, −12, −3, and 7 ppm. Though the Al–O–P bond is more ionic in nature, the chemical shift difference between Q P 1 (1 Al ) and Q P 2 (0 Al ) is very small compared to the difference between Q P 1 (0 Al ) and Q P 1 (1 Al ) . This indicates the difficulty in assigning the deconvoluted peaks of 31 P MAS-NMR to more specific structural units.…”

“…Though the Al−O−P bond is more ionic in nature, the chemical shift difference between Q P 1 (1Al) and Q P 2 (0Al) is very small compared to the difference between Q P 1 (0Al) and Q P 1 (1Al). 38 This indicates the difficulty in assigning the deconvoluted peaks of 31 P MAS-NMR to more specific structural units. Therefore, we assume that these deconvoluted lines could be a mixture of several Q P n (mAl) units.…”

Role of Ag+ Ions in Determining Ce3+ Optical Properties in Fluorophosphate and Sulfophosphate Glasses

“…As discussed previously, confirmation of the fluorine content is further complicated by its low atomic mass, leading to a comparably large error on analyzed fractions. 17,41 The refractive index n d was determined on a Pulfrich refractometer with a precision of ±0.0005. We used a doublebeam spectrophotometer (Cary5000, Agilent) with a spectral resolution of 1 nm to record the optical absorption from 800 to 200 nm.…”

“…3,16 In a previous report, we discussed Ag doping in fluorophosphate (PF) and sulfophosphate (PS) glass matrices. 17 Ag + −RE interactions without the obfuscation from stronger surface plasmon resonance (SPR) of Ag nanoparticles. Furthermore, these investigations revealed the importance of the glass matrix and nearest-neighbor interactions in determining the optical properties of Ag + .…”

“…The optical absorption, photoluminescence (PL) emission, and excitation spectra were used to study the Ag + − Ce 3+/4+ interactions in the two different matrices, drawing from our previous structural analysis of the base glasses. 17…”