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

Abstract

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.

Silicon-Induced UV Transparency in Phosphate Glasses and Its Application to the Enhancement of the UV Type B Emission of Gd3+

“…Still, it turns out that the estimated maximum E opt value obtained for the 0.5Si glass of 4.88 (±0.33) eV is higher than the reported for the Si codoped glass containing 0.4 mol % silver oxide at 4.71 (±0.21) eV. 8 Thus, it seems that in the latter case the presence of Ag + ions presented some absorption in the UV as considered. 8 In Figure 2, the PL of the 0.1−0.5Si glasses is examined under excitation at 275 nm in comparison to the host as reference.…”

“…8 Besides the traditional assignment of reduced metallic impurities, 15,16 the formation of P−O−Si bonds supported by 31 P nuclear magnetic resonance spectroscopy was considered in connection with the improved light transmission in the UV. 8 A model was proposed suggesting an oxygen-assisted process was linked to the incorporation of oxidized silicon into the phosphate glass network and electron trapping in nonbridging oxygens; i.e., the formation of Si−O •− and Si−O−O •− defects was postulated. 8 Hence, the formation of such species in the presence case may be considered, concurrent with the incorporation of SiO 4 tetrahedra expected from oxidized silicon acting as network former.…”

“…8 A model was proposed suggesting an oxygen-assisted process was linked to the incorporation of oxidized silicon into the phosphate glass network and electron trapping in nonbridging oxygens; i.e., the formation of Si−O •− and Si−O−O •− defects was postulated. 8 Hence, the formation of such species in the presence case may be considered, concurrent with the incorporation of SiO 4 tetrahedra expected from oxidized silicon acting as network former. Similarly, an improvement in UV transparency was recently reported for glasses melted together with multiwall carbon nanotubes 17 and graphite.…”

“…Apart from the traditional view of reduction of metallic impurities (e.g., Fe 3+ ), 15,16,19 this behavior could be a reflect of a suppression of charge transfer transitions (O 2− → Ba 2+ ions in the present case) accompanying structural modifications. 8,17 An attempt to analyze the absorption data for the 0.5Si glass as the most distinct case in the framework of a Tauc's plot 20 is made in the top inset of Figure 1 in comparison to the host. In this context, the power law expression for the absorption coefficient α(ν) as a function of photon energy (E = hν) given by…”

“…Such melting conditions have been previously found effective for preparing Si-containing glasses. 8,10,12 Silicon and/or gadolinium doping was done by adding Si powder (Alfa Aesar, crystalline, −140 mesh, 98%) and/or Gd 2 O 3 (Alfa Aesar, 99.9%) quantities in mol % in relation to network former P 2 O 5 .…”