Eu2+/Eu3+ activated phosphate glasses synthesized via melting with multi-wall carbon nanotubes

Nanodiamond-induced modifications of Eu-doped phosphate glasses toward photonic applications: A synergistic physico-chemical approach

“…Such lowering in the transmission around 320 nm is attributed to the 4f 7 to 4f 6 5d inter-configurational transitions in Eu 2+ ions which are quite intense due to the allowed character for the light absorption process. 18,19 The results resemble the recently reported for the glasses melted with Eu 2 O 3 and MWCNTs in our group, 20 however the current spectra are achieved with ten times lower carbon (C ND ) loadings. Similar evolution in transmission spectra were also reported by Tratsiak et al 16 and Liang et al 19 following the conversion from Eu 3+ to Eu 2+ in silicate and borophosphate glasses, respectively.…”

“…A similar result was recently reported for a glass melted with 0.3 wt% MWCNT together with Eu 2 O 3 where the PL intensity for the 613 nm peak increased relative to the Eu reference. 20 In addition, a similar result was observed by Nogami et al 18 who first performed the Eu 3+ -Eu 2+ reduction in Al 2 O 3 -SiO 2 solgel glass under 20%H 2 -80%N 2 atmosphere, followed by heating in air at 800 1C which led to partial Eu 2+ -Eu 3+ re-oxidation. It was reported that the luminescence intensity for the Eu 3+ ions increased after the heating in air approaching a value larger than 1.5 times the intensity before the 20%H 2 -80%N 2 treatment.…”

“…It indicates the co-existence of both oxidation states of europium as similarly observed in the work reported in ref. 20, and further reflected in the results from PL measurements (vide infra). Hence, in analogy to recent work evaluating the role of MWCNTs, 20 the partial Eu 3+ -Eu 2+ reduction occurring in the melt via carbon provided by ND (C ND ) may be represented as…”

“…2(a) for the transmission decreasing following the increase in ND content is not followed, as it was similarly observed for the glasses melted with MWCNTs and Eu 2 O 3 as reported. 20 As pointed by Tratsiak et al, 16 many excitation-reabsorption processes involving Eu 2+ 2 Eu 2+ and Eu 2+ -Eu 3+ interactions may occur that can lead to a diminution of the PL intensities. Given that the Eu 2+ -Eu 3+ transfer was indicated in Fig.…”

“…While the ND would be promoting the reduction of Eu 2 O 3 , some losses are expected due to oxidation in air. However, these are suggested to be less than the losses with MWCNTs derived carbon doping 20 in connection with the high chemical stability of ND and resistance to oxidation.…”