Highly Photoluminescent Sulfide Clusters Confined in Zeolites

Abstract

The design, synthesis and photoluminescence characterization of sulphide cluster-based zeolitic materials with the general formula Na8[SiAlO4]6SxCl2-2x is presented in this report. The employed experimental conditions, which included the thermal treatment of sodium Linde type A (Na-LTA) zeolites, yielded highly photoluminescent sulphurzeolites and remarkably large Stokes shifts. An emission band at 650 nm for samples with low sulphur contents is observed when excited at 380 nm, which is fully consistent with S2clusters as light emitting centres. These orange emitting materials display External Quantum Efficiencies reaching 53% with peculiar high temperature stability of photoluminescence up to 450ºC. For higher S/Cl molar ratios a gradual conversion to Near-Infrared (NIR) light emitting centres is observed with a maximum at 780 nm. This novel NIR luminescent species with External Quantum Efficiencies of about 10% are attributed to polysulfide clusters (tentatively S4 2species). Giving the high EQE values, large Stokes shifts, and thermal stability, the materials presented in this report can find applications in light down-conversion systems or as phosphors in lighting devices.

Tunable white emission of silver-sulfur-zeolites as single-phase LED phosphors

“…This would mean that the orange-reddish part in the luminescence might result from the presence of pure Ag-CLs. This 620-635 nm emission, on the other hand, could also be related to S-species excitable at 380 nm and emitting at around 650 nm as observed by Ruivo et al [27]. However, as already mentioned, the vibronic structure in the AgSzeolites and the absorption peak related to S-species in the DRS spectra are no longer observed in the AgSzeolites.…”

“…The orange emission originating from the presence of S-species inside the cages of SOD zeolites (Szeolites) [27], changes to a bright white emission upon the incorporation of Ag + -ions, under 350 nm illumination (figure 1). This change is also observed in the 2D excitation/emission plots of the AgS-zeolites (figure 2), displaying a broad emission across the whole visible range for both AgS-zeolite samples (sample A and B, see sample preparation).…”

“…Indeed, during exchange an average of 1.5 Ag + ions for each S present in the parent S-zeolites were added. This parent S-zeolite has the SOD framework structure [27]. Therefore, we checked the luminescent properties of the Ag-exchanged S-free sodalite zeolites (Ag-SOD) with different Ag-loadings, all displaying an orange-red emission (figures 3 and S5).…”

Unravelling the Origin of the Yellow-Orange Luminescence in Natural and Synthetic Scapolites

“…So far, the yellow orange luminescence of scapolite, 12,13 sodalite 10,14-16 and tugtupite 17 has been ascribed to (S2)polyanions without any formal proof. The presence of the same isolated anionic groups is also suspected to account for the emission of other aluminosilicates (zeolites 18 ) and alkali halides 13,[19][20][21][22][23] . The aim of this study is to provide a definite proof that the cause of the luminescence is indeed single charged sulfur dimers by combining experimental and theoretical approaches.…”

Tunable Luminescence from Stable Silver Nanoclusters Confined in Microporous Zeolites

“…The use of co-dopants to modulate the emission properties of silver nanoclusters confined in zeolites has been extended to chalcogenide species. This idea was pursued by Baekelant and collaborators, who realized the synthesis of broadband, white emissive Ag/S-zeolites, [41] by using yellow emissive sulfurzeolites developed by Ruivo and co-workers [42] as their starting materials and, after a cation exchange procedure (using silver cations), a tunable white emissive zeolite-based phosphors were obtained. The presence of both Ag-NCs and new emissive Ag-S species in SOD zeolites was revealed through steady-state and time-resolved photoluminescence spectroscopy.…”