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

Abstract

Metal clusters confined inside zeolite materials display remarkable luminescent properties, making them very suitable as potential alternative phosphors in white LED applications. However, up to date, only single-color emitters have been reported for luminescent metal-exchanged zeolites. In this study, we synthesized and characterized white emitting silver-sulfur zeolites, which show a remarkable color tunability upon the incorporation of silver species in highly luminescent sulfur-zeolites. Via a combined steady-state and time-resolved photoluminescence spectroscopy characterization, we suggest that the observed luminescence and tunability arise from the presence of two different species. The first associated to an orange-red emitting silver cluster (Ag-CL), whereas the second is related to a blue-white emitting SAg species. The relative contribution of both luminescent species depends on the synthesis procedure. It was shown that the formation of the blue-white emitting SAg species is favored upon a heat-treatment of the samples.

Tunable Luminescence from Stable Silver Nanoclusters Confined in Microporous Zeolites

“…Here, the white light emission's warmth and quality were controlled by the ratio of the coexisting emitting species indirectly regulated by the annealing temperature. [41] In line with these results, the use of thermally treated silver-exchanged FAUY zeolites with tunable emission (from green to cyan) in the fabrication of a white LED was reported by Yao and co-workers, providing the proofof-concept for a LED prototype (Figure 7b) with a high CRI of 9.23, by combining a UV chip-on-board with the whiteemitting silver-zeolite based composite. [31] Subsequently, Yao and collaborators reported the development of single-phase white-emitting composites based on silver-zeolites for use in near-UV(NUV)-LEDs, using two different approaches.…”

“…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.…”

“…d) Electroluminescent spectrum of the as-fabricated warm WLEDs using silver-zeolites, inset: digital photographs of the as-fabricated warm WLEDs with a UV chip at around 395 nm; and CIE chromaticity coordinates of the as-fabricated warm WLEDs. a) Reproduced with permission [41]. Copyright 2020, IOP Publishing.…”

X‐Ray‐Induced Growth Dynamics of Luminescent Silver Clusters in Zeolites

“…[22][23][24] The nature of the clusters that can be formed from these ion-exchanged starting materials depends on the interaction of the cation(s) with the matrix, which in the case of zeolites is determined primarily by the topology of the framework, the framework charge, cation type and interaction with other extra-framework cations. The formation of metal clusters from extra-framework cations requires an extra stimulus which can be provided by UV photon irradiation, 17, 25-26 thermal treatment, 10,[26][27] solid-gas reactions, 28 electron beams 29 or X-rays. [30][31][32] Whilst the determination of the exact nature of the metal clusters has been the focus of several recent studies, 10,[33][34][35] the dynamics of small cluster formation and growth is significantly less well studied.…”

The Role of a Confined Space on the Reactivity and Emission Properties of Copper(I) Clusters

“…A valuable, cheaper, and a more environmentally friendly alternative is the use of metal complexes ( Armaroli et al, 2007 ; Costa et al, 2012 ; Keller et al, 2018 ; Weber et al, 2018 ) and in this respect, silver has resulted in excellent luminophores with outstanding emission quantum yields when the clusters are protected by the environment. ( Fenwick et al, 2016 ; Baekelant et al, 2019 ; Baekelant et al, 2020 ).…”