Tunable Luminescence from Stable Silver Nanoclusters Confined in Microporous Zeolites

Abstract

properties associated with nanoclusters' molecule-like structure and energetics. Most notably, metal nanoclusters rose to research prominence in connection to the discovery of outstanding optoelectronic properties and have found practical application within catalysis, bioimaging, lighting and molecular sensing. [1][2][3][4][5][6] However, nanocluster' stabilization remains a significant impediment owing to their tendency to merge and form ever-larger aggregates at the loss of their interesting properties. Therefore, research efforts have been devoted to developing novel synthetic strategies to stabilize isolated metal nanoclusters; [7] popular approaches have often taken the form of using organic scaffolds such as DNA/RNA, proteins, and polymers. [8][9][10][11][12][13][14][15][16] The use of organic molecules gives rise to high synthesis yields, good luminescence performance, and strong compatibility with living organism, making them excellent candidates as fluorophores. Unfortunately, a main drawback is their poor long-term stability, especially in solid form, hindering their application, e.g., within lighting devices. On the other hand, template-mediated strategies based on the self-organization of the metal nanocluster within a confined volume (so-called "ship-in-a-bottle" approach) provide a promising alternative, one where the size and shape of the final metal nanocluster are dictated by the spatial restrictions imposed by the rigid host nanostructure. [17] To date, common templating structures have included glass matrices, [18] metal-organic frameworks, [19] and porous aluminosilicate zeolite crystals. [20] Here, we will shine light on zeolites as a promising scaffold for the assembly of highly luminescent and functional silver nanoclusters (Ag-NCs) within their (nano)porous interior (Figure 1a-c). As a host framework, zeolites possess molecular-sized channels and cages which enable them to confine molecules or metal (oxide) clusters inside their crystalline interior in a controlled fashion. Moreover, the framework is negatively charged, requiring counter-balancing extra-framework cations, which can be easily replaced through simple exchange methods. As shown in Figure 1d, forming the caged Ag-NCs involves a scalable bottom-up approach, whereby Ag + ions are made to self-assemble into nanoclusters via energy-driven activation (thermal treatment, photoactivation, or X-rays irradiation). Once the cluster is assembled, its optical response can be further tuned by the intentional exchange of additional guest

Tunable luminescence of silver-exchanged SOD zeolite thermally treated under mild conditions

“…, discrete energy levels). 1–9 Nevertheless, there is a strong tendency for silver nanoclusters to aggregate into large non-fluorescent species, limiting their applications. 10–12 Zeolites have a specific pore-cage structure and facile ion exchange capability, and thus they can be used as desirable scaffolds to stabilize nanoclusters.…”

N-Cholyl d-Penicilamine Micelles Templated Red Light-Emitting Silver Nanoclusters: Fluorometric Sensor for S2– Ions and Bioimaging Application Using Zebrafish Model

“…AgNCs with tunable emission properties can be prepared using bioactive peptides in an aqueous medium . Romolini et al reported tunable luminescence from stable AgNCs confined in microporous zeolites . The synthesis of AgNCs embedded zein films as antimicrobial coating materials for food packaging has been reported .…”

“…28 Romolini et al reported tunable luminescence from stable AgNCs confined in microporous zeolites. 29 The synthesis of AgNCs embedded zein films as antimicrobial coating materials for food packaging has been reported. 30 Jin and co-workers synthesized Ag 7 NCs with high yield by the reduction of AgNO 3 using meso-2,3-dimercaptosuccinic acid (DMSA) ligands.…”

Luminescence Control of Silver Nanoclusters by Tailoring Extra-Framework Cations in FAU-Y Zeolite: Implications for Tunable Emission

“…The nanoclusters consisting of only a few atoms or ions possess a discrete molecule-like energy band and thus show size-dependent luminescence performance. In the recent years, Ag NCs with different sizes, topologies, and chemical states have attracted much research interest due to their pronounced optical properties like high quantum yield approaching that of commercial phosphors and tunable emission in the visible region, which open up new vistas in potential photocatalytic, imaging, detection, and illumination applications. − However, Ag NCs undergo aggregation easily due to their high surface energy and thus lose their radiative emission ability. ,, In order to spatially and chemically stabilize Ag NCs and obtain the desired optical properties, two types of scaffolds were generally applied during the synthesis process: (1) soft organic molecules like DNA, peptides, and polymers, and (2) a rigid inorganic matrix including glasses and zeolites, whereby the few-atom size clusters can be stabilized by immobility. − …”

“…1−4 However, Ag NCs undergo aggregation easily due to their high surface energy and thus lose their radiative emission ability. 1,5,6 In order to spatially and chemically stabilize Ag NCs and obtain the desired optical properties, two types of scaffolds were generally applied during the synthesis process: (1) soft organic molecules like DNA, peptides, and polymers, and (2) a rigid inorganic matrix including glasses and zeolites, whereby the few-atom size clusters can be stabilized by immobility. 7−10 Zeolites are microporous crystalline aluminosilicates constituted by a framework of interconnected TO 4 tetrahedra (T = Si or Al) with a tailored structure and varied extra-framework cations.…”