Abstract
Silver (Ag) clusters confined in matrices possess remarkable luminescence properties, but little is known about their structural and electronic properties. We characterized the bright green luminescence of Ag clusters confined in partially exchanged Ag-Linde Type A (LTA) zeolites by means of a combination of x-ray excited optical luminescence-extended x-ray absorption fine structure, time-dependent-density functional theory calculations, and time-resolved spectroscopy. A mixture of tetrahedral Ag4(H2O) x2+ (x = 2 and x = 4) clusters occupies the center of a fraction of the sodalite cages. Their optical properties originate from a confined two-electron superatom quantum system with hybridized Ag and water O orbitals delocalized over the cluster. Upon excitation, one electron of the s-type highest occupied molecular orbital is promoted to the p-type lowest unoccupied molecular orbitals and relaxes through enhanced intersystem crossing into long-lived triplet states.
Highlights
F ew-atom luminescent silver clusters (AgCLs) [1] stabilized through organic [2,3,4,5,6] or inorganic [7,8,9] templates have emerged as promising candidates for a broad range of applications in lighting, imaging, sensing, and therapeutics [4]
We present a detailed investigation of the structural and electronic properties of partially Ag-exchanged Ag3K9-Linde Type A (LTA) zeolite by use of three complementary techniques
With x-ray excited optical luminescence (XEOL), the x-ray absorption fine structure (EXAFS) signal is detected exclusively from the Ag atom fraction involved in the peter. lievens@kuleuven.be (PL) process at the Ag K-edge, selectively determining the structure of the emitting Ag species [12]
Summary
F ew-atom luminescent silver clusters (AgCLs) [1] stabilized through organic (such as peptides, proteins, polymers, and DNA) [2,3,4,5,6] or inorganic (such as glasses and zeolites) [7,8,9] templates have emerged as promising candidates for a broad range of applications in lighting, imaging, sensing, and therapeutics [4]. The analysis of the XEOL-detected signal shows that the species at the origin of the brightgreen PL observed in Ag3K9-LTA are Ag4 clusters with short Ag-Ag distances of 2.82 Å, in which each Ag atom is bound to two water molecules at 2.36 Å.
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