Crystal and Solution Photoluminescence of MAg₂₄(SR)₁₈ (M = Ag/Pd/Pt/Au) Nanoclusters and Some Implications for the Photoluminescence Mechanisms

Abstract

We prepare a series of MAg 24 (SR) 18 (M = Ag/Pd/ Pt/Au) nanoclusters (NCs) with similar core−inner shell−outer shell structures and investigate their crystal and solution photoluminescence. The core silver atom replacement by the Pd/Pt/Au atom obviously tunes the geometric and electronic structures of Ag 25 (SR) 18 NC. The crystal photoluminescence intensities sequence hints a core-atom-directing charge transfer from the ligands to the metal kernels. Both the calculated NPA charge and the measured Ag inner shell −S terminal bond length support the proposed mechanism. Further experiments show the solvent influence on the NCs photoluminescence supported by the blue-shift of emissions of MAg 24 (SR) 18 NCs and the solvent-dependent photoluminescence intensity sequences. Especially, for PtAg 24 (SR) 18 , the quantum yield is almost 100-fold greater in CH 3 CN (18.6%) than in CH 2 Cl 2 (0.2%). However, the emission wavelengths of the series of NCs are barely influenced by the solvent type. This work indicates the importance of the core atom and the solvent to the photoluminescence of core−inner shell−outer shell silver NCs, having important implications for the photoluminescence mechanisms and tuning of noble metal nanoparticles.

Alternating Array Stacking of Ag26Au and Ag24Au Nanoclusters

“…High-quality,d ark single crystals that adopted the space group P1 were obtained via slow diffusion of hexane into aD CM solution at 0 8 8C. Indeed, a À1c harged Ag 24 Au (2, 18 was reported by the Bakr, [12] Zhu, [13] and Wu [14] groups.Inthis work we also separately obtained an anionic Ag 24 Au(2-EBT) 18 nanocluster,w hose composition was determined by elemental analysis (Supporting Information, Table S1), TGA and XPS (Supporting Information, Figures S7-S9;f or some additionally qualitative characterizations, [15] see the Supporting Information, Figures S11 and S12). A weight loss of 52.67 %w as in perfect agreement with the theoretic value of [Ag 26 Au(2-EBT) 18 (PPh 3 ) 6 ][Ag 24 Au(2-EBT) 18 ]( organic,5 2.54 wt %; metal, 47.46 wt %; Supporting Information, Figure S3).…”

Elucidating the Doping Effect on the Electronic Structure of Thiolate‐Protected Silver Superatoms by Photoelectron Spectroscopy

“…[5] TheA g 13 and Ag 32 cores form the closed-shell electronic configurations (1S) 2 (1P) 6 and (1S) 2 -(1P) 6 (1D) 10 ,r espectively:1 S, 1P,a nd 1D represent superatomic orbitals with angular momenta of 0, 1, and 2, respectively. [7][8][9] Thiolate-protected Ag clusters have attracted researchers due to specific properties such as photoluminescence [10] although they are generally less stable than the gold analogues.Doping with heteroatoms is apromising approach to enhance the stability and further improve the properties of the Ag clusters.S tate-of-the-art synthesis based on coreduction [11,12] and galvanic replacement [13,14] allowed us to precisely define the number, element, and location of the heteroatom(s) introduced into the Ag clusters.F or example, as ingle Ma tom (M = Au,P d, Pt) can be integrated exclusively at the central position of an icosahedral Ag 13 core of [Ag 25 (SPhMe 2 ) 18 ] À[1] to form M@Ag 12 cores in [AuAg 24 (SPhMe 2 ) 18 ] À[13] and [MAg 24 (SPhCl 2 ) 18 ] 2À (M = Pd, Pt) [11] (Scheme 1). [7][8][9] Thiolate-protected Ag clusters have attracted researchers due to specific properties such as photoluminescence [10] although they are generally less stable than the gold analogues.Doping with heteroatoms is apromising approach to enhance the stability and further improve the properties of the Ag clusters.S tate-of-the-art synthesis based on coreduction [11,12] and galvanic replacement [13,14] allowed us to precisely define the number, element, and location of the heteroatom(s) introduced into the Ag clusters.F or example, as ingle Ma tom (M = Au,P d, Pt) can be integrated exclusively at the central position of an icosahedral Ag 13 core of [Ag 25 (SPhMe 2 ) 18 ] À[1] to form M@Ag 12 cores in [AuAg 24 (SPhMe 2 ) 18 ] À[13] and [MAg 24 (SPhCl 2 ) 18 ] 2À (M = Pd, Pt) [11] (Scheme 1).…”

“…[6] Structural similarities to gold analogues indicate that the thiolate-protected Ag clusters represent another family of chemically modified superatoms. Both the undoped Ag 13 and doped M@Ag 12 cores form ac losed electron configuration, (1S) 2 -(1P) 6 .These atomically defined bimetallic clusters provide an ideal platform to study the effect of single-atom doping on their properties.O ptical spectroscopy (Figure 1a)a nd voltammetry [15] showed that the doping slightly modulates the HOMO-LUMO gap of [Ag 25 (SPhMe 2 ) 18 ] À .T he stability [13,15] and photoluminescence quantum yield (PLQY) [10] of [Ag 25 -(SPhMe 2 ) 18 ] À were improved by doping with asingle atom of Pt or Au,b ut were degraded by Pd atom doping.I tw as proposed that the improved stability and PLQYs of [AuAg 24 -(SPhMe 2 ) 18 ] À and [PtAg 24 (SPhMe 2 ) 18 ] 2À are related to the electronic structures,since their stability and PLQYs decrease in the order of the electron affinity of the dopant (Au > Pt > Ag > Pd). Both the undoped Ag 13 and doped M@Ag 12 cores form ac losed electron configuration, (1S) 2 -(1P) 6 .These atomically defined bimetallic clusters provide an ideal platform to study the effect of single-atom doping on their properties.O ptical spectroscopy (Figure 1a)a nd voltammetry [15] showed that the doping slightly modulates the HOMO-LUMO gap of [Ag 25 (SPhMe 2 ) 18 ] À .T he stability [13,15] and photoluminescence quantum yield (PLQY) [10] of [Ag 25 -(SPhMe 2 ) 18 ] À were improved by doping with asingle atom of Pt or Au,b ut were degraded by Pd atom doping.I tw as proposed that the improved stability and PLQYs of [AuAg 24 -(SPhMe 2 ) 18 ] À and [PtAg 24 (SPhMe 2 ) 18 ] 2À are related to the electronic structures,since their stability and PLQYs decrease in the order of the electron affinity of the dopant (Au > Pt > Ag > Pd).…”

“…[7][8][9] Thiolate-protected Ag clusters have attracted researchers due to specific properties such as photoluminescence [10] although they are generally less stable than the gold analogues.Doping with heteroatoms is apromising approach to enhance the stability and further improve the properties of the Ag clusters.S tate-of-the-art synthesis based on coreduction [11,12] and galvanic replacement [13,14] allowed us to precisely define the number, element, and location of the heteroatom(s) introduced into the Ag clusters.F or example, as ingle Ma tom (M = Au,P d, Pt) can be integrated exclusively at the central position of an icosahedral Ag 13 core of [Ag 25 (SPhMe 2 ) 18 ] À[1] to form M@Ag 12 cores in [AuAg 24 (SPhMe 2 ) 18 ] À[13] and [MAg 24 (SPhCl 2 ) 18 ] 2À (M = Pd, Pt) [11] (Scheme 1). [10] Thec atalytic activity of [Ag 25 (SPhMe 2 ) 18 ] À for the carboxylation of terminal alkynes to give propionic acid was enhanced by Pt or Pd doping, but further improved by Au doping. [10] Thec atalytic activity of [Ag 25 (SPhMe 2 ) 18 ] À for the carboxylation of terminal alkynes to give propionic acid was enhanced by Pt or Pd doping, but further improved by Au doping.…”

The Synthesis of Chiral Ag4Pd2(SR)8 by Nonreplaced Galvanic Reaction

“…During the past decade, atomically precise doped nanoclusters (NCs, ultrasmall nanoparticles with size less than ≈2 nm) have gained considerable attention from nanoscientists because of the synergistic or even new properties (e.g., catalytic and optical properties) of doped NCs compared to their homometallic counterparts . A general synthesis method is the synchro‐synthesis (i.e., the mixed metal precursors are concurrently reduced by reducing agent like NaBH 4 ), such as the preparation of Au 24 Pd(SR) 18 , Au 24 Pt(SR) 18 , Au 25− x Ag x (SR) 18 , Au 38− x Ag x (SR) 18 , Au 36 Pd 2 (SR) 18 , Au 36 Pt 2 (SR) 24 , Ag 24 Pd(SR) 18 , Ag 24 Pt(SR) 18 , Ag 32 Au 12 (SR) 30 , and [Au 12+ n Cu 32 (SR) 30+ n ] NCs (SR: thiolate). Due to the limitation of synchro‐synthesis in obtaining more atomically disperse alloy nanoclusters, a novel synthesis method dubbed antigalvanic reaction (AGR) was introduced by Wu in 2012 and a few atomically disperse alloy nanoclusters have been facilely obtained so far, such as Ag 2 Au 25 (SR) 18 , HgAu 24 (SR) 18 , CdAu 24 (SR) 18 , Cd 5 Au 26 (PPh 3 ) 12 (SR) 12 , and Cd 4 Au 20 (SH)(SR) 19 (Note that, AGR or pseudo‐AGR can also be employed to synthesize monometal nanoclusters, for some examples, see the syntheses of Au 28 (SR) 20 , Au 44 (SR) 32 , and Au 24 (SR) 20 .…”