a 200-fold quantum yield boost in the photoluminescence of ... · principle for highly fluorescent...
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A 200-fold Quantum Yield Boost in the Photoluminescence of Silver-Doped AgxAu25-x Nanoclusters: The 13th Silver Atom
Matters
Shuxin Wang, Xiangming Meng, Anindita Das, Tao Li, Yongbo Song, Tiantian Cao, Xiuyi Zhu,
Manzhou Zhu,* and Rongchao Jin
Department of Chemistry, Anhui UniversityHefei, Anhui 230601 (China)
Department of Chemistry, Carnegie Mellon UniversityPittsburgh, PA 15213 (USA)
Angew. Chem. Int. Ed. 2014, 53, 2376 –2380
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The chemical reaction between [Au11(PPh3)8Cl2]+ and n-alkanethiol
CnH2n+1SH (n=2, 8, 10, 12, 14, 16, and18) serendipitously yielded stable Au25 cluster compounds with the formula, [Au25(PPh3)10(SCnH2n+1)5Cl2]2+
M. Zhu, et al., J. Am. Chem. Soc. 2008, 130, 5883
Tatsuya Tsukuda et al., J. Phys. Chem. C 2007, 111, 7845
Au25(SR)18
INTRODUCTION
Fluorescence in biology and other fields
QDs, lanthanide NPs, carbon Nanodots
Metal clusters: low toxicity, stability LOWER QY
Surface engineering, doping, etc to improve QY
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Synthesis routes for biicosahedral AgxAu25-x clusters
Au nanoparticles (PPh3-protected)
[AgxAu25-x (PPh3)10-(SC2H4Ph)5Cl2]2+
[Au11(PPh3)8Cl2]+
Ag-thiolates A
g-th
iola
tes
Synthesis routes for biicosahedral Au25 clusters
[Au11(PPh3)8Cl2]+
n-alkanethiols
[Au25(PPh3)10(SCnH2n+1)5Cl2]2+
AuPPh3Cl + n-hexanethiol
Tert-butylamine-Borane complex
3h, stir, 25 oCMethanol purification
[Au25(PPh3)10(SC6H13)5Cl2]2+
(D. Lee et al. Langmuir 2012, 28, 7049)
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UV-vis spectra and TEM images of raw materials
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ESI mass spectra
[Au25(PPh3)10(SC2H4Ph)5Cl2]2+
Product I: nanoparticle route
Product II:Au11 route
General formula of I and II is [AgxAu25-x (PPh3)10-(SC2H4Ph)5Cl2]2+
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ESI-TOF Mass Spectrum of Au25
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ESI-TOF Mass Spectrum of Product I
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ESI-TOF Mass Spectrum of Product II
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UV/Vis and photoluminescence spectra of Au25, I, and II
413
675370
427
λem of Au25: 827 nm: QY: 0.1%
λem of II: 680 nm: QY: 40.1%
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X-ray structures of: a) [Au25(PPh3)10(SC2H4Ph)5Cl2]2+, b) I, and c) II. M=metal atom
Also proved by the 1H-NMR, 31P-NMR and 1H-1H COSY NMR
Products I and II were crystallized
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DPV and SWV of product II
HOMO-LUMO gap of Au25: 1.54 eV
HOMO-LUMO gap of II: 1.79 eV
This shows that emission of Au25 clusters and the product II is due to the HOMO-LUMO transitions
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Comparison of bond lengths in the nanocluster structures
Electronic structure of Au25 rod clusters
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Fluorescence confocal images
Excitation: 405 or 633 nm laser
[AgxAu25-x(PPh3)10(SC2H4OH)5Cl2]2+
human cancer cell 7402
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Summary and conclusions
Identified a highly fluorescent Ag13Au12 nanocluster by comparing two series of Ag-doped AgxAu25-x nanoclusters prepared by two different routes.
Au nanoparticles with AgI thiolate gives rise to AgxAu25-x with x12, with all of these species only weakly fluorescent (QY:0.2%).
Au11 clusters with AgI-thiolate gives rise to AgxAu25-x with x13, and the unique Ag13Au12 species in the distribution is highly luminescent (QY:40.1%).
The atomic-level structural and electronic insight provides a promising design principle for highly fluorescent metal nanoclusters, and may stimulate future work on the deep understanding of the atomic-level origin of fluorescence from metal nanoclusters, as well as on the development of applications in biolabeling, sensing, and other fields.