Ligand-protected Au clusters are non-bleaching fluorescence markers in bio- and medical applications. Here we show that their fluorescence can be an intrinsic property of the Au cluster itself. We find a very intense and sharp fluorescence peak located at λ=739.2 nm (1.68 eV) for Au20 clusters in a Ne matrix held at 6 K. The fluorescence reflects the Highest Occupied Molecular Orbital-Lowest Unoccupied Molecular Orbital (HOMO-LUMO) diabatic bandgap of the cluster. Au20 shows a very rich absorption fine structure reminiscent of well defined molecule-like quantum levels. These levels are resolved since Au20 has only one stable isomer (tetrahedral); therefore our sample is mono-disperse in cluster size and conformation. Density-functional theory (DFT) and time-dependent DFT calculations clarify the nature of optical absorption and predict both main absorption peaks and intrinsic fluorescence in fair agreement with experiment.

1.
M.
Haruta
,
N.
Yamada
,
T.
Kobayashi
, and
S.
Iijima
,
J. Catal.
115
,
301
(
1989
).
2.
M.
Valden
,
X.
Lai
, and
D. W.
Goodman
,
Science
281
,
1647
(
1998
).
4.
C.
Zhang
,
Y.
He
,
H. P.
Cheng
,
Y. Q.
Xue
,
M. A.
Ratner
,
X. G.
Zhang
, and
P.
Krstic
,
Phys. Rev. B
73
,
125445
(
2006
).
5.
T. G.
Schaaff
and
R. L.
Whetten
,
J. Phys. Chem. B
104
,
2630
(
2000
).
6.
P.
Zhang
,
X.
Yang
,
Y.
Wang
,
N.
Zhao
,
Z.
Xiong
, and
C.
Huang
,
Nanoscale
6
,
2261
(
2014
).
7.
A.
Cecconello
,
C.-H.
Lu
,
J.
Elbaz
, and
I.
Willner
,
Nano Lett.
13
,
6275
(
2013
).
8.
J. H.
Guo
,
L. Z.
Liu
,
X. B.
Zhu
,
X. L.
Wu
, and
P. K.
Chu
,
Appl. Phys. Lett.
104
,
141910
(
2014
).
9.
H.
He
,
C.
Xie
, and
J.
Ren
,
Anal. Chem.
80
,
5951
(
2008
).
10.
C.-L.
Liu
,
T.-M.
Liu
,
T.-Y.
Hsieh
,
H.-W.
Liu
,
Y.-S.
Chen
,
C.-K.
Tsai
,
H.-C.
Chen
,
J.-W.
Lin
,
R.-B.
Hsu
,
T.-D.
Wang
,
C.-C.
Chen
,
C.-K.
Sun
, and
P.-T.
Chou
,
Small
9
,
2103
(
2013
).
11.
P.
Reineck
,
D.
Gomez
,
S. H.
Ng
,
M.
Karg
,
T.
Bell
,
P.
Mulvaney
, and
U.
Bach
,
ACS Nano
7
,
6636
(
2013
).
12.
Y.
Wang
,
Y.
Wang
,
F.
Zhou
,
P.
Kim
, and
Y.
Xia
,
Small
8
,
3769
(
2012
).
13.
S.
Wang
,
X.
Meng
,
A.
Das
,
T.
Li
,
Y.
Song
,
T.
Cao
,
X.
Zhu
,
M.
Zhu
, and
R.
Jin
,
Angew. Chem., Int. Ed.
53
,
2376
(
2014
).
14.
Y.
Xu
,
J.
Sherwood
,
Y.
Qin
,
D.
Crowley
,
M.
Bonizzoni
, and
Y.
Bao
,
Nanoscale
6
,
1515
(
2014
).
15.
Z.
Wu
and
R.
Jin
,
Nano Lett.
10
,
2568
(
2010
).
16.
X.
Wen
,
P.
Yu
,
Y.-R.
Toh
,
X.
Ma
,
S.
Huang
, and
J.
Tang
,
Nanoscale
5
,
10251
(
2013
).
17.
C. M.
Aikens
,
J. Phys. Chem. A
113
,
10811
(
2009
).
18.
S.
Malola
,
L.
Lehtovaara
,
J.
Enkovaara
, and
H.
Häkkinen
,
ACS Nano
7
,
10263
(
2013
).
19.
J. C.
Idrobo
,
W.
Walkosz
,
S.
Yip
,
S.
Oeguet
,
J.
Wang
, and
J.
Jellinek
,
Phys. Rev. B
76
,
205422
(
2007
).
20.
H. C.
Weissker
,
H. B.
Escobar
,
V. D.
Thanthirige
,
K.
Kwak
,
D.
Lee
,
G.
Ramakrishna
,
R. L.
Whetten
, and
X.
López-Lozano
,
Nat. Commun.
5
,
3785
(
2014
).
21.
G.
Barcaro
,
L.
Sementa
,
A.
Fortunelli
, and
M.
Stener
,
Phys. Chem. Chem. Phys.
17
,
27952
(
2015
).
22.
K. L.
Dimuthu
,
M.
Weerawardene
, and
C. M.
Aikens
,
J. Am. Chem. Soc.
138
,
11202
(
2016
).
23.
G. A.
Bishea
and
M. D.
Morse
,
J. Chem. Phys.
95
,
5646
(
1991
).
24.
W.
Harbich
,
S.
Fedrigo
,
J.
Buttet
, and
D.
Lindsay
,
Z. Phys. D
19
,
157
(
1991
).
25.
S.
Fedrigo
,
W.
Harbich
, and
J.
Buttet
,
J. Chem. Phys.
99
,
5712
(
1993
).
26.
S.
Lecoultre
,
A.
Rydlo
,
C.
Felix
,
J.
Buttet
,
S.
Gilb
, and
W.
Harbich
,
J. Chem. Phys.
134
,
074302
(
2011
).
27.
J.
Li
,
X.
Li
,
H. J.
Zhai
, and
L. S.
Wang
,
Science
299
,
864
(
2003
).
28.
I. M.
Goldby
,
B.
von Issendorff
,
L.
Kuipers
, and
R. E.
Palmer
,
Rev. Sci. Instrum.
68
,
3327
(
1997
).
29.
M. A.
Rottgen
,
K.
Judai
,
J. M.
Antonietti
,
U.
Heiz
,
S.
Rauschenbach
, and
K.
Kern
,
Rev. Sci. Instrum.
77
,
013302
(
2006
).
30.
F.
Conus
,
J. T.
Lau
,
V.
Rodrigues
, and
C.
Félix
,
Rev. Sci. Instrum.
77
,
113103
(
2006
).
31.
P. B.
Johnson
and
R. W.
Christy
,
Phys. Rev. B
6
,
4370
(
1972
).
33.
S.
Lecoultre
,
A.
Rydlo
,
C.
Félix
, and
W.
Harbich
,
Eur. Phys. J. D
52
,
187
(
2009
).
34.
X.
Wen
,
P.
Yu
,
Y.
Toh
,
A.
Hsu
,
Y.
Lee
, and
J.
Tang
,
J. Phys. Chem. C
116
,
19032
(
2012
).
35.
J. P.
Perdew
,
K.
Burke
, and
M.
Ernzerhof
,
Phys. Rev. Lett.
77
,
3865
(
1996
).
36.
A.
Tkatchenko
and
M.
Scheffler
,
Phys. Rev. Lett.
102
,
073005
(
2009
).
37.
A.
Ambrosetti
,
A. M.
Reilly
,
R. A.
DiStasio
, and
A.
Tkatchenko
,
J. Chem. Phys.
140
,
18A508
(
2014
).
38.
L. M.
Ghiringhelli
,
P.
Gruene
,
J. T.
Lyon
,
D. M.
Rayner
,
G.
Meijer
,
A.
Fielicke
, and
M.
Scheffler
,
New J. Phys.
15
,
083003
(
2013
).
39.
V.
Blum
,
R.
Gehrke
,
F.
Hanke
,
P.
Havu
,
V.
Havu
,
X.
Ren
,
K.
Reuter
, and
M.
Scheffler
,
Comput. Phys. Commun.
180
,
2175
(
2009
).
40.
M.
Casida
,
Recent Advances in Density-Functional Methods
(
World Scientific
,
1995
), p.
155
.
41.
A. D.
Becke
,
J. Chem. Phys.
98
,
5648
(
1993
).
42.
B.
Anak
,
M.
Bencharif
, and
F.
Rabilloud
,
RSC Adv.
4
,
13001
(
2014
).
43.
R. A.
Kendall
,
E.
Aprà
,
D. E.
Bernholdt
,
E. J.
Bylaska
,
M.
Dupuis
,
G. I.
Fann
,
R. J.
Harrison
,
J.
Ju
,
J. A.
Nichols
,
J.
Nieplocha
,
T. P.
Straatsmab
,
T. L.
Windus
, and
A. T.
Wong
,
Comput. Phys. Commun.
128
,
260
(
2000
).
44.
D.
Jiang
,
M.
Kühn
,
Q.
Tang
, and
F.
Weigend
,
J. Phys. Chem. Lett.
5
,
3286
(
2014
).
45.
O.
Gritsenko
,
P.
Schipper
, and
E.
Baerends
,
Chem. Phys. Lett.
302
,
199
(
1999
).
46.
C. F.
Guerra
,
J. G.
Snijders
,
G.
te Velde
, and
E. J.
Baerends
,
Theor. Chem. Acc.
99
,
391
(
1998
).

Supplementary Material

You do not currently have access to this content.