Understanding and predicting thiolated gold nanoclusters from first principles De-en Jiang Chemical Sciences Division, Oak Ridge National Laboratory 8 October 2009 @ Ole Miss

A slide for grad students

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Organizational structure University

College A

National Lab

Directorate A Directorate B

Directorate C

College B

College C

Dept 1

Dept 2

Dept 3

Division 1

Division 2

Division 3

Prof. A

Prof. B

Prof. C

Group A

Group B

Group C

Chemical Sciences Division

• 14 research groups • 95 staff members • 33 postdocs

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Nanomaterials Chemistry Group • • • •

Five staff members Six postdocs One part-time Two visiting scientists

Shannon Mahurin

Xiao-Guang Sun

Sheng Dai group leader

Gary Baker

Overview

Dharmaratne, Krick, and Dass, JACS, 131, 13604 (2009).

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Why are gold nanoparticles important?

Labeling proteins; Drug delivery; Sensing; Catalysis

Cited 2172 times by 9/26/2009.

The Brust method: a major breakthrough in nanogold research

Cited 2273 times by 9/26/2009.

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Au102(SR)44: A Science Cover

Jadzinsky et al., Science, 2007, 318, 430-433.

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Our hypothesis • Staple motifs are the preferred Au-thiolate bonding motif for all gold clusters.

SR

R S

SR Au SR

RS

SR

RS Au

SR

SR

RS Au

RS

Isolate adsorption

Au

Au

Au S R

staple

polymer

Our method and approach • • •

Plane-wave DFT with GGA-PBE for a gold cluster in a simulation box Run DFT-based molecular dynamics to see if staple motifs can evolve out with time from isolated thiolate groups Compute optical spectra with TD-DFT and compare with experiment – A quality check for the viability of a structure model

∧

H Ψ =EΨ Input • Atomic numbers • Atom positions

Output Jaguar @ ORNL: 149,504 processors.

• Energy • Potential-energy surface • Forces • Vibrational frequencies

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One staple motif dramatically changes the underlying structure

(a)

(b)

(c)

(d)

-2.77 eV/SR

-3.44 eV/SR

Jiang et al., J. Am. Chem. Soc., 2008, 130, 2777-2779.

Electronic structure changes Au38(MT)2 Density of states (eV-1)

25 20 15

Au38(MT)24

EFermi 10 5

Au38(MT)14

0 -0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

Energy (eV)

•

HOMO-LUMO gap increases with number of staples on the surface. Jiang et al., J. Am. Chem. Soc., 2008, 130, 2777-2779.

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The dimer motif is also needed for smaller clusters

(a)

(b)

0

(c)

5ps

10 ps

Jiang et al., J. Am. Chem. Soc., 2008, 130, 2777-2779.

The gold-thiolate interface

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Au102(SR)44

Jadzinsky et al., Science, 2007, 318, 430-433.

What is a superatom? Atom

Superatom

Structure

Nucleus + electrons

Bonding network + valence electrons

Electronic levels

1s, 2s, 2p, 3s, 3p, 3d, 4s, 4p, 4d, 5s, …

1s, 1p, 1d, 2s, 1f, 2p,…

Shell-closing electron count

2, 10, 18, 36, 54, 86

2, 8, 18, 20, 34, 40, 58, …

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Early experiments

Clemenger, Phys. Rev. B, 32, 1359 (1985).

How do we count valence electrons for thiolated gold clusters?

Number of thiolates

• N=M–L–q Charge Number of Au atoms

Au102(SR)44 102 – 44 – 0 = 58 58 is a magic number!

Walter et al., PNAS, 2008.

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Thiolated gold superatom complexes

Au(III) Au(I) Au(0-I)

a. Dissolve HAuCl4 in THF b. Add PhCH2CH2SH, leading to clear solution c. Add NaBH4, leading to thiolated gold nanoparticles. Dharmaratne, Krick, and Dass, JACS, 131, 13604 (2009).

Au25(SR)18-

25 – 18 – (-1) = 8 8 is a magic number! Akola et al., J. Am. Chem. Soc., 2008, 130, 3753-3754. Heaven et al., J. Am. Chem. Soc., 2008, 130, 3755-3756. Zhu et al., J. Am. Chem. Soc., 2008, 130, 5883-5885.

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From Superatomic Au25(SR)18− to Superatomic M@Au24(SR)18q Core−Shell Clusters

x=q+2 Au25(SR)18−

M@Au24(SR)18q

q

−2

−1

0

+1

x

0

1

2

3

4

EC

d10s0

d10s1,

s2p1

s2p2

M

Ni, Pd, Pt

Cu, Ag Li, Na, K, Rb, Cs

B, Al, Ga, In, Tl

C, Si, Ge, Sn, Pb

s1

d10s2,

s2

Zn, Cd, Hg Be, Mg, Ca, Sr, Ba

+2

Jiang and Dai, Inorg. Chem., 2009, 48, 2720.

DFT confirmation Main groups

Homo-Lumo Gap (eV)

1.6 Pt

1.5

d10

1.4 1.3

Ni

Pd

Au

1.2 1.1 1.0 0.9

• • •

Cu

Ag

d10s1

d10s2

Hg Zn

3

Cd

4 Element Period

5

Homo-Lumo Gap (eV)

Transition metals

Ge

1.2 1.1

Sn

Be

s2p2

Ga Al

1.0

In

s2p1

0.9 0.8

Li

2

s1

Mg

s2

3 4 Element Period

5

All transition-metal atoms are good dopants. Many main-group elements cannot fit in the shell due to their large size. Electron count from the shell structure is very powerful! Jiang and Dai, Inorg. Chem., 2009, 48, 2720.

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Interaction between the dopant and the Au24(SR)18 framework Main groups

Interaction Energy (eV)

9 8

Pd

7 6

Cu

Ag

5 4

Zn

Au Cd

3 2

• •

Pt

Ni

3

Hg

4 Element Period

5

Interaction Eenergy (eV)

Transition metals 7

Al Ge

Be

Sn

6 Ga

Mg

In

5 Li 4

2

3 4 Element Period

5

Similar trend to the Homo-Lumo gap It’s thermodynamically favorable for many of the good dopants to replace the center Au atom, especially for Ni, Pd, Pt. Jiang and Dai, Inorg. Chem., 2009, 48, 2720.

An idea to realize the M@Au24(SR)18q clusters

Tsukuda and coworkers, J. Am. Chem. Soc., 2005.

?

+

[{Pd@Au12}(Ph3P)8Cl4]

[Pd@Au24(SG)18]2-

Laupp and Strähle, Angew. Chem., 1994.

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Magnetic doping of the Au25(SR)18− superatom

x=q+2+5 Au25(SR)18−

M@Au24(SR)18q

q

-1

0

x

6

7

+1 8

EC

d5s1

d5s2

d 6d 2

M

Cr

Mn

Fe

Jiang and Whetten, Phys. Rev. B, 80, 115402 (2009).

DFT confirmation M

q

µT

µM

EInt (eV)

Cr

-1

5

3.53

6.18

Mn

0

5

3.92

6.52

Fe

+1

3

3.01

6.54

-1.4

Orbital energy (eV)

-1.6 EF

-1.8 -2.0

1P 1P

-2.2 -2.4

Cr 3d Down

Up Spin

Jiang and Whetten, Phys. Rev. B, 80, 115402 (2009).

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The missing thiolated gold superatom complex

Electron-shell closing for a square-well potential: Jin, JACS, 2008. Murray, JACS, 2008.

Dass, JACS, 2009.

Au25(SR)18-

2,

8, 18,

Au68(SR)34

20, 34, 40, 58,

Au44(SR)282-

68, …

Au102(SR)44

Price and Whetten, JACS, 2005.

Kornberg, Science, 2007.

What are the smallest thiolated gold superatom complexes?

From inside out: Assuming a Platonic-solid core

Au25(SR)18-

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Tetrahedron as a core

2

Au6(SR)4

G.O.

+

2

Au8(SR)6

2 Au10(SR)8

•

The trimer motif matches best the curvature. 1. Jiang et al., J. Phys. Chem. C, 113, 17291 (2009). 2. Jiang et al., J. Phys. Chem. C, 113, 16983 (2009).

The octahedron core +

3

3 RS(AuSR)2

Au6

Au12(SR)9+ 3.012 2.876

3.052

2.875 2.852

2.813

2.760

Jiang et al., J. Phys. Chem. C, 113, 17291 (2009).

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Homo and Lumo of Au12(SR)9+

180º

LUMO+1 0.50 eV

LUMO 1.70 eV HOMO

Jiang et al., J. Phys. Chem. C, 113, 17291 (2009).

Absorbance (a.u.)

Optical absorption of Au12(SR)9+

Homo
Lumo

1.5

2.0

2.5

3.0

3.5

Photon energy (eV)

• •

Well separated peaks. Molecule-like adsorption spectrum.

Jiang et al., J. Phys. Chem. C, 113, 17291 (2009).

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Cover art of J. Phys. Chem C: 8 Oct 2009 issue

Au12(SR)9 isolated

Zhang et al., Anal. Chem., 2009, 81, 1676.

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Two suggestions to realize small thiolated gold clusters

Tsukuda and coworkers, J. Am. Chem. Soc., 2005.

Ying and coworkers, J. Am. Chem. Soc., 2009.

Mingos, Gold Bulletin, 1984.

Thiolated gold superatom complexes

Dharmaratne, Krick, and Dass, JACS, 131, 13604 (2009).

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Au38(SR)24 experimental results: A unique chemical species

Tsukuda and coworkers, J. Am. Chem. Soc., 128, 6036 (2006); J. Am. Chem. Soc., 130, 8608 (2008).

Au38(SR)24: Previous models and our model

(a)

(c)

(b)

0

-0.2 eV

-1.6 eV

(a) Häkkinen et al., J. Phys. Chem. B 2006, 110, 9927-9931 (b) Garzon et al., Phys. Rev. Lett. 2000, 85, 5250-5251 (c) Jiang et al., J. Am. Chem. Soc., 2008, 130, 2777-2779.

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Computed optical spectra Absorbance cross section (a.u.2)

1.00

0.75

0.02

0.01

0.50 0.00 0.6

0.8

0.25

0.00 0.0

1.0

1.2

Exp.

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

Photon energy (eV) Experiment from: Tsukuda and coworkers, J. Phys. Chem. C 2007, 111, 4153.

A reexamination of Au38(SR)24

0 6 monomer 4 dimer

-1.3 eV

-1.1 eV

3 monomer 6 dimer

8 dimer

Jiang et al., J. Phys. Chem. C, 112, 13905 (2008).

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The dimer-dominated model: From outside in (a)

(b)

(d)

(c)

•

What we miss: a high-symmetry core. Jiang et al., J. Phys. Chem. C, 112, 13905 (2008).

Optical absorption of our dimer-dominated model

Absorbance cross section

1.00

0.75

0.50

Exp.

0.25 Computed

0.00 0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

Photon energy (eV) Jiang et al., J. Phys. Chem. C, 112, 13905 (2008).

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Prof. T. Tsukuda’s suggestions

Au25 core

fcc

Bi-icosahedra

Tsukuda and coworkers, J. Am. Chem. Soc. 2008, 130, 8608.

Zeng’s most stable structure • Face-sharing bi-icosahedron core: Au23 • 6 dimers and 3 monomers

Pei, Gao, Zeng, J. Am. Chem. Soc. 2008, 130, 7830.

~2.0 eV higher Jiang et al., J. Phys. Chem. C, 112, 13905 (2008).

~5.0 eV higher Garzon et al., Phys. Rev. Lett. 2000, 85, 5250; Häkkinen et al., J. Phys. Chem. B 2006, 110, 9927.

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Zeng’s structure: in comparison with experiment

XRD

Optical absorption

Pei, Gao, Zeng, J. Am. Chem. Soc. 2008, 130, 7830.

Explanation for the stability of Au38(SR)24 • • • •

Superatom complex model 38-24=14 valence electrons Configuration: 1s2 1p6 1d6 Prolate ligand field leads to d-level spiting dxy

dx2-y2

↑↓

↑↓

dxz

dyz

↑↓

dz2

W. A. de Heer, Rev. Mod. Phys., 65, 611 (1993).

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Summary 

The gold-thiolate interface is dominated by RS-Au-SR and RSAu-SR-Au-SR motifs.



Superatom complex is a useful concept to understand the electronic structure of thiolated gold nanoclusters;



For the shell-closing electron count of 2, we predict that Au12(SR)9+ in the form of an Au6 octahedron protected by three dimer motifs to be the superior candidate;

Jadzinsky et al., Science, 2007.

Akola et al., J. Am. Chem. Soc., 2008. Heaven et al., J. Am. Chem. Soc., 2008. Zhu et al., J. Am. Chem. Soc., 2008.

Jiang et al, JPCC, 2009.

Acknowledgements • • •

•

DOE Basic Energy Sciences Program ORNL LDRD Seed Money Fund Collaborators – Sheng Dai, ORNL – Robert Whetten, Georgia Tech – Weidong Luo, Vanderbilt/ORNL – Murilo Tiago, ORNL
Brazil – Zhongfang Chen, University of Puerto Rico Helpful discussions – Tatsuya Tsukuda, Hokkaido University – Rongchao Jin, Carnegie Mellon University – Hannu Häkkinen, University of Jyvaskyla

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A quote from R. E. Smalley “Carbon has wired within it, as part of its birthright ever since the beginning of this universe, the genius for spontaneously assembling into fullerenes.” - Smalley, Nobel lecture in 1996.

“Gold and thiols have wired within them the genius for spontaneously assembling into nanoparticles.”

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