Mn doping in atomic gold clusters: Geometry, Optical
and Magnetic properties
A. Pradhani1 and S. Rath1,*
1
School of Basic Sciences, Indian Institute of Technology Bhubaneswar, Toshali Bhawan, Satyanagar,
Bhubaneswar-751007, Odisha, India
Corresponding author’s e-mail: srath@iitbbs.ac.in
*
Abstract
In this report we have achieved the stability of a
planar hexagonal+1 Au8 (8 atom gold) cluster and Mn atom is
doped in the cluster assembly to induce magnetic properties.
We have studied change in optical and magnetic properties
due to introduction of Mn atoms into the stable planar
hexagonal+1 Au8 cluster. Structure and geometry of Au8
cluster and Mn doped gold clusters have been optimised by
DFT level calculation using Gaussian 09 package. This study
evidenced the stability of the Mn doped gold atomic clusters
and open up the understanding of the structure dependent
properties for material performance and applications with
atomic precision.
procedure is same as above mentioned. The structure
and geometry of Au8 and Mn doped gold clusters have
been optimised by DFT level calculation using Gaussian
09 package [2]. The influence of Mn doping on optical
properties is studied using Absorption and Circular
Dichroism (CD) measurements. And magnetic
properties of Mn doped gold clusters have been studied.
Figures
Keywords: Gold cluster, Mn doping, Optical properties,
Magnetic Properties, Circular Dichroism.
Introduction
Free standing micro-clusters (MCs) (condensestate of less than tens of atoms) and its superior
structures is a strong pursuit of the researchers for new
generation of atomic sensors and device applications.
But there are countless challenges in both theoretical
and experimental methods to understand the existence,
structure and behavior of the smallest possible MCs
with atomic precision. As per the theoretical prediction,
the Au8 exhibits planar star shape in the free space as
the lowest energy structure, though, planar hexagonal+1
shape structure is an isoenergetic isomer [1]. Here, we
report the synthesis and identification of the
hexagonal+1 shaped Au8 clusters in the aqueous phase.
Effect of Mn doping to the gold clusters optical and
magnetic properties have been studied.
For the synthesis of Au clusters, first Au ions
obtained from Gold chloride tetrahydrate and allowed to
interact with L-Cystein methyl ester (LCME)
hydrochloride for complex formation in an aqueous
solution followed by the reduction of the Au ion in
presence of ice-cold solution of sodium borohydrate
(NaBH4). Immediately after one day, the Au8 clusters
have been observed and are confirmed from optical
absorption studies and Raman scattering measurements.
For Mn doping different molar percentage of MnCl2 is
added during synthesis to get Mn ions and rest of the
Fig. 1. Circular Dichroism (upper curves) and Optical
absorption (lower curves) for Au8 clusters (a) and Mn
doped Au8 cluster (b).
Results
We can observe the contribution of Mn doping
in gold cluster resulting in shift in total absorption peak
to higher wavelength (lower curve in Fig. 1(b)) and is
well resolved in CD plot (upper curve in Fig. 1(b)) due
to opposite polarised absorption of Mn to Gold atoms.
References
[1] S. Rath, S. Nozaki, D. Palagin, V. Matulis, O.
Ivashkevich and S. Maki, “Aqueous-based synthesis of
atomic gold clusters:Geometry and optical properties”,
Appl. Phys. Lett 97, 053103-1 – 3 (2010).
[2] D. Dong, K. Xiao-Yu, G. Jian-jun and Z. Ben-Xia,
“Density functional theory study of AunMn(n=1-8)
clusters”, JPCS 71, 770-775 (2010).