Photon Factory Activity Report 2014 #32(2015) B

6A/2013G533

Synthesis of Pd Particles in Surfactant Aggregates in Ionic Liquids
Masafumi HARADA*1, Chihiro ASANO1, and Kenji SAIJO2
1
Department of Clothing Environmental Science, Faculty of Human Life and Environment,
Nara Women’s University, Nara 630-8506, Japan2
Department of Polymer Chemistry, Graduate School of Engineering,
Kyoto University, Kyoto 615-8510, Japan
1 Introduction
In recent years, ionic liquids (ILs) have been paid
much attention as novel green media for the synthesis ofinorganic materials [1,2]. Micellar aggregations ofnonionic surfactants in ILs have been also studied
intensively [3]. However, few reports have described thesynthesis of metal particles in micellar aggregates in ILs.
In this study we have performed the size-controlled
synthesis of Pd particles in a series of micellar aggregatesconsisted of nonionic surfactant Brij in various ILs basedon the 1-alkyl-3-methylimidazolium cation by means of
SAXS measurements.
2 Experimental
Colloidal dispersions of Pd particles were synthesized
by the decomposition of palladium acetylacetonate,Pd(acac)2, in the mixture of nonionic surfactant (Brij-30,Brij-52, Brij-56, Brij-58, Brij-35, Brij-700) and 1-octyl-3methylimidazolium tetrafluoroborate ([OMIm][BF4]) (or1-octyl-3-methylimidazolium
hexafluorophosphate([OMIm][PF6])) at fixed weight ratio. For example, in thecase of Brij-52/[OMIm][BF4] binary system, 1.2 g of
Brij-52 was added to 2 mL of [OMIm][BF4], followed by
the addition of 11 mg Pd(acac)2 and mixed vigorously.
Subsequently, the mixture solution was poured into a cell(optical path length 1 mm), and the sample was stepwise
heated from RT to 333, 353, 373, 393, 413, 433, and 453
K. The in-situ SAXS measurements were performed ateach temperature at BL-6A. The scattering data wasdetected by a PILATUS 1M.
3 Results and Discussion
Fig. 1 shows the SAXS profiles of the colloidal
dispersions of Pd particles at different temperatures (up to453 K) in the presence of Brij-52 or Brij-58 mixed with
[OMIm][BF4]. These SAXS profiles show that all thesamples have a broad peak (centered around 1.7 nm-1 forBrij-52/[OMIm][BF4] and 2.2 nm-1 for Brij58/[OMIm][BF4]) observed in a q range larger than 1.5
nm-1 and a second inner shoulder peak in a q range
shorter than 1.2 nm-1. The former is characteristic of theinterference peak due to the existence of ordering for ILs,
and the latter is related to interferences due to theinteraction between two neighboring Pd particles. The
intensity of the second peak increases and its position
shifts to lower q with increasing temperature. The

Table 1 Average particle size (nm) of Pd particles synthesized atdifferent temperature in various binary systems
SampleBrij-30/[OMIm][BF4]
Brij-52/[OMIm][BF4]
Brij-56/[OMIm][BF4]
Brij-58/[OMIm][BF4]
Brij-56/[OMIm][PF6]Brij-35/[OMIm][PF6]Brij-700/[OMIm][PF6]353K 373K 393K 413K 433K 453K
2.4
3.0
4.1 5.9
6.2
6.5
1.4
1.4
1.8 2.2
3.1
1.6
1.6 2.4
3.4
2.2
2.5 2.9
3.8
4.8
1.9 3.0
4.3
4.5
2.4
2.7 3.5
4.0
5.2
2.9
3.9 4.4
4.4
4.7

(a)

(b)

Fig. 1. SAXS profiles of the Pd colloidal solutions synthesized
during stepwise raising the reaction temperature in the binary
system of (a) Brij-52/[OMIm][BF4] and (b) Brij-58/[OMIm][BF4].

variation of average size of Pd particles with temperature
is listed in Table 1. The detailed analysis is in progress.
References[1] Z. Ma et al., Adv. Mater. 2010, 22, 261.
[2] J. Dupont et al., Chem. Soc. Rev. 2010, 39, 1780.
[3] R. Rai, S. Pandey, Langmuir 2014, 30, 10156.
*harada@cc.nara-wu.ac.jp