A betaine adduct of N-heterocyclic carbene and carbodiimide, an efficient ligand to produce ultra-small ruthenium nanoparticles

Article abstract of DOI:10.1039/c5cc00211g

The betaine adduct of N-heterocyclic carbene and carbodiimide (ICy·^(p-tol)NCN) was found to be a very efficient ligand to prepare very small (1-1.3 nm) ruthenium nanoparticles (RuNPs). The coordination of the ligand on the metal surface takes place through the carbodiimide moiety. The resulting RuNPs led to decarbonylation of THF and showed size selectivity for styrene hydrogenation. This journal is

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Betaine adduct of N-heterocyclic carbene and
carbodiimide, an efficient ligand to produce ultra-small
ruthenium nanoparticles†
Cite this: DOI: 10.1039/x0xx00000x
Received 00th January 2012,
Accepted 00th January 2012
a
b
b
b
a
L. M. Martínez-Prieto, C. Urbaneja, P. Palma, J. Cámpora,* K. Philippot* and B.
c
DOI: 10.1039/x0xx00000x
Chaudret*
www.rsc.org/
The betaine adduct of N-heterocyclic carbene and such NHC-NCN betaines has not been yet investigated, but they
carbodiimide (ICy.(p-tol)NCN) was found to be a very efficient
combine a number of properties that can make them valuable ligands
for NP synthesis. For example, their configuration can be assimilated
to that of carboxylate or amidinate ligands but displaying an overall
electrically neutral character. However, owing to their zwitterionic
structure, the N atoms of NHC-NCN compounds are strongly basic
ligand to prepare very small (1-1.3 nm) ruthenium
nanoparticles (RuNPs). The coordination of the ligand on the
metal surface takes place through the carbodiimide moiety.
The resulting RuNPs led to decarbonylation of THF and and may coordinate to transition metals more strongly than typical
showed a size selectivity for styrene hydrogenation.
electrically neutral ligands do. In addition, they have a modular
design that allows easy variations of the pending groups linked to the
nitrogen atoms which may open new routes for controlling the
surface properties of MNPs. Moreover, depending on the nature of
the ionic moieties, these betaines can show different properties and
Particles of metals at the nanometer scale, namely nanoparticles
(NPs), are known to display interesting physical and chemical
properties and this confers them a high potential for application in
6
1
lead to different applications in organic synthesis and catalysis.
diverse areas like catalysis or others. For both physical and
Thus, betaines are ligands which offer both a zwitterionic character
and a large steric protection due to the four arms they contain. They
could be ideal for lowering NP rate of growth, thus favouring
nucleation over growth and therefore for producing smaller
nanoparticles. With this aim we looked at the synthesis of RuNPs
using the betaine ligand 1,3-dicyclohexylimidazolium-2- di-p-
chemical aspects, a lot of changes are expected to occur at the
frontier of the molecular and the solid states where nanoparticles are
situated. But to be able to explore these changes and to investigate
the resulting properties, it is necessary to selectively produce very
small and well-controlled nano-objects. Thus, a main objective in the
field is to develop appropriate tools to produce well-defined objects
.
(p-tol)
2
tolylcarbodiimide (ICy
NCN) as stabilizer in different Ru/ligand
at the nanometer-size. If methods exist for synthesizing large
ratios. The coordination mode of this novel ligand at the ruthenium
surface as well as its location and the presence of extended faces at
RuNP surface were determined by NMR. Moreover, a test catalytic
reaction (styrene hydrogenation) was performed to probe the
reactivity of these RuNPs.
molecular complexes (clusters) and for growing the particles with a
small mean diameter, it is very difficult to control the size growth in
3
the range of e.g. 1 nm. In our group, we have been working for a
4
long time on the synthesis of RuNPs. Typical sizes are in the range
1
-4 nm (with a great majority around 1.5-1.8 nm) depending on the
stabilizer used for their preparation. Until now, it appeared to us
difficult to obtain RuNPs smaller than 1 nm although our favourite The ligand ICy.(p-tol)NCN was readily obtained from the reaction of
(
p-
ruthenium
precursor,
namely
(1,5-cyclooctadiene)(1,3,5- 1,3-dicyclohexylimidazolidene (ICy) and di-p-tolylcarbodiimide (
tol)
cyclooctatriene)ruthenium (0) [Ru(COD)(COT)], is very easy to
NCN) (see ESI†). Further details on the synthesis, characterization
decompose in mild reaction conditions which can make the and coordination chemistry of this and other NHC-CNC ligands will
7
nucleation step more favourable than the growth of NPs. Thus, the be reported elsewere. Ru nanoparticles were synthesized with this
search for effective ligands to stop the NP growth at a desired size betaine adduct following our organometallic approach as previously
4
like 1 nm or less, constitutes one of our goals. From previous results, described. A THF solution of the complex [Ru(COD)(COT)] was
we know that strongly coordinating ligands can limit the growth of treated at room temperature (r.t.) under 3 bar H
2
in the presence of
NCN/Ru ratios were
high ability to coordinate at NP surface (both Ru and Pt) due to their applied, namely 0.1, 0.2 and 0.5 molar equivalent (equiv.) giving rise
.
(p-tol)
(p-tol)
the particles (vide supra). As N-heterocyclic carbenes showed a very ICy
NCN (Scheme 1). Various ICy.
5
.
(p-tol)
.(p-tol)
specific electron donor properties, we considered the use of more to RuNP samples called Ru-ICy
NCN0.1, Ru-ICy
NCN0.2 and
complex ligands derived from NHC-carbenes. More precisely, N- Ru-ICy.(p-tol)NCN0.5, respectively. In all the situations a black stable
Heterocyclic carbenes (NHCs) form stable zwitterionic adducts colloidal solution was obtained which was subsequently purified by
(
betaines) with carbodiimides (NCN). The coordination chemistry of precipitation in pentane, finally affording the RuNPs as a black
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together on Figure 2 for comparison purpose. As it can be seen, most
of the ligand signals can be clearly identified on the spectrum of the
NPs. Besides prominent signals corresponding to the p-tolyl methyl
group centered at ca. 25 ppm, a broad resonance at 30 ppm for the
cyclohexyl substituents and a characteristic low field narrow peak at
6
0 ppm attributed to the nitrogen-bound methyne group, the
spectrum of the NPs displays a peak at ca. 120 ppm for the aromatic
imidazolium backbone and signals at ca. 130 ppm for the aromatic
rings of p-toluene. But, the signals for the imidazolium and
13
carbodiimide quaternary NCN atoms, observed as singlets in the
C
MAS-NMR spectrum of the free ligand at 144.7 and 150.1 ppm
respectively, are not observed. The lack of visibility of these two
peaks could be attributed to a line broadening induced by
coordination of the ligand at the metal surface, as previously
observed with NHC-carbenes for example. Another hypothesis
could be a decomposition of the betaine ligand during the formation
of the NPs. Such a decomposition could cause the break of the NNC-
CNN bond and afford carbene and carbodiimide units.
Scheme 1. Synthesis of ruthenium nanoparticles in the presence of
.
(p-tol)
ICy
NCN as stabilizer.
3
a
In order to elucidate the nature of the molecules coordinated on the
ruthenium surface, different experiments were carried out, such as
.
(p-tol)
the reaction of Ru-ICy
of Ru-ICy
NCN0.1 with octanethiol or the oxidation
.
(p-tol)
NCN0.2. Given that thiols are well-known as strong
coordinating ligands at metal surfaces, this experiment aimed at
releasing the coordinated molecules from the NP surface, and detect
them by H and C{ H} solution NMR. A suspension of Ru-ICy·
6 6
NCN0,1 in C D was treated with 10 equiv. of octanethiol and then
1
0
1
13
1
(p-
tol)
Figure 1. TEM images and the corresponding size histograms of Ru-
.
(p-tol)
.(p-tol)
†
ICy
NCN0.1(left) and Ru-ICy
NCN0.2(right).
heated at 65 °C. Spectra recorded after 24h of reaction (S4, ESI ) did
not show the presence of free ICy
.
(p-tol)
NCN ligand in the liquid
powder. Transmission Electronic Microscopy (TEM) images and the phase. However, di-n-octyl disulfide was observed (triplet and
.
(p-tol)
corresponding size histograms of purified Ru-ICy
Ru-ICy
NCN0.1 and quintuplet at 2.55 and 1.61 ppm, respectively). The presence of
NCN0.2NPs are given in Figure 1. As previously disulfide was attributed to the catalytic oxidation of octanethiol into
.
(p-tol)
5
a,8
observed with NHC-carbenes and other stabilizers, smaller NPs disulfide at the RuNP surface as previously observed during the
1
1
were formed when increasing the amount of ligand from 0.1 to 0.2 synthesis of RuNPs stabilized with an excess of octanethiol. These
.
(p-tol)
.(p-tol)
equiv. Indeed, in sample Ru-ICy
diameter of ca. 1.3 (0.2) nm, whilst for Ru-ICy
have a mean size of ca. 1.0 (0.2) nm. Nevertheless, Ru-ICy
NCN0.1, the NPs have a mean results indicated first that the ICy
NCN ligand was not displaced
.
(p-tol)
NCN0.2, they at all from the NP surface. Second, octanethiol could react at the
.
(p-
metal surface to form disulfide, showing that Ru sites remain
tol)
NCN0.5 NPs have also a mean diameter of ca. 1.0 (0.2) nm (S1, available for its coordination and reaction. As another attempt to
ESI ). These results indicate that the ligand concentration influences decoordinate the molecules from the metallic surface, the Ru-ICy
†
.(p-
tol)
the NP mean diameter until a certain limit since adding more than
NCN0.2 NPs were treated under oxidative conditions. Such
0
.2 equiv. of betaine does not change the NP mean size. A similar reaction test was previously applied with diphosphine-stabilized
behaviour was previously observed with a sulfonated diphosphine RuNPs for which it was not possible to prove by direct solution
9
and explained as a steric hindrance phenomenon. In all cases the NMR studies the coordination of the phosphine ligands while free
NPs are well-distributed on the TEM grid and display a relatively phosphine oxide was released and became visible after oxidation.12
narrow size distribution. High Resolution Transmission Electron For that purpose, a suspension of the NPs in EtOH was refluxed
(
p-tol)
†
Microscopy (HRTEM) images of Ru-ICy.
NCN0.1 (S2, ESI )
revealed the presence of highly crystalline NPs retaining the
hexagonal close packed (hcp) structure of bulk Ru. Fourier analysis
applied to this image shows reflections to the (101), (101) and (100)
atomic planes. Wide-Angle X-ray Scattering (WAXS) analysis
.
(p-tol)
performed on solid powder of Ru/ICy
NCN0.1 confirmed that
these NPs are crystalline with a hcp structure. The Radial
Distribution Function (RDF) analysis does not indicate oxidation,
but shows metallic Ru NPs with a single domain and a coherence
length close to ca. 1 nm, which is in agreement with the HRTEM
†
observations (S3, ESI ).
In order to understand the influence of ICy·(p-tol)NCN on the size
control during the RuNP preparation, we investigated its
coordination at the metallic surface by NMR spectroscopy. Thus, the
RuNPs were analyzed by magic angle spinning solid-state NMR
1
13
(
MAS-NMR) with and without H- C cross-polarization (CP). CP-
13
1
Figure 2. Bottom: CP-MAS C{ H} NMR spectrum of betaine
(
p-tol)
(
MAS NMR spectra of Ru-ICy·
NCN0.1 recorded on a purified
.(p-tol)
13
1
adduct ICy
NCN. Top: CP- MAS C{ H} NMR spectrum of
p-tol)
NP sample and on the free ICy·
NCN ligand are presented
Ru-ICy.(p-tol)NCN0.1 NPs.
2
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under air at 80 °C for 4h. After this treatment we observed the
release of molecules in solution that correspond to ICy.(p-tol)NCN
ligand, as determined by ElectroSpray Ionization Mass Spectrometry
†
(
ESI-MS) (S5, ESI ). Thus, it can be assumed that the betaine ligand
remains intact when coordinated at the metal surface. As a
consequence, the absence of signals at 144 ppm and 150 ppm in the
1
3
C MAS-NMR spectrum of the NPs is most probably due to a line
broadening arising from the coordination of the ligand at the
ruthenium surface through the NCN nitrogen atoms which may be
reinforced by the sigma-donor ability of the carbene moiety. This
coordination mode could be evidenced by doing a blank test
consisting in using the carbodiimide ligand ( NCN (0.2 equiv.) to
Figure 3. MAS C{ H} NMR spectra of Ru-ICy.(p-tol)NCN0.1 (left)
1
3
1
and Ru-ICy.(p-tol)NCN0.2 after exposure to CO (1 bar, 20h, at r.t.).
13
p-tol)
prepare RuNPs. In these conditions, ca. 1.6 (0.4) nm were obtained
†
while COt are. This observation is in agreement with the lack of for
mobility observed terminal CO which can result from the nearby
coordination of betaine ligands thus limiting their moving. As the
main difference between the two RuNP samples is the decrease in
(
S6, ESI ), thus proving the ability of the NCN motif to coordinate at
the metallic surface.
The next step was to probe the surface state of the particles by
measuring their capacity to bind CO by Fourier transform infrared
.
(p-
size with increased ligand quantity (ca.1.0 nm for Ru-ICy
tol)
.(p-tol)
NCN0.2 against ca. 1.3 nm for Ru-ICy
NCN0.1), a plausible
1
3
1
13
(
1
(
FT-IR) and MAS
C{ H} and CP MAS
C{ H} NMR.
explanation could be that the coordination of CO in a bridging mode
is hindered by a lack of available faces on the surface for the smaller
p-tol)
Interestingly, FT-IR spectra of purified NPs Ru-ICy
NCN0.2 showed a band displaying the characteristic of a
CO absorption between 1900 and 2000 cm before their exposure to
NCN0.1 and
.
(p-tol)
Ru-ICy
.
(p-tol)
(p-tol)
13
.(p-tol)
Ru-ICy
NCN0.2
.
Nevertheless, either in Ru-ICy
NCN0.1 or
-
1
.
Ru-ICy
NCN0.2 NPs, CO is mainly coordinated in terminal
.
(p-tol)
CO. Moreover, for the Ru-ICy
NCN0.1 sample, the intensity of
mode. This can result from the very small size of the NPs, where the
face surfaces is limited and most ruthenium atoms concentrate on
edges and apexes, where coordination in a terminal mode is more
favorable.
the band did not change after CO exposure (1 bar; r.t.), suggesting
that the NP surface was already saturated by CO after synthesis. Ru-
.
(p-tol)
ICy
NCN0.2 showed a different band intensity suggesting that in
this case the Ru surface was not totally covered by CO, (S7 and S8,
†
ESI ). Then, the question was: where does CO come from?
The small size and specific electronic configuration of MNPs make
them interesting systems for many catalytic reactions. In particular
RuNPs are able to catalyze both the hydrogenation of alkenes and
arenes under mild conditions while molecular complexes are just
Considering the reaction conditions for the RuNPs synthesis, the
only source of CO could be THF, through a decarbonylation process
which would release propane. We thus analyzed the composition of
the reaction sky resulting from the NP synthesis mixture by gas
phase NMR and Mass Spectrometry (MS). After the synthesis of Ru-
1
4
active in alkene hydrogenation. Styrene hydrogenation can thus be
applied as a model reaction to probe the surface reactivity of MNPs
because it offers the possibility of measuring the selectivity between
vinyl and aromatic hydrogenation. Thus, we investigated the
.
(p-tol)
ICy
NCN0.1, we observed two peaks at 0.75 and 1.20 ppm by gas
†
phase NMR corresponding to propane (S9, ESI ). By MS both
compounds, CO and propane, were detected (S10, ESI ). In addition,
following a previously reported procedure, the RuNPs were reacted
with 2-norbornene and the amount of norbornane formed was
†
.
(p-tol)
1
3
performance of Ru-ICy
NCN NPs in styrene hydrogenation in
mild reaction conditions. Table 1 reports the results obtained in
.
(p-tol)
.(p-
.
(p-tol)
styrene hydrogenation with Ru-ICy
NCN0.1 and Ru-ICy
measured by G.C. analysis (see ESI†). Ru-ICy
NCN0.1 and Ru-
tol)
.(p-tol)
.
(p-tol)
NCN0.2 at r.t. in THF. Ru-ICy NCN0.1 hydrogenates styrene
first to ethylbenzene and then to ethylcyclohexane. The Ru-ICy
NCN0.1 catalyst allowed the total hydrogenation of styrene into
ICy
NCN0.2 NPs display, 0.0 and 0.6 H per surface Ru (Table
.
(p-
S1, ESI†); These values are lower than usual ones for other RuNPs
and evidence elimination of hydrides from the surface probably due
to a full or partial coverage of the Ru surface by CO, respectfully.
Altogether, these data demonstrate that CO is coordinated at the
RuNP surface, as the result of a decarbonylation process of THF
used as solvent during their synthesis, hence evidencing the high
tol)
.
(p-tol)
2
4h. While using Ru-ICy
NCN0.2 as nanocatalyst, the
hydrogenation rate of the vinyl group remained similar to that of Ru-
.
(p-tol)
ICy
NCN0.1, the hydrogenation rate of the arene moiety
decreased. The selectivity for vinyl hydrogenation was therefore
lightly improved: 74 % of the ethylbenzene was hydrogenated to
ethylcyclohexane after 24 h. As the presence of available faces are
1
3
1
surface reactivity of these NPs. The MAS C{ H} NMR spectrum
.
(p-tol)
of solid samples of Ru-ICy
NCN0.1 NPs exposed to 1 bar of
CO at r.t. (Figure 3 left) displays two signals attributed to adsorbed
CO molecules: a broad peak at δ ~ 229 ppm that can be assigned to
1
5
1
3
necessary to hydrogenate aromatic rings, these catalysis results
.
(p-tol)
corroborate the fact that less faces are present in Ru-ICy
NCN0.2
.
(p-tol)
.(p-
1
3
NPs than in Ru-ICy
NCN0.1 ones. This makes Ru-ICy
NCN0.2 NPs to have a behavior in catalysis more similar to that of
CO coordinated in a bridging mode (COb) and a sharp resonance at
tol)
1
3
δ = 199 ppm due to CO coordinated in a terminal mode (COt).
From previous works, bridging CO molecules are expected to be
coordinated onto faces and terminal ones onto corners and edges.13
1
6
molecular complexes than to facetted nanoparticles.
Moreover, the presence of spinning bands (*) suggests that COt are Conclusions
static on the surface. The limitation of CO mobility on the metallic
surface can be explained by the coordination of betaine ligands in
A betaine adduct of NHC and carbodiimide (NHC-NCN) has been
close proximity of the ruthenium sites where CO are coordinated. On
identified as a new ligand capable of stabilizing very small Ru
1
3
1
†
the CP MAS C{ H} NMR spectrum (S11, ESI ), the intensity of
the signal for bridging CO is decreased compared to that of the
terminal ones. This means that bridging CO groups are not affected
by cross polarization from close hydrogen carriers while terminal
COs are. It can be thus assumed that bridging CO groups are not
located in the vicinity of hydrogen carriers (namely, betaine ligands)
(p-tol)
nanoparticles. Specifically, ICy·
NCN gave rise to ultra-small
and crystalline Ru NPs. A clear relationship was observed between
(p-tol)
the ICy·
NCN/Ru ratio used in the NP synthesis and the mean
size of the obtained NPs. In particular ca. 1.3 nm NPs were produced
(p-tol)
when 0.1 equiv. of ICy·
NCN per Ru were used and ca. 1.0 nm
NPs in the case of 0.2 equiv. This difference in size leads to different
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Table 1. Hydrogenation of styrene with Ru-ICy.(p-tol)NCN NPs.
Journal Name
Hydrogenation of Styrene at 25 °C
Reaction time (h)
RuNPs
0
1
3
5
22
24
Ru-ICy.(p-tol)NCN0.1
Ru-ICy.(p-tol)NCN0.2
100:0:0
100:0:0
0:97:3
0:98:2
0:77:23
0:82:18
0:52:48
0:70:30
0:4:96
0:0:100
0:31:69
0:26:74
Products ratio in % to A:B:C (A = styrene; B = ethylbenzene; C = ethylcyclohexane). Catalytic conditions: Tª = 25 °C; Rus/styrene ~ 1:
3
00; Ru
s
~ 0,03 mmol; H
2
Pressure = 3 bar. Conversion determined by G.C.
1
Nanoparticles. From Theory to Application ed. G. Schmid, Wiley-
VCH, Weinheim 2004.
availabilities in terms of accessible faces at the metal surface, the
smallest RuNPs displaying less faces as expected. This was
evidenced by studying the coordination of CO as well as the
hydrogenation of styrene as model substrate. While larger NPs (Ru-
2
3
Term “size” refers to “mean diameter”
a) K. Philippot and B. Chaudret, C.R. Chimie 2003, 6, 1019. b) C.
.
(p-tol)
Vollmer, E. Redel, K. Abu-Shandi, R. Thomann, H. Manyar, C.
Hardacre and C. Janiak, Chem. - A Eur. J. 2010, 16, 3849. c) D.
Marquardt, C. Vollmer, R. Thomann, P. Steurer, R. Mülhaupt, E.
Redel and C. Janiak, Carbon 2011, 49, 1326.
ICy
NCN0.1) were able to transform totally styrene into
ethylcyclohexane in mild reaction conditions, the smaller particles
.
(p-tol)
Ru-ICy
NCN0.2 NPs provided a partial selectivity into ethyl
benzene. Such behaviour in catalysis is expected for molecular
complexes but not for facetted RuNPs. Thus, even if they are not
perfectly defined, these ca. 1 nm RuNPs display a reactivity at the
frontier between the molecular and solid states. The next step would
be to determine the nano-object size or ligand-covering at which the
hydrogenation of the arene ring is totally blocked while keeping that
of the external double-bond in styrene hydrogenation. Furthermore,
decarbonylation of THF, the solvent used for the synthesis of these
NPs was evidenced for the first time and is probably related to the
high reactivity of these ultra-small RuNPs. This result makes these
new RuNPs of interest for exploring other type of catalytic reactivity
at the border of the molecular and the solid states.
4
5
a) Organometallic Ruthenium Nanoparticles and Catalysis, K.
Philippot, P. Lignier and B. Chaudret, in Ruthenium in Catalysis.
Topics in Organometallic Chemistry, eds. Dixneuf, P. H., Bruneau,
C.; Springer International Publishing 2014.b) P. Lara, K. Philippot,
and B. Chaudret, ChemCatChem 2013, 5, 28.
a) P. Lara, O. Rivada-Wheelaghan, S. Conejero, R. Poteau, K.
Philippot and Chaudret, Angew. Chem. Int. Ed. 2011, 50, 12080. b) P.
Lara, A. Suárez, V. Collière, K. Philippot and B. Chaudret,
ChemCatChem 2014, 6, 87.
6
7
8
L. Delaude, Eur. J. Inorg. Chem. 2009, 1681.
J. Cámpora et al., to be submitted.
The authors thank CNRS, UPS-Toulouse, INSA, CSIC, IIQ, Spanish
and Regional Andalusian Governments (grants CTQ2012-30962 and
FQM6276) and EU (ERC Advanced Grant, NANOSONWINGS
M. Zahmakiran, K. Philippot, S. Özkar and B. Chaudret, Dalton
Trans. 2011, 41, 590.
2
009-246763) for financial support. We also thank V. Collière and
L. Datas for TEM facilities (TEMSCAN, UPS), P. Lecante
CEMES, CNRS) for WAXS measurements, C. Bijani and Y.
9
M. Guerrero, Y. Coppel, N. T. T. Chau, A. Roucoux, A. Denicourt-
Nowicki, E. Monflier, H. Bricout, P. Lecante, K. Philippot,
ChemCatChem, 2013, 12, 3802.
(
Coppel for NMR measurements, and A. Márquez Esteban for useful
help on the synthesis of betaine ligand ICy.
(p-tol)
10 I. Favier, S. Massou, E. Teuma, K. Philippot, B Chaudret and M.
NCN.
Gomez, Chem. Comm. 2008, 3296.
1
1
1 C. Pan, K. Pelzer, K. Philippot, B. Chaudret, F. Dassenoy, P. Lecante
and M.-J. Casanove, J. Am. Chem. Soc. 2001, 123, 7584.
2 J. García-Antón, M. R. Axet, S. Jansat, K. Philippot, B. Chaudret, T.
Pery, G. Buntkowsky and H.-H. Limbach, Angew. Chem. Int. Ed.
2008, 47, 2074.
Notes and references
a
Laboratoire de Chimie de Coordination; CNRS; LCC; 205, Route de
Narbonne, F-31077. Université de Toulouse, UPS, INPT, LCC, 31077
Toulouse, France. E-mail: karine.philippot@lcc-toulouse.fr
b
Instituto de Investigaciones Químicas, CSIC - Universidad de Sevilla.
1
1
3 F. Novio, K. Philippot and B. Chaudret, Catal Lett 2010, 140, 1.
4 Nanoparticles and Catalysis, ed. D. Astruc, Wiley-VCH, Weinheim,
2008.
C/ Américo Vespucio, 49, 41092 Sevilla, Spain. E-mail:
campora@iiq.csic.es
c
LPCNO; Laboratoire de Physique et Chimie des Nano-Objets,
1
1
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UMR5215 INSA-CNRS UPS, Institut des Sciences appliquées, 135,
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†
Electronic Supplementary Information (ESI) available: [details of any
supplementary information available should be included here]. See
DOI: 10.1039/c000000x/
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| J. Name., 2012, 00, 1-3
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