chemical reaction of transition metal clusters (fe, co, ni...
TRANSCRIPT
-
Chemical reaction of transition metal clusters (Fe, Co, Ni) with ethanol by
using FT-ICR mass spectrometer
Shuhei INOUE a) and Shigeo MARUYAMA b)
a) Department of Mechanical System Engineering, Hiroshima University
1-4-1 Kagamiyama, Higashi Hiroshima-shi, 739-8527, Japan
b) Department of Mechanical Engineering, The University of Tokyo
7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
Chemical reactions of transition metal cluster ions (Fe, Co, Ni) with ethanol
were investigated by using an FT-ICR mass spectrometer. Metal clusters of about 10-20
atoms were generated by a pulsed laser-vaporization and supersonic-expanded cluster
beam was directly introduced into FT-ICR mass spectrometer. Observed reactions are
simple chemisorptions of ethanol and dehydrogenated chemisorptions strongly depend
on metal species and their cluster sizes. In case of Co cluster, detailed dehydrogenation
reaction steps were elucidated through several isotope experiments using C2H5OD,
CD3CH2OH, C2D5OD in addition to C2H5OH. A qualitative tendency that the reaction
pattern changed along the periodic table (Fe → Co → Ni) was observed. The
dependency of chemisorption rate on metal cluster size were similar for 3 metals,
however, the cluster sizes at the maximum reaction rate are in the order of Fe < Co < Ni,
which also obeys the order in the periodic table.
-
1. INTRODUCTION
The carbon nanotube (CNT) 1 discovered in 1991 has the network structure
with hexagonal rings and pentagonal rings of carbon atoms. The carbon nanotube is
classified into two types; one is single-walled carbon nanotube (SWNT) 2 and the other
multi-walled carbon nanotube (MWNT). 1 CNTs are expected as new materials from
various physical and chemical characters based on the geometric unique structure. So
far, a number of researches attempting to apply SWNTs to e.g. electrodes, 3, 4 AFM tips,
5, 6 nano-wires, 7 and field emitters 8, 9 have been performed actively.
At present, mainly due to its scalable nature, CVD 10-15 method is regarded as
the most suitable technique to produce SWNTs industrially. Among them, the HiPco
(High-Pressure CO) method 16 has been recognized as a most commercially feasible
approach to produce large amount of relatively high quality SWNTs continuously.
Recently, Maruyama et al. 17 proposed a new CVD method where alcohols (e.g. ethanol
and methanol) were first employed as a carbon source for the synthesis of SWNTs. The
method, named as alcohol CCVD (ACCVD) method, is superior to other CVD methods
since they can produce high-quality SWNTs at relatively low temperature. However, its
synthetic mechanism has not made clear yet, so fundamental investigations for growth
mechanism is essential for the further improvement of ACCVD method.
In CVD methods, transition metals such as Fe, Ni, Co are used as a catalyst,
and Co are also employed in other fields, and many researches 18-24 are proceeded on a
cluster level. However, most of existing researches are restricted to small size clusters
(less than 10 atoms) mainly because generating large-sized cluster is rather difficult. In
this report, we have explored a basic reaction mechanism of larger size clusters (Fe, Co
and Ni) with ethanol, in which we simulated actual catalyst size used in the CCVD
-
processes for SWNT production.
2. EXMERIMENTAL
The experimental apparatus are based on the same design concept as the
apparatus in Smalley's group 19 and the detailed characteristics are described in
elsewhere. 26-29 Figures. 1 and 2 show the cluster beam source and direct injection
FT-ICR apparatus, respectively. The metal cluster ion beam was generated outside of
magnetic field by the laser-vaporization cluster beam source shown in Fig. 1. A pulsed
gas valve, the sample motion mechanism and a skimmer were installed in a 6-inch
6-way UHV cross. A solid sample disk was vaporized by the focused beam of Nd: YAG
laser (2nd harmonics) while timed pulsed gas was injected to the nozzle. In the
atmosphere of helium gas, vaporized atoms condensed to clusters, and then, were
carried and cooled by the supersonic expansion of helium gas. The cluster beam was
directly injected to the magnetic field through a skimmer with the opening diameter of 2
mm and a deceleration tube.
The FT-ICR is the unique mass spectroscopy based on the ion-cyclotron motion of
clusters in a strong magnetic field. The ion cyclotron frequency f is inversely
proportional to the ion mass M as follows.
M
Bqf
π2=
Extremely high mass-resolution at high mass-range such as resolution of 1 amu at
10,000 amu range can be obtained. Furthermore, since the ions can be trapped in the
vacuum for a few minutes, it is possible to perform the chemical reaction experiments.
The ICR cell, 42 mm I.D. 150 mm long cylinder was placed in a stainless-steel tube
-
(SUS316) of 84 mm I.D. which penetrated the homogeneous 5.826 Tesla
super-conducting magnet commercially available for NMR. Two turbo-pumps
(300 s/l ) fore-pumped by a smaller turbo-pump of 50 s/l were placed at the floor in
order to avoid the effect of strong magnetic field. The typical background pressure was
3×10-10 Torr.
For the chemical reaction experiments, ethanol gas was supplied to the cell by a
pulsed valve for a fixed period. The pulse value was adjusted so that the pressure at the
ICR cell chamber became at 1-2×10-8 Torr. After pumping out, cluster ions were excited
to detect the mass distribution.
3. RESULTS AND DISCUSSION
3.1. COBALT CLUSTERS
Figure 3(a) shows a typical spectrum of cobalt clusters as injected from the cluster
beam source. In this figure, a horizontal axis denotes cluster size (upper measure is a
number of cobalt atom and lower measure is atomic mass unit), and a vertical axis
expresses signal intensity. There are small peaks between pure cobalt clusters, which are
water molecule (H2O, 18 amu) chemisorbed on the clusters. Fig. 3(b-d) shows results of
reaction with ethanol (at R.T., 1×10-8 Torr ) for 0.2, 0.5 and 1.0 second each. After 0.5 s
reaction products begin to be observed, and there are many reaction products seen in Fig.
3(d). It is very interesting that there are two reaction types. In case of Con (12
-
(C2H5OH) is 46 amu, so this reaction must be simple chemisorptions, however it is not
clear from this data whether an ethanol molecule is dissociated or not on the cluster
surface. We guess the ethanol atom is chemisorbed dissociatively on the cluster surface,
as the reason discussed later. Fig. 4 shows the expansion view of fig. 3(d). Almost the
same reaction patterns are seen in each graph. In Type-A reaction main products are
almost four species where each products are shifted from pure cobalt clusters by 9, 11,
42, 46 amu. All of other signals show intermediate products. Type-A can be divided into
two kinds, one is one molecule reaction (Type-A1) and the other is two-molecules
reaction (Type-A2). Signals at 42 and 46 amu are classified into Type-A1, where 46 amu
means simple chemisorptions and 42 amu means dehydrogenation. In Type-A2 reaction,
on the other hand, two ethanol molecules are reacted on cobalt clusters and H2O or H2
molecules are dissociated, as expressed below:
Type-A1: Con+ + C2H5OH → Con(C2H6O)
+ or Con(C2H2O)+ + 2H2
Type-A2: Con+ + 2C2H5OH → Con(C4H6O)
+ + H2O + 3H2
or (Eqs. 1)
Con+ + 2C2H5OH → Con(C4H4O)
+ + H2O + 4H2
Type-B: Con+ + C2H5OH → Con(C2H6O)
+
It is should be important to know which hydrogen atoms are dissociated. Figure 5 shows
the isotope experiment of cobalt clusters reacted with ethanol. The ethanol isotopes in
which one or more hydrogen atoms in the ethanol molecule are replaced by deuterium
atoms (a: normal ethanol, CH3CH2OH, b: ethanol-d, CH3CH2OD, c: ethanol-d3,
CD3CH2OH, d: ethanol-d6, CD3CD2OD) are used in the experiment. In Fig.5 spectrum
are expanded from Co14 to Co15, upper horizontal axis means cluster number and
-
numbers in smaller font size (18 and 42) indicate the distance from Co14 in atomic mass
unit. The “18” usually means water chemisorption. The triangle-marked peaks
correspond to the chemisorption of an ethanol molecule followed by dehydrogenation,
and square-marked peaks correspond to a simple chemisorption of an ethanol. Captions
in this figure such as "4amu", "5amu" and so on are distance between these triangle- and
square-marked peaks. Figure 5(a) shows the reference reaction spectrum that is the
expansion view of Fig. 4(d). In Fig. 5(a) the mass difference between simple
chemisorption and dehydrogenate chemisorption is 4 amu, indicating that there must be
4 hydrogen atoms dissociated. In Fig.5 (b), since ethanol-d has one deuterium atom, the
mass change depends on weather D atom is dissociated or not. In this reaction when it
presumes from the dominant spectrum(←?), 3 H atoms and 1 D atom are dissociated.
The small peaks appeared at 42 amu and 46 amu positions from Co14 are the products
of H/D exchange (shown in Eqs.2).
( )( ) ( )
+→+
++→+++
++
HHDOCCoDOHCCo
HDHOHCCoODHCCo
2n22n
222n52n Dehydrogenated and H/D exchange
(Eqs.2)
( )( ) ( )
+→+
→+++
++
DOHHCCoHODHCCo
ODHCCoODHCCo
52n52n
52n52n Simple and H/D exchange
In case of fig.5(c), following to the same theory, dissociated atoms are 2D and
2H atoms. The signals appeared at 42 amu and 50 amu positions are also the products of
H/D exchange. Comparing these dehydrogenated chemisorption and H/D exchange
results the reaction mechanism can be clear. At first the position of dissociated atoms
are known, two of them are from the first carbon atom (methyl), one is from second
-
carbon atom, and the last is from hydroxyl. The H/D exchange often seems to occur,
however exchanged atoms are different between dehydrogenation chemisorption and
simple chemisorption.
In case of simple chemisorption reaction, the mass of H/D exchanged signal is
smaller than original by 1 amu (shown fig.5(b)) that is why D atom is dissociated and H
atom is chemisorbed, on the other hand as shown in fig.5(c) the mass of H/D exchanged
signal is larger than original by 1 amu so only hydroxyl bond (shown in fig.6(a)) can be
exchangeable. Though there are five C-H (or C-D) bonds that are CH3 and CH2, CH3
bonds cannot be exchangeable. If this process takes place at CH3 (or CD3) site, final
products must be shown at larger position in Fig.5 (b) and smaller position in Fig.5 (c).
If there are some exchanges happen as a result signals are shown as Fig. 5, intermediate
products should be shown. That is why this exchange can happen at only hydroxyl bond
site.
In case of dehydrogenation chemisorption, original H or D atoms are shown Fig.
6(b), and H/D exchangeable site might be methyl bond, because H/D exchange signals
are shown at larger position in Fig. 5(b), and shown at smaller position in Fig. 5(c).
These are the results of being replaced by D from H in Fig. 5(b) and of being replaced
by H from D in Fig. 5(c).
Figure5 (d) shows the result of chemical reaction with C2D5OD. In this figure
dehydrogenation signal must be shown at 8 amu from simple chemisorbed signal,
however the signal peak is located at 9 amu from simple chemisorbed signal. It is
possible to say that all D atoms have been replaced by H atoms since there are many
hydrogen atoms as this reason. To see lower mass there are water chemisorbed signals,
usually 19amu signal (* shown in fig.5(d)) should not appear based on its natural
-
isotope existence. However in this reaction D atoms are so rich that all H atoms can be
replaced as shown in Eq. 3.
OHDCHODODDCOH 52522 +→+ (3)
Though D atoms are rich enough, there is no signal that is replaced water
molecule by Two D atoms. If water molecules keep molecular state, both H atoms are
still the same condition, so it is implausible that only one atom can be replaced by D
atom. That is the reason why water molecules must not remain in the molecular state on
the cobalt cluster, but they are chemisorbed dissociatively.
Figure7 is the chemical reaction with ethanol-d3. In this figure intermediate stage
signal is weak but obviously observed. From this result the first step of dehydrogenation
is a dissociation of hydrogen (H-D), because the mass of them are 3 amu. Since the
hydrogen atom of a hydroxyl bond is easy to be replaced, it seems that hydrogen atoms
marked by *1 shown in Fig. 8 are first removed by dehydrogenation. From these
experiments, as shown in Fig. 8, at first hydrogen atoms (shown as *1) are dissociated
as hydrogen atom, and O and C atoms (shown as C2) may be adsorbed on metal. Then
H atoms (shown as *2) are dissociated as a molecule, and 2 C atoms would form double
bond with metal.
Generally reaction mechanism is different between cation and anion clusters, so
that it is important to know both reaction mechanisms. Figure 9 shows cobalt anion
clusters reacted with ethanol (a: normal, b: -d, c: -d3), obviously different reaction
mechanism is seen. It turns out that the hydrogen atom of a hydroxyl has been
dissociated judging from a reaction result. There are no simple chemisorptions and
dehydrogenation chemisorptions, but only either one of H or D atom is dissociated and
H/D exchange does not happen. Because anion clusters might be generated under the
-
low energy condition, ethanol molecule is not bonded dissociatively but associatively
with cluster side. The ethanol molecule may retain its structure and bonded with cluster
side through the oxygen atom. If the ethanol molecule chemisorbed dissociatively with
cobalt clusters, H/D exchange may occur like the reaction of cation clusters.
3.2. NICKEL CLUSTERS
Figure10(a) shows the typical spectrum of as-injected nickel clusters. Since
there are five isotopes in case of nickel, the spectra become very complex. However,
FT-ICR mass-resolution is high enough to compare with their mass distribution based
on natural existence. Figures 10(B, C) show the result of reaction, where all products
are seen just before the next nickel cluster signal as shown in gray. It is difficult to
identify its reaction mechanism because of its variety of isotope. However it can be
surmised that it is an dehydrogenation chemisorption reaction as shown in Fig. 10(B, C)
judging from the distribution of an isotope. Fig. 10(B, C) are expansion view of Fig.
10(A-b, A-c) each that are surrounded with square. It can be clear that four hydrogen
atoms are dissociated from a cluster side like the case of cobalt shown in Fig. 10(B).
These dissociated four atoms may be the same as the cobalt case because 2H and 2D are
dissociated, which is the same as cobalt case. In case of cobalt H/D exchange has
occurred, and this also occurred in the case of nickel. Comparing with large peaks to
small peaks that consist isotope distribution of nickel clusters, the height of large peaks
must be about five times higher than that of small peaks in subjected to natural
existence shown in Fig. 11(a). If about 20 % of deuterium atoms are replaced by
hydrogen atoms, spectrum shapes are in good agreement with experimental data shown
in Fig.11(b, c). This assumption will lead the same reaction mechanism that
-
exchangeable atom is deuterium.
3.3. IRON CLUSTERS
Figure12(a) shows the typical spectrum of as-injected iron clusters. Since iron
also has isotopes, the signal is complicated too. As shown in Fig.12(b) , the reaction
products have appeared just beneath the strong iron signal. In order to investigate the
atomic weight of reaction products, Fig. 13(a) shows an expanded view of the portion
surrounded by square in Fig.12(b). Spectra of iron clusters may show unique isotope
distribution, but these spectra are in good agreement with ideal distribution shown in
Fig. 13(b). All of representative signal peaks marked with ▲, ■, ● and ○ show
perfect consistencies. In this reaction ethanol-d3 molecule shows simple chemisorption,
because the mass difference between the representative signals is 49 amu shown in Fig.
13(a). As to the H/D exchange process it is difficult to identify, but the peaks observed
between large peaks are so weak that H/D exchange might not occur.
3.4. COMPARISON OF THREE METALLIC KINDS
As we have discussed through this paper, Fe (4s2, 3d6), Co (4s2, 3d7) and Ni
(4s2, 3d8) are considered to have almost the same properties. Here, there are two
interesting phenomena we have noticed. One is about the reaction mechanism and the
other is about the reaction rate. In this experiment, the reaction mechanism of transition
metal clusters (Fe, Co, Ni) also change in order of atomic number. In the case of iron,
the reaction with the ethanol molecule was nothing but a simple chemisorption, and in
case of nickel, four hydrogen atoms were dissociated from the clusters. However in case
of cobalt, which is situated between iron and nickel on the periodic table, two kinds of
-
reaction pattern were shown. In this result, indicating the reaction mechanism also
changes with atomic number. Interestingly, the reaction mechanism changes in
accordance with the order in the periodic table. Figure.14 exhibits relative rate constant
of each transition metal cluster with ethanol. In case of alkali metal clusters, they show
magic number behavior based on super shell theory, however there is no report of magic
number for transition metal clusters. Figure 14 presents the relationship between
chemical reactivity and the cluster size, for the cases of Fe, Co, and Ni. Although their
curves shows qualitatively same tendencies, this comparison clearly reveals that the
most reactive cluster size shift larger as the atomic number is increased even by one or
two. Authors speculates that this could be a partial reason of why the adequate catalysis
different along atmospheric temperature and reaction species.
ACKNOWLEDMENT
The authors greatly thank Mr. Y. Murakami (The University of Tokyo) for
revising English. This work was supported by Grant-in-Aid for Scientific Research
(#12450082) from MEXT, Japan. S. Inoue was financially supported by Grant-in-Aid
for JSPS Fellow from MEXT, Japan.
REFERENCES
1 S. Iijima, Nature, 354, 56 (1991).
2 S. Iijima and T. Ichihashi, Nature, 363, 603 (1993).
3 S. J. Tans, M. H. Devoret, H. J. Dai, A. Thess, R. E. Smalley, L. J. Geerligs and C.
Dekker, Nature, 386, 474 (1997).
4 M. Bockrath, D. H. Cobden, P. L. McEuen, N. G. Chopra, A. Zettl , A. Thess , R. E.
-
Smalley , Science, 275, 1922 (1997).
5 H. J. Dai, J. H.Hafner, A. G. Rinzler, D. T. Colbert and R. E. Smalley, Nature, 384,
147 (1996).
6 H. Nishijima, S. Kamo, S. Akita, Y. Nakayama, K. I. Hohmura, S. H. Yoshimura and
K. Takeyasu, Appl. Phys. Lett., 74, 4061 (1999).
7 B. I. Yakobson, M. P. Campbell, C. J. Brabec, J. Bernholc, Comp. Mat. Sci., 8 ,
341(1997).
8 W. A. de Heer, A. Chatelain, and D. Ugarte, Science, 270, 1179 (1995).
9 Y. Saito, and U. Mori, Jpn. J. Appl. Phys., 37, 346 (1998).
10 H. J. Dai, A. Rinzler, P. Nikolaev, A. Thess, D. T. Colbert and R. E. Smalley, Chem.
Phys. Lett., 260, 471 (1996).
11 H. M. Cheng,F. Li, G. Su, H.-Y. Pan, L. -L. He, X. Sun and M. S. Dresselhaus, Appl,
Phys. Lett., 72, 3282 (1998).
12 K. Mukhopadhyay, A. Koshio, T. Sugai, N. Tanaka, H. Shinohara, Z.Konya and J. B.
Nagy, Chem. Phys. Lett., 303, 117 (1999).
13 A. M. Rao, E. Richter, S. Bandow, B. Chase, P. C. Eklund, K. A. Williams, S. Fang,
K. R. Subbaswamy, M. Menon, A. Thess, R. E. Smalley, G. Dresselhaus, M. S.
Dresselhaus, Science, 275, 187 (1997).
14 M. Yudasaka, R. Yamada, N. Sensui, T. Wilkins, T. Ichihashi and S. Iijima, J. Phys.
Chem. B, 103, 6224 (1999).
15 H. Kataura, Y. Kumazawa, Y. Maniwa, Y. Ohtsuka, R. Sen, S. Suzuki and Y.
Achiba,Carbon, 38, 1691 (2000).
16 P. Nikolaev, M. J. Bronikowski, R. K. Bradley, F. Rohmund, D. T. Colbert, K. A.
Smith and R. E. Smalley, Chem. Phys. Lett., 313, 91 (1999).
-
17 S. Maruyama, R. Kojima, Y. Miyauchi, S. Chiashi and M. Kohno, Chem. Phys. Lett.,
360, 229 (2002).
18 Åse Marit Leere Øiestad, Einar Uggerud, Chem. Phys., 262, 169 (2000).
19 J. Conceicao, R. T. Laaksonen, L.-S. Wang, T. Guo, P. Nordlander and R. E. Smalley,
Phys. Rev. B, 51, 4668 (1995).
20 R. Georgiadis, E. R. Fisher, and P. B. Armentrout, J. Am. Chem. Soc., 111, 4251
(1989).
21 M. P. Irion and A. Selinger ,Ber. Bunsenges. Phys. Chem. 93, 1408 (1989).
22 W. D. Vann , R. C. Bell and A. W. Castleman Jr., J. Phys. Chem. A, 103, 10846
(1999).
23 M. Ichihashi , T. Hanmura , R. T. Yadav and T. Kondow ,J. Phys. Chem. A., 104,
11885 (2000).
24 T. Hanmura , M. Ichihashi and T. Kondow , J. Phys. Chem. A,106, 4525 (2002).
25 S. Maruyama, L. R. Anderson and R. E. Smalley, Rev. Sci. Instrum., 61, 3686
(1990).
26 M. Kohno, S. Inoue, A. Yabe and S. Maruyama, Micro. Thermophys. Eng., 7, 33
(2003).
27 S. Maruyama, M. Kohno and S. Inoue, Therm. Sci. Eng., 7, 69 (1999).
28 S. Maruyama, Y. Yamaguchi, M. Kohno and T. Yoshida, Fullerene Science and
Technology, 7, 621 (1999).
29 A. G. Marshall and F. R. Verdun, "Fourier Transforms in NMR, Optical, and Mass
Spectrometry" Amsterdam, Elsevier, (1990).
-
Window
To ICR Cell
Fast Pulsed Valve
Expansion
Cone
“Waiting” Room
Target Disc
Gears
Gears
Window
Feedthrough
for Up-down
Feedthrough
for Rotation
Vaporization
Laser
FIG. 1. Laser-vaporization cluster beam source.
-
Turbopump
Gate Valve
Cluster Source
6 Tesla Superconducting Magnet
100 cm
DecelerationTube
Front Door
Screen Door
Rear Door
Excite & DetectionCylinder
Electrical Feedthrough
Gas Addition
Ionization Laser
Probe Laser
FIG. 2. FT-ICR apparatus with direct injection cluster beam source.
-
800 1200
12 16 20 24
Mass (amu)
Intensity (arbitrary)
(a)as injected
(b)0.2s
(c)0.5s
(d)1.0s
Number of Cobalt Atoms
C2H5OH (46amu)
C2H2O (42amu)
FIG. 3. Chemical reaction of cobalt clusters with ethanol.
-
Mass (amu)
(a)Co13–14
(b)Co14–15
(c)Co15–16
Co13+
Co14+
Co14+
Co15+
Co15+ Co16+
1842
46
119 25 27
FIG.4. Expansion view of FIG.3(d).
-
820 840 860 880
14 15
Mass (amu)
Intensity (arbitrary)
(a)C2H5OH
(b)C2H5OD
(c)CD3CH2OH
(d)C2D5OD
18
Number of Cobalt Atoms
42
4amu
5amu
6amu
9amu
*
FIG.5 Chemical reaction of Co14+ with ethanol (normal, -d, -d3, -d6).
-
H - C - C -O -H*
H H
H H
H - C - C -O -H*
H H
H H
(a) H* is exchangeable site. (Simple chemisorption)
- C - C -O -
H* H
- C - C -O -
H* H
(b) H* is exchangeable site. (Dehydrogenation chemisorption)
FIG.6 H/D exchangeable site.
-
940 960 980 1000
Mass (amu)
Intensity (arbitrary)
46amu
Co16+
intermediate
FIG.7 First step reaction of Co17+ with ethanol-d3.
-
C1 C2*2
*2
*1
*1
Hydrogen
Carbon
Oxygen
C1 C2*2
*2
*1
*1
Hydrogen
Carbon
Oxygen
FIG.8 Dehydrogenation Reaction.
-
1180 1200 1220 1240
20 21
Mass (amu)
Intensity (arbitrary)
(a) CH3CH2OH
(b) CH3CH2OD
(c) CD3CH2OH
45amu
45amu
48amu
Number of cobalt atoms
FIG.9 Chemical reaction of Co20- with ethanol (normal, -d, -d3).
-
500 600 700 800
9 10 11 12 13 14
Mass (amu)
Intensity (arbitrary)
(a)as injected
(b)with CH 3CH 2OH
(c)with CD 3CH 2OH
Number of Nickel Atoms
(A) Reaction with ethanol and ethanol-d3.
520 540 560 580
Mass (amu)
Intensity (arbitrary) Ni9
+
42amu
700 720 740
Mass (amu)
Intensity (arbitrary)
43amu
Ni12
(B) Expansion view of A-b. (C) Expansion view of A-c.
FIG.10 Chemical reaction of nickel clusters with ethanol.
-
(a) calc. Ni12
(b) 20%H/D exchange
(c) experimental data
FIG.11 The ratio of H/D exchange for Ni12+.
(a) This is ideal distribution calculated from isotope ratio.
(b) Assuming 20% of D atoms are replaced by H atoms.
(c) This is the reaction product of Ni12+ + ethanol-d3.
-
400 600 800 1000
8 10 12 14 16 18
Mass (amu)
Intensity (arbitrary)
(a)as injected
(b)with CD 3CH 2OH
Number of Iron Atoms
FIG.12 Chemical reaction of iron clusters with ethanol-d3.
-
620 640 660
Mass (amu)
Intensity (arbitrary)
(a) exp.
(b) calc.
49amu
Fe11+
FIG.13 Expansion view of Fe11+.
-
5 10 15 20Number of Atoms
Relative Reaction Rate (arb. unit)
CobaltNickel
Iron
FIG.14 Relative rate constant of Fe, Co and Ni clusters with ethanol.