Synthesis of a Gold–Metal Oxide Core–Satellite Nanostructure for In Situ SERS Study of CuO-Catalyzed Photooxidation

Article abstract of DOI:10.1002/ange.202007462

This work reports on an assembling–calcining method for preparing gold–metal oxide core–satellite nanostructures, which enable surface-enhanced Raman spectroscopic detection of chemical reactions on metal oxide nanoparticles. By using the nanostructure, we study the photooxidation of Si?H catalyzed by CuO nanoparticles. As evidenced by the in situ spectroscopic results, oxygen vacancies of CuO are found to be very active sites for oxygen activation, and hydroxide radicals (*OH) adsorbed at the catalytic sites are likely to be the reactive intermediates that trigger the conversion from silanes into the corresponding silanols. According to our finding, oxygen vacancy-rich CuO catalysts are confirmed to be of both high activity and selectivity in photooxidation of various silanes.

Full text of DOI:10.1002/ange.202007462

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Akzeptierter Artikel
Titel: Synthesis of Au-Metal Oxide Core-Satellite Nanostructure for In
Situ SERS Study of CuO-Catalyzed Photooxidation
Autoren: Kaifu Zhang, Ling Yang, Yanfang Hu, Chenghao Fan, Yaran
Zhao, Lu Bai, Yonglong Li, Faxing Shi, Jun Liu, and Wei Xie
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Zitierweise: Angew. Chem. Int. Ed. 10.1002/anie.202007462
Link zur VoR: https://doi.org/10.1002/anie.202007462

10.1002/ange.202007462
Angewandte Chemie
RESEARCH ARTICLE
Synthesis of Au-Metal Oxide Core-Satellite Nanostructure for In
Situ SERS Study of CuO-Catalyzed Photooxidation
Kaifu Zhang, Ling Yang, Yanfang Hu, Chenghao Fan, Yaran Zhao, Lu Bai, Yonglong Li, Faxing Shi,
Jun Liu, and Wei Xie*
[a]
K. F. Zhang, L. Yang, Y. F. Hu, C. H. Fan, Dr. Y. R. Zhao, L. Bai, Y. L. Li, F. X. Shi, J. Liu, Prof. Dr. W. Xie*
Key Lab of Advanced Energy Materials Chemistry (Ministry of Education), Renewable Energy Conversion and Storage Center
College of Chemistry, Nankai University
Weijin Rd. 94, Tianjin 300071, China
E-mail: wei.xie@nankai.edu.cn
Supporting information for this article is given via a link at the end of the document.
Abstract: This work reports on an assembling-calcining method for
preparing Au-metal oxide core-satellite nanostructure, which enable
surface-enhanced Raman spectroscopic detection of chemical
reactions on metal oxide nanoparticles. By using the nanostructure,
we study the photooxidation of Si-H catalyzed by CuO nanoparticles.
As evidenced by the in situ spectroscopic results, oxygen vacancies
of CuO are found to be very active sites for oxygen activation, and
hydroxide radicals (*OH) adsorbed at the catalytic sites are likely to
be the reactive intermediates that trigger the conversion from silanes
to the corresponding silanols. According to our finding, oxygen
vacancy-rich CuO catalysts are confirmed to be of both high activity
and selectivity in photooxidation of various silanes.
the charge carriers. Representative examples include
photocatalytic reduction of CO2 on BiOBr, Fe2O3-catalyzed
photoelectrochemical water splitting and photocatalytic aerobic
couplings of primary amines to imines on WO3.[11] Nevertheless,
rational design of an oxide catalyst for a specific reaction is
generally challenging because of the unknown catalytic sites and
the reactive intermediates that are difficult to be detected
experimentally.
During the last years, surface-enhanced Raman spectroscopy
(SERS) has attracted great attention in the detection of
heterogeneous catalysis.[12] As an ultra-sensitive and surface-
selective vibrational spectroscopic technique, SERS exhibits
remarkable capability of interfacial characterization, including
finding out catalytic sites at nanometer resolution[13] and
identifying intermediate species on catalyst surface.[14]
Bifunctional nanostructures integrating catalysts and plasmonic
substrates are usually required to enable SERS enhancement on
the catalyst surface.[15] A prominent example is the core-satellite
nanostructure with a plasmonic Au or Ag core and many small
metal catalysts assembled on the surface of the core, where the
catalyst nanoparticles borrow the SERS activity from the
plasmonic core. This type of bifunctional nanostructures has been
extensively used in SERS detection of various metal nanoparticle-
catalyzed reactions,[16] but not yet been explored for catalytic
reactions on oxide nanoparticles. The main challenge is the
difficulty in synthesizing small and monodispersed oxide satellites
with strong affinity to the metal core surface.
Introduction
Silanols are the monomer compounds for the synthesis of silicon-
based organic polymers, which are excellent heat-resistant liquid
or rubber-like materials and have been widely used in industry.[1]
In organic chemistry, the Si-OH groups are usually used as
guiding groups for C-H activation,[2] and as electron donors in
metal-catalyzed cross-coupling reactions.[3] Besides, they are
also important bioisosteres in pharmaceutical chemistry.[4]
Despite the long history of silanol synthesis without using
catalysts,[5,6] catalytic oxidation of silanes has attracted great
attention in the past decade because of its high yield/selectivity
and also capability of producing complex silanol molecules.[7]
However, homogeneous catalysts for the silane to silanol
oxidation need further separation/purification steps after
synthesis and result in high energy consumption and loss of
catalyst; heterogeneously catalytic silane oxidation typically
involves expensive noble metals[8] that could be easily detached
from the support material during the reaction and also lead to
catalyst loss. Ideally, a cheap and support-free heterogeneous
catalyst with high activity/selectivity would overcome the above
limitations and considerably promote the development of silanol
synthesis.
In this work, we reported an assembling-calcining method to
synthesize Au-metal oxide core-satellite nanostructures:
assembling monodispersed small metal nanoparticles on a large
Au core and then calcining them into the corresponding oxide
satellites. Via this new approach, we can prepare various
bifunctional substrates for SERS detection of reactions on
different oxide catalysts. Specifically, Au-CuO core-satellite
nanostructures were employed to study the catalytic silane to
silanol oxidation. We chose CuO as the candidate catalyst
because they have recently been found to be catalytically active
for C-H oxidation,[17] which implies the possible activity for other
catalytic oxidation reactions (vide infra). According to the in situ
spectroscopic results, CuO exhibits surprisingly excellent catalytic
performance for selective photooxidation of Si-H to Si-OH and the
catalytic sites are the oxygen vacancies on the CuO surface.
Furthermore, we tested our spectroscopic findings by performing
Metal oxides are promising heterogeneous catalysts because
of their lower cost and higher stability compared with the
corresponding metals.[9] The defect sites on the metal oxide
surfaces, including oxygen and metal vacancies, are typical
catalytic centers for various chemical reactions.[10] In
photocatalysis, the vacancies further serve as trapping sites to
capture hot electrons or holes, which would benefit separation of
1
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10.1002/ange.202007462
Angewandte Chemie
RESEARCH ARTICLE
experiments to synthesis silanol compounds with high yield and
selectivity using commercial CuO powder as the catalyst.
general oxidative catalytic activity (vide supra), especially for the
reactions under light illumination. Therefore, we further tested
CuO-catalyzed photooxidation of silane by using dimethyl(4-
(methylthio)phenyl)silane (4-DMPSE) as the model reactant. After
incubation with the nanostructures, the 4-DMPSE molecules
adsorb on the CuO catalyst but not on the Au core isolated by the
silica shell.[15] As the SERS substrates in our experiments, Au
nanoparticle cores have to be used but the plasmon-induced
surface effects during the SERS measurements may change the
reaction rate or even result in unwanted side reactions. To protect
the catalysts from direct contact with the Au surface, the silica
shell is required for encapsulation of the Au nanoparticles.[18]
Figure 2c shows that the SERS bands of 4-DMPSE at 1283 and
1587 cm-1, which can be assigned to the in-plane bending[19] and
symmetric stretching[15] of phenyl ring, respectively, decline upon
the laser illumination. Within 10 min, the spectrum shows
characteristic profile of dimethyl(4-(methylthio)phenyl)silanol (4-
DMPSO, see Figure S7), indicating the oxidation of Si-H to Si-OH.
In negative control experiments, the Si-H cannot be oxidized on
Au nanoparticles or without light illumination (Figure S8). To
further clarify the role of CuO in this reaction, we performed in situ
SERS monitoring on CuO nanoparticles prepared using the same
batch of Cu nanoparticles but calcined at different temperatures,
i.e. 250 and 300 °C. The photooxidation of the model reactant on
CuO prepared at 250 °C (CuO-250) is faster (Figure 2d & S9).
These results confirm the bifunctional activity of the Au-CuO
nanostructure and more importantly, give rise to the question:
what decides the catalytic activity of CuO in silane oxidation?
Results and Discussion
The bifunctional Au-CuO core-satellite nanostructures with both
SERS and catalytic activity were synthesized via an assembling-
calcining approach. We first coated the large plasmonic Au cores
with an ultrathin silica shell. Then the silica coated Au cores were
incubated with mercaptopropyltrimethoxylsilane (MPTMS) to form
many thiol groups on the silica surface. After that many small Cu
nanoparticles were assembled on the Au core via strong covalent
Cu-S bonds to form Au-Cu core-satellite nanostructures (see
Figure S1-S3). The as prepared nanostructures were oxidized
into Au-CuO nanostructure through a calcination process with a
heating rate of 10 °C/min in air atmosphere (Figure 1a). The
calcination temperature is controlled to produce CuO with
different oxygen vacancy densities, but not higher than 300 °C so
as to maintain the structural morphology (Figure S4). Electron
microscopic images and elemental analysis (Figure 1b-e) indicate
uniform satellite coating and high monodispersity of the products.
This in situ satellite-oxidation method is of extensive applicability
for preparing plasmonic core-metal oxide satellite nanostructure
(Figure 1f, S5 & S6), which provides a promising general SERS
platform to characterize metal oxide-catalyzed chemical reactions.
a
Au@SiO2
Calcination
Cu
O
CuO
O vacancy
NO2
a
b
4-NTP
0.8
0.6
0.4
0.2
0.0
S
CuO-250 + H2O2
Au
e
d
b
4,4' DMAB
CuO-250
Cu
NH2
Au
10
Cu
t
O
Si
4-ATP
Au-Au
1000
Au
Cu
S
0
2
4
6
8
O
2 nm
Energy (keV)
c Au-CuO
0
30 60 90
CuO
HAADF
Au
O
Cu
O
1200
1400
1600
SiO2
Au
Raman shift (cm-1)
Raman shift (cm-1
)
100 nm
c
d0.6
CuO-250
CuO-300
Au
Au Ni
O
Au
Au
Ag O
Ni
Cu
CuPd O
f
0.4
0.2
0.0
Au-Cu2O
Au-NiO
Au-(PdO/CuO)
Au-(Ag/NiO)
0
100 200 300 400 500 600
Time (s)
Figure 1. (a) Scheme of the synthesis of Au-CuO core-satellite nanostructure.
TEM image with elemental line scan profiles (b), HAADF-STEM image and EDS
elemental mappings (c), HRTEM image (d), and SEM image (e) of the Au-CuO
nanostructure. (f) TEM and corresponding elemental mappings of various Au-
metal oxide core-satellite nanostructure. Scale bar: 20 nm.
Figure 2. (a) SERS spectra of 4-ATP oxidation reactions on the Au-CuO core-
satellite nanostructures. (b) Relative contribution of 4-NTP during the 4-ATP
oxidation reaction. (c) SERS spectra of 4-DMPSE oxidation at different reaction
times. (d) Relative contributions of 4-DMPSO on CuO calcined at 250 and
300 °C as a function of reaction time.
To verify the SERS and catalytic activity of the Au-CuO core-
satellite nanostructures, 4-aminothiophenol (4-ATP) was used as
a model reactant for SERS detection CuO-catalyzed oxidation. A
six-electron oxidation from 4-ATP to 4-nitrothiophenol (4-NTP)
was detected by SERS in the presence of H2O2 oxidant (Figure
2a, blue curve). Even without the addition of H2O2, a 2-electron
oxidation of 4-ATP to 4,4’-dimercaptoazobenzene (DMAB) could
be detected (Figure 2a, red curve) because of the photo-
generated hot holes. This supports the hypothesis that CuO is of
Rietveld refinement ex situ XRD data (Figure 3a) shows that
lattice oxygen occupancy of CuO-250 is lower than that of the
CuO-300 (Table S1). The oxygen vacancies, which can regulate
the atomic arrangement and charge density distribution of the
metal oxide, have been recognized as the active sites in various
catalytic reactions.[10] In density functional theory (DFT)
calculation (Figure 3b and S10), with one oxygen vacancy on an
2
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10.1002/ange.202007462
Angewandte Chemie
RESEARCH ARTICLE
optimized CuO (111) surface, the bader charge of the 2
neighboring Cu atoms decrease dramatically from 0.97 and 0.87
|e| to 0.54 and 0.63 |e|, respectively, indicating electron
transference to the Cu atoms (Figure S11). In addition, the two
Cu atoms near the oxygen vacancy exhibit much lower magnetic
moment (-0.02 ~ -0.09 μB) compared with the others (|0.5| ~ |0.6|
μB), showing a valence state of +1 (4s03d10). The calculation is
entirely consistent with the experimental evidence from XRD
(Table S2). We further verified the results by electron
paramagnetic resonance (EPR) spectroscopy and X-ray
photoelectron spectroscopy (XPS). CuO-250 exhibits stronger
EPR signal than CuO-300 at g-factor of 2.003 (Figure 3c), which
is in agreement with the DFT calculation that more unpaired
electrons on Cu due to the oxygen vacancies. This change
influences also the electronic structure of oxygen atoms: the CuO-
250 shows stronger XPS band of oxygen adjacent to the
vacancies at 531.4 eV (Figure 3c & S12). Synchrotron radiation-
based X-ray absorption fine structure (XAFS) spectroscopy was
employed to study the local geometric structure of the CuO
catalysts. Cu coordination numbers were extracted from Fourier
transform extended X-ray absorption fine structure (EXAFS) data
(see Figure S13 and Table S3). Compared with CuO-300, the Cu-
O peak of CuO-250 at about 1.5 Å is weaker (Figure 3d),
indicating that the Cu atoms in CuO-250 possess in average a
smaller coordination number (2.3 versus 2.6). This further
supports the above-mentioned experimental and calculation
results that there are more oxygen vacancies in CuO-250 than in
CuO-300.
corresponding bandgaps of CuO-250 and CuO-300 were
measured to be 1.04 and 1.12 eV, respectively (Figure 4b). And
the measured valence band (VB) potentials (2.04 - 2.11 eV) fulfill
the energy transfer for H2O2 activation into *OH (Figure S14 &
S15), a highly oxidative intermediate.[10j]
b1.6
Total
Cu 3d
O 2p
1.0
0.8
0.6
0.4
0.2
0.0
30
20
10
0
a
CuO-250
CuO-300
Ovac CuO

1.2
CuO-250
CuO-300
1.04 eV
1.12 eV
0.8
0.4
0.0
0
1
2
3
Clean CuO
h (eV)
-10
-0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6
400
800
1200
Wavelength (nm)
1600
2000
E-E (eV)
f
0
c
d
CuO-300
CuO-250
1.8
1.2
0.8
0.4
0.0
-30
-60
-90
Lig
ht on
f
ht of
Lig
-120
-150
-180
CuO-300
CuO-250
0
60
120 180 240 300
Time (s)
-0.4 -0.3 -0.2 -0.1 0.0 0.1 0.2
Potential E (V vs SCE)
Figure 4. (a) DOS density calculation. UV-visible-infrared absorption spectra,
(inset: band gap estimation spectra) (b), Photocurrent (c), and Mott-Schottky
plots (d) of CuO-250 and CuO-300.
Under visible light illumination, the photocurrent of CuO-250 is
much higher than that of CuO-300 (Figure 4c) and thus more
charge carriers can be generated in CuO-250. The decrease of
the CuO-250 photocurrent during the first few cycles is due to the
surface oxidation of the catalysts. At the first excitation, the fresh
catalysts have more oxygen vacancies and result in the strongest
photocurrent. During the measurement, some of the oxygen
vacancies are refilled because of the presence of active oxygen
species under light excitation. After 2-3 cycles, this effect reaches
a maximum and the surface density of oxygen vacancies
becomes constant (Figure 4c, red curve). The carrier density can
be calculated by the following equation:
CuO-300
Calculated
Bragg position
a
b
CuO-250
Calculated
Bragg position
O vacancy
Cu
O
30
40
50
60
70
80
2θ (°)
c
10
8
529.8
531.4
O 1s
10
d
Cu-O
CuO-300
CuO-250
CuO ref
g=2.003
6
9
1.4 1.6 1.8
R (Å)
EPR
351
4
Nd=(2/e0ɛrɛ0)[d(1/C2)/dE]-1
(1)
352
Magnetic field (mT)
CuO-300
2
Ovac
where Nd is the carrier density, e0 is the electron charge, εr is the
permittivity of CuO (εr=25)[10d] and ε0 is the permittivity of vacuum.
The calculated values of CuO-250 and CuO-300 are 8.0×1021 and
CuO-250
0
534 531 528 525 522 519
Binding energy (eV)
0
1
2
3
4
5
6
7
R (Å)
6.4×1021 cm-3 (Figure 4d),
respectively. Meanwhile,
Figure 3. (a) XRD patterns of CuO-250 and CuO-300. (b) Structure optimization
of CuO (111) surface with oxygen vacancy. XPS & EPR spectra (c) and Fourier-
transform EXAFS curves (d) of CuO-250 and CuO-300.
photoluminescence (PL) emission spectra (Figure S16) show
efficient inhibition of charge recombination by the oxygen
vacancies. These results together suggest that the oxygen
vacancies improve the light absorption and charge carrier
generation of the CuO nanoparticles.
The presence of oxygen vacancies results in an obviously
density of states (DOS) enhancement at the conduction band
edge (Figure 4a), which was confirmed by the higher intensity and
red-shifted edge of CuO-250 absorption, compared with CuO-300
(Figure 4b), and indicates more photo-induced charge carriers
that can be transferred to the conduction band minimum (CBM).
These vacancies also bring in several new intermediate energy
levels, which can narrow the band gap to extend the light
absorption region for photocatalytic reactions. Experimentally, the
Activation of H2O2 oxidant molecules on the CuO surface is a
critical step for the photocatalytic oxidation of silanes. In general,
surface oxygen vacancies expose the low coordination number
metal atoms to the reactants and are catalytic sites in many metal
oxide-catalyzed reactions.[10] The coordinationally unsaturated Cu
sites where the electrons are highly delocalized can facilitate the
H2O2 adsorption. Differential charge density calculation was used
3
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10.1002/ange.202007462
Angewandte Chemie
RESEARCH ARTICLE
to understand the electron transfer between CuO and H2O2.
According to the calculation, the coordinationally unsaturated Cu
mention that no other oxygen species was detected in this
reaction. Because both the calculations and experimental results
confirm the catalytic conversion of H2O2 to *OH, which has
recently been reported to be a typical oxidative intermediate in
H2O2 involved reactions,[14c,d] we propose that *OH is the reactive
intermediate that participates the final conversion from Si-H to Si-
OH.
a
clean CuO (111)
H2O2*
Ovac CuO (111)
H2O2*
b
0
-0.83 eV
-0.84 eV
-0.2 eV
2 *OH
1.5
3.0
4.5
-1.03 eV
Based on the above mechanistic understanding, we performed
photocatalytic oxidation of Si-H from the perspective of synthetic
chemistry. In order to prove the general applicability of our finding
and bridge the gap between in situ detection and practical
catalysis, we further chose conventional CuO powder that can be
easily produced in industrial scale, instead of using the highly
monodispersed CuO nanoparticles synthesized in the lab. First,
oxidation of dimethylphenylsilane to dimethylphenylsilanol was
performed to optimize the reaction conditions (see Table S4) of
the catalysis. The reaction in MeCN solvent is faster than that in
other solvents, because of the lower chemical stability of H2O2 in
polar solvent. Our result shows that the reactivity follows the same
trend of the solvent polarity. Therefore, the solvent which
determines the H2O2 to *OH reaction rate on the catalyst surface
plays an important role in this reaction. Table 1 summarizes the
photooxidation of various silanes into the corresponding silanols
under the optimized conditions. Notably, two or three Si-H groups
can be simultaneously transformed to Si-OH without formation of
siloxane, indicating both the high catalytic activity and selectivity.
Compared with the previously reported silane to silanol oxidations,
the photocatalytic synthesis using cheap CuO powder catalyst
shows obvious advantages in both silanol yield and selectivity
(Table S5).
-3.3 eV
2 *OH
-4.14 eV
H2O2*
new peaks
*OD
HO*

c
OH
O-O
CuO-300
CuO-250
CuO-250 in D2O2
CuO-250 in H2O2
new peaks
660 690 720
870 900
)
Raman shift (cm-1
*OH
CuO-250 in H2O
Au@SiO2 in H2O2
CuO in H2O2
H2O2
650 700
650
700
750
800
850
900
800 850 900
Raman shift (cm-1)
Raman shift (cm-1)
Raman shift (cm-1
)
Figure 5. a) The geometric configurations of absorbed H2O2 on CuO (111)
surface. White, red and brown balls stand for H, O and Cu atoms, respectively.
(b) Potential energy diagram of the H2O2 dissociation. (c) In situ SERS detection
of the reactive *OH species.
atoms at the oxygen vacancy sites donate their available d-orbital
electrons into the σ O-O antibonding orbital (σ*) and weaken the
O-O bond strength. The weakened O-O bond length of H2O2
adsorbed at the oxygen vacancy site is 1.48 Å while the H2O2 on
the clean CuO surface exhibits an O-O bond length of 1.47 Å
(Figure S17). After the adsorption (Figure 5a), because of an
exothermic -3.30 eV potential difference (Figure 5b), the H2O2
molecule can easily form two *OH fragments and fills the vacancy
site. As an important proof, the *OH species was detected by in
situ SERS using the Au-CuO nanostructure. In Figure 5c, the
Raman band at 876 cm-1 can be assigned to the O-O stretching
mode of H2O2.[20] In the presence of CuO nanoparticles (satellites
of the nanostructure), a new band appears at 708 cm-1 (green
curve in Figure 5c), of which the intensity is higher on CuO-250
nanoparticles than on the less oxygen vacancy counterpart
(Figure 5c inset). This new band is very likely to be from the
oxidative *OH species. To verify our hypothesis, D2O2 was used
instead of the H2O2 oxidant. Two Raman bands appear at 675 and
832 cm-1 (dark blue curve), corresponding respectively to the 708
and 876 cm-1 bands in H2O2 solution. The redshift is caused by
the heavier D atom that lowers the vibration frequency. We
calculated the band position caused by the isotopic effect
according to the mass variation (Supplementary Note 1) and the
calculated position at 687 cm-1 is close to the corresponding
experimental result at 675 cm-1. A typical radical-trapping reagent
5,5-dimethyl-1-pyrroline N-oxide (DMPO) was employed to
further confirm the generation of *OH (Figure S18) and the EPR
peaks from *OH increase over time. This result is also in
agreement with the increasing fluorescence signal when
terephthalic acid (TA) is used as a probe to generate fluorescent
2-hydroxyterephthalic acid (TAOH) (Figure S19). It’s important to
Table 1. Scope of CuO-catalyzed oxidation of silanes[a]
.
2a, 1.5 h, 99% yield
2d, 1.5 h, 99% yield
2b, 2 h, 99% yield
2c, 6 h, 99% yield
2f, 12.5 h, 98% yield
2e, 3 h, 98.3% yield
2g, 4 h, 98% yield 2h, 3 h, 98.1% yield
2i, 3h, 93% yield
[a] Reaction conditions: 1 (1 mmol), H2O2 (10 mmol), CuO (10 mg), 45 °C
irradiated under Xe lamp (100 mW/cm2), determined by GC using internal
standard technique.
4
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10.1002/ange.202007462
Angewandte Chemie
RESEARCH ARTICLE
We calcined the CuO powder at different temperatures (400,
600 and 800 °C) to alter the oxygen vacancy density of the original
catalyst to a certain level. Both the XPS and EPR results (Figure
S20-22) indicate that the density of oxygen vacancies decreases
after calcination at higher temperatures. These CuO powder
samples were used to catalyze the synthetic silane to silanol
photooxidation. Since the surface area of the catalyst is an
important parameter for determining the catalytic activity, we
characterized the specific surface areas via N2 adsorption-
desorption experiments. The results in Figure S23 show that the
specific surface area decreases after calcination. We took into
account this difference when the catalytic activities of the calcined
CuO powder were compared. It is clearly shown in Figure 6a that
the CuO powder with more oxygen vacancies exhibits higher
catalytic activity for the silane oxidation reaction, which is in
agreement with the SERS results on CuO nanoparticles.
Furthermore, the EPR spectra (Figure S24) of the reaction
mixture show increasing *OH concentration with the illumination
time and again entirely consistent with the SERS results. These
experimental data suggest the important role of oxygen vacancies
and *OH in the synthesis of silanols and more importantly, confirm
that the conclusion from in situ SERS study is applicable to
synthetic chemistry.
both the chemical and physical stability under reaction conditions.
Specifically, unlike the noble metal nanoparticle catalysts, the
robust CuO powder do not need any support material; and thus
no catalyst detachment or loss that results in activity decrease
occurs in the CuO powder-catalyzed reactions.
Conclusion
In conclusion, a general method was developed for preparing Au-
metal oxide core-satellite nanostructure as a SERS platform to
study metal oxide-catalyzed reactions. Specifically, silane to
silanol photooxidation on CuO nanoparticles was investigated.
According to sufficient spectroscopic results and computational
simulations, the oxygen vacancies on the CuO surface provide
abundant coordinationally unsaturated Cu atoms for the collection
of photogenerated electrons and are suggested to be the catalytic
sites of H2O2 adsorption and activation. In situ SERS spectra
show direct evidence of surface-adsorbed *OH, which is likely to
be the oxidative intermediate species and responsible for the
oxidation of Si-H. By using industrial level CuO as catalysts,
visible light-driven oxidation of various silane molecules to the
corresponding silanols has been achieved with high yield and
selectivity. The new photocatalytic approach is therefore of
practical applicability for silanol synthesis. This work shows a
promising way toward rational design of high-performance metal
oxide nanocatalysts.
100
a
CuO
CuO-400
80
CuO-600
CuO-800
60
Acknowledgements
40
20
0
This work was supported by the National Natural Science
Foundation of China (21861132016
&
21775074), the
Fundamental Research Funds for the Central Universities-Nankai
University (000082), the 111 project (B12015), and the National
Key R&D Program (2017YFA0206702 & 2016YFB0901502).
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Keywords: surface-enhanced Raman spectroscopy• metal
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oxide • reaction intermediate • catalysis • photooxidation
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[1]
a) V. Chandrasekhar, R. Boomishankar, S. Nagendran, Chem. Rev
2004, 104, 5847-5910. b) M. Jeon, J. Han, J. Park, ACS Catal. 2012, 2,
1539-1549. c) G. Z. Li, L. C. Wang, H. L. Ni, C. U. Pittman, J. Inorg.
Organomet. Polym. 2001, 11, 123-154. d) J. F. Brown, L. H. Vogt, J. Am.
Chem. Soc. 1965, 87, 4313-4317. e) E. G. Rochow, W. F. Gilliam, J. Am.
Chem. Soc. 1941, 63, 798-800.
60
40
20
0
[2]
a) C. Huang, N. Ghavtadze, B. Chattopadhyay, V. Gevorgyan, J. Am.
Chem. Soc. 2011, 133, 17630-17633 (b) M. Mewald, J. A. Schiffner, M.
Oestreich, Angew. Chem. Int. Ed. 2012, 124, 1797-1799.
[3]
[4]
[5]
a) H. Zhou, C. Moberg, J. Am. Chem. Soc. 2012, 134, 15992-15999. S.
E. Denmark, C. S. Regens, Acc. Chem. Res. 2008, 41, 1486-1499.
a) A. K. Franz, S. O. Wilson, J. Med. Chem. 2013, 56, 388-405. R.
Ramesh, D. S. Reddy, J. Med. Chem. 2018, 61, 3779-3798.
1
2
3
4
5
Regeneration
a) R. O. Sauer, J. Am. Chem. Soc. 1944, 66, 1707-1710. b) J. A. Cella,
J. C. Carpenter, J. Organomet. Chem. 1994, 480, 23-26. c) E. G. Rochow,
W. F. Gilliam, J. Am. Chem. Soc. 1941, 63, 798-800.
Figure 6. (a) Catalytic oxidation of dimethylphenylsilane using CuO, CuO-400,
CuO-600, and CuO-800 catalysts, respectively. (b) Catalytic durability of CuO.
[6]
a) P. D. Lickiss, R. Lucas, J. Organomet. Chem. 1995, 521, 229-234. b)
K. Valliant-Saunders, E. Gunn, G. R. Shelton, D. A. Hrovat, W. T. Borden,
J. M. Mayer, Inorg. Chem. 2007, 46, 5212-5219. c) L. H. Sommer, L. A.
Ulland, G. A. Parker, J. Am. Chem. Soc. 1972, 94, 3469-3471. d) L.
Spialter, L. Pazdernik, S. Bernstein, W. A. Swansiger, G. R. Buell, M. E.
Freeburger, J. Am. Chem. Soc. 1971, 93, 5682-5686.
The durability of heterogeneous catalyst is critical for the
potential use in chemical industry. Figure 6b shows the stability of
the CuO powder after several reaction cycles (see also Figure
S25). The excellent durability of the CuO catalyst is attribute to
5
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[7]
a) K. K. Wang, J. M. Zhou, Y. T. Jiang, M. M. Zhang, C. Wang, D. Xue,
W. J. Tang, H. M. Sun, J. L. Xiao, C. Q. Li, Angew. Chem. Int. Ed. 2019,
58, 6380-6384. b) E. A. Ison, R. A. Corbin, M. M. Abu-Omar J. Am. Chem.
Soc. 2005, 127, 11938-11939. c) D. Limnios, C. G. Kokotos, ACS Catal.
2013, 3, 2239-2243. d) I. D. Rettig, J. Van, J. B. Brauer, W. T. Luo, T. M.
McCormick, Dalton Trans. 2019, 48, 5665-5673.
37, 885-897. d) S. Cong, Y. Y. Yuan, Z. G. Chen, J. Y. Hou, M. Yang, Y.
L. Su, Y. Y. Zhang, L. Li, Q. W. Li, F. X. Geng, Z. G. Zhao, Nat. Commun.
2015, 6, 7800. e) Z. Y. Zhang, V. Merk, A. Hermanns, W. E. S. Unger, J.
Kneipp, ACS Catal. 2017, 7, 7803-7809.
[14] a) N. Bodappa, M. Su, Y. Zhao, J. B. Le, W. M. Yang, P. Radjenovic, J.
C. Dong, J. Cheng, Z. Q. Tian, J. F. Li, J. Am. Chem. Soc. 2019, 141,
12192-12196. b) J. L. Wang, R. A. Ando, P. H. C. Camargo, Angew.
Chem. Int. Ed. 2015, 54, 6909-6912. c) H. S. Su, H. S. Feng, Q. Q. Zhao,
X. G. Zhang, J. J. Sun, Y. H. He, S. C. Huang, T. X. Huang, J. H. Zhong,
D. Y. Wu, B. Ren, J. Am. Chem. Soc. 2020, 142, 1341-1347. d) J. C.
Dong, X. G. Zhang, V. Briega-Martos, X. Jin, J. Yang, S. Chen, Z. L.
Yang, D. Y. Wu, J. M. Feliu, C. T. Williams, Z. Q. Tian, J. F. Li, Nat.
Energy 2019, 4, 60-67.
[8]
a) Z. Chen, Q. Zhang, W. X. Chen, J. C. Dong, H. R. Yao, X. B. Zhang,
X. J. Tong, D. S. Wang, Q. Peng, C. Chen, W. He, Y. D. Li, Adv. Mater.
2018, 30, 1704720-1704728. b) J. John, E. Gravel, A. Hagge, H. Y. Li, T.
Gacoin, E. Doris, Angew. Chem. Int. Ed. 2011, 123, 7675-7678. c) A. L.
Torre, M. C. Gime´nez-Lo´pez, M. W. Fay, G. A. Rance, W. A.
Solomonsz, T. W. Chamberlain, P. D. Brown, A. N. Khlobystov, ACS
Nano 2012, 6, 2000-2007. d) C. Q. Wang, X. Li, L. Jin, P. H. Lu, C. Dejoie,
W. X. Zhu, Z. N. Wang, W. Bi, R. E. Dunin-Borkowski, K. Chen, M. S. Jin,
Nano Lett. 2019, 19, 6363-6369. e) T. Mitsudome, S. Arita, H. Mori, T.
Mizugaki, K. Jitsukawa, K. Kaneda, Angew. Chem. Int. Ed. 2008, 120,
8056-8058. f) K. Kamata, K. Yonehara, Y. Sumida, K. Hirata, S. Nojima,
N. Mizuno, Angew. Chem. Int. Ed. 2011, 50, 12062-12066. g) J. D. Lin,
Q. Y. Bi, L. Tao, T. Jiang, Y. M. Liu, H. Y. He, Y. Cao, Y. D. Wang, ACS
Catal. 2017, 7, 1720-1727. h) E. J. Rayment, A. Mekareeya, N.
Summerhill, E. A. Anderson, J. Am. Chem. Soc. 2017, 139, 6138-6145.
a) B. M. Hunter, H. B. Gray, A. M. Mꢀller, Chem. Rev. 2016, 116, 14120-
14136. b) J. T. Grant, J. M. Venegas, W. P. McDermott, Ive Hermans,
Chem. Rev. 2018, 118, 2769-2815. c) O. Jung, M. L. Pegis, Z. X. Wang,
G. Banerjee, C. T. Nemes, W. L. Hoffeditz, J. T. Hupp, C. A.
Schmuttenmaer, G. W. Brudvig, J. M. Mayer, J. Am. Chem. Soc. 2018,
140, 4079-4084. d) A. Mclaren, T. Valdes-Solis, G. Q. Li, S. C. Tsang, J.
Am. Chem. Soc. 2009, 131, 12540-12541. X. L. Mou, B. S. Zhang, Y. Li,
L. D. Yao, X. J. Wei, D. S. Su, W. J. Shen, Angew. Chem. Int. Ed. 2012,
51, 2989-2993.
[15] a) W. Xie, B. Walkenfort, S. Schlücker, J. Am. Chem. Soc. 2013, 135,
1657-1660. b) W. Xie, S. Schlücker, Nat. Commun. 2015, 6, 7570-7575.
[16] a) C. S. Wondergem, T. Hartman, B. M. Weckhuysen, ACS Catal. 2019,
9, 10794-10802. b) Y. R. Zhao, L. L. Du, H. X. Li, W. Xie, J. Chen, J.
Phys. Chem. Lett. 2019, 10, 1286-1291. c) Y. L. Li, Y. F. Hu, F. X. Shi,
H. X. Li, W. Xie, J. Chen, Angew. Chem. Int. Ed. 2019, 58, 9049-9053.
d) H. Zhang, X. G. Zhang, J. Wei, C. Wang, S. Chen, H. L. Sun, Y. H.
Wang, B. H. Chen, Z. L. Yang, D. Y. Wu, J. F. Li, Z. Q. Tian, J. Am. Chem.
Soc. 2017, 139, 10339-10346.
[9]
[17] a) X. K. Guo, M. X. Xu, M. Y. She, Y. Zhu, T. T. Shi, Z. X. Chen, L. M.
Peng, X. F. Guo, M. Lin, W. P. Ding, Angew. Chem. Int. Ed. 2020, 59,
2606-2611. b) M. T. Greiner, T. E. Jones, A. Klyushin, A. Knop-Gericke,
R. Schlꢁgl, J. Am. Chem. Soc. 2017, 139, 11825-11832. c) J. B. Reitz,
E. I. Solomon, J. Am. Chem. Soc. 1998, 120, 11467-11478. d) P. N.
Amaniampong, Q. T. Trinh, K. D. O. Vigier, D. Q. Dao, N. H. Tran, Y. Q.
Wang, M. P. Sherburne, F. Jerome, J. Am. Chem. Soc. 2019, 141,
14772-14779. e) P. N. Amaniampong, Q. T. Trinh, B. Wang, A. Borgna,
Y. H. Yang, S. H. Mushrif, Angew. Chem. Int. Ed. 2015, 54, 8928-8933.
f) Y. M. Huang, Z. Liu, G. P. Gao, G. Xiao, A. J. Du, S. Bottle, S. Sarina,
H. Y. Zhu, ACS Catal. 2017, 7, 4975-4985.
[10] a) J. B. Zhang, R. G. Yin, Q. Shao, T. Zhu, X. Q. Huang, Angew. Chem.
Int. Ed. 2019, 58, 1-6. b) H. Li, J. Shang, Z. H. Ai, L. Z. Zhang, J. Am.
Chem. Soc. 2015, 137, 6393-6399. c) C. J. Zhang, A. Michaelides, D. A.
King, S. J. Jenkins, J. Phys. Chem. C 2009, 113, 6411-6417. d) Z. L.
Wang, L. Zhang, T. U. Schlli, Y. Bai, S. A. Monny, A. J. Du, L. Z. Wang,
Angew. Chem. Int. Ed. 2019, 58, 1-7. e) H. Wang, D. Y. Yong, S. C. Chen,
S. L. Jiang, X. D. Zhang, W. Shao, Q. Zhang, W. S. Yan, B. C. Pan, Y.
Xie, J. Am. Chem. Soc. 2018, 140, 1760-1766. f) J. Li, X. Wu, W. F. Pan,
G. K. Zhang, H. Chen, Angew. Chem. Int. Ed. 2018, 57, 491-495. g) C.
X. Guo, Y. Zheng, J. R. Ran, F. X. Xie, M. Jaroniec, S. Z. Qiao, Angew.
Chem. Int. Ed. 2017, 56, 8539-8543. h) Y. Guo, S. W. Chen, Y. G. Yu, H.
R. Tian, Y. L. Zhao, J. C. Ren, C. Huang, H. D. Bian, M. Y. Huang, L. An,
Y. Y. Li, R. Q. Zhang, J. Am. Chem. Soc. 2019, 141, 8407-8411. i) J. Di,
C. Chen, C. Zhu, P. Song, J. Xiong, M. X. Ji, J. D. Zhou, Q. D. Fu, M. Z.
Xu, W. Hao, J. X. Xia, S. Z. Li, H. M. Li, Z. Liu, ACS Appl. Mater.
Interfaces 2019, 11, 30786-30792. j) Y. S. Mao, P. F. Wang, L. N. Li, Z.
W. Chen, H. T. Wang, Y. Li, S. H. Zhan, Angew. Chem. Int. Ed. 2020, 59,
3685-3690.
[18] J. F. Li, Y. F. Huang, Y. Ding, Z. L. Yang, S. B. Li, X. S. Zhou, F. R. Fan,
W. Zhang, Z. Y. Zhou, D. Y. Wu, B. Ren, Z. L. Wang, Z. Q. Tian, Nature
2010, 464, 392-395.
[19] P. Bock, N. Gierlinger, J Raman Spectrosc. 2019, 50, 778-792.
[20] P. A. Giguere, T. K. K. Srinvasan, J Raman Spectrosc. 1974, 2, 125-132.
[11] a) J. Wu, X. D. Li, W. Shi, P. G. Ling, Y. F. Sun, X. C. Jiao, S. Gao, L.
Liang, J. Q. Xu, W. S. Yan, C. M. Wang, Y. Xie, Angew. Chem. Int. Ed.
2018, 57, 8719-8723. b) Z. L. Wang, X. Mao, P. Chen, M. Xiao, S. A.
Monny, S. C. Wang, M. Konarova, A. J. Du, L. Z. Wang, Angew. Chem.
Int. Ed. 2019, 58, 1030-1034. c) N. Zhang, X. Y. Li, H. C. Ye, S. M. Chen,
H. X. Ju, D. B. Liu, Yu. Lin, W. Ye, C. M. Wang, Q. Xu, J. F. Zhu, L. Song,
J. Jiang, Y. J. Xiong, J. Am. Chem. Soc. 2016, 138, 8928-8935.
[12] a) V. Joseph, C. Engelbrekt, J. D. Zhang, U. Gernert, J. Ulstrup, J. Kneipp,
Angew. Chem. Int. Ed. 2012, 51, 7592-7596. b) W. Xie, C. Herrmann, K.
Kompe, M. Haase, S. Schlücker, J. Am. Chem. Soc. 2011, 133, 19302-
19305. c) S. Park, P. Yang, P. Corredor, M. J. Weaver, J. Am. Chem.
Soc. 2002, 124, 2428-2429. d) A. G. M. da Silva, T. S. Rodrigues, V. G.
Correia, T. V. Alves,R. S. Alves, R. A. Ando, F. R. Ornellas, J. Wang, L.
H. Andrade, P. H. C. Camargo, Angew. Chem. Int. Ed. 2016, 55, 7111-
7115. e) E. M. V. S. Lantman, T. Deckert-Gaudig, A. J. G. Mank, V.
Deckert, B. M. Weckhuysen, Nat. Nanotechnol. 2012, 7, 583-586.
[13] a) J. H. Zhong, X. Jin, L. Y. Meng, X. Wang, H. S. Su, Z. L. Yang, C. T.
Williams, B. Ren, Nat. Nanotechnol. 2017, 12, 132-136. b) H. Zhang, C.
Wang, H. L. Sun, G. Fu, S. Chen, Y. J. Zhang, B. H. Chen, J. R. Anema,
Z. L. Yang, J. F. Li, Z. Q. Tian, Nat. Commun. 2017, 8, 15447. c) M. J.
Banholzer, J. E. Millstone, L. Qin, C. A. Mirkin, Chem. Soc. Rev. 2008,
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Entry for the Table of Contents
?
CuO
SiO2
Au
A general method for synthesizing plasmonic metal-metal oxide core-satellite nanostructure is reported. On these nanostructure
small metal oxide NP-catalyzed chemical reactions can be detected by surface-enhanced Raman spectroscopy. As a proof-of-
concept study, oxygen vacancy sites on CuO Nanoparticles are found to be very active in photooxidation reactions.
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