A facile preparation of graphene-based MxSy visible light driven photocatalyst and study of photochemically generating of oxygen species

Article abstract of DOI:10.1080/15533174.2013.865234

The as-synthesized graphene-M_xS_y (Sb₂S₃, MnS₂, SnS) composites via a facile hydrothermal method efficiently catalyzed the photodegradation of methylene orange (MO) with high concentration in aqueous solutions under visible light irradiation. The generation of reactive oxygen species were detected through the oxidation reaction from 1,5-diphenyl carbazide (DPCI) to 1,5-diphenyl carbazone (DPCO). Based on the high photocatalytic activity, the graphene-SnS composite can be expected to be a practical visible light photocatalyst.

Full text of DOI:10.1080/15533174.2013.865234

Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry (2015) 45, 1693–1700
Copyright © Taylor & Francis Group, LLC
ISSN: 1553-3174 print / 1553-3182 online
DOI: 10.1080/15533174.2013.865234
A Facile Preparation of Graphene-Based MxSy Visible Light
Driven Photocatalyst and Study of Photochemically
Generating of Oxygen Species
LEI ZHU, SOURAV SARKAR, SHU YE, KEFAYAT ULLAH, ZE-DA MENG, and WON-CHUN OH
Department of Advanced Materials Science and Engineering, Hanseo University, Chungnam, Korea
Received 20 October 2013; accepted 3 November 2013
The as-synthesized graphene–MxSy (Sb2S3, MnS2, SnS) composites via a facile hydrothermal method efficiently catalyzed the
photodegradation of methylene orange (MO) with high concentration in aqueous solutions under visible light irradiation. The
generation of reactive oxygen species were detected through the oxidation reaction from 1,5-diphenyl carbazide (DPCI) to 1,5-
diphenyl carbazone (DPCO). Based on the high photocatalytic activity, the graphene-SnS composite can be expected to be a
practical visible light photocatalyst.
Keywords: metal sulfide, hydrothermal synthesis, composite, visible light
Introduction
enhanced properties such as high catalytic activity and excel-
lent electrochemical properties. Recently, semiconductor
Graphene, since its first discovery in 2004, is a single layer of nanoparticles such as TiO2, Ag2S, and CdS quantum do have
carbon atoms arranged in a 2D honeycombed lattice and has also been utilized to decorate graphene nanosheets to prepare
unusual electronic properties that arise from the hybridiza- graphene-based nanomaterials with remarkable optical and
tion of unbound fourth electrons in orbitals extending verti- photovoltaic properties.[4–6]
cally above and below the plane spreading across the whole
Metal sulfides, as important semiconductors, have been
of the graphene sheet.[1] This inexpensive material possesses used in many new application areas, such as quantum size
good thermal and electrical conductivity, good mechanical effect, nonlinear optical properties, laser communication,
strength, and more surface area than expensive carbon nano- and light-emitting diodes.[7] Antimony sulfide (Sb2S3) is a
tubes (CNTs). Graphene sheets have a unique ability to pro- layer-structured direct bandgap semiconductor with ortho-
mote fast electron transfer kinetics for a wide range of electro rhombic crystal structure. Sb2S3 is considered as a promising
active species. In addition, functionalized graphene has made material Yong et al.[8] has been reported it has high photoca-
the realization of composite electrodes possible.
talytic degradation rate for methylene blue under sunlight,
It has been also demonstrated that graphene, with zero and the photocatalytic degradation rate of methylene blue is
band gap and high carrier mobilities and concentrations, up to 84.31% after 20 min degradation, exhibiting obvious
shows nearly ballistic transport at room temperature.[2] Exfo- visible-light activity. Manganese disulphide (MnS2) also
liated graphene sheets are predicted to have a large surface belongs to VII–VI compound semiconductor materials.
area close to 2600 m2g¡1 [3]
making graphene nanosheets a MnS2 has a golden-yellow color. The optical band gap is
,
highly desirable and ideal candidate for use in two-dimen- around 3.1 eV.[9] As well-known SnS is a kind of narrow
sional (2D) catalyst support. The properties of graphene can band gap semiconductor, and has been employed in solar
be extended by integrating it with other nanomaterials to cells, detectors, and medical diagnostics because of the near-
form unique hybrid materials. One approach is to decorate infrared absorption.[10] Both experiments and theory calcula-
the surface of graphene sheets with nanocrystals. The fabrica- tion suggest that SnS is a suitable material for solar energy
tion of graphene materials decorated by metal nanoparticles conversion.
is expected to lead to graphene nanocrystal hybrids with
1,5-diphenyl carbazide (DPCI) can be oxidized by oxidiz-
ing substances into 1,5-diphenyl carbazone (DPCO), which
can be extracted by organic solvents and display an obvious
absorbance in a certain range of wavelength.[11]
In this paper, we reported the synthesis graphene nano-
sheets coated with metal sulfides (MxSy D Sb2S3, MnS2, SnS)
nanoparticles obtained directly via a facile solvothermal
method. The intrinsic characteristics of resulting composite
Address correspondence to Won-Chun Oh, Department of
Advanced Materials Science and Engineering, Hanseo Univer-
sity, Chungnam 356-706, Korea. E-mail: wc_oh@hanseo.ac.kr
Color versions of one or more of the figures in the article can be
found online at www.tandfonline.com/lsrt.

1694
Zhu et al.
were studied by X-ray diffraction (XRD) and scanning elec- several times, and dried at 80ꢀC for 12 h. The preparation
tron microscopy (SEM) with energy dispersive X-ray (EDX) procedure is shown in Figure 1a.
analysis. The photocatalytic activity of the as-synthesized
composite was evaluated by degradation of different organic
dyes methylene orange (MO) and 1,5-diphenyl carbazide
(DPCI) in aqueous solution under visible light irradiation.
Characterization
The reasons for improving the photocatalytic activity of gra-
phene-MxSy composites were also discussed.
Crystallographic structure of the composites photocata-
lysts were obtained by XRD (Shimatz XD-D1, Japan) at
room temperature with Cu Ka radiation (λ
D
0.154056 nm) and a graphite monochrometer, operated at
40 KV and 30 mA. UV-vis absorbance spectra were mea-
sured between 300 and 800 nm using a UV-vis spectro-
photometer (Neosys-2000). The morphologies of the
photocatalysts were analyzed by SEM (JSM-5200 JOEL,
Japan) at 3.0 keV, which was equipped with an energy-
dispersive analysis system of X-ray analysis (EDX).
Transmission electron microscopy (TEM, JEOL, JEM-
2010, Japan) with an accelerating voltage of 200 kV was
used to examine the size and distribution of the photoca-
talysts. The BET surface areas of the photocatalysts were
determined through nitrogen adsorption at 77 K using a
BET analyzer (Monosorb, USA). All the samples were
degassed at 623 K before the measurement. The UV-vis
spectra for MO solution degraded by as-prepared compo-
sites photocatalysts under visible light irradiation were
recorded using a UV-Vis (Optizen Pop Mecasys Co., Ltd.,
Korea) spectrometer.
Experimental
Materials
Sulfuric acid (H2SO4), potassium permanganate (KMnO4),
hydrogen peroxide (H2O2) and antimony trichloride
(SbCl3), manganese(II) chloride anhydrous (MnCl2), tin
(&) chloride dihydrate (SnCl2¢2H2O), and sodium thiosul-
fate anhydrous (Na2S2O3) were supplied by Daejung
Chemical Co., Ltd, Korea. MO (C14H14N3NaO3S,
99.99C%) was used as model pollutant which purchased
from Duksan Pure Chemical Co., Ltd, Korea. Table 1
shows the structure and properties of MO. Ammonium
hydroxide (NH3H2O) were purchased from Duksan Pure
Chemical Co. (Korea) and used as received. All chemicals
used without further purification and all experiments were
carried out using distilled water.
Synthesis of Graphene-MxSy Nanocomposites
Photocatalytic Studies
Graphite oxide (GO) was prepared from graphite accord-
ing to the Hummers-Offeman method in our early
reports.[12,13] In a typical experiment, about 20 mg GO
was dispersed in 150 mL distilled water and then exfoli-
ated to generate GONS dispersion solution by ultrasonica-
tion for 1 h. Subsequently, 0.003 mol of SbCl3, MnCl2,
SnCl2¢2H2O powder were added to the GONS aqueous
dispersion followed by ultrasonication for 20min, respec-
tively. Afterwards, sodium thiosulfate anhydrous
(Na2S2O3) and 10 mL ammonium hydroxide (NH3H2O)
were added to the mixture under various stirring for
30 min. The ammonia promised it to obtain maximal
charge so as to prevent the aggregation of graphene oxide
caused by salt effect,[14] which was in favor of the uniform
distribution of MxSy nanoparticle on GNS. After that, an
excess amount of hydrazine hydrate (85%, 50 mL) was
slowly added into the solution with vigorous stirring at
70ꢀC for another 4 h. The solution was transferred into a
Teflon-lined stainless steel autoclave that was sealed. The
contents were then warmed to 160ꢀC for 8 h. The final
product was rinsed with distilled water and ethanol for
In an ordinary photocatalytic test performed at room temper-
ature, graphene-MxSy nanocomposites were added into
organic dye MO solution (2.00 £ 10¡5 mol/L, 100 mL) and
maintained in dark. Before turning on the visible lamp, the
solution mixed with composite was magnetic agitated for
30 min in the dark, allowing the adsorption/desorption equi-
librium to be reached. Then, the solution was irradiated with
visible lamp (18 W, wavelength D 460 nm). Samples were
then withdrawn regularly from the reactor by an order of 30,
60, 90, and 120 min and immediately centrifuged to separate
any suspended solid before analysis. The concentration of
organic dye solution during the visible light photocatalytic
degradation reaction was monitored through measuring the
absorbance of the solution samples with UV-vis spectropho-
tometer (Optizen Pop Mecasys Co., Ltd., Korea) at λmax
465 nm of MO by using a calibration curve since no reaction
by products absorb at these wavelength.
D
Table 2 Visible light photocatalytic degradation rate (kapp) con-
stants and BET surface areas of graphene-Sb2S3, graphene-
MnS2 and graphene-SnS
Table 1 The molecular structure and absorbance maximum
(λmax) of organic dye
Sample
BET (m2/g)
kapp (min¡1
)
Graphene-Sb2S3
Graphene-MnS2
465 nm Graphene-SnS
37.63
49.56
25.94
3.3£10¡3
6.2£10¡3
8.6£10¡3
Organic dye
Molecular structure
λmax
Methylene orange (MO)

Graphene-Based MxSy Visible Light Driven Photocatalyst
1695
Fig. 1. (a) Schematic illustration of deposition of MxSy on the graphene and (b) XRD pattern of GO, graphene, graphene-Sb2S3, gra-
phene-MnS2, and graphene-SnS.
Evaluation of Reactive Oxygen Species
MnS2, SnS) photocatalysts was 2.00 £ 10¡3 mol/L and
1.00 g/L, respectively. Among them, the reactors were put
into a visible light apparatus away from light directly
under visible light irradiation. After 120 min irradiation,
from each sample 10.00 mL solution was taken exactly
and extracted with benzene. And then, all extracted solu-
Firstly, six 10.00 mL DPCI stock solutions (1.00 £ 10¡2
mol/L) were added into three 80 mL volumetric flasks,
respectively. And then 50 mg of three different photocata-
lysts were added to above DPCI solutions, respectively. All
of the three solutions were diluted to 50 mL with double-
distilled water. For all three solutions, the final DPCI con- tions were diluted to 10.00 mL with benzene solution and
centration and the amount of graphene-MxSy (Sb2S3,
their UV-vis spectra were determined.

1696
Zhu et al.
Fig. 2. EDX elemental microanalysis: (a) graphene-Sb2S3, (b) graphene-MnS2, (c) graphene-SnS.
ꢀ
Results and Discussion
cubic lattice with the cell constant aD4.3284 A, that is consis-
tent with the reported data for SnS.[18] However, no signal
for any other phases about GO (001) or graphene (002) can
be detected in graphene-MxSy composite. According to the
published paper,[19] GO can be reduced to graphene during
the solvothermal reaction and the synthesized graphene
sheets can restack to form poorly ordered graphite along the
stacking direction. Earlier studies have shown that if the regu-
lar stack of GO or graphite is broken, for example, by exfoli-
ation, their diffraction peaks may also become weak or even
disappear.[20]
Material Characterization
XRD peak patterns of GO, graphene and graphene-MxSy
composites are shown in Figure 1b. From Figure 1b, it can
be seen that the diffractogram of graphene exhibits the typi-
cal peaks at 25.9ꢀ and 42.7ꢀ, corresponding to the (002) and
(100) reflections of graphite (Joint Committee for Powder
Diffraction Studies (JCPDS) No. 01-0646),[15] respectively.
For graphene-MxSy composites, the XRD diffraction peaks
in the pattern can be indexed to an orthorhombic phase of
Sb2S3, which are good matched with the values reported in
the literature.[16] And the graphene-MnS2 with the peaks
around at around 2u of 33.0ꢀ and 55.2ꢀ, which are well
matched with the Joint Committee Powder Diffraction
Standards (JCPDS) data for MnS2.[17] In graphene-SnS com-
To better identify the elemental composition of the syn-
thesized material, EDX measurements were carried out by
the EDX spectrometer attached to SEM. Typical EDX
spectroscopy for sample graphene-MxSy (Sb2S3, MnS2,
SnS) is shown in Figure 2, confirms the existence of C, Sb,
Mn, Sn, and S elements. It is obvious that the C signal is
posite all the diffraction peaks could be indexed to a simple attributed to the supporting RGO, while Sb and S are

Graphene-Based MxSy Visible Light Driven Photocatalyst
1697
from Sb2S3, Mn, and S are from MnS2, Sn and S are from
SnS particles. The result determines the composition of
MxSy nanoparticles has attached on RGO.
The morphology of GO and graphene-MxSy nanocompo-
sites was investigated by SEM. In Figure 3, it can be clearly
seen that the pure graphene oxide sheets naturally aggregate
and stack to multilayers with numerous edges. The morphol-
ogy of graphene-MxSy composites has a substantial difference
from that of the GO sheets. Meanwhile, the spherical Sb2S3,
MnS2, and SnS nanoparticles were distributed tightly and
evenly on graphene sheets, which formed a graphene-based
nanostructure composite. More detailed information of the
surface state and particle size can be confirmed by the TEM.
In Figure 4, it could be seen that Sb2S3, MnS2, SnS nanopar-
ticles were uniformly distributed on a single layered graphene
sheets. The size of metal sulfide spheres was calculated to be
around 5–10 nm.
Adsorption and Photodecolorization Process
Since the photo-oxidation reaction usually takes place at the
catalyst surface, the adsorption characteristics of the system
are expected to be quite important on the photocatalytic
process. The ability of the MO to be adsorbed on the nano-
composite surface was tested using suspensions of MO and
graphene-MxSy (DSb2S3, MnS2, SnS) composite in dark con-
ditions.
The
degradation efficiency of MO (2.00 £ 10¡5 mol/L, 100mL)
was investigated under visible light irradiation with a cata-
lyst amount of 0.03 g. As shown in Figure 5a, the adsorp-
tion effect of graphene-MnS2 was better than that of any
other samples due to the relatively higher surface area. The
adsorptive effect of graphene-SnS was the lowest one. Gra-
phene-MnS2 has the largest BET surface area, which can
enhance the adsorptive effect. In the degradation step, the
graphene-Sb2S3, graphene-MnS2, and graphene-SnS compos-
ite showed a good degradation effect. From which we can
obviously see that the graphene-SnS composites have a
more excellent photocatalytic activity toward the photode-
gradation of MB, which is due to the following reasons: (a)
graphene nanosheets with wondrously high charge mobility
acting as good electron acceptors[21] are expected to improve
the interfacial electron transfer and restrain the electron/
hole (e¡/hC) pair recombination of SnS; (b) graphene nano-
sheets with very high surface area to volume ratios and
extremely high specific surface area[20] can enhance the dis-
persion of SnS nanoparticles and allow for greater photon
absorption on the photocatalytic surface.
A representative nitrogen adsorption isotherm of graphene-
MxSy (DSb2S3, MnS2, SnS) composite is presented in Figure 5b.
The formation of type IV adsorption isotherms confirmed the
major presence of mesopores on the surfaces of the samples.
Characteristic features of the Type IV isotherm are its hysteresis
loop, which is associated with capillary condensation taking
place in mesopores, and the limiting uptake over a range of
high p/pꢀ. The initial part of the Type IV isotherm is attributed
Fig. 3. SEM micrographs of as-prepared samples: (a) graphene-
Sb2S3, (b) graphene-MnS2, (c) graphene-SnS.

1698
Zhu et al.
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
(a)
Graphene-MnS
Graphene-Sb2S3
Graphene-SnS
a
2
-20
0
20
40
60
80
100
120
140
160
Visible light irradiation time(min)
120
100
80
60
40
20
0
(b)
Graphene-MnS2
Graphene-Sb2S3
Graphene-SnS
e
V
0.0
0.2
0.4
0.6
0.8
1.0
P/P0
Fig. 5. (a) Effect of the MO decolorization process in presence of
graphene-Sb2S3, graphene-MnS2 and graphene-SnS photocata-
lysts; (b) nitrogen adsorption isotherm of graphene-Sb2S3, gra-
phene-MnS2 and graphene-SnS photocatalysts.
adsorbent in a non-porous form. This indicates that the gra-
phene-MxSy (DSb2S3, MnS2, SnS) composites studied were
mainly mesoporous in character, with a minor presence of wider
pores where capillary condensation occurred. As shown in
Table 2, the BET surface area of graphene-Sb2S3, as well as gra-
phene-MnS2 and graphene-SnS nanocomposites were 37.63 m2/
g, 49.56 m2/g, and 25.94 m2/g, respectively.
After adsorption–desorption equilibrium was achieved,
the photocatalytic degradation of MO under visible light
obeys pseudo-first-order kinetics with respect to the concen-
tration of MO:
Fig. 4. TEM micrographs of as-prepared samples: (a) graphene-
Sb2S3, (b) graphene-MnS2, (c) graphene-SnS.
¡ dc/dt D kapp
c
to monolayer-multilayer adsorption since it follows the same
path as the corresponding part of a Type II isotherm obtained t D0, with the cads being the initial concentration in the bulk
with the given adsorptive on the same surface area of the solution after dark adsorption and t the reaction time) will
Integration of equation (with the restriction of cDcads at

Graphene-Based MxSy Visible Light Driven Photocatalyst
1699
1.5
1.0
0.5
0.0
lead to the following expected relation:
¡ lnðc=cadsÞ D kapp
t
(a) Photocatalyst+VL(0 min)
(b) Graphene-MnS2+VL(120 min)
(c) Graphene-Sb2S3+VL(120 min)
(d) Graphene-SnS+VL(120 min)
where c and cads are the reactant concentration at time t D t
and t D 0, respectively; and kapp and t are the apparent reac-
tion rate constant and time, respectively. According to the
equation, a plot of -ln(c/cads) versus t will yield a slope of
kapp. The results are displayed in Figure 6 and listed in Table
2. The linearity of plot suggests that the photodegradation
reaction approximately follows the pseudo first-order kinetics
with kapp of 0.0086 min¡1 for degradation MO over the gra-
phene-SnS composites under visible light.
(d)
(c)
(b)
(a)
300
400
500
600
700
800
Figure 7 is the UV-vis spectra of OPCO extract liquors in
the presence of graphene-SnS composite under visible light
irradiation. DPCI can be oxidized by oxidizing substances
into DPCO. Under visible light irradiation, the graphene-SnS
samples turns into the excited state. That is, some electrons
are transited from valence band (VB) to conduction band
(CB). Simultaneity, the electron-hole pairs form on the sur-
face or in the inner of graphene-SnS samples. The electrons
and holes react with the molecular oxygen (O2) dissolved in
aqueous solution and water molecules (H2O) absorbed on the
surface of graphene-SnS, thus produce the superoxygen radi-
cal anions (ꢁO2¡) and hydroxyl radicals (ꢁOH). These ꢁOH
can oxidize DPCI into DPCO. The DPCO can be extracted
by the solvent of benzene and show an absorbance at 560 nm
wavelength. Sequentially, the produce and output of ꢁOH
can be easily detected, and the photodegradation activity can
be easily detected. From Figure 7, it can be obviously seen
that, under visible light irradiation, the absorption peaks of
DPCO around 560 nm show an obvious increase compared
with the corresponding ones without any irradiation.[22]
For different irradiation time of graphene-MxSy samples
under visible light, the DPCO solution exhibits different
absorbance. The absorbance peaks of DPCO extract
liquors as the order of graphene-MnS2 < graphene-Sb2S3 <
Wavelength (nm)
Fig. 7. UV-vis spectra of DPCO extract liquors in the presence of
graphene-MxSy composites under visible light irradiation.
graphene-SnS. It indicated that the photodegradation activity
of graphene-SnS is good.
Under irradiation by visible lamp, the graphene nano-
sheets acting as good electron acceptors can accept the
electrons by light irradiation. Meanwhile, the MxSy can
be also excited to produce the electrons and holes in the
conduction band (CB) and valence band (VB) of MxSy.
Then the electrons accepted by graphene nanosheets from
light can transfer into the CB of MxSy, thereby increasing
the number of electrons as well as the rate of electron-
induced redox reactions. It can be proposed that transfer
also happens in the graphene-MxSy composites between
graphene and MxSy, retarding the e¡/hC recombination
and increasing the photon efficiency. The generated elec-
trons (e¡) probably react with dissolved oxygen molecules
and produce oxygen peroxide radical O2ꢁ¡, the positive
charged hole (hC) may react with the OH¡ derived from
H2O to form hydroxyl radical OHꢁ.
1.5
1.4
MxSy C hv ! eꢂ C hC .MxSy/
(1)
1.3
graphene-MnS2
graphene-Sb2S3
graphene-SnS
eꢂ C Graphene ! GrapheneðeꢂÞ
(2)
(3)
1.2
ꢁ ¡
GrapheneðeꢂÞ C O2 ! O2
1.1
1.0
ꢁ
ꢁ
ꢁ ¡
O2 C H2O ! OH C H2O C H2O2
h C .MxSy/ C H2O/ ¡ OH ! OHꢁ C H C
O2ꢁ ¡ or OHꢁ C Rh:B ! Degradation
(4)
(5)
(6)
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
Based on the above experimental results, we can conclude
that this degradation mechanism is suitable to explain the
results of MO photocatalytic degradation using the as-pre-
pared visible light driven graphene-MxSy composite photoca-
talysts. The scheme of excitation and charge transfer process
between MxSy particles and graphene nanosheets under visi-
ble light irradiation is shown in Figure 8.
0
20
40
60
80
100
120
140
160
Irraidition time (min)
Fig. 6. Apparent first-order kinetics of MO degradation over gra-
phene-Sb2S3, graphene-MnS2, and graphene-SnS photocatalysts
under visible light irradiation.

1700
Zhu et al.
Fig. 8. Schematic diagram of the charge transfer between graphene and MxSy under visible light irradiation.
Conclusions
5. Pan, S. G.; Liu, X. H.; Wang, X. Mater. Charact. 2011, 62,1094.
6. Gao, Z. Y.; Liu, N.; Wu, D. P.; Tao, W. G.; Xu, F.; Jiang, K. Appl.
Surf. Sci. 2012, 258, 2473.
In this study, graphene-MxSy(DSb2S3, MnS2, SnS) compo-
sites photacatalyst has been synthesized by a facile hydro-
thermal method. The formed metal sulfide triggered by
precipitation reaction uniformly distributed on the gra-
phene sheets. The adsorption and surface properties as
structural and chemical composition of the graphene-MxSy
composites were investigated. The quantities of generated
hydroxyl radicals can be analysis by DPCI degradation.
The results demonstrated that the degradation of MO solu-
tion under visible light irradiation, causing its concentra-
tion in the aqueous solution can be attributed to the
synthetic effects of electro-assisted photocatalytic decom-
position by MxSy and graphene. Graphene-SnS composite
exhibit the highest photocatalytic activity and relativity
high adsorption effect of graphene.
7. Huang, M. H.; Mao, S.; Feick, H.; Yan, H. Q.; Wu, Y. Y.;
Kind, H.; Weber, E.; Russo, R.; Yang, P. D. Science 2001, 292,
1897.
8. Yong, G. B.; Zhu, Q.; Xiang, S.; Chen, L. X.; Tan, Z. G.; Xu, J. G.
Acta Chim. Sinica 2010, 68, 2199
9. Pathan, H. M.; Lokhande, C. D. Bull. Mater. Sci. 2004, 27, 85.
€
10. Hickey, S. G.; Waurisch, C.; Rellinghaus, B.; Eychmuller, A. J.
Am. Chem. Soc. 2008, 130, 14978.
11. Wang, J.; Guo, Y. W.; Liu, B.; Jin, X. D.; Liu, L. J.; Xu, R.; Kong,
Y. M.; Wang, B. X. Ultrason. Sonochem. 2011, 18, 177.
12. Ghosh, T.; Oh, W. C. J. Photocatal. Sci. 2012, 3, 17.
13. Oh, W. C.; Zhang, F. J. Asian J. Chem. 2011, 23, 875.
14. Li, D.; Muller, M. B.; Gilje, S.; Wallace, G. G. Nat. Nanotechnol.
2008, 3, 101.
15. Oh, W. C.; Chen, M. L.; Zhang, F. J. J. Ind. Eng. Chem. 2010,
16, 321.
16. Alemi, A.; Joo, S. W.; Hanifehpour, Y.; Khandar, A.; Morsali, A.
and Min, B. K. J. Nanomater. 2011, ID 186528.
17. Hastings, J.; Elliott, N.; Corliss, L. Phys. Rev. 1959, 115, 13.
€
18. Hickey, S. G.; Waurisch, C.; Rellinghaus, B.; Eychmuller, A. J.
References
Am. Chem. Soc. 2008, 130, 14978.
19. Zhang, H.; Lv, X. J.; Li, Y. M.; Wang, Y.; Li, J. H. ACS Nano
2010, 4, 380.
20. Cai, D.; Song, M. J. Mater. Chem. 2007, 17, 3678.
21. Cao, A. N.; Liu, Z.; Chu, S. S.; Wu, M. H.; Ye, Z. M.; Cai, Z. W.;
Chang, Y. L.; Wang, S. F.; Gong, Q. H.; Liu, Y. F. Adv. Mater.
2010, 22, 103.
1. Zhu, Y.; Murali, S.; Cai, W.; Li, X.; Suk, J. W.; Potts, J. R.; Ruoff,
R. S. Adv. Mater. 2010, 22, 3906.
2. Novoselov, K. S.; Geim, A. K.; Morozov, S. V. Nature 2005, 438,
197.
3. Stankovich, S.; Dikin, D. A.; Dommett, G. H. B.; Kohlhass, K. M.
Nature 2006, 442, 282.
4. Sun, S.; Gao, L.; Liu, Y. Appl. Phys. Lett. 2010, 96, 083113.
22. Meng, Z. D.; Ghosh, T.; Zhu, L.; Choi, J. G.; Park, C. Y.; Oh, W.
C. J. Mater. Chem. 2012, 22, 16127.

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