Research Article Synthesis and Structural Characterization...

Research ArticleSynthesis and Structural Characterization of Al

2O3-Coated MoS

2

Spheres for Photocatalysis Applications

S V Prabhakar Vattikuti and Chan Byon

School of Mechanical Engineering Yeungnam University Gyeongsan 712-749 Republic of Korea

Correspondence should be addressed to Chan Byon cbyonynuackr

Received 8 April 2015 Revised 21 May 2015 Accepted 27 May 2015

Academic Editor Junyou Yang

Copyright copy 2015 S V P Vattikuti and C ByonThis is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in anymedium provided the originalwork is properly cited

This paper reports the synthesis of novel monodisperse Al2O3-coated molybdenum disulfide nanospheres (ie core-shell

structures) using a one-step facile hydrothermal method XPS analysis confirmed the purity and stable structure of the Al2O3-

coated MoS2nanospheres A possible growth mechanism of the core-shell structure is also reported along with their influence

on the photodegradation process of rhodamine B (RhB) The Al2O3-coated MoS

2nanospheres demonstrate good photocatalytic

activity and chemical stability compared to MoS2spheres TG-DTA analysis provided insight into the decomposition process of

the precursor solution and the stability of the nanoparticles The enhanced photocatalytic activity makes the Al2O3-coated MoS

2

nanospheres a promising candidate as a photocatalyst that could be used in place of traditional Al2O3MoS

2photocatalyst for the

removal of pollutants from waste water

1 Introduction

Molybdenum disulfide (MoS2) is one of the important tran-

sition metal dichalcogenides (TMDs) with indirect band gap(123 eV) semiconductor characteristics [1] Because of theiroutstanding properties like mechanical-to-electrochemicalcapabilities MoS

2is used in wide spectrum of applications

in catalytic support materials [2 3] solar cells [4] batteries[5] solid lubricants [6] and gas sensors [7] These uniqueproperties have attracted many researchers to design newsynthesis approaches for uniform and well-controlled MoS

2

nanostructures Synthesis methods include chemical vapordeposition [8] wetness impregnationmethod [9] hydrother-mal methods [10] and solid state reaction [11] These tech-niques have been used to prepare various morphologiesof MoS

2 like fullerene-like (IF) structures nanoflowers

nanorods nanosheets nanoplates and nanospheresIn a recent report Wang et al demonstrated that carbon-

decorated MoS2nanospheres have better cycling perfor-

mance with good capacity as a Na-iron battery anode [12]MoS2is clearly one of the most significantly and broadly

used TMDs for transistors due to its favorable band gap

compared to graphene In addition MoS2is also a suitable

candidate for photocatalytic materials MoS2is an indirect

narrow-band-gap semiconductor with good stability againstphotocorrosion in solution [13] General issueswith semicon-ductor catalysts in the conversion of solar energy to hydrogenare poor charge transport ability slow kinetics for evolutionreactions poor stability and the hydrophobic nature of thecatalyst [14 15] On the other hand individual MoS

2catalyst

has lower charge separation due to its poor crystallinityDespite previous efforts there has been no material

system that can simultaneously satisfy all the criteria for cost-effective photoelectrochemical hydrogen production andnew materials with new properties are needed To overcomethese problems core-shell structures of MoS

2coupled with

another material with different activity are promising Suchstructures could enable charge separation by gathering elec-trons and holes The major parameters for the selection ofshellmaterials are band alignment and small latticemismatchbetween the core and shell materials [16] There are very fewstudies that have focused on preparing MoS

2nanosphere

structures Wu et al [17] synthesized MoS2microspheres

(with diameter up to 2120583m) using a solvothermal method

Hindawi Publishing CorporationJournal of NanomaterialsVolume 2015 Article ID 978409 9 pageshttpdxdoiorg1011552015978409

2 Journal of Nanomaterials

Ammonium heptamolybdate

tetrahydrate

Hydrothermal

L-Cysteine+TSC

Hydrothermal

Al(NO3)3 middot 9H2O

MoS2 nanospheres MoS2 nanospheresAl2O3-coated

Figure 1 Schematic illustration of the methodology for the formation of Al2O3-coated MoS

2nanospheres

with the addition of SUDEI Wu et al [18] prepared MoS2

nanospheres (with average diameter of 100 nm) using HCl asa surfactant Park et al [19] synthesized MoS

2nanospheres

with high capacity and cycle stability for lithium ion batteriesusing L-cysteine in a surfactant-assisted solvothermal route

Common ways to synthesize core-shell structures aredecorating the core particles with a surface coating [5] or shellformation using surface modification processes [20] In thisstudy we report the influence of Al

2O3as a shell material

on the photocatalytic activity of MoS2nanosphere core-

shell structures under UV light irradiation We studied thevariations of the activity and selectivity in the degradation ofrhodamine B (RhB) using Al

2O3-coated MoS

2nanospheres

as a catalyst

2 Experimental Procedure

A schematic illustration of the methodology for the for-mation of Al

2O3-coated MoS

2nanospheres is shown in

Figure 1 For the synthesis 03 g of ammonium heptamolyb-date tetrahydrate and 017 g of L-cysteine were dissolved in30mLof deionizedwaterThis solutionwas stirred vigorouslyfor 1 h at 80∘C The suspension was continuously stirredand refluxed near pH 1 Then 12mmol of Al(NO

3)3sdot9H2O

and 03mmol of trisodium citrate dehydrate (TSC) wereadded to the stirred solution and again stirred for 30minat 80∘C Then the solution was transferred to a Teflon-linedautoclave and heated at 230∘C for 24 h Finally the resultingprecipitates were collected by centrifugation and then theprecipitates were washed three times with acetone and waterThe obtained precipitates were dried at 250∘C for 6 h andsintering at 450∘C for 2 h

The structural properties of the obtained precipitateswere characterized by powder X-ray diffraction (XRD) witha Shimadzu Labx XRD 6100 using Cu-K120572 radiation (120582= 014056 nm) The scan range was 10ndash80∘ and the scanspeed was 3 degminThe nanoparticles were analyzed with atransmission electron microscope (TEM Hitachi H-7000) at100 kV and a high-resolution TEM (HRTEM Tecnai G2 F 20

Inte

nsity

(au

)

(00

2)

(00

4)

(10

2) (1

03

)

(10

4)

(11

0)

(00

8)

(11

4)

10 20 30 40 50 60 70

(a)

Position (2120579)

MoS2Al2O3lowast

(0 1

2)

(1 1

0)

(0 0

6) (0

2 4

)

(0 1

8)

lowastlowast

lowastlowast

lowast

(b)

Figure 2 XRD pattern ofMoS2nanospheres (curve (a)) and Al

2O3-

coated MoS2nanospheres (curve (b))

S-Twin TEM) at an accelerating voltage of 210 kVThe opticalproperties of the nanoparticles were studied using UV-visible spectroscopy (Cary 5000 UV-Vis spectrophotometry)Thermogravimetric (TG) and differential thermal analysis(DTA) were carried out on a SDT Q600 thermogravimetricanalyzer under N

2flow at a rate of 30 cm3min The furnace

temperature was increased from room temperature to 900∘Cat a heating rate of 10∘C per minute The purity of thefinal product was examined by X-ray photoelectron spec-troscopy (XPS Thermo Scientific K-alpha surface analysisinstrument)

The photocatalytic experiments were carried out at thenatural pH of the RhB organic pollutant solution The pho-toreactor has a 150-W mercury lamp with a main emissionwavelength of 254 nm as an internal light source whichis surrounded by a quartz vessel The suspension includes

Journal of Nanomaterials 3

200 nm

(a)

100 nm

(b)

200 nm

(c)

200 nm

(d)

Figure 3 TEM images of ((a) (b)) MoS2nanospheres ((c) (d)) Al

2O3-coated MoS

2nanospheres

the Al2O3-decorated MoS

2nanosphere catalyst and aqueous

RhB (100mL 10mgL) which completely surrounds the lightsource Before irradiation the suspension was stirred in thedark for 30min to obtain a good dispersion and to ensureadsorption-desorption equilibrium between the organic pol-lutant molecules and the catalyst During light irradiationthe samples of the reaction solution were collected at givenintervals and examined using an optical spectrophotometer

3 Results and Discussions

The XRD patterns of MoS2nanospheres and Al

2O3-coated

MoS2nanospheres were shown in Figure 2 In case of MoS

2

sphere sample exhibits three well-resolved peaks which canbe indexed as the 002 103 and 110 reflections of the 2Dhexagonal structure which is matched with JCPDS number77-1716 On the other hand XRD pattern of Al

2O3-coated

MoS2sample exhibits hexagonal structure whereas Al

2O3

layer is been crystallized which is corresponding to JCPDSnumber 78-2426The coexisting peaks of Al

2O3-coatedMoS

2

nanospheres corresponding to the 012 110 006 024 and 018

crystal plane are ascribed to 120574-Al2O3phase for the sintered

samples at 450∘C [21 22]The diffraction lines characteristicsof MoS

2and Al

2O3and no other elemental peaks were

detectedThe morphology of the MoS

2nanospheres and Al

2O3-

coated MoS2nanospheres was examined using TEM as

shown in Figure 3 MoS2nanospheres were coated with

Al2O3using Al(NO

3)3sdot9H2O as a precursor via a hydrother-

mal method For better understanding of the morphologyof the composite we initially tested the MoS

2nanospheres

without using Al precursors The morphology of the MoS2

nanospheres is shown in Figures 3(a) and 3(b) The MoS2

materials reveal typical sphere-like morphology with severalnanometers in diameter On the other hand the MoS

2

spheres obtained using Al precursors retained their sphericalmorphology with the formation of a uniform layer forminga core-shell structure (Figures 3(c) and 3(d)) The averagethickness of theAl

2O3layer around the periphery of theMoS

2

is about 15 nmFurther understanding of the structural and composi-

tional characterizations of Al2O3-coated MoS

2nanospheres

was obtained using HRTEM The HRTEM image of an edge


(a) (b)

316 Aring

213 Aring

5 nm

(c)

(d)

STEM HAADF detector (STEM HAADF

1 120583m

(e)

Mo

1 120583m

(f)

S

1 120583m

(g)

O

1 120583m

(h)

Al

1 120583m

(i)

Figure 4HR-TEM images ((a)ndash(e)) of Al2O3-coatedMoS

2nanospheres ((f)ndash(i))HR-TEMelementalmapping images of Al

2O3-coatedMoS

2

nanospheres

portion of a core-shell sphere is shown in Figures 4(a)ndash4(d)The HRTEM image (Figure 4(a)) confirms that the Al

2O3

colloids are aggregated on the MoS2nanospheres The lattice

fringes of the core-shell structure with lattice spacings ofabout 0213 and 0316 nm could be attributed to the (103) and(110) planes of 2H-MoS

2 respectively Figures 4(e)ndash4(i) show

typical energy dispersive X-ray spectrometer (EDX) elemen-tal mappings of the core-shell spheres of various elements inthe core-shell structure alongwith its TEM imageTheMo SAl or O signals are predominantly distributed in the core andshell regions within the selected area respectively Figure 5shows the EDXmapping of Al

2O3-coatedMoS

2nanospheres

There are no other traces observed

ElementMoSAlO

Weight ()2491

5642

287

878

Atomic ()3395

4565

323

3029

Cou

nts

400

300

200

100

Mo

Mo

MoMo

Mo

S

O

Al

10 20 30 40

Energy (keV)

162000 acquire EDX acquire HAADF area 1

ElementMoSAlO

Weight ()g ( )2491

5642

287

878

Atomic ()3395

4565

323

3029

Mo

Mo

MoMo

Mo

S

O

Al

Figure 5 HR-TEM EDX data of Al2O3-coated MoS

2nanospheres

Journal of Nanomaterials 5W

eigh

t (

)

120

100

80

60

40

Temperature (∘C)0 200 400 600 800 1000

Exo up Universal V45A TA instruments

4725

Hea

t flow

(Wg

)

0

minus2

minus4

08

06

04

02

00

minus02

Der

iv W

eigh

t (

∘ C)

Figure 6 TG-DTA analysis of Al2O3-coated MoS

2nanospheres

Thermogravimetric and differential thermal analysis(TG-DTA) was conducted to quantitatively determinethe Al

2O3

content present in the Al2O3-coated MoS

2

nanospheres as shown in Figure 6 The initial weight lossbelow 220∘C is ascribed to the evaporation of physicallyabsorbed water from the product whereas the weight lossbetween 550 and 680∘C that occurred with an exothermicpeak at 650∘C could essentially be attributed to thedecomposition and separation of the Al

2O3layer The Al

2O3

content was estimated to be approximately 4725 by weightThe electronic states of themetals and sulfur in theAl

2O3-

coated MoS2nanospheres were tested using XPS as shown

in Figures 7(a)ndash7(e) The XPS survey spectra of the Al2O3-

coated MoS2nanospheres are shown in Figure 7(a) The

Al2p XPS spectra were estimated for the Al2O3-coated MoS

2

nanospheres to examine the chemical state of Al The Mo3dS2P Al2p andO1s peaks from the Al

2O3-coatedMoS

2sphere

sample (Figures 7(b)ndash7(e)) show no presence of additionchemical states The binding energy difference Δ119864 betweenthe Al2p and 2s levels is 5334 eV for the Al

2O3-coated MoS

2

nanospheresTheXPS results strongly indicate that Al speciesinteracted with the MoS

2nanospheres and are preferentially

formed in the Al2O3-MoS2composite using Al(NO

3)3sdot9H2O

as a precursor The Al2p and O1s peaks were centered at7445 eV and 53236 eV as described elsewhere [23]

The S2p spectrum shows a supplementary peak at16458 eV coexisting with an O1s peak which is ascribedto the oxidation of sulfur The formation of covalent S-Obonding without breakage of the Mo-S bond is likely dueto the oxidation state of sulfur No S-O bond is observed inthe S2s spectrum which suggests that only the top surfaceof sulfur atoms of MoS

2are oxygen functionalized This is

good evidence that the Al2O3formed a bond with MoS

2

nanospheres resulting in the formation of the core-shellstructureThe XPS binding energies Δ1198641 (Mo 2p

32minus S 2p

32)

and Δ1198642 (Mo 3d52minus S 2p

32) of the Al

2O3-coated MoS

2

nanospheres are 703 and 6709 eV respectivelyThe UV-Vis spectrum of the synthesized Al

2O3-coated

MoS2nanospheres is shown in Figure 8(a) The absorption

edge at 275 nm could be attributed to the absorption ofAl2O3-MoS2in the UV region The absorption spectrum

shows two absorption edges at 603 and 660 nm These areattributed to excitonic transitions of the Brillouin region atthe 119870 point which is consistent with an earlier report [24]The energy separation between the two absorption peaks (at603 and 660 nm) is 015 eV due to the spin-orbit splittingat the 119870 point at the surface of the valence band [24]Moreover there is weak absorbance in the visible region at awavelength of 425 nmThe UV-absorption behavior of MoS

2

strongly depends on its size due to quantum effects [25]For example the absorption edges of MoS

2nanoparticles

with average diameters of about 45 and 9 nm have edgesat 470 and 700 nm respectively in the visible light region[26] In contrast bulk MoS

2(with a band gap of 123 eV)

has an absorption peak at around 1040 nm [25] MoS2-based

composites have diverse absorption edges with respect totheir dimensional parameters [26]

The indirect band gap is estimated using the Tauc equa-tion with optical absorption data for near the band edge [24](120572ℎ])12 = 119860(ℎ] minus 119864

119892) The band gaps (119864

119892) are determined

from extrapolation of a linear fit onto the 119909-axis A plot of(120572ℎ])12 versus the photon energy (ℎ]) and the intercept ofthe tangent to the 119909-axis gives the band gap of the Al

2O3-

coatedMoS2nanospheres as shown in Figure 8(b)The band

gap energy of Al2O3-coated MoS

2nanospheres was found to

be 242 eVFigure 9 shows the progressive changes of the UV-

Vis absorption spectra of RhB solution in the presence ofAl2O3-coated MoS

2nanosphere catalyst under UV light as

a function of time The strong absorption peak of the RhBsolution at 564 nm gradually decreases from dark conditionsto 60min and the color of the solution turns from pinkto colorless at the end of the photodegradation processFigure 10 shows the photodegradation efficiency of MoS

2

nanospheres and Al2O3-coated MoS

2nanosphere catalysts

under UV light in RhB solution The results are shown asthe relative concentration (119862119862

0) as a function of irradiation

time where 1198620and 119862 (mgL) are the initial and final

concentrations of the pollutant solutionAblank experimentwas carried out in the absence of pho-

tocatalyst for comparison which showed no obvious changein the RhB concentration within 60min The introductionof MoS

2nanospheres and Al

2O3-coated MoS

2nanosphere

catalysts can greatly enhance the photocatalytic activity underUV light Interestingly the Al

2O3-coated MoS

2nanosphere

photocatalysts displayedmuch higher photodegradation per-formance than the MoS

2nanospheres and more than 97 of

the RhBwas degraded within 60minThe presence of Al2O3-

coated MoS2nanospheres plays a key role in the photocat-

alytic degradation process The significant enhancement inphotoactivity can be ascribed to the favorable van der Waalssurfaces of the Al

2O3-coated MoS

2nanospheres

Figure 11 shows a kinetic plot of the photocatalyticdegradation of RhB over time under UV light irradiationas ln(119862119862

0) The removal efficiency of the Al

2O3-coated

MoS2nanospheres was much faster than that of the MoS

2

nanosphere catalyst To understand the photostability andreusability of the photocatalyst four successive recyclingtests of the photocatalysts were done for the degradation ofRhB under UV light as shown in Figure 12 There were no


1200 1000 800 600 400 200 0

0

100000

200000

300000

Inte

nsity

(au

)

Binding energy (eV)

Mo-3d5 3d3 S2s

Mo-

3p3

3p1

O1s

Mo3

s C1s

S2p

Al2

sA

l2p

Mo4

p

(a)

222 224 226 228 230 232 234 236 238 2400

4000

8000

12000

16000

20000

Cou

nts

Binding energy (eV)

Mo 3d52

Mo 3d32

(b)

158 160 162 164 166 1680

2000

4000

6000

8000

10000

Cou

nts

Binding energy (eV)

S 2p32

S 2p12

S-O

(c)

66 69 72 75 78 81 84 870

1000

2000

3000

Cou

nts

Binding energy (eV)

Al2p

(d)

526 528 530 532 534 536 538 540 542 544 5460

10000

20000

30000

Binding energy (eV)

Cou

nts

O1s

(e)

Figure 7 XPS data of Al2O3-coated MoS

2nanospheres (a) survey spectrum (b) Mo 3d (c) S2p (d) Al2p and (e) O1s

significant changes in photocatalytic activity which showsthe steadiness of the degradation efficiency of RhB solutionThis result implies that the Al

2O3-coated MoS

2nanosphere

photocatalysts have high stability during the photocatalyticoxidation of the pollutant molecules and are reusable

The catalytic activity increased with the Al2O3-coated

MoS2nanospheres Figure 13 shows the RhB removal effi-

ciency of the Al2O3-coatedMoS

2photocatalytic nanospheres

with 5mg of catalyst and 50mL of 10mgLminus1 RhB solutionThe pollutant removal efficiency and the adsorption amount


200 400 600 800 1000

03

04

05

06

07

08

09Ab

sorb

ance

Wavelength (nm)

(a)

18 20 22 24 26 28 30 32

030

035

040

045

050

(120572h)

12

Photon energy h (eV)

(b)

Figure 8 (a) UV-Vis light spectra of the Al2O3-coated MoS

2nanospheres (b) Tauc plots of Al

2O3-coated MoS

2nanospheres

400 500 600 700

02

04

06

08

10

Wavelength (nm)

Abso

rban

ce (a

u)

Dark10 min20 min30 min

40 min50 min60 min

Figure 9 Time-dependent UV-Vis absorbance spectra of Al2O3-

coated MoS2nanospheres of the rhodamine B solution samples at

different times

at equilibrium (qe) were calculated using the followingequation

Pollutant removal efficiency (PR) =100 (119862

0minus 119862)

1198620

(1)

where 1198620and 119862 (mgL) are the initial and final concentra-

tions of the pollutant respectively 119881 is the volume of thepollutant solution and 119898 (g) is the mass of the catalyst TheAl2O3-coated MoS

2nanospheres exhibit high RhB removal

efficiency (95) in contrast to the (69) MoS2nanosphere

sample It is well known that catalytic ability increases with

0 10 20 30 40 50 60 7000

02

04

06

08

10

UV irradiationDark

Without catalyst

Time (min)

MoS2 nanospheresMoS2 nanospheres

minus10

CC

0

Al2O3-coated

Figure 10 Photodegradation rate of the rhodamine B underUV light and light irradiation time for without catalyst MoS

2


2nanospheres

increasing content of the catalyst with respect to processingtime and other environmental conditions like temperatureand pH In this work the degradation rate of the RhBsolution also increased with increasing catalyst content dueto the small particle size and good dispersibility of theAl2O3-coated MoS

2nanoparticles which facilitate electron

migration between the catalyst and pollutant The Al2O3-

coated MoS2nanospheres exhibit high catalytic activity due

to the high dispersibility of the Al2O3coating around the

MoS2nanospheres which secured more efficient charge

transfer between the MoS2and Al

2O3

The MoS2behaves as the photoactive center which is

generating excited photoelectron pairs under UV irradiation


10 20 30 40 50 6000

04

08

12

16

20

24

28

Time (min)

MoS2 nanospheres catalystMoS2 nanospheres catalyst

minusln

CC

0

Al2O3-coated

Figure 11The kinetic plot of Al2O3-coatedMoS

2nanospheres pho-

tocatalytic degradation of rhodamine B under UV light irradiation

0 60 120 180 240

0

20

40

60

80

100

4th cycle3rd cycle2nd cycle

Time (min)

1st cycle

(CC

0)

lowast10

0

Figure 12 Recycling photocatalytic degradation of rhodamine Bin the presence of Al

2O3-coated MoS

2nanospheres photocatalytic

under UV light irradiation

while the Al2O3provides better adsorption sites in the vicin-

ity of the MoS2 The presence of insulating layers of Al

2O3

on the surface ofMoS2nanospheres suppresses the unwanted

charge recombination thus enhancing the photocatalyticactivity The greater photocatalytic activity of Al

2O3-coated

MoS2nanospheres can be explained as follows The HRTEM

mapping results indicated that the periphery of theMoS2was

covered with Al2O3 Under UV light irradiation both MoS

2

and Al2O3are photoexcited and holes and electrons form in

the valance band and conduction band The photogeneratedholes and electrons are transferred within the valance andconduction bands of both the MoS

2and Al

2O3materials

This tendency helps to extend the charge carriersThe excitedelectrons and holes react with dissolved oxygen in the wateror directly oxidize the pollutant molecules to form oxide

0 10 20 30 40 50 600

20

40

60

80

100

RhB

rem

oval

effici

ency

()

Time (min)

MoS2 nanospheresAl2O3-coated MoS2 nanospheres

Figure 13 RhB removal efficiency of Al2O3-coated MoS

2nano-

spheres photocatalytic adsorption conditions 5mg catalyst 50mL10mgLminus1 RhB solution (conditions 5mg of catalyst and 50mL of10mgLminus1 RhB solution)

radicals (O2∙minus) and hydroxyl radicals (∙OH) which are

responsible for the degradation of RhBA possible mechanism for formation of MoS

2Al2O3

core-shell structure is suggested involving MoS2spheres

acting as a template for the formation of the coatednanospheres Due to hydrothermal reactions between themetal-oxoanions and surfactant cations form a compositephase at the surfactantinorganic interfacesThus nucleationdomains were formed during the hydrothermal reactionbetween MoO4

2minus and S2minus and formed MoS2spheres In this

manner the diameter of the nanospheres is no longer limitedby the micelle dimensions A spherical phase of MoS

2is

formed during hydrothermal treatment under the syntheticconditions in which L-cysteine acts as a sulfur source tostabilize the spherical organization of Mo and S speciesThe Al species of the precursor solution can absorb to thesurface of MoS

2spheres and layer upon layer is formed by

the electrostatic interaction The TSC could be considereda crucial component for the growth mechanism of Al

2O3

coating because it acts as a capping agent for the formation ofthe coating surface on the MoS

2nanospheres The complete

synthetic mechanism is expressed in Figure 1

4 Conclusions

Al2O3-coated MoS

2nanospheres were successfully synthe-

sized using a simple hydrothermal method The Al2O3

shell materials serve as additional electron sources that cansignificantly recover the electron conduction in MoS

2 which

favors the photodegradation of the pollutant We revealedthe appropriate selection of surfactants that could facilitatethe adherence of Al species to the surfaces of the coresHydrothermally synthesized Al

2O3-coatedMoS

2nanosphere

catalysts show photocatalytic activity higher than that of the


MoS2nanosphere catalyst due to the enhanced crystallites

with highmetal content whichminimize the poisoning effectof sulfur by the chemisorption process

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This research was supported by the Basic Science ResearchProgram through theNational Research Foundation of Korea(NRF) and funded by theMinistry of Science ICT andFuturePlanning (2014R1A2A2A01007081)

References

[1] H S S Ramakrishna Matte A Gomathi A K Manna et alldquoMoS

2and WS

2analogues of graphenerdquo Angewandte Chemie

International Edition vol 49 no 24 pp 4059ndash4062 2010[2] Y Li H Wang L Xie Y Liang G Hong and H Dai ldquoMoS

2

nanoparticles grown on graphene an advanced catalyst for thehydrogen evolution reactionrdquo Journal of the American ChemicalSociety vol 133 no 19 pp 7296ndash7299 2011

[3] J J Lee H Kim and S HMoon ldquoPreparation of highly loadeddispersed MoS

2Al2O3catalysts for the deep hydrodesulfuriza-

tion of dibenzothiophenesrdquoApplied Catalysis B Environmentalvol 41 no 1-2 pp 171ndash180 2003

[4] D Song M Li Y Jiang et al ldquoFacile fabrication of MoS2

PEDOT-PSS composites as low-cost and efficient counter elec-trodes for dye-sensitized solar cellsrdquo Journal of Photochemistryand Photobiology A Chemistry vol 279 pp 47ndash51 2014

[5] C Zhang H B Wu Z Guo and X W Lou ldquoFacile synthesis ofcarbon-coated MoS

2nanorods with enhanced lithium storage

propertiesrdquo Electrochemistry Communications vol 20 pp 7ndash102012

[6] H-H Chien K-J Ma S V P Vattikuti C-H Kuo C-B Huoand C-L Chao ldquoTribological behaviour of MoS

2Au coatingsrdquo

Thin Solid Films vol 518 no 24 pp 7532ndash7534 2010[7] M Donarelli S Prezioso F Perrozzi et al ldquoResponse to NO

2

and other gases of resistive chemically exfoliated MoS2-based

gas sensorsrdquo Sensors and Actuators B Chemical vol 207 pp602ndash613 2015

[8] Y Shi Y Wang J I Wong et al ldquoSelf-assembly of hierarchicalMoS119909CNT nanocomposites (2ltxlt3) towards high perfor-

mance anode materials for lithium ion batteriesrdquo ScientificReports vol 3 article 2169 8 pages 2013

[9] K Hagiwara T Ebihara N Urasato and T Fujikawa ldquoApplica-tion of 129Xe NMR to structural analysis of MoS

2crystallites on

MoAl2O3hydrodesulfurization catalystrdquo Applied Catalysis A

General vol 285 no 1-2 pp 132ndash138 2005[10] Y Feldman G L Frey M Homyonfer et al ldquoBulk synthesis of

inorganic fullerene-like MS2 (M = Mo W) from the respectivetrioxides and the reaction mechanismrdquo Journal of the AmericanChemical Society vol 118 no 23 pp 5362ndash5367 1996

[11] W K Hsu B H Chang Y Q Zhu et al ldquoAn alternative routeto molybdenum disulfide nanotubesrdquo Journal of the AmericanChemical Society vol 122 no 41 pp 10155ndash10158 2000

[12] J Wang C Luo T Gao A Langrock A C Mignerey and CWang ldquoAn advancedMoS

2carbon anode for high-performance

sodium-ion batteriesrdquo Small vol 11 pp 473ndash481 2015[13] R Coehoorn C Haas J Dijkstra C J F Flipse R A De Groot

and A Wold ldquoElectronic structure of MoSe2 MoS

2 and WSe

2

I Band-structure calculations and photoelectron spectroscopyrdquoPhysical Review B vol 35 no 12 pp 6195ndash6202 1987

[14] J A Glasscock P R F Barnes I C Plumb and N SavvidesldquoFormation of fractal-like structures driven by carbon nano-tubes-based collapsed hollow capsulesrdquoThe Journal of PhysicalChemistry C vol 111 pp 331ndash337 2007

[15] O Khaselev and J A Turner ldquoA monolithic photovoltaic-photoelectrochemical device for hydrogen production viawatersplittingrdquo Science vol 280 no 5362 pp 425ndash427 1998

[16] R G Chaudhuri and S Paria ldquoCoreshell nanoparticles classesproperties synthesis mechanisms characterization and appli-cationsrdquo Chemical Reviews vol 112 no 4 pp 2373ndash2433 2012

[17] D M Wu X D Zhou X Fu H Q Shi D B Wang and Z SHu ldquoSynthesis and characterization of molybdenum disulfidemicro-sized solid spheresrdquo Journal of Materials Science vol 41no 17 pp 5682ndash5686 2006

[18] Z Wu DWang and A Sun ldquoSurfactant-assisted fabrication ofMoS2nanospheresrdquo Journal of Materials Science vol 45 no 1

pp 182ndash187 2010[19] S-K Park S-H Yu SWoo et al ldquoA facile and green strategy for

the synthesis ofMoS2nanospheres with excellent Li-ion storage

propertiesrdquoCrystEngComm vol 14 no 24 pp 8323ndash8325 2012[20] J Li P Wu Y Ye et al ldquoElectronic structure of MoSe

2 MoS

2

and WSe2 I Band-structure calculations and photoelectron

spectroscopyrdquo CrystEngComm vol 16 no 4 pp 517ndash521 2014[21] G Paglia C E Buckley A L Rohl et al ldquoBoehmite derived120574-alumina system 1 structural evolution with temperaturewith the identification and structural determination of a newtransition phase 1205741015840-aluminardquo Chemistry of Materials vol 16no 2 pp 220ndash236 2004

[22] M Trueba and S P Trasatti ldquo120574-alumina as a support forcatalysts a review of fundamental aspectsrdquo European Journal ofInorganic Chemistry vol 2005 no 17 pp 3393ndash3403 2005

[23] F Lan Z Lai R Yan et al ldquoEpitaxial growth of single-crystallinemonolayer MoS

2by two-step methodrdquo ECS Solid State Letters

vol 4 pp 19ndash21 2015[24] R Coehoorn C Haas and R A de Groot ldquoElectronic structure

of MoSe2 MoS

2 and WSe

2 II The nature of the optical

band gapsrdquo Physical Review B Condensed Matter and MaterialsPhysics vol 35 no 12 pp 6203ndash6206 1987

[25] K K Kam and B A Parkinson ldquoDetailed photocurrent spec-troscopy of the semiconducting group VI transition metaldichalcogenidesrdquo Journal of Physical Chemistry vol 86 no 4pp 463ndash467 1982

[26] T R Thurston and J P Wilcoxon ldquoPhotooxidation of organicchemicals catalyzed by nanoscaleMoS

2rdquoThe Journal of Physical

Chemistry B vol 103 no 1 pp 11ndash17 1999

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of



CeramicsJournal of


CompositesJournal of

NanoparticlesJournal of



International Journal of

Biomaterials


NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014


CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research



MetallurgyJournal of


BioMed Research International

MaterialsJournal of


Nano

materials


Journal ofNanomaterials


Ammonium heptamolybdate

tetrahydrate

Hydrothermal

L-Cysteine+TSC

Hydrothermal

Al(NO3)3 middot 9H2O

MoS2 nanospheres MoS2 nanospheresAl2O3-coated

Figure 1 Schematic illustration of the methodology for the formation of Al2O3-coated MoS

2nanospheres

with the addition of SUDEI Wu et al [18] prepared MoS2

nanospheres (with average diameter of 100 nm) using HCl asa surfactant Park et al [19] synthesized MoS

2nanospheres

with high capacity and cycle stability for lithium ion batteriesusing L-cysteine in a surfactant-assisted solvothermal route

Common ways to synthesize core-shell structures aredecorating the core particles with a surface coating [5] or shellformation using surface modification processes [20] In thisstudy we report the influence of Al

2O3as a shell material

on the photocatalytic activity of MoS2nanosphere core-

shell structures under UV light irradiation We studied thevariations of the activity and selectivity in the degradation ofrhodamine B (RhB) using Al

2O3-coated MoS

2nanospheres

as a catalyst

2 Experimental Procedure

A schematic illustration of the methodology for the for-mation of Al

2O3-coated MoS

2nanospheres is shown in

Figure 1 For the synthesis 03 g of ammonium heptamolyb-date tetrahydrate and 017 g of L-cysteine were dissolved in30mLof deionizedwaterThis solutionwas stirred vigorouslyfor 1 h at 80∘C The suspension was continuously stirredand refluxed near pH 1 Then 12mmol of Al(NO

3)3sdot9H2O

and 03mmol of trisodium citrate dehydrate (TSC) wereadded to the stirred solution and again stirred for 30minat 80∘C Then the solution was transferred to a Teflon-linedautoclave and heated at 230∘C for 24 h Finally the resultingprecipitates were collected by centrifugation and then theprecipitates were washed three times with acetone and waterThe obtained precipitates were dried at 250∘C for 6 h andsintering at 450∘C for 2 h

The structural properties of the obtained precipitateswere characterized by powder X-ray diffraction (XRD) witha Shimadzu Labx XRD 6100 using Cu-K120572 radiation (120582= 014056 nm) The scan range was 10ndash80∘ and the scanspeed was 3 degminThe nanoparticles were analyzed with atransmission electron microscope (TEM Hitachi H-7000) at100 kV and a high-resolution TEM (HRTEM Tecnai G2 F 20

Inte

nsity

(au

)

(00

2)

(00

4)

(10

2) (1

03

)

(10

4)

(11

0)

(00

8)

(11

4)

10 20 30 40 50 60 70

(a)

Position (2120579)

MoS2Al2O3lowast

(0 1

2)

(1 1

0)

(0 0

6) (0

2 4

)

(0 1

8)

lowastlowast

lowastlowast

lowast

(b)

Figure 2 XRD pattern ofMoS2nanospheres (curve (a)) and Al

2O3-

coated MoS2nanospheres (curve (b))

S-Twin TEM) at an accelerating voltage of 210 kVThe opticalproperties of the nanoparticles were studied using UV-visible spectroscopy (Cary 5000 UV-Vis spectrophotometry)Thermogravimetric (TG) and differential thermal analysis(DTA) were carried out on a SDT Q600 thermogravimetricanalyzer under N

2flow at a rate of 30 cm3min The furnace

temperature was increased from room temperature to 900∘Cat a heating rate of 10∘C per minute The purity of thefinal product was examined by X-ray photoelectron spec-troscopy (XPS Thermo Scientific K-alpha surface analysisinstrument)

The photocatalytic experiments were carried out at thenatural pH of the RhB organic pollutant solution The pho-toreactor has a 150-W mercury lamp with a main emissionwavelength of 254 nm as an internal light source whichis surrounded by a quartz vessel The suspension includes


200 nm

(a)

100 nm

(b)

200 nm

(c)

200 nm

(d)


2O3-coated MoS

2nanospheres






2O3-coated


2


2O3-coated


2O3


2O3-coatedMoS

2




2and Al



2nanospheres and Al

2O3-



Al2O3using Al(NO



2nanospheres




2



2



2nanospheres



(a) (b)

316 Aring

213 Aring

5 nm

(c)

(d)


1 120583m

(e)

Mo

1 120583m

(f)

S

1 120583m

(g)

O

1 120583m

(h)

Al

1 120583m

(i)



2O3-coatedMoS

2

nanospheres


2O3





2O3-coatedMoS

2nanospheres


ElementMoSAlO

Weight ()2491

5642

287

878

Atomic ()3395

4565

323

3029

Cou

nts

400

300

200

100

Mo

Mo

MoMo

Mo

S

O

Al

10 20 30 40

Energy (keV)


ElementMoSAlO

Weight ()g ( )2491

5642

287

878

Atomic ()3395

4565

323

3029

Mo

Mo

MoMo

Mo

S

O

Al


2nanospheres


eigh

t (

)

120

100

80

60

40

Temperature (∘C)0 200 400 600 800 1000


4725

Hea

t flow

(Wg

)

0

minus2

minus4

08

06

04

02

00

minus02

Der

iv W

eigh

t (

∘ C)


2nanospheres


2O3


2


2O3layer The Al

2O3


2O3-





2


2O3-coatedMoS

2sphere


2O3-coated MoS

2




3)3sdot9H2O





2


32minus S 2p

32)


32) of the Al

2O3-coated MoS

2


2O3-coated




2


2nanoparticles






119892) The band gaps (119864



2O3-








2








2nanospheres and Al

2O3-coated MoS

2nanosphere


2O3-coated MoS

2nanosphere






2O3-coated MoS

2nanospheres



2O3-coated


2



1200 1000 800 600 400 200 0

0

100000

200000

300000

Inte

nsity

(au

)

Binding energy (eV)

Mo-3d5 3d3 S2s

Mo-

3p3

3p1

O1s

Mo3

s C1s

S2p

Al2

sA

l2p

Mo4

p

(a)

222 224 226 228 230 232 234 236 238 2400

4000

8000

12000

16000

20000

Cou

nts

Binding energy (eV)

Mo 3d52

Mo 3d32

(b)

158 160 162 164 166 1680

2000

4000

6000

8000

10000

Cou

nts

Binding energy (eV)

S 2p32

S 2p12

S-O

(c)

66 69 72 75 78 81 84 870

1000

2000

3000

Cou

nts

Binding energy (eV)

Al2p

(d)

526 528 530 532 534 536 538 540 542 544 5460

10000

20000

30000

Binding energy (eV)

Cou

nts

O1s

(e)




2O3-coated MoS

2nanosphere








200 400 600 800 1000

03

04

05

06

07

08

09Ab

sorb

ance

Wavelength (nm)

(a)

18 20 22 24 26 28 30 32

030

035

040

045

050

(120572h)

12


(b)



2O3-coated MoS

2nanospheres

400 500 600 700

02

04

06

08

10

Wavelength (nm)

Abso

rban

ce (a

u)


40 min50 min60 min



different times



0minus 119862)

1198620

(1)






0 10 20 30 40 50 60 7000

02

04

06

08

10

UV irradiationDark

Without catalyst

Time (min)


minus10

CC

0

Al2O3-coated


2


2nanospheres








2O3




10 20 30 40 50 6000

04

08

12

16

20

24

28

Time (min)


minusln

CC

0

Al2O3-coated


2nanospheres pho-


0 60 120 180 240

0

20

40

60

80

100


Time (min)

1st cycle

(CC

0)

lowast10

0


2O3-coated MoS





2O3



2O3-coated




2



2and Al

2O3materials


0 10 20 30 40 50 600

20

40

60

80

100

RhB

rem

oval

effici

ency

()

Time (min)



2nano-




2Al2O3





2is




2O3




4 Conclusions

Al2O3-coated MoS




2 which


2O3-coatedMoS

2nanosphere







Acknowledgments


References


2and WS



2











2Au coatingsrdquo


2






2crystallites on









2 and WSe

2










2 MoS

2







of MoSe2 MoS

2 and WSe














CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




200 nm

(a)

100 nm

(b)

200 nm

(c)

200 nm

(d)


2O3-coated MoS

2nanospheres






2O3-coated


2


2O3-coated


2O3


2O3-coatedMoS

2




2and Al



2nanospheres and Al

2O3-



Al2O3using Al(NO



2nanospheres




2



2



2nanospheres



(a) (b)

316 Aring

213 Aring

5 nm

(c)

(d)


1 120583m

(e)

Mo

1 120583m

(f)

S

1 120583m

(g)

O

1 120583m

(h)

Al

1 120583m

(i)



2O3-coatedMoS

2

nanospheres


2O3





2O3-coatedMoS

2nanospheres


ElementMoSAlO

Weight ()2491

5642

287

878

Atomic ()3395

4565

323

3029

Cou

nts

400

300

200

100

Mo

Mo

MoMo

Mo

S

O

Al

10 20 30 40

Energy (keV)


ElementMoSAlO

Weight ()g ( )2491

5642

287

878

Atomic ()3395

4565

323

3029

Mo

Mo

MoMo

Mo

S

O

Al


2nanospheres


eigh

t (

)

120

100

80

60

40

Temperature (∘C)0 200 400 600 800 1000


4725

Hea

t flow

(Wg

)

0

minus2

minus4

08

06

04

02

00

minus02

Der

iv W

eigh

t (

∘ C)


2nanospheres


2O3


2


2O3layer The Al

2O3


2O3-





2


2O3-coatedMoS

2sphere


2O3-coated MoS

2




3)3sdot9H2O





2


32minus S 2p

32)


32) of the Al

2O3-coated MoS

2


2O3-coated




2


2nanoparticles






119892) The band gaps (119864



2O3-








2








2nanospheres and Al

2O3-coated MoS

2nanosphere


2O3-coated MoS

2nanosphere






2O3-coated MoS

2nanospheres



2O3-coated


2



1200 1000 800 600 400 200 0

0

100000

200000

300000

Inte

nsity

(au

)

Binding energy (eV)

Mo-3d5 3d3 S2s

Mo-

3p3

3p1

O1s

Mo3

s C1s

S2p

Al2

sA

l2p

Mo4

p

(a)

222 224 226 228 230 232 234 236 238 2400

4000

8000

12000

16000

20000

Cou

nts

Binding energy (eV)

Mo 3d52

Mo 3d32

(b)

158 160 162 164 166 1680

2000

4000

6000

8000

10000

Cou

nts

Binding energy (eV)

S 2p32

S 2p12

S-O

(c)

66 69 72 75 78 81 84 870

1000

2000

3000

Cou

nts

Binding energy (eV)

Al2p

(d)

526 528 530 532 534 536 538 540 542 544 5460

10000

20000

30000

Binding energy (eV)

Cou

nts

O1s

(e)




2O3-coated MoS

2nanosphere








200 400 600 800 1000

03

04

05

06

07

08

09Ab

sorb

ance

Wavelength (nm)

(a)

18 20 22 24 26 28 30 32

030

035

040

045

050

(120572h)

12


(b)



2O3-coated MoS

2nanospheres

400 500 600 700

02

04

06

08

10

Wavelength (nm)

Abso

rban

ce (a

u)


40 min50 min60 min



different times



0minus 119862)

1198620

(1)






0 10 20 30 40 50 60 7000

02

04

06

08

10

UV irradiationDark

Without catalyst

Time (min)


minus10

CC

0

Al2O3-coated


2


2nanospheres








2O3




10 20 30 40 50 6000

04

08

12

16

20

24

28

Time (min)


minusln

CC

0

Al2O3-coated


2nanospheres pho-


0 60 120 180 240

0

20

40

60

80

100


Time (min)

1st cycle

(CC

0)

lowast10

0


2O3-coated MoS





2O3



2O3-coated




2



2and Al

2O3materials


0 10 20 30 40 50 600

20

40

60

80

100

RhB

rem

oval

effici

ency

()

Time (min)



2nano-




2Al2O3





2is




2O3




4 Conclusions

Al2O3-coated MoS




2 which


2O3-coatedMoS

2nanosphere







Acknowledgments


References


2and WS



2











2Au coatingsrdquo


2






2crystallites on









2 and WSe

2










2 MoS

2







of MoSe2 MoS

2 and WSe














CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




(a) (b)

316 Aring

213 Aring

5 nm

(c)

(d)


1 120583m

(e)

Mo

1 120583m

(f)

S

1 120583m

(g)

O

1 120583m

(h)

Al

1 120583m

(i)



2O3-coatedMoS

2

nanospheres


2O3





2O3-coatedMoS

2nanospheres


ElementMoSAlO

Weight ()2491

5642

287

878

Atomic ()3395

4565

323

3029

Cou

nts

400

300

200

100

Mo

Mo

MoMo

Mo

S

O

Al

10 20 30 40

Energy (keV)


ElementMoSAlO

Weight ()g ( )2491

5642

287

878

Atomic ()3395

4565

323

3029

Mo

Mo

MoMo

Mo

S

O

Al


2nanospheres


eigh

t (

)

120

100

80

60

40

Temperature (∘C)0 200 400 600 800 1000


4725

Hea

t flow

(Wg

)

0

minus2

minus4

08

06

04

02

00

minus02

Der

iv W

eigh

t (

∘ C)


2nanospheres


2O3


2


2O3layer The Al

2O3


2O3-





2


2O3-coatedMoS

2sphere


2O3-coated MoS

2




3)3sdot9H2O





2


32minus S 2p

32)


32) of the Al

2O3-coated MoS

2


2O3-coated




2


2nanoparticles






119892) The band gaps (119864



2O3-








2








2nanospheres and Al

2O3-coated MoS

2nanosphere


2O3-coated MoS

2nanosphere






2O3-coated MoS

2nanospheres



2O3-coated


2



1200 1000 800 600 400 200 0

0

100000

200000

300000

Inte

nsity

(au

)

Binding energy (eV)

Mo-3d5 3d3 S2s

Mo-

3p3

3p1

O1s

Mo3

s C1s

S2p

Al2

sA

l2p

Mo4

p

(a)

222 224 226 228 230 232 234 236 238 2400

4000

8000

12000

16000

20000

Cou

nts

Binding energy (eV)

Mo 3d52

Mo 3d32

(b)

158 160 162 164 166 1680

2000

4000

6000

8000

10000

Cou

nts

Binding energy (eV)

S 2p32

S 2p12

S-O

(c)

66 69 72 75 78 81 84 870

1000

2000

3000

Cou

nts

Binding energy (eV)

Al2p

(d)

526 528 530 532 534 536 538 540 542 544 5460

10000

20000

30000

Binding energy (eV)

Cou

nts

O1s

(e)




2O3-coated MoS

2nanosphere








200 400 600 800 1000

03

04

05

06

07

08

09Ab

sorb

ance

Wavelength (nm)

(a)

18 20 22 24 26 28 30 32

030

035

040

045

050

(120572h)

12


(b)



2O3-coated MoS

2nanospheres

400 500 600 700

02

04

06

08

10

Wavelength (nm)

Abso

rban

ce (a

u)


40 min50 min60 min



different times



0minus 119862)

1198620

(1)






0 10 20 30 40 50 60 7000

02

04

06

08

10

UV irradiationDark

Without catalyst

Time (min)


minus10

CC

0

Al2O3-coated


2


2nanospheres








2O3




10 20 30 40 50 6000

04

08

12

16

20

24

28

Time (min)


minusln

CC

0

Al2O3-coated


2nanospheres pho-


0 60 120 180 240

0

20

40

60

80

100


Time (min)

1st cycle

(CC

0)

lowast10

0


2O3-coated MoS





2O3



2O3-coated




2



2and Al

2O3materials


0 10 20 30 40 50 600

20

40

60

80

100

RhB

rem

oval

effici

ency

()

Time (min)



2nano-




2Al2O3





2is




2O3




4 Conclusions

Al2O3-coated MoS




2 which


2O3-coatedMoS

2nanosphere







Acknowledgments


References


2and WS



2











2Au coatingsrdquo


2






2crystallites on









2 and WSe

2










2 MoS

2







of MoSe2 MoS

2 and WSe














CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




eigh

t (

)

120

100

80

60

40

Temperature (∘C)0 200 400 600 800 1000


4725

Hea

t flow

(Wg

)

0

minus2

minus4

08

06

04

02

00

minus02

Der

iv W

eigh

t (

∘ C)


2nanospheres


2O3


2


2O3layer The Al

2O3


2O3-





2


2O3-coatedMoS

2sphere


2O3-coated MoS

2




3)3sdot9H2O





2


32minus S 2p

32)


32) of the Al

2O3-coated MoS

2


2O3-coated




2


2nanoparticles






119892) The band gaps (119864



2O3-








2








2nanospheres and Al

2O3-coated MoS

2nanosphere


2O3-coated MoS

2nanosphere






2O3-coated MoS

2nanospheres



2O3-coated


2



1200 1000 800 600 400 200 0

0

100000

200000

300000

Inte

nsity

(au

)

Binding energy (eV)

Mo-3d5 3d3 S2s

Mo-

3p3

3p1

O1s

Mo3

s C1s

S2p

Al2

sA

l2p

Mo4

p

(a)

222 224 226 228 230 232 234 236 238 2400

4000

8000

12000

16000

20000

Cou

nts

Binding energy (eV)

Mo 3d52

Mo 3d32

(b)

158 160 162 164 166 1680

2000

4000

6000

8000

10000

Cou

nts

Binding energy (eV)

S 2p32

S 2p12

S-O

(c)

66 69 72 75 78 81 84 870

1000

2000

3000

Cou

nts

Binding energy (eV)

Al2p

(d)

526 528 530 532 534 536 538 540 542 544 5460

10000

20000

30000

Binding energy (eV)

Cou

nts

O1s

(e)




2O3-coated MoS

2nanosphere








200 400 600 800 1000

03

04

05

06

07

08

09Ab

sorb

ance

Wavelength (nm)

(a)

18 20 22 24 26 28 30 32

030

035

040

045

050

(120572h)

12


(b)



2O3-coated MoS

2nanospheres

400 500 600 700

02

04

06

08

10

Wavelength (nm)

Abso

rban

ce (a

u)


40 min50 min60 min



different times



0minus 119862)

1198620

(1)






0 10 20 30 40 50 60 7000

02

04

06

08

10

UV irradiationDark

Without catalyst

Time (min)


minus10

CC

0

Al2O3-coated


2


2nanospheres








2O3




10 20 30 40 50 6000

04

08

12

16

20

24

28

Time (min)


minusln

CC

0

Al2O3-coated


2nanospheres pho-


0 60 120 180 240

0

20

40

60

80

100


Time (min)

1st cycle

(CC

0)

lowast10

0


2O3-coated MoS





2O3



2O3-coated




2



2and Al

2O3materials


0 10 20 30 40 50 600

20

40

60

80

100

RhB

rem

oval

effici

ency

()

Time (min)



2nano-




2Al2O3





2is




2O3




4 Conclusions

Al2O3-coated MoS




2 which


2O3-coatedMoS

2nanosphere







Acknowledgments


References


2and WS



2











2Au coatingsrdquo


2






2crystallites on









2 and WSe

2










2 MoS

2







of MoSe2 MoS

2 and WSe














CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




1200 1000 800 600 400 200 0

0

100000

200000

300000

Inte

nsity

(au

)

Binding energy (eV)

Mo-3d5 3d3 S2s

Mo-

3p3

3p1

O1s

Mo3

s C1s

S2p

Al2

sA

l2p

Mo4

p

(a)

222 224 226 228 230 232 234 236 238 2400

4000

8000

12000

16000

20000

Cou

nts

Binding energy (eV)

Mo 3d52

Mo 3d32

(b)

158 160 162 164 166 1680

2000

4000

6000

8000

10000

Cou

nts

Binding energy (eV)

S 2p32

S 2p12

S-O

(c)

66 69 72 75 78 81 84 870

1000

2000

3000

Cou

nts

Binding energy (eV)

Al2p

(d)

526 528 530 532 534 536 538 540 542 544 5460

10000

20000

30000

Binding energy (eV)

Cou

nts

O1s

(e)




2O3-coated MoS

2nanosphere








200 400 600 800 1000

03

04

05

06

07

08

09Ab

sorb

ance

Wavelength (nm)

(a)

18 20 22 24 26 28 30 32

030

035

040

045

050

(120572h)

12


(b)



2O3-coated MoS

2nanospheres

400 500 600 700

02

04

06

08

10

Wavelength (nm)

Abso

rban

ce (a

u)


40 min50 min60 min



different times



0minus 119862)

1198620

(1)






0 10 20 30 40 50 60 7000

02

04

06

08

10

UV irradiationDark

Without catalyst

Time (min)


minus10

CC

0

Al2O3-coated


2


2nanospheres








2O3




10 20 30 40 50 6000

04

08

12

16

20

24

28

Time (min)


minusln

CC

0

Al2O3-coated


2nanospheres pho-


0 60 120 180 240

0

20

40

60

80

100


Time (min)

1st cycle

(CC

0)

lowast10

0


2O3-coated MoS





2O3



2O3-coated




2



2and Al

2O3materials


0 10 20 30 40 50 600

20

40

60

80

100

RhB

rem

oval

effici

ency

()

Time (min)



2nano-




2Al2O3





2is




2O3




4 Conclusions

Al2O3-coated MoS




2 which


2O3-coatedMoS

2nanosphere







Acknowledgments


References


2and WS



2











2Au coatingsrdquo


2






2crystallites on









2 and WSe

2










2 MoS

2







of MoSe2 MoS

2 and WSe














CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




200 400 600 800 1000

03

04

05

06

07

08

09Ab

sorb

ance

Wavelength (nm)

(a)

18 20 22 24 26 28 30 32

030

035

040

045

050

(120572h)

12


(b)



2O3-coated MoS

2nanospheres

400 500 600 700

02

04

06

08

10

Wavelength (nm)

Abso

rban

ce (a

u)


40 min50 min60 min



different times



0minus 119862)

1198620

(1)






0 10 20 30 40 50 60 7000

02

04

06

08

10

UV irradiationDark

Without catalyst

Time (min)


minus10

CC

0

Al2O3-coated


2


2nanospheres








2O3




10 20 30 40 50 6000

04

08

12

16

20

24

28

Time (min)


minusln

CC

0

Al2O3-coated


2nanospheres pho-


0 60 120 180 240

0

20

40

60

80

100


Time (min)

1st cycle

(CC

0)

lowast10

0


2O3-coated MoS





2O3



2O3-coated




2



2and Al

2O3materials


0 10 20 30 40 50 600

20

40

60

80

100

RhB

rem

oval

effici

ency

()

Time (min)



2nano-




2Al2O3





2is




2O3




4 Conclusions

Al2O3-coated MoS




2 which


2O3-coatedMoS

2nanosphere







Acknowledgments


References


2and WS



2











2Au coatingsrdquo


2






2crystallites on









2 and WSe

2










2 MoS

2







of MoSe2 MoS

2 and WSe














CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




10 20 30 40 50 6000

04

08

12

16

20

24

28

Time (min)


minusln

CC

0

Al2O3-coated


2nanospheres pho-


0 60 120 180 240

0

20

40

60

80

100


Time (min)

1st cycle

(CC

0)

lowast10

0


2O3-coated MoS





2O3



2O3-coated




2



2and Al

2O3materials


0 10 20 30 40 50 600

20

40

60

80

100

RhB

rem

oval

effici

ency

()

Time (min)



2nano-




2Al2O3





2is




2O3




4 Conclusions

Al2O3-coated MoS




2 which


2O3-coatedMoS

2nanosphere







Acknowledgments


References


2and WS



2











2Au coatingsrdquo


2






2crystallites on









2 and WSe

2










2 MoS

2







of MoSe2 MoS

2 and WSe














CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials








Acknowledgments


References


2and WS



2











2Au coatingsrdquo


2






2crystallites on









2 and WSe

2










2 MoS

2







of MoSe2 MoS

2 and WSe














CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



Research Article Synthesis and Structural Characterization...

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Transcript of Research Article Synthesis and Structural Characterization...