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Search Results: 1 - 10 of 18821 matches for " Won-Chun Oh "
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MWCNT-Based Ag2S-TiO2 Nanocomposites Photocatalyst: Ultrasound-Assisted Synthesis, Characterization, and Enhanced Catalytic Efficiency
Lei Zhu,Ze-Da Meng,Won-Chun Oh
Journal of Nanomaterials , 2012, DOI: 10.1155/2012/586526
Abstract: Multiwalled carbon nanotube based nanoscale Ag2S and TiO2 composites have successfully synthesized via a facile ultrasound-assisted method. The nanocomposites were characterized by Fourier transform infrared (FT-IR) spectroscopy, UV-vis absorption spectra, BET surface area measurements, X-ray diffraction (XRD), and transmission electron microscopy (TEM). The Ag2S-TiO2/CNT nanocomposites exhibited much higher photocatalytic activity than pure TiO2 for the degradation of Rhodamine B (Rh.B) under UV and visible light. The improved photocatalytic activities may be attributed to increased adsorbability of Rh.B molecules and increased charge transfer rate in the presence of a one-dimensional MWCNT network.
The Improved Photocatalytic Properties of Methylene Blue for V2O3/CNT/TiO2 Composite under Visible Light
Ming-Liang Chen,Won-Chun Oh
International Journal of Photoenergy , 2010, DOI: 10.1155/2010/264831
Abstract: Multiwall carbon nanotube (MWCNT), vanadyl acetylacetonate (V(acac)3), and titanium n-butoxide (TNB) were used as carbon, vanadium oxide, and titanium oxide precursor to prepare V2O3/CNT/TiO2 composite. The obtained composite was characterized by BET surface area measurement, X-ray diffraction, transmission electron microscopy, and energy dispersive X-ray analysis. In addition, we used methylene blue (MB) solution under condition of visible light irradiation to determine their photocatalytic degradation efficiency. In conclusion, the V2O3/CNT/TiO2 composite had excellent photocatalytic degradation for MB solution under visible light. 1. Introduction In recent years, a great deal of interest has been devoted to the photocatalytic degradation of organic water pollutants on semiconductor particles. Anatase TiO2 has been widely employed in these studies, mainly due to its outstanding photocatalytic activity and stability. The current bottleneck with TiO2 photocatalysis lies in its low quantum yield, which depends on the ratio of the surface charge carrier transfer rate to the electron-hole recombination [1]. The influence of various transition metal ions on the photoactivity of TiO2 for many reactions has been studied with the aim of improving the efficiency of the photocatalytic process. Different doping effects have been reported in the literature, perhaps due to the widely varying experimental conditions for sample preparation and for the determination of photoactivity employed by different researchers [1–8]. Among the transition metal ions, vanadium ion is attractive because vanadium doping can increase carrier lifetime [2] and apparently also extend the absorption range of TiO2 [2, 3, 8]. Vanadium-doped TiO2 samples have been the object of many papers, including preparation and characterization, spectroscopic features, dynamics of charge-transfer trapping, and photocatalytic behavior [2–15]. Under visible light irradiation, doping of vanadium in TiO2 increased its photocatalytic activity [10–15]. Carbon materials can be used as support materials, due to their flexibility as support in tailoring the catalyst properties to specific needs [16]. Activated carbon has many advantages if utilized as catalyst support: resistant to acidic or basic media, stable at high temperatures in an inert atmosphere, possible to tailor its pore structure and chemical nature of the surface, and so forth [17]. However, activated carbon support also suffers several drawbacks: low mechanical stability which induces the formation of fines during operation and high tortuosity,
Synthesis and highly visible-induced photocatalytic activity of CNT-CdSe composite for methylene blue solution
Chen Ming-Liang,Oh Won-Chun
Nanoscale Research Letters , 2011,
Abstract: Carbon nanotube-cadmium selenide (CNT-CdSe) composite was synthesized by a facile hydrothermal method derived from multi-walled carbon nanotubes as a stating material. The as-prepared products were characterized by X-ray diffraction, scanning electron microscopy with energy dispersive X-ray analysis, transmission electron microscopy (TEM), and UV-vis diffuse reflectance spectrophotometer. The as-synthesized CNT-CdSe composite efficiently catalyzed the photodegradation of methylene blue in aqueous solutions under visible-light irradiation, exhibiting higher photocatalytic activity.
HydrothermalSynthesisofPorousAg2SSensitizedTiO2CatalystsandTheirPhotocatalyticActivitiesintheVisibleLightRange
ZHU Lei,MENG Zeda,TRISHA Ghosh,OH Won-Chun
催化学报 , 2012, DOI: 10.1016/S1872-2067(10)60296-3
Abstract: ?PorousAg2SsensitizedTiO2catalystsweresynthesizedbythehydrothermalprocess.ThecrystallizationandporousstructureoftheAg2S/TiO2compositephotocatalystswereinvestigatedbyX-raydiffraction,scanningelectronmicroscopywithenergydispersiveX-rayanalysis,UV-Visdiffusereflectancespectroscopy,andN2adsorption.TheAg2S/TiO2compositesweremainlycomposedofanataseTiO2andacanthiteAg2S.TheabsorptionedgewavelengthsofTiO2andtheAg2S/TiO2compositepreparedwith3mmolNa2S·5H2Owere400and800nm,respectively,thatis,theabsorptionedgeofthecompositehadapronouncedredshift.ThephotocatalyticactivityundervisiblelightwasinvestigatedbythedegradationofmethylenebluewithaUV-Visspectrophotometer.ThephotocatalyticactivitiesundervisiblelightoftheAg2S/TiO2photocatalystsweremuchhigherthanthatofTiO2.
EnhancedSonocatalyticDegradationofRhodamineBbyGraphene-TiO2CompositesSynthesizedbyanUltrasonic-AssistedMethod
ZHU Lei,Trisha GHOSH,Chong-Yeon PARK,MENG Ze-Da,OH Won-Chun
催化学报 , 2012, DOI: 10.1016/S1872-2067(11)60430-0
Abstract: ?Aseriesofgraphene-TiO2compositeswasfabricatedfromgrapheneoxideandtitaniumn-butoxide(TNB)byanultrasonic-assistedmethod.ThestructureandcompositionofthenanocompositeswerecharacterizedbyRamanspectroscopy,BETsurfaceareameasurements,X-raydiffraction,transmissionelectronmicroscopy,andultraviolet-visibleabsorptionspectroscopy.TheaveragesizeoftheTiO2nanoparticlesonthegraphenenanosheetswascontrolledataround10–15nmwithoutusingsurfactant,whichisattributedtothepyrolysisandcondensationofdissolvedTNBintoTiO2byultrasonicirradiation.ThecatalyticactivityofthecompositesunderultrasonicirradiationwasdeterminedusingarhodamineB(RhB)solution.Thegraphene-TiO2compositespossessedahighspecificsurfacearea,whichincreasedthedecolorizationrateforRhBsolution.ThisisbecausethegrapheneandTiO2nanoparticlesinthecompositesinteractstrongly,whichenhancesthephotoelectricconversionofTiO2byreducingtherecombinationofphotogeneratedelectron-holepairs.
SynthesisofGraphene-CdSeCompositebyaSimpleHydrothermalMethodandItsPhotocatalyticDegradationofOrganicDyes
OH Won-Chun,CHEN Mingliang,CHO Kwangyoun,KIM Cheolkyu,MENG Zeda,ZHU Lei
催化学报 , 2011, DOI: 10.1016/S1872-2067(10)60264-1
Abstract: ?Agraphene-CdSecompositewassynthesizedbyafacilehydrothermalmethod,andcharacterizedbyX-raydiffraction,scanningelectronmicroscopywithenergydispersiveX-rayanalysis,transmissionelectronmicroscopyandUV-visdiffusereflectancespectrophotometry.Thegraphene-CdSecompositeefficientlycatalyzedthephotodegradationofmethyleneblue(MB),methylorange(MO)andrhodamineB(Rh.B)inaqueoussolutionunderUVorvisiblelightirradiation.Thegraphene-CdSecompositeexhibitedahigherphotocatalyticactivityfortheMBsolution.
RareEarthOxide-TreatedFullereneandTitaniaCompositeswithEnhancedPhotocatalyticActivityfortheDegradationofMethyleneBlue
MENG Zada,ZHU Lei,CHOI Jong-geun,PARK Chong-yeon,OH Won-chun
催化学报 , 2011, DOI: 10.1016/S1872-2067(10)60258-6
Abstract: ?Rareearthoxide-treatedfullereneandtitaniacomposites(Y-fullerene/TiO2)werepreparedbythesol-gelmethod.Theproductshadinterestingsurfacecompositions.X-raydiffractionpatternsofthecompositesshowedthattheY-fullerene/TiO2compositescontainedasingleandclearanatasephase.Thesurfacepropertieswereobservedbyscanningelectronmicroscopy,whichgaveacharacterizationofthetextureontheY-fullerene/TiO2compositesandshowedahomogenousdistributionoftitaniumparticles.Theenergy-dispersiveX-rayspectrashowedthepresenceofCandTiwithstrongYpeaks.ThecompositeobtainedwasalsocharacterizedwithtransmissionelectronmicroscopyandUV-Visspectroscopy.ThephotocatalyticresultsshowedthattheY-fullerene/TiO2compositeshadexcellentactivityforthedegradationofmethyleneblueundervisiblelightirradiation.ThiswasattributedtoboththeeffectsonthephotocatalysisofthesupportedTiO2bychargetransferbythefullerene,andtheintroductionofyttriumtoenhancephoto-generatedelectrontransfer.
RhodamineBdegradationandreactiveoxygenspeciesgenerationbyaZnSe-graphene/TiO2sonocatalyst
Lei Zhu,Sun-Bok Jo,Shu Ye,Kefayat Ullah,Won-Chun Oh
催化学报 , 2014, DOI: 10.1016/S1872-2067(14)60158-3
Abstract: ?NanostructuredZnSe-graphene/TiO2wassynthesizedbyahydrothermal-assistedapproach.ZnSe-graphene/TiO2exhibitedfavorableadsorptionofrhodamineB,awidewavelengthabsorptionrange,andefficientchargeseparation.Reactiveoxygenspeciesweregeneratedbytheoxidationof1,5-diphenylcarbazideto1,5-diphenylcarbazone.Thesonocatalyticreactionmechanismwasproposed.Thesefindingspotentiallybroadentheapplicationsofsonocatalytictechnologies.
EnhancedvisiblelightphotocatalyticactivityofAg2S-graphene/TiO2nanocompositesmadebysonochemicalsynthesis
Ze-Da Meng,Lei Zhu,Kefayat Ullah,Shu Ye,Qian Sun,Won-Chun Oh
催化学报 , 2013, DOI: 10.1016/S1872-2067(12)60611-1
Abstract: ?Ag2S-graphene/TiO2compositesweresynthesizedbyafacilesonochemicalmethod.TheproductswerecharacterizedbyX-raydiffraction,scanningelectronmicroscopy,energydispersiveX-rayspectroscopy,transmissionelectronmicroscopy,andUV-Visdiffusereflectancespectrophotometry.Duringthesynthesisreaction,thereductionofgrapheneoxideandloadingofAg2SandTiO2particleswereachieved.TheAg2S-graphene/TiO2compositespossessedalargeadsorptioncapacityfordyes,anextendedlightabsorptionrange,andefficientchargeseparationproperties.Hence,inthephotodegradationofrhodamineB,asignificantenhancementinthereactionratewasobservedwiththeAg2S-graphene/TiO2compositesascomparedtopureTiO2.Thegenerationofreactiveoxygenspecieswasdetectedbytheoxidationof1,5-diphenylcarbazideto1,5-diphenylcarbazone.ThehighactivitywasattributedtothesynergeticeffectsofhighchargemobilityandtheredshiftintheabsorptionedgeoftheAg2S-graphene/TiO2composites.
Modifiedhydrothermalsynthesisandcharacterizationofreducedgrapheneoxide-silverselenidenanocompositeswithenhancedreactiveoxygenspeciesgeneration
Lei Zhu,Shu Ye,Asghar Ali,Kefayat Ulla,Kwang Youn Cho,Won-Chun Oh
催化学报 , 2015, DOI: 10.1016/S1872-2067(14)60275-8
Abstract: ?Avisible-lightphotocatalystcontainingAg2Seandreducedgrapheneoxide(RGO)wassynthesizedbyafacilesonochemical-assistedhydrothermalmethod.X-raydiffraction,scanningelectronmicroscopywithenergy-dispersiveX-rayanalysis,andultraviolet-visiblediffusereflectancespectroscopyresultsindicatedthattheRGO-Ag2SenanocompositecontainedsmallcrystallineAg2Senanoparticlesdispersedovergraphenenanosheetsandabsorbedvisiblelight.Thehighcrystallinityofthenanoparticlesincreasedphotocatalyticactivitybyfacilitatingchargetransport.N2adsorption-desorptionmeasurementsrevealedthattheRGO-Ag2Senanocompositecontainednumerousporeswithanaveragediameterof9nm,whichshouldallowreactantmoleculestoreadilyaccesstheAg2Senanoparticles.TheRGO-Ag2SenanocompositeexhibitedhigherphotocatalyticactivitythanbulkAg2SenanoparticlestodegradeorganicpollutantrhodamineBandindustrialdyeTexbriteBA-Lundervisible-lightirradiation(λ>420nm).ThegenerationofreactiveoxygenspeciesinRGO-Ag2Sewasevaluatedthroughitsabilitytooxidize1,5-diphenylcarbazideto1,5-diphenylcarbazone.ThesmallsizeoftheAg2SenanoparticlesinRGO-Ag2Sewasrelatedtotheuseofultrasonicationduringtheirformation,revealingthatthisapproachisattractivetoformporousRGO-Ag2Sematerialswithhighphotocatalyticactivityundervisiblelight.
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