Plasmonic substrates comprising gold nanostars efficiently regenerate cofactor molecules

Article abstract of DOI:10.1039/c6ta01770c

The light harvesting capacity of plasmonic nanoparticles is a fundamental feature for catalysing chemical reactions close to their surface. The efficiency of the photochemical processes depends not only on the geometrical aspects on a single particle level but also on the complexity of the multiparticle architectures. Although, the effect of the particle geometry is progressively understood in the relevant photochemical processes (water splitting and hydrogen evolution), there are experimental and theoretical needs for understanding the role of the shape in the multiparticle systems in the photocatalytic processes. Here we have shown that macroscopic plasmonic substrates comprising gold nanostars exhibit better efficiencies than nanorods or cubes in the photoregeneration of cofactor molecules. We performed photochemical and photoelectrochemical measurements, supported by theoretical simulations, showing that the unique geometry of nanostars-radially distributed spikes-contributes to stronger light absorption by the plasmonic film containing that type of nanoparticles.

Full text of DOI:10.1039/c6ta01770c

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Iglesias, J. Barroso, D. Martinez-Solis, J. M. Taboada Varela, F. Obelleiro Basteiro, V. Pavlov, A. Chuvilin
and M. Grzelczak, J. Mater. Chem. A, 2016, DOI: 10.1039/C6TA01770C.
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DOI: 10.1039/C6TA01770C
JournalꢀNameꢀ
ꢀ
ARTICLEꢀ
PlasmonicꢀSubstratesꢀComprisingꢀGoldꢀNanostarsꢀefficientlyꢀ
regenerateꢀcofactorꢀmoleculesꢀꢀ
RECEIVEDꢀ00thꢀJanuaryꢀ20xx,ꢀ
Acceptedꢀ00thꢀJanuaryꢀ20xxꢀ
a
b
c
d
c
AnaꢀSánchez-Iglesias, ꢀJavierꢀBarroso, ꢀDiegoꢀM.ꢀSolís, ꢀJoséꢀM.ꢀTaboada, ꢀFernandoꢀObelleiro, ꢀ
ꢀ
b
ꢀe,f
a,f ꢀ
ValeryꢀPavlov, ꢀAndreyꢀChuvilin ꢀandꢀMarekꢀGrzelczak *
DOI:ꢀ10.1039/x0xx00000xꢀ
Lightꢀharvestingꢀcapacityꢀofꢀplasmonicꢀnanoparticlesꢀisꢀaꢀfundamentalꢀfeatureꢀforꢀcatalysingꢀchemicalꢀreactionꢀcloseꢀtoꢀ
theirꢀsurface.ꢀTheꢀefficiencyꢀofꢀtheꢀphotochemicalꢀprocessesꢀdependsꢀnotꢀonlyꢀonꢀtheꢀgeometricalꢀaspectsꢀonꢀtheꢀsingleꢀ
particleꢀlevelꢀbutꢀalsoꢀonꢀtheꢀcomplexityꢀofꢀtheꢀmultiparticleꢀarchitectures.ꢀAlthough,ꢀtheꢀeffectꢀofꢀtheꢀparticlesꢀgeometryꢀisꢀ
progressivelyꢀ understoodꢀ inꢀ theꢀ relevantꢀ photochemicalꢀ processesꢀ (waterꢀ splitting,ꢀ hydrogenꢀ evolution),ꢀ thereꢀ areꢀ
experimentalꢀ andꢀ theoreticalꢀ needsꢀ forꢀ understandingꢀ theꢀ roleꢀ ofꢀ theꢀ shapeꢀ inꢀ theꢀ multiparticleꢀ systemsꢀ onꢀ theꢀ
photocatalyticꢀ processes.ꢀ Hereꢀ weꢀ showedꢀ thatꢀ macroscopicꢀ plasmonicꢀ substratesꢀ comprisingꢀ goldꢀ nanostarsꢀ exhibitꢀ
betterꢀefficienciesꢀthanꢀnanorodsꢀorꢀcubesꢀinꢀtheꢀphotoregenerationꢀofꢀcofactorꢀmolecules.ꢀWeꢀperformedꢀphotochemicalꢀ
andꢀ photoelectrochemicalꢀ measurements,ꢀ supportedꢀ byꢀ theoreticalꢀ simulations,ꢀ showingꢀ thatꢀ theꢀ uniqueꢀ geometryꢀ ofꢀ
nanostarsꢀ-ꢀradiallyꢀdistributedꢀspikesꢀ-ꢀcontributesꢀtoꢀstrongerꢀlightꢀabsorptionꢀbyꢀtheꢀplasmonicꢀfilmꢀcontainingꢀthatꢀtypeꢀ
ofꢀnanoparticles.ꢀ
www.rsc.org/ꢀ
ꢀ
ꢀ
whileꢀ anisotropicꢀ particles,ꢀ ofꢀ similarꢀ volume,ꢀ absorb/scatterꢀ
lightꢀinꢀtheꢀinfraredꢀspectralꢀrangeꢀ(700-1200ꢀnm).ꢀTheꢀopticalꢀ
featuresꢀ ofꢀ theꢀ particlesꢀ canꢀ beꢀ furtherꢀ alteredꢀ inꢀ aꢀ
multiparticleꢀ scenario,ꢀ inꢀ whichꢀ strongꢀ plasmonꢀ couplingꢀ
Introductionꢀꢀ
ꢀ
Theꢀ uniqueꢀ propertiesꢀ ofꢀ surfaceꢀ plasmonꢀ resonanceꢀ ensureꢀ
consolidationꢀofꢀnobleꢀmetalꢀnanoparticlesꢀinꢀphotochemistry,ꢀ
aꢀ fieldꢀ ofꢀ researchꢀ andꢀ technologyꢀ commandedꢀ currentlyꢀ byꢀ
enableꢀ intenseꢀ electricꢀ fieldꢀ enhancement,ꢀ whichꢀ benefitsꢀ
light-materꢀinteractions.ꢀThus,ꢀtheꢀspectroscopicꢀsensitivityꢀtoꢀ
geometryꢀonꢀsingle-ꢀandꢀmulti-particleꢀlevelsꢀcanꢀbeꢀexploitedꢀ
toꢀ constructꢀ deviceꢀ thatꢀ absorbꢀ acrossꢀ theꢀ fullꢀ solarꢀ
1
–15
semiconductors. ꢀ Someꢀ ofꢀ theꢀ photochemicalꢀ processesꢀ
haveꢀbeenꢀproposedꢀrecentlyꢀinꢀwhichꢀplasmonicꢀnanoparticlesꢀ
autonomouslyꢀ catalyseꢀ chemicalꢀ reactions,ꢀ suchꢀ asꢀ waterꢀ
24,25
spectrum.
ꢀ
16
17
18,19
ꢀ Accordingꢀ toꢀ recentꢀ works,ꢀ plasmonicꢀ nanoparticlesꢀ canꢀ
oxidation, ꢀhydrogenꢀevolution, ꢀSuzukiꢀcoupling,
oxidation
ꢀalcoholꢀ
20,21
22
ꢀorꢀreductionꢀofꢀnitroaromaticꢀcompounds. ꢀ
increaseꢀtheꢀrateꢀofꢀchemicalꢀreactionꢀbyꢀmultipleꢀmechanismsꢀ
includingꢀ photo-thermalꢀ effect,ꢀ electricꢀ near-fieldꢀ
ꢀ
Inꢀ aꢀ conventionalꢀ photocatalyticꢀ systemꢀ basedꢀ onꢀ
1
1,15
enhancement,ꢀgenerationꢀofꢀhotꢀelectrons.
mechanisticꢀpathways,ꢀtheꢀparticlesꢀshapeꢀplaysꢀanꢀimportantꢀ
ꢀInꢀallꢀofꢀtheseꢀ
semiconductor,ꢀ theꢀ performanceꢀ inꢀ theꢀ catalyticꢀ processꢀ
dependsꢀonꢀtheꢀbandꢀgapꢀenergyꢀofꢀtheꢀmaterial.ꢀInꢀplasmon-
basedꢀphotochemistry,ꢀtheꢀphotocatalyticꢀcapacityꢀofꢀparticlesꢀ
isꢀruledꢀbyꢀtheꢀenergyꢀofꢀtheꢀsurfaceꢀplasmons,ꢀwhichꢀisꢀinꢀturnꢀ
26
role.ꢀLongꢀetꢀal. ꢀdemonstratedꢀthatꢀtheꢀplasmonicꢀPdꢀconcaveꢀ
nanostructuresꢀ exhibitꢀ superiorꢀ catalyticꢀ performanceꢀ thanꢀ
cubesꢀ orꢀ octahedrons.ꢀ Theyꢀ ascribedꢀ suchꢀ behavingꢀ toꢀ
photothermalꢀeffectꢀandꢀlocalꢀheatꢀatꢀtheꢀreactionꢀsites.ꢀTrinhꢀ
2
3
relatedꢀtoꢀtheꢀshapeꢀandꢀsizeꢀofꢀtheꢀnanoparticles. ꢀInꢀgeneral,ꢀ
theꢀisotropicꢀparticlesꢀwithꢀaꢀdiameterꢀbelowꢀ20ꢀnmꢀinꢀcolloidalꢀ
phaseꢀabsorbꢀlightꢀinꢀtheꢀvisibleꢀspectralꢀrangeꢀ(400-600ꢀnm)ꢀ
19
etꢀ al. ꢀ showedꢀ thatꢀ plasmonicꢀ Pdꢀhexagonsꢀ areꢀ betterꢀ than,ꢀ
again,ꢀ cubesꢀ andꢀ octahedronsꢀ inꢀ plasmon-assistedꢀ Suzukiꢀ
coupling,ꢀ drivenꢀ byꢀ theꢀ hotꢀ electronꢀ pathway.ꢀ Fromꢀ broaderꢀ
perspective,ꢀ itꢀ becomesꢀ straightforwardꢀ thatꢀ theꢀ
photocatalyticꢀefficiencyꢀofꢀplasmonicꢀnanoparticlesꢀincreasesꢀ
withꢀ decreasingꢀ theꢀ symmetryꢀ andꢀ theꢀ volumeꢀ ofꢀ theꢀ
a.
BionanoplasmonicsꢀLaboratory,ꢀCICꢀbiomaGUNE,ꢀPaseoꢀdeꢀMiramónꢀ182,ꢀ20009ꢀ
b. Donostia,ꢀSanꢀSebastián,ꢀSpain;ꢀꢀꢀ
BiosensingꢀLaboratory,ꢀCICꢀbiomaGUNE,ꢀPaseoꢀdeꢀMiramónꢀ182,ꢀ20009ꢀDonostia,ꢀ
SanꢀSebastián,ꢀSpain;ꢀꢀꢀ
DepartamentoꢀdeꢀTeoríaꢀdeꢀlaꢀSeñalꢀyꢀComunicaciones,ꢀUniversityꢀofꢀVigo,ꢀ36301ꢀ
27–29
nanocrystal.
ꢀ Forꢀ example,ꢀ goldꢀ nanorodsꢀ exhibitꢀ betterꢀ
c.
photocatalyticꢀ propertiesꢀ thanꢀ isotropicꢀ nanoparticlesꢀ
(spheres,ꢀcubesꢀorꢀplates),ꢀwhichꢀisꢀdueꢀstrongꢀenhancementꢀofꢀ
30
d. Vigo,ꢀSpain;ꢀ
DepartamentoꢀdeꢀTecnologíaꢀdeꢀlosꢀComputadoresꢀyꢀdeꢀlasꢀComunicaciones,ꢀ
UniversityꢀofꢀExtremadura,ꢀ10003ꢀCáceres,ꢀSpain;ꢀ
CICꢀnanoGUNEꢀAv.ꢀDeꢀTolosaꢀ76,ꢀ20018ꢀDonostia-SanꢀSebastián,ꢀSpain;ꢀ
e.
theꢀ fieldꢀ insideꢀ theꢀ nanocrystal. ꢀ Thus,ꢀ inspiredꢀ byꢀ recentꢀ
f.
Ikerbasque,ꢀBasqueꢀFoundationꢀforꢀScience,ꢀ48013ꢀBilbao,ꢀSpain.ꢀ
theoreticalꢀandꢀexperimentalꢀdevelopment,ꢀweꢀexpectꢀthatꢀtheꢀ
ꢀ
ElectronicꢀSupplementaryꢀInformationꢀ(ESI)ꢀavailable:ꢀTEMꢀimages,ꢀSizeꢀanalysisꢀof
theꢀ nanoparticles,ꢀ Controlꢀ experimentꢀ ofꢀ photoelectrochemicalꢀ measurements,
SEMꢀimages.ꢀSeeꢀDOI:ꢀ10.1039/x0xx00000xꢀ
Thisꢀjournalꢀisꢀ©ꢀTheꢀRoyalꢀSocietyꢀofꢀChemistryꢀ20xxꢀ
J.ꢀName.,ꢀ2013,ꢀ00,ꢀ1-3ꢀ|ꢀ1ꢀꢀ
Pleaseꢀdoꢀnotꢀadjustꢀmarginsꢀ

Page 3 of 9
Journal of Materials Chemistry A
ARTICLEꢀ
JournalꢀNameꢀ
branchedꢀnanoparticlesꢀcanꢀbringꢀaꢀsignificantꢀcontributionꢀtoꢀ nanoparticlesꢀareꢀprovidedꢀinꢀtheꢀsupportingꢀinfoVriemwaAtrtiioclne ꢀO(nsleineeꢀ
theꢀ plasmon-assistedꢀ photochemistry,ꢀ inꢀ aꢀ similarꢀ mannerꢀ asꢀ FigureꢀS1-2).ꢀTheꢀas-preparedꢀparticlesꢀ wD eO rI :e 1ꢀ 0s .t1 a0 b3 9i l /i sC e6 dT Aꢀ w0 1i 7t 7h 0ꢀ Ca ꢀ
theyꢀ contributedꢀ inꢀ theꢀ fieldꢀ ofꢀ surfacedꢀ enhancedꢀ cationicꢀ surfactantꢀ (cethyltrimethylammoniumꢀ bromideꢀ -ꢀ
31
spectroscopy. ꢀ Theꢀ presenceꢀ ofꢀ multipleꢀ andꢀ non-evenlyꢀ CTAB)ꢀ inꢀ water.ꢀ Sinceꢀ theꢀ presenceꢀ ofꢀ Ptꢀ isꢀ essentialꢀ inꢀ
33
distributedꢀ spikesꢀ inꢀ theꢀ goldꢀ nanostarsꢀ canꢀ improveꢀ lightꢀ photochemicalꢀ reaction, ꢀ weꢀ subjectedꢀ theꢀ as-preparedꢀ
harvestingꢀ thatꢀ inꢀ turnꢀ altersꢀ theꢀ enhancementꢀ ofꢀ electricꢀ particlesꢀtowardꢀtheꢀovergrowthꢀwithꢀPt.ꢀTheꢀreductionꢀofꢀPtꢀ
3
2
+
tookꢀplaceꢀinꢀtheꢀpresenceꢀofꢀAg ꢀionsꢀthatꢀensuredꢀformationꢀ
near-fieldꢀandꢀtheꢀgenerationꢀofꢀenergeticꢀchargeꢀcarriers. ꢀ
Theꢀ presenceꢀ ofꢀ co-catalystꢀ onꢀ theꢀ particlesꢀ surfaceꢀ canꢀ ofꢀsmallꢀdomains,ꢀpartiallyꢀcoveringꢀtheꢀsurface.ꢀInꢀtheꢀabsenceꢀ
ꢀ
additionallyꢀ improveꢀ theꢀ rateꢀ ofꢀ theꢀ desiredꢀ reaction.ꢀ Whileꢀ ofꢀsilver,ꢀtheꢀplatinumꢀreducesꢀinꢀtheꢀformꢀofꢀaꢀcompactꢀshellꢀ
bareꢀ plasmonicꢀ particlesꢀ mayꢀ exhibitꢀ negligibleꢀ catalyticꢀ hinderingꢀtheꢀinteractionꢀofꢀlightꢀwithꢀgoldꢀandꢀthusꢀdecreasingꢀ
3
3,35
activityꢀitꢀcanꢀbeꢀimprovedꢀinꢀtheꢀpresenceꢀinꢀtheꢀpresenceꢀofꢀaꢀ theꢀphotochemicalꢀperformance.
ꢀ
ꢀꢀ
Theꢀ analysisꢀ byꢀ Scanningꢀ Electronꢀ Microscopyꢀ (SEM)ꢀ
3
3
34
16
surfaceꢀmetal,ꢀsuchꢀasꢀPt, ꢀPd, ꢀCo, ꢀorꢀNi. ꢀTheseꢀsurfaceꢀ
35
metalsꢀfacilitateꢀbindingꢀeventsꢀofꢀtheꢀmoleculesꢀthatꢀundergoꢀ confirmedꢀ theꢀ presenceꢀ ofꢀ Ptꢀ onꢀ Auꢀ particles.ꢀ Asꢀ shownꢀ inꢀ
chemicalꢀconversion,ꢀdecreasingꢀtheꢀkineticꢀenergyꢀrequiredꢀtoꢀ Figureꢀ 1ꢀ a,ꢀ dꢀ andꢀ g,ꢀ theꢀ presenceꢀ ofꢀ brightꢀ spotsꢀ onꢀ theꢀ
runꢀtheꢀreaction.ꢀTheꢀspatialꢀdistributionꢀofꢀco-catalystꢀonꢀtheꢀ particlesꢀsurfaceꢀcorrespondꢀtoꢀPtꢀdomains.ꢀTheꢀEDXꢀmappingꢀ
36
photocatalystꢀmetalꢀisꢀalsoꢀanꢀimportantꢀfactor.ꢀWengꢀetꢀal. ꢀ onꢀ theꢀ individualꢀ particleꢀ furtherꢀ revealedꢀ thatꢀ Ptꢀ domainsꢀ
haveꢀ shownꢀ thatꢀ non-centrosymmetricꢀ architectureꢀ inꢀ CdSe- distributeꢀmostlyꢀonꢀtheꢀedgesꢀofꢀcubesꢀandꢀstars,ꢀwhileꢀinꢀtheꢀ
Au-PtꢀhybridꢀsystemꢀimprovesꢀhotꢀelectronsꢀtransferꢀfromꢀAuꢀ caseꢀ ofꢀ goldꢀ nanorods,ꢀ Ptꢀ locatesꢀ onlyꢀ onꢀ theꢀ tips.ꢀ Suchꢀ
andꢀPtꢀsubunits,ꢀminimisingꢀtheirꢀthermalisation.ꢀThus,ꢀfindingꢀ differenceꢀ inꢀ spatialꢀ distributionꢀ relatesꢀ toꢀ theꢀ crystallineꢀ
theꢀ mostꢀ optimalꢀ shapeꢀ andꢀ surfaceꢀ propertiesꢀ ofꢀ theꢀ structureꢀ ofꢀ theꢀ initialꢀ goldꢀ nanoparticles.ꢀ Single-crystallineꢀ
plasmonicꢀnanoparticlesꢀisꢀcurrentlyꢀaꢀkeyꢀtaskꢀinꢀtheꢀstronglyꢀ goldꢀnanorodsꢀexhibitꢀhigherꢀsurfaceꢀanisotropyꢀthatꢀallowsꢀPtꢀ
progressingꢀfieldꢀofꢀall-metalꢀphotochemistry.ꢀ
ꢀ
depositionꢀ onlyꢀ onꢀ theꢀ tips.ꢀ Theꢀ lateralꢀ partꢀ ofꢀ theꢀ rodsꢀ isꢀ
40
Theꢀ presentꢀ workꢀ focusesꢀ onꢀ comparativeꢀ studyꢀ ofꢀ theꢀ blockedꢀ byꢀ silver-basedꢀ species. ꢀ Althoughꢀ cubesꢀ areꢀ alsoꢀ
shapeꢀ effectꢀ ofꢀ theꢀ goldꢀ nanoparticlesꢀ onꢀ theꢀ single-crystalline,ꢀ theꢀ surfaceꢀ energyꢀ isꢀ ratherꢀ isotropicꢀ –ꢀ
photoregenerationꢀ ofꢀ theꢀ coenzymeꢀ moleculesꢀ (nicotinamideꢀ equallyꢀcoveredꢀbyꢀ{111}ꢀfacets.ꢀThus,ꢀtheꢀPtꢀreductionꢀtakesꢀ
adenineꢀdinucleotideꢀ-ꢀNADH)ꢀusingꢀtriethanolamineꢀ(TEAOH)ꢀ placesꢀsimultaneouslyꢀonꢀtheꢀedgesꢀandꢀtheꢀflatꢀparts.ꢀInꢀtheꢀ
asꢀ aꢀ sacrificialꢀ agent.ꢀ Weꢀ haveꢀ recentlyꢀ shownꢀ thatꢀ Pt- caseꢀofꢀnanostars,ꢀtheꢀPtꢀreductionꢀtakesꢀplaceꢀonꢀtheꢀwholeꢀ
decoratedꢀ goldꢀ nanorodsꢀ canꢀ regenerateꢀ NADHꢀ whenꢀ spikesꢀsurface.ꢀAlthoughꢀstarsꢀtipsꢀareꢀhighlyꢀanisotropic,ꢀtheꢀ
33
irradiatedꢀ withꢀ visibleꢀ orꢀ infraredꢀ light. ꢀ Here,ꢀ weꢀ testedꢀ twinnedꢀplanesꢀ(visibleꢀonꢀHRTEMꢀimages)ꢀserveꢀasꢀnucleationꢀ
41
cubes,ꢀ rodsꢀ andꢀ star-likeꢀ nanoparticlesꢀ inꢀ photochemicalꢀ andꢀ pointsꢀforꢀPt, ꢀleadingꢀtoꢀtheꢀhomogenousꢀdistributionꢀofꢀco-
photoelectrochemicalꢀ experiments,ꢀ showingꢀ thatꢀ goldꢀ catalystꢀdomains.ꢀꢀ
nanostarsꢀareꢀtheꢀmostꢀcatalyticallyꢀactive.ꢀWeꢀattributeꢀsuchꢀ
behaviourꢀ toꢀ theꢀ greaterꢀ capacityꢀ ofꢀ lightꢀ harvestingꢀ byꢀ
nanostarsꢀ inꢀ aggregatedꢀ stateꢀ -ꢀ plasmonicꢀ substratesꢀ -ꢀ asꢀ
comparedꢀ toꢀ rodsꢀ orꢀ cubes.ꢀ Numericalꢀ simulationsꢀ ofꢀ
multiparticleꢀsystemꢀconfirmedꢀexperimentalꢀevidences.ꢀꢀ
ꢀ
Fabricationꢀofꢀplasmonicꢀsubstratesꢀcontainingꢀ
particlesꢀofꢀdifferentꢀshapesꢀ
Priorꢀtheꢀsynthesisꢀofꢀtheꢀparticlesꢀweꢀassumedꢀthatꢀtheꢀstar-
likeꢀ geometryꢀ consistsꢀ ofꢀ isotropicꢀ coreꢀ andꢀ one-dimensionalꢀ
spikesꢀ pointingꢀ outwards.ꢀ Thus,ꢀ toꢀ performꢀ aꢀ comparativeꢀ
photochemicalꢀ studyꢀ asꢀ preciseꢀ asꢀ possible,ꢀ weꢀ decidedꢀ toꢀ
synthesiseꢀcube-likeꢀnanoparticlesꢀwithꢀtheꢀdimensionsꢀsimilarꢀ
toꢀ thatꢀ ofꢀ nanostarsꢀ core,ꢀ andꢀ nanorodsꢀ withꢀ dimensionsꢀ
similarꢀ toꢀ thatꢀ ofꢀ nanostarꢀ spikes.ꢀ Weꢀ choseꢀ seed-mediatedꢀ
growthꢀ approachꢀ toꢀ obtainꢀ nanoparticlesꢀ ofꢀ threeꢀ desiredꢀ
37
38
39
shapes:ꢀ cubic, ꢀ rodlike, ꢀ andꢀ star-like ꢀ (Figureꢀ 1).ꢀ Forꢀ goldꢀ
nanocubes,ꢀ theꢀ meanꢀ valueꢀ ofꢀ edgeꢀ wasꢀ equalꢀtoꢀ 31.9ꢀ ±ꢀ 1.9ꢀ
nm.ꢀ Forꢀ goldꢀ nanorods,ꢀ theꢀ averageꢀ widthꢀ andꢀ lengthꢀ wereꢀ
ꢀ
45.2ꢀ±ꢀ5.1ꢀandꢀ10.9ꢀ±ꢀ1.0ꢀnm,ꢀrespectivelyꢀ(aspectꢀratioꢀ=ꢀ4.1).ꢀ
Inꢀtheꢀcaseꢀofꢀnanostars,ꢀtheꢀcoreꢀdiameterꢀwasꢀ39.9ꢀ±ꢀ5.9ꢀnm.ꢀ
Figureꢀ1.ꢀElectronꢀmicroscopyꢀanalysisꢀofꢀPt-coatedꢀgoldꢀnanoparticlesꢀwithꢀdifferentꢀ
shapes:ꢀcubeꢀ(a-c),ꢀrodꢀ(d-f)ꢀandꢀstarꢀ(g-i).ꢀSEMꢀimagesꢀ(a,ꢀd,ꢀg)ꢀandꢀEDXꢀmappingꢀ(b,ꢀe,ꢀ
Regardingꢀtheꢀspikes,ꢀtheꢀlengthꢀandꢀwidthꢀatꢀtheꢀbaseꢀwereꢀ h)ꢀ confirmingꢀ theꢀ presenceꢀ ofꢀ Ptꢀ onꢀ theꢀ goldꢀ surface.ꢀ (c,ꢀ f,ꢀ i)ꢀ HRTEMꢀ imagesꢀ ofꢀ theꢀ
4
1.8ꢀ ±ꢀ 9.6ꢀ andꢀ 13.1ꢀ ±ꢀ 2.8ꢀ nm,ꢀ respectively.ꢀ Detailedꢀ nanoparticlesꢀ showingꢀ epitaxialꢀ overgrowthꢀ ofꢀ theꢀ Ptꢀ domains.ꢀ Allꢀ particlesꢀ wereꢀ
coveredꢀwithꢀ10%ꢀmolꢀofꢀPt.ꢀꢀ
geometricalꢀ characterizationꢀ andꢀ TEMꢀ imagesꢀ ofꢀ theꢀ
2
ꢀ|ꢀJ.ꢀName.,ꢀ2012,ꢀ00,ꢀ1-3ꢀ
Thisꢀjournalꢀisꢀ©ꢀTheꢀRoyalꢀSocietyꢀofꢀChemistryꢀ20xxꢀ
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Journal of Materials Chemistry A
Page 4 of 9
JournalꢀNameꢀ
Theꢀ HRTEMꢀ analysisꢀ revealedꢀ thatꢀ Ptꢀ domainsꢀ areꢀ
ꢀARTICLEꢀ
ꢀ
Photochemistryꢀandꢀphotoelectrochemi
characterisationꢀofꢀplasmonicꢀsubstratesꢀꢀ
V
c
ie
a
w Article Online
l
ꢀ
DOI: 10.1039/C6TA01770C
crystallineꢀ (Figureꢀ 1ꢀ c,ꢀ f,ꢀ i),ꢀ thus,ꢀ confirmingꢀ theꢀ presenceꢀ ofꢀ
tightꢀheterojunctionꢀbetweenꢀbothꢀmetalsꢀ(Forꢀmoreꢀdetailedꢀ
characterisationꢀ seeꢀ supportingꢀ information,ꢀ Figureꢀ S3).ꢀ
Importantly,ꢀtheꢀsizeꢀofꢀPtꢀdomainsꢀwasꢀsimilarꢀinꢀallꢀsamples:ꢀ
ꢀ
Priorꢀ photochemicalꢀ characterisation,ꢀ theꢀ particlesꢀ wereꢀ
33
immobilisedꢀ onꢀ solidꢀ substrateꢀ (plasmonicꢀ substrate). ꢀ Slowꢀ
evaporationꢀ ofꢀ theꢀ solutionꢀ containingꢀ bareꢀ goldꢀ particlesꢀ orꢀ
Pt-coatedꢀonꢀaꢀglassꢀsubstrateꢀledꢀtoꢀtheꢀformationꢀofꢀopaqueꢀ
filmsꢀconsistingꢀofꢀrandomlyꢀdistributedꢀparticlesꢀ(FigureꢀS7).ꢀInꢀ
allꢀcasesꢀweꢀkeptꢀconstantꢀamountꢀofꢀmetallicꢀgoldꢀ(5ꢀmg).ꢀꢀ
2
0
ꢀ
.0ꢀ±ꢀ0.4ꢀnmꢀ(nanostars),ꢀ2.4ꢀ±ꢀ0.5ꢀnmꢀ(nanocubes)ꢀandꢀ2.8ꢀ±ꢀ
.5ꢀnmꢀꢀ(nanorods).ꢀ ꢀ
TheꢀUV-vis-NIRꢀmeasurementsꢀofꢀtheꢀcolloidalꢀsolutionsꢀofꢀ
bareꢀ andꢀ Pt-coatedꢀ particlesꢀ confirmedꢀ successfulꢀ Ptꢀ
reduction.ꢀRegardlessꢀofꢀtheꢀinitialꢀshapeꢀofꢀgoldꢀparticles,ꢀtheꢀ
presenceꢀofꢀplatinumꢀcausedꢀtheꢀredshiftꢀofꢀlocalisedꢀsurfaceꢀ
plasmonꢀ bandsꢀ (LSPB)ꢀ thatꢀ isꢀ dueꢀ toꢀ relativeꢀ changesꢀ inꢀ theꢀ
aspectꢀratio.ꢀForꢀtheꢀgoldꢀnanocubes,ꢀtheꢀplasmonꢀbandꢀshiftedꢀ
fromꢀ557ꢀtoꢀ570ꢀnmꢀ(Figureꢀ2a),ꢀwhileꢀInꢀtheꢀcaseꢀofꢀnanorodsꢀ
andꢀnanostarsꢀtheꢀlongitudinalꢀplasmonꢀbandsꢀredshiftedꢀbyꢀ57ꢀ
andꢀ36ꢀnm,ꢀrespectivelyꢀ(Figureꢀ2b,ꢀc).ꢀToꢀfurtherꢀconfirmꢀsuchꢀ
opticalꢀ behavingꢀ weꢀ performedꢀ numericalꢀ simulationsꢀ ofꢀ theꢀ
particlesꢀwithꢀdifferentꢀmorphologyꢀusingꢀwaterꢀasꢀaꢀmedium.ꢀ
Weꢀemployedꢀtheꢀmethodologyꢀthatꢀimplementsꢀacceleratedꢀ
calculationsꢀ basedꢀ onꢀ surfaceꢀ integralꢀ equationsꢀ withꢀ theꢀ
methodꢀ ofꢀ momentsꢀ formulationꢀ andꢀ theꢀ multilevelꢀ fastꢀ
ꢀ
Plasmonicꢀ substratesꢀ containingꢀ differentꢀ particleꢀ shapesꢀ
wereꢀsubjectedꢀtowardꢀNADHꢀphotoregeneration.ꢀInꢀaꢀtypicalꢀ
experiment,ꢀtheꢀsubstrateꢀwasꢀimmersedꢀinꢀaꢀmixtureꢀ(1ꢀmL)ꢀ
+
containingꢀNAD ꢀ(1ꢀmM),ꢀphosphateꢀbufferꢀ(pH8)ꢀandꢀTEAOHꢀ
+
1ꢀ M).ꢀ Theꢀ reductionꢀ ofꢀ NAD ꢀ wasꢀ initiatedꢀ underꢀ lightꢀ
(
2
irradiationꢀ (400ꢀ –ꢀ 1200ꢀ nm,ꢀ 150ꢀ mWꢀ cm )ꢀ atꢀ 35ꢀ °C.ꢀ Theꢀ
plasmonicꢀ substratesꢀ couldꢀ beꢀ removedꢀ fromꢀ theꢀ solutionꢀ atꢀ
anyꢀ timeꢀ forꢀ spectroscopicꢀ validationꢀ ofꢀ theꢀ regenerationꢀ
processꢀ (Figureꢀ S5).ꢀ Sinceꢀ NADHꢀ exhibitsꢀ aꢀ characteristicꢀ
absorptionꢀbandꢀatꢀ340ꢀnmꢀ(molarꢀabsorptionꢀcoefficientꢀ6220ꢀ
1
1
M cm ),ꢀUV-Visꢀspectroscopyꢀprovidesꢀaꢀconvenientꢀqualitativeꢀ
controlꢀofꢀtheꢀprocess.ꢀOverall,ꢀsixꢀsubstratesꢀwereꢀevaluated,ꢀ
threeꢀ containingꢀ bareꢀ goldꢀ nanoparticlesꢀ andꢀ otherꢀ threeꢀ
containingꢀPt-coatedꢀnanoparticles.ꢀRegardlessꢀofꢀtheꢀparticlesꢀ
shape,ꢀ theꢀ regenerationꢀ ofꢀ NADHꢀ wasꢀ foundꢀ toꢀ beꢀ ~6ꢀ timesꢀ
higherꢀforꢀPt-coatedꢀparticlesꢀasꢀcomparedꢀtoꢀtheꢀbareꢀones.ꢀ
Importantly,ꢀ theꢀ bestꢀ performingꢀ nanoparticlesꢀ wereꢀ goldꢀ
nanostarsꢀbothꢀwithoutꢀandꢀwithꢀPtꢀonꢀtheꢀsurface,ꢀsuggestingꢀ
thatꢀ branchedꢀ geometryꢀ isꢀ moreꢀ efficientꢀ inꢀ theꢀ presentꢀ
processꢀ(Figureꢀ3).ꢀꢀ
42,43
multipoleꢀ algorithm.
ꢀ Theꢀ inputꢀ parametersꢀ ofꢀ individualꢀ
particlesꢀwereꢀbasedꢀonꢀtheꢀTEMꢀandꢀSEMꢀmeasurements.ꢀForꢀ
nanocubes,ꢀPtꢀwasꢀlocatedꢀonꢀtheꢀedges,ꢀwhileꢀforꢀnanorods,ꢀ
onꢀtheꢀtipsꢀ(Figureꢀ2d,ꢀeꢀ-ꢀinsets).ꢀInꢀtheꢀcaseꢀofꢀtheꢀnanostars,ꢀ
theꢀPtꢀshellꢀwasꢀplacedꢀonꢀtheꢀentireꢀsurfaceꢀofꢀspikesꢀ(Figureꢀ
2
fꢀ-ꢀinset)ꢀ(Forꢀdetailedꢀparameterisationꢀofꢀeachꢀparticleꢀseeꢀ
Figureꢀ S4).ꢀ Theꢀ simulatedꢀ spectraꢀ correlateꢀ wellꢀ withꢀ
experimentalꢀresults,ꢀshowingꢀexpectedꢀredshiftꢀandꢀdumpingꢀ
ofꢀ theꢀ plasmonꢀ band,ꢀ confirmingꢀ theꢀ strongꢀ interactionꢀ
ꢀ
Typically,ꢀ theꢀ photoregenerationꢀ ofꢀ NADHꢀ involvesꢀ theꢀ
-
+
44,45
transferꢀ ofꢀ 2e ꢀ andꢀ H ꢀ fromꢀ TEAOHꢀ toꢀ NADH,ꢀ whichꢀ isꢀ
accomplishedꢀ byꢀ simultaneousꢀ oxidationꢀ andꢀ reductionꢀ
reactions.ꢀ Toꢀ ensureꢀ thatꢀ theꢀ processꢀ takesꢀ placeꢀ onꢀ theꢀ
particlesꢀ surface,ꢀ weꢀ evaluatedꢀ theꢀ interactionꢀ ofꢀ TEAOHꢀ
moleculesꢀ withꢀ plasmonicꢀ nanoparticlesꢀ byꢀ comparingꢀ theꢀ
positionꢀofꢀtheꢀmaximumꢀofꢀLSPBꢀinꢀwaterꢀandꢀ0.1ꢀMꢀTEAOH.ꢀ
TheꢀLSPBꢀblueꢀshiftedꢀ2ꢀnmꢀinꢀtheꢀcaseꢀofꢀcubesꢀandꢀ3ꢀnmꢀforꢀ
nanorodsꢀandꢀstarsꢀ(FigureꢀS6).ꢀSuchꢀbehavingꢀisꢀtypicalꢀforꢀtheꢀ
particlesꢀ thatꢀ areꢀ exposedꢀ toꢀ theꢀ electron-richꢀ environmentꢀ
andꢀ provesꢀ theꢀ spontaneousꢀ electronꢀ injectionꢀ fromꢀ theꢀ
betweenꢀbothꢀmetals.
ꢀꢀ
46
moleculesꢀtoꢀparticles. ꢀAlthoughꢀtheꢀPtꢀdomainsꢀareꢀcrucialꢀ
forꢀoxidationꢀofꢀTEAOHꢀmolecules,ꢀitꢀisꢀhardꢀtoꢀassessꢀtoꢀwhatꢀ
+
extendꢀ theꢀ reductionꢀ ofꢀ NAD ꢀ toꢀ NADHꢀ takesꢀ placeꢀ onꢀ
33
platinum. ꢀSinceꢀtheꢀphotooxidationꢀofꢀTEAOHꢀisꢀaꢀmultistepꢀ
processꢀ involvingꢀ theꢀ formationꢀ ofꢀ manyꢀ intermediateꢀ
47
species, ꢀ weꢀ foundꢀ itꢀ appropriateꢀ toꢀ performꢀ separateꢀ
photoelectrochemicalꢀanalysisꢀofꢀtheꢀoxidationꢀreaction.ꢀ
ꢀ
ꢀ
Figureꢀ2.ꢀOpticalꢀcharacterisationꢀofꢀtheꢀnanoparticlesꢀinꢀsolution.ꢀ(a-c)ꢀexperimentalꢀ
andꢀ(d-f)ꢀsimulatedꢀspectraꢀofꢀtheꢀbareꢀgoldꢀ(red)ꢀandꢀPt-coatedꢀ(grey)ꢀnanoparticlesꢀ
withꢀcubicꢀ(a,d),ꢀrod-likeꢀ(b,ꢀe)ꢀandꢀstar-likeꢀmorphologyꢀ(c,ꢀf).ꢀInsetsꢀinꢀ(d-e)ꢀrepresentꢀ
three-dimensionalꢀimagesꢀofꢀtheꢀparticlesꢀusedꢀinꢀsimulations.ꢀ
Thisꢀjournalꢀisꢀ©ꢀTheꢀRoyalꢀSocietyꢀofꢀChemistryꢀ20xxꢀ
J.ꢀName.,ꢀ2013,ꢀ00,ꢀ1-3ꢀ|ꢀ3ꢀ
Pleaseꢀdoꢀnotꢀadjustꢀmarginsꢀ

Page 5 of 9
Journal of Materials Chemistry A
ARTICLEꢀ
JournalꢀNameꢀ
components,ꢀdependsꢀonꢀtheꢀparticlesꢀshapeꢀandVꢀieinwcArreticaleseOsnꢀlinineꢀ
DOI: 10.1039/C6TA01770C
theꢀfollowingꢀorder:ꢀcubes,ꢀrods,ꢀandꢀstars,ꢀwhichꢀisꢀinꢀaꢀgoodꢀ
agreementꢀ withꢀ photochemicalꢀ reactionsꢀ (Figureꢀ 3).ꢀ Theꢀ
2
photocurrentꢀofꢀtheꢀnanostarsꢀaddedꢀ250ꢀµA/cm ꢀafterꢀ10ꢀsꢀofꢀ
illumination,ꢀ whichꢀ isꢀ 3.5ꢀ andꢀ 1.5ꢀ timesꢀ higherꢀ thanꢀ thatꢀ ofꢀ
nanocubesꢀ andꢀ nanorods,ꢀ respectively.ꢀ Aꢀ similarꢀ trendꢀ weꢀ
foundꢀ forꢀ theꢀ “fast”ꢀ component:ꢀ theꢀ photocurrentꢀ ofꢀ theꢀ
nanostarsꢀ wasꢀ 2.5ꢀ andꢀ 1.5ꢀ timesꢀ higherꢀ thanꢀ thatꢀ ofꢀ theꢀ
nanocubesꢀ andꢀ nanorods,ꢀ respectively.ꢀ SEMꢀ inspectionꢀ
confirmedꢀmorphologicalꢀstabilityꢀofꢀtheꢀnanoparticlesꢀ(Figureꢀ
S10).ꢀ Overall,ꢀ theꢀ photoelectrochemicalꢀ measurementsꢀ
correlateꢀ withꢀ photochemicalꢀ reaction,ꢀ showingꢀ thatꢀ
photoelectrocatalyticꢀ effectꢀ playsꢀ anꢀ importantꢀ roleꢀ andꢀ isꢀ
strictlyꢀrelatedꢀtoꢀtheꢀparticlesꢀshape.ꢀꢀ
ꢀ
Figureꢀ3.ꢀPhotochemicalꢀregenerationꢀofꢀcofactorꢀmoleculesꢀ(NADH)ꢀunderꢀvisibleꢀlightꢀ
irradiationꢀ onꢀ theꢀ plasmonicꢀ substrateꢀ containingꢀ differentꢀ particlesꢀ shapes.ꢀ (inset)ꢀ
Schemeꢀ showingꢀ theꢀ reactionꢀ ofꢀ simultaneousꢀ oxidationꢀ ofꢀ TEAOHꢀ andꢀ reductionꢀ ofꢀ
+
NAD ꢀ toꢀ NADH.ꢀ Theꢀ finalꢀ concentrationꢀ ofꢀ NADHꢀ afterꢀ twoꢀ hoursꢀ reactionꢀ inꢀ theꢀ
presenceꢀ ofꢀ plasmonicꢀ substrateꢀ containingꢀ differentꢀ particleꢀ shapes.ꢀ Redꢀ barsꢀ
representedꢀtheꢀconcentrationꢀofꢀtheꢀNADHꢀwhenꢀbareꢀnanoparticlesꢀwereꢀused;ꢀtheꢀ
greyꢀcolumnsꢀcorrespondꢀtoꢀPt-coatedꢀnanoparticles.ꢀInꢀallꢀexperiments,ꢀtheꢀsubstratesꢀ
+
wereꢀimmersedꢀinꢀtheꢀsolutionꢀcontainingꢀTEAOHꢀ(1M),ꢀNAD ꢀ(1ꢀmM)ꢀandꢀphosphateꢀ
2
bufferꢀ(pH8)ꢀandꢀirradiatedꢀwithꢀlightꢀ(400-1200ꢀnm,ꢀ150ꢀmW/cm )ꢀatꢀ35ꢀ°Cꢀforꢀtwoꢀ
hours.ꢀ
ꢀ
ꢀ
Photoelectrochemicalꢀmeasurementsꢀconfirmedꢀtheꢀtrendsꢀ
observedꢀ forꢀ differentꢀ particlesꢀ shapesꢀ inꢀ photochemicalꢀ
reactions.ꢀ Weꢀ performedꢀ photoelectrochemicalꢀ studiesꢀ ofꢀ
TEAOHꢀoxidationꢀonꢀtheꢀelectrodeꢀcoatedꢀwithꢀnanoparticles.ꢀ
Weꢀ usedꢀ three-electrodeꢀ systemꢀ (DropSens)ꢀ consistingꢀ ofꢀ
carbonꢀworkingꢀelectrode,ꢀsilverꢀpseudo-reference,ꢀandꢀcarbonꢀ
counterꢀ electrode.ꢀ Theꢀ solutionsꢀ containingꢀ particlesꢀ wereꢀ
drop-castedꢀonꢀtheꢀworkingꢀelectrodesꢀandꢀslowlyꢀevaporatedꢀ
atꢀ theꢀ ambientꢀ conditionꢀ toꢀ maximiseꢀ theirꢀ homogenousꢀ
distribution.ꢀAlthoughꢀweꢀnoticedꢀtheꢀinevitableꢀformationꢀofꢀ
coffeeꢀringsꢀonꢀtheꢀelectrodesꢀedges,ꢀtheꢀsurfaceꢀcoverageꢀwasꢀ
similarꢀ inꢀ allꢀ samplesꢀ containingꢀ particlesꢀ ofꢀ differentꢀ shapesꢀ
(
ꢀ
FigureꢀS7).ꢀ
Theꢀelectrodeꢀwasꢀcoveredꢀwithꢀaꢀ0.05ꢀmLꢀofꢀtheꢀsolutionꢀ
ꢀ
containingꢀ TEAOHꢀ (1M)ꢀ andꢀ phosphateꢀ buffer.ꢀ Toꢀ obtainꢀtheꢀ
amperometricꢀi-tꢀcurve,ꢀtheꢀcurrentꢀwasꢀstabilisedꢀforꢀ6ꢀminꢀatꢀ
circuitꢀpotentialꢀ(ca.ꢀ-0.36ꢀV).ꢀThenꢀtheꢀlightꢀwasꢀswitchedꢀonꢀ
forꢀ10ꢀsecondsꢀandꢀanꢀimmediateꢀincreaseꢀinꢀtheꢀcurrentꢀwasꢀ
Figureꢀ 4.ꢀ Photoelectrochemicalꢀ characterisationꢀ ofꢀ TEAOHꢀ oxidationꢀ onꢀ theꢀ
nanoparticlesꢀwithꢀdifferentꢀshapes.ꢀ(a)ꢀAmperometricꢀi-tꢀcurvesꢀforꢀbareꢀcubes,ꢀrodsꢀ
andꢀstarsꢀ(redꢀlines)ꢀandꢀplatinum-coatedꢀ(greyꢀlines).ꢀꢀPhotocurrentꢀexhibitsꢀ‘fast’ꢀ(0.5ꢀ
s)ꢀ andꢀ ‘slow’ꢀ componentꢀ (10ꢀ s).ꢀ (b)ꢀ Fastꢀ currentꢀ componentꢀ forꢀ threeꢀ samplesꢀ
observedꢀ(Figureꢀ4).ꢀWeꢀnoticedꢀthatꢀtheꢀpresenceꢀofꢀPtꢀonꢀtheꢀ containingꢀPt-coatedꢀparticlesꢀofꢀdifferentꢀshapesꢀshowingꢀbetterꢀperformanceꢀofꢀstarsꢀ
goldꢀsurfaceꢀwasꢀcrucialꢀtoꢀoxidiseꢀTEAOH.ꢀInꢀtheꢀpresenceꢀofꢀ thanꢀrodsꢀandꢀcubes.ꢀInꢀallꢀexperiments,ꢀtheꢀelectrodesꢀwereꢀimmersedꢀinꢀtheꢀsolutionꢀ
containingꢀTEAOHꢀ(1M),ꢀphosphateꢀbufferꢀ(pHꢀ8)ꢀandꢀirradiatedꢀwithꢀlightꢀ(400-1200ꢀ
Pt,ꢀ theꢀ photocurrentꢀ wasꢀ approximatelyꢀ tenꢀ timesꢀ higherꢀ asꢀ
comparedꢀ toꢀ theꢀ photocurrentꢀ obtainedꢀ fromꢀ theꢀ bareꢀ goldꢀ
2
nm,ꢀ150ꢀmW/cm )ꢀatꢀ0ꢀVꢀatꢀ25ꢀ°C.ꢀEachꢀelectrodeꢀwasꢀcoveredꢀbyꢀtheꢀsameꢀamountꢀofꢀ
nanoparticlesꢀinꢀtermꢀofꢀmetallicꢀgold.ꢀ
nanoparticlesꢀregardlessꢀtoꢀtheirꢀshapeꢀ(redꢀlineꢀinꢀFigureꢀ4aꢀ
andꢀ Figureꢀ S8ꢀ andꢀ S9).ꢀ Suchꢀ improvementꢀ isꢀ dueꢀ toꢀ lowꢀ
interfacialꢀenergyꢀbarrierꢀbetweenꢀPtꢀandꢀAuꢀandꢀsuggestsꢀtheꢀ
ꢀ
SinceꢀtheꢀpresenceꢀofꢀPtꢀonꢀtheꢀgoldꢀparticlesꢀsurfaceꢀwasꢀ
crucialꢀforꢀachievingꢀtheꢀphotochemicalꢀreaction,ꢀweꢀmeasuredꢀ
theꢀrelativeꢀamountꢀofꢀthisꢀmetalꢀforꢀtheꢀdifferentꢀplasmonicꢀ
substrates.ꢀ Forꢀ estimationꢀ ofꢀ Pt/Auꢀ ratioꢀ weꢀ usedꢀ XPSꢀ
techniquesꢀ (Figureꢀ S11),ꢀ showingꢀ thatꢀ starsꢀ andꢀ cubesꢀ
containedꢀaꢀsimilarꢀamountꢀofꢀsurfaceꢀplatinumꢀwithꢀrespectꢀtoꢀ
gold:ꢀPt/Auꢀ=ꢀ0.22ꢀ(Stars),ꢀPt/Auꢀ=ꢀ0.20ꢀ(cubes).ꢀGoldꢀnanorodsꢀ
containedꢀlessꢀPtꢀ(Pt/Auꢀ=ꢀ0.09)ꢀthatꢀisꢀdueꢀtheꢀlimitedꢀsurfaceꢀ
areaꢀaccessibleꢀforꢀPtꢀ-ꢀtips.ꢀRelativelyꢀsimilarꢀvaluesꢀofꢀPtꢀandꢀ
Auꢀ forꢀ differentꢀ shapesꢀ suggestꢀ thatꢀ theꢀ morphologyꢀ ofꢀ theꢀ
initialꢀ particlesꢀ isꢀ aꢀ keyꢀ parameterꢀ thatꢀ determinesꢀ theꢀ
distributionꢀ ofꢀ theꢀ particlesꢀ inꢀ theꢀ filmꢀ andꢀ definesꢀ theirꢀ
interactionꢀwithꢀincidentꢀlight.ꢀ
36
contributionꢀofꢀtheꢀphotoelectrocatalyticꢀprocess. ꢀꢀ
Forꢀ allꢀ theꢀ particlesꢀ coatedꢀ withꢀ Pt,ꢀ theꢀ photocurrentꢀ
ꢀ
consistedꢀofꢀtwoꢀtemporalꢀcomponents:ꢀaꢀfastꢀcomponentꢀthatꢀ
raisedꢀ withꢀ timeꢀ constantꢀ ~0.5ꢀ sꢀ andꢀ anꢀ additionalꢀ slowꢀ
componentꢀ thatꢀ constantlyꢀ increasedꢀ withꢀ aꢀ timeꢀ ofꢀ ~10ꢀ sꢀ
(
Figureꢀ 4a).ꢀ Theꢀ originꢀ ofꢀ theꢀ “fast”ꢀ componentsꢀ isꢀ theꢀ
contributionꢀ ofꢀ theꢀ photoelectrocatalyticꢀ processꢀ thatꢀ canꢀ
involveꢀhotꢀelectronsꢀgenerationꢀthatꢀimmediatelyꢀflowꢀtoꢀtheꢀ
48
counterꢀelectrode. ꢀTheꢀ“slow”ꢀcomponentsꢀisꢀaꢀresultꢀofꢀtheꢀ
49
photothermalꢀ effectꢀ ofꢀ theꢀ illumination. ꢀ Importantly,ꢀ theꢀ
magnitudeꢀ ofꢀ photocurrent,ꢀ forꢀ bothꢀ slowꢀ andꢀ fastꢀ
4
ꢀ|ꢀJ.ꢀName.,ꢀ2012,ꢀ00,ꢀ1-3ꢀ
Thisꢀjournalꢀisꢀ©ꢀTheꢀRoyalꢀSocietyꢀofꢀChemistryꢀ20xxꢀ
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Journal of Materials Chemistry A
Page 6 of 9
JournalꢀNameꢀ
ꢀARTICLEꢀ
3
µm ꢀ(Figureꢀ5d),ꢀwithꢀaꢀminimumꢀdistanceꢀbetweenꢀparticlesꢀ
DOI: 10.1039/C6TA01770C
surfaceꢀ ofꢀ 1ꢀ nm.ꢀ Theꢀ calculatedꢀ scatteringꢀ spectraꢀ displayedꢀ
Opticalꢀpropertiesꢀofꢀplasmonicꢀsubstratesꢀ–ꢀ
experimentalꢀandꢀnumericalꢀcharacterisationꢀꢀ
View Article Online
typicalꢀ broadening,ꢀ suggestingꢀ multipleꢀ plasmonꢀ couplings,ꢀ
whichꢀ areꢀ inꢀ aꢀ goodꢀ agreementꢀ withꢀ theꢀ experimentalꢀ
reflectanceꢀspectraꢀ(compareꢀFigureꢀ5bꢀandꢀ5c).ꢀTheseꢀresultsꢀ
indicateꢀ thatꢀ nanostarsꢀ inꢀ aggregatedꢀ modeꢀ scatterꢀ lessꢀ
amountꢀofꢀlightꢀasꢀcomparedꢀtoꢀtheꢀnanocubesꢀorꢀnanorods.ꢀ
Weꢀhypothesise,ꢀthen,ꢀthatꢀsuchꢀopticalꢀresponseꢀisꢀrelatedꢀtoꢀ
theꢀintrinsicꢀshapeꢀofꢀtheꢀindividualꢀbuildingꢀblocks.ꢀDuringꢀtheꢀ
dryingꢀprocess,ꢀtheꢀnanorodsꢀorꢀcubesꢀsedimentꢀin-parallelꢀtoꢀ
theꢀ substrateꢀ surface,ꢀ pointingꢀ sidewiseꢀ towardꢀ theꢀ incidentꢀ
light,ꢀ therebyꢀ increasingꢀ theꢀ contributionꢀ ofꢀ theꢀ specularꢀ
reflection.ꢀ Inꢀ theꢀ caseꢀ ofꢀ nanostars,ꢀ however,ꢀ radialꢀ
distributionꢀ ofꢀ spikesꢀ increasesꢀ theꢀ diffuseꢀ reflection,ꢀ and,ꢀ
therefore,ꢀminimiseꢀtheꢀamountꢀofꢀlightꢀthatꢀisꢀbouncedꢀbackꢀ
toꢀ theꢀ medium.ꢀ Suchꢀ differenceꢀ inꢀ opticalꢀ propertiesꢀ inꢀ
aggregatedꢀ stateꢀ isꢀ especiallyꢀ visibleꢀ inꢀ theꢀ caseꢀ ofꢀ goldꢀ
nanorodsꢀandꢀnanostars.ꢀAlthoughꢀtheꢀmaximumꢀofꢀLSPBꢀforꢀ
bothꢀ geometriesꢀ inꢀ solutionꢀ isꢀ veryꢀ similarꢀ (Figureꢀ 2),ꢀ theꢀ
reflectanceꢀ aboveꢀ 800ꢀ nmꢀ isꢀ muchꢀ largerꢀ inꢀ theꢀ caseꢀ ofꢀ
nanorodsꢀ thanꢀ forꢀ stars,ꢀ confirmingꢀ moreꢀ efficientꢀ lightꢀ
071ꢀ(rods)ꢀandꢀ501ꢀ(nanostars),ꢀfillingꢀaꢀfilm-likeꢀboxꢀofꢀ0.03ꢀ
absorptionꢀbyꢀtheꢀplasmonicꢀsubstrateꢀcontainingꢀnanostars.ꢀ
Basedꢀ onꢀ experimentalꢀ resultsꢀ weꢀ assumeꢀ thatꢀ betterꢀ lightꢀ
absorptionꢀ determinesꢀ theꢀ superiorꢀ photocatalyticꢀ
performanceꢀ ofꢀ theꢀ substrateꢀ containingꢀ nanostars,ꢀ asꢀ
comparedꢀtoꢀtheꢀnanorodsꢀorꢀcubes.ꢀVisualꢀinspectionꢀshowsꢀ
thatꢀtheꢀsubstratesꢀcontainingꢀcubesꢀandꢀrodsꢀareꢀshinierꢀthanꢀ
theꢀ substratesꢀ containingꢀ nanostars,ꢀ whichꢀ areꢀ practicallyꢀ
blackꢀ(seeꢀinsetꢀinꢀFigureꢀ5b).ꢀDiffuseꢀreflectionꢀmeasurementsꢀ
confirmedꢀ suchꢀ observation,ꢀ revealingꢀ thatꢀ theꢀ substratesꢀ
containingꢀ goldꢀ nanorodsꢀ orꢀ cubesꢀ reflectꢀ moreꢀ lightꢀ inꢀ theꢀ
spectralꢀ rangeꢀ aboveꢀ 500ꢀ nmꢀ (Figureꢀ 5b).ꢀ Theꢀ differenceꢀ inꢀ
lightꢀreflectionꢀforꢀallꢀshapesꢀisꢀevenꢀmoreꢀpronouncedꢀatꢀtheꢀ
maximumꢀ ofꢀ theꢀ intensityꢀ ofꢀ theꢀ incidentꢀ lightꢀ (ca.ꢀ 700ꢀ nm)ꢀ
thatꢀ weꢀ usedꢀ inꢀ allꢀ experimentsꢀ (Figureꢀ 5a),ꢀ additionallyꢀ
affectingꢀphotochemicalꢀperformance.ꢀꢀ
ꢀ
Toꢀfurtherꢀcorrelateꢀourꢀexperimentalꢀresults,ꢀweꢀsimulatedꢀ
scatteringꢀ crossꢀ sectionꢀ spectraꢀ ofꢀ substratesꢀ comprisingꢀ
nanoparticlesꢀ withꢀ differentꢀ shapes.ꢀ Eachꢀ modelꢀ plasmonicꢀ
substrateꢀcontainedꢀrandomlyꢀpackedꢀparticles:ꢀꢀ2194ꢀ(cubes),ꢀ
8
ꢀ
Figureꢀ5.ꢀOpticalꢀcharacterisationꢀofꢀtheꢀplasmonicꢀsubstrate.ꢀ(a)ꢀSpectralꢀfeatureꢀofꢀtheꢀlampꢀusedꢀinꢀallꢀexperiments.ꢀ(b)ꢀDiffuseꢀreflectionꢀspectraꢀofꢀsubstratesꢀcomprisingꢀcubes,ꢀ
rodsꢀandꢀstars,ꢀshowingꢀbetterꢀlightꢀharvestingꢀcapacityꢀbyꢀstar-containingꢀplasmonicꢀsubstrates.ꢀ(inset)ꢀImagesꢀofꢀtheꢀsubstratesꢀcomprisingꢀgoldꢀnanoparticles.ꢀ(c)ꢀSimulatedꢀ
scatteringꢀcrossꢀsectionꢀspectraꢀofꢀtheꢀsubstrateꢀcomprisingꢀthreeꢀdifferentꢀmorphologies.ꢀ(d)ꢀTopꢀviewꢀ(upperꢀpanel)ꢀandꢀsideꢀviewꢀ(lowerꢀpanel)ꢀofꢀmodelledꢀarchitecturesꢀusedꢀ
3
forꢀspectraꢀsimulationsꢀinꢀc:ꢀnanoparticlesꢀwithꢀdifferentꢀgeometriesꢀcompactedꢀinꢀaꢀ0.3ꢀμm ꢀboxꢀ(minimumꢀsurface-to-surfaceꢀseparationꢀisꢀ1ꢀnm).ꢀ
ꢀ
ꢀ
ꢀ chargeꢀ separation.ꢀ Singleꢀ spikeꢀ locatedꢀ onꢀ theꢀ starꢀ coreꢀ isꢀ aꢀ
Itꢀisꢀimportantꢀtoꢀstress,ꢀthatꢀspike-like,ꢀorꢀconicalꢀshapeꢀisꢀ non-centrosymmetricꢀobjectꢀbecauseꢀofꢀitsꢀunequalꢀwidthꢀonꢀ
moreꢀ appropriateꢀ forꢀ photochemicalꢀ applicationꢀ thanꢀ theꢀtips.ꢀTherefore,ꢀweꢀpostulateꢀthatꢀtheꢀuniqueꢀgeometryꢀofꢀ
nanorods,ꢀ orꢀ cylinder.ꢀ Although,ꢀ weꢀ cannotꢀ compare,ꢀ atꢀ theꢀ theꢀspikeꢀtipsꢀcanꢀrenderꢀbetterꢀphotochemicalꢀconversionꢀonꢀ
presentꢀ stage,ꢀ theꢀ performanceꢀ ofꢀ spikeꢀ onlyꢀ andꢀ nanorods,ꢀ nanostarsꢀthanꢀotherꢀshapes.ꢀꢀ
weꢀcanꢀsupportꢀourꢀspeculationꢀbyꢀtheꢀrecentꢀworkꢀbyꢀWengꢀetꢀ
ꢀ
Finally,ꢀ theꢀ uniqueꢀ geometryꢀ ofꢀ nanostarsꢀ -ꢀ radialꢀ spikeꢀ
36
al., ꢀ whoꢀ showedꢀ thatꢀ nanoparticlesꢀ thatꢀ lackꢀ theꢀ centralꢀ distributionꢀ -ꢀ hindersꢀ closeꢀ contactꢀ betweenꢀ theꢀ particlesꢀ inꢀ
symmetryꢀ exhibitꢀ betterꢀ performanceꢀ dueꢀ toꢀ moreꢀ efficientꢀ theꢀplasmonicꢀfilm,ꢀfacilitatingꢀtheꢀformationꢀofꢀtheꢀporesꢀthatꢀ
Thisꢀjournalꢀisꢀ©ꢀTheꢀRoyalꢀSocietyꢀofꢀChemistryꢀ20xxꢀ
J.ꢀName.,ꢀ2013,ꢀ00,ꢀ1-3ꢀ|ꢀ5ꢀ
Pleaseꢀdoꢀnotꢀadjustꢀmarginsꢀ

Page 7 of 9
Journal of Materials Chemistry A
ARTICLEꢀ
JournalꢀNameꢀ
improvesꢀtheꢀaccessꢀofꢀtheꢀmoleculesꢀtoꢀtheꢀparticlesꢀsurface.ꢀ acquiredꢀ usingꢀ Dualꢀ Beamꢀ SEM/FIBꢀ Heliosꢀ 450SVꢀiemw iAcrtricolescOonlpineeꢀ
Thus,ꢀ theꢀ activeꢀ surfaceꢀ areaꢀ ofꢀ theꢀ plasmonicꢀ substrateꢀ (FEI,ꢀ Netherlands)ꢀ atꢀ 5ꢀ andꢀ 10ꢀkVꢀ a Dc Oc eI :l e1 0r .a1 0t i3o 9 n/ Cꢀ 6 vT oA l0t 1a 7g7 e0 sC .ꢀ
containingꢀnanostarsꢀcanꢀbeꢀhigherꢀthanꢀthatꢀofꢀtheꢀnanorodsꢀ Photoelectrochemistry.ꢀ Theꢀ electrochemicalꢀ measurementsꢀ
andꢀcubesꢀ(FigureꢀS12).ꢀ
wereꢀ performedꢀ withꢀ anꢀ Autolabꢀ PGSTAT302Nꢀ potentiostatꢀ
controlledꢀbyꢀtheꢀNOVAꢀsoftware.ꢀWeꢀusedꢀdisposableꢀscreen-
printedꢀcarbonꢀelectrodesꢀ(SPCES,ꢀDropSens)ꢀthatꢀconsistꢀofꢀaꢀ
three-electrodeꢀsystemꢀsupportedꢀonꢀaꢀceramicꢀsubstrate.ꢀTheꢀ
workingꢀelectrodeꢀconsistsꢀonꢀcarbonꢀ(4ꢀmmꢀdiameter).ꢀSilverꢀ
andꢀ carbonꢀ wereꢀ usedꢀ asꢀ theꢀ pseudo-referenceꢀ andꢀ counterꢀ
electrodes,ꢀrespectively.ꢀAllꢀmeasurementsꢀwereꢀcarriedꢀoutꢀatꢀ
roomꢀtemperature.ꢀ
Conclusionsꢀ
Inꢀ conclusions,ꢀ weꢀ studiedꢀ theꢀ shapeꢀ effectꢀ ofꢀ theꢀ platinumꢀ
coatedꢀ goldꢀ nanoparticlesꢀ inꢀ theꢀ photoregenerationꢀ ofꢀ
cofactorꢀ
molecules.ꢀ
Inꢀ
photochemicalꢀ
andꢀ
photoelectrochemicalꢀ measurements,ꢀ weꢀ foundꢀ thatꢀ
substratesꢀ comprisingꢀ branchedꢀ nanoparticlesꢀ areꢀ betterꢀ
photocatalystꢀasꢀcomparedꢀtoꢀtheꢀrod-ꢀorꢀcube-likeꢀparticles.ꢀ
Weꢀexplainꢀsuchꢀbehaviourꢀbyꢀtheꢀgeometricalꢀfeaturesꢀofꢀgoldꢀ
nanostarsꢀ thatꢀ efficientlyꢀ harvestꢀ lightꢀ improvingꢀ
photoelectrocatalyticꢀeffect.ꢀFutureꢀworksꢀenvisageꢀtheꢀstudyꢀ
ofꢀphotochemicalꢀperformanceꢀusingꢀnanostarsꢀwithꢀdifferentꢀ
spikesꢀlength.ꢀThisꢀworkꢀopensꢀupꢀpossibilitiesꢀforꢀefficientꢀall-
metalꢀ photochemistryꢀ andꢀ establishꢀ theꢀ basementꢀ forꢀ theꢀ
designꢀofꢀplasmonicꢀcatalyticꢀmaterials.ꢀ
OpticalꢀModelling.ꢀSpectralꢀsimulationsꢀwereꢀcarriedꢀoutꢀusingꢀ
aꢀ numericalꢀ methodꢀ basedꢀ onꢀ theꢀ surfaceꢀ integralꢀ equation-
42
methodꢀ ofꢀ momentsꢀ (SIE-MoM)ꢀ formulationꢀ (M3ꢀ solver). ꢀ
Withꢀ thisꢀ methodology,ꢀ theꢀ metallicꢀ nanostructuresꢀ areꢀ
replacedꢀbyꢀequivalentꢀelectricꢀandꢀmagneticꢀcurrentsꢀplacedꢀ
overꢀtheꢀparticleꢀboundaryꢀsurfacesꢀandꢀinterfaces.ꢀThisꢀbringsꢀ
aboutꢀ importantꢀ advantagesꢀ withꢀ respectꢀ toꢀ volumetricꢀ
approaches,ꢀstronglyꢀreducingꢀtheꢀcomputationꢀdomainꢀasꢀonlyꢀ
theꢀ materialꢀ boundariesꢀ andꢀ interfacesꢀ mustꢀ beꢀ
parameterized.ꢀ Additionally,ꢀ thisꢀ methodologyꢀ yieldsꢀ veryꢀ
accurateꢀ andꢀ stableꢀ solutions,ꢀ particularlyꢀ whenꢀ dealingꢀ withꢀ
resonantꢀmetallicꢀresponse,ꢀasꢀtheꢀsingularꢀbehaviorꢀofꢀfieldsꢀisꢀ
analyticallyꢀ handledꢀ byꢀ theꢀ Green’sꢀ functionꢀ andꢀ itsꢀ
derivatives.ꢀ Throughꢀ Maxwell’sꢀ equationsꢀ andꢀ boundaryꢀ
conditionsꢀforꢀtheꢀtotalꢀfields,ꢀaꢀsetꢀofꢀSIEsꢀisꢀderivedꢀforꢀtheꢀ
unknownꢀ surfaceꢀ equivalentꢀ currents.ꢀ Theseꢀ SIEsꢀ areꢀ
subsequentlyꢀ discretizedꢀ byꢀ applyingꢀ aꢀ Galerkinꢀ MoMꢀ
procedureꢀ inꢀ termsꢀ ofꢀ aꢀ setꢀ ofꢀ basisꢀ andꢀ testingꢀ functions,ꢀ
Experimentalꢀ
Materialsꢀ
Goldꢀ (III)ꢀ chlorideꢀ hydrateꢀ (HAuCl4),ꢀ sodiumꢀ citrateꢀ tribasicꢀ
dihydrate,ꢀ hexadecyltrimethylammoniumꢀ bromideꢀ (CTAB),ꢀ
hexadecyltrimethylammoniumꢀ chlorideꢀ (CTAC),ꢀ silverꢀ nitrateꢀ
(AgNO3),ꢀ hydrochloricꢀ acidꢀ (HCl),ꢀ ascorbicꢀ acid,ꢀ sodiumꢀ
borohydrideꢀ (NaBH4)ꢀ andꢀ potassiumꢀ (II)ꢀ tetrachloroplatinateꢀ
50
leadingꢀtoꢀaꢀdenseꢀN×Nꢀmatrixꢀsystemꢀofꢀlinearꢀequations ꢀ(Nꢀ
beingꢀ theꢀ numberꢀ ofꢀ basisꢀ functionsꢀ usedꢀ toꢀ expandꢀ theꢀ
unknownꢀequivalentꢀcurrents).ꢀ
(K2PtCl4)ꢀ wereꢀ purchasedꢀ fromꢀ Sigma-Aldrichꢀ andꢀ wereꢀ usedꢀ
withoutꢀfurtherꢀpurification.ꢀ
ꢀ
ꢀ Forꢀ theꢀ realisticꢀ simulationꢀ ofꢀ theꢀ large-scaleꢀ plasmonicꢀ
systemsꢀconsideredꢀhere,ꢀcomprisingꢀassembliesꢀofꢀmoreꢀthanꢀ
Characterisationꢀ
Spectroscopy.ꢀUV-Visꢀspectraꢀwereꢀcollectedꢀusingꢀaꢀscanningꢀ 8000ꢀnanoparticles,ꢀSIE-MoMꢀwasꢀexpeditedꢀviaꢀtheꢀmultilevelꢀ
spectrophotometerꢀ Agilentꢀ 8453ꢀ UV/Visꢀ diode-arrayꢀ fastꢀ multipoleꢀ algorithm-fastꢀ Fourierꢀ transformꢀ (MLFMA-
51,52
spectrophotometer.ꢀDiffuseꢀreflectionꢀspectraꢀwereꢀtakenꢀwithꢀ FFT),
ꢀ andꢀ combinedꢀ withꢀ robustꢀ Schwarzꢀ domainꢀ
53
spectrophotometerꢀ Maya2000ꢀ Proꢀ (Oceanꢀ Optics)ꢀ equippedꢀ decompositionꢀ preconditioning, ꢀ resultingꢀ inꢀ aꢀ highꢀ
withꢀreflectionꢀprobeꢀ(OceanꢀOptics,ꢀQR400-7-UV-BX)ꢀlocatedꢀ algorithmicꢀ efficiencyꢀ —computationalꢀ costꢀ ofꢀ O(NlogN)—ꢀ
inꢀ 6.35ꢀ mmꢀ holderꢀ usingꢀ asꢀ aꢀ referenceꢀ diffuseꢀ reflectanceꢀ alongꢀ withꢀ high-scalabilityꢀ viaꢀ parallelizationꢀ usingꢀ multicoreꢀ
standardꢀ(PTFE,ꢀWS-1).ꢀTheꢀilluminationꢀsourceꢀwasꢀaꢀ150ꢀWꢀ computerꢀclusters.ꢀ
®
™
quartzꢀ halogenꢀ fiberꢀ opticꢀ illuminatorꢀ (Fiber-Lite ꢀ MI-150 ,ꢀ
ꢀ
Theꢀ simulationsꢀ wereꢀ carriedꢀ outꢀ onꢀ aꢀ workstationꢀ withꢀ
Dolan-JennerꢀIndustries).ꢀXPSꢀexperimentsꢀwereꢀperformedꢀinꢀ fourꢀ 16-coreꢀ Intelꢀ Xeonꢀ E7-8867v3ꢀ 45ꢀ MBꢀ Smart-Cacheꢀ
aꢀSPECSꢀSageꢀHRꢀ100ꢀspectrometerꢀwithꢀaꢀnon-monochromaticꢀ processorsꢀ atꢀ 2.50GHzꢀ Aꢀ highꢀ surfaceꢀ meshꢀ densityꢀ wasꢀ
X-rayꢀsourceꢀ(MagnesiumꢀKαꢀlineꢀofꢀ1253.6ꢀeVꢀenergyꢀandꢀ250ꢀ consideredꢀleadingꢀtoꢀdenseꢀmatrixꢀsystemsꢀofꢀ5.7,ꢀ7.6ꢀandꢀ4.1ꢀ
W).ꢀ Theꢀ samplesꢀ wereꢀ placedꢀ perpendicularꢀ toꢀ theꢀ analyserꢀ millionꢀ unknownsꢀ forꢀ theꢀ substratesꢀ comprisingꢀ cubes,ꢀ rodsꢀ
-5
axisꢀandꢀcalibratedꢀusingꢀtheꢀ3d5/2ꢀlineꢀofꢀAgꢀwithꢀaꢀfullꢀwidthꢀatꢀ andꢀstarsꢀrespectively.ꢀAꢀrelativeꢀerrorꢀnormꢀofꢀ10 ꢀwasꢀsetꢀtoꢀ
halfꢀmaximumꢀ(FWHM)ꢀofꢀ1.1ꢀeV.ꢀTheꢀselectedꢀresolutionꢀforꢀ stopꢀ theꢀ Krylovꢀ iterativeꢀ solver.ꢀ Consideringꢀ theꢀ above,ꢀ theꢀ
theꢀ spectraꢀ wasꢀ 15ꢀ eVꢀ ofꢀ Passꢀ Energyꢀ andꢀ 0.15ꢀ eV/step.ꢀ Allꢀ computationꢀtimesꢀperꢀwavelengthꢀrangedꢀfromꢀ402ꢀsꢀ(atꢀ400ꢀ
Measurementsꢀ wereꢀ madeꢀ inꢀ anꢀ ultraꢀ highꢀ vacuumꢀ (UHV)ꢀ nm)ꢀ toꢀ 2450ꢀ sꢀ (atꢀ 1000ꢀ nm)ꢀ forꢀ theꢀ cubesꢀ substrate,ꢀ 382ꢀ toꢀ
8
chamberꢀatꢀaꢀpressureꢀaroundꢀ5·10 ꢀmbar.ꢀ
-
2057ꢀsꢀforꢀtheꢀrodsꢀsubstrate,ꢀandꢀ466ꢀtoꢀ3138ꢀsꢀforꢀtheꢀstarsꢀ
Electronꢀ Microscopy.ꢀ (Scanning)ꢀ Transmissionꢀ electronꢀ substrate.ꢀTheꢀmemoryꢀusageꢀrangedꢀfromꢀ27ꢀtoꢀ93ꢀGBꢀforꢀtheꢀ
microscopyꢀ((S)TEM)ꢀimagesꢀwereꢀcollectedꢀwithꢀaꢀJEOLꢀJEM- cubesꢀsubstrate,ꢀ71ꢀtoꢀ149ꢀGBꢀforꢀtheꢀrodsꢀsubstrate,ꢀandꢀ23.5ꢀ
1
400PLUSꢀ operatingꢀ atꢀ 120kVꢀ andꢀ Titanꢀ 60-300ꢀ TEM/STEMꢀ toꢀ67ꢀGBꢀforꢀtheꢀstarsꢀsubstrate.ꢀ
(
FEI,ꢀ Netherlands)ꢀ operatingꢀ atꢀ 300ꢀkV.ꢀ EDXꢀ mappingꢀ wasꢀ
ꢀ
Syntheticꢀproceduresꢀ
performedꢀ inꢀ scanningꢀ modeꢀ usingꢀ Spectralꢀ Imagingꢀ (SI)ꢀ
capability.ꢀ Scanningꢀ electronꢀ microscopyꢀ (SEM)ꢀ imagesꢀ wereꢀ
6
ꢀ|ꢀJ.ꢀName.,ꢀ2012,ꢀ00,ꢀ1-3ꢀ
Thisꢀjournalꢀisꢀ©ꢀTheꢀRoyalꢀSocietyꢀofꢀChemistryꢀ20xxꢀ
Pleaseꢀdoꢀnotꢀadjustꢀmarginsꢀ

Journal of Materials Chemistry A
Page 8 of 9
JournalꢀNameꢀ
ꢀARTICLEꢀ
Synthesisꢀofꢀgoldꢀnanocubes.ꢀ.ꢀTheꢀsynthesisꢀofꢀgoldꢀcubesꢀwasꢀ substrateꢀwasꢀremovedꢀfromꢀtheꢀcuvetteꢀandꢀtheꢀVsieowluArttiicolenOꢀwnlianesꢀ
3
7
DOI: 10.1039/C6TA01770C
carriedꢀ outꢀ byꢀ aꢀ seededꢀ growthꢀ process. ꢀ Toꢀ prepareꢀ goldꢀ analyzedꢀbyꢀUV-Visꢀspectroscopy.ꢀTheꢀconcentrationꢀofꢀNADHꢀ
seeds,ꢀgoldꢀsaltꢀHAuCl4ꢀ(0.5ꢀmM)ꢀwasꢀreducedꢀbyꢀNaBH4ꢀ(0.3ꢀ wasꢀ determinedꢀ basedꢀ onꢀ absorptionꢀ bandꢀ intensityꢀ atꢀ 340ꢀ
mM)ꢀinꢀtheꢀpresenceꢀofꢀCTACꢀ(5ꢀmL,ꢀ100ꢀmM).ꢀAnꢀaliquotꢀofꢀ nm.ꢀ
seedꢀ solutionꢀ (0.025ꢀ mL)ꢀ wasꢀ addedꢀ toꢀ aꢀ growthꢀ solutionꢀ PhotoelectrochemicalꢀoxidationꢀofꢀTEAOH.ꢀFirst,ꢀtheꢀsolutionsꢀ
containingꢀCTACꢀ(50ꢀmL,ꢀ100ꢀmM),ꢀHAuCl4ꢀ(2.5ꢀmL,ꢀ10ꢀmM),ꢀ ofꢀ goldꢀ nanoparticlesꢀ (bareꢀ orꢀ Pt-functionalized,ꢀ 10ꢀ mL,ꢀ 0.5ꢀ
AgNO3ꢀ (0.5ꢀ mL,ꢀ 10ꢀ mM),ꢀ HClꢀ (1ꢀ mL,ꢀ 1000ꢀ mM)ꢀ andꢀ ascorbicꢀ mM)ꢀ inꢀ CTABꢀ (100ꢀ mM)ꢀ wereꢀ centrifugedꢀ twiceꢀ andꢀ
acidꢀ(0.5ꢀmL,ꢀ100ꢀmM).ꢀTheꢀreactionꢀwasꢀgentlyꢀshakenꢀafterꢀ redispersedꢀinꢀwaterꢀtoꢀobtainꢀaꢀfinalꢀconcentrationꢀofꢀgoldꢀ6ꢀ
theꢀadditionꢀofꢀtheꢀseedsꢀandꢀleftꢀundisturbedꢀovernight.ꢀTheꢀ mM.ꢀ Sixꢀ solutionsꢀ inꢀ totalꢀ ofꢀ bareꢀ andꢀ Pt-functionalizedꢀ
solutionꢀ wasꢀ centrifugedꢀ twiceꢀ (5500ꢀ rpm,ꢀ 30ꢀ min)ꢀ andꢀ nanoparticlesꢀ(18.5ꢀµL,ꢀ6ꢀmM)ꢀwereꢀdropcastedꢀonꢀtheꢀworkingꢀ
redispersedꢀinꢀCTABꢀ(100ꢀmM)ꢀtoꢀobtainꢀaꢀfinalꢀconcentrationꢀ electrodeꢀofꢀscreen-printedꢀcarbonꢀelectrodeꢀandꢀevaporatedꢀ
ofꢀgoldꢀequalꢀtoꢀ0.5ꢀmM.ꢀ
Synthesisꢀ ofꢀ goldꢀ nanorods.ꢀ Goldꢀ nanorodsꢀ wereꢀ preparedꢀ theꢀ electrodeꢀ wasꢀ coveredꢀ withꢀ photochemicalꢀ mixtureꢀ ꢀ (50ꢀ
atꢀroomꢀtemperatureꢀduringꢀ12ꢀhours.ꢀPriorꢀtheꢀmeasurementsꢀ
38
usingꢀ Ag-assistedꢀ seededꢀ growth. ꢀ Seedsꢀ wereꢀ preparedꢀ byꢀ µL,ꢀ TEAOHꢀ (1M),ꢀ phosphateꢀ bufferꢀ (0.1ꢀ M)).ꢀ Allꢀ experimentsꢀ
reductionꢀofꢀHAuCl4ꢀ(5ꢀmL,ꢀ0.25ꢀmM)ꢀwithꢀNaBH4ꢀ(0.3ꢀmL,ꢀ10ꢀ wereꢀ performedꢀ inꢀ theꢀ exactꢀ manner:ꢀ onceꢀ theꢀ openꢀ circuitꢀ
mM)ꢀinꢀaqueousꢀCTABꢀsolutionꢀ(100ꢀmM).ꢀAnꢀaliquotꢀofꢀseedꢀ potentialꢀreachedꢀtheꢀsteadyꢀstateꢀ(ca.ꢀ-0.36ꢀV),ꢀtheꢀlampꢀ(400-
2
solutionꢀ(0.12ꢀmL)ꢀwasꢀaddedꢀtoꢀaꢀgrowthꢀsolutionꢀcontainingꢀ 1200ꢀnm,ꢀ150ꢀmW/cm )ꢀwasꢀswitchedꢀonꢀandꢀcorrespondingꢀ
CTABꢀ(50ꢀmL,ꢀ100ꢀmM),ꢀHAuCl4ꢀ(0.5ꢀmL,ꢀ50ꢀmM),ꢀascorbicꢀacidꢀ outputꢀcurrentꢀwasꢀrecordedꢀduringꢀ10ꢀseconds.ꢀ
(
0.4ꢀmL,ꢀ100ꢀmM),ꢀAgNO3ꢀ(0.6ꢀmL,ꢀ10ꢀmM)ꢀandꢀHClꢀ(0.95ꢀmL,ꢀ
000ꢀmM).ꢀTheꢀmixtureꢀwasꢀleftꢀundisturbedꢀatꢀ30ꢀ°Cꢀforꢀ2h.ꢀ
1
Acknowledgementsꢀ
Theꢀ solutionꢀ wasꢀ centrifugedꢀ twiceꢀ (8000ꢀ rpm,ꢀ 30ꢀ min)ꢀ andꢀ
redispersedꢀinꢀCTABꢀ(100ꢀmM)ꢀtoꢀobtainꢀaꢀfinalꢀconcentrationꢀ
ofꢀgoldꢀequalꢀtoꢀ0.5ꢀmM.ꢀ
ThisꢀworkꢀwasꢀsupportedꢀbyꢀtheꢀSpanishꢀMinistryꢀofꢀEconomyꢀ
andꢀCompetitivenessꢀ(MAT2013-49375-EXP,ꢀBIO2014-59741-R)ꢀ
andꢀ BBVAꢀ Foundationꢀ -ꢀ “ꢀ Primeraꢀ convocatoriaꢀ deꢀ ayudasꢀ
fundaciónꢀ BBVAꢀ aꢀ investigadores,ꢀ innovadoresꢀ yꢀ creadoresꢀ
culturales”.ꢀD.M.S.,ꢀJ.M.T,ꢀandꢀF.Oꢀacknowledgeꢀfundingꢀfromꢀ
theꢀ Europeanꢀ Regionalꢀ Developmentꢀ Fundꢀ (ERDF)ꢀ andꢀ theꢀ
Spanishꢀ Ministryꢀ ofꢀ Economyꢀ andꢀ Competitivenessꢀ (Projectsꢀ
MAT2014-58201-C2-1-R,ꢀ MAT2014-58201-C2-2-R),ꢀ fromꢀ theꢀ
ERDFꢀandꢀtheꢀGalicianꢀRegionalꢀGovernmentꢀunderꢀagreementꢀ
forꢀfundingꢀtheꢀAtlanticꢀResearchꢀCenterꢀforꢀInformationꢀandꢀ
Communicationꢀ Technologiesꢀ (AtlantTIC),ꢀ andꢀ fromꢀ theꢀ ERDFꢀ
andꢀ theꢀ Extremaduraꢀ Regionalꢀ Governmentꢀ (Juntaꢀ deꢀ
Extremadura)ꢀ underꢀ Projectꢀ IB13185.ꢀ Weꢀ thankꢀ Drꢀ Luisꢀ Yateꢀ
forꢀassistanceꢀwithꢀXPSꢀanalysis.ꢀ
SynthesisꢀofꢀgoldꢀNanostars.ꢀTheꢀsurfactant-freeꢀmethodꢀwasꢀ
39
usedꢀtoꢀprepareꢀgoldꢀnanostars. ꢀAꢀsolutionꢀgoldꢀseedsꢀ(~14ꢀ
nm,ꢀ 0.5ꢀ mL,ꢀ [Au]ꢀ =ꢀ 0.5ꢀ mM)ꢀ preparedꢀ byꢀ Turkevichꢀ methodꢀ
wasꢀaddedꢀtoꢀanꢀaqueousꢀsolutionꢀ(50ꢀmL)ꢀcontainingꢀHAuCl4ꢀ
(
0.25ꢀmM)ꢀandꢀHClꢀ(1ꢀmM),ꢀfollowedꢀbyꢀadditionꢀofꢀAgNO3ꢀ(10ꢀ
mM,ꢀ 0.15ꢀ mL)ꢀ andꢀ ascorbicꢀ acidꢀ (100ꢀ mM,ꢀ 0.25ꢀ mL).ꢀ Toꢀ
increaseꢀtheꢀstabilityꢀofꢀtheꢀobtainedꢀnanostars,ꢀCTABꢀ(10ꢀmL,ꢀ
1
00ꢀmM)ꢀwasꢀaddedꢀtoꢀtheꢀgrowthꢀsolution.ꢀUponꢀsynthesis,ꢀ
theꢀ solutionꢀ wasꢀ centrifugedꢀ twiceꢀ (4500ꢀ rpm,ꢀ 30ꢀ min)ꢀ andꢀ
redispersedꢀinꢀCTABꢀ(100ꢀmM)ꢀtoꢀobtainꢀaꢀfinalꢀconcentrationꢀ
ofꢀgoldꢀequalꢀtoꢀ0.5ꢀmM.ꢀ
Platinumꢀ reductionꢀ onꢀ goldꢀ nanoparticles.ꢀ Platinumꢀ
40
overgrowthꢀwasꢀcarriedꢀoutꢀinꢀtheꢀpresenceꢀofꢀsilverꢀions. ꢀToꢀ
aꢀdispersionꢀofꢀgoldꢀnanoparticlesꢀ(10ꢀmL,ꢀ[Au]ꢀ=ꢀ0.5ꢀmM)ꢀwasꢀ
addedꢀAgNO3ꢀ(0.04ꢀmL,ꢀ10ꢀmM)ꢀandꢀK2PtCl4ꢀ(0.05ꢀmL,ꢀ10ꢀmM)ꢀ Notesꢀandꢀreferencesꢀ
andꢀ theꢀ mixtureꢀ leftꢀ forꢀ 30ꢀ minꢀ atꢀ 40ꢀ °Cꢀ toꢀ allowꢀ forꢀ
complexationꢀ ofꢀ theꢀ platinumꢀ saltꢀ withꢀ CTAB,ꢀ followedꢀ byꢀ
additionꢀ ofꢀ ascorbicꢀ acidꢀ (0.1ꢀ mL,ꢀ 100ꢀ mM)ꢀ maintainingꢀ theꢀ
ꢀ
1
ꢀ S.ꢀGao,ꢀK.ꢀUenoꢀandꢀH.ꢀMisawa,ꢀAcc.ꢀChem.ꢀRes.,ꢀ2011,ꢀ44,ꢀ251–
260.ꢀ
temperatureꢀ atꢀ 40ꢀ °Cꢀ forꢀ 12ꢀ h.ꢀ Ptꢀ coatedꢀ goldꢀ nanoparticlesꢀ 2ꢀ S.ꢀ C.ꢀ Warrenꢀ andꢀ E.ꢀ Thimsen,ꢀ Energyꢀ Environ.ꢀ Sci.,ꢀ 2012,ꢀ 5,ꢀ
wereꢀwashedꢀtwiceꢀbyꢀcentrifugationꢀandꢀredispersedꢀinꢀwaterꢀ
toꢀobtainꢀaꢀfinalꢀconcentrationꢀofꢀgoldꢀequalꢀtoꢀ6ꢀmM.ꢀ
5133–5146.ꢀ
3
4
5
6
7
ꢀ S.ꢀLinic,ꢀP.ꢀChristopherꢀandꢀD.ꢀB.ꢀIngram,ꢀNatꢀMater,ꢀ2011,ꢀ10,ꢀ
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11–921.ꢀ
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781–2817.ꢀ
Plasmonicꢀ substrates.ꢀ As-preparedꢀ Pt-coatedꢀ goldꢀ
nanoparticlesꢀ (0.5ꢀ mM,ꢀ 50ꢀ mL,ꢀ [CTAB]ꢀ =ꢀ 0.1ꢀ M)ꢀ wereꢀ
centrifugedꢀ andꢀ redispersedꢀ inꢀ CTABꢀ (1ꢀ mM,ꢀ 2ꢀ mL).ꢀ Theꢀ
solutionꢀwasꢀagainꢀcentrifugedꢀandꢀredispersedꢀinꢀpureꢀwaterꢀ
2
ꢀ S.ꢀ Linic,ꢀ P.ꢀ Christopher,ꢀ H.ꢀ Xinꢀ andꢀ A.ꢀ Marimuthu,ꢀ Acc.ꢀ Chem.ꢀ
Res.,ꢀ2013,ꢀ46,ꢀ1890–1899.ꢀ
ꢀ J.ꢀC.ꢀScaianoꢀandꢀK.ꢀStamplecoskie,ꢀJ.ꢀPhys.ꢀChem.ꢀLett.,ꢀ2013,ꢀ4,ꢀ
(
1ꢀ mL).ꢀ Parafilmꢀ wasꢀ usedꢀ toꢀ wrapꢀ theꢀ edgesꢀ ofꢀ theꢀ glassꢀ
substrateꢀ(0.8ꢀxꢀ2.5ꢀcm)ꢀtoꢀproduceꢀaꢀcontainer.ꢀTheꢀsolutionꢀofꢀ
nanoparticlesꢀwasꢀthenꢀplacedꢀinꢀtheꢀcontainerꢀandꢀevaporatedꢀ
atꢀroomꢀtemperatureꢀduringꢀ3-5ꢀdays.ꢀ
1
177–1187.ꢀ
ꢀ M.ꢀXiao,ꢀR.ꢀJiang,ꢀF.ꢀWang,ꢀC.ꢀFang,ꢀJ.ꢀWangꢀandꢀJ.ꢀYu,ꢀJ.ꢀMater.ꢀ
Chem.ꢀA,ꢀ2013,ꢀ1,ꢀ5790–5805.ꢀ
Photochemicalꢀregenerationꢀofꢀcofactorꢀmolecules.ꢀPlasmonicꢀ 8ꢀ C.ꢀWangꢀandꢀD.ꢀAstruc,ꢀChem.ꢀSoc.ꢀRev.,ꢀ2014,ꢀ43,ꢀ7188–7216.ꢀ
substrateꢀ wasꢀ immersedꢀ inꢀ photochemicalꢀ mixtureꢀ (1ꢀ mL,ꢀ inꢀ 9ꢀ C.ꢀClavero,ꢀNatureꢀPhoton,ꢀ2014,ꢀ8,ꢀ95–103.ꢀ
1
0ꢀ M.ꢀJ.ꢀKale,ꢀT.ꢀAvanesianꢀandꢀP.ꢀChristopher,ꢀACSꢀCatal.,ꢀ2013,ꢀ4,ꢀ
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1ꢀ G.ꢀBaffouꢀandꢀR.ꢀQuidant,ꢀChem.ꢀSoc.ꢀRev.,ꢀ2014,ꢀ43,ꢀ3898–3907.ꢀ
quartzꢀcuvette)ꢀconsistingꢀofꢀphosphateꢀbufferꢀ(0.1ꢀM,ꢀpHꢀ8),ꢀ
+
NAD ꢀ (1ꢀ mM)ꢀ andꢀ TEAOHꢀ (1M).ꢀ Theꢀ cuvetteꢀ wasꢀ irradiatedꢀ
1
withꢀ visible/infraredꢀ light.ꢀ Afterꢀ twoꢀ hoursꢀ theꢀ plasmonicꢀ
Thisꢀjournalꢀisꢀ©ꢀTheꢀRoyalꢀSocietyꢀofꢀChemistryꢀ20xxꢀ
J.ꢀName.,ꢀ2013,ꢀ00,ꢀ1-3ꢀ|ꢀ7ꢀ
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