SURFACE CHEMISTRY

Real-space and real-time observationof a plasmon-induced chemicalreaction of a single moleculeEmiko Kazuma,1 Jaehoon Jung,2 Hiromu Ueba,3 Michael Trenary,4 Yousoo Kim1*

Plasmon-induced chemical reactions of molecules adsorbed on metal nanostructuresare attracting increased attention for photocatalytic reactions. However, the mechanismremains controversial because of the difficulty of direct observation of the chemicalreactions in the plasmonic field, which is strongly localized near the metal surface.We useda scanning tunneling microscope (STM) to achieve real-space and real-time observationof a plasmon-induced chemical reaction at the single-molecule level. A single dimethyldisulfide molecule on silver and copper surfaces was dissociated by the optically excitedplasmon at the STM junction. The STM study combined with theoretical calculationsshows that this plasmon-induced chemical reaction occurred by a direct intramolecularexcitation mechanism.

Localized surface plasmon (LSP) resonancesof metal nanostructures can focus light nearthe metal surface to sizes below the diffrac-tion limit (1), and the generated localizedelectric field can be used for near-field op-

tical spectroscopies (2, 3). In addition, LSPs facil-itate highly efficient conversion of solar energyin photovoltaics (4, 5) and photocatalysts (5, 6).In particular, plasmon-induced chemical re-actions of molecules adsorbed on metal nano-structures are attracting increased attention asphotocatalysts (7, 8) that can form bonds (9–13)or dissociate them (13–16). An indirect hot-electron transfer mechanism (Fig. 1A) (7, 8) hasbeen invoked for these reactions. Electron-holepairs are generated in the metal nanostructuresby nonradiative decay of the LSP (7, 17, 18), andthe hot electrons transfer to form a transient neg-ative ion (TNI) state of the adsorbed molecule(7). Recently, plasmon-induced dissociations ofO2 (14) and H2 (15) molecules were observedand explained by a mechanism in which the dis-sociation reactions proceed through vibrationalexcitation after the transfer of hot electrons gen-erated TNI states.We propose a direct intramolecular excitation

mechanism (Fig. 1B) on the basis of direct ob-servation of a plasmon-induced chemical reactionof a single molecule. The LSP resonantly exciteselectrons from the occupied state to the un-occupied state in the electronic structure of anadsorbate. Single molecules in the strongly local-ized plasmonic field near the metal surface canbe observed in real space and real time. We suc-

cessfully made such observations through exper-imental studies with the LSP excited within thenanogap between a metal substrate and a Ag tipof a scanning tunneling microscope (STM).Figure 2, A and B, illustrates our experimental

scheme for investigating the plasmon-inducedchemical reaction with the STM. Dimethyl di-sulfide [(CH3S)2] was selected as a target mole-cule for the plasmon-induced chemical reaction.To excite the LSP optically, the Ag tip with acurvature radius of ~60 nm (fig. S1) was posi-tioned over the bare metal surface, and the sam-ple bias voltage (Vs) and tunneling current (It)were set to 20 mV and 0.2 nA, respectively.Tunneling electrons at a bias of 20 mV cannotexcite vibrational modes related to any kind ofreaction, such as rotation, desorption, or disso-ciation of the molecule (19, 20).The LSP generates a strong electric field in the

nanogap (Fig. 2C and fig. S2). Figure 2, D and E,shows the spatial distribution of isolated (CH3S)2molecules on Ag(111) before and after the excita-tion of the LSP with p-polarized light at 532 nm.Although individual (CH3S)2 molecules appear aselliptical protrusions in the STM images, somemolecules near the tip position were transformedinto two identical ball-shaped protrusions afterthe excitation of the LSP (fig. S3). The dissoci-ated chemical species have the same appearanceas CH3S molecules obtained by injecting tunnel-ing electrons into a (CH3S)2 molecule (19–21).This implies that the S–S bond in (CH3S)2 wasdissociated by the LSP. Notably, other reac-tions, such as rotation or desorption, were notobserved.The dissociation ratio (N/N0), which we de-

fined as the number of (CH3S)2 molecules (N )after LSP excitation divided by the number ofpreadsorbed molecules (N0), was measured forquantitative analyses. Figure 2F shows plots ofln(N/N0) as a function of the irradiation time(t) in the four areas depicted with concentricrings (Fig. 2B). The linearity of the plots shows

that the dissociation, (CH3S)2 → 2CH3S, is afirst-order reaction. The slopes of the lines inFig. 2F determine the dissociation rate constant(k). The rate constant was largest in area one anddecreased with lateral distance from the tip(Fig. 2G). We calculated the electromagneticfield intensity in the nanogap (Egap) (Fig. 2C)using the Ag tip with a curvature radius of 60 nmand a cone angle of 15° estimated from the scan-ning electronmicroscopy images shown in fig. S1(see the supplementary text and fig. S2). Thelateral distribution of Egap is also shown in Fig.2G. From comparison of k with Egap, we con-clude that the plasmon-induced dissociation hasa strong correlation with the electric field in-tensity of the optically excited LSP.To explore a plausible mechanism for the

plasmon-induced dissociation, we first examinedthewavelength (l) dependence of the dissociationyield on Ag(111) (fig. S3). The rate constant di-vided by the number of incident photons per sec-ond is equivalent to the yield of plasmon-induceddissociation (YLSP). The wavelength at the max-imum intensity of YLSP (lMax) and the thresholdwavelength of YLSP (lTh) obtained in area one(Fig. 3A) were ~532 nm (~2.33 eV) and ~780 nm(~1.59 eV), respectively. The plasmon-induceddissociation of (CH3S)2 was also examined on aCu(111) substrate (Fig. 3B and fig. S4), whichhas a different electronic structure and plas-monic properties. TheYLSP l spectrum for Cu(111)had lMax =~670nm (~1.85 eV) and lTh =~980nm(~1.27 eV).In contrast, the photodissociation yield (Yphoton)

measured when the sample was exposed to lightwith the tip retracted by more than 2 mm fromthe surface exhibited peak and threshold wave-lengths at ~450 nm (~2.76 eV) and ~635 nm(~1.95 eV) on Ag(111) and ~450 and ~670 nm onCu(111), respectively. Our previous work (21) re-vealed that photodissociation of the S−S bond in(CH3S)2molecules adsorbed on Ag(111) and Cu(111)surfaces occurs through direct electronic excita-tion from the highest occupied molecular orbital(HOMO)– to the lowest unoccupiedmolecular or-bital (LUMO)–derived orbitals of (CH3S)2, that is,from the nonbonding lone pair–type orbitals onthe S atoms (nS) to the antibonding orbital local-ized at the S−S bond (s*SS) (supplementary text).The hybridization between (CH3S)2 and the

metal substrate reduced the optical energy gapinto the range of visible light. Furthermore,LUMO-derived molecular states with less over-lapwith themetal substrate were formed, whichresulted in longer excited-state lifetimes thanwould be the case for strong overlap with the sub-strate. Thus, photodissociation occurs throughthe direct excitation between the frontier MOs,and the shape of the Yphoton l spectra reflectedthe densities of states (DOSs) of both the HOMOand LUMO (fig. S5). In contrast, the YLSP l spec-tra had a shape similar to that of the simulatedEgap l spectra (Fig. 3C) in the wavelength regionswhere photodissociation occurs. This similarityindicates that the LSP was an excitation sourceand that the YLSP strongly depended on the en-ergy profiles of the LSP. A similar wavelength

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1Surface and Interface Science Laboratory, RIKEN, Wako,Saitama 351-0198, Japan. 2Department of Chemistry,University of Ulsan, 93 Daehak-ro, Nam-gu, Ulsan 680-749,Republic of Korea. 3Graduate School of Science andEngineering, University of Toyama, Toyama 930-8555,Japan. 4Department of Chemistry, University of Illinois atChicago, Chicago, IL 60607, USA.*Corresponding author. Email: ykim@riken.jp

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dependence on Ag and Cu was also observed inthe enhancement of surface-enhanced Ramanscattering (SERS) intensities (22). In addition,the maximum intensity of YLSP on Ag(111) andCu(111) was ~400 and ~300 times as high asthat of Yphoton, respectively, which was caused bythe strong enhancement of the electric field bythe LSP (Fig. 3C).In the indirect hot-electron transfer mecha-

nism (Fig. 1A), the YLSP is determined both by theenergy distribution of hot electrons and by theDOSs of the LUMOs. Energy distributions of hotelectrons and holes generated by the decay ofLSPs are sensitive to the electronic band struc-ture of metals (17, 18). If the energy of the LSPswas lower than the threshold energy for directinterband transitions of the metals, both elec-trons and holes would be equitably distrib-uted from zero to the energy of the LSP throughphonon-assisted transitions (18). In contrast, at

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Fig. 2. Real-space investigations of the plasmon-induced chemicalreaction. (A) Schematic illustration of the experiment for the real-spaceinvestigation of the plasmon-induced chemical reaction in the nanogapbetween a Ag tip and a metal substrate. The tip was positioned over themetal surface during light irradiation with the feedback loop turned on tomaintain the gap distance. The Vs and It were kept at 20 mV and 0.2 nA.hn, Planck’s constant (h) multiplied by frequency (n). (B) Division ofthe STM image into four areas depicted with 10-nm wide concentric ringsfor analysis. (C) Simulated spatial distribution of the electric field at the1-nm gap under p-polarized light at 532 nm. E0, incident electric field.Topographic STM images of (CH3S)2 molecules on Ag(111) (D) before and

(E) after irradiation with p-polarized light at 532 nm (~7.6 × 1017 photonscm−2 s−1, 2 s) (Vs = 20 mV, It = 0.2 nA, 43 nm by 43 nm). The tip waspositioned at the center of area one during light irradiation. (F) Timedependence of the dissociation ratio (N/N0) under irradiation withp-polarized light at 532 nm (~5.9 × 1016 photons cm−2 s−1) in the fourareas shown in (B). Each data point represents the average of results fromsix trials. The dotted lines denote single exponential functions fitted to thedata points [ln(N/N0) = −kt]. Error bars indicate SD. (G) The rate constantk obtained at areas one through four and the calculated lateral profileof electric field intensity at 0.1 nm above the substrate surface (z = 0.1 nm)under 533-nm light. x = 0 nm corresponds to the center of the tip.

BA C

Fig. 1. Excitation mechanisms for plasmon-induced chemical reactions. (A) Indirecthot-electron transfer mechanism. Hot electrons (e−) generated via nonradiative decay of anLSP transferred to form the TNI states of the molecule. (B) Direct intramolecular excitation mechanism.The LSP induces direct excitation from the occupied state to the unoccupied state of the adsorbate.(C) Charge transfer mechanism.The electrons are resonantly transferred from the metal to the molecule.

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higher energies, direct transitions dominate, andthe relative probability density of hot carriersdramatically increases.If the plasmon-induced dissociation of (CH3S)2

occurred through hot-electron transfer, the YLSPl spectra would have exhibited a step change atthe threshold energy of the interband transitionat ~3.0 and ~2.0 eV for Ag and Cu, respectively(23), and increased at the higher energies, be-cause the LUMO states are distributed broadlyabove the Fermi level (EF) (fig. S5). In addition,the hot electrons generated by the direct transi-tions of Cuhave a broad energy distribution aboveEF (18) and can be transferred into the LUMOstates, resulting in the excitation of vibrationalmodes lying along the reaction coordinate. How-ever, the expected spectral change at the thresh-old energy of the interband transition of themetal was not observed. Moreover, the overallshapes of the YLSP l spectra reflected not onlythe shape of theEgap l spectra (Fig. 3C) but also theshape of the Yphoton l spectra, that is, the energydistribution of the DOSs for both the HOMO (nS)and the LUMO (s*SS) (Fig. 3, A and B). Thus, wecould exclude the indirect hot-electron transfermechanism for this plasmon-induced dissociation.Furthermore, hot-hole transfer in Cu, where hotholes are much more energetic than hot elec-trons (17, 18), could also be excluded by theshape of the Yphoton l spectrum. We concludethat the LSP efficiently induces and enhancesthe dissociation reaction through the same reac-tion pathway as photodissociation (nS → s*SS),on the basis of the direct intramolecular excita-tion mechanism (Fig. 1B).The YLSP l spectra also had tails extending

to longer wavelengths where photodissociationnever occurred. This finding suggests that theLSP also enabled direct intramolecular excitationfrom the MO in-gap states near EF (supplemen-tary text and figs. S5 to S7) to s*SS (MOin-gap →s*SS), as well as the HOMO-LUMO transition(nS → s*SS). The computationally estimated en-ergy gaps between EF and the edge of the LUMOstate are ~1.0 and~0.80 eV onAg(111) andCu(111),respectively (fig. S5). Thismodel is consistentwiththe threshold energy of the YLSP on Ag(111) beinggreater than that on Cu(111). Dissociationwas alsoapparently induced by direct intramolecular exci-tation of MOin-gap → s*SS. The DOS of the in-gapstates is much smaller than that of the frontierelectronic states (figs. S5 to S7), and thus thedirect excitation of MOin-gap → s*SS is expectedto be a much less efficient process than that ofHOMO-LUMO transition (nS → s*SS). How-ever, the LSP generated a strong electric fieldlocalized at the interface between the adsorb-ate and the metal and enabled dissociationeven through inefficient excitation pathways(MOin-gap → s*SS).A charge transfer from metals to molecules

(Fig. 1C) was proposed to explain chemical en-hancement effects in SERS (24–26) on the basisof LSPs. The Raman intensities of pyridine mole-cules adsorbed on coinage metals such as Ag, Cu,and Au were enhanced by electron transfer fromthe highest occupied state (the valence shell s

orbital) of the metal near the EF to the un-occupied MOs (24, 25). In addition, the chargetransfer mechanism was invoked recently to de-scribe a plasmon-induced chemical transforma-tion (27) in which the electrons near the EF ofplasmonic metal nanoparticles were transferredto adsorbed molecules. In the plasmon-induceddissociation of (CH3S)2, the charge transfer fromnear the EF to s*SS (EF → s*SS) was also takeninto account to explain the tails of the YLSP lspectra in the low-energy region because theenergy gaps between EF and s*SS were about1.0 to 2.0 eVand0.8 to 1.5 eVonAg(111) andCu(111),respectively (fig. S5).Real-time observationwith an STMallowed us

to measure the rates of plasmon-induced chem-ical reactions for single molecules, thereby pro-viding insights into the elementary reactionpathways that cannot be accessed by conven-tional spectroscopies and the analyses of YLSPl spectra. It is highly sensitive to the change inthe gap distance (d) (28), and thus real-time in-formation can be collected by tracing It underlight irradiation (Fig. 4A). Figure 4B shows thecurrent trace when the STM tip was positionedover a target molecule adsorbed on Ag(111) andexposed to p-polarized light at 532 nm. A suddendrop of It reflected the change in d from d1 to d2(Fig. 4A) caused by molecular dissociation, andthe dissociation rate was determined by theinverse of the time required for the plasmon-induced dissociation (tR).Notably, no reaction could be induced with

tunneling electrons at aVs of 20mV, and thermalexpansion of the tipwas negligible because It wasstable on the metal surface under light irradia-tion (fig. S8). The gap distance d (Fig. 4C) iscontrolled by It, where ItºVsexpð�Ad

ffiffiffiffi

Fp Þ (Vs =

20 mV; A, coefficient; and F, barrier height). Weinvestigated the dependence of d on the dissoci-ation rate (1/tR) at the single-molecule level (Fig.4C and fig. S9). We note that 1/tR exhibited ddependence similar to that of the calculatedelectric field intensity (Fig. 4D and fig. S10). Thisrelation indicates that the reaction is caused bythe LSP and suggests that the reactivity is de-termined by the coupling between the electricfield of the LSP and a transition dipole momentof the molecule.In the indirect hot-electron transfer mecha-

nism, the reactions are initiated from the TNIstates formed by the hot-electron transfer tomolecules via an inelastic electron tunneling (IET)process (8) (Fig. 1A).We can obtain further knowl-edge of reaction pathways initiated from the TNIstates formed by electron transfer from themetalto themolecule via the IET process with the STM(19, 20). In addition, the IET process examinedwith the STM enables us to describe the elemen-tary processes of vibrational or electronic excita-tion resulting in molecular motion or reaction,which reflects the local DOS of the adsorbedmolecules (28). Both the hot electrons of the LSPand the tunneling electrons had a broad energydistribution from the EF to the energy of the LSP(17, 18) and the applied Vs, respectively (fig. S11).Thus, the reaction pathways in the same energy

regions should be the same regardless of theexcitation source: hot electrons or tunnelingelectrons. Rotation (Fig. 4E) and dissociation (Fig.4F) of (CH3S)2 on Ag(111) were induced throughvibrational excitation with inelastically tunneledelectrons at energies higher than ~0.28 and~0.36 eV, respectively (Fig. 4G). Dissociation oc-curred through vibrational excitation of the C–H

Kazuma et al., Science 360, 521–526 (2018) 4 May 2018 3 of 5

Fig. 3. Wavelength dependence of the plasmon-induced chemical reaction and of theplasmonic electric field.Wavelengthdependence of YLSP of (CH3S)2 molecules on(A) Ag(111) (blue diamonds) and (B) Cu(111)(red circles). Insets in (A) and (B) show YLSP

for 700 to 980 nm. Each data point representsthe average of results from six trials. Thephotodissociation yields without the excitationof the LSP [Yphoton, previously reported in (21)](black circles) are also shown. The yield isdetermined from k divided by the number ofincident photons per second (~6.0 × 1016 to6.5 × 1016 photons cm−2 s−1 for both plasmon-induced dissociation and photodissociation).Error bars indicate SD. (C) Calculated electricfield intensity for a 1-nm gap between a Agtip and the metal substrates under p-polarizedlight. The simulated point is z = 0.1 nm abovethe substrate surfaces and x = 0 nm.

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stretch mode (19) and a combination of the C–Hstretch and the S–S stretch modes (20). Moreover,dissociation induced with tunneling electronswas accompanied by rotation, which resultedin small changes in It followed by its suddendrop (Fig. 4F). Rotation before dissociation wasalso observed in the dissociation of O2 on Pt(111)through vibrational excitation via the IET pro-cess with an STM (29).

We conclude that the energy of the TNI statesformed by electron transfer from themetal to themolecule was dissipated to the vibrationally ex-cited states according to the nondissociative po-tential energy surface (Fig. 4I and fig. S12), whichresulted in both rotation and dissociation of(CH3S)2, and rotation is a precursor for dissoci-ation. The small changes of It caused by rotationbefore its sudden dropwere also observed for the

dissociation reaction inducedwith tunneling elec-trons at 2.3 V (Fig. 4H) and 2.0 and 1.0 V (fig. S13),an energy region almost equal to that of the hotelectrons of the LSP excited with light at 532,620, and 1240 nm, respectively. Thus, the IETprocess through vibrational excitation at thelower energy region is always included in thereaction pathway when the electrons are distrib-uted from the EF to the upper energy level, which

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Fig. 4. Real-time STM results for the plasmon-induced chemicalreaction and IET-induced reactions of a single molecule. (A) Schematicillustration of the real-time observation of the plasmon-induced chemicalreaction. (B) Current trace for detecting the dissociation event for the targetmolecule (STM images) on Ag(111) induced by the LSPexcited with p-polarizedlight at 532 nm (~2.7 × 1015 photons cm−2 s−1).The Ag tip was positionedabove the molecule marked by the asterisk in the STM image.The fixed gapresistance (Vs = 20mVand It = 2.0 nA) was applied and the feedback loop wasturned off to maintain the tip height at t = 2.0 s. Light irradiation started att = 4.0 s.The light was turned off and the feedback loop was turned on att = 18 s.The tunneling conditions at t = 0 to 2.0 s and 18 to 20 s are Vs = 20mVand It = 0.2 nA.The time required for the plasmon-induced dissociation (tR) isdirectly read from the current trace. (C) Gap distance d dependence of thedissociation rate (1/tR) obtained under p-polarized light at 532 nm (~1.3 × 1015

photons cm−2 s−1). Each data point represents the average of results for 12molecules. Error bars indicate SD. (D) Gap distance dependence of the

calculated electric field intensity at 532 nm.The simulated point is z = 0.1 nmabove the substrate surface and x = 0 nm. (E to H) IET-induced reactions inthe dark. Current trace was measured on the molecules with the feedbackloop turned off.The tunneling conditions were (E) Vs = 0.30 V and It = 8.0 nA,(F) 0.38 V and 8.0 nA, and (H) 2.3 V and 1.0 nA. The current changesindicated by red and green arrows correspond to rotation and dissociation,respectively. (G) Action spectrum for the rotation and dissociation of the(CH3S)2 molecules induced by injecting tunneling electrons. The initialcurrent was set to 8.0 nA. Each data point represents the average of resultsfrom 16 trials. Error bars indicate SD. At 360 mV, the dissociation and therotation occurred 1 time and 15 times in 16 trials, respectively.The scale barsin the STM images in (B), (E), (F), and (H) are 0.5 nm. Schematicillustrations of the potential energy surface for the plasmon-induced chemicalreactions on the basis of (I) the indirect hot-electron transfer mechanismand (J) the direct intramolecular excitationmechanism are shown.ℏw, Planck’sconstant h divided by 2p ðℏÞ multiplied by the angular frequency ðwÞ.

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is higher than the vibrational energies of theground state.If the plasmon-induced dissociation proceeded

through vibrational excitation, current changescaused by rotation should appear before the dis-sociation. However, changes in It before thesudden drop were not observed (Fig. 4B andfig. S9). This difference excluded the hot-electron–mediated process, which always involved vibra-tional excitation in the TNI state (Fig. 4I), as anelementary pathway for the plasmon-induceddissociation of (CH3S)2. By considering the mech-anistic insight obtained from the YLSP l spectra(Fig. 3), we concluded that the plasmon-induceddissociation of (CH3S)2 occurred through thedirect dissociation pathway from neutral excitedstates generated by direct intramolecular excita-tion (Fig. 4J). In addition, if the potential energysurface of the excited state formed by chargetransfer from the metal states to s*SS was dis-sociative for the S–S bond cleavage (fig. S12C),the charge transfer mechanism could also con-tribute to the plasmon-induced dissociation inthe low-energy region (supplementary text). How-ever, it is difficult to quantify the contribution ofthe charge transfer mechanism, because the ex-cited state formed by charge transfer (fig. S12C)cannot be simply described in the STM experi-ment because of the broad energy distribution ofthe tunneling electrons.The LUMOs of (CH3S)2wereweakly hybridized

with the metal substrates (21). The weak hybrid-ization suppressed the relaxation of the excitedstate and thus allowed access to the dissociativepotential energy surface from the neutral excitedstate (Fig. 4J), which was theoretically predictedfor the photodissociation of (CH3S)2molecules inthe gas phase (30). In contrast, the MOs of O2

andH2, for which plasmon-induced dissociationwas explained by the indirect hot-electron trans-fer mechanism, were strongly hybridized withmetal substrates (14, 15). This suggests that thedegree of hybridization betweenMOs andmetalsplays a crucial role in the plasmon-induced chem-ical reactions.Our real-space and real-time STM study com-

bined with theoretical calculations revealed that

the plasmon-induced dissociation of the S–S bondin a single (CH3S)2 molecule on Ag and Cu sur-faces occurred principally by the direct intra-molecular excitation to the LUMO state of theantibonding S–S (s*SS) orbital through a decay ofthe optically excited LSP in the nanogap betweenthe Ag tip and the metal surface. The presentresults underline that the plasmon-induced chem-ical reactions of the molecule with the electronicstates less hybridized with metals are explainedby the direct intramolecular excitation mecha-nismbut not by the indirect hot-electron transfermechanism. These findings provide deep insightsinto the interaction between LSPs and moleculesatmetal surfaces for designing efficient plasmon-induced photocatalysis in a highly controlledfashion.

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ACKNOWLEDGMENTS

We appreciate Y. Hasegawa for supporting the preparation ofAg tips. We thank J. Yoshinobu for helpful discussions. Funding:The present work was supported in part by a Grant-in-Aid forScientific Research (A) (15H02025), a Grant-in-Aid for YoungScientists (B) (16K17862), and the RIKEN postdoctoral researchers(SPDR) program. J.J. acknowledges the financial support ofthe National Research Foundation under the Next Generation CarbonUpcycling Project (grant 2017M1A2A2043144) of the Ministry ofScience and Information and Communication Technology, Republicof Korea. H.U. was supported by Ministry of Education, Culture,Sports, Science and Technology Grants-in-Aid for Scientific Research(KAKENHI) grant C-2539000, which allows him to continue towork after retirement from the University of Toyama. M.T.acknowledges support from a grant from the NSF (CHE-1464816).We are grateful for the use of the HOKUSAI-GreatWave supercomputersystem of RIKEN. Author contributions: E.K. designed and carriedout the experiments and the finite-difference time-domain calculations.J.J. carried out the density functional theory calculations. E.K., J.J.,H.U., M.T., and Y.K. contributed to the interpretation of the results andwrote the manuscript. Y.K. planned and supervised the project.Competing interests: The authors declare no competing financialinterests. Data and materials availability: All data are presented inthe main text and supplementary materials.

SUPPLEMENTARY MATERIALS

www.sciencemag.org/content/360/6388/521/suppl/DC1Materials and MethodsSupplementary TextFigs. S1 to S13Table S1References (31–51)

13 June 2017; resubmitted 15 August 2017Accepted 7 March 201810.1126/science.aao0872

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moleculeReal-space and real-time observation of a plasmon-induced chemical reaction of a single

Emiko Kazuma, Jaehoon Jung, Hiromu Ueba, Michael Trenary and Yousoo Kim

DOI: 10.1126/science.aao0872 (6388), 521-526.360Science 

, this issue p. 521Scienceelectrons of the molecule into unoccupied states and cleaving the sulfur-sulfur bond.plasmons at different distances from the molecule. The plasmons drove the reaction directly by exciting the valencesurface dissociation of a dimethyl disulfide molecule on silver and copper surfaces. A silver STM tip created localized

used a scanning tunneling microscope (STM) to induce and map out theet al.reactions of adsorbed molecules. Kazuma Light can excite plasmons at a metal surface, which can then decay and create hot electrons that induce chemical

Direct plasmon chemistry

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REFERENCES

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