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Vibrational strong coupling is an emerging method for modulation of ground-state molecular properties. Spectroscopic information about the vibrational coupling state is essential for determination ...

Hydrogen bonding interactions among water molecules play a critical role in chemical reactivity, dynamic proton mobility, static dielectric behavior, and the thermodynamic properties of water. In this study, we demonstrate the modification of ionic conductivity of water through hybridization with a vacuum electromagnetic field by strongly coupling the O─H stretching mode of H

7 pags., 4 figs., Electrogenerated chemiluminescence (ECL) mi- croscopy shows promise as a technique for mapping chemical reactions on single nanoparticles. The technique¿s spatial resolution is limited by the quantum yield of the emission and the diffusive nature of the ECL process. To improve signal intensity, ECL dyes have been coupled with plasmonic nano- particles, which act as nanoantennas. Here, we characterize the optical properties of hexagonal arrays of gold nanodisks and how they impact the enhancement of ECL from the coreaction of tris(2,2¿-bipyridyl)dichlororuthenium(II) hexahydrate and tripro- pylamine. We find that varying the lattice spacing results in a 23- fold enhancement of ECL intensity because of increased dye-array near-field coupling as modeled using finite element method simulations., This work was primarily supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, CPIMS Program under Award #DE-339SC0016534. We also acknowledge funding from the Robert A. Welch Foundation (Grant C-1787 to C.F.L. and Grant C-1664 to S.L.) We would like to thank support from the U.S. National Science Foundation (Grant ECCS-1710697) and Ministerio de Ciencia, Innovación y Universidades of Spain (Grant TEM-FLU PID2019-109502GA-I00), as well as the UNM Center for Advanced Research Computing, for providing the part of the computational resources used in this work. We also thank Grants-in-Aid for Scientific Research (JP 16H06506) from MEXT, and the Photoexcitonix Project of Hokkaido University.

The proton permeation ability of graphene has been highlighted for use as proton exchange membranes in electrochemical devices. However, the tunability of proton permeation is still limited. We hav...

Modal strong coupling between a localized surface plasmon resonance and Fabry–Perot cavity accelerates plasmon-induced oxygen evolution reactions (OERs). In this study, graphene-based electrochemic...

Understanding molecular processes at nanoparticle surfaces is essential for designing active photocatalytic materials. Here, we utilize nuclear magnetic resonance (NMR) spectroscopy to track photocatalytic hydrogen evolution using donor molecules and water isotopologues. Pt-TiO

With implication of developments of plasmonic biochips, we investigated laser trapping of cyanobacteria (CB) on a gold nanostructure, where a nanopyramidal dimer array was integrated. Upon near-inf...

Exotic electronic excitations beyond normal selection rules would open novel possibilities for photoenergy conversion. The large intensity gradient of electromagnetic fields resulting from the confinement of localized surface plasmons at the molecular scale could exceed the limit of light–matter interactions via modification of electronic excitation selection rules. We discuss the possible application of surface-enhanced Raman scattering as a probe for exotic electronic excitations by reviewing studies on small numbers of molecules at the surface of plasmonic metal nanostructures. Future innovative photo-functionalization is also discussed by considering the excited states produced by the exotic electronic excitations.

Plasmon-induced carrier transfer at metallic nanoparticle/semiconductor heterojunctions has received great attention because of its tremendous potential in applications, such as photocatalysis and photoelectric and energy conversion. The interfacial structure of the heterojunction is known to play an important role in charge transfer as well as the subsequent chemical reactions. Here, we studied the Au nanoparticle (Au-NP)-loaded (100)-, (110)-, and (111)-oriented single-crystalline strontium titanate (STO) as a model to investigate the effects of interfacial structure on the plasmon-induced charge separation between the metallic nanoparticles and semiconductors. Via photoelectrochemical characterizations, we found that the efficiency of the plasmon-induced water oxidation reaction on STO(100) is more than 1.4 times higher than that on the other two orientation facets. This enhancement was demonstrated to stem from the high oxidation ability of plasmon-induced holes captured in the surface states. Furthermore, the molecular processes of water oxidation were investigated by monitoring the surface oxidation status of Au-NP/STO as intermediates of plasmon-induced water oxidation using in situ electrochemical surface-enhanced Raman spectroscopy. The onset potential of Au-O vibrations on Au-NP/STO(100) was determined to be 0.4 V more negative than that of Au-NP/STO(110), further confirming the higher oxidation ability of the plasmon-induced holes. Our observation provides an opportunity to efficiently modulate plasmon-excited hot-carrier reaction processes for photochemical applications through interfacial engineering.

We demonstrate the size-dependent separation and permanent immobilization of DNA on plasmonic substrates by means of plasmonic optical tweezers. We found that a gold nanopyramidal dimer array enhanced the optical force exerted on the DNA, leading to permanent immobilization of the DNA on the plasmonic substrate. The immobilization was realized by a combination of the plasmon-enhanced optical force and the thermophoretic force induced by a photothermal effect of the plasmons. In this study, we applied this phenomenon to the separation and fixation of size-different DNA. During plasmon excitation, DNA strands of different sizes became permanently immobilized on the plasmonic substrate forming micro-rings of DNA. The diameter of the ring was larger for longer DNA (in base pairs). When we used plasmonic optical tweezers to trap DNA of two different lengths dissolved in solution (φx DNA (5.4 kbp) and λ-DNA (48.5 kbp), or φx DNA and T4 DNA (166 kbp)), the DNA were immobilized, creating a double micro-ring pattern. The DNA were optically separated and immobilized in the double ring, with the shorter sized DNA and the larger one forming the smaller and larger rings, respectively. This phenomenon can be quantitatively explained as being due to a combination of the plasmon-enhanced optical force and the thermophoretic force. Our plasmonic optical tweezers open up a new avenue for the separation and immobilization of DNA, foreshadowing the emergence of optical separation and fixation of biomolecules such as proteins and other ncuelic acids.

ConspectusUnder visible light illuminations, noble metal nanostructures can condense photon energy into the nanoscale region. By precisely tuning the metal nanostructures, the ultimate confinement of photoenergy at the molecular scale can be obtained. At such a confined photon energy field, various unique photoresponses of molecules, such as efficient visible light energy conversion processes or efficient multielectron transfer reactions, can be observed. Light-matter interactions also increase with the condensation of photons with nanoscale regions, leading to efficient light energy utilizations. Moreover, the strong field confinement can often modulate electronic excitations beyond normal selection rules. Such unique electronic excitations could realize innovative photoenergy conversion systems. On the other hand, such interactions lead to changes in the optical absorption property of the system via the formation of hybridized electronic energy states. This hybridized state is expected to have the potential to modulate the chemical reaction pathways. Taking these facts into consideration, a probe for the molecular absorption process with high sensitivity allows us to find novel ways for further precise tuning of light-matter interactions. In this Account, we review phenomena of unique electronic excitations from the perspective of our previous investigations using surface-enhanced Raman scattering (SERS) spectroscopy at electrified interfaces. Because the enhancement mechanism of Raman scattering at interfaces is deeply correlated with the photon absorption process accompanied by the electronic excitations between molecules and electrode surfaces, the detailed SERS investigations of the well-defined system can provide information on the electronic excitation processes. Through SERS observations of single-molecule junctions at electrodes or well-defined low-dimensional carbon materials, we have observed the characteristic Raman bands containing additional polarization tensors, indicating the occurrence of electronic polarization induced by electronic excitations based on a distinct selection rule. The origins for the observed facts were attributed to the highly condensed electric field producing the huge intensity gradient at the nano scale. The electrochemical potential control of the system would be valuable for the control of the excitation process. Additionally, from Raman spectra of dye molecules coupled to the plasmonic field, the changes in the Raman scattering intensity depending on the strength of interactions suggested the modulation of the absorption characteristics of the system. In addition, we have proved that the electrochemical potential control method can be a powerful tool for the active tuning of the light-matter interaction, leading to the change in the light absorption property. The molecular behaviors of dyes in the strong-coupling regime were reversibly tuned to show intense SERS. The current descriptions provide novel insights for these unique electronic excitations, realized by the plasmon excitation, that lead to advanced photoenergy conversions beyond the limits of present systems.

The vibrational strong coupling, where vibrational energy states of molecules and an optical cavity mode are hybridized, is an emerging method for the modification of ground-state thermochemical reactivity of molecules. Here, we report that vibrational strong coupling promotes ionic conductivity of aqueous electrolyte. A Fabry-Pérot cavity were fabricated for the spectroscopic analysis and electrochemical impedance measurements of electrolyte solution. We observed the splitting of vibrational state of water in optical cavity with the Rabi splitting energy of 760 cm−1 by matching cavity mode frequency to OH stretching mode frequency of water molecules. From the electrochemical impedance measurements, we discovered the modulation of relative dielectric constants and one-fold promotion of proton conductivity of the aqueous electrolyte. This study demonstrates that the use of vibrational strong coupling system for the promotion of ionic conductivity utilized for the electrochemical energy conversion system without light pumping.

Membrane fusion (MF) is one of the most important and ubiquitous processes in living organisms. In this study, we developed a novel method for MF of liposomes. Our method is based on laser-induced bubble generation on gold surfaces (a plasmonic nanostructure or a flat film). It is a simple and quick process that takes about 1 min. Upon bubble generation, liposomes not only collect and become trapped but also fuse to form long tubes beneath the bubble. Moreover, during laser irradiation, these long tubes remain stable and move with a waving motion while continuing to grow, resulting in the creation of ultralong tubes with lengths of about 50 μm. It should be noted that the morphology of these ultralong tubes is analogous to that of a sea anemone. The behavior of the tubes was also monitored by fluorescence microscopy. The generation of these ultralong tubes is discussed on the basis of Marangoni convection and thermophoresis.

The efficient visible light energy conversion to the electrochemical reaction system is an important challenge in the field of photoelectrochemistry. The visible light driven hydrogen evolution reaction can be recognized as one of the important targets. Recently, the introduction of the plasmonic metal nanostructures into the semiconductor electrodes has been received much attention because the system which is recognized as the plasmonic photoconversion electrode realizes the visible light response characters. Although various systems have been achieved both the cathodic and anodic reactions through the selection of the materials, the molecular process or charge transfer process have not been fully understood yet. In this study, we have proposed the plasmonic cathode system by combining the p-type semiconductor electrode with the plasmonic nanostructures and examined the both the electron transfer process.We have confirmed the unique isotope effects which cannot be observed the conventional cathode system, reflecting novel characteristics of molecular process at the plasmonic cathodes.

Plasmonic chemical reactions triggered by the excitation of a localized surface plasmon show unique reactivity in a highly localized electric field. In this study, visible light driven hydrogen evo...

Proton plays a critical role in electrochemical systems to control electrochemical reactivity or isotopic enrichment. Graphene is intensively investigated owing to its unique electronic structure and device fabrication. Through the structural tunability of graphitic materials by chemical or physical modification of the surface, graphene is revealed to be an ideal material for proton manipulation. Here, we review the use of graphene or graphitic materials toward the manipulation of proton with regard to the following three points. (1) Electronic properties of graphene: The electronic band structure of graphene can be modified by metal contacts owing to the interaction with a metal surface. (2) Molecular control of graphitic interface: The chemical structure of graphene can be modified, as is done in molecular chemistry, and can be used as a catalytic platform. (3) Proton conduction by graphene: Proton transport through a graphene layer occurs with a unique mechanism such as tunneling. We provide a perspective on the use of graphitic materials toward controlling the behavior of protons on the basis of the aforementioned points. From the above, graphene can be used as a platform for proton manipulation.

Electrochemical surface-enhanced Raman scattering measurements of single layer graphene provide unique information on resonant excitation induced by localized surface plasmons under controlled electron or hole doping. The highly confined electromagnetic field from the LSPs of the Au nanodimer structures prepared on defect-free graphene can generate holes and electrons of the electrochemical potentials beyond the limit of far-field light illumination. The electrochemical in situ SERS spectra prove nonzero wavevector excitation through the observation of normally forbidden Raman bands in graphene. The present findings point to a novel approach to breaking the limit of optoelectronic interactions and photochemical reactions of graphene and other semiconductors.

Electrochemical surface-enhanced Raman scattering measurements of a monomolecule layer have been performed using a single Au dimer structure with a well-defined gap distance. Through the bianalyte ...

Surface-enhanced Raman scattering measurements have been conducted using plasmonic dimer structures under electrochemical potential control. We have confirmed the potential dependence of the adsorp...

The surface enhanced-Raman spectroscopy (SERS) of the graphene was measured using Au nanodimers prepared by angle-resolved nanosphere lithography and 785 nm laser with increasing power. It is found that the ratio between D band and 2D band changes with laser power. The change is attributed to the effect of localized surface plasmon (LSP), which causes the restructuring of Au nanodimers and oxidation of graphene. We established the method to characterize the formation of the defects in graphene using SERS.

The oxygen evolution reaction is essential in the solar production of chemical fuels, green hydrogen. Plasmonic metal-semiconductor systems can be potentially used for the production. Hot electrons generated by localized surface plasmon resonance are rapidly injected into the semiconductor, and concentrated hot holes oxidize water on the catalysts for oxygen evolution. Using Ni-modified Au/TiO2, in situ electrochemical surface-enhanced Raman spectroscopy was performed over the pH range of 7–13. Significantly enhanced photocurrents at near-neutral conditions were generated with low-energy photons (1.58 eV). The results prove that nickel-based catalysts accelerated the four-electron multistep reaction via plasmon-assisted water oxidation.

To control of the motion of individual molecules at room temperature, optical tweezers could be the choice of the methods to realize the desirable selectivity with high resolution in time and space. In this study, we demonstrated plasmonic optical trapping of small molecules at the gap of a single metal nanodimer immersed in an electrolyte solution. In situ electrochemical surface-enhanced Raman scattering measurements proved that the plasmonic structure realized selective molecular condensation leading to the formation of unique mixed molecular phases that were distinct from those under thermodynamic equilibrium in nano scale.

Plasmon-induced chemical reactions triggered by near-infrared light illumination might enable efficient photo energy conversion. Here, electrochemical oxidative polymerization of a conductive polymer was conducted on plasmonic photoconversion electrodes. The absolute electrochemical potential of the generated holes was estimated from the redox potentials of the monomers. In addition, well-defined plasmonic structures were examined to better understand the relationship between the excited plasmon mode and spatial distribution of reaction active sites. Rod structures with various lengths had distinct spatial distributions of reaction active sites that depended on the higher plasmon modes, as visualized by Raman measurements.

Highly localized electric field induced by the excitation of the localized surface plasmon provides huge gradient of the field intensity in nano-scale. Such gradient results in exotic perturbation for molecules at electrified interfaces with plasmonically-active metal nanostructures. In this study, plasmon-induced hydrogen evolution reactions have been successfully induced by the combination of the plasmonic metal nanostructures on the p-type GaP semiconductor electrode. Through various photoelectrochemical measurements, it was found that the present system showed the relatively higher efficiency under the neutral condition compared with the acidic and the basic conditions. In addition, the unique molecular process has been observed by using the isotopic water molecules. By the examination of the isotopic effect, the effect of the field localization on the reaction was discussed.

Highly reproducible control of metal plasmonic nanostructures has been achieved via precise tuning of the electrochemical Au dissolution reaction that occurs at the surfaces of well-defined bridged nanodisk dimer structures on an atomic scale. It was found that the scattering intensity is strongly suppressed during the transition from the conductive mode to the gap mode of the localized surface plasmon resonance during the period when the gap is formed and increased between Au nanodisks. The characteristic shift of the plasmon mode during this suppression of the scattering intensity verifies the excitation of the bonding quadrupolar mode, which appears only at sub-nanometer gap distances (d < 1 nm). Electrochemical potential control demonstrates that the scattering suppression states with estimated gap distances of less than 1 nm can be maintained for more than 100 s under ambient conditions. The method and phenomena presented here will be useful in the preparation of plasmonic structures for ultimate light confinement applications.

Single layer graphene was used to determine the electrochemical potential of plasmonic nano-structures for photoelectrochemical energy conversions. From electrochemical Raman measurements of the graphene layer under near-infrared light, illumination has revealed the relationship between the photoenergy conversion ability and the Fermi level of the plasmonic structure. The determination is based on in situ monitoring of G and 2D Raman bands of the graphene layer on plasmonic structures. The correlation plots of G and 2D bands show the dependence on the photoconversion ability. The present electrochemical Raman measurements provide detailed understanding of the plasmon-induced charge transfer process for further developments on the ability.

The vibrational characteristics of ligand-capped lead sulfide (PbS) quantum dots (QDs) were clarified via electrochemical surface-enhanced Raman spectroscopy (EC-SERS) using a hybridized system of gold (Au) nanodimers and PbS QDs under electrochemical potential control. Enhanced electromagnetic field caused by the coupling of QDs with plasmonic Au nanodimers allowed the characteristic behavior of the ligand oleic acid (OA) on the PbS QD surface to be detected under electrochemical potential control. Binding modes between the QDs and OA molecules were characterized using synchronous two-dimensional correlation spectra at distinct electrochemical potentials, confirming that the bidentate bridging mode was probably the most stable mode even under relatively negative potential polarization. Changes in binding modes and molecular orientations resulted in fluctuations in EC-SERS spectra. The present observations strongly recommend the validity of the QD–plasmonic nanostructure coupled system for sensitive molecular detection via EC-SERS.

We tuned the plasmonic properties of the Au lattice structure by electrochemical potential control. Au lattice structures with different values of the spacing, diameter, and height show characteristic optical properties determined by the surface lattice resonance of the localized surface plasmon mode. Electrochemical potential control can change the metal structures through metal dissolution, as well as the energy of the electrons in metals. In situ real time observation of the optical properties of Au lattice structures by electrochemical dark-field scattering microscopy shows the fine-tuning of the plasmonic properties with characteristic resonance energy and controlled spectral width. By controlling surface dissolution of the Au lattice structure at a rate of a few nanometers per minute, we tuned the plasmonic properties and achieved a spectral width of 0.145 eV at a maximum resonance of 1.74 eV (714 nm).

In situ electrochemical Raman spectroscopic measurements of defect-free monolayer graphene on various substrates were performed under electrochemical potential control. The G and 2D Raman band wavenumbers (ωG, ω2D) of graphene were found to depend upon the electrochemical potential, i.e., the charge density of graphene. The values of ωG and ω2D also varied depending on the choice of substrates. On metal substrates where graphene was synthesized by chemical vapor deposition, a strong blue shift of ω2D was induced, which could not account for the strain and charge doping. We attributed the blue shift of ω2D to a change in the electronic properties of graphene induced by distinct electronic interactions with the metal substrates. To explain the unique characteristics in the Raman spectrum of graphene on various substrates, a novel mechanism is proposed considering reduction of the Fermi velocity in graphene owing to dielectric screening from the metal substrates.

Here we report the tuning of a number of excited dye molecules that were strongly coupled with the localized surface plasmons (LSPs) of Au nanostructures by electrochemical potential control. Using the redox-state-tuned dye molecules and several types of metal nanostructures with distinct LSP energies, active control of the high coupling strength was achieved via an electrochemical potential-based control method. One interesting finding of the present work is that the parabolic behavior of the coupling strength in the range between 0.10 and 0.27 eV is dependent on the electrochemical potential; this has not been observed previously. Anticrossing plots showing the energies of the upper and lower states of the coupling to the LSP energy suggest that the number of dye molecules contained in the cavity-confined LSP field is controlled not only by the redox states of the dye molecules but also by the interactions between the dyes and the metal surfaces. The present finding provides a novel route to control lig...

Efficient use of light energy is regarded as a key factor in solution of the energy problems for a sustainable society. The highly concentrated photon energy generated by localized surface plasmon resonance excitation in the vicinity of metal nanostructures can enhance light-matter interaction. Optimization of the interactions between plasmons and electrons in materials can lead to novel light energy applications. To overcome the current limitations for these interactions, the plasmon field must be focused to an extremely small size close to the molecular scale. Formation of the plasmonic field at the quantum limit may cause interesting phenomena with unique photo responses to appear. Recently, following the development of nanofabrication techniques, detailed investigations have been undertaken to understand this process. In this focus review, we describe recent advances in the strong interactions between highly localized photons and electrons in nanomaterials, including molecules, nanocarbons, and quantized nanoparticles. First, we outline the plasmonic properties that depend on the metal nanostructures. In addition, we describe surface-enhanced Raman scattering (SERS), which is used to detect interactions between plasmons and materials. The importance of the resonant electronic excitation process, which is a chemical effect based on the charge transfer contribution, is discussed while considering unique molecular selectivity in SERS. We then highlight the unique photoresponse properties that are used for ultra-sensitive detection of single molecules by the localized plasmon field. This a major advantage of application of the plasmon field. Next, we introduce strong coupling between plasmons and excitons. This coupling state is promising because of its ability to modify the intrinsic optical properties of materials via creation of a novel absorption wavelength region to accumulate the light energy. Finally, we discuss the use of plasmon excitation for effective chemical reactions accompanied by electron transfer. We conclude that reduction of light to the molecular scale would open the novel routes for energy manipulation required by the next generation of society.

The intensity of Raman scattering from dye molecules strongly coupled with localized surface plasmons of metal nanostructures was controlled by the electrochemical potential. Through in situ electrochemical extinction and surface-enhanced Raman scattering measurements, it is found that the redox state of the molecules affects the coupling strength, leading to the change in the intensity of the Raman scattering. Analysis of the Raman spectrum provides information on the molecules in strong coupling states showing effective enhancement of Raman scattering.

The effect of plasmon excitation on metal nanostructures was investigated under electrochemical potential control with intense pulsed laser illumination. The well-defined Au nano-rod structures showed a distinct thermal effect in the form of shape transformation, in the absence of the plasmon-induced electron transfer reaction. It was found that the shape transformation only occurred under the resonance condition of the localized surface plasmon mode excitation.

The discovery of the enhancement of Raman scattering by molecules adsorbed on nanostructured metal surfaces is a landmark in the history of spectroscopic and analytical techniques. Significant experimental and theoretical effort has been directed toward understanding the surface-enhanced Raman scattering (SERS) effect and demonstrating its potential in various types of ultrasensitive sensing applications in a wide variety of fields. In the 45 years since its discovery, SERS has blossomed into a rich area of research and technology, but additional efforts are still needed before it can be routinely used analytically and in commercial products. In this Review, prominent authors from around the world joined together to summarize the state of the art in understanding and using SERS and to predict what can be expected in the near future in terms of research, applications, and technological development. This Review is dedicated to SERS pioneer and our coauthor, the late Prof. Richard Van Duyne, whom we lost during the preparation of this article., Funding is acknowledged from the European Research Council (ERC Advanced Grant No. 787510-4DBIOSERS to L.M.L.-M., ERC Advanced Grant No. 789104-eNANO to F.J.G.A., ERC Starting Grant No. 259432-MULTIBIOPHOT to J.K., ERC Consolidator Grant No. 772108-DarkSERS); the Department of Education of the Basque Government (Grant No. IT1164-19 to J.A.); the Spanish MINECO (CTQ2017-88648-R to R.A.-P., MAT2016-77809-R to I.P.-S. and J.P.-J.); the EPSRC (EP/P034063/1 to S.B., EP/L027151/1 to J.B., EP/L014165/1 to D.G. and K.F.); IDUN-Danish National Research Foundation (DNRF122) and Villum Fonden (Grant No. 9301) to A.B.; the National Research Foundation of Korea (Grant No. 2019R1A2C3004375 to J.B.); the German Science Foundation, DFG (SFB 1278 Polytarget (Project B4) to V.D., Grant No. SCHL 594/13-1 to S.S., Germany’s Excellence Strategy (EXC 2089/1-390776260) to S.M.); the Federal Ministry of Education and Research, Germany (BMBF) (Grant InfectoGnostics 13GW0096F to D.C.-M. and J.P.); DARPA-16-35-INTERCEPT-FP-018 to L.F.; the UK BBSRC (Grant No. BB/L014823/1 to R.G.); the Department of Science and Technology (DST Nanomission Project SR/NM/NS-23/2016 to K.G.T.); the U.S. National Science Foundation (Grant No. CHE-1707859 to A.J.H., Center for Sustainable Nanotechnology CHE-1503408 (Centers for Chemical Innovation Program) to C.L.H., Center for Chemical Innovation Chemistry at the Space-Time Limit (CaSTL) CHE-1414466 to G.C.S. and R.P.V.D., Grant No. CHE-1807269 to K.A.W.); the Knut and Alice Wallenberg Foundation to M.K.; the Office of Naval Research (Grant No. N00014-18-1-2876 to N.A.K.); Royal Society of New Zealand Te Apa̅rangi to E.L.R. and B.A.; Singapore Ministry of Education, Tier 1 (RG11/18) to X.Y.L.; the Photoexcitonix Project in Hokkaido Univ., Japan, to K.M.; BioNano Health-Guard Research Center funded by the Ministry of Science and ICT (MSIT) of Korea as Global Frontier Project (Grant No. H-GUARD_2013M3A6B2078947) to J.-M.N.; NSFC of P. R. China (Grant No. 21705015 to Y.O., Grant No. 21633005 to B.R.); National Key R&D Program (2017YFA0206902) to C.X. This work was coordinated under the Maria de Maeztu Units of Excellence Program from the Spanish State Research Agency—Grant No. MDM-2017-0720.