Local surface plasmon resonance (LSPR)-induced oxidation of semiconducting and metallic single-walled nanotubes (SWNTs) on the nanometer scale was investigated using surface-enhanced Raman scattering (SERS) measurements. An isolated SWNT was supported on a well-defined Au nanodimer structure that possesses an LSPR field at the nanogap under light irradiation, and highly intense SERS spectra of the SWNT at the gap region were measured. SERS analysis under O2-saturated solutions and the addition of reactive oxygen species inhibitors demonstrated that condensed singlet oxygen (1O2), which is one of the reactive oxygen species, was efficiently generated from a semiconducting SWNT at the nanogap by the LSPR field and led to the local oxidation of the tube. In contrast to the semiconducting SWNT, no defect formation was observed in a metallic SWNT, probably because of rapid quenching of the photoexcited state. This selective local defect formation by LSPR-induced oxidation of a semiconducting SWNT would provide novel nanoprocessing and nanofunctionalization methods for the fabrication of future SWNT-based nanodevices.Keywords: carbon nanotube; defect; nanoprocessing; plasmon; reactive oxygen species;

A new molecular manipulation method in the self-spreading lipid bilayer membrane by combining Brownian ratchet and molecular filtering effects is reported. The newly designed ratchet obstacle was developed to effectively separate dye–lipid molecules. The self-spreading lipid bilayer acted as both a molecular transport system and a manipulation medium. By controlling the size and shape of ratchet obstacles, we achieved a significant increase in the separation angle for dye–lipid molecules compared to that with the previous ratchet obstacle. A clear difference was observed between the experimental results and the simple random walk simulation that takes into consideration only the geometrical effect of the ratchet obstacles. This difference was explained by considering an obstacle-dependent local decrease in molecular diffusivity near the obstacles, known as the molecular filtering effect at nanospace. Our experimental findings open up a novel controlling factor in the Brownian ratchet manipulation that allow the efficient separation of molecules in the lipid bilayer based on the combination of Brownian ratchet and molecular filtering effects.

Single molecular tracking was carried out for a lipid molecule (TR-DHPE) in a self-spreading lipid bilayer (egg-PC) on a glass substrate with and without Ag nanoarchitectures. Without Ag architectures, the mean square displacement (MSD) analyses demonstrated that lipid molecules diffuse randomly within the self-spreading lipid bilayer with a diffusion coefficient of 3.1 μm2/s, which is comparable to the value for an artificial solid supported lipid bilayer. However, in the presence of the Ag architectures, TR-DHPE molecules undergo hop diffusion between two neighboring compartments surrounded by the Ag architectures. Smaller diffusion coefficients observed for the substrates with the Ag architectures are attributable to the suppressed diffusion at the gap between the Ag architectures. The escape probability from the initial compartment to the neighboring compartment estimated from the MSD analysis agreed well with the values estimated from the compartment configuration, which proves that the Ag nanoarchitectures act as a diffusion barrier.

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 the orientation of 4,4′-bipyridine molecules on HER was examined by in-situ electrochemical SERS.•Effective catalysis on HER in 0.1 M NaClO4 solution was observed.•Specific electronic interaction of molecules with electrode confirmed by non-totally symmetric mode is key for effective HER.The orientation of 4,4′-bipyridine molecules during the catalysis of the hydrogen evolution reaction was examined by in-situ electrochemical surface-enhanced Raman scattering measurements. The effect of addition of 4,4′-bipyridine molecules was examined using solutions with distinct pH. Characteristic changes in the Raman bands of 4,4′-bipyridine molecule were observed at a more negative potential than the hydrogen evolution potential in 0.1 M NaClO4 solution where improved catalytic activity was observed. The changes in the molecule orientation are discussed by the comparison with calculated spectrum. Addition to the changes in the orientations of adsorbed 4,4′-bipyridine molecules, the evolution of the Raman band assigned to non-totally symmetric mode suggests a specific electronic interaction between the molecule and the electrode to accelerate the hydrogen evolution reaction. These unique futures of HER catalysis and SERS spectrum were not observed in 0.1 M HClO4 and 0.1 M NaOH solutions.

Spatially selective deposition of conductive polymer was observed at the Au nanostructures supported on TiO2 electrodes via plasmon-induced photopolymerization of pyrrole monomers. The reactions were triggered by the excitation of localized surface plasmon resonance under near-infrared light illumination to the plasmon-active Au nanostructures. The morphological characteristics of the deposited polypyrrole prove the localization of the reaction-active sites in the plasmon-induced oxidation-reaction system. In addition, the estimation of reaction characteristics provides information on the spatial distribution and the electrochemical potential of the holes to contribute to the reaction. The unique polymer-growing process observed in the present system provides information on the mechanism of plasmon-induced oxidation reaction occurring at the active sites.

An electrochemical deposition technique was developed to realize high yield and selective synthesis of target carbon nanomaterials. The electrochemical reduction of halogenated carbons, such as carbon tetrachloride, in an ionic liquid was found to result in the formation of a thick graphitic carbon film over a Ni substrate, whereas polyacetylene formation was confirmed in the presence of a small amount of H2O. Such a novel high yield, selective carbon synthesis is expected to be a promising technique for the design of various carbon nanomaterials.

The electrochemical properties of a monolayer graphene grown on a Au(111) electrode were studied using cyclic voltammetry (CV) and electrochemical scanning tunneling microscopy (EC-STM). CV and EC-STM measurements in 0.1 M H2SO4 aqueous solution revealed that graphene grown on the reconstructed (22 × √3) Au(111) structure effectively inhibited potential-induced structural transitions between reconstructed (22 × √3) and unreconstructed (1 × 1), and the adsorption/desorption of SO42– ions, which are intrinsic behavior of the bare Au(111) surface. The underlying reconstructed structure was significantly stabilized by covering with monolayer graphene over a wide potential range between −0.2 V and +1.35 V vs Ag/AgCl (saturated KCl), which is much wider than that for bare Au(111) (−0.2 to + 0.35 V vs Ag/AgCl (saturated KCl)). Such high stability has not been reported to date; therefore, these results are considered to be important for understanding the fundamentals of surface reconstruction and also serve to open a new branch of electrochemistry related to graphene/metal–electrolyte interfaces.

Characteristic plasmon-induced enhancement of photocurrent has been observed by coupling PbS quantized particles (PbS QDs) with Au nanoparticles. A controlled size of ultrasmall PbS QDs modified with distinct ligands of 3-mercaptopropionic acid (MPA) or oleic acid was used to construct plasmon-active electrodes for three-electrode electrochemical measurements. The enhanced photoelectrochemical response of PbS QDs excited by localized surface plasmon resonance was observed at a relatively wide wavelength region. MPA capped the smaller PbS QD results in the enhancements of photocurrent at shorter wavelength light illumination below 500 nm where the plasmonic enhancement generally competes with multiexciton generation. The size-dependent resonance of PbS QDs with Au nanoparticles was discussed considering the energy of localized surface plasmon of the coupled system.

The cooperative effect of hydrogen and halogen bonds on the two-dimensional (2D) molecular arrangement on highly oriented pyrolytic graphite (HOPG) was studied by scanning tunneling microscopy. The terephthalic acid (TPA) molecule, which has two carboxyl groups attached at the para positions of a benzene ring, formed a one-dimensional (1D) linear non-covalent network structure on HOPG by hydrogen bonds between the carboxyl groups of neighboring molecules. However, unlike the TPA molecule, Br substituted TPA molecules were found to form different non-covalent network structures. Owing to Br⋯O halogen and hydrogen bonds, bromo-substituted TPA (2-bromoterephthalic acid) formed a 1D ladder-like non-covalent network structure, whereas dibromo-substituted TPA (2,5-dibromoterephthalic acid) formed a 2D non-covalent lattice network on HOPG. These results strongly indicate that Br⋯O halogen bonds significantly contribute to determine the molecular assembly as well as hydrogen bonds for molecules containing bromine groups and hydrogen bonding groups. These results provided deep fundamental insight into the cooperative effect of halogen and hydrogen bonds in 2D molecular assemblies. In addition, we have demonstrated that these interactive bonds are promising for the precise design of 2D molecular architectures.

A new molecular manipulation method in the self-spreading lipid bilayer membrane by combining Brownian ratchet and molecular filtering effects is reported. The newly designed ratchet obstacle was developed to effectively separate dye–lipid molecules. The self-spreading lipid bilayer acted as both a molecular transport system and a manipulation medium. By controlling the size and shape of ratchet obstacles, we achieved a significant increase in the separation angle for dye–lipid molecules compared to that with the previous ratchet obstacle. A clear difference was observed between the experimental results and the simple random walk simulation that takes into consideration only the geometrical effect of the ratchet obstacles. This difference was explained by considering an obstacle-dependent local decrease in molecular diffusivity near the obstacles, known as the molecular filtering effect at nanospace. Our experimental findings open up a novel controlling factor in the Brownian ratchet manipulation that allow the efficient separation of molecules in the lipid bilayer based on the combination of Brownian ratchet and molecular filtering effects.

Polarized Raman scattering measurement was carried out using a hybridized system of Ag nanodimer structures and organic dye molecules. Tuning of the localized surface plasmon resonance energy leads to modulation of the hybridized polariton energy. The anticrossing behavior of the polariton energy implies a strong coupling regime with maximum Rabi splitting energy of 0.39 eV. The observation proves the effective Raman enhancement via the excitation of the upper and the lower branches of the hybridized states at the gap of the metal dimer. Maximum Raman enhancement was obtained at an optimized resonant energy between the hybrid states and Raman excitation.Keywords: dye exciton; localized surface plasmon resonance; polarized Raman measurement; strong coupling; surface-enhanced Raman scattering;

Nitrogen-doped graphene materials with abundant pyridinic and quaternary nitrogen species were selectively synthesized by thermal surface polymerization of nitrogen-containing aromatic molecules. Catalytic studies revealed that the oxygen reduction by nitrogen-doped graphene, containing pyridinic and quaternary nitrogen species, proceeds via a four- and two-electron reduction pathway, respectively, in alkali-based solutions.

The molecular orientation and diffusion of dye molecules in artificial lipid bilayers were observed using total internal reflection fluorescence microscopy. An artificial lipid bilayer composed of a ternary lipid mixture of 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC), 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC), and cholesterol was used. The molecular orientation, which was obtained through defocused imaging, clarified the microscopic features, including cholesterol-induced changes in the local packing structure. Diffusion analysis gave insights into the macroscopic aspects of phase distribution in the heterogeneous bilayer system. Combining these two independent investigations, we revealed the effect of cholesterol addition on microscopic local packing and macroscopic phase structures. Our observations showed a transition from a DLPC-network-like structure to a DPPC-network-like structure upon the addition of cholesterol, which was not evident from previous domain shape observations. The present single-molecule observations yielded the actual phase structure that controls the motion of molecules in the membrane. The results imply that the orientation and diffusivity of molecules offer useful information regarding the phase distribution, which may be hindered by the apparent phase structure in a heterogeneous lipid bilayer that contains cholesterol.

Localized laser-induced heating of an individual Au nano-dimer was quantitatively evaluated by measuring the surface-enhanced Raman scattering (SERS) from an isolated single-walled carbon nanotube (SWNT) supported above the nano-gap between the two metal centres of the dimer. The SERS measurement showed an apparent wavenumber shift in the G-band of the Raman spectra with an increase in the power of the illuminated laser light, indicating the laser-induced local thermal elevation of the Au nano-dimer. In addition, it was found that the effect of the laser illumination on the thermal elevation in air was larger than that in aqueous solution, indicating that the localized laser-heating effect is strongly influenced by the surrounding environment. The present technique provides a measure of the highly localized heating effect of plasmonic metal nanostructures under photo-illumination.

We examined an emission of light from a single metallic nanoparticle based on surface plasmon (SP) resonance for determination of three-dimensional orientation of nanoparticles as well as their optical properties. The defocused image of individual Au nanorods (Au NRs) is recorded by changing the focus distance under total internal reflection microscopy (TIRM) observations. Numerical and statistical analysis revealed that the observed light distribution patterns of Au NRs defocused images were classified into two groups. One is explained by considering that a single dipole dominates its light emission property. The other is explained by assuming the presence of multidipoles. This result leads us to a consideration that the emission of light coupled with the transverse and the longitudinal SP modes was observed reflecting the optical characteristics of NRs. Additionally, unique multiple ring patterns were also observed by placing Au NRs at the vicinity of nanoscopic structure, reflecting the distance between NRs and the wall of the structure in the scale less than a few tens of nanometers. The inclusive SP measurement for both the transverse and longitudinal axes of these anisotropic metal NRs using a defocused imaging system brings us reliable optical and conformational information.

The in situ observation of geometrical and electronic structural dynamics of a single molecule junction is critically important in order to further progress in molecular electronics. Observations of single molecular junctions are difficult, however, because of sensitivity limits. Here, we report surface-enhanced Raman scattering (SERS) of a single 4,4′-bipyridine molecule under conditions of in situ current flow in a nanogap, by using nano-fabricated, mechanically controllable break junction (MCBJ) electrodes. When adsorbed at room temperature on metal nanoelectrodes in solution to form a single molecule junction, statistical analysis showed that nontotally symmetric b1 and b2 modes of 4,4′-bipyridine were strongly enhanced relative to observations of the same modes in solid or aqueous solutions. Significant changes in SERS intensity, energy (wavenumber), and selectivity of Raman vibrational bands that are coincident with current fluctuations provide information on distinct states of electronic and geometrical structure of the single molecule junction, even under large thermal fluctuations occurring at room temperature. We observed the dynamics of 4,4′-bipyridine motion between vertical and tilting configurations in the Au nanogap via b1 and b2 mode switching. A slight increase in the tilting angle of the molecule was also observed by noting the increase in the energies of Raman modes and the decrease in conductance of the molecular junction.

Single-wall carbon nanotubes (SWCNTs) were produced by an electrochemical route by applying a small negative potential to a solution of acetic acid over a Au surface supporting Ni nanocatalysts. Ni nanocatalysts were grown electrochemically on Au surface and their particle sizes were controlled by deposition time. Raman spectroscopy and scanning probe microscopy observations of the catalyst and as-deposited samples and revealed that the catalyst structure strongly affects the SWCNT diameter distribution. The deposited carbon structure depended on the catalyst particle size and structure. Raman spectra confirmed the existence of selectively grown semiconducting SWCNTs with very narrow diameter distribution.

A new approach is proposed for two-dimensional molecular separation based on the Brownian ratchet mechanism by use of a self-spreading lipid bilayer as both a molecular transport and separation medium. In addition to conventional diffusivity-dependence on the ratchet separation efficiency, the difference in the intermolecular interactions between the target molecules and the lipid bilayer is also incorporated as a new separation factor in the present self-spreading ratchet system. Spreading at the gap between two ratchet obstacles causes a local change in the lipid density at the gap. This effect produces an additional opportunity for a molecule to be deflected at the ratchet obstacle and thus causes an additional angle shift. This enables the separation of molecules with the same diffusivity but with different intermolecular interaction between the target molecule and surrounding lipid molecules. Here we demonstrate this aspect by using cholera toxin subunit B (CTB)–ganglioside GM1 (GM1) complexes with different configurations. The present results will unlock a new strategy for two-dimensional molecular manipulation with ultrasmall devices.

Polarized SERS was measured at the substrate with an Ag nano-dimer array immersed in 4,4′-bipyridine solution. The orientation of the molecule at the gap of the dimer changed the polarization of the scattering photons.

The molecular distribution and spreading dynamics of self-spreading lipid bilayers can be tuned by surface-modified metallic nanoarchitectures. Interactions between lipids and molecules in the surface modification alter the self-spreading behavior at the gate regions between adjacent nanoarchitectures, leading to molecular filtering/concentrating effects and modification of the dynamics. The hydrophilic surface can tune the spreading velocity without changing the molecular distribution in the spreading bilayer, whereas the hydrophobic surface provides a molecular concentrating function to the nanogates. This indicates that a combination of unmodified/hydrophobic/hydrophilic nanoarchitectures has a wide range of potential applications since it can be used to independently control the self-spreading dynamics and the molecular distribution.

We have investigated the origin of molecule filtering system based on a chemical potential barrier produced by thermodynamically driven molecular flow in a nanoscopic space at nanogates. Single molecule tracking experiments prove that the highly localized potential barrier allows for selective manipulation of the target molecule. We propose the presence of a force, a few fN per molecule, to decelerate the molecule's movement at the nanogate, which is comparable to or larger than the force applied by conventional electrophoretic operation. The present force can be tuned by changing the nanogate width at the nanometre level. These findings allow us to propose an accurate design of novel devices for molecular manipulation on an ultra small scale using a very small number of molecules without any external biases.

This Perspective describes studies aimed at effective excitation of molecules by localized surface plasmon polaritons. Recently developed bottom-up and top-down techniques allow the controlled fabrication of well-defined metal structures exhibiting desirable localization of plasmon energy. Under certain conditions, molecules display unique florescence and Raman scattering behavior in such localized fields, suggesting selective resonant excitation of specific electronic/vibrational modes. Finally, several examples of improvements in the efficiencies of photochemical and photoelectrochemcal systems are briefly discussed to find a way to overcome challenges for enhancement of photoenergy conversion in future.

A new methodology for nanoscopic molecular filtering was developed using a substrate with a periodic array of metallic nanogates with various widths between 75 and 500 nm. A self-spreading lipid bilayer was employed as the molecular transport and filtering medium. Dye-labeled molecules doped in the self-spreading lipid bilayer were filtered after the spreading less than a few tens of micrometers on the nanogate array. Quantitative analysis of the spreading dynamics suggests that the filtering effect originates from the formation of the chemical potential barrier at the nanogate region, which is believed to be due to structural change such as compression imposed on the spreading lipid bilayer at the gate. A highly localized chemical potential barrier affects the ability of the doped dye-labeled molecules to penetrate the gate. The use of the self-spreading lipid bilayer allows molecular transportation without the use of any external field such as an electric field as is used in electrophoresis. The present system could be applied micro- and nanoscopic device technologies as it provides a completely nonbiased filtering methodology.

We report the effect of local surface plasmon resonance (LSPR) of Ag nanoparticles on the emission properties of photoactivated Ag clusters. The prepared Ag nanoparticles showed strong surface enhanced Raman scattering (SERS) upon green laser excitation (514.5 nm), which indicates the appearance of an effective field enhancement. Along with the strong SERS, selective emission from the photoactivated Ag cluster was also observed only for the emissive Ag cluster that was resonant with the LSPR. The coupling with the LSPR also demonstrated the ability to observe the emission from only a single emissive site, even if several nonresonant emissive clusters are present in close proximity.

The self-spreading dynamics of lipid bilayers were investigated at controlled electrolyte concentrations. The self-spreading velocity increased when the concentration of NaCl was increased from 1 to 100 mM. Comparing the experimentally determined spreading energy with that estimated from theoretical models, we found that the self-spreading dynamics were well explained by considering the van der Waals interaction, double layer interaction and hydration interaction energies between the self-spreading bilayer and the substrate. The characteristic behavior at high concentration is attributable to the increase in the density of the lipid layer, originating from the effective shielding of the molecular charges by the electrolyte ions in solution. The distribution of doped dye-labeled molecule within the spreading bilayer was also controllable by tuning the electrolyte concentration. All of these findings were explained by systematic changes in bilayer–substrate or inter-molecular interactions depending on the electrolyte concentration.

The dynamic evolution of a gold nanojunction has been investigated by incorporation of molecular dynamics (MD) simulation and mechanically controllable break junction (MCBJ) in a wide range of strain rates, covering nonequilibrium, quasi-equilibrium, and equilibrium tensile states. Theoretical simulations corresponding to the nonequilibrium and quasi-equilibrium states demonstrated that the metallic nanojunction spontaneously grew in the time scale of ∼1 ns. In the final stage, the gap increment revealed a unique stepwise feature, corresponding to the atomic-resolved tip reconstruction. When strain rate varied from 489.6 to 0.245 m/s, the gap was reduced from 4.0 to 1.3 nm. In the regime of equilibrium stretching, i.e., several nanometers per second, the experimental MCBJ results gave a mean gap size of 0.4 ± 0.1 nm, which showed less strain rate dependence. This value corresponded well to the absolute value of the stepwise increment of the gap due to the local tip recrystallization as estimated by the MD simulation. The agreement between theoretical modeling and experimental measurement demonstrates that the combination is a good strategy in nanoscience.

We studied the quantized conductance behavior of mechanically fabricated Pt nanoconstrictions under electrochemical potential control in H2SO4, Na2SO4, and NaOH solutions. There was no clear feature in the conductance histogram, when the electrochemical potential of the nanoconstrictions was kept at the double layer or the under potential deposited hydrogen potential. At the hydrogen evolution potential, the conductance histograms showed clear features around 0.5 and 1 G0 in the H2SO4 solution. In Na2SO4, and NaOH solutions, a 1 G0 feature with a shoulder appeared in the histogram. The quantized conductance behavior of Pt nanoconstrictions could be controlled by the electrochemical potential and solution pH.

Resonant Raman scattering spectra of single-walled carbon nanotube–sodium dodecyl sulfate (SWNT–SDS) bundles adsorbed on Au electrodes have been investigated in aqueous electrolytes. Raman intensities of the radial breathing mode (RBM) with 785-nm laser excitation were monitored at different electrode potentials between −0.5 and +0.8 V relative to the SCE. Six resolved RBM peaks assignable to different diameter tubes all decreased in intensity when the electrode was positively biased, because of depletion of valence-band electrons associated with resonant excitation. The attenuation occurred at more positive potentials for narrower-diameter tubes with higher RBM frequencies consistent with their larger bandgaps. The results suggest the Fermi level is equilibrated in bundled SWNTs in contrast with the large Fermi-level shifts reported for isolated SWNTs.

Spectral features of Raman scattering of isolated single-walled carbon nanotubes (SWNT) on gold surface in aqueous solution was investigated under electrochemical potential control. Spectrum of the radial breathing mode of SWNT was dependent upon the electrode potential. Change in the intensity of the spectrum was reversible. Distinct difference in the potential dependence was observed at SWNT with different diameter. Absolute potential of the Fermi level of individual tubes was estimated from the potential dependence. Observations suggest that the work function of the tube becomes larger in a manner inversely proportional to the diameter of SWNT. Linewidth of the spectrum also showed potential dependence at the metallic tubes. Characteristics of the spectral changes induced by electrochemical doping were correlated to the difference in electronic density of individual SWNT with distinct diameter and chirality.

We have mechanically fabricated Ni and Cu nano-constrictions in solution to study their quantized conductance behavior under electrochemical potential control. Conductance quantization was observed at both metals in solution at room temperature for the first time. The conductance of Cu nano-constriction was quantized in units of G0(=2e2/h)G0(=2e2/h). A sharp 1G0 peak was observed in the conductance histogram. For Ni, a rather broad peak at 1–1.5G0 was observed in the histogram. The conductance quantization behavior was discussed by comparing previously documented results of nano-constrictions fabricated in air or ultra-high vacuum conditions, with those fabricated in solution.

The molecular orientation and diffusion of dye molecules in artificial lipid bilayers were observed using total internal reflection fluorescence microscopy. An artificial lipid bilayer composed of a ternary lipid mixture of 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC), 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC), and cholesterol was used. The molecular orientation, which was obtained through defocused imaging, clarified the microscopic features, including cholesterol-induced changes in the local packing structure. Diffusion analysis gave insights into the macroscopic aspects of phase distribution in the heterogeneous bilayer system. Combining these two independent investigations, we revealed the effect of cholesterol addition on microscopic local packing and macroscopic phase structures. Our observations showed a transition from a DLPC-network-like structure to a DPPC-network-like structure upon the addition of cholesterol, which was not evident from previous domain shape observations. The present single-molecule observations yielded the actual phase structure that controls the motion of molecules in the membrane. The results imply that the orientation and diffusivity of molecules offer useful information regarding the phase distribution, which may be hindered by the apparent phase structure in a heterogeneous lipid bilayer that contains cholesterol.

Localized laser-induced heating of an individual Au nano-dimer was quantitatively evaluated by measuring the surface-enhanced Raman scattering (SERS) from an isolated single-walled carbon nanotube (SWNT) supported above the nano-gap between the two metal centres of the dimer. The SERS measurement showed an apparent wavenumber shift in the G-band of the Raman spectra with an increase in the power of the illuminated laser light, indicating the laser-induced local thermal elevation of the Au nano-dimer. In addition, it was found that the effect of the laser illumination on the thermal elevation in air was larger than that in aqueous solution, indicating that the localized laser-heating effect is strongly influenced by the surrounding environment. The present technique provides a measure of the highly localized heating effect of plasmonic metal nanostructures under photo-illumination.

Polarized SERS was measured at the substrate with an Ag nano-dimer array immersed in 4,4′-bipyridine solution. The orientation of the molecule at the gap of the dimer changed the polarization of the scattering photons.

Nitrogen-doped graphene materials with abundant pyridinic and quaternary nitrogen species were selectively synthesized by thermal surface polymerization of nitrogen-containing aromatic molecules. Catalytic studies revealed that the oxygen reduction by nitrogen-doped graphene, containing pyridinic and quaternary nitrogen species, proceeds via a four- and two-electron reduction pathway, respectively, in alkali-based solutions.

The molecular distribution and spreading dynamics of self-spreading lipid bilayers can be tuned by surface-modified metallic nanoarchitectures. Interactions between lipids and molecules in the surface modification alter the self-spreading behavior at the gate regions between adjacent nanoarchitectures, leading to molecular filtering/concentrating effects and modification of the dynamics. The hydrophilic surface can tune the spreading velocity without changing the molecular distribution in the spreading bilayer, whereas the hydrophobic surface provides a molecular concentrating function to the nanogates. This indicates that a combination of unmodified/hydrophobic/hydrophilic nanoarchitectures has a wide range of potential applications since it can be used to independently control the self-spreading dynamics and the molecular distribution.

The self-spreading dynamics of lipid bilayers were investigated at controlled electrolyte concentrations. The self-spreading velocity increased when the concentration of NaCl was increased from 1 to 100 mM. Comparing the experimentally determined spreading energy with that estimated from theoretical models, we found that the self-spreading dynamics were well explained by considering the van der Waals interaction, double layer interaction and hydration interaction energies between the self-spreading bilayer and the substrate. The characteristic behavior at high concentration is attributable to the increase in the density of the lipid layer, originating from the effective shielding of the molecular charges by the electrolyte ions in solution. The distribution of doped dye-labeled molecule within the spreading bilayer was also controllable by tuning the electrolyte concentration. All of these findings were explained by systematic changes in bilayer–substrate or inter-molecular interactions depending on the electrolyte concentration.