Language：English   Publishing type：Research paper (scientific journal)  

In this study, we focus on the antimicrobial properties of tempeh, a soybean fermented food, against oral bacteria. Tempeh showed antimicrobial activity against dental caries pathogenic bacterium Streptococcus mutans at a final concentration of 1 mg/mL. An antimicrobial substance contained in tempeh was present in the 100 kDa or greater fraction generated by ultrafiltration, but it was found not to be proteinaceous by native-PAGE, SDS-PAGE and protein degradation tests. Next, when the fraction was purified with an ODS column, the 80% and 100% methanol eluates showed antimicrobial activity against S. mutans. The 100% methanol eluate was further subjected to a 2nd column purification, and isolation of the target was confirmed by HPLC. When the isolated material was analyzed by ESI-MS, the m/z was 279.234. Further analysis by Raman spectroscopy revealed a peak similar to linoleic acid. This substance also possessed antimicrobial properties equivalent to linoleic acid.

DOI： 10.1016/j.ijfoodmicro.2020.108645

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

We evaluated the hot carrier generation in two-dimensional (2D) silver nanoparticle (AgNP) arrays under light illumination at different wavelengths, 458, 532, 671, and 785 nm. The 2D AgNP arrays were tailored to match the plasmon resonance to each excitation wavelength in order to fulfill the on-resonant condition. We selected para-aminothiophenol (p-ATP) as a probe molecule, which is chemically transformed into 4,4'-dimercaptoazobenzene (DMAB) upon light illumination. The reaction is driven by hot carriers emitted from a plasmonic surface. For evaluation of hot carrier generation, we monitored the chemical transformation from p-ATP into DMAB with surface-enhanced Raman scattering. The normalized Raman intensity of DMAB was plotted against the total exposure, where the peak intensity increased as the total exposure increased because of the increase of the number of DMAB molecules. The saturation of the peak growth was observed, indicating that the chemical transformation was completed, at different exposures for each wavelength. The total exposure required for completing the chemical transformation was smaller at 458 nm by at least similar to 10(5) times than that at 785 nm, although the difference of the photon energy was only 1.7 times. The growth of the Raman peak was related to the laser intensity as well, where the higher laser intensity showed a more rapid growth. These results indicated that more hot carriers with sufficient energy for the chemical transformation were generated at shorter excitation wavelengths as well as at higher laser intensities.

DOI： 10.1021/acs.jpcc.0c04034

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Surface-enhanced Raman scattering (SERS) spectra of organic compounds, para-methylthiophenol (p-MT), decylamine and 1-butanethiol (1-BT), were measured using a two-dimensional silver nanoparticle array at 532 nm excitation. For p-MT, it was observed that Raman peaks grew at 1580 and 1690 cm(-1), which were never observed in the normal Raman spectrum, indicating oxidation from the methyl to carboxyl group. For both decylamine and 1-BT, an intensive SERS peak grew at 1580 cm(-1). We measured the time-resolved SERS spectra of 1-BT at the laser intensity of 185 W mm(-2) and confirmed that the spectral shapes changed as the total exposure increased. Another SERS peak was also observed at 3050 cm(-1) for decylamine and 1-BT. From these results, it was considered that unsaturated bonds were formed in the alkanes, meaning that alkenes were produced from alkanes. Additionally, the SERS spectrum revealed that the chemically transformed alkane possesses a methyl group. The result indicates that dehydrogenation preferentially occurs at the secondary carbons, which is consistent with the stability of radicals on carbon atoms. The laser intensity threshold for plasmon-mediated chemical transformation was experimentally observed to be 2.7 and 40 W mm(-2) for p-MT and 1-BT, respectively. The higher laser intensity is necessary for oxidation of alkanes compared with aromatic compounds, which is consistent with the chemical stability of organic compounds.

DOI： 10.1039/c9cp00129h

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

Hydrophobic effect was utilized to self-assemble gold nanoparticles into oligomer structures, or plasmonic dimers, trimers, and so on. Langmuir-Blodgett film of n-octadecanamine was prepared on a glass substrate. Citrate-stabilized gold nanoparticles were adsorbed onto the film, resulting hydrophobic point decoration. The gold nanoparticles with the point decoration were removed from the substrate and self-assembled into plasmonic dimers in ethanol. The products were observed by an atomic force microscope, where not only dimers but also trimers and other aggregates were found. The yield of the plasmonic dimer was similar to 13% without any purifications. We measured the scattering spectrum of the single plasmonic dimer, exhibiting the optical anisotropy. (C) 2018 The Japan Society of Applied Physics

DOI： 10.7567/JJAP.57.120311

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Applied Physics  

In a previous report, a self-growing approach was proposed for fabricating complex silver nanostructures, where silver dendrites were grown at silver nanoseeds in silver ion solution owing to plasmonic heating with ultraviolet light. Structures were deformed or destroyed when they were extracted with acetone and dried in air. In this Letter, we discuss the use of supercritical carbon dioxide fluid for the nondestructive extraction of nanostructures. We show the experimental results and discuss the laser power dependence of resultant structures. Another experiment was performed for nanostructure growth inside an agarose gel as a matrix. Silver nanostructures were immobilized without damage in an agarose skeleton network.

DOI： 10.7567/APEX.11.025201

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE  

We developed a method to collect micro- and nano-vesicles on a glass substrate using the optical pressure of a laser beam. The laser beam was focused on the glass substrate which sandwiches a suspension containing micro- or nano-sized vesicles prepared by a phospholipid. The optical pressure generated at the interface of the medium and the vesicles accelerated the vesicles to form aggregates on the glass surface. Two types of glass substrates, hydrophilic and aminated ones, showed no difference in the adsorption property of the vesicles. Time to be required for collecting a certain amount of the vesicles was inversely proportional to the concentration of the vesicles. To enhance the collection efficiency, gold nanoparticles were added to the suspension of the vesicles. We found that gold nanoparticles reduced the collection time as short as 1/10-times.

DOI： 10.1117/12.2317724

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society  

We describe a process for collecting micro- and nanovesicles on a glass substrate using the optical pressure of a laser beam. The laser beam was focused on a glass substrate that sandwiched a solution containing vesicles prepared using a phospholipid. The optical pressure generated at the surface of the vesicles pulled them into the center of the beam where they formed an aggregate on the glass surface. The vesicles prepared with a buffer solution were successfully collected via adsorption onto the glass surface, whereas the vesicles prepared with pure water exhibited no such tendency. The time required to collect a certain amount of vesicles was inversely proportional to their concentration. To enhance the collection efficiency, we added gold nanoparticles to the vesicle solution. The addition of gold nanoparticles into the solution reduced the collection time to one-tenth of that without it, and this was attributed to thermal mixing promoted by the heat generated by the absorption from the gold nanoparticles in the solution, as well as to an enhancement of light scattering induced by the gold nanoparticles. The optical collection of vesicles coupled with gold nanoparticles shows a promise for the collection of trace amounts of extracellular vesicles in biological fluids.

DOI： 10.1021/acsomega.8b00033

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

A technique of selective electroless plating onto PLA-ABS (Polylactic Acid-Acrylonitrile Butadiene Styrene) composite structures fabricated by three-dimensional (3D) printing is demonstrated to construct 3D microwave metamaterials. The reducing activity of the PLA surface is selectively enhanced by the chemical modification involving Sn2+ in a simple wet process, thereby forming a highly conductive Ag-plated membrane only onto the PLA surface. The fabricated metamaterial composed of Ag-plated PLA and non-plated ABS parts is characterized experimentally and numerically to demonstrate the important bi-anisotropic microwave responses arising from the 3D nature of metallodielectric structures. Our approach based on a simple wet chemical process allows for the creation of highly complex 3D metal-insulator structures, thus paving the way toward the sophisticated microwave applications of the 3D printing technology. Published by AIP Publishing.

DOI： 10.1063/1.4986203

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Noble metallic nanostructures provide a platform for high-sensitivity spectroscopic sensing with significantly enhanced electromagnetic fields due to surface plasmon polaritons. However, target molecules can be transformed into other molecules under irradiation with an excitation laser during the surface-enhanced measurement, which thus disturbs detection of unknown samples. In this paper, we perform Raman measurements of p-aminothiophenol on gold nanosurfaces with and without deposition of SiO2 thin films at the surface. The Raman signals, are enhanced on both substrates, but the deposition of the glass thin film clearly prevents the chemical transformation. This indicates that hot electrons are effective for Chemical transformation and that thin glass films are sufficient to prevent this while still benefiting from surface plasmons.

DOI： 10.1021/acs.jpcc.7b02345

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC ANALYTICAL CHEMISTRY  

Coalescence of oil droplets in an oil-in-water (O/W) emulsion was achieved with heating and optical trapping. Three types of O/W emulsions were prepared by adding a mixture of butanol and n-decane to an aqueous solution containing a cationic surfactant (cetyltrimethylammonium bromide, CTAB), an anionic surfactant (sodium dodecyl sulfate, SDS), or a neutral hydrophilic polymer (polyethylene glycol, PEG) as an emulsifier. Two oil droplets in the emulsions were randomly trapped in a square capillary tube by two laser beams in order to induce coalescence. Coalescence of the droplets could not be achieved at room temperature (25 degrees C) regardless of the type of emulsifier. Conversely, the droplets prepared with PEG coalesced at a temperature higher than 30 degrees C, although the droplets with ionic surfactants CTAB and SDS did not coalesce even at the elevated temperature due to their electrostatic repulsion. The size of the resultant coalesced droplet was consistent with that calculated from the size of the two droplets of oil, which indicated successful coalescence of the two droplets. We also found that the time required for the coalescence could be correlated with the temperature using an Arrhenius plot.

DOI： 10.2116/analsci.33.709

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Authorship：Lead author  

DOI： 10.1063/1.4952997

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

Gold/silver nanoparticles were trapped at the oil/water interface of oil droplets dispersed in water. The metallic nanoparticles were self-assembled into a uniform two-dimensional large array structure through the aggregation and coalescence of the nanoparticle-covered oil droplets. The plasmon resonance of the array structure was tunable and a surface-enhanced Raman scattering measurement was performed with the silver nanoparticle array. The enhancement factor was similar to 10(5) and enhanced Raman signals were observed over the whole array (greater than or similar to cm(2)) with high reproducibility, which is an advantage of a self-assembly method using a liquid/liquid interface. (C) 2016 The Japan Society of Applied Physics

DOI： 10.7567/APEX.9.075003

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Noble metallic nanosurface exhibits both plasmonic and catalytic functions. Surface-enhanced Raman scattering of para-aminothiophenol (p-ATP) was measured on a highly uniform two-dimensional silver nanoparticle array at different intensities of an excitation laser (532 nm) ranging from 4 to 4000 W/mm(2). It was observed that p-ATP was chemically transformed to 4,4'-dimercaptoazobenzene (DMAB) with the laser intensities of >= 40 W/mm(2) during the Raman measurement. At 4 W/mm(2), the Raman peaks of DMAB disappeared, which indicates that the laser intensity was insufficient for the chemical transformation although it was sufficient for the Raman measurement. The highly uniform silver nanoparticle array allowed quantitative analysis on the Raman peak intensity. The threshold of the chemical transformation from p-ATP to DMAB was estimated to be similar to 48.8 W/mm(2) on the silver nanoparticle array whose enhancement factor is similar to 10(4).

DOI： 10.1021/acs.jpcc.6b01756

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：OSA - The Optical Society  

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The thermoacidophilic iron-oxidizing archaeon Acidianus brierleyi is a microorganism that could be useful in the removal of inorganic As from wastewater, because it simultaneously oxidizes As(III) and Fe(II) to As(V) and Fe(III) in an acidic culture medium, resulting in the immobilization of As(V) as FeAsO₄. To investigate the oxidation mechanism, speciation of the As species in both the cells and its culture media is an important issue. Here we describe the successive determination of As(III), As(V), and total As in A. brierleyi and its culture medium via a facile method based on inductively coupled plasma-optical emission spectroscopy (ICP-OES) with a flow injection pretreatment system using a mini-column packed with an anion-exchange resin. The flow-injection pretreatment system consisted of a syringe pump, a selection valve, and a switching valve, which were controlled by a personal computer. Sample solutions with the pH adjusted to 5 were flowed into the mini-column to retain the anionic As(V), whereas As(III) was introduced into ICP-OES with no adsorption on the mini-column due to its electrically neutral form. An acidic solution (1 M HNO₃) was then flowed into the mini-column to elute As(V) followed by ICP-OES measurement. The same sample was also subjected to ICP-OES without being passed through the mini-column in order to determine the total amounts of As(III) and As(V). The method was verified by comparing the results of the total As with the sum of As(III) and As(V). The calibration curves showed good linearity with limits of detection of 158, 86, and 211 ppb for As(III), As(V), and total As, respectively. The method was successfully applicable to the determination of the As species contained in the pellets of A. brierleyi and their culture media. The results suggested that the oxidation of As(III) was influenced by the presence of Fe(II) in the culture medium, i.e., Fe(II) enhanced the oxidation of As(III) in A. brierleyi. In addition, we found that no soluble As species was contained in the cell pellets and more than 60% of the As(III) in the culture medium was oxidized by A. brierleyi after a 6-day incubation.

DOI： 10.1016/j.talanta.2014.01.057

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Hydro gel formed by 5'-guanosine monophosphate (GMP) in the presence of a potassium ion is expected to exhibit interesting selectivity in capillary electrophoretic separations. Here, we estimated the conditional association constants between the hydro gel (G-gel) and aromatic compounds by capillary electrophoresis in order to investigate the separation selectivity that is induced by the G-gel. Several aromatic compounds were separated in a solution containing GMP and potassium ion at different concentrations. The association constants were calculated by correlating the electrophoretic mobilities of the analytes obtained experimentally using a concentration of G-gel. During semi-quantitative estimation, naphthalene derivatives had larger association constants (K-ass = 10.3-16.8) compared with those of benzene derivatives (K-ass = 3.91-5.31), which means that the binding sites of G-gel match better to a naphthalene ring than to a benzene ring. A hydrophobic interaction was also found when the association constants for alkyl resorcinol were compared with those of different hydrocarbon chains. The association constants of nucleobases and tryptophan ranged from 6.05 to 12.6, which approximated the intermediate values between benzene and naphthalene derivatives. Consequently, the selective interaction between G-gel and aromatic compounds was classified as one of three types: (1) an intercalation into stacked planar GMP tetramers; (2) a hydrophobic interaction with a long alkyl chain; or, (3) a small contribution of steric hindrance and/or hydrogen bonding with functional groups such as amino and hydroxyl groups. (C) 2013 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.chroma.2013.02.090

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

A series of C-2v symmetrical two-photon absorption compounds with anthracene core, 2,7-bis[2-(4-substituted phenyl)-vinyl]-9,10-dipentyloxyanthracenes designated as I, II and III (the substituted groups at the 4-position of phenyl of I, II and III were dimethylamino, methyl and cyano, respectively) were designed and synthesized as initiators in two-photon induced polymerization (TPIP). The anthracene ring was modified by linking vinylphenyl groups to the 2,7-position to extend conjugation system length and two pentyloxy groups to the 9,10-position to serve as electronic donors. Two-photon absorption cross section of I was around 300 GM, which was much larger than the 10 GM of II and 29 GM of III at 800 nm. I of 0.18% molar ratio in resin composed of methacrylic acid and dipentaerythritol hexaacrylate exhibited a dramatically low threshold of 0.64 mW compared with commercial photoinitiator benzil at a scanning speed 10 mu m s(-1). Moreover, the threshold of photoinitiator I was only increased to 2.53 mW at a scanning speed of 1000 mu m s(-1). The dependency of threshold on the concentration and exposure time was in accordance with theoretical calculation. Finally, a reasonable mechanism of the two-photon initiating process was proposed. This study provides good prospects for developing low threshold photoinitiator in TPIP.

DOI： 10.1039/c2cp42512b

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

The morphology and size dependence of silver microstructures in a novel microfabrication process, fatty salts-assisted multiphoton photoreduction (MPR), were investigated by using the fatty salts with different carbon chain lengths (C (n) : n=4,5,7,9) under varied powers and irradiation times of a femtosecond near-infrared laser with the wavelength of 800 nm. Not only the feature size of the silver structures was reduced but also the surface smoothness was improved by increasing the chain length of the fatty salts. The highest resolution of a silver line was obtained to be 285 nm, which exceeded the diffraction limit. The fatty salts-assisted MPR microfabrication approach would provide an efficient protocol for fabricating metallic micro/nanostructures with fine morphology and size and could play an important role in the fabrication of the metallic micro/nanostructures for applications in photonics and electronics as well as in sensors.

DOI： 10.1007/s00339-009-5270-7

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

DOI： 10.1002/smll.200801179

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Two-photon-induced metal ion reduction technique is developed for fabricating 3D metallic micro/nano structures. The fabrication of continuous and electrically conductive silver structures with a minimum width of 100nm are demonstrated. Moreover, the realization of self-supporting 3D silver microstructures is demonstrated. This technique will become a promising tool for realizing three-dimensional plasmonic metamaterials.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

Three-dimensional silver/polymer conjugated microstructures were fabricated by site-selective metal deposition on photopolymer structures in the sub-micrometer scale. Photopolymerizable resins with and without an amide group were independently prepared, and a three-dimensional polymer structure was fabricated with those resins by means of the two-photon-induced photopolymerization technique to confine the photopolymerization to a sub-micrometer volume. Silver was selectively deposited on the surface of the amide-containing polymer parts by electroless plating. This method can provide 3D arbitrary silver/polymer composite microstructures with sub-micrometer resolution.

DOI： 10.1007/s00339-007-4298-9

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

The lateral spatial resolution (LSR) in two-photon induced polymerization was improved to 80 nm by using an anthracene derivative (9,10-bis-pentyloxy-2,7-bis[2-(4-dimethylamino-phenyl)-vinyl]anthracene (BPDPA)) as a highly sensitive and efficient photoinitiator. Photocurable resin containing 0.18 mol % BPDPA exhibited a low polymerization threshold of 0.64 mW at 800 nm. Theoretical calculations showed that the LSR can be increased by reducing the laser power, indicating that the LSR could be improved using more sensitive initiators in the future. (c) 2007 American Institute of Physics.

DOI： 10.1063/1.2717532

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

We propose micro-fabrication technique that enables us to obtain arbitrary 3D micro/nano metallic structures by scanning the laser beam spot in three dimensions. The spatial resolution and the electrical conductivity of the fabricated structures are discussed.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Novel A-pi-D-pi-A V-shaped 3,6-bis(phenylethynyl)carbazole based chromophores were designed and synthesized as two-photon polymerization (TPP) initiators combining a large two-photon absorption cross-section with facilitated radical formation. 9-Benzyl-3,6-bis(4-nitrophenylethynyl) carbazole (4d) shows a strong two-photon absorption around 800 nm and exhibits very high two-photon polymerization initiating sensitivity with a threshold power of 0.8 mW at the concentration of 0.18 mol%, which is much lower than the threshold power of 6.37 mW found for benzil. The corresponding threshold of laser exposure intensity for TPP is 3.06 x 10(7) mJ cm(-2). The lowest loading of 4d is up to 0.012 mol% with a threshold power of 3.2 mW.

DOI： 10.1039/b616792f

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Optical Society of America (OSA)  

Three-dimensional (3D) metallic fine structures were fabricated with nano/ micrometer resolution. 3D polymer structures were firstly prepared by two-photon absorpti on polymerizati on, and silver was deposited on the polymer templates through electrochemical metal deposition. © 2007 OSA.

DOI： 10.1364/meta.2007.wd3

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Language：English   Publisher：AMER CHEMICAL SOC  

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We report on selective metal deposition over complex polymer structures formed by two-photon induced photopolymerization technique. Periodic three-dimensional micro/nanostructures are fabricated by means of a microlens array to produce multiple spots from a single-beam femtosecond laser. An electroless plating method is used to deposit a thin silver film onto the sample surface. The glass slide surface supporting the structures is chemically modified to avoid silver coating of the substrate. Our technique enables to produce complex metallic structures with arbitrary shapes under ambient conditions. (c) 2006 American Institute of Physics.

DOI： 10.1063/1.2178261

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：OPTICAL SOC AMER  

An experimental protocol for the realization of three-dimensional periodic metallic micro/nanostructures over large areas is presented. Simultaneous fabrication of hundreds of three-dimensional complex polymer structures is achieved using a two-photon photopolymerization (TPP) technique combined with a microlens array. Metallization of the structures is performed through the deposition of thin and highly conductive films by electroless plating. A chemical modification of the photopolymerizable resin and the production of a hydrophobic coating on the glass surface supporting the structures are realized. This process prevents metal deposition on the substrate and restricts adhesion on polymer. Our technique can produce periodic and/or isolated metallic structures with arbitrary shape, created by more than 700 individual objects written in parallel.

DOI： 10.1364/OPEX.14.000800

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

Recently, fabrication of metal micro-pattern has attracted a great attention. For such purpose, site-selective activation is crucial for metal deposition on a substrate, and it can be achieved through lithography, chemical vapor deposition and micro-contact printing. Here, we propose to control the activation point three-dimensionally (3D) through two-photon absorption (TPA) polymerization method, which leads to 3D site-selective deposition. Two types of photopolymer were prepared for deposition control of metal through electroless plating method. One was a commercially available resin, which is typically inactive to metal deposition. Another was a modified resin containing suitable functional groups for metal adhesion. We created a 3D polymer structure consisting of those two components by localizing each resin through TPA method. The fabricated structures were immersed in an electroless plating solution of silver. The partially silver coated sample was observed by a scanning electron microscope after washing and desiccation. Metal microstructure supported with polymer can be realized by 3D site-selective metal deposition. Therefore, it is a useful technique for 3D aligned metallic microstructures without any contacts each other.

DOI： 10.1117/12.681511

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPIE-INT SOC OPTICAL ENGINEERING  

We report on selective metal deposition over complex polymer structures formed by two-photon induced photopolymerization (TPP) technique. Periodic three-dimensional (3D) polymer micro/nanostructures are fabricated by means of a microlens array to produce multiple spots from a single-beam femtosecond laser amplified by a regenerative amplifier. The photopolymerizable resin and the glass substrate are chemically modified, and a pre-treatment with SnCl2 is applied before realizing a uniform silver coating by electroless plating. This preparation enables a selective deposition of small silver particles only on the polymer surface all over the sample and to avoid metal deposition on the substrate. Electrical measurements show the structures to be highly conductive with typical resistivities p similar to 10(-7) Omega m, only a few times larger than the value for bulk silver. By taking advantage of the high accuracy and arbitrary shape modeling of TPP fabrication, we can realize complex periodic and/or metallic micro-nanostructures which were so far out of reach. Thus, a straightforward application could be the realization of metamaterials. The processing efficiency of our technique is demonstrated with the fabrication of several large samples, created by more than 700 objects written in parallel and metallized with silver.

DOI： 10.1117/12.681430

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Materials Research Society  

Two-photon-induced photopolymerization is useful for fabricating 3D micro/nano-structures with the resolution of the sub-diffraction limit. By using this method, photonic crystal was created with pre-compensation of shrinkage of photopolymer. On the contrary, the shrinkage was utilized to reduce the structure size. A micro-lens array was used to produce a mass of structures in parallel. Furthermore, metallization of the 3D polymer templates was conducted by electroless metal plating. These fabrication techniques are applicable to functional micro/nano devices. © 2006 Materials Research Society.

DOI： 10.1557/proc-0921-t02-01

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

A tightly focused femtosecond laser has been established as a unique tool for micronanostructure fabrication due to its intrinsic three-dimensional processing. In this letter, we utilize a microlens array to produce multiple spots for parallel fabrication, giving rise to a revolutionary augmentation for our previously developed single-beam two-photon photopolymerization technology [S. Kawata, H.-B. Sun, T. Tanaka, and K. Takada, Nature (London) 412, 697 (2001)]. Two- and three-dimensional multiple structures, such as microletter set and self-standing microspring array, are demonstrated as examples of mass production. More than 200 spot simultaneous fabrication has been realized by optimizing the exposure condition for the photopolymerizable resin, i.e., a two-order increase of yield efficiency. Potential applications of this technique are discussed. (C) 2005 American Institute of Physics.

DOI： 10.1063/1.1855404

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：INST PURE APPLIED PHYSICS  

It is generally difficult to deposit metal on an occluded part of a structure or inside a long tubular structure. In this paper, we report an electroless plating method that is useful for metal deposition onto internal obscured regions of a complex structure, and we show that the technique can deposit metal over a wide area. We demonstrate gold deposition inside a capillary tube and a complex concave structure of micrometer scale consisting of polystyrene microbeads sandwiched between glass plates.

DOI： 10.1143/JJAP.44.L1134

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Picosecond and femtosecond lasers having different pulsewidths were employed for the generation of multi-color laser emission via stimulated Raman scattering and four-wave Raman mixing using a KGd(WO4)(2) crystal. Seven emission lines, consisting of high-order Stokes and anti-Stokes emissions, were observed at a laser pulsewidth of 20 ps and a pulse energy of 70 muJ. (C) 2003 Elsevier B.V. All rights reserved.

DOI： 10.1016/S0030-4018(03)01675-4

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

A tunable narrow-band picosecond dye laser emitting in the ultraviolet region was amplified using a Ce:LiCaAlF6 crystal pumped by the fourth-harmonic emission of a Nd:Y3Al5O12 laser. The single-pass gain obtained exceeded 2 in the spectral range of 288 to 297 nm. (C) 2003 American Institute of Physics.

DOI： 10.1063/1.1576294

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

A new design and the characteristics of operating a distributed-feedback dye laser (DFDL) pumped by the fourth-harmonic emission of a Q-switched Nd:YAG laser are described. An ultraviolet nearly transform-limited picosecond pulse was generated by means of two right-angle prisms in the pumping geometry, and the laser wavelength was continuously tunable from 318 to 369 nm using two dye solutions (BM-terphenyl and BMQ). The application of this DFDL to the lifetime measurement of a fluorescent dye is also presented. (C) 2003 American Institute of Physics.

DOI： 10.1063/1.1529298

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SOC APPLIED SPECTROSCOPY  

Characteristic hard X-rays emitted from a laser-produced plasma induced by focusing a femtosecond KrF laser pulse are employed for elemental analysis. The emission spectrum of the hard X-ray arising from a stainless steel sample is measured by means of a single-photon-counting X-ray detector equipped with a multichannel analyzer. The elemental analysis is carried out from the photon energy of the Kalpha. line observed in the X-ray emission spectrum, and a calibration curve is constructed for Fe using stainless steel samples prepared at different concentrations (SUS-301, 310, and 316). A continuum band was overlapped on the sharp Kalpha lines in the Xray spectrum, which made the assignment of the weak characteristic Kalpha lines arising from minor elements difficult. In order to suppress this undesirable emission, a prepulse technique was employed. The continuum emission was shifted toward lower energies, and, as a result, the characteristic Kalpha lines were more clearly observable. The potential advantages of the present approach are also discussed in this study.

DOI： 10.1366/000370202760295395

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SOC APPLIED SPECTROSCOPY  

DOI： 10.1366/000370202760295511

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

We report on the generation of a background-free nearly transform-limited picosecond pulse using a simple quenching scheme in a distributed feedback dye laser. The pulsewidth and spectral linewidth were 65 ps and 10 pm, respectively. The product of these values is 0.650, which is close to the transform limit of 0.441 for a Gaussian pulse. (C) 2002 American Institute of Physics.

DOI： 10.1063/1.1470242

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC ANALYTICAL CHEMISTRY  

A distributed-feedback dye laser with a quenching cavity was designed and constructed for generating a tunable picosecond pulse with a narrow spectral linewidth. This nearly transform-limited pulse was succeedingly amplified by a triple-pass off-axis amplifier. The pulse duration and the spectral linewidth were 60 ps and 9.4 pm, respectively. The amplified pulse was frequency-doubled by second-harmonic generation, producing a 0.5-mJ pulse with no background emission. The potential advantage of this laser in the analysis of dioxin based on supersonic jet/resonance-enhanced multiphoton ionization/mass spectrometry is discussed.

DOI： 10.2116/analsci.18.243

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

A new approach for elemental analysis, which is based on the measurement of the hard x ray emitted from a laser-produced plasma is reported here. Since the K-shell emission is characteristic of the element in a sample, Cu, Zn, Fe, Co, and Ni were readily confirmed to be present in brass and kovar alloys by measuring the x-ray emission spectrum over an energy range from 2 to 30 keV. (C) 2001 American Institute of Physics.

DOI： 10.1063/1.1405790

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

K-shell emission spectra of iron, copper, and molybdenum in the range of 1.5-20 keV using a 500 fs KrF excimer laser have been observed and are reported herein. (C) 2001 American Institute of Physics.

DOI： 10.1063/1.1342777

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：INTS PURE APPLIED PHYSICS  

The beam quality of a femtosecond dye/KrF excimer laser was improved using a pinhole, prepared from an acrylic plate. The pinhole acts as a volume light absorber that discriminates high-order transverse modes of the laser beam. A breakdown at the surface of the pinhole, which degrades the quality of the transmitted beam, can be avoided using this spatial filter. This approach was useful in minimizing self-phase modulation, which exhausts the limited laser energy and reduces the Raman output. A conversion efficiency of some vibrational and rotational emissions was improved, even though the laser pulse energy was substantially reduced by mode filtering.

DOI： 10.1143/JJAP.39.5115

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The majority of commercial photomasks and X-ray masks produced at present are manufactured by a multistep process which involves the use of etching. This route imposes a limitation on the resolution that can be achieved. We describe here a new approach which utilises a recently synthesised range of organometallic compounds designed to undergo direct conversion to metal under the influence of electron beam irradiation. This opens up the prospect of a novel route for the production of both X-ray masks and EUV masks in essentially a single processing step. The attainable resolution is better than 300nm, since the process involves the direct deposition of metal atoms under the influence of a focused electron beam.
The method is very versatile in that a whole range of metals and metal alloys can be deposited, e.g. gold, platinum and palladium and their corresponding alloys. We describe here the production of a gold X-ray mask, which was used in conjunction with a compact laser plasma source.

DOI： 10.1016/S0167-9317(98)00064-1

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：OPTICAL SOC JAPAN  

A dye laser emitting at four different frequencies separated by 293.5 (=587/2) cm(-1) is made by inserting an etalon in the resonator cavity of the laser. This laser beam is focused into molecular hydrogen (rotational Raman shift frequency, 587 cm(-1)) to generate a multicolor laser beam consisting of more than 10 rotational lines in the vicinity of the fundamental lines by four-wave Raman mixing. Such rotational lines also occur in the vicinity of the vibrational Raman lines. Thus more than 25 emission lines appear simultaneously. This approach is useful to multiply the line density, i.e., the emission lines within a specified wavelength region.

DOI： 10.1007/BF02932065

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Language：Japanese   Publisher：(一社)日本未病学会  

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Language：Japanese  

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Language：Japanese   Publisher：(NPO)日本歯科保存学会  

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Language：Japanese  

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Language：Japanese   Publisher：日本分子イメージング学会  

ラマン分光法は、試料にレーザー光を照射して生じるラマン散乱光を解析することにより、試料中に存在する化学結合や分子種を同定することができる。本手法は、蛍光標識のような前処理が不要であり、非破壊で試料の化学情報を取得できる優れた手法である。また、光学顕微鏡と組み合わせることにより、ミクロンスケールでの観察が可能である。しかしながら、蛍光と比べてラマン散乱光は非常に弱いため、希薄な試料の測定が困難とされてきた。そこで本稿では、貴金属ナノ構造に形成される表面プラズモンを利用した表面増強ラマン散乱を紹介する。レーザー焦点を試料中でスキャンすると、試料中の化学的情報を示すラマンマッピング/イメージングを行える。ラマンマッピング/イメージングにおける照明方法の工夫やタグの利用、ラマン信号の増強について述べる。(著者抄録)

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Language：Japanese   Publisher：日本分子イメージング学会  

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Language：Japanese   Publisher：The Japan Society of Applied Physics  

<p>In recent years, "hot electrons", with kinetic energy that is higher than the surrounding electrons, are attracting attention. Hot electrons are studied for their use in photochemistry and the enhancement of the efficiency of photo-electron conversion although hot electrons are not preferred during measurement. It is necessary to irradiate light with a sufficiently short wavelength beyond the band gap to excite electrons to a high energy state. However, hot electrons can be generated by using localized surface plasmon resonance. Here, we will outline the processes from the method of generating hot electrons to the transfer of the hot electrons generated in metals to semiconductors or adsorbed molecules through an interface, and the induced chemical reaction for the application to energy generation.</p>

DOI： 10.11470/oubutsu.88.10_659

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Language：Japanese  

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Language：Japanese   Publisher：The Laser Society of Japan  

DOI： 10.2184/lsj.36.174

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Language：Japanese   Publisher：日本分析化学会  

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Applicant：独立行政法人理化学研究所

Application no：特願2007-174980  Date applied：2007.7.3

Announcement no：特開2009-013453  Date announced：2009.1.22

Patent/Registration no：特許第4761167号  Date registered：2011.6.17 

J-GLOBAL

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Applicant：独立行政法人理化学研究所

Application no：特願2007-174981  Date applied：2007.7.3

Announcement no：特開2009-013454  Date announced：2009.1.22

Patent/Registration no：特許第4753049号  Date registered：2011.6.3 

J-GLOBAL

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Applicant：独立行政法人理化学研究所

Application no：特願2006-077393  Date applied：2006.3.20

Announcement no：特開2007-253354  Date announced：2007.10.4

Patent/Registration no：特許第4901253号  Date registered：2012.1.13 

J-GLOBAL

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