Izumi, Japan
Izumi, Japan

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Tokonami S.,Osaka Prefecture University | Nishida K.,Osaka Prefecture University | Nishimura Y.,Osaka Prefecture University | Hidaka S.,Osaka Prefecture University | And 3 more authors.
Research on Chemical Intermediates | Year: 2014

We investigated the optical response of a huge number of silver nanoparticles (AgNPs) densely assembled on an organic microsphere, i.e., AgNP-fixed bead, under the collective phenomena of localized surface plasmons. For this purpose, various optical properties of such a AgNP-fixed bead were analyzed in aqueous solution by dark-field optical microscopy and laser Raman microscopy. In particular, in comparison with the optical spectrum of single AgNPs, significant spectral broadening and redshift were observed due to plasmonic superradiance with decreasing interparticle distance to the subnanoscale when using small binder molecules in the AgNP-fixed bead. Furthermore, we observed surface-enhanced Raman scattering and clarified the sensitivity of the signal intensity to the size of the binder molecules between the AgNPs, which can be explained based on optical response theory using a discrete integral with spherical cells. These results and discussion provide a guiding principle for broadband plasmonic light absorbers and for highly sensitive detection of small molecules and nanoscale biomaterials based on vast numbers of nanogaps produced by a bottom-up self-assembly process. © 2014 Springer Science+Business Media Dordrecht.


Shiigi H.,Osaka Prefecture University | Morita R.,Osaka Prefecture University | Muranaka Y.,Osaka Prefecture University | Tokonami S.,Osaka Prefecture University | And 4 more authors.
Journal of the Electrochemical Society | Year: 2012

A synthetic route for mass production of monodisperse gold nanoclusters and nanoparticles is presented. A nanometer-sized raspberry-like architecture, consisting of an aggregation of repeated sequences of a three dimensional gold nanoparticle (AuNP)-organic component-AuNP arrangement, has been prepared with a single-step procedure in a biphasic organic/water system. In the biphasic mixture, reduction of Au3+ by aniline monomers affords nanoclusters as well as a polyaniline colloid that controls the growth of the clusters into nanoparticles. The reaction parameters (ratio of reactants, time, and temperature) can be varied to control the size of the nanoclusters and nanoparticles from 0.73 nm to 5.5 nm in the polyaniline matrix. Finally, electrochemical degradation of the polyaniline matrix affords isolated monodisperse nanoclusters and nanoparticles. © 2012 The Electrochemical Society.


Tokonami S.,Osaka Prefecture University | Nishida K.,Osaka Prefecture University | Hidaka S.,Osaka Prefecture University | Yamamoto Y.,GreenChem. Inc. | And 2 more authors.
Journal of Physical Chemistry C | Year: 2014

The enhanced optical response due to localized surface plasmons (LSPs) in interacting metallic nanostructures provides a promising avenue for the detecting small biological molecules, whereas an unconventional spectral modulation of LSPs would be obtained under the coupling of the different kinds of metallic nanostructures with nanoscale separations via small molecules. Here, we unexpectedly found an anomalous condition of light scattering from heterogeneous metallic nanostructures, i.e., silver-nanoparticle fixed bead (AgNP-FB) and gold nanorods (AuNRs) coupled via DNA, in which the light scattering dramatically suppressed in the broad UV region although it was enhanced in the visible region. Based on ultrafast computation under cluster approximation, this anomaly was attributed to the broadband cancellation of collective modes of interband transitions in AuNRs and LSPs in a single AgNP-FB. This mechanism has a high potential to apply for detection of DNA in zmol order even under white light source. © 2014 American Chemical Society.


Nishimura Y.,Osaka Prefecture University | Nishida K.,Osaka Prefecture University | Yamamoto Y.,GreenChem. Inc. | Ito S.,Osaka University | And 2 more authors.
Journal of Physical Chemistry C | Year: 2014

Local molecular states and biological materials in small spaces ranging from the microscale to nanoscale can be modulated for medical and biological applications using the photothermal effect (PTE). However, there have been only a few reports on exploiting the collective phenomena of localized surface plasmons (LSPs) to increase the amount of light-induced heat for the control of material states and the generation of macroscopic assembled structures. Here, we clarify that microbeads covered with a vast number of Ag nanoparticles can induce a large PTE and generate a submillimeter bubble within several tens of seconds under the synergetic effect of the light-induced force (LIF) and photothermal convection enhanced by collective phenomena of LSPs. Control of the phase transition induced by such a "collective photothermal effect" enables rapid assembling of macroscopic structures consisting of nanomaterials, which would be used for detection of a small amount of proteins based on light-induced heat coagulation. © 2014 American Chemical Society.


Shiigi H.,Osaka Prefecture University | Tokonami S.,Osaka Prefecture University | Yamamoto Y.,Osaka Prefecture University | Yamamoto Y.,GreenChem. Inc. | Nagaoka T.,Osaka Prefecture University
Analytical Sciences | Year: 2012

Electrical and electrochemical methods are well established as very useful techniques in the field of biosensing because they can easily handle signals and devices. This paper provides an overview of biosensing using a nanometer-sized space functionally. Placed effectively on the electrode, the nanospace offers several advantages, such as increased sensitivity, improved selectivity, decreased response time, and the potential for instrument miniaturization. Given the impressive technological progress of nanospace biosensors and its growing impact on analytical science, this review offers an easyto-understand presentation describing the history, recent advances, new methods, and future prospects of nanospace biosensors. © The Japan Society for Analytical Chemistry.


Tokonami S.,Osaka Prefecture University | Shirai S.,Osaka Prefecture University | Ota I.,Osaka Prefecture University | Shibutani N.,Osaka Prefecture University | And 3 more authors.
Journal of the Electrochemical Society | Year: 2011

We developed a green electroless plating method that enables saving of resources and reduction in emissions to the environment because it uses a self-assembling reaction between gold nanoparticles (AuNPs) and a nontoxic thiol binder. In this method, a uniform surface coating and thickness reflected by the diameter of AuNPs were obtained on micrometer-sized core plastic beads. Thermal analysis has revealed that AuNP adsorption is based on the chemical reaction and interaction among the AuNP, binder, and bead. Further, the AuNP-plated microbead has high physical, electrical, and thermal stabilities, which would enable its practical applications. © 2011 The Electrochemical Society.


Tokonami S.,Osaka Prefecture University | Hidaka S.,Osaka Prefecture University | Nishida K.,Osaka Prefecture University | Yamamoto Y.,Osaka Prefecture University | And 3 more authors.
Journal of Physical Chemistry C | Year: 2013

The collective phenomenon of localized surface plasmons (LSPs) in a high-density collection of interacting metallic nanoparticles (NPs) is a crucial issue in various research fields such as optical physics, photochemistry, and biological science. Here, we report the dark-field measurement of the chemically controlled optical response of LSPs in densely assembled collection of a vast number of gold NPs on a microsphere (AuNP-covered bead). Remarkably, AuNP-covered beads exhibit plasmonic superradiance depending on sizes of binder molecules, where the giant spectral broadening more than 400 meV and significant enhancement of scattering have been observed. Furthermore, self-consistent theoretical analysis has also revealed that multipole collective modes contribute to the superradiance, leading to the enhancement by 2 orders of magnitude in both the far-field scattering and the localized fields of broadband light. The results obtained provide an innovative design principle for solar energy conversion and optical biosensors with incoherent light. © 2013 American Chemical Society.


Bui P.T.,Osaka Prefecture University | Nishino T.,Osaka Prefecture University | Yamamoto Y.,Osaka Prefecture University | Yamamoto Y.,GreenChem. Inc. | Shiigi H.,Osaka Prefecture University
Journal of the American Chemical Society | Year: 2013

Electron transfer through a noncovalent interaction bears essential relevance to the functions of bottom-up supramolecular assembly. However, rather little knowledge regarding such phenomena at the single-molecule level is currently available. Herein we report the direct quantification of electron-transfer processes for a single noncovalently linked porphyrin-fullerene dyad. Facilitated electron transfer via a charge-transfer interaction in-between was successfully measured by utilizing a fullerene molecular tip. The rectification property of the supramolecular assembly was determined and quantitatively assessed. The present study opens up a way to explore quantitatively the rich electronic properties of supramolecules at the single-molecule level. © 2013 American Chemical Society.


Shiigi H.,Osaka Prefecture University | Muranaka Y.,Osaka Prefecture University | Yamamoto Y.,Osaka Prefecture University | Yamamoto Y.,GreenChem. Inc. | Nagaoka T.,Osaka Prefecture University
Analytical Sciences | Year: 2013

A single-step strategy has been developed for synthesizing a micrometer-sized structure by using the raspberry-like hybrid as a building block comprising a repeated sequence of a three-dimensional gold nanoparticle (AuNP)-aniline oligomer- AuNP arrangement. The hybrid holds a high density of highly dispersible AuNPs without any contact with each other, and therefore the microstructure has many nanometer-sized gaps between the adjacent AuNPs for both electrical and optical sensing. We have discussed how the formation mechanism of the microstructure is based on using the hybrid. © 2013 The Japan Society for Analytical Chemistry.


Kosuga A.,Osaka Prefecture University | Yamamoto Y.,Osaka Prefecture University | Miyai M.,Osaka Prefecture University | Matsuzawa M.,Osaka Prefecture University | And 7 more authors.
Nanoscale | Year: 2015

A photothermal film (PTF) with densely assembled gold nanoparticle-fixed beads on a polymer substrate is fabricated. Remarkably, a temperature rise higher than 40°C is achieved in the PTF with only 100 seconds of artificial solar irradiation, and the output power of the thermoelectric device was enhanced to be one order higher than that without PTF. These results will pioneer a rapid solar thermoelectric device. © The Royal Society of Chemistry 2015.

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