Browsing by Author "Asahi, Tsuyoshi"

Now showing 1 - 8 of 8

Comparative Investigation of Ultrafast Photoinduced Processes in Salicylidene-Aminopyridine in Solution and Solid State
(2009-07-09)
Sliwa, Michel
;
Mouton, Nicolas
;
Ruckebusch, Cyril
;
Aloise, Stephane
;
Poizat, Olivier
Photodynamics and excited-state intramolecular proton transfer (ESIPT) of N-(3,5-ditert-butylsalicylidene)-4-aminopyridine (4P) and N-(3,5-ditert-butylsalicylidene)-2-aminopyridine (2P) are studied by steady-state and transient optical spectroscopy in solution and solid state (microcrystalline powder). These two compounds are representative of anils Classes A and B, respectively. The results confirm that in solution both compounds have a similar dynamic behavior: upon excitation at 390 nm, ESIPT leads to different cis-keto* fluorescent species which relax to the photochromic trans-keto photoproduct within a few tens of picoseconds. Furthermore, for the first time, picosecond data are recorded for the two classes of anils in the solid state: in 2P, two cis-keto* fluorescent excited state species (23 and 250 ps lifetime) are relaxing exclusively to the cis-keto ground state, whereas in 4P, a single cis-keto* fluorescent species is observed which leads to the trans-keto photoproduct in 250 ps via an intermediate metastable species.
Fabrication of gold nanoparticle-doped zeolite L crystals and characterization by optical microscopy: Laser ablation- and crystallization inclusion-based approach
(2008-10-02)
Hashimoto, Shuichi
;
Uwada, Takayuki
;
Masuhara, Hiroshi
;
Asahi, Tsuyoshi
;
應用化學系
This letter reports the optical microscopy characterization of gold nanoparticle-doped zeolite L crystals prepared by applying two key techniques: laser ablation and crystallization inclusion. The former allowed the stable formation of Au NPs in the synthesis gel, while the latter permitted the encapsulation of Au NPs exceeding the pore openings of the zeolite crystals, still maintaining the crystal structure as a whole. The microscopy characterization was performed by exploiting single particle light scattering spectroscopy and imaging techniques which offered the Rayleigh scattering images of individual An particles within the crystals and the scattering spectra ascribable to the surface plasmon resonance band of Au NPs embedded. This is a unique demonstration for the application of laser ablation-induced NPs in solution to practical use for fabricating a nanocomposite material. Furthermore, the present results revealed that the dark field microscopy is capable of visualizing metal nanoparticles as small as 40 nm diameter confined in the light scattering crystalline medium.
Nanosecond laser preparation of C(60) aqueous nanocolloids
(2009-09-05)
Sugiyama, Teruki
;
Ryo, Sen-ichi
;
Oh, Isamu
;
Asahi, Tsuyoshi
;
Masuhara, Hiroshi
C(60) aqueous nanocolloids were prepared by irradiating a suspended aqueous solution of C(60) with intense nanosecond 532 and 355 nm laser pulses. The initial submicron crystal of C(60) was fragmented into nanoparticles, resulting in a transparent yellow solution which was followed by UV/vis absorption spectroscopy. The obtained absorption spectra were similar to those for C(60) bulk film and its nanoparticles, which have a size on the order of 10 nm, and their formation had thresholds with respect to laser fluence. The nanoparticles were confirmed by their SEM observation and by examining the centrifuging effect on the colloids, while possible photochemical decomposition was excluded by (13)C NMR analysis of 1,2-dichlorobenzene-d(4) solution, where the possible products can be dissolved in addition to C(60) nanoparticles. The present result is the first demonstration of the preparation of pure and very stable C(60) aqueous nanocolloids without any additives. The formation mechanism and potential application to biological testing and toxicity are discussed. (C) 2009 Elsevier B.V. All rights reserved.
Nanosecond laser preparation of C-60 aqueous nanocolloids
(2009-09-05)
Sugiyama, Teruki
;
Ryo, Sen-ichi
;
Oh, Isamu
;
Asahi, Tsuyoshi
;
Masuhara, Hiroshi
C-60 aqueous nanocolloids were prepared by irradiating a suspended aqueous solution of C-60 with intense nanosecond 532 and 355 nm laser pulses. The initial submicron crystal of C-60 was fragmented into nanoparticles, resulting in a transparent yellow solution which was followed by UV/vis absorption spectroscopy. The obtained absorption spectra were similar to those for C-60 bulk film and its nanoparticles, which have a size on the order of 10 nm, and their formation had thresholds with respect to laser fluence. The nanoparticles were confirmed by their SEM observation and by examining the centrifuging effect on the colloids, while possible photochemical decomposition was excluded by C-13 NMR analysis of 1,2-dichlorobenzene-d(4) solution, where the possible products can be dissolved in addition to C-60 nanoparticles. The present result is the first demonstration of the preparation of pure and very stable C-60 aqueous nanocolloids without any additives. The formation mechanism and potential application to biological testing and toxicity are discussed. (C) 2009 Elsevier B.V. All rights reserved.
Photochemical Reaction of p-hydroxycinnamic-thiophenyl Ester in the Microcrystalline State
(2010-11-18)
Usman, Anwar
;
Asahi, Tsuyoshi
;
Sugiyama, Teruki
;
Masuhara, Hiroshi
;
Tohnai, Norimitsu
We have studied the photochromic reaction of p-hydroxycinnamic-thiophenyl ester in the microcrystalline state We attributed the fluorescence spectral evolution of the microcrystal under UV irradiation to the photoinduced trans-to-cis isomerization The photocyclic behavior of the chromophore was demonstrated by cis-to-trans back reaction under a subsequent visible light irradiation In addition the [2 2] topochemical photocyclodimer was observed as another photoproduct It is considered that the cooperative photoisomerization is initiated at the local lattice distortion and free spaces around the [2 + 2] cyclodimer near the crystal sui lace and the photoisomerization induces larger lattice deformation and further photoisomerization in the interior of the crystal
Photochemical Reaction of p-hydroxycinnamic-thiophenyl Ester in the Microcrystalline State
(2010-11-18)
Usman, Anwar
;
Asahi, Tsuyoshi
;
Sugiyama, Teruki
;
Masuhara, Hiroshi
;
Tohnai, Norimitsu
We have studied the photochromic reaction of p-hydroxycinnamic-thiophenyl ester in the microcrystalline state We attributed the fluorescence spectral evolution of the microcrystal under UV irradiation to the photoinduced trans-to-cis isomerization The photocyclic behavior of the chromophore was demonstrated by cis-to-trans back reaction under a subsequent visible light irradiation In addition the [2 2] topochemical photocyclodimer was observed as another photoproduct It is considered that the cooperative photoisomerization is initiated at the local lattice distortion and free spaces around the [2 + 2] cyclodimer near the crystal sui lace and the photoisomerization induces larger lattice deformation and further photoisomerization in the interior of the crystal
Single particle spectroscopy and tracking of gold nanospheres in living cells by conforcal light scattering microsopy
(2008)
Asahi, Tsuyoshi
;
Uwada, Takayuki
;
Louit, Guillaume
;
Masuhara, Hiroshi
;
應用化學系
Spectral and 3-Dimensional Tracking of Single Gold Nanoparticles in Living Cells Studied by Rayleigh Light Scattering Microscopy
(2009-07-09)
Louit, Guillaume
;
Asahi, Tsuyoshi
;
Tanaka, Go
;
Uwada, Takayuki
;
Masuhara, Hiroshi
Using a confocal Rayleigh light scattering microspectroscopy and imaging system, we followed and recorded the scattering spectra of single gold nanoparticles interacting with living mouse fibroblast cells, during the scale of I h. A white light continuum produced by a femtosecond laser was focused on gold nanoparticles with a diameter of 80 nm, while an incubation system ensured viability of the living cells. After reporting spectral characteristics of gold nanoparticles and their target fibroblasts, separately and in combination, tracking sequences of single nanoparticles in contact with a single cell are described. Through the study of three separate and representative cases, transitory as well as plasmon resonance band shifts, which can be linked to biological events, have been observed and are discussed here.