Tatsuya Shoji

Tatsuya Shoji
Kanagawa University · Faculty of Science

Doctor of Philosophy

About

61
Publications
2,443
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
1,169
Citations

Publications

Publications (61)
Article
Full-text available
Nano-objects, such as quantum dots (QDs), are essential units for the construction of functional materials and devices in current technologies. The establishment of a versatile scheme to sort desired components from a crude product is crucial for bringing out the full potential of the original materials. However, it is still challenging to separate...
Article
Full-text available
Membrane fusion (MF) is one of the most important and ubiquitous processes in living organisms. In this study, we developed a novel method for MF of liposomes. Our method is based on laser-induced bubble generation on gold surfaces (a plasmonic nanostructure or a flat film). It is a simple and quick process that takes about 1 min. Upon bubble gener...
Article
Laser Chemistry In their Research Article (e202117227), Yasuyuki Tsuboi et al. report an optical tweezer technique using nanotextured Si that can efficiently trap polymer chains. The fluorescence color of the perylene‐labeled polymer chains can be controlled by changing the laser intensity.
Article
The ability to modulate, tune, and control fluorescence colour has attracted much attention in photonics-related research fields. Thus far, it has been impossible to achieve fluorescence colour control (FCC) for material with a fixed structure, size, surrounding medium, and concentration. Here, we propose a novel approach to FCC using optical tweez...
Article
The ability to modulate, tune, and control fluorescence colour has attracted much attention in photonics-related research fields. The most examined approach has been the design and synthesis of luminescent materials such as luminescent nanocrystals (i.e., quantum dots). However, thus far, it has been impossible to achieve fluorescence colour contro...
Article
The ability to modulate, tune, and control fluorescence colour has attracted much attention in photonics-related research fields. The most examined approach has been the design and synthesis of luminescent materials such as luminescent nanocrystals (i.e., quantum dots). However, thus far, it has been impossible to achieve fluorescence colour contro...
Article
We demonstrate liquid-liquid phase separation involving both coacervation and coil-to-globule phase transition of a thermoresponsive polymer. By focusing a near-infrared laser beam into an aqueous solution of poly(N-isopropylacrylamide) (PNIPAM), a single phase-separated polymer microdroplet can be formed and stably trapped at the focal point. Such...
Article
The optical trapping of polymer beads of different diameters d of 100, 200, 500, 1000, and 3000 nm on planar (F-Si) and nanostructured (BSi) crystalline silicon was investigated at laser wavelengths λ = 808 and 1064 nm, respectively. We demonstrate that BSi surfaces can enhance the optical gradient force required to grip nanoparticles (100 nm) in c...
Article
Thermo-responsive phase separation mechanisms of aqueous poly(N-isopropylacrylamide) (PNIPAM) solutions were investigated using an optical tweezer combined with a Raman microspectroscope. A near infrared laser beam (λ=1064 nm) was focused into the solution to produce and trap a single polymer microdroplet under an optical microscope. The laser beam...
Article
For the development of next‐generation wearable and implantable devices that connect the human body and machines, the adhesion of a conductive hydrogel is required. In this study, a conductive hydrogel is adhered using an electrophoretic approach through polyion complex formation at the interface of the hydrogels. Cationic and anionic conductive hy...
Article
Full-text available
We demonstrate the size-dependent separation and permanent immobilization of DNA on plasmonic substrates by means of plasmonic optical tweezers. We found that a gold nanopyramidal dimer array enhanced the optical force exerted on the DNA, leading to permanent immobilization of the DNA on the plasmonic substrate. The immobilization was realized by a...
Article
We report the optical trapping of many particles with feasible laser powers by the nanostructured semiconductor-assisted (NASSCA) trapping technique. Furthermore, we have found that the random array of silicon needles with spacings substantially smaller than the nanoparticle sizes is advantageous not only for the trapping force-field enhancement bu...
Article
We demonstrate a prominent color change of optically-trapped octahedral gold nanoparticles (OGPs) under thermal fluctuations in water using a tightly focused near-infrared laser beam. Monodisperse OGPs with an average edge length of 67 ± 6.5 nm were synthesized using a polyol method. Using dark-field microscopy, we observed characteristic trapping...
Conference Paper
Full-text available
Poly(N-isopropylacrylamide) (PNIPAM) exhibits phase separation with lower critical solution temperature (LCST). In the 1990s, Masuhara and co-workers reported the first demonstration of optical trapping of PNIPAM forming a micrometer-sized polymer droplet. Since then, this technique has attracted much attention to create a molecular assembly in a m...
Article
Full-text available
Plasmonic optical tweezers (POT) has a high potential for manipulation of nanomaterials due to an enhanced optical force. However, unfavorable thermal effects induced by plasmon excitation have frequently hindered the manipulation. For this issue, we have recently developed a novel non-plasmonic optical tweezers using a nanostructured silicon subst...
Article
Full-text available
We studied the dependence on tacticity of the dynamic phase separation behavior of thermoresponsive poly(N,N-diethylacrylamide) (PDEA) in an aqueous solution. Using a laser temperature-jump technique combined with transient photometry, we determined the time constants of the phase separation, and found that both atactic and isotactic-rich PDEAs had...
Article
Poly(N-isopropylacrylamide) (PNIPAM) as a representative water-soluble thermo-responsive polymer exhibits a coil-to-globule phase transition followed by phase separation upon temperature increase, leading to the formation of polymer-rich domains in solution. Quantitative analysis of polymer concentration in polymer-rich domains is a challenging tas...
Article
Full-text available
Nowadays, optical tweezers have undergone explosive developments in accordance with a great progress of lasers. In the last decade, a breakthrough brought optical tweezers into the nano-world, overcoming the diffraction limit. This is called plasmonic optical tweezers (POT). POT are powerful tools used to manipulate nanomaterials. However, POT has...
Article
The usage of hydrogel has greatly expanded to wide fields due to their eco-friendly properties. In this study, we demonstrated a rapid repair of broken hydrogels utilizing microgel architectures, which were prepared by adhesion of oppositely charged microgels. Mechanical strength of microgel architectures were able to be controlled by changing a ch...
Article
In the present study, we explored plasmonic optical trapping (POT) of nanometer-sized organic crystals, carbocyanine dye aggregates (JC-1). JC-1 dye forms both J- and H- aggregates in aqueous solution. POT behavior was analyzed using fluorescence microspectroscopy. POT of JC-1 aggregates was realized in an increase in their fluorescence intensity f...
Article
We demonstrate that a poly(N-isopropylacrylamide) (PNIPAM) microassembly, formed by plasmonic optical trapping, can provide the platform for a highly sensitive detection technique for fluorescent and nonfluorescent organic molecules dissolved in aqueous solution. PNIPAM microassemblies can be easily formed by a combination with a photothermal effec...
Article
Back Cover: The laser temperature-jump technique combined with transient photometry is a powerful tool for investigation of the dynamic phase separation behavior in aqueous solutions of thermoresponsive polymers. In this paper two types of phase separation mechanisms (fast and slow processes) of poly(N,N-diethylacrylamide) (PDEA) are presented. It...
Article
The dynamic phase separation behavior in aqueous solutions of poly(N,N-diethylacrylamide) (PDEA), which is a representative thermoresponsive polymer, is studied using a laser temperature-jump technique combined with transient photometry, with which the time constant for phase separation can be determined. Two components of the time constant (τfast...
Article
The dynamic and static phase separation behavior in aqueous poly(N-isopropylacrylamide) (PNIPAM) solutions is highly sensitive to the tacticity of PNIPAM. We investigated the phase separation dynamics of aqueous solutions of PNIPAM with different tacticities (atactic and syndiotactic-rich types), and found that the phase separation dynamics of synd...
Article
Full-text available
Aqueous solutions of thermo-responsive polymers represented by poly(N-isopropylacrylamide) (PNIPAM) exhibit a coil-to-globule phase transition followed by phase separation upon temperature increase. These polymers are promising smart materials that can form the basis for drug delivery systems. In order to apply these polymers as smart materials, it...
Article
Poly(lactic-co-glycolic acid) (PLGA) nanoparticles with bicyclol (5%) and 3-n-butyl-6-bromophthalid (Br-NBP) (3%) were prepared by an emulsification-solvent evaporation technique. The PLGA nanoparticles were for the first time successfully characterized by a laser trapping/confocal Raman spectroscopic technique only using individual PLGA nanopartic...
Article
Localized surface plasmons exert a strong radiation force on nanoparticles in the vicinity of noble metal nanostructures, resulting in optical trapping. Such plasmon-based optical trapping is one of the hot topics in the field of nanophotonics and can be applied to molecular manipulation techniques. In this review paper, we describe the plasmon-bas...
Article
The paper demonstrates that a confocal Raman microspectroscope combined with optical tweezers is a promising technique to estimate polymer concentration in polymer-rich domain in phase-separated-aqueous polymer solution. The sample polymer is poly-(N-isopropylacrylamide) (PNIPAM) that is well-known as a representative thermo-responsive polymer. Opt...
Article
This Perspective describes recent progress in optical trappings of nanoparticles based on localized surface plasmon. This plasmonic optical trapping has great advantages over the conventional optical tweezers, being potentially applicable for a molecular manipulation technique. We review this novel trapping technique from the viewpoints of (i) plas...
Conference Paper
Localized surface plasmons (LSPs) have been investigated for applications such as highly sensitive spectroscopies and the enhancement of photochemical reactions. These applications are enabled by the enhancement effect of an incident resonant electromagnetic field (EMF) at the surfaces of noble metallic nanostructures. In particular, the applicatio...
Conference Paper
We demonstrated that localized surface plasmon enables to efficient optical trapping of nanoparticles and polymer chains due to the enhancement effect of an incident resonant electromagnetic field at the surfaces of noble metallic nanostructures.
Article
We demonstrate the efficient trapping of myoglobin (Mb), which is a small protein, in aqueous solution using a 1064 nm laser beam. Conventional optical tweezers exert barely sufficient radiation force (RF) on nanometer-sized dielectric objects, such as small proteins and organic molecules, for manipulation of them. One possible candidate to enhance...
Article
We discovered for aqueous thermoresponsive polymer solutions that only a slight change in stereoregularity of the polymer can drastically accelerate phase separation. Single molecule fluorescence tracking (SMT) for an isotactic-slight-rich (meso-diad-rich) polymer sample solution revealed an interpolymer nanonetwork even before phase separation, an...
Article
The use of localized surface plasmons (LSPs) for highly sensitive biosensors has already been investi-gated, and they are currently being applied for the optical manipulation of small nanoparticles. The ob-jective of our work is the optical trapping of -DNA on a metallic nanostructure with femtosecond pulsed (fs) laser irradiation. Cw laser irradi...
Article
We present a novel laser processing technique for nanoholes formation (d similar to 100 nm) on a polymer film based on resonant excitation of surface plasmon of Au nanoparticles. We succeeded in fabrication of a porous film with controlling of the density and position of the nanoholes in the film. The fundamental mechanism of the processing is supe...
Article
The dynamics of thermoresponsive phase-separation processes in aqueous poly(N-isopropylacrylamide) (PNIPAM) was studied using a laser temperature-jump technique combined with photometry. The time constant for phase separation (τ) was determined with high accuracy for various molecular weights (Mw) and concentrations (C) of PNIPAM in solution. For t...
Article
Nanostructure-enhanced optical trapping of polymer beads was investigated by means of fluorescence microspectroscopy. It was found that trapping behavior was quite sensitive to the particle size as well as excitation light intensity. We present a 2D closely packed assembly of polystyrene nanospheres on a gold nanostructure that is triggered by gap-...
Article
Full-text available
In optical trapping using photon force much enhanced by localized surface plasmon (LSP) in solution, we found that a resonant excitation effect can further enhance photon force. In this LSP-based optical trapping under a resonant excitation condition, an incident laser beam excites both LSP and electronic resonant transition of a target object simu...
Article
Optical trapping of flexible polymer chains to a metallic nanostructured surface was explored by microscopic imaging and confocal fluorescence spectroscopy. A fluorescence-labeled poly(N-isopropylacrylamide) was targeted, being a representative thermo-responsive polymer. Upon resonant plasmonic excitation, it was clearly observed that polymers were...
Article
Localized-surface-plasmon (LSP)-enhancement effect on one-photon photochromic ring-opening reaction of two diarylethene (DE) derivatives was studied using absorption spectroscopy. DEs were doped in polymer films and those were coated onto Au-nanoparticles-integrated substrates. Acceleration of the one-photon photochromic reactions was observed in t...
Article
We examined optical cavity effects on the 2-photon absorption efficiency of a dye (Rohdamine B; RhB) doped in polymer microspheres (ion-exchanging resin and poly(methyl methacrylate) (PMMA)). When 1064 nm pulsed-laser light was irradiated on single polymer microspheres doped with RhB under an optical microscope, we clearly observed dye fluorescence...
Article
One of the recent hot topics in the fields of plasmonics and related nanophotonics is optical trapping of nano/microparticles based on surface plasmon. Experimental demonstration of such trapping by gap-mode plasmon has hitherto been limited so far to a few reports in which submicrometer polymer beads were trapped with intense irradiation at MW/cm2...
Article
In this paper, we demonstrated that the photon forces that are generated by a near-infrared (1064 nm) focused laser beam can manipulate (optically trap) small amino acid molecules in aqueous solutions. Under observation with an optical microscope, we observed the gradual growth of a particle-like assembly of objects at the focal point during laser...
Article
Optical trapping of lysozyme, cytochrome c, or myoglobin based on photon pressure generated by focusing 1064 nm laser beam in an aqueous solution was explored. For all the proteins, microparticle formation was observed at the focal point under an optical microscope. Furthermore, the microparticles were identified to the molecular assemblies of the...
Article
We demonstrate that a photochromic reaction can be driven by irradiation from a weak, near-infrared continuous-wave (NIR-CW) laser light. A two-photon ring-opening photochromic reaction of a diarylethene (DE) derivative can be induced by irradiation with a NIR-CW laser light (lambda = 808 nm). An ultrathin polymer film doped with DE in its closed f...
Article
We examined a method to refine a technique to prepare close-packed monolayers of cylindrical zeolite L crystals tethered on a substrate through covalent linkages, which was developed recently for popular use. We attempted to fabricate both vertical and horizontal–unidirectional alignments of the zeolite particles. The vertical alignment for centime...
Article
In this paper, we demonstrated a novel technique to promote crystallization of hen egg-white lysozyme in heavy water. The technique was essentially based on aggregation of the protein molecules by photon pressure generated under irradiation of a cw 1064 nm laser beam to the protein solution. When photon pressure was kept being exerted for 1-2 h on...

Network

Cited By