Site-selective integration of monolayer-protected inorganic nanoparticles onto surface monolayer templates by a solvent-induced lift-off process.
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Crystallization↗
Biomedical subjects
Kensuke Akamatsu
Publications and source records attributed to Kensuke Akamatsu.
A DNA duplex with extremely enhanced thermal stability based on controlled immobilization on gold nanoparticles.
The effect of DNA loadings on the thermal stability of DNA duplex immobilized on gold nanoparticles has been investigated. The modestly loaded duplexes on the gold nanoparticles showed enhanced thermal stability, as compared to that of the free duplex (without gold nanoparticles). However, the highly loaded duplex showed stability similar to that of free duplex. The stability could be controlled over a wide temperature range simply by varying the salt concentration (over 50 degrees C). Additionally, the gold nanoparticles with modestly loaded oligonucleotides could be used as nanoprobes for effective and fast strand exchange reactions, based on the increased thermal stability of the immobilized duplex. These results indicate that the interaction between the duplex and the nanoparticle surface plays an important role in determining the stability of the duplex.
Base Sequence↗
Site-selective direct photochemical deposition of copper on glass substrates using TiO2 nanocrystals.
Deposition of copper thin films was achieved by a photocatalytic reaction of site-selectively adsorbed TiO(2) nanocrystals for direct fabrication of copper circuit patterns on glass substrates. The nanocrystal monolayers absorbed on hydrophobic surface templates serve as an effective photocatalyst, producing metallic copper and formic acid via oxidation of methanol in solution. The formic acid generated has also been suggested to serve as an electron donor that accelerates copper deposition through a UV-mediated autocatalytic reaction, even after nanocrystals are embedded into the grown copper films. The thickness of the deposited copper films was easily controlled by varying the UV irradiation time, irradiation power, and initial concentration of methanol as a hole scavenger. The process presented herein provides an effective methodology for resist-free, direct metallization of insulating substrates.
Letter↗
SPR sensor chip for detection of small molecules using molecularly imprinted polymer with embedded gold nanoparticles.
Molecularly imprinted polymer gel with embedded gold nanoparticle was prepared on a gold substrate of a chip for a surface plasmon resonance (SPR) sensor for fabricating an SPR sensor sensitive to a low molecular weight analyte. The sensing is based on swelling of the imprinted polymer gel that is triggered by an analyte binding event within the polymer gel. The swelling causes greater distance between the gold nanoparticles and substrate, shifting a dip of an SPR curve to a higher SPR angle. The polymer synthesis was conducted by radical polymerization of a mixture of acrylic acid, N-isopropylacrylamide, N,N'-methylenebisacrylamide, and gold nanoparticles in the presence of dopamine as model template species on a sensor chip coated with allyl mercaptan. The modified sensor chip showed an increasing SPR angle in response to dopamine concentration, which agrees with the expected sensing mechanism. Furthermore, the gold nanoparticles were shown to be effective for enhancing the signal intensity (the change of SPR angle) by comparison with a sensor chip immobilizing no gold nanoparticles. The analyte binding process and the consequent swelling appeared to be reversible, allowing one the repeated use of the presented sensor chip.
Gold↗
Controlling interparticle spacing among metal nanoparticles through metal-catalyzed decomposition of surrounding polymer matrix.
Systematic and reproducible control over average interparticle spacing of Pt, Ni, and Cu nanoparticles embedded in polyimide thin layers was achieved. The metal-catalyzed decomposition of polyimide matrixes surrounding metal nanoparticles causes a decrease in the composite layer thickness, while maintaining the size of nanoparticles. This ability provides an effective methodology for the preparation of metal/polymer nanocomposites with tailored microstructures and holds great promise toward the fundamental understanding of the physical interactions among metal nanoparticles.
Journal Article↗
Stereocontrolled synthesis and optical properties of all-cis poly(phenylene vinylenes) (PPVs): a method for direct patterning of PPVs.
Geometrically pure, all-cis poly(phenylene vinylenes) (PPVs) are synthesized by Suzuki-Miyaura-type polycondensation of 2,5-dioctyloxy-1,4-benzenediboronic acid with (Z,Z)-bis(2-bromoethenyl)benzenes, which are prepared by ruthenium-catalyzed (Z)-selective double hydrosilylation of diethynylbenzenes, followed by bromodesilylation of the resulting (Z,Z)-bis(2-silylethenyl)benzenes with N-bromosuccinimide. The all-cis PPVs thus obtained undergo one-way photoisomerization to the corresponding trans-PPVs both in solution and in the solid. This phenomenon is applied to direct microscale patterning of PPVs onto a quartz substrate.
Journal Article↗
Band gap engineering of CdTe nanocrystals through chemical surface modification.
We demonstrate band gap control of CdTe nanocrystals by selective surface modification using alkanethiol molecules. Both absorption and emission wavelengths can be tuned simply by mixing a dispersion of the nanocrystals with alkanethiol at room temperature, resulting in blue shifts in the optical spectra during reaction. The degree of blue shift depends on both the concentration of alkanethiols and the reaction time, thereby providing kinetic control over the emission peak wavelength of the nanocrystals in mild conditions. The observed spectral changes are suggested to be caused by a decrease in the size of the CdTe core through formation of CdTe1-x(SC10)x shells because of specific exchange of Te with alkanethiolates. The results reported herein provide a new band gap engineering scheme for semiconductor nanocrystals and offer opportunities for the design of ligand-stabilized semiconductor nanocrystals with tunable composition and optical properties.
Journal Article↗
Synthesis, surface modification, and multilayer construction of mixed-monolayer-protected CdS nanoparticles.
Herein, we describe a study aimed at synthesizing mixed-monolayer-protected CdS nanoparticles and investigating the reactivity of surface-bound functional groups in order to facilitate the immobilization of nanoparticles on a solid substrate as well as the construction of a three-dimensional nanocomposite. CdS nanoparticles initially prepared by the reverse micelle method were used to modify nanoparticle surfaces with 1-decanethiol molecules by ligand exchange. Subsequently, 11-mercapto-1-undecanol was partially incorporated by a place exchange reaction, thereby providing stable, mixed-monolayer-protected CdS nanoparticles. The nanoparticles obtained at each step were characterized by FT-IR and UV-vis spectroscopy, transmission electron microscopy, and elemental analysis. The reactivity of surface hydroxyl groups was verified by a reaction with isocyanate-bearing molecules that provide carbamate bonds in high yields at ambient temperature. The obtained mixed-monolayer-protected nanoparticles were also successfully immobilized on a glass substrate through a carbamate-bond-forming reaction that could be further utilized for multilayer construction in a layer-by-layer fashion.
Cadmium Compounds↗
Direct patterning of copper on polyimide using ion exchangeable surface templates generated by site-selective surface modification.
We demonstrate site-selective chemical surface modification by dispensing potassium hydroxide solution onto polyimide, which confines source metallic ions that can subsequently be used in resist- and mask-free fabrication of copper circuit patterns. Metallization can be achieved by a wet chemical method, providing control over metal/polymer interfacial structures. Because the approach is compatible with other existing printing technologies and much simpler than conventional lithography-based methods, we propose that the present surface template method may be of general application in fabrication of metallized polymers as well as in development of integrated circuits with a variety of electronic circuit elements.
Journal Article↗
Composite of Au nanoparticles and molecularly imprinted polymer as a sensing material.
A molecularly imprinted polymer with immobilized Au nanoparticles (Au-MIP) is reported as a novel type of sensing material. The sensing mechanism is based upon the variable proximity of the Au nanoparticles immobilized in the imprinted polymer, which exhibits selective binding of a given analyte accompanied by swelling that causes a blue-shift in the plasmon absorption band of the immobilized Au nanoparticles. Using adrenaline as the model analyte, it was shown that molecular imprinting effectively enhanced the sensitivity and selectivity, and accordingly, Au-MIP selectively detects the analyte at 5 microM. The combination of molecular imprinting and the Au nanoparticle-based sensing system was shown to be a general strategy for constructing sensing materials in a tailor-made fashion due to wide applicability of the imprinting technique and the independence of the sensing mechanism from the analyte recognition system.
Chemistry Techniques, Analytical↗