Fundamental research on the label-free detection of protein adsorption using near-infrared light-responsive plasmonic metal nanoshell arrays with controlled nanogap

In this work, we focused on the label-free detection of simple protein binding using near-infrared light-responsive plasmonic nanoshell arrays with a controlled interparticle distance. The nanoshell arrays were fabricated by a combination of colloidal self-assembly and subsequent isotropic helium plasma etching under atmospheric pressure. The diameter, interparticle distance, and shape of nanoshells can be tuned with nanometric accuracy by changing the experimental conditions. The Au, Ag, and Cu nanoshell arrays, having a 240-nm diameter (inner, 200-nm polystyrene (PS) core; outer, 20-nm metal shell) and an 80-nm gap distance, exhibited a well-defined localized surface plasmon resonance (LSPR) peak at the near-infrared region. PS@Au nanoshell arrays showed a 55-nm red shift of the maximum LSPR wavelength of 885 nm after being exposed to a solution of bovine serum albumin (BSA) proteins for 18 h. On the other hand, in the case of Cu nanoshell arrays before/after incubation to the BSA solution, we found a 30-nm peak shifting. We could evaluate the difference in LSPR sensing performance by changing the metal materials

Multiscale element mapping of buried structures by ptychographic x-ray diffraction microscopy using anomalous scattering

We propose an element mapping technique of nano-meso-microscale structures buried within large and/or thick objects by ptychographic x-ray diffraction microscopy using anomalous scattering. We performed quantitative imagings of both the electron density and Au element of Au/Ag nanoparticles at the pixel resolution of better than 10 nm in a field of view larger than 5 × 5 μm2 by directly phasing ptychographic coherent diffraction patterns acquired at two x-ray energies below the Au L3 edge. This method provides us with multiscale structural and elemental information for understanding the element/property relationship linking nanoscale structures to macroscopic functional properties in material and biological systems. © 2011 American Institute of Physics.Yukio Takahashi, Akihiro Suzuki, Nobuyuki Zettsu, Yoshiki Kohmura, Kazuto Yamauchi, and Tetsuya Ishikawa, "Multiscale element mapping of buried structures by ptychographic x-ray diffraction microscopy using anomalous scattering", Appl. Phys. Lett. 99(13), 131905 (2011) https://doi.org/10.1063/1.3644396

High-resolution projection image reconstruction of thick objects by hard x-ray diffraction microscopy

Hard x-ray diffraction microscopy enables us to observe thick objects at high spatial resolution. The resolution of this method is limited, in principle, by only the x-ray wavelength and the largest scattering angle recorded. As the resolution approaches the wavelength, the thickness effect of objects plays a significant role in x-ray diffraction microscopy. In this paper, we report high-resolution hard x-ray diffraction microscopy for thick objects. We used highly focused coherent x rays with a wavelength of ∼0.1 nm as an incident beam and measured the diffraction patterns of a ∼150-nm -thick silver nanocube at the scattering angle of ∼3°. We observed a characteristic contrast of the coherent diffraction pattern due to only the thickness effect and collected the diffraction patterns at nine incident angles so as to obtain information on a cross section of Fourier space. We reconstructed a pure projection image by the iterative phasing method from the patched diffraction pattern. The edge resolution of the reconstructed image was ∼2 nm, which was the highest resolution so far achieved by x-ray microscopy. The present study provides us with a method for quantitatively observing thick samples at high resolution by hard x-ray diffraction microscopy. © 2010 The American Physical Society.Yukio Takahashi, Yoshinori Nishino, Ryosuke Tsutsumi, Nobuyuki Zettsu, Eiichiro Matsubara, Kazuto Yamauchi, and Tetsuya Ishikawa. Phys. Rev. B 82(21), 214102 (2010)

Towards high-resolution ptychographic x-ray diffraction microscopy

Ptychographic x-ray diffraction microscopy is a lensless imaging technique with a large field of view and high spatial resolution, which is also useful for characterizing the wavefront of an x-ray probe. The performance of this technique is degraded by positioning errors due to the drift between the sample and illumination optics. We propose an experimental approach for correcting the positioning errors and demonstrate success by two-dimensionally reconstructing both the wavefront of the focused x-ray beam and the complex transmissivity of the weakly scattering objects at the pixel resolution of better than 10 nm in the field of view larger than 5 μm. This method is applicable to not only the observation of organelles inside cells or nano-mesoscale structures buried within bulk materials but also the characterization of probe for single-shot imaging with x-ray free electron lasers. © 2011 American Physical Society.Yukio Takahashi, Akihiro Suzuki, Nobuyuki Zettsu, Yoshiki Kohmura, Yasunori Senba, Haruhiko Ohashi, Kazuto Yamauchi, and Tetsuya Ishikawa. Phys. Rev. B 83(21), 214109 (2011)

Growth Manner of Octahedral-Shaped Li(Ni_1/3Co_1/3Mn_1/3)O₂ Single Crystals in Molten Na₂SO₄

The synthesis of shape-controlled crystals has been a highly attractive research topic in modern materials chemistry. In this work, the growth of Li­(Ni_1/3Co_1/3Mn_1/3)­O₂ (NCM) crystals in molten sulfate or carbonate salts (flux) at 1000 °C was systematically studied under various conditions. In situ X-ray diffraction during the growth and thermogravimetry-differential thermal analysis revealed that the growth of NCM crystals in the flux was controlled by liquid-phase sintering according to the Ostwald ripening principle. We studied the effect of Na⁺ in the flux on the crystal shapes and found that Na⁺ was critical in forming octahedral crystals with well-developed facets. Single crystals with well-developed facets were obtained homogeneously from Na₂SO₄, while truncated polyhedral crystals of smaller size were obtained from Li₂SO₄. The shape-controlled NCM crystals showed discharge capacities approaching 160 mAh g^–1 in the operating voltage range of 2.8–4.4 V vs Li/Li⁺ under a low current density of 0.1 C, independent of flux composition. This suggests that the Li⁺ and transition-metal ions in the individual NCM crystals were highly ordered into hexagonal arrangements belonging to the <i>R</i>3̅<i>m</i> space group, without cation mixing