Newly synthesized naphthalene diimide derivative having ferrocene and b-cyclodextrin, FNC, bound to DNA duplex with threading intercalation mode. Atomic force microscopic observation showed that its complex was changed to globule structure with the excess ratio of FNC to DNA base pair and its structure was broken upon addition of an adamantane divertive. Spectrophotometric and electrochemical studies suggested that this globule is formed by the formation of inclusion complex between ferrocene and b-cyclodextrin of FNC bound to DNA duplex and its collapse occurs by the exchange of ferrocene with the adamantane.
We succeeded in preparation of well-defined Au homo, Ag homo and Au-Ag hetero-dimer structures with controlled gap distances and structure size. These structure were used for in-situ surface-enhanced Raman scattering (SERS) measurements. Controlled adsorption of 2,2’-bipyridine and 4,4’-bipyridine molecules onto the metal surface in an aqueous solution resulted in characteristic SERS peak shifts reflecting switching of the adsorption site of molecule at the gap of the Au-Ag hetero-dimer. Changes in the relative intensities and the wavenumbers of the SERS bands provide information on the adsorption environment of the target molecule at the single molecule level.
We demonstrate a new bio-sensing method using the reflective property of a metallic mesh device (MMD). The MMD can work as a band-pass filter in the terahertz (THz) region and its sensing mechanism is attributed to localization of the electromagnetic field on the surface of the device due to the periodic structure. The refractive index of a liquid sample can be estimated by calculating the shift in the reflectance spectrum before and after the sample is attached to the device. The results indicate that the reflection measurement method is effective for solution measurement and also MMDs could function as sensors for detecting the affinity of its near-surface property for water.
Here we demonstrate a ‘nanowire memristor’ using bottom-up grown metal oxide nanowire, which is a tool to investigate the memory performance and the physical mechanism of nanoscale memristive switching. The nanowire memristor clearly showed the excellent memory performance at nanoscale and the experimental evidences for the physical mechanism, which had not been feasible for conventional thin film capacitor devices.
Combining the use of liquid polyethylene glycol (PEG) as a capture medium with the sputter deposition technique, we developed the easy and simple preparation method of gold nanoparticles (Au NPs) in liquid PEG without any chemical reactions. It is revealed that the particle size and shape are strongly dependent on the preparation temperature of PEG. Detailed investigation of the temperature-dependent properties of PEG suggests that the collision frequency of sputtered Au particles (atoms and small clusters) is one of the most important factors for the determination of particle size and shape. We discuss the stabilization effects of the capture media from the viewpoint of the structures of the Au NPs and their formation processes. We also investigated the heat-treatment effect on Au NPs that were previously generated in PEG at 20 °C. It is established that the size of the Au NPs can be controlled by post-heating and that this effect on the previously generated Au NPs is quite different from the temperature effect during initial preparation. Furthermore, we tried to control the structure of Au NPs by addition of some substances. We selected two substances: typical ionic liquid, 1-butyl-3-methylimidazorium tetrafluoroborate, and thiolated PEG, which had thiol group and methoxy group as terminal substituents. As a result, it was confirmed that the size of Au NPs synthesized in PEG was altered by the addition of stabilizing agents.
Vascular endothelial growth factor (VEGF) plays a very important role in angiogenesis. However, as vascular imaging at the molecular level is currently impossible, the detailed in vivo dynamics of VEGF and its receptor (VEGF-R) were not understood well. In this study, to reveal the in vivo distribution of VEGF and VEGF-R, we established a mouse model of ischemia and induced angiogenesis in the gastrocnemius. We then developed VEGFconjugated fluorescent nano-particles and treated VEGF-R-expressing cells with the probe, showing its high affinity for VEGF-R. To observe the molecular distribution of VEGF-R, we performed in vivo imaging of the gastrocnemius in the ischemic leg using the fluorescent probe. The results suggest that only a several fold difference in VEGFreceptor expression levels is involved in the formation of branched vasculature during angiogenesis.
We have investigated the reactions of CO with O2 on size-selected copper cluster ions, Cun + (n = 4−18) and Cun − (n = 4−11), at the collision energy of 0.2 eV by use of a guided ion beam-tandem mass spectrometer. Preadsorption of O2 improves the CO-adsorption cross section of Cun + (n ≥ 9), and coadsorption products, CunO2 +(CO), are observed. In contrast, oxygen-adsorbed copper anions, CunO2 −, in particular Cu5O2 − and Cu9O2 −, were found to show the evidence of CO oxidation, forming the monoxide CunO−. The density functional theory calculation indicates that CO oxidation on Cu5O2 − proceeds via a low-energy pathway compared with that on Cu5O2 +. One of the key factors driving the CO oxidation on a copper cluster is likely due to the structural rearrangement of the copper cluster.
Semiconductor nanoclusters and nanoparticles of cadmium chalcogenides have attracted special attention due to their unique optical properties. We particularly take notice of host-guest chemistry and molecular events at the small cluster surface and have exploring unique functions by designing the organic environment around the cluster. In this article we review our recent approaches utilizing molecular clusters with a general formula of Cd10S16R12 having twelve surface organic groups. Aryl-substituted clusters trapped ammonium cations among the surface aromatics through cation-π interaction, and such an intercalative cation binding caused a notable enhancement of the cluster photoluminescence at ~600 nm. It was also found that PEG-coated clusters having inner hydrophobic binding sites show selective turn-on photoluminescence responses toward lipophilic phenols.