Enhanced Magneto‐optical Properties of Semiconductor EuS Nanocrystals Assisted by Surface Plasmon Resonance of Gold Nanoparticles

Remarkable magneto‐optical properties of a new isolator material, that is, europium sulfide nanocrystals with gold (EuS–Au nanosystem), has been demonstrated for a future photo‐information technology. Attachment of gold particles that exhibit surface plasmon resonance leads to amplification of the magneto‐optical properties of the EuS nanocrystals. To construct the EuS–Au nanosystems, cubic EuS and spherical Au nanocrystals have been joined by a variety of organic linkers, that is, 1,2‐ethanedithiol (EDT), 1,6‐hexanedithiol (HDT), 1,10‐decanedithiol (DDT), 1,4‐bisethanethionaphthalene (NpEDT), or 1,4‐bisdecanethionaphthalene (NpDDT) . Formation of these systems was observed by XRD, TEM, and absorption spectra measurements. The magneto‐optical properties of the EuS–Au nanosystem have been characterized by using Faraday rotation spectroscopy. The Faraday rotation angle of the EuS–Au nanosystem is dependent on the Au particle size and interparticle distance between EuS and Au nanocrystals. Enhancement of the Faraday rotation of EuS–Au nanosystems was observed. The spin configuration in the excited state of the EuS–Au nanosystem was also investigated using photo‐assisted electron paramagnetic resonance.     

7,7,8,8‐Tetraaryl‐o‐quinodimethane Stabilized by Dibenzo Annulation: A Helical π‐Electron System That Exhibits Electrochromic and Unique Chiroptical Properties

When two benzene rings are fused to a tetraaryl‐o‐quinodimethane skeleton, sterically hindered helical molecules 1 acquire a high thermodynamic stability. Because the tetraarylbutadiene subunit contains electron‐donating alkoxy groups, 1 undergo reversible two‐electron oxidation to 2 ²⁺, which can be isolated as deeply colored stable salts. Intramolecular transfer of the point chirality (e.g., sec‐butyl) on the aryl groups to helicity induces a diastereomeric preference in dications 2 b ²⁺ and 2 c ²⁺, which represents an efficient method for enhancing circular‐dichroism signals. Thus, those redox pairs can serve as new electrochiroptical response systems. X‐ray analysis of dication 2 ²⁺ revealed π–π stacking interaction of the diarylmethylium moieties, which is also present in solution. The stacking geometry is the key contributor to the chirosolvatochromic response.     

Graphene Nanocomposites Based Electrochemical Sensing Platform for Simultaneous Detection of Multi-drugs

Three reduced graphene oxide nanocomposites were employed to achieve the simultaneous electrochemical determination of multi-drugs including acetaminophen (ACTM), carbendazim (CB) and ciprofloxacin (CFX). All nanocomposite modified electrodes showed improved current responses for three drugs. Notably cauliflower-like platinum nanoparticles decorated reduced graphene oxide modified electrode (or Pt−RGO/GCE) exhibited the best performance in terms of electrochemical stability. Using Pt−RGO/GCE, the linear detect ranges of 30–120 μM, 25–115 μM and 10–25 μM, and detection limit values of 3.49, 2.96, and 1.53 μM were achieved for ACTM, CB and CFX respectively. The electrode was further used for the successful determination of above drugs in tap and river water using differential pulse voltammetry. From the obtained results, we believe that Pt-RGO/GCE is highly promising for the fabrication of robust electrochemical sensors for simultaneously determining ACTM, CB and CFX or similar types of drugs in the future.     

Control of diameter of ZnO nanorods grown by chemical vapor deposition with laser ablation of ZnO

We made a study of controlling diameters of well-aligned ZnO nanorods grown by low-pressure thermal chemical vapor deposition combined with laser ablation of a sintered ZnO target, which was developed by us. Until now, it has been impossible to control diameters of ZnO nanorods, while the growth orientation was maintained well-aligned. In this study we developed a multi-step growth method to fabricate well-aligned nanorods whose diameters could be controlled. Metal Zn vapor and O₂ are used as precursors to grow ZnO nanorods. N₂ is used as a carrier gas for the precursors. A substrate is an n-Si (111) wafer. A sintered ZnO target is placed near the substrate and ablated by a Nd–YAG pulsed laser during ZnO nanorod growth. The growth temperature is 530 C and the pressure is 66.5 Pa. A vertical growth orientation of ZnO nanorods to the substrate is realized in the first-step growth although the diameter cannot be controlled in this step. When an O₂ flow rate is 1.5 sccm, well-aligned nanorods with 100 nm diameter are grown. Next, the second-step nanorods are grown on only the flat tip of the first-step nanorods. The diameters of the second-step nanorods can be controlled by adjusting the O₂ flow rate, and the growth direction is kept the same as that of the first-step nanorods. When the O₂ flow rate in second-step growth is smaller than 0.6 sccm, the diameter of the second-step nanorods is 30–50 nm. When the O₂ flow rate is between 0.75 and 3.0 sccm, the diameter is almost same as that of the first-step nanorods. When the O₂ flow rate is larger than 4.5 sccm, the diameter is increased with increasing O₂ flow rate. Further, the third-step ZnO nanorods with gradually increased diameters can be grown on the second-step nanorods with 1.5 sccm O₂ flow rate and without laser ablation.     

Photochemical Behavior of Single‐Walled Carbon Nanotubes in the Presence of Propylamine

This report describes the photochemical behavior of single‐walled carbon nanotubes (SWNTs) in the presence of propylamine. The SWNTs are characterized by absorption and Raman spectroscopy. The spectral changes due to photoirradiation indicate that reactions occur predominantly with the metallic SWNTs and small‐diameter SWNTs. The detection of amine radicalcation species by ESR spectroscopy reveals photoinduced electron transfer from the amine to the excited SWNTs. After exposure of the photoirradiated SWNTs to air, the characteristic spectra were recovered, except for that of the small‐diameter SWNTs. The results suggest that, after photoreduction of the SWNTs, subsequent selective sidewall functionalization of the small‐diameter SWNTs occurs.     

Steric effects upon transition states of radical addition polymerizations

Transition states (TSs) of radical addition homopolymerization reactions of methyl acrylate, methyl methacrylate, dimethyl itaconate, and N-methyl itaconimide were examined with two-unit radical models using MOPAC (PM3 UHF) semiempirical method. Calculated activation energies (E_as) show good correlations with experimental values. Calculated activation entropies (−ΔS^‡s) are found to be well proportional to E_as. The entropy terms play an important role as well as E_a in radical additions. E_a depends on the angle (θ_rs) between reaction points of radical and of monomer at TS. The bond length between reaction points at TS is constant regardless of monomers studied. The geometries and thermodynamical properties calculated here for TS indicate the importance of steric effects caused by substituted group(s) rather than electronic perturbation energies reported previously. © 1996 John Wiley & Sons, Inc.     

Static light scattering from poly(ethylene oxide) in methanol

Static light scattering measurements were performed on dilute solutions of monodisperse poly(ethylene oxide) (PEO) in methanol at 25°C. PEOs of five different molecular weights ranging from nominal M_w = 8.6 × 10⁴ to 9.13 × 10⁵ were used. Linear Zimm plots were obtained for all the PEO samples: no downturn was observed at small angles, indicating that no large aggregates of PEO molecules exist in the solution. From the plots, values of the weight-average molecular weight, M_w, the radius gyration, R_G, and the second virial coefficient, A₂, were successfully determined for respective PEOs. Observed relationship between R_G and M_w indicates that methanol is certainly a good solvent for the polymer. © 1996 John Wiley & Sons, Inc.     

Efficient deanilidation of phosphoranilidates by the use of nitrites and acetic anhydride

Reagent systems of sodium– and tetrabutylammonium nitrite–acetic anhydride were proved to be extremely efficient for the deanilidation of nucleoside 3′-phosphoranilidates, whose reactions were rapid with the former and instant with the latter. It was further found that the reagent system is applicable to oligonucleotide synthesis provided that the exocyclic amino groups of 2′-deoxyadenosine, 2′-deoxyguanosine, and 2′-deoxycytidine were protected by succinylation.     

Distribution of aquatic plants and absorption of radionuclides by plants through the leaf surface in brackish Lake Obuchi, Japan, bordered by nuclear fuel cycle facilities

We investigated the distribution of aquatic plants and the absorption of radionuclides by them in the brackish Lake Obuchi, Japan, which is bordered by nuclear fuel cycle facilities. We studied 5 species of submerged plants: Zannichellia palustris, Ruppia maritima, Potamogeton pectinatus, Zostera japonica, and Z. marina. The plants contained many elements, including radionuclides. The concentrations of ²³⁸U, ¹³⁷Cs, and ⁹⁰Sr in Z. marina were 11.3-12.4, 0.000-0.144, and 0.151-0.202 Bq^.kg^-1 dw, respectively. Those in Z. japonica were 5.2-8.8, 0.000-0.267, and 0.081-0.175 Bq^.kg^-1 dw, respectively. The concentrations of these radionuclides in the plants tended to be higher in higher-salinity regions than in lower-salinity regions of the lake. We found a close relationship between photosynthetic activity and the absorption of stable Sr by plants in the laboratory. Salinity, illumination, and water temperature influenced the photosynthetic activity of the plants and the consequent absorption of elements.     

Proteome analysis of Oncorhynchus species during embryogenesis

To understand the molecular mechanisms underlying normal and abnormal development of two salmonids, masu salmon (Oncorhynchus masou) and rainbow trout (O. mykiss), we used two-dimensional (2-D) electrophoresis to construct a series of 2-D maps during the embryonic period. We identified all visible protein spots on the 2-D map by assigning numbers for masu salmon and rainbow trout, and we determined N-terminal sequences of proteins for one hundred of the spots, that appear at very high concentrations in the whole embryos of masu salmon and rainbow trout. We also characterized embryonic stages according to the periods of appearance of spots. Most of the N-terminal sequences were identical or at least highly similar to partial sequences reported for vitellogenin (Vtg) of O. mykiss. A potential proteolytic processing of Vtg for rainbow trout is discussed in relation to the time of appearance and relative position of Vtg fragments within the complete protein sequence.