Optimum hole-opening condition for Cisplatin incorporation in single-wall carbon nanohorns and its release

We enclosed cisplatin (CDDP), an anticancer drug, inside single-wall carbon nanohorns (SWNH) with holes opened by being heated from room temperature to a target temperature (475-580 degrees C) in flowing dry air, with an increase rate of 1 degrees C/min. The optimum target temperature was found to be 500 degrees C, in terms of the least amount of CDDP deposited outside the SWNH, when the quantity of CDDP encapsulated inside the SWNH was 12 wt %. The incorporated CDDP was slowly released from the SWNH in phosphate buffer saline, and the released quantity was 80%, which was greatly improved from the previous value of 15%. This indicated that a CDDP-containing SWNH could become more potentially useful for biological applications.     

Electronic interplay on illuminated aqueous carbon nanohorn-porphyrin ensembles

Tetracationic water-soluble porphyrin (H(2)P(4+)) has been immobilized by pi-pi stacking interactions onto the skeleton of carbon nanohorns (CNH), without disrupting their pi-electronic network. The stable aqueous solution of the CNH-H(2)P(4+) nanoensemble was examined by both electron microscopy and spectroscopic techniques. The efficient fluorescence quenching of the H(2)P(4+) moiety in the CNH-H(2)P(4+) nanoensemble was probed by steady-state as well as time-resolved fluorescence emission spectroscopy, suggesting charge separation from the photoexcited H(2)P(4+) to CNH. In the presence of methyl viologen dication (MV(2+)) and a hole trap, accumulation of the reduced species of methyl viologen was observed by the photoillumination of CNH-H(2)P(4+), suggesting that the electron migration from the initially formed charge-separated state takes place. Transient absorption spectroscopy gave further insights on the transient species such as the charge-separated state (CNH(*-))-(H(2)P(4+))(*+), which was consumed in the presence of MV(2+) and hole shifter, leaving the reduced methyl viologen.     

The current state of sol-gel technology

The current state of sol-gel technology has been reviewed mainly from the standpoint of microstructures of materials which can be achieved by the sol-gel method. It has been shown that the sol-gel method makes it possible to produce a great variety of high technology materials by providing the existing substances with a significant microstructure and producing the material with a novel microstructure. There are microstructures characterized by micropores, preferential crystal orientation, inorganic-organic and inorganic-inorganic composites of hybrid nature and gradient composition. These characteristic microstructures are related to the properties and applications of the materials.     

β-Methallylrhodium(III) supported on a vanadium oxide cluster: Synthesis,structure, and reaction

Reaction of [(³-C₄H₇)₂Rh(CH₃CN)₂]PF₆(³-C₄H₇ = -methallyl) with [n-Bu₄N](VO₃) gives a new ³-allyl cluster [n-Bu₄N]₂[{(³-C₄H₇)₂Rh}₂ (V₄O₁₂)] (I) which is readily converted into a diene cluster, [n-Bu₄N]₂ [{(⁴-C₈H₁₄)Rh}₂(V₄O₁₂)] (II) (C₈H₁₄=2,5-dimethyl-1,5-hexadiene) by reacting with CO or P(OEt)₃;I andII have been characterized crystallographically.     

Selective matching of catalyst element and carbon source in single-walled carbon nanotube synthesis on silicon substrates

We have studied the compatibility of various catalysts for ethylene and ethanol chemical vapor deposition (CVD) syntheses of single-walled carbon nanotubes (SWNTs) on Si substrates. A strong selectivity between the catalyst elemental species and carbon source was found; SWNT yield for Fe (Co) catalysts was much higher for ethylene (ethanol) CVD than for ethanol (ethylene) CVD. This strong and completely opposite selectivity implies significantly different SWNT growth mechanisms for ethanol and ethylene CVD on Si substrates.     

Stekeospecific transformation of D-sugar to L-sugar in complex aminoglycoside. Synthesis of a kanamycin B analog having 2,6-diamino-2,4,6-trideoxy-L-arabino-hexopyranose

A 4′-ene derivative of kanamycin B ($\text{4}$) was derived from the epoxide ($\text{1}$) by oxidative elimination of the 4′-phenylseleno group into the allylic alcohol ($\text{3}$). The title compound, 0-(2,6-diamino-2,4,6-trideoxy-β-L-arabino-hexopyranosyl)-(1→4)-0-[3-amino-3-deoxy-α-D-glucopyranosyl-(1→6)]-2-deoxystreptamine ($\text{6}$) was obtained from $\text{4}$ by stereospecific hydrogenation followed by removal of the masking groups, changing the D-sugar moiety of the 4-0-glycoside portion into an L-sugar.     

Potentiometric flow-injection determination of trace chlorine based on its redox reaction with an iron(III)/iron(II) buffer

A very sensitive and rapid potentiometric determination of trace chlorine in water is described. The method is based on the transient potential changes which appears during the reduction of dissolved chlorin with an iron(III)/iron(II) potential buffer containing chloride and sulfuric acid. The sample is injected into a water carrier stream and merged with a stream of this potential buffer solution; chlorine is reduced during passage through a short reaction coil. The potential change from the baseline is measured with a flow-through ORP (oxidation-reduction potential) electrode. Potential changes (peak heights) are proportional to chlorine concentrations from 10^?7 M to 10^?5 M. The detection limit is 5 × 10^?8 M (3.5 μgl^?1 as Cl₂). The sample throughput is 45 h^?1. Reproducibility is in the range 2.5–1.1%. Results for potable water agree with those obtained by the o-tolidine method.     

Graft copolymers having hydrophobic backbone and hydrophilic branches. III. Synthesis of graft copolymers having oligovinylpyrrolidone as hydrophilic branch

Graft copolymers were synthesized by the esterification reaction between acrylic copolymers and carboxyl group terminated vinylpyrrolidone oligomer using phase transfer catalysts. Acrylic copolymers were obtained by the radical copolymerization of β-bromoethyl methacrylate, chloromethylstyrene or glycidyl methacrylate with methyl methacrylate. Hydrophilic oligomers were prepared by the radical oligomerization of vinylpyrrolidone using β-mercaptopropionic acid as chain transfer agent. The degree of esterification increased with decreasing the molecular weight of oligomer and with increasing the number of potential grafting sites on polymer backbones. The water dispersibility of graft copolymers increased with increasing the nitrogen content and was therefore dependent on the branch oligomer content.     

Kinetics and mechanism of the base hydrolysis of cis-eq-[Cr(NCS)(S-pdtra)]−, trans-eq-[Cr(NCS)(edtrp)]− and trans-eq-[Cr(NCS)(R-pdtrp)]− complexes. Strong rate enhancement for NCS− ligand release with an increase of [OH−] only for the trans-equatorial isomers

The [Cr(NCS)(edtrp)]⁻, [Cr(NCS)(R-pdtrp)]⁻ and [Cr(NCS)(S-pdtra)]⁻ complexes, that are derivatives of the trans-equatorial isomers of [Cr(edtrp)(H₂O)]° and [Cr(R-pdtrp)(H₂O)]° and the cis-equatorial isomer of [Cr(S-pdtra)-(H₂O)]° (edtrp = ethylenediamine-N,N,N′-tripropionate, R-pdtrp = R-propane-1,2-diamine-N,N,N′-tripropionate, S-pdtra = S-propane-1,2-diamine-N,N,N′-triacetate) undergo aquation in alkaline media with a strong dependence of the rate on [OH⁻] for the trans-equatorial isomers and a very weak dependence for the cis-equatorial isomer. The thiocyanate ligand release follows a stereoretentive course for all reactants. Based on kinetic data the reaction mechanism has been discussed. Rate differences between the isomers are interpreted in terms of an interchange via a conjugate base (I c.b.) mechanism, assuming an equilibrium between the cis-equatorial-Cr^III-S-pdtra complexes with penta- and tetradentate coordination of the edta-like ligand. This revised version was published online in June 2006 with corrections to the Cover Date.