Controlling the incorporation and release of C60 in nanometer-scale hollow spaces inside single-wall carbon nanohorns

We succeeded in large-scale preparation of single-wall carbon nanohorns (SWNH) encapsulating C60 molecules in a liquid phase at room temperature using a "nano-precipitation" method, that is, complete evaporation of the toluene from a C60-SWNH-toluene mixture. The C60 molecules were found to occupy 6-36% of the hollow space inside the SWNH, depending on the initial quantity of C60. We showed that the C60 in C60@SWNHox was quickly released in toluene, and the release rate decreased by adding ethanol to toluene. Numerical analysis of the release profiles indicated that there were fast and slow release processes. We consider that the incorporation quantity and the release rate of C60 were controllable in/from SWNHs because SWNHs have large diameters, 2-5 nm.     

Opening mechanism of internal nanoporosity of single-wall carbon nanohorn

Single-wall carbon nanohorn (SWNH), which is a tubular particle with a cone cap, was oxidized in an oxygen flow at various temperatures. N(2) adsorption at 77 K, thermogravimetry (TG), differential thermal analysis (DTA), transmission electron microscopy, and Raman spectroscopy measurements were carried out on the oxidized SWNHs. The specific surface area of the oxidized SWNHs can be controlled by oxidation temperature, giving the maximum value of 1420 m(2)/g. The pore size distribution by the BJH method and the comparison plot of the N(2) adsorption isotherms of SWNH oxidized at different temperatures against that of as-grown SWNH revealed the minimum oxidation temperature for opening internal nanopores. TG-DTA analyses determined the components of as-grown SWNH: amorphous carbon 2.5 wt %, defective carbon at the cone part 15 wt %, tubular carbon 70 wt %, and graphitic carbon 12 wt %. These systematic analyses provided the exact internal nanopore volume of 0.49 mL/g for pure SWNH particles.     

Studies on the adsorption of organic materials inside thick carbon nanotubes

We clarified the adsorption sites inside the single-wall carbon nanohorns (SWNHs), a type of single-wall carbon nanotubes having thick diameters of 2-5 nm, through the thermogravimetric analysis of the desorption of xylene and benzene from SWNHs. The influence of the sizes of holes piercing through the SWNH walls was also examined. Three types of adsorption sites were found inside the SWNH tubes, which were assigned to the tube tips, the sidewalls, and central regions of the hollow spaces. The experimental results also suggested that the adsorbed xylene and benzene were stabilized mainly by weak self-interactions at the central regions and their quick desorption was caused by the weak self-interactions.     

Carbon isotope ratio analysis of organic moieties from fossil mummified wood: establishing optimum conditions for off-line pyrolysis extraction using gas chromatography/mass spectrometry

Mummified fossil wood was studied using off-line pyrolysis-gas chromatography/mass spectrometry to reveal detailed insights into the pyrolysis conditions that are needed to obtain simultaneously sufficient amounts of both cellulose and lignin markers for stable carbon isotope analyses. The off-line pyrolysis was applied at a range of temperatures (200, 250 and 300 degrees C) and times (1 and 2 h) to determine the optimum temperature and time that yielded the highest quantity of true markers for lignin and cellulose. Increasing the time from 1 to 2 h had no effect whereas increasing the temperature led to large differences. The products released during the low-temperature pyrolysis were mostly related to thermally labile moieties. Only at 300 degrees C were sufficient amounts of products released that represent true cellulose and lignin building blocks and which could be studied using gas chromatography/combustion isotope ratio mass spectrometry.     

Cisplatin suppository: preparation, release characteristics and clinical evaluation

Cisplatin (CDDP) has attracted attention as a chemotherapeutic agent for the treatment of uterine endometrial carcinoma but causes serious side effects, including renal toxicity. CDDP suppositories containing NaCl at different concentrations were prepared to enhance the efficacy and to reduce the side effects of CDDP. The release characteristics, melting point and viscosity of the suppositories were first studied. The rate of CDDP release increased as the NaCl concentration increased: it was 12% 12 h after administration of suppositories containing no NaCl, but 32% with 0.2% NaCl. The melting point was raised by addition of NaCl: 35.5 degrees C without NaCl and 36.5 degrees C with 0.2% NaCl. Addition of 0.2% NaCl doubled the viscosity. Clinically, the suppository containing 0.06% NaCl was given to 3 patients with endometrial carcinoma twice a week for 3 weeks to examine serum CDDP levels and endometrial absorption. Patients with endometrial carcinoma showed different peak plasma platinum (Pt) levels which were as low as 0.12, 0.06 and 0.22 micrograms Pt/ml with similar patterns of change in the level. Radiographic analysis revealed many Pt particles in sections of necrosed endometria after 21d of the treatment. No side effects of CDDP were found in biochemical testing or subjective symptoms.     

Quantum effects on hydrogen isotope adsorption on single-wall carbon nanohorns

H(2) and D(2) adsorption on single-wall carbon nanohorns (SWNHs) have been measured at 77 K, and the experimental data were compared with grand canonical Monte Carlo simulations for adsorption of these hydrogen isotopes on a model SWNH. Quantum effects were included in the simulations through the Feynman-Hibbs effective potential. The simulation predictions show good agreement with the experimental results and suggest that the hydrogen isotope adsorption at 77 K can be successfully explained with the use of the effective potential. According to the simulations, the hydrogen isotopes are preferentially adsorbed in the cone part of the SWNH with a strong potential field, and quantum effects cause the density of adsorbed H(2) inside the SWNH to be 8-26% smaller than that of D(2). The difference between H(2) and D(2) adsorption increases as pressure decreases because the quantum spreading of H(2), which is wider than that of D(2), is fairly effective at the narrow conical part of the SWNH model. These facts indicate that quantum effects on hydrogen adsorption depend on pore structures and are very important even at 77 K.     

Synthesis of ultrafine Gd2O3 nanoparticles inside single-wall carbon nanohorns

The large diameter of single-wall carbon nanohorns (SWNHs) allows various molecules to be easily incorporated in hollow nanospaces. In this report, we prove that the nanospaces of SWNHs even work as the chemical reaction field at high temperature; that is, Gd-acetate clusters inside SWNHs were transformed into ultrafine Gd(2)O(3) nanoparticles with their particle size retained even after heat-treatment at 700 degrees C. This indicates that the confinement of the Gd-acetate clusters in a deep potential well of the SWNH nanospaces prevented a migration to form larger particles, giving rise to ultrafine Gd(2)O(3) nanoparticles of 2.3 nm in average diameter, which is much smaller than the case without SWNHs. The Gd(2)O(3) nanoparticles thus obtained were demonstrated to be actually useful to the magnetic resonance imaging. We believe that the presented effectiveness of the inner hollow spaces of SWNHs, therefore, also those of the carbon nanotubes, for high-temperature chemical reactions should be highlighted, and that the thus produced novel nanomaterials are promising to expand the fields of nanoscience.     

Preparing a magnetically responsive single-wall carbon nanohorn colloid by anchoring magnetite nanoparticles

A single-wall carbon nanohorn (SWNH) colloid was made to be magnetically responsive by anchoring magnetite nanoparticles prepared by the homogeneous mixing of FeCl(2)-FeCl(3) and NaOH solutions. Transmission electron microscopy observation showed the high dispersion of magnetite particles of 2-9 nm on the surface of the SWNH colloid, coinciding with the broad X-ray diffraction peaks of the magnetites. The magnetization measurements showed that the magnetite nanoparticles-anchored SWNH (mag-SWNH) colloid has the hybrid property of ferrimagnetism and superparamagnetism. It was demonstrated that mag-SWNH colloid dispersed in water by sonication responded to an external magnetic field, gathering toward a magnet. N(2) adsorption experiments showed the high nanoporosity of mag-SWNHs and that magnetite nanoparticles were preferably anchored at "nanowindow" sites and the entrance sites of interstitial pores. This magnetically responsive SWNH colloid should contribute to the field of drug delivery.     

Effect of temperature and solvent composition on extraction of fumonisins B1 and B2 from corn products

Fumonisins B1 and B2 were extracted from naturally contaminated corn products by using different extraction solvent compositions (methanol-water, acetonitrile-methanol-water, ethanol-water, and 100% water) and a range of temperatures from ambient to 150 degrees C. Ground samples of several corn products and 1 rice sample were mixed with an adsorbent material (Hydromatrix), and the fumonisins were extracted in 2 sequential 5 min static extractions at various temperatures. The combined extracts were cleaned up and analyzed by reversed-phase liquid chromatography with fluorescence detection after o-phthaldialdehyde-mercaptoethanol derivatization. The results showed a clear influence of temperature and solvent composition on recovery of fumonisins from some matrixes. With acetonitrile-methanol-water (1 + 1 + 2) the quantity of fumonisins extracted from naturally contaminated taco shells almost tripled in going from 23 degrees to 80 degrees C, and increased by another 30% when ethanol-water (3 + 7) was used as extraction solvent at 80 degrees C. Similar results were obtained with nacho chips. These effects were less pronounced with cornmeal, and small differences due to temperature and solvent composition were observed for corn flakes and rice. The ethanol-water extraction solvent combinations were specifically evaluated in an effort to use the cheapest, least toxic, and most environmentally friendly solvents for organic residue analysis. At 80 degrees C, ethanol-water combinations performed equally or better than methanol-water (8 + 2) or acetonitrile-methanol-water (1 + 1 + 2), combinations which are commonly used for fumonisin extractions. Even 100% water was successful for extracting fumonisins from the products, except for rice. However, increased amounts of water created technical problems and required an increased amount of Hydromatrix in the samples prior to extraction.     

HPLC determination of cis-diamminedichloroplatinum(II) in plasma and urine with UV detection and column-switching

A method for determining cis-diamminedichloroplatinum(II) (CDDP), an anticancer drug, in plasma and urine by HPLC with UV detection and column-switching has been developed. Typical conditions were as follows. An apparatus was composed of two columns, two pumps, a UV detector, a sample injector with a 100 microL loop, a switching valve, a column oven and a recorder. A Rheodyne model 7125 sample injector was used as the switching valve. A precolumn (4.6 mm ID x 25 cm) was packed with MCI GEL CK10S (a strong cation exchanger), and an analytical column (4.6 mm ID x 5 cm) was packed with MCI GEL CDR10 (a strong anion exchanger). Both columns were connected in series via the switching valve. The CDDP-containing fraction of the effluent from the precolumn was loaded to the analytical column by column-switching and the effluent from the analytical column was monitored at 210 nm. An eluent of 0.3 M sodium dihydrogen phosphate was pumped at a flow rate of 1 mL/min and the columns were maintained at 40 degrees C. CDDP was eluted at about 11 min and the identity of the peak of CDDP on the chromatogram was confirmed by its 3-dimensional chromatogram and analysis of platinum in the column effluent. Under the conditions described above, a linear relationship was obtained between peak height and concentration of CDDP up to 100 microM. Correlation efficients were 0.998 for plasma and 0.999 for urine. The detection limit was 0.1 microM for CDDP in both plasma and urine (S/N = 3,0.005 AUFS). The reproducibility was within 3% for 10 determinations.(ABSTRACT TRUNCATED AT 250 WORDS)     

Controlled release of vitamin E from thermo-responsive polymeric physico-gel

Thermo-sensitive copolymer consists of poly(2-ethoxyethyl vinyl ether) and poly(hydroxyethyl vinyl ether) (EOVE200-HOVE400), whose sol-gel transition temperature was 20.5 degrees C, was synthesized and its applicability to a drug delivery system was examined. Vitamin E (VE) was enclosed in EOVE200-HOVE400 and the release of VE was measured by varying the temperature 10<-->30 degrees C. There was no release of VE from EOVE200-HOVE400 at 30 degrees C, while VE was released when the temperature was reduced to 10 degrees C.     

Microwave-assisted extraction method for the determination of atrazine and four organophosphorus pesticides in oranges by gas chromatography (GC)

A simple and rapid microwave assisted extraction (MAE) method is presented for the determination of atrazine and four organophosphorus pesticides (parathionmethyl, chlorpyriphos, fenamiphos and methidathion) in orange peel. The experimental variables that affect the MAE method, such as temperature, sample quantity, extraction time, nature and volume of organic solvents, were optimized. The MAE method was optimized using an experimental design. The results suggest that temperature and sample quantity are statistically significant factors. It was concluded that the five pesticides could be efficiently extracted from 1.5-2.5 g of orange peel with 10 mL of hexane/acetone (1: 1) mixture at 90 degrees C in 9 min with microwave power set at 50% (475 W). After optimization these factors, recoveries ranged from 93 to 101% with a relative standard deviation ranging from 1 to 3%. The extracts were analyzed by gas chromatography with a nitrogen-phosphorus detector (GC-NPD).     

Comprehensive two-dimensional gas chromatography of volatile and semi-volatile components using a diaphragm valve-based instrument

A high-temperature configuration for a diaphragm valve-based gas chromatography (GCXGC) instrument is demonstrated. GCxGC is a powerful instrumental tool often used to analyze complex mixtures. Previously, the temperature limitations of valve-based GCxGC instruments were set by the maximum operating temperature of the valve, typically 175 degrees C. Thus, valve-based GCxGC was constrained to the analysis of mainly volatile components; however, many complex mixtures contain semi-volatile components as well. A new configuration is described that extends the working temperature range of diaphragm valve-based GCxGC instruments to significantly higher temperatures, so both volatile and semi-volatile compounds can be readily separated. In the current investigation, separations at temperatures up to 250 degrees C are demonstrated. This new design features both chromatographic columns in the same oven with the valve interfacing the two columns mounted in the side of the oven wall so the valve is both partially inside as well as outside the oven. The diaphragm and the sample ports in the valve are located inside the oven while the temperature-restrictive portion of the valve (containing the O-rings) is outside the oven. Temperature measurements on the surface of the valve indicate that even after a sustained oven temperature of 240 degrees C, the portions of the valve directly involved with the sampling from the first column to the second column track the oven temperature to within 1.2% while the portions of the valve that are temperature-restrictive remain well below the maximum temperature of 175 degrees C. A 26-component mixture of alkanes, ketones, and alcohols whose boiling points range from 65 degrees C (n-hexane) to 270 degrees C (n-pentadecane) is used to test the new design. Peak shapes along the first column axis suggest that sample condensation or carry-over in the valve is not a problem. Chemometric data analysis is performed to demonstrate that the resulting data have a bilinear structure. After over 6 months of use and temperature conditions up to 265 degrees C, no deterioration of the valve or its performance has been observed.     

α,β-聚[N-(丁二酸基)- L-天冬酰胺]的合成及其顺铂大分子药物的细胞毒性

L-天冬氨酸在H2O/三乙胺混合溶剂中直接均相开环聚(L-天冬酰亚胺)(PSI), 合成α,β-聚[N-(丁二酸基)-L-天冬酰胺](PSAA). 研究了H2O和三乙胺的混合体积比对反应物溶解性能的影响, 并用FTIR和1H NMR表征了PSAA的结构. 以PSAA和α,β-聚(L-天冬氨酸)(PAsp)为载体, 与顺式二氯二氨合铂(Ⅱ)(CDDP)络合, 合成了PSAA-CDDP和PAsp-CDDP大分子药物. 结果表明, 载体PSAA和PAsp对Bel7402细胞的毒性均低于同浓度的聚赖氨酸; PSAA-CDDP的水溶性良好, 载药量较高, 达到了14.6%, 其药物控制释放性能较好; PSAA-CDDP和PAsp-CDDP的细胞毒性随着其浓度的增大而增大, 且细胞毒性PAsp-CDDP相似文献   

Quasi one-dimensional nanopores in single-wall carbon nanohorn colloids using grand canonical Monte Carlo simulation aided adsorption technique

The average interstitial nanopore structure of single-wall carbon nanohorn (SWNH) assemblies was determined using X-ray diffraction and grand canonical Monte Carlo (GCMC) simulation aided N(2) adsorption at 77 K. The interstitial nanopores of SWNH assemblies can be regarded as quasi one-dimensional pores due to the partial orientation of the SWNH particles; the average pore width of the interstitial pores is 0.6 nm. Good agreement between the GCMC simulation of a structural model with one-dimensional interstitial nanopores and an experimental adsorption isotherm below P/P(0) = 10(-4) is evidence of the quasi one-dimensionality of the interstitial nanopores. A snapshot from the GCMC simulation showed one-dimensional growth of adsorbed N(2) molecules.     

Improved hydrogen release from LiB0.33N0.67H2.67 with noble metal additions

The hydrogen release behavior of the quaternary hydride LiB(0.33)N(0.67)H(2.67) has been successfully improved through the incorporation of small quantities of noble metal. Adding 5 wt % Pd either as Pd metal particles or as PdCl(2) reduced the temperature T(1/2) corresponding to the midpoint of the hydrogen release reaction by DeltaT(1/2) = -43 degrees C and -76 degrees C, respectively. PtCl(2) and Pt nanoparticles supported on a Vulcan carbon substrate proved to be even more effective, with DeltaT(1/2) = -90 degrees C. The amount of NH(3) released during dehydrogenation is reduced compared to that from additive-free material, and, more importantly, at temperatures below 210 degrees C hydrogen is released with no detectable NH(3). In contrast to additive-free LiB(0.33)N(0.67)H(2.67), which melts completely above 190 degrees C and releases hydrogen from the liquid state only above approximately 250 degrees C, hydrogen release from LiB(0.33)N(0.67)H(2.67) + 5 wt % Pt/Vulcan carbon is accompanied by partial melting plus a cascade through a series of solid intermediate phases. Calorimetric measurements indicate that both additive-free and Pt-added LiB(0.33)N(0.67)H(2.67) release hydrogen exothermically, and hence the reverse reaction is thermodynamically unfavorable. By exposing partially dehydrogenated samples to high H(2) pressures at modest temperatures, fractional hydrogen uptake (roughly 15% of the released hydrogen) has been achieved. The mechanism by which noble metals promote hydrogen release is not known, but the behavior is consistent with that expected for a catalyst, including a large effect with small additions and saturation of the effect at low concentration.     

Ultrasound treatment acceleration of solvent extraction for fumigant residues from wheat

Concerns about consumer and worker safety and the fate of fumigants have fuelled strong efforts to determine their residues in foodstuffs. Fumigants are usually extracted from commodities with solvent at room temperature (25 degrees C). In this paper, solvent extraction of methyl bromide, phosphine, carbonyl sulfide, and carbon disulfide using ultrasonic acceleration or heating was evaluated. Wheat samples plus solvent, in gas-tight bottles, were placed in an ultrasonic chamber or an oven (50 degrees C), and fumigants were released into the headspace over the solvent. Completeness of extraction was demonstrated within 2 h for ultrasonic extraction, 7-20 h for 50 degrees C heating, and 8-35 h for room temperature extraction. The rapidity of extraction was mainly due to ultrasonic vibration rather than increased temperature.     

Room-temperature hydrogen uptake by TiO(2) nanotubes

TiO(2) nanotubes can reproducibly store up to approximately 2 wt % H(2) at room temperature and 6 MPa. However, only about 75% of this stored hydrogen can be released when the hydrogen pressure is lowered to ambient conditions, suggesting that both physisorption and chemisorption are responsible for the hydrogen uptake. FTIR spectroscopy, temperature-programmed desorption (TPD), and pressure-composition (P-C) isotherms suggest that 75% of the H(2) is physisorbed and can be reversibly released upon pressure reduction. Approximately 13% is weakly chemisorbed and can be released at 70 degrees C as H(2), and approximately 12% is bonded to oxide ions and released only at temperatures above 120 degrees C as H(2)O.     

Analyses of carcinogenic aromatic amines released from harmful azo colorants by Streptomyces SP. SS07

Extracellular fluid protein (ECFP) of Streptomyces species SS07 has been used to reduce water soluble azo dyes and the carcinogenic amines released have been compared with that from chemical reduction. The effect of temperature, pH and contact time on the recovery of amines using ECFP was studied. The ECFP releases carcinogenic amines at a pH of 9.2 and a temperature of 37 degrees C for a contact period of 24 h. The reduction products were analyzed with HPLC and their structures confirmed by LC-MS and GC-MS. It was observed that both the ECFP and chemical reduction methods released similar type of amine products. In the case of dye samples, compared to chemical reduction, 5-20% increase in the release of carcinogenic amines by ECFP was observed. The percentage of amine products released by chemical reduction was higher for leather garment samples compared to ECFP treatment.     

In situ quadrupole mass spectrometry study of atomic-layer deposition of ZrO2 using Cp2Zr(CH3)2 and water

Reactions during the atomic layer deposition (ALD) process of ZrO(2) from Cp(2)Zr(CH(3))(2) and deuterated water as precursors were studied with a quadrupole mass spectrometer (QMS) at 210-440 degrees C. The detected reaction byproducts were CpD (m/z = 67) and CH(3)D (m/z = 17). Almost all (90%) of the CH(3) ligands were released during the Cp(2)Zr(CH(3))(2) precursor pulse because of exchange reactions with the OD-terminated surface, and the rest, during the D(2)O pulse. About 40% of the CpD was released during the metal precursor pulse, and 60%, during the D(2)O pulse. ALD-type self-limiting growth was confirmed from 210 to 400 degrees C. However, below 300 degrees C the growth rate was low. Precursor decomposition affected the film growth mechanism at temperatures exceeding 400 degrees C.