Synthesis and field emission of diamond-like carbon nanorods on TiO2/Ti nanotube arrays

Highly ordered TiO2/Ti nanotube arrays were fabricated by anodic oxidation method in 0.5 wt% HF. Using prepared TiO2/Ti nanotube arrays deposited Ni nanoparticles as substrate, high quality diamond-like carbon nanorods (DLCNRs) were synthesized by a conventional method of chemical vapor deposition at 750 degrees C in nitrogen atmosphere. DLCNRs were analyzed by filed emission scanning electron microscopy and Raman spectrometer. It is very interesting that DLCNRs possess pagoda shape with the length of 3-10 mu m. Raman spectra show two strong peaks about 1332 cm (1) and 1598 cm (1), indicating the formation of diamond-like carbon. The field emission measurements suggest that DLCNRs/TiO2/Ti has excellent field emission properties, a low turn-on field about 3.0 V/mu m, no evident decay at 3.4 mA/cm(2) in 480 min. (C) 2009 Elsevier B. V. All rights reserved.

The level and distribution of chromosomal aberration of tomato seeds at different penetration depths of carbon ions

The relationship between the penetration depth and the level and distribution of chromosomal aberration of the root tip cells were investigated by exposure of the superposed tomato seeds to 80 MeV/u carbon ions. The results showed that on the entrance of the beam the chromosomal aberration level was low. Damage such as breaks and gaps were dominant. At the Bragg peak, the chromosomal aberration level was high. The yields of dicentrics, rings and disintegrated small chromosomes increased but the yields of breaks and gaps decreased. These results are consistent with the distribution of the physical depth dose pro. le of carbon ions. It is effective to deposit the Bragg peak on the seeds to induce hereditary aberration in the mutation breeding with heavy ions.

Assessment of DNA damage of Lewis lung carcinoma cells irradiated by carbon ions and X-rays using alkaline comet assay

DNA damage and cell reproductive death determined by alkaline comet and clonogenic survival assays were examined in Lewis lung carcinoma cells after exposure to 89.63 MeV/u carbon ion and 6 MV X-ray irradiations, respectively. Based on the survival data, Lewis lung carcinoma cells were verified to be more radiosensitive to the carbon ion beam than to the X-ray irradiation. The relative biological effectiveness (RBE) value, which was up to 1.77 at 10% survival level, showed that the DNA damage induced by the high-LET carbon ion beam was more remarkable than that induced by the low-LET X-ray irradiation. The dose response curves of '' Tail DNA (%)'' (TD) and "Olive tail moment" (OTM) for the carbon ion irradiation showed saturation beyond about 8 Gy. This behavior was not found in the X-ray curves. Additionally, the carbon ion beam produced a lower survival fraction at 2 Gy (SF2) value and a higher initial Olive tail moment 2 Gy (OTM2) than those for the X-ray irradiation. These results suggest that carbon ion beams having high-LET values produced more severe cell reproductive death and DNA damage in Lewis lung carcinoma cells in comparison with X-rays and comet assay might be an effective predictive test even combining with clonogenic assay to assess cellular radio sensitivity

Protective effects of melatonin against low- and high-LET irradiation

To investigate the protective effects of melatonin against high-LET ionizing radiation, V79 Chinese hamster cells were irradiated with 100 keV/mu m carbon beam. Parallel experiments were performed with 200 kV X-rays. To avoid the impact from extra solvents, melatonin was dissolved directly in culture medium. Cells were cultured in melatonin medium for 1 hr before irradiation. Cell inactivation was measured with conventional colony forming assay, medium containing 6-thioguanine was used for the selection of mutants at hprt locus, and the cell cycle was monitored by flow cytometry. Both carbon beam and X-rays induced cell inactivation, hprt gene mutation and cell cycle G2 block dose-dependently. But carbon beam showed stronger effects as indicated by all three endpoints and the relative biological effectiveness (RBE) was 3.5 for cell killing (at 10% survival level) and 2.9 for mutation induction (at 5 x 10(-5) mutants/ cell level). Melatonin showed protective effects against ionizing radiation in a dose-dependent manner. In terms of cell killing, melatonin only increased the survival level of those samples exposed to 8Gy or larger of X-rays or 6 Gy or larger of carbon beam. In the induction of hprt mutation and G2 block, melatonin reduced such effects induced by carbon beam but not by X-rays. The results suggest that melatonin reduces the direct interaction of particles with cells rather than an indirect interaction. Further studies are required to disclose the underlying mechanisms.

The hyper-radiosensitivity effect of human hepatoma SMMC-7721 cells exposed to low dose gamma-rays and C-12 ions

Hypersensitive response of mammalian cells in cell killing to X- and gamma-rays has been reported at doses below 1 Gy. The purpose of this study was to examine the low dose sensitivity of human hepatoma SMMC-7721 cells irradiated with Co-60 gamma-rays and 50 MeV/u C-12 ions. Experiments using gamma-rays and charged particle irradiation were performed, particularly in the low dose range from 0 to 2 Gy. The survival effect of SMMC-7721 cells was measured by means of standard clonogenic assay in conjunction with a cell sorter. The result indicates SMMC-7721 cells showed hyper-radiosensitive response at low doses and increased radio-resistance at larger single doses for the carbon ions (LET = 45.2 keV/mu m) and the gamma-rays. However, the HRS/IRR effect caused by high-LET irradiation is different from that by low-LET radiation. This might possibly be due to the difference in the mode of energy deposition by particle beam and low-LET irradiation.

Melatonin modulates acute testicular damage induced by carbon ions in mice

The present study was performed to obtain evidence of the radioprotective function of melatonin at different administration levels on carbon ion-induced mouse testicular damage. Outbred Kun-Ming strain mice were divided into six groups, each composed of eight animals: control group, melatonin alone group, irradiation group and three melatonin plus irradiation-treated groups. An acute study was carried out to determine alterations in DNA-single strand break, cell apoptosis, and oxidative stress parameters as well as histopathology in mouse testis 24 h after whole-body irradiation with a single dose of 4 Gy Tie results showed that pre-treatment and post-treatment with high-dose melatonin (10 mg/kg) both significantly alleviated carbon ion-induced acute testicular damage, a greater radioprotective effect being observed in the pre-treatment group. On the other hand, low-dose melatonin (1 mg/kg) had a limited radioprotective effect on irradiation-induced degeneration and DNA lesions in mouse testis. Taken together, the data suggest that prophylactic treatment with a higher dose of melatonin is probably advisable to protect against the effects of heavy-ion irradiation.

Inactive and mutagenic effects induced by carbon beams of different LET values in a red yeast strain

To evaluate biological action of microorganism exposed to charged particles during the long distance space exploration. Induction of inactivation and mutation in a red yeast strain Rhodotorula glutinis AY 91015 by carbon beams of different LET values (14.9-120 0 keV mu m(-1)) was investigated It was found that survival curves were exponential, and mutation curves were linear for all LET values The dependence of inactivation cross section on LET approached saturation near 120 0 keV mu m(-1) The imitation cross section saturated when LET was higher than 582 keV mu m(-1) Meanwhile, the highest RBEI for inactivation located at 120 0 key mu m(-1) and the highest RBEm for mutation was at 58.2 key mu m(-1) The experiments imply that the most efficient mutagenic part of the depth dose profile of carbon ion is at the plateau region with intermediate LET value in which energy deposited is high enough to Induce mutagenic lesions but too low to induce over kill effect in the yeast cells (C) 2010 Elsevier B V All rights reserved

Molecular vibration spectroscopy study of irradiation effect in C-60 films induced by low energy ion

Irradiation effect in C-60 films induced by 170 keV B ion was investigated by means of Fourier transform infrared (FTIR) and Raman spectroscopies. The damage cross section sigma and the effective damage radius R are deduced from the experimental data of all four IR active modes and evident four Raman active modes of C-60 molecule. The differences on irradiation sensitivity and structural stability of the different active modes of C-60 molecule are compared. The results indicate that T-1u (4) of infrared active mode and A(g) (1) of Raman active mode are most sensitive for B ion irradiation. On the other hand T-1u (2) of infrared active mode and H-g (3) of Raman active mode are comparatively stable under B ion irradiation. (C) 2010 American Institute of Physics. [doi:10.1063/1.3512968]

Performance comparison of low-temperature direct alcohol fuel cells with different anode catalysts

Low-temperature polymer electrolyte membrane fuel cells directly fed by methanol and ethanol were investigated employing carbon supported Pt, PtSn and PtRu as anode catalysts, respectively. Employing Pt/C as anode catalyst, both direct methanol fuel cell (DMFC) and direct ethanol fuel cell (DEFC) showed poor performances even in presence of high Pt loading on anode. It was found that the addition of Ru or Sn to the Pt dramatically enhances the electro-oxidation of both methanol and ethanol. It was also found that the single cell adopting PtRu/C as anode shows better DMFC performance, while PtSn/C catalyst shows better DEFC performance. The single fuel cell using PtSn/C as anode catalyst at 90degreesC shows similar power densities whenever fueled by methanol or ethanol. The cyclic voltammetry (CV) and single fuel cell tests indicated that PtRu is more suitable for DMFC while PtSn is more suitable for DEFC. (C) 2003 Elsevier B.V. All rights reserved.

Ammonia-treated activated carbon as support of a Ru-Ba catalyst for ammonia synthesis

Ammonia-treated activated carbon has been studied as a support of Ru-Ba catalyst for ammonia synthesis. It is shown that the introduction of nitrogen leads to a decrease of ammonia synthesis activity for the catalysts with a low Ba/Ru molar ratio, while no significant changes are obtained for the catalysts with a high Ba/Ru molar ratio, confirming that electronegative impurities suppress the activity in ammonia synthesis and consume part of the promoters.

Iron and inorganic carbon in Liaodong Gulf sediments of Bohai Sea in China

Iron in seawater is an essential trace metal for phytoplankton that plays an important role in the marine carbon cycle. But most studies focused on oceanic iron fertilization in high nutrient low chlorophyll (HNLC) seawaters. A study of inorganic carbon (IC) forms and its influencing factors was presented in Liaodong Gulf sediments, and especially the influence of iron was discussed in detail. Inorganic carbon in Liaodong Gulf sediments was divided into five forms: NaCl, NH3·H2O, NaOH, NH2OH·HCl and HCl. The concentration of NaCl and NaOH forms were similar and they only occupied the minority of total inorganic carbon (TIC). However, NH3·H2O, NH2OH·HCl and HCl forms were the principal forms of TIC and accounted for more than 80% of TIC. Especially, the percentage of NH3·H2O form was much higher than that in the Changjiang River Estuary and Jiaozhou Bay sediments. All forms of inorganic carbon were influenced by organic carbon,pore water, iron, pH, redox potential(Eh) and sulfur potential(Es) in sediments, moreover, the influences had different characteristics for different IC forms. However, the redox reactions of iron affected mainly active IC forms. Iron had little effect on NH2OH·HCl and HCl forms of IC which were influenced mainly by pH. Iron had a stronger influence on NaCl, NaOH and NH3·H2O forms of IC; the influence of Fe2+ was higher than Fe3+ and its effect on NH3·H2O form was stronger than on NaCl and NaOH forms.

Strengthening carbon deposition of polyolefin using combined catalyst as a general method for improving fire retardancy

Combination of Ni2O3 and solid acid with Bronsted acid sites and Lewis acid sites (such as HZSM-5 and H-beta) could dramatically improve fire retardancy of polyolefin, including polypropylene and linear low-density polyethylene. This is mainly attributed to the formation of a large amount of residual char from degradation products of polyolefin in the intermediate stage of combustion. Thus, the amount of flammable components diffusing into the flame zone was small.

Simultaneous determination of dopamine, ascorbic acid and uric acid with electrospun carbon nanofibers modified electrode

A novel carbon-nanofiber-modified carbon-paste electrode (CNF-CPE) was employed for the simultaneous determination of dopamine (DA), ascorbic acid (AA) and uric acid (UA) with good selectivity and high sensitivity. The CNFs were prepared by combination of electrospinning technique with thermal treatment method and were used without any pretreatment. In application to determination of DA, AA and UA in the ternary mixture, the pristine CNF-CPE exhibited well-separated differential pulse voltammetric peaks with high catalytic current. Low detection limits of 0.04 mu M, 2 mu M and 0.2 mu M for DA, AA and UA were obtained, with the linear calibration curves over the concentration range 0.04-5.6 mu M, 2-64 mu M and 0.8-16.8 mu M, respectively.

Synthesis of carbon nanofibers for mediatorless sensitive detection of NADH

Highly sensitive amperometric detection of dihydronicotinamide adenine dinucleotide (NADH) by using novel synthesized carbon nanofibers (CNFs) without addition of any mediator has been proposed. The CNFs were prepared by combination of electrospinning technique with thermal treatment method and were applied without any oxidation pretreatment to construct the electrochemical sensor. In amperometric detection of NADH, a linear range up to 11.45 mu M with a low detection limit of 20 nM was obtained with the CNF-modified carbon paste electrode (CNF-CPE).

Hydrogenation of phenol in scCO(2) over carbon nanofiber supported Rh catalyst

A catalyst of Rh nanoparticles supported on a carbon nanofiber, 5 wt.% Rh/CNF, with an average size of 2-3 nm has been prepared by a method of incipient wetness impregnation. The catalyst presented a high activity in the ring hydrogenation of phenol in a medium of supercritical CO2 (scCO(2)) at a low temperature of 323 K. The presence of compressed CO2 retards hydrogenation of cyclohexanone to cyclohexanol under the reaction conditions used, and this is beneficial for the formation of cyclohexanone, increasing the selectivity to cyclohexanone.