Based on an equivalent resistance-capacitance network, the complex conductivity and the relative complex permittivity of single wall carbon nanotubes (SWNTs)/polymer composite are theoretically investigated in the fre...Based on an equivalent resistance-capacitance network, the complex conductivity and the relative complex permittivity of single wall carbon nanotubes (SWNTs)/polymer composite are theoretically investigated in the frequency range of 0.30-18 GHz using the logarithmic rule. Both the real and imaginary parts of the permittivities of SWNTs and polymer are considered in detail. The calculated complex permittivity spectra of SWNTs/poly(ethyl methacrylate) composite films are in good agreement with the available experimental data. The influences of SWNTs concentration on both the complex conductivity and the dielectric loss tangent of the composite are presented in the microwave frequency range. A linear relationship between microwave conductivity and frequency is found.展开更多
Because the physical and chemical properties of nanosized materials mostly differ from the existing microsized materials, their potential impacts on human health and the envi-ronment will be topics under the serious d...Because the physical and chemical properties of nanosized materials mostly differ from the existing microsized materials, their potential impacts on human health and the envi-ronment will be topics under the serious discussions in press and in a number of international scientific journals. We analyze and summarize the existing data of the experimental study on the biological activities and adverse effects of nanoscale materials/particles including single wall carbon nanotubes, multi wall carbon nanotubes, titanium oxide and iron powders. Though some biological behaviors of nanoscale materials observed cannot be understood on the basis of the current knowledge, as the existing data are mostly preliminary, it is too early to make some ex-clusive conclusions on biological activities (or the toxicity) of any of nanoscale materials. The experimental techniques, the current topics, and the future research directions for this new re-search field are also discussed.展开更多
Single wall carbon nanotubes (SWNTs) modified gold electrodes were prepared by using two different methods. The electrochemical behavior of cytochrome c on the modified gold electrodes was investigated. The first...Single wall carbon nanotubes (SWNTs) modified gold electrodes were prepared by using two different methods. The electrochemical behavior of cytochrome c on the modified gold electrodes was investigated. The first kind of SWNT modified electrode (noted as SWNT/Au electrode) was prepared by the adsorption of carboxyl terminated SWNTs from DMF dispersion on the gold electrode. The oxidatively processed SWNT tips were covalently modified by coupling with amines (AET) to form amide linkage. Via Au—S chemical bonding, the self assembled monolayer of thiol unctionalized nanotubes on gold surface was fabricated so as to prepare the others SWNT modified electrode (noted as SWNT/AET/Au electrode). It was shown from cyclic voltammetry experiments that cytochrome c exhibited direct electrochemical responses on the both electrodes, but only the current of controlled diffusion existed on the SWNT/Au electrode while both the currents of controlled diffusion and adsorption of cytochrome c occurred on the SWNT/AET/Au electrode. Photoelastic Modulation Infared Reflection Absorption Spectroscopy (PEM IRRAS) and Quartz Crystal Microbalance (QCM) were employed to verify the adsorption of SWNTs on the gold electrodes. The results proved that SWNTs could enhance the direct electron transfer process between the electrodes and redox proteins.展开更多
The phosphorus-doped single wall carbon nanotube(PSWCNT) is studied by using First-Principle methods based on Density Function Theory(DFT).The formation energy,total energy,band structure,geometry structure and densit...The phosphorus-doped single wall carbon nanotube(PSWCNT) is studied by using First-Principle methods based on Density Function Theory(DFT).The formation energy,total energy,band structure,geometry structure and density of states are calculated.It is found that the formation energy of the P-doped single carbon nanotubes increases with diameters;the total energy of carbon nanotubes with the same diameter decreases as the doping rate increases.The effects of impurity position on the impurity level are discussed.It illustrates that the position of the impurity level may depend on the C-P-C bond angle.According to the above results,it is feasible to substitute a carbon atom with a phosphorus atom in SWCNT.It is also found that P-doped carbon nanotubes are N type semiconductor.展开更多
With the rapid development of nanotechnology, nanomaterials have been used in numerous fields. However, these nanomaterials could also result in risk for human and environmental health. To make a comparison of the hea...With the rapid development of nanotechnology, nanomaterials have been used in numerous fields. However, these nanomaterials could also result in risk for human and environmental health. To make a comparison of the health effects of three different kinds of nanomaterials, 28 male BALB/c mice were randomly divided into four groups. Three experimental groups were exposed to different kinds of nanomaterials including graphene, graphene oxide and single wall carbon nanotubes （SWCNTs） by intraperitoneal injection while the control group received a saline injection. The exposure dose of experimental groups was 4mg/kg. After seven days, sections of mice kidney were taken, the organ coefficient of both kidney and brain was counted, and the reactive oxygen species （ROS） level, glutathione （GSH） and malondialdehyde （MDA） content was measured. Our results showed that in the experimental groups, the organ coefficient and GSH content in mice kidneys and brains decreased, whereas the ROS level and MDA content increased, when compared with the control. The graphene oxide group was statistically significant （p 〈 0.05）, while the SWCNTs group had extremely significant difference （p〈0.01）. Morphological changes in the kidney were also seen in the experimental groups. These results demonstrate that oxidative damage to mice kidneys and brains induced by SWCNTs and graphene oxide is more severe than graphene. The degree of damage caused by these three typical nanomaterials is different, probably due to several parameters including particle size, surface character, and shape.展开更多
An extensive study of Fischer-Tropsch synthesis on nanostructure supports with high surface area such as nanostructure -y-alumina, single wall carbon nanotubes （SWNTs）, and the hybrid of SWNTs/nanostructure -y-alumi...An extensive study of Fischer-Tropsch synthesis on nanostructure supports with high surface area such as nanostructure -y-alumina, single wall carbon nanotubes （SWNTs）, and the hybrid of SWNTs/nanostructure -y-alumina has been investigated. The nanostructure γ-alumina was promoted with lanthanum to obtain better performance of catalyst and 15 wt% cobalt loading was the basis of our investigation. Fischer- Tropsch synthesis was performed in a fixed bed reactor under different reaction conditions （220-240 ℃, 15-25 bar, H2/CO ratio of 2, GHSV of 900-1400） in order to study the effects of temperature, pressure and gas hourly space velocity （GHSV） changes on hydrocarbon selec- tivity and catalyst activity. The catalysts were extensively characterized by different methods including X-ray diffraction （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, inductively coupled plasma （ICP）, hydrogen （H2） chemisorption and temperature-programmed reduction （TPR）. The results showed that the yield of hybrid supported catalyst （55.4%） is higher than that of nanos- tructure -y-alumina supported catalyst （55.0%） and lower than that of SWNTs supported cobalt catalyst （71.0%）. The hybrid supported catalyst showed higher reduction degree and dispersion of cobalt particles. The temperature, pressure and GHSV effects on hybrid supported catalyst were studied and results showed that higher pressure favors the chain growth and temperature increase leads to the increases in methane selec- tivity and CO conversion. Higher hydrocarbon selectivity and CO conversion showed positive relationship with increasing GHSV while lower hydrocarbon selectivity diminishes.展开更多
基金the Science Research Program of Educational Department of Hunan Province of China (Grant No. 07C640)the Doctor Foundation of China (Grant No. 20030532008)
文摘Based on an equivalent resistance-capacitance network, the complex conductivity and the relative complex permittivity of single wall carbon nanotubes (SWNTs)/polymer composite are theoretically investigated in the frequency range of 0.30-18 GHz using the logarithmic rule. Both the real and imaginary parts of the permittivities of SWNTs and polymer are considered in detail. The calculated complex permittivity spectra of SWNTs/poly(ethyl methacrylate) composite films are in good agreement with the available experimental data. The influences of SWNTs concentration on both the complex conductivity and the dielectric loss tangent of the composite are presented in the microwave frequency range. A linear relationship between microwave conductivity and frequency is found.
基金the National Natural Science Foundation of China(Grant No.10490180)the Ministry of Science and Technology of China(Grant No.2001CCA03800)+2 种基金 the Chinese Academy of Sciences National Center for Nanoscience and Nanotechnology Institute of High Energy Physics.
文摘Because the physical and chemical properties of nanosized materials mostly differ from the existing microsized materials, their potential impacts on human health and the envi-ronment will be topics under the serious discussions in press and in a number of international scientific journals. We analyze and summarize the existing data of the experimental study on the biological activities and adverse effects of nanoscale materials/particles including single wall carbon nanotubes, multi wall carbon nanotubes, titanium oxide and iron powders. Though some biological behaviors of nanoscale materials observed cannot be understood on the basis of the current knowledge, as the existing data are mostly preliminary, it is too early to make some ex-clusive conclusions on biological activities (or the toxicity) of any of nanoscale materials. The experimental techniques, the current topics, and the future research directions for this new re-search field are also discussed.
基金theNaturalScienceFoundationofAnhuiProvince (No .990 4612 9)theMajorStateBasicResearchDevelopmentProramofGuangdongProvince (No .c3 190 2 )
文摘Single wall carbon nanotubes (SWNTs) modified gold electrodes were prepared by using two different methods. The electrochemical behavior of cytochrome c on the modified gold electrodes was investigated. The first kind of SWNT modified electrode (noted as SWNT/Au electrode) was prepared by the adsorption of carboxyl terminated SWNTs from DMF dispersion on the gold electrode. The oxidatively processed SWNT tips were covalently modified by coupling with amines (AET) to form amide linkage. Via Au—S chemical bonding, the self assembled monolayer of thiol unctionalized nanotubes on gold surface was fabricated so as to prepare the others SWNT modified electrode (noted as SWNT/AET/Au electrode). It was shown from cyclic voltammetry experiments that cytochrome c exhibited direct electrochemical responses on the both electrodes, but only the current of controlled diffusion existed on the SWNT/Au electrode while both the currents of controlled diffusion and adsorption of cytochrome c occurred on the SWNT/AET/Au electrode. Photoelastic Modulation Infared Reflection Absorption Spectroscopy (PEM IRRAS) and Quartz Crystal Microbalance (QCM) were employed to verify the adsorption of SWNTs on the gold electrodes. The results proved that SWNTs could enhance the direct electron transfer process between the electrodes and redox proteins.
基金Supported by the Natural Science Foundation of Fujian Province of China (Grant No. A0220001)
文摘The phosphorus-doped single wall carbon nanotube(PSWCNT) is studied by using First-Principle methods based on Density Function Theory(DFT).The formation energy,total energy,band structure,geometry structure and density of states are calculated.It is found that the formation energy of the P-doped single carbon nanotubes increases with diameters;the total energy of carbon nanotubes with the same diameter decreases as the doping rate increases.The effects of impurity position on the impurity level are discussed.It illustrates that the position of the impurity level may depend on the C-P-C bond angle.According to the above results,it is feasible to substitute a carbon atom with a phosphorus atom in SWCNT.It is also found that P-doped carbon nanotubes are N type semiconductor.
基金Acknowledgements This work was financially supported by the National Natural Science Foundation of China （Grant No. 51136002）, the China Key Technologies R＆D Program （2012BAJ02B03） and the Key Project of International Cooperation from the Chinese Ministry of Science and Technology （No. 2010DFA31790）.
文摘With the rapid development of nanotechnology, nanomaterials have been used in numerous fields. However, these nanomaterials could also result in risk for human and environmental health. To make a comparison of the health effects of three different kinds of nanomaterials, 28 male BALB/c mice were randomly divided into four groups. Three experimental groups were exposed to different kinds of nanomaterials including graphene, graphene oxide and single wall carbon nanotubes （SWCNTs） by intraperitoneal injection while the control group received a saline injection. The exposure dose of experimental groups was 4mg/kg. After seven days, sections of mice kidney were taken, the organ coefficient of both kidney and brain was counted, and the reactive oxygen species （ROS） level, glutathione （GSH） and malondialdehyde （MDA） content was measured. Our results showed that in the experimental groups, the organ coefficient and GSH content in mice kidneys and brains decreased, whereas the ROS level and MDA content increased, when compared with the control. The graphene oxide group was statistically significant （p 〈 0.05）, while the SWCNTs group had extremely significant difference （p〈0.01）. Morphological changes in the kidney were also seen in the experimental groups. These results demonstrate that oxidative damage to mice kidneys and brains induced by SWCNTs and graphene oxide is more severe than graphene. The degree of damage caused by these three typical nanomaterials is different, probably due to several parameters including particle size, surface character, and shape.
基金supported by the Iran National Science Foundation (INSF) under the contract number 87040961the Iranian Nano Technology Initiative Council
文摘An extensive study of Fischer-Tropsch synthesis on nanostructure supports with high surface area such as nanostructure -y-alumina, single wall carbon nanotubes （SWNTs）, and the hybrid of SWNTs/nanostructure -y-alumina has been investigated. The nanostructure γ-alumina was promoted with lanthanum to obtain better performance of catalyst and 15 wt% cobalt loading was the basis of our investigation. Fischer- Tropsch synthesis was performed in a fixed bed reactor under different reaction conditions （220-240 ℃, 15-25 bar, H2/CO ratio of 2, GHSV of 900-1400） in order to study the effects of temperature, pressure and gas hourly space velocity （GHSV） changes on hydrocarbon selec- tivity and catalyst activity. The catalysts were extensively characterized by different methods including X-ray diffraction （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, inductively coupled plasma （ICP）, hydrogen （H2） chemisorption and temperature-programmed reduction （TPR）. The results showed that the yield of hybrid supported catalyst （55.4%） is higher than that of nanos- tructure -y-alumina supported catalyst （55.0%） and lower than that of SWNTs supported cobalt catalyst （71.0%）. The hybrid supported catalyst showed higher reduction degree and dispersion of cobalt particles. The temperature, pressure and GHSV effects on hybrid supported catalyst were studied and results showed that higher pressure favors the chain growth and temperature increase leads to the increases in methane selec- tivity and CO conversion. Higher hydrocarbon selectivity and CO conversion showed positive relationship with increasing GHSV while lower hydrocarbon selectivity diminishes.
