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1.
DNA-carbon nanotube hybrids (DNA-CN) are novel nanoscale materials that consist of single-wall carbon nanotubes (SWCN) coated with a self-assembled monolayer of single-stranded DNA (ssDNA). Recent experiments on DNA-CN have shown that this material offers a remarkable set of technologically useful properties such as facilitation of SWCN sorting, chemical sensing, and detection of DNA hybridization. Despite the importance of DNA-CN, a detailed understanding of its microscopic structure and physical properties is lacking. To address this, we have performed classical all-atom molecular dynamics (MD) simulations exploring the self-assembly mechanisms, structure, and energetic properties of this nanomaterial. MD reveals that SWCN induces ssDNA to undergo a spontaneous conformational change that enables the hybrid to self-assemble via the pi-pi stacking interaction between ssDNA bases and SWCN sidewall. ssDNA is observed to spontaneously wrap about SWCN into compact right- or left-handed helices within a few nanoseconds. Helical wrapping is driven by electrostatic and torsional interactions within the sugar-phosphate backbone that result in ssDNA wrapping from the 3' end to the 5' end. 相似文献
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We use non-equilibrium molecular dynamics (NEMD) to compute the thermal conductivity (κ) of orthogonally ordered cross-bar structures of single-walled carbon nanotubes. Such structures exhibit extremely low thermal conductivity in the range of 0.02-0.07 W m(-1) K(-1). These values are five orders of magnitude smaller than the axial thermal conductivity of individual carbon nanotubes, and are comparable to the thermal conductivity of still air. 相似文献
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Bandaru PR 《Journal of nanoscience and nanotechnology》2007,7(4-5):1239-1267
The experimentally verified electrical properties of carbon nanotube structures and manifestations in related phenomena such as thermoelectricity, superconductivity, electroluminescence, and photoconductivity are reviewed. The possibility of using naturally formed complex nanotube morphologies, such as Y-junctions, for new device architectures are then considered. Technological applications of the electrical properties of nanotube derived structures in transistor applications, high frequency nanoelectronics, field emission, and biological sensing are then outlined. The review concludes with an outlook on the technological potential of nanotubes and the need for new device architectures for nanotube systems integration. 相似文献
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Expressions for radiation-induced forces are presented for the case of a Rayleigh particle near the focus of a Gaussian laser beam at near-resonant conditions. Classical electromagnetic theory was used to obtain the dependence of the scattering and gradient forces on the incident laser frequency, the beam convergence angle, and the spatial position of the particle with respect to the focus. Approximative numerical analysis performed for particles with a single resonant absorption peak demonstrates the occurrence of up to 50-fold enhanced trapping forces at near-resonant frequencies. The use of this technique of gradient force enhancement may provide optical tweezers with enhanced trapping strengths and a degree of specificity. 相似文献
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In this paper, we report on Raman scattering and Surface Enhanced Raman Scattering (SERS) studies of single walled carbon nanotubes (SWNTs) and carbon nanotube/conjugated polymers composites. We demonstrate that under SERS conditions we induce an abnormal anti-Stokes Raman emission, that can be interpreted as being due to a “single-beam pumped” Coherent Anti-Stokes Raman Scattering (CARS) effect. We also investigate in detail the anti-Stokes/Stokes (aS/S) intensity ratios of the radial breathing modes (RBMs) of SWNTs as a function of several parameters. From calculations, we show that resonance phenomena mostly explain the aS/S intensity ratio anomalies, but only at low frequencies. In addition, we describe results obtained with polymers like poly(bithiophene) (PBTh) polymerized on carbon nanotube thin films which exhibit also an amplification of its high frequency Raman modes in the anti-Stokes branch, generated by the plasmon excitation of metallic tubes. This phenomenon occurs in several other materials such as composites based on SWNTs and conjugated polymers such as poly(3,4-ethylenedioxythiophene) (PEDOT) and polyparaphenylene-vinylene (PPV) for modes located around 1500 cm−1. 相似文献
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The transmittance of β-ZnP2 crystals is measured as a function of the incident light polarization, photon energy, and sample thickness over the transmission window of the crystals. The results attest to anomalous light propagation through β-ZnP2, which is attributable to refractive-index nonuniformity. The intrinsic edge in β-ZnP2 for the E ∥ c polarization is shown to be dominated by indirect and direct allowed transitions for α below and above 1 cm?1, respectively. The 300-K indirect band gap of β-ZnP2 is evaluated. 相似文献
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The nature of the blackening caused by high-temperature electrolysis of 8 and 12 mol % yttria-stabilized zirconia single crystals has been investigated by studying the optical absorption between 260 and 700 nm. In the early stages the band edge remained at 271 nm, the crystal became red and the transmission showed a broad minimum centred at 480 nm; in the later stages the crystal became black and the transmission was reduced drastically over the whole visible range. The low transmission was shown, by integrating sphere measurements, to be due to absorbing centres. These were attributed to the formation of vacancy aggregates which ultimately produced colloidal metallic particles. 相似文献
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Christoforos Chatzikomis Sebastian W. Pattinson Krzysztof K. K. Koziol Ian M. Hutchings 《Journal of Materials Science》2012,47(15):5760-5765
The controlled deposition of carbon nanotubes (CNTs) has many potential applications in areas such as microfluidics and field emission arrays. The use of inkjet printing to deposit catalyst offers numerous advantages for these, particularly the ability to print arbitrary patterns at low cost. We use inkjet technology to deposit iron salts, which act as a catalyst from which CNTs are subsequently grown by chemical vapour deposition. In this study, we study the effect of the iron salt concentration on ink viscosity, as well as the printing quality using optical and electron microscopy. We find that the iron salt concentration has a significant effect on the pattern quality and, most importantly, allows for the production of controllable ring-like shapes with feature size smaller than that achievable by the print-head alone. These shapes are the result of a variation of the coffee-stain effect, and could be useful particularly in fabricating microfluidic devices. We show that iron salts are suitable CNT catalysts for deposition by inkjet printing, and that their concentration is crucial both for print quality as well as for the production of novel patterns by making use of the drying behaviour of the ink. 相似文献
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Using ab initio calculations we have studied the optical linear response of different configurations of twisted trilayer graphene systems. We have found that when one of the outer layers is rotated the system shows an angle-dependent optical spectrum as its twisted bilayer counterpart; however, in this case there are two absorption peaks located in the visible range of the spectrum and one more in the intermediate infrared range for large relative rotation angles. When two layers are rotated the spectrum exhibits only two absorption peaks in the visible range revealing information about the two relative rotation angles between the layers in the structure. All these absorption peaks in the visible range shift to the intermediate infrared range for small angles. 相似文献
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Absorption of the electromagnetic radiation by metal particles in a quasistatic region was estimated within the framework of a classical theory. The calculated values agree in the order of magnitude with experimental data on the frequency dependence of the effective absorption factor of silver, gold, and aluminum particles. The size effect in optical absorption in the near IR spectral range is discussed. 相似文献
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James Meredith Richard EbsworthStuart R. Coles Benjamin M. WoodKerry Kirwan 《Composites Science and Technology》2012
Natural fibre composites represent an environmentally sustainable alternative to conventional glass and carbon fibre composites. Fibres derived from plants are renewable and have low levels of embodied energy compared to synthetic fibres. They are also low cost, low density, have high specific properties, are non-abrasive and less harmful during handling. 相似文献
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The fundamental absorption edges of some samples of V2O5-P2O5 and V2O5-P2O5-TeO2 glasses were measured in the short wavelength part of the visible region, and it was found that the fundamental absorption of these glasses is dependent on composition and arises from direct forbidden transitions and occurs at a photon energy in the range 1.9 to 2.6 eV, depending on composition. 相似文献
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The tensile and compressive tests of glass–epoxy composites with 1–200 s−1 strain rates which are typical strain rate range during automobile crash accidents were performed in order to measure the strength variation with respect to strain rate. The tests were performed using both a horizontal type pneumatic impact tester and a conventional dynamic universal test machine with strain-rate-increase mechanisms. Also, the impact energy absorption characteristics of glass fiber reinforced composites were estimated using the newly proposed progressive impact fracture model. From the experiments and predictions, it was found that the proposed method predicted relatively well the experimental results. 相似文献
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复合材料结构的能量吸收 总被引:3,自引:0,他引:3
针对缠绕成型的 [± 75 ]n玻璃纤维 /聚酯和 [0 /± 75 ]n玻璃纤维 /环氧树脂圆柱管的轴向与非轴向压缩失效行为及能量吸收特性进行了研究 (轴压的倾斜角度变化范围 0~ 2 5°) ,分析了复合材料圆柱管的宏观破坏模式和能量吸收机理 ,比较了轴向与非轴向载荷下能量吸收的特点 .研究表明 :复合材料圆柱管在偏轴角度下其压缩损伤过程可分为 3个阶段 ,即初始引发阶段、稳态渐进阶段以及压实或失稳阶段 ;圆柱管的压缩行为和吸能能力主要取决于偏轴压缩角度和载荷位移历程 相似文献
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The authors report on the optical properties of multi-dimensional ZnO hybrid structures, consisting of film (2D)/nanorods (1D)/sapphire substrate (2D), grown by metalorganic chemical vapor deposition (MOCVD). Photoluminescence investigations reveal that the sample with top layer grown at a decreased growth temperature of 240 °C and increased reactor pressure of 5 Torr exhibits superior emission properties. The presence of strong E2high optical phonon mode at 438.5 cm− 1 in the visible micro-Raman spectra demonstrates the wurtzite nature of ZnO. Although the ultraviolet Raman scattering measurements of the hybrid structures reveal the presence of in-plane tensile stress in the top ZnO layer, the sample with the improved emission performance shows the release of tensile stress. 相似文献
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《Materials Research Bulletin》2006,41(2):448-454
Optical absorption edge spectra have been measured by diffuse reflectance spectroscopy on a complete suite of rare earth sesquisulfide compounds of varying structure type. Optical band gaps were extracted from these data. The observed band gaps tend to vary with crystal structure type but many compounds with the same structure have similar band gaps independently of the particular rare earth ion. The ordered α-structure has a substantially lower band gap than the defect γ-structure for all compounds examined except for La2S3. 相似文献