Electrowetting in carbon nanotubes

We demonstrate reversible wetting and filling of open single-wall carbon nanotubes with mercury by means of electrocapillary pressure originating from the application of a potential across an individual nanotube in contact with a mercury drop. Wetting improves the conductance in both metallic and semiconducting nanotube probes by decreasing contact resistance and forming a mercury nanowire inside the nanotube. Molecular dynamics simulations corroborate the electrocapillarity-driven filling process and provide estimates for the imbibition speed and electrocapillary pressure.     

Crossed nanotube junctions

Junctions consisting of two crossed single-walled carbon nanotubes were fabricated with electrical contacts at each end of each nanotube. The individual nanotubes were identified as metallic (M) or semiconducting (S), based on their two-terminal conductances; MM, MS, and SS four-terminal devices were studied. The MM and SS junctions had high conductances, on the order of 0.1 e(2)/h (where e is the electron charge and h is Planck's constant). For an MS junction, the semiconducting nanotube was depleted at the junction by the metallic nanotube, forming a rectifying Schottky barrier. We used two- and three-terminal experiments to fully characterize this junction.     

High-performance carbon nanotube fiber

With their impressive individual properties, carbon nanotubes should form high-performance fibers. We explored the roles of nanotube length and structure, fiber density, and nanotube orientation in achieving optimum mechanical properties. We found that carbon nanotube fiber, spun directly and continuously from gas phase as an aerogel, combines high strength and high stiffness (axial elastic modulus), with an energy to breakage (toughness) considerably greater than that of any commercial high-strength fiber. Different levels of carbon nanotube orientation, fiber density, and mechanical properties can be achieved by drawing the aerogel at various winding rates. The mechanical data obtained demonstrate the considerable potential of carbon nanotube assemblies in the quest for maximal mechanical performance. The statistical aspects of the mechanical data reveal the deleterious effect of defects and indicate strategies for future work.     

Electrically induced optical emission from a carbon nanotube FET

Polarized infrared optical emission was observed from a carbon nanotube ambipolar field-effect transistor (FET). An effective forward-biased p-n junction, without chemical dopants, was created in the nanotube by appropriately biasing the nanotube device. Electrical measurements show that the observed optical emission originates from radiative recombination of electrons and holes that are simultaneously injected into the undoped nanotube. These observations are consistent with a nanotube FET model in which thin Schottky barriers form at the source and drain contacts. This arrangement is a novel optical recombination radiation source in which the electrons and holes are injected into a nearly field-free region. Sucha source may form the basis for ultrasmall integrated photonic devices.     

Multifunctional carbon nanotube yarns by downsizing an ancient technology

By introducing twist during spinning of multiwalled carbon nanotubes from nanotube forests to make multi-ply, torque-stabilized yarns, we achieve yarn strengths greater than 460 megapascals. These yarns deform hysteretically over large strain ranges, reversibly providing up to 48% energy damping, and are nearly as tough as fibers used for bulletproof vests. Unlike ordinary fibers and yarns, these nanotube yarns are not degraded in strength by overhand knotting. They also retain their strength and flexibility after heating in air at 450 degrees C for an hour or when immersed in liquid nitrogen. High creep resistance and high electrical conductivity are observed and are retained after polymer infiltration, which substantially increases yarn strength.     

Bolometric infrared photoresponse of suspended single-walled carbon nanotube films

The photoresponse in the electrical conductivity of a single-walled carbon nanotube (SWNT) film is dramatically enhanced when the nanotube film is suspended in vacuum. We show here that the change in conductivity is bolometric (caused by heating of the SWNT network). Electron-phonon interactions lead to ultrafast relaxation of the photoexcited carriers, and the energy of the incident infrared (IR) radiation is efficiently transferred to the crystal lattice. It is not the presence of photoexcited holes and electrons, but a rise in temperature, that results in a change in resistance; thus, photoconductivity experiments cannot be used to support the band picture over the exciton model of excited states in carbon nanotubes. The photoresponse of suspended SWNT films is sufficiently high that they may function as the sensitive element of an IR bolometric detector.     

Single-molecule torsional pendulum

We have built a torsional pendulum based on an individual single-walled carbon nanotube, which is used as a torsional spring and mechanical support for the moving part. The moving part can be rotated by an electric field, resulting in large but fully elastic torsional deformations of the nanotube. As a result of the extremely small restoring force associated with the torsional deformation of a single molecule, unusually large oscillations are excited by the thermal energy of the pendulum. By diffraction analysis, we are able to determine the handedness of the molecule in our device. Mechanical devices with molecular-scale components are potential building blocks for nanoelectromechanical systems and may also serve as sensors or actuators.     

Angular momentum conservation in dipolar energy transfer

Conservation of angular momentum is a familiar tenet in science but has seldom been invoked to understand (or predict) chemical processes. We have developed a general formalism based on Wigner's original ideas concerning angular momentum conservation to interpret the photo-induced reactivity of two molecular donor-acceptor assemblies with physical properties synthetically tailored to facilitate intramolecular energy transfer. Steady-state and time-resolved spectroscopic data establishing excited-state energy transfer from a rhenium(I)-based charge-transfer state to a chromium(III) acceptor can be fully accounted for by F?rster theory, whereas the corresponding cobalt(III) adduct does not undergo an analogous reaction despite having a larger cross-section for dipolar coupling. Because this pronounced difference in reactivity is easily explained within the context of the angular momentum conservation model, this relatively simple construct may provide a means for systematizing a broad range of chemical reactions.     

Subnanometer motion of cargoes driven by thermal gradients along carbon nanotubes

An important issue in nanoelectromechanical systems is developing small electrically driven motors. We report on an artificial nanofabricated motor in which one short carbon nanotube moves relative to another coaxial nanotube. A cargo is attached to an ablated outer wall of a multiwalled carbon nanotube that can rotate and/or translate along the inner nanotube. The motion is actuated by imposing a thermal gradient along the nanotube, which allows for subnanometer displacements, as opposed to an electromigration or random walk effect.     

Water-assisted highly efficient synthesis of impurity-free single-walled carbon nanotubes

We demonstrate the efficient chemical vapor deposition synthesis of single-walled carbon nanotubes where the activity and lifetime of the catalysts are enhanced by water. Water-stimulated enhanced catalytic activity results in massive growth of superdense and vertically aligned nanotube forests with heights up to 2.5 millimeters that can be easily separated from the catalysts, providing nanotube material with carbon purity above 99.98%. Moreover, patterned, highly organized intrinsic nanotube structures were successfully fabricated. The water-assisted synthesis method addresses many critical problems that currently plague carbon nanotube synthesis.     

有机肥料对实现“碳达峰、碳中和”的作用

有机肥料以农业废弃物为主要原料,含有丰富的有机质,具有改良土壤微生态环境,提高肥料利用率,增强作物抗逆性,促进作物生长等作用,符合农业绿色发展的要求,对“碳达峰、碳中和”目标的实现,能够发挥重要作用。本研究总结相关文献资料,从国家政策、节能减排、农业废弃物资源化利用、提高土壤和植物固碳等角度,对有机肥料在实现“双碳”目标所发挥的作用进行阐述分析,并对有机肥料产业的发展提出一些建议,以期为有机肥料的推广应用和“双碳”目标的实现提供参考。     

企业集团对节能减排的影响研究——来自中国上市公司的经验证据

从企业集团这一组织视角,关注如何推进企业节能减排,对于中国企业绿色转型、国家"双碳"目标的实现有着十分重要的现实意义。基于"结构决定战略"的理论视角和资源基础理论,以2003—2020年中国A股上市公司为研究样本进行实证分析,结果表明:企业集团可以有效促进企业节能减排。进一步研究发现,企业集团通过提升绿色创新水平和改变成本结构促进企业的节能减排。分产权性质和地理位置进行异质性讨论,发现企业集团促进企业节能减排的作用对国有企业显著,中部地区大于西部地区,东部地区效果最弱。     

High winds of neptune: a possible mechanism

Neptune receives only 1/900th of the earth's solar energy, but has wind speeds of nearly 600 meters per second. How the near-supersonic winds can be maintained has been a puzzle. A plausible mechanism, based on principles of angular momentum and energy conservation in conjunction with deep convection, leads to a regime of uniform angular momentum at low latitudes. In this model, the rapid retrograde winds observed are a manifestation of deep convection, and the high efficiency of the planet's heat engine is intrinsic from the room allowed at low latitudes for reversible processes, the high temperatures at which heat is added to the atmosphere, and the low temperatures at which heat is extracted.     

低碳背景下县域经济发展方式转变的对策研究

加强节能减排,实现低碳发展,不仅是国家“十二五”规划纲要所提出的约束性目标,更是促进经济提质增效升级的必经途径.目前,我国县域经济仍以“高投入、高消耗、高排放”为主要特征,转变经济发展方式已成为县级政府所面临的迫切任务.为此,必须依据低碳发展理念和《2014 ～2015年节能减排低碳发展行动方案》的具体要求,培育有利于经济发展方式转变的要素基础和制度基础,加快推进产业结构的优化和升级,深化经济管理体制改革,不断进行制度创新,实施有利于科技进步的政策,完善环境管理制度,实现县域经济又好又快发展.     

Nanotube molecular wires as chemical sensors

Chemical sensors based on individual single-walled carbon nanotubes (SWNTs) are demonstrated. Upon exposure to gaseous molecules such as NO(2) or NH(3), the electrical resistance of a semiconducting SWNT is found to dramatically increase or decrease. This serves as the basis for nanotube molecular sensors. The nanotube sensors exhibit a fast response and a substantially higher sensitivity than that of existing solid-state sensors at room temperature. Sensor reversibility is achieved by slow recovery under ambient conditions or by heating to high temperatures. The interactions between molecular species and SWNTs and the mechanisms of molecular sensing with nanotube molecular wires are investigated.     

中国城市化发展、能源消费与碳排放的实证研究

选取了1995年至2007年我国29个省市面板数据,建立以城市化水平为被解释变量,能源消费和碳排放作为解释变量的模型,通过协方差分析检验和Haus man检验的分析结果,确定研究模型的形式为固定影响变截距模型,最后,通过对拟合模型的结果分析,实证结果表明：高能耗、高排放、粗放式经济发展方式不利于城市化水平的提高;同时,各省市的城市化发展水平也存在差异.因此,各省市应在城市化工业化进程中推进产业结构和能源消费结构调整使其朝着更有利于节能环保的方向演进,节能减排政策的调整重点应该放在能源强度和能源消费碳强度上.     

特征线法在燃气管道动态模拟中的应用

对燃气管道不稳定流进行了研究，推导了了计算管内燃气流动的特征线法和公式。特征线法从基于流体力学基本原理推导出来的连续性方程、动量方程和能量方程出发，将难以求解的偏微分方程组转移为便于工程数值计算的等价差分方程组，从而解决了燃气管道中快瞬交流的计算问题。特征线法物理概念明确，数学分析严谨，计算精度高。     

Macroscopic fibers and ribbons of oriented carbon nanotubes

A simple method was used to assemble single-walled carbon nanotubes into indefinitely long ribbons and fibers. The processing consists of dispersing the nanotubes in surfactant solutions, recondensing the nanotubes in the flow of a polymer solution to form a nanotube mesh, and then collating this mesh to a nanotube fiber. Flow-induced alignment may lead to a preferential orientation of the nanotubes in the mesh that has the form of a ribbon. Unlike classical carbon fibers, the nanotube fibers can be strongly bent without breaking. Their obtained elastic modulus is 10 times higher than the modulus of high-quality bucky paper.     

DNA-templated carbon nanotube field-effect transistor

The combination of their electronic properties and dimensions makes carbon nanotubes ideal building blocks for molecular electronics. However, the advancement of carbon nanotube-based electronics requires assembly strategies that allow their precise localization and interconnection. Using a scheme based on recognition between molecular building blocks, we report the realization of a self-assembled carbon nanotube field-effect transistor operating at room temperature. A DNA scaffold molecule provides the address for precise localization of a semiconducting single-wall carbon nanotube as well as the template for the extended metallic wires contacting it.     

中国碳排放变化的因素分解与减排路径研究

能源及其引致的碳排放等相关问题已经成为影响人类社会发展全局和全球政治经济格局的重大战略问题.中国是世界上最大的发展中国家，面临着更严峻的能源挑战.节约能源、大幅度改善能源效率是我国应对能源和气侯变化挑战的一条极其重要且有效途径.本文综合考量了能源结构、能源强度、能源效率及经济增长等4个因素对碳排放的影响，基于因素分解模型，应用LMDI分解方法对中国一次能源利用的CO2排放及碳排放强度变化进行了研究，研究发现二氧化碳排放增加主要是由于经济增长、人口规模扩大引起的.在此基础上提出了碳减排的政策建议.