单壁碳纳米管-DNA复合物的微观结构和电化学性质

对单壁碳纳米管-DNA复合物(SWCNT-DNA)的微观结构和电化学性质进行了研究.TEM观察表明:通过DNA辅助超声,绝大多数成束单壁管离散为单根分散的碳管.AFM结果进一步证明DNA均匀缠绕在单根离散的碳纳米管外壁,形成稳定的SWCNT-DNA复合物.这一自组装过程同时也是碳管的纯化过程,催化剂颗粒在超声过程中被除去.初步探讨了SWCNT-DNA复合物的电化学电容性质,结果显示:通过与单链DNA(ss-DNA)的杂化作用,SWCNTs的电化学性质得到改善.与SWCNTs相比,SWCNT-DNA复合物的比电容提高了117.9%.     

Polarization driven covalently-bonded octahedral-twinning and backbone-peripheral-helical nanoarchitectures

We report the novel superstructural chiral polar-surface induced backbone-peripheral-helical (BPH) hierarchical architecture of zincblende SiC made possible by precise helical epitaxy. We show by direct image that this architecture has the mother-daughter relationship. The center of the BPH consists of periodic octahedral modular units with chiral sidewalls. By forming Si-C covalent bonds at the sidewalls, a daughter SiC wire spontaneously vine-grows in a peripherally helical way on the mother wire. All of the information of the mother wire, including twinning, polarity and even stacking fault, are completely copied and inherited by the daughter wire one-by-one at the atomic level. Our findings thus provide a simple growth method and the necessary atomistic mechanism for novel polar surface driven superstructural twinning and subsequent BPH growth, which should be universal for zincblende semiconductors and even could be true for other noncentral-symmetric compounds.     

Metal oxide nanoarchitectures for environmental sensing

Metal oxide materials are widely used for gas sensing. Capable of operating at elevated temperatures and in harsh environments, they are mechanically robust and relatively inexpensive and offer exquisite sensing capabilities, the performance of which is dependent upon the nanoscale morphology. In this paper we first review different routes for the fabrication of metal oxide nanoarchitectures useful to sensing applications, including mesoporous thin films, nanowires, and nanotubes. Two sensor test cases are then presented. The first case examines the use of highly uniform nanoporous Al2O3 for humidity sensing; we find that such materials can be successfully used as a wide-range humidity sensor. The second test case examines the use of TiO2 nanotubes for hydrogen sensing. Going from a nitrogen atmosphere to one containing 1000 ppm of hydrogen, at 290 degrees C, 22-nm-diameter titania nanotubes demonstrate a 10(4) change in measured resistance with no measurement hysteresis.     

Self-assembled ultrafine hierarchical ZnS treelike nanoarchitectures

Ultrafine hierarchical tree-shaped nanoarchitectures of ZnS were synthesized by a H₂-assisted thermal evaporation and condensation technique. Morphology and composition of the ZnS deposit were studied by means of field emission scanning electron microscopy, high-resolution transmission electron microscopy and energy dispersive X-ray spectroscopy. The deposit was found to consist of a layer of oriented submicrorods partly covered by microsheets and randomly oriented submicrowires, and three-dimensional treelike nanoarchitectures grew epitaxially on various submicrorods, microsheets, and submicrowires. The growth of the nanostructures is a spontaneous and self-assembled process. Vapor-solid (VS) growth mechanism is proposed for the formation of the treelike nanostructures because catalyst was not introduced during the synthesis process. This novel hierarchical ZnS nanoarchitecture may offer great potential for applications, including three-dimensional nanoelectronics and high efficient spatial resolved photon detector.     

Majority multiplexing-economical redundant fault-tolerant designs for nanoarchitectures

Motivated by the need for economical fault-tolerant designs for nanoarchitectures, we explore a novel multiplexing-based redundant design scheme at small (/spl les/100) and very small (/spl les/10) redundancy factors. In particular, we adapt a strategy known as von Neumann multiplexing to circuits of majority gates with three inputs and for the first time exactly analyze the performance of a multiplexing scheme for very small redundancies, using combinatorial arguments. We also develop an extension of von Neumann multiplexing that further improves performance by excluding unnecessary restorative stages in the computation. Our results show that the optimized three-input majority multiplexing (MAJ-3 MUX) outperforms the latest scheme presented in the literature, known as parallel restitution (PAR-REST), by a factor between two and four, for 48/spl les/R/spl les/100. Our scheme performs extremely well at very small redundancies, for which our analysis is the only accurate one. Finally, we determine an upper bound on the maximum tolerable failure probability when any redundancy factor may be used. This bound clearly indicates the advantage of using three-input majority gates in terms of reliable operation.     

氢氧化钙的固碳功能性研究-CO2浓度与碳化时间的影响

矿物固碳是降低大气中CO2浓度的有效方法之一,但是目前大量的研究集中于提高矿物固碳效率,而忽略了碳化产物的二次利用问题。本文采用氢氧化钙固碳,研究了CO2浓度和碳化时间对碳化速率以及碳化产物强度的影响。研究发现,在相同CO2浓度下,氢氧化钙碳化速率随碳化时间的延长而逐渐提高;随着CO2浓度的增加,氢氧化钙的碳化速度不断增大;随碳化时间的延长,碳化产物的强度不断提高,但是当碳化时间超过24 h后,碳化产物的强度明显下降。高浓度CO2环境对氢氧化钙碳化产物的强度发展不利,随CO2浓度的增加碳化产物的强度逐渐降低。通过SEM、EDS和XRD分析发现,随着碳化时间的延长,氢氧化钙表面形成方解石型碳酸钙层,阻碍了碳化进程;当碳化时间达到28 d时,由于碳酸钙层的胀裂,碳化产物的强度出现明显下降。     

Synthesis of flower-like silver nanoarchitectures at room temperature

Novel flower-like silver nanoarchitectures were synthesized via a facile and environmentally benign route in the presence of citric acid and ascorbic acid. The flower-like structures are composed of nano-petals of ca. 20 nm in thickness. The products were characterized with X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The growth mechanism of flower-like silver nanoarchitectures involves a film-fold process. Some crucial factors affect the nanocrchitectures growth, such as, pH, the concentration of citric acid, and the concentration of ascorbic acid, have also been discussed.     

Bioinspired photonic nanoarchitectures from graphitic thin films

Bioinspired, regular, rectangular (with periodicities of 600 nm and 700 nm), and random (with average characteristic distances of 600 nm and 750 nm) two dimensional (2D) photonic nanoarchitectures of 60 nm thickness were produced in graphite by Focused Ion Beam (FIB) nanomachining and subsequent controlled oxidation. The color of the nanoarchitectures was modified by the conformal deposition of 90 nm Al₂O₃. The regular patterns generate iridescent colors, while the random ones exhibit a remarkably constant color with the variation of the illumination and viewing conditions.     

Programmable assembly of nanoarchitectures using genetically engineered viruses

Biological systems possess inherent molecular recognition and self-assembly capabilities and are attractive templates for constructing complex material structures with molecular precision. Here we report the assembly of various nanoachitectures including nanoparticle arrays, hetero-nanoparticle architectures, and nanowires utilizing highly engineered M13 bacteriophage as templates. The genome of M13 phage can be rationally engineered to produce viral particles with distinct substrate-specific peptides expressed on the filamentous capsid and the ends, providing a generic template for programmable assembly of complex nanostructures. Phage clones with gold-binding motifs on the capsid and streptavidin-binding motifs at one end are created and used to assemble Au and CdSe nanocrytals into ordered one-dimensional arrays and more complex geometries. Initial studies show such nanoparticle arrays can further function as templates to nucleate highly conductive nanowires that are important for addressing/interconnecting individual nanostructures.     

Surface-area-tuned, quantum-dot-sensitized heterostructured nanoarchitectures for highly efficient photoelectrodes

Harvesting solar energy to produce clean hydrogen from photoelectrolysis of water presents a valuable opportunity to find alternatives for fossil fuels. Three- dimensional nanoarchitecturing techniques can afford enhanced photoelectrochemical properties by improving geometrical and structural effects. Here, we report quantum-dot sensitized TiO2-Sb：SnO2 heterostructures as a model electrode to enable the optimization of the structural effects through the creation of a highly conductive pathway using a transparent conducting oxide （TCO）, coupled with a high surface area, by introducing branching and low interfacial resistance via an epitaxial relationship. An examination of various morphologies （dot, rod, and lamella shape） of TiO2 reveals that the rod-shaped TiO2-Sb：SnO2 is a more effective structure than the others. A photoelectrode fabricated using optimized CdS--TiO2-Sb：SnO2 produces a photocurrent density of 7.75 mA/cm2 at 0.4 V versus a reversible hydrogen electrode. These results demonstrate that constructing a branched heterostructure based on TCO can realize highperformance photoelectrochemical devices.     

Hydrothermal synthesis of 3D α-MnS flowerlike nanoarchitectures

Complex three dimensional (3D) α-MnS flowerlike hierarchical architectures with 1-2 mm in diameter built up of ultrathin nanosheets, with ∼ 600 nm in length, 150-300 nm in width, and about 10-20 nm in thickness, have been synthesized firstly by a simple hydrothermal method free from templates or matrixes and organic additives. Adjacent flowerlike architectures can further expand and eventually self-assemble themselves into interconnected porous continuous networks. Selected area electron diffraction (SEAD) pattern and high resolution transmission electron microscope (HRTEM) image indicate that the nanosheet is a well-developed single crystal. Studies show that the formation of complexes in the reaction system is vital to the morphology of the final product. A clear perspective is shown here that more complex nanostructured materials could be chemically synthesized.     

Carbon based electronic materials: applications in electron field emission

The influence of the different types of bonding present in a range of carbon based materials is discussed as a precursor to describing the field emission characteristics of carbon cold cathode materials. Some of the controlling factors which govern electron emission from carbon based cathodes are discussed. It is shown that from disordered carbon films the interplay between the clustered sp² phase and the insulating sp³ matrix is important. The transition from a ‘back contact’ to ‘front surface’ controlled emission mechanism is described in terms of the sp² content and field penetration. A possible reason for high field enhancement factors found in disordered films also is provided. It is further shown that changes to the sp² phase by current stressing can improve the field emission characteristics. Emission from carbon nanotubes is also discussed and the prospects for new types of nanotube – polymer composite based cathodes are also considered.     

Multifunctional core-shell-like nanoarchitectures for hybrid supercapacitors with high capacity and long-term cycling durability

Nano Research - Transition metal oxide/hydroxide with multifunctional hierarchical nanostructures has attracted widespread attention in supercapacitors (SCs) because of their large accessible...     

Thin-film-based nanoarchitectures for soft matter: controlled assemblies into two-dimensional worlds

Controlling the organization of molecular building blocks at the nanometer level is of utmost importance, not only from the viewpoint of scientific curiosity, but also for the development of next-generation organic devices with electrical, optical, chemical, or biological functions. Self-assembly offers great potential for the manufacture of nanoarchitectures (nanostructures and nanopatterns) over large areas by using low-energy and inexpensive spontaneous processes. However, self-assembled structures in 3D media, such as solutions or solids, are not easily incorporated into current device-oriented nanotechnology. The scope of this review is therefore to introduce the expanding methodology for the construction of thin-film-based nanoarchitectures on solid surfaces and to try to address a general concept with emphasis on the availability of dynamic interfaces for the creation and manipulation of nanoarchitectures. In this review, the strategies for the construction of nanostructures, the control and manipulation of nanopatterns, and the application of nanoarchitectures are described; the construction strategies are categorized into three classes: i) π-conjugated molecular assembly in two dimensions, ii) bio-directed molecular assembly on surfaces, and iii) recent thin-film preparation technologies.