1、转一些经典的纳米图片（包括一些动画）纳米尺度的图片概念真正的纳米尺度 Carbon nanotube dative junction assembly Dative (dipolar) bonds are a potentially valuable form of noncovalent interaction for use in diamondoid and macromolecular nanostructures. These interactions require a lone pair donor, such as the lone pair of nitrogen, and
2、an acceptor, such as the empty sp2 orbital or boron. Boron and nitrogen are both good structural replacements for the C-H fragments found in hydrocarbons (nitrogen because it is isoelectronic with the C-H unit, boron because it can accommodate three covalent bonds to leave the last orbital empty). I
3、n this design, carbon nanotubes are functionalized with adamantane-based dative hinges that lock each fragment into place to form the extended network. (grey = carbon, white = hydrogen, blue = nitrogen, green = boron; left: van der Waals rendering. right: ball-and-stick rendering) These designs are
4、the result of a collaboration with Dr. Ralph Merkle into the application of the dative bond in molecular building block approaches for molecular-based materials design.Carbon nanotube dative junction assembly Crimp junctions for perpendicular carbon nanotube scaffolding In this design, two rigid dia
5、mondoid rings are fused at a quasi-tetrahedral junction and sized, through the addition or subtraction of repeat subunits in each ring, to accommodate two carbon nanotubes of different diameters. The crimping of the nanotubes is a result of van der Waals packing of the rings, a feature that can be e
6、nhanced or removed by adjusting the ring size. (grey = carbon, white = hydrogen, blue = nitrogen, red = oxygen) Low-friction bearing assembly with two carbon allotropes In this design, two diamondoid rings replace small segments of a carbon nanotube, providing a lock for a third, larger ring. The la
7、rger ring includes a stitch-work of oxygens to create an electron-rich interior whose effective circular van der Waals packing just touches that of the nanotube framework. Rigid rod-based nanomechanical gear assembly Here, a five-fold rotation axis in a single rigid rod is coupled to four rings comp
8、osed of 15 subunits each. A pagodanoid junction is included along this rigid rod to raise the five sections of the assembly to create an elevated gearing system. The image at left is a van der Waals representation. At right, only the oxygen and nitrogen atoms are shown (as spheres) to highlight the
9、rod interior. (grey = carbon, white = hydrogen, blue = nitrogen, red = oxygen) All images are the result of molecular mechanics structure calculations using either Tinker (MM2 parameters) or NAMD (CHARMM). Images were made with VMD. VMD and NAMD are developed with NIH support by the Theoretical and
10、Computational Biophysics group at the Beckman Institute, University of Illinois at Urbana-Champaign. Tinker is a product of the Ponder Lab in the Department of Biochemistry and Molecular Biophysics at the Washington University School of Medicine. E. Zelman and Apple Computer are thanked for their ge
11、nerous donation of resources. 纳米团簇的制备 Core/shell nanoparticles Gold Nano Anchors Put Nanowires in Their Place Scanning electron microscope image shows rows of horizontal zinc-oxide nanowires grown on a sapphire surface. The gold nanoparticles are visible on the ends of each row Illustration shows ho
12、w crystalline zinc oxide nanowires (blue) push “seeds“ of gold nanoparticles (red) forward as they grow Researchers at the National Institute of Standards and Technology (NIST) have demonstrated a technique for growing well-formed, single-crystal nanowires in placeand in a predictable orientationon
13、a commercially important substrate. The method uses nanoparticles of gold arranged in rows on a sapphire surface as starting points for growing horizontal semiconductor “wires“ only 3 nanometers (nm) in diameter. Other methods produce semiconductor nanowires more than 10 nm in diameter. NIST chemist
14、s work was highlighted in the Oct. 11 issue of Applied Physics Letters.* Part of the vision of nanotechnology is the possibility of building powerful, extraordinarily compact sensors and other devices out of atomic-scale components. So-called “nanowires”long thin crystals of, e.g., a semiconductor c
15、ould not only link nanoelectronic devices like conventional wire but also function as devices themselves, tipped with photodetector or light-emitting elements, for example. An obvious stumbling block is the problem of working with components so small that only the most sophisticated measurement inst
16、ruments can even track them. To date, the most successful nanowire alignment method involved growing large numbers of the rod-like crystals on a suitable base like blades of grass, shearing them off, mixing them in a solvent, and forcing them to align by either flow or surface confinement on the tes
17、t substrate to orient most of the crystals in a specific horizontal direction. Further photolithography steps are required to ensure that nanowires are positioned correctly. In contrast, the NIST technique grows arrays of nanowires made of zinc oxide, a semiconductor widely used in optoelectronics,
18、with precise alignments. The gold “anchors“ are placed with a chemical etching step and the orientation of the wireshorizontal, vertical or at a 60 degree angle from the surfaceis determined by tweaking the size of the gold particles. “Anatomy of a Nanoprobe“ Professor Charles M. Lieber Group A sche
19、matic illustration of the chemical force microscopy setup used to stretch and break duplex DNA. The inset shows a cartoon representations between two complementary strands immobilized on the tip and sample surfaces. The DNA shown in the cartoon corresponds to the relaxed B-DNA conformation Magnetic
20、Nanotubes Dr. Rafal E. Dunin-Borkowski, University of Cambridge Department of Materials Science if one pinion gear is exactly opposite a shaft-gear tooth, its 90-degree partners will be opposite shaft-gear grooves. Thus, energy fluctuations at the tooth-meshing frequency will cancel, leaving only hi
21、gher-frequency, lower-amplitude fluctuations as barriers to rotation. The shafts rotate in the casing on standard sliding-interface bearings, using the same principle to achieve smooth motion. The lowest quality bearings are those between the pinion gears and the casing, which lack the regularity re
22、quired for high smoothness. The structure is designed to be built chiefly of hydrogen (white), carbon (gray), silicon (black), nitrogen (blue), phosphorus (purple), oxygen (red), and sulphur (yellow). The larger size of second-row atoms helps in constructing tapered gears and reduces the number of atoms needed to construct the outer cylinder of the casing. Such structures are far beyond the state of the art of chemical synthesis today, but their design and modeling is becoming straightforward. - K. Eric Drexler
