Interesting tech developments in nanotech, nanostructured materials, etc.
Ken Novak's Weblog
Saturday, January 31, 2004
Gold and Silver Nanotubes
: "Scientists at the Weizmann Institute of Science (WIS) in Israel have produced a new type of nanotube made of gold or silver. These nanotubes, which are produced at room temperature
, don't have the mechanical strength of the more common carbon nanotubes. But they have unique electrical and optical properties, making them ideally suited "to form the basis for future nanosensors, catalysts and chemistry-on-a-chip systems."" 11:04:58 PM
Monday, January 26, 2004
Quantum Dots and Programmable Matter: Quick intro to an amazing future for materials science. With reference to Wired article and FAQ: "A quantum dot is any device capable of confining electrons in three dimensions, in a space small enough that their quantum (wavelike) behavior dominates over their classical (particle-like) behavior. Under cryogenic conditions, this typically occurs with dimensions of 1000 nm (0.001 mm) or less. At room temperature, confinement spaces of 20-30 nm or smaller are required.
Once the electrons are confined, they repel one another and also obey the Pauli Exclusion Principle, which forbids any two electrons from having the same quantum state. Thus, the electrons in a quantum dot will form shells and orbitals highly reminiscent of (though larger than) the ones in an atom, and will in fact exhibit many of the optical, electrical, thermal, and (to some extent) chemical properties of an atom. This electron cloud is therefore referred to as an artificial atom. ..
Q13: How is programmable matter made?
A13: Current forms of programmable matter fall into three types: colloidal films, bulk crystals, and quantum dot chips which confine electrons electrostatically. Quantum dots can be grown chemically as nanoparticles of semiconductor surrounded by an insulating layer. These particles can then be deposited onto a substrate, such as a semiconductor wafer patterned with metal electrodes, or they can be crystalized into bulk solids by a variety of methods. Either substance can be stimulated with electricity or light (e.g., lasers) in order to change its properties.
Electrostatic quantum dots are patterns of conductor (usually a metal such as gold) laid down on top of a quantum well, such that varying the electrical voltage on the conductors can drive electrons into and out of a confinement region in the well -- the quantum dot. This method offers numerous advantages over nanoparticle ("colloidal") films, including a greater control over the artificial atom's size, composition, and shape. Numerous quantum dots can be placed on the same chip, forming a semiconductor material with a programmable dopant layer near its surface.
Rolling such chips into cylindrical fibers produces "wellstone," a hypothetical woven solid whose bulk properties are broadly programmable. ..
Q21: What is programmable matter good for?
A21: Almost anything. It can improve the efficient collection, storage, distribution, and use of energy from environmental sources. It can be used to create novel sensors and computing devices, probably including quantum computers. It can create materials which are not available by other means, and which change their apparent composition on demand. Currently, the design of new materials is a time- and labor-intensive process; with programmable matter, it becomes a real-time issue, similar to the design and debugging of software. ..
Single-electron transistors, a form of quantum dot, were first proposed by A.A. Likharev in 1984 and constructed by Gerald Dolan and Theodore Fulton at Bell Laboratories in 1987. The first semiconductor SET, a type of quantum dot sometimes referred to as a designer atom, was invented by Marc Kastner and John Scott-Thomas at MIT in 1989. The term "artificial atom" was coined by Kastner in 1993. Wil McCarthy was the first to use the term "programmable matter" in connection with quantum dots, and to propose a mechanism for the precise, 3D control of large numbers of quantum dots inside a bulk material. The most interesting forms of this device or substance -- known as "quantum dot fiber" or "wellstone" -- are not produceable using circa 2003 technology, although related products may be. The term "wellstone" was coined by McCarthy's business associate, Gary E. Snyder. " 5:45:00 PM
Tuesday, January 20, 2004
Friday, January 16, 2004
Nanotox 2004: "There is accumulating evidence that nanoparticles can have very toxic properties. Many nanoparticle systems are known to have exotic structural, electronic and hence chemical properties, when compared to their bulk counterparts, principally as a result of their reduced dimensions. However very little is known about the interaction between the surface chemistry of nanoparticles and ‘wet’ biochemistry.
There are a variety of novel materials that have become part of the human environment over the past fifty years; some are unintentionally inhaled or ingested, whilst others are introduced into the body intentionally and have been studied in detail, for example prosthetic implants. The revolution in nanotechnology is currently driving these and other biointeractive devices to smaller and smaller lengthscales. Other groups are actively engaged in interfacing biomolecules into ‘biocomputing devices’.
The primary aim of this meeting is to bring together experts in the science of materials, particularly nanoscale materials, with biomedical scientists studying the health effects of nanoparticle exposure. This meeting will attempt to advance understanding of the molecular mechanisms for toxicity and develop novel methods of research based on the latest technologies...
The venue for the meeting is the world famous Daresbury Laboratories in Cheshire, .. home to the new SuperSTEM atomic resolution analysis facility consisting of a suite of aberration-corrected scanning transmission electron microscopes capable of sub-Angstrom chemical imaging and spectroscopy ideal for the study of nanoparticles."
Wired carries a story before the conference: "There is an established risk with some novel materials. Research in this month's issue of Toxicological Sciences concludes that carbon nanotubes, which have a huge variety of potential applications, can be more toxic than quartz, which is considered a serious occupational health hazard. " 11:42:42 PM
Wednesday, January 14, 2004
Can Nanoparticles Enter Our Brains?
: "In a study carried out on rats, U.S. researchers have shown that carbon nanoparticles can move inside the brain after being inhaled
, and also move from the lungs into the bloodstream. Both Nature
and the Guardian
publish interesting stories about this potential new danger to our health. Let's start with Nature.
Günter Oberdörster of the University of Rochester in New York and colleagues tracked the progress of carbon particles that were only 35 nanometres in diameter and had been inhaled by rats. In the olfactory bulb -- an area of the brain that deals with smell -- nanoparticles were detected a day after inhalation, and levels continued to rise until the experiment ended after seven days.
.. Little is known about what effect nanoparticles will have when they reach the brain. The toxicity of the nanoparticles that are currently being used to build prototype nanosized electronic circuits -- such as carbon nanotubes, which are produced in labs around the world -- has not been thoroughly assessed.
But Donaldson says that there is a growing feeling that other nanoparticles, such as those produced by diesel exhausts, may be damaging to some parts of our body. He estimates that people in cities take in about 25 million nanoparticles with every breath. These particles are believed to increase respiratory and cardiac problems, probably by triggering an inflammatory reaction in the lungs.."
Chemists Grow Nano Menagerie
: "Researchers from Sandia National Laboratories have found a simple way to make tiny, complicated shapes from zinc oxide, including arrays of vertically-aligned rods, flat disks, and columns that resemble stacks of coins. The researchers grew the structures, which are similar to those found in biomaterials, by seeding a solution with zinc oxide nanoparticles. They were able to produce different shapes by changing the amount of citrate in the solution at different points during particle growth.
Zinc oxide is a widely-used, inexpensive ceramic material that has useful optical and semiconductor properties and can also be used as a catalyst. The material is already used in solar cells, microsensors and decontamination systems...
Zinc oxide nanostructures could be used as catalysts within the next two years, for chemical and biological sensing into five years, and for more efficient photovoltaics in something more than five years, according to the researchers. The work appeared in the November 23, 2003 issue of Nature Materials." Zinc oxide has been shown to catalyze the conversion of methane to carbon nanotubes and hydrogen. 10:19:34 PM
Nanotubes Detect Nerve Gas
: "Naval Research Laboratory researchers have found that carbon nanotubes are sensitive to extremely small concentrations—less than one part per billion—of chemical nerve agents. .. The researchers worked out a simple procedure to fabricate nanotube-based sensors from random networks of single-walled carbon nanotubes and used a prototype to detect dimethyl methylphosphonate, which simulates the nerve agent sarin. The networks of nanotubes form transistors; the presence of a nerve agent increases the nanotubes' resistance to electricity.
The sensors are very inexpensive, require very little power, and could be used to detect sub-parts-per-billion concentrations of nerve agents, other chemical warfare agents, and other toxic chemicals, according to the researchers. They made a prototype sensor contained in a quartz tube one-eighth of an inch wide by two inches long.
The researchers also showed that the nanotube network sensors can be combined with filters coated with polymers that are sensitive to certain chemicals to make sensors that detect specific chemicals. Arrays of the sensors could be incorporated into handheld or remotely-operated devices designed to detect a variety of substances, according to the researchers. Carbon nanotube sensors could become practical within two to five years, according to the researchers. " 10:16:58 PM
Body Handles Nanofiber Better
: "Researchers from Purdue University have made a discovery that may help: carbon nanofibers are surprisingly compatible with human tissue. The material could eventually be used to create better bone and neural implants. .. The researchers experiments showed that increasing the amount of carbon nanofibers in a polycarbonate urethane composite implant increased the functions of nerve and bone-forming cells and decreased the function of scar-tissue formation. The results imply that compatibility has to do with the size of the fibers that make up the materials.
The researchers have also shown that other materials that contain surfaces with nano-size features are also more compatible with the human body. Carbon nanofiber materials could be used in orthopedics in five to ten years, but it will be one to two decades before neural applications are practical, according to the researchers. " 10:14:21 PM
Sunday, January 11, 2004
Nanoparticles and health
: "In a study carried out on rats, U.S. researchers have shown that carbon nanoparticles can move inside the brain after being inhaled, and also move from the lungs into the bloodstream. Both Nature and the Guardian publish interesting stories about this potential new danger to our health." 8:28:05 AM