Stories tagged materials
Growing nanowires horizontally yields "Nano-LEDs
Nano light emitters: Single row of nanowires (cylinders with red tops) with fin-shaped nanowalls extending outward (National Institute of Standards and Technology)Courtesy NIST These “nano-LEDs” may one day have their light-emission abilities put to work serving miniature devices such as nanogenerators or lab-on-a-chip systems. NIST.gov
In recent work published in ACS Nano,* Nikoobakht and Herzing increased the thickness of the gold catalyst nanoparticle from less than 8 nanometers to approximately 20 nanometers. The change resulted in nanowires that grew a secondary structure, a shark-like “dorsal fin” (referred to as a “nanowall”) where the zinc oxide portion is electron-rich and the gallium nitride portion is electron-poor. The interface between these two materials—known as a p-n heterojunction—allows electrons to flow across it when the nanowire-nanowall combination was charged with electricity. In turn, the movement of electrons produced light and led the researchers to dub it a “nano LED.”
Tags : Materials science
Materials scientists figure out ways to make things stronger, cheaper, or better. A favorite technique is nano-self-assembly. Just mix together the right ingredients and "presto", you get a wonder material. Another great development would be for the material to be self-repairing.
Self healing solar cells
MIT scientist, Michael Strano, and his team have created a material made up of seven different compounds including carbon nanotubes, phospholipids, and proteins. Under the right conditions they spontaneously assemble themselves into a light-harvesting structure that produces an electric current. The assembly breaks apart when a surfactant (think soapy solution) is added but reassemble when it is removed. These new self-healing solar cells are already about double the efficiency of today’s best solar cells but could potentially be many times more efficient.
Learn more about self-healing solar cells
- Self Healing Solar MIT News
- Self-Healing Solar Cells Could Have Indefinite Lifespan Wired Science
- Photoelectrochemical complexes for solar energy conversion that chemically and autonomously regenerate Nature Chemistry (abstract)
Quest for the best optical display
Better resolution displaysCourtesy Yutaka Tsutano
I have been waiting for the new iPod Touch. I want a display screen so sharp, it looks like a photograph. The "retina display" creates an image out of pixels that are only 78 nanometers. How small is that? Well, more than 300 of these pixels are packed in each inch. Supposedly this is the limit for human perception, or as some fanboys might say, "It doesn't get any better than this!"
Plasmonic nanoresonators
University of Michigan researchers can do better, though, Their paper in Nature Communications titled, Plasmonic nanoresonators for high-resolution colour filtering and spectral imaging explains how pixels of only 10 microns can be produced.
Such pixel densities could make the technology useful in projection displays, as well as wearable, bendable or extremely compact displays, according to the researchers.
How does it work?
The resonators are kind of like a light filter. Two nano thin layers of metal selectively allow light to pass through small sets of slits. The slit spacing determines which wavelength of light makes it through the slits.
Red light emanates from slits set around 360 nanometers apart; green from those about 270 nanometers apart, and blue from those approximately 225 nanometers apart. The differently spaced gratings essentially catch different wavelengths of light and resonantly transmit through the stacks. LinuxForDevices.com
These displays are simpler, use fewer parts, are more efficient, and should be cheaper to make. I am not going to wait, though.
Cotton for filtersCourtesy Martin Labar
Safe drinking water saves lives
Clean, safe drinking is desperately needed throughout the world. Usually filters "filter out" bacteria by having openings too small to get through. Trouble is, though, that the tiny holes get plugged up, stopping the flow of water. Stanford researchers have now developed a filter about 80,000 times faster than filters that trap bacteria.
Cheap and easy
The filter was made by dipping plain cotton cloth (from Walmart) in a mixture of silver nanowires and carbon nanotubes (for a few minutes). By charging the filter with 20 volts of electricity, over 98 percent of Escherichia coli bacteria were killed as they passed through. Even in remote or primitive areas, the electricity could be supplied by a small solar panel, or a couple 12-volt car batteries, or be generated from a stationary bicycle or by a hand-cranked device.
Cui said the next steps in the research are to try the filter on different types of bacteria and to run tests using several successive filters.
"With one filter, we can kill 98 percent of the bacteria," Cui said. "For drinking water, you don't want any live bacteria in the water, so we will have to use multiple filter stages."
Learn more
High-speed filter uses electrified nanostructures to purify water at low cost Stanford University News
Graphene, the wonder material
Graphene: Unzip it and add oxygen to get graphene oxideCourtesy Dr Thomas Szkopek If you look at my posts about graphene you will understand why I think graphene is a super material. One chemically converted graphene product of interest (CCG) is graphene oxide (GO). Graphene oxide, an insulating version of graphene, is expected to be used for all kinds of material and electronic applications. Graphene oxide is also biodegradable. Bacteria from the genus Shewanella easily convert GO to harmless graphene.
Safer, more efficient way to make graphene oxide
A new paper in ACSNano from the lab of Rice chemist James Tour demonstrates an environmentally friendly way to make bulk quantities of graphene oxide (GO). Scientists have been making GO since the 19th century, but the new process eliminates the need for explosive or toxic ingredients.
The researchers suggested the water-soluble product could find use in polymers, ceramics and metals, as thin films for electronics, as drug-delivery devices and for hydrogen storage, as well as for oil and gas recovery. Science Dailey
Learn more about improved synthesis of graphene oxide
Graphene oxide gets green EurekaAlert
Solar cells made from common materials
Solar cells for everyoneCourtesy Dominic
Solar cells produce less than 1/1000 of the Earth's electricity. This is mainly because they are expensive and are made from rare, hard to obtain materials.
An IBM research team, managed by David Mitzi, is working on photovoltaic cells that are made from common materials.
The new solar cells are also cheaper to manufacture, using a “printing” technique that uses a hydrazine solution containing copper and tin with nanoparticles of zinc dispersed within it. The solution is then spin-coated and heat treated in the presence of selenium or sulfur vapor. PhysOrg
9.6% Efficiency
This new material, called kesterite, was 6.8% efficient in 2009. IBM increased the efficiency to 9.8% and is planning to increase the efficiency above 11 per cent, which is equal to or better than the traditional solar cells.
Abstract of published paper: High-Efficiency Solar Cell with Earth-Abundant Liquid-Processed Absorber Advanced Materials
U.S. Ski Team members Julia Mancuso, Ted Ligety and Scott Macartney, and Katharine Flores, an associate professor in the Department of Materials Science and Engineering at Ohio State University, explain how the materials used to make skis play a vital role in their performance on the mountain.
Liquid GlassCourtesy HustvedtSoon almost every product you purchase will be coated with liquid glass. It repels bacteria, water and dirt, is highly flexible and breathable, and is easy to clean using only water or a simple wipe with a damp cloth.
Nanopool, who makes "Liquid Glass" says it is available in Germany now, and will be in the UK early in 2010.
Quantum force bonding
Using their secret process, NanoPool extracts silicon dioxide molecules from glass and mixes them with water or ethanol. When sprayed on various materials, a 100 nanometer coating offers protection against bacteria, graffiti, stains and is food safe and environmentally friendly.
Source:
Spray-on liquid glass is about to revolutionize almost everything PhysOrg.com
GrapheneCourtesy Carbophiliac
Graphene is great
Graphene is a single atom thick layer of carbon atoms in a honeycomb like arrangement (read more about graphene here in ScienceBuzz.org)
Graphene transistors are the fastest
Transistors are like valves that can turn the flow of electricity off and on. Computers can use transistors and logic circuits to solve all kinds of problems. These problems can be solved faster if the transistors can turn on and off faster. Transistors made out of graphene now can switch on and off 100 billion times per second (100 GigaHertz). State-of-the-art silicon transistors of the same gate length have a switching frequency of about 40 GigaHertz.
IBM develops next-generation transistors
IBM just announced their breakthrough in the magazine Science.
Uniform and high-quality graphene wafers were synthesized by thermal decomposition of a silicon carbide (SiC) substrate. The graphene transistor itself utilized a metal top-gate architecture and a novel gate insulator stack involving a polymer and a high dielectric constant oxide. The gate length was modest, 240 nanometers, leaving plenty of space for further optimization of its performance by scaling down the gate length. ScienceDaily
Flash memory: Today's content king.Courtesy Nrbelex
MRAM
MRAM (magnetoresistive random access memory) flips the magnetisation of a region 180 degrees relative to another permanently magnetised region to store a 0 or a 1. MRAM is nanosecond fast but if made too small and close together will "cross talk".
FeRAM
FeRAM (ferroelectric random access memory) use small external electric fields to polarize ferroelectric crystals. FeRAMs low energy requirement and speed advantage is offset by the requirement that every memory bit requires a space hogging capacitor.
PCRAM
PCRAM (phase-change random access memory) use laser light or current to change a materials structure. If the current pulse is long, the material orders itself into its crystalline state (a conductor). If the pulse is short, the material cools abruptly into the amorphous state (an insulator). These memory regions can be made quite small, but the downside is that the melting requires lots of energy.
RRAM
RRAM (resistive random access memory) use high voltages to drive off or reabsorb oxygen bound within molecules like titanium oxide. When the oxygen leaves, it leaves behind holes in the crystal and excess electrons that are available for conduction. This process requires almost no electrical current, making them very energy efficient. Another exciting property is that RRAMs can represent more than a 0 or 1. They are able to adopt any number of values for their resistance (memristors) which could make them models for the analogue computational elements (synapses) inside the human brain.
Racetrack memory
Racetrack memory moves tiny domains of magnetism along wires. The domains are moved along the wire by a current and written or read when they pass sensor heads. If the wires can be coiled into 3 D, the memory per volume will increase several hundred times.
Source: New Scientist
