David Kirkpatrick

July 22, 2010

Improving the application of nanocoatings

Nanocoatings do a lot of good, particularly with making solar cells more efficient. The trick is they haven’t been too easy to apply to big areas. Researchers at Stanford have helped change that issue.

From the link:

Nanoscale wires, pores, bumps, and other textures can dramatically improve the performance of solar cells, displays, and even self-cleaning coatings. Now researchers at Stanford University have developed a simpler, cheaper way to add these features to large surfaces.

Nanoscale structures offer particular advantages in devices that interact with light. For example, a thin-film solar cell carpeted with nano pillars is more efficient because the pillars absorb more light and convert more of it into electricity. Other nanoscale textures offer similar advantages in optical devices like display backlights.

The problem is scaling up to large areas, says Yi Cui, a Stanford professor of materials science and engineering who led the new work. “Many methods are really complex and don’t solve the problem,” says Cui. Lithography can be used to carve out nanoscale features with precise dimensions, but it’s expensive and difficult. Simpler techniques, such as spin-coating a surface with nanoparticles or using acids to etch it with tiny holes, don’t allow for much precision.

Nanosphere smear: Using a spinning rod to deposit an ink suspension of silica nanospheres is a simple way to create bumpy, nanotextured coatings like these three.

Credit: ACS/Nano Letters

July 17, 2010

Manufacturing carbon nanotubes at room temperature

This document outlines a method of creating carbon nanotubes that doesn’t require high temperature or pressure. This potentially will dramtically lower the cost of manufacturing carbon nanotubes.

From the link:

We develop a new chemical route to carbon nanotubes at room temperature. Graphite powder was immersed in a mixed solution of nitric and sulphuric acid with potassium chloride. After heating the solution up to 70‰ and leaving them in the air for 3 days, we obtained carbon nanotube bundles. The process could readily give an easy way of preparing carbon nanotubes without high temperature and high pressure. We develop a new chemical route to carbon nanotubes at room temperature. Graphite powderwas immersed in a mixed solution of nitric and sulphuric acid with potassium chloride. After heatingthe solution up to 70‰ and leaving them in the air for 3 days, we obtained carbon nanotube bundles.The process could readily give an easy way of preparing carbon nanotubes without high temperatureand high pressure.
And:
In summary, we have presented a simple chemical method for producing CNTs in liquid solution at 70‰ without any pressure treatment. The CNTs form bundles containing crystalized and multi-walled single CNTs with a diameter of around 14.6nm. The electron diffraction patterns demonstrate its zigzag edge structure. We expect this new synthesizing method may produce cheap CNTs and as a result open an easy access to the industrial device based on CNTs.
Here’s an illustration and an image from the link:
FIG. 1: (a) mixture of graphite, sulfuric acid (H2SO4, and nitric acid (HNO3). (b) potassium chlorate (KClO3) was put in the solution. (c) floating carbons produced from the pro- cess (b) were transferred into DI water. (d) the sample was dried after filtration. The process (b) and (c) were repeated 4 times.

FIG. 3: (a) transmission electron microscope (TEM) images of CMT bundles. Panels (b) and (c) magnificently present the regions pointed by number 1 and 2 in panel (a), respectively. A single CNT noticed by an arrow in panel (b) proves CNT’s flexibility. (d) the enlarged region of panel (c) (arrow 3), revealing a multi-walled nanotube with a diameter of 14.6nm.

July 16, 2010

Solar plus nanotech equals lower cost cells

I always love covering news that combines solar and nanotechnology, particularly when the combo leads to lower costs for solar power. I’ve previously blogged about nanopillars leading increased solar efficiency.

From the first link:

A material with a novel nanostructure developed by researchers at the University of California, Berkeley could lead to lower-cost solar cells and light detectors. It absorbs light just as well as commercial thin-film solar cells but uses much less semiconductor material.

The new material consists of an array of nanopillars that are narrow at the top and thicker at the bottom. The narrow tops allow light to penetrate the array without reflecting off. The thicker bottom absorbs light so that it can be converted into electricity. The design absorbs 99 percent of visible light, compared to the 85 percent absorbed by an earlier design in which the nanopillars were the same thickness along their entire length. An ordinary flat film of the material would absorb only 15 percent of the light.

Thick and thin: A scanning electron microscope image shows dual-diameter light-trapping germanium nanopillars.

Credit: Ali Javey, UC Berkeley

Nanotech and breast cancer

Nanotechnology is proving to be a key component in the fight against cancer and I’ve done a lot of blogging about the topic. Here’s another breakthrough on that front, this time targeting breast cancer with an arsenic nanoparticle.

From the second link, the release:

New Arsenic Nanoparticle Blocks Aggressive Breast Cancer

New technology targets cancer prevalent in young women

By Marla Paul

CHICAGO — You can teach an old drug new chemotherapy tricks. Northwestern University researchers took a drug therapy proven for blood cancers but ineffective against solid tumors, packaged it with nanotechnology and got it to combat an aggressive type of breast cancer prevalent in young women, particularly young African-American women.

That drug is arsenic trioxide, long part of the arsenal of ancient Chinese medicine and recently adopted by Western oncologists for a type of leukemia. The cancer is triple negative breast cancer, which often doesn’t respond well to traditional chemotherapy and can’t be treated by potentially life-saving targeted therapies. Women with triple negative breast cancer have a high risk of the cancer metastasizing and poor survival rates.

Prior to the new research, arsenic hadn’t been effective in solid tumors. After the drug was injected into the bloodstream, it was excreted too rapidly to work. The concentration of arsenic couldn’t be increased, because it was then too toxic.

A new arsenic nanoparticle — designed to slip undetected through the bloodstream until it arrives at the tumor and delivers its poisonous cargo — solved all that. The nanoparticle, called a nanobin, was injected into mice with triple negative breast tumors. Nanobins loaded with arsenic reduced tumor growth in mice, while the non-encapsulated arsenic had no effect on tumor growth. The arsenic nanobins blocked tumor growth by causing the cancer cells to die by a process known as apoptosis.

The nanobin consists of nanoparticulate arsenic trioxide encapsulated in a tiny fat vessel (a liposome) and coated with a second layer of a cloaking chemical that prolongs the life of the nanobin and prevents scavenger cells from seeing it. The nanobin technology limits the exposure of normal tissue to the toxic drug as it passes through the bloodstream. When the nanobin gets absorbed by the abnormal, leaky blood vessels of the tumor, the nanoparticles of arsenic are released and trapped inside the tumor cells.

“The anti-tumor effects of the arsenic nanobins against clinically aggressive triple negative breast tumors in mice are extremely encouraging,” said Vince Cryns, associate professor of medicine and an endocrinologist at Northwestern Medicine and a member of the Robert H. Lurie Comprehensive Cancer Center of Northwestern University. “There’s an urgent need to develop new therapies for poor prognosis triple negative breast cancer.”

Cryns and Tom O’Halloran, director of the Chemistry of Life Processes Institute at Northwestern, are senior authors of a paper on the research, which will be published July 15 in Clinical Cancer Research and featured on the journal cover. Richard Ahn, a student in the medical scientists training program at Northwestern, is lead author.

“Everyone said you can’t use arsenic for solid tumors,” said O’Halloran, also associate director of basic sciences at the Lurie Cancer Center. “That’s because they didn’t deliver it the right way. This new technology delivered the drug directly to the tumor, maintained its stability and shielded normal cells from the toxicity. That’s huge.”

The nanoparticle technology has great potential for other existing cancer drugs that have been shelved because they are too toxic or excreted too rapidly, Cryns noted. “We can potentially make those drugs more effective against solid tumors by increasing their delivery to the tumor and by shielding normal cells from their toxicity,” he said. “This nanotechnology platform has the potential to expand our arsenal of chemotherapy drugs to treat cancer.”

“Working with both professors O’Halloran and Cryns has enabled us to develop the nanobins and hopefully create a new platform for the effective treatment of triple negative breast cancer,” Ahn said. “Having both a basic science mentor and breast cancer mentor is ideal training for me as a future physician-scientist.”

Looking ahead, the challenge now is to refine and improve the technology. “How do we make it more toxic to cancer cells and less toxic to healthy cells?” asked Cryns, also the director of SUCCEED, a Northwestern Medicine program to improve the quality of life for breast cancer survivors.

Northwestern scientists are working on decorating the nanobins with antibodies that recognize markers on tumor cells to increase the drug’s uptake by the tumor.  They also want to put two or more drugs into the same nanobin and deliver them together to the tumor.

“Once you fine-tune this, you could use what would otherwise be a lethal or highly toxic dose of the drug, because a good deal of it will be directly released in the tumor,” O’Halloran said.

The research was supported by the National Cancer Institute-funded Northwestern University Center of Cancer Nanotechnology Excellence. Northwestern has one of seven such centers in the United States.

(Northwestern Medicine is comprised of Northwestern University Feinberg School of Medicine and Northwestern Memorial Hospital.)

Marla Paul is the health sciences editor

Here’s PhysOrg’s coverage of this story.

July 15, 2010

Acid bath may lead to armchair quantum wires

More nanotech news.

The release:

Nanotubes pass acid test

Rice researchers’ method untangles long tubes, clears hurdle toward armchair quantum wire

HOUSTON – (July 14, 2010) – Rice University scientists have found the “ultimate” solvent for all kinds of carbon nanotubes (CNTs), a breakthrough that brings the creation of a highly conductive quantum nanowire ever closer.

Nanotubes have the frustrating habit of bundling, making them less useful than when they’re separated in a solution. Rice scientists led by Matteo Pasquali, a professor in chemical and biomolecular engineering and in chemistry, have been trying to untangle them for years as they look for scalable methods to make exceptionally strong, ultralight, highly conductive materials that could revolutionize power distribution, such as the armchair quantum wire.

The armchair quantum wire — a macroscopic cable of well-aligned metallic nanotubes — was envisioned by the late Richard Smalley, a Rice chemist who shared the Nobel Prize for his part in discovering the the family of molecules that includes the carbon nanotube. Rice is celebrating the 25th anniversary of that discovery this year.

Pasquali, primary author Nicholas Parra-Vasquez and their colleagues reported this month in the online journal ACS Nano that chlorosulfonic acid can dissolve half-millimeter-long nanotubes in solution, a critical step in spinning fibers from ultralong nanotubes.

Current methods to dissolve carbon nanotubes, which include surrounding the tubes with soap-like surfactants, doping them with alkali metals or attaching small chemical groups to the sidewalls, disperse nanotubes at relatively low concentrations. These techniques are not ideal for fiber spinning because they damage the properties of the nanotubes, either by attaching small molecules to their surfaces or by shortening them.

A few years ago, the Rice researchers discovered that chlorosulfonic acid, a “superacid,” adds positive charges to the surface of the nanotubes without damaging them. This causes the nanotubes to spontaneously separate from each other in their natural bundled form.

This method is ideal for making nanotube solutions for fiber spinning because it produces fluid dopes that closely resemble those used in industrial spinning of high-performance fibers. Until recently, the researchers thought this dissolution method would be effective only for short single-walled nanotubes.

In the new paper, the Rice team reported that the acid dissolution method also works with any type of carbon nanotube, irrespective of length and type, as long as the nanotubes are relatively free of defects.

Parra-Vasquez described the process as “very easy.”

“Just adding the nanotubes to chlorosulfonic acid results in dissolution, without even mixing,” he said.

While earlier research had focused on single-walled carbon nanotubes, the team discovered chlorosulfonic acid is also adept at dissolving multiwalled nanotubes (MWNTs). “There are many processes that make multiwalled nanotubes at a cheaper cost, and there’s a lot of research with them,” said Parra-Vasquez, who earned his Rice doctorate last year. “We hope this will open up new areas of research.”

They also observed for the first time that long SWNTs dispersed by superacid form liquid crystals. “We already knew that with shorter nanotubes, the liquid-crystalline phase is very different from traditional liquid crystals, so liquid crystals formed from ultralong nanotubes should be interesting to study,” he said.

Parra-Vasquez, now a postdoctoral researcher at Centre de Physique Moleculaire Optique et Hertzienne, Universite’ de Bordeaux, Talence, France, came to Rice in 2002 for graduate studies with Pasquali and Smalley.

Study co-author Micah Green, assistant professor of chemical engineering at Texas Tech and a former postdoctoral fellow in Pasquali’s research group, said working with long nanotubes is key to attaining exceptional properties in fibers because both the mechanical and electrical properties depend on the length of the constituent nanotubes. Pasquali said that using long nanotubes in the fibers should improve their properties on the order of one to two magnitudes, and that similar enhanced properties are also expected in thin films of carbon nanotubes being investigated for flexible electronics applications.

An immediate goal for researchers, Parra-Vasquez said, will be to find “large quantities of ultralong single-walled nanotubes with low defects — and then making that fiber we have been dreaming of making since I arrived at Rice, a dream that Rick Smalley had and that we have all shared since.”

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Co-authors of the paper are graduate students Natnael Behabtu, Colin Young, Anubha Goyal and Cary Pint; Pulickel Ajayan, the Benjamin M. and Mary Greenwood Anderson Professor in Mechanical Engineering and Materials Science and of chemistry, and Robert Hauge, a distinguished faculty fellow in chemistry, all at Rice; and Judith Schmidt, Ellina Kesselman, Yachin Cohen and Yeshayahu Talmon of the Department of Chemical Engineering, Technion-Israel Institute of Technology, Haifa, Israel.

The Air Force Office of Scientific Research, the Air Force Research Laboratory, the National Science Foundation Division of Materials Research, the Robert A. Welch Foundation, the United States-Israel Binational Science Foundation and the Evans-Attwell Welch Postdoctoral Fellowship funded the research.

Read the abstract at: http://pubs.acs.org/doi/abs/10.1021/nn100864v

For more about Rice’s 25th anniversary Year of Nano celebrations, visit: http://buckyball.smalley.rice.edu/year_of_nano/

Nanotech improves submarine sonar

Filed under: et.al. — Tags: , , , , , — David Kirkpatrick @ 2:05 am

Carbon nanotubes really are an amazing material.

The release:

Submarines could use new nanotube technology for sonar and stealth

IMAGE: Submarines of the future could be equipped with “nanotube speakers ” to help improve sonar to probe the ocean depths and make the vessels invisible to enemies.

Click here for more information.

Speakers made from carbon nanotube sheets that are a fraction of the width of a human hair can both generate sound and cancel out noise — properties ideal for submarine sonar to probe the ocean depths and make subs invisible to enemies. That’s the topic of a report on these “nanotube speakers,” which appears in ACS’ Nano Letters, a monthly journal.

Ali Aliev and colleagues explain that thin films of nanotubes can generate sound waves via a thermoacoustic effect. Every time that an electrical pulse passes through the microscopic layer of carbon tubes, the air around them heats up and creates a sound wave. Chinese scientists first discovered that effect in 2008, and applied it in building flexible speakers. In a remarkable demonstration, which made its way onto YouTube, the Chinese nanoscientists stuck a sheet of nanotubes onto the side of a flag, and attached it to an mp3 player. They used the nanotube-coated flag to play a song while it flapped in the breeze. But they did not test its ability to operate under water.

Aliev’s group took that step, showing that nanotube sheets produce the kind of low-frequency sound waves that enable sonar to determine the location, depth, and speed of underwater objects. They also verified that the speakers can be tuned to specific frequencies to cancel out noise, such as the sound of a submarine moving through the depths.

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ARTICLE FOR IMMEDIATE RELEASE “Underwater Sound Generation Using Carbon Nanotube Projectors”

DOWNLOAD FULL TEXT ARTICLE http://pubs.acs.org/stoken/presspac/presspac/full/10.1021/nl100235n

July 12, 2010

Latest advance in nanoscience research

News like this is important because a lot of the science of nanotechnology is so new it’s essentially a high-wire act without a net. Working to set some baselines in nanoscience help to improve the entire field.

The release:

University of Toronto chemists make breakthrough in nanoscience research

TORONTO, ON – A team of scientists led by Eugenia Kumacheva of the Department of Chemistry at the University of Toronto has discovered a way to predict the organization of nanoparticles in larger forms by treating them much the same as ensembles of molecules formed from standard chemical reactions.

“Currently, no model exists describing the organization of nanoparticles,” says Kumacheva. “Our work paves the way for the prediction of the properties of nanoparticle ensembles and for the development of new design rules for such structures.”

The focus of nanoscience is gradually shifting from the synthesis of individual nanoparticles to their organization in larger structures. In order to use nanoparticle ensembles in functional devices such as memory storage devices or optical waveguides, it is important to achieve control of their structure.

According to the researchers’ observations, the self-organization of nanoparticles is an efficient strategy for producing nanostructures with complex, hierarchical architectures. “The past decade has witnessed great progress in nanoscience – particularly nanoparticle self-assembly – yet the quantitative prediction of the architecture of nanoparticle ensembles and of the kinetics of their formation remains a challenge,” she continues. “We report on the remarkable similarity between the self-assembly of metal nanoparticles and chemical reactions leading to the formation of polymer molecules. The nanoparticles act as multifunctional single units, which form reversible, noncovalent bonds at specific bond angles and organize themselves into a highly ordered polymer.”

“We developed a new approach that enables a quantitative prediction of the architecture of linear, branched, and cyclic self-assembled nanostructures, their aggregation numbers and size distribution, and the formation of structural isomers.”

Kumacheva was joined in the research by postdoctoral fellows Kun Liu, Nana Zhao and Wei Li, and former doctoral student Zhihong Nie, along with Professor Michael Rubinstein of the University of North Carolina. As polymer chemists, the team took an unconventional look at nanoparticle organization.

“We treated them as molecules, not particles, which in a process resembling a polymerization reaction, organize themselves into polymer-like assemblies,” says Kumacheva. “Using this analogy, we used the theory of polymerization and predicted the architecture of the so-called ‘molecules’ and also found other, unexpected features that can find interesting applications.”

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The findings were published in a report titled “Step-Growth Polymerization of Inorganic Nanoparticles” in the July 9 issue of Science. The research was funded with support from an NSERC Discovery Grant from the Natural Sciences and Engineering Research Council of Canada and Canada Research Chair funding.

July 8, 2010

Drug delivery system, electromagnetic fields and nanotech

Medical news about nanotechnology.

The release:

Researchers develop drug delivery system using nanoparticles triggered by electromagnetic field

KINGSTON, R.I. July 8, 2010 – A new system for the controlled delivery of pharmaceutical drugs has been developed by a team of University of Rhode Island chemical engineers using nanoparticles embedded in a liposome that can be triggered by non-invasive electromagnetic fields.

The discovery by URI professors Geoffrey Bothun and Arijit Bose and graduate student Yanjing Chen was published in the June issue of ACS Nano.

According to Bothun, liposomes are tiny nanoscale spherical structures made of lipids that can trap different drug molecules inside them for use in delivering those drugs to targeted locations in the body. The superparamagnetic iron oxide nanoparticles the researchers embed in the shell of the liposome release the drug by making the shell leaky when heat-activated in an alternating current electromagnetic field operating at radio frequencies.

“We’ve shown that we can control the rate and extent of the release of a model drug molecule by varying the nanoparticle loading and the magnetic field strength,” explained Bothun. “We get a quick release of the drug with magnetic field heating in a matter of 30 to 40 minutes, and without heating there is minimal spontaneous leakage of the drug from the liposome.”

Bothun said that the liposomes self-assemble because portions of the lipids are hydrophilic – they have a strong affinity for water – and others are hydrophobic – they avoid water. When he mixes lipids and nanoparticles in a solvent, adds water and evaporates off the solvent, the materials automatically assemble themselves into liposomes. The hydrophobic nanoparticles and lipids join together to form the shell of the liposome, while the water-loving drug molecules are captured inside the spherical shell.

“The concept of loading nanoparticles within the hydrophobic shell to focus the activation is brand new,” Bothun said. “It works because the leakiness of the shell is ultimately what controls the release of the drugs.”

The next step in the research is to design and optimize liposome/nanoparticle assemblies that can target cancer cells or other disease-causing cells. In vitro cancer cell studies are already underway in collaboration with URI pharmacy professor Matthew Stoner.

“We are functionalizing the liposomes by putting in different lipids to help stabilize and target them so they can seek out particular cancer cell types,” he said. “We are building liposomes that will attach to particular cells or tumor regions.”

Bothun said that research on nanomedicine shows great promise, but there are still many challenges to overcome, and the targeting of appropriate cells may be the greatest challenge.

“Any ability to target the drug is better than a drug that goes everywhere in your system and generates off-target effects,” he said, noting that the hair loss and nausea from anti-cancer drugs are the result of the high drug concentrations needed for treatment and the drug’s affect on non-target cells. “If you can get an assembly to a targeted site without losing its contents in the process, that’s the holy grail.”

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July 6, 2010

Nano-scale light mills now a reality

I’ll just say, wow! The NEMS applications are particularly interesting.

From the link:

While those wonderful light sabers in the Star Wars films remain the figment of George Lucas’ fertile imagination, light mills – rotary motors driven by light – that can power objects thousands of times greater in size are now fact. Researchers with the Lawrence Berkeley National Laboratory and the University of California Berkeley have created the first nano-sized light mill motor whose rotational speed and direction can be controlled by tuning the frequency of the incident light waves. It may not help conquer the Dark Side, but this new light mill does open the door to a broad range of valuable applications, including a new generation of nanoelectromechanical systems (NEMS), nanoscale solar light harvesters, and bots that can perform in vivo manipulations of DNA and other biological molecules.

Nano-sized light mill drives micro-sized disk (w/ Video)

This STM image shows a gammadion gold light mill nanomotor embedded in a silica microdisk. Inset is a magnified top view of the light mill.

July 3, 2010

Toward quantum computing

This news comes from the University of Maryland offering another advancement toward a quantum computer — something that is ways off yet — that involves nanotechnology.

The release:

UM Scientists Advance Quantum Computing & Energy Conversion Tech

COLLEGE PARK, Md. — Using a unique hybrid nanostructure, University of Maryland researchers have shown a new type of light-matter interaction and also demonstrated the first full quantum control of qubit spin within very tiny colloidal nanostructures (a few nanometers), thus taking a key step forward in efforts to create a quantum computer.

Published in the July 1 issue of Nature, their research builds on work by the same Maryland research team published in March in the journal Science (3-26-10). According to the authors and outside experts, the new findings further advance the promise these new nanostructures hold for quantum computing and for new, more efficient, energy generation technologies (such as photovoltaic cells), as well as for other technologies that are based on light-matter interactions like biomarkers.

“The real breakthrough is that we use a new technology from materials science to ‘shed light’ on light-matter interactions and related quantum science in ways that we believe will have important applications in many areas, particularly energy conversion and storage and quantum computing,” said lead researcher Min Ouyang, an assistant professor in the department of physics and in the university’s Maryland NanoCenter. “In fact, our team already is applying our new understanding of nanoscale light-matter interactions and advancement of precise control of nanostructures to the development of a new type of photovoltaic cell that we expect to be significantly more efficient at converting light to electricity than are current cells.”

Ouyang and the other members of the University of Maryland team — research scientist Jiatao Zhang, and students Kwan Lee and Yun Tang — have created a patent-pending process that uses chemical thermodynamics to produce, in solution, a broad range of different combination materials, each with a shell of structurally perfect mono-crystal semiconductor around a metal core. In the research published in this week’s Nature, the researchers used hybrid metal/semiconductor nanostructures developed through this process to experimentally demonstrate “tunable resonant coupling” between a plasmon (from metal core) and an exciton (from semiconductor shell), with a resulting enhancement of the Optical Stark Effect. This effect was discovered some 60 years ago in studies of the interaction between light and atoms that showed light can be applied to modify atomic quantum states.

Nanostructures, Large Advances
“Metal-semiconductor heteronanostructures have been investigated intensely in the last few years with the metallic components used as nanoscale antennas to couple light much more effectively into and out of semiconductor nanoscale, light-emitters,” said Garnett W. Bryant, leader of the Quantum Processes and Metrology Group in the Atomic Physics Division of the National Institute of Standards and Technology (NIST). “The research led Min Ouyang shows that a novel heteronanostructure with the semiconductor surrounding the metallic nanoantenna can achieve the same goals. Such structures are very simple and much easier to make than previously attempted, greatly opening up possibilities for application. Most importantly, they have demonstrated that the light/matter coupling can be manipulated to achieve coherent quantum control of the semiconductor nanoemitters, a key requirement for quantum information processing,” said Bryant, who is not involved with this research. Bryant also is a scientist in the Joint Quantum Institute, a leading center of quantum science research that is a partnership between NIST and the University of Maryland.

Ouyang and his colleagues agree that their new findings were made possible by their crystal-metal hybrid nanostructures, which offer a number of benefits over the epitaxial structures used for previous work. Epitaxy has been the principle way to create single crystal semiconductors and related devices. The new research highlights the new capabilities of these UM nanostructures, made with a process that avoids two key constraints of epitaxy — a limit on deposition semiconductor layer thickness and a rigid requirement for “lattice matching.”

The Maryland scientists note that, in addition to the enhanced capabilities of their hybrid nanostructures, the method for producing them doesn’t require a clean room facility and the materials don’t have to be formed in a vacuum, the way those made by conventional epitaxy do. “Thus it also would be much simpler and cheaper for companies to mass produce products based on our hybrid nanostructures,” Ouyang said.

UM: Addressing Big Issues, Exploring Big Ideas
Every day University of Maryland faculty and student researchers are making a deep impact on the scientific, technological, political, social, security and environmental challenges facing our nation and world. Working in partnership with federal agencies, and international and industry collaborators, they are advancing knowledge and solutions in a areas such as climate change, global security, energy, public health, information technology, food safety and security, and space exploration.

—————-

Schematic of hybrid core-shell growth process

“Tailoring light-matter-spin interactions in colloidal hetero-nanostructures” Jiatao Zhang, Yun Tang, Kwan Lee, Min Ouyang, Nature, July 1, 2010.

This work was supported by the Office of Naval Research, the National Science Foundation (NSF), and Beckman Foundation. Facility support was from Maryland Nanocenter and its Nanoscale Imaging, Spectroscopy, and Properties Laboratory, which is supported in part by the NSF as a Materials Research Science and Engineering Centers shared experiment facility.

July 2, 2010

Nanotechnology and dentistry

Filed under: Science — Tags: , , , , , — David Kirkpatrick @ 1:08 am

Okay, for many, many years I’ve been reading about all sorts of breakthroughs, innovations and miraculous-sounding dental treatments that never really seem to pan out (remember that cavity removing painless gel anyone?), but I couldn’t resist throwing this bit of nanotech out there.

The release:

Nano-sized advance toward next big treatment era in dentistry

IMAGE: Dentists may use a special nano-sized film in the future to bring diseased teeth back to life rather than remove them.

Click here for more information.

Scientists are reporting an advance toward the next big treatment revolution in dentistry — the era in which root canal therapy brings diseased teeth back to life, rather than leaving a “non-vital” or dead tooth in the mouth. In a report in the monthly journal ACS Nano, they describe a first-of-its-kind, nano-sized dental film that shows early promise for achieving this long-sought goal.

Nadia Benkirane-Jessel and colleagues note that root canal procedures help prevent tooth loss in millions of people each year. During the procedure, a dentist removes the painful, inflamed pulp, the soft tissue inside the diseased or injured tooth that contains nerves and blood vessels. Regenerative endodontics, the development and delivery of tissues to replace diseased or damaged dental pulp, has the potential to provide a revolutionary alternative to pulp removal.

The scientists are reporting development of a multilayered, nano-sized film — only 1/50,000th the thickness of a human hair — containing a substance that could help regenerate dental pulp. Previous studies show that the substance, called alpha melanocyte stimulating hormone, or alpha-MSH, has anti-inflammatory properties. The scientists showed in laboratory tests alpha-MSH combined with a widely-used polymer produced a material that fights inflammation in dental pulp fibroblasts. Fibroblasts are the main type of cell found in dental pulp. Nano-films containing alpha-MSH also increased the number of these cells. This could help revitalize damaged teeth and reduce the need for a root canal procedure, the scientists suggest.

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ARTICLE FOR IMMEDIATE RELEASE
“Nanostructured Assemblies for Dental Application”

DOWNLOAD FULL TEXT ARTICLE
http://pubs.acs.org/stoken/presspac/presspac/full/10.1021/nn100713m

Graphene 2.0

Yep, I’m going to be lazy just cop part of the title of this release, well really more of an article than an out-and-out press release. Sounds like a pretty cool graphene transistor with potential real world applications.

The release:

Graphene 2.0: a new approach to making a unique material

June 30, 2010

Since its discovery, graphene—an unusual and versatile substance composed of a single-layer crystal lattice of carbon atoms—has caused much excitement in the scientific community. Now, Nongjian (NJ) Tao, a researcher at the Biodesign Institute at Arizona State University has hit on a new way of making graphene, maximizing the material’s enormous potential, particularly for use in high-speed electronic devices.

Along with collaborators from Germany’s Max Planck Institute, the Department of Materials Science and Engineering, University of Utah, and Tsinghua University, Beijing, Tao created a graphene transistor composed of 13 benzene rings.

The molecule, known as a coronene, shows an improved electronic band gap, a property which may help to overcome one of the central obstacles to applying graphene technology for electronics. Tao is the director of the Biodesign Institute’s Center for Bioelectronics and Biosensors and electrical engineering professor in the Ira A. Fulton Schools of Engineering. The group’s work appears in the June 29 advanced online issue of Nature Communications.

Eventually, graphene components may find their way into a broad array of products, from lasers to ultra-fast computer chips; ultracapacitors with unprecedented storage capabilities; tools for microbial detection and diagnosis; photovoltaic cells; quantum computing applications and many others.

As the name suggests, graphene is closely related to graphite. Each time a pencil is drawn across a page, tiny fragments of graphene are shed. When properly magnified, the substance resembles an atomic-scale chicken wire. Sheets of the material possess exceptional electronic and optical properties, making it highly attractive for varied applications.

“Graphene is an amazing material, made of carbon atoms connected in a honeycomb structure,” Tao says, pointing to graphene’s huge electrical mobility—the ease with which electrons can flow through the material. Such high mobility is a critical parameter in determining the speed of components like transistors.

Producing usable amounts of graphene however, can be tricky. Until now, two methods have been favored, one in which single layer graphene is peeled from a multilayer sheet of graphite, using adhesive tape and the other, in which crystals of graphene are grown on a substrate, such as silicon carbide.

In each case, an intrinsic property of graphene must be overcome for the material to be suitable for a transistor. As Tao explains, “a transistor is basically a switch—you turn it on or off. A graphene transistor is very fast but the on/off ratio is very tiny. ” This is due to the fact that the space between the valence and conduction bands of the material—or band gap as it is known—is zero for graphene.

In order to enlarge the band gap and improve the on/off ratio of the material, larger sheets of graphene may be cut down to nanoscale sizes. This has the effect of opening the gap between valence and conductance bands and improving the on/off ratio, though such size reduction comes at a cost. The process is laborious and tends to introduce irregularities in shape and impurities in chemical composition, which somewhat degrade the electrical properties of the graphene.  “This may not really be a viable solution for mass production,” Tao observes.

Rather than a top down approach in which sheets of graphene are reduced to a suitable size to act as transistors, Tao’s approach is bottom up—building up the graphene, molecular piece by piece. To do this, Tao relies on the chemical synthesis of benzene rings, hexagonal structures, each formed from 6 carbon atoms. “Benzene is usually an insulating material, ” Tao says. But as more such rings are joined together, the material’s behavior becomes more like a semiconductor.

Using this process, the group was able to synthesize a coronene molecule, consisting of 13 benzene rings arranged in a well defined shape. The molecule was then fitted on either side with linker groups—chemical binders that allow the molecule to be attached to electrodes, forming a nanoscale circuit. An electrical potential was then passed through the molecule and the behavior, observed. The new structure displayed transistor properties, showing reversible on and off switches.

Tao points out that the process of chemical synthesis permits the fine-tuning of structures in terms of ideal size, shape and geometric structure, making it advantageous for commercial mass production. Graphene can also be made free of defects and impurities, thereby reducing electrical scattering and providing material with maximum mobility and carrier velocity, ideal for high-speed electronics.

In conventional devices, resistance is proportional to temperature, but in the graphene transistors by Tao et al., electron mobility is due to quantum tunneling, and remains temperature independent—a signature of coherent process.

The group believes they will be able to enlarge the graphene structures through chemical synthesis to perhaps hundreds of rings, while still maintaining a sufficient band gap to enable switching behavior. The research opens many possibilities for the future commercialization of this uncommon material, and its use in a new generation of ultra high-speed electronics.

Written by Richard Harth
Biodesign Institute Science Writer

June 16, 2010

Hard disk storage and nanotechnology

Filed under: Science, Technology — Tags: , , , , — David Kirkpatrick @ 12:50 am

Hard disks made of a nanosphere magnetic recording medium may offer simply stunning amounts of storage space.

From the link:

A new magnetic recording medium made up of tiny nanospheres has been devised by European researchers. The technology may lead to hard disks able to store more than a thousand billion bits of information in a square inch.

With consumer PCs now being sold with hard disks of a  or more – enough to record more than two years of music –  seems to be expanding without limit. But the limits are there and industry insiders know that they are approaching fast.

Also:

A spacing of 25 nanometres between spheres is equivalent to a storage density of one terabit (1000 gigabits) per square inch. Using the same approach with smaller spheres researchers should be able to attain densities up to six times higher.

June 15, 2010

The thick or thin solar question …

… has been solved by nanotech based on coaxial cable.

From the link:

“Many groups around the world are working on nanowire-type solar cells, most using crystalline semiconductors,” said co-author Michael Naughton, a professor of physics at Boston College. “This nanocoax cell architecture, on the other hand, does not require crystalline materials, and therefore offers promise for lower-cost solar power with ultrathin absorbers. With continued optimization, efficiencies beyond anything achieved in conventional planar architectures may be possible, while using smaller quantities of less costly material.”

Optically, the so-called nanocoax stands thick enough to capture light, yet its architecture makes it thin enough to allow a more efficient extraction of current, the researchers report in PSS’s Rapid Research Letters. This makes the nanocoax, invented at Boston College in 2005 and patented last year, a new platform for low cost, high efficiency solar power.

Boston College researchers report developing a “nanocoax” technology that can support a highly efficient thin film solar cell. This image shows a cross section of an array of nanocoax structures, which prove to be thick enough to absorb a sufficient amount of light, yet thin enough to extract current with increased efficiency, the researchers report in the journal Physica Status Solidi. Credit: Boston College

June 11, 2010

Friday video fun — graphene into fullerene

This time it’s fun with science watching graphene turn into buckyballs.

PhysOrg has an article covering this video with additional images.

From the link:

Peering through a transmission electron microscope (TEM), researchers from Germany, Spain, and the UK have observed graphene sheets transforming into spherical fullerenes, better known as buckyballs, for the first time. The experiment could shed light on the process of how fullerenes are formed, which has so far remained mysterious on the atomic scale.

“This is the first time that anyone has directly observed the mechanism of fullerene formation,” Andrei Khlobystov of the University of Nottingham toldPhysOrg.com. “Shortly after the discovery of fullerene (exactly 25 years ago), the ‘top down’ mechanism of fullerene assembly was proposed. However, it was soon rejected in favor of a multitude of different ‘bottom up’ mechanisms, mainly because people could not understand how a flake of  could form a fullerene and because they did not have means to observe the fullerene formation in situ.”

Nanoscale circuits on graphene

Via KurzweilAI.net — For all those fresh graduates out there, one word — graphene.

Simple way to create nanocircuitry on graphene developed
KurzweilAI.net, June 11, 2010

method of drawing nanoscale circuits onto atom-thick sheets of graphene has been developed by researchers at the U.S. Naval Research Laboratory, Georgia Institute ofTechnology, and the University of Illinois at Urbana-Champaign.


(University of Illinois at Urbana-Champaign)

The simple, quick one-step process for creating nanowires, based on thermochemical nanolithography (TCNL), tunes the electronic properties of reduced graphene oxide, allowing it to switch from being an insulating material to a conducting material.

Scientists who work with nanocircuits are enthusiastic about graphene because electrons meet with less resistance when they travel along graphene compared to silicon and because today’s silicon transistors are nearly as small as allowed by the laws of physics. Graphene also has the edge due to its thickness – it’s a carbon sheet that is a single atom thick.

However, no one knew how to produce graphene nanostructures with such a reproducible or scalable method until now.

More info: Georgia Institute of Technology

June 10, 2010

Nantech making better heat sinks

Really making a whole lot better heat sinks.

The release:

NANOTECH YIELDS MAJOR ADVANCE IN HEAT TRANSFER, COOLING TECHNOLOGIES

6-9-10

The journal publication this story is based on is available online: http://bit.ly/cBAKfE

CORVALLIS, Ore. – Researchers at Oregon State University and the Pacific Northwest National Laboratory have discovered a new way to apply nanostructure coatings to make heat transfer far more efficient, with important potential applications to high tech devices as well as the conventional heating and cooling industry.

These coatings can remove heat four times faster than the same materials before they are coated, using inexpensive materials and application procedures.

The discovery has the potential to revolutionize cooling technology, experts say.

The findings have just been announced in the International Journal of Heat and Mass Transfer, and a patent application has been filed.

“For the configurations we investigated, this approach achieves heat transfer approaching theoretical maximums,” said Terry Hendricks, the project leader from the Pacific Northwest National Laboratory. “This is quite significant.”

The improvement in heat transfer achieved by modifying surfaces at the nanoscale has possible applications in both micro- and macro-scale industrial systems, researchers said. The coatings produced a “heat transfer coefficient” 10 times higher than uncoated surfaces.

Heat exchange has been a significant issue in many mechanical devices since the Industrial Revolution.

The radiator and circulating water in an automobile engine exist to address this problem. Heat exchangers are what make modern air conditioners or refrigerators function, and inadequate cooling is a limiting factor for many advanced technology applications, ranging from laptop computers to advanced radar systems.

“Many electronic devices need to remove a lot of heat quickly, and that’s always been difficult to do,” said Chih-hung Chang, an associate professor in the School of Chemical, Biological and Environmental Engineering at Oregon State University. “This combination of a nanostructure on top of a microstructure has the potential for heat transfer that’s much more efficient than anything we’ve had before.”

There’s enough inefficiency in heat transfer, for instance, that for water to reach its boiling point of 100 degrees centigrade, the temperature of adjacent plates often has to be about 140 degrees centigrade. But with this new approach, through both their temperature and a nanostructure that literally encourages bubble development, water will boil when similar plates are only about 120 degrees centigrade.

To do this, heat transfer surfaces are coated with a nanostructured application of zinc oxide, which in this usage develops a multi-textured surface that looks almost like flowers, and has extra shapes and capillary forces that encourage bubble formation and rapid, efficient replenishment of active boiling sites.

In these experiments, water was used, but other liquids with different or even better cooling characteristics could be used as well, the researchers said. The coating of zinc oxide on aluminum and copper substrates is inexpensive and could affordably be applied to large areas.

Because of that, this technology has the potential not only to address cooling problems in advanced electronics, the scientists said, but also could be used in more conventional heating, cooling and air conditioning applications. It could eventually find its way into everything from a short-pulse laser to a home air conditioner or more efficient heat pump systems. Military electronic applications that use large amounts of power are also likely, researchers said.

The research has been supported by the Army Research Laboratory. Further studies are being continued to develop broader commercial applications, researchers said.

“These results suggest the possibility of many types of selectively engineered, nanostructured patterns to enhance boiling behavior using low cost solution chemistries and processes,” the scientists wrote in their study. “As solution processes, these microreactor-assisted, nanomaterial deposition approaches are less expensive than carbon nanotube approaches, and more importantly, processing temperatures are low.”

About the OSU College of Engineering: The OSU College of Engineering is among the nation’s largest and most productive engineering programs. In the past six years, the College has more than doubled its research expenditures to $27.5 million by emphasizing highly collaborative research that solves global problems, spins out new companies, and produces opportunity for students through hands-on learning.

Nanotech coating by Oregon State University.

This nanoscale-level coating of zinc oxide on top of a copper plate holds the potential to dramatically increase heat transfer characteristics and lead to a revolution in heating and cooling technology, according to experts at Oregon State University and the Pacific Northwest National Laboratory. (Photo courtesy of Oregon State University)

June 9, 2010

Lithium-air battery news

Good news, that is. A nanotech catalyst improves the efficiency of lithium-air batteries to record levels and gets them that much closer to practical application in places like electric vehicles.

From the link:

A catalyst developed by researchers at MIT makes rechargeable lithium-air batteries significantly more efficient–a step toward making these high-energy-density batteries practical for use in electric vehicles and elsewhere.

The catalyst consists of nanoparticles of a gold and platinum alloy; in testing it was able to return 77 percent of the energy used to charge the battery as electricity when discharged. That’s up from the previously published record of about 70 percent, the researchers say. The work, which was reported online this week in the Journal of the American Chemical Society, suggests a new approach to lithium-air battery catalysts that could lead to the even higher efficiencies of 85 to 90 percent needed for commercial batteries.

Lithium-air batteries, which generate electricity by reacting lithium metal and oxygen from the air, are attractive for their potential to store vast amounts of energy. They could be a practical way to store more than three times as much energy, by weight, as today’s lithium-ion batteries, extending the range of electric vehicles, for example.

Air catalyst: Gold and platinum alloy nanoparticles (the dark areas) sit on top of a carbon black substrate (the lighter patterns); together, these materials improve the efficiency of lithium-air batteries.
Credit: Yi-Chun Lu

June 8, 2010

Manufacturing graphene …

Filed under: Science, Technology — Tags: , , , , — David Kirkpatrick @ 3:41 pm

… just got a little bit easier. This is good news out of Rice University. I written this many times, but there’s simply too much smoke in the graphene hype for there not to be a serious fire somewhere. I’m guessing some combination of display technology for handheld electronics is one of the best areas to monitor for market-ready graphene applications.

From the link:

Single-atom-thick sheets of carbon called graphene have some amazing properties: graphene is strong, highly electrically conductive, flexible, and transparent. This makes it a promising material to make flexible touch screens and superstrong structural materials. But creating these thin carbon sheets, and then building things out of them, is difficult to do outside the lab.

Now an advance in making and processing graphene in solution may make it practical to work with the material at manufacturing scale. Researchers at Rice University have made graphene solutions 10 times more concentrated than any before. They’ve used these solutions to make transparent, conductive sheets similar to the electrodes on displays, and they’re currently developing methods for spinning the graphene solutions to generate fibers and structural materials for airplanes and other vehicles that promise to be less expensive than today’s carbon fiber.

Making material: Sheets of graphene lay atop a mat of single-walled carbon nanotubes.
Credit: N. Behabtu/Rice University

June 4, 2010

A cyborg transistor

Via KurzweilAI.net — Interesting, if not a little bit creepy.

Part-human, part-machine transistor devised
Discovery News, June 2, 2010

University of California, Merced scientists have embedded a carbon nanotube-based transistor inside a lipid bilayer (cell-like membrane) and powered it with an ion pump and a solution of adenosine triphosphate (ATP) to fuel the ion pump.


Artist’s representation of a new transistor that’s contained within a cell-like membrane (Scott Dougherty, LLNL)

The research could lead to new types of man-machine interactions where embedded devices could relay information about the inner workings of disease-related proteins or toxins inside the cell membrane, and eventually even treat diseases. It could also lead to new ways to read, and even influence, brain or nerve cells.

The headline is misleading — the device is simply biomimetic. – Ed.
Read Original Article>>

June 2, 2010

Copper nanowires may improve solar cells and displays

This is an interesting use of nanotech because it looks like it might be market-ready much sooner than later, and as team member Benjamin Wiley puts it, “If we are going to have these ubiquitous electronics and solar cells we need to use materials that are abundant in the earth’s crust and don’t take much energy to extract.”

Also from the link:

A team of Duke University chemists has perfected a simple way to make tiny copper nanowires in quantity. The cheap conductors are small enough to be transparent, making them ideal for thin-film solar cells, flat-screen TVs and computers, and flexible displays.

“Imagine a foldable iPad,” said Benjamin Wiley, an assistant professor of chemistry at Duke. His team reports its findings online this week in .

Nanowires made of  perform better than carbon nanotubes, and are much cheaper than silver nanowires, Wiley said

May 27, 2010

Nanotech and optics

Very cool findings about light-activated nanoshells.

The release:

Optical Legos: Building nanoshell structures

Self-assembly method yields materials with unique optical properties

IMAGE: Heptamers containing seven nanoshells have unique optical properties.

Click here for more information.

HOUSTON — (May 27, 2010) — Scientists from four U.S. universities have created a way to use Rice University’s light-activated nanoshells as building blocks for 2-D and 3-D structures that could find use in chemical sensors, nanolasers and bizarre light-absorbing metamaterials. Much as a child might use Lego blocks to build 3-D models of complex buildings or vehicles, the scientists are using the new chemical self-assembly method to build complex structures that can trap, store and bend light.

The research appears in this week’s issue of the journal Science.

“We used the method to make a seven-nanoshell structure that creates a particular type of interference pattern called a Fano resonance,” said study co-author Peter Nordlander, professor of physics and astronomy at Rice. “These resonances arise from peculiar light wave interference effects, and they occur only in man-made materials. Because these heptamers are self-assembled, they are relatively easy to make, so this could have significant commercial implications.”

Because of the unique nature of Fano resonances, the new materials can trap light, store energy and bend light in bizarre ways that no natural material can. Nordlander said the new materials are ideally suited for making ultrasensitive biological and chemical sensors. He said they may also be useful in nanolasers and potentially in integrated photonic circuits that run off of light rather than electricity.

The research team was led by Harvard University applied physicist Federico Capasso and also included nanoshell inventor Naomi Halas, Rice’s Stanley C. Moore Professor in Electrical and Computer Engineering and professor of physics, chemistry and biomedical engineering.

Nordlander, the world’s leading theorist on nanoparticle plasmonics, had predicted in 2008 that a heptamer of nanoshells would produce Fano resonances. That paper spurred Capasso’s efforts to fabricate the structure, Nordlander said.

The new self-assembly method developed by Capasso’s team was also used to make magnetic three-nanoshell “trimers.” The optical properties of these are described in the Science paper, which also discusses how the self-assembly method could be used to build even more complex 3-D structures.

Nanoshells, the building blocks that were used in the new study, are about 20 times smaller than red blood cells. In form, they resemble malted milk balls, but they are coated with gold instead of chocolate, and their center is a sphere of glass. By varying the size of the glass center and the thickness of the gold shell, Halas can create nanoshells that interact with specific wavelengths of light.

“Nanoshells were already among the most versatile of all plasmonic nanoparticles, and this new self-assembly method for complex 2-D and 3-D structures simply adds to that,” said Halas, who has helped develop a number of biological applications for nanoshells, including diagnostic applications and a minimally invasive procedure for treating cancer.

###

Additional co-authors of the new study include Rice graduate students Kui Bao and Rizia Bardhan; Jonathan Fan and Vinothan Manoharan, both of Harvard; Chihhui Wu and Gennady Shvets, both of the University of Texas at Austin; and Jiming Bao of the University of Houston. The research was supported by the National Science Foundation, the Air Force Office of Scientific Research, the Department of Defense, the Robert A. Welch Foundation, the Department of Energy and Harvard University.

PhysOrg covers this story here.

More nanotech medical treatment

Filed under: Science, Technology — Tags: , , , , , — David Kirkpatrick @ 4:23 pm

Both via KurzweilAI.net, and both as a follow-up to my previous post on killing tumors with gold nanoparticles.

First up is using carbon nanotubes as a radiotherapy delivery system:

Nanocapsule delivers radiotherapy
PhysOrg.com, May 26, 2010

Oxford University chemists have encapsulated radionuclides within carbon nanotubes and set new records for highly concentrated in vivo radiodosage, while demonstrating zero leakage of isotopes to high-affinity organs, such as the thyroid.


Artist’s rendition of nanocapsules (Gerard Tobias)
Read Original Article>>

And second is using nanoporous particles as a molecular therapy deliver system to tumors:

Nanoporous Particles Deliver Novel Molecular Therapies to Tumors
PhysOrg.com, May 26, 2010

Using nanoporous silicon particles, two teams of investigators have created drug delivery vehicles capable of ferrying labile molecular therapies deep into the body, creating new opportunities for developing innovative anticancer therapies.
Read Original Article>>

Killing tumors with gold nanoparticles

Via KurzweilAI.net — The latest in fighting cancer with nanotechnology.

Self-Assembling Gold Nanoparticles Use Light to Kill Tumor Cells
PhysOrg.com, May 26, 2010

Researchers at the University of California, Los Angeles, have developed a method for creating supramolecular assemblies of gold nanoparticles that function as highly efficient photothermal agents for delivery to tumors, using a laser beam to heat the nanoparticles above 374 degreesC, the temperature at which explosive microbubbles form.
Read Original Article>>

May 26, 2010

Graphene as quantum dots

Nanoelectronics is a major — and important — field right now, and graphene and its cousin graphane are very important materials research components. Both of the nanomaterials are getting a lot of  hype, particularly graphene, but there’s far too much smoke for there not to be at least a little fire. It’s exciting to keep watch on the news to see the breakthroughs as they happen, and eventually cover real-world, market-ready uses for graphene and graphane.

The release:

Graphane yields new potential

Rice physicists dig theoretical wells to mine quantum dots

Graphane is the material of choice for physicists on the cutting edge of materials science, and Rice University researchers are right there with the pack – and perhaps a little ahead.

Researchers mentored by Boris Yakobson, a Rice professor of mechanical engineering and materials science and of chemistry, have discovered the strategic extraction of hydrogen atoms from a two-dimensional sheet of graphane naturally opens up spaces of pure graphene that look – and act – like quantum dots.

That opens up a new world of possibilities for an ever-shrinking class of nanoelectronics that depend on the highly controllable semiconducting properties of quantum dots, particularly in the realm of advanced optics.

The theoretical work by Abhishek Singh and Evgeni Penev, both postdoctoral researchers in co-author Yakobson’s group, was published online last week in the journal ACS Nano and will be on the cover of the print version in June. Rice was recently named the world’s No. 1 institution for materials science research by a United Kingdom publication.

Graphene has become the Flat Stanley of materials. The one-atom-thick, honeycomb-like form of carbon may be two-dimensional, but it seems to be everywhere, touted as a solution to stepping beyond the limits of Moore’s Law.

Graphane is simply graphene modified by hydrogen atoms added to both sides of the matrix, which makes it an insulator. While it’s still technically only a single atom thick, graphane offers great possibilities for the manipulation of the material’s semiconducting properties.

Quantum dots are crystalline molecules from a few to many atoms in size that interact with light and magnetic fields in unique ways. The size of a dot determines its band gap – the amount of energy needed to close the circuit – and makes it tunable to a precise degree. The frequencies of light and energy released by activated dots make them particularly useful for chemical sensors, solar cells, medical imaging and nanoscale circuitry.

Singh and Penev calculated that removing islands of hydrogen from both sides of a graphane matrix leaves a well with all the properties of quantum dots, which may also be useful in creating arrays of dots for many applications.

“We arrived at these ideas from an entirely different study of energy storage in a form of hydrogen adsorption on graphene,” Yakobson said. “Abhishek and Evgeni realized that this phase transformation (from graphene to graphane), accompanied by the change from metal to insulator, offers a novel palette for nanoengineering.”

Their work revealed several interesting characteristics. They found that when chunks of the hydrogen sublattice are removed, the area left behind is always hexagonal, with a sharp interface between the graphene and graphane. This is important, they said, because it means each dot is highly contained; calculations show very little leakage of charge into the graphane host material. (How, precisely, to remove hydrogen atoms from the lattice remains a question for materials scientists, who are working on it, they said.)

“You have an atom-like spectra embedded within a media, and then you can play with the band gap by changing the size of the dot,” Singh said. “You can essentially tune the optical properties.”

Along with optical applications, the dots may be useful in single-molecule sensing and could lead to very tiny transistors or semiconductor lasers, he said.

Challenges remain in figuring out how to make arrays of quantum dots in a sheet of graphane, but neither Singh nor Penev sees the obstacles as insurmountable.

“We think the major conclusions in the paper are enough to excite experimentalists,” said Singh, who will soon leave Rice to become an assistant professor at the Indian Institute of Science in Bangalore. “Some are already working in the directions we explored.”

“Their work is actually supporting what we’re suggesting, that you can do this patterning in a controlled way,” Penev said.

When might their calculations bear commercial fruit? “That’s a tough question,” Singh said. “It won’t be that far, probably — but there are challenges. I don’t know that we can give it a time frame, but it could happen soon.”

###

Funding from the Office of Naval Research supported the work. Computations were performed at the Department of Defense Supercomputing Resource Center at the Air Force Research Laboratory.

May 13, 2010

Molecular nanobots

Via KurzweilAI.net — very cool! As always, I’ve included the entire KurzweilAI post. This one is a bit longer than usual.

How to make a molecular nanobot
KurzweilAI.net, May 13, 2010

Scientists have programmed an autonomous molecular nanorobot made out of DNA to start, move, turn, and stop while following a DNA track.


(Paul Michelotti)

The development could ultimately lead to molecular systems that could be used for medical therapeutic devices and molecular-scale reconfigurable robots—robots made of many simple units that can reposition or even rebuild themselves to accomplish different tasks.

Molecular robots, in theory, could be programmed to sense their environment (say, the presence of disease markers on a cell), make a decision (that the cell is cancerous and needs to be neutralized), and act on that decision (deliver a cargo of cancer-killing drugs). Or they could be programmed to assemble complex molecular products.

“In normal robotics, the robot itself contains the knowledge about the commands, but with individual molecules, you can’t store that amount of information, so the idea instead is to store information on the commands on the outside,” says Nils G. Walter, professor of chemistry and director of the Single Molecule Analysis in Real-Time (SMART) Center at the University of Michigan in Ann Arbor. And you do that by “imbuing the molecule‘s environment with informational cues,” says Milan N. Stojanovic, a faculty member in the Division of Experimental Therapeutics at Columbia University.

“We were able to create such a programmed or ‘prescribed’ environment using DNA origami,” explains Hao Yan, professor of chemistry and biochemistry at Arizona State University. DNA origami is a type of self-assembledstructure made from DNA that can be programmed to form nearly limitless shapes and patterns. Exploiting the sequence-recognition properties of DNA base pairing, DNA origami are created from a long single strand of DNA and a mixture of different short synthetic DNA strands that bind to and “staple” the long DNA into the desired shape. The origami used in the Nature study was a rectangle that was 2 nanometers (nm) thick and roughly 100 nm on each side.

The researchers constructed a trail of molecular “bread crumbs” on the DNA origami track by stringing additional single-stranded DNA molecules, or oligonucleotides, off the ends of the staples. These represent the cues that tell the molecular robots what to do—start, walk, turn left, turn right, or stop, for example—akin to the commands given to traditional robots.

To build the 4-nm-diameter molecular robot, the researchers started with a common protein called streptavidin, which has four symmetrically placed binding pockets for a chemical moiety called biotin. Each robot leg is a short biotin-labeled strand of DNA, “so this way we can bind up to four legs to the body of our robot,” Walter says. “It’s a four-legged spider,” quips Stojanovic. Three of the legs are made of enzymatic DNA, which is DNA that binds to and cuts a particular sequence of DNA. The spider also is outfitted with a “start strand”—the fourth leg—that tethers the spider to the start site (one particular oligonucleotide on the DNA origami track). “After the robotis released from its start site by a trigger strand, it follows the track by binding to and then cutting the DNA strands extending off of the staple strands on the molecular track,” Stojanovic explains.

“Once it cleaves,” adds Yan, “the product will dissociate, and the leg will start searching for the next substrate.” In this way, the spider is guided down the path laid out by the researchers. Finally, explains Yan, “the robot stops when it encounters a patch of DNA that it can bind to but that it cannot cut,” which acts as a sort of flypaper.

Using atomic force microscopy and single-molecule fluorescence microscopy, the researchers were able to watch spiders crawling over the origami, showing that they were able to guide their molecular robots to follow four different paths.

More info: Caltech news and Molecular robots guided by prescriptive landscapes

May 12, 2010

Semi-conductor nanocrystals and quantum computing

Another step toward quantum computing.

The release:

Quantum move toward next generation computing

McGill researchers make important contribution to the development of quantum computing

This release is available in French.

IMAGE: These images show the electrostatic energy given off when electrons are added to a quantum dot. They were made with an atomic-force microscope.

Click here for more information.

Physicists at McGill University have developed a system for measuring the energy involved in adding electrons to semi-conductor nanocrystals, also known as quantum dots – a technology that may revolutionize computing and other areas of science. Dr. Peter Grütter, McGill’s Associate Dean of Research and Graduate Education, Faculty of Science, explains that his research team has developed a cantilever force sensor that enables individual electrons to be removed and added to a quantum dot and the energy involved in the operation to be measured.

Being able to measure the energy at such infinitesimal levels is an important step in being able to develop an eventual replacement for the silicon chip in computers – the next generation of computing. Computers currently work with processors that contain transistors that are either in an on or off position – conductors and semi-conductors – while quantum computing would allow processors to work with multiple states, vastly increasing their speed while reducing their size even more.

Although popularly used to connote something very large, the word “quantum” itself actually means the smallest amount by which certain physical quantities can change. Knowledge of these energy levels enables scientists to understand and predict the electronic properties of the nanoscale systems they are developing.

“We are determining optical and electronic transport properties,” Grütter said. “This is essential for the development of components that might replace silicon chips in current computers.”

IMAGE: These images show the electrostatic energy given off when electrons are added to a quantum dot. They were made with an atomic-force microscope.

Click here for more information.

The electronic principles of nanosystems also determine their chemical properties, so the team’s research is relevant to making chemical processes “greener” and more energy efficient. For example, this technology could be applied to lighting systems, by using nanoparticles to improving their energy efficiency. “We expect this method to have many important applications in fundamental as well as applied research,” said Lynda Cockins of McGill’s Department of Physics.

The principle of the cantilever sensors sounds relatively simple. “The cantilever is about 0.5 mm in size (about the thickness of a thumbnail) and is essentially a simple driven, damped harmonic oscillator, mathematically equivalent to a child’s swing being pushed,” Grütter explained. “The signal we measure is the damping of the cantilever, the equivalent to how hard I have to push the kid on the swing so that she maintains a constant height, or what I would call the ‘oscillation amplitude.’ “

Dr. Aashish Clerk, Yoichi Miyahara, and Steven D. Bennett of McGill’s Dept. of Physics, and scientists at the Institute for Microstructural Sciences of the National Research Council of Canada contributed to this research, which was published online late yesterday afternoon in the Proceedings of the National Academy of Sciences. The research received funding from the Natural Sciences and Engineering Research Council of Canada, le Fonds Québécois de le Recherche sur la Nature et les Technologies, the Carl Reinhardt Fellowship, and the Canadian Institute for Advanced Research.

###

Graphene transistor

Filed under: Science, Technology — Tags: , , , , , — David Kirkpatrick @ 12:23 am

One step toward nanoelectronics.

From the link:

For years, scientists and researchers have been looking into the properties of carbon nanotubes and graphene for use in nanoelectronics. “There is no real mass application of devices based on graphene and carbon nanotubes,” Zhenxing Wang tells PhysOrg.com. “This is really an opportunity for them to show their capabilities.”

Wang is part of a group at the Key Laboratory for the Physics and Chemistry of  at Peking University in Beijing. Along with Zhiyong Zhang, Huilong Xu, Li Ding, Sheng Wang, and Lian-Mao Peng, Wang tested a top-gate  field-effect transistor based frequency doubler in order to gauge its performance. They were able to show that a graphene based frequency doubler can provide more than 90% converting efficiency, while the corresponding value is not larger than 30% for conventional frequency doubler. Their work is published in : “A high-performance top-gate graphene field-effect transistor based frequency doubler.”

May 11, 2010

Graphene as a heat sink

Filed under: Science, Technology — Tags: , , , , — David Kirkpatrick @ 12:43 am

Nanotech news from UC Riverside.

The release:

Hot new material can keep electronics cool

Few atomic layers of graphene reveal unique thermal properties

IMAGE: Alexander Balandin is a professor of electrical engineering in the Bourns College of Engineering at the University of California, Riverside.

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Professor Alexander Balandin and a team of UC Riverside researchers, including Chun Ning Lau, an associate professor of physics, have taken another step toward new technology that could keep laptops and other electronic devices from overheating.

Balandin, a professor of electrical engineering in the Bourns College of Engineering, experimentally showed in 2008 that graphene, a recently discovered single-atom-thick carbon crystal, is a strong heat conductor. The problem for practical applications was that it is difficult to produce large, high quality single atomic layers of the material.

Now, in a paper published in Nature Materials, Balandin and co-workers found that multiple layers of graphene, which are easier to make, retain the strong heat conducting properties.

That’s also a significant discovery in fundamental physics. Balandin’s group, in addition to measurements, explained theoretically how the materials’ ability to conduct heat evolves when one goes from conventional three-dimensional bulk materials to two-dimensional atomically-thin films, such as graphene.

The results published in Nature Materials may have important practical applications in removal of dissipated hear from electronic devices.

Heat is an unavoidable by-product when operating electronic devices. Electronic circuits contain many sources of heat, including millions of transistors and interconnecting wiring. In the past, bigger and bigger fans have been used to keep computer chips cool, which improved performance and extended their life span. However, as computers have become faster and gadgets have gotten smaller and more portable the big-fan solution no longer works.

New approaches to managing heat in electronics include incorporating materials with superior thermal properties, such as graphene, into silicon computer chips. In addition, proposed three-dimension electronics, which use vertical integration of computer chips, would depend on heat removal even more, Balandin said.

Silicon, the most common electronic material, has good electronic properties but not so good thermal properties, particularly when structured at the nanometer scale, Balandin said. As Balandin’s research shows, graphene has excellent thermal properties in addition to unique electronic characteristics.

“Graphene is one of the hottest materials right now,” said Balandin, who is also chair of the Material Sciences and Engineering program. “Everyone is talking about it.”

Graphene is not a replacement for silicon, but, instead could be used in conjunction with silicon, Balandin said. At this point, there is no reliable way to synthesize large quantities of graphene. However, progress is being made and it could be possible in a year or two, Balandin said.

Initially, graphene would likely be used in some niche applications such as thermal interface materials for chip packaging or transparent electrodes in photovoltaic solar cells, Balandin said. But, in five years, he said, it could be used with silicon in computer chips, for example as interconnect wiring or heat spreaders. It may also find applications in ultra-fast transistors for radio frequency communications. Low-noise graphene transistors have already been demonstrated in Balandin’s lab.

Balandin published the Nature Materials paper with two of his graduate students Suchismita Ghosh, who is now at Intel Corporation, and Samia Subrina, Lau. one of her graduate students, Wenzhong Bao, and Denis L. Nika and Evghenii P. Pokatilov, visting researchers in Balandin’s lab who are based at the State University of Moldova.

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The University of California, Riverside (www.ucr.edu) is a doctoral research university, a living laboratory for groundbreaking exploration of issues critical to Inland Southern California, the state and communities around the world. Reflecting California’s diverse culture, UCR’s enrollment of over 19,000 is expected to grow to 21,000 students by 2020. The campus is planning a medical school and has reached the heart of the Coachella Valley by way of the UCR Palm Desert Graduate Center. The campus has an annual statewide economic impact of more than $1 billion.

May 5, 2010

Dracula would like this nanotech …

… because it’s perfectly non-reflecting.

The release:

Perfectly non-reflecting

Research News May 2010

A new nanocoating ensures a perfectly non-reflecting view on displays and through eyeglasses. The necessary surface structure is applied to the polymeric parts during manufacture, obviating the need for a separate process step. The hybrid coating has further advantages: the components are scratch-proof and easy to clean.

Link: download picture

Moths are the prototype. As they search for food at dusk they have to hide from predators. Their presence must not be betrayed by reflections on their facet eyes. On other insects these eyes shimmer, but the moth’s eyes are perfectly non-reflecting. Tiny protuberances smaller than the wavelength of light form a periodic structure on the surface. This nanostructure creates a gentle transition between the refractive indices of the air and the cornea. As a result, the reflection of light is reduced and the moth remains undetected.

Research scientists at the Fraunhofer Institute for Mechanics of Materials IWM in Freiburg have adopted this artifice and adapted it to a range of different applications. On eyeglasses, cell phone displays, fitting or panel covers, transparent surfaces are generally only useful if they allow viewing without light reflecting back. Whereas conventional methods apply the anti-reflective coating in a separate step after production, the Fraunhofer scientists have found a way of reducing light reflection during actual manufacture of the part or component: »We have modified conventional injection molding in such a way that the desired nanostructure is imparted to the surface during the process,« explains Dr. Frank Burmeister, project manager at the IWM.

For this the researchers have developed a hard material coating which reproduces the optically effective surface structure. »We use this to coat the molding tools,« says Burmeister. »When the viscous polymer melt is injected into the mold, the nanostructures are transferred directly to the component.« Because no second process step is required, manufacturers achieve an enormous cost saving and also increase efficiency. »Normally the component would have to undergo an additional separate process to apply the anti-reflex coating,« Burmeister adds.

Normal plexiglass and some anti-reflex coatings are particularly sensitive, but the scientists are producing wipe-resistant and scratch-proof surfaces. For this purpose the injection mold is additionally flooded with an ultra-thin organic substance made of polyurethane. Burmeister: »The substance runs into every crevice and hardens, like a two-component adhesive.« The result is an extremely thin nanocoating of polyurethane on which the optically effective surface structures, which are just one ten-thousandth of a millimeter thick, are also reproduced. Working in cooperation with industrial partners, the research scientists now aim to develop components for the auto industry, for example, which are not only attractive to look at but also hard-wearing and easy to clean.

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