To form practical nanotech circuits from arrays of nanowires, it is necessary to integrate different types of nanowires into multifunctional circuits. Two different types of nanowires (cadmium selenide for light sensors and germanium core/silicon shell for field-effect transistors) have been integrated on a chip to detect and amplify optical signals. From Lawrence Berkeley National Laboratory (credit PhysOrg.com) “A First in Integrated Nanowire Sensor Circuitry“:

Scientists at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory and the University of California at Berkeley have created the world’s first all-integrated sensor circuit based on nanowire arrays, combining light sensors and electronics made of different crystalline materials. Their method can be used to reproduce numerous such devices with high uniformity.

Nanostructures made with specific chemical, electronic, and other properties have a number of advantages over the same materials in bulk. For example, a nanowire is an ideal shape for a light detector; being virtually one-dimensional, practically “all surface,” a nanowire is not only highly sensitive to light energy, but its electronic response is greatly enhanced as well.

To be practical, however, the photosensors must be integrated with electronics on the same chip. And the materials that make an ideal photosensor are necessarily different from those that make a good transistor.

“Our integration of arrays of nanowires that perform separate functions and are made of heterogeneous substances — and doing this in a way that can be reproduced on a large scale in a controlled way — is a first,” says Ali Javey, who led the research team. Javey is a staff scientist in Berkeley Lab’s Materials Sciences Division (MSD) and an assistant professor in the Electrical Engineering and Computer Sciences Department at UC Berkeley. He and his colleagues report their work in the August 1 edition of Proceedings of the National Academy of Sciences [abstract].

…Results of the Javey group’s integrated nanowire circuit showed successful photoresponse in 80 percent of the circuits, with fairly small variations among them. Where circuits did fail, the causes were due to defects in fabrication of the circuit connections (10 percent), failure in photosensor printing (5 percent), or defective nanowires (5 percent). The relatively high yield of complex operational circuits proved the potential of the technology, with improvements readily achievable by optimizing nanowire synthesis and fabrication of the devices.

“In the future, we can foresee using a variety of different optical sensors to create nanoscale devices sensitive to multiple colors in high-resolution,” says Javey. “And that’s just the beginning. We contemplate printing nanowire sensor circuitry — photosensors, chemical sensors, biosensors — not on silicon but on paper or plastic tape. This could be used, easily and with instant results, where spills have occurred, or to test air quality, or to test for disease organisms — almost any use for a sensor that you can imagine.”

—Jim

Nanotech methods offer a variety of ways to alter the properties of nanostructures to optimize drug delivery. A process that allows the fabrication of different shapes of particles varying in size from about 100 nm to several micrometers demonstrates that long particles are internalized by cancer cells more efficiently than are round particles. From the University of North Carolina at Chapel Hill (credit PhysOrg.com) “UNC study: shape, not just size, impacts effectiveness of emerging nano-medicine therapies“:

In the budding field of nanotechnology, scientists already know that size does matter.

But now, researchers at the University of North Carolina at Chapel Hill have shown that shape matters even more — a finding that could lead to new and more effective methods for treating cancer and other diseases, from diabetes and multiple sclerosis to arthritis and obesity.

A team of researchers led by Joseph DeSimone, Ph.D., Chancellor’s Eminent Professor of Chemistry in UNC’s College of Arts and Sciences and William R. Kenan, Jr. Distinguished Professor of Chemical Engineering at North Carolina State University, and Stephanie Gratton, a graduate student in DeSimone’s lab, have demonstrated that nanoparticles designed with a specific shape, size and surface chemistry are taken up into cells and behave differently within cells depending on these attributes.

Their findings appear in this week’s online early edition of the journal PNAS, the Proceedings of the National Academy of Sciences [abstract].

…Using PRINT® (Particle Replication in Non-wetting Templates) technology — a technique invented in DeSimone’s lab that allows scientists to design and produce “custom-made” nanoparticles — the UNC researchers made particles with specific shapes, sizes and surface charges. DeSimone said the aim is to optimize particle attributes for specific therapeutic objectives.

“This would mean that we could deliver lower dosages of drugs to specific cells and tissues in the body and actually be more effective in treating the cancer,” said DeSimone, who is also a member of UNC’s Lineberger Comprehensive Cancer Center and the co-principal investigator for the Carolina Center for Cancer Nanotechnology Excellence.

…the scientists discovered that long, rod-shaped particles (diameter, 150 nanometers; height, 450 nanometers) were internalized by cells approximately four times faster than lower aspect ratio particles (diameter, 200 nanometers; height, 200 nanometers), and traveled significantly further into the cells as well.

More information about the PRINT® process can be found on the web site of the DeSimone research group.
—Jim

Nanotech has fashioned from graphene a one atom-thick membrane impermeable even to helium gas. From “World’s Thinnest Balloon Developed: Just One Atom Thick“:

Researchers in New York are reporting development of the world’s thinnest balloon, made of a single layer of graphite just one atom thick. This so-called graphene sealed microchamber is impermeable to even the tiniest airborne molecules, including helium.

It has a range of applications in sensors, filters, and imaging of materials at the atomic level.

Paul L. McEuen and colleagues note that membranes are fundamental components of a wide variety of physical, chemical and biological systems, found in everything from cellular compartments to mechanical pressure sensing. Graphene, a single layer of graphite, is the upper limit: A chemically stable and electrically conducting membrane just one atom thick. The researchers wanted to answer whether such an atomic membrane would be impermeable to gas molecules and easily incorporated into other devices.

Their data showed that graphene membranes were impermeable to even the smallest gas molecules. These results show that single atomic sheets can be integrated with microfabricated structures to create a new class of atomic scale membrane-based devices.

The research was published in Nano Letters (abstract)
—Jim

Nanotech has taken a major step along the road to molecular electronics with the demonstration that one molecule of benzene can form a highly conductive junction between two platinum electrodes. From an article on nanotechweb.org, written by Belle Dumé (requires free registration) “Ballistic breakthrough could lead to molecular logic gates“:

The first highly-conductive connection between a single organic molecule and a metal electrode has been made by an international team of physicists. This achievement could lead to the development of ‘molecular electronics’ devices with the potential to be smaller and faster than conventional transistors and logic gates.

The majority of electronic devices are made from just a handful of semiconductor materials — the most common being silicon. However, some organic molecules such as DNA appear to have electronic properties similar to traditional semiconductors and some researchers believe that some types of molecules could be used to make electronic devices.

A potential benefit of such devices is that molecules are extremely small compared to semiconductor structures, which could help manufacturers pack more and more circuits onto a chip.

However, it has proven very difficult to connect single molecules to a metal electrode such that electrons are conducted easily between the two. These junctions are essential for making real-world devices like transistors and logic gates.

…Now, Jan van Ruitenbeek of the University of Leiden in the Netherlands along with colleagues in Australia, Germany and Spain may have solved this problem by making the first highly conductive molecular junctions. This involved binding benzene molecules directly to platinum metal electrodes, and the team found that the conductance of these devices reaches the maximum value possible for a single electron channel.

…”What makes this work stand out is that [the scientists] have presented a new way to attach organic molecules to metal electrodes, by forming a direct metal-carbon bond, and have proven conclusively that their devices have a strong metal-molecule link,” commented Latha Venkataraman of Columbia University in an American Physical Society Viewpoint article on the research. “This enables them to overcome a major barrier in molecular based devices,” she said.

The research was published in Physical Review Letters (abstract).
—Jim

The SmallTimes web site reports the introduction of H.R. 6661, which establishes a prize competition for five key areas of nanotech. From “Nanotechnology prize competition bill to drive U.S. innovation“:

Congressman Dan Lipinski (D-IL) , Vice Chairman of the House Science and Technology Committee, and Congressman (R-MO) Todd Akin, have introduced H.R. 6661, the Nanotechnology Innovation and Prize Competition Act, which establishes an X-Prize competition for nanotechnology.

H.R. 6661 would stimulate public-private partnership and focus investment towards key goals. The bill identifies five key categories — green nanotechnology, alternative energy, human health, nanoelectronics, and commercialization of consumer products — and establishes a board comprised of government and private sector experts to select criteria for prize competitions.

…The bill also authorizes the government to contract with an outside organization, such as the X-PRIZE Foundation, to administer the competition. This organization, and the board, also will recruit private contributions to fund the prize awards. In this way, H.R. 6661 enables the government to leverage a relatively small amount of resources to stimulate a much greater level of investment in nanotech research.

—Jim

A pioneering UK program aimed at developing a nanofactory has made a £1.53M ($3M) award to Professor Philip Moriarty of the University of Nottingham to support a five-year series of experiments to investigate the possibility of diamond mechanosynthesis, testing the theoretical proposals recently made by Robert Freitas and Ralph Merkle. Details are contained in the following press release from the Nanofactory Collaboration: “Nanofactory Collaboration Colleague Awarded $3M to Conduct First Diamond Mechanosynthesis Experiments“

Professor Philip Moriarty [1] of the Nanoscience Group [2] in the School of Physics at the University of Nottingham (U.K.) [3] has been awarded a five-year £1.53M ($3M) grant [4] by the U.K. Engineering and Physical Sciences Research Council (EPSRC) [5] to perform a series of laboratory experiments designed to investigate the possibility of diamond mechanosynthesis (DMS). DMS is a proposed method for building diamond nanostructures, atom by atom, using the techniques of scanning probe microscopy under ultra-high vacuum conditions. Moriarty’s project, titled “Digital Matter? Towards Mechanised Mechanosynthesis,” was funded under the Leadership Fellowship program [6] of EPSRC. Moriarty’s experiments begin in October 2008.

The Nottingham work grew out of continuing discussions on DMS between Moriarty and Robert Freitas [7], a Senior Research Fellow at the Institute for Molecular Manufacturing (IMM) (Palo Alto, California, U.S.) [8]. These discussions started in January 2005 [9].

Freitas and Ralph Merkle [10], also a Senior Fellow at IMM, founded the Nanofactory Collaboration [11] in 2001 to pursue molecular manufacturing via DMS. Since then they have produced a series of papers [12,13] reporting a set of careful density functional theory (DFT) and quantum chemistry calculations on fundamental mechanosynthetic reactions in diamondoid systems. In April 2008 the two IMM researchers published the results [13] of a comprehensive three-year project to computationally analyze a complete set of DMS reaction sequences and an associated minimal set of tooltips that could be used to build basic diamond and graphene (e.g., carbon nanotube) structures. These structures include all of the tools themselves along with the necessary tool recharging reactions. A particularly useful result of this study was the proposal of an experimentally viable route towards the fabrication of a rechargeable toolset that can extract hydrogen, deposit carbon, and donate hydrogen to a diamond surface.

Moriarty is interested in testing the viability of positionally-controlled atom-by-atom fabrication of diamondoid materials as described in the Freitas-Merkle minimal toolset theory paper. Moriarty’s efforts will be the first time that specific predictions of DFT in the area of mechanosynthesis will be rigorously tested by experiment. His work also directly addresses the requirement for “proof of principle” mechanosynthesis experiments requested in the 2006 National Nanotechnology Initiative (NNI) review [14], in the 2007 Battelle/Foresight nanotechnology roadmap [15], and by EPSRC’s Strategic Advisor for Nanotechnology, Richard Jones (Physics, Sheffield University, U.K.) [16].

“We congratulate Philip for his tremendous success in securing funding for this pathbreaking effort,” said Freitas. “We look forward to working together closely with his experimental team as this exciting project goes forward over the next five years.”

“We invite computational theorists and scanning probe experimentalists in the nanoscience community to join our Collaboration,” added Merkle. “There’s lots of interesting work to do. The first important steps toward practical realization are now underway.”

The EPSRC announcement of the grant can be found here.
—Jim

From The Economist, a look at Russia’s technology, including nanotech:

After years of high oil prices, money is again no object: in 2007 Russia put 130 billion roubles ($5.5 billion) into a state corporation for nanotechnologies that is being likened to the Manhattan Project…

But the big problem for high technology in Russia is neither money nor ideas. It is the country’s all-pervasive bureaucracy, weak legal system and culture of corruption. This may explain why the nanotechnology corporation has so far found only one project to invest in (and that is registered in the Netherlands).

On a visit to Russia in 2006 I was told to expect about half of Russia’s nanotech funding to be sidetracked due to corruption. Maybe they are going slowly on purpose, to try to reduce that. —Christine

Nanotech researchers have constructed a UV laser that they expect will eventually be able to manipulate and precisely deposit Group III and Group V atoms to construct composite materials atom-by-atom. From nanotechweb.org, written by Jacqueline Hewett (requires free registration) “UV laser builds structures atom-by-atom“:

A laser system emitting at 326 nm could be ideal for manipulating Group three atoms such as indium (In), say researchers from the University of Bonn in Germany. The source looks particularly promising for atomic nanofabrication (ANF), an application involving the precise handling and direct deposition of atoms using laser light.

We are experimenting with a laser-cooled In atomic beam,” researcher Jae-Ihn Kim from Bonn’s Institute of Applied Physics told optics.org. “The goal of our research is to generate a fully 3D structured (In,Al)As crystal with periodically modulated In concentration. It is conceivable to generate fully 3D nanostructures with ANF.”

While the potential of ANF is clear, it relies on the availability of lasers emitting at the short ultraviolet wavelengths that match the transitions found in group three atoms. Indium, for example, has a transition at 325.6 nm. This is where Kim and his colleague Dieter Meschede come in with their fibre-based source that frequency triples 977 nm light to 326 nm.

…With a practical 326 nm source in place, Kim has several goals. “In the short term, an indium atomic beam will be laser collimated to enhance the beam flux and reduce the transverse velocity of indium atoms in the beam, which is the requirement to generate narrow structures,” he said. “In the long term, a source of single indium atoms may be constructed to generate structures more accurately on an atom-by-atom basis.”

Kim and Meschede also plan to extend the ANF technique to Group five elements, with a view to creating novel composite materials.

The research was published in Optics Express (abstract).
—Jim

Many nanotech applications would be furthered by the development of efficient and flexible methods for forming large areas of nanometer-scale arrays created by molecular assembly. Sturdy structures ordered with nanometer precision have now been formed by combining supramolecular assembly of ordered networks with self-assembled monolayers. From Chemistry World, written by Ruth Tunnell “Nanostructures made easy“:

Scotland-based chemists have invented a new way to build nanoscale arrays of molecules over a large surface area: a technique that may be key to making nanostructures in sophisticated sensors, catalysts, and tiny computer parts.

Their solution-based chemistry works by corralling atoms into tiny dimples, themselves created when molecules self-assemble onto a gold surface.

‘We have shown that it is possible to control the assembly of single molecules,’ says Manfred Buck, who led the group at St Andrews University. ‘The copper atoms in our final structure are less than 5 nanometres apart, which opens up the possibility of studying materials with extremely small dimensions.’

The team’s chemical patterning provides an alternative route to nanostructures created by conventional lithography, which etches away patterns in surfaces, but can struggle to be precise on scales of a few nanometres over large areas.

Buck’s team first created a honeycomb-shaped network on top of a gold surface, by mixing together melamine and a derivative of perylene (perylene-3,4,9,10-tetracarboxylic diimide or PTCDI). These two molecules spontaneously form a supramolecular network over the surface, creating pores which can be filled by other particles.

The chemistry of this spontaneous network-forming is well understood. The allure of forming a template which could subsequently be used to sculpt structures means the system has been investigated many times before. But this type of assembly normally requires high vacuum conditions so that it can be seen with scanning tunnelling microscopy, and there is little chance of using the fragile structure in real applications.

Buck’s network, by contrast, was stable enough to be dunked in different solutions of thiols (molecules with sulfur caps). This allowed monolayer films of thiol molecules to organise into coils inside the pores - as the sulfur atoms preferred to be near the gold than lie on top of the melamine/PTCDI layer. The team finally inserted copper atoms between the gold substrate and thiol molecules, making a nanoscale atomic structure strong enough to be handled under ambient conditions.

The research was published in Nature (abstract).
—Jim

A role for nanotech applications can be seen in the responses to the US energy crisis made by both candidates for the US Presidency. In remarks prepared for delivery in Lansing, Michigan Senator Barack Obama called for new energy for America. Among the many steps he advocated:

The second step I’ll take is to require that 10% of our energy comes from renewable sources by the end of my first term — more than double what we have now. To meet these goals, we will invest more in the clean technology research and development that’s occurring in labs and research facilities all across the country and right here at MSU, where you’re working with farm owners to develop this state’s wind potential and developing nanotechnology that will make solar cells cheaper.

A recent MSU news release highlighted the energy applications of a new nanomaterial developed in the laboratory of MSU researcher Lawrence Drzal—xGnP Exfoliated Graphite NanoPlatelets.

“XGnP can either be used as an additive to plastics or by itself it can make a transformational change in the performance of many advanced electronic and energy devices,” Drzal said. “It can do so because it’s a nanoparticle with a unique shape made from environmentally benign carbon, and it can be made at a very reasonable cost.”

As a step toward solving American energy problems, Senator John McCain has suggested a national prize of $300 million for anyone who can develop a better, more efficient car battery. Although Senator McCain did not mention nanotechnology in his proposal, nanotech solutions for better batteries were mentioned in several comments posted in response to the article.
—Jim