World's smallest radio stations: Two molecules communicate via single photons

 We know since the dawn of modern physics that although events in our everyday life can be described by classical physics, the interaction of light and matter is down deep governed by the laws of quantum mechanics. Despite this century-old wisdom, accessing truly quantum mechanical situations remains nontrivial, fascinating and noteworthy even in the laboratory. Recently, interest in this area has been boosted beyond academic curiosity because of the potential for more efficient and novel forms of information processing.

In one of the most basic proposals, a single atom or molecule acts as a quantum bit that processes signals that have been delivered via single photons. In the past twenty years scientists have shown that single molecules can be detected and single photons can be generated. However, excitation of a molecule with a photon had remained elusive because the probability that a molecule sees and absorbs a photon is very small. As a result, billions of photons per second are usually impinged on a molecule to obtain a signal from it.

One common way to get around this difficulty in atomic physics has been to build a cavity around the atom so that a photon remains trapped for long enough times to yield a favorable interaction probability. Scientists at ETH Zurich and Max Planck Institute for the Science of Light in Erlangen have now shown that one can even interact a flying photon with a single molecule. Among many challenges in the way of performing such an experiment is the realization of a suitable source of single photons, which have the proper frequency and bandwidth. Although one can purchase lasers at different colors and specifications, sources of single photons are not available on the market.

So a team of scientists led by Professor Vahid Sandoghdar made its own. To do this, they took advantage of the fact that when an atom or molecule absorbs a photon it makes a transition to a so-called excited state. After a few nanoseconds (one thousand millionth of a second) this state decays to its initial ground state and emits exactly one photon. In their experiment, the group used two samples containing fluorescent molecules embedded in organic crystals and cooled them to about 1.5 K (-272 °C). Single molecules in each sample were detected by a combination of spectral and spatial selection.

To generate single photons, a single molecule was excited in the “source” sample. When the excited state of the molecule decayed the emitted photons were collected and tightly focused onto the “target” sample at a distance of a few meters. To ensure that a molecule in that sample “sees” the incoming photons, the team had to make sure that they have the same frequency. Furthermore, the precious single photons had to interact with the target molecule in an efficient manner. A molecule is about one nanometer is size (100000 times smaller than the diameter of a human hair) but the focus of a light beam cannot be smaller than a few hundred nanometers.

This usually means that most of the incoming light goes around the molecule, i.e. without them seeing each other. However, if the incoming photons are resonant with the quantum mechanical transition of the molecule, the latter acts as a disk that is comparable to the area of the focused light. In this process the molecule acts as an antenna that grabs the light waves in its vicinity. The results of the study published in Physical Review Letters provide the first example of long-distance communication between two quantum optical antennas in analogy to the 19th century experiments of Hertz and Marconi with radio antennas. In those early efforts, dipolar oscillators were used as transmitting and receiving antennas.

In the current experiment, two single molecules mimic that scenario at optical frequencies and via a nonclassical optical channel, namely a single-photon stream. This opens many doors for further exciting experiments in which single photons act as carriers of quantum information to be processed by single emitters.

The experimental work was performed at ETH Zurich before the group of Prof. Sandoghdar moved to the newly founded Max Planck Institute for the Science of Light in Erlangen in 2011.

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The above story is reprinted from materials provided by ETH Zürich, via AlphaGalileo.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

Y. L. A. Rezus, S. G. Walt, R. Lettow, A. Renn, G. Zumofen, S. Götzinger, and V. Sandoghdar. Single-Photon Spectroscopy of a Single Molecule. Physical Review Letters, 108, 093601; Feb 27, 2012

Note: If no author is given, the source is cited instead.

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The world's smallest magnetic data storage unit

Scientists from IBM and the German Center for Free-Electron Laser Science (CFEL) have built the world's smallest magnetic data storage unit. It uses just twelve atoms per bit, the basic unit of information, and squeezes a whole byte (8 bit) into as few as 96 atoms. A modern hard drive, for comparison, still needs more than half a billion atoms per byte. CFEL is a joint venture of the research centre Deutsches Elektronen-Synchrotron DESY in Hamburg, the Max-Planck-Society (MPG) and the University of Hamburg. "With CFEL the partners have established an innovative institution on the DESY campus, delivering top-level research across a broad spectrum of disciplines," says DESY research director Edgar Weckert.

The nanometre data storage unit was built atom by atom with the help of a scanning tunneling microscope (STM) at IBM's Almaden Research Center in San Jose, California. The researchers constructed regular patterns of iron atoms, aligning them in rows of six atoms each. Two rows are sufficient to store one bit. A byte correspondingly consists of eight pairs of atom rows. It uses only an area of 4 by 16 nanometres (a nanometre being a millionth of a millimetre). "This corresponds to a storage density that is a hundred times higher compared to a modern hard drive," explains Sebastian Loth of CFEL, lead author of the Science paper.

Data are written into and read out from the nano storage unit with the help of an STM. The pairs of atom rows have two possible magnetic states, representing the two values '0' and '1' of a classical bit. An electric pulse from the STM tip flips the magnetic configuration from one to the other. A weaker pulse allows to read out the configuration, although the nano magnets are currently only stable at a frosty temperature of minus 268 degrees Centigrade (5 Kelvin). "Our work goes far beyond current data storage technology," says Loth. The researchers expect arrays of some 200 atoms to be stable at room temperature. Still it will take some time before atomic magnets can be used in data storage.

For the first time, the researchers have managed to employ a special form of magnetism for data storage purposes, called antiferromagnetism. Different from ferromagnetism, which is used in conventional hard drives, the spins of neighbouring atoms within antiferromagnetic material are oppositely aligned, rendering the material magnetically neutral on a bulk level. This means that antiferromagnetic atom rows can be spaced much more closely without magnetically interfering with each other. Thus, the scientist managed to pack bits only one nanometre apart.

"Looking at the shrinking of electronics components we wanted to know if this can be driven into the realm of single atoms," explains Loth. But instead of shrinking existing components the team chose the opposite approach: "Starting with the smallest thing - single atoms - we built data storage devices one atom at a time," says IBM research staff member Andreas Heinrich. The required precision is only mastered by few research groups worldwide.

"We tested how large we have to build our unit to reach the realm of classical physics," explains Loth, who moved from IBM to CFEL four months ago. Twelve atoms emerged as the minimum with the elements used. "Beneath this threshold quantum effects blur the stored information." If these quantum effects can somehow be employed for an even denser data storage is currently a topic of intense research.

With their experiments the team have not only built the smallest magnetic data storage unit ever, but have also created an ideal testbed for the transition from classical to quantum physics. "We have learned to control quantum effects through form and size of the iron atom rows," explains Loth, leader of the Max Planck research group 'dynamics of nanoelectric systems' at CFEL in Hamburg and the Max-Planck-Institute for Solid State Research at Stuttgart, Germany. "We can now use this ability to investigate how quantum mechanics kicks in. What seperates quantum magnets from classical magnets? How does a magnet behave at the frontier between both worlds? These are exciting questions that soon could be answered."

A new CFEL laboratory offering ideal conditions for this research will enable Loth to follow up these questions. "With Sebastian Loth, one of the world's leading scientists in the field of time-resolved scanning tunneling microscopy has joined CFEL," stresses CFEL research coordinator Ralf Köhn. "This perfectly complements our existing expertise for the investigation of the dynamics in atomic and molecular systems."

Original publication:
Sebastian Loth, Susanne Baumann, Christopher P. Lutz, D. M. Eigler, Andreas J. Heinrich; Bistability in Atomic-Scale Antiferromagnets; Science, 13. Januar 2012

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Targeted proton transfer within a molecule: Smallest conceivable switch

 For a long time miniaturization has been the magic word in electronics. Dr. Willi Auwaerter and Professor Johannes Barth, together with their team of physicists at the Technische Universitaet Muenchen (TUM), have now presented a novel molecular switch in the journal Nature Nanotechnology. Decisive for the functionality of the switch is the position of a single proton in a porphyrin ring with an inside diameter of less than half a nanometer. The physicists can set four distinct states on demand.

Porphyins are ring-shaped molecules that can flexibly change their structure, making them useful for a wide array of applications. Tetraphenylporphyrin is no exception: It likes to take on a saddle shape and is not limited in its functionality when it is anchored to a metal surface. The molecule holds has a pair of hydrogen atoms that can change their positions between two configurations each. At room temperature this process takes place continuously at an extremely rapid rate.

In their experiment, the scientists suppressed this spontaneous movement by cooling the sample. This allowed them to induce and observe the entire process in a single molecule using a scanning tunneling microscope. This kind of microscope is particularly well suited for the task since -- in contrast to other methods -- it can be used not only to determine the initial and final states, but also allows the physicists to control the hydrogen atoms directly. In a further step they removed one of the two protons from the inside of the porphyrin ring. The remaining proton could now take on any one of four positions. A tiny current that flows through the fine tip of the microscope stimulates the proton transfer, setting a specific configuration in the process.

Although the respective positions of the hydrogen atoms influence neither the basic structure of the molecule nor its bond to the metallic surface, the states are not identical. This small but significant difference, taken together with the fact that the process can be arbitrarily repeated, forms the basis of a switch whose state can be changed up to 500 times per second. A single tunneled electron initiates the proton transfer.

The molecular switch has a surface area of only one square nanometer, making it the smallest switch implemented to date. The physicists are thrilled by their demonstration and are also very happy about new insights into the mechanism behind the proton transfer resulting from their study. Knud Seufert played a key role with his experiments: "To operate a four-state switch by moving a single proton within a molecule is really fascinating and represents a true step forward in nano-scale technologies."

This research was funded by the European Research Council (ERC Advanced Grant MolArt, No. 247299), the Excellence Cluster Munich-Centre for Advanced Photonics (MAP) and the Institute for Advanced Study of the TU Muenchen.

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The above story is reprinted from materials provided by Technische Universitaet Muenchen.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

Willi Auwärter, Knud Seufert, Felix Bischoff, David Ecija, Saranyan Vijayaraghavan, Sushobhan Joshi, Florian Klappenberger, Niveditha Samudrala, Johannes V. Barth. A surface-anchored molecular four-level conductance switch based on single proton transfer. Nature Nanotechnology, 2011; DOI: 10.1038/NNANO.2011.211

World's smallest steam engine: Heat engine measuring only a few micrometers works as well as its larger counterpart, although it sputters

 What would be a case for the repair shop for a car engine is completely normal for a micro engine. If it sputters, this is caused by the thermal motions of the smallest particles, which interfere with its running. Researchers at the University of Stuttgart and the Stuttgart-based Max Planck Institute for Intelligent Systems have now observed this with a heat engine on the micrometre scale. They have also determined that the machine does actually perform work, all things considered. Although this cannot be used as yet, the experiment carried out by the researchers in Stuttgart shows that an engine does basically work, even if it is on the microscale. This means that there is nothing, in principle, to prevent the construction of highly efficient, small heat engines.

A technology which works on a large scale can cause unexpected problems on a small one. And these can be of a fundamental nature. This is because different laws prevail in the micro- and the macroworld. Despite the different laws, some physical processes are surprisingly similar on both large and small scales. Clemens Bechinger, Professor at the University of Stuttgart and Fellow of the Max Planck Institute for Intelligent Systems, and his colleague Valentin Blickle have now observed one of these similarities.

"We've developed the world's smallest steam engine, or to be more precise the smallest Stirling engine, and found that the machine really does perform work," says Clemens Bechinger. "This was not necessarily to be expected, because the machine is so small that its motion is hindered by microscopic processes which are of no consequence in the macroworld." The disturbances cause the micromachine to run rough and, in a sense, sputter.

The laws of the microworld dictated that the researchers were not able to construct the tiny engine according to the blueprint of a normal-sized one. In the heat engine invented almost 200 years ago by Robert Stirling, a gas-filled cylinder is periodically heated and cooled so that the gas expands and contracts. This makes a piston execute a motion with which it can drive a wheel, for example.

"We successfully decreased the size of the essential parts of a heat engine, such as the working gas and piston, to only a few micrometres and then assembled them to a machine," says Valentin Blickle. The working gas in the Stuttgart-based experiment thus no longer consists of countless molecules, but of only one individual plastic bead measuring a mere three micrometres (one micrometre corresponds to one thousandth of a millimetre) which floats in water. Since the colloid particle is around 10,000 times larger than an atom, researchers can observe its motion directly in a microscope.

The physicists replaced the piston, which moves periodically up and down in a cylinder, by a focused laser beam whose intensity is periodically varied. The optical forces of the laser limit the motion of the plastic particle to a greater and a lesser degree, like the compression and expansion of the gas in the cylinder of a large heat engine. The particle then does work on the optical laser field. In order for the contributions to the work not to cancel each other out during compression and expansion, these must take place at different temperatures. This is done by heating the system from the outside during the expansion process, just like the boiler of a steam engine. The researchers replaced the coal fire of an old-fashioned steam engine with a further laser beam that heats the water suddenly, but also lets it cool down as soon as it is switched off.

The fact that the Stuttgart machine runs rough is down to the water molecules which surround the plastic bead. The water molecules are in constant motion due to their temperature and continually collide with the microparticle. In these random collisions, the plastic particle constantly exchanges energy with its surroundings on the same order of magnitude as the micromachine converts energy into work. "This effect means that the amount of energy gained varies greatly from cycle to cycle, and even brings the machine to a standstill in the extreme case," explains Valentin Blickle. Since macroscopic machines convert around 20 orders of magnitude more energy, the tiny collision energies of the smallest particles in them are not important.

The physicists are all the more astonished that the machine converts as much energy per cycle on average despite the varying power, and even runs with the same efficiency as its macroscopic counterpart under full load. "Our experiments provide us with an initial insight into the energy balance of a heat engine operating in microscopic dimensions. Although our machine does not provide any useful work as yet, there are no thermodynamic obstacles, in principle, which prohibit this in small dimensions," says Clemens Bechinger. This is surely good news for the design of reliable, highly efficient micromachines.

The above story is reprinted from materials provided by Max-Planck-Gesellschaft.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

Valentin Blickle and Clemens Bechinger. Realization of a micrometre-sized stochastic heat engine. Nature Physics, 11 December 2011 DOI: 10.1038/NPHYS2163

Nano car has molecular 4-wheel drive: Smallest electric car in the world

 Reduced to the max: the emission-free, noiseless 4-wheel drive car, jointly developed by Empa researchers and their Dutch colleagues, represents lightweight construction at its most extreme. The nano car consists of just a single molecule and travels on four electrically-driven wheels in an almost straight line over a copper surface. The "prototype" can be admired on the cover of the latest edition of Nature.

To carry out mechanical work, one usually turns to engines, which transform chemical, thermal or electrical energy into kinetic energy in order to, say, transport goods from A to B. Nature does the same thing; in cells, so-called motor proteins -- such as kinesin and the muscle protein actin -- carry out this task. Usually they glide along other proteins, similar to a train on rails, and in the process "burn" ATP (adenosine triphosphate), the chemical fuel, so to speak, of the living world.

A number of chemists aim to use similar principles and concepts to design molecular transport machines, which could then carry out specific tasks on the nano scale. According to an article in the latest edition of science magazine "Nature," scientists at the University of Groningen and at Empa have successfully taken "a decisive step on the road to artificial nano-scale transport systems." They have synthesised a molecule from four rotating motor units, i.e. wheels, which can travel straight ahead in a controlled manner. "To do this, our car needs neither rails nor petrol; it runs on electricity. It must be the smallest electric car in the world -- and it even comes with 4-wheel drive" comments Empa researcher Karl-Heinz Ernst.

Range per tank of fuel: still room for improvement

The downside: the small car, which measures approximately 4x2 nanometres -- about one billion times smaller than a VW Golf -- needs to be refuelled with electricity after every half revolution of the wheels -- via the tip of a scanning tunnelling microscope (STM). Furthermore, due to their molecular design, the wheels can only turn in one direction. "In other words: there's no reverse gear," says Ernst, who is also a professor at the University of Zurich, laconically.

According to its "construction plan" the drive of the complex organic molecule functions as follows: after sublimating it onto a copper surface and positioning an STM tip over it leaving a reasonable gap, Ernst's colleague, Manfred Parschau, applied a voltage of at least 500 mV. Now electrons should "tunnel" through the molecule, thereby triggering reversible structural changes in each of the four motor units. It begins with a cis-trans isomerisation taking place at a double bond, a kind of rearrangement -- in an extremely unfavourable position in spatial terms, though, in which large side groups fight for space. As a result, the two side groups tilt to get past each other and end up back in their energetically more favourable original position -- the wheel has completed a half turn. If all four wheels turn at the same time, the car should travel forwards. At least, according to theory based on the molecular structure.

To drive or not to drive -- a simple question of orientation

And this is what Ernst and Parschau observed: after ten STM stimulations, the molecule had moved six nanometres forwards -- in a more or less straight line. "The deviations from the predicted trajectory result from the fact that it is not at all a trivial matter to stimulate all four motor units at the same time," explains "test driver" Ernst.

Another experiment showed that the molecule really does behave as predicted. A part of the molecule can rotate freely around the central axis, a C-C single bond -- the chassis of the car, so to speak. It can therefore "land" on the copper surface in two different orientations: in the right one, in which all four wheels turn in the same direction, and in the wrong one, in which the rear axle wheels turn forwards but the front ones turn backwards -- upon excitation the car remains at a standstill. Ernst und Parschau were able to observe this, too, with the STM.

Therefore, the researchers have achieved their first objective, a "proof of concept," i.e. they have been able to demonstrate that individual molecules can absorb external electrical energy and transform it into targeted motion. The next step envisioned by Ernst and his colleagues is to develop molecules that can be driven by light, perhaps in the form of UV lasers.

Story Source:

The above story is reprinted from materials provided by Empa.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

Tibor Kudernac, Nopporn Ruangsupapichat, Manfred Parschau, Beatriz Maciá, Nathalie Katsonis, Syuzanna R. Harutyunyan, Karl-Heinz Ernst, Ben L. Feringa. Electrically driven directional motion of a four-wheeled molecule on a metal surface. Nature, 2011; 479 (7372): 208 DOI: 10.1038/nature10587

Note: If no author is given, the source is cited instead.

New technique maps twin faces of smallest Janus nanoparticles

 New drug delivery systems, solar cells, industrial catalysts and video displays are among the potential applications of special particles that possess two chemically distinct sides. These particles are named after the two-faced Roman god Janus and their twin chemical faces allow them to form novel structures and new materials.

However, as scientists have reduced the size of Janus particles down to a few nanometers in diameter -- about the size of individual proteins, which has the greatest potential for drug therapy -- their efforts have been hampered because they haven't had a way to accurately map the surfaces of the particles that they produce. This uncertainty has made it difficult to evaluate the effectiveness of these particles for various applications and to improve the methods researchers are using to produce them.

Now, a team of Vanderbilt chemists has overcome this obstacle by developing the first method that can rapidly and accurately map the chemical properties of the smallest of these Janus nanoparticles.

The results, published online this month in the German chemistry journal Angewandte Chemie, address a major obstacle that has slowed the development and application of the smallest Janus nanoparticles.

The fact that Janus particles have two chemically distinct faces makes them potentially more valuable than chemically uniform particles. For example, one face can hold onto drug molecules while the other is coated with linker molecules that bind to the target cells. This advantage is greater when the different surfaces are cleanly separated into hemispheres than when the two types of surfaces are intermixed.

For larger nanoparticles (with sizes above 10 nanometers), researchers can use existing methods, such as scanning electron microscopy, to map their surface composition. This has helped researchers improve their manufacturing methods so they can produce cleanly segregated Janus particles. However, conventional methods do not work at sizes below 10 nanometers.

The Vanderbilt chemists -- Associate Professor David Cliffel, Assistant Professor John McLean, graduate student Kellen Harkness and Lecturer Andrzej Balinski -- took advantage of the capabilities of a state-of-the-art instrument called an ion mobility-mass spectrometer (IM-MS) that can simultaneously identify thousands of individual particles.

The team coated the surfaces of gold nanoparticles ranging in size from two to four nanometers with two different chemical compounds. Then they broke the nanoparticles down into clusters of four gold atoms and ran these fragments through the IM-MS.

Molecules from the two coatings were still attached to the clusters. So, by analyzing the resulting pattern, the chemists showed that they could distinguish between original nanoparticles where the two surface compounds were completely separated, those where they were randomly mixed and those that had an intermediate degree of separation.

"There is no other way to analyze structure at this scale except X-ray crystallography," said Cliffel, "and X-ray crystallography is extremely difficult and can take months to get a single structure."

"IM-MS isn't quite as precise as X-ray crystallography but it is extremely practical," added McLean, who has helped pioneer the new instrument's development. "It can provide structural information in a few seconds. Two years ago a commercial version became available so people who want to use it no longer have to build one for themselves."

The research was funded in part by a grant from the National Institutes of Health.

Story Source:

The above story is reprinted (with editorial adaptations ) from materials provided by Vanderbilt University. The original article was written by David Salisbury.

Journal Reference:

Kellen M. Harkness, Andrzej Balinski, John A. McLean, David E. Cliffel. Nanoscale Phase Segregation of Mixed Thiolates on Gold Nanoparticles. Angewandte Chemie International Edition, 2011; DOI: 10.1002/anie.201102882

Researchers make visible the structure of the smallest crystals

 A radical new way of making structures visible at the nano level has been developed at Johannes Gutenberg University Mainz (JGU). This new method makes it possible to determine with precision the arrangement of atoms and molecules in a diverse range of materials from cement to pharmaceuticals. The procedure, which is still in its infancy, comes from the field of electron microscopy and can resolve the structure of the tiniest crystals.

The method was developed by Dr. Ute Kolb's working group at the Institute of Physical Chemistry at Mainz University and is now receiving international attention. In cooperation with researchers from Spain and China, the method has now allowed the structure of a new type of fine-pore zeolite to be established, a study that the journal Science published in the end of August 2011. "We have opened a door to the world of nanostructures," is how Dr. Ute Kolb describes her working group's success.

The arrangement of atoms and molecules in a solid has a decisive influence on the physical properties of that material. Such structures were analyzed for the first time back in 1895 using X-rays, a method that has since become a standard procedure. The beginnings of the research in this area included the discovery in 1912 that crystals are made up of small grids, a characteristic that is responsible for the diversity of thermal, electrical, visual, and mechanical properties found in such substances. "The fact that this method had and still has a huge influence on our understanding of solids and their properties is reflected in the number of Nobel prizes awarded on the basis of structural analyses," says Kolb, describing the success story that is X-ray structural analysis.

In the age of nanotechnology, however, science is focusing increasingly on very small particles, which can no longer be captured by way of X-ray structural analysis. For example, an X-ray structural analysis of a single crystal is only possible up to a crystal size of around one micrometer, i.e. one thousandth of a millimeter. Below this threshold, in the sphere of nanostructures, electron diffraction tomography or automated diffraction tomography (ADT) allows scientists to make a similar determination of the structure of individual crystallites for the first time. "It is as if we have switched on a light in the world of nanostructures," says Kolb. As is the case with electron microscopy, the method is generally based on the concept of an electron beam being directed at an object and diffracted as a result. The diffraction behavior allows the location of the atoms to be established.

Together with her working group, Kolb has developed single-crystal electron diffraction tomography, to give it is full name, over the past 10 years. They had their first major success in 2009 with the determination of the structure of barium sulfate. "Since then, the number of materials whose structure we have been able to uncover has exploded," comments Kolb. The most recent example is the determination of the structure of the zeolite ITQ-43 in cooperation with Spanish and Chinese scientists. Zeolites are crystals that are created from a compound of aluminum and silicate. They have small pores which makes them interesting for the field of energy and environmental technology because of their potential use as adsorbers, ion exchangers or catalysts for example. In water treatment, they can help to filter out heavy metals; in the oil and gas industry, their introduction was like a mini revolution for crude oil cracking. We also encounter them in our everyday lives, in washing powders for instance. Avelino Corma and his team of researchers from the Technical University of Valencia synthesized a zeolite with small and medium-sized pores, the combination of which acts like a funnel, thereby enhancing its catalytic properties still further. How the complex crystal structure was analyzed using ADT is described by the team of researchers in their recent article in Science.

"The smaller the zeolite crystals are, the higher their catalytic efficiency," explains Kolb. With crystals the size of around 100 nanometers, which is similar to one eight-hundredth of a human hair, automated diffraction tomography is often the only way by which the structure can be fully and clearly resolved. "There is a large number of natural and synthetic solid materials for which our method may be used -- materials which are not available or cannot be manufactured in a suitable crystal size." So, over the past two years, Kolb has placed a wide range of materials under her microscope, from color pigments and titanate used in solar technology right up to minerals like charoite, a precious Russian gemstone.

In comparison with conventional electron microscopy characterizations, electron diffraction tomography is considerably faster, more accurate, and more complete. Whereas before, structures were researched for two years, using ADT a result can be obtained within just one day. Even beam-sensitive materials are, in principle, suitable for the method, which Kolb describes as "computer tomography for crystals." ADT also shares a characteristic with computer tomography that has played a major role in its success: the experimental sample under the electron microscope is gradually tipped over in order to gather data from a wide variety of different positions. Using this trick, scientists can avoid the key problem found in this area: the strong interaction of the electron beam with the sample has, up to now, made the electron diffraction much more difficult.

Since 2008, Dr. Ute Kolb has been Senior Lecturer at the Institute of Physical Chemistry and at the Center for High Resolution Electron Microscopy at Mainz University, concentrating on the field of electron crystallography. She presented her most recent work at a conference in Madrid in August 2011, where she was also elected to the Executive Committee of the Commission for Electron Crystallography of the International Union of Crystallography.

In order to advance the development of the method, the Mainz-based chemists are collaborating with Professor Dr. Elmar Schömer of the Institute of Computer Science as well as with Professor Dr. Thorsten Raasch of the Institute of Mathematics at Johannes Gutenberg University Mainz.

Story Source:

The above story is reprinted (with editorial adaptations ) from materials provided by Universität Mainz.

Journal Reference:

J. Jiang, J. L. Jorda, J. Yu, L. A. Baumes, E. Mugnaioli, M. J. Diaz-Cabanas, U. Kolb, A. Corma. Synthesis and Structure Determination of the Hierarchical Meso-Microporous Zeolite ITQ-43. Science, 2011; 333 (6046): 1131 DOI: 10.1126/science.1208652

World's smallest electric motor made from a single molecule

 The smallest electrical motor on the planet, at least according to Guinness World Records, is 200 nanometers. Granted, that's a pretty small motor -- after all, a single strand of human hair is 60,000 nanometers wide -- but that tiny mark is about to be shattered in a big way.

Chemists at Tufts University's School of Arts and Sciences have developed the world's first single molecule electric motor, a development that may potentially create a new class of devices that could be used in applications ranging from medicine to engineering.

In research published online Sept. 4 in Nature Nanotechnology, the Tufts team reports an electric motor that measures a mere 1 nanometer across, groundbreaking work considering that the current world record is a 200 nanometer motor. A single strand of human hair is about 60,000 nanometers wide.

According to E. Charles H. Sykes, Ph.D., associate professor of chemistry at Tufts and senior author on the paper, the team plans to submit the Tufts-built electric motor to Guinness World Records.

"There has been significant progress in the construction of molecular motors powered by light and by chemical reactions, but this is the first time that electrically-driven molecular motors have been demonstrated, despite a few theoretical proposals," says Sykes. "We have been able to show that you can provide electricity to a single molecule and get it to do something that is not just random."

Sykes and his colleagues were able to control a molecular motor with electricity by using a state of the art, low-temperature scanning tunneling microscope (LT-STM), one of about only 100 in the United States. The LT-STM uses electrons instead of light to "see" molecules.

The team used the metal tip on the microscope to provide an electrical charge to a butyl methyl sulfide molecule that had been placed on a conductive copper surface. This sulfur-containing molecule had carbon and hydrogen atoms radiating off to form what looked like two arms, with four carbons on one side and one on the other. These carbon chains were free to rotate around the sulfur-copper bond.

The team determined that by controlling the temperature of the molecule they could directly impact the rotation of the molecule. Temperatures around 5 Kelvin (K), or about minus 450 degrees Fahrenheit (oF), proved to be the ideal to track the motor's motion. At this temperature, the Tufts researchers were able to track all of the rotations of the motor and analyze the data.

While there are foreseeable practical applications with this electric motor, breakthroughs would need to be made in the temperatures at which electric molecular motors operate. The motor spins much faster at higher temperatures, making it difficult to measure and control the rotation of the motor.

"Once we have a better grasp on the temperatures necessary to make these motors function, there could be real-world application in some sensing and medical devices which involve tiny pipes. Friction of the fluid against the pipe walls increases at these small scales, and covering the wall with motors could help drive fluids along," said Sykes. "Coupling molecular motion with electrical signals could also create miniature gears in nanoscale electrical circuits; these gears could be used in miniature delay lines, which are used in devices like cell phones."

The Changing Face of Chemistry

Students from the high school to the doctoral level played an integral role in the complex task of collecting and analyzing the movement of the tiny molecular motors.

"Involvement in this type of research can be an enlightening, and in some cases life changing, experience for students," said Sykes. "If we can get people interested in the sciences earlier, through projects like this, there is a greater chance we can impact the career they choose later in life."

As proof that gaining a scientific footing early can matter, one of the high school students involved in the research, Nikolai Klebanov, went on to enroll at Tufts; he is now a sophomore majoring in chemical engineering.

This work was supported by the National Science Foundation, the Beckman Foundation and the Research Corporation for Scientific Advancement.

Tufts University, located on three Massachusetts campuses in Boston, Medford/Somerville, and Grafton, and in Talloires, France, is recognized among the premier research universities in the United States. Tufts enjoys a global reputation for academic excellence and for the preparation of students as leaders in a wide range of professions. A growing number of innovative teaching and research initiatives span all campuses, and collaboration among the faculty and students in the undergraduate, graduate and professional programs across the university is widely encouraged.

Story Source:

The above story is reprinted (with editorial adaptations) from materials provided by Tufts University.

Journal Reference:

Heather L. Tierney, Colin J. Murphy, April D. Jewell, Ashleigh E. Baber, Erin V. Iski, Harout Y. Khodaverdian, Allister F. McGuire, Nikolai Klebanov, E. Charles H. Sykes. Experimental demonstration of a single-molecule electric motor. Nature Nanotechnology, 2011; DOI: 10.1038/NNANO.2011.142

World's smallest magnetic field sensor: Researchers explore using organic molecules as electronic components

Further development of modern information technology requires computer capacities of increased efficiency at reasonable costs. In the past, integration density of the relevant electronic components was increased constantly. In continuation of this strategy, future components will have to reach the size of individual molecules. Researchers from the KIT Center for Functional Nanostructures (CFN) and IPCMS have now come closer to reaching this target.

For the first time, a team of scientists from KIT and the Institut de Physique et Chimie des Matériaux de Strasbourg (IPCMS) have now succeeded in combining the concepts of spin electronics and molecular electronics in a single component consisting of a single molecule. Components based on this principle have a special potential, as they allow for the production of very small and highly efficient magnetic field sensors for read heads in hard disks or for non-volatile memories in order to further increase reading speed and data density.

Use of organic molecules as electronic components is being investigated extensively at the moment. Miniaturization is associated with the problem of the information being encoded with the help of the charge of the electron (current on or off). However, this requires a relatively high amount of energy. In spin electronics, the information is encoded in the intrinsic rotation of the electron, the spin. The advantage is that the spin is maintained even when switching off current supply, which means that the component can store information without any energy consumption.

The German-French research team has now combined these concepts. The organic molecule H2-phthalocyanin that is also used as blue dye in ball pens exhibits a strong dependence of its resistance, if it is trapped between spin-polarized, i.e. magnetic electrodes. This effect was first observed in purely metal contacts by Albert Fert and Peter Grünberg. It is referred to as giant magnetoresistance and was acknowledged by the Nobel Prize for Physics in 2007.

The giant magnetoresistance effect on single molecules was demonstrated at KIT within the framework of a combined experimental and theoretical project of CFN and a German-French graduate school in cooperation with the IPCMS, Strasbourg. The results of the scientists are now presented in the journal Nature Nanotechnology.

Karlsruhe Institute of Technology (KIT) is a public corporation and state institution of Baden-Wuerttemberg, Germany. It fulfills the mission of a university and the mission of a national research center of the Helmholtz Association. KIT focuses on a knowledge triangle that links the tasks of research, teaching, and innovation.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Karlsruhe Institute of Technology.

Journal Reference:

Stefan Schmaus, Alexei Bagrets, Yasmine Nahas, Toyo K. Yamada, Annika Bork, Martin Bowen, Eric Beaurepaire, Ferdinand Evers, Wulf Wulfhekel. Giant magnetoresistance through a single molecule. Nature Nanotechnology, 2011; DOI: 10.1038/nnano.2011.11

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