Quantum Tunneling Creates A Never Before Seen Shape For Water Molecules

New state of water: Strange 6-sided molecule found

 

A strange new behavior of water molecules has been observed inside crystals of beryl, a type of emerald, caused by bizarre quantum-mechanical effects that let the water molecules face six different directions at the same time.

Under normal conditions, the two hydrogen atoms in each water molecule are arranged around the oxygen atom in an open "V" shape, sometimes compared to a boomerang or Mickey Mouse ears.

But in a new experiment, scientists have found that hydrogen atoms of some water molecules trapped in the crystal structure of the mineral beryl become "smeared out" into a six-sided ring. 

The ring shape is caused by the "quantum tunneling" of the molecules, a phenomenon that lets subatomic particles pass or "tunnel" through seemingly-impossible physical barriers.

In this scenario, the atoms of the water molecule are "delocalized" among six possible directions inside natural hexagonal pores or channels that run though the crystal structure of the beryl, so it partially exist in all six positions at the same time, the researchers said.

Inside crystals 

Scientists from Oak Ridge National Laboratory (ORNL) in Tennessee and the Rutherford Appleton Laboratory in the United Kingdom observed the newly discovered effect in blue aquamarine crystals purchased at a gem show. Blue aquamarine; green and red emerald; pink morganite; gold heliodor; and clear goshenite gemstones are all varieties of the mineral beryl (beryllium aluminum cyclosilicate) with traces of other chemicals that give the crystals their characteristic colors.

"We chose beryl because it has a crystal structure that has channels in it, about 5 angstroms [5 ten-millionths of a millimeter] across — a little bit bigger than a water molecule — and it's known from spectroscopic data that natural beryls have water in them," said Larry Anovitz, a geochemist at ORNL and one of the authors of a paper on the new research. "We already know from lots of other studies that as you put water in smaller and smaller pores it starts to affect the properties of the water — the freezing point drops, the density changes, all sorts of things. So, we wanted to know, if you made that pore so small that you only can get a single molecule of water into it, what would that would do to the properties of water?"

What happened next was unexpected, Anovitz told Live Science.

"We knew that natural beryl would have water in these channels in the structure, so we could go and look at that and see what the properties were," he said. "But we didn't know that the properties would turn out to be so strange when we looked." 

Seeing a new state 

At ORNL's Spallation Neutron Source facility, after cooling the beryl crystals to very low temperatures, the scientists measured the lowest-energy states of the atoms in the trapped water molecules with neutron-scattering experiments, which use a beam of subatomic neutron particles to chart the motion of atoms and molecules.

"When we started looking at peaks in the inelastic neutron spectrum for this sample, we saw a number of peaks in the spectrum that, instead of getting bigger with temperature — which is what is expected to happen — they got smaller with temperature," Anovitz said.

"There are two ways this could happen — either by quantum tunneling or magnetic transitions — and we were able to prove that this is actually the quantum tunneling of the water molecules," he said.

Interactions between water molecules and the walls of the hexagonal channels usually force the water into the center of the channel, with both hydrogen "mouse ears" facing the same one of the six sides.

In their lowest energy states, the water molecules do not have enough energy to rotate to one of the adjacent positions.

But in the areas where the channels narrow so just a single water molecule can fit, the atoms in the water molecule can "tunnel" through the energy barrier that prevents rotation. And the new experiments reveal that the molecules were forming a "double-top" shape, with the proton nucleus of each hydrogen atom delocalizing into a six-sided ring around the central oxygen atom, the researchers said.

Measuring the molecules 

Alexander Kolesnikov, a physicist at ORNL and the lead author of the new paper, said additional studies at the Rutherford Appleton Laboratory had determined that the kinetic energy of the hydrogen protons in the six-sided water molecules was about 30 percent lower than in molecules of water in its normal state, or "bulk water."

"That is a direct indication that this is a quantum property due to the tunneling of water in this beryl channel," Kolesnikov told Live Science. "In classical terms, the kinetic energy would be expected to be something comparable to all other bulk water.

"This is not a new phase of water [like ice or steam] — it's not completely in the gas phase, but it's close to a gas phase," he added. "But at low temperatures, due to quantum delocalization, the kinetic energy of the protons significantly decreases, and they propagate under this [energy] barrier. So, I would say this is kind of a new state of the water molecule."

Anovitz said that quantum tunneling was known to occur in other substances but that the effect was usually limited to subatomic particles rather than larger particles like water molecules.

Quantum tunneling was also known to take place among hydrogen atoms in methyl-group molecules, which are arranged in a triangular pyramid shape around a carbon atom, but the molecules looked the same shape after the tunneling transition, he said.

"With water, when it's moving around this six-fold axis in the beryl channel, it doesn't look the same anymore — and that's something that's never been seen before," Anovitz said. 

Reference:

The findings were published April 22 in the journal Physical Review Letters.

Quantum Tunneling of Water in Beryl: A New State of the Water

Phys. Rev. Lett. 116, 167802

ONRL

The structural memory of water persists on a picosecond timescale

Long-lived sub-structures exist in liquid water as discovered using novel ultrafast vibrational spectroscopies.

Mainz/Amsterdam. A team of scientists from the Max Planck Institute for Polymer Research (MPI-P) in Mainz, Germany and FOM Institute AMOLF in the Netherlands have characterized the local structural dynamics of liquid water, i.e. how quickly water molecules change their binding state.

Using innovative ultrafast vibrational spectroscopies, the researchers show why liquid water is so unique compared to other molecular liquids. This study has recently been published in the scientific journal Nature Communications.

With the help of a novel combination of ultrafast laser experiments, the scientists found that local structures persist in water for longer than a picosecond, a picosecond (ps) being one thousandth of one billionth of a second (10-12 s). This observation changes the general perception of water as a solvent. “71% of the earth’s surface is covered with water. As most chemical and biological reactions on earth occur in water or at the air water interface in oceans or in clouds, the details of how water behaves at the molecular level are crucial. Our results show that water cannot be treated as a continuum, but that specific local structures exist and are likely very important” says Mischa Bonn, director at the MPI-P.

Water is a very special liquid with extremely fast dynamics. Water molecules wiggle and jiggle on sub-picosecond timescales, which make them undistinguishable on this timescale. While the existence of very short-lived local structures - e.g. two water molecules that are very close to one another, or are very far apart from each other - is known to occur, it was commonly believed that they lose the memory of their local structure within less than 0.1 picoseconds.

The proof for relatively long-lived local structures in liquid water was obtained by measuring the vibrations of the Oxygen-Hydrogen (O-H) bonds in water. For this purpose the team of scientists used ultrafast infrared spectroscopy, particularly focusing on water molecules that are weakly (or strongly) hydrogen-bonded to their neighboring water molecules. The scientists found that the vibrations live much longer (up to about 1 ps) for water molecules with a large separation, than for those that are very close (down to 0.2 ps). In other words, the weakly bound water molecules remain weakly bound for a remarkably long time.

Max Planck Institute for Polymer Research

Nanotechnology World Association

By accident, a researcher caught this microscopic image of an evaporating water droplet

https://lnkd.in/e-dduXV

Just add water: Stanford engineers develop a computer that operates on water droplets

Manu Prakash, an assistant professor of bioengineering at Stanford, and his students have developed a synchronous computer that operates using the unique physics of moving water droplets. Their goal is to design a new class of computers that can precisely control and manipulate physical matter.

Video by Kurt Hickman

Stanford bioengineer Manu Prakash and his students have developed a synchronous computer that operates using the unique physics of moving water droplets.

Computers and water typically don't mix, but in Manu Prakash's lab, the two are one and the same. Prakash, an assistant professor of bioengineering at Stanford, and his students have built a synchronous computer that operates using the unique physics of moving water droplets.

The computer is nearly a decade in the making, incubated from an idea that struck Prakash when he was a graduate student. The work combines his expertise in manipulating droplet fluid dynamics with a fundamental element of computer science – an operating clock.

"In this work, we finally demonstrate a synchronous, universal droplet logic and control," Prakash said.

Because of its universal nature, the droplet computer can theoretically perform any operation that a conventional electronic computer can crunch, although at significantly slower rates. Prakash and his colleagues, however, have a more ambitious application in mind.

"We already have digital computers to process information. Our goal is not to compete with electronic computers or to operate word processors on this," Prakash said. "Our goal is to build a completely new class of computers that can precisely control and manipulate physical matter. Imagine if when you run a set of computations that not only information is processed but physical matter is algorithmically manipulated as well. We have just made this possible at the mesoscale."

The ability to precisely control droplets using fluidic computation could have a number of applications in high-throughput biology and chemistry, and possibly new applications in scalable digital manufacturing.

The results are published in the current edition of Nature Physics.

The crucial clock
For nearly a decade since he was in graduate school, an idea has been nagging at Prakash: What if he could use little droplets as bits of information and utilize the precise movement of those drops to process both information and physical materials simultaneously. Eventually, Prakash decided to build a rotating magnetic field that could act as clock to synchronize all the droplets. The idea showed promise, and in the early stages of the project, Prakash recruited a graduate student, Georgios "Yorgos" Katsikis, who is the first author on the paper.





Computer clocks are responsible for nearly every modern convenience. Smartphones, DVRs, airplanes, the Internet – without a clock, none of these could operate without frequent and serious complications. Nearly every computer program requires several simultaneous operations, each conducted in a perfect step-by-step manner. A clock makes sure that these operations start and stop at the same times, thus ensuring that the information synchronizes.

The results are dire if a clock isn't present. It's like soldiers marching in formation: If one person falls dramatically out of time, it won't be long before the whole group falls apart. The same is true if multiple simultaneous computer operations run without a clock to synchronize them, Prakash explained.

"The reason computers work so precisely is that every operation happens synchronously; it's what made digital logic so powerful in the first place," Prakash said.

A magnetic clock
Developing a clock for a fluid-based computer required some creative thinking. It needed to be easy to manipulate, and also able to influence multiple droplets at a time. The system needed to be scalable so that in the future, a large number of droplets could communicate amongst each other without skipping a beat. Prakash realized that a rotating magnetic field might do the trick.

Katsikis and Prakash built arrays of tiny iron bars on glass slides that look something like a Pac-Man maze. They laid a blank glass slide on top and sandwiched a layer of oil in between. Then they carefully injected into the mix individual water droplets that had been infused with tiny magnetic nanoparticles.

Next, they turned on the magnetic field. Every time the field flips, the polarity of the bars reverses, drawing the magnetized droplets in a new, predetermined direction, like slot cars on a track. Every rotation of the field counts as one clock cycle, like a second hand making a full circle on a clock face, and every drop marches exactly one step forward with each cycle.

A camera records the interactions between individual droplets, allowing observation of computation as it occurs in real time. The presence or absence of a droplet represents the 1s and 0s of binary code, and the clock ensures that all the droplets move in perfect synchrony, and thus the system can run virtually forever without any errors.

"Following these rules, we've demonstrated that we can make all the universal logic gates used in electronics, simply by changing the layout of the bars on the chip," said Katsikis. "The actual design space in our platform is incredibly rich. Give us any Boolean logic circuit in the world, and we can build it with these little magnetic droplets moving around."

The current paper describes the fundamental operating regime of the system and demonstrates building blocks for synchronous logic gates, feedback and cascadability – hallmarks of scalable computation. A simple-state machine including 1-bit memory storage (known as "flip-flop") is also demonstrated using the above basic building blocks.

A new way to manipulate matter
The current chips are about half the size of a postage stamp, and the droplets are smaller than poppy seeds, but Katsikis said that the physics of the system suggests it can be made even smaller. Combined with the fact that the magnetic field can control millions of droplets simultaneously, this makes the system exceptionally scalable.

"We can keep making it smaller and smaller so that it can do more operations per time, so that it can work with smaller droplet sizes and do more number of operations on a chip," said graduate student and co-author Jim Cybulski. "That lends itself very well to a variety of applications."

Prakash said the most immediate application might involve turning the computer into a high-throughput chemistry and biology laboratory. Instead of running reactions in bulk test tubes, each droplet can carry some chemicals and become its own test tube, and the droplet computer offers unprecedented control over these interactions.

From the perspective of basic science, part of why the work is so exciting, Prakash said, is that it opens up a new way of thinking of computation in the physical world. Although the physics of computation has been previously applied to understand the limits of computation, the physical aspects of bits of information has never been exploited as a new way to manipulate matter at the mesoscale (10 microns to 1 millimeter).

Because the system is extremely robust and the team has uncovered universal design rules, Prakash plans to make a design tool for these droplet circuits available to the public. Any group of people can now cobble together the basic logic blocks and make any complex droplet circuit they desire.

"We're very interested in engaging anybody and everybody who wants to play, to enable everyone to design new circuits based on building blocks we describe in this paper or discover new blocks. Right now, anyone can put these circuits together to form a complex droplet processor with no external control – something that was a very difficult challenge previously," Prakash said.

"If you look back at big advances in society, computation takes a special place. We are trying to bring the same kind of exponential scale up because of computation we saw in the digital world into the physical world." 

Source: http://www.nanotechnologyworld.org/#!Just-add-water-Stanford-engineers-develop-a-computer-that-operates-on-water-droplets/c89r/557640b30cf2312d79770768 

Need a water filter? Peel a tree branch

A false-color electron microscope image showing E. coli bacteria
(green) trapped over xylem pit membranes (red and blue) in the
sapwood after filtration.
IMAGE COURTESY OF THE RESEARCHERS

If you’ve run out of drinking water during a lakeside camping trip, there’s a simple solution: Break off a branch from the nearest pine tree, peel away the bark, and slowly pour lake water through the stick. The improvised filter should trap any bacteria, producing fresh, uncontaminated water. 

In fact, an MIT team has discovered that this low-tech filtration system can produce up to four liters of drinking water a day — enough to quench the thirst of a typical person. 

In a paper published this week in the journal PLoS ONE, the researchers demonstrate that a small piece of sapwood can filter out more than 99 percent of the bacteria E. coli from water. They say the size of the pores in sapwood — which contains xylem tissue evolved to transport sap up the length of a tree — also allows water through while blocking most types of bacteria. 

Co-author Rohit Karnik, an associate professor of mechanical engineering at MIT, says sapwood is a promising, low-cost, and efficient material for water filtration, particularly for rural communities where more advanced filtration systems are not readily accessible. 

“Today’s filtration membranes have nanoscale pores that are not something you can manufacture in a garage very easily,” Karnik says. “The idea here is that we don’t need to fabricate a membrane, because it’s easily available. You can just take a piece of wood and make a filter out of it.”

The paper’s co-authors include Michael Boutilier and Jongho Lee from MIT, Valerie Chambers from Fletcher-Maynard Academy in Cambridge, Mass., and Varsha Venkatesh from Jericho High School in Jericho, N.Y.

Tapping the flow of sap

There are a number of water-purification technologies on the market today, although many come with drawbacks: Systems that rely on chlorine treatment work well at large scales, but are expensive. Boiling water to remove contaminants requires a great deal of fuel to heat the water. Membrane-based filters, while able to remove microbes, are expensive, require a pump, and can become easily clogged. 

Sapwood may offer a low-cost, small-scale alternative. The wood is comprised of xylem, porous tissue that conducts sap from a tree’s roots to its crown through a system of vessels and pores. Each vessel wall is pockmarked with tiny pores called pit membranes, through which sap can essentially hopscotch, flowing from one vessel to another as it feeds structures along a tree’s length. The pores also limit cavitation, a process by which air bubbles can grow and spread in xylem, eventually killing a tree. The xylem’s tiny pores can trap bubbles, preventing them from spreading in the wood.

“Plants have had to figure out how to filter out bubbles but allow easy flow of sap,” Karnik observes. “It’s the same problem with water filtration where we want to filter out microbes but maintain a high flow rate. So it’s a nice coincidence that the problems are similar.” 

Seeing red

To study sapwood’s water-filtering potential, the researchers collected branches of white pine and stripped off the outer bark. They cut small sections of sapwood measuring about an inch long and half an inch wide, and mounted each in plastic tubing, sealed with epoxy and secured with clamps. 

Before experimenting with contaminated water, the group used water mixed with red ink particles ranging from 70 to 500 nanometers in size. After all the liquid passed through, the researchers sliced the sapwood in half lengthwise, and observed that much of the red dye was contained within the very top layers of the wood, while the filtrate, or filtered water, was clear. This experiment showed that sapwood is naturally able to filter out particles bigger than about 70 nanometers. 

However, in another experiment, the team found that sapwood was unable to separate out 20-nanometer particles from water, suggesting that there is a limit to the size of particles coniferous sapwood can filter. 

Picking the right plant

Finally, the team flowed inactivated, E. coli-contaminated water through the wood filter. When they examined the xylem under a fluorescent microscope, they saw that bacteria had accumulated around pit membranes in the first few millimeters of the wood. Counting the bacterial cells in the filtered water, the researchers found that the sapwood was able to filter out more than 99 percent of E. coli from water. 

Karnik says sapwood likely can filter most types of bacteria, the smallest of which measure about 200 nanometers. However, the filter probably cannot trap most viruses, which are much smaller in size. 

Karnik says his group now plans to evaluate the filtering potential of other types of sapwood. In general, flowering trees have smaller pores than coniferous trees, suggesting that they may be able to filter out even smaller particles. However, vessels in flowering trees tend to be much longer, which may be less practical for designing a compact water filter. 

Designers interested in using sapwood as a filtering material will also have to find ways to keep the wood damp, or to dry it while retaining the xylem function. In other experiments with dried sapwood, Karnik found that water either did not flow through well, or flowed through cracks, but did not filter out contaminants. 

“There’s huge variation between plants,” Karnik says. “There could be much better plants out there that are suitable for this process. Ideally, a filter would be a thin slice of wood you could use for a few days, then throw it away and replace at almost no cost. It’s orders of magnitude cheaper than the high-end membranes on the market today.”

While the pores in sapwood are too big to filter out salts, Saurya Prakash, an assistant professor of mechanical engineering at Ohio State University, says the design could be useful in parts of the world where people collect surface water, which can be polluted with fine dust and particles of decaying plant and animal matter. Most of this detritus, Prakash says, could easily be filtered out by the group’s design. 

“The xylem tissue acts as a natural filter, similar to a manmade membrane,” says Prakash, who was not involved in the research. “The study by the Karnik group shows that use of abundant, naturally occurring materials could pave the way for a new generation of water filters that are potentially low-cost enough to be disposable.”

This research was supported by the James H. Ferry Jr. Fund for Innovation in Research Education.

Source: http://web.mit.edu/newsoffice/2014/need-a-water-filter-peel-a-tree-branch-0226.html

Glass or Plastic? Container’s Properties Affect the Viscosity of Nanoscale Water

Water pours into a cup at about the same rate regardless of whether the water bottle is made of glass or plastic.

But at nanometer-size scales for water and potentially other fluids, whether the container is made of glass or plastic does make a significant difference. A new study shows that in nanoscopic channels, the effective viscosity of water in channels made of glass can be twice as high as water in plastic channels. Nanoscopic glass channels can make water flow more like ketchup than ordinary H2O.

The effect of container properties on the fluids they hold offers yet another example of surprising phenomena at the nanoscale. And it also provides a new factor that the designers of tiny mechanical systems must take into account.

“At the nanoscale, viscosity is no longer constant, so these results help redefine our understanding of fluid flow at this scale,” said Elisa Riedo, an associate professor in the School of Physics at the Georgia Institute of Technology. “Anyone performing an experiment, developing a technology or attempting to understand a biological process that involves water or another liquid at this size scale will now have to take the properties of surfaces into account.”

Those effects could be important to designers of devices such as high resolution 3D printers that use nanoscale nozzles, nanofluidic systems and even certain biomedical devices.

Considering that nano-confined water is ubiquitous in animal bodies, in rocks, and in nanotechnology, this new understanding could have a broad impact.

Research into the properties of liquids confined by different materials was sponsored by the Department of Energy’s Office of Basic Sciences and the National Science Foundation. The results were reported September 19 in the journal Nature Communications.

The viscosity differences created by container materials are directly affected by the degree to which the materials are either hydrophilic – which means they attract water – or hydrophobic – which means they repel it. The researchers believe that in hydrophilic materials, the attraction for water – a property known as “wettability” – makes water molecules more difficult to move, contributing to an increase in the fluid’s effective viscosity. On the other hand, water isn’t as attracted to hydrophobic materials, making the molecules easier to move and producing lower viscosity.

In research reported in the journal, this water behavior appeared only when water was confined to spaces of a few nanometers or less – the equivalent of just a few layers of water molecules. The viscosity continued to increase as the surfaces were moved closer together.

The research team studied water confined by five different surfaces: mica, graphene oxide, silicon, diamond-like carbon, and graphite. Mica, used in the drilling industry, was the most hydrophilic of the materials, while graphite was the most hydrophobic. 

“We saw a clear one-to-one relationship between the degree to which the confining material was hydrophilic and the viscosity that we measured,” Riedo said.

Experimentally, the researchers began by preparing atomically-smooth surfaces of the materials, then placing highly-purified water onto them. Next, an AFM tip made of silicon was moved across the surfaces at varying heights until it made contact. The tip – about 40 nanometers in diameter – was then lifted up and the measurements continued.

As the viscosity of the water increased, the force needed to move the AFM tip also increased, causing it to twist slightly on the cantilever beam used to raise and lower the tip. Changes in this torsion angle were measured by a laser bounced off the reflective cantilever, providing an indication of changes in the force exerted on the tip, the viscous resistance exerted – and therefore the water’s effective viscosity.

“When the AFM tip was about one nanometer away from the surface, we began to see an increase of the viscous force acting on the tip for the hydrophilic surfaces,” Riedo said. “We had to use larger forces to move the tip at this point, and the closer we got to the surface, the more dramatic this became.”

Those differences can be explained by understanding how water behaves differently on different surfaces.

“At the nanoscale, liquid-surface interaction forces become important, particularly when the liquid molecules are confined in tiny spaces,” Riedo explained. “When the surfaces are hydrophilic, the water sticks to the surface and does not want to move. On hydrophobic surfaces, the water is slipping on the surfaces. With this study, not only have we observed this nanoscale wetting-dependent viscosity, but we have also been able to explain quantitatively the origin of the observed changes and relate them to boundary slip. This new understanding was able to explain previous unclear results of energy dissipation during dynamic AFM studies in water.”

While the researchers have so far only studied the effect of the material properties in water channels, Riedo expects to perform similar experiments on other fluids, including oils. Beyond simple fluids, she hopes to study complex fluids composed of nanoparticles in suspension to determine how the phenomenon changes with particle size and chemistry.

“There is no reason why this should not be true for other liquids, which means that this could redefine the way that fluid dynamics is understood at the nanoscale,” she said. “Every technology and natural process that uses liquids confined at the nanoscale will be affected.”

In addition to Riedo, co-authors of the paper included Deborah Ortiz-Young, Hsiang-Chih Chiu and Suenne Kim, who were at Georgia Tech when the research was done, and Kislon Voitchovsky of the Ecole Polytechnique Federale de Lausanne in Switzerland.

Source: http://www.gatech.edu/newsroom/release.html?nid=238821