Toward a smart graphene membrane to desalinate water: Penn State University


Graphene H2O towardasmartA scalable graphene-based membrane for producing clean water Credit: Aaron Morelos-Gomez. Credit: Pennsylvania State University

An international team of researchers, including scientists from Shinshu University (Japan) and the director of Penn State’s ATOMIC Center, has developed a graphene-based coating for desalination membranes that is more robust and scalable than current nanofiltration membrane technologies. The result could be a sturdy and practical membrane for clean water solutions as well as protein separation, wastewater treatment and pharmaceutical and food industry applications.

“Our dream is to create a smart  that combines high flow rates, high efficiency, long lifetime, self-healing and eliminates bio and inorganic fouling in order to provide clean water solutions for the many parts of the world where clean water is scarce,” says Mauricio Terrones, professor of physics, chemistry and materials science and engineering, Penn State. “This work is taking us in that direction.”

The hybrid membrane the team developed uses a simple spray-on technology to coat a mixture of graphene oxide and few-layered graphene in solution onto a backbone support membrane of polysulfone modified with polyvinyl alcohol. The support membrane increased the robustness of the hybrid membrane, which was able to stand up to intense cross-flow, high pressure and chlorine exposure. Even in early stages of development, the membrane rejects 85 percent of salt, adequate for agricultural purposes though not for drinking, and 96 percent of dye molecules. Highly polluting dyes from textile manufacturing is commonly discharged into rivers in some areas of the world.

Chlorine is generally used to mitigate biofouling in membranes, but chlorine rapidly degrades the performance of current polymer membranes. The addition of few-layer graphene makes the new membrane highly resistant to chlorine.

Graphene is known to have high mechanical strength, and porous graphene is predicted to have 100 percent salt rejection, making it a potentially ideal material for desalination membranes. However, there are many challenges with scaling up graphene to industrial quantities including controlling defects and the need for complex transfer techniques required to handle the two-dimensional material. The current work attempts to overcome the scalability issues and provide an inexpensive, high quality membrane at manufacturing scale.

The work was performed in the Global Aqua Innovation Center and the Institute of Carbon Science and Technology at Shinshu University, Nagano, Japan, where Terrones is also a Distinguished Invited Professor. The team includes researchers Aaron Morelos-Gomez, Josue Ortiz-Medina and Rodolfo Cruz-Silva, former Ph.D. students of Terrones. Morelos-Gomez is lead author on a paper published online on August 28 in Nature Nanotechnology describing their work titled “Effective NaCL and dye rejection of hybrid graphene oxide/graphene layered membranes.” The Japanese researchers, Hiroyuki Muramatsu, Takumi Araki, Tomoyuki Fukuyo, Syogo Tejima, Kenji Takeuchi, and Takuya Hayashi, were also led by Professor Morinobu Endo.

First author Aaron Morelos-Gomez says, “Our membrane overcomes the water solubility of graphene oxide by using polyvinyl alcohol as an adhesive making it resistant against strong water flow and high pressures. By mixing  with  we could also improve significantly its chemical resistance.”

Professor Morinobu Endo concludes that “this is the first step towards more effective and smart membranes that could self-adapt depending on their environment.”

 Explore further: Graphene sieve turns seawater into drinking water

More information: Aaron Morelos-Gomez et al. Effective NaCl and dye rejection of hybrid graphene oxide/graphene layered membranes, Nature Nanotechnology (2017). DOI: 10.1038/nnano.2017.160

Read more at: https://phys.org/news/2017-09-smart-graphene-membrane-desalinate.html#jCp

Read more at: https://phys.org/news/2017-09-smart-graphene-membrane-desalinate.html#jCp

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U of Pennsylvania: Large Scale Production of Graphene + Graphene Updates and Videos


Graphene Mem 050815 3-anewapproach
Draw a line with a pencil and it’s likely that somewhere along that black smudge is a material that earned two scientists the 2010 Nobel Prize in Physics. The graphite of that pencil tip is simply multiple layers of carbon atoms; where those layers are only one atom thick, it is known as graphene.

The properties of a material change at the nanoscopic scale, making graphene the strongest and most conductive substance known. Instead of marking mini-golf scores on paper, this form of carbon is suited for making faster and smaller electronic circuitry, flexible touchscreens, chemical sensors, diagnostic devices, and applications yet to be imagined.

Graphene is not yet as ubiquitous as plastic or silicon, however, and producing the material in bulk remains a challenge. Because graphene’s properties rely on it being only one atom thick, until recently, it was only possible to make it in small patches or flakes.

Physicists at Penn have discovered a way around these limitations, and have spun out their research into a company called Graphene Frontiers. Graphene Frontiers

 


More About Graphene

Turning saltwater into clean drinking water is an expensive, energy-intensive process, but could the wonder material graphene make it more accessible?

New Discovery Could Unlock Graphene’s Full Potential – 


Read More:

3D GrapheneFollow this direct link to Seeker.com for more information and Videos about the ‘Wonder Material’ of Graphene.

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Graphene sieve turns seawater into drinking water

“Graphene-oxide membranes have attracted considerable attention as promising candidates for new filtration technologies. Now the much sought-after development of making membranes capable of sieving common salts has been achieved. New research demonstrates the real-world potential of providing clean drinking water for millions of people who struggle to access adequate clean water sources.
The new findings from a group of scientists at The University of Manchester were published today in the journal Nature Nanotechnology. Previously graphene-oxide membranes have shown exciting potential for gas separation and water filtration.”

MIT Researchers develop new (low energy) way to Clear Pollutants from Water: w/ Video


MIT-PurifyingWater-1_0Researchers have developed a new method for removing even extremely low levels of unwanted compounds from water. The new method relies on an electrochemical process to selectively remove organic contaminants such as pesticides, chemical waste products, and pharmaceuticals. Photo: Melanie Gonick/MIT

Electrochemical method can remove even tiny amounts of contamination.

When it comes to removing very dilute concentrations of pollutants from water, existing separation methods tend to be energy- and chemical-intensive. Now, a new method developed at MIT could provide a selective alternative for removing even extremely low levels of unwanted compounds.

The new approach is described in the journal Energy and Environmental Science, in a paper by MIT postdoc Xiao Su, Ralph Landau Professor of Chemical Engineering T. Alan Hatton, and five others at MIT and at the Technical University of Darmstadt in Germany.

The system uses a novel method, relying on an electrochemical process to selectively remove organic contaminants such as pesticides, chemical waste products, and pharmaceuticals, even when these are present in small yet dangerous concentrations. The approach also addresses key limitations of conventional electrochemical separation methods, such as acidity fluctuations and losses in performance that can happen as a result of competing surface reactions. Watch the Video:

Current systems for dealing with such dilute contaminants include membrane filtration, which is expensive and has limited effectiveness at low concentrations, and electrodialysis and capacitive deionization, which often require high voltages that tend to produce side reactions, Su says. These processes also are hampered by excess background salts.

In the new system, the water flows between chemically treated, or “functionalized,” surfaces that serve as positive and negative electrodes. These electrode surfaces are coated with what are known as Faradaic materials, which can undergo reactions to become positively or negatively charged. These active groups can be tuned to bind strongly with a specific type of pollutant molecule, as the team demonstrated using ibuprofen and various pesticides. The researchers found that this process can effectively remove such molecules even at parts-per-million concentrations.

Previous studies have usually focused on conductive electrodes, or functionalized plates on just one electrode, but these often reach high voltages that produce contaminating compounds. By using appropriately functionalized electrodes on both the positive and negative sides, in an asymmetric configuration, the researchers almost completely eliminated these side reactions. Also, these asymmetric systems allow for simultaneous selective removal of both positive and negative toxic ions at the same time, as the team demonstrated with the herbicides paraquat and quinchlorac.

The same selective process should also be applied to the recovery of high-value compounds in a chemical or pharmaceutical production plant, where they might otherwise be wasted, Su says. “The system could be used for environmental remediation, for toxic organic chemical removal, or in a chemical plant to recover value-added products, as they would all rely on the same principle to pull out the minority ion from a complex multi-ion system.”

The system is inherently highly selective, but in practice it would likely be designed with multiple stages to deal with a variety of compounds in sequence, depending on the exact application, Su says. “Such systems might ultimately be useful,” he sugggests, “for water purification systems for remote areas in the developing world, where pollution from pesticides, dyes, and other chemicals are often an issue in the water supply. The highly efficient, electrically operated system could run on power from solar panels in rural areas for example.”

Unlike membrane-based systems that require high pressures, and other electrochemical systems that operate at high voltages, the new system works at relatively benign low voltages and pressures, Hatton says. And, he points out, in contrast to conventional ion exchange systems where release of the captured compounds and regeneration of the adsorbents would require the addition of chemicals, “in our case you can just flip a switch” to achieve the same result by switching the polarity of the electrodes.

The research team has already racked up a series of honors for the ongoing development of water treatment technology, including grants from the J-WAFS Solutions and Massachusetts Clean Energy Catalyst competitions, and the researchers were the top winners last year’s MIT Water Innovation Prize. The researchers have applied for a patent on the new process. “We definitely want to implement this in the real world,” Hatton says. In the meantime, they are working on scaling up their prototype devices in the lab and improving the chemical robustness.

This technique “is highly significant, as it extends the capabilities of electrochemical systems from basically nonselective toward highly selective removal of key pollutants,” says Matthew Suss, an assistant professor of mechanical engineering at Technion Institute of Technology in Israel, who was not involved in this work. “As with many emerging water purification techniques, it must still must be tested under real-world conditions and for long periods to check durability. However, the prototype system achieved over 500 cycles, which is a highly promising result.”

These researchers “have systematically explored a variety of device configurations and a variety of contaminants,” says Kyle Smith, a professor of mechanical science and engineering at the University of Illinois, who also was not involved in this work. “In the process they have identified general design principles by which to achieve selective removal of contaminants. In this regard, I find Hatton and co-workers’ study to be very thorough and thoughtful. It provides a framework or paradigm for other researchers to emulate.” But, he adds, “A significant challenge that remains is the scale-up of these technologies.”

The team also included Kai-Jher Tan, Johannes Elbert, and Robert R. Taylor Professor of Chemistry Timothy Jamison at MIT; and Christian Ruttiger and Markus Gallei at the Technical University of Darmstadt. The work was supported by a seed grant from the Abdul Latif Jameel World Water and Food Security Lab (J-WAFS) at MIT.

New water filtration process uses 1,000 times less energy


New research could transform how we filter water Credit: University of Limerick

A new process for water filtration using carbon dioxide consumes one thousand times less energy than conventional methods, scientific research published recently has shown.

The research was led by Dr Orest Shardt of University of Limerick, Ireland together with Dr Sangwoo Shin (now at University of Hawaii, Manoa), while they were post doctoral researchers at Princeton University (United States) last year.

With global demand for clean water increasing, there is a continuing need to improve the performance of water treatment processes. Dr Shardt expects this new method which uses CO2 could be applied in a variety of industries such as mining, food and beverage production, pharmaceutical manufacturing and water treatment.

The research, published in open-access scientific journal Nature Communications, indicates that the new process could be easily scaled up, “suggesting the technique could be particularly beneficial in both the developing and developed worlds”. 
The new method could also be used to remove bacteria and viruses without chlorination or ultraviolet treatment.

“We are at the early stages of developing this concept. Eventually, this new method could be used to clean water for human consumption or to treat effluent from industrial facilities,” Dr Shardt stated.

Currently, water filtration technologies such as microfiltration or ultrafiltration use porous membranes to remove suspended particles and solutes. 

These processes trap and remove suspended particles, such as fine silt, by forcing the suspension through a porous material with gaps that are smaller than the particles. 
Energy must be wasted to overcome the friction of pushing the water through these small passages. These kinds of filtration processes have drawbacks such as high pumping costs and a need for periodic replacement of the membranes due to fouling. 

The research by Drs Shardt and Shin demonstrates an alternative membraneless method for separating suspended particles that works by exposing the colloidal suspension to CO2.

“The demonstration device is made from a standard silicone polymer, a material that is commonly used in microfluidics research and similar to what is used in household sealants. 

While we have not yet analysed the capital and operating costs of a scaled-up process based on our device, the low pumping energy it requires, just 0.1% that of conventional filtration methods, suggests that the process deserves further research,” said Dr Shardt.

“What we need to do now is to study the effects of various compounds, such as salts and dissolved organic matter that are present in natural and industrial water to understand what impact they will have on the process. 

This could affect how we optimise the operating conditions, design the flow channel, and scale-up the process,” he continued.

Since joining the €86 million Bernal Institute at University of Limerick last September, Dr Shardt is continuing his research on the mathematical modelling and simulation of the water purification process and the physical phenomena on which it is based.


“As a new arrival to Ireland,
I’m now looking for motivated PhD students to work with me in this area. I am sure that creative students will find new ways to improve the process and apply it in unexpected ways,” Dr Shardt concluded.

More information: Sangwoo Shin et al, Membraneless water filtration using CO2, 

Nature Communications (2017). DOI: 10.1038/ncomms15181

Provided by: University of Limerick

Turning Saltwater N2 Clean drinking Water ~ Graphene Could Solve the World’s Water Crisis: Video


Graphene Desal 1-simulationsp

Published on Apr 29, 2017

Turning  saltwater into clean drinking water is an expensive, energy-intensive process, but could the wonder material graphene make it more accessible?
New Discovery Could Unlock Graphene’s Full Potential

Watch the Video:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 




U of Illinois & Ben-Gurion U Create ‘Ultra’ Filtration Membranes that remove viruses from drinking water


 

Nanofiltration 2161011_orig

Current membrane filtration methods require intensive energy to adequately remove pathogenic viruses without using chemicals like chlorine, which can contaminate the water with disinfection byproducts. Researchers at UIUC and BGU collaborated on the new approach for virus pathogen removal, which was published in the current issue of Water Research.

“This is an urgent matter of public safety,” the researchers say. “Insufficient removal of human Adenovirus in municipal wastewater, for example, has been detected as a contaminant in U.S. drinking water sources, including the Great Lakes and worldwide.”

Researchers from Ben-Gurion University of the Negev (BGU) and the University of Illinois at Urbana-Champaign (UIUC) have developed novel ultrafiltration membranes that significantly improve the virus-removal process from treated municipal wastewater used for drinking in water-scarce cities (Water Research, “Improvement of virus removal using ultrafiltration membranes modified with grafted zwitterionic polymer hydrogels”).

The norovirus, which can cause nausea, vomiting and diarrhea, is the most common cause of viral gastroenteritis in humans, and is estimated to be the second leading cause of gastroenteritis-associated mortality. Human adenoviruses can cause a wide range of illnesses that include the common cold, sore throat (pharyngitis), bronchitis, pneumonia, diarrhea, pink eye (conjunctivitis), fever, bladder inflammation or infection (cystitis), inflammation of the stomach and intestines (gastroenteritis), and neurological disease.

 

In the study, Prof. Moshe Herzberg of the Department of Desalination and Water Treatment in the Zuckerberg Institute for Water Research at BGU and his group grafted a special hydrogel coating onto a commercial ultrafiltration membrane. The “zwitterionic polymer hydrogel” repels the viruses from approaching and passing through the membrane. It contains both positive and negative charges and improves efficiency by weakening virus accumulation on the modified filter surface. The result was a significantly higher rate of removal of waterborne viruses, including human norovirus and adenovirus.Nanofiltration II Membrane-Layers-01

 

“Utilizing a simple graft-polymerization of commercialized membranes to make virus removal more comprehensive is a promising development for controlling filtration of pathogens in potable water reuse,” says Prof. Nguyen, Department of Chemical Engineering, UIUC.
Source: American Associates, Ben-Gurion University of the Negev

 

Researchers develop hybrid nuclear desalination technique with improved efficiency


3-newtechnologAssociate Professor I.M. Kurchatov and graduate student R.A. Alexandrov work at the research stand of water purification. Credit: National Research Nuclear University

Lack of fresh water requires development of new desalination methods, including advanced nuclear desalination and water treatment and recycling; requirements for drinking water and other uses may be different.Desal-Hadera--Israel-2

 

To improve environmental safety and desalination technology, it is necessary to solve a global scientific and technological problem—the creation of an integrated water supply system based on the use of new high-efficiency desalination methods such as nuclear membrane desalination or hybrid technologies. These methods should be combined with recycling and treatment of residues to a level that corresponds with environmental requirements.

The majority of modern desalination technologies are based on distillation of thermal energy, including nuclear desalination, or using desalination membranes (reverse osmosis and electrodialysis membranes). In the process of distillation, salt water is boiled, and produced steam leaves the system and is condensed as fresh water. If a nuclear reactor is used as the heat source, the method is called nuclear desalination.

The membrane method of reverse osmosis is based on the filtering of salt water under the influence of differential pressure across a semipermeable membrane allowing water molecules and excluding salts; the pressure differential should be more than the so-called osmotic pressure (~ 30 atm. for seawater). In membrane electrodialysis, ions penetrate through the so-called ion-exchange membranes, and fresh water remains in the channel.

These membrane methods can be used in conjunction with nuclear desalination (hybrid desalination technologies), i.e., they can be added to existing nuclear facilities, where there is a relatively cheap access to thermal energy.

For the normal functioning of desalination plants, quality of the source water must meet certain strict requirements. This entails the need for a pre-treatment system, the cost of which is sometimes two to three times more than the cost of the itself.

Scientists from the National Research Nuclear University MEPhI (Russia) have developed a new technology and technological schemes for a pretreatment unit taking into account data on the composition of pollutants, salinity and performance of water treatment systems. It is based on the reagent methods with hydrodynamic activation of the process of pollutant withdrawal in coagulation, flocculation and adsorption, which reduces the unit’s size and cost. Moreover, the majority of the sparingly soluble salts can be removed in the pretreatment unit, which increases the efficiency of the system as a whole.

From the pre-water treatment unit, salt water flows into the desalination unit, a very energy-intensive process. Hybrid desalination schemes are proposed to reduce the energy consumption of the desalination process. These schemes use distillation and membrane methods in combination, to produce both drinking water and process water.

In addition, the project proposes the development of an integrated technological system of recycling and desalination systems to reduce environmental burdens and improve the energy efficiency of the system as a whole.

The results are intended to be used in complex projects of the State Corporation Rosatom, in particular, in relation to nuclear power plants in Egypt, where it is planned to realize a nuclear technology.

Explore further: Drinking water from the sea using solar energy

 

Turning Seawater into Drinking Water ~ Graphene Sieves May Hold the Key


Graphene Seives 58e264acaef12A graphene membrane. Credit: The University of Manchester

 

“By 2025 the UN expects that 14% of the world’s population will encounter water scarcity.”

Graphene-oxide membranes have attracted considerable attention as promising candidates for new filtration technologies. Now the much sought-after development of making membranes capable of sieving common salts has been achieved.

New research demonstrates the real-world potential of providing for millions of people who struggle to access adequate clean water sources.

The new findings from a group of scientists at The University of Manchester were published today in the journal Nature Nanotechnology. Previously graphene-oxide membranes have shown exciting potential for gas separation and water filtration.

Graphene-oxide membranes developed at the National Graphene Institute have already demonstrated the potential of filtering out small nanoparticles, organic molecules, and even large salts. Until now, however, they couldn’t be used for sieving common salts used in technologies, which require even smaller sieves.

Previous research at The University of Manchester found that if immersed in water, graphene-oxide membranes become slightly swollen and smaller salts flow through the membrane along with water, but larger ions or molecules are blocked.

The Manchester-based group have now further developed these and found a strategy to avoid the swelling of the membrane when exposed to water. The in the membrane can be precisely controlled which can sieve common salts out of salty water and make it safe to drink.

As the effects of climate change continue to reduce modern city’s water supplies, wealthy modern countries are also investing in desalination technologies. Following the severe floods in California major wealthy cities are also looking increasingly to alternative water solutions.

WEF 2017 graphene-water-071115-rtrde3r1-628x330 (2)World Economic Forum: Can Graphene Make the World’s Water Clean?

 

 

 

 

When the common salts are dissolved in water, they always form a ‘shell’ of around the salts molecules. This allows the tiny capillaries of the graphene-oxide membranes to block the from flowing along with the water. Water molecules are able to pass through the membrane barrier and flow anomalously fast which is ideal for application of these membranes for desalination.

Professor Rahul Nair, at The University of Manchester said: “Realisation of scalable membranes with uniform pore size down to atomic scale is a significant step forward and will open new possibilities for improving the efficiency of desalination .

“This is the first clear-cut experiment in this regime. We also demonstrate that there are realistic possibilities to scale up the described approach and mass produce graphene-based membranes with required sieve sizes.”

Mr. Jijo Abraham and Dr. Vasu Siddeswara Kalangi were the joint-lead authors on the research paper: “The developed membranes are not only useful for desalination, but the atomic scale tunability of the pore size also opens new opportunity to fabricate membranes with on-demand filtration capable of filtering out ions according to their sizes.” said Mr. Abraham.

By 2025 the UN expects that 14% of the world’s population will encounter water scarcity. This technology has the potential to revolutionize water filtration across the world, in particular in countries which cannot afford large scale desalination plants.

It is hoped that graphene-oxide systems can be built on smaller scales making this technology accessible to countries which do not have the financial infrastructure to fund large plants without compromising the yield of fresh produced.

Explore further: Researchers develop hybrid nuclear desalination technique with improved efficiency

More information: Tunable sieving of ions using graphene oxide membranes, Nature Nanotechnology, nature.com/articles/doi:10.1038/nnano.2017.21

Reusable carbon nanotubes could be the water filter of the future, says RIT study


Carbon NT Water Filter 136842_web

 

A new class of carbon nanotubes could be the next-generation clean-up crew for toxic sludge and contaminated water, say researchers at Rochester Institute of Technology.

Enhanced single-walled carbon nanotubes offer a more effective and sustainable approach to water treatment and remediation than the standard industry materials–silicon gels and activated carbon–according to a paper published in the March issue of Environmental Science Water: Research and Technology.

RIT researchers John-David Rocha and Reginald Rogers, authors of the study, demonstrate the potential of this emerging technology to clean polluted water. Their work applies carbon nanotubes to environmental problems in a specific new way that builds on a nearly two decades of nanomaterial research. Nanotubes are more commonly associated with fuel-cell research.

Graphene Mem 050815 3-anewapproachAlso Read About: UC BERKELEY: NANOTECHNOLOGY CAN HELP DELIVER AFFORDABLE, CLEAN WATER WITH GRAPHENE MEMBRANE: VIDEO

 

 

“This aspect is new–taking knowledge of carbon nanotubes and their properties and realizing, with new processing and characterization techniques, the advantages nanotubes can provide for removing contaminants for water,” said Rocha, assistant professor in the School of Chemistry and Materials Science in RIT’s College of Science.

Rocha and Rogers are advancing nanotube technology for environmental remediation and water filtration for home use.

“We have shown that we can regenerate these materials,” said Rogers, assistant professor of chemical engineering in RIT’s Kate Gleason College of Engineering. “In the future, when your water filter finally gets saturated, put it in the microwave for about five minutes and the impurities will get evaporated off.”

Carbon nanotubes are storage units measuring about 50,000 times smaller than the width of a human hair. Carbon reduced to the nanoscale defies the rules of physics and operates in a world of quantum mechanics in which small materials become mighty.

“We know carbon as graphite for our pencils, as diamonds, as soot,” Rocha said. “We can transform that soot or graphite into a nanometer-type material known as graphene.”

A single-walled carbon nanotube is created when a sheet of graphene is rolled up. The physical change alters the material’s chemical structure and determines how it behaves. The result is “one of the most heat conductive and electrically conductive materials in the world,” Rocha said. “These are properties that only come into play because they are at the nanometer scale.”

The RIT researchers created new techniques for manipulating the tiny materials. Rocha developed a method for isolating high-quality, single-walled carbon nanotubes and for sorting them according to their semiconductive or metallic properties. Rogers redistributed the pure carbon nanotubes into thin papers akin to carbon-copy paper.

“Once the papers are formed, now we have the adsorbent–what we use to pull the contaminants out of water,” Rogers said.

The filtration process works because “carbon nanotubes dislike water,” he added. Only the organic contaminants in the water stick to the nanotube, not the water molecules.

“This type of application has not been done before,” Rogers said. “Nanotubes used in this respect is new.”

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Co-authors on the paper are Ryan Capasse, RIT chemistry alumnus, and Anthony Dichiara, a former RIT post-doctoral researcher in chemical engineering now at the University of Washington.

Harnessing the Transformative Possibilities of the “Nanoworld”


4-harnessingth

Snow Crystal Landscape. Credit: Peter Gorges

Scientists have long suspected that the way materials behave on the nanoscale – that is when particles have dimensions of about 1–100 nanometres – is different from how they behave on any other scale. A new paper in the journal Chemical Science provides concrete proof that this is the case.

The laws of thermodynamics govern the behavior of materials in the macro world, while quantum mechanics describes behavior of particles at the other extreme, in the world of single atoms and electrons.

But in the middle, on the order of around 10–100,000 molecules, something different is going on. Because it’s such a tiny scale, the particles have a really big surface-area-to-volume ratio. This means the energetics of what goes on at the surface become very important, much as they do on the atomic scale, where is often applied.

Classical thermodynamics breaks down. But because there are so many particles, and there are many interactions between them, the quantum model doesn’t quite work either.

And because there are so many particles doing different things at the same time, it’s difficult to simulate all their interactions using a computer. It’s also hard to gather much experimental information, because we haven’t yet developed the capacity to measure behaviour on such a tiny scale.

This conundrum becomes particularly acute when we’re trying to understand crystallisation, the process by which particles, randomly distributed in a solution, can form highly ordered crystal structures, given the right conditions.

Chemists don’t really understand how this works. How do around 1018 molecules, moving around in solution at random, come together to form a micro- to millimetre size ordered crystal? Most remarkable perhaps is the fact that in most cases every crystal is ordered in the same way every time the crystal is formed.

However, it turns out that different conditions can sometimes yield different crystal structures. These are known as polymorphs, and they’re important in many branches of science including medicine – a drug can behave differently in the body depending on which polymorph it’s crystallised in.

What we do know so far about the process, at least according to one widely accepted model, is that particles in solution can come together to form a nucleus, and once a critical mass is reached we see crystal growth. The structure of the nucleus determines the structure of the final crystal, that is, which polymorph we get.Nanoparticle 2 051316 coated-nanoparticle

What we have not known until now is what determines the structure of the nucleus in the first place, and that happens on the nanoscale.

In this paper, the authors have used mechanochemistry – that is milling and grinding – to obtain nanosized , small enough that surface effects become significant. In other words, the chemistry of the nanoworld – which structures are the most stable at this scale, and what conditions affect their stability, has been studied for the first time with carefully controlled experiments.

And by changing the milling conditions, for example by adding a small amount of solvent, the authors have been able to control which polymorph is the most stable. Professor Jeremy Sanders of the University of Cambridge’s Department of Chemistry, who led the work, said “It is exciting that these simple experiments, when carried out with great care, can unexpectedly open a new door to understanding the fundamental question of how surface effects can control the stability of nanocrystals.”

Joel Bernstein, Global Distinguished Professor of Chemistry at NYU Abu Dhabi, and an expert in and structure, explains: “The authors have elegantly shown how to experimentally measure and simulate situations where you have two possible nuclei, say A and B, and determine that A is more stable. And they can also show what conditions are necessary in order for these stabilities to invert, and for B to become more stable than A.”

“This is really news, because you can’t make those predictions using classical thermodynamics, and nor is this the quantum effect. But by doing these experiments, the authors have started to gain an understanding of how things do behave on this size regime, and how we can predict and thus control it. The elegant part of the experiment is that they have been able to nucleate A and B selectively and reversibly.”

One of the key words of chemical synthesis is ‘control’. Chemists are always trying to control the properties of materials, whether that’s to make a better dye or plastic, or a drug that’s more effective in the body. So if we can learn to control how molecules in a solution come together to form solids, we can gain a great deal. This work is a significant first step in gaining that control.

Explore further: Surface chemistry offers new approach to directing crystal formation in pharmaceutical industry

More information: A. M. Belenguer et al. Solvation and surface effects on polymorph stabilities at the nanoscale, Chem. Sci. (2016). DOI: 10.1039/C6SC03457H

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Read Genesis Nanotechnology ~ Phantom Matter comes 2 Life+Graphene Super Caps 2 Power Tesla Rival Battery+NanoNeuro 2 treat stroke, epilepsy, Parkinson’s disease, cardiac conditions, and many others + ..http://buff.ly/2eCo78v