Research on solubility yields promise for pharmaceutical, other industries

 A method for increasing solubility (the ability of one substance to dissolve into another), developed by a graduate student at the Hebrew University of Jerusalem Casali Institute of Applied Chemistry, has yielded promising commercial benefits for industry, particularly in pharmaceuticals, cosmetics and agriculture.

The method, developed by Katy Margulis-Goshen, a Ph.D. student of Prof. Shlomo Magdassi, produces a rapid conversion of oil-in-water microemulsions, containing an insoluble substance, into a dry powder composed of nanoparticles which can easily be dissolved in water or other biological fluids.

For her work, Marguis-Goshen, who immigrated to Israel from the Ukraine in 1990, was chosen as one of the winners of this year's Kaye Innovation Awards at the university.

The process she developed is of unique industrial importance, since it leads to a significant increase in solubility and dissolution properties of almost any active ingredient, without a high energy investment.

Enhancing such solubility is especially important in the field of pharmaceutics, where nearly 50% of the newly discovered drugs cannot be administered or are very poorly absorbed due to their low solubility. Increasing solubility is also important in the field of agriculture, since the majority of insecticides are highly hydrophobic (resistant to mixing with water), and their regular application therefore requires the use of organic solvents, which are harmful to the farmer and the environment.

In cosmetics, active cosmetic ingredients for dermal delivery are usually also water resistant, so that incorporating them into non-greasy, water-based formulations is of great importance.

The new process invented by Margulis-Goshen can be also applied in many other fields, such as nutrition and the manufacture of printing ink and paint.

If the active ingredient, for example, is a water-resistant drug, the powder developed in her method may be injected or incorporated into capsules, tablets and other fast-dissolving drug formulations. Such dosage forms have shown a tremendous increase in dissolution rate in water and biological fluids. They are expected to improve bioavailability of the drug, minimize its side effects by reducing the total dose needed, and allow drug targeting. A very significant improvement in drug dissolution has been shown in this way in tests with three drugs.

Similar beneficial results have been shown in applying the invention to the conversion of hydrophobic pesticides into a powder, allowing a reduction of at least six times in the effective concentration of the pesticide with utilization of water instead of organic solvents as the dispersing medium. In cosmetics, the powder containing active cosmetic ingredient may be incorporated into new, stable, water-based formulations.

Story Source:

The above story is reprinted from materials provided by Hebrew University of Jerusalem, via AlphaGalileo.

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

Novel device removes heavy metals from water

 Engineers at Brown University have developed a system that cleanly and efficiently removes trace heavy metals from water. In experiments, the researchers showed the system reduced cadmium, copper, and nickel concentrations, returning contaminated water to near or below federally acceptable standards. The technique is scalable and has viable commercial applications, especially in the environmental remediation and metal recovery fields.

Results appear in the Chemical Engineering Journal.

An unfortunate consequence of many industrial and manufacturing practices, from textile factories to metalworking operations, is the release of heavy metals in waterways. Those metals can remain for decades, even centuries, in low but still dangerous concentrations.

Ridding water of trace metals "is really hard to do," said Joseph Calo, professor emeritus of engineering who maintains an active laboratory at Brown. He noted the cost, inefficiency, and time needed for such efforts. "It's like trying to put the genie back in the bottle."

That may be changing. Calo and other engineers at Brown describe a novel method that collates trace heavy metals in water by increasing their concentration so that a proven metal-removal technique can take over. In a series of experiments, the engineers report the method, called the cyclic electrowinning/precipitation (CEP) system, removes up to 99 percent of copper, cadmium, and nickel, returning the contaminated water to federally accepted standards of cleanliness. The automated CEP system is scalable as well, Calo said, so it has viable commercial potential, especially in the environmental remediation and metal recovery fields. The system's mechanics and results are described in a paper published in the Chemical Engineering Journal.

A proven technique for removing heavy metals from water is through the reduction of heavy metal ions from an electrolyte. While the technique has various names, such as electrowinning, electrolytic removal/recovery or electroextraction, it all works the same way, by using an electrical current to transform positively charged metal ions (cations) into a stable, solid state where they can be easily separated from the water and removed. The main drawback to this technique is that there must be a high-enough concentration of metal cations in the water for it to be effective; if the cation concentration is too low -- roughly less than 100 parts per million -- the current efficiency becomes too low and the current acts on more than the heavy metal ions.

Another way to remove metals is through simple chemistry. The technique involves using hydroxides and sulfides to precipitate the metal ions from the water, so they form solids. The solids, however, constitute a toxic sludge, and there is no good way to deal with it. Landfills generally won't take it, and letting it sit in settling ponds is toxic and environmentally unsound. "Nobody wants it, because it's a huge liability," Calo said.

The dilemma, then, is how to remove the metals efficiently without creating an unhealthy byproduct. Calo and his co-authors, postdoctoral researcher Pengpeng Grimshaw and George Hradil, who earned his doctorate at Brown and is now an adjunct professor, combined the two techniques to form a closed-loop system. "We said, 'Let's use the attractive features of both methods by combining them in a cyclic process,'" Calo said.

It took a few years to build and develop the system. In the paper, the authors describe how it works. The CEP system involves two main units, one to concentrate the cations and another to turn them into stable, solid-state metals and remove them. In the first stage, the metal-laden water is fed into a tank in which an acid (sulfuric acid) or base (sodium hydroxide) is added to change the water's pH, effectively separating the water molecules from the metal precipitate, which settles at the bottom. The "clear" water is siphoned off, and more contaminated water is brought in. The pH swing is applied again, first redissolving the precipitate and then reprecipitating all the metal, increasing the metal concentration each time. This process is repeated until the concentration of the metal cations in the solution has reached a point at which electrowinning can be efficiently employed.

When that point is reached, the solution is sent to a second device, called a spouted particulate electrode (SPE). This is where the electrowinning takes place, and the metal cations are chemically changed to stable metal solids so they can be easily removed. The engineers used an SPE developed by Hradil, a senior research engineer at Technic Inc., located in Cranston, R.I. The cleaner water is returned to the precipitation tank, where metal ions can be precipitated once again. Further cleaned, the supernatant water is sent to another reservoir, where additional processes may be employed to further lower the metal ion concentration levels. These processes can be repeated in an automated, cyclic fashion as many times as necessary to achieve the desired performance, such as to federal drinking water standards.

In experiments, the engineers tested the CEP system with cadmium, copper, and nickel, individually and with water containing all three metals. The results showed cadmium, copper, and nickel were lowered to 1.50, 0.23 and 0.37 parts per million (ppm), respectively -- near or below maximum contaminant levels established by the Environmental Protection Agency. The sludge is continuously formed and redissolved within the system so that none is left as an environmental contaminant.

"This approach produces very large volume reductions from the original contaminated water by electrochemical reduction of the ions to zero-valent metal on the surfaces of the cathodic particles," the authors write. "For an initial 10 ppm ion concentration of the metals considered, the volume reduction is on the order of 106."

Calo said the approach can be used for other heavy metals, such as lead, mercury, and tin. The researchers are currently testing the system with samples contaminated with heavy metals and other substances, such as sediment, to confirm its operation.

The research was funded by the National Institute of Environmental Health Sciences, a branch of the National Institutes of Health, through the Brown University Superfund Research Program.

Editors: Brown University has a fiber link television studio available for domestic and international live and taped interviews, and maintains an ISDN line for radio interviews. For more information, call (401) 863-2476.

Story Source:

The above story is reprinted from materials provided by Brown University.

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

Journal Reference:

Pengpeng Grimshaw, Joseph M. Calo, George Hradil. Cyclic electrowinning/precipitation (CEP) system for the removal of heavy metal mixtures from aqueous solutions. Chemical Engineering Journal, 2011; 175: 103 DOI: 10.1016/j.cej.2011.09.062

Mystery of car battery's current solved

Chemists have solved the 150 year-old mystery of what gives the lead-acid battery, found under the hood of most cars, its unique ability to deliver a surge of current.

Lead-acid batteries are able to deliver the very large currents needed to start a car engine because of the exceptionally high electrical conductivity of the battery anode material, lead dioxide. However, even though this type of battery was invented in 1859, up until now the fundamental reason for the high conductivity of lead dioxide has eluded scientists.

A team of researchers from Oxford University, the University of Bath, Trinity College Dublin, and the ISIS neutron spallation source, have explained for the first time the fundamental reason for the high conductivity of lead dioxide.

A report of the research appeared in a recent issue of Physical Review Letters.

'The unique ability of lead acid batteries to deliver surge currents in excess of 100 amps to turn over a starter motor in an automobile depends critically on the fact that the lead dioxide which stores the chemical energy in the battery anode has a very high electrical conductivity, thus allowing large current to be drawn on demand,' said Professor Russ Egdell of Oxford University's Department of Chemistry, an author of the paper.

'However the origin of conductivity in lead oxide has remained a matter of controversy. Other oxides with the same structure, such as titanium dioxide, are electrical insulators.'

Through a combination of computational chemistry and neutron diffraction, the team has demonstrated that lead dioxide is intrinsically an insulator with a small electronic band gap, but invariably becomes electron rich due to the loss of oxygen from the lattice, causing the material to be transformed from an insulator into a metallic conductor.

The researchers believe these insights could open up new avenues for the selection of improved materials for modern battery technologies.

Professor Egdell said: 'The work demonstrates the power of combining predictive materials modelling with state-of-the-art experimental measurements.'

Story Source:

The above story is reprinted from materials provided by University of Oxford.

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

Journal Reference:

David Scanlon, Aoife Kehoe, Graeme Watson, Martin Jones, William David, David Payne, Russell Egdell, Peter Edwards, Aron Walsh. Nature of the Band Gap and Origin of the Conductivity of PbO_{2} Revealed by Theory and Experiment. Physical Review Letters, 2011; 107 (24) DOI: 10.1103/PhysRevLett.107.246402

Record conductivity achieved in strained lattice organic semiconductor

By packing molecules closer together, chemical engineers at Stanford have dramatically improved the electrical conductivity of organic semiconductors. The advance could herald flexible electronics, more efficient solar panels, and perhaps even better television screens.

Organic semiconductors could usher in an era of foldable smartphones, better high-definition television screens and clothing made of materials that can harvest energy from the sun needed to charge your iPad, but there is one serious drawback: Organic semiconductors do not conduct electricity very well.

In a paper recently published in the journal Nature, researchers at Stanford led by chemical engineer Zhenan Bao have changed that equation by improving the ability of the electrons to move through organic semiconductors. The secret is in packing the molecules closer together as the semiconductor crystals form, a technique engineers describe as straining the lattice.

Bao and her colleagues have more than doubled the record for electrical conductivity of an organic semiconductor and shown an eleven-fold improvement over unstrained lattices of the same semiconductor.

"Strained lattices are no secret. We've known about their favorable electrical properties for decades and they are in use in today's silicon computer chips, but no one has been successful in creating a stable strained lattice organic semiconductor with a very short distance between molecules, until now," said Bao.

In the past, engineers have tried to compress the lattices in these materials by synthetically growing the crystals under great pressure. "But, as soon as you release the pressure, the crystal just goes back to its natural, unstrained state," said Bao. "We've been able to stabilize these crystals in tighter formations than ever before."

Fine-tuning

Bao's team used a solution shearing technique similar to a coating process well known in the semiconductor industry. Solution shearing involves a thin liquid layer of the semiconductor sandwiched between two metal plates. The lower plate is heated and the upper plate floats atop the liquid, gliding across it like a barge. As the top plate moves, the trailing edge exposes the solution to a vaporized solvent and, heated by the lower plate, the crystals form into a thin film.

"Using a process so similar to current industry technology is important, as it could speed these new semiconductors to market," said Bao.

The engineers can then "tune" the speed at which the top plate moves, the thickness of the solution layer, the temperature of the lower plate, and other engineering factors to achieve optimal results.

The crystals form in differing structures based on the speed at which the top plate moves. These differences are clearly evident in photographs. At slow speeds, the crystals form in long, straight structures, in line with the direction the top plate is moving. At higher speeds, the crystals form wildly irregular patterns, and in other speeds the patterns resemble tiny snowflakes.

The engineers next tested the various crystalline patterns for their electrical properties. They found that optimal electrical conductivity was achieved when the top plate moved at 2.8 millimeters per second, a speed in the middle of the range they tested.

"In comparing the photographs of the crystals, it is not the longest, straightest structures that result in the best electrical characteristics," said Bao, "but the one with a shorter, yet highly consistent pattern."

New structures, new analyses

Bao's new semiconductor proved challenging in at least one other regard: Measurement and visualization of the lattices to understand how and why they work. To gain this understanding, she turned to Stefan Mannsfeld, PhD, a staff scientist and expert in x-ray scattering at Stanford Synchrotron Radiation Lightsource, a co-author of the paper.

"We have been able to improve how we analyze the relative brightness of the peaks we can see in x-ray diffraction images," said Mannsfeld. "Previously this was only possible when analyzing relatively big single crystals, but we have for the first time been able to duplicate this for very thin films of these crystals."

With improved analysis, the team was able to understand the physics behind the improvement. "Our analysis made it possible not only to see the impact of the strain on the lattice geometry, but also to determine the exact way in which the molecules pack in the lattice. As a result we obtained a better understanding of why such structures improve the molecule-to-molecule electrical coupling that improves the electrical efficiency," said Mannsfeld.

In the paper, Bao describes her new technique as general enough as to be applicable to other materials that might someday yield even better electrical characteristics in in a wide range of organic semiconductors.

Stanford doctoral candidates Guarav Giri and Eric Verploegen, former post-doctoral scholar Hector Becerril, PhD, in Bao's lab and Michael F. Toney, PhD, of the Stanford Synchrotron Radiation Lightsource, contributed to this research.

Story Source:

The above story is reprinted from materials provided by Stanford School of Engineering. The original article was written by Andrew Myers.

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

Journal Reference:

Gaurav Giri, Eric Verploegen, Stefan C. B. Mannsfeld, Sule Atahan-Evrenk, Do Hwan Kim, Sang Yoon Lee, Hector A. Becerril, Alán Aspuru-Guzik, Michael F. Toney, Zhenan Bao. Tuning charge transport in solution-sheared organic semiconductors using lattice strain. Nature, 2011; 480 (7378): 504 DOI: 10.1038/nature10683