Pigment discovery expanding into new colors

Chemists at Oregon State University have discovered that the same crystal structure they identified two years ago to create what may be the world's best blue pigment can also be used with different elements to create other colors, with significant potential in the paint and pigment industries.

First on the list, appropriately, is a brilliant orange pigment – appropriate for the OSU Beavers whose team colors are black and orange, and a university in a "Powered by Orange" advancement campaign.

But the broader potential for these pigments, researchers say, is the ability to tweak essentially the same chemical structure in slightly different ways to create a whole range of new colors in pigments that may be safer to produce, more durable and more environmentally benign than many of those that now exist.

Among the possibilities, they say, are colors that should be of interest to OSU's athletic rival 40 miles down the road at the University of Oregon – yellow and green.

"The basic crystal structure we're using for these pigments was known before, but no one had ever considered using it for any commercial purpose, including pigments," said Mas Subramanian, the Milton Harris Professor of Materials Science in the OSU Department of Chemistry.

"All of these colors should share the same characteristics of being extremely stable, durable, and resistant to heat and acid," he said. "And they are based on the same crystal structure, so minor adjustments to the technology will produce very different colors and very high quality pigments."

OSU has already applied for a patent on this technology, samples are now being tested by private industry, and the latest findings were published recently in Inorganic Chemistry, a journal of the American Chemical Society. The research has been supported by the National Science Foundation.

This invention evolved from what was essentially an accidental discovery in 2009 in an OSU lab, where Subramanian was exploring some manganese oxides for interesting electronic properties. At one stage of the process, when a sample had been heated to almost 2,000 degrees Fahrenheit, the compound turned a vivid blue.

It was found that this chemistry had interesting properties that affects the absorption of light and consequently its color. So Subramanian and his research team, including OSU professor emeritus Art Sleight, quickly shifted their electronics research into what may become a revolution in the paint and pigment industry. Future applications may range from inkjet printers to automobiles or even ordinary house paint.

The work created, at first, a beautiful blue pigment, which had properties that had eluded humans for thousands of years, dating back to the Han dynasty in China, ancient Egyptians and Mayan culture. Most previous blue pigments had various problems with toxicity, durability and vulnerability to heat or acid. Some are carcinogenic, others emit cyanide.

Expanding that research, the scientists further studied this unusual "trigonal-bypyramidal coordination" of crystalline structure, atoms that are combined in a certain five-part coordinated network. The initial blue color in the pigment came from the manganese used in the compound. The scientists have now discovered that the same structure will produce other colors simply by substituting different elements.

"The new orange pigment is based on iron, and we might use copper and titanium for a green pigment," Subramanian said. "Yellow and deep brown should be possible, and we should be able to make a new red pigment. A lot of red pigments are now made with cadmium and mercury, which can be toxic.

"These should all be very attractive for commercial use," he said.

Provided by Oregon State University (news : web)

Pigment discovery expanding into new colors

 Chemists at Oregon State University have discovered that the same crystal structure they identified two years ago to create what may be the world's best blue pigment can also be used with different elements to create other colors, with significant potential in the paint and pigment industries.

First on the list, appropriately, is a brilliant orange pigment -- appropriate for the OSU Beavers whose team colors are black and orange, and a university in a "Powered by Orange" advancement campaign.

But the broader potential for these pigments, researchers say, is the ability to tweak essentially the same chemical structure in slightly different ways to create a whole range of new colors in pigments that may be safer to produce, more durable and more environmentally benign than many of those that now exist.

Among the possibilities, they say, are colors that should be of interest to OSU's athletic rival 40 miles down the road at the University of Oregon -- yellow and green.

"The basic crystal structure we're using for these pigments was known before, but no one had ever considered using it for any commercial purpose, including pigments," said Mas Subramanian, the Milton Harris Professor of Materials Science in the OSU Department of Chemistry.

"All of these colors should share the same characteristics of being extremely stable, durable, and resistant to heat and acid," he said. "And they are based on the same crystal structure, so minor adjustments to the technology will produce very different colors and very high quality pigments."

OSU has already applied for a patent on this technology, samples are now being tested by private industry, and the latest findings were published recently in Inorganic Chemistry, a journal of the American Chemical Society. The research has been supported by the National Science Foundation.

This invention evolved from what was essentially an accidental discovery in 2009 in an OSU lab, where Subramanian was exploring some manganese oxides for interesting electronic properties. At one stage of the process, when a sample had been heated to almost 2,000 degrees Fahrenheit, the compound turned a vivid blue.

It was found that this chemistry had interesting properties that affects the absorption of light and consequently its color. So Subramanian and his research team, including OSU professor emeritus Art Sleight, quickly shifted their electronics research into what may become a revolution in the paint and pigment industry. Future applications may range from inkjet printers to automobiles or even ordinary house paint.

The work created, at first, a beautiful blue pigment, which had properties that had eluded humans for thousands of years, dating back to the Han dynasty in China, ancient Egyptians and Mayan culture. Most previous blue pigments had various problems with toxicity, durability and vulnerability to heat or acid. Some are carcinogenic, others emit cyanide.

Expanding that research, the scientists further studied this unusual "trigonal-bypyramidal coordination" of crystalline structure, atoms that are combined in a certain five-part coordinated network. The initial blue color in the pigment came from the manganese used in the compound. The scientists have now discovered that the same structure will produce other colors simply by substituting different elements.

"The new orange pigment is based on iron, and we might use copper and titanium for a green pigment," Subramanian said. "Yellow and deep brown should be possible, and we should be able to make a new red pigment. A lot of red pigments are now made with cadmium and mercury, which can be toxic.

"These should all be very attractive for commercial use," he said.

Story Source:

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

Journal Reference:

Peng Jiang, Jun Li, Arthur W. Sleight, M. A. Subramanian. New Oxides Showing an Intense Orange Color Based on Fe3 in Trigonal-Bipyramidal Coordination. Inorganic Chemistry, 2011; 50 (13): 5858 DOI: 10.1021/ic200535c

Twinkle, twinkle, quantum dot: New particles can change colors and tag molecules

 Engineers at Ohio State University have invented a new kind of nano-particle that shines in different colors to tag molecules in biomedical tests.

These tiny plastic nano-particles are stuffed with even tinier bits of electronics called quantum dots. Like little traffic lights, the particles glow brightly in red, yellow, or green, so researchers can easily track molecules under a microscope.

This is the first time anyone has created fluorescent nano-particles that can change colors continuously.

Jessica Winter, assistant professor of chemical and biomolecular engineering and biomedical engineering, and research scientist Gang Ruan describe their patent-pending technology in the online edition of the journal Nano Letters.

Researchers routinely tag molecules with fluorescent materials in order to see them under the microscope. Unlike the more common fluorescent molecules, quantum dots shine very brightly, and could illuminate chemical reactions especially well, allowing researchers to see the inner workings of living cells.

A bottleneck to combating major diseases like cancer is the lack of molecular or cellular-level understanding of biological processes, the engineers explained.

"These new nanoparticles could be a great addition to the arsenal of biomedical engineers who are trying to find the roots of diseases," Ruan said.

"We can tailor these particles to tag particular molecules, and use the colors to track processes that we wouldn't otherwise be able to," he continued. "Also, this work could be groundbreaking for the field of nanotechnology as a whole, because it solves two seemingly irreconcilable problems with using quantum dots."

Quantum dots are pieces of semiconductor that measure only a few nanometers, or billionths of a meter, across. They are not visible to the naked eye, but when light shines on them, they absorb energy and begin to glow. That's what makes them good tags for molecules.

Due to quantum mechanical effects, quantum dots "twinkle" -- they blink on and off at random moments. When many dots come together, however, their random blinking is less noticeable. So, large clusters of quantum dots appear to glow with a steady light.

Blinking has been a problem for researchers, because it breaks up the trajectory of a moving particle or tagged molecule that they are trying to follow. Yet, blinking is also beneficial, because when dots come together and the blinking disappears, researchers know for certain that tagged molecules have aggregated.

"Blinking is good and bad," Ruan explained. "But one day we realized that we could use the 'good' and avoid the 'bad' at the same time, by grouping a few quantum dots of different colors together inside a micelle."

A micelle is a nano-sized spherical container, and while micelles are useful for laboratory experiments, they are easily found in household detergents -- soap forms micelles that capture oils in water. Ruan created micelles using polymers, with different combinations of red and green quantum dots inside them.

In tests, he confirmed that the micelles appeared to glow steadily. Those stuffed with only red quantum dots glowed red, and those stuffed with green glowed green. But those he stuffed with red and green dots alternated from red to green to yellow.

The color change happens when one or another dot blinks inside the micelle. When a red dot blinks off and the green blinks on, the micelle glows green. When the green blinks off and the red blinks on, the micelle glows red. If both are lit up, the micelle glows yellow.

The yellow color is due to our eyes' perception of light. The process is the same as when a red pixel and green pixel appear close together on a television or computer screen: our eyes see yellow.

Nobody can control when color changes happen inside individual micelles. But because the particles glow continuously, researchers can use them to track tagged molecules continuously. They can also monitor color changes to detect when molecules come together.

Winter and Ruan said that the particles could also be used in fluid mechanics research -- specifically, micro-fluidics. Researchers who are developing tiny medical devices with fluid separation channels could use quantum dots to follow the fluid's path.

The same Ohio State research team is also developing magnetic particles to enhance medical imaging of cancer, and it may be possible to combine magnetism with the quantum dot technology for different kinds of imaging. But before the particles would be safe to use in the body, they would have to be made of biocompatible materials. Carbon-based nanomaterials are one possible option.

In the meantime, Winter and Ruan are going to continue developing the color-changing quantum dot particles for studies of cells and molecules under the microscope. They are also going to explore what happens when quantum dots of another color -- for instance, blue -- are added to the mix.

The university will look to license the technology for industry, and Winter and Ruan have created a Web site for the technologies they are developing: http://nanoforneuro.com.

This research was supported by the National Science Foundation, an endowment from the William G. Lowrie family to the Department of Chemical and Biomolecular Engineering, and the Center for Emergent Materials at Ohio State.

Story Source:

The above story is reprinted (with editorial adaptations) from materials provided by Ohio State University. The original article was written by Pam Frost Gorder.

Journal Reference:

Gang Ruan, Jessica O. Winter. Alternating-Color Quantum Dot Nanocomposites for Particle Tracking. Nano Letters, 2011; 11 (3): 941 DOI: 10.1021/nl103233b