An
accidental discovery in a laboratory at Oregon State University has apparently
solved a quest that over thousands of years has absorbed the energies of
ancient Egyptians, the Han dynasty in China, Mayan cultures and more – the
creation of a near-perfect blue pigment.
Through much of recorded human
history, people around the world have sought inorganic compounds that could be
used to paint things blue, often with limited success. Most had environmental
or durability issues. Cobalt blue, developed in France in the early 1800s, can
be carcinogenic. Prussian blue can release cyanide. Other blue pigments are not
stable when exposed to heat or acidic conditions.
But chemists at OSU have discovered new compounds based on
manganese that should address all of those concerns. They are safer to produce,
much more durable, and should lead to more environmentally benign blue pigments
than any being used now or in the past. They can survive at extraordinarily
high temperatures and don’t fade after a week in an acid
bath.
The findings were recently published in the Journal of the American Chemical Society, and a patent has been applied for on the
composition of the compound and the process used to create it. The research was
funded by the National Science Foundation.
“Basically, this was an accidental discovery,” said Mas Subramanian, the
Milton Harris Professor of Materials Science in the OSU Department of
Chemistry. “We were exploring manganese oxides for some interesting electronic
properties they have, something that can be both ferroelectric and
ferromagnetic at the same time. Our work had nothing to do with looking for a
pigment.
“Then one day a graduate student who is working on the project was taking
samples out of a very hot furnace while I was walking by, and it was blue, a
very beautiful blue,” he said. “I realized immediately that something amazing
had happened.”
What
had happened, the researchers said, was that at about 1,200 °C – almost 2,000
°F – this otherwise innocuous manganese oxide turned into a vivid blue compound
that could be used to make a pigment able to resist heat and acid, be
environmentally benign and cheap to produce from a readily available
mineral.
The newest – and possibly the best – blue pigment in world history was
born, due to manganese ions being structured in an unusual “trigonal bipyramidal
coordination” in the presence of extreme heat.
“Ever since the early Egyptians developed some of the first blue
pigments, the pigment industry has been struggling to address problems with
safety, toxicity and durability,” Subramanian said.
The pigment may eventually find uses in everything from inkjet printers
to automobiles, fine art or house paint, researchers say. The scientists said
in their journal article that the new compound yields “a surprisingly intense
and bright blue color,” and they have outlined its structure and
characteristics in detail. Collaborating on the work were researchers in the
Materials Department at the University of California/Santa
Barbara.
“A lot of the most interesting discoveries are not really planned, we’ve
seen that throughout history,” Subramanian said. “There is luck involved, but I
also teach my students that you have to stay alert to recognize something when
it happens, even if it isn’t what you were looking for. Luck favors the alert mind.”
For more information,
contact Mas Subramanian, 541/737.8235 or e-mail
mas.subramanian@oregonstate.edu.
