Charles Redmond
Headquarters, Washington, D.C.                                                
November 15, 1993
(Phone:  202/358-1757)

Jim Doyle
Jet Propulsion Laboratory, Pasadena, Calif.
(Phone:  818/354-5011)

RELEASE:  93-209

JPL TEAM DEVELOPS SPECIAL POLLUTION DETECTION GLASS

     NASA Jet Propulsion Laboratory (JPL), Pasadena, Calif., 
scientists have developed a multifunctional glass that detects 
pollutants in the air by a dramatic change in color, according to 
a paper published today in a scientific journal.

     Dr. Albert Stiegman, a JPL chemist, and his associates 
described the development in a paper, "Vanadia/Silica Xerogels and 
Nano-Composites," published today in the journal Chemistry of 
Materials.

     "The most interesting property of this new glass is its 
ability to function as a chemical sensor," Stiegman said.

     His co-authors included Drs. Hellmut Eckert of the Department 
of Chemistry, University of California at Santa Barbara and Gary 
Plett, Soon Sam Kim, Mark Anderson and Andre Yavrouian of JPL.

     He described the sensor as a new metal-containing silica gel 
glass.  This type of glass is hard and transparent like 
conventional window glass but, on a microscopic level, is highly 
porous like a sponge.

     To make the new pollution sensors, the metal vanadium is 
placed into the porous channels.  Molecules of gasses present in 
the atmosphere seep into the channels, attach to the metal and 
change its color. The glass radiates that color.

     For example, the presence of hydrogen sulfide and nitrous 
oxide, two important pollutants, turns the glass to a deep amber 
and a lemon yellow color, respectively.  Formic acid turns it dark 
green.  Ammonia turns it pale yellow.

     The material also shows a distinct preference for certain 
gases.  It appears to favor the absorption of formaldehyde over 
that of water, which in turn is clearly favored over ammonia, 
Stiegman said.

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     NASA contracted for the work seeking a sensor for planetary 
atmospheres.  Stiegman said, however, that the material could be 
equally important in the detection and monitoring of atmospheric 
pollutants on Earth.

     Furthermore, he said, the material is hard, transparent and 
easily can be fabricated into optical compounds required for a 
sensing device.  Because it is completely inorganic, it can 
withstand large temperature extremes and harsh environments 
without degradation.

     "Taken together," he said, "we feel that these properties 
recommend this material as a new and potentially important new 
type of environmental chemical sensing element."

     The work by Stiegman and his colleagues was done under 
contract to NASA. 

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