11/15/93:  JPL TEAM DEVELOPS SPECIAL POLLUTION DETECTION GLASS

Charles Redmond
Headquarters, Washington, D.C.                  November 15, 1993

Jim Doyle
Jet Propulsion Laboratory, Pasadena, Calif.

RELEASE:  93-209

     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.

     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.

- end -
---
  Via FTL BBS (404-292-8761) and NASA Spacelink (205-895-0028)
