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Stephani's Project Page - RISE Summer 2006 |
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Intern: Stephani Gulbrandsen, Materials,
Franklin W. Olin College of Engineering
Mentor: Ansanga Ransighe
Faculty Supervisor: Steven Buratto
Department: Chemistry and Biochemistry |
IN SITU DEPOSITION OF PT/RU METAL NANOCLUSTERS FOR USE IN DIRECT METHANOL FUEL CELLS
Tin oxide nanowires grown by way of the vapor-liquid-solid (VLS) method are a
proven gas sensing element. Tin oxide nanowire devices were constructed by
laying down VLS grown tin oxide nanowires on silica wafers and then evaporating
titanium and gold through a copper grid contact mask. The devices were then
assembled into a usable circuit that would allow for current to be recorded.
With a constant voltage, pressure, volume and temperature, the current is
dependent entirely on the absence or existence of gas in the system. Results
show that the presence of oxygen gas greatly lowers the current of the circuit
while the presence of carbon monoxide raises the current. Surface defects in
the tin oxide nanowire are what allow conductance through the circuit. Oxygen
attaches to these receptor sites, lowering the current. Carbon monoxide reopens
these receptor sites, raising the current. The samples were then modified with
an aminopropyl trimethoxy silane monolayer which reduces the number of
available defects thus causing a less intense decrease in current with the
addition of oxygen. The ability to change the sensitivity and selectivity
makes these nanowire devices useful in a variety of applications and since they
use conductometric based sensing they are easy to integrate into modern silicon
based technology.
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