Graphene Gas Sensor
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Abstract
Gas permeation through graphene membranes has received considerable
attention for water purification and molecular sieving applications. However,
characterization of the permeation has been limited to long timescales
of minutes. This thesis shows a method for measuring gas permeation
through porous graphene membranes at the microsecond timescale. Suspended
porous graphene membranes, with an average pore size of 14 nm
and a single 400 nm pore, are brought into sinusoidal motion by optothermal
actuation. By monitoring the frequency dependent phase delay between
actuation signal and mechanical motion, the gas dependent permeation time
of the porous membrane is determined. The permeation time constant is
demonstrated to be proportional to the square root of the molecular mass,
indicating an effusion dominated permeation mechanism. The determination
of permeation at timescales below 1 ms using a femtoliter gas cavity
opens up opportunities for novel nanoscale porous graphene based gas sensors,
with very fast response times.