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 THE
QUARTZ PIEZOELECTRIC EFFECT
A
piezoelectric material generates an electric
charge when mechanically deformed, conversely,
when an external electric field is applied
to piezoelectric materials they mechanically
deform.
The
quartz is a piezoelectric material so it
has the ability to measure the mass of the
thin films sticked to its surface because
the measured resonant frequency depends
on the mass material deposided on the quartz
crystal surface, this frequency changes
accordingly to the well established Sauerbrey
equation.
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QCM - Quartz Crystal Microbalance
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The quartz crystal at the begin and
the quartz crystal coated with a film sensible
to the substance to be revealed.
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The substance to be revealed is put in
contact with the treated quartz. It begins
an affinity reaction between the analyte
to be revealed and the quartz.
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An increase of the mass on the quartz
crystal lead to a frequency falling and
a decrease of the mass on the quartz crystal
lead to a frequency rising.
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EQCM - Electrochemical Quartz Crystal Microbalance
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In solid state voltammetry, mass changes
occur at the electrode surface as oxidation
and reduction occur.
The
Quartz Crystal Microbalance utilises the
inverse piezoelectric qualities of quartz
crystals to measure changes in attached
surface mass.
This
figure shows a schematic representation
of the Electrochemical Quartz Crystal Microbalance
(EQCM) instrumentation.
In the electrochemical application the voltammetry
is carried out using one side of the quartz
crystal, exposed to the solution in the
electrochemical cell, as the working electrode.
This EQCM setup allows simultaneous measurement
of mass and current in a voltammetric experiment.
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