Nanotechnology-Enabled Sensors

96 Chapter 3: Transduction Platforms
Fig. 3.20 The electric bi-layer.
LSV and CV techniques were proposed at the beginning of the 1950s
when their related theories were described. 9 However, the use of these
methods only received considerable attention in 80s and 90s when capabilities
for interpreting the relevant responses, fast data acquisition systems
and availability of computational tools for processing experimental data
became widely available.
The electrochemical process and the shape of I-V characteristics obtained
during voltammetry depend on diffusion and capacitive currents.
Diffusion current
The following are the most common conditions in the observation of
diffusion current:
(a) The voltammetric system is mixed up constantly. In this case, the thickness
of the diffusion layer remains constant. The diffusion current depends
on the difference of target analyte concentrations on the surface of the
electrode and in bulk of the solution as well as the thickness of the diffusion
layer, δ.
The diffusion current can be calculated from the general Faradiac relationship:
12
i ( t)
= ( dN / dt)nF
, (3.68)