Page 78 - MODERN ELECTROCHEMISTRY

22 CHAPTER 1

from the ions and molecules in solution (separating parallel and vertical beam
information by subtracting the vertical from that of the parallel signal is only an
approximation for metal–solution systems). This technique is called Fourier transform
IR absorption spectroscopy (FTIRAS). The Fourier transform is used in the mathe-
matics of calculating the results. While the process is complex, the results are relatively
simple and helpful. One of these is shown in Fig. 1.11.
This methodology reveals the tell-tale signal of bonds present in intermediate
radicals on the electrode surface if the electrochemical reaction is operating in a steady
state, i.e., the reaction is in its final pathway with the final rate-determining step. The
exciting possibility of advanced versions of the FTTRAS technique is that really rapid
(millisecond) changes in the spectra of the surface radicals can be recorded. Then,
changes in the nature and concentration of radicals that may occur during the switch-
ing-on phase of the electrical current could be measured. This can provide much
information on the buildup and structure of the pathway of the reaction occurring on
the surface. When this happens, fast-reacting surface spectroscopic measurements will
become a principal aid to studies of mechanisms in electrochemistry.

1.9. RELAY STATIONS PLACED INSIDE PROTEINS CAN CARRY AN
ELECTRIC CURRENT
The body contains several thousand different enzymes that are catalysts for
specific bioreactions. Without them, biochemical pathways in the body would not
function.
Diabetics have a need for a glucose meter that would show the glucose concen-
tration in the blood at any moment without having to take a sample. If the glucose
builds up too much, the meter would send out a signal telling the wearer of the need
for insulin.
Glucose gets oxidized with the cooperation of an enzyme called glucose oxidase,
which has a molecular diameter of 86 Å. Suppose we could immobilize glucose
oxidase on an organic semiconductor such as polypyrrole, and the electrons produced
when glucose in the blood is oxidized could be brought out through the glucose oxidase
to work a meter on the wrist: our aim would be achieved, and diabetics could monitor
their condition at any time by a glance at the wrist. 10
One could carry this idea further. Since enzymes are so specific in reacting to only
certain molecules, one could imagine a future “general diagnoser,” a plaque with a
series of enzymes adsorbed on microelectrodes that are exposed to the blood, with
each able to pick out the molecules that indicate the presence of specific diseases.
Oxidation reactions would provide electrons and an electrical signal would indicate
the disease through the circuitry, which would identify the enzyme from which the
current originated. For such an idea to work, one must have electronic conductivity of

10
A wrist glucose meter? Not yet, but several are in development.