Electrochemistry and molecular recognition

1
Electrochemistry and molecular recognition
2
Non-Faradiac process Process such as absorption
or desorption, in which charge does not across
the interface, but external current can flow
because of the surface potential change etc.
(e.g. Cd)
3
(No Transcript)
4
Electrical Double Layer
IHP OHP
ss si so
Total current density
5
300A (10-2M) Diffuse layer
6
(No Transcript)
7
(No Transcript)
8
(No Transcript)
9
(No Transcript)
10
(No Transcript)
11
(No Transcript)
12
Cyclic Voltammetry
E Ei vt (forward sweep) E Es vt (reverse
sweep) I initial S Switching
13
Cell Design should exclude oxygen and moisture.
Glove boxes or glove bags are necessary sometimes.
14
Solvents Should be stable to the redox
conditions Electrolytes Bu4NBF4 Bu4NPF6 Bu4NClO4
e.g. Bu4NPF6 in CH3CN 3.4 to 2.9 v
15
Working electrodes The WE should have a facile
electron transfer with electroactive species.
The factors behind are not well
understood. Pretreatment or polishing of the
electrode-surface is necessary. Pt, glassy
carbon, gold, silver, amalgams are common
materials for the WE.
16
Reference electrodes Electrode potential does not
change when current increases.
17
(No Transcript)
18
Faradiac process Electron transfer causes
oxidation and reduction to occur. This process is
governed by Faradays law (e.g. R)
19
(No Transcript)
20
(No Transcript)
21
E1/2 (EpcEpa)/2 Eo
(RT/nF)lnz where z (D(O)/D(R))1/2
22
CV for absorbed monolayer CV curve for
reduction of absorbed O and sweep
reversal. Dep.1/2 3.53RT/nF
23
(No Transcript)
24
Schematic configuration of photoactivated
molecular switches
25
(No Transcript)
26
(No Transcript)
27
(No Transcript)
28
(No Transcript)
29
(A) Chronoamperometric responses of the assembly
consisting of the ferrocene-functionalized
b-cyclodextrin threaded onto the azotranslocation
benzene-alkyl chain and blocked by the anthracene
barrier. (a) Monolayer in trans-azobenzene state.
(b) Monolayer in cis-azobenzene state. (B) Cyclic
variation of the electron transfer rates of trans
the ferrocene-functionalized b-cyclodextrin in
the molecular train- shuttle upon reversible
photoisomerization of the monolayer (?)monolayer
in trans-azobenzene state, (?) monolayer in
cis-azobenzene state.
30
(No Transcript)
31
(A) Cyclic voltammetric response of cytochrome c
(0.1mM) at a mixed 6a/b and pyridine
monolayer-modified electrode in (a) the 6a and
(b) the 6b states. Inset switching behavior of
the system circles and squares represent the
photoisomerizable units in the spiropyran and the
merocyanine states, respectively. (B) The same
system with COx (1 mM) and O2 and in (a) the 6a
and (b) the 6b states. Inset Switching behavior
(as for part A).
32
(No Transcript)
33
From Enzyme to Molecular Device. Exploring
the Interdependence of Redox and Molecular
Recognition
34
(No Transcript)
35
(No Transcript)
36
(No Transcript)
37
Phenyl receptor 6a, which cannot form appreciable
aromatic-aromatic contacts with bound flavin 1,
causes an 18 mV shift in the E1/2 of flavin 1 to
less negative values, accompanied by an
enhancement of the reversible reoxidation wave.
These two effects are indicative of the
stabilization of Fl(rad) - by hydrogen bonding,
as observed in the flavin 1-receptor 2 complex.
The p-stacking receptors 6b,c, however, shift the
flavin 1 E1/2 to more negative values, making
flavin 1 harder to reduce.
38
Size and Polarizability
39
(No Transcript)
40
(No Transcript)