Best seen broken into four categories Part 1: Ion Selective Electrodes Part 3: Step Voltammetry Part 2: Amperometric Sensors Part 4: Cyclic Voltammetry

Why Voltammetry at all? Isnt ISE / Amperometrics good enough? According to the Prof – apparently not!  Reduction potentials and electron stoichiometry of redox reactions  Reversibility of redox reactions undergone by a molecule  Diffusion coefficients of species in stable oxidation states (3) Step Voltammetry

[O] = 5 mM Can be reduced to R via O + e -  R E 0 (standard reduction potential) = V Solution stirred continuously Step Voltammetry E electrode / V Time / s What does excitation profile look like?

[O] = 5 mM Can be reduced to R via O + e -  R E 0 (standard reduction potential) = V Solution stirred continuously Step Voltammetry I / A Time / s 0 What form does current vs time take? What about when [O] = 2.5 mM ? What about if solution unstirred ([O] = 5 mM) ?

Elementary Steps of an Electrode Reaction Mr. Electrode Stirrer e Bulk solutionInterface Oxidised species heads towards interface Mr. Electrode donates electron to oxidised species Reduced species heads into bulk solution

Mass Transport E electrode E0E0 +ve -ve time Mr. Electrode Concentration Gradients

Quantifying the Concentration Gradients

Cottrell Equation

A + e -  A - has E 0 = -0.1 V vs SHE Question The excitation profile shown below was applied to an unstirred solution containing 1 mM A and no A -. What will the current-time profile look like? The excitation profile shown below was applied to an unstirred solution containing 1 mM A - and no A. What will the current- time profile look like?

Accounting for Potential Dependence of the Current |i| = nFAk het (E)C analyte at electrode surface

Questions The excitation profiles shown on the right were applied to an unstirred solution containing 100% of the oxidised form of a Mn complex in two independent, but otherwise identical, experiments. What will the current vs. time profile look like in each case?

Questions The excitation profiles shown on the right were applied to a stirred solution containing 100% of the reduced form of a Mo complex in two independent, but otherwise identical, experiments. What will the current versus time profile look like in each case?

Questions The excitation profiles shown on the right were applied to an unstirred solution in two independent, but otherwise identical, experiments. The solution contained 50% of the oxidised form of an Fe complex and 50% of the reduced form of this complex. What will the current versus time profile look like in each case?

Best seen broken into four categories Part 1: Ion Selective Electrodes Part 3: Step Voltammetry Part 2: Amperometric Sensors Part 4: Cyclic Voltammetry

Also known as Linear Sweep (4) Cyclic Voltammetry E (V) E0E0 +ve -ve I (A) 0 +ve -ve time

Why a peak shape??? Ultimately leads to formation of cyclic voltamogram

How to read cyclic voltammograms

Buckminsterfullerene Examples How many redox active centres in buckminsterfullerene?

More Examples

Effect of Scan Rates

Electron Transfer Kinetics Effect of Scan Rates

Reaction Mechanism Effect of Scan Rates