Project Update October 11th 2010

							Electrode Array
GK-12 Meeting
November 2nd 2010
   Megan Easterly




                    1
Electrochemistry
   Oxidation
       Loss of electrons
       Electrode removes
        electrons from the solution
       Anodic peak current
   Reduction
       Gain of electrons
       Electrode gives electrons
        to the solution
       Cathodic peak current

                                      2
Electrodes
   Working (WE)
       Where the reaction of interest
        occurs
       Current is measured
   Reference (RE)
       Measures WE potential by
        maintaining a stable potential
   Auxillary (AE)
       Electron provider/remover
   Electrolyte
       Electrically conductive solution
                                           3
Gold Electrode Array

   8 Au working
   1 Au reference
   1 Au auxillary
   Study FDCA             2    1 8   7



                     aux                  ref




                           3   4 5    6



                                                4
     Ferrocenedicarboxylic Acid (FDCA)

        E0 ferrocene = +0.361 V vs. NHE




Bard, A.; Faulkner, L., “Electrochemical Methods. Fundamentals and Applications” 2nd Ed. Wiley, New York. 2001
Image courtesy of Dr. Karst research group:                                                              5
http://www.uni-muenster.de/Chemie.ac/karst/research/projects/hyphenated%20techniques.htm
     The Math

         Randles-Sevcik equation
                                                           3                     1
         ip  (2.69 10 )n ADOv C                 5            2                     2    *
                                                                                          O
                 i p  peak current (A)
                  n  number of electrons transferred per mole (moles)
                  A  electrode area (cm)
                                        2


                DO  diffusion coefficient (cm/sec)
                                             2


                 v  scan rate (V/sec)
                CO  concentration (moles/cm)
                 *                         3




Bard, A.; Faulkner, L., “Electrochemical Methods. Fundamentals and Applications” 2nd Ed. Wiley, New York. 2001
                                                                                                        6
Simultaneous Detection

   External reference and auxillary




                                       7
Simultaneous Detection

   Normalized currents to
    electrode area
   Linearity
       > 0.9990
   Sensitivity (μA*mm-2*mM-1)
       Ox 1.43 ± 0.07
       Red -1.46 ± 0.07



                                 8
DPV of FDCA

   Optimal potential
    determination
       vs. AgAgCl
           0.43 V
       vs. Au
           0.37 V
   Ran individually



                        9
Amperometry of FDCA

   On-chip reference
    and auxillary
       0.37 V
   Individual detection




                           10
Amperometry of FDCA

   Normalized to electrode area
   Linearity
       > 0.9987
   Sensitivity
       22.44 ± 12.93
    nA*mm-2*mM-1




                                   11
New Mask

   Well defined areas
       Working = 0.09 mm2
       Reference = 2.25 mm2
       Auxillary = 2.25 mm2
       Spacing = 0.3 mm




                               12
     Future Work

         Fabrication of new electrode array
         Chemiluminescence detection of NO donor
         Calibration of electrodes using NO
         Modification of Au array
             Nafion
             Polypyrrole




Diab, N.; Oni, J.; Schulte, A.; Radtke, I.; Blochl, A.; Schuhmann, W., Talanta, 61, 2003, 43-51
                                                                                                  13