1. Hydrogen Peroxide Detection Using Biogenic and Synthetic MnO 2 Shu Feng, Jim Nurmi, Paul Tratynek Satya Chinni, Brad Tebo Department of Environmental and Biomolecular Systems OGI School of Science and Engineering Oregon Health & Science University

2. H 2 O 2 Detection with MnO 2 Electrodes Cyclic Voltammetry (CV) –Voltage is applied across a working electrode and a counter electrode, scanning between 0 and 1.2 V. –When oxidation or reduction occurs, the current increases, causing a peak. –With cyclic voltammetry using a MnO 2 electrode, H 2 O 2 is oxidized at ~0.7 V, creating a current peak when H 2 O 2 is present. 2H 2 O 2  O 2 + 2H 2 O

3. H 2 O 2 Detection with MnO 2 Electrodes Chronoamperometry (CA) –In chronoamperometry, voltage is held constant and current is recorded. –Since in the CV the current peak caused by H 2 O 2 occurred around 0.7 V, the voltage is held at 0.7 V and H 2 O 2 is added at regular intervals. –Plateau height of current is linear to concentration of H 2 O 2 in cell.

4. Electrode Designs Gold Micron-Cavity Powder Disk Electrode – Difficult to make sure MnO 2 powder is well packed –Background signal of the gold is much higher than the signal with MnO 2 packed Wax-Impregnated Graphite Electrode –Difficult to control amount of MnO2 on electrode, as well as to control uniformity of powder on the surface Background signal of gold electrode Signal of MnO 2 Peak from H 2 O 2 No H 2 O 2 present

5. Electrode Designs Glassy Carbon Electrode with Spin Coated MnO 2 –Excess MnO 2 solution is pipetted onto the electrode surface. –By controlling spin speed, an even coat can be achieved. –However, after a long period of time in solution, MnO 2 eventually falls off. Electrode HeadSpin Coating Apparatus Close-up views of the electrode surface Uneven MnO 2 surface after time in solution

6. Electrode Validation Standard Curve –Addition of H 2 O 2 consistently displays linearity with current plateau height. –However, behavior of electrode changes over time and length of exposure to H 2 O 2.

7. Electrode Validation Standard Additions –A sample of unknown concentration is injected into solution and CA is run. –Volumes of a standard concentration are injected to create a calibration curve that can be used to solve for concentration of the unknown.

8. Conclusions Gold micron-cavity powder disk electrode has a high background signal from gold. Amount of MnO 2 is difficult to control for on the wax impregnated graphite electrode. Spin coated carbon electrode produces a evenly coated electrode, but produces a varied response. –Standard addition allows these electrodes to be used as a sensor. Biogenic and synthetic MnO 2 electrodes both have H 2 O 2 sensing capabilities, but the differences between them need to be further studied.

9. Goals For Next Summer’s Intern… (or me in the next week) Determine effects of aging of the electrode and MnO 2 powder Further characterize electrode behavior in different electrolyte conditions (pH, concentration, etc) More biogenic vs. synthetic MnO 2 comparison Resolve problems with using sensor in seawater Acknowledgments Jim Nurmi Paul Tratynek Satya Chinni Brad Tebo Vanessa Green EBS Department