Intrinsic Dipole Moment Measurement of Bioinspired Macromolecules

1. Intrinsic Dipole Moment Measurement of Bioinspired Macromolecules Aleksandr A. Gerasimenko1, Brent Millare1, Duoduo Bao1, M. Khalid Ashraf2, Roger Lake2 and Valentine I. Vullev1 1Department of Bioengineering, University of California, Riverside, CA 92521 2Department of Electrical Engineering, University of California, Riverside

2. Outline • Introduction: Photovoltaics and α-Helices • Project • Method: Confirmation • Experimental • Data/Results • Conclusion and Future Direction • References and Acknowledgments

3. Background: Photovoltaic Cells • Photoelectric effect--Photoexcitation occurs when light energy is equal to the band gap • Single-junction and multi-junction cells • Charge recombination results in significant loss of power • Energy of electron is lost as heat and energy level falls • Recombination result in low cost-efficiency http://science.nasa.gov/headlines/y2002/solarcells.htm

4. Background: Polypeptide α-Helices • Polypeptide α-helices have a relatively large intrinsic dipole moment (i.e. ~4-5 Debye per residue). • This large dipole moment generates local electric fields of the order of 1GV/m. Charge transfer and charge transport through polypeptide α−helices manifest rectification that is ascribed to the intrinsic dipole moment of the macromolecular scaffolds. [1-4]

5. Bioinspired Electret Application

6. Project We plan to engineer bioinspired macromolecular electrets—molecules with large intrinsic dipole moments—and integrate them into nanometer-thick layers for charge-transfer rectification. • The investigation will concentrate on oligo-ortho-arylamides, a class of macromolecules shown by ab initio density functional theory (DFT) calculations to possess large dipole moments. [5-8]

7. Dipole Moment Measurement

8. Method: Dipole Measurement • Need to measure the dipole moment measurement of the oligo-ortho-arylamide. • Triangular waveform • Capacitor cell • Calibration • Density Measurements Densitometer Capacitor, Oscilloscope Hedestrand Equation Debye Equation

9. Method: Confirmation • Calibration curve was created Dielectric Constant Calibration

10. Method: Confirmation • For a series of solutions, the dielectric constants (εs) and densities (ρs) of the solutions can be described as linear functions of the mole fraction of solute (X2). Dielectric Measurements Density Measurements α= 10.029 b= 0.003389 Experimental Dipole = 5.17 D Actual Value = 4.18 D [9] Reasonable Error 23.6%

11. Compound Synthesis Synthesis of N2-hexanoylanthranylamide. • Combine 2-Aminobenzamide, 4-Dimethylaminopyridine and Dimethylformamide (DMF) in a 1:1.2:5 ratio, respectively, until dissolved. • Slowly add n-Caproyl Chloride in a 1:5 ratio with the reactant in an ice bath. • Let the reaction take place under argon conditions at room temperature.

12. Compound Confirmation H-NMR Spectrum of N2-hexanoylanthranylamide.

13. Data • N2-hexanoylanthranylamide in Benzene • The optimal electrode height was found to be at 100µm. • Due to low Permittivity of Benzene

14. Data • N2-hexanoylanthranylamide in Benzene dipole moment Dielectric Measurements Density Measurements α= 2.402 b= 1016.3 Experimental Dipole Moment = 25.926 D

15. Conclusion • Confirmation experiment shows good agreement between experimental and theoretical values for the dipole moment of Benzonitrile. • Serves to validate method for determining the dipole moment. • Compound was synthesized and structure confirmed via H-NMR spectroscopy. • The experimental value for the dipole moment of N2-hexanoylanthranylamide did not agree strongly with theoretical values. • More experiments must be performed to determine where errors are being made.

16. Future Direction • Optimization of experiment to produce more accurate and more precise results. • Possible densitometer upgrades, and the purchase of a refractometer. • Optimization of compound (i.e. larger dipole moment) by addition of doping groups • Applying molecules into electret layers for application in solar cells.Will provide charge transfer rectification and virtually 100% charge transfer quantum yield.

17. References • Galoppini, E. and Fox, M. A., "Effect of the Electric Field Generated by the Helix Dipole on PhotoinducedIntramolecular Electron Transfer in Dichromophoric .alpha.-Helical Peptides," Journal of the American Chemical Society 118, 2299-2300 (1996). • Knorr, A., Galoppini, E. and Fox, M. A., "Photoinducedintramolecular electron transfer in dichromophore-appended .alpha.-helical peptides: spectroscopic properties and preferred conformations," Journal of Physical Organic Chemistry 10, 484-498 (1997). • Morita, T., Kimura, S., Kobayashi, S. and Imanishi, Y., "Photocurrent Generation under a Large Dipole Moment Formed by Self-Assembled Monolayers of Helical Peptides Having an N-Ethylcarbazolyl Group," Journal of the American Chemical Society 122, 2850-2859 (2000). • Yasutomi, S., Morita, T., Imanishi, Y. and Kimura, S., "A Molecular Photodiode System That Can Switch Photocurrent Direction," Science 304, 1944-1947 (2004). • Sessler, G. M., "Physical principles of electrets," Topics in Applied Physics 33, 13-80 (1980). • Gerhard-Multhaupt, R., Gross, B. and Sessler, G. M., "Recent progress in electret research," Topics in Applied Physics 33, 383-431 (1987). • Bauer, S., Bauer-Gogonea, S., Dansachmuller, M., Graz, I., Leonhartsberger, H., Salhofer, H. and Schwoediauer, R., "Modern electrets," Proceedings - IEEE Ultrasonics Symposium, 370-376 (2003). • Goel, M., "Electret sensors, filters and MEMS devices: new challenges in materials research," Current Science 85, 443-453 (2003). • Lide, D. R. Handbook of Chemistry and Physics (73rd Edition). Boca Raton, FL: CRC

18. Acknowledgments I would like to thank the NSF and the UCR Briteprograms for allowing me to undergo this REU program. Additionally, I would like to deeply and sincerely thank my lab group for this amazing opportunity to learn. Many thanks to: Duoduobao Brent Millare Dr. Vullev Jun Wang