Aleksandr A. Gerasimenko1, Brent Millare1, Duoduo Bao1, M. Khalid Ashraf2, Roger Lake2 and Valentine I. Vullev1

1Department of Bioengineering, University of California, Riverside, CA 925212Department of Electrical Engineering, University of California, Riverside

Intrinsic Dipole Moment Measurement of Bioinspired Macromolecules

Introduction: Photovoltaics and α-Helices

Project

Method: Confirmation

Experimental

Data/Results

Conclusion and Future Direction

References and Acknowledgments

Outline

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

Background: Photovoltaic Cells

http://science.nasa.gov/headlines/y2002/solarcells.htm

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]

Background: Polypeptide α-Helices

Bioinspired Electret Application

We plan to engineer bioinspired macromolecular electrets—molecules with large intrinsic dipole moments—and integrate them into nanometer-thick layers for charge-transfer rectification.

Project

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]

Dipole Moment Measurement

Need to measure the dipole moment measurement of the oligo-ortho-arylamide.

Triangular waveform Capacitor cell Calibration

Density Measurements

Method: Dipole Measurement

Tk

NPPP

B

v33

2

0

002

02

02

1

21

1

1

12

11

102

2

31

2

1

aMbM

MP

21 bXs

21s aXεε Debye Equation

Hedestrand Equation

Densitometer

Capacitor, Oscilloscope

Calibration curve was created

Method: Confirmation

Electrode Height/Wave HeightCompound ε 100µm 200µm 400µm

Hexane 2.0 0.00169 0.00098 0.000546Hexadecane 2.06 0.00191 0.00191 0.000597

CCl4 2.2 0.00201 0.00117 0.00065Benzene 2.3 0.00258 0.00132 0.000685p-Xylene 2.3 0.00203 0.00118 0.000654Toluene 2.38 0.00218 0.00126 0.000702

Chloroform 4.8 0.00457 0.00264 0.00145Dichloromethane 9.1 0.00748 0.00504 0.00278

0.01.02.03.04.05.06.07.08.09.0

10.0

f(x) = 3314.47176578974 xR² = 0.999414085322211

Die

lect

ric

Co

nst

an

t,

ε

Wave Height (µm)

Dielectric Constant Calibration

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).

Method: Confirmation

2.5

2.4

2.3

2.2

2.1

Die

lect

ric C

onst

ant

50x10-3

40302010Mole Fraction (10e-3)

0.8

0.6

0.4

0.2

0.0

Den

sity

(g/

ml)

50x10-3

40302010Mole Fraction (10e-3)

21 aXs 2 1bX s

α = 10.029 b = 0.003389

Experimental Dipole = 5.17 DActual Value = 4.18 D [9]Reasonable Error 23.6%

Dielectric Measurements Density Measurements

0

12

1

1

1

12

11

10

2

3121

9

N

aMbMMTkB

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.

Compound Synthesis

NH2

O

H2N

N

N

+

DMFCl

O

+N

H2N

O

O H

25oC

+ HCl

Compound Confirmation

H-NMR Spectrum of N2-hexanoylanthranylamide.

NH2N

O

O H

N2-hexanoylanthranylamide in Benzene The optimal electrode height was found to be at 100µm.

Due to low Permittivity of Benzene

Data

N2-hexanoylanthranylamide in BenzeneConcentration (µM) ε Wave Height Mole Fraction Density

100 2.415 0.002326 9.07E-06 0.8814200 2.418 0.00233 1.81E-05 0.8813300 2.435 0.002347 2.72E-05 0.8814400 2.419 0.002331 3.63E-05 0.8816500 2.474 0.002388 4.54E-05 0.8814600 2.460 0.002374 5.44E-05 0.8815700 2.454 0.002367 6.35E-05 0.8817800 2.448 0.002361 7.26E-05 0.8818900 2.493 0.002408 8.16E-05 0.8818

1000 2.508 0.002423 9.07E-05 0.8818

N2-hexanoylanthranylamide in Benzene dipole moment

Data

2.50

2.48

2.46

2.44

2.42

Die

lect

ric C

onst

ant

80x10-6

604020Mole Fraction, X (10e-6)

0.8818

0.8817

0.8816

0.8815

0.8814

0.8813

Den

sity

(g/

ml)

5x10-3

4321Mole Fraction (10e-6)

Dielectric Measurements Density Measurements

α = 2.402 b = 1016.3

Experimental Dipole Moment = 25.926 D

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.

Conclusion

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.

Future Direction

1. Galoppini, E. and Fox, M. A., "Effect of the Electric Field Generated by the Helix Dipole on Photoinduced Intramolecular Electron Transfer in Dichromophoric .alpha.-Helical Peptides," Journal of the American Chemical Society 118, 2299-2300 (1996).

2. Knorr, A., Galoppini, E. and Fox, M. A., "Photoinduced intramolecular electron transfer in dichromophore-appended .alpha.-helical peptides: spectroscopic properties and preferred conformations," Journal of Physical Organic Chemistry 10, 484-498 (1997).

3. 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).

4. Yasutomi, S., Morita, T., Imanishi, Y. and Kimura, S., "A Molecular Photodiode System That Can Switch Photocurrent Direction," Science 304, 1944-1947 (2004).

5. Sessler, G. M., "Physical principles of electrets," Topics in Applied Physics 33, 13-80 (1980).6. Gerhard-Multhaupt, R., Gross, B. and Sessler, G. M., "Recent progress in electret research," Topics

in Applied Physics 33, 383-431 (1987).7. 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).

8. Goel, M., "Electret sensors, filters and MEMS devices: new challenges in materials research," Current Science 85, 443-453 (2003).

9. Lide, D. R. Handbook of Chemistry and Physics (73rd Edition). Boca Raton, FL: CRC

References

I would like to thank the NSF and the UCR Brite programs 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:

Duoduo baoBrent MillareDr. VullevJun Wang

Acknowledgments