Transcript Intrinsic Dipole Moment Measurement of Bioinspired

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
Outline

Introduction: Photovoltaics and α-Helices

Project

Method: Confirmation

Experimental

Data/Results

Conclusion and Future Direction

References and Acknowledgments
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
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]
Bioinspired Electret Application
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 oligoortho-arylamides, a class
of macromolecules
shown by ab initio density
functional theory (DFT)
calculations to possess
large dipole moments. [5-8]
Dipole Moment Measurement
Method: Dipole Measurement

Need to measure the dipole moment measurement of
the oligo-ortho-arylamide.
Densitometer

Triangular waveform
 Capacitor cell
 Calibration

Density Measurements
s  1  bX2
Capacitor, Oscilloscope
Hedestrand Equation
    1  1 
0
M b   3M 1a 

  M 2  1   
P 2    1
2





2






2

1
1
1




1
 1


Debye Equation
εs  ε1  aX2
P
0
2
N0  2
 P P 
3 0 3k BT
0
2
0
2v
Method: Confirmation
Calibration curve was created
Compound
Hexane
Hexadecane
CCl4
Benzene
p-Xylene
Toluene
Chloroform
Dichloromethane
ε
2.0
2.06
2.2
2.3
2.3
2.38
4.8
9.1
Electrode Height/Wave Height
100µm
200µm
400µm
0.00169
0.00098
0.000546
0.00191
0.00191
0.000597
0.00201
0.00117
0.00065
0.00258
0.00132
0.000685
0.00203
0.00118
0.000654
0.00218
0.00126
0.000702
0.00457
0.00264
0.00145
0.00748
0.00504
0.00278
Dielectric Constant Calibration
Dielectric Constant, ε

10.0
9.0
y = 3214.8x + 0.1519
8.0
R² = 0.9996
7.0
6.0
5.0
4.0
3.0
2.0
1.0
0.0
0.0005
0.001
0.0015
0.002
Wave Height (µm)
0.0025
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
 s  1  aX2
0.8
2.4
Density (g/ml)
Dielectric Constant
2.5
Density Measurements
2.3
2.2
s  1  bX2
0.6
0.4
0.2
2.1
0.0
10
20
30
40
Mole Fraction (10e-3)
-3
50x10
α = 10.029
     1  1 
M b   3M 1a  

  M 2  1   
9 0 k BT    1
2

   1  2  1 





2

1  
1
1 




N0
10
20
30
40
Mole Fraction (10e-3)
-3
50x10
b = 0.003389
Experimental Dipole = 5.17 D
Actual Value = 4.18 D [9]
Reasonable Error 23.6%
Compound Synthesis
Synthesis of N2-hexanoylanthranylamide.
O
H2N
N
NH2
O
O
+
+
N
Cl
DMF
25oC
H2N
H
N
O
+ HCl
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 Confirmation
H-NMR Spectrum of N2-hexanoylanthranylamide.
O H
H2N
N
O
Data
N2-hexanoylanthranylamide in Benzene
 The optimal electrode height was found to be at
100µm.

 Due to low Permittivity of Benzene
N2-hexanoylanthranylamide in Benzene
Concentration (µM)
ε
Wave Height Mole Fraction
2.415
0.002326
9.07E-06
100
2.418
0.00233
1.81E-05
200
2.435
0.002347
2.72E-05
300
2.419
0.002331
3.63E-05
400
2.474
0.002388
4.54E-05
500
2.460
0.002374
5.44E-05
600
2.454
0.002367
6.35E-05
700
2.448
0.002361
7.26E-05
800
2.493
0.002408
8.16E-05
900
2.508
0.002423
9.07E-05
1000
Density
0.8814
0.8813
0.8814
0.8816
0.8814
0.8815
0.8817
0.8818
0.8818
0.8818
Data

N2-hexanoylanthranylamide in Benzene dipole moment
Dielectric Measurements
Density Measurements
0.8818
2.50
Density (g/ml)
Dielectric Constant
0.8817
2.48
2.46
0.8816
0.8815
0.8814
2.44
0.8813
2.42
20
40
60
Mole Fraction, X (10e-6)
α = 2.402
-6
80x10
1
2
3
Mole Fraction (10e-6)
b = 1016.3
Experimental Dipole Moment = 25.926 D
4
5x10
-3
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 N2hexanoylanthranylamide did not agree strongly with
theoretical values.

More experiments must be performed to determine
where errors are being made.
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.
References
1.
2.
3.
4.
5.
6.
7.
8.
9.
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).
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).
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
Acknowledgments
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 bao
Brent Millare
Dr. Vullev
Jun Wang