Computational study for sensing mechanism (MD and DFT)

3. Results & Discussion

3.6. Computational study for sensing mechanism (MD and DFT)

- 58 -

Figure 3-24. Statistical comparisons of the sensing results for the liquid-phase analytes (□) and calculated induced dipole moments of calix[8]arene/liquid-phase analytes (◇).²⁹ S indicates average value of ID/IBASE and the error bar represents the one standard deviation.

10

^-1

10

⁰

10

¹

10

²

10

³

S

1

n -H ex an e

To lu en e

DI w ate r

Et ha no l

Me th an

ol 1 2 3 4 5 6

7 (debye ) Induced Di pole Moment

- 60 -

Figure 3-25. Calculated charge transfers (CT) and binding energies (BE) of calix[8]arene for various liquid-phase analytes. Charge density field mappings of right side represent deformation (def.) density field for methanol, ethanol, DI water and total charge density field for toluene and n-hexane, respectively. The atomic charges are labeled on each atom and the direction of charge migration is presented in figure as arrow.³⁰

Methanol

Ethanol

DI water

Toluene

n-Hexane

Table 3. Summary of sensing demonstration and the results of computational study

Sensing Solvent

Order of ID / IBASE

Molecular Structure

Available Interaction with C[8]A

Relative Polarity [𝑬_𝐓^𝐍]^a)

Simulation Result^b)

Lipo -philic (𝐶−𝐻⋯π)

Hydro -philic (𝑂−𝐻⋯𝑂)

Molecular Dipole Moment [debye]^c)

Relative Molecular

Polarity^d)

Induced Dipole Moment [debye]^e)

Methanol 1 O O 0.762 1.736 (1.70) 0.923 4.751

Ethanol 2 O O 0.654 1.685 (1.69) 0.896 4.476

DI water 3 X O 1.000 1.881 (1.85) 1.000 4.117

Toluene 4 O X 0.099 0.406 (0.36) 0.216 2.203

n-Hexane 5 O X 0.009 0.001 (0.00) 0.001 1.838

a) Normalized 𝐸_T^N ; the scale of 𝐸_T^N ranges from 0.000 for tetramethylsilane (TMS), the least polar solvent, to 1.000 for water, the most polar solvent.³¹

b) The results of computational study were done by student Gwan Yeong Jung (research advisor: Prof. Sang Kyu Kwak, UNIST).

c) The values in parentheses refer to molecular dipole moments from the reference.³²

d) Relative molecular polarity is calculated by relative molecular dipole moments on the basis of value of DI water.

e) Induced dipole moment is the averaged molecular dipole moment of calix[8]arene from MD simulation.

- 62 -

4. Conclusion

In conclusion, we demonstrated novel solvent-resistant OFETs by using cross-linkable azide functional groups. P3HT-azide copolymer showed high solvent resistance as well as excellent electrical performance. Photo-crosslinking method provides solvent resistance without disturbing molecular packing structure of the semiconducting layer, showing maintained electrical properties after cross- linking. Solvent resistance of the OFETs has been investigated by washing the devices with organic solvents, exhibiting excellent electrical characteristics with stable operation comparing with pristine P3HT-based OFETs. Air-stability of the cross-linked P3HT-azide was higher than that of the pristine P3HT.

Furthermore, solvent-resistant OFET-based sensor that detects liquid-phase analytes has been demonstrated. C[8]A, a calixarene derivative, was introduced to enhance sensitivity and selectivity of the OFET-based sensors. The sensing demonstrations of the sensors for various liquid-phase analytes and pH solutions have been conducted and well-defined sensing results were demonstrated based on combined effects between the sensors and liquid-phase analytes; enhanced electron-withdrawing /donating characteristics depending on the analytes and binding events between C[8]A and the molecules of analytes. The sensitivity of the sensors with C[8]A showed lower detection limits comparing to those of without C[8]A layer. Selectivity test of the sensors has also been carried out by alternate injection of different organic solvents, showing distinct response toward each solvent. The sensors with cross-linked P3HT-azide copolymer also showed rather higher reusability than those with non-cross-linked copolymer. The low-voltage operating and flexible sensors were fabricated using polymer dielectric and polymer substrate. The trend of the sensing results agreed with computational studies at the atomistic level. This report provides a feasible methodology for the fabrication of the OFET-based sensor for liquid-phase organic solvents.

5. Reference

1. (a) Braga, D.; Horowitz, G., High-Performance Organic Field-Effect Transistors. Adv.

Mater. 2009, 21 (14-15), 1473-1486; (b) Kang, B.; Jang, M.; Chung, Y.; Kim, H.; Kwak, S. K.; Oh, J. H.; Cho, K., Enhancing 2D growth of organic semiconductor thin films with macroporous structures via a small-molecule heterointerface. Nat. Commun.

2014,

5, 4752; (c) Knopfmacher, O.; Hammock, M. L.; Appleton, A. L.; Schwartz, G.; Mei, J.; Lei, T.; Pei, J.; Bao, Z., Highly stable organic polymer field-effect transistor sensor for selective detection in the marine environment. Nat. Commun. 2014, 5, 2954; (d) Dimitrakopoulos, C. D.; Mascaro, D. J., Organic thin-film transistors: A review of recent advances. Ibm Journal of Research and Development 2001, 45 (1), 11-27.

2. Kim, J.; Han, A.; Seo, J.; Oh, J.; Yang, C., beta-Alkyl substituted Dithieno[2,3-d;2 ',3 '-d ']benzo[1,2-b;4,5-b ']dithiophene Semiconducting Materials and Their Application to Solution-Processed Organic Transistors. Chem. Mater. 2012, 24 (17), 3464-3472.

3. (a) Oh, J. H.; Lee, H. W.; Mannsfeld, S.; Stoltenberg, R. M.; Jung, E.; Jin, Y. W.; Kim, J.

M.; Yoo, J.-B.; Bao, Z., Solution-processed, high-performance n-channel organic microwire transistors. Proceedings of the National Academy of Sciences

2009, 106 (15),

6065-6070; (b) Yu, H.; Bao, Z.; Oh, J. H., High-Performance Phototransistors Based on Single-Crystalline n-Channel Organic Nanowires and Photogenerated Charge-Carrier Behaviors. Adv. Funct. Mater. 2013, 23 (5), 629-639; (c) Yu, H.; Joo, P.; Lee, D.; Kim, B.- S.; Oh, J. H., Photoinduced Charge-Carrier Dynamics of Phototransistors Based on Perylene Diimide/Reduced Graphene Oxide Core/Shell p–n Junction Nanowires. Advanced Optical Materials 2014.

4. (a) Mushrush, M.; Facchetti, A.; Lefenfeld, M.; Katz, H. E.; Marks, T. J., Easily Processable Phenylene−Thiophene-Based Organic Field-Effect Transistors and Solution- Fabricated Nonvolatile Transistor Memory Elements. J. Am. Chem. Soc.

2003, 125 (31),

9414-9423; (b) Baeg, K.-J.; Khim, D.; Kim, J.; Yang, B.-D.; Kang, M.; Jung, S.-W.; You, I.-K.; Kim, D.-Y.; Noh, Y.-Y., High-Performance Top-Gated Organic Field-Effect Transistor Memory using Electrets for Monolithic Printed Flexible NAND Flash Memory.

Adv. Funct. Mater. 2012, 22 (14), 2915-2926; (c) Baeg, K. J.; Noh, Y. Y.; Ghim, J.; Kang, S. J.; Lee, H.; Kim, D. Y., Organic Non-Volatile Memory Based on Pentacene Field-Effect Transistors Using a Polymeric Gate Electret. Adv. Mater. 2006, 18 (23), 3179-3183.

5. (a) Torsi, L.; Magliulo, M.; Manoli, K.; Palazzo, G., Organic field-effect transistor sensors:

a tutorial review. Chem. Soc. Rev. 2013, 42 (22), 8612-8628; (b) Khan, H. U.; Roberts, M.

E.; Johnson, O.; Knoll, W.; Bao, Z., The effect of pH and DNA concentration on organic thin-film transistor biosensors. Org. Electron.

2012, 13 (3), 519-524; (c) Lipomi, D. J.;

Vosgueritchian, M.; Tee, B. C. K.; Hellstrom, S. L.; Lee, J. A.; Fox, C. H.; Bao, Z., Skin- like pressure and strain sensors based on transparent elastic films of carbon nanotubes.

Nature Nanotechnology 2011, 6 (12), 788-792; (d) Sokolov, A. N.; Roberts, M. E.; Bao, Z., Fabrication of low-cost electronic biosensors. Mater. Today 2009, 12 (9), 12-20.

6. (a) McCarthy, M. A.; Liu, B.; Donoghue, E. P.; Kravchenko, I.; Kim, D. Y.; So, F.; Rinzler, A. G., Low-Voltage, Low-Power, Organic Light-Emitting Transistors for Active Matrix Displays. Science

2011,

332 (6029), 570-573; (b) Dinelli, F.; Capelli, R.; Loi, M. A.;

Murgia, M.; Muccini, M.; Facchetti, A.; Marks, T. J., High-Mobility Ambipolar Transport

- 64 -

7. Tsao, H. N.; Cho, D.; Andreasen, J. W.; Rouhanipour, A.; Breiby, D. W.; Pisula, W.;

Müllen, K., The Influence of Morphology on High-Performance Polymer Field-Effect Transistors. Adv. Mater. 2009, 21 (2), 209-212.

8. (a) Roberts, M. E.; Mannsfeld, S. C. B.; Tang, M. L.; Bao, Z., Influence of Molecular Structure And Film Properties on the Water-Stability and Sensor Characteristics of Organic Transistors. Chem. Mater.

2008,

20 (23), 7332-7338; (b) Torsi, L.; Farinola, G. M.;

Marinelli, F.; Tanese, M. C.; Omar, O. H.; Valli, L.; Babudri, F.; Palmisano, F.; Zambonin, P. G.; Naso, F., A sensitivity-enhanced field-effect chiral sensor. Nat. Mater. 2008, 7 (5), 412-417; (c) Someya, T.; Dodabalapur, A.; Huang, J.; See, K. C.; Katz, H. E., Chemical and Physical Sensing by Organic Field-Effect Transistors and Related Devices. Adv. Mater.

2010, 22 (34), 3799-3811.

9. (a) Mabeck, J. T.; Malliaras, G. G., Chemical and biological sensors based on organic thin- film transistors. Anal. Bioanal. Chem. 2006, 384 (2), 343-353; (b) Roberts, M. E.; Sokolov, A. N.; Bao, Z., Material and device considerations for organic thin-film transistor sensors.

J. Mater. Chem.

2009,

19 (21), 3351-3363; (c) Lin, P.; Yan, F., Organic Thin-Film Transistors for Chemical and Biological Sensing. Adv. Mater. 2012, 24 (1), 34-51; (d) Liao, C.; Yan, F., Organic Semiconductors in Organic Thin-Film Transistor-Based Chemical and Biological Sensors. Polym. Rev. 2013, 53 (3), 352-406.

10. (a) Roberts, M. E.; Mannsfeld, S. C. B.; Queralto, N.; Reese, C.; Locklin, J.; Knoll, W.;

Bao, Z., Water-stable organic transistors and their application in chemical and biological sensors. Proc. Natl. Acad. Sci. U. S. A.

2008,

105 (34), 12134-12139; (b) Sessolo, M.;

Rivnay, J.; Bandiello, E.; Malliaras, G. G.; Bolink, H. J., Ion-Selective Organic Electrochemical Transistors. Adv. Mater. 2014, 26 (28), 4803-4807.

11. Hammock, M. L.; Knopfmacher, O.; Naab, B. D.; Tok, J. B.-H.; Bao, Z., Investigation of Protein Detection Parameters Using Nanofunctionalized Organic Field-Effect Transistors.

ACS Nano 2013, 7 (5), 3970-3980.

12. Guo, Y.; Du, C.; Yu, G.; Di, C.-a.; Jiang, S.; Xi, H.; Zheng, J.; Yan, S.; Yu, C.; Hu, W.;

Liu, Y., High-Performance Phototransistors Based on Organic Microribbons Prepared by a Solution Self-Assembly Process. Adv. Funct. Mater. 2010, 20 (6), 1019-1024.

13. (a) Mannsfeld, S. C. B.; Tee, B. C.-K.; Stoltenberg, R. M.; Chen, C. V. H.-H.; Barman, S.;

Muir, B. V. O.; Sokolov, A. N.; Reese, C.; Bao, Z., Highly sensitive flexible pressure sensors with microstructured rubber dielectric layers. Nat. Mater. 2010, 9 (10), 859-864;

(b) Ramuz, M.; Tee, B. C.-K.; Tok, J. B.-H.; Bao, Z., Transparent, Optical, Pressure- Sensitive Artificial Skin for Large-Area Stretchable Electronics. Adv. Mater. 2012, 24 (24), 3223-3227.

14. Schwartz, G.; Tee, B. C.-K.; Mei, J.; Appleton, A. L.; Kim, D. H.; Wang, H.; Bao, Z., Flexible polymer transistors with high pressure sensitivity for application in electronic skin and health monitoring. Nat. Commun. 2013, 4, 1859.

15. (a) Sokolov, A. N.; Roberts, M. E.; Johnson, O. B.; Cao, Y.; Bao, Z., Induced Sensitivity and Selectivity in Thin-Film Transistor Sensors via Calixarene Layers. Adv. Mater. 2010, 22 (21), 2349-2353; (b) Magliulo, M.; Mallardi, A.; Mulla, M. Y.; Cotrone, S.; Pistillo, B.

R.; Favia, P.; Vikholm-Lundin, I.; Palazzo, G.; Torsi, L., Electrolyte-Gated Organic Field- Effect Transistor Sensors Based on Supported Biotinylated Phospholipid Bilayer. Adv.

Mater.

2013,

25 (14), 2090-2094; (c) Huang, W.; Besar, K.; LeCover, R.; Rule, A. M.;

Breysse, P. N.; Katz, H. E., Highly Sensitive NH3 Detection Based on Organic Field-Effect

Transistors with Tris(pentafluorophenyl)borane as Receptor. J. Am. Chem. Soc. 2012, 134

(36), 14650-14653.

16. Khan, H. U.; Roberts, M. E.; Knoll, W.; Bao, Z., Pentacene Based Organic Thin Film Transistors as the Transducer for Biochemical Sensing in Aqueous Media. Chem. Mater.

2011, 23 (7), 1946-1953.

17. (a) Kim, B. J.; Miyamoto, Y.; Ma, B.; Frechet, J. M. J., Photocrosslinkable Polythiophenes for Efficient, Thermally Stable, Organic Photovoltaics. Adv. Funct. Mater. 2009, 19 (14), 2273-2281; (b) Kim, H. J.; Han, A.-R.; Cho, C.-H.; Kang, H.; Cho, H.-H.; Lee, M. Y.;

Frechet, J. M. J.; Oh, J. H.; Kim, B. J., Solvent-Resistant Organic Transistors and Thermally Stable Organic Photovoltaics Based on Cross-linkable Conjugated Polymers. Chem. Mater.

2012, 24 (1), 215-221.

18. Drees, M.; Hoppe, H.; Winder, C.; Neugebauer, H.; Sariciftci, N. S.; Schwinger, W.;

Schaffler, F.; Topf, C.; Scharber, M. C.; Zhu, Z.; Gaudiana, R., Stabilization of the nanomorphology of polymer-fullerene "bulk heterojunction'' blends using a novel polymerizable fullerene derivative. J. Mater. Chem. 2005, 15 (48), 5158-5163.

19. Li, L.; Gao, P.; Baumgarten, M.; Müllen, K.; Lu, N.; Fuchs, H.; Chi, L., High Performance Field-Effect Ammonia Sensors Based on a Structured Ultrathin Organic Semiconductor Film. Adv. Mater. 2013, 25 (25), 3419-3425.

20. Kim, B. J.; Miyamoto, Y.; Ma, B.; Fréchet, J. M. J., Photocrosslinkable Polythiophenes for Efficient, Thermally Stable, Organic Photovoltaics. Adv. Funct. Mater.

2009,

19 (14), 2273-2281.

21. Synthesis of P3HT-azide copolymer was done by Hyeong Jun Kim (research advisor: Prof.

Bumjoon J. Kim, KAIST)

22. Synthetic characterizations of the P3HT-azide copolymer were performed by Hyeong Jun Kim (research advisor: Prof. Boomjun J. Kim, KAIST)

23. Synthetic characterizations of the P3HT-azide copolymer were performed by Hyeong Jun Kim (research advisor: Prof. Boomjun J. Kim, KAIST)

24. Ito, Y.; Virkar, A. A.; Mannsfeld, S.; Oh, J. H.; Toney, M.; Locklin, J.; Bao, Z., Crystalline Ultrasmooth Self-Assembled Monolayers of Alkylsilanes for Organic Field-Effect Transistors. J. Am. Chem. Soc. 2009, 131 (26), 9396-9404.

25. (a) Kazarinoff, P. D.; Shamburger, P. J.; Ohuchi, F. S.; Luscombe, C. K., OTFT performance of air-stable ester-functionalized polythiophenes. J. Mater.Chem.

2010,

20 (15), 3040-3045; (b) Drees, M.; Hoppe, H.; Winder, C.; Neugebauer, H.; Sariciftci, N. S.;

Schwinger, W.; Schaffler, F.; Topf, C.; Scharber, M. C.; Zhu, Z. G.; Gaudiana, R., Stabilization of the nanomorphology of polymer-fullerene "bulk heterojunction'' blends using a novel polymerizable fullerene derivative. J. Mater.Chem. 2005, 15 (48), 5158-5163.

26. Majewski, L. A.; Kingsley, J. W.; Balocco, C.; Song, A. M., Influence of processing conditions on the stability of poly(3-hexylthiophene)-based field-effect transistors. Appl.

Phys. Lett. 2006, 88 (22).

27. (a) Hutchison, G. R.; Ratner, M. A.; Marks, T. J.; Naaman, R., Adsorption of Polar Molecules on a Molecular Surface. J. Phys. Chem. B 2001, 105 (15), 2881-2884; (b) Li, B.; Sauvé, G.; Iovu, M. C.; Jeffries-EL, M.; Zhang, R.; Cooper, J.; Santhanam, S.; Schultz, L.; Revelli, J. C.; Kusne, A. G.; Kowalewski, T.; Snyder, J. L.; Weiss, L. E.; Fedder, G. K.;

McCullough, R. D.; Lambeth, D. N., Volatile Organic Compound Detection Using Nanostructured Copolymers. Nano Lett. 2006, 6 (8), 1598-1602; (c) Li, B.; Lambeth, D.

N., Chemical Sensing Using Nanostructured Polythiophene Transistors. Nano Lett. 2008,

- 66 -

Dodabalapur, A., Nanoscale chemical sensor based on organic thin-film transistors. Appl.

Phys. Lett. 2004, 85 (26), 6386-6388.

29. The induced dipole moments of calix[8]arene/liquid-phase analytes (◇) were calculated by student Gwan Yeong Jung (research advisor: Prof. Sang Kyu Kwak, UNIST).

30. The calculations about charge tansfer (CT) by density functional theory (DFT) were done by student Gwan Yeong Jung (research advisor: Prof. Sang Kyu Kwak, UNIST).

31. Reichardt, C.; Welton, T., Solvents and Solvent Effects in Organic Chemistry, 4th Ed. 4th ed. ed.; Wiley-VCH: Weinheim, Germany, 2010.

32. Haynes, W. M., CRC Handbook of Chemistry and Physics: a Ready-Reference Book of

Chemical and Physical Data , 95th Ed. CRC Press: Boca Raton, Florida, 2014.

6. Acknowledgements ( 감사의 글 )

먼저, 항상 저를 전적으로 믿어주시고 지원을 아끼지 않는 우리 가족에게 감사의 말씀을 드립니다. 항상 아들을 최고라고 믿어 의심치 않으시는 아버지, 제게 언제나 기댈 수 있는 버팀목이 되어주심에 감사합니다. 아들생각에 하루하루 즐겁게 생활하시는 어머니, 아들 잘 생활하고 있으니 걱정 붙들어 매셔도 될 것 같습니다. 항상 나를 형으로서 존중해주고 형 대신 부모님 가까이서 昏定晨省하는 고마운 우리 창렬이, 항상 고맙다.

항상 조카 많이 생각해 주시고 챙겨주시는 작은아버지, 작은어머니께도 감사의 말씀을 드립니다. 하느님의 은총 아래 행복하게 생활하는 우리 식구가 있기에 힘내서 연구 생활할 수 있었던 것 같습니다.

학부 3 학년때부터 유니스트 유기전자연구실에서 연구실 생활을 시작했습니다.

이곳에서 연구라는 것이 무엇인가를 배우게 되었고, 유기전자연구실의 초석을 다지는데 일조하겠다는 마음으로 연구실 선배, 동기, 후배님들과함께 많은 우여곡절을 겪으면서 생활하다 보니 어느덧 석사과정 연구를 마무리하게 되었습니다. 저의 석사과정 연구를 마무리 할 수 있도록 물심양면으로 도와주신 많은 분들께 감사의 마음을 이렇게 글로나마 전합니다.

유기전자에 대한 지식이 많이 부족하던 학부생 시절부터 연구실 생활을 할 수 있는 기회를 주시고 연구자로서의 자세에 대해서 진심을 다해 지도해 주신 오준학 교수님께 감사의 말씀을 드립니다. 아직도 많이 부족하지만 교수님의 훌륭하신 지도 아래 연구자로서의 모습을 갖추어 가는 것 같습니다. 앞으로도 연구생활 열심히, 그리고 잘 해서 교수님께서 자랑스러워 하실 수 있는 제자가 되도록 하겠습니다. 또한 연구실 이전 건에서 쉽지 않은 도움을 주신 김병수 교수님, 바쁘신 와중에도 석사 졸업 논문 committee 가 되어주신 고현협 교수님께도 감사의 말씀을 드립니다. 전용석 교수님, 박종남 교수님께도 감사의 마음을 전합니다.

많은 우여곡절이 있었지만 同苦同樂하면서 탄탄한 전우애를 키워나간 연구실 선배, 동기, 후배님들에게 정말 감사를 드립니다. 여러분들이 있기에 연구실 생활이 즐겁고 행복했습니다. 연구실 초창기에 방장을 맡으시면서 연구실의 기틀을 잡아나가신 아름누나, 항상 밝은 모습으로 후배들을 대해주시고 궂은일 마다 않고 솔선수범