THESIS FOR THE DEGREE OF MASTER OF SCIENCE Advisor: Jae-Do Nam, Professor Vapor-phase Polymerized Thin Films and Seeding-polymerized Nanofibers Membranes of Poly(3,4-ethylenedioxythiophene) for Optoelectronic Applications Sungkyunkwan University Department of Polymer Science and Engineering THUY LE TRUONG THESIS FOR THE DEGREE OF MASTER OF SCIENCE Advisor: Jae-Do Nam, Professor Vapor-phase Polymerized Thin Films and Seeding-polymerized Nanofibers Membranes of Poly(3,4-ethylenedioxythiophene) for Optoelectronic Applications Sungkyunkwan University Department of Polymer Science and Engineering THUY LE TRUONG THESIS FOR THE DEGREE OF MASTER OF SCIENCE Advisor: Jae-Do Nam, Professor Vapor-phase Polymerized Thin Films and Seeding-polymerized Nanofibers Membranes of Poly(3,4-ethylenedioxythiophene) for Optoelectronic Applications The Thesis is Submitted to the Graduate School of the Sungkyunkwan University in Partial Fulfillment of the Requirements for the Degree of Master of Science in Polymer Science and Engineering (Master Program) 2007 04 Sungkyunkwan University Department of Polymer Science and Engineering THUY LE TRUONG Approved in Partial Fulfillment of the Requirements for the Degree of Master of Science 2007 06 CURRICULUM VITAE Personal Information Name: THUY LE TRUONG Sex: Female Home address: Dap Da Town, An Nhon District, Binh Dinh Province, Vietnam Nationality: Vietnamese Education 2005 -2007.7: Sungkyunkwan University (SKKU), South Korea (Master of Science) Thesis: “Vapor-phase Polymerized Thin Films and Seeding-polymerized Nanofibers Membranes of Poly(3,4-ethylenedioxythiophene) for Optoelectronic Applications” instructed by professor Jae-Do Nam 1997 9-2002 2: Chemical Technology Faculty at Hochiminh City University of Technology, Vietnam (Bachelor of Engineering) Thesis topic: “The effect of nanoclay on the properties of polyimide films” instructed by professor Huu Nieu Nguyen Work Experiences 2002 - 2005 2: Researcher- Faculty member Department of Materials Technology, Hochiminh City University of Technology, Vietnam Working as a member of the project “Fabrication of nano carbon particles for applications in microelectronics and information recording” conducted by PhD Khe C Nguyen List of Publication and Submitted Papers Thuy Le Truong, Dong-Ouk Kim, Youngkwan Lee, Tae-Woo Lee, Jong Jin Park, Lyongsun Pu, Jae-Do Nam, Surface smoothness and conductivity control of vapor-phase polymerized poly(3,4-ethylenedioxythiophene) thin coating for flexible optoelectronic applications, Submitted to Thin Solid Films (2006) Thuy Le Truong, Youngkwan Lee, Hyouk Ryeol Choi, Ja Choon Koo, Huu Nieu Nguyen, Nguyen Dang Luong, and Jae-Do Nam, Poly(3,4-ethylenedioxythiophene) Vapor-phase Polymerization on Glass Substrate for Enhanced Surface Smoothness and Electrical, Macromolecular Research, 15 (2007) Khe C Nguyen, Le Van Thang, Doan Duc Chanh Tin, Tran Viet Toan, Nguyen Thuy Ai, Truong Thuy Le, Luu Tuan Anh, Dang Mau Chien, Vo Hong Nhan, The process of micropattern image from liquid nano carbon, Society for Imaging Science and Technology, 01 Digital Fabrication, Baltimore, 209 (2005) List of conference presentations Thuy Le Truong, Dong-Ouk Kim, Youngkwan Lee, Jae-Do Nam, Vapor-phase Thin-Film Coating of PEDOT on Polymeric Substrate for Electroluminescent Devices, 9th Science & Technology Conference of HCM City University of Technology, Vietnam, 8-11 (2005) Kim Dong-Ouk, Thuy Le Truong, Lee Pyoung Chan, Yoon Song-sik , Nam Jae-Do, Optical and Electrical Characteristics of Multi-Wall Carbon Nanotubes(MWNTs)/Poly(methyl methacrylate) Nano-composite Film, The Polymer Society of Korea, 30(2), 273, (2005) T L Truong, D O Kim, J H Lee, S J Kang, J D Nam The Polymer Society of Korea, 31(1), 2PS-78, (2006) T L Truong, D O Kim, Y Lee, T W Lee, J J Park, L Pu, J D Nam, Vapor-phase Polymerized PEDOT on PET Substrate Films, 2006 SKKU PTI-CAS CIAC Joint Symposium on Polymers, Sunkyunkwan University, May 2006 Thuy Le Truong, Huu Nieu Nguyen, Do Thanh Thanh Son, and Jae-Do Nam, Poly(3,4ethylenedioxythiophene)/Gold Nanocomposite Thin Films, the 9th seminar on “Nanomaterials and Nanocomposites: Processing and Performance”, sponsored by AUN/SEED-net project, Japan International Cooperation Agency (JICA), 142-150, 2006 Research interests • Conducting polymer, advanced material, nanotechnology, applied chemical/physical research areas and analysis methods in chemistry and physics • Organic Polymer Electroluminescence • Biosensors and Chemical Sensors • Polymer, Metal, and Inorganic Nanoparticle Synthesis • Self-Assembly Layer Structuring • Nanocomposite Porous Structure ACKNOWLEDGEMENTS Without the contributions of others, this research would not be possible, deeply thank you: Professor Jae-Do Nam Committee members All my colleagues from Functional Nanocomposites Laboratory All professors, and support staffs of School of Engineering, Sungkyungkwan University - Thank you very much to my dear Vietnamese friends in SKKU for all wholehearted encouragement and advice - To be grateful to my family in Vietnam, my Mum, my Dad, my sisters and my brothers, who always stand by and comfort me throughout my life CONTENTS List of Tables······································································································· iii List of Schemes··································································································· iii List of Figures ····································································································· iv Part I: Surface Morphology and Conductivity Control of Vapor-phase Polymerized Poly (3,4-ethylenedioxythiophene) Thin Films for Optoelectronic Applications Abstract····················································································································································2 I.1 Introduction ·······································································································································2 I.2 Background ·······································································································································7 I.2.1 Polythiphene ··························································································································7 I.2.2 Synthesis Methods··················································································································7 I.2.3 Applications ························································································································· 10 I.3 Experimental Section ······················································································································ 11 I.3.1 Materials ······························································································································11 I.3.2 Surface Treatment ················································································································11 I.3.3 Oxidative Polymerization of EDOT with Fe(OTs)3 by VPP···············································11 I.3.4 Characterization··················································································································· 12 I.4 Results and Discussions ················································································································· 14 I.4.1 Surface Treatment ·············································································································· 14 I.4.2 Effect of a Weak Base·········································································································· 18 I.4.3 Effect of Glycerol ··············································································································· 27 I.5 Conclusions ···································································································································· 31 References············································································································································· 32 Part II: Fabrication of Porous Electrochemical Membranes Based on PEDOT Nanofibers/Au Nanoparticles ··········································································· 35 i Abstract················································································································································· 36 II.1 Introduction ··································································································································· 37 II.2 Experimental Section····················································································································· 40 II.2.1 Synthesis of PEDOT Nanofibers ···················································································· 40 II.2.2 Synthesis of PEDOT/Carboxylated-Au Nanoparticles Composites ······························ 40 II.3 Results and Discussions ················································································································ 41 II.5 Conclusions ··································································································································· 44 References············································································································································· 45 Abstract················································································································································· 46 ii [17] T.A Skotheim, R.L Elsenbaumer, J.R Reynolds, Handbook of Conducting Polymer, Marcel Dekker, New York, Second Edition, 1998 [18] B.L Groenendaal, F Jonas, D Freitag, H Pielartzik, J.R Reynolds, Adv Mater 12 (2000) 481 [19] F Jonas, G Heywang, Electrochim Ecta 39 (1994) 1345 [20] M Kemerink, S Timpanaro, M.M De Kok, E.A Meulenkamp, F.J Touwslager, J Phys Chem B 108 (2004) 18820 [21] A.M Higgins, S.J Martin, P.C Jukes, M Geoghegan, R.A.L Jones, S Langridge, R Cubitt, S Kirchmeyer, A Wehrume, I Grizzie, J Mater Chem 13 (2003) 2814 [22 P.C Jukes, S.J Martin, A.M Higgins, M Geoghegan, R.A.L Jones, S Langridge, A Wehrum, S Kirchmeyer, Adv Mater (2004) 807 [23] M.P De Jong, L.J Van Ijzendoorn, M.J.A De Voigt, Appl Phys Lett 77 (2000) 2255 [24] L Groenendaal, G Zotti, F Jonas, Synth Met 118 (2001) 105 [25] J Kim, E Kim, Y Won, H Lee, K Suh, Synth Met 139, (2003) 485 [26] B Winther-Jensen, F.C Krebs, Sol Energy Mater Sol Cells 90 (2006) 123 [27] A.J Ma kinen, I.G Hill, R Shashidhar, N Nikolov, Z.H Kafafi, Appl Phys Lett 79 (2001) 557 [28] T Granlund, L.A.A Pettersson, O Inganas, J Appl Phys 89 (2001) 5897 [29] J Huang, P.F Miller, J.S Wilson, A.J De Mello, J.C De Mello, D.D.C Bradley, Adv Mater 15 (2005) 290 [30] J.Y Kim, J.H Jung, D.E Lee, J Joo, Synth Met 126 (2002) 311 [31] R Kiebooms, A Aleshin, K Hutchison, F Wudl, A Heeger, Synth Met 101 (1999) 436 [32] D.M De Leeuw, P.A Kraakman, P.F.G Bongaerts, C.M.J Mutsaers, D.B.M Klaassen, Synth Met 66 (1994) 263 [33] Y.H Ha, N Nikolov, S.K Pollack, J Mastrangelo, B.D Martin, Adv Funct Mater 14 (2004) 615 [34] M Izu, T Ellison, Sol Energy Mater Sol Cells 78 (2003) 613 [35] T Makela, S Jussila, H Kossonen, T.G Backlund, H.G.O Sandberg, H Stubb, Synth Met 153 33 (2005) 285 [36] S.C Lima, S.H Kim, J.H Lee, H.Y Yu, Y.S Park, D.J Kim, T.Y Zyunga, Mater Sci Eng B 121 (2005) 211 [37] M.J Lee, C.P Judge, S.W Wright, Solid State Electron 44 (2000) 1431 [38] A.Y Natori, C.D Canestraro, L.S Romanb, A.M Ceschin, Mater Sci Eng B 122 (2005) 231 [39] Lukkari, J.; Alanko, M.; Pitkänen, V.; Kleemola, K.; Kankare, J J Phys Chem., 98 (1994) 8525 [40] http://en.wikipedia.org/wiki/Polythiophene#endnote_Tourillon_and_Garnier_1982 [41] L A A Pettersson, F Carlsson, O Inganäs, H Arwin, Thin Solid Films, 356 (1998) 313 [42] www.bayer.com [43] G Beamson, D Briggs, High Resolution XPS of Organic Polymers: The Scienta ESCA300 Database; Wiley: Chichester, England, 1992 [44] A Snis, S.F Matar, O Plashkevych, H Agren, J Chem Phys 111 (1999) 9678 [45] P Snauwaert, R Lazzaroni, J Riga, J.J Verbist, D Gonbeau, J Chem Phys 92 (1990) 2187 [46] G.A Schick, Z Sun, Langmuir 10 (1994) 3105 [47] J.F Moulder, W.F Stickle, P.E Sobol, K.D Bomben, In “Handbook of X-Ray Photoelectron Spectroscopy” (J Chastain, Ed.), Perkin–Elmer, Minneapolis, 1992 34 Part II Fabrication of Porous Electrochemical Membranes Based on PEDOT Nanofibers/Au Nanoparticles 35 Abstract Fabrication of Porous Electrochemical Membranes Based on PEDOT Nanofibers/Au Nanoparticles Poly(3,4-ethylenedioxythiophene) (PEDOT) has recently been found two main kinds of applications as materials in electronic devices and as selective layers in chemical/bio sensors However, sensors based on electrochemical processes due to the change in conductance have not been seriously approached In this study, we fabricate porous electrochemical membranes based on PEDOT nanofibers and Au nanoparticles for sensing applications in detecting metallic ions Diameter of PEDOT fibers was controlled ranging from 40 to 60 nm to increase surface area Au nanoparticles were directly synthesized on PEDOT nanofibers to connect selective receptors with PEDOT fibers This system may not only be used to fabricate biosensors but also replace gold plates in conventional sensors KEYWORDS: Poly(3,4-ethylenedioxythiophene); Au nanoparticles; nanofibers; chemical/bio sensors; porous electrochemical membranes 36 II.1 Introduction Sensors and biosensors have recently attracted interest on account of their applications in the detection of ions, clinical dianostics, environmental monitoring and bioprocess monitoring [1-3] In particular, the development of PEDOT based sensors is intensely investigated research area due to many advantageous properties such as transparency, flexibility, good film-forming, high conductivity, and stability [4-10] PEDOT have been used the first as an amperometric sensor for detection of glucose [5,6] PEDOT also synthesized inside the pores of track-etch membrance in the presence of a positively charged poly(N-methyl-4-pyridine) was reported as glucose biosensors that operate by direct communication between the enzyme, glucose oxidase and the electroactive macromolecules [7] A direct reagentless conductimetric sensor based on PEDOT has been developed for the detection of both an antigen and an antibody in an immunoassay [8] An amperomteric tyrosinase biosensor based on PEDOT has fabricated for estimation of herbicides and phenolic compounds [9] Besides, PEDOT was reported to be a good candidate for DNA detection A label-free DNA sensor was fabricated by the physical entrapment of DNA during the electropolymerization of EDOT The concept of the DNA sensor is based on the change in the conformation of the polymer due to the formation of a DNA duplex As a result, this system has a potential for the direct detection and quantification of target DNA [10] Recently, potentiometric Ag+ sensors were prepared by galvanostatic electropolymerization of EDOT on glassy carbon electrodes by using silver 7,8,9,10,11,12-hexabromocarborane (Ag+CB11H6Br-6 ) as supporting electrolyte [2] Consequently, it is concluded that the applications of PEDOT in sensing devices and biosensors have recently aroused much interest Over the past decade, sensors based on “self-assembled monolayers” (SAMs) of thiolcontaining ligands on gold plate surfaces have generated a powerful tool to monitor the sensing process at monolayer/solution interfaces [1] These devices play important roles in detecting redox active/inactive metal ions and anions including Cu2+, Pb2+, Ca2+, Mg2+ NO3-, CF3COO-, SO42-, H2PO4-, ClO4-, PF6- , SCN-, Cl-, Br-, NO3- and HSO4-, etc [1] 37 In principle, devices based on electrochemal systems significantly relate to processes at the interface between an electrode and electrolyte solution The larger the interface area, the larger will be the rate of the process This has been a motivating factor for fabrication of porous electrodes with high surface area, which may allow every volume element of the electrode materials at the molecular level to be in contact with the electrolyte solution Recently, gold nanoparticles functionalized with SAMs of various thiol containing molecules were reported to be used for various chemical and biological sensors [11-13] Previous studies showed that an immobilized colloidal Au monolayer could be used to investigate biotin–streptavidin interaction Moreover, gold biosensors modified with a self-assembled monolayer of a glucosecarrying polymer chain were prepared for detection of Con A Other studies further demonstrated that a new label-free optical sensor was able to display biomolecular interaction in real time at the surface Based on the potentiality of both PEDOT and Au nanoparticles, PEDOT nanofibers/Au nanocomposite membranes may offer new systems of electrochemical device in sensing applications There has been a variety of methods used to obtain PEDOT nanofibers such as hard templates, soft templates (surfactants), electrospinning and seeding polymerization One of the useful features of hard plate method is effectiveness in controlling diameter, length, and orientation of one-dimensional nano-structured materials However, the templates as track-etched membrance and anodic aluminm oxide are usually removed by chemical process, which makes the structure of PEDOT may be destroyed or form undesirable aggregated structures [14] Since the PEDOT system is relatively insoluble in most solvents, it is necessary to combine it with matrix polymers for the electrospinning process, which could limit significantly the membrane electric properties Of these methods above, the seeding polymerization is a one of the simple ways of obtaining nanofibers at room temperature [15] However, it should be mentioned that the diameter of PEDOT fibers has been controlled to produce uniform nanofibers with average diameters not exceed 100 nm to meet the requirements for potential uses in electric devices, sensors, and supercapacitors, etc In this study, porous electrochemical membranes based on PEDOT nanofibers and Au 38 nanoparticles were fabricated for sensing applications in detecting metallic ions Our effort is to control diameter of PEDOT fibers ranging from 40 to 60 nm and directly synthesize Au nanoparticles on PEDOT nanofibers so as to achieve uniform size and increased surface area Au nanoparticle surfaces were modified by self-assemble monolayers of mercaptocarboxylic acid as selective receptors to bind electrochemically active metal ions, which can be detected using cyclic voltammetry 39 II.2 Experimental section II.2.1 Synthesis of PEDOT Nanofibers Our experiments were carried out according to a similar experimental method as reported elsewhere [15] However, in order to obtain PEDOT nanofibers with smaller diameter, polymerization process was performed in a dilute medium In a typical reaction, EDOT monomer (0.17 g) was added to 30 ml of a magnetically stirred solution of aq 1.0M camphorsulfonic acid (CSA) After complete dissolution of EDOT, mg V2O5 was added to EDOT solution, and then ml of a solution of (NH4)2S2O8 (0.11 g) in aq 1.0M CSA was added right after that to initiate the polymerization After h, the black precipitate of PEDOT nanofibers was suction filtered several times and freeze-dried for 24 h II.2.2 Synthesis of PEDOT/carboxylated- Au nanoparticles composites Freshly synthesized PEDOT nanofibers (12 mg) were added to 20 mL of an aqueous 0.01M HAuCl4 solution After h, the PEDOT-Au composite solution was centrifuged at 4000 rpm for 10 minutes, then suction filtered, and finally freeze-dried for 24 h The surface of Au nanoparticles was functionalized by adding small amount of HS-CH2)2 COOH to PEDOT fibers/Au solution After gentle stirring for 30 minutes at room temperature, and left the mixture be there 24 hours, the mixture was washed to separate the unbound HS-CH2)2 COOH from the carboxylated Au nanoparticles by centrifugation for 15 at 5000 rpm Washing step was repeated three times, the carboxylated Au nanoparticles/PEDOT fiber composites were freeze-dried for further experiments 40 II.3 Results and Discussions Figure II-1 shows that the PEDOT fibers with an average diameter in the range from 40 to 60 nm The reasons for the fibrillar morphology in all seeded systems are not clear until now However, it is believed that polymerization first occurs on the surface of the seed template, and then polymer growth triggers a continuous seeding process In order to obtain PEDOT fibers, the V2O5 sacrificial seeds must survive long enough to initiate fibrillar polymer growth, say, the polymerization rate should be faster than the rate of dissolution of V2O5 seeds [15] Zhang reported that the V2O5 plays an important role in helping orchestrate a change in morphology in this seeded system ICP-MS analysis shows that there is no residual Vanadium in the product, indicating that the V2O5 seed template is dissolved in CSA solution and removed completely during washing processes As with other conducting polymer, conducting PEDOT fibers can react with gold ions in solution without any reducing agents (Scheme II-1) Doped PEDOT functions as a reductant, and thus, is oxidized to a higher oxidation state during the reduction of Au3+ to Au nanoparticles Figure II-2 shows the presence of individual Au nanoparticles along the surface of the PEDOT fibers This result is well consistent with the spontaneous electroless deposition of silver nanoparticles along the walls of the PEDOT nanotubes when exposed to solutions of AgNO3 without reducing agents [16] It is supposed that Au nanoparticles can be spontaneously adsorbed on PEDOT fiber through interaction between Au atoms and thiol groups (-S-) of the PEDOT backbone chains, contributing to well defined, stable two-dimensional arrays of gold nanoparticles EDX and ICP-MS analysis demonstrated that the content of Au nanoparticles on the PEDOT fibers is about 35-40 wt % (table II-1 and II-2) 41 A B Figure II-1 SEM image of PEDOT nanofibers (A), and high resolution image (B) 42 Figure II-2 SEM image of PEDOT fibers/Au nanoparticles membrane S S * O O HAuCl4 O Au O O S S * S S O O O O O O * S O O O S Au O * O Scheme II-1 Schematic representation of the gold particle replication processes on the PEDOT surface 43 Table II-1 EDX analysis of PEDOT/Au composites membranes Element Weight % Atomic % CK 34.44 62.82 OK 17.09 23.40 SK 14.68 10.03 Au M 33.79 3.76 Totals 100.00 Table II-2 ICP-MS analysis of PEDOT/Au composites membranes Element Au V Weight% 39.11 Limit of detection II.4 Conclusions PEDOT nanofibers with diameter ranging from 40-60 nm were synthesized by using seeding polymerization in dilute medium Au nanoparticles were directly deposited on PEDOT nanofibers without any reducing agents well dispersed on PEDOT surface through interaction between Au atoms and thiol groups (-S-) of the PEDOT backbone chains to form a novel materials system 44 References [1] S Zhang, C M Cardona, L Echegoyen, Chem Commun., 2006, 4461 [2] Z Mousavi, J Bobacka, A Lewenstam, A Ivaska, Journal of Electroanalytical Chemistry, 593 (2006) 219 [3] J Janata, M Josowicz, nature materials, (2003) 19 [4] A Michalska, K Maksymiuk, Talanta, 63 (2004) 109 [5] A Kros, S W F M van Hövell, N A J M Sommerdijk and R J M Nolte, Adv Mater 13 (2001) 1555 [6] B Piro, L A Dang, M C Dham, S Fabiano and T M Canh, J Electroanal Chem 542 (2001) 101 [7] A Kros, R J M Nolte, N A., J M Sommerdijk, Adv Mater 14 (2002) 1779 [8] M Kanungo, D N Srivastava, A Kumar, A Q Contractor, Chem commun 2002, 680 [9] C Vedrine, S Fabiano, C Tran-Minh, Talanta 59 (2003) 535 [10] K Krishnamoorthy, R S Gokhale, A Q Contractor, A Kumar, Chem, commun 2004, 820 [11] S Chah, M R Hammond, R N Zare, Chemistry & Biology 12 (2005) 323 [12] J J Storhoff, S S Marla, P Bao, S Hagenow, H Mehta, A Lucas, V Garimella, T Patno, W Buckingham, W Cork, U R Muller, Biosensors and Bioelectronics 19 (2004) 875 [13] J Matsui, K Akamatsu, N Hara, D Miyoshi, H Nawafune, K Tamaki, N Sugimoto, Anal Chem 77 (2005) 4282 [14] Z X Wei, Z M Zhang, M X Wan, Langmuir 18 (2002) 917 [15] X Zhang, A G MacDiarmid, S K Manohar, Chem Commun., 2005, 5328 [16] X Zhang, J-S Lee, Gil S Lee, D-K Cha, M J Kim, D J Yang, S K Manohar, Macromolecules 39 (2006) 470 45 ABSTRACT Part I 광전자학 응용을 위한 기상중합 Poly(3,4ethylenedioxythiophene) 필름의 표면 morphology와 전도 도 조정 Thuy Le Truong 고분자공학과 성균관대학원 Poly(3,4-ethylenedioxythiophene)의 표면 morphology는 flexible PET substrate film 위에 싸이오펜 단량체의 기상중합 함으로써 연구 되어진다 Fe(III)- tosylate(Fe(OTs)3)과의 향상된 친수성을 고려 및 PEDOT뿐만 아니라 싸이오펜 단량체와의 적절한 수소결합을 위한 amine, amide groups 생성을 위해 PET 표면은 표면 거칠기가 2nm 이하를 유지하는 ethylene diamine을 이용해 수정되어진다 PEDOT thin film의 표면 거칠기와 전도도를 조절하기 위해 반응지연제로서의 pyridine을 혼합하여 중합속도를 줄인다 Pyridine과 glycerol의 광학조건은 500S/cm 의 전도도와 표면거칠기 2nm 이하에서 0,5 몰비의 pyridine/Fe(OTs)3 과 4~5wt%의 glycerol조건에서 알아내어진다 Keywords: Poly(3,4-ethylenedioxythiophene); vapor-phase polymerization; Fe(III)-tosylate polyethyleneterphthalate 46 Part II PEDOT Nanofibers/Au nanoparticles를 이용한 다공성 전 자화학적 막 제조 Thuy Le Truong 고분자공학과 성균관대학원 Poly(3,4-ethylenedioxythiophene)은 전자 부품에서의 재료로서와 화학/생물학적 감지기로서의 선택적 layer 로서의 2가지 응용을 위해 최근에 발명되었다 그러나, conductance의 변화 때문에 전자화학적 processes에 기초한 감지기는 중요하게 받아 들여지고 있지는 않다 이번 연구에서는 금속이온을 발견하면서 PEDOT nanofibers와 Au nanoparticles를 바탕으로하는 다공성 전자화학적 막을 제조하였다 표면적을 증가 시키위하여 PEDOT nanofiber의 직경은 40~60nm 사이의 범위로 조절한다 Au nanoparticles는 PEDOT fibers와 어떤 선택적 수용체를 연결시키기 위하여 PEDOT nanofibers위에 바로 합성되어진다 이 mechanism은 생체감지기 제조 뿐만 아니라 기 존의 금속 plates를 대체하는 용도로도 쓰여질 것이다 Keywords: Poly(3,4-ethylenedioxythiophene); Au nanoparticles; chemical/ biosensors; porous electrochemical membranes 47 nanofibers; [...]... (A) and high resolution SEM image (B) of PEDOT nanofibers ················42 Figure II-1 SEM image of porous PEDOT /Au membranes ·····························································43 v Part I Surface Mophology and Conductivity Control of Vapor- phase Polymerized Poly( 3,4 -ethylenedioxythiophene) Thin Films for Optoelectronic Applications ABTRACT Surface Morphology and Conductivity Control of Vapor- phase. .. and Conductivity Control of Vapor- phase Polymerized Poly( 3,4 -ethylenedioxythiophene) Thin Films for Optoelectronic Applications As with other conducting polymers, poly( 3,4 -ethylenedioxythiophene) is considered as a promising material for optoelectronic devices In most of those optoelectronic applications as buffer or electrode layers, the surface and/ or interface of PEDOT coating layer substantially... mobility, quantum efficiency and stability of charge carriers as well as assembled devices Previous studies show that the effect of dielectric surface on charge mobility is due to surface-induced morphology of polythiophene In this sense, the vapor- phase polymerization (VPP) of PEDOT is a promising technology in various optoelectronic applications to provide a thin, uniform, and highlyconductive PEDOT... spectra of the untreated PET films (A), EDA-treated PET films (B), and the high-resolution XPS analysis of N1s peaks of EDA-treated PET films for different treatment times (C) The deconvoluted peaks of the EDA-treated PET for 20 min in (C) show amine and amide N-C bonds at 399.6 and 401.7 eV, respectively All EDA treatments were performed at 40 oC 15 Figure I-5 shows the water contact angle and surface... PEDOT Polymerization rate was reduced by incorporating pyridine as a reaction retardant to control the surface roughness and conductivity of PEDOT thin films The optimal conditions of pyridine and glycerol were found at a pyridine/Fe(OTs)3 molar ratio of 0.5 and a glycerol concentration of 4~5 wt%, respectively, 2 providing the conductivity up to 500 S/cm and the surface roughness < 2 nm KEYWORDS: Poly( 3,4 -ethylenedioxythiophene); ... Scheme I-2 Structure of Baytron P (PEDOT: PSS) [42] Generally, Baytron P is a soluble polymer in the doped state with conductivity of 10 S/cm [42] Vapor- phase polymerization Vapor phase polymerization is a versatile technique that can be used to obtain highly conducting coatings of conjugated polymer on both conducting and nonconducting substrates The method is based on the use of organic ferric sulfonates... PSS)·············································································· 9 Scheme I-3 Vapor- phase reaction of EDA with the ester groups of the PET films ··························14 Scheme I-4 A proposed mechanism for the effect of pyridine on PEDOT polymerization (a) and (b) pyridine coordinates with the Fe(OTs)3 through the successive substitution of pyridine with the alcohol ligands via the unbonded electrons in N, (c) the stability of cation radical of EDOT ···································································································24... Transparency of PEDOT films as a function of the pyridine/Fe(OTs)3 molar ratio ········22 Figure I-12 pH of Fe(OTs)3 solution as a function of the Py concentration········································23 Figure I-13 Surface roughness and the surface resistivity of PEDOT-coated PET films (A), and the iv conductivity and thickness of PEDOT coating on glass substrates (B) as a function of glycerol concentrations... chamber, which contains EDA to evaporate and fill therein, for the gas -phase EDA treatment of PET films at 40 oC for 10 ~ 40 min in the atmospheric pressure The EDA-treated PET films were rinsed in DI (deionized) water in order to completely remove the EDA, which was checked with litmus paper, and dried at 50 oC for 10 min prior to use I.3.3 Oxidative polymerization of EDOT with Fe(OTs)3 by VPP The... Various amount of pyridine and glycerol was added to the Fe(OTs)3 solution After drying, the samples were transferred to a gas -phase polymerization chamber (Fig I-3) using a similar experimental setup and method as reported elsewhere [2] The chamber was flushed with nitrogen during polymerization, and heated to 50 oC The EDOT was placed at the bottom of the chamber and the vapor- phase polymerization