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Electrochemical polymerization of polypyrrole (PPy) and poly(3-hexylthiophene) (P3HT) using functionalized single-wall carbon nanotubes
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Colloids and Surfaces A: Physicochem. Eng. Aspects 313–314 (2008) 72–76
Electrochemical polymerization of polypyrrole (PPy) and poly(3-hexylthiophene) (P3HT) using functionalized single-wall carbon nanotubes Hyung Min Park, Ki Hwan Kim, Seok Ho Lee, Dong Hyuk Park, Young Ki Hong, Jinsoo Joo ∗ Department of Physics, Korea University, Seoul 136-701, Republic of Korea Received 31 October 2006; accepted 29 April 2007 Available online 31 May 2007
Abstract We report on the synthesis and characteristics of polypyrrole (PPy) nanowires and poly(3-hexylthiophene) (P3HT) films by using functionalized single-wall carbon nanotubes (F-SWCNTs). The F-SWCNTs were prepared by the process of ultrasonication of SWCNTs mixture with nitric and sulfuric acid (3:1 volume ratio) solution. The F-SWCNTs has the pending carboxylic acid group ( COOH). The PPy nanowires and bulky P3HT film were electrochemically polymerized based on the Al2 O3 nanoporous template and on the ITO glass, respectively, by using the F-SWCNTs as a dopant in electrolyte. We compared the structural characteristics between the arc-grown SWCNTs and the F-SWCNTs through a scanning electron microscope (SEM), a Fourier transform infrared (FT-IR) spectroscope, a Raman spectroscope, an X-ray photoelectron spectroscope, and an elemental analysis. The formation of PPy nanowires and bulky P3HT film were confirmed through SEM and FT-IR experiments. © 2007 Elsevier B.V. All rights reserved. Keywords: Electrochemical polymerization; Polypyrrole; Poly(3-hexylthiophene); Single-wall carbon nanotube; Functionalization
1. Introduction Single-wall carbon nanotubes (SWCNTs) have attracted a considerable attention due to their unique electrical and mechanical properties. The SWCNTs have a high strength and a one-dimensional structure with a high aspect ratio [1–4]. They show remarkable optical properties and electrical conductivity, arranging from semiconducting to metallic behavior. -Conjugated polymers can be highly conducting states after chemical doping. Through the formation of the nanocomposites of -conjugated polymers with SWCNTs, electrical and optical properties for both materials can be optimized [5,6]. The -conjugated polymers with SWCNTs have been studied for the use of organic photovoltaic cells, because of excellent hole and electron transport property of the polymers and SWCNTs, respectively [7]. Polypyrrole (PPy) is one of promising conducting polymers for commercial uses with environmen-
∗
Corresponding author. Tel.: +82 2 3290 3103; fax: +82 2 927 3292. E-mail address: [email protected] (J. Joo).
0927-7757/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.colsurfa.2007.04.077
tal stability. Poly(3-hexylthiophene) (P3HT) has shown a high mobility and good processibility owing to solubility. The functionalization of SWCNTs (F-SWCNTs) with the carboxylic acid groups ( COOH) on the surface can contribute to synthesize polymer–CNT nanocomposites [8–12]. In this paper, we report on the synthesis of the PPy/ F-SWCNTs composite nanowires and the P3HT/F-SWCNTs composite films. The structural characteristics of the polymers/F-SWCNTs were confirmed by a Fourier transform infrared (FT-IR) spectroscope, an X-ray photoelectron spectroscope (XPS), and a scanning electron microscope (SEM) experiments. 2. Experimental 2.1. F-SWCNTs Arc-grown SWCNTs (1–10 nm in diameter and 5–20 m in length) were provided by Iljin Nanotech Co., Ltd. The purity of the raw SWCNT materials was about 30–40 wt%. For carboxylation, SWCNTs (50 mg) were ultrasonicated for 24 h in
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a mixture of concentrated nitric and sulfuric acid (3:1 volume ratio) solution, which induced to the formation of the carboxylic acid group ( COOH) at the ends or on side of SWCNTs [13,14]. After ultrasonication, the acid and SWCNTs mixture was neutralized by using the distilled water or NaOH (2 M) solution. The F-SWCNTs were precipitated via centrifugation for 1 h [15]. The F-SWCNTs with carboxylic acid groups were soluble in distilled water due to hydrophilic property. 2.2. Electrochemical polymerization of PPy nanowires and bulky P3HT films For electrochemical polymerization of PPy nanowires, the electrolyte consisted of pyrrole monomers (0.5 M) and FSWCNTs (10 wt%) dispersed in distilled water. The thermally evaporated Au onto one side of the Al2 O3 nanoporous membrane and the stainless steal were used as working and counter electrodes, respectively. The electrochemical polymerization of pyrrole was performed at the voltage of 3 V for 50 min [16]. PPy nanowires were polymerized in the pore of Al2 O3 membrane. The Al2 O3 template was removed with 2 M HF or 2 M NaOH solution. We used the 3HT monomers (0.2 M) and F-SWCNTs (6 wt%) with a surfactant of Tween 20 (2 wt%) in de-ionized water in order to synthesize bulky P3HT film. The indium tin oxide (ITO) glass and the stainless steal were used as working and counter electrodes, respectively. The bulky P3HT films were electrochemically polymerized at the voltage of 5–7 V for 5–10 min.
Fig. 1. SEM images of: (a) arc-grown SWCNTs and (b) F-SWCNTs with carboxylic acid group. Inset of (b): schematical molecular picture of the F-SWCNTs with the COOH groups.
2.3. Measurements We compared the structural characteristics of the arc-grown SWCNTs and the F-SWCNTs through a SEM (JSM-5200, JEOL), a FT-IR (FTS-60, Bio-Rad), a Raman spectroscope (LabRam HR, Jobin-Yvon), an XPS (SSI, 2803-S), and an elemental analysis (EA, Flash EA 1112 Series, CE instruments/ThermoQuest Italia). 3. Results and discussion SEM images of the arc-grown SWCNTs and F-SWCNTs are shown in Fig. 1(a and b), respectively. The arc-grown SWCNTs have impurities and aggregations of carbons, as shown in Fig. 1(a). Fig. 1(b) shows the cross-sectional view of the aggregated F-SWCNT samples. FT-IR spectra of the SWCNTs and F-SWCNTs treated with distilled water and NaOH solvent are shown in Fig. 2. Like graphite, the FT-IR spectrum of the pristine SWCNTs was featureless due to extremely low infrared absorption intensities [17–20]. We compared the FT-IR spectra for F-SWCNTs neutralized by distilled water and by NaOH solvent. The characteristic peaks of FT-IR spectra of two kinds of F-SWCNTs were almost the same positions as shown in Fig. 2. The peak at 3400 cm−1 was assigned to the OH stretching mode of the COOH group. The peak at 1725 cm−1 corresponded to the C O stretching mode, indicating the formation of the COOH groups on the nanotubes. The peak at 1600 cm−1 represented
the C C graphitic stretching mode in the SWCNTs. The peak at 1225 cm−1 was assigned to C O stretching mode [21]. Raman spectra of the arc-grown SWCNTs and F-SWCNTs are shown in Fig. 3. Three radial breath modes (RBMs) of the arc-grown SWCNTs were observed at 148, 166, and 179 cm−1 , as shown in the bottom curve of the inset of Fig. 3. A single RBM line, however, was observed at 176 cm−1 in the F-SWCNTs with a relatively low intensity due to the effect of residue impurities, as shown in the inset of Fig. 3 (the second and third curves from bottom) [22,23]. Electrochemical purification for F-SWCNTs was performed during polymerization. Then, we observed the
Fig. 2. FT-IR spectra of arc-grown SWCNTs and F-SWCNTs.
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H.M. Park et al. / Colloids and Surfaces A: Physicochem. Eng. Aspects 313–314 (2008) 72–76 Table 1 Elemental analysis (EA) of arc-grown SWCNTs and F-SWCNTs with carboxylic acid group
Fig. 3. Raman spectra of arc-grown SWCNTs and F-SWCNTs treated with distilled water or NaOH solvent. Inset: magnification of Raman spectra for RBMs.
single RBM at 189 cm−1 for the F-SWCNTs (top curve of the inset of Fig. 3). That is, the impurities could not involved in the F-SWCNTs. After functionalization, the disorder-induced Raman mode for SWCNTs was observed at 1349 cm−1 [24]. The peak of graphite tangential mode was detected at 1587 cm−1 . Table 1 lists the constituent elements of the SWCNTs and the FSWCNTs obtained from an elemental analysis. Relative increase of hydrogen and oxygen elements in the F-SWCNTs suggests the formation of carboxylic acid group ( COOH).
Fig. 4. C 1s XPS spectra of: (a) SWCNTs and (b) F-SWCNTs.
Sample
N (%)
C (%)
H (%)
O (%)
SWCNTs F-SWCNTs
0.09 2.03
77.17 ± 0.12 44.72
0.16 ± 0.02 1.33
7.59 ± 0.03 24.91
The carbon 1s (C 1s) XPS spectra of SWCNTs and FSWCNTs were shown in Fig. 4(a and b), respectively. The C 1s XPS spectrum of SWCNTs in Fig. 4(a) was decomposed with four peaks at 284.2, 285.2, 286.1, and 288.0 eV, in which the percent of the peak area was 70.2, 22.0, 7.6, and 0.2%, respectively. The peak at 284.2 eV was assigned to sp2 C C bonding resulting from SWCNTs and amorphous carbon [25]. The peak at 285.2 eV was attributed to sp3 C C bonding of the amorphous carbons [25]. The peaks at 286.1 and 288.0 eV corresponded to C O and C O bonding, respectively [26]. The SWCNTs contained some extent of the amorphous carbon and the relatively low contents of C O and C O originated from the absorption of oxygen [26]. The C 1s XPS spectrum of F-SWCNTs as shown in Fig. 4(b) was also decomposed with four peaks at 284.3, 285.1, 286.4, and 288.0 eV, in which the percent of the peak area was 66.7, 2.9, 14.4, and 16.0%, respectively. The area ratio of C O (at 286.4 eV) and C O (at 288.0 eV) bonding to sp2 C C (at 284.3 eV) bonding of F-SWCNTs were 21.6 and 24.0%, which confirmed the covalently bonded carboxylic acid group onto the SWCNTs.
Fig. 5. SEM images of: (a) PPy nanowires and (b) bulky P3HT film.
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at 1457 cm−1 represented the symmetric ring stretching mode. The peak at 1355 cm−1 were due to the methyl deformation mode [30]. The four peaks at 3400, 1725, 1600, and 1080 cm−1 originated from the characteristic peaks of the F-SWCNTs. The results of FT-IR spectra of bulky P3HT/F-SWCNTs film confirmed the successful polymerization. 4. Conclusion The F-SWCNTs with carboxylic acid groups were fabricated through the ultrasonicating method of the arc-grown SWCNTs mixture in the nitric and sulfuric acid (3:1 volume ratio) solvent. The PPy nanowires and bulky P3HT films were electrochemically polymerized by using F-SWCNTs as a dopant. We observed the formation of self-assembled micro or nanotubes on the P3HT/F-SWCNT film surface. From FT-IR and Raman spectra, we confirmed that the F-SWCNTs were used as a dopant of PPy or P3HT and single-wall carbon nanotubes composites. Acknowledgements This work was supported in part by the second Brain Korea 21 (BK21) project and the Korean Research Foundation (KRF Grant-J03602). References Fig. 6. FT-IR spectra of: (a) PPy nanowires and (b) bulky P3HT film.
SEM images of the PPy/F-SWCNTs nanowires and bulky P3HT/F-SWCNTs film are showed in Fig. 5. The diameter and length of PPy/F-SWCNTs nanowires were ∼200 nm and ∼20 m, respectively. The P3HT/F-SWCNTs film was polymerized on the ITO electrode. We observed the formation of self-assembled micro or nanotubules of P3HT/F-SWCNTs surface, as shown in Fig. 5(b). During polymerization, 3HT monomers were gathered onto the F-SWCNTs with carboxylic acid group [27]. The diameter of the P3HT tubules was ∼200 nm. Fig. 6(a) shows the FT-IR spectra of PPy nanowires using F-SWCNTs or conventional tetra-butylammonium hexafluorophosphate (TBAPF6 ) as a dopant [28]. The peak at 3400 cm−1 was due to OH stretching mode of the COOH group. The peak at 1556 cm−1 was assigned to the C C or C C stretching mode. The peak at 1471 cm−1 was due to the ring breathing mode from C C, C C, or C N. The peak at 1034 cm−1 represented C H and N H in plane deformation. The peak of at 916 and 847 cm−1 represented C H bending and ring breathing centered on ␣-carbon, respectively. From the FT-IR spectra of the PPy/F-SWCNTs nanowires, we confirmed the polymerization of PPy. The FT-IR spectra of bulky P3HT/F-SWCNTs film are shown in Fig. 6(b) [29]. The peaks of 2854, 2923, and 2950 cm−1 were assigned to CH2 out of phase mode, CH2 in phase mode, and CH3 asymmetry stretching mode, respectively. The peak
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Colloids and Surfaces A: Physicochem. Eng. Aspects 313–314 (2008) 72–76
Electrochemical polymerization of polypyrrole (PPy) and poly(3-hexylthiophene) (P3HT) using functionalized single-wall carbon nanotubes Hyung Min Park, Ki Hwan Kim, Seok Ho Lee, Dong Hyuk Park, Young Ki Hong, Jinsoo Joo ∗ Department of Physics, Korea University, Seoul 136-701, Republic of Korea Received 31 October 2006; accepted 29 April 2007 Available online 31 May 2007
Abstract We report on the synthesis and characteristics of polypyrrole (PPy) nanowires and poly(3-hexylthiophene) (P3HT) films by using functionalized single-wall carbon nanotubes (F-SWCNTs). The F-SWCNTs were prepared by the process of ultrasonication of SWCNTs mixture with nitric and sulfuric acid (3:1 volume ratio) solution. The F-SWCNTs has the pending carboxylic acid group ( COOH). The PPy nanowires and bulky P3HT film were electrochemically polymerized based on the Al2 O3 nanoporous template and on the ITO glass, respectively, by using the F-SWCNTs as a dopant in electrolyte. We compared the structural characteristics between the arc-grown SWCNTs and the F-SWCNTs through a scanning electron microscope (SEM), a Fourier transform infrared (FT-IR) spectroscope, a Raman spectroscope, an X-ray photoelectron spectroscope, and an elemental analysis. The formation of PPy nanowires and bulky P3HT film were confirmed through SEM and FT-IR experiments. © 2007 Elsevier B.V. All rights reserved. Keywords: Electrochemical polymerization; Polypyrrole; Poly(3-hexylthiophene); Single-wall carbon nanotube; Functionalization
1. Introduction Single-wall carbon nanotubes (SWCNTs) have attracted a considerable attention due to their unique electrical and mechanical properties. The SWCNTs have a high strength and a one-dimensional structure with a high aspect ratio [1–4]. They show remarkable optical properties and electrical conductivity, arranging from semiconducting to metallic behavior. -Conjugated polymers can be highly conducting states after chemical doping. Through the formation of the nanocomposites of -conjugated polymers with SWCNTs, electrical and optical properties for both materials can be optimized [5,6]. The -conjugated polymers with SWCNTs have been studied for the use of organic photovoltaic cells, because of excellent hole and electron transport property of the polymers and SWCNTs, respectively [7]. Polypyrrole (PPy) is one of promising conducting polymers for commercial uses with environmen-
∗
Corresponding author. Tel.: +82 2 3290 3103; fax: +82 2 927 3292. E-mail address: [email protected] (J. Joo).
0927-7757/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.colsurfa.2007.04.077
tal stability. Poly(3-hexylthiophene) (P3HT) has shown a high mobility and good processibility owing to solubility. The functionalization of SWCNTs (F-SWCNTs) with the carboxylic acid groups ( COOH) on the surface can contribute to synthesize polymer–CNT nanocomposites [8–12]. In this paper, we report on the synthesis of the PPy/ F-SWCNTs composite nanowires and the P3HT/F-SWCNTs composite films. The structural characteristics of the polymers/F-SWCNTs were confirmed by a Fourier transform infrared (FT-IR) spectroscope, an X-ray photoelectron spectroscope (XPS), and a scanning electron microscope (SEM) experiments. 2. Experimental 2.1. F-SWCNTs Arc-grown SWCNTs (1–10 nm in diameter and 5–20 m in length) were provided by Iljin Nanotech Co., Ltd. The purity of the raw SWCNT materials was about 30–40 wt%. For carboxylation, SWCNTs (50 mg) were ultrasonicated for 24 h in
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a mixture of concentrated nitric and sulfuric acid (3:1 volume ratio) solution, which induced to the formation of the carboxylic acid group ( COOH) at the ends or on side of SWCNTs [13,14]. After ultrasonication, the acid and SWCNTs mixture was neutralized by using the distilled water or NaOH (2 M) solution. The F-SWCNTs were precipitated via centrifugation for 1 h [15]. The F-SWCNTs with carboxylic acid groups were soluble in distilled water due to hydrophilic property. 2.2. Electrochemical polymerization of PPy nanowires and bulky P3HT films For electrochemical polymerization of PPy nanowires, the electrolyte consisted of pyrrole monomers (0.5 M) and FSWCNTs (10 wt%) dispersed in distilled water. The thermally evaporated Au onto one side of the Al2 O3 nanoporous membrane and the stainless steal were used as working and counter electrodes, respectively. The electrochemical polymerization of pyrrole was performed at the voltage of 3 V for 50 min [16]. PPy nanowires were polymerized in the pore of Al2 O3 membrane. The Al2 O3 template was removed with 2 M HF or 2 M NaOH solution. We used the 3HT monomers (0.2 M) and F-SWCNTs (6 wt%) with a surfactant of Tween 20 (2 wt%) in de-ionized water in order to synthesize bulky P3HT film. The indium tin oxide (ITO) glass and the stainless steal were used as working and counter electrodes, respectively. The bulky P3HT films were electrochemically polymerized at the voltage of 5–7 V for 5–10 min.
Fig. 1. SEM images of: (a) arc-grown SWCNTs and (b) F-SWCNTs with carboxylic acid group. Inset of (b): schematical molecular picture of the F-SWCNTs with the COOH groups.
2.3. Measurements We compared the structural characteristics of the arc-grown SWCNTs and the F-SWCNTs through a SEM (JSM-5200, JEOL), a FT-IR (FTS-60, Bio-Rad), a Raman spectroscope (LabRam HR, Jobin-Yvon), an XPS (SSI, 2803-S), and an elemental analysis (EA, Flash EA 1112 Series, CE instruments/ThermoQuest Italia). 3. Results and discussion SEM images of the arc-grown SWCNTs and F-SWCNTs are shown in Fig. 1(a and b), respectively. The arc-grown SWCNTs have impurities and aggregations of carbons, as shown in Fig. 1(a). Fig. 1(b) shows the cross-sectional view of the aggregated F-SWCNT samples. FT-IR spectra of the SWCNTs and F-SWCNTs treated with distilled water and NaOH solvent are shown in Fig. 2. Like graphite, the FT-IR spectrum of the pristine SWCNTs was featureless due to extremely low infrared absorption intensities [17–20]. We compared the FT-IR spectra for F-SWCNTs neutralized by distilled water and by NaOH solvent. The characteristic peaks of FT-IR spectra of two kinds of F-SWCNTs were almost the same positions as shown in Fig. 2. The peak at 3400 cm−1 was assigned to the OH stretching mode of the COOH group. The peak at 1725 cm−1 corresponded to the C O stretching mode, indicating the formation of the COOH groups on the nanotubes. The peak at 1600 cm−1 represented
the C C graphitic stretching mode in the SWCNTs. The peak at 1225 cm−1 was assigned to C O stretching mode [21]. Raman spectra of the arc-grown SWCNTs and F-SWCNTs are shown in Fig. 3. Three radial breath modes (RBMs) of the arc-grown SWCNTs were observed at 148, 166, and 179 cm−1 , as shown in the bottom curve of the inset of Fig. 3. A single RBM line, however, was observed at 176 cm−1 in the F-SWCNTs with a relatively low intensity due to the effect of residue impurities, as shown in the inset of Fig. 3 (the second and third curves from bottom) [22,23]. Electrochemical purification for F-SWCNTs was performed during polymerization. Then, we observed the
Fig. 2. FT-IR spectra of arc-grown SWCNTs and F-SWCNTs.
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H.M. Park et al. / Colloids and Surfaces A: Physicochem. Eng. Aspects 313–314 (2008) 72–76 Table 1 Elemental analysis (EA) of arc-grown SWCNTs and F-SWCNTs with carboxylic acid group
Fig. 3. Raman spectra of arc-grown SWCNTs and F-SWCNTs treated with distilled water or NaOH solvent. Inset: magnification of Raman spectra for RBMs.
single RBM at 189 cm−1 for the F-SWCNTs (top curve of the inset of Fig. 3). That is, the impurities could not involved in the F-SWCNTs. After functionalization, the disorder-induced Raman mode for SWCNTs was observed at 1349 cm−1 [24]. The peak of graphite tangential mode was detected at 1587 cm−1 . Table 1 lists the constituent elements of the SWCNTs and the FSWCNTs obtained from an elemental analysis. Relative increase of hydrogen and oxygen elements in the F-SWCNTs suggests the formation of carboxylic acid group ( COOH).
Fig. 4. C 1s XPS spectra of: (a) SWCNTs and (b) F-SWCNTs.
Sample
N (%)
C (%)
H (%)
O (%)
SWCNTs F-SWCNTs
0.09 2.03
77.17 ± 0.12 44.72
0.16 ± 0.02 1.33
7.59 ± 0.03 24.91
The carbon 1s (C 1s) XPS spectra of SWCNTs and FSWCNTs were shown in Fig. 4(a and b), respectively. The C 1s XPS spectrum of SWCNTs in Fig. 4(a) was decomposed with four peaks at 284.2, 285.2, 286.1, and 288.0 eV, in which the percent of the peak area was 70.2, 22.0, 7.6, and 0.2%, respectively. The peak at 284.2 eV was assigned to sp2 C C bonding resulting from SWCNTs and amorphous carbon [25]. The peak at 285.2 eV was attributed to sp3 C C bonding of the amorphous carbons [25]. The peaks at 286.1 and 288.0 eV corresponded to C O and C O bonding, respectively [26]. The SWCNTs contained some extent of the amorphous carbon and the relatively low contents of C O and C O originated from the absorption of oxygen [26]. The C 1s XPS spectrum of F-SWCNTs as shown in Fig. 4(b) was also decomposed with four peaks at 284.3, 285.1, 286.4, and 288.0 eV, in which the percent of the peak area was 66.7, 2.9, 14.4, and 16.0%, respectively. The area ratio of C O (at 286.4 eV) and C O (at 288.0 eV) bonding to sp2 C C (at 284.3 eV) bonding of F-SWCNTs were 21.6 and 24.0%, which confirmed the covalently bonded carboxylic acid group onto the SWCNTs.
Fig. 5. SEM images of: (a) PPy nanowires and (b) bulky P3HT film.
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at 1457 cm−1 represented the symmetric ring stretching mode. The peak at 1355 cm−1 were due to the methyl deformation mode [30]. The four peaks at 3400, 1725, 1600, and 1080 cm−1 originated from the characteristic peaks of the F-SWCNTs. The results of FT-IR spectra of bulky P3HT/F-SWCNTs film confirmed the successful polymerization. 4. Conclusion The F-SWCNTs with carboxylic acid groups were fabricated through the ultrasonicating method of the arc-grown SWCNTs mixture in the nitric and sulfuric acid (3:1 volume ratio) solvent. The PPy nanowires and bulky P3HT films were electrochemically polymerized by using F-SWCNTs as a dopant. We observed the formation of self-assembled micro or nanotubes on the P3HT/F-SWCNT film surface. From FT-IR and Raman spectra, we confirmed that the F-SWCNTs were used as a dopant of PPy or P3HT and single-wall carbon nanotubes composites. Acknowledgements This work was supported in part by the second Brain Korea 21 (BK21) project and the Korean Research Foundation (KRF Grant-J03602). References Fig. 6. FT-IR spectra of: (a) PPy nanowires and (b) bulky P3HT film.
SEM images of the PPy/F-SWCNTs nanowires and bulky P3HT/F-SWCNTs film are showed in Fig. 5. The diameter and length of PPy/F-SWCNTs nanowires were ∼200 nm and ∼20 m, respectively. The P3HT/F-SWCNTs film was polymerized on the ITO electrode. We observed the formation of self-assembled micro or nanotubules of P3HT/F-SWCNTs surface, as shown in Fig. 5(b). During polymerization, 3HT monomers were gathered onto the F-SWCNTs with carboxylic acid group [27]. The diameter of the P3HT tubules was ∼200 nm. Fig. 6(a) shows the FT-IR spectra of PPy nanowires using F-SWCNTs or conventional tetra-butylammonium hexafluorophosphate (TBAPF6 ) as a dopant [28]. The peak at 3400 cm−1 was due to OH stretching mode of the COOH group. The peak at 1556 cm−1 was assigned to the C C or C C stretching mode. The peak at 1471 cm−1 was due to the ring breathing mode from C C, C C, or C N. The peak at 1034 cm−1 represented C H and N H in plane deformation. The peak of at 916 and 847 cm−1 represented C H bending and ring breathing centered on ␣-carbon, respectively. From the FT-IR spectra of the PPy/F-SWCNTs nanowires, we confirmed the polymerization of PPy. The FT-IR spectra of bulky P3HT/F-SWCNTs film are shown in Fig. 6(b) [29]. The peaks of 2854, 2923, and 2950 cm−1 were assigned to CH2 out of phase mode, CH2 in phase mode, and CH3 asymmetry stretching mode, respectively. The peak
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