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1 DOI: /NCHEM.1655 Supplementary Information Initiation of Carbon Nanotube Growth by Well-Defined Carbon Nanorings Haruka Omachi 1, Takuya Nakayama 1, Eri Takahashi 2, Yasutomo Segawa 1, and Kenichiro Itami 1,3, * 1 Department of Chemistry, Graduate School of Science, Nagoya University Chikusa, Nagoya , Japan. 2 Synthetic Organic Chemistry Laboratories, Research & Development Management Headquarters, FUJIFILM Corporation Ushijima, Kaisei-machi, Ashigarakami-gun, Kanagawa , Japan. 3 Institute of Transformative Bio-Molecules (WPI-ITbM), Nagoya University Chikusa, Nagoya , Japan. itami.kenichiro@a.mbox.nagoya-u.ac.jp Table of Contents 1. Synthesis and Analysis of Carbon Nanotubes S2 S12 2. Analysis of Thermal Stability of [12]CPP S13 S22 3. References S23 NATURE CHEMISTRY 1

2 1. Synthesis and Analysis of Carbon Nanotubes General All solvents (acetone, methanol, ethanol, toluene, and 1,2-dichroroethane) were obtained from commercial suppliers and used without further purification. Sapphire substrates (double side polished) were purchased from Hi Solar Co., Ltd.. Cycloparaphenylenes ([9]CPP and [12]CPP) were synthesized as reported, S1,S2 recrystallized, and dried over 100 C with reduced pressure prior to the ring-to-tube synthesis of CNTs. Typical Procedure for the Synthesis of Carbon Nanotubes from CPPs Sapphire or silicon substrates (5 mm 5 mm) were cleaned by ultrasonication in acetone and methanol, followed by ozone cleaning. 10 µl of a 0.5 mm CPP solution in toluene or 1,2-dichroroethane was then spin-coated at 4000 rpm on a substrate. The thus-prepared reaction substrate was put on a quartz boat, having an arm covered with steal wires (for moving by a magnet), and placed into a quartz tube but outside of a chamber. The furnace was heated up to 500 C with vacuuming by the pump. After reaching 500 C, ethanol was flowed by the vacuum until the pressure was stabilized around 1 Torr. The reaction substrate was placed in the heating area, and then heated at 500 C for 15 min with the flow of ethanol gas. Finally, the reaction substrate was withdrawn from the heating area and cooled to room temperature rapidly. Under these conditions, [12]CPP and [9]CPP were successfully converted into CNTs as shown in Fig. 2. NATURE CHEMISTRY 2

3 Analysis of CNTs by Raman Spectroscopy Raman spectra of the synthesized CNTs were measured using HR-800 (Horiba Jovin Yvon) equipped with Ar + ion and He-Ne lasers operated at 488 nm and 633 nm, respectively. A notch filter was used to filter out Rayleigh radiation, and Raman signal was detected by charge-coupled device (CCD). A 50x, 0.75 NA objective lens was used to focus the laser light onto the samples. All measurements were carried out at room temperature and atmospheric conditions. Shown in Fig. S1 are the full-scale Raman spectra of CNTs grown from [12]CPP including RBM area ( cm 1 ), D-band area (~1350 cm 1 ), and G-band area (~1600 cm 1 ). Shown in Fig. S2 are Raman spectra of CNTs grown from [12]CPP (RBM area; excited by 488 nm laser) taken at different spots on the substrate. Shown in Fig. S3 are the full-scale Raman spectra of CNTs grown from [9]CPP. Shown in Fig. S4 are the Raman spectra of CNTs grown from [9]CPP (RBM area; excited by 633 nm laser) taken at different spots on the substrate. Shown in Fig. S5 and S6 are the Raman spectra of [12]CPP and [9]CPP, respectively. NATURE CHEMISTRY 3

4 Intensity /a.u. Raman shift /cm 1 Figure S1. Full-scale Raman spectra of CNTs grown from [12]CPP. Intensity /a.u. Intensity /a.u. Raman shift /cm 1 Raman shift /cm 1 Figure S2. Raman spectra of CNTs grown from [12]CPP (RBM area; excited by 633 nm laser) taken at different spots on the substrate. NATURE CHEMISTRY 4

5 Intensity /a.u. Raman shift /cm 1 Figure S3. Full-scale Raman spectra of CNTs grown from [9]CPP. Intensity /a.u. Intensity /a.u. Raman shift /cm 1 Raman shift /cm 1 Figure S4. Raman spectra of CNTs grown from [9]CPP (RBM area; excited by 633 nm laser) taken at different spots on the substrate. NATURE CHEMISTRY 5

6 Intensity /a.u. Intensity /a.u. Raman shift /cm 1 Figure S5. Raman spectra of [12]CPP. Intensity /a.u. Raman shift /cm 1 Figure S6. Raman spectra of [9]CPP. NATURE CHEMISTRY 6

7 Transmission Electron Microscopy Transmission electron microscopy (TEM) observation of CNTs was performed using a JEM-2100F (JEOL) operated at acceleration voltage of 80 kev at room temperature under high vacuum (10 8 Torr). For TEM observations, samples were dispersed in 1,2-dichroroethane by ultrasonication for 30 min, and the supernatant was dropped onto a copper-coated TEM grid coated with thin carbon film. After a vacuum heat treatment at 250 C for 6 h to remove remaining 1,2-dichroroethane, TEM observation was carried out. TEM images were recorded by CCD (MSC794 1k x 1k, gatan) with an exposure time of typically 1 3 s. Shown in Fig. S7 and S8 are additional TEM images of CNTs grown from [12]CPP (Fig. S7) and [9]CPP (Fig. S8). Fig. S9 are the low-magnification TEM images of CNTs grown from [9]CPP. NATURE CHEMISTRY 7

8 Figure S7. Other TEM images of CNTs grown from [12]CPP. NATURE CHEMISTRY 8

9 Supplementary Information (Omachi, Nakayama, Takahashi, Segawa, Itami) Initiation of Carbon Nanotube Growth by Well-Defined Carbon Nanorings DOI: /NCHEM.1655 Figure S8. Other TEM images of CNTs grown from [9]CPP. NATURE CHEMISTRY S9 9

10 Supplementary Information (Omachi, Nakayama, Takahashi, Segawa, Itami) Initiation of Carbon Nanotube Growth by Well-Defined Carbon Nanorings DOI: /NCHEM.1655 Figure S9. Low-magnification TEM images of CNTs grown from [9]CPP. NATURE CHEMISTRY S10 10

11 Elemental Analysis Elemental analysis of the CNTs grown from [9]CPP was conducted with the energy dispersive X-ray (EDX) spectroscopy using a JEM-2100F (JEOL). Shown in Fig. S10 are the EDX spectra of synthesized CNTs (a) and TEM grid for background data (b). Shown in Fig. S11 is the TEM image of the area where the EDX measurements were conducted. (a) (b) Figure S10. EDX measurements of CNTs (a) and TEM grid for background data (b). NATURE CHEMISTRY 11

12 DOI: /NCHEM.1655 Supplementary Information (Omachi, Nakayama, Takahashi, Segawa, Itami) Initiation of Carbon Nanotube Growth by Well-Defined Carbon Nanorings Figure S11. TEM Image of the area where the EDX measurements were conducted. NATURE CHEMISTRY S12 12

13 2. Analysis of Thermal Stability of [12]CPP General All reagents ([12]CPP, biphenyl, p-terphenyl, p-quaterphenyl, p-quinquephenyl, and p-sexiphenyl) were obtained from commercial suppliers (TCI and Wako Pure Chemical Industries) and used without further purification. Thermogravimetric/Differential Thermal Analysis Thermogravimetric/differential thermal analysis (TG/DTA) spectra were measured using TGDTA 6200 AST-2 (SII Nanotechnology Inc.). First, TG/DTA profile of [12]CPP was taken (Fig. S12). The sample (4 mg) was gradually heated from 30 to 600 C at the rate of 10 C/min, and then cooled to 35 C at the rate of 50 C/min. The initial weight loss was seen till 173 C, which is most likely due to the loss of solvents containing in the sample. Above this temperature, no clear weight loss was seen below 497 C. This experiment showed that the sample decomposed above 500 C. Through aryl aryl bond cleavage, [12]CPP molecule is likely converted to the corresponding oligo-p-phenyl. As the temperature increases, the initially formed oligo-p-phenyl slowly decomposes into short oligo-p-phenyls. We assume that the weight loss observed above 500 C stems from the loss of biphenyl (bp = 255 C) and p-terphenyl (bp = 389 C) at these temperatures. Further detailed TG/DTA experiments were then conducted. Shown in Fig. S13 S18 are the TG/DTA spectra of [12]CPP at 300, 400, 425, 450, 475, and 500 C. In these experiments, the sample (4 mg) was gradually heated from 30 C to predefined temperature gradually at the rate of 20 C/min under nitrogen atmosphere, and then cooled to 30 C. After reaching the desired temperature, the samples were heated for additional 15 min prior to cooling room temperature (the rate of cooling: 50 C/min). The rates of heating are as following; 10 C/min for C experiment, 15 C/min for C experiment, 20 C/min for C/ C/ C/ C experiments). NATURE CHEMISTRY 13

14 Figure S12. TG/DTA profile of [12]CPP. NATURE CHEMISTRY 14

15 Figure S13. TG/DTA spectra of [12]CPP at 300 C. NATURE CHEMISTRY 15

16 Figure S14. TG/DTA spectra of [12]CPP at 400 C. NATURE CHEMISTRY 16

17 Figure S15. TG/DTA spectra of [12]CPP at 425 C. NATURE CHEMISTRY 17

18 Figure S16. TG/DTA spectra of [12]CPP at 450 C. NATURE CHEMISTRY 18

19 Figure S17. TG/DTA spectra of [12]CPP at 475 C. NATURE CHEMISTRY 19

20 Figure S18. TG/DTA spectra of [12]CPP at 500 C. NATURE CHEMISTRY 20

21 Infrared Spectroscopic Analysis Infrared (IR) spectra were measured using Varian 3100FT-IR (Varian). KBr pellets of [12]CPP samples, used for TG/DTA analysis, were analyzed. Shown in Fig. S19 are the full-range IR spectra of [12]CPP samples after heating at 300, 400, 475, 500, and 600 C. Above 475 C, peaks around 700 and 770 cm 1 emerged. These peaks can be assigned as those of mono-substituted benzene derivatives (p-oligophenyls). These results are in line with other experiments showing that the C C bond cleavage of [12]CPP occurs at C. Absorbance (normalized) RT 300 ºC 400 ºC 475 ºC 500 ºC 600 ºC wavenumber /cm 1 Figure S19. Full-range IR spectra of [12]CPP samples after heating at 300, 400, 475, 500, and 600 C. NATURE CHEMISTRY 21

22 Fluorescence Spectra Measurement Fluorescence (FL) spectra were measured using FP-6600 (JASCO), by placing the solid samples between quartz boards (25 mm thick). The [12]CPP samples, used for TG/DTA analysis, were analyzed. FL spectra of p-oligophenyls (p-terphenyl, p-quaterphenyl, p-quinquephenyl, and p-sexiphenyl), the reference compounds, were also taken. Shown in Fig. S20 are the FL spectra of those samples. Judging from these spectra, it is clear that significant structural changes of [12]CPP occur around 450 C, and that the products formed above 450 C are most likely p-oligophenyls, C C bond cleavage products of [12]CPP. These results clearly show that the CPP-initiated CNT growth and the decomposition of CPP (C C bond cleavage) occur at similar temperatures ( C). Fluorescence intensity /a.u.!3!4!5! RT 300 ºC 425 ºC 450 ºC 500 ºC 600 ºC p-sexiphenyl (6) p-quinquephenyl (5) p-quaterphenyl (4) p-terphenyl (3) wavelength /nm Figure S20. FL spectra of [12]CPP samples after heating at 300, 425, 450, 475, 500, and 600 C, and p-oligophenyls. NATURE CHEMISTRY 22

23 3. References [S1] [S2] a) Segawa, Y., Šenel, P., Matsuura, S., Omachi, H. & Itami, K. [9]Cycloparaphenylene: Nickel-mediated Synthesis and Crystal Structure Chem. Lett. 40, (2011). b) Ishii, Y., Nakanishi, Y., Omachi, H., Matsuura, S., Matsui, K., Shinohara, H., Segawa, Y. & Itami, K. Size-selective synthesis of [9] [11] and [13]cycloparaphenylenes. Chem. Sci. 3, (2012). a) Takaba, H., Omachi, H., Yamamoto, Y., Bouffard, J. & Itami, K. Selective synthesis of [12]cycloparaphenylene. Angew. Chem. Int. Edn 48, (2009). b) Segawa, Y., Miyamoto, S., Omachi, H., Matsuura, S., Šenel, P., Sasamori, T., Tokitoh, N. & Itami, K. Concise synthesis and crystal structure of [12]cycloparaphenylene. Angew. Chem. Int. Edn 50, (2011). NATURE CHEMISTRY 23