Electrochemical Behavior of Metallic and Semiconducting Single-Wall Carbon Nanotubes

Supplementary Material for

Bromination of graphene with pentagonal, hexagonal zigzag and armchair,

and heptagonal edges

Jungpil Kim, Yasuhiro Yamada*, Ryo Fujita, Satoshi Sato

Graduate School of Engineering, Chiba University, 1-33 Yayoi, Inage, Chiba 263-8522, Japan

*Corresponding author. Tel/Fax: +81-43-290-3376. E-mail address:[email protected] u.jp (Y. Yamada).

S1. Experimental (Empirical and simulated UV-Vis)

The brominated naphthalene and azulene as well as bromine-substituted naphthalene such as 1-bromonaphtahlene (Tokyo Chemical Industry Co., Ltd.), 2-bromonaphthalene

(Tokyo Chemical Industry Co., Ltd.), 1,4-dibromonaphthalene (Wako Pure Chemical

Industries, Ltd.), and 2,7-dibromonaphthalene (Sigma-Aldrich Co., Ltd.) were analyzed by

UV-Vis spectroscopy (UV-1240 Shimadzu Corp.). n-Hexane was used as a solvent for UV-Vis spectroscopy. The absorption wavelengths were calculated by means of time-dependent density functional theory [S1] using B3LYP/6-31+G(d,p) integral=grid=ultrafine level

(solvent=hexane). Charge was set as 0 and spin multiplicity (M) was set as 1. The scaling factor of 1.02 was multiplied with the simulated UV-Vis spectra to compensate for the difference between empirical and simulated spectra. Proposed peak shifts of absorption were calculated by dividing the simulated peak shifts of absorption by 1.90 to apply the simulated peak shifts to actual peak shifts (Tables S1 and S2).

S2. Results

The brominated position on naphthalene and azulene was examined by empirical

1 and simulated UV-Vis spectroscopies. The difference of peak positions of absorption between empirical and simulated UV-Vis spectra was obtained using naphthalene, 1- bromonaphtahlene, 2-bromonaphthalene, 1,4-dibromonaphthalene, and 2,7- dibromonaphthalene. Figure S1 shows the actual and simulated peak shifts of 1- bromonaphtahlene, 2-bromonaphthalene, 1,4-dibromonaphthalene, and 2,7- dibromonaphthalene from the peak top of naphthalene. Empirical and simulated peak positions of absorbance were compared and a liner relationship was obtained (Fig. S1). Thus, we utilized the simulated peak positions (y), adjusted by a scaling factor obtained from the intercept of this liner relationship in Fig. S1 (1.90) using the equation written in Fig. S1 (y =

1.90 x), for assignment of empirical peak positions (x).

Figure S2 shows actual UV-Vis spectra of naphthalene and azulene before and after bromination. The peak top of naphthalene (217 nm) was shifted to high wavelength (223 nm) by bromination (Fig. S2a). The peak top of azulene (275 nm) was also shifted to high wavelength (280 and 284 nm) by bromination (Fig. S2b). These empirical values of positive shifts by bromination were compared with simulated values. Table S1 shows peak shifts of simulated and proposed UV-Vis spectra of mono- and di-bromonaphthalene from a peak top of naphthalene. Table S2 shows peak shifts of simulated and proposed UV-Vis spectra of mono- and di-bromoazulene from a peak top of azulene. Proposed peak shifts of absorption of

1-bromonaphthalene (+7 nm in Table S1), 1,4-dibromonaphthalene (+5 nm in Table S1), and

1,5-dibromonaphthalene (+9 nm in Table S1) from a peak top of naphthalene were close to an actual peak shift of absorption of brominated naphthalene (+6 nm in Fig. S2a) from the peak top of naphthalene, indicating the existence of 1-bromonaphthalene, 1,4-dibromonaphthalene, and 1,5-dibromonaphthalene in brominated naphthalene. Proposed peak shifts of absorption of mono-bromoazulene such as 1-bromoazulene (+5 nm in Table S2), 2-bromoazulene (+7 nm in Table S2), and 6-bromoazulene (+8 nm in Table S2) from a peak top of azulene were close

2 to an actual peak shift of absorption of brominated azulene (+5 and +9 nm in Fig. S2b) from a peak top of azulene. Among di-bromoazulenes (Table S2), there are many possible structures which have a close peak shift to an actual peak shift of absorption of brominated azulene, indicating the difficulty of distinction of brominated positions of di-bromoazulenes.

Calculated Ef values based on two proposed mechanisms were compared. One mechanism is reaction of arene with a Br radical (Fig. S3a) and another mechanism is formation of an arene radical and a hydrogen radical (Fig. S3b). Ef value calculated from the mechanism through formation of an arene radical and a hydrogen radical was much larger than that calculated from the mechanism through reaction of arene with a Br radical (Fig. S3).

Thus, the mechanism of Fig. S3a was utilized in the main manuscript of this work.

References

[S1] Stratmann RE, Scuseria GE, Frisch MJ (1998) An efficient implementation of time- dependent density-functional theory for the calculation of excitation energies of large molecules. J Chem Phys 109:8218-8224.

3 Table S1 Peak shifts of simulated and proposed UV-Vis spectra of mono- and dibromonaphthalene from a peak top of naphthalene.

Simulated absorption peak shifts Proposed absorption peak shifts Structures from a peak top of naphthalenea / nm from a peak top of naphthaleneb / nm 1-Monobromonaphthalene 13 7 2-Monobromonaphthalene 21 11 1,2-Dibromonaphthalene 26 14 1,3-Dibromonaphthalene 25 13 1,4-Dibromonaphthalene 10 5 1,5-Dibromonaphthalene 18 9 1,6-Dibromonaphthalene 21 11 1,7-Dibromonaphthalene 27 14 1,8-Dibromonaphthalene 22 12 2,3-Dibromonaphthalene 29 15 2,6-Dibromonaphthalene 29 15 2,7-Dibromonaphthalene 31 16 a The peak top of naphthalene (217 nm) was used as a reference peak. b These values were calculated by dividing simulated absorption peak shifts by 1.90.

4 Table S2 Peak shifts of simulated and proposed UV-Vis spectra of mono- and dibromoazulene from a peak top of azulene.

Simulated absorption peak shifts Proposed absorption peak shifts Structures from a peak top of azulenea / nm from a peak top of azuleneb / nm 1-Bromoazulene 10 5 2-Bromoazulene 13 7 4-Bromoazulene -1 -1 5-Bromoazulene 2 1 6-Bromoazulene 15 8 1,2-Dibromoazulene 25 13 1,3-Dibromoazulene 20 10 1,4-Dibromoazulene 21 11 1,5-Dibromoazulene 13 7 1,6-Dibromoazulene 27 14 1,7-Dibromoazulene 16 8 1,8-Dibromoazulene 12 6 2,4-Dibromoazulene 16 8 2,5-Dibromoazulene 21 11 2,6-Dibromoazulene 21 11 4,5-Dibromoazulene 15 8 4,6-Dibromoazulene 17 9 4,7-Dibromoazulene -1 -1 4,8-Dibromoazulene 12 6 5,6-Dibromoazulene 19 10 5,7-Dibromoazulene 3 2 a The peak top of azulene (275 nm) was used as a reference peak. b These values were calculated by dividing sim ulated absorption peak shifts by 1.90.

5 Fig. S1 Actual and simulated peak shifts of UV-Vis spectra of 1-bromonaphtahlene, 2- bromonaphthalene, 1,4-dibromonaphthalene, and 2,7-dibromonaphthalene from the peak of naphthalene.

6 Fig. S2 Actual UV-Vis spectra of PAHs and brominated PAHs. (a) Naphthalene (bold black line) and brominated naphthalene (thin red line). Naphthalene was brominated in 10 wt.% bromine solution. (b) Azulene (bold black line) and brominated azulene (thin red line).

Azulene was brominated in 1.0 wt.% bromine solution.

Fig. S3 Calculated Ef values based on two proposed mechanisms. (a) Reaction of an arene with a Br radical. (b) Formation of an arene radical and a hydrogen radical. White spheres hydrogen atom. Gray spheres carbon atom. Red spheres bromine atom.