What a rule surfactants play in synthesis CNTs array

1. What a rule surfactants play in synthesis CNTs array Shuchen Zhang, Yanhe Zhang 2013-05-27

2. Outline Background Problem Surfactants and CNTs Conclusion Acknowledgement

3. Background Single-walled carbon nanotubes (SWNTs) have been regarded as one of the best candidates for future application in next generation integrated circuits due to their unique structures and superb properties: 1)High strength; 2)Excellent electrical properties ; 3)Absorbtion band (infrared wavelengths ). Fig.1 Schematic ofthe process from graphene to CNTs

4. Background 2n+m=3q Fig.3 Schematic ofzigzag, armchair, and chiral CNTs Fig.2 Schematic ofCNTs

5. Background 1）the band structure of graphene is relatively simple； 2）but for CNT, its band structure is relatively complicated, related to diameter and chiral, etc. Fig.4 States density of different CNTs Fig.5 Band structure of graphene

6. Problem 2n+m=3q × Fig.6 Band structure of graphene

7. Surfactant and CNTs Selective Band Structure Modulation of Single-Walled Carbon Nanotubes in Ionic Liquids 1) PFOA, SDS, LDS, PPFOS, PDS 2) They can be classified two kinds: ① PFOA, SDS, LDS； ②PPFOS, PDS. Fig.7 Absorbance spectrum of CNTs with different surfactants Jinyong Wang, and Yan Li, J. Am. Chem. Soc., 2009

8. Surfactant and CNTs TypeⅠ:E22 transitions (∼1100 nm) of S-nanotubes(∼1.5-1.7 nm) and E11transitions (∼750 nm) of M-nanotubes(∼1.5 nm). TypeⅡ:E33 transitions(∼550-650 nm) of S-nanotubes(∼1.5-1.7 nm). TypeⅢ:E33 electronic transitions (∼400-500 nm) of S-nanotubes(∼1.2-1.4 nm) Fig.8 Absorbance spectra and Raman spectra Jinyong Wang, and Yan Li, J. Am. Chem. Soc., 2009

9. Surfactant and CNTs Due to the modification, electrons should transfer from the SWCNTs to the surfactants, thus resulted in the positive charging of SWCNTs. It can be clearly seen that shift of the Fermi energy and the band structure occur as a result of charge transfer. Fig.9 Band structure of S- and M-CNTs Jinyong Wang, and Yan Li, J. Am. Chem. Soc., 2009

10. Surfactant and CNTs The possible interaction mechanism: Because of the large positive charge density of the cations, the high-energy electrons of the SWCNTs near the Fermi level transfer to the lowest unoccupied orbitals of the cations. A stable “cation-π” complex is formed at the nanotube surface. Fig.10 Possible interaction mechanism Jinyong Wang, and Yan Li, J. Am. Chem. Soc., 2009

11. Surfactant and CNTs Sorting out Semiconducting Single-Walled Carbon Nanotube Arrays by Washing off Metallic Tubes Using SDS Aqueous Solution Fig.11 Schematic illustration of sorting out s- SWNT arrays Yue Hu , Yabin Chen , Pan Li , a nd Jin Zhang *, Small., 2013

12. Surfactant and CNTs Fig.13 Compare the AFM and Raman before and after sorting Fig.12 SEM and AFM of CNTs before sorting Yue Hu , Yabin Chen , Pan Li , a nd Jin Zhang *, Small., 2013

13. Surfactant and CNTs Statistical result indicates that the SWNTs with bigger average diameter changes are mostly disappeared after separation while SWNTs with smaller average diameter changes. Fig.14 SEM and AFM to character the variation of CNTs Yue Hu , Yabin Chen , Pan Li , a nd Jin Zhang *, Small., 2013

14. Surfactant and CNTs Fig.15 SEM for separation and the FET of CNTs after sorting Yue Hu , Yabin Chen , Pan Li , a nd Jin Zhang *, Small., 2013

15. Conclusion In order to get a perfect array only made by s-CNTs, we have made great effort to sorting out the s-CNTs from to the CNTs mixture by their difference, especially the density of state. However, these methods still retain some problems: 1) Sorting out the s-CNTs in the solution will bring about a great question, making an array is difficult; 2) Sorting out the s-CNTs on the substrate will lead to a low product of s-CNTs to hard to be an array; 3) A good method to separate the s-CNTs with the m-CNTs also lead to defect on the CNTs and hard to get a pure CNTs.

16. Acknowledgements • Pro. Yan • All the audiences

17. Thank You !