Structure dependent reactivity of single walled carbon nanotubes with benzenediazonium salts

• Main Author: Yeap, Siew Hooi.
• Other Authors: Chen Yuan
• Format: Final Year Project
• Language: English
• Published: 2009
• Subjects: DRNTU::Engineering::Nanotechnology
• Online Access: http://hdl.handle.net/10356/16580
• Institution: Nanyang Technological University

In most of the application for SWNT, nanotubes with pure electronic properties are needed. 4-chlorobenzenediazonium salt, which is an electron-withdrawing agent, was studied for its selective reactivity with HiPco-derived SWNT as well as Co-MCM-41-derived SWNT. It was found that, at room temperature, pH 9.10 and salt concentration of 0.3584mM, the overall selectivity was found to be high for metallic SWNT as compared to semiconducting SWNT. It is dictated by the readiness of electron transfer across the Fermi level to stabilize a charge-transfer transition state preceding bond formation. Compared with HiPco-derived SWNT, SWNT derived using Co-MCM-41 has smaller diameter range. It was expected that with smaller diameter range, the selectivity will be higher towards metallic tube as small diameter semiconducting tube will have larger energy band gap which reduce the readiness of electron transfer. Interestingly, the reverse was found to be true. Under the same reaction temperature, pH 9.03, semiconducting SWNT has slightly better selectivity compared to metallic SWNT. Salt concentration was varied to investigate the extent of reaction. Only semiconducting tube with chirality (6, 5) completely reacted at reaction time of 10min. This result was consistent with the formation of diazoanhydride by the diazonium molecule under basic condition. However, the selectivity trend of Co-MCM-41 SWNT for semiconducting tubes at both acidic and alkaline condition was the same.