Manipulating Electron
Transfer between Single-Walled
Carbon Nanotubes and Diazonium Salts for High Purity Separation by
Electronic Type
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Abstract
Diazonium salts preferentially react with metallic single-walled
carbon nanotubes (SWNT) over semiconducting SWNT, enabling the separation
of SWNT by electronic type. Therefore, the reaction selectivity of
diazonium salts for metallic SWNT is crucial for high purity separation
of both metallic and semiconducting SWNT. Herein, we developed an
efficient method of increasing the reaction selectivity by manipulating
the redox potential of diazonium salts. The electron affinity of diazonium
salts is effectively lowered when the para-substituent of the diazonium
salts is an electron-donating group, (i.e., 4-hydroxy and 4-propargyloxy)
rather than an electron-withdrawing group (i.e., 4-nitro, 4-carboxy,
and 4-cholro). The reduction potential of 4-hydroxyphenyl and 4-propargyloxyphenyl
diazonium salt was greater than the oxidation potential of semiconducting
SWNT; therefore, the electron transfer reaction between these two
reagents was effectively suppressed, leading to a highly selective
reaction for metallic SWNT. We confirmed that this highly selective
reaction scheme can be used to separate SWNT, and high purity semiconducting
SWNT can be obtained via density-induced separation