The electronic structures of single-walled carbon nanotubes(SWCNTs)were modulated by filling with tetracyanoquinodimethane(TCNQ),a strong electron acceptor.The structures of TCNQ-filled SWCNTs were checked by X-ray diffraction analysis,high-resolution transmission electron microscopy and Raman spectroscopy.Optical absorption spectroscopy demonstrated an enhanced reactivity between aryl diazonium and semiconducting SWCNTs. The electronic structures of single-walled carbon nanotubes (SWCNTs) were modulated by filling with tetracyanoquinodimethane (TCNQ), a strong electron acceptor. The structures of TCNQ-filled SWCNTs were checked by X-ray diffraction analysis, high-resolution transmission electron microscopy and Raman spectroscopy. Optical absorption spectroscopy demonstrated an enhanced reactivity between aryl diazonium and semiconducting SWCNTs.