Study on frequency upconverion of multiwalled carbon nanotubes
多壁纳米碳管的频率上转换效应研究

The absorption and photoluminescence spectrum of MWNTs have been measured. The optical frequency upconversion has been observed from MWNTs. The photoluminescence spectrum,which was observedonexcitationat1064nm,consistedofabroadstructuredband,peakingatapproximately780nm.Van Hove Singularities (VHS) in the density of states of multiwalled carbon nanotubes have been discoveredfromabsorptionspectrum.Thepeaks,correspondingtoVHS,locatedat685nm,719nm,894nm.The mechanism describing the underlying processes shows that the excitation involves double-photon absorption followed by non-radiative vibrational decay to the VHS states. Subsequently, the luminescence is produced by radiative transition.