多壁纳米碳管的频率上转换效应研究

Study on frequency upconverion of multiwalled carbon nanotubes

实验上测量了多壁纳米碳管的吸收光谱和光致发光谱,观察到了多壁纳米碳管的光频率上转换效应,激发波长为1064nm,发射光谱为带状光谱,峰值波长为780nm.由吸收光谱上观察到了纳米碳管的态密度分布的范霍夫奇点,这些奇点对应的吸收峰位置为685nm,719nm和894nm.上转换过程是纳米碳管的电子经双光子吸收,再经无辐射跃迁布居在范霍夫奇点,最后经辐射跃迁而产生荧光.

The absorption and photoluminescence spectrum of MWNTs have been measured. The optical frequency upconversion has been observed from MWNTs. The photoluminescence spectrum, which was observed on excitation at 1064 nm, consisted of a broad structured band, peaking at approximately 780 nm. Van Hove Singularities （VHS） in the density of states of multiwalled carbon nanotubes have been discovered from absorption spectrum. The peaks, corresponding to VHS, located at 685 nm, 719 nm, 894 nm. 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.