Single-wall carbon nanotubes (SWCNTs) in liquid suspension have been observed to emit delayed, microsecond-scale fluorescence arising from upconverted triplet excitons that are directly created through energy transfer from singlet oxygen molecules (1O2). The singlet oxygen is produced through quenching of an optically excited organic sensitizer. The mechanism of this delayed fluorescence has been deduced from measurements of time-resolved emission kinetics, delayed emission spectra, and polarization-resolved excitation-emission spectra. The observed strong dependence of 1O2 sensitization efficiency on SWCNT structure suggests that (7,6) triplet excitons have an energy near 970 meV. The yields for E11T → E11S upconversion are found to be in the range of several percent. These yields increase with increasing temperature and decrease with increasing excitation intensities, reflecting thermal activation and triplet-triplet exciton annihilation processes.

中文翻译：

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碳纳米管通过单线态氧敏化三重激子延迟荧光

已经观察到液体悬浮液中的单壁碳纳米管 (SWCNT) 会发出延迟的微秒级荧光，这是由上转换的三线态激子产生的，这些激子是通过单线态氧分子 (1O2) 的能量转移直接产生的。单线态氧是通过淬灭光激发的有机敏化剂产生的。这种延迟荧光的机制是从时间分辨发射动力学、延迟发射光谱和偏振分辨激发发射光谱的测量中推导出来的。观察到的 1O2 敏化效率对 SWCNT 结构的强烈依赖性表明 (7,6) 三线态激子具有接近 970 meV 的能量。发现 E11T → E11S 上转换的产率在几个百分点的范围内。