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Intrinsic and Extrinsic Fluorescence in Carbon Nanodots: Ultrafast Time‐Resolved Fluorescence and Carrier Dynamics
Author(s) -
Wen Xiaoming,
Yu Pyng,
Toh YonRui,
Hao Xiaotao,
Tang Jau
Publication year - 2013
Publication title -
advanced optical materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.89
H-Index - 91
ISSN - 2195-1071
DOI - 10.1002/adom.201200046
Subject(s) - picosecond , materials science , nanosecond , fluorescence , femtosecond , nanodot , scattering , molecular physics , excitation , ultrashort pulse , optoelectronics , optics , physics , laser , quantum mechanics
Using a femtosecond resolved up‐conversion technique, the ultrafast carrier dynamics in fluorescent carbon nanodots are investigated in order to shed light on the mysterious origins of their fluorescence. These experiments reveal that the fluorescence of carbon nanodots consists of two spectral overlapped bands that can be ascribed to the intrinsic and extrinsic fluorescence. The intrinsic band exhibits a small bandwidth of 175 meV at 459 nm, and it is attributed to the sp 2 nano domains. The extrinsic band originates from the surface states with a much broader bandwidth of 450 meV. The relaxation with time constants of a few picoseconds, tens of picoseconds, and a few nanoseconds are attributed to optical phonon scattering, acoustic phonon scattering, and carrier (e–h pair) recombination, respectively. A fast trapping is observed from the nano domains into the surface states with a time constant of 400 fs. The excitation wavelength‐dependent fluorescence can arise from the abundant carboxyl functional groups on the surface.