Phys Chem Chem Phys. 2016 Feb 07;18(5):3838-45. doi: 10.1039/c5cp07558k. Epub 2016 Jan 14.

Ultrafast carrier dynamics of carbon nanodots in different pH environments.

Physical chemistry chemical physics : PCCP

Laizhi Sui, Wuwei Jin, Suyu Li, Dunli Liu, Yuanfei Jiang, Anmin Chen, Hang Liu, Ying Shi, Dajun Ding, Mingxing Jin

PMID: 26763126 DOI: 10.1039/c5cp07558k

Abstract

Ultrafast carrier relaxation dynamics in fluorescent carbon nanodots is investigated by femtosecond transient absorption spectra at different pH environments so as to understand the mechanism of fluorescence for the first time. Utilizing multi-wavelength global analysis to fit the measured signal via a sequential model, four different relaxation channels are found, which are attributed to electron-electron scattering and surface state trapping, optical phonon scattering, acoustic phonon scattering and electron-hole recombination respectively. The results reveal that the surface states are mainly composed of different oxygen-containing functional groups (epoxy, carbonyl and carboxyl) and carbon atoms on the edge of the carbon backbone and can effectively trap a large number of photo-excited electrons. The deprotonation of carboxyl groups at high pH will change the distribution of π electron cloud density between the carbon backbone and surface states and consequently, compared with the excited electrons in the acidic and neutral environments, those in the alkaline environment can be more easily trapped by the surface within 1 ps, thereby giving rise to stronger fluorescence emission.

Publication Types

• Journal Article
• Research Support, Non-U.S. Gov't