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Hidden relaxation channels in aqueous methylene blue after functionalization of graphene oxide probed by transient absorption spectroscopy
MingXing Jin
Author NameAffiliationE-mail
MingXing Jin Institute of Atomic and Molecular Physics, Jilin University mxjin@jlu.edu.cn 
Abstract:
The mixture of graphene oxide (GO) and dye molecules may provide some new applications due to unique electronic, optical and structural properties. Methylene blue (MB), a typical anionic dye, can attach on GO via π-π stacking and electrostatic interaction, and the molecule removal process on GO has been observed. However, it remains unclear about the ultrafast carrier dynamics and the internal energy transfer pathways of the system which is composed of GO and MB. We have employed ultrafast optical pump-probe spectroscopy to investigate the excited dynamics of the GO-MB system dispersed in water by exciting the samples at 400 nm pump pulse. The pristine MB and GO dynamics are also analyzed in tandem for a direct comparison. Utilizing the global analysis to fit the measured signal via a sequential model, five lifetimes are acquired: 0.56 ± 0.05 ps, 2.78 ± 0.5 ps, 9.7 ± 1.5 ps, 64.7 ± 8 ps and > 1 ns. The ultrafast dynamics corresponding to these lifetimes is analyzed and the new relaxation processes are found in the GO-MB system, compared with the pristine MB. The results reveal that the functionalization of GO can alter the known decay pathways of MB via the energy transfer from GO to MB in system, the increased intermediate state, and the promoted the energy transfer from triplet state MB to ground state oxygen molecules dissolved in aqueous sample.
Key words:  transient absorption spectroscopy  methylene blue  functionalization of graphene oxide  relaxation channels.
FundProject:
Hidden relaxation channels in aqueous methylene blue after functionalization of graphene oxide probed by transient absorption spectroscopy
金明星
摘要:
The mixture of graphene oxide (GO) and dye molecules may provide some new applications due to unique electronic, optical and structural properties. Methylene blue (MB), a typical anionic dye, can attach on GO via π-π stacking and electrostatic interaction, and the molecule removal process on GO has been observed. However, it remains unclear about the ultrafast carrier dynamics and the internal energy transfer pathways of the system which is composed of GO and MB. We have employed ultrafast optical pump-probe spectroscopy to investigate the excited dynamics of the GO-MB system dispersed in water by exciting the samples at 400 nm pump pulse. The pristine MB and GO dynamics are also analyzed in tandem for a direct comparison. Utilizing the global analysis to fit the measured signal via a sequential model, five lifetimes are acquired: 0.56 ± 0.05 ps, 2.78 ± 0.5 ps, 9.7 ± 1.5 ps, 64.7 ± 8 ps and > 1 ns. The ultrafast dynamics corresponding to these lifetimes is analyzed and the new relaxation processes are found in the GO-MB system, compared with the pristine MB. The results reveal that the functionalization of GO can alter the known decay pathways of MB via the energy transfer from GO to MB in system, the increased intermediate state, and the promoted the energy transfer from triplet state MB to ground state oxygen molecules dissolved in aqueous sample.
关键词:  transient absorption spectroscopy  methylene blue  functionalization of graphene oxide  relaxation channels.
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