Department of Mechanical and Aerospace Engineering, West Virginia University , Morgantown, West Virginia 26506-6106, United States.
ACS Nano. 2014 Jan 28;8(1):1002-13. doi: 10.1021/nn405843d. Epub 2013 Dec 26.
The peak fluorescence emission of conventional fluorophores such as organic dyes and inorganic quantum dots is independent of the excitation wavelength. In contrast, the position of the peak fluorescence of graphene oxide (GO) in a polar solvent is heavily dependent on the excitation wavelength. The present work has discovered that the strong excitation wavelength dependent fluorescence in GO is originated from the "giant red-edge effect", which breaks Kasha's rule. When GO sheets are present in a polar solvent, the solvation dynamics slow down to the same time scale as the fluorescence due to the local environment of the GO sheet. Consequently, the fluorescence peak of GO broadens and red-shifts up to 200 nm with an increase in the excitation wavelength. The giant red-edge effect of GO disappears in a nonpolar solvent, leading to a narrow fluorescence peak that is independent of the excitation wavelength. Discovery of the underlying strong excitation wavelength dependent fluorescence mechanism provides guidelines for the design of graphene oxide-based optical devices.
传统荧光染料和无机量子点等荧光团的荧光发射峰峰值不依赖于激发波长。相比之下，氧化石墨烯（GO）在极性溶剂中的荧光发射峰峰值位置严重依赖于激发波长。本工作发现，GO 中强激发波长依赖性荧光源于“巨大红边效应”，这打破了 Kasha 规则。当 GO 片存在于极性溶剂中时，由于 GO 片的局部环境，溶剂化动力学会减慢到与荧光相同的时间尺度。因此，随着激发波长的增加，GO 的荧光峰会展宽并红移高达 200nm。GO 的巨大红边效应在非极性溶剂中消失，导致荧光峰变窄且不依赖于激发波长。对这种强激发波长依赖荧光机制的发现为基于氧化石墨烯的光学器件的设计提供了指导。
