Origin of Strong Excitation Wavelength Dependent Fluorescence of Graphene Oxide

Abstract

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.

The phosphorescence and excitation-wavelength dependent fluorescence kinetics of large-scale graphene oxide nanosheets

“…9,11,13,[16][17][18][19][20] This is in accordance with Wu's theory, where the ngerprint photoluminescence of the functional groups in GO was certied. Three PL peaks originate from the s*-n, p-p* and p*-n electronic transitions between the antibonding and bonding molecular orbitals.…”

“…17 Wu's study proved that in water, the solvation dynamics with the same time-scale as the uorescence s uo y s solv can induce the 'red-edge effect' of GO in an aqueous solution. Consequently, the uorescence will broaden and redshi with an increase in the excitation wavelength.…”

“…26 The third explanation is that the excitationwavelength dependent uorescence comes from the 'giant red-edge effect'. 17 In other words, the solvation dynamics are slowed down to the same time-scale as that of uorescence in a polar solvent due to the local environment of the GO-like materials. 17 In this study, both, the samples in solution ( Fig.…”

“…17 In other words, the solvation dynamics are slowed down to the same time-scale as that of uorescence in a polar solvent due to the local environment of the GO-like materials. 17 In this study, both, the samples in solution ( Fig. 2(a)) and as a solid lm (Fig.…”

Other Nanoparticles: general discussion

“…In graphene oxide, the emission wavelength can be tuned by changing the excitation wavelength, which is mainly due to the huge red-edge effect and excited state proton transfer, as reported by several groups. [1][2][3] Nadiya Dragneva asked: It seems like the modied Hummers method is the most popular method for graphene oxide production. Are there any defects present in your structure as a result of using this method?…”