Excitation-wavelength Dependent Fluorescence of Ethyl 5-(4-aminophenyl)-3-amino-2,4-dicyanobenzoate

Abstract

The excitation wavelength dependence of the steady-state and time-resolved emission spectra of ethyl 5-(4-aminophenyl)-3-amino-2,4-dicyanobenzoate (EAADCy) in tetrahydrofuran (THF) at room temperature has been examined. It is found that the ratio of the fluorescence intensity of the long-wavelength and short-wavelength fluorescence bands strongly depends on the excitation wavelength, whereas the wavelengths of the fluorescence excitation and fluorescence bands maxima are independent on the observation/excitation wavelengths. The dynamic Stokes shift of fluorophore in locally excited (LE) and intramolecular charge transfer (ICT) states has been studied with a time resolution about 30 ps. The difference between Stokes shift in the LE and ICT states was attributed to the solvent response to the large photoinduced dipole moment of EAADCy in the fluorescent charge transfer state. On this base we can state that, the relaxation of the polar solvent molecules around the fluorophore was observed.

Plasmon-Modulated Excitation-Dependent Fluorescence from Activated CTAB Molecules Strongly Coupled to Gold Nanoparticles

“…The emission peak of EDFs red-shifts as the excitation wavelength increases, which is usually explained as the red-edge effect in the multilevels10111213. Several remarkable examples of EDFs reported in the literature include fluorescent polar molecules and carbon-based nanomaterials, such as carbon nanotubes141516, carbon quantum dots71718192021222324, graphene quantum dots (G-QDs)252627282930, and pyromellitic diimide nanowires31.…”

“…The excitation-dependent fluorophores (EDFs) have received considerable attention because of their tunable fluorescence spectrum with some unique advantages and prospective applications in material sciences and biology 1 2 3 4 5 6 7 8 9 . The emission peak of EDFs red-shifts as the excitation wavelength increases, which is usually explained as the red-edge effect in the multilevels 10 11 12 13 . Several remarkable examples of EDFs reported in the literature include fluorescent polar molecules and carbon-based nanomaterials, such as carbon nanotubes 14 15 16 , carbon quantum dots 7 17 18 19 20 21 22 23 24 , graphene quantum dots (G-QDs) 25 26 27 28 29 30 , and pyromellitic diimide nanowires 31 .…”

Concanavalin A-conjugated gold nanoparticle/silica quantum dot (AuNPs/SiQDs-Con A)-based platform as a fluorescent nanoprobe for the bioimaging of glycan-positive cancer cells

“…In some cases, the fluorescence peak wavelength can change to longer emission wavelengths with an increase in the excitation wavelength (red-edge effect), which is mainly initiated by available multiple electron states or several conformers of the molecule. 36 The excitation in the UV domain (especially under 300 nm) provides restrictions in biological media and may cause noisy spectral peaks. In addition, the penetration depth of these wavelengths is limited.…”

Carbon Dots: An Insight into Their Application in Heavy Metal Sensing

“…Likewise, another important feature of CDs corresponds to the dependence of the fluorescence emission on the excitation wavelength ( exc ), which is known as wavelength-dependent behaviour or giant red-edge effect [46]. This behaviour in organic dyes and inorganic complexes results from a variety of solute-solvent interactions in the ground and excited states under the conditions of restricted mobility [47,48]. This phenomenon does not fit with Vavilov's law and Kasha's rule, which state that the emission energy is independent of the excitation energy within the absorption band and that fluorescence normally occurs from the lowest vibrational level of the first excited electronic state, respectively [49].…”