Fluorescence spectroscopy based characterisation method for aggregation behaviour of rhodamine B (RhB) in water, ethanol, and propanol

Abstract

The aggregation behaviour of rhodamine B (RhB) dye has been studied with the change in the concentration of the RhB in water, ethanol and propanol using absorption and laser induced fluorescence spectroscopy. The dimer and monomer fluorescence emissions were observed simultaneously in all the solvents. The monomer to dimer fluorescence intensity ratio I M I D , where IM = Monomer fluorescence intensity, ID = Dimer fluorescence intensity, has been calculated and found that at a certain concentration of RhB the magnitude of the ratio is different in different solvents. The ratio I M I D becomes equivalent to one for 1.5 gm l−1, 3 gm l−1 and 4.2 gm l−1, (gm l−1: gram litre−1) concentration of RhB in water, ethanol and propanol respectively. This concentration of RhB at which the ratio I M I D become unity is proposed as ‘critical concentration’. Above this critical concentration the dimeric fluorescence dominates and below which the monomeric fluorescence dominates. The parameter ‘critical concentration’ provides a condition of equilibrium between the monomer and their aggregates. Moreover, in the solvent for which the magnitude of critical concentration is less the fluorophore molecule aggregates more easily and vice versa. The ratio I M I D and critical concentration quantify the aggregation process of the fluorophore in the solvent. Hence, the ‘critical concentration’ value of the fluorophore (RhB) could be assumed as the characteristic parameter to study the aggregation behaviour of the fluorophore in solvents. The described method has the merit of use in the study of lasing ability and the wavelength tunability of the dye laser gain media as well as in the heavy metal sensing technology in water. This method may also be extended for other fluorophores and solvents.

Functionalization and Structural Evolution of Conducting Quasi-One-Dimensional Chevrel-Type Telluride Nanocrystals

“…The primary and more intense peak in the high-energy region is commonly assigned to the monomeric form of RhB, while the secondary shoulder peak is assigned to the dimeric form of RhB. − Consistent with the literature, we found in the spectra of the standard drop-casted RhB samples on Si/SiO 2 (continuous black curve, Figure C) that the intensity of the dimer peaks grew and all peaks red-shifted relative to the solution-phase fluorescence spectra of RhB (dashed black curve, Figure C). As we expected, this is mainly due to the aggregation of the molecules to form dimers with increasing concentrations. , Comparing these drop-casted RhB samples on Si/SiO 2 with the freestanding crystals of RhB (red curve, Figure C), our results are consistent with the expected significant red shifting of the freestanding crystals, which are highly ordered and predominantly dimerized in contrast to the less-ordered and more polydispersed aggregates of the drop-casted RhB samples …”

“…As we expected, this is mainly due to the aggregation of the molecules to form dimers with increasing concentrations. 75,76 Comparing these drop-casted RhB samples on Si/SiO 2 with the freestanding crystals of RhB (red curve, Figure 7C), our results are consistent with the expected significant red shifting of the freestanding crystals, which are highly ordered and predominantly dimerized in contrast to the less-ordered and more polydispersed aggregates of the drop-casted RhB samples. 77 We measured the concentration-dependent PL spectra of the drop-cast samples from the standard RhB solutions to further assess the relative amounts of RhB species on the surface of the nanocrystals (Figure 7D).…”

Enhanced Stability and Energy Transfer in Perovskite Nanocrystals: Paving the Way for Moisture-Resistant Light-Harvesting Devices

“…The purpose was to gain a better understanding of how the concentration of the acceptor affects its emission (at 575 nm). In contrast to the steadily increasing emission observed for RITC without PNCs, we noted a striking initial increase followed by a decrease or a plateau region at higher concentrations when PNCs were introduced (Figure C). , This suggests that the rising concentration of RITC alone is not the sole cause of the 575 nm emission changes. Importantly, for each donor, there exists a distinct concentration of RITC at which the emission of the acceptor plateaus, indicating saturation of the donor’s surface with the acceptor dye.…”

Electrospinning of Cyclic Olefin Copolymer for the Production of Highly Aligned Dye‐Doped Optical Fibers

“…The red shift of the absorption as well as the broadening of the spectral peaks can be explained by the aggregation of dye molecules and formation of RhB dimers. [ 50 ] This phenomenon is not observable in RhB solutions and RhB‐doped COC fibers, because the solvent molecules and COC matrix act as media to keep sufficient distance between RhB molecules and prevent their aggregation. [ 51 ] However, almost no change in photophysical properties of NPLs solid films in comparison with NPLs in solution can be seen.…”