Eosin B Research Articles

Hydrogen-Bond-Assisted Excited-State Deactivation at Liquid/Water Interfaces

The excited-state dynamics of eosin B (EB) at dodecane/water and decanol/water interfaces has been investigated with polarization-dependent and time-resolved surface second harmonic generation. The results of the polarization-dependent measurements vary substantially with (1) the EB concentration, (2) the age of the sample, and (3) the nature of the organic phase. All of these effects are ascribed to the formation of EB aggregates at the interface. Aggregation also manifests itself in the time-resolved measurements as a substantial shortening of the excited-state lifetime of EB. However, independently of the dye concentration used, the excited-state lifetime of EB at both dodecane/water and decanol/water interfaces is much longer than in bulk water, where the excited-state population undergoes hydrogen-bond-assisted non-radiative deactivation in a few picoseconds. These results indicate that hydrogen bonding between EB and water molecules at liquid/water interfaces is either much less efficient than in bulk water or does not enhance non-radiative deactivation. This strong increase of the excited-state lifetime of EB at liquid/water interfaces opens promising avenues of applying this molecule as a fluorescent interfacial probe.

Ultrafast Excited-State Dynamics of Eosin B: A Potential Probe of the Hydrogen-Bonding Properties of the Environment

The photophysics of two dyes from the xanthene family, eosin B (EB), and eosin Y (EY) has been investigated in various solvents by femtosecond transient absorption spectroscopy, first, to clarify the huge disparity of the EB fluorescence lifetimes reported in literature, and, second, to understand the mechanism responsible for the ultrafast excited-state deactivation of EB in water. The excited-state lifetime of EB was found to be much shorter in water and in other protic solvents, due to the occurrence of hydrogen-bond assisted nonradiative deactivation. This mechanism is associated with the hydrogen bonds between the solvent molecules and the nitro groups of EB, which become stronger upon optical excitation due to the charge-transfer character of the excited-state. This process is not operative with EY, where the nitro groups are replaced by bromine atoms. Therefore, the excited-state lifetime of EB in solution is directly related to the strength of the solvent as a hydrogen-bond donor, offering the possibility to build a corresponding scale based on the fluorescence quantum yield or lifetime of EB. This scale of hydrogen-bonding strength could be especially useful for studies of liquid interfaces by time-resolved surface second harmonic generation.

Fluorescence quenching method for the determination of bleomycins A5 and A2 with halofluorescein dyes

In weak acidic medium, the anticancer antibiotics bleomycin A5 (BLMA5) and bleomycin A2 (BLMA2) bind with halofluorescein dyes, such as erythrosin (Ery), eosin Y (EY) and eosin B (EB), to form ion-association complexes, which causes fluorescence quenching of halofluorescein dyes. The quenching values (DeltaF) are directly in proportional to the concentrations of bleomycins over the range 0.09-2.5 microg/mL. Based on this, a fluorescence quenching method for the determination of BLMA5 and BLMA2 has been developed. The dynamic range is 0.12-2.5 microg/mL for the determination of BLMA5 and 0.09-2.0 microg/mL for BLMA2, with detection limits (3sigma) of 0.04 microg/mL for BLMA5, 0.03 microg/mL for BLMA2, respectively. It has been applied to determine the two antibiotics in human serum, urine and rabbit serum samples. The recovery is in the range 90-102%. In this work, the optimum reaction conditions and the spectral characteristics of the fluorescence are investigated. The reasons for fluorescence quenching are discussed, based on the fluorescence theory.

A Highly Sensitive Spectrophotometric Assay of Bleomycins Based on the Fading Reaction of Some Halofluorescein Dyes

AbstractIn weak acidic medium, anticancer antibiotics bleomycin A5 (BLMA5) and bleomycin A2 (BLMA2) can react with halofluorescein dyes such as erythrosin (Ery), eosin Y (EY), eosin B (EB) and rose bengal (RB) by virtue of electrostatic attraction and hydrophobic force to form the ion‐association complexes, which can result in the fading reactions of four halofluorescein dyes. The maximum fading wavelengths of these four dyes were located at 527 nm for Ery, 515 nm for EY, 517 nm for EB and 546 nm for RB, respectively. The decrements of absorbance ((A) were directly proportional to the concentrations of bleomycin in a certain range. A new method for the determination of bleomycins anticancer drugs based on fading reactions of halofluorescein dyes has been developed. The method was not only highly sensitive but also simple and rapid. The molar absorptivities (ε) ranged from 1.5×105 to 7.5×105 L·mol−1·cm−1. It was applied to determination of the bleomycins in human serum, urine and rabbit serum samples. In this work, the spectral properties and the optimum reaction conditions were investigated. The structure of ion‐association complexes and the reaction mechanism were discussed.

Photo-oxidation of benzyl alcohol under natural weathering conditions

The photocatalytic oxidation of benzyl alcohol has been investigated by the following carbonyl compound formation. Measurements were made under natural weathering conditions (sunlight and oxygen) in the existence of titanium dioxide or sensitized titanium dioxide. Sensitization of titanium dioxide has been done by the impregnation of Riboflavin (RF), Safranine O (SO), Methyl red (MR), Eosin B (EB), and Methyl blue (MB) on anatase (Degussa P25). The photo-oxidation of benzyl alcohol was found to be fell in the sequence: Riboflavin > Safranine O > Naked TiO 2 > Methyl red > Eosin B > Methyl blue. The formation of benzaldehyde during the photocatalytic reaction has been studied by using FTIR, HPLC and spectrophotometric measurements.

A highly sensitive resonance Rayleigh scattering method for the determination of bleomycinA 5 and bleomycinA 2 with some halofluorescein dyes

In a weak acidic medium, bleomycinA 5 (BLMA 5) and bleomycinA 2 (BLMA 2) can react with halofluorescein dyes such as erythrosine (Ery), eosin Y (EY), eosin B (EB) and Rose Bengal (RB) by virtue of electrostatic attraction and hydrophobic force to form ion-association complexes, which can result in the large-scale enhancement of resonance Rayleigh scattering (RRS) and the appearance of new RRS spectra. The increments of scattering intensity (Δ I) were directly proportional to the concentrations of bleomycin (BLM) in certain ranges. The detection limits for BLMA 5 and BLMA 2 ranged from 0.017 to 0.062 μg ml −1. The Ery system had the highest sensitivity and its detection limit (3 σ) was 0.017 μg ml −1 for BLMA 5 and 0.018 μg ml −1 for BLMA 2, respectively. Using Ery as a RRS probe, a new highly sensitive method for the determination of BLM anticancer drugs has been developed. It was applied in the determination of BLMA 5 and BLMA 2 in serum and urine samples. The recovery was from 99.0% to 103.0%. In this work, the RRS spectral characteristics of the binding products and the optimum conditions of the reaction were investigated. The mechanism of ion-association reaction and the reasons of enhancement of resonance light scattering were discussed.

Differential Cyclic Voltfluorometry and Chronofluorometry of the Transfer of Fluorescent Ions across the 1,2-Dichloroethane-Water Interface

The time derivative of fluoresence vs time curves recorded with voltage-scan fluorometry (Kakiuchi, T.; Takasu, Y.; Senda, M. Anal. chem. 1992, 64, 3096-3100) for the transfer of the divalent anionic form of Eosin B (EB) across the 1,2-dichloroethane-water interface gives curves isomorphic to the cyclic voltammograms of ion transfer of EB when the concentration of EB in the aqueous phase is in the micromolar range or lower

Case study — James Capel's recovery from the city bombing

ZnO nanoparticles (NPs) were synthesized using solution combustion method with different urea percent (UP) i.e. U1, U2, U3 and U4. The obtained ZnO NPs were characterized using X-ray diffraction (XRD), high-resolution transmission electron microscope (HR-TEM), UV–Vis spectroscopy and photoluminescence spectroscopy (PL). XRD analysis confirmed the wurtzite structure of the prepared ZnO NPs and the estimated average crystallite size reduced from 28.03 nm to 17.33 nm with increasing of UP. HR-TEM image showed an irregular spherical shape for the prepared ZnO NPs. The absorption spectra analysis exhibited that the optical energy band gap (Eg) for the ZnO NPs increased with increasing of UP from 2.84 eV to 3.13 eV. Two groups (I and II) of dye sensitized solar cell (DSSCs) device based on the synthesized ZnO NPs were fabricated. In group I, 0.32 mM Eosin B (EB) used as photosensitizer for the samples U1, U2, U3 and U4, which showed that the overall conversion efficiency (η) increased from 0.09% to 0.13%, under a light intensity of 100 mW/cm2 due to the increasing of UP. Group II, different photosensitizer EB, Eosin Y (EY) and Rhodamine B (RB) used to sensitized the U4, where the EY exhibited the best all of them. The conversion efficiency presented a significant improvement from 0.13 to 1.26%. The combustion method can be considered as a promising method to produce good photoanode semiconductors such ZnO subsequently increase the efficiency of the solar cell.

Intersystem crossing rates and saturation parameters in the triplet state for rhodamine, fluorescein, and acridine dyes

The saturation of the population in the triplet state T1 using a laser excitation ESR technique was observed directly at 77 K. The saturation parameters Isat and the singlet-to-triplet intersystem crossing rate kST were determined for acridine red (AO), rhodamine S (RS), rhodamine B (RB), rhodamine 6G (R6G), fluorescein disodium salt (FDS), 2′,7′-dichlorofluorescein (DF), eosin Y (EY), eosin B (EB), acridine orange (AR), and acridine yellow (AY) in rigid ethanolic solutions. On the basis of the results, the intersystem crossing mechanisims of rhodamine (type R), fluorescein (type F), and acridine (type A) types of the ten dyes are discussed.