Photoconversion of 2-methylphenol, 4-methylphenol, and 2-amino-4-methylphenol in water

We have used fluorescence spectroscopy to study photoconversions of 2-methylphenol (2-MP), 4-methylphenol (4-MP), and 2-amino-4-methylphenol (2-A-4-MP) in water when excited by UV radiation from different sources. We discuss the effect of the acidity of the medium and dissolved oxygen on photoconversions of the indicated methylphenols. The photodegradation efficiency for 2-MP and 4-MP decreases in the absence of oxygen. The photoconversion efficiency for methylphenols in alkaline medium is higher when irradiated by light with λ_rad = 283 nm, while in neutral medium it is higher when irradiated by light with λ_rad = 222 nm. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 5, pp. 566–572, September–October, 2006.     

Influence of Complexing and Excitation Energy on Spectral and Luminescent Properties of 2-Amino-4-Methylphenol

Energy level diagrams of 2-amino-4-methylphenol and its complexes with water are calculated by the method of intermediate neglect of differential overlap (INDO). It is demonstrated that the substitution by the amino group results in the dependence of the quantum fluorescence yield on the excitation energy. The decrease of the quantum fluorescence yield of 2-amino-4-methylphenol in going from hexane to water is explained. Complexing of the 2-amino-4-methylphenol molecule with water with the formation of the H-bond reduces the quantum fluorescence yield compared to the isolated molecule due to the increased efficiency of the S₁ → T₄ conversion.__________Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 71–76, March, 2005.     

Effect of humic acids on phototransformation of methylphenols in water

We have studied photolysis of a mixture of 2-methylphenol (2-MP) and 4-methylphenol (4-MP) in distilled water and in water containing humic acids. The samples were irradiated under different conditions: by monochromatic light with λ ∼ 222, 283, and 308 nm; by polychromatic light from a mercury lamp in the wavelength region 290–600 nm. We have shown that a mixture of methylphenols is efficiently degraded with irradiation by a KrCl exciplex lamp (λ_rad ∼ 222 nm). Preliminary treatment of peat before extraction of the humic acids has an effect on the extent of photoconversion of the methylphenols. Regardless of the type of humic acids, their presence in solution inhibits photoconversion. The greatest extent of degradation of the methylphenols in aqueous solutions with humic acid additives is detected for irradiation by a KrCl exciplex lamp or a mercury lamp, but it is lower than the extent of degradation of the mixture of methylphenols in water. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 4, pp. 577–582, July–August, 2008.     

Phenol and anisol fluorescence quenching in aqueous micellar solutions

Phenol and anisol fluorescence quenching in aqueous micellar solutions is investigated on addition of H ₂ O ₂. It is established that the efficiency of interaction of the phenol molecule in water with hydrogen peroxide is higher than of anisol. In the phenol-H ₂ O ₂ system, the buildup of phenol fluorescence occurs in the presence of an anionic-reagent detergent. A decrease in the efficiency of phenol fluorescence quenching by hydrogen peroxide in aqueous solutions in the presence of CTAB and triton X-100 micelles is observed. The micellar media increase the efficiency of interaction of anisol with a quencher in comparison with phenol. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 73–79, April, 2006.     

Luminescence investigations of the degradation of 2-methylphenol and 4-methylphenol in water

Fluorescent characteristics of the photo- and biotransformations of 2-methylphenol, 4-methylphenol and their mixtures in water exposed to uv radiation of various sources and to Penicillium tardum H-2 culture have been studied. The toxicity of these solutions has also been investigated by means of bioluminescent testing. Preliminary exposure of a 4-methylphenol solution (10⁻³ M) to uv radiation with λ ∼ 308 nm or to the radiation of a mercury lamp inhibited the subsequent microbiological degradation. Efficient decomposition of methylphenol molecules in the mixture was detected when it was exposed to the radiation of a mercury lamp or to 222-nm radiation and then subject to biodecomposition. The irradiation of solutions of 2-methylphenol and 4-methylphenol and their low-concentration mixtures with 308-nm uv radiation or with the radiation of a mercury lamp resulted in detoxication of the solutions. Extreme toxicity was shown by 4-methylphenol solutions on exposure to uv radiation with λ ∼ 222 nm. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 88–98, December, 2008.     

Fluorescence of N,N-di(2-carboxyethyl)-<Emphasis Type="Italic">p</Emphasis>-anisidine in solution and crystalline states

The fluorescence properties of N,N-di(2-carboxyethyl)-p-anisidine (I) in solvents of various nature and in the crystalline state have been studied at room temperature (273 K) and at the boiling point of liquid nitrogen (77 K). Fluorescence in aqueous solutions of I with protonated (λ _ex /λ _fl ^max = 225/290 nm) and unprotonated (λ _ex /λ _fl ^max = 270/380 nm) amino nitrogen has been detected. On going from aqueous solutions to nonaqueous, the fluorescence band of unprotonated I experiences a blue shift and its intensity rises. The fluorescence intensity of the band in aprotic polar solvents is higher than that in protic solvents. A linear dependence of the fluorescence intensity of deprotonated I on Cu(II) concentration (ranging from 1.0 to 5.0 mg/dm³) in aqueous solution has been found. The fluorescence intensity of I in aqueous solutions at 77 K and pH 1–6 has been shown to increase in the presence of Zn(II) (1–170 mg/dm³) and Cd(II) (2–330 mg/dm³) although a similar dependence is not observed at 293 K.     

多组分水溶液中的石油磺酸盐与OP—10的荧光发射光谱

含苯氧基的非离子型和阴离子型表面活性剂在一定激发波长下可发出特定波长的荧光，在稀溶液中荧光发射强度与其浓度成正比，不受溶液里存在的其他物质的影响，在适当条件下相互之间也无影响。本文报道了用荧光检测复合驱油体系中的ＯＰ１０、石油磺酸盐和ＯＰ１０＋石油磺酸盐的结果。此法选择性高，灵敏度高，操作简便，可望用于复合驱油体系中表面活性剂的分析、研究。     

Induced Intersystem Crossing at the Fluorescence Quenching of Laser Dye 7-Amino-1,3-Naphthalenedisulfonic Acid by Paramagnetic Metal Ions

The fluorescence and triplet state quenching of 7-amino-1,3-naphthalenesulfonic acid by paramagnetic metal ions have been investigated in an aqueous medium. The basic mechanism of the fluorescence quenching involves the static and dynamic electron transfer to the paramagnetic cation. The induced S₁→T₁ intersystem crossing at fluorescence quenching of the fluorophore by Cu²⁺ cation has been found. There is a correlation between triplet state quenching rate constants and values of the efficient paramagnetic susceptibility and spin of the cations. The rate constants for the quenching pathways have been calculated.     

FIA-Fluorimetric Determination of the Pesticide 3-Indolyl Acetic Acid

The paper presents the determination of the pesticide 3-indolyl acetic acid based on its native fluorescence; the method has been optimised either in a flow injection analysis (FIA) assembly or in batch. Maximum fluorescence intensity was observed at basic pH solutions at λ_exc = 280 nm and λ_em = 364 nm. The influence of different empirical parameters as pH, surfactants presence, solvent polarity, solved oxygen amount, and temperature was studied; highest outputs only required the pH in aqueous solutions to be adjusted over the range 9.5–10.5. Different calibration ranges were obtained by working with three different sensitivity scales of the fluorimeter either in flow injection analysis or batch. With the high sensitivity scale and FIA, the linear dynamic range was from 0.005 to 0.6 mg L⁻¹ 3-indolyl acetic acid; with an relative standard deviation (RSD) of 4.9% inter-day reproducibility. A large series of potential interferents was studied and finally, the method was applied to several water samples.     

Spectroscopic Study of the Interaction of Styrylcyanine Dyes Sbo,Sil and Their Derivatives with Bovine Serum Albumin

The spectral-luminescent characteristics of newly synthesized styrylcyanine dyes on the base of dyes Sbo ((E)-2-(4-(dimethylamino)styryl)-3-methylbenzo[d]oxazol-3-ium iodide) and Sil ((E)-2-(4-(dimethylamino)styryl)-1,3,3-trimethyl-3H-indolium perchlorate) in aqueous solutions without and in the presence of bovine serum albumin (BSA) were studied. It was established that the absorption spectra of dyes Tol-6, Dbo-10 and Dil-10 with increasing amount of BSA appear new bands with λ_max = 505 nm, λ_max = 512 nm and λ_max = 566 nm, respectively, whose intensity increases in proportion to the amount of albumin. The intensity of the glow of the main band of fluorescence in the presence of BSA sharply increases. The binding constant (K) and the number of binding sites (N) of studied dyes with BSA were determined. The dependence of binding constants with BSA on the dipole moment of dye molecules was determined, which indicates that besides electrostatic forces of attraction between molecules styrylcyanine dyes with BSA, hydrophobic interactions are essential.     

Luminescence of Nile red as indicator of composition of nanoparticles from diketonate complexes of trivalent metals

We study the sensitization of fluorescence of Nile red in nanoparticles formed in aqueous solutions of complexes of Al, In, Sc, and Lu with DBM, DBM, and phen and of complexes of In with MBTA and phen. We show that, at concentrations of Nile red of 2–50 nM and complexes of 10–30 μM, the fluorescence intensity of Nile red in aqueous solutions increases by 1.5–2 orders of magnitude compared to its fluorescence in H₂O. We find that, at these concentrations of Nile red in solutions of complexes Al, the dye is completely contained in nanoparticles from these complexes. We show that Nile red molecules are inhomogeneously distributed in nanoparticles from complexes and, upon the completion of the formation of nanoparticles, dye molecules tend to be localized in regions of nanoparticles formed from diketonate complexes M(diketone)₃phen (M is Lu or In) and Al(DBM)₃. Upon the localization of Nile red in these regions, the maximum of its fluorescence spectrum shifts toward ∼600 nm and, upon the penetration of Nile red into nanoparticles from Sc complexes, the shift of the maximum of its fluorescence spectrum compared to the spectrum in water does not exceed 10 nm. The shifts of the spectra are collated with the ability of ions to form diketonate and hydroxy diketonate complexes. We demonstrate that the fluorescence of Nile red is efficiently sensitized, not only upon its penetration into nanoparticles formed from complexes, but also upon its adsorption on the nanoparticle surface when Nile red molecules are introduced in solutions of already formed nanoparticles.     

Direct methanol fuel cells: The influence of methanol on the reduction of oxygen over Pt/C catalysts with different particle sizes

Two Pt/C catalysts with different particle sizes (Pt/C: 2.5 nm, Pt/C-700Ar: 5.1 nm) were investigated by applying a half-cell configuration —rotating disk electrode (RDE) technique in H₂SO₄ aqueous solutions in the absence of or in the presence of methanol with different concentrations. Pt/C catalyst exhibited higher mass activity in H₂SO₄ aqueous solution without methanol and slightly lower mass activity in H₂SO₄ plus 0.1 mol/L CH₃OH in comparison with that of Pt/C-700Ar catalyst. On the contrary,single direct methanol fuel cell (DMFC) tests showed that Pt/C exhibited higheroxygen reduction reaction (ORR) activity and better cell performance, mainly due to the different kinds of electrolyte properties. Furthermore, it suggested that a better single DMFC performance could be obtained with a smaller particle size Pt-based cathode catalyst. Paper presented at the Patras Conference on Solid State Ionics — Transport Properties, Patras, Greece, Sept. 14 — 18, 2004.     

Fluorimetric Study on Molecular Recognition of β-cyclodextrin with 2-amino-9-fluorenone

The molecular recognition interaction of β-cyclodextrin (β-CDx) was investigated using 2-amino-9-fluorenone (2AFN) by UV, steady-state fluorescence and time-resolved fluorescence measurements in aqueous solution at various pH. The effect of acidity on the ground and excited state equilibria between the neutral and the monocationic forms of 2AFN in water and in β-CDx environments are studied. Based on the change in the fluorescence spectrum and lifetimes of 2AFN by the addition of β-CDx, it is found that the unsubstituted part of the 2AFN is encapsulated in the hydrophobic cavity of β-CDx. The unusual red shift obtained for the protonation of amino group in water and β-CDx solution is due to large solvent relaxation of the monocation. The structure of the 1:1 inclusion complex between 2AFN and β-CDx has been proposed on the basis of ground and excited state pK _a values and the bond distances obtained by MOPAC/AM 1 data.     

Synthesis and Luminescence Properties of Two Novel Lanthanide (III) Perchlorate Complexes with Bis(benzoylmethyl) Sulfoxide and Benzoic Acid

Two novel ternary rare earth complexes of Tb(III) and Dy(III) perchlorates with bis(benzoylmethyl) sulfoxide (L) and benzoic acid (L′) had been synthesized and characterized by elemental analysis, coordination titration analysis, molar conductivity, IR, TG-DSC, ¹HNMR and UV spectra. The results indicated that the composition of these complexes was REL₅L′(ClO₄)₂·nH₂O (RE= Tb(III), Dy(III); L=C₆H₅COCH₂SOCH₂COC₆H₅, L′=C₆H₅COO; n = 6,8). The fluorescence spectra illustrated that the ternary rare earth complexes presented stronger fluorescence intensities, longer lifetimes and higher fluorescence quantum efficiencies than the binary rare earth complexes REL₅·(ClO₄)₃·2H₂O. After the introduction of the second ligand benzoic acid group, the relative fluorescence emission intensities and fluorescence lifetimes of the ternary complexes REL₅L′(ClO₄)₂·nH₂O (RE= Tb(III), Dy(III)) enhanced more obviously than the binary complexes. This indicated that the presence of both organic ligands bis(benzoylmethyl) sulfoxide and the second ligand benzoic acid could sensitize fluorescence intensities of rare earth ions, and the introduction of benzoic acid group was resulted in the enhancement of the fluorescence properties of the ternary rare earth complexes. The phosphorescence spectra were also discussed.     

The Studies of Enhanced Fluorescence in the Two Novel Ternary Rare-Earth Complex Systems

Two novel ternary rare-earth complexes SmL₅·L^’·(ClO₄)₂·7H₂O and EuL₅·L^’·(ClO₄)₂·6H₂O (the first ligand L = C₆H₅COCH₂SOCH₂COC₆H₅, the second ligand L^’ = C₆H₄OHCOO⁻) were synthesized and characterized by element analysis, molar conductivity, coordination titration analysis, IR, TG-DSC, ¹HNMR and UV spectra. The detailed luminescence studies on the rare-earth complexes showed that the ternary rare-earth complexes presented stronger fluorescence intensities, longer lifetimes, and higher fluorescence quantum efficiencies than the binary rare-earth materials. After the introduction of the second ligand salicylic acid group, the relative emission intensities and fluorescence lifetimes of the ternary complexes LnL₅·L^’·(ClO₄)₂·nH₂O (Ln = Sm, Eu; n = 7, 6) enhanced more obviously than the binary complexes LnL₅·(ClO₄)₃·2H₂O. This indicated that the presence of both organic ligand bis(benzoylmethyl) sulfoxide and the second ligand salicylic acid could sensitize fluorescence intensities of rare-earth ions, and the introduction of salicylic acid group was a benefit for the fluorescence properties of the ternary rare-earth complexes. The fluorescence spectra, fluorescence lifetime and phosphorescence spectra were also discussed.     

Photophysical studies of xanthene dye in alkanols and in presence of inorganic ions

Eosin Y belongs to a xanthene group. It is an anionic fluorescent dye. The absorbance and fluorescence of Eosin Y have been investigated in a series of alkanols (methanol to propanol). When the solvents are added to the aqueous solution of Eosin Y (EY) the absorbance and fluorescence intensity are enhanced. The alkanols are found to affect the absorption and fluorescence spectra of the dye. On the basis of solvent adsorption model the binding constants of the dye with alkanols have been estimated. The interaction of solvent molecule with dye in aqueous solution is specific in nature. The fluorescence quenching of Eosin Y by the inorganic ions [Fe(CN)₆]⁻³, [Fe(CN)₆]⁻⁴ and Cl⁻ was also observed. The ions influenced the quenching process to different extents. The rate constants of quenching were calculated using the Stern-Volmer equation. The equilibrium constant of dye in presence of inorganic ions are determined by Scott equation.     

Thioflavin T Displays Enhanced Fluorescence Selectively Inside Anionic Micelles and Mammalian Cells

Thioflavin T (ThT) has been widely employed to detect amyloid fibrils in tissues and recently in presence of SDS micelles. However, the contribution of membranes or micelles to ThT fluorescence has never been investigated. In this paper, we show for the first time that the anionic micellar microenvironment of SDS has a profound impact on the absorption and fluorescence spectra of ThT in sharp contrast to cationic (CTAB) and neutral micelles (Triton X-100 & Tween 20). Unlike CTAB or Triton X-100 or Tween 20 micelles, formation of SDS micelles shifts the λ_max for ThT absorption from 412 nm in buffer to 428 nm inside the micelle, with a 28% increase in the peak molar absorptivity and a ∼13 fold increase in ThT fluorescence (λ_max = 489 nm). Extending these observations to cell plasma membranes, we show that ThT can quickly enter and appear selectively fluorescent inside mammalian cells like BHK21 and HT29, against a dark background owing to negligible fluorescence from free ThT in aqueous medium. The above results suggest that ThT can be a useful probe for live cell imaging and for selectively labeling micelles on the basis of the charge in the polar headgroup. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Fluorescent properties of thiochrome in solvents of different polarity

Spectral and fluorescent properties of thiochrome in solvents of different polarity were studied. It was found that the pK_a value of the transition between the cationic and neutral forms of thiochrome in aqueous solutions increased from ∼5.5 to 9.7 upon photoexcitation. It is supposed that protonation takes place in the excited state of the molecule resulting in fluorescence quenching of the thiochrome neutral form in aqueous solutions at neutral pH values. The fluorescence quantum yield of thiochrome increased by ∼2.2 times upon the transition from aqueous solutions to alcohols or polar aprotic solvents. It was found that an increase of the solvent polarity led to an increase in the Stokes shift from 3200 to 4200 cm⁻¹ for the thiochrome neutral form emission. The change in the dipole moment upon excitation into the S1-state was estimated to be less than 3D.     

Synthesis and Fluorescence Studies of Some New Fluorophores and Their Effect on Hybridization of Oligodeoxyribonucleotides

Some novel fluorophores, viz. 6-(6-isobutyrylamino-1,3-dioxo-1H,3H-benzo[de]isoquinolin-2-yl)-hexanoic acid (1), 6-(6-dimethylamino-1,3-dioxo-1H, 3H-benzo[de]isoquinolin-2-yl)-hexanoic acid (2), 6-(6-benzoylamino-1, 3-dioxo-1H, 3H-benzo[de]isoquinolin-2-yl)-hexanoic acid (3), 6-(6-amino-1-oxo-1H, 3H-benzo[de]isoquinolin-2-yl)-hexanoic acid (4) and 6-(6-amino-1H,3H-benzo[de] isoquinolin-2-yl)-hexanoic acid (5) have been designed, synthesized and characterized. Their comparative fluorescence has been studied in different organic solvents and aqueous solutions containing inorganic ions. Out of these, two fluorophores, 1 and 2 have been used for labelling of nucleosides which were finally converted into their phosphoramidites, and used for labelling of oligodeoxyribonucleotides through covalent attachment. These fluorophores after attachment on oligodeoxyribonucleotides showed good fluorescence signals and higher hybridisation affinity than unlabelled oligodeoxyribonucleotides.     

Stoichiometrically Different Inclusion Complexes of 2-Aminofluorene and 2-Amino-9-Hydroxyfluorene in β-Cyclodextrin: A Spectrofluorimetric Study

β-cyclodextrin (β-CDx) forms inclusion complexes with 2-aminofluorene (2AF) and 2-amino-9-hydroxyfluorene (2AHF) in different stoichiometries (Guest-host ratio 1:1 and 1:2 respectively) which is discussed on the basis of study by absorption and fluorescence spectroscopy. The ground and the excited state acidity constants for the neutral‒monocation equilibrium of the two fluorophores in aqueous β-CDx medium are determined by spectrophotometric and fluorimetric titration methods respectively. The dual fluorescence observed for 2AHF monocation in aqueous solution is due to the formation of monocation-water exciplex. This monocation-water exciplex formation is hindered in β-CDx solution by the inclusion complexation. Based on the results obtained, the structures of the inclusion complexes are proposed.