Cyanamide-Modified Iron(III) Oxide Photocatalysts for Degradation of Phenol in the Presence of Urea and Formaldehyde

Cyanamide as the source of carbon and nitrogen was used to modify iron(III) oxide (Fe2O3) photocatalyst. While X-ray diffraction (XRD) patterns confirmed that the cyanamide-modified Fe2O3 photocatalysts have comparable crystallinity to that of the unmodified Fe2O3, the diffuse reflectance ultraviolet-visible (DR UV-vis) spectra obviously showed additional light absorption around 500-800 nm on the cyanamide-modified Fe2O3, resulting in a better absorption capability under visible light irradiation. The presence of cyanamide modifier decreased the fluorescence emission intensity of Fe2O3, implying the reduced electron-hole recombination on the Fe2O3 and/or blocked emission sites by the modifier. The presence of carbon and nitrogen on the modified Fe2O3 photocatalysts was confirmed by the elemental analyzer. Photocatalytic activities of Fe2O3 and cyanamide-modified Fe2O3 were then evaluated for degradation of phenol under UV and visible light irradiation. Modification of Fe2O3 with cyanamide significantly improved the degradation of phenol from 30 to 75% under UV light irradiation and from 0 to 80% under visible light irradiation. Photocatalytic degradation of phenol was also investigated in the presence of urea or formaldehyde or both urea and formaldehyde. Even though the percentage of phenol degradation decreased in the presence of other pollutants, it was demonstrated that cyanamide modified iron(III) oxide photocatalysts still gave good activity towards degradation of phenol even in the presence of other organic pollutants.

A Novel Fluorescence “Turn-Off” Sensor Base On A Triazole-Linked BINOL-Glucose Derivative For The Sensitive Detection of Copper Ion

A novel sensitive chiral fluorescent “turn-off” sensor based on 3,3′-positions modified triazole-linked BINOL-Glucose derivative has been synthesized via “click” reaction. The fluorescence emission intensity of (S, β-D)-1 was almost completely quenched along with obvious color change from yellow to green upon the coordination with a Cu(II) ion while other metal ions had no obvious change. The detection limit of the sensor (S, β-D)-1 toward copper ion was calculated to be 0.31 μmol L-1. The stoichiometry ratio of (S, β-D)-1-Cu2+ complex was proved to be 1:1 by the analysis of NMR spectroscopic, ESI-MS data and the job’s plot. HNMR spectroscopic and IR were also used to study the mechanism, demonstrated copper ion was coordinated with (S, β-D)-1 by 1+1complex formation.

FLUORESCENCE CHARACTERISTICS OF FLUORESCEIN AND EOSIN Y SOLUTIONS IN WATER-MICELLAR SURFACTANT MEDIA

The effect of cationic, anionic and nonionic surfactants on the fluorescence properties of fluorescein and eosin Y aqueous solutions has been investigated. It has been found that sodium dodecyl sulfate does not affect the position of the maximum wavelengths of solutions of fluorescein and eosin Y in the study of the effect of an anionic surfactant on the fluorescence emission intensity of dyes. The intensity of the signal of the dye solutions when changing the concentration of anionic surfactant changes little. As the concentration of non-ionic surfactant increases, the fluorescence emission intensity of the fluorescein solutions decreases. In contrast, with increasing concentration of Triton X-100, there is an increase in the signal intensity of solutions of more hydrophobic eosin Y with subsequent access to the "plateau" at СТХ-100≥5.1·10–2 mol/L. The position of the maxima fluorescence emission wavelengths for the fluorescein solutions in the 0-1.0·10–5 mol/L range of concentrations of cationic surfactant cetylpyridinium chloride remain unchanged. The position of the maxima shifts to the long-wavelength region of the spectrum at higher concentrations of CPC. The nature of the position dependence of the fluorescence emission maxima of eosin Y solutions in the presence of cationic surfactants is similar. The effect of fluorescence quenching has also been shown in the study of the influence of organic substances of cationic nature on the signal intensity of fluorescein solutions. It has been shown that the concentration dependence is linear in the (0.1–4.0)·10–1 mol/L range of isoniazid molecule concentrations. The data obtained can be implemented in the development of conditions and methods for the determination of pharmacologically active substances of cationic nature by reaction with fluorescein in medicines.

Synthesis and photophysical evaluation of new fluorescent 7-arylethynyl-7-deazaadenosine analogs

Three new fluorescent 7-deaza-2′-deoxyadenosine analogs were synthesized via the Sonogashira cross-coupling reaction of 7-iodo-7-deaza-2′-deoxyadenosine with 1-ethynylpyrene, 2-ethynyl-6-methoxynaphthalene, and 9-ethynylphenanthrene. The spectral properties of these analogs were evaluated in dioxane, EtOH, and H2O to determine their potential for use as environmentally sensitive fluorescent probes. All three analogs displayed large solvatofluorochromicity in H2O, relative to their emission wavelengths in dioxane or EtOH. Moreover, all three analogs exhibited microenvironmental sensitivity of their fluorescence emission intensity, being moderate to high quantum yields in dioxane and EtOH and significantly lower in H2O. Various attempts to perform domino cross-coupling and annuation reactions on 7-deaza-7-alkynyladenine derivatives to form a new fused tricyclic adenine analog were unsuccessful.

Micelle-enhanced flow injection analysis

Surface-active agents are organic compounds of amphiphilic nature. When the concentration of surfactants is higher than a certain value, the monomers adhere to form well-defined aggregates known as micelles. These micelles have been employed in flow injection analysis (FIA) for various purposes. In chemiluminescence-based FIA, micelles can improve sensitivity by changing the chemical structures of the reagents, facilitating intramicellar energy transfer, accelerating the reaction kinetics, or stabilizing the excited singlet states. Micelles can improve sensitivity in FIA/ultraviolet-visible by electrostatic or solubilization effects. In FIA/fluorescence, emission intensity is considerably enhanced in micellar media due to the protective environment that restricts nonemissive energy transfer processes. If FIA is coupled with flame atomic absorption, the signals are enhanced with surfactants due to the decreased surface tension that results in the generation of smaller droplets during the aspiration and nebulization processes. In addition, surfactants promote the enrichment of the analyte in the double layer at the air-water interface. The FIA/cloud point extraction technique is based on using surfactants as alternatives to organic solvents. This review discusses the different roles of micelles in FIA methods.

Photoisomerization and optical properties of a subphthalocyanine–azobenzene–subphthalocyanine triad

A novel subPc–AB–subPc triad exhibits on–off switching of the fluorescence emission intensity upon reversible trans ↔ cis photoisomerization of the azobenzene moiety. NMR spectroscopy provides additional evidence for the conformational change.

Reply to the ‘Comment on “Simple fluorescence-based detection of Cr(iii) and Cr(vi) using unmodified gold nanoparticles”’ by M. R. Hormozi-Nezhad, J. Mohammadi and A. Bigdeli, Anal. Methods, 2015, 7, DOI: 10.1039/c5ay00005j

AuNP aggregation by Cr(iii) causes the reduction of the fluorescence emission intensity at 582 nm (λex = 490 nm).

Investigation of fluorescence properties of cyanidin and cyanidin 3-o-β-glucopyranoside

The absorption and fluorescence emission spectra of cyanidin and cyanidin 3-O-?-glucopyranoside (Cy3Glc) at pH 5.5 in aqueous solution have been studied. The most effective fluorescence excitations of cyanidin were at the UV absorption maxima at 220 and at 230 nm and at higher wavelengths at 270 and at 280 nm. Cyanidin exhibits fluorescence emission maxima at 310 nm and in the visible range at 615 nm. For the Cy3Glc most effective fluorescence excitation was at 220 and at 230 nm and at higher wavelengths at 300 and at 310 nm. Cy3Glc has fluorescence emission spectra with the maximum at 380 nm and does not show fluorescence emission in the visible range. If compare fluorescence emission spectra of cyanidin and Cy3Glc it can be seen that fluorescence emission intensity for cyanidin is significantly higher than that for Cy3Glc. These results reveals the impact of 3-glucosidic substitution at C-3 of aglycone (to form Cy3Glc) on the significantly decrease in fluorescence emission intensity, and disappearance of the fluorescence emission in visible wavelength range.

A study of fluorescence emission intensity of reaction products between selected amino acdis and DFO, 1,2-indanedione and 1,2-indanedione - zinc chloride

The study shows the results of fluorescence emission intensity measurements of the reaction products of selected amino acids with DFO, 1,2-IND and 1,2-IND - zinc chloride on absorptive surfaces. Conducted research addressed the following variables: type of developing reagent, type of surface, type of amino acid and sample storage time. It was confirmed that the above factors affected the fluorescence intensity of developed fingerprints. Furthermore, the studies proved that fluorescence intensity of reaction products between amino acids and 1,2- IND stored for 1 or 7 days increased for the majority of samples upon addition of zinc chloride to the developing reagent. For samples stored for 4 months the highest fluorescence emission intensity was observed for DFO. No significant differences were found in fluorescence spectral characteristics of tested compounds, depending on the type of surface.

Photo-Induced Fluorescence Enhancement of BOPIM–dma in Moderate Polar Solvents

The photo-induced fluorescence enhancement for a BOPIM derivate, which was found weak or no fluorescence in solvents due to twisted intramolecular charge transfer (TICT) was investigated. The quenching process because of TICT state is substantially removed and fluorescence emission intensity increased remarkably, induced by UV-irradiation. This phenomenon could only found in moderate polar solvent, such as CHCl3, THF and 1, 4-dioxane (DIOX), but not in more polarity solvent, such as CH3CN, CH3OH. It is indicated that the transformation from TICT to ICT state take place easily in moderate polar solvents.