Siddik Icli

A Panchromatic Boradiazaindacene (BODIPY) Sensitizer for Dye-Sensitized Solar Cells

A novel distyryl-substituted boradiazaindacene (BODIPY) dye displays interesting properties as a sensitizer in DSSC systems, opening the way to further exploration of structure-efficiency correlation within this class of dyes.

Photophysical and photochemical characteristics of an azlactone dye in sol-gel matrix; a new fluorescent pH indicator

Abstract The photophysical and photochemical properties of an azlactone derivative, 4-(p-N,N-dimethylaminophenylmethylene)-2-phenyl-5-oxazolone, (DPO) in a sol-gel matrix have been examined. The fluorescence quantum yield, radiative lifetime, fluorescence lifetime, fluorescence rate constant and singlet energy values of the DPO dye were determined in a modified tetraethyl orthosilicate (TEOS) solid matrix by absorption and emission spectroscopy and obtained data were compared with the results of measurements in acetonitrile (MeCN) and tetrahydrofuran (THF) solution. The sol-gel matrix enhanced the fluorescence quantum yield (Qf=0.296) and fluorescence emission lifetime (τf=0.47 ns) compared to Qf=0.0027–0.0025 and τf=0.02–0.03 ns for solutions in MeCN and THF. The acidity constant of DPO was found to be as pKa=5.1 in the transparent sol-gel matrix. The dye doped sol-gel exhibited a pH sensitivity in pH range 3.0–7.0.

Electrochromic and electroluminescent devices based on a novel branched quasi-dendric fluorene-carbazole-2,5-bis(2-thienyl)-1H-pyrrole system

We report here the synthesis of a novel branched quasi-dendric system, 9,9′-(9,9′-dihexylfluorene-2,7-diyl)bis[3,6-bis(2,5-bis(2-thienyl)pyrrol-1-yl)carbazole], (FCSNS), in four steps, followed by coating onto an ITO-coated glass surface by an electropolymerization process to give a very stable cross-linked polymeric film (poly-FCSNS). The yellowish-green color of this film in its neutral state changed reversibly to black upon oxidation. An electrochromic device, assembled in the sandwich configuration [ITO/anodically coloring polymer (poly-FCSNS)//gel electrolyte//cathodically coloring polymer/(PEDOT)/ITO], exhibited a relatively short response time (about 1 s), a high redox stability, and a high coloration efficiency (1624 cm2C−1). In addition to electrochromic studies, organic light-emitting diode (OLED) work was also carried out using FCSNS. A multilayer OLED having a configuration of ITO/PEDOT:PSS/FCSNS/Alq3/LiF : Al was fabricated, and it showed a turn-on voltage of approximately 6 V and exhibited a bright green emission with a luminance of 3700 cd m−2. The maximum luminous efficiency was found to be 2.0 cd A−1 at 14 V and 11.75 mA cm−2. The emitted light from the OLED device is green, and has the color coordinates of (x, y) (0.33, 0.54) according to CIE. Electrochemical and optical properties were also studied by using cyclic voltammetry, UV-Vis absorption and fluorescence spectroscopy, respectively.

Adsorption of dyes on Sahara desert sand.

Sahara desert sand (SaDeS) was employed as a mineral sorbent for retaining organic dyes from aqueous solutions. Natural sand has demonstrated a strong affinity for organic dyes but significantly lost its adsorption capacity when it was washed with water. Therefore, characterization of both natural and water washed sand was performed by XRD, BET, SEM and FTIR techniques. It was found that water-soluble kyanite, which is detected in natural sand, is the dominant factor affecting adsorbance of cationic dyes. The sand adsorbs over 75% of cationic dyes but less than 21% for anionic ones. Among the dyes studied, Methylene Blue (MB) demonstrated the strongest affinity for Sahara desert sand (Q(e)=11.98 mg/g, for initial dye solution concentration 3.5 x 10(-5)mol/L). The effects of initial dye concentration, the amount of the adsorbent, the temperature and the pH of the solution on adsorption capacity were tested by using Methylene Blue as model dye. Pseudo-first-order, pseudo-second-order and intraparticle diffusion models were applied. It was concluded that adsorption of Methylene Blue on Sahara desert sand followed pseudo-second order kinetics. Gibbs free energy, enthalpy change and entropy change were calculated and found -6411 J/mol, -30360 J/mol and -76.58 J/mol K, respectively. These values indicate that the adsorption is an exothermic process and has a spontaneous nature at low temperatures.

Spectral-luminescent and solvatochromic properties of anticancer drug camptothecin

The spectral characteristics of camptothecin have been investigated in solvents of various polarity and proton donating ability. The effect of the solvent on the spectral characteristics and the dipole moment in the excited state have been estimated. Different theoretical approaches have been compared in order to estimate the excited-state dipole moment. It has been shown that camptothecin’s emission is very sensitive to quenching with Co2+ ions.

Nuclear magnetic resonance spectra of two reductively ethylated fuels

Abstract A lignite (67.2% C daf) and a coal (89.0% C daf) have been reductively ethylated by Sternbergs procedure 4 and the spectra, in particular the 1 H and 13 C n.m.r. spectra, of the products have been obtained. The distribution of hydrogen atoms and, in less detail, of carbon atoms in the reductively ethylated fuels has been determined. It is emphasized that both reductively ethylated fuels contained a variety of structures. The carbon aromaticities of the reductively ethylated lignite and the reductively ethylated coal were 0.41 ± 0.08 and 0.40 − 0.54 respectively. The aromatic nuclei of the reductively ethylated coal were more highly substituted than those of the reductively ethylated lignite. The 1 H n.m.r. spectra indicate that the reductively ethylated coal and lignite possessed ≈3.5 and ≈2.5 substituents per benzene ring respectively. Resolved absorption in the 13 C n.m.r. spectra suggests lower figures than these and it was evident that some of the benzene rings in both materials but especially in the reductively ethylated lignite were lightly substituted. The 13 C n.m.r. spectra show that both materials contained branched and unbranched paraffin chains. Much of the 13 C n.m.r. spectra however consisted of unresolved absorptions and the 13 C n.m.r. measurements suggest that the reductively ethylated materials consisted of rigid, relatively immobile molecules of moderate molecular weight. 13 C n.m.r. absorption by carbon atoms adjacent to aromatic rings was amongst that which was not resolved — though the rings themselves gave resolved absorptions — and this suggests that the aromatic rings were on the periphery of a rigid, perhaps alicyclic, structure.

A comparative study of the photophysical properties of perylenediimides in liquid phase, PVC and sol-gel host matrices

Abstract The photophysical and photochemical properties of three different perylenediimide derivatives, N , N ′-di-dodecylperylene-3,4,9,10-bis(dicarboximide), N , N ′-di-(1-dehydroabietyl)perylene-3,4,9,10-bis(dicarboximide) and N , N ′-di-(4-carboxy phenyl)perylene-3,4,9,10-bis(dicarboximide) ( N -DODEPER, ABIPER and PECA, respectively), were determined in immobilized phases (PVC films, both plasticized and non-plasticized, and sol-gel matrix) using steady state fluorescence spectroscopy and compared with the data in solution phase. It was found that the plasticizers support the interaction of the dyes with the quencher and bis-(2-ethylhexyl)phthalate (DOP) itself acts as a quencher for the perylenediimide derivatives with aromatic substituents. The sol-gel matrix imparted serious changes to the properties of the perylenediimides.

Pyridine extracts of solid fuels

Abstract Pyridine extracts of a coking coal and of two lignites have been further separated and the 1H and 13C n.m.r. spectra of the various fractions have been recorded. Three methods of separation were investigated: gel-permeation chromatography, successive extraction with petroleum ether and with benzene as used by previous workers for supercritical-gas extracts, and the classical extraction of the fractions. Gel-permeation chromatography gave most promise of effective separation but the fractions obtained often contained too little material to give n.m.r. spectra. The n.m.r. spectra of the chloroform-soluble material from the pyridine extracts of the coking coal were consistent with a material consisting of polynuclear aromatic nuclei joined through simple bridge structures and possibly also through direct carbon—carbon linkages. The nuclei were substituted by branched and unbranched paraffin chains, some of which were 7 or 8 carbon atoms long. It is probable that alicyclic structures were also present. The aromatic nuclei were mobile in solution. 60% of the carbon atoms were aromatic, and it can therefore be calculated that the molecular weight per aromatic nucleus was 200–300. It is suggested that 13C n.m.r. spectra may be used to characterize chemicals likely to confer coking properties on solid fuels.

A Comparative Study of Supported TiO2 as Photocatalyst in Water Decontamination at Solar Pilot Plant Scale

The degradation of gallic acid and imidacloprid with supported Millennium PC500 and Degussa P25 TiO2 is reported. TiO2 particles were immobilized using a titanium sol-solution and direct deposition on glass supports. The film characterization was done by x-ray diffraction, scanning electron microscopy, and atomic force microscopy, and degradation of organic compounds was monitored by high-performance liquid chromatography, total organic carbon analyzer, and ion chromatography. The experiments were performed under sunlight in compound parabolic collector plants with flat supports inside the glass tubes. Photocatalytic activity of the films was compared and identified. Although sol-gel coatings had better mechanical properties, mineralization was observed to be approximately five times slower than paste-deposited films. Photoactivity of the films decreased with silver deposition due to the nature of the organic compounds. The rate constants were calculated to be between 2×10–1 and 6×10–2 mg m2/kJ for organic compounds, and 6×10–2 and 6×10–3 for total organic carbon.

Photostability studies of thermomesomorphic derivatives of 2, 5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione

Abstract In this study, the photophysical characteristics, like molar extinction coefficients, Stokes shifts, quantum yields, radiative and fluorescence lifetimes, fluorescence rate constants, radiationless deactivation rate constants, and singlet energies of the fluorescent mesomorphic diketopyrrolopyrrole derivatives, (DPPDs), 3,6-bis(4-octyloxyphenyl)-2,5-dihydro-2,5-dimethylpyrrolo[3,4-c]pyrrole-1,4-dione (DPPD-1) and 3,6-bis(4′-butylbiphenyl-4-yl)-2,5-dihydro-2,5-dimethylpyrrolo[3,4-c]pyrrole-1,4-dione (DPPD-2) have been determined. The photostability studies were carried out under xenon arc lamp, direct and concentrated sunlight in solution of chloroform and tetrahydrofuran as well as in solid state, embedded in matrices of polyvinyl chloride (PVC) and sol-gel. The studies reveal that the photostabilities of the DPPD derivatives in PVC and sol-gel matrices are enhanced compared to solutions of chloroform and tetrahydrofuran.