Samia A. Kosa

Structure-property relationship of naphthalene based donor-π-acceptor organic dyes for dye-sensitized solar cells: Remarkable improvement of open-circuit photovoltage

Four new donor–π–acceptor organic dyes (YF01–04), containing naphthalene-substituted amines as an electron donor and cyanoacrylic acid as an electron acceptor, were designed and synthesized, and their photophysical properties and dye-sensitized solar cells (DSCs) performances were characterized. Dyes YF02 and YF04, with 2,6-disubstituted naphthalene frameworks, were superior than their analog dyes YF03 and YF01, having 1,2-disubstituted naphthalene moiety, in incident-photo-to-current conversion efficiency (IPCE) and total solar-to-electric conversion efficiency (η). The DSCs based on YF02, comprised of diphenylamine moiety as the donor, produced the highest η of 5.29% compared to 4.03% of the analog dye YF04, which has pyrrolidine as the donor. Remarkably, a high open-circuit photovoltage (Voc) of 0.799–0.807 V was achieved in the cases of YF02–03, which have diphenylamine-donors. To better understand the structure–property relationship for DSCs application, molecular modelling was performed on YF01–04 and vertical electronic excitations were calculated using long-range corrected energy functional WB97XD and CAM-B3LYP at the basis set level DGDZVP, which were in excellent agreement with the experimental results. Moreover, the equilibrium molecular geometries of dyes YF01–04 were calculated at the density function theory (DFT) level using the hybrid energy functional B3LYP and basis set DGDZVP. The torsion angles (θ) between the naphthalene moiety and diphenylamine donor in YF02 and YF03 were more twisted than that of the pyrrolidine-donor dyes YF01 and YF04, precluding efficient intermolecular π–π charge transfer, which translated into high Voc. Compared to the reference dye TA-St-CA, which is based on diphenylamine as an electron donor linked to a phenyl ring, YF02 achieved higher Voc, which indicated that naphthalene substituted with diphenylamine is more efficient in retarding charge recombinations.

Anion induced azo-hydrazone tautomerism for the selective colorimetric sensing of fluoride ion

The design, synthesis, characterization and their anion sensing properties of two receptors capable of exhibiting azo-hydrazone tautomerism are reported. The anion sensing properties have been investigated using electronic, fluorescence and nuclear magnetic spectral studies in addition to electrochemical and visual detection experiments. Both the receptors selectively bind fluoride ion with >100 nm red-shift in the electronic spectrum and the color changes from yellow to red. The results of the spectral studies revealed that the sensing mechanism involves fluoride ion induced change of chromophore from C=N (hydrazone form) to N=N (azo form) in these receptors leading to the visible color change. Density Functional Theory calculations were conducted to rationalize the optical response of the receptors.

Design, synthesis and characterization of indole based anion sensing receptors

The design and synthesis of six new receptors (R1–R6) and their anion sensing properties through multiple channels are reported. These receptors are constructed in such a way that they possess indole groups as the binding sites and different acceptors units of varying electron acceptor strengths. Receptors R1, R3 and R5 could recognize fluoride ions visually and spectroscopically with high selectivity over other anions in DMF, which was demonstrated by a visual detection experiment and UV-Vis, fluorescence and 1H NMR spectral studies. The remaining three receptors (R2, R4 and R6) exhibited colour changes with both fluoride and cyanide ions. The binding constants for fluoride binding by these receptors were determined to be in the order of 104 to 106 M−1 and found to depend on the electron accepting property of the acceptor unit in the intra molecular charge transfer (ICT) transition existing with the indole donor units. 1H NMR titration experiments not only provide evidence for the existence of H-bonding interactions between the indolic N–H groups of these receptors and F−, but also offer key insight into the strengths of the receptor–anion complexes of stoichiometry 1:2. The higher fluoride binding ability of the receptor containing the naphthoquinone signalling unit has been interpreted in terms of the greater electron deficiency of the acceptor unit (quinone) and enhanced H-bond donating character of the indole N–H group. The results of the electrochemical and DFT computation studies corroborate well with the spectroscopic studies.

Extraction of nanosized cobalt sulfide from spent hydrocracking catalyst

The processes used for the extraction of metals (Co, Mo, and Al) from spent hydrotreating catalysts were investigated in this study. A detailed mechanism of the metal extraction process is described. Additionally, a simulation study was performed to understand the sulfidizingmechanism. The suggested separation procedure was effective and achieved an extraction of approximately 80-90%. In addition, the sulfidization mechanism was identified. This sulfidizing process for Co was found to involve an intermediate, the structure of which was proposed. This proposed intermediate was confirmed through simulations. Moreover, the activities of the spent and the regenerated catalyst were examined in the cracking of toluene. The modification of the spent catalyst through the use of different iron oxide loadings improved the catalytic activity.

Deuterium Isotope Effect on Bulk Heterojunction Solar Cells. Enhancement of Organic Photovoltaic Performances Using Monobenzyl Substituted Deuteriofullerene Acceptors

A series of novel monobenzyl-substituted deuteriofullerenes (BnDCs) were synthesized efficiently through Co-catalyzed selective monofunctionalization of C60. Bulk heterojunction solar cells, based on poly(3-hexylthiophene) as the donor and BnDCs as the acceptors, exhibited higher photovoltaic performances as compared to the corresponding protonated BnHCs devices.

Adsorption of Polyvinylpyrrolidone over the Silica Surface: As Affected by Pretreatment of Adsorbent and Molar Mass of Polymer Adsorbate

The adsorption of polyvinylpyrrolidone over the surface of silica has been investigated. The impact of molar mass of the polymer, pH, and pretreatment temperature of silica particles have been evaluated by means of FTIR spectroscopy and electrophoretic measurements. The silica particles used have narrow particle size distribution. The zeta potential of the aqueous silica suspension was decreased with the increase in pH. The amount of polymer adsorbed was increased with the increase in pretreatment temperature, time, concentration, pH, zeta potential, and molar mass of the polymer. The addition of polymer to the system increased the zeta potential due to adsorption of polymer on the surface of the particles. However, the impact increased with the increase in molecular mass of the polymer. The IR spectra obtained before and after adsorption of polymer concluded that, mostly, hydrogen bonding is responsible for the adsorption phenomena; however, hydrophobic interactions also play a significant role. The mechanism has been investigated and established through FTIR spectroscopy.

Preparation and Properties of Novel Quaternized Metal–Polymer Matrix Nanocomposites

A new class of PANI/Sn(II)SiO3/FCNTs nanocomposite was synthesized by mixing polyaniline into the gel of Sn(II)SiO3 followed by FCNTs (Polyaniline/Sn(II)SiO3/Functionalized Carbon nanotubes). The physico-chemical characterization was carried out by scanning electron microscope, XRD (X-ray Diffraction), FTIR (Fourier Transform Infrared Spectroscopy), ultraviolet–visible spectroscopy, and simultaneous thermogravimetric analysis studies. The ion-exchange capacity (1.2 meq/g) and distribution studies were also determined to understand the ion-exchange capabilities. The DC electrical conductivity studies revile it in the range of 3–5 × 10−3 S/cm. On the basis of distribution studies, ion-selective membrane electrode was designed for Hg(II). The analytical utility of this membrane was established by using it as an indicator electrode in electrometric titrations. GRAPHICAL ABSTRACT

Effect of Pr, Sm, and Tb doping on the morphology, crystallite size, and N 2 O decomposition activity of Co 3 O 4 nanorods

Cobalt(II,III) oxide, Co3O4, is a promising catalyst for nitrous oxide direct decomposition. In this paper we report effect of doping with some rare earth (RE) elements (Pr, Sm, and Tb) on the morphology and crystallite size of Co3O4 nanorods. The various precursors (RE/Co oxalates) were prepared via the microwave assisted method and subsequent calcination. The decomposition pathway of these precursors was followed using thermogravimetric analysis (TGA). Based on thermal analysis results, Pr-, Sm-, and Tb-doped Co3O4 samples were obtained via the calcination in static air at 500°C for their oxalate precursors. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and hydrogen temperature programmed reduction (H2-TPR) were used to characterize the RE-doped cobalt oxide catalysts. The activity of the prepared catalysts was investigated for N2O direct decomposition and compared with that of the undoped Co3O4 catalyst. It was shown that the promoted Co3O4 catalysts revealed higher activity compared to the unpromoted one. The dependence of the activity on both the catalysts particle size and the reduction behaviour was discussed.

The photocatalytic activity of TiO 2 -zeolite composite for degradation of dye using synthetic UV and jeddah sunlight

In this research different composites of impregnated TiO2 with LTA or FAU zeolites were used as different weight% ratio for photodegradation of organic dye. Normal laboratory UV-lamps were used as a source of UV irradiation. In addition a setup of system of mirrors was used to collect real Jeddah sunlight. A comparison of UV and real sunlight photodegradation activity showed that the real sunlight enhances new centers of active sites exhibiting higher catalytic activity than that of UV irradiated samples.

Impact of Block Length and Temperature over Self-Assembling Behavior of Block Copolymers

Self-assembling behavior of block copolymers having water-soluble portion as one of the blocks plays key role in the properties and applications of the copolymers. Therefore, we have synthesized block copolymers of different block length and investigated their self-assembling behavior with reference to concentration and temperature using surface tension and conductance measurement techniques. The results obtained through both techniques concluded that critical micelles concentration (CMC) was decreased from 0.100 to 0.078 g/dL with the increase in length of water insoluble block and 0.100 to 0.068 g/dL for the increased temperature. was also decreased with the increase in temperature of the system, concluding that the micellization process was encouraged with the increase in temperature and block length. However, values were highest for short block length copolymer. The surface excess concentration obtained from surface tension data concluded that it was highest for short block length and vice versa and was increased with the increase in temperature of the system. However, the minimum area per molecule was largest for highest molecular weight copolymers or having longest water insoluble block and decreases with the increase in temperature.