Ekram Y. Danish

Emulsion-templated porous materials (PolyHIPEs) for selective ion and molecular recognition and transport: applications in electrochemical sensing

Functionalised emulsion-templated polymers (PolyHIPEs) are reported as new materials for electroanalytical applications. PolyHIPEs, which are prepared from high internal phase emulsions (HIPEs), were tailored by optimisation of polymerisation conditions to yield well-defined, tubular, porous membranes. The PolyHIPE membrane backbone was activated by incorporating ionophores, graphite particles, electron mediators and enzymes. The results show that a valinomycin ionophore impregnated, plasticised membrane shows a Nernstian response to K+ ions with improved detection limits and selectivity coefficients compared to traditional PVC membranes. The graphite/mediator/enzyme loaded membranes exhibit quasi-reversible redox behaviour with semi-infinite linear diffusion at fast scan rates tending to radial diffusion at slow scan rates. Additionally, composite, asymmetric membrane structures with a porous PolyHIPE membrane and a PVC membrane exclude proteins such as BSA (bovine serum albumin) and α1 acid glycoprotein (AAG). These preliminary results demonstrate that plasticised membranes with functionalised skeletons and with controllable porosity such as PolyHIPE membranes are very promising for the fabrication of sensors with integrated separation.

Impact of Metal Ions in Porphyrin-Based Applied Materials for Visible-Light Photocatalysis: Key Information from Ultrafast Electronic Spectroscopy

Protoporphyrin IX-zinc oxide (PP-ZnO) nanohybrids have been synthesized for applications in photocatalytic devices. High-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and steady-state infrared, absorption, and emission spectroscopies have been used to analyze the structural details and optical properties of these nanohybrids. Time-resolved fluorescence and transient absorption techniques have been applied to study the ultrafast dynamic events that are key to photocatalytic activities. The photocatalytic efficiency under visible-light irradiation in the presence of naturally abundant iron(III) and copper(II) ions has been found to be significantly retarded in the former case, but enhanced in the latter case. More importantly, femtosecond (fs) transient absorption data have clearly demonstrated that the residence of photoexcited electrons from the sensitizer PP in the centrally located iron moiety hinders ground-state bleach recovery of the sensitizer, affecting the overall photocatalytic rate of the nanohybrid. The presence of copper(II) ions, on the other hand, offers additional stability against photobleaching and eventually enhances the efficiency of photocatalysis. In addition, we have also explored the role of UV light in the efficiency of photocatalysis and have rationalized our observations from femtosecond- to picosecond-resolved studies.

Preparation and characterization of Pd doped ceria-ZnO nanocomposite catalyst for methyl tert-butyl ether (MTBE) photodegradation.

A series of binary oxide catalysts (ceria-ZnO) were prepared and doped with different amounts of palladium in the range of 0.5%-1.5%. The prepared catalysts were characterized by SEM, TEM, XRD and XPS, as well as by N2 sorptiometry study. The XPS results confirmed the structure of the Pd CeO2-x-ZnO. The photocatalytic activity of these catalysts was evaluated for degradation of MTBE in water. These photocatalyst efficiently degrade a 100ppm aqueous solution of MTBE upon UV irradiation for 5h in the presence of 100mg of each of these photocatalysts. The removal of 99.6% of the MTBE was achieved with the ceria-ZnO catalyst doped with 1% Pd. In addition to the Pd loading, the N2 sorptiometry study introduced other factors that might affect the catalytic efficiency is the catalyst average pore sizes. The photoreaction was determined to be a first order reaction.

Assessment of metal contents in spices and herbs from Saudi Arabia

In the recent years, there has been a growing interest in monitoring heavy metal contamination of spices/herbs. Spices and herbs are sources of many bioactive compounds that can improve the tastes of food as well as influence digestion and metabolism processes. In the present study, the levels of some essential and toxic elements such as iron (Fe), zinc (Zn), copper (Cu), chromium (Cr), manganese (Mn), cobalt (Co), nickel (Ni), lead (Pb), and cadmium (Cd), present in common spices/herbs that were purchased from the local market in Saudi Arabia, were analyzed by atomic absorption spectroscopy after digestion with nitric acid/hydrogen peroxide mixture. Samples from the following spices/herbs were used: turmeric, cloves, black pepper, red pepper, cumin, legume, cinnamon, abazir, white pepper, ginger, and coriander. The concentration ranges for the studied elements were found as 48.8–231, 4.7–19.4, 2.5–10.5, below detection level (BDL)–1.0, 8.8–490, 1.0–2.6, and BDL–3.7 µg g−1 for Fe, Zn, Cu, Cr, Mn, Ni, and Pb, respectively, while Cd and Co levels were below the detection limit. Consumers of these spices/herbs would not be exposed to any risk associated with the daily intake of 10 g of spices per day as far as metals Fe, Zn, Cu, Cr, Mn, Ni, and Pb are concerned.

The Efficient Photocatalytic Degradation of Methyl Tert-butyl Ether Under Pd/ZnO and Visible Light Irradiation

Methyl tert‐butyl ether is a commonly used fuel oxygenate that is present in gasoline. It was introduced to eliminate the use of leaded gasoline and to improve the octane quality because it aids in the complete combustion of fuel by supplying oxygen during the combustion process. Over the past decade, the use of MTBE has increased tremendously worldwide. For obvious reasons relating to accidental spillage, MTBE started to appear as an environmental and human health threat because of its nonbiodegradable nature and carcinogenic potential, respectively. In this work, MTBE was degraded with the help of an advanced oxidation process through the use of zinc oxide as a photocatalyst in the presence of visible light. A mixture of 200 mg of zinc oxide in 350 mL of 50 ppm MTBE aqueous solution was irradiated with visible light for a given time. The complete degradation of MTBE was recorded, and approximately 99% photocatalytic degradation of 100 ppm MTBE solution was observed. Additionally, the photoactivity of 1% Pd‐doped ZnO was tested under similar conditions to understand the effect of Pd doping on ZnO. Our results obtained under visible light irradiation are very promising, and they could be further explored for the degradation of several nondegradable environmental pollutants.

Kinetics and Photodegradation Study of Aqueous Methyl tert-Butyl Ether Using Zinc Oxide: The Effect of Particle Size

Zinc oxide of different average particle sizes 25 nm, 59 nm, and 421 nm as applied in the photodegradation of MTBE. This study was carried out in a batch photoreactor having a high pressure mercury lamp. Zinc oxide of particle size of 421 nm was found to be the most effective in degrading MTBE in an aqueous solution. On using this type of ZnO in a solution of 100 ppm MTBE, the concentration of MTBE has decreased to 5.1 ppm after a period of five hours. The kinetics of the photocatalytic degradation of MTBE was found to be a first order reaction.

The Effect of Loading Palladium on Zinc Oxide on the Photocatalytic Degradation of Methyl tert‐Butyl Ether (MTBE) in Water

A series of heterogeneous catalysts was prepared by doping zinc oxide with different palladium loadings in the range of 0.5%–1.5%. The prepared catalysts were characterized by SEM, TEM and XRD. These catalysts were applied to study the degradation of Methyl tert‐Butyl Ether (MTBE). An amount of 100 mg of each of these catalysts was added to an aqueous solution of 100 ppm of MTBE. The resulting mixtures were irradiated with UV light for a period of 5 h. A 99.7% removal of MTBE was achieved in the case of the zinc oxide photocatalyst particles doped with 1% Pd. The photoreaction was found to be a first‐order one.

Performance of cellulose acetate-ferric oxide nanocomposite supported metal catalysts toward the reduction of environmental pollutants

Water contamination by toxic compounds has become one of the most serious problems worldwide. Catalytic reduction using metal nanoparticles offer opportunities for environmental benefits. In this study, cellulose acetate-ferric oxide nanocomposite (CA/Fe2O3) was prepared and used as support for metal nanoparticles. After adsorption of Ag, Cu or Ni ions from aqueous solutions, metal ions associated with CA/Fe2O3 were treated with sodium borohydride to prepare Ag, Cu and Ni nanoparticles loaded CA/Fe2O3. The CA/Fe2O3 supported Ag, Cu or Ni nanoparticles was evaluated as a catalyst for pollutants degradation. Silver nanoparticles (Ag@CA/Fe2O3) exhibit remarkable decomposition for methyl orange dye and p-nitrophenol in short time. The rate constant for methyl orange and p-nitrophenol were 8.58×10-3 and 4.77×10-3s-1, respectively. Besides the good catalytic activities of Ag@CA/Fe2O3, the catalyst could be easily recovered from the reaction medium by pulling the catalyst after completion of the reduction reaction. The recovered catalyst can be recycled several times if their exposure time to air was minimal.

Facile synthesis of light harvesting semiconductor bismuth oxychloride nano photo-catalysts for efficient removal of hazardous organic pollutants

In the present work, bismuth oxychloride nanoparticles–a light harvesting semiconductor photocatalyst–were synthesized by a facile hydrolysis route, with sodium bismuthate and hydroxylammonium chloride as the precursor materials. The as-synthesized semiconductor photocatalysts were characterized using X-ray diffraction analysis, Fourier transform infra-red spectroscopy, Raman spectroscopy, Field emission scanning electron microscopy, X-ray photoelectron spectroscopy and Photoluminescence spectroscopy techniques. The crystal structure, morphology, composition, and optical properties of these facile synthesized bismuth oxychloride nanoparticles (BiOCl NPs) were compared to those of traditional bismuth oxychloride. In addition, the photocatalytic performance of facile-synthesized BiOCl NPs and traditional BiOCl, as applied to the removal of hazardous organic dyes under visible light illumination, is thoroughly investigated. Our results reveal that facile-synthesized BiOCl NPs display strong UV-Vis light adsorption, improved charge carrier mobility and an inhibited rate of charge carrier recombination, when compared to traditional BiOCl. These enhancements result in an improved photocatalytic degradation rate of hazardous organic dyes under UV-Vis irradiance. For instance, the facile-synthesized BiOCl NPs attained 100% degradation of methylene blue and methyl orange dyes in approximately 30 mins under UV-Vis irradiation, against 55% degradation for traditional BiOCl under similar experimental conditions.

Cellulose acetate-iron oxide nanocomposites for trace detection of fluorene from water samples by solid-phase extraction technique

ABSTRACT In this study, cellulose acetate (CA)/iron oxide nanocomposites (NC1 and NC2) were synthesized and utilized as extractors for the selective separation of fluorene from aqueous samples. The selectivity of nanocomposites to different organic compounds was assessed. Based on the results, fluorene was the most quantitatively adsorbed on NC2. Batch method was performed by varying the initial fluorene concentrations and contact time. Langmuir and Freundlich isotherms were used for modeling the experimental data and were best correlated by the Langmuir model. Adsorption data were also followed the pseudo-second-order kinetic model. Finally, validation of the developed method was achieved for fluorene determination in real water samples.