Dina M. Fouad

Studies on the photo-catalytic activity of semiconductor nanostructures and their gold core-shell on the photodegradation of malathion.

This work is devoted to the synthesis of different semiconductor nanoparticles and their metal core-shell nanocomposites such as TiO2, Au/TiO2, ZnO, and Au/ZnO. The morphology and crystal structures of the developed nanomaterials were characterized by transmission electron microscopy (TEM) and x-ray diffraction (XRD). These materials were used as catalysts for the photodegradation of malathion, which is one of the most commonly used pesticides in developing countries. The degradation of 10 ppm malathion under ultraviolet (UV) and visible light in the presence of different synthesized nanocomposites was analyzed using high performance liquid chromatography (HPLC) and UV-visible spectra. A comprehensive study was carried out for the catalytic efficiency of the prepared nanoparticles. Moreover, the effects of different factors that could influence catalytic photodegradation, such as different light sources, surface coverage and the nature of the organic contaminants, were investigated. The results indicate that the core-shell nanocomposite of semiconductor-gold serves as a better catalytic system than the semiconductor nanoparticles themselves.

Photodegradation of Chloridazon Using Coreshell Magnetic Nanocompsites

A new synthesized magnetic nanoparticle of Fe3O4 and coreshell Fe3O4@Au is prepared chemically. A comparative study between the photocatalytic activity between Fe3O4 and core shell Au-Fe3O4 nanoparticles has been studied on the effect of UV and sun light on the photodegradation of chloridazon. The particle has been prepared using chemical methods and the particle size and shape have been examined via transmission electron microscopy (TEM). Analysis of the degradation of 20 ppm chloridazon under ultraviolet (UV) and visible light was analyzed with high-performance liquid chromatography (HPLC) and UV-Visible Spectra. Influence of different parameters on the activity photodegradation rate has been studied. The results indicate that the Fe3O4@Au nanoparticles are much more active catalyst in presence of sun light than pure Fe3O4 nanomaterials which have maximum absorption at 560 nm.

Spectroscopic characterization of magnetic Fe3O4@Au core shell nanoparticles.

The magnetic nanoparticles iron oxide (Fe3O4) nanoparticles and iron oxide/gold core-shell (Fe3O4/Au) nanoparticles were synthesized and their catalytic photo-degradation activity towards malathion as example of organophosphorus pesticides were reported. Iron oxide (Fe3O4) magnetic nanoparticle was successfully prepared through co-precipitation method by the reduction of ferric chloride (FeCl3) using ascorbic acid. The morphology of the prepared nanoparticles was characterized by the TEM and XRD (X-ray diffraction) techniques. Degradation of 10 ppm of malathion in the presence of these nanoparticles under UV radiation was monitored using (HPLC) and UV-visible spectra. Fe3O4/Au nanoparticles showed higher efficiency in photo-degradation of malathion than Fe3O4 ones.

Selective Electrochemical Detection of Epinephrine Using Gold Nanoporous Film

Epinephrine (EP) is one of the important catecholamine neurotransmitters that play an important role in the mammalian central nervous system. Therefore, it is necessary to determine the change of its concentrations. Nanoporous materials have wide applications that include catalysis, energy storages, environmental pollution control, wastewater treatment, and sensing applications. These unique properties could be attributable to their high surface area, a large pore volume, and uniform pore sizes. A gold nanoporous layer modified gold electrode was prepared and applied for the selective determination of epinephrine neurotransmitter at low concentration in the presence of several other substances including ascorbic acid (AA) and uric acid (UA). The constructed electrode was characterized using scanning electron microscopy and cyclic voltammetry. The resulting electrode showed a selective detection of epinephrine with the interferences of dopamine and uric acid over a wide linear range (from 50 źM to 1 mM). The coverage of gold nanoporous on the surface of gold electrode represents a promising electrochemical sensor with high selectivity and sensitivity.

Comparison of an Indirect Format ELISA on Modified Graphite and Polystyrene Surfaces against Triazines

An indirect format enzyme-linked immuno-sorbent assay (ELISA) on graphite rods (Ø 0.8 mm x 20 mm) and, for comparison, on microtiter plates has been developed against terbuthylazine. For this purpose, a series of 2-aminoalkyl-4-chloro-6-terbuthyl-s-triazine-2,6- diamine ELISA haptens with alkyl spacer lengths of 2, 4, 6, and 8 CH2 groups has been synthesized. The graphite rods or the microtiter plates were covered by a polymerized glutaraldehyde network, and the ELISA haptens have been coupled by imino coupling to the free aldehyde groups of that network. ε-Aminocaproic acid has been used as an agent to block unspecific binding sites. The ELISA was run in a competitive mode, where the immobilized ELISA hapten and the solute terbuthylazine as a target analyte compete for the solute antibody.

Ni(II), Co(II), and Cu(II) Ternary Complexes Containing 2,4,6‐tris(2‐Pyridyl)‐1,3,5‐triazine as Primary Ligand and Dithiooxamide, Thiosemicarbazide as Secondary Ligands

A series of novel dinuclear, mixed‐ligand complexes having the general formula [M2(tpt)(L)4]Cl4 · nH2O where M=Ni(II), Co(II) or Cu(II); tpt = 2,4,6‐tris(2‐pyridyl)‐1,3,5‐triazine; L = dithiooxamide (dto) or thiosemicarbazide (tsc); n = 2–4, have been synthesized and characterized. The tpt molecule is flexidentate, where it can behave as di‐ or tridentate dinucleating ligand. The coordination mode of tpt to M(II) apparently occurs through the pyridyl and a triazine nitrogen atoms. All the mixed‐ligand complexes are dinuclear with a bridging tpt molecule and having an octahedral structure. The complexes were characterized by chemical analyses, spectral, molar conductance and thermal studies.

Green synthesis of magnetic mesoporous silica nanocomposite and its adsorptive performance against organochlorine pesticides

Green synthesis of nanomaterials has received increasing attention as an eco-friendly technology in materials science. Here, we have used two types of extractions from green tea leaf (i.e., total extraction and tannin extraction) as reducing agents for a rapid, simple and one-step synthesis method of mesoporous silica nanoparticles/iron oxide nanocomposite based on deposition of iron oxide onto mesoporous silica nanoparticles. Mesoporous silica nanoparticles/iron oxide nanocomposite were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, energy-dispersive X-ray, vibrating sample magnetometer, N2 adsorption and high-resolution transmission electron microscopy. Mesoporous silica nanoparticles/iron oxide nanocomposite was used as a solid adsorbent for removal of lindane pesticide from aqueous solutions. The developed system possesses the advantages of silica as core that include large surface area and advantages of iron oxide (shell) that include the capability to interact with chlorinated compounds and ability to release by using external magnetic field. UV-Vis technique was used as a simple and easy method for monitoring the removal of lindane. Effects of pH and temperature on the removal efficiency of the developed mesoporous silica nanoparticles/iron oxide nanocomposite toward lindane pesticide were also investigated. Fourier transform infrared spectroscopy, high-performance liquid chromatography and gas chromatography techniques were used to confirm the high ability of mesoporous silica nanoparticles/iron oxide nanocomposite for sensing and the capture of lindane molecules with high sorption capacity (about 99%) that could develop a new eco-friendly strategy for detection and removal of pesticide and as a promising material for water treatment.

Development of a new immunosensor for the detection of dopamine.

Graphite immunoelectrodes as immunosensors using indirect immobilization of a hapten were investigated for their applicability to detect dopamine hydrochloride at low levels. Conditions were optimized to achieve the highest sensitivity using the indirect immobilization of dopamine hydrochloride through a polymerized glutaraldehyde network on microtiter plates using ELISA technique. The conditions were later transferred to the graphite rods (ø 0.8 m × 20 mm) and a comparison between the two different sensitivities (IC50 midpoint of test) was carried out. Graphite electrodes showed higher sensitivity towards dopamine than ELISA, since they were able to detect dopamine with a midpoint of test of 0.2 mmol/l while using ELISA they were able to detect dopamine hydrochloride at 2 mmol/l