Abd Khamim Ismail

Two-phase electrodriven membrane extraction combined with liquid chromatography for the determination of tricyclic antidepressants in aqueous matrices

A two-phase low-voltage electrodriven membrane extraction (EME) method combined with high performance liquid chromatography (HPLC) was developed for the determination of tricyclic antidepressants (TCAs) in aqueous matrices. Three TCAs, namely imipramine (IMI), amitriptyline (AMI) and chlorpromazine (CHLO) were used as target analytes. The drugs were extracted from aqueous sample solutions through a porous polypropylene membrane filter impregnated with 2-nitrophenyl octyl ether (NPOE) that served as a supported liquid membrane (SLM), and into an acceptor phase with a potential difference of 10 V applied over the SLM. EME parameters such as the type of organic solvent, the pH of sample solution, the extraction voltage, extraction time and stirring rate were evaluated and optimized. Optimal extractions were accomplished using NPOE as the organic solvent, a sample solution of pH 6, an extraction time of 10 min, and 10 V as the driving force with the whole assembly agitated at 1200 rpm. Under the optimized extraction conditions, the method demonstrated good linearity with coefficients of determination, r2 ≥ 0.9987 in the concentration range of 0.5–1000 µg L−1 for water, and 1.0–1000 µg L−1 for urine and good limits of detection in the range of 0.05–0.08 µg L−1 and 0.1–0.3 µg L−1 in water and urine samples, respectively. The method showed high enrichment factors in the range of 91–128 and high relative recoveries in the range of 98.4–103.1% and 86.7–107.4%, for water and urine samples, respectively with RSDs of <9.0% (n = 3). This method was successfully applied to the determination of the drugs in water and human urine samples. The proposed method offered good features such as simplicity, easy handling, fast extraction time, low voltage and minimum organic solvent consumption which meet the green chemistry concept.

The impact of AsH 3 overflow time and indium composition on the formation of self-assembled In x Ga 1 x As quantum dots studied by atomic force microscopy

We have performed atomic force microscopy to investigate the effect of various indium compositions and various AsH3 flow times during cooling on the formation of self-assembled InxGa1 − xAs quantum dots (QDs). The InxGa1 − xAs QDs were grown by metal-organic chemical vapour deposition using the Stranski-Krastanow (S-K) growth mode. The migration of group III species in the growth of InxGa1 − xAs QDs is influenced by the AsH3 flow during the cooling period due to the increasing surface population of the active arsenic species. It influences the size and density of the dots on the surface. For various indium compositions, an increase in InxGa1 − xAs QD density with increasing indium composition is observed. It indicates that the dot density depends on lattice parameters. The dot density is inversely proportional to surface diffusion (ρ ∝ R/D), with D = (2kT/h)/a2 exp(−ED/kT). In the growth of InxGa1 − xAs QDs using the S-K growth mode, the dots were formed on the surface as the effect of elastic strain relaxation due to the lattice mismatch. Increasing indium composition affects the lattice mismatch of the InxGa1 − xAs/GaAs QD system, which influences the dot formation on the surface. However, due to the stochastic nature of the nucleation of self-assembled growth, control of the spatial ordering of the QDs has proved to be extremely challenging.

Ionic liquid-impregnated agarose film two-phase micro-electrodriven membrane extraction (IL-AF-μ-EME) for the analysis of antidepressants in water samples

The aim of this study was to investigate and apply supported ionic liquid membrane (SILM) in two-phase micro-electrodriven membrane extraction combined with high performance liquid chromatography-ultraviolet detection (HPLC-UV) for pre-concentration and determination of three selected antidepressant drugs in water samples. A thin agarose film impregnated with 1-hexyl-3-methylimidazolium hexafluorophosphate, [C6MIM] [PF6], was prepared and used as supported ionic liquid membrane between aqueous sample solution and acceptor phase for extraction of imipramine, amitriptyline and chlorpromazine. Under the optimized extraction conditions, the method provided good linearity in the range of 1.0-1000μgL-1, good coefficients of determination (r2=0.9974-0.9992) and low limits of detection (0.1-0.4μgL-1). The method showed high enrichment factors in the range of 110-150 and high relative recoveries in the range of 88.2-111.4% and 90.9-107.0%, for river water and tap water samples, respectively with RSDs of ≤7.6 (n=3). This method was successfully applied to the determination of the drugs in river and tap water samples. It is envisaged that the SILM improved the perm-selectivity by providing a pathway for targeted analytes which resulted in rapid extraction with high degree of selectivity and high enrichment factor.

Study of silicon quantum dots structure growth using radio frequency magnetron sputtering

Nanodots, also known as quantum dots, consist of 100s–1000s of atoms of semiconductor nanoparticles and are approximately 10 – 100 nm in sizes. Silicon nanodots have, in particular, emerged over the last 10 years as a hot area of research due to the fact that a reduction in size of this semiconducting material to the nanometer scale dramatically alters their physical properties.

Rapid Determination of Non-steroidal Anti-inflammatory Drugs in Aquatic Matrices by Two-phase Micro-electrodriven Membrane Extraction Combined with Liquid Chromatography

Two-phase micro-electrodriven membrane extraction (EME) procedure for the pre-concentration of selected non-steroidal anti-inflammatory drugs (NSAIDs) in aquatic matrices was investigated. Agarose film was used as interface between donor and acceptor phase in EME which allowed for selective extraction of the analytes prior to high performance liquid chromatography-ultraviolet detection. Charged analytes were transported from basic aqueous sample solution through agarose film into 1-octanol as an acceptor phase at 9 V potential. Response surface methodology in conjunction with the central composite design showed good correlations between extraction time and applied voltage (R2 > 0.9358). Under optimized extraction conditions, the method showed good linearity in the concentration range of 0.5-500 μg L-1 with coefficients of determination, r2≥ 0.9942 and good limits of detection (0.14-0.42 μg L-1) and limits of quantification (0.52-1.21 μg L-1). The results also showed high enrichment factors (62-86) and good relative recoveries (72-114%) with acceptable reproducibilities (RSDs ≤ 7.5% n = 3). The method was successfully applied to the determination of NSAIDs from tap water and river water samples. The proposed method proved to be rapid, simple and requires low voltage and minute amounts of organic solvent, thus environmentally friendly.

Interdependencies of Critical Radius, Critical Energy and Surface Energy (CRESE) in Silicon Self-Assembled Nanodots

The interdependence parameters in the growth of silicon self-assembled nanodots are investigated. Accordingly, the critical radius, critical energy change and surface energy can be interpreted in terms of cubic function, where it produced a critical surface energy NS* and the corresponding r* and G*, called a CRESE point at a fixed growth temperature T when solved mathematically. It is defined as a limiting point at which equilibrium of the critical parameters take place at a constant temperature. Experiments were performed on the samples of amorphous silicon nanodots fabricated onto different non-crystalline substrates. A further analysis on the NS*-T plots revealed inverse linear relationships which converged at a CID point (o*,T*) when projected near the solidification temperature of silicon. The results suggested strong influence of atomic bonding at the nucleus-surface interface combined with higher surface roughness. In conclusion, there exists an equilibrium condition among the growth parameters which stabilizes the growth of amorphous silicon nanodots, as well as the existence of CRESE’s ideal destination (CID).

Stacked structures In 0.5 Ga 0.5 As/GaAs quantum dots: Growth and characterization

Stacked structures of self-assembled In0.5Ga0.5As/GaAs quantum dots (QDs) have been grown using Metal-Organic Chemical Vapor Deposition (MOCVD) with different number of stacks. High Resolution X-Ray Diffraction (HR-XRD) and Transmission Electron Microscope (TEM) characterization revealed that the formation of stacked self-assembled In0.5Ga0.5As QDs on GaAs (100) substrates were misaligned vertically and no visible defect has been detected from the cross-sectional TEM characterization. In addition, photoluminescence (PL) peak position is blue-shifted and PL intensity dramatically increased with increasing number of stacks. The peak and intensity of the PL measurement strongly depend on the structural of stacked self-assembled QDs and also the number of QDs layers.

Morphology and optical properties of self-assembled in0.5Ga 0.5as quantum dots with different spacer layer thickness

Uncapped double stacked In0.5Ga0.5As quantum dots (QDs) with different spacer layer thicknesses were grown using metal-organic chemical vapour deposition (MOCVD). The precursors used for the growth of the GaAs layer and In0.5Ga0.5As QDs were trimethylgallium (TMGa), trimethylindium (TMIn), and arsine (AsH3). The morphology and optical properties of the self-assembled In0.5Ga0.5As QDs were investigated and characterized using atomic force microscopy (AFM) and photoluminescence (PL). The AFM images revealed that the sizes of the dots on the topmost were not uniformly distributed. The average size of the dots fluctuated as the GaAs spacer layer thickness increased. A room temperature PL measurement was used to establish the quality and quantity of the stacked QDs. The PL peak position remained at 1148 nm for all samples of QDs; however, the PL intensity increased as spacer layer thickness increased. The structure of the spacer layer in the stacked QD affected the morphology of the topmost surface of the QDs. The PL measurement coherently reflected the AFM characterization, in which the strong PL spectra were caused by the uniformity and high density of the QDs. The surface morphology, structure, and optical properties of the stacked QDs are attributed to seed-layer (first layer) formation of dots and spacer layer structures.