Synthesis of palladium nanoparticles on organically modified silica: Application to design of a solid-state electrochemiluminescence sensor for highly sensitive determination of imipramine

Organically modified silica substrate containing amine and vinyl functional groups were used for reduction and stabilization of palladium nanoparticles. Uniform spherical nanoparticles of palladium with average diameter of 10 nm were formed on silica substrate by direct contact of the substrate with an aqueous solution of palladium precursor, without the addition of any chemical reducer. Moreover, a sensitive and selective solid state electrochemiluminescence sensor was fabricated for the determination of imipramine, based on Ru(bpy)₃²⁺-palladium nanoparticles doped carbon ionic liquid electrode. In this process, imipramine acts as a co-reactant for Ru(bpy)₃²⁺. It is believed that the enhancement of the electrochemiluminescence signal in the presence of palladium nanoparticles in the composite is due to palladium catalytic effect on electrochemical and also chemical process involved in formation of Ru(byp)₃²⁺*. In addition, the results confirmed that, the rigid composite electrode shows the characteristic of microelectrode arrays. The proposed method was applied to the determination of imipramine in tablets and urine samples. The electrochemiluminescence intensity showed good linearity with the imipramine concentration from 1–100 pM, with a detection limit of 0.1 pM.     

The Effect of Lateral Guiding Mechanism on Noise Characteristics in Semiconductor Lasers

A comparison between intensity noise spectra and also the line shapes of gain-guided, weakly-index-guided, and strongly-index-guided semiconductor lasers are made using numerical solution of Maxwell-Bloch equations including spontaneous emission noise.     

Flotation-separation and ICP-AES determination of ultra trace amounts of copper, cadmium, nickel and cobalt using 2-aminocyclopentene-1-dithiocarboxylic acid.

A rapid flotation method for separation and enrichment of ultra trace amounts of copper(II), cadmium(II), nickel(II) and cobalt(II) ions from water samples is established. At pH 6.5 and with sodium dodecylsulfate used as a foaming reagent, Cu2+, Cd2+, Ni2+ and Co2+ were separated simultaneously with 2-aminocyclopentene-1-dithiocarboxylic acid (ACDA) added to 1 l of aqueous solution. The proposed procedure of preconcentration is applied prior to the determination of these four analytes using inductivity coupled plasma-atomic emission spectrometry (ICP-AES). The effects of pH, concentration of ACDA, applicability of different surfactants and foreign ions on the separation efficiency were investigated. The preconcentration factor of the method is 1000 and the detection limits of copper(II), cadmium(II), nickel(II) and cobalt(II) ions are 0.078, 0.075, 0.072 and 0.080 ng ml(-1), respectively.     

Development of an optode membrane for high pH values

The development of an optical pH sensor for high pH values is described based on the immobilization of Aniline Blue on an optically transparent triacetylcellulose membrane. The membrane is useful for repetitive and reversible pH measurements in the pH range of 8.8-13. The relative standard deviation is about 1.6% and 2% for seven measurements of the maximum change at 579 nm from pH 9 to 10.8 and from pH 11.1 to 12.8, respectively. Other advantages of the sensor include rapid equilibration time, long term stability, reversibility, high sensitivity, freedom from interference of other cations and ease of fabrication.     

Zeolite/Fe3O4 as a new sorbent in magnetic solid‐phase extraction followed by gas chromatography for determining phthalates in aqueous samples

In the present study, for the first time, we successfully employed zeolite/Fe₃O₄ as a new magnetic nanoparticle sorbent in magnetic solid‐phase extraction for determining phthalates in aqueous samples. Gas chromatography with flame ionization detection was used to detect the target analytes as a powerful instrumental analysis. Affecting parameters in the extraction process, including the amount of adsorbent, adsorption and desorption time, and volume of desorption solvent, were optimized using a response surface methodology based on central composite design. Under the optimum conditions, the linear range for dibutyl phthalate and bis(2‐ethylhexyl phthalate) was varied in the interval of 10–1700 and 10–1200 μg/L, respectively. Limits of detection were 2.80 μg/L for dibutyl phthalate and 3.20 μg/L for bis(2‐ethylhexyl phthalate). The recovery value for the extraction of target analytes was between 97 and 111%. The repeatability and reproducibility of the new proposed method were obtained: 10–13% and 13–13.5%, respectively. The increased sensitivity in using the proposed method has been demonstrated. Compared with previous methods, the new proposed method is an accurate, rapid, and reliable sample‐pretreatment method.     

Nanofibrous Tubular Membrane for Blood Hemodialysis

As the most important components of a hemodialysis device, nanofibrous membranes enjoy high interconnected porosity and specific surface area as well as excellect permeability. In this study, a tubular nanofibrous membrane of polysulfone nanofibers was produced via electrospinning method to remove urea and creatinine from urine and blood serums of dialysis patients. Nanofibrous membranes were electrospun at a concentration of 11.5 wt% of polysulfone (PS) and dimethylformamide (DMF)/tetrahydrofuran (THF) with a ratio of 70/30. The effects of the rotational speed of collectors, electrospinning duration, and inner diameter of the tubular nanofibrous membrane on the urea and creatinine removal efficiency of the tubular membrane were investigated through the hemodialysis simulation experiments. It was found that the tubular membrane with an inner diameter of 3 mm elecrospun at shorter duration with lower collecting speed had the highest urea and creatinine removal efficiency. The hemodialysis simulation experiment showed that the urea and creatinine removal efficiency of the tubular membrane with a diameter of 3 mm were 90.4 and 100%, respectively. Also, three patients’ blood serums were tested with the nanofibrous membrane. The results showed that the creatinine and urea removal rates were 93.2 and 90.3%, respectively.     

Determining the effect of centrifugal and electrical forces on the jet behaviors,the nanofiber structure,and morphology

The increasing demand for nanofibers production has led to the rapid growth of the usage of electro‐centrifugal spinning (ECS) systems especially in recent years. Besides the rapid developments, fabrication of novel fibrous materials with novel techniques is still under investigation. Polyvinylepyrrolidone (PVP) is one of the multifunctional materials, which has attracted scientific interests to be employed in a variety of advanced applications. The main objective of the present study was therefore to explore the effects of essential parameters involved in fabrication of PVP nanofibers via an ECS system. The effects of rotational speed (197‐4051 r/min) and applied voltage (0‐14 kV) on the structural and morphological properties of nanofibers were also investigated. Analyses of the scanning electron microscope (SEM) images were performed with Digimizer and SPSS16.0 software to characterize the diameter distribution of the nanofibers. The degree of crystallinity was evaluated by the X‐ray diffraction method. In order to explain the unexpected results, further investigations were performed on the motion of the jet and flow rate. The results showed that instead of nanofibers, microparticles were formed at lower voltages and rotational speeds. The increase in the applied voltage resulted in a decrease in the minimum rotational speed that is required to form continuous fluid jet. The bending instabilities were changed from whipping to spiraling at the voltages above 10 kV. This resulted in the minimum fiber diameter at a voltage between 6 and 10 kV. Moreover, the applied voltage slightly affected the degree of crystallinity. No significant change was observed in the degree of crystallinity by varying the rotational speed.     

Flow injection determination of cationic surfactants by using N-bromosuccinimide and N-chlorosuccinimide as new oxidizing agents for luminol chemiluminescence

Two highly sensitive chemiluminescence (CL) systems are described. The method is based on the CL generated during the oxidation of luminol by N-bromosuccinimide (NBS) and N-chlorosuccinimide (NCS) in alkaline medium. The emission intensity is reduced by the presence of some surfactants at concentrations lower than critical micelle concentration (cmc).A new, simple, rapid and selective flow injection CL method for the determination of cationic surfactants such as dodecyltrimethylammonium bromide (DTAB), cetyltrimethylammonium bromide (CTAB) and cetylpyridinium chloride (CPC) is proposed. Their determinations are based on the reducing effect on the emission intensity of NBS-luminol and NCS-luminol chemiluminescent reactions. The effect of analytical and flow injection analysis (FIA) variables on these CL systems and on the determination of the cationic surfactants are discussed. The optimum parameters for the determination of cationic surfactants were studied and were found to be the following: luminol, 1×10⁻⁶ M; NBS and NCS both, 5×10⁻² M; NaOH, 5×10⁻² M and flow rate, 3.5 ml min⁻¹.