Mahmood Kazemzad

A LANTHANIDE NANOPARTICLE-BASED LUMINESCENT PROBE FOR FOLIC ACID

AbstractWe report on a novel luminescent method for the detection of folic acid (FA), a member of the vitamin B family. Y2O3 nanoparticles were doped with europium(III) ions and surface-modified with captopril. Their fluorescence is quenched by FA, and intensity is a function of folic acid concentration in the 0.1 – 40xa0μM concentration range. The detection limit is 83xa0nM of FA at pH 7 and room temperature.n FigureIn this work, we propose a novel method based on the changes in the fluorescence intensity of nanoparticles. Modified Eu-doped Y2O3 nanoparticles by captopril have been used as a probe for the detection of folic acid.

CHROMATICITY DEPENDENCE ON Eu CONCENTRATION IN Y2O3:Eu NANOPOWDERS

Y2O3:Eu nanopowders were synthesized by urea combustion method containing different concentration of Eu. The synthesized Y2O3:Eu nanopowders were characterized by X-ray diffractometry, scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), energy dispersive X-ray analysis (EDX) and photoluminescence spectroscopy (PL). The particle size was calculated to be in the range of 15–30 nm using Scherrers formula. The Ia-3 structure of synthesized Y2O3:Eu nanopowders were confirmed with X-ray diffractometry. The crystallinity of Y2O3:Eu nanopowders were confirmed by SAED and TEM images. The 5D0–∑7FJ (J = 0, 1, 2, 3) and 5D1–7F1 transitions bands were observed at 575–650 and 530–550 ranges in the photoluminescence spectrum. The concentration quenching was estimated to be about 5 mol% of Eu. The best chromaticity to the standard red color was observed with the sample containing 3 mol% of Eu.

A norepinephrine biosensor based on a glassy carbon electrode modified with carbon nanotubes

Immobilized enzyme tyrosinase on single-walled carbon nanotubes (SWCNTs) was used to measure the norepinephrine concentration in injections. A simple method was investigated to prepare a modified glassy carbon (GC) electrode with CNTs. First, CNT solution was cast on the electrode surface and dried to form a CNT/GC electrode. Then, tyrosinase (TR) immobilized on the surface of the CNT/GC electrode. The cyclic voltammograms (CVs) in aqueous solution indicated that the CNTs could promote the direct electron transfer of tyrosinase and a pair of stable redox couple appeared. Tyrosinase can catalyze the oxidation of norepinephrine to norepinephrine quinone. When norepinephrine was added to the electrochemical cell, the oxidation peak current of the TR/SWCNT/GC electrode increased and gives a catalytic current. Based on this, a biosensor for determination of norepinephrine has been developed. This method had adequate accuracy, sensitivity and precision; in addition, the biosensor showed good repeatability and stability to assay norepinephrine in bulk form and pharmaceutical dosage forms.

Y2O3: Eu,Zn nanocrystals as a fluorescent probe for the detection of biotin

AbstractWe report on the application of nanocrystals (NCs) of the type Y2O3: Eu,Zn as a probe for the fluorescent detection of biotin in aqueous solution. The NCs were dispersed in water in the presence of various surface modifiers including mercaptoethanol (ME), monoethanolamine and ethylene glycol. Both the absorbance of surfactant and the stability of the suspensions were investigated in order to optimize the experimental conditions. ME is found to be the most suitable surfactant for stabilization of the suspended NCs. Their photoluminescence intensity is found to be quenched by biotin. The Stern-Volmer constant for the quenching process is 7.6u2009×u2009103xa0M−1. This NC probe can be applied to the detection of biotin in the 1–60xa0μM concentration range with detection limit of 1.89xa0μM. The possible mechanisms of quenching also are discussed.n FigurePhotograph of cuvettes containing the modified Y2O3: Eu, Zn NCs suspension with and without biotin before (A, B) and after (C, D) excitation with UV lamp (254xa0nm).

EFFECT OF STRONTIUM DOPING ON NANOSTRUCTURE AND CHROMATICITY OF Y2O3:Eu COMPOUNDS

In this work, various nano-sized samples of Y2O3, Y2O3:Eu and Y2O3:Eu, Sr were prepared by urea solution combustion method. Then the resultant nanopowders were investigated by means of X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FTIR) and photo-luminescence emission spectra. Furthermore, the CIE color coordinate of samples were calculated from photoluminescence emission spectra. Results showed that by doping of strontium, the photoluminescence intensity and chromaticity of Y2 O3:Eu phosphor was enhanced while crystallite size was decreased.

PREPARATION OF NICKEL OXIDE EMBEDDED SELF ORGANIZED TITANIA NANOTUBES ARRAY BY NEW ALGINATE METHOD AS A SUPERCAPACITOR ELECTRODE

Potentiostatic two step anodizing of titanium utilized for preparation of self organized titania nanotubes arrays with diameter of 150 nm. Then the new alginate method has been applied for incorporation of NiO into the nanotubes. The prepared hybrid materials have been characterized by various methods including field emission scanning electron microscopy, X-ray diffractometry and cyclic voltammetry analyses. The X-ray diffraction patterns of samples were also studied by Rietvelds method. Results showed that the prepared electrode containing anatase, rutile and NiO phases with fraction of 70, 8, and 22%, respectively. It was found that by application of the new method, porous NiO uniformly coated on nanotubes surface and great enhancement of specific capacitance from 0.14 to 3.8 mF cm-2 could be obtained. The prepared nanocomposites are promising materials for supercapacitance application and also for solar energy harvesting systems.

ELECTROCHEMICAL PREPARATION OF NEW ORGANOSILICONE COMPOUNDS FOR FUNCTIONALIZING OF MESOPOROUS SILICA

Electrochemistry has been introduced as a powerful tool in order to prepare new organometallic reagents for functionalizing of mesoporous silica. Preparation of the reagents was based on electrochemical oxidation of dihydroxybenzene derivatives in the presence of 3-(trimethoxysilyl)-1-propanethiol as a nucleophile. The mechanisms of electrochemical reactions were studied by voltammetric studies. Mesoporous silica SBA-15 was also synthesized in this work through sol-gel hydrothermal method using Genapol PF-10 as structure directing compound. The prepared mesoporous silica was characterized by FT-IR analysis and Barrett–Joiner–Halenda (BJH) pore size and Brunauer–Emmett–Teller (BET) surface area measurement methods using N2 adsorption–desorption isotherm. Finally, the organometallic reagent was covalently grafted on the surface of mesoporous silica. Functionalizing of this material with the new reagent was confirmed by Fourier transform infrared (FT-IR) spectroscopy. The functionalized mesoporous silica by new reagent can be utilized in biological applications.

Simultaneous control of rod length and pore diameter of SBA-15 for PPL loading

Mesoporous silica materials are attractive materials for immobilizing enzymes because of their well-ordered structures, large surface area are pore volume. Diffusion of large enzyme molecules such as porcine pancreatic lipase (PPL) through the lengthy channels of MPS takes place too slowly. Therefore, the squat of the enzyme at the pore mouth entrance, actually makes the rest of the channel useless. In this study, to overcome this problem, synthesis parameters of SBA-15 were changed, since along with pore diameter increasing, the mesochannel length becomes shorter. The main point to obtain a well-ordered 2D hexagonal pore structure was the pre-hydrolysis of tetraethyl orthosilicate (TEOS) before the addition of 1,3,5-trimethyl benzene as a micelle swelling agent. Due to the strong effect of zirconium in changing the morphology of SBA-15 particles, we modified SBA-15 in the presence of a small amount of ZrOCl2 in the synthesis solution under acidic conditions. As a result, mesochannel length of SBA-15-Zr was shortened from 600 to <200xa0nm. The morphology of mesoporous silica was also changed from rod-like to platelet, because of the accelerating effect of Zr(IV) on the self-assembly rate of P123 and TEOS condensation. Characteristic results conducted by low angle XRD, high resolution transmission electron microscopy and nitrogen adsorption, confirmed tuning effect of Zr(IV) in SBA-15. Furthermore, it was shown that the number of pore entrances increases with decreasing the length of SBA-15 mesochannels, leading to obvious improvement of enzyme uptake. PPL has been successfully immobilized in the mesoporous channels of SBA-15-Zr. The total amount of lipase adsorbed on the mesoporous SBA-15-Zr was measured by thermal gravimetric analysis. The largest PPL adsorption capacity was 784xa0mg/g belonging to the SBA-15-Zr with the length of 150xa0nm and the mean pore size diameter of 9.22xa0nm.

EFFECT OF pH ON THE ELECTRODEPOSITION OF Cu(In, Al)Se2 FROM AQUEOUS SOLUTION IN PRESENCE OF CITRIC ACID AS COMPLEXING AGENT

Effect of pH on the one-step electrodeposition of Cu(In, Al)Se2 chalcopyrite layer in the presence of citric acid has been investigated by applying different electrochemical and characterization techniques. It has been observed that at pH of 1.5, nanocrystalline phase of chalcopyrite and small amount of binary phase of Cu2Se with overall composition of Cu0.91In0.32Al0.39Se2 have been deposited. On the other hand, at pH of 4, the film composition changed to Cu1.9In0.05Al0.21Se2 and an additional binary phase of copper selenide (CuSe) has also been formed. Morphological investigation illustrated that smooth and compact layer with fine spherical particles having the size of ~20 nm has been obtained at pH of 1.5 whereas mixture of planar and spherical particles with size of 450–550 nm have been formed at pH of 4. In alkaline environment (pH~9), the deposition current has been noticeably decreased and no deposition occurred due to the formation of a stable complex of citric acid with metal ions. The mechanism of citric acid interaction with metal ions at different pH has also been studied by cyclic voltammetry measurement.

Preparation of activated carbon monolith by application of phenolic resins as carbon precursors

In the current work, activated carbon monoliths have been prepared by application of different phenolic hydrocarbons namely catechol and resorcinol as carbon precursors. For synthesis of carbon monolith, the precursors have been mixed with Genapol PF10 as template and then polymerized in the presence of lysine as catalyst. Then the polymerized monolith carbonized in inert atmosphere at 700 ○C and activated by water steam at 550 ○C. It was found that resorcinol polymerization is easier than catechol and occurred at 90○C while for polymerization of catechol elevated temperature of 120 ○C at hydrothermal condition is necessary. The prepared activated carbon samples have been characterized by various analysis methods including scanning electron microscopy (SEM), surface area measurement, and transmission electron microscopy (TEM). The adsorptions of three different aromatic hydrocarbons by the prepared activated carbon samples have also been investigated by high performance liquid chromatography (HPLC) and UV–Vis spectroscopy. It was found that carbon monolith prepared by catechol as carbon precursor has higher adsorpability and strength in comparison with the other sample. The higher performance of carbon monolith prepared by catechol can be associated with its higher active sites in comparison with resorcinol.