Yadolah Ganjkhanlou

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.

Modified Eu-doped Y2O3 nanoparticles as turn-off luminescent probes for the sensitive detection of pyridoxine

Europium-doped yttrium oxide nanoparticles (Y2 O3 :Eu NPs) modified by captopril were prepared in aqueous solution. In this study, we report the effect of pyridoxine hydrochloride on the photoluminescence intensity of Y2 O3 :Eu NPs in pH 7.2 buffer solution. By increasing the pyridoxine concentration, the luminescence intensity of Y2 O3 :Eu NPs is quenched. The results show that this method demonstrates high sensitivity for pyridoxine determination. A linear relationship is observed between 0.0 and 62.0 μM with a correlation coefficient of 0.995 and a detection limit of 0.023 μM.

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.

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.

EFFECT OF SURFACTANTS ON THE SIZE, COLOR, PHOTOLUMINESCENCE AND RESISTIVITY OF INDIUM TIN OXIDE NANOPARTICLES PREPARED BY CO-PRECIPITATION METHOD

Indium tin oxide (ITO) nanoparticles were synthesized by co-precipitation method using ammonia as a precipitator in absence/presence of various surfactants (LABS and Triton X-100). The synthesized nanoparticles were investigated by scanning electron microscopy, resistance measurement, photoluminescence (PL) spectroscopy and X-ray diffractometry (XRD) techniques. The XRD patterns of nanoparticles were also studied by Rietveld refinement method for calculation of crystallite size, micro-strain and lattice parameter. The results indicate that by application of LABS and Triton X-100 as surfactant the particle size was increased. Two luminescence bands were observed in PL spectra of ITO nanoparticles with the excitation energy lower than their band gaps. It was found that the ratios of luminescence bands have relation with resistances and colors of ITO nanoparticles. In addition, the band structure of ITO nanoparticles was described considering the obtained results.

EFFECT OF Zn ADDITION ON LUMINESCENCE OF Y2O3:Eu NANOPOWDERS USING SOLUTION COMBUSTION METHOD

In this study, the effect of Zn doping on photoluminescence, Chromaticity and structural properties of Y2O3:Eu compound were studied. For this purpose, various Y2O3:Eu samples containing different Zn2+ concentration and distribution were prepared by combustion method. The resultant samples were characterized by X-ray diffractometry (XRD), Photoluminescence spectroscopy (PL) and scanning electron microscopy (SEM). The XRD patterns of samples were also examined by Rietveld refinement method and results showed that the samples had nano-sized crystallites. It has been also shown that doping of Zn2+ ion in structure of Y2O3:Eu compound can effectively enhance the PL intensity and chromaticity of Y2O3:Eu compound, while doping of Zn at surface of Y2O3:Eu powder reduces PL intensity, crystallinity and chromaticity of this compound.