PurposeTo evaluate the effect of flux, activator and co‐activator on solid state synthesis of SrAl2O4: Eu2 + , Dy3 +  phosphor, where boric oxide, europium oxide and dispersium oxide were used, respectively.Design/methodology/approachTo optimise synthesis condition of long lasting phosphorescence SrAl2O4 phosphor, boric oxide was used as a flux. To improve relative intensity of SrAl2O4: Eu2 +  phosphor, the critical concentration of Eu2 +  was determined. The effect of various concentration of co‐activator on afterglow properties, the effect of Dy3 +  ion on the emission and excitation spectra were examined.FindingsThe SrAl2O4: Eu2 + , Dy3 +  phosphor powders have been synthesised by solid state reaction method. The result of XRD patterns indicated that, addition of 5 mol% B2O3 enhanced the formation of SrAl2O4 at 1,200°C. Investigation on the variation of emission intensity of different phosphors containing different amounts of Eu2 +  revealed that after 6 mol% of Eu2 +  concentration, quenching process occurred. Dy3 +  formed trap levels and results demonstrated that increasing concentration of Dy3 +  up to 5 mol% reduced the relative intensity and increased the decay time.Originality/valueUsing B2O3 as a flux and solid state reaction method for preparation of this phosphor is in good agreement with industrial production and make it economic, because of reduced sintering temperature.

Purpose -The purpose of this paper is to study the effect of synthesis conditions on properties of TiO 2 nanoparticles to be used for photocatalysis and also producing TiO 2 using a low temperature method. Design/methodology/approach -TiO 2 nanoparticles were synthesised via a sol-gel method at low temperature and the effect of parameters such as: synthesis temperature, HNO 3 concentration, calcination temperature and synthesis time on properties of TiO 2 were studied. The effects of the physico-chemical properties of TiO 2 , its concentration and light intensity on photocatalytic properties of TiO 2 nanoparticles were investigated also. Findings -The results showed that TiO 2 with Anatase phase were formed at 80-1008C by using proper HNO 3 concentration, synthesis time and calcinations temperature. Calcinations programme and temperature and also the synthesis time affect the formation of TiO 2 crystalline phase (i.e. Rutile and Brookite), their surface area and crystallite size. To evaluate the photocatalytic properties of TiO 2 nanoparticles, fluorescein was used as a model molecule. Results showed that degradation of fluorescein could be described by pseudo-first order kinetics. The effect of TiO 2 concentration and light intensity on photocatalytic activity showed that increasing concentration of TiO 2 and the light intensity would increase the degradation of fluorescein. Originality/value -The method used in this work to prepare TiO 2 nanoparticles is an economic method for low temperature synthesis of TiO 2 nanoparticles with high photocatalytic activity, which could find numerous applications in coating technology.

Thin films of titanium dioxide with high surface area are prepared by sol-gel dip-coating technique. In this regards, Titania nano sols with high photocatalytic activity were prepared by dissolving titanium alkoxide in alcohol and water under acidic conditions. Photocatalytic activities of titanium dioxide thin films were measured in the presence of methylene blue. Microstructure and photocatalytic activity of the films, nanopowders and titanium dioxide sols were investigated using X-ray diffraction, scanning electron microscopy, specific surface area, zeta sizer and ultraviolet-visible spectrometry techniques. Particle size analysis of sols showed that the mean particle sizes were 15 to 128 nm. X-ray diffraction analyses revealed that anatase crystal structure was produced with crystallite size below 11 nm. Increasing mass percent of anatase phase and specific surface area, enhance the photocatalytic activity. Scanning electron microscopy images showed that the addition of methylcellulose as a dispersant, not only produced rough texture in the thin film, but also enhanced photocatalytic activity. The thin films prepared by using nitric acid as a stabilizer, revealed higher photocatalytic activity, surface area and sol stability and these data were more than those prepared with acetic acid.

PurposeThe purpose of this paper is to evaluate the effect of copolymer and starting material concentrations in homogeneous precipitation synthesis of Yttria nanoparticles and red‐emitting nanophosphors Y2O3:Eu3+. N‐isopropylacrylamide and acrylic acid (NIPAM/AAc) and urea are used.Design/methodology/approachTo optimise synthesis condition of Y2O3:Eu3+ nanophosphor NIPAM/AAc copolymer was used as a modifier and the effect of various concentration of yttrium ions, urea and precipitation time on size, morphology and emission spectra were investigated.FindingsUsing NIPAM/AAc copolymer shows significant improvement on size and dispersion of nanoparticles. It is found that yttrium concentration, varying between 0.006 and 0.03 M, has a profound impact on the average size of particles, which systematically increases from 65 to over 165 nm. The rate of precipitation reaction, however, is shown to be independent of yttrium concentration. In contrast, as urea concentration increases from 0.2 to 5 M, the average particle size exhibits a gradual decrease from 183 to 70 nm. At extremely high urea concentration such as 5 M, a significant level of inter‐particle agglomeration is observed.Originality/valueBased on this paper, the authors have successfully prepared some promising nanophosphors. The nanoparticles are studied by X‐ray diffraction, transmission electronic microscopy, zeta sizer, Infra red and photoluminescence spectroscopy.

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