Vol 1 No 2 (2019)

Published: 2019-10-16

Abstract views: 1869   PDF downloads: 1040  

Page 112-117

Synthesis of M­­­­­­₁₋₃ₓAl₂O₄:Eu²⁺ₓ/Dy³⁺₂ₓ (M²⁺= Sr²⁺, Ca²⁺ and Ba²⁺) phosphors with long-lasting phosphorescence properties via co-precipitation method

blankpage Jinkai Li, Bin Liu, Qi Chen, Yizhong Lu, Zongming Liu

The long afterglow fluorescent material of M1-3xAl2O4:Eu2+x/Dy3+2x (M2+ = Sr2+, Ca2+ and Ba2+) phosphors are successfully synthesized by calcining precursor obtained via co-precipitation method at 1300 oC for 4 h with reducing atmosphere (20% H2 and 80% N2. The phase evolution, morphology and afterglow fluorescent properties are systematically studied by the various instruments of XRD, FE-SEM, PLE/PL spectroscopy and fluorescence decay analysis. The PL spectra shows that the Sr1-3xAl2O4:Eu2+x/Dy3+2x phosphors display vivid green emission at ~519 nm (4f65d1→4f7 transition of Eu2+) with monitoring of the maximum excitation wavelength at ~334 nm (8S7/26IJ transition of Eu2+), among which the optimal concentration of Eu2+ and Dy3+ is 15 at % and 30 at %, respectively. The color coordinates and temperature of Sr1-3xAl2O4:Eu2+x/Dy3+2x phosphors are approximately at (~0.27, ~0.57) and ~6700 K, respectively. On the above basis, the M0.55Al2O4:Eu2+0.15/Dy3+0.3 (M2+ = Ca2+ and Ba2+) phosphors is obtained by the same method. The PL spectra of these phosphors shows the strongest blue emission at ~440 nm and cyan emission at ~499 nm under ~334 nm wavelength excitation, respectively, which are blue shifted comparing to Sr1-3xAl2O4:Eu2+x/Dy3+2x phosphors. The color coordinates and temperatures of M0.55Al2O4:Eu2+0.15/Dy3+0.3 (M2+ = Ca2+ and Ba2+) phosphors are approximately at (~0.18, ~0.09),~2000 K and (~0.18, ~0.42), ~11600 K, respectively. In this work, long afterglow materials of green, blue and cyan aluminates phosphors with excellent properties have been prepared, in order to obtain wide application in the field of night automatic lighting and display.

Abstract views: 1822   PDF downloads: 997  

Page 108-111

Pulsed light treatment in food

blankpage Jessika Gonçalves dos Santos Aguilar

Currently, there is a necessity for new technologies that are less harmful to the environment. Consumers have become increasingly demanding towards the quality of the processed products they consume as well as their environmental impact. Pulsed light (PL) technology is a green technology capable of maintaining food quality and safety without impairing nutritional value. PL has been used in the treatment of different food and its constituents. This mini-review aims to describe the basic principle of PL functioning as well as provide examples of the newest applications in the food industry.

Abstract views: 1405   PDF downloads: 824  

Page 102-107

Morphological stability of worm-like vesicles consisting of amphiphilic diblock copolymer against external stress

blankpage Eri Yoshida

The morphological stability of vesicles consisting of an amphiphilic poly(methacrylic acid)-block-poly(methyl methacrylate-random-methacrylic acid) diblock copolymer, PMAA-b-P(MMA-r-MAA), was investigated against the external stresses of pH, salt concentration and polyamine.  The worm-like vesicles underwent a partial fusion at pH 12, however, they retained the worm-like shape at pH 13 due to electrostatic repulsion.  On the other hand, the spherical vesicles were completely fused at pH 12, transformed into a sheet and did not retain their shape under the higher basic condition.  Similarly, the worm-like vesicles retained their morphology in 0.1-mol% solutions of sodium chloride and sodium dodecyl sulfate, while the spherical vesicles caused division and fusion even at much lower concentrations.  Poly(2-dimethylaminoethyl methacrylate) (PDMAEMA) transformed the worm-like vesicle into a cleavable sheet, while it changed the spherical vesicles into a sheet without a specific form.  It was found that this transformation based on the acid-base interaction between the carboxylic acid of the MAA block and the amine of the PDMAEMA was dependent on the molecular weight of the PDMAEMA.  The short PDMAMA retarded the fusion of the vesicles.

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Page 77-80

Diffusion transport of Ca(NO₃)₂ aqueous solution in porous glass membranes

blankpage Vyacheslav N. Pak, Yulia Yu. Gavronskaya

 Diffusion coefficients of Ca(NO3)2 in its passage through the set of porous glass membranes at 20–70oC were determined and discussed in terms of the structuring of the water boundary layers near the silica surface.

Abstract views: 1578   PDF downloads: 880   HTML downloads: 337  

Page 67-76

Magnetite nanoparticles coat around activated γ-alumina spheres: A case of novel protection of moisture-sensitive materials against hydration

blankpage Jaroslav Kupčík, Petr Mikysek, Dana Pokorná, Radek Fajgar, Petra Cuřínová, Karel Soukup, Josef Pola

Protection of various materials against hydration is of continuing interest to chemists and material scientists. We report on stabilization of porous surface of activated γ-alumina spheres (AAS) against hydration by an adhesive coat of nano-magnetite particles. The nano-Fe3O4-coated AAS were prepared in the ultrasound-agitated suspension of magnetite nanoparticles in heptane and were characterized by using X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM), BET surface area analysis and X-ray photoelectron spectroscopy (XPS). It is deduced that nanoparticle-alumina bonding interaction in non-polar organic solvent is enhanced by van der Waals attractive forces and that sonication induces changes in alumina morphology only in regions of contact between alumina and magnetite nanoparticles. The coated AAS submerged in still water avoid hydration and remain permeable by small gaseous (N2) molecules, while those soaked in moving water lose part of their coat and undergo hydration. The pristine and the coated AAS were briefly compared for their ability to degrade model antibiotics by using LC-MS analysis. It is confirmed that the degradation of trimethoprim is more efficient on the coated AAS. Our results are challenging for further research of Coulombic interactions between nano-particles and appropriate solid supports.

Abstract views: 1361   PDF downloads: 852   HTML downloads: 564  

Page 58-66

Study of impregnated cellulose thermal treatment process and properties of obtained active carbon

blankpage Nina K. Luneva, Tatiana I. Ezovitova, Viacheslav V. Shevchuk, Alexander A Ratko

Single-stage process of obtaining active carbon by thermal processing of plant raw materials (mixture of different types of wood sawdust), impregnated with the mixture of phosphoric acid, urea and nitric acid salts has been developed. Active influence of impregnates on the process of carbonization and formation of carbon residue has been formed. It is established that carbon residue obtained in the interval of heating 20°С–(500°С–700)°С, possesses high sorption activity to the vapors of organic compounds and has ion-exchange capacity. It has been showed that the value of carton residue depending on the impregnate used in the wood increases compared to the yield of non-treated initial raw materials by 3.1 times at 600°С and by 4.2 times at 700°С.

Abstract views: 2836   PDF downloads: 975   HTML downloads: 633  

Page 1-7

Azo-dye adsorption activity of iron(III) loaded novolac-based network sorbents

blankpage Samaresh Ghosh, Mridula Acharyya

Iron(III) loaded novolac-based network adsorbents 1 and 2 were studied for efficient removal of azo-dye pollutants from aqueous solutions. The adsorption behavior was evaluated by using methyl orange and orange-G as model azo dyes. The effect of parameters such as contact time and initial dye concentration on the adsorption of azo dyes was studied. The results showed that loading of Fe(III) onto the sorbent networks has noticeable effect on azo-dye sorption capacity. The adsorption equilibrium data were fitted to Freundlich isotherm model. Besides, the reusability of the dye loaded sorbents was investigated on adjusting pH of solutions.

Abstract views: 2877   PDF downloads: 1704  

Page 81-101

Recent progress on electrochemical production of hydrogen peroxide

blankpage Aniqa Sehrish, Romana Manzoor, Kai Dong, Yuanyuan Jiang, Yizhong Lu

Hydrogen peroxide (H2O2), first synthesized in 1818 through the acidification of barium peroxide (BaO2) with nitric acid, is a clear and colorless liquid which is entirely miscible with water and variety of organic solvents such as carboxylic esters. Anthraquinone process (an old production process of H2O2), a batch process carried out in large facilities is an energy demanding process that requires large facilities, and involves oxidation of anthraquinone molecules and sequential hydrogenation. Moreover, the direct synthesis method enables production in a continuous mode as well as it permits small scale, decentralized production. Many drawbacks associated with these processes such as, energetic inefficiency and inherent disadvantages have motivated researchers, industry and academia to find out alternative for synthesis of H2O2. Electrochemical route based on catalyst selectively reduce oxygen to hydrogen peroxide. O2 is cathodically reduced to produce H2O2 via 2-electron pathway or 4-electron pathway to get H2O. Electrolysis of water has an important place in storage and electrochemical energy conversion process where problem is to choose a sufficiently stable and active electrode for anodic oxygen evolution reaction. Most commonly used catalysts on the cathode are carbon based materials such as carbon black, carbon nanotubes, graphite, carbon sponge, and carbon fiber. In perspective of expanding demand of production and usage of hydrogen peroxide we review the past literature to summarize different production processes of H2O2. In this review paper, we mainly focus on electrochemical production of hydrogen peroxide along with other alternatives such as, anthraquinone method for industrial H2O2 production and direct synthesis process. We also review the catalytic activity, selectivity and stability for enhanced yield of H2O2. From revision of experimental and theoretical data from the past literature; we argue that successful implementation of electrochemical H2O2 production can be realized on the basis of stable, active and selective catalyst.