نشریه علوم و فناوری رنگ
سال چهاردهم شماره 4 (پیاپی 54، زمستان 1399)

In this study, thyme extract was used for green synthesis of tin oxide nanoparticles on bentonite (SnO2 NPs@bent). The aqueous extract of thyme was applied as an effective reducing agent and a green stabilizer in this synthetic approach. SnO2 NPs@bent was characterized by various methods such as infrared Fourier spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray energy diffraction spectroscopy (EDS). After the assurance of the successful synthesis of tin oxide nanoparticles on bentonite, its photocatalytic activity was investigated for the degradation of the organic dye of eriochrome black T, under direct sunlight. The new catalyst exhibited a good catalytic activity, so that the related peak to the eriochrome black T in the UV spectrum decreased over time, until it disappeared completely after 5 hours. In this study, no chemicals or toxic solvents were used, neither in stage of the catalyst production nor in stage of the organic dye degradation, and all conditions were green and safe.

In this paper, mesoporous PAA/dextran-polyaniline core-shell nanofibers were prepared with the combination of electrospinning and in-situ polymerization methods and their heavy metal adsorption ability was investigated. The result showed that PAA and dextran can be fully crosslinked through the esterification reaction via a heat-treatment method. Polyaniline with flake-like structure was deposited on the nanofiber surface resulted in high surface area and mesoporous structure of nanofibers. The number of pores was increased by removing the calcium carbonate nanoparticles incorporated on the nanofiber surface during the polymerization process. Investigation of the variables affecting the adsorption process showed that the adsorption efficiency increased with increasing adsorbent and gradually reached a constant value. As the concentration of lead metal decreased, the percentage of removal decreased and the amount of removed metal varied at different pH values. HT-PAA / dextran nanofibers showed relatively high adsorption capacity for Pb, which increased to 951.1 mg / g after aniline polymerization on the surface of the nanofibers. The synthesized nanofibers showed a high maximum adsorption capacity of 1111.11 mg/g for Pb obtained from the Langmuir isotherm model.

Amaranth scientifically named Amaranthus celosia cristata belonged to Amaranthaceae is one of the plants which contains betalain pigments. In this study, after extraction of Amaranthus leaves by two solvents (methanol-water acidified and non-acidified) and two methods (dehydration and solid-liquid extraction), the stability of the selected extract was investigated under various conditions such as pH, temperature, light and darkness. The results of pH effect on extract stability showed that the highest adsorption was related to pH=5 and the lowest to pH=8. With increasing temperature (4 to 60°C), the extract stability decreased significantly. Moreover, increasing the incubation time of the extract at any temperature (except 4°C) caused a significant reduction in the stability of the extract (p <0.05). Storage of the extract in different light conditions (darkness, visible light and ultraviolet) for different periods of time showed that the highest stability was related to the dark conditions and increasing the storage time reduced the stability of the extract in each case. The results showed that the extract was more stable at temperatures below 25 °C, pH=5 and darkness. This natural colorant can be used in food products such as ice cream, ice syrup, yogurt, and in the coloring of easily-swallowed candy, sweets, and mid-cream.

In the last decade, carbon nanofibers have been considered as an effective adsorbent in the removal of water and wastewater pollutants due to their specific properties such as high surface area and length to diameter ratio. Increasing the surface porosity and surface area of special carbon nanofibers by physical and chemical activation methods have increased their efficiency in removing pollutants. In this study, the activated carbon nanofibers were produced in four steps of electrospinning of polyacrylonitrile solution in dimethylformamide as precursor, followed by stabilization, carbonization and physical activation of electrospun nanofibers. At each stage of production, by changing the parameters affecting the process and analyzing the final product with DSC, FTIR, XRD, SEM and BET tests, optimum production conditions were determined to achieve maximum stabilization, carbonization and activation efficiency. Finally, produced activated carbon nanofibers applied as an adsorbent in removal treatment dye solution and were able to absorb 20-37% more than other conventional adsorbents such as chitin and activated carbon.

In this study, a nanocomposite hydrogel was synthesized based on gelatin and nickel oxide nanoparticles using acrylamide (AAm) and 2-Acrylamido-2-methylpropane sulfonic acid (AMPS) by radical polymerization method. The reaction was performed in the presence of ammonium presulfate as an initiator and methylene bis acrylamide as a crosslinker. The structure of nanocomposite hydrogels were characterized by Fourier transform infrared spectroscopy (FT-IR), thermal gravimetric analysis (TGA), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Crystal violet was selected as a template for cationic dyes. The adsorption was optimized by changing various parameters such as contact time, temperature, pH, and initial concentration of dye. In optimal conditions, the maximum amount of dye adsorption from aqueous solutions at low concentrations (10 ppm) was approximately 97.5%, and at high concentrations (700 ppm) was about 99.5%. The results of this study showed that the hydrogels can be applied as efficient absorbent for the removal of cationic dyes from aqueous solutions. The adsorption process follows Langmuir isotherm model and pseudo second order kinetic.

In this work, three imidazole compounds were synthesized as fluorescent materials for organic light-emitting diodes (OLEDs). In the step, single and multi-layers OLEDs using imidazole compounds have been fabricated.  The highest luminous efficiency was observed with the compound (1). Diode fabricated with thiophene increased efficiency with respect to other compounds. Also, in the electroluminescence spectrum of the phenyl ring, electroplex emission was achieved. The results show that the color of devices depends on functional groups. The effect of various thicknesses (90,100 and 150 nm) on the electron mobility of devices with space-charge-limited current (SCLC) method was investigated. The highest mobility at the optimum thickness of 90 nm was achieved.

In this study, a 10% w/w PolyorthoAminophenol/Ferric oxide nanoparticle (PoAP / Fe3O4) nanocomposite film was chemically prepared, then a polymer mixture with other polymers such as polyvinyl alcohol (PVA), polyvinyl pyrolidone (PVP), polyvinylacetate (PVAc), pure polyacrylate (PA) and polyacrylate/styrene (PAS)  was prepared in N-methylpyrrolidone solvent. The results showed that the corrosion resistance behavior of the nanocomposite depends on the added polymer matrix, so that the best protection is obtained when pure polyacrylate is used PoAP / Fe3O4 nanocomposite is characterized by the use of scanning electron microscopy (SEM), infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) to determine the structure and morphology and magnetometry (VSM) to determine magnetic properties. Corrosion protection of coatings on stainless steel 304 metal in 3.5% sodium chloride solution was evaluated by electrochemical methods at ambient temperature. Corrosion test was performed with potentiostat-galvanostat apparatus with three electrodes.