Self-organization of an optomagnetic CoFe2O4-ZnS nanocomposite : preparation and characterization

We report an advanced method for the self-organization of an optomagnetic nanocomposite composed of both fluorescent clusters (ZnS quantum dots, QDs) and magnetic nanoparticles (CoFe2O4). ZnS nanocrystals were prepared via an aqueous method at different temperatures (25, 50, 75, and 100 degrees C). Their structural, optical and chemical properties were comprehensively characterized by X-ray diffraction (XRD), UV-vis, photoluminescence (PL) spectroscopy, scanning electron microscopy (SEM), dynamic light scattering (DLS), transmission electron microscopy (TEM), and infrared spectroscopy (FT-IR). The highest PL intensity was observed for the cubic ZnS nanoparticles synthesized at 75 degrees C which were then stabilized electrosterically using thioglycolic acid. The photophysical analysis of the capped QDs with a particle size in the range 9-25 nm revealed that the emission intensity and the optical band gap increases compared to uncapped nanocrystals (3.88 to 4.02 eV). These band gaps are wider than that of bulk ZnS resulting from the quantum confinement effect. Magnetic nanoparticles were synthesized via a co-precipitation route and a sol-gel process was used to form the functionalized, silica-coated CoFe2O4. Finally, thiol coordination was used for binding the QDs to the surface of the magnetic nanoparticles. The fluorescence intensity and magnetic properties of the nanocomposites are related to the ratio of ZnS and CoFe2O4. An optomagnetic nanocomposite with small size (12-45 nm), acceptable saturation magnetization (about 6.7 emu g(-1)), and satisfactory luminescence characteristics was successfully synthesized. These systems are promising candidates for biological and photocatalytic applications

The Exact Morphology of Metal Organic Framework MIL-53(Fe) Influences its Photocatalytic Performance

Controllable synthesis of Metal-organic frameworks (MOFs) with well-defined morphology, composition and size is of great importance towards understanding their structure-property relationship in various applications. Herein, the effect of morphology of photocatalysts on their optical behavior and photocatalytic efficiency was identified utilizing physical synthetic parameters for methylene blue removal. For this purpose, MIL-53(Fe) was fabricated as an efficient photocatalyst via solvothermal approach using chloride and nitrate salts as different secondary block unit (SBU) sources. Each of the powders obtained by two metal sources was synthesized at three different temperatures (120, 150, and 180 degrees C). The fabricated MOFs were methodically investigated and characterized in terms of structural, textural, morphological and optical. The obtained empirical data confirmed that the particles synthesized at 120 degrees C using iron chloride exhibit the highest efficiency for methylene blue removal. This could be associated to their high surface area and UV light absorption in comparison with other samples. These results can be considered in future research to maximize degradation of organic dyes as a serious pollutant in wastewater