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Synthesis of maghemite (γ-Fe2O3) nanoparticles by thermal-decomposition of magnetite (Fe3O4) nanoparticles

Abstract

In this research work, we prepared γ-Fe2O3 nanoparticles by thermal-decomposition of Fe3O4. The Fe3O4 nanoparticles were synthesized via co-precipitation method at room temperature. This simple, soft and cheap method is suitable for preparation of iron oxide nanoparticles (γ-Fe2O3; Fe3O4). The samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), vibrating sample magnetometer and differential scanning calorimeter (DSC). The XRD and FT-IR results indicated the formation of γ-Fe2O3 and Fe3O4 nanoparticles. The TEM images showed that the γ-Fe2O3 and Fe3O4 were spherical, and their size was 18 and 22 nm respectively. Magnetic properties have been measured by VSM at room temperature. Hysteresis loops showed that the γ-Fe2O3 and Fe3O4 nanoparticles were super-paramagnetic.

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Evaluation of the acid properties of aluminossilicate MCM-22 material synthesized under static conditions

Abstract

The hydrothermal synthesis of MCM-22 zeolite was carried out using silica, sodium aluminate and hexamethyleneimine, under static conditions at 150 °C for a period of 10 days, followed by washing with deionized water, drying overnight and calcination at 650 °C. The obtained material was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The XRD analysis evidenced that MCM-22 presented a well defined MWW structure. The FT-IR spectrum confirmed the efficiency of the hexamethyleneimine as an organic template used to direct the structure of the MCM-22 zeolite under static conditions. The SEM image indicated that the particles are spherical in shape, with a diameter of ca. 10 μm. The acid properties of the MCM-22 zeolite, as determined by n-buthylamine adsorption, were investigated in the temperature ranges of 105 to 300 °C and 300 to 525 °C, relative to medium and strong acid sites, respectively.

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Synthesis and characterization of indium tin oxide nanoparticles via reflux method

Abstract

Synthesis of indium tin oxide (ITO) nanoparticles by reflux method without chlorine contamination at different pHs, temperatures, solvents and concentrations has been studied. Indium chloride, tin chloride, water, ethanol and Triton X-100 were used as starting materials. Structure, size, surface morphology and transparency of indium tin oxide nanoparticles were studied by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and UV-Vis spectrophotometry. XRD patterns showed that 400 °C is the lowest temperature for synthesis of ITO nanoparticles because metal hydroxide does not transform to metal oxide in lower temperature. FT-IR results showed the transformation of hydroxyl groups to oxide. SEM images showed that pH is the most important factor affecting the nanoparticles size. The smallest nanoparticles (40 nm) were obtained at pH = 8.8. The size of crystallites was decreased by lowering of concentration (0.025 M).

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Factors influencing preparation of polyaniline doped with hydrochloric acid

Abstract

Factors influencing the reaction of chemical polymerization during aniline doping with hydrochloric acid (HCl) have been studied in this work. The optimal parameters for the preparation of polyaniline were determined as follows: aniline concentration - 4 mass %, molar ratios of oxidant (NH4)2S2O8:aniline - 1.2:1 and 1.3:1, the concentration of dopant - 1 mol/L. Fourier transform infrared spectroscopy (FT-IR) was applied to characterize the structure of polyaniline.

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Studies of Zn-Al-Ce mixed oxides as catalysts for diesel soot combustion

Studies of Zn-Al-Ce mixed oxides as catalysts for diesel soot combustion

A series of Zn-Al-Ce mixed oxides was synthesized by a co-precipitation method. The obtained samples were characterized with respect to composition (XRF), structure (XRD, FT-IR) and texture (BET). Zn-Al-Ce mixed oxides were tested as catalysts of diesel soot combustion. The best catalytic activity was found for Zn2Ce oxide system, which operated in the temperature range of 350-500°C.

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Synthesis, Characterization and Synthetic Applications of Fly-ash:H3PO4 Nanocatalyst

Abstract

The solid acidic nanocatalyst fly-ash:H3PO4 was prepared and characterized by FT-IR, SEM, EDS and TEM analysis. This catalyst was utilized for aldol condensation, coupling and cyclization reaction. The effect of catalytic activity of this fly-ash:H3PO4 nanocatalyst was studied with the obtained yield of products under solvent-free conditions. In this synthetic reaction the obtained yields were more than 95 %.

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Lignosulfonate and silica as precursors of advanced composites

Abstract

Advanced silica/lignosulfonate composites were obtained using magnesium lignosulfonate and silica precipitated in a polar medium. For comparative purposes analogous synthesis was performed using commercial silica Aerosil®200. Lignosulfonates are waste products of paper industry and their application in new multifunctional materials is of great economic interest. The composites obtained were subjected to thorough characterization by determination of their physicochemical, dispersive-morphological and electrokinetic properties. Their particle size distribution was measured, SEM images were taken, FT-IR analysis and colorimetric study were made, thermal and electrokinetic stabilities and parameters of porous structure were also determined. The results can be of interest in further application studies

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Beyond Dinitrophenol Interaction with Tryptophan-Based Compounds

Abstract

The effects of 2,4-dinitrophenol (2,4-DNP) on the spectroscopic parameters (UV-Vis or FT-IR absorbance) or fluorescence emission of tryptophan and glycyl-tryptophan were studied. A quenching phenomenon of fluorescence was observed, attributed to interactions between the indole ring of the fluorophore and the aromatic ring of the quencher. The analysis of fluorescence spectra confirms that the quenching is dictated by 2,4-DNP concentration and pH. A combined mechanism of static and dynamic quenching was detected. The quenching phenomenon observed in this work could be employed to explain the mechanism of action of such compounds on large fluorescent peptides or proteins.

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Green synthesis of silver nanoparticles using tannins

[1] Gould I.R., Lenhard J.R., Muenter A.A., Godleski S.A. Farid S., J. Am. Chem. Soc., 122 (2000), 11934. http://dx.doi.org/10.1021/ja002274s [2] You C.C., Chompoosor A., Rotello V.M., Nano Today, 2 (2007), 34. http://dx.doi.org/10.1016/S1748-0132(07)70085-3 [3] Schimd G., Chem. Rev., 92 (1992), 1709. http://dx.doi.org/10.1021/cr00016a002 [4] Deheer W.A., Rev. Mod. Phys., 65 (1993), 611. http://dx.doi.org/10.1103/RevModPhys.65.611 [5

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Chemical modification of alginic acid by ultrasonic irradiation

]. Pereira, L., Sousa, A., Coelho, H., Use of FTIR, FT-Raman and 13C-NMR spectroscopy for identification of some seaweed phycocolloids, Biomolecular Engineering. 2003, 20, 223-228 [22]. Sartori, C, Finch, D. .S, Ralph B., Gilding, K. Polymer, 1997, 38 (1):43-51. [23]. Nivens, D. E., Ohman, D. E., Williamn, J., Franklin M. J., J Bacteriol. 2001;183:1047-57. [24]. Matsuhiro, B., Torres, S., Guerrero, J., Block structure in alginic acid from Lessonia vadosa (Laminariales, phaeophyta), J. Chil. Chem. Soc. 2007, 52, (1), 1-9.

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