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A series of nitrogen-doped photoluminescent carbon dots (N-doped CDs) with a proper quantum yield was prepared through microwave-assisted pyrolysis of citric acid and urea as the carbon and nitrogen sources, respectively. The obtained N-doped CDs were fully characterized by high-resolution transmission electron microscopy, elemental analysis, Fourier transform infrared spectroscopy, and X-ray diffraction pattern. The average size of the synthesized N-doped CDs was determined using high-resolution transmission electron microscopy analysis was approximately 7 nm and the interlayer distance was 0.29 nm, which was consistent with the results obtained by X-ray diffraction. The optical characteristics of the samples were determined by UV-Vis and photoluminescent spectroscopy. The aqueous solution of N-doped CDs showed a multicolor emission wavelength, in the range of 350 to 650 nm, dependent on the nitrogen-doped percentage. With increasing the nitrogen percentage, the emission spectra, depending on the excitation wavelength, have one or two peaks in the green and blue regions, which can be considered in applications such as special bioimaging and related fields. [ABSTRACT FROM AUTHOR]

Abstract: Cobalt–zinc ferrite (Co0.8Zn0.2Fe2O4) was prepared by combustion method, using cobalt, zinc and iron nitrates. The crystallinity of the as-burnt powder was developed by annealing at 700°C. Crystalline phase was investigated by XRD. Using Williamson–Hall method, the average crystallite sizes for nanoparticles were determined to be about 27nm before and 37nm after annealing, and residual stresses for annealed particles were omitted. The morphology of the annealed sample was investigated by TEM and the mean particle size was determined to be about 30nm. The final stoichiometry of the sample after annealing showed good agreement with the initial stoichiometry using atomic absorption spectrometry. Magnetic properties of the annealed sample such as saturation magnetization, remanence magnetization, and coercivity measured at room temperature were 70emu/g, 14emu/g, and 270Oe, respectively. The Curie temperature of the sample was determined to be 350°C using AC-susceptibility technique. [ABSTRACT FROM AUTHOR]

Abstract: In this work zinc substituted cobalt ferrite nanoparticles (Co0.5Zn0.5Fe2O4) have been synthesized by the coprecipitation method, using stable ferric, zinc and cobalt salts with sodium hydroxide, at different solution temperatures, from room temperature to 363K. The cobalt–zinc ferrite crystalline phase, the particle size and the morphology of the resulting nanoparticles were studied by X-ray diffraction and transmission electron microscopy. The average crystallite size of each sample was calculated from the broadening of the most intense peak (311), using Scherrer''s formula and the results show crystallite sizes increased from 6 to 8nm by increasing the solution temperature from room temperature to 363K respectively. Room temperature VSM measurements show that the prepared nanoparticles have superparamagnetic behavior and did not saturate at maximum field of 800kA/m. The variation of AC-susceptibility of the samples with respect to temperature was measured and it was found that the blocking temperature increased from 198 to 270K by increasing the solution temperature from room temperature to 363K respectively. FTIR spectra of the samples have been analyzed in the frequency range 400–4000cm−1, which also confirms the results of XRD. [Copyright &y& Elsevier]

Abstract: In this work, Mn0.7Zn0.3Fe2O4 and Ni0.7Zn0.3Fe2O4 nanoparticles with super-paramagnetic properties and size distribution from 10 to 52nm were investigated. These particles were produced by a low-temperature solid-state reaction method without the ball-milling process. The size and morphology of the nanocrystallites were determined by X-ray diffraction, transmission electron microscopy and scanning tunneling microscopy methods. Magnetic measurements such as alternating gradient field magnetometers were used to justify the super-paramagnetic properties of these nanoparticles. Their microwave absorption in the range of 8–18GHz was studied by a vector network analyzer. Responses of the device under tests were studied. Also, the percentage of the resin, the size and thickness of the mount were determined. The band width of 2.3GHz was obtained with reflection-loss/written-loss of −16dB around 10.4GHz. [ABSTRACT FROM AUTHOR]