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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]

Mn-Zn ferrites are widely interested in the application as current-compensated chokes due to their astounding features. In this study, nanocrystalline Mn-Zn ferrite (Mn0.8Zn0.2Fe2O4) was synthesized using the coprecipitation method. The structures and magnetic properties of the resulting powder were assessed using X-ray diffractometer (XRD), transmission electron micrographs (TEM), magnetic properties at room temperature (AGFM) and Curie temperature measurement. XRD pattern confirmed the formation of nanocrystalline Mn-Zn ferrite with average crystallite sizes in 11.3 nm. The magnetic measurements revealed that they have superparamagnetic behavior. The electromagnetic properties of these cores including the output voltage versus input voltage, quality factor and impedance versus frequency at four sintered temperatures were assessed. The results demonstrated that the fabricated smart core sintered at low temperature (800 °C) could efficiently be appropriate for work in a test frequency of 15 MHz. This encouraging feature suggests that it is worthwhile for application in modern switch-mode power supply modules. [ABSTRACT FROM AUTHOR]