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Aug 2023 DOI 10.14302/issn.2377-2549.jndc-23-4461
Kripal RamCorresponding author
The synthesis of II-VI semiconductor nanocrystals doped with transition metal ions is particularly difficult. In the case of manganese doped CdSe nanocrystals produced via chemical route it is necessary to achieve small incorporation of manganese ions. The incorporation of manganese ions in CdSe nanocrystals has been confirmed by the study of Energy Dispersive Spectroscopy, Photoluminescence and Electron Paramagnetic Resonance spectra. The CdSe nanocrystals have cubic structure, the average crystallite size lies between 3-6 nm and increases with the variation of doping concentration of Mn2+ ions as characterized by X-ray diffraction. The structural properties of CdSe semiconductor nanocrystals are also studied by High Resolution Transmission Electron Microscopy, Scanning Electron Microscopy and UV- Visible Absorption Spectroscopy. The energy band gaps have been determined by UV/V is absorption study with the help of Tauc plot and are 2.54 eV, 2.27 eV and 2.24 eV as concentration of Mn2+ions in CdSe semiconductor nanocrystals increases from 0% to 0.75%. The crystallite size is also obtained from the UV-Visible absorption study; this varies from 1.69 to 1.78 nm with increase of Mn2+ concentration from 0% to 0.75% which is in agreement with X-ray diffraction result. Further, the magnetic and electronic properties of Mn2+ doped CdSe nanocrystals are studied using EPR spectra and the values of g factor, second-rank axial zero-field splitting parameter D and hyperfine parameter A are calculated. EPR measurements reveal that the dopant ions are incorporated in CdSe semiconductor nanocrystals.
Jun 2020 DOI 10.14302/issn.2689-2855.jan-19-3048
Yesigat AntenehCorresponding author
Addis Ababa University, Addis Ababa, Ethiopia
Superconductivity and magnetism were previously thought as incompatible until the discovery of some rare earth ternary compounds that shows the coexistence of superconductivity and magnetism. In some of the recently discovered iron based layered superconductors superconductivity and diamagnetic order system are coexist. That occurs in only 11 and 122 family. The present works we examine the possibility of coexistence of superconductivity and disorder of magnetic spin is called spin glass when freeze the system that can show the superconductivity and spin glass coexist. In this present work we can examine the possibility of coexistence of superconductivity and spin glass in detailed 11 family of Fe1+ySexTe1−x compound. We show that spin glass like behavior is present in FST for x = 0.1 - 0.15 we present evidence form magnetization measurement and characterized the short-range order with neutron scattering. One of our main results is that the short-range order is structural as well as magnetic order. The factor of magnetic order exchange in long range depend on temperature, pressure, number of doping and other external factor discussed it. We found mathematical expression for superconductor transition TC, spin glass temperature TgSusceptibility x(q), and retardation time τ using for born approximation and digamma function depend on wave vector(q) and cut off frequency(ω) in the region coexistence of superconductivity and spin glass in Fe1+ySexTe1−xcompound. Aim: To improve the coexistence of superconductivity and spin glass and to examine the associated Factor of electron doping and temperature in experimental and theoretical aspect of their coexistence.
Jan 2020 DOI 10.14302/issn.2689-2855.jan-19-2744
Kejian DengCorresponding author
Key Laboratory of Catalysis and Materials Sciences of the State Ethnic Affairs Commission & Ministry of Education, South-Central University for Nationalities, Wuhan, 430074, Hubei, China
In order to distinguish the roles of four types of nitrogen species in oxygen reduction reaction, the ketoamine condensation reactions between the ketone group of graphene oxide and amidogen of aniline and o-phenylenediamine were employed to generate –C=N- bond at the edge of graphene nanoplatelets, and then nitrogen-doped graphene nanoplatelets with pyrrolic N, pyridinic N and pyridinic N+-O- rather than graphitic nitrogen were obtained by post thermal treatments. The resulting catalysts were characterized by X-ray diffraction analysis, X-ray photoelectron spectroscopy and electrochemical measurements. It is found that edge-selectively nitrogen-doped graphene nanopaltelets with nitrogen content of up to 4.28 atom% have been prepared. Nitrogen doping helps to improve activity of oxygen reduction reaction slightly, suggesting nitrogen doping at the edge of graphene does not contribute a lot to the enhancement of activity.