No abstract

No abstract

No abstract

We report single-phase syntheses of undoped 2H-MoS2 as well as Mn and Fe doped MoS2 by a facile hydrothermal route. The formation of the 2H-MoS2 phase was confirmed by XRD and was corroborated with Raman spectra. The morphology of the doped and undoped MoS2 nanostructures comprised sheets, as revealed by TEM and STEM images. The fine granular structure was observed by high resolution TEM micrographs. The STEM-EDS results show dopant concentrations of ∼1 atom% corresponding to Mn and Fe in doped MoS2. The undoped MoS2 revealed diamagnetic behavior at room temperature and paramagnetic behavior in the range (100 to 300 K). The Mn-MoS2 sample displayed ferromagnetism below 20 K with a coercive field of ∼50 Oe. Such a sample may be utilized for magnetic switching purposes at low temperatures. The onset of the antiferromagnetic interaction was observed below 145 K in Fe-MoS2 samples. They have been understood in terms of long-range magnetic interactions amongst the dipole moments mediated via surface defects as well as the interaction between the dipoles and the surface charges. The findings are corroborated with the help of EPR studies.

Au-Cu alloy nanostructures have been synthesized in aqueous phase through co-reduction of HAuCl 4 .3H 2 O and CuCl 2 .2H 2 O by glucose in presence of hexadecylamine at ∼80°C. By changing the synthesis conditions, nanostructures of various shapes such as nanowires, multiply twinned tripod, tetrapod, etc were observed. Systematic variation of the synthesis condition not only leads to change in size and particle morphology but also develops various other crystallographic characters in the nanoparticles. Alloying behavior of Au-Cu has been examined through transmission electron microscope operating in its conventional and analytical modes coupled with high resolution phase contrast microscopy. These results suggested that nanostructures are composed of homogeneous Au-Cu alloy. Preferential attachment along {111} and {100} crystallographic facets of Au-Cu alloy nanoparticles led to the formation of nanowires. Multiply twinned branched shape Au-Cu (width of branch ∼30 nm) nanostructures exhibit localized surface plasmon resonance maxima in the near-infrared region. The branched shape Au-Cu alloy nanostructures display better surface enhanced Raman scattering response in the detection of methylene blue as compared to spherical Au nanoparticles.

No abstract

No abstract

No abstract