We report here enhancement of ferromagnetism in pure ZnO upon thermal annealing with the ferromagnetic transition temperature Tc above room temperature. We observe a finite coercive field upto 300K and a finite thermoremanent magnetization upto 340K for the annealed sample. We propose that magnetic moments can form at anionic vacancy clusters. Ferromagnetism can occur due to either superexchange between vacancy clusters via isolated F + centers, or through a limited electron delocalization between vacancy clusters. Isolated vacancy clusters or isolated F + centers give rise to a strong paramagnetic like behaviour below 10K.

Undoped and Mn doped ZnO samples with different percentage of Mn content (1 mol%, 2 mol% and 3mol%) were synthesized by a simple solvo-thermal method. We have studied the structural, chemical and optical properties of the samples by using x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive x-ray (EDX) analysis, Fourier transform infrared (FTIR) spectroscopy and UV-VIS spectroscopy. The XRD spectra show that all the samples are hexagonal wurtzite structures. The lattice parameters calculated for the Mn doped ZnO from the XRD pattern were found to be slightly larger than those of the undoped ZnO, which indicates substitution of Mn in ZnO lattice. SEM photograph shows the grain size of undoped ZnO is bigger than the Mn doped ZnO's indicating hindrance of grain growth upon Mn doping. As the Mn doping increases the optical band gap decreases for the range of Mn doping reported here.

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Graphene−nucleobase interaction is gaining importance due to its possible therapeutic applications. The dispersion interaction plays a major role in stacked aromatic compounds, such as graphene with amino acids or nucleobases. We have carried out detailed quantum chemical calculations of complexes of nanographene sheets and the nucleobases of DNA and RNA using dispersion corrected density functional theory. Binding energies show a trend as observed earlier by different theoretical and experimental measurements. However, in our present investigation, the optimized structures of the complex as well as isolated graphene show significant curvature, similar features are also observed by our Atomic Force Microscopic studies. Analysis of Natural Bond Orbital charges indicates the possibility of weak hydrogen bond-like interactions involving pyramidal amino groups of the nucleobases and π-center of the nanographene.

In this paper we report the structural, magnetic, and transport properties of nanoparticles of Pr0.5Ca0.5MnO3(PCMO). On comparing our results with that of bulk PCMO, we find that there is a likely destabilization of charge ordering in nanoparticles of PCMO. The investigation has been done with particle sizes as small as 15nm synthesized by polyol route. The size reduction (by keeping the chemical composition unchanged) reduces the orthorhombic c axis preferentially and thus reduces the orthorhombic distortion. The size reduction to 15nm enhances the ferromagnetic moment at low temperatures and strongly suppresses the activated charge transport which is seen in the bulk samples of charge ordered PCMO.