Europium doped zinc oxide nanoparticles have been synthesized using a chemical route. The amount of doped europium was varied which shows the changes in the photoluminescence (PL) intensity. The post synthesis annealing effect on the properties of ZnO nanoparticles has also been investigated. In general, PL is broad and a white light is emitted which originates from ZnO and the intra-4f transitions of Eu3+ ions. The x-ray diffraction patterns do not show any Eu-related peaks for as-synthesized ZnO nanoparticles as well as for annealed samples. X-ray absorption spectroscopy reveals that europium ions are present on the surface of the core of ZnO and inside the shell of zinc hydroxide [Zn(OH2)] after annealing.

Efficient field electron emission from ZnO nanoparticles synthesized by a chemical route has been observed. Nanostructures were synthesized in three different morphologies, namely needles, rods, and spheres. The field emission studies carried out in diode configuration show that the onset fields required to draw a current density of ∼0.1 µA cm−2 from the needles, rods, and spherical particles were 2.3, 2.5, and 3.5 V µm−1, respectively. The field emission current and applied field follow the Fowler–Nordheim (F–N) relationship. The observed results indicate that the field emission characteristics of chemically grown ZnO nanostructures are at par with those reported for solid–vapour phase grown ZnO nanostructures.

No abstract

The detailed structural characterization of nanoparticles is a very important issue since it enables a precise understanding of their electronic, optical and magnetic properties. Here we introduce a new method for modeling the structure of very small particles by means of powder X-ray diffraction. Using thioglycerol-capped ZnO nanoparticles with a diameter of less than 3 nm as an example we demonstrate that our ensemble modeling method is superior to standard XRD methods like, e.g., Rietveld refinement. Besides fundamental properties (size, anisotropic shape and atomic structure) more sophisticated properties like imperfections in the lattice, a size distribution as well as strain and relaxation effects in the particles and-in particular-at their surface (surface relaxation effects) can be obtained. Ensemble properties, i.e., distributions of the particle size and other properties, can also be investigated which makes this method superior to imaging techniques like (high resolution) transmission electron microscopy or atomic force microscopy, in particular for very small nanoparticles. For the particles under study an excellent agreement of calculated and experimental X-ray diffraction patterns could be obtained with an ensemble of anisotropic polyhedral particles of three dominant sizes, wurtzite structure and a significant relaxation of Zn atoms close to the surface.

Semiconductor nanoparticles exhibit size dependent properties, when their size is comparable to the size of Bohr diameter for exciton. This can be exploited to increase fluorescence efficiency or increase the internal magnetic field strength in doped semiconductors. Nanoparticles are usually unstable and can aggregate. It is therefore necessary to protect them. Surface passivation using capping molecules or by making coreYshell particles are some useful ways. Here synthesis and results on doped and un-doped nanoparticles of ZnS, CdS and ZnO will be discussed. We shall present results on coreYshell particles using some of these nanoparticles and also discuss briefly the effect of Mn doping on hyperfine interactions in case of CdS nanoparticles.