Luminescent materials (or phosphors) are generally characterized by the emission of light with energy beyond thermal equilibrium. More vividly this means: The nature of luminescence is different from that of black-body radiation. Luminescence can occur as a result of many different kinds of excitation, which is reflected in expressions such as photo-, electro-, chemi-, thermo-, sono-, or triboluminescence. In practice, most often the excitation is via X-rays, cathode rays, or UV emission of a gas discharge. The role of the phosphor is to convert the incoming radiation into visible light. In addition to the type of excitation, two other terms are used quite often to classify luminescent materials. Both can be related to the decay time (s): fluorescence (s < 10 ms) and phosphorescence (s > 0.1 s). [1] The luminescence of inorganic solids, which is the focus of this contribution, can be traced to two mechanisms: luminescence of localized centers and luminescence of semiconductors (Fig. 1). [1,2] The first case is represented by transitions between energy levels of single ions (e.g., f±f transitions of Eu 3+ in Y 2 O 3 :Eu 3+ ) or complex ions (e.g., the charge-transfer transition on [WO 4 ] 2± in CaWO 4 ). In the case of luminescent centers, the transition rate is (more or less strongly) correlated to the relevant quantum-mechanical selection rules, and reflected in the intensity as well as the decay time of the transition. Excitation and emission can be (as shown in Fig. 1) both localized to one center (e.g., [WO 4 ] 2± in CaWO 4 ) or separated from each other: excitation on sensitizer (e.g., Ce 3+ in LaPO 4 :Ce 3+ ,Tb 3+ ) is followed by emission on activator (e.g., Tb 3+ in LaPO 4 :Ce 3+

Nanoscientists boldly go to the frontiers of the smallest solids in basic science and their technical application. In their Review on H. Goesmann and C. Feldmann point to the visionary potential of nanoparticulate functional materials. After a general introduction of the topic, the optical, electrical, magnetic, and catalytic properties of nanoparticles as well as their potential for upgrading materials are summarized. Moreover, fundamentally novel shapes and compositions of matter are presented.

The polyol synthesis of nanoparticles is reviewed, including metals, oxides, main-group elements and recent strategies to expand the method's limits.

transparent conducting oxides (ZnO:In 3+ ), and catalytically active oxides (CeO 2 ; Mn 3 O 4 ; V 2 O 5 ) are prepared with the polyol method. All these materials are yielded as crystalline, spherical, and almost monodisperse particles, 30±200 nm in size. Characterization is carried out based on scanning electron microscopy (SEM), X-ray powder diffraction (XRD), optical spectroscopy, and conductance measurements. The preparation via the polyol method is singled out due to its broad and easy applicability. The resulting material properties are similar to or better than nanoscale materials prepared by other measures. Some materials and their properties, e.g., ZnS:Ag + ,Cl ± as a phosphor, ZnCo 2 O 4 and Cu(Fe,Cr)O 4 as pigments, and ZnO:In 3+ as transparent conductive oxide, are presented for the first time at the nanoscale.

Ionic liquids are credited with a number of unusual properties. These include a low vapor pressure, a wide liquid-phase range, weakly coordinating properties, and a high thermal/chemical stability. These properties are certainly of great interest for inorganic synthesis and the creation of novel inorganic compounds. On the other hand, the synthesis repertoire for preparing inorganic compounds has always been broad, ranging from syntheses in solutions and melts to solid-state reactions, and from crystal growth in the gas phase to high-pressure syntheses. What new aspects can ionic liquids then add to the synthesis of inorganic compounds? This Minireview uses some early examples to show that the use of ionic liquids indeed provides access to unusual inorganic compounds.

Nanoparticulate functional materials offer manifold perspectives for the increasing miniaturization and complexity of technical developments. Nanoparticles also make a major contribution to utilization of materials that is sparing of natural resources. Besides these obvious aspects, however, the importance of nanoparticles is due to their fundamentally novel properties and functions. These include photonic crystals and efficient luminophors, single particles and thin films for electronic storage media and switching elements, magnetic fluids and highly selective catalysts, a wide variety of possibilities for surface treatments, novel materials and concepts for energy conversion and storage, contrast agents for molecular biology and medical diagnosis, and fundamentally novel forms and structures of materials, such as nanocontainers and supercrystals. Creating high-quality nanoparticles requires that numerous parameters, involving the particle core and surface, colloidal properties, and particle deposition, are taken into consideration during synthesis of the material. An appropriate characterization and evaluation of the properties requires the incorporation of a wide range of expertise from widely differing areas. These circumstances are what challenges and appeals to the nanoscientist.

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