Rare‐earth fluorides are a class of materials with considerable potential in optical applications. Fluoride lattices typically permit high coordination numbers for the hosted rare‐earth ions, and the high ionicity of the rare‐earth‐to‐fluorine bond leads to a wide bandgap and very low vibrational energies. These factors make rare‐earth fluorides very useful in optical applications employing vacuum ultraviolet and near‐infrared excitation. The preparation of nanometer‐sized particles has opened the door for new properties and devices if the performance of their macroscopic counterparts can be conserved in the nanometer regime. However, at small particle sizes, defect surface states and adhering water reduce the optical efficiency. These shortcomings can be reduced by applying protective shells around the luminescent cores, which can also be involved in the luminescent process.

Transparent luminescent nanocomposites were obtained using the bulk polymerization of transparent dispersions containing manganese-doped ZnS nanoparticles with a crystallite size of 2 nm in a mixture of methyl methacrylate and acrylic acid. The effective diameter in the monomer dispersions is 22 nm as determined using dynamic light scattering and depends on the composition of the continuous phase but is significantly higher than the primary crystallite size of the ZnS:Mn nanoparticles initially obtained from the precipitation reaction. The dispersions are stable up to 8 months. Deprotonated carboxylate groups are detected in IR spectra (1547, 1437 cm-1) of particles isolated from a stable dispersion indicating the presence of surface-bound acrylate molecules. Thermal bulk polymerization of the entire dispersions is suitable for production of luminescent acrylic glasses with an emission maximum at 590 nm (330 nm excitation) and a quantum yield of 29.8%. Ultramicrotome cuts of the nanocomposites with a thickness of 50−100 nm were prepared for transmission electron microscopic investigations. In the micrographs, a low degree of agglomeration is observed and the agglomerate diameter is below 20 nm. In the nanocomposites, light scattering and turbidity is minimized due to the small particle size and high degree of dispersion, resulting in highly transparent acrylic glasses with a transmittance as high as 87% (600 nm).

Review: Non‐conventional phosphor host materials such as cryptands (see Figure) or zeolites now offer potential alternatives to the traditional inorganic solid‐state materials which find applications in e.g. fluorescent lamps, T.V. sets, or X‐ray detectors. Recent efforts to further optimize conventional materials are reviewed and a forward look is taken at the new‐generation materials which could further extend the physical limits of luminescence.

Water-dispersible and (bio)functionalizable nanoclays have a considerable potential as inexpensive carriers for organic molecules like drugs and fluorophores. Aiming at simple design strategies for red-emissive optical probes for the life sciences from commercial precursors with minimum synthetic effort, we systematically studied the dye loading behavior and stability of differently functionalized laponites. Here, we present a comprehensive study of the absorption and emission properties of the red emissive hydrophobic and neutral dye Nile Red, a well-known polarity probe, which is almost insoluble and nonemissive in water. Adsorption of this probe onto disk-shaped nanoclays was studied in aqueous dispersion as function of dye concentration, in the absence and presence of the cationic surfactant cetyltrimethylammonium bromide (CTAB) assisting dye loading, and as a function of pH. This laponite loading strategy yields strongly fluorescent nanoclay suspensions with a fluorescence quantum yield of 0.34 at low dye loading concentration. The dye concentration-, CTAB-, and pH-dependent absorption, fluorescence emission, and fluorescence excitation spectra of the Nile-Red-nanoclay suspensions suggest the formation of several Nile Red species including emissive Nile Red monomers facing a polar environment, nonemissive H-type dimers, and protonated Nile Red molecules that are also nonfluorescent. Formation of all nonemissive Nile Red species could be suppressed by modification of the laponite with CTAB. This underlines the great potential of properly modified and functionalized laponite nanodisks as platform for optical probes with drug delivery capacities, for example, for tumor and therapy imaging. Moreover, comparison of the Nile Red dimer absorption spectra with absorption spectra of previously studied Nile Red aggregates in dendrimer systems and micelles and other literature systems reveals a considerable dependence of the dimer absorption band on microenvironment polarity which has not yet been reported so far for H-type dye aggregates.

The neutral organic dye indigo forms an inorganic-organic hybrid material with nanoclays (see picture; blue circles on disks symbolizing indigo, spheres indicating liberated cations) and can thus be transferred into aqueous solution. Solids recovered from these solutions resemble the ancient Maya Blue pigment. The method can also be applied to other hydrophobic species and may open the gate for novel solution chemistry, including photonic and catalytic applications.

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Rare earth ion‐exchanged zeolites exhibit a tremendous enhancement of luminescence upon treatment with suitable organic complexing agents, as reported here. For Eu3+ exchanged zeolite X, the β‐diketone 1‐thienyl‐4,4,4‐trifluoro‐1,3‐butane‐1,3‐dione leads to the formation of intra‐zeolite complexes. Fully coordinated complexes within the supercages may be obtained by the additional coordination of 1,10‐phenanthroline (see Figure).

Optical and structural properties of rare earth complexes with 2-pyridine carboxylic acid (' Hpic ') are evaluated by luminescence spectroscopy, decay measurements, X-ray crystal structure determination, FTIR, DTA and metal content analysis. Corresponding Tb 3+ and Eu 3+ complexes of this ligand are extraordinarily efficient with respect to their luminescence. In the crystalline state the series is isostructural and composed of M[Ln(pic) 4 ]ÁnH 2 O (M ¼ Na, NH 4 ; Ln ¼ Eu, Gd, Tb, Ho) with pic-linked [Ln(pic) 4 ] À units forming a chainlike structure, which gives rise to a one-dimensional exchange communication between the rare earth ions; this energy transfer being confined to the chains. Energy transfer of the Coulomb type between the ligands appears to be of significance only, if suitable rare earth acceptor states are not accessible, as is shown for a series of [La(pic) 4 ] À series, in which La 3+ is gradually substituted by Tb 3+ or Eu 3+ .