New, accurate Lennard-Jones parameters for trivalent lanthanide ions, tested on [18]crown-6

The binding affinities of [18]crown-6 and La3+, Nd3+, Gd3+, and Yb3+ have been reproduced in MeOH with Monte Carlo free-energy perturbation calculations which used newly derived Lennard-Lones parameters for the Ln3+ ions. The figure shows the complex of a lanthanide ion and the crown ether

Improvement in the Luminescence Properties and Processability of LaF3/Ln and LaPO4/Ln Nanoparticles by Surface Modification

The surface of lanthanide(III)-doped LaPO4 nanoparticles was modified by reaction with an alcohol, leading to a covalent bond between the ligand and the particle surface. The surface of lanthanide(III)-doped LaF3 nanoparticles was modified to alter the solubility of the nanoparticles and study the influence of surface effects on the luminescence of lanthanide ions doped in the nanoparticles. The coordinated organic ligands can be modified by a quantitative exchange reaction in solution or by using functionalized ligands during the synthesis. Variation of the ratio of ligand to core reagents had a significant influence on the size of the nanoparticles. Smaller nanoparticles were formed with a higher ligand ratio. The optical properties of these nanoparticles show a strong dependence on nanoparticle size, indicating the influence of quenching probably by CH and OH groups at or near the surface of the nanoparticle cores. The luminescence lifetime of LaF3/Eu nanoparticles varied from 6.5 to 7.4 ms for nanoparticles with an average size of 7.1 to 8.4 nm. A significant reduction of the quenching from the surface of the nanoparticles was obtained by the synthesis of core-shell nanoparticles, in which a shell of LaF3 was grown epitaxially around the doped core nanoparticles. This leads to an increase in the luminescence lifetime of the Eu3+ ion and the observation of emissions from the 5D2 energy level, in addition to emissions from the 5D1 and 5D0 levels. The quantum yield of LaF3/Ce,Tb nanoparticles could be increased from 24 to 54% by the growth of a LaF3 shell around the nanoparticles

Complexation of neutral molecules by synthetic hosts

The interactions of neutral polar molecules with synthetic (macrocyclic) hosts are described. Extraction, NMR spectroscopy, polarography, and membrane transport studies have been carried out in order to understand these interactions. A step-wise process is described in which ultimately a general approach for a rational design of hosts is obtained. This approach has finally led to the first transfer of urea across a membrane by a neutral host (carrier) in which binding sites are placed in such a way that all possible interactions with urea are indeed used