Europium-directed self-assembly of a luminescent supramolecular gel from a tripodal terpyridine-based ligand

Eu(III), the last piece in the puzzle: Europium-induced self-assembly of ligands having a C(3)-symmetrical benzene-1,3,5-tricarboxamide core results in the formation of luminescent gels. Supramolecular polymers are formed through hydrogen bonding between the ligands. The polymers are then brought together into the gel assembly through the coordination of terpyridine ends by Eu(III) ions (blue dashed arrow: distance between two ligands in the strand direction).     

Self-assembled 3D architectures of LuBO3:Eu(3+): phase-selective synthesis, growth mechanism, and tunable luminescent properties

Rhombohedral-calcite and hexagonal-vaterite types of LuBO(3):Eu(3+) microparticles with various complex self-assembled 3D architectures have been prepared selectively by an efficient surfactant- and template-free hydrothermal process for the first time. X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectrometry, transmission electron microscopy, high-resolution transmission electron microscopy, selected area electron diffraction, photoluminescence, and cathodoluminescence spectra as well as kinetic decays were used to characterize the samples. The pH, temperature, concentration, solvent, and reaction time have a crucial influence on the phase formation, shape evolution, and microstructure. The reaction mechanism is considered as a dissolution/precipitation process; it is proposed that the self-assembly evolution occurs by homocentric layer-by-layer growth. Under UV excitation and low-voltage electron beam excitation, calcite-type LuBO(3):Eu(3+) particles show a strong orange emission corresponding to the (5)D(0)-->(7)F(1) transition of Eu(3+) whereas vaterite-type LuBO(3):Eu(3+) particles exhibit a strong red emission with much higher R/O values (that is, chromatically redder fluorescence than that of crystals grown from a direct solid-state reaction). The tunable luminescent properties have potential applications in fluorescent lamps and field emission displays.     

Contribution of charge-transfer mechanisms to surface-enhanced Raman scattering with near-IR excitation.

Surface-enhanced Raman scattering under near-IR excitation is investigated for p-aminothiophenol (PATP) molecules that are either adsorbed on an electrochemically roughened silver electrode or embedded in an Au/PATP/Ag molecular junction assembled on an indium-doped tin oxide electrode. The contribution from chemical enhancement can be amplified relative to the contribution from electromagnetic enhancement, because the energy of the near-IR excitation is far from the surface plasmon resonance of the nanosized metal particles. The energy required for the charge-transfer process for the Au/PATP/Ag molecular junction is much lower than that of the PATP molecules adsorbed on the electrochemically roughened silver electrode. Coadsorption of chloride ions on the metal nanoparticles may result in an alteration of the local Fermi level of the metal nanoparticles, thus leading to better energy matching between the energy level of the interconnecting PATP molecules and the Fermi level of the metal nanoparticles.