Synthesis and photophysical properties of an Eu(II)-complex/PS blend: role of Ag nanoparticles in surface-enhanced luminescence

Toward Opto-Structural Correlation to Investigate Luminescence Thermometry in an Organometallic Eu(II) Complex

Lanthanide-based luminescent materials have unique properties and are well-studied for many potential applications. In particular, the characteristic 5d → 4f emission of divalent lanthanide ions such as Eu^II allows for tunability of the emissive properties via modulation of the coordination environment. We report the synthesis and photoluminescence investigation of pentamethylcyclopentadienyleuropium(II) tetrahydroborate bis(tetrahydrofuran) dimer (1), the first example of an organometallic, discrete molecular Eu^II band-shift luminescence thermometer. Complex 1 exhibits an absolute sensitivity of 8.2 cm^-1 K^-1 at 320 K, the highest thus far observed for a lanthanide-based band-shift thermometer. Opto-structural correlation via variable-temperature single-crystal X-ray diffraction and fluorescence spectroscopy allows rationalization of the remarkable thermometric luminescence of complex 1 and reveals the significant potential of molecular Eu^II compounds in luminescence thermometry.

White and Tunable Emission from and Rhodamine B Detection by Modified Zinc Oxide Nanowalls

To gain better optical and optoelectrical properties, doping trivalent lanthanide cations into host materials is a very attractive approach in nanoscience. Here, we use a transparent conducting oxide, zinc oxide, as the host material to directly embed trivalent terbium cations without the need for any postgrowth treatment, and we investigate the photophysical effect of the dopant. Trivalent Tb cations embedded in ZnO nanowalls produce hypersensitive green emission (at 545 nm, corresponding to the ⁵D₄ → ⁷F₅ transition) and convert the emission color of ZnO from yellow into white. Evidently, the photoluminescence emission intensity of Tb(III) is further increased by close to 10-fold due to the plasmonic effect introduced by noble metal (Ag and Pt) nanoparticles. The characteristic Tb(III) emission is found to be tunable from white to red and is examined for its potential chemosensing application for rhodamine B involving a plausible cascade energy transfer mechanism from ZnO to rhodamine B via Tb(III) cations.

Research into europium complexes as magnetic resonance imaging contrast agents (Review)

Europium (Eu) is a paramagnetic lanthanide element that possesses an outstanding luminescent property. Eu complexes are ideal fluorescence imaging (FI) agents. Eu²⁺ has satisfactory relaxivity and optical properties, and can realize magnetic resonance (MRI)-FI dual imaging applications when used with appropriate cryptands that render it oxidatively stable. By contrast, based on the chemical exchange saturation transfer (CEST) mechanism, Eu³⁺ complexes can provide enhanced MRI sensitivity when used with optimal cryptands, incorporated into polymeric CEST agents or blended with Gd³⁺. Eu complexes are promising in MRI-FI dual imaging applications and have a bright future.

Structural and photophysical properties of HPPCO (4-hydroxy-5-phenyl-6H-pyrido[3,2,1-jk]carbazol-6-one) derivatives

Proton-substitution effects of 4-hydroxy-5-phenyl-6H-pyrido[3,2,1-jk]carbazol-6-one (HPPCO) on structural and photophysical properties were presented. HPPCO crystallized in the orthorhombic space group Pbca with an intermolecular hydrogen bonding between OH and oxygen atom of the carbonyl. The proton-substituted derivatives, 6-oxo-5-phenyl-6H-pyrido[3,2,1-jk]carbazol-4-yl acetate (OPPCA) and 6-oxo-5-phenyl-6H-pyrido[3,2,1-jk]carbazol-4-yl benzoate (OPPCB), crystallized in the monoclinic P2₁/c space group. For OPPCA and OPPCB, a weak interaction between carbonyl oxygen atom in the substituted group and carbon atom in the fused ring was responsible for three-dimensional arrangements. In addition, 6-oxo-5-phenyl-6H-pyrido[3,2,1-jk]carbazol-4-yl furan-2-carboxylate (OPPCF), and 6-oxo-5-phenyl-6H-pyrido[3,2,1-jk]carbazol-4-yl naphthoate (OPPCN) were also synthesized. HPPCO and the four derivatives excited by ultraviolet (UV) light produced blue emission. Proton substitution of the OH group significantly increased the radiative transitions and moderately decreased the non-radiative transitions. Consequently the luminescence quantum yields of the derivatives enhanced more than 4.6-fold, no matter what the groups were substituted. Structural and optical properties were further determined using density functional theory (DFT) and ZINDO calculations. The planar structure of the pyridocarbazole-fused ring resulted in π→π(*) electronic transitions within the main frame, with an additional transition from the n(O) of carbonyl to the π(*) of the main frame. The three excited states that arose from these transitions were responsible for the blue luminescence.

Formation and nonlinear optical properties of Ag nanocrystals capped with the conjugated ligand carbazolyl styryl terpyridine

NLO (non-linear optics) properties of the optical organic molecules were significantly improved when capped with nano-Ag.

Sensitized luminescence of Eu(III) complexes with Schiff-base and 1,10-phenanthroline: role of Schiff-base as a sensitizer

The synthesis and characterization of two europium(III) complexes, [Eu(L)(H2O)]Cl and [Eu(L)(phen)(H2O)]Cl (L=N,N'-bis(salicylidene)-3,6-dioxa-1,8-diaminooctanato and phen=1,10-phenanthroline) are reported. Exciting the Eu(III) complexes with near-UV light resulted in sensitized red luminescence by a transfer of energy from the triplet excited states of L to the Eu(III) ion. Introducing phen to the complex increased the quantum yield of the L-sensitized luminescence of [Eu(L)(phen)(H2O)](+) by more than 18 times relative to [Eu(L)(H2O)](+). The optimized structures and the configurational interaction singles (CIS) of the [Eu(L)(phen)(H2O)](+) and [Eu(L)(H2O)](+) molecules were theoretically studied using ab initio Hartree-Fock (HF). The theoretical calculations showed that the first nearly degenerate 1A and 2A excited states, more specifically the π→π(*) transitions of the two phenolate terminals, contributed significantly to the energy transfer process. Although the phen excitation route was forbidden in [Eu(L)(phen)(H2O)](+), the coordination of phen enhanced the absorbing ability of L markedly and caused the energy transfer from the 1A and 2A states to the (5)D1 and (5)D0 states of Eu(III) to predominate over any radiative and nonradiative processes occurring between the excited states and the ground states of the L moiety. Consequently, the quantum yield of the sensitized luminescence was enhanced significantly in [Eu(L)(phen)(H2O)](+).