Novel Thiazole-Containing Complexing Agents and Luminescence of Their Europum(III) and Terbium(III) Chelates

The synthesis of novel thiazole-containing complexing agents and their luminescence properties with Eu^III and Tb^III ions are reported. One of these terpyridine analogues was also tested as an Eu^III labelling reagent, and its luminescence properties as an antibody conjugate were studied.     

New method of determining the young’s Modulus of (Ga,Mn)As nanowhiskers with a scanning electron microscope

Arrays of (Ga,Mn)As nanowhiskers have been grown by molecular-beam epitaxy. The scanning electron microscopy study of the surface morphology of the samples has revealed the appearance of mechanical vibrations of individual nanowhiskers. To describe the vibrations, a model has been developed for the determination of the Young’s modulus of (Ga,Mn)As nanowhiskers.     

A dissociative fluorescence enhancement technique for one-step time-resolved immunoassays

The limitation of current dissociative fluorescence enhancement techniques is that the lanthanide chelate structures used as molecular probes are not stable enough in one-step assays with high concentrations of complexones or metal ions in the reaction mixture since these substances interfere with lanthanide chelate conjugated to the detector molecule. Lanthanide chelates of diethylenetriaminepentaacetic acid (DTPA) are extremely stable, and we used EuDTPA derivatives conjugated to antibodies as tracers in one-step immunoassays containing high concentrations of complexones or metal ions. Enhancement solutions based on different β-diketones were developed and tested for their fluorescence-enhancing capability in immunoassays with EuDTPA-labelled antibodies. Characteristics tested were fluorescence intensity, analytical sensitivity, kinetics of complex formation and signal stability. Formation of fluorescent complexes is fast (5 min) in the presented enhancement solution with EuDTPA probes withstanding strong complexones (ethylenediaminetetra acetate (EDTA) up to 100 mM) or metal ions (up to 200 μM) in the reaction mixture, the signal is intensive, stable for 4 h and the analytical sensitivity with Eu is 40 fmol/L, Tb 130 fmol/L, Sm 2.1 pmol/L and Dy 8.5 pmol/L. With the improved fluorescence enhancement technique, EDTA and citrate plasma samples as well as samples containing relatively high concentrations of metal ions can be analysed using a one-step immunoassay format also at elevated temperatures. It facilitates four-plexing, is based on one chelate structure for detector molecule labelling and is suitable for immunoassays due to the wide dynamic range and the analytical sensitivity.     

Carrier dynamics in strain-induced InGaAsP/InP quantum dots

Carrier dynamics of strain-induced InGaAsP/InP quantum dots (QDs) is investigated. In this structure, self-assembled InAs islands on the surface act as stressors and create a lateral confinement potential in the near surface InGaAsP/InP quantum well. Photoluminescence (PL) measurements reveal that decreasing the distance from the QD to the surface significantly diminishes the QD–PL intensity, presumably due to surface states of the InAs islands. Moreover, time-resolved measurements show a faster decay of the QD–PL with decreasing distance. To analyze the carrier dynamics, rate equation model is applied and surface state-related transitions are taken into account. The model is found to agree with measurements, and thus provides a possible explanation for the observed temporal behavior of the carriers.     

GaN/GaAs(1 0 0) superlattices grown by metalorganic vapor phase epitaxy using dimethylhydrazine precursor

Superlattices of cubic gallium nitride (GaN) and gallium arsenide (GaAs) were grown on GaAs(1 0 0) substrates using metalorganic vapor phase epitaxy (MOVPE) with dimethylhydrazine (DMHy) as nitrogen source. Structures grown at low temperatures with varying layer thicknesses were characterized using high resolution X-ray diffraction and atomic force microscopy. Several growth modes of GaAs on GaN were observed: step-edge, layer-by-layer 2D, and 3D island growth. A two-temperature growth process was found to yield good crystal quality and atomically flat surfaces. The results suggest that MOVPE-grown thin GaN layers may be applicable to novel GaAs heterostructure devices.     

Strain-induced quantum dot superlattice

Coupled double quantum dots and quantum dot superlattices are formed by utilizing the strain of an InP island on top of a near-surface multi-quantum-well structure. The number and composition of the quantum wells together with the thickness of the barrier separating the quantum wells are varied to investigate the coupling of the wave functions of the carriers confined in separate vertically stacked dots. Photoluminescence studies show that the reduction of the barrier thickness and the increase of the number of wells enhance the coupling, which is observed as red shift and narrowing of the quantum dot peak. The calculated shifts of the peak positions agree closely with the experimental values.     

Development of Luminescent Terbium(III) Chelates for Protein Labelling: Effect of triplet-state energy level

The synthesis of novel Tb^III labels suitable for protein labelling are reported. Their luminescence properties as antibody conjugates were measured and compared to the results of corresponding Tb^III chelates of the parent ligand structures. When the lowest triplet-state energy level of the parent donor ligand was over 23000 cm^?1, i.e., the energy gap between the ⁵D₄ level of Tb^III and the lowest triplet-state energy level of the ligand exceeded 2600 cm^?1, the label derivative with a long decay time (τ = 1.35–2.93 ms) and a high luminescence yield (?. Φ = 3770–4560) was found to be suitable for bioaffinity assays.     

Development of Luminescent Europium(III) and Terbium(III) chelates of 2,2′:6′,2″- terpyridine derivatives for protein labelling

The synthesis and luminescence properties are reported for 20 different chelates composed of 2,2′:6′,2″-terpyridine as the energy-absorbing and donating group, Eu^IIIand Tb^III as the emitting ions, methylenenitrilo(acetic acids) as the stabel chelate-forming moieties, and isothiocyanato or(4,6-dichloro-1,3,5-triazin-2-yl)amino groups as the activated moieties for coupling to biomolecules.     

New Heteroaromatic Complexing Agents and Luminescence of Their Europium(III) and Terbium(III) Chelates

Twelve heteroaromatic complexing agents 9a–I were synthesized with the purpose to develop suitable labels for time-resolved luminescence-based bioaffinity assays. The relative luminescence yields, excitation maxima, and emission decay constants of their europium(III) and terbium(III) chelates were determined. According to these results, 2,2′,2″,2?-[(2,2′-bipyridine-6,6′-diyl)bis(methylenenitrilo)]tetrakis (acetic acid) ( 9e ) and 2,2′,2″,2?-[(2,2′:6′,2″-terpyridine-6,6″-diyl)bis(methylenenitrilo)] tetrakis(acetic acid) ( 91 ) are the most promising agents.