A series of blue-green-yellow-red emitting Cu(I) complexes: Molecular structure and photophysical performance.

In this work, we designed a series of [Cu(NN)(PPh3)2]BF4 complexes with different optical edge values and emission colors from blue to red, where NN and PPh3 denoted a diamine ligand and triphenylphosphine, respectively. Six NN ligands with various conjugation chains (short π chain, modest π chain and long π chain) were selected. A systematical comparison between these Cu(I) complexes was performed, so that the correlation between NN structure and [Cu(NN)(PPh3)2] photophysical performance was tentatively discussed. Their single crystal structure was found consistent with literature ones, forming a typical tetrahedral coordination geometry. Density functional theory calculation indicated that their onset electronic transition showed a mixed character of metal-to-ligand-charge-transfer and ligand-to-ligand-charge-transfer. Detailed analysis on photophysical parameters suggested that the absorption edge of [Cu(NN)(PPh3)2]BF4 complex was controlled by conjugation length in diamine ligand. A wide absorption edge needed a short conjugation chain in diamine ligand. Similar tendency was found for their emission spectra. In addition, a long conjugation chain in diamine ligand widened emission spectra obviously. Emission dynamics showed slim correlation with diamine ligand conjugation length since the excited state was controlled mainly by dynamic procedure and steric factor of diamine ligands.

Engineering Charge Transfer Characteristics in Hierarchical Cu2S QDs @ ZnO Nanoneedles with p⁻n Heterojunctions: Towards Highly Efficient and Recyclable Photocatalysts.

Equipped with staggered gap p-n heterojunctions, a new paradigm of photocatalysts based on hierarchically structured nano-match-shaped heterojunctions (NMSHs) Cu2S quantum dots (QDs)@ZnO nanoneedles (NNs) are successfully developed via engineering the successive ionic layer adsorption and reaction (SILAR). Under UV and visible light illumination, the photocatalytic characteristics of Cu2S@ZnO heterojunctions with different loading amounts of Cu2S QDs are evaluated by the corresponding photocatalytic degradation of rhodamine B (RhB) aqueous solution. The results elaborate that the optimized samples (S3 serial specimens with six cycles of SILAR reaction) by means of tailored the band diagram exhibit appreciable improvement of photocatalytic activities among all synthesized samples, attributing to the sensitization of a proper amount of Cu2S QDs. Such developed architecture not only could form p⁻n junctions with ZnO nanoneedles to facilitate the separation of photo-generated carries but also interact with the surface defects of ZnO NNs to reduce the electron and hole recombination probability. Moreover, the existence of Cu2S QDs could also extend the light absorption to improve the utilization rate of sunlight. Importantly, under UV light S3 samples demonstrate the remarkably enhanced RhB degradation efficiency, which is clearly testified upon the charge transfer mechanism discussions and evaluations in the present work. Further supplementary investigations illustrate that the developed nanoscale Cu2S@ZnO heterostructures also possess an excellent photo-stability during our extensive recycling photocatalytic experiments, promising for a wide range of highly efficient and sustainably recyclable photocatalysts applications.

High-performance oxygen sensors based on Eu(III) complex/polystyrene composite nanofibrous membranes prepared by electrospinning.

An optical oxygen sensor based on an Eu(III) complex/polystyrene (PS) composite nanofibrous membrane is prepared by electrospinning. The emission intensity of [Eu(TTA)(3) (phencarz)] (TTA=2-thenoyltrifluoroacetonate, phencarz=2-(N-ethylcarbazolyl-4)imidazo[4,5-f]1,10-phenanthroline) decreases with increasing oxygen concentration, and thus the [Eu(TTA)(3) (phencarz)]/PS composite nanofibrous membranes can be used as an optical oxygen-sensing material based on emission quenching caused by oxygen. Elemental analysis, UV/Vis absorption spectra, scanning electron microscopy (SEM), fluorescence microscopy, luminescence-intensity quenching Stern-Volmer plots, and excited-state decay analysis are used to characterize the obtained oxygen-sensing materials. A high sensitivity (I(N2) /I(O2)) of 3.38 and short response and recovery times (t(↓) =5.0, t(↑) =8.0 s) are obtained. These results are the best values reported for oxygen sensors based on Eu(III) complexes. The high surface area-to-volume ratio and porous structure of the electrospun nanofibrous membranes are taken to be responsible for the outstanding performance.

Improved photoluminescence properties of a novel europium(III) complex covalently grafted to organically modified silicates.

A series of novel organic-inorganic hybrid materials with a Eu(III) complex [(C(2)H(5))(4)N][Eu(DBM)(3)(DBM-OH)] (DBM=dibenzoylmethanate, DBM-OH=p-hydroxydibenzoylmethanate) covalently bonded into vinyl-modified silica networks have been successfully assembled through a sol-gel process. DBM-OH was grafted to the coupling agent 3-(triethoxysilyl)propylisocyanate (TESPIC), and the as-obtained molecular precursor DBM-Si was used as a bridge molecule both coordinate to Eu(3+) and forming an inorganic Si-O network with tetraethoxysilane (TEOS) and vinyltriethoxysilane (VTES) after cohydrolysis and co-condensation processes. The luminescence properties of VTES/TEOS composite hybrid materials were systematically studied in comparison to those of TEOS-derived hybrid material and pure [(C(2)H(5))(4)N][Eu(DBM)(4)], respectively. The results indicate that the luminescent quantum efficiencies of VTES/TEOS composite hybrid materials are greatly improved. And it is interesting to find that the luminescent intensity of VTES/TEOS composite hybrid material is enhanced by optimizing the molar ratio of VTES to TEOS (VTES:TEOS=4:6) by 3.3 and 2.4 times compared with TEOS-derived hybrid material and pure [(C(2)H(5))(4)N][Eu(DBM)(4)], respectively. In addition, the thermal stability of the emission was also improved considerably. The results presented in this paper indicate that the use of vinyl-modified silicates as a matrix opens the door to improving the photoluminescence properties of Eu(III) complexes.

Highly sensitive oxygen sensors based on Cu(I) complex-polystyrene composite nanofibrous membranes prepared by electrospinning.

The first optical oxygen sensor based on Cu(I) complex-polystyrene composite nanofibrous membranes, showing high sensitivity (I(0)/I(100) = 15.56), good linear Stern-Volmer characteristics (R(2) = 0.9966) and short response/recovery time (t(decrease) (s) = 7 and t(increase) (s) = 14), has been prepared; these results represent the best values reported for oxygen sensors based on Cu(I) complexes.