Electrochemical impedance spectroscopy of ZnO nanostructures

The paper reports on the use of electrochemical impedance spectroscopy to determine the doping character and carrier density of freshly prepared and annealed ZnO nanostructures. The ZnO nanostructures were obtained by chemical oxidation of metallic Zn in a 5% N,N-dimethylformamide (DMF) aqueous solution at 95 °C for 24 h. The as-grown nanostructured ZnO samples display a high donor density of 3.71 ± 0.88 × 10²¹ cm^?3. Annealing at 100 and 200 °C did not have any effect on the donor density while thermal annealing at 300 °C in air for 1 h induced a decrease in the doping concentration without affecting the surface morphology.     

SYNTHESIS AND PHOTOLUMINESCENCE OF AN ANTHRACENE-CONTAINING HYPERBRANCHED POLY（ARYLENEETHYNYLENE）

A hyperbranched poly（aryleneethynylene） containing anthracene chromophore was synthesized by palladiumcatalyzed cross-coupling reaction of 2,4,6-triiodophenyl 9-anthracenylcarboxylate with 9,9-bis[4-（2-propynyloxy）phenyl]- 9H-fluorene. The structure and properties of the polymer are characterized and evaluated by NMR, IR, UV, PL and TGA analyses. The polymer is soluble in common organic solvents, possesses high thermal stability （Td 〉 330℃）, and emits a strong blue light of 465 nm in both solution and solid states.     

Structural analysis of xCsCl(1−x)Ga2S3 glasses by means of DFT calculations and Raman spectroscopy

The alkali metal halide doping of gallium‐sulfide glasses yields improvements in the optical, thermal and glass forming properties. To understand these improvements, the short‐range order of xCsCl(1 − x)Ga₂S₃ glasses was probed by Raman spectroscopy. Raman spectra have been interpreted using density functional theory (DFT) harmonic frequency calculations on specific clusters of GaS₄H₄ and/or GaS₃H₃Cl tetrahedral subunits. The assignment of the observed vibrational bands confirms the main structural conclusions obtained with X‐ray and neutron diffraction experiments and gives some new insights into the gallium‐network present in the xCsCl(1 − x)Ga₂S₃ glasses. At the lowest concentration, the observed spectrum may be interpreted with small clusters such as dimers and trimers connected by corner‐sharing (CS) GaS₄H₄ tetrahedral subunits. The vibrational fingerprints of tri‐clusters with three‐fold coordinated sulfur atoms have also been identified; however, no Raman signature of chlorine‐doped subunits has been found to be caused by their insufficient intensity. For higher CsCl concentrations, distinct spectral features corresponding to chlorine‐doped clusters appear and are increasing in intensity with x. In other words, undoped and Cl‐doped tetrahedra coexist in the xCsCl(1 − x)Ga₂S₃ glasses. The added chlorine atoms induce a fragmentation of the glass network and replace the sulfur atoms in the CS tetrahedral environment. The comparison of the observed spectra with theoretical predictions and diffraction data favoured one‐fold coordinated chlorine atoms in the glass network. Copyright © 2009 John Wiley & Sons, Ltd.     

Cu-Catalyzed Desulfonylative Amination of Benzhydryl Sulfones

A new method for the synthesis of benzhydryl amines from the reaction of readily available sulfone derivatives with amines is described. The Cu-catalyzed desulfonylative amination not only provides structurally diverse benzhydryl amines in good yields, but is also applicable to iterative and intramolecular aminations. Control experiments suggested that the formation of a Cu-carbene intermediate generated from the sulfone substrate, which represents a new route for desulfonylative transformations.     

Design of a lattice-matched III–V–N/Si photovoltaic tandem cell monolithically integrated on silicon substrate

In this paper, we present a comprehensive study of high efficiencies tandem solar cells monolithically grown on a silicon substrate using GaAsPN absorber layer. InGaAs(N) quantum dots and GaAsPN quantum wells have been grown recently on GaP/Si susbstrate for applications related to light emission. For photovoltaic applications, we consider the GaAsPN diluted nitride alloy as the top junction material due to both its perfect lattice matching with Si and ideal bandgap energy for current generation in association with the Si bottom cell. Numerical simulation of the top cell is performed. The effect of layer thicknesses and doping on the cell efficiency are evidenced. In these structures a tunnel junction (TJ) is needed to interconnect both the top and bottom sub-cells. We compare the simulated performances of different TJ structures and show that the GaP(n+)/Si(p+) TJ is promising to improve performances of the current–voltage characteristic.     

Symbolic dynamics and Arnold diffusion

We consider hyperbolic tori of three degrees of freedom initially hyperbolic Hamiltonian systems. We prove that if the stable and unstable manifold of a hyperbolic torus intersect transversaly, then there exists a hyperbolic invariant set near a homoclinic orbit on which the dynamics is conjugated to a Bernoulli shift. The proof is based on a new geometrico-dynamical feature of partially hyperbolic systems, the transversality-torsion phenomenon, which produces complete hyperbolicity from partial hyperbolicity. We deduce the existence of infinitely many hyperbolic periodic orbits near the given torus. The relevance of these results for the instability of near-integrable Hamiltonian systems is then discussed. For a given transition chain, we construct chain of hyperbolic periodic orbits. Then we easily prove the existence of periodic orbits of arbitrarily high period close to such chain using standard results on hyperbolic sets.     

Unusual light-driven amplification through unexpected regioselective photogeneration of five-membered azaheterocyclic AIEgen

Developing versatile synthetic methodologies with merits of simplicity, efficiency, and environment friendliness for five-membered heterocycles is of incredible importance to pharmaceutical and material science, as well as a huge challenge to synthetic chemistry. Herein, an unexpected regioselective photoreaction to construct a fused five-membered azaheterocycle with an aggregation-induced emission (AIE) characteristic is developed under mild conditions. The formation of the five-membered ring is both thermodynamically and kinetically favored, as justified by theoretical calculation and experimental evidence. Markedly, a light-driven amplification strategy is proposed and applied in selective mitochondria-targeted cancer cell recognition and fluorescent photopattern fabrication with improved resolution. The work not only delivers the first report on efficiently generating a fused five-membered azaheterocyclic AIE luminogen under mild conditions via photoreaction, but also offers deep insight into the essence of the photosynthesis of fused five-membered azaheterocyclic compounds.

A multifunctional, AIE-based, fused five-membered azaheterocycle is photogenerated with light-driven amplification to combat the photobleaching issue and fabricate display materials.     

Polymorph selectivity of an AIE luminogen under nano-confinement to visualize polymer microstructures

Despite the huge progress of luminescent molecular assemblies over the past decade, it is still challenging to understand their confined behavior in semi-crystalline polymers for constrained space recognition. Here, we report a polymorphic luminogen with aggregation-induced emission (AIE), capable of selective growth in polymer amorphous and crystalline phases with distinct color. The polymorphic behaviors of the AIE luminogen embedded within the polymer network are dependent on the size of nano-confinement: a thermodynamically stable polymorph of the AIE luminogen with green emission is stabilized in the amorphous phase, while a metastable polymorph with yellow emission is confined in the crystalline phase. The information on polymer crystalline and amorphous phases is transformed into distinct fluorescence colors, allowing a single AIE luminogen as a fluorescent marker for visualization of polymer microstructures in terms of amorphous and crystalline phase distribution, quantitative polymer crystallinity measurement, and spatial morphological arrangement. Our findings demonstrate that confinement of the AIE luminogen in the polymer network can achieve free space recognition and also provide a correlation between microscopic morphologies and macroscopic optical signals. We envision that our strategy will inspire the development of other materials with spatial confinement to incorporate AIE luminogens for various applications.

A polymorphic AIEgen is capable of selective growth in amorphous and crystalline polymer phases with distinct color for microstructure visualization.     

Crosslinking photosensitized by a ruthenium chelate as a tool for labeling and topographical studies of G-protein-coupled receptors

The purpose was to apply oxidative crosslinking reactions to the study of recognition and signaling mechanisms associated to G-protein-coupled receptors. Using a ruthenium chelate, Ru(bipy)(3)(2+), as photosensitizer and visible light irradiation, in the presence of ammonium persulfate, we performed fast and efficient covalent labeling of the B(2) bradykinin receptor by agonist or antagonist ligands possessing a radio-iodinated phenol moiety. The chemical and topographical specificities of these crosslinking experiments were investigated. The strategy could also be applied to the covalent labeling of the B(1) bradykinin receptor, the AT(1) angiotensin II receptor, the V(1a) vasopressin receptor and the oxytocin receptor. Interestingly, we demonstrated the possibility to covalently label the AT(1) and B(2) receptors with functionalized ligands. The potential applications of metal-chelate chemistry to receptor structural and signaling studies through intramolecular or intermolecular crosslinking are presented.