Solvent-free synthesis of 4H-pyranonaphthoquinones using highly active and stable polymer-grafted layered double hydroxides (LDHs-g-POEGMA) as an efficient and reusable heterogeneous catalyst

Research on Chemical Intermediates - Benzo[g]chromene-5,10-diones (chromene-diones) have been synthesized by an efficient, simple and green one-pot domino protocol by multi-component condensation...     

Strongly Coupled Cyclometalated Ruthenium Triarylamine Chromophores as Sensitizers for DSSCs

A series of anchor‐functionalized cyclometalated bis(tridentate) ruthenium(II) triarylamine hybrids [Ru(dbp‐X)(tctpy)]^2? [ 2 a ]^2?–[ 2 c ]^2? (H₃tctpy=2,2′;6′,2′′‐terpyridine‐4,4′,4′′‐tricarboxylic acid; dpbH=1,3‐dipyridylbenzene; X=N(4‐C₆H₄OMe)₂ ([ 2 a ]^2?), NPh₂ ([ 2 b ]^2?), N‐carbazolyl [ 2 c ]^2?) was synthesized and characterized. All complexes show broad absorption bands in the range 300–700 nm with a maximum at about 545 nm. Methyl esters [Ru(Me₃tctpy)(dpb‐X)]⁺ [ 1 a ]⁺–[ 1 c ]⁺ are oxidized to the strongly coupled mixed‐valent species [ 1 a ]²⁺–[ 1 c ]²⁺ and the Ru^III(aminium) complexes [ 1 a ]³⁺–[ 1 c ]³⁺ at comparably low oxidation potentials. Theoretical calculations suggest an increasing spin delocalization between the metal center and the triarylamine unit in the order [ 1 a ]²⁺<[ 1 b ]²⁺<[ 1 c ]²⁺. Solar cells were prepared with the saponified complexes [ 2 a ]^2?–[ 2 c ]^2? and the reference dye N719 as sensitizers using the I₃^?/I^? couple and [Co(bpy)₃]^3+/2+ and [Co(ddpd)₂]^3+/2+ couples as [B(C₆F₅)₄]^? salts as electrolytes (bpy=2,2′‐bipyridine; ddpd=N,N′‐dimethyl‐N,N′‐dipyridin‐2‐yl‐pyridine‐2,6‐diamine). Cells with [ 2 c ]^2? and I₃^?/I^? electrolyte perform similarly to cells with N719 . In the presence of cobalt electrolytes, all efficiencies are reduced, yet under these conditions [ 2 c ]^2? outperforms N719 .     

A 3D image encryption technique using computer-generated integral imaging and cellular automata transform

A novel three-dimensional (3D) image encryption approach by using the computer-generated integral imaging and cellular automata transform (CAT) is proposed, in which, the two-dimensional (2D) elemental image array (EIA) digitally recorded by light rays coming from the 3D image is mapped inversely through the virtual pinhole array according to the ray-tracing theory. Next, the encrypted image is generated by using the 2D CAT scrambling transform for the 2D EIA. The reconstructed process is carried out by using the modified computational integral-imaging reconstruction (CIIR) technique; the depth-dependent plane images are reconstructed on the output plane. The reconstructed 3D image quality of the proposed scheme can be greatly improved, because the proposed encryption scheme carries out in a computer which can avoid the light diffraction caused by optical device CIIR, and solves blur problem caused by CIIR by using the pixel-averaging algorithm. Furthermore, the CAT-based encryption algorithm is an error-free encryption method; CAT as an orthogonal transformation offers considerable simplicity in the calculation of the transform coefficient, that is, it can improve the quality of the reconstructed image by reducing energy loss compared with the traditional complicated transform process. To show the effectiveness of the proposed scheme, we perform computational experiments. Experimental results show that the proposed scheme outperforms conventional encryption methods.     

Porous PVdF-HFP/P123 electrolyte membrane containing flexible quasi-solid-state dye-sensitized solar cells produced by the compression method

Flexible quasi-solid-state dye-sensitized solar cells (DSSCs) with porous poly(vinylidenefluoride-co-hexafluoropropylene) (PVdF-HFP)/polyethylene oxide-co-polypropylene oxide-co-polyethylene oxide (P123) electrolyte membranes were fabricated and their photocurrent–voltage (I–V) characteristics are studied. Flexible TiO₂ photoelectrodes were prepared using the compression method and porous PVdF-HFP/P123 membranes, by the nonsolvent-induced phase inversion technique. To activate the electrolyte membrane, the membrane was immersed in liquid-state electrolyte. Increased compression pressure improved the interconnection between TiO₂ nanoparticles, enhancing the photovoltaic performances of the flexible liquid-state DSSCs to a maximum of 3.92% efficiency. Meanwhile, the overall pore structure of the PVdF-HFP/P123 membranes was controlled by varying the blend ratio of P123 to PVdF-HFP. Membranes higher in P123 content gave larger pores and pore volume, increasing the electrolyte uptake of the porous membrane, and thus the ionic conductivity of the electrolyte membrane as well. The photovoltaic characteristics of the flexible quasi-solid-state DSSCs containing a porous PVdF-HFP/P123 electrolyte membrane showed a maximum at 50 wt% P123 content, which gave a short-circuit current density (J_sc) value of 7.28 mA/cm², an open-circuit voltage (V_oc) of 0.67 V, a fill factor (FF) of 0.61 and an energy conversion efficiency (η) of 2.98%. Furthermore, the device designed in this study showed good durability compared to those based on liquid-state electrolyte.     

Magnetic and optical properties of self-organized InMnAs quantum dots

Ten layers of self-assembled InMnAs quantum dots with InGaAs barrier were grown on high resistivity (1 0 0) p-type GaAs substrates by molecular beam epitaxy (MBE). The presence of ferromagnetic structure was confirmed in the InMnAs diluted magnetic quantum dots. The ten layers of self-assembled InMnAs quantum dots were found to be semiconducting, and have ferromagnetic ordering with a Curie temperature, T_C=80 K. It is likely that the ferromagnetic exchange coupling of sample with T_C=80 K is hole mediated resulting in Mn substituting In and is due to the bound magnetic polarons co-existing in the system. PL emission spectra of InMnAs samples grown at temperature of 275, 260 and 240 °C show that the interband transition peak centered at 1.31 eV coming from the InMnAs quantum dot blueshifts because of the strong confinement effects with increasing growth temperature.     

Imprinted bidirectional waveguide platform for large-core optical transceiver

We introduce a new configuration for large-core optical transceiver platforms based on asymmetric three-dimensional multimode Y junctions. We developed a simply structured bidirectional waveguide platform without using a wavelength division multiplexing filter or angled mirror. This structure was designed with two different size waveguides by using the three-dimensional ray-tracing method. This structure transmitted nearly 100% power in each direction, upstream and downstream. This simple and cost-effective structure was fabricated by the imprint process using a metallic master fabricated by an ultraprecision machining method. The experimental results show that this structure is suitable for bidirectional communications in large-core optical transceivers at 155 Mbits/s.